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BONUS 180-PAGE JAVCAR CATALOG AUSTRALIA'S DYNAMIC - ELECTRONICS MAGAZINE~ SERVICING - VINTAGE RADIO - COMPUTERS - AMATEUR RADIO - PROJECTS TO BUILD THERMOSTATIC SWITCH FOR CAR RADIATOR FANS BUILD A TELEPHONE CALL TIMER HOW TO COPE WITH DAMAGED COMPUTER DIRECTORIES TURN DOWN YOUR HOT WATER SYSTEM AND SAVE MONEY Do you want a higher performance from your Capacitors? Ask Adilam about Wima Today's high performance electronic equipment demands far more than just a run of the mill capacitors. Whether your application requires close tolerance capacitors for equalisation and filter circuits, or low power factor at high frequencies for high-Q gyrators and oscillators, Wima is the brand for you. Adilam has a wide range of Wima precision capacitors in polyester, polycarbonate and polyproplene dieletric. All come in miniature moulded plastic cases which are clearly labelled. And they all have precision pin spacings (multiples of Polyester 2.5mm) so that you know they will always fit precisely into your boards. Wima has developed an extensive range of capacitors for use in pulse applications, in resonant circuits and switchmode power supplies, in line defl ection circuits and other applications where long life and reliability at higher voltages are crucial. Also available are a range of Metalized Paper Capacitors, which have superior properties including non flammability for use in across the mains applications 250 Volt 440 Volt AC. Polycarbonate FOR GENERAL APPLICATIONS Decoupling, Coupling and by-pass applications. FOR SPECIAL APPLICATIONS AT HIGH FREQUENCY For resonant circuits, switching mode power supplies, line deflection systems. temperature stabilized oscillator circuits Where an almost constant temperature effet is required; filters, memories, timers, balancing capacitors. Adilam Elccb 011ics ::a: The Component Specialistt DISTRIBUTORS: Polypropylene FOR SPECIAL APPLICATIONS Paper FOR RADIO INTERFERENCE SUPPRESSION Class X2 and class V. Excellent flame retardent properties. For use in main RFI suppression applications. MELBOURNE: SYDNEY: 3 Nicole Close, North Bayswater 3153 P.O. Box 664, Bayswater 3153 Telephone: (03) 761 4466 Facsimile: (03) 761 4161 Toll Free: (008) 800 482 Suite 1, Ramsgate Plaza, 191 Ramsgate Road, Sans Souci 2219 Telephone: (02) 529 2277 Facsimile: (02) 529 5893 ADELAIDE: N.S. Electronics Ph : (08) 46 8531 Fax : (08) 340 1456 BRISBANE: St. Lucia Electronics PERTH: Pro-spec Distributors Ph : (07) 252 7466 Fax : (07) 252 2862 Ph : (09) 362 5011 Fax: (09) 361 7592 Vol.5, No.3. March 1992 FEATURES 4 The Electronic Dentist from Siemens Review A computer makes the fillings 8 How To Adjust Your Hot Water System by Leo Simpson Turn down the heat & save power 34 The Story Of Electrical Energy, Pt.18 by Bryan Maher LOOKING FOR A NEW stereo amplifier to replace your ageing clunker? This new design delivers 50W per channel into Bohm loads & fits in a midi-sized case. Details page 22. How the Broadwater was tamed 70 Updating The Resistor & Capacitor Scene by Leo Simpson From now on, it's 1 % resistors & MKT capacitors PROJECTS TO BUILD 16 TV Transmitter For VHF VCRs by John Clarke Transmits signals to a remote TV set without messy cables 22 Studio Twin Fifty Stereo Amplifier by Leo Simpson & Bob Flynn High performance in a compact package 42 Thermostatic Switch For Car Radiator Fans by John Clarke Can be adjusted to suit your car's engine 62 Build A Telephone Call Timer by Darren Yates Keep tabs on those long-distance calls SPECIAL COLUMNS 50 Amateur Radio by Gurry Crutt The AR-1500 & AR-2800 scanning receivers THIS MODIFIED TV transmitter can now be ·used to transmit signals from any VCR to a remote TV set without messy cables or splitters. Turn to page 16. 52 Computer Bits by Jennifer Bonnitchu Coping with damaged directories & file allocation errors 54 Serviceman's Log by the TV Serviceman VCR tape transport problems 72 Vintage Radio by John Hill A look at valve substitutions 78 Remote Control by Bob Young Voltage losses in speed controllers DEPARTMENTS A 2 Publisher's Letter 13 Circuit Notebook 15 News Update 60 Computer Update 77 Bookshelf 80 Subscriptions Page Product Showcase Ask Silicon Chip Order Form Market Centre 96 Advertising Index 92 Notes & Errata 84 90 93 94 HAS THE THERMOSTAT failed on your car's electric radiator fan? This electronic thermostat can replace it & can be adjusted to switch on at a temperature to suit your particular vehicle. Construction starts on page 42. MARCH 1992 1 Publisher & Editor-in-Chief Leo Simpson , B.Bus. Editor Greg Swain , B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates Reader Services Ann Jenkinson Sharon Macdonald Sales & Marketing Mgr. Sharon Lightner Phone (02) 979 5644 Mobile phone (018) 28 5532 Regular Contributors Brendan Akhurst Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX Marque Crozman John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Magazine Printers Pty Ltd, Alexandria, NSW; Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $42 per year in Australia. For overseas rates, see the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Editorial & advertising offices: Unit 1a/77-79 Bassett Street, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 2 SILICON CHIP PUBLISHER'S LETTER The truth about fax machines These days, virtually every business organisation has a fax machine. If you want to communicate quickly, at any hour, to virtually anywhere in the western world, the fax is unbeatable. In our office here at SILICON CHIP, the fax machine is used a great deal by our readers and advertisers. Quite a few of our readers now send their letters in by fax and that is how we then send the reply. Depending on who is in the office on any one day, we can often send a reply within an hour or so of receiving a fax. And it is a much quicker way of sending in orders, although they must be accompanied by your credit card number, expiry date and signature. But fax machines can a pest. First of all, there are junk faxes. These are faxes from organisations who seem to think that all we do is stay glued to the machine waiting for their breathless messages. Well, we don't know what other organisations do with these faxes but we have a waste paper basket right next to the fax machine. We have no use for press releases which are not related to electronics in some way and which are not accompanied by a photo. Some public relations organisations think that a thousand words is worth more than a picture. And inevitably, junk faxes are preceded by a "fax cover sheet". This is a header sheet with the company's name on it and the sender's details, telling you that the next sheet or sheets are from the named company. You would be surprised just how common this sort of nonsense is. So not only does the receiving company have to waste paper in getting the fax, there is also the waste of the "fax cover sheet". Then there are the organisations who get an error message after sending a fax which may run to as much as 10 pages or more. Most of the time such error messages (saying that the pages have not been sent) are wrong but the usual response is to send the whole 10 pages again. Wouldn't it be nice to pick up the phone instead and ask if the first fax was received? A little common sense would save a lot of fax paper. The correct way to use a fax is to grab a single sheet of paper, type or write down your message and send it. If you need to use more than one sheet of paper then your message is probably too long. As our own correspondents could testify, more than 95% of our letters in reply fit easily on one page. So if you are in the habit of sending out faxes, think about the company or organisation that you are sending it to. Do you really need to send two or more sheets when one will do? And if you are from a public relations organisation , think about your "public relations". Do they really need to receive your fax? And finally, what about those companies who use fax machines with polling facilities? These machines will dial a number as many times as it takes to get a message through. This can be a real pain to the person on the receiving end as he keeps getting "bleeped" by a fax machine with the wrong number. We have had this happen twenty or thirty times before the machine or its operator finally realises that it's dialling the wrong number. It must drive receptionists mad and the cost in phone calls to the organisations concerned must be very high. So fax machines can be a boon but they can also be a pest if they are not used sensibly. Leo Simpson New FLUKE Series 10 multimeters VSI Easy-Connect The First Truly Intelligent PHONE-FAX LINE SHARING DEVICE NO Confusing Voice Messages. NO Periods of Silence. NO Unusual Dial Tones. NO Delays. NO Frustrated Callers. The EASY-CONNECT is totally transparent. Your callers will never know it's on the line ! Save Installation and rental costs for a separate llne. Switches Incoming Fax calls automatically on receipt of calling Fax tones. Latest VOICE PRIORITY technology. Installs In minutes on ANY PHONE SOCKET using aupplled connectors. DOES NOT REQUIRE EXPENSIVE TELECOM INSTALLATION. Adds HOLD FACILITY to all phones. Puts a call on hold from any phone. Manual Transfer to Fax before. during or after voice conversation. Can lnterupt a voice conversation, to send or receive a Fax, then resume. Works with or without an Answering Machine. Pulse/Tone dial compatlable. WIii operate with Fax. Phone, Modem and Answering Machine on one llne . No restriction to the number of extensions or other devices connected to It. Compact Design, being a llttle larger and heavier than a packet or ciga r ettes. Proven Rellablllty backed up with a 2 YEAR Exchange Warranty. Also works with Commander, Keyphone or PABX (technlcal Installation r equ'd) The EASY - CONNECT Is compatible with the changing needs. Provides Lightning protection for the Fax and other devices connected to It. Made In the U.S.A. Telecom Australia Permit Number: A90/14B/0342. Size: 85mm x 90mm x 33mm. Wgt: 225g. Our ..1-/0T"" new product for '92 FLUKE 10 ■ 4000 count display. ■ Continuity beeper. ■ Diode Test. ■ Sleep Mode. ■ AC voltage. ■ DC vol,age. ■ Ohms range. ■ 2 year warranty. Only $105.00 FLUKE 11 ■ 4000 count disp lay. ■ Continuity beeper. ■ Diode Test. ■ Sleep Mode. ■ AC/DC voltage. ■ Ohms range. ■ V Chek. ■ Capacitance. ■ 2 year warranty. Only $135.00 FLUKE 12 ■ 4000 count display. ■ Continuity beeper. ■ Diode Test. Sleep Mode. AC/DC voltage. ■ Ohms range. ■ V Chek . ■ Capacitance. ■ Continuity Capture. ■ Min/Max recording. ■ Relative ti me stamp. ■ 2 year warranty. ■ ■ Only $399.00 Only $155.00 my-power 200 inverter What is my-power 7 My-power is a sensational breakthrough that converts 12 volt power from a battery, to 240 volt mains power. By simply plugging my-power into your cigarette lighter socket, a host of standard electrical app liances can be used where mains power is unavailable. What will my-power run 7 My-power 200 has a continuous rating of 140 watts when connected to a fully charged battery. For intermittent periods 200 watts can be drawn and for starting motor driven appliances, my-power will supply up to a massive 400 watts for short bursts. As a guide, most appliances with a name plate rating of up to 200 watts should be suitable for operation with my-power. Continuous power: 140 watts, 200 watts peak. Protection: Overload, Undervoltage, Overvoltage, Fused Input & Output. Low battery indicator/ audio buzzer. LED indicators monitor IN/OUT volts. Siz.e: 50mm x 135mm x 7 II IIil!III I II I) Only $199.00 2 YEAR Exchange Warranty PS-2 Adaptors IBM Joystick PS-2 male to DB-9 male. QS-123 XT I AT Joystick Free floating mode. Auto cantering mode. 2 fire buttons. ■ Autofire capacity. ■ ■ ■ Only $9.50 Only $ 29.95 KEEN Mouse IBM Games Card KEM-260 3 button mouse QS-120 Joystick Card ■ ■ ■ Microsoft/Mouse System compatible. 260-2600 DPI. Includes mouse driver. Only $34.95 Gas soldering iron Chassis Punch Battery Charger This fantastic new iron is fully self • powered and portab le. One easy refill by a standard butane can allow up to 60 minutes of continuous use with a temperature range up to 400 deg. C. Features a clear reservoir to see exactly how much gas is left. ■ Replacement 2mm lip $4.95 ■ Replacement Catalytic converter $4.95 Size: 16, 18, 20, 30mm Reamer: 3 to 12mm Made in Japan. ■ Charges 1 to 4 pcs ·AA· size NiCads. ■ and/or 1 pcs. 9V NiCad. ■ Charging Indicator. ■ Charging time: 14-16 hours. ■ Polarity reverse protections. ■ IBM PC/XT / AT compatible. ■ ■ speed. 3 position speed selector. 12 months warranty. ■ 2 x DB-15 game ports. ■ On-line selectable clock Only $ 25.95 Fuji "AA" NiCad 1.2 volt <at> 500mAH Made in Japan Only $2.95 each Mini VAC 9 volt battery operated _.,-,.::~====:,,~~=te, ""~ ;&1~ <rnt - ;;;::.;_9 - Now $49.95 - Q DavidReid ~ Electronics A.C.N. 001-372-372 Only $12.95 127 York St, SYDNEY 2000 Ph: (02) 2671385 P.O. Box Q103,SYDNEY 2000 Fax: (02) 261 8905 Only $ 9.95 ~~•:ei ~•~ei'" 0 0 Postal Charges $5 - $25 ······•·· $4.00 $26 - $50 ...... $6.00 $51 - $100 ..... $7.00 $101 - $499 .. $9.00 $500 • ....... ..... FREEi CEREC is a completely new system that combines 3dimensional scanning, computer-aided design, and numerically-controlled milling to make ceramic tooth fillings. It will make it possible for dentists to produce and insert ceramic fillings in a single session. Fast ceramic fillings for teeth THE ELECTRONIC A MALGAM, epoxy resins and gold are the standard materials for fillings. Now, however, ceramic fillings are possible, thanks to the CEREC system developed by Dr Werner H. Mormann and Dr Marco Brandestini in collaboration with Siemens. The search for an alternative to traditional metal fillings has been on for about 20 years. Ten years ago, about 95% of posterior restorations (ie, fillings for back teeth) were of amalgam (gold plays a minor role in this area). Today, amalgam is only used for about 50% of restorations, with tooth-col4 SILICON CHIP oured composite resin materials being used for the other 50% . The reason for this trend may, among other things, be that amalgam has suffered from a good deal of public debate regarding health-risks. The goal since 1980 has therefore been to find tooth-coloured restoration materials for posterior teeth. Such fillings have been in use since 1958, which was when new composite resin materials were being developed in the US. However, these materials have two serious disadvantages. The first of these is that they lose surface substance due to masticatory abrasion (ie, chewing). The second problem is that they shrink during polymerization and this can mean a reduction in volume of 2-3%. That's why large composite resin fillings never make a perfect seal, even from the .very beginning. This material is therefore unsuitable for restoring pos- Top of page: this photo shows a dentist using the CEREC optical scanner to scan a patient's tooth cavity. The impression is immediately displayed on the computer monitor. terior tooth cavities and for bearing the stresses of chewing. Since 1980, it has been found that both problems - abrasion and shrinkage - can be brought under control if the filling is processed as an inlay outside the oral cavity. This inlay can then be bonded into the tooth using the same composite resin material. That was the basic discovery on which the development of the CEREC system rests. In fact, the inlay method is the basis of gold fillings too. The big disadvantage of the conventional inlay technique is that an impression must be taken which the dental technician then uses to form the inlay. The dentist has to seal the cavity and remove the temporary filling again in the next session. Only then can the gold inlay be inserted. The big advantage of amalgam and traditional composite resin fillings is that they can be completed in a single session. So that became the goal: to be able to produce a tooth-coloured inlay at the dentist's office in a single sitting. In 1980, Dr Mormann tested all the possible ways of producing such inlays using the conventional method of impression, cast and counter cast. However, because these required the dentist to function as a dental technician, it quickly became clear that an insufficient resolution. But the problem intrigued him. Shortly after, he came to the conclusion that only an optical scanning method could do the task. Their first experiment was conducted in 1982. It proved that it is possible to measure dental cavities precisely using a special video camera; that is, to take an optical impression. What evolved from this was an active triangulation method in which a striped pattern is projected onto the cavity and a recording is made from which a computer can calculate the depth of each pixel. So, the basic principle, using the inlay technique in conjunction with an optical scanning method, was taken care of. But the story didn't end there. There were a number of goals that still had to be met. For instance, the dentist should be able to use the system directly. The system should make it easy and simple to scan a cavity in just fractions of a second. The data should be immediately available, and the dentist should be able to process it directly. Finally, by using a numerically-controlled milling machine, the system should make it possible for the dentist to make inlays in just a few minutes. Developing the milling machine wasn't as easy as originally anticipated. At first, they simply enlarged and strengthened a dental drill and made it 3-dimensionally mobile using a complex motor drive system. This was not entirely successful. After that, the machine was drastically simplified, limiting it to three degrees of freedom, and utilising just one milling disc, which creates the completed inlay from a ceramic block in just a few minutes. The idea of confining the milling head to just three degrees of freedom might sound limiting but it works in most cases. Dental decay usually follows a typical pattern. This leads to certain standard types of cavity preparation for which inlays can be easily produced by the CEREC system. Preparation does not differ in prin- DENTIST improved production method would be necessary. It was then realised that the main obstacle was the lack of a cavity scanning system. Optical scanning Dr Mormann at first thought about scanning with ultrasound. He discussed this with the co-inventor of the CEREC system, Dr Brandestini, who at that time was working intensively at Advanced Technologies Laboratories Inc in Seattle, Washington, on ultrasound scanners for medial diagnostics. He explained that ultrasound would not be feasible because of its This monitor photograph shows the optical scan of a patient's tooth and the area to be restored by a ceramic inlay. Using the information gathered from the optical scan, the computer controlled milling machine manufactures a ceramic inlay to restore the tooth. It does this in only a few minutes. ciple from conventional inlay preparation. However, the machine can't work hollow parts on the inlay, Therefore, during cavity preparation, the dentist simply has to keep CEREC's design rules and operation in mind . . The tooth can then be prepared with as little loss of substance as with other methods. A dentist skilled in this method can restore the full range of inlay and onlay cavities in his surgery. Inlay cavities are always designed so that the filling can be inserted from MARCH 1992 5 I ins were not durable enough - and, although they are much improved since first introduced, they are still not as strong as ceramics. · Ceramics have a lot of advantages. They can be produced to perfectly match tooth colour and they are nonsoluble, durable and stable in the oral cavity. Although ceramics are nonelastic and can break when subjected to overload, they are in this respect no different from dental enamel. Ceramics also stand up to machineprocessing very well. Generally, because factory produced material has fewer flaws than individually fired dental porcelain, it is easier control its quality than it is with blocks produced in dental labs. Other materials Dr Werner H. Mormann, of the Dental Institute of Zurich, in Switzerland, is a co-developer of the CEREC ceramic inlay method of tooth restoration. Intended mainly to replace amalgam fillings, it is hope that the method may eventually be used for full crown restorations. one direction and so that all the cavity margins and surfaces can be seen from a viewing angle which coincides with the insertion axis of the cavity. This makes it possible to record the shape with a single scan. The idea is that if a dentist is capable of preparing a cavity in this way, he is also capable of holding a camera and man- Compared with amalgam fillings (below), the new CEREC ceramic inlay fillings (right) are virtually invisible. These fillings had been in place for two years when photographed. 6 SILICON CHIP ipulating it just like a normal examination mirror. In Switzerland, a CEREC restoration costs two to three times as much as an amalgam filling. But on the other hand, if the dentist makes an impression of the area to be restored, and sends it out to a lab so that an inlay can be made, then the total cost is five to eight times as high as an amalgam filling. So CEREC-produced fillings often offer substantial savings, and then save patients the trouble of having to come in a second time. Ceramic material Dr Mormann discovered during the development stage that composite res- In principle, composite resins are suitable provided they can be industrially manufactured in suitably sized blocks. Glass ceramics can also be used and have the advantage of having almost exactly the same degree of hardness as dental enamel. In addition, their physical properties are pretty similar to those of dental enamel. The one disadvantage of this material, namely that it was transparent, has been solved: tooth-coloured, natural-looking glass ceramics are now available. Today, CEREC can produce inlays, onlays, and veneers very simply and quickly for anterior applications. These can be used as aesthetic half crowns to restore the labial surfaces of anterior teeth. Onlays and veneers are a step in the direction of full crowns, which is the ultimate aim. Acknowledgement: our thanks to Siemens Ltd for photos and permission to reproduce material from Siemens Review, Volume 57, March/April 1990. SC BUILD YOUR OWN FAX/MODEM ONLY $299.00 Time saving The Comma Fax/Modem will also receive faxes in background while you continue to work. When faxing out the Fax/Modem will redial an engaged number so you can be sure your faxes are sent. The software also automatically keeps a complete log of both incoming and outgoing faxes. Also supported are cover pages, broadcast faxes, and scheduling. The software keeps a database type register ofregularly used fax numbers for easy retrieval This is a fully featured kit The Comma Fax/Modem is a commercially designed kit you can build. It will turn your PC (or Macintosh) into both a fax machine which can transmit faxes up to 9600 baud, as well as a Modem which supports both 1200 and 2400 baud. You get all the necessary components as well as a professional case, and power supply . You also receive FREE Fax/Modem software. All this for less than $300. The Comma Fax/Modem uses the latest technology in digital signal processing to ensure lasting troublefree operation. Send faxes from home The Comma Fax/Modem is a fully featured fax machine similar to units costing over $1000, which will transmit faxes at up to 9600bp. Your faxes can now be sent directly from your PC without having to print them first. Programs supported such as Ventura Publisher, Wordperfect, Windows, TIFF and Dr Halo to name but a few. You can view incoming faxes on-screen or print them using a standard dot matrix printer. Incoming files can also be exported in either TIFF or PCX format for use in most popular graphic packages. Only print the faxes you want to keep - just think of the savings on expensive fax paper. As well it's also a modem The Comma Fax/Modem is a fully AT command series V compatible modem. Features include V22/V22bis standards (V21/23 is an option) both 1200 and 2400 baud rates are supported as well as auto answer, dialing and disconnect. You will find it compatible with all popular communication services including most bulletin boards. Now Available MNP and V42bis option. V21/23 option. $99.00 $39.00 FREE Software With each kit you will receive the QL2 Fax/Modem software featuring both pull-down menus and mouse support. Value packed kit Each kit has been specially prepared to ensure you are able to build the Comma Fax/Modem with a minimum of specialised skills. We have also weighed each kit to ensure every component is included. There is also a step-by-step guide to testing your Fax/Modem throughout the building process. Note: This device does not have an Austel permit in force. Connection to Telecom lines is an offence. 105MB HDD IDE Drive This card does it all 19ms 3.5" Hard Drive. This drive would normally cost $799.00. This month only IDE2 x Hard Disk controller with 2 x Floppy Disk Controller and 2 Serial Ports, 1 Parallel and 1 Games port. $589.00 $75.00 We also stock a range of motherboards, external disk drives, hard disk drives, add-on interface cards, as well as a huge range of cables, adaptors, switch boxes and chips. Call today for competitive pricing. DEALER INQUIRIES WELCOME TRY PC MARKETPLACE SUPERFAST MAILORDER - PHONE OR FAX TODAY! pfii{ (jfeesons PC MARKETPLACE Pty Ltd FREIGHT CHARGES PHONE (02) 418 6711 FAX Include $10 with order for all normal items. Heavy items e.g. monitors add $15. 14 day money back guarantee. (02)4186713 Mail Order Address: P.O. Box 1100 Lane Cove NSW2066 e Order by phone (use credit card), by lax or by mail. Unless insurance is declined it will be charged at 1% of total p..1rchase. This is for your protection. PRICES CURRENT FOR NIONTH OF PUBLICATION OR WHILE STOCKS LAST SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE M OST electric hot water systems have their thermostats set to around 70°C or 75°C during manufacture but that does not mean that's where you should keep it. 75°C is really far hotter than you need for most tasks and, in fact , it can be dangerous. For example, if you have a young child in the shower and suddenly the cold water flow is reduced, as can happen if a washing machine solenoid cuts in, then the child can be badly scalded before it has the presence of mind to step out of the hot water stream. Similarly, if you turn on a hot water tap which has just been used, you may scald yourself before you realise it. A much safer and more sensible thermostat setting is around 65°C. This greatly reduces the risk of scalding in the examples described above and has two other benefits. We've already mentioned the first: saving electricity. TURN DO HEAT & SAVE Power loss We estimate that a typical small domestic hot water system (say around 60 litres) will continuously lose somewhere in the vicinity of 100 watts. The actual amount of power loss is proportional to the difference between the thermostat setting and the ambient temperature. So the higher the thermostat setting, the greater the power loss. If you don't believe the power loss is 100 watts or more, just note how hot the area around the tank can be if it is installed underneath your kitchen sink. It gets quite warm, doesn't it? If the power loss is 100 watts, that amounts to 2.4 kilowatt-hours a day and around 900 kilowatt-hours per year. At a typical cost of 10 cents per kilowatt hour, the annual cost will be around $90. That is what you are paying for having hot water continuously available. But consider what happens when you reduce the thermostat setting from 70°C to 60°C. Now the temperature difference between thermostat setting and an ambient temperature of 20°C drops from 50°C to 40°C. With that smaller temperature difference, you can expect the continuous power lost to be reduced to around 80%. The saving from this, around $18 for this example, is not large but is still worthwhile considering you can have it for just a few minutes work. 8 SILICON CHIP Switch off the power at the fusebox and remove the hot water fuse before removing the tank inspection cover. The thermostat is a small dial that you can adjust with your screwdriver. Set it to 60°C, which is a much safer setting for showers and hand washing. Note the use of a screwdriver with an insulated shaft - another worthwhile safety measure. For a much larger hot water system, say 200 litres or more, the continuous power loss is proportionally less, but still may be around 200 watts or more. That amounts to around 1800 kilowatt-hours per year although with large systems such as this, the cost probably won't be as great because most will be off-peak systems having a much lower electricity tariff. Stopping the tank from boiling One risk of a high thermostat setting on some larger hot water systems is that the water may begin to boil before the thermostat cuts off the power. The reason this happens is that the large volume of water can be relatively slow to mix and so some parts of the tank can be well under 70°C while other parts, just above the heating elements, can actually be boiling. In cases such as this , the water may boil for five minutes or more before the thermostat finally cuts off. This is wasteful because it usually leads to the pressure relief valve being operated on a mains pressure tank or may lead to an overflow on a gravity feed system. If you have ever drawn hot water off first thing in the morning and have found that the water was literally boiling, then it is probable that that is exactly what has been happening. The risk of scalding in these circumstances is high. Setting the tank thermostat back to between 60°C and 65°C greatly reduces this risk. By the way, most hot water systems THE POWER By LEO SIMPSON You can save money on your hot water costs by turning down the thermostat. This applies equally to off-peak and quick recovery hot water systems. By turning down the thermostat your hot water tank may also last longer and you reduce the risk of scalding, particularly to young children. are also fitted with an over-temperature cutout so that if the thermostat fails, the cutout operates to prevent the system boiling for more than a short length of time. usually find that it has been set at around 70°C. Use your screwdriver to rotate the small pointer back to around 60°C. While you have the cover off, inspect the wire connections to the heater element. Make sure that they are not burnt or charred - a sure sign of a poor connection. These should be remedied before the tank side cover plate is screwed back in place. If your hot water system is an offpeak gravity feed unit, it will be in the ceiling and therefore harder to gain access to. If the system has been installed for five years or more, it is a good idea to change the rubber valve in the stopcock - you will find this in the header tank at the side or on top of the main tank. Turn the water supply off before you do this job and make sure you have a new valve handy before you go up in the ceiling. When you have replaced the cover on the side of the tank, don't forget to turn the power on again - otherwise you might have lukewarm water for your morning shower. Points to note Before concluding, we should note that a large number of hot water systems (mostly made by Rheem) do not have adjustable thermostats - they are fixed at around 70°C and so you are stuck with it. If you ever have a new system installed - and that means every 10 years or so for most mains pressure systems - make sure that you specify a tank with an adjustable thermostat and have the installing electrician set it to around 60°C. Rheem do make hot water systems with adjustable thermostats and they also have an adjustable thermostat kit which can be fitted by their service people to most of their systems. When fitted, you can change the thermostat setting simply by turning a small knob on the side of the tank. Thus, it is completely safe and much more convenient. The total cost of the installation is in the vicinity of $100. For more information, contact the service department of Rheem Australia Ltd in your state. After having set back the thermostat, you may notice that it takes slightly longer for the water to run hot from the taps - if it takes too long, then you can always adjust the thermostat back up a little but don't go back to the original setting. You may also be concerned that your dishwasher will now take a little longer in its cycle - because it will need to heat the water a little more than before. However, you will still have a saving in energy and you have reduced that risk of scalding - a most important benefit. Another point is that if your hot water tank is only just adequate for your requirements, setting the thermostat down too far may mean that you could occasionally run out of hot water during the winter months. You can reduce the loss of heat from your hot water tank by fitting it with an external insulating blanket which could be made up from old carpet, underfelt or rockwool batts. This won't make a lot of difference in summer but can give significant energy savings in the winter months. And finally, a note of caution: remember that 240VAC electricity is lethal. You must disconnect the power before removing that side cover ·on the tank. And if you are not at all sure how to adjust the thermostat, leave it strictly alone. If necessary, consult your local electrician. SC Setting the thermostat Changing the thermostat setting is relatively easy and you need only one tool - a straight bladed screwdriver. The first thing to do is to go to your electricity meter box and turn off the power to the hot water tank. It is a good idea to pull out the hot water system fuse too -just to make doubly sure that the power is off. Having switched the power off, remove the screws to the large cover plate on the side of the tank. You should now see the thermostat setting dial. It is quite small and you will .~1\f;...;..r..i:~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB [, front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. MARCH 1992 9 RITRON ADD PRICE TO BASE SYSTEM COST. 512K VGA CARD ..$50 c2sa. 21 ·.••·& 80286-16 CPU ( 386SX-21) i..,.,..,...__,,_,__,_, 1 MEG RAM EXPANDABLE TO 4 MEG 21 Mhz LANDMARK SPEED TEST 1.2M JAPANESE BRAND F.D.D 42M HARD DISK DRIVE 28ms ACCESS 101 EXTENDED "'CLICK"" KEYBOARD JAPANESE KEYBOARD SWITCHES P.INI CASE & 200W POWER SUPPLY SUPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28"" DP 2 SERIAL, PARALLEL, GAME PORTS 3 YEAR ""AUSTRALIAN"' PARTS & LABOUR WARRANTY 256K VGA CARD. COMPATIBLE SPREADSHEET, WORDPROCESSOR & DATABASE SOFTWARE INCLUDED. ASSEMBLED & TESTED IN AUSTRALIA IBM' $1 ' 195 $1,045 TAX INC. 80386SX-16 CPU 1 MEG RAM EXP TO 4 MEG 27Mhz LANDMARK SPEED TEST 1.2M JAPANESE F.D.D. 512K VGA CARD 43M HARD DISK DRIVE, 101 EXTENDED "'CLICK"' KEYBOARD CASE & 200W POWER SUPPLY SUPA VGA COLOUR MONITOR 1024x768 Res 0.28"'DP SERIAL PARALLEL GAMES PORTS 3 YEAR "'AUSTRALIAN"' PARTS & LABOUR WARRANTY COMPATIBLESPREADSHEET, WORDPROCESSOR & DATABASESOFTWARE MINI IBM• $1 395 INCLUDED. • SHAREWARE SOFTWARE ' ASSEMBLED & TESTED . $1,150 TAX EX. TAX INC. TAX EX EXECUTIVE 'SHAREWARESOFTWARE ASSEMBLED & TESTED IN AUSTRALJA. $1 495 ' $1,290 TAX INC. TAXEX RITRON EXECUTIVE 1 80386-33 CPU 64K CACHE ON BOARD MEMORY 1 MEG RAM EXP TO 16 MEG 57Mhz LANDMARK SPEED TEST 43 MEG HARD DISK 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "'CLICK"' KEYBOARD SERIAL PARALLEL GAMES PORTS SUPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28" DP CASE & 200W POWER SUPPLY 512K VGA CARD (256 COLOURS) COMPATIBLE 3 YEAR "'AUSTRALIAN"' PARTS & LABOUR WARRANTY SPEADSHEET, WORDPROCESSOR & DATABASE SOFTWARE INCLUDED. MINI 'SHAREWARESOFTWARE ASSEMBLED & TESTED IN AUSTRALIA. IBM• $1 795 ' TAX INC. 80486SX·20 CPU 1 MEG RAM EXP TO 32 MEG 75Mhz LANDMARK SPEED TEST 43 MEG HARD DISK 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "'CLICK"' KEYBOARD SERIAL, PARALLEL, GAMES PORTS, 1 MEG VGA CARD !>UPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28"' DP CASE & 200W POWER SUPPLY 3 YEAR "'AUSTRALIAN"' PARTS & LABOUR WARRANTY SPEADSHEET, WORDPROCESSOR & DATABASE SOFTWARE INCLUDED. •SHAREWARE SOFTWARE MINI TAX INC. ASSEMBLED & TESTED IN AUSTRALIA. $2,095 ~~ TAX EX. WITH 200 MEG DRIVE $2,795 TAX INC. $2,395 TAX EX. RITRON EXECUTIVE 80486-33 CPU 256K ON BOARD CACHE. 1 MEG OF RAl'II EXP TO32M 157Mhz LANDMARK SPEED TEST 85 MEG HARD DISK 1.2M JAPANESE F.D.D 101 EXTENDED "'CLICK"' KEYBOARD SE RIAL, PARALLEL; GAMES PORTS 512K VGA CARD. COMPATIBLE SVGA COLOUR MONITOR (1024 x 768 Resolution) 0.2B"'DP CASE & 200W POWER SUPPLY 3 YEAR "'AUSTRALIAN"' PARTS & LABOUR WARRANTY MINI BRAND IBM• SPREADSHEET, WORDPROCESSOR & DATABASE SOFTWARE. ASSEMBLED & TESTED IN AUSTRALIA. ' MINI $1,775 $1,495 TAX EX 386-33 128K..... $1995 80386-40 CPU 64K CACHE ON BOARD MEMORY 1 MEG RAM EXP TO 16 MEG 65 Mhz LANDMARK SPEED TEST 105 MEG HARD DISK 12ms ACCESS TIME 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "CLICK" KEYBOARD SERIAL, PARALLEL, GAMES PORTS 512K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28"' DP CASE & 200W POWER SUPPLY 3 YEAR "'AUSTRALIAN"' PARTS & LABOUR WARRANTY SPEADSHEET, WORDPROCESSOR & DATABASE SOFTWARE INCLUDED. •sHAREWARE SOFTWARE ( 486-157) ( 486-75 ) $ 1 995 1 MEG add .. $75 2 MEG add .. $150 DOS 5.0 AN EXTRA .... ................... $100 DR DOS 6.00.$129 WINDOWS 3.00.$129 SOUND CARDS SOUND COMMANDER ...... ............... $149 THUNDER BOARD:........ ............ .... . $199 SOUNDBLASTER 11 .... .................. ... $249 SOUNDBLASTER PR0 .... ................. $389 FLOPTICAL DRIVE add ................... $839 21 _Pd:/BYTE DISC TO SUIT... ............ $39 386-65 ) 386-57 80386SX25M 1 MEG RAM EXP .To 4 MEG 27Mhz LANDMARK SPEED TEST 1.2M JAPANESE F.D.D. 512K VGA CARD 43M HARD DISK DRIVE, 101 EXTENDED ""CLICK"' KEYBOARD P.INI CASE & 200W POWER SUPPLY SUPA VGA COLOUR MONITOR 1024 x 768 Res 0.28"' D.P SERIAL PARALLEL GAMES PORTS 3 YEAR " AUSTRALIAN"' PARTS & LABOUR WARRANTY IBM• COMPATIBLESPREADSHEET, WORDPROCESSOR & DA.TABASESOFTWARE INCLUDED. EXTRA RAM Jd'E:~~~~ c RITRON RITRON lM VGA CARD .. $150 TO CHANGE A 40M HARD DRIVE TO A 85M HD add $175 52M HD ••.• $50 126M HD add $350 105M HD ••$225 200m HD add $850 180M IID •. $750 $2,745 TAX INC. .•. $2,595rAXINC. $2,350 TAX EX. • $2,295 TAXEX. WITH 200 MEG DRIVE ROD IRVING ELECTRONICS Est. 1977. MAIL ORDER HOTLINE: 008 33 57 57. (ORDERS ONLY) ENQUIRES: (03) 543 7877 HEAD OFACE: 56 RENYER RD, CLAYTON. PH: (03) 543 2166. FAX (03) 543 2648 CITY 48 A'BECKETT ST. MELBOURNE. PH. (03) 663 6151 / (03) 6391640. FAX: 6391641 . OAKLEIGH: 240C HUNTINGDALE RD, OAKLEIGH. PH: (03) 562 8939 NORTHCOTE 425 HIGH ST. NORTHCOTE, PH. 489 8866. FAX: 489 8131. SYDNEY:74 PARRAMATTA RD, STANMORE. PH: (02) 519 3134. FAX: (02) 516 5024 MELBOURNE DEALER: BLUESTAR COMPUTERS: 271 MAROONDAH HWY, RINGWOOD, 3134. PHONE: (03) 8701800 FAX: (03) 879 3027 WITH 200 MEG DRIVE $3445 $2,995 TAX INC 80486-33 CPU 256K ON BOARD CACHE. 4 MEG OF RAM 157Mhz LANDMARK SPEED TEST . 200 MEG HARD DISK 12ms ACCESS TIME 1.2M JAPANESE BRAND F.D.D 3.5"' 1.44M JAPANESE BRAND F.D.D 101 EXTENDED "CLICK"' KEYBOARD SERIAL, PARALLEL, GAMES PORTS 1 MEG VGA CARD. COMPATIBLE SUPA VGA COLOUR MONITOR (1024 x 76ll','Res) 0.28" DP TOWER CASE & 220W POWER SUPPLY 3 YEAR "'AUSTRALIAN" PARTS & LABOUR WARRANTY , SPEADSHEET, WORDPRCESSOR & DATABASE SOFTWARE. IBM' ASSEMBLED& TESTED IN AUSTRALIA. TAXEX FREIGHT CHARGE BASED ON 35KG COMPUTER SYSTEM Melb-Metro.$12.00 Sydney....... $17.00 Adelaide ..... $17.00 Bribane ...... $24.00 Canberra .... $18.00 Darwin ........ $40.00 Perth ........••. $31.00 Tasmania••.•$53.00 $3 895 IDEAL CAD MACHINE! Vic country•... $19.00 NSW country.$39.00 S.A country... $39.00 OLD country.$55.00 W.A country.. $74.00 lnsurance:$1 I $100 Value. ' TAX INC. $3,395 TAX EX. All sales tax exempt orders to • RITRONICS WHOLESALE 56 Renver Rd, Clayton, Victoria . Ph• (03) 543 2166 Fax: (03) 543 2648 MAIL ORDER & CORRESPONDENCE P.O BOX 620, CLAYTON, VICTORIA. 3168. Errors & ommlasona excepted. Prices & apecltlcatlona subject to change. "IBM, PC, XT, AT, are registered trademarks of International Business Machines. PRICES AT AUS$= US $0.74 1. g boxes 10+ OXES OF TEN DISKS LIFETIME WARRANTY 1·9+ 10+ 50+ 100+ 500+ 5 1/4" 5 1/4" 3 1/2" 31/2" OS/OD $4.50 $4.40 $4.30 $3.25 $3.95 DS/HD $8.50 $8.25 $8.10 $7.50 $6.90 DS/0D $7.90 $7.70 $7.50 $7.00 $6.60 DS/HD $14.95 $13.75 $13.50 $12.00 $11.00 31/2"00 $19.95 3 1/2"HD $45.95 5 1/4"00 $14.95 5 1/4"HO $23.95 ,, 11111,/ I"4i<at>il?i1isii<at>iJ ii rnJ& Jips wARRAifrv, -r~ $18.95 $42.95 $12.95 $22.95 3 3 5 5 1/2"00 $28.50 1/2"HO $53.50 1/4"00 $22.95 1/4"HO $27.95 $27.95 $52.50 $21 .95 $26.95 3 1/2"00 $23.95 3 1/2"HD $39.95 51/4"DQ$12.95 5 1/4"HD $19.95 $22.95 $37.95 $11.95 $18.95 KYOCERA LASER F-800T. 8 pages per minute! ·-- . / 6 Pages per Minute! The EPL-4000 is the latest EPSON high performance laser printer, combining reliability and a wide range of features. The EPL-4000 col)'lbines a semi conductor laser with the electrophotographic technology used in office copiers to give you high quality printing that is both fast and quiet The imaging system used by the printer is driven by a powerful processor that allows the printer to compose an entire page in internal memory before printing. The printer manipulates the page it l)olds in its memory to provide you with many features not found on other types of printers, including the ability to mix text and graphics, create predefined forms, and print with a range of fonts normally associated with typeset ·material. only$ 1695 -~,.~?) Compact & economical 8 page per minute laser printer. Ideal for a first time user or as a full featured laser personal printer for the PC user. The F-800T has 70 resident fonts-far more than any comparable printer-with all the major international character sets. PRESCIBE allows you to develop your own new typestyles. The F-800T also has the IC-card optionavailable for storing and printing logos, forms and other images. It acts as a HP LaserJet Series II, IBM Pro Printer, Epson FX80, Oume Sprint II, NEC Spinwriter, Diablo 630 and as a Line Printer. You can print on paper, Lables, overhead transparancies and envelopes or single sheets. It also has the ability to choose how much of the memory you want allocated as standard RAM and as video RAM. The F-800T is an advanced and reliable printer at an economical price, made by one of the worId·s most reliable manufactures. only $1895 Double your disk storage with .... DR DOS 6.0 INSITE 1325VM 20MB FLOPTICAL DRIVE At last a floppy drive that is truly multi-purpose. You now can load and save all the 3.45" format software you are used to Bnd in the same drive backup at 20 Mego bytes per disc. This truly remarkable drive is• GIANT leap forward in removable technology. Features: Comes with a "Grassroots" SCSI host adaptor card. Has an on board BIOS, so no drivers are required. Will BOOT MS-DOS using either 20MB, or 1.44MB or 720 KB disketts DOS compatible with MS-DOS 3.3, 4.01 and 5.00 BIOS compatible with PHOENIX 286 and 386 ver 3.10 AWARD 286 end 386 ver 3.02 20MB Diskettes con be bought pre~ow•level formatted Low-level formatting can be done with LFMT program aupplied or using DEBUG "G: CDS0:6•• The unit can BOOT the system as drive "A:" or "B:" In either 720K, 1.44MB or 20MB format ••••••••••••••••••••••••••••••••••••••••••• Drive $849:00 20 M Discs to Suit... .....................$39.00 Each. I __ __J The most odvanced, fully DOS-compatible operating system available today. It·s everything you need to run your DOS, Windows, and networking appliactions faster. To maximize hard disk perform ance. To keep your system and data secure. Ansd to make your PC easier and more convenient to use. In addition to superior DOS technology, you get a complete set of fully integrated PC utilities. MEMORYMAX: moves DR DOS buffers, drivers, TSRs and networking software outside the 640K memory area, leaving more memory for your DOS. Network and Windows applications. DISKMAX: improves your pc·s overall performance so you can get more work done in less time. Its optional automatic file compression feature potentially double• your hard disk storage apace. TASKMAX:Leta you lood up to 20 programs at the same time and quickly switch from one lo another as well as copy and paste text and numerical data .. ...... .... $129.00 NEW SOUND CARDS The MY.POWER 200 is a pocket sized inverter with punch. My-Power will power a myriad of applionces including Tv·s, videos, drills, lights, laptops and computers, fax machines to name just a few.Continuous power rating is 140 watts but we choose to size this on its intermittent rating of 200 watts as it will run most appliances with a name plate ratings of 200 watts. Surge rating is a very real 400 watts• incredible for• unit that weights less than half a kilo and fits in your pocket My·Power is convenient too, supplied ready to plug into a vehicle cigarette lighter socket. $199.00 ROD IRVING ELECTRONICS Pty. Ltd. THUNDER BOARD 100% Comapible with Adlib Sound Blaster cards for PC games plus: Thunder Master: power, easy to use Graphical sound Digital Audio Sampling. Dynamic filtering.• 11 Voice FM Synthesizer SOUND COMMANDER • 11 Voice FM music • Software Volume Control• Playback Digitized Voice. • includes high quality speakers • Compatible with 1oo·s of music, games and business s oftware ······-······· ...·················............ $199.00 ····· ············· ......................... $149.00 ACN.005428 437 HEAD OFFICE: 56 RENYER RD, CLAYTON . PH: (03) 543 2166. FAX (03) 543 2648 CITY 48 A•BECKETT ST. MELBOURNE. PH. 663 635116391640. FAX: 6391641. OAKLEIGH: 240C HUNTINGDALE RD, OAKLEIGH. PH: 562 8939 NORTHCOTE425 HIGH ST. NORTHCOTE, PH. 489 8866. FAX: 48118131 . SYDNEY:74 PARRAMATTA RD, STAN MORE. PH: (02) 51 a 3134. FAX: (02) 519 3868 BLUESTAR COMPUTERS: 271 MAROONDAH HWY. RINGWOOD. PH: (03) 8701800 • Postage rates $1 - $9.99 ...... $3.00 $10 - $24.99 .. $3.50 $25 - $49.99 .. $4.50 $50 - $99.99 ..$6.00 $100 • $1911 ... $7.00 $200 • $500... FREE $500 PLUS .. FREE Th•• po•tage rates a N baalc postage only up to 0 ;:a:lght. :~~-Y~ , ..,... wt, .. TOLL FREE MAILPR0ER HOTLINE: 008 33 5757 CIRCU TNOT Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. r--~--,----------11-----------......-----<11t------.----.....-------•12VVIA COURTESY 10k 1000 16VW 100 16VW + - 1k + - FUSE 270k BV NOM. V • 02 03 1N914 1N914 ,._ TO COURTESY LAMPS 330k 470 + 16VW 10k 220k 05 1N914 DOOR SWITCHES -:- 4V NOM. 6.Bk +12V ,1 16VW 220k .,. 1.Sk, - This circuit not only provides a convenient courtesy light delay but also automatically turns off the courtesy lights after seven minutes if a door is accidentally left open. The delay is cancelled by switching on the car's tail lights. TAIL LIGHT CIRCUIT Courtesy light delay for cars This circuit provides a convenient turn-off delay for your car's courtesy lights - a feature that some later model cars already have. It allows the driver to find the ignition switch and passengers to fasten their safety belts, after the doors have been closed. An additional feature of the circuit is that power is cut off to the courtesy lights if a door has been left open for more than seven minutes. This is very worthwhile considering that the courtesy lights in some cars represent a 1 big drain on the battery. If a car door is accidentally left ajar overnight, it can flatten the battery. Another feature involves automatic cancellation of the courtesy light delay once the driver turns on the tail lights. The circuit is arranged for cars which have earth switched at the door buttons (some Fords switch positive). The circuit uses an LM324 quad op amp IC as the controller. The lamps are switched via the relay and transistor Ql which is controlled by ICla, operating as a comparator. When a door is opened, one of the door switches closes and pulls pin 2 of Converting the pattern generator for NTSC The colour TV pattern generator described in the November and December 1991 issues is capable of producing video signals suitable for NTSC TV sets. In order to do this, pin 14 of IC16 (the TEA2000 colour encoder) must be connected to the ground supply rail (left open circuit for PAL) and the 8.86MHz colour burst crystal must be changed to 7.15909MHz. The 390Q and 470n resistors at pin 6 of IC16 may require adjusting for best modulation depth. Note that we have not tested this modification. John Clarke, SILICON CHIP. 12 SILICON CHIP ICla low via diode D3. When the door switch opens again, the lO0µF capacitor at pin 2 discharges via the parallel 270kQ resistor, giving a 30-second courtesy light delay. IClc monitors the tail light. When these are turned on, IClc's output goes high and pulls pin 2 of ICla high via diode D5. This turns off Ql and the courtesy lights. IClb, in conjunction with the lO00µF capacitor at its pin 9 input, provides the 7-minute timeout feature. It works as follows. When a door switch closes, it pulls the junction of the lkQ resistor and Dl low via diode D2. This causes the lO00µF capacitor at pin 9 of IClb to gradually charge (towatds 0V) via the 330kQ resistor in parallel with Dl. When pin 9 drops below pin 10, after about seven minutes, IClb's output goes high and pulls pin 2 of ICla high via LED 1 and diode D4. This causes ICla's output to go low and switch off Ql. G. Host, Douhleview, WA. ($25) S1 A I I I 240VAC + : I 33n I N + 4700 4700 + + Adjustable 20V power supply This circuit can deliver 3 amps or more and has a maximum DC voltage of a little over 20 volts. It is designed around the readily available LM317T adjustable 3-terminal regulator and has a PNP power transistor to boost the current output. The transformer has an 18V secondary rated at 6 amps and this feedp to bridge rectifier and two 4700µF capacitors to give around 25 volts DC. This voltage is fed to the emitter of the MJ2955 transistor and to the input of the LM317 via a 33Q resistor. In effect, the transistor operates as a variS2 able current source in 0-0+ parallel with and controlled by the 3-terminal regulator. With a 33 33Q resistor between base and emitter, the transistor is forced to provide most of the output current. This transistor should be mounted on a fairly large heatsink because at low output voltage settings and high currents, it will dissipate a lot of power. Steve Jenkins, Surrey Downs, SA. ($20) +9-12V + 100 16VW! 10k 4 22k VR1 2M .001 4 IC1 555 C1 22 + 16VWI LL VR2 2M .,. Traffic lights for model train layouts One feature which can add considerable realism to a model train layout is to add traffic lights to an intersection. This circuit uses three 555 timers which are interlocked. Each light _001 IC2 555 VR3 2M 5 C2 + 22 16VW.I: LL .,. has its own time delay, as set by trimpots VRl, VR2 & VR3. VR2 should be set so that the orange LED is on for only a short time. When IC3 turns LED 3 off, it also triggers ICl via pin 2 which turns on red LED 1, and so the sequence recommences. Note that LEDs for the Breakout board for games port Following the article entitled "Experiments For Your Games Card" in the January 1992 issue, Bob Barnes of RCS adio has produced a breakout board for the games port. It has 15 small solder pads, corresponding to the leads from a DB15 socket ON an IBM-compatible games card. Each input pad then connects to a larger Fectangular pad for easy connection of external components. The board is coded 07101921 and is available at $5.80 plus $2 postage and packing. Contact RCS Radio Pty Ltd, 651 Fo est Road, Bexley, NSW 2207. Phone (02) 587 3491. .001 IC3 555 LE03 GREEN' C3, + 22, 16VW_ILL .,. crossroads of an intersection are placed in parallel with those for the three ICs; ie, a green LED in parallel with red LED 1, a red LED in parallel with green LED 3 and an orange LED in parallel with LED 2. Mats Nilsson, Whalan, NSW. ($25) Card Br•a~out Ill l_!II Box 071019211 A22s9 This board makes it easy to interface to the games port. MARCH 1992 13 CIRCUIT NOTEBOOK - Using your games port for data input This circuit continues the theme of the article entitled "Experiments For Your Games Card" in the January 1992 issue. Here the joystick input is used. This port cannot be used for highly accurate data acquisition since it is only four bits wide, but it is ideal for testing the state of an external device. The disadvantage is that data cannot be transmitted, only received. The circuit consists of four optocouplers to isolate the computer from any external voltages, plus four transistors to turn the couplers on or off. Note that this circuit inverts the in- CTD puts, so this must be compensated for in the software. Of course, if the external .device being monitored produces signals inside the 0-5V range, it could be connected directly to the games port. The optocoupler LEDs and switching transistors, Q 1-Q4, are powered from an external supply to provide full isolation. Power for the optocoupler phototransistors circuit is derived from pin 1 of the games port. The software was written in Turbo Pascal and consists of just three procedures. The state of the "joystick" switches is read using interrupt 15h and stored in the variable settings. This is then inverted and the low nibble removed to make it easier to { Interface to the real world via the IBM games port. Written by Steven J. Merrifield, December 1991, uses "inverting" optocouplers to isolate the computer. } work with. The value in settings is then compared to a set of constants to determine which switches are closed. These sets can be easily worked out by deriving a truth table for the four switches. Finally, the states of the switches are displayed, showing which are high and which are low. To make this program more useful, further comparisons would be needed as well as follow-up procedures to act on the results. For example, a reed switch could be connected to a door and whenever the door was opened, the computer could sound an alarm, or increment a counter. S. J. Merrifield, Newlyn, Vic. ($25) +5·20V u - - - - - lSOLATED FROM COMPUTER ------PIN1 Program GamesPortlnterface; uses dos; Var Settings : byte; Pin2, Pin?, Pin10, Pin14 : boolean; Procedure ReadPort; { AL bits 7 to 4 indicate switch settings } Var Regs : registers; Begin Regs.AH :=$84; Regs.DX := 0 lntr($15,Regs); Settings :=Regs.AL; End; Procedure Workout; Begin Settings :=not(Settings); { Compensate for inversion by Q1 -Q4} Settings :=Settings shr 4; {Remove low nibble, leaving bits 7 to 4} if not Odd(Settings) then Pin2 := true else Pin2 := false; if Settings in (0, 1,4,5,8,9, 12, 13] then Pin? := true else Pin? := false; if Settings in (0, 1,2,3,8,9, 10, 11] then Pin14 := true else Pin14 := false; if Settings< 8 then Pin10 := true else Pin10 := false; End; Procedure ShowStatus; var A,B ,C,D : string ; Begin if Pin2 then A:= 'HIGH' else A:= 'LOW'; if Pin? then B := 'HIGH' else B := 'LOW'; if Pin14 then C := 'HIGH' else C := 'LOW'; if Pin10 then D := 'HIGH' else D := 'LOW'; writeln('lnput A is '.A); writeln('lnput Bis ',B); writeln('lnput C is ',C); writeln('lnput Dis ',D); End; Begin ReadPort; WorkOut; ShowStatus; End. 14 SILICON CHIP - - - - - - PIN 10 IBM GAMES PORT News Update New pager looks like a wristwatch Late last year, the Swiss company Swatch introduced a world first: a wristwatch with an analog display and an integrated pager. It has initially gone on sale in Switzerland and there are plans to launch it in other countries over the next two years. Two innovations which helped keep its size down have been patented. One, the integrated antenna, is recognisable as five horizontal metallic strips across the dial. The other, a battery compartment in the form of a simple extension to the strap, slots into the case and facilitates fast, easy battery changes. IREE and IE Aust to have trial marriage Two of Australia's best known engineering associations have announced an historic 3-year trial of closer association which, if successful, could lead to full amalgamation. The 2600-strong Institution of Radio and Electronics Engineers Australia (IREE) has agreed to create and manage a technical society of the Institution of Engineers, Australia (IEAust), to be known as the IREE The quartz wristwatch movement was specially developed for the Pager and is unaffected by high and low temperatures within the normal range. The hands can be moved in either direction for time setting. The Pager has been tested and ap- Society. In return, IEAust, which has 60,000 members, will accept responsibility for accrediting electronics and related engineering courses at degree level and will work with the IREE in representation to governments and the promotion of electronics engineering to young people as a career. The IREE Society will provide a full range of professional development programs for its members in the fields of electronics, radio communications, telecommunications and digital systems. Such activities will include tech- Winner of the Miracle Piano Teaching System Following the draw of the "Win a Miracle Piano Teaching System" during January, the winner was Mr John Norris of Cairns, in Queensland. Our photo shows John (right) receiving his prize from William Roberts, Manager of the Dick Smith Electronics store in Cairns. Our thanks to the staff of Dick Smith Electronics for their donation of the Miracle Piano and their help in the arrangements. proved by the PTT (the Swiss telecom authorities) and is fully functional from the moment of purchase. It can be contacted anywhere in Switzerland by four pre-specified numbers of the owner's choice, each of which is allocated its own acoustic signal. When the owner does not wish to be disturbed, it can either be switched off or put into SILENCE mode, in which case incoming calls are stored for later retrieval. The unit will retail in Switzerland for 250 francs (about $A250). But don't rush off to Switzerland to buy a Swatch Pager just yet though. They only function in that country. You will just have to wait for what surely must be the next status symbol. nical meetings, conferences, seminars, publications and continuing education, as well as the collection and provision of information concerning commerce, industry, government, education and research interests. IEAust President Martin Thomas has welcomed the new arrangements as being "timely" and in the interests of the nation's electronics and communications industries. "These industries have a much greater capacity for growth and increased employment than other sections of manufacturing industry, including prospects for exporting products and services," Mr Thomas said. "But this potential will be realised only if individual enterprises have an engineering design and development capability equal to the best in the world." Members of IEAust and the IREE will'be able to use each organisation's facilities under the agreement and attend all activities and functions at "member rates". For further information contact Mr Martin Thomas, President, Institution of Engineers, Australia, phone (02) 922 2666 ; or Dr Dennis Cooper, President, Institution of Radio and Electronics Engineers, phone (02) 868 0222. SC MARCH 1992 15 TV transmitter for VHFVCRs This simple add-on board will allow you to use the TV Transmitter described in December 1991 with VCRs that have a VHF output. The project can now be used to transmit signals from any VCR to a remote TV set without the need for cables and splitters. By JOHN CLARKE In the December 1991 issue, we published a TV Transmitter for use with VCRs that had a modulated UHF output at about channel 3 7. This channel frequency was dictated by the size of the two 3-element Yagi antennas that are so crucial to the performance of the unit. Unfortunately, VCRs with modulated UHF outputs are relatively far and few between - about 3% of all VCRs, we gather. Instead, most VCRs have a modulated output in the VHF band, generally switchable between channel O and channel 1. We can't use these channels with our TV transmitter however, since the resulting Yagi antennas would be far too big for indoor use. Basic concept The original TV Transmitter operated by amplifying the modulated UHF output signal from the VCR and then coupling it to the transmitting antenna. This antenna then radiated the signal to a second identical antenna connected to the remote TV set. Fortunately, it's quite easy to modify the circuit to work with VCRs that have a VHF output. All we have to do is add a UHF modulator (tuned to channel 37) in front of the original transmitter. The video and audio outputs from the VCR are now fed to the modulator and the resulting RF output (at channel 3 7) fed to the RF input of the transmitter which then operates exactly as before. Fig.1 shows the general arrangement of the modified transmitter. Note that it is the video output that's now used to drive the TV transmitter;. not the modulated VHF output. The VHF output connects instead to the main TV receiver in the conventional manner. Because the video and audio outputs of the VCR are connected to the TV Transmitter, these outputs have been duplicated on the TV Transmitter so that they can also be fed to a hifi amplifier or to a video monitor. We have also made provision for VCRs with stereo sound, although readers should note that the left and right audio channels are mixed together to form a mono signal before being fed to the transmitter. If a mono VCR is used, the audio output from the VCR can connect to either the left or right audio input on the TV Transmitter. Circuit details The new TV Transmitter can be used with all VCRs and has a useful range of about 15 metres, provided the correct antennas are used. Note that the TO TV output (designated on the front panel) is no longer used. 16 SILICON CHIP Refer now to Fig.2 for the complete circuit details. The power amplifier section is virtually identical to the December 1991 transmitter, except that it no longer includes a splitter to drive the main TV set. This splitter is no longer necessary, since the VHF output from the VCR now drives the main TV set - see Fig.1. As before, the power amplifier uses two OM350 hybrid wideband amplifier ICs (ICl & IC2). These each have a nominal gain of 18dB over the frequency range from 40-860MHz. The ANTENNA TV ANTENNA ANTENNA Warning! VIDEO OUT VCR ANTENNA IN L AUDIO OUT R VHF OUT * * VIDEO IN L UOIO IN AUDIO R OUT R L VIDEO OUT 75n TVNIOEO CABLE TRANSMIT OFFC.ON RF OUT TO HI-FI AMPLIFIER UHF CHANNEL 37 SIGNAL i! TV RECEIVER Although this is a low-power device with limited range, it may interfere with neighbouring TV receivers if used incorrectly. The onus is on the user of this equipment to ensure that such interference does not occur. In particular, do not point the transmitting antenna toward neighbouring TV antennas. lation level. A separate RCA socket is also connected in parallel with the video input socket to provide the video output signal. This video signal can be fed to your TV set (if it has a separate video input) or to a video monitor. The RF signal from the modulator is at UHF channel 3 7 and this signal is coupled to pin 1 of amplifier IC1 via a 220pF capacitor. Power for the modulator is derived directly from the 12V supply rail and is bypassed using a .01µF ceramic capacitor. Note that the 47Q resistor used to supply zener diode ZD1 in the original circuit has been reduced to 33Q. This change ensures that ZD1 remains in regulation despite the increased current now drawn by the circuit due to the UHF modulator. REMOTE TV RECEIVER TO VIDEO MONITOR *FOR MONO VCRS • CONNECT AUDIO OUT OF VCR TO EITHER L OR R AUDIO INPUT ON TV TRANSMITTER Fig.1: this block diagram shows the general arrangement of the TV Transmitter. It is now driven by the audio & video outputs from the VCR (not by the RF output). The RF output drives the main TV set is the usual manner. via 2.ZkQ resistors to give a mono signal. This is then AC-coupled to the audio input of the modulator via a ZZµF bipolar electrolytic capacitor. The left & right audio input sockets are also paralleled to provide the left & right audio outputs. These outputs may be connected to a hifi amplifier or to a stereo monitor, as mentioned previously. The video input signal is fed to the modulator via a 22µF bipolar capacitor and level control VR1. This level control is set to give the correct modu- two amplifiers operate in cascade, with IC1 driven by the RF signal from the UHF modulator. Apart from that, only a few other parts are required to complete the unit. The left & right channel audio inputs are fed in via RCA sockets and mixed Fig.2 (below): the signals from the VCR are first fed to a UHF modulator. THs generates an output at channel 37 & drives an output stage consisting of two OM350 hybrid amplifier I Cs. Construction There are two PC boards associated ----• TRANSMIT ON/OFF 33n S1 0.5W 12VOCl+ " ' ! " ' - - ¥ N ~ + - - - - - . - - . . . . . - - - ' INPUT-~ .00111 NOT USED &DOSTER SUPPLY LEFT AUDIO INPUT (FROM VCR) RIGHT .,. CHANNEL 37 UHF OUTPUT (TO RF INPUT) L1 II II .001•1. II 11 II L2 " 75n RF INPUT (FROM UHF MODULATOR) ~------~OpF 1 22opF ~ >"-+---tl--:-0 . LEFT AUDIO OUTPUT RIGHT oJf~i~~o TRANSMITTER ANTENNA UHF MODULATOR HL-RMBT-E36H L1,L2: PHILIPS 4312 020 36700 sovw VIDEO INPUT (FROM VCR) VIDEO OUTPUT BP y ~BOOSTER OUTPUT (NOTUSEO) VR1 ,_ _ _--13 VIDEO 2.2k IN TV MODULATOR/TRANSMITTER CASE MARCH 1992 17 S1 • IC2 OM350 ·••!>1 C• + - • I TOP -~ tl <at> OM350 •• ! i) 1 • --- -- ~ l2 - VIEW • -;s ·11111V !Cl .001"0" blNPUl ~ 220pF L1 • BASE VIEW Fig.3: install the parts on the two sides of the amplifier PC board as shown here & don't forget to install the "pin-throughs" where indicated. Be careful when installing the two !Cs, as they can be damaged if overheated. RF chokes Lt & L2 are supplied ready wound. on the base side. There are also several "pin-through" points , where a short piece of tinned copper wire is passed through the hole and soldered on both sides of the board. Start the board assembly by installing the 33Q resistor, ZDl and the two ICs. ZDl's anode lead must be soldered to both sides of the board, while its cathode lead should be looped to provide thermal stress relief. The two with this project. The first board, code SC02212911, carries the two amplifier ICs and is identical to the board described in December 1991. The second board, code SC02204921, carries the UHF modulator and its associated resistors and capacitors. Fig.3 shows the assembly details for the amplifier board. Note that some parts are mounted on the top side of the board while others are mounted AMPLIFIER PCB IC1 IN IC2 OUT VIDEO~ 22uF . L---mu-. AUOI L ~-'---~ R 22uF 0 O S v Re-f:TID-,-------------------. • IN • • HL-RMBH36H OUT RF OUT 18 ICs should be pushed down as far as possible and their pins soldered on the underside of the board only. Note that the two ICs are hybrid devices and can be damaged if overheated. In fact, it's best to tin the copper pads on the board before installing these ICs to assist in fast soldering times . The remaining parts are mounted on the base side of the PC board. Note that some component leads do not pass through holes in the PC board but solder directly to the pads. Keep all component leads as short as possible. Do not mount the two sockets at this stage; that step comes later. Work can now begin on the SC02204921 PC board. Begin by installing PC stakes at the seven external wiring points, then install all the minor components. Finally, install the modulator with the sockets facing the edge of the PC board. With the PC boards complete, the three Dynamark labels can be carefully affixed to the plastic case and holes drilled to accept the switch and the various sockets. The cutout for the switch can be made by first drilling a hole at the position indicated and then carefully filing it to the required shape. The mounting positions for the two 75Q PAL sockets are marked using the amplifier PC board as a template. To do this , place the board against the side of the case with the base side facing outwards. Check that the socket holes line up with the labelling on the front panel, then carefully mark the holes with a pencil and lightly centre punch them. The socket holes can now be drilled and reamed to size, as can the holes for the modulator sockets and test switch. This done, mark out and drill the two mounting SILICON CHIP • Fig.4: the UHF modulator is mounted on a separate small PC board, together with a few minor components. Install PC stakes at the external wiring points & use shielded cable for the video & audio input leads. PARTS LIST Only four components are mounted on the top side of the amplifier PC board the two OM350 ICs & the 47Q resistor. Note that "pin-throughs" must also be installed at three locations. 1 double-sided PC board, code SC02212911, 30 x 97mm 1 PC board coded SC02204921, 39x101mm 1 plastic case, 130 x 67 x 43mm 1 UHF modulator, HL-RMBTE36H, preset to channel 37 1 Dynamark front panel label, 125 x 64mm 1 Dynamark label, 60 x 38mm 1 Dynamark label, 121 x 35mm 6 RCA panel sockets 1 2.1 mm DC panel socket 1 2.1 mm DC line plug 2 panel-mount 75Q PAL sockets 1 DPDT slider switch 2 Philips 4312 020 36700 chokes (L 1,L2) 1 2.2kQ miniature horizontal trimpot 2 Yagi antennas (see December 1991) 2 3mm x 6mm screws 1 3mm nuts Wire & cable The remaining parts in the power amplifier stage are installed on the base side of the PC board. Keep all component leads as short as possible. 1 75Q RF cable terminated with male & female PAL plugs 1 mono or stereo audio cable, RCA to RCA 1 video cable to suit (see test) 1 100mm-length twin shielded audio cable 1 100mm-length single shielded audio cable 1 100mm-length red hookup wire 1 100mm-length black hookup wire Semiconductors 2 Philips OM350 wideband amplifier ICs (IC1 ,IC2) 1 12V 1W zener diode (ZD1) Capacitors 2 22µF S0VW bipolar electrolytics 1 .01 µF ceramic 2 .001 µF ceramic capacitors 3 220pF capacitors Resistors 2 2.2kQ 0.25W 133n o·.sw Th e UHF modulator is supplied pre-tuned to channel 37. It also contains the necessary circuitry to generate a test pattern (a white bar down a black screen). Note: constructional details for the Yagi antennas used with this project were given in the December 1991 issue. Do not use different antennas - the correct antennas are vital to ensure adequate range. MARCH 1992 19 Fig.5: this is the full-size artwork for the modulator PC board. Full-size patterns for the amplifier PC board & for the front panel were published in the December 1991 issue. Two small Yagi antennas, one at each end of the transmission path, are required to ensure adequate range. These antennas must be pointed directly at each other. Full constructional details are in the December 1991 issue. holes for the modulator board. Note that this board is mounted directly on the base of the case without standoffs, to allow sufficient clearance between the modulator and the case lid. At this stage, the various hardware items can be mounted in the case. Secure the six RCA sockets to the end of the case first, followed by the two 75Q PAL input sockets, the power input socket, the on/off switch and, OUT + + + OUT finally, the modulator board. Before mounting the amplifier board, it is first necessary to install the four power supply leads. These leads are then run to the DC input socket and on/off switch. Make sure that the socket polarity is correct, with the centre pin positive as shown on the front panel label. At this stage, it's also a good idea to check that the centre contact of the DC plug is also positive with respect to the outer contact. If it isn't, swap one set of leads (either to the plug or to the socket) around now. The amplifier board can now be fitted to the PAL sockets and the centre pins and earth lugs soldered (see Fig.3). Note that the latter are soldered to the groundplane on the base side of the PC board. Complete the assembly by wiring up the RCA sockets and by running supply leads to the modulator PC board. Testing Before testing the unit, you must first tune your remote TV set to the TEST + VIDEO IN + + + VIDEO LEFT RIGHT IN + RF OUT TO INPUT Fig.6: here are actual size artworks for the RCA input socket panel (left) & the modulator panel. 20 SILICON CHIP + a II QUALITY NO BRAND DISKETTES 5.25" 5.25" 3.5" 3.5" DSDD DSHD DSDD DSHD $4.70 $8.95 $8.50 $16.95 *************** JAPANESE BRAND ._;: •, t i / / f,, _ FLOPPY DRIVES ~~"- SUPER . ',:;,..3.5" 1.44M $99.00 ?z..,~PECIAL ~ 5.25" 1.2M $125.00 -~~~ ----------EPROMS 2716 ............. $9.95 2732A ........... $7.50 27C32 ......... $11.50 2764 ............. $6.50 27C64 .......... . $7.00 27128 .... .. .... . $7.50 27C128 ......... $8.00 27256 .... .. .. ... $8.50 27C256 .... ..... $9.00 27512 .. .. .... . $12.50 27C512 ...... . $13.50 27C 1001 ..... $23.50 RAMS 6116 ...... .. .... . $4.50 6264 ............ . $9.50 62256 ...... .. . $17.50 628128 ....... $60.00 SERIAL PORT CHIPS 8250 ............. $7.50 82450 ......... $17.50 16C450 ....... $18.00 16C550 ....... $29.50 ** ** ** ** *** * *** ~ _{.~~~~!N~~~r~~ ~ nr I\""~··/~ The modulator PC board is secured directly to the base of the case while the amplifier board is installed by fitting it over the three PAL sockets & then soldering the centre pins. Take care with supply polarity. signal from the UHF modulator. This is done as follows: (1) connect a lead from the RF OUT of the TV Transmitter to the antenna socket of the remote TV set. (2) Set the modulator TEST switch to the up position and apply power to the TV Transmitter. (3) Tune the TV set to channel 37 to receive the test pattern (a white bar down a black screen). To test on transmission, you will need a couple of Yagi antennas as described in the December 1991 is- The RCA input sockets are paralleled to preserve the original video & audio output signals from the VCR. sue. Connect the TV Modulator/Transmitter as shown in Fig. l. The left and right audio channels will require leads fitted with RCA plugs at both ends, while the video connection will probably need a BNC to RCA lead. You also have to connect a 75Q coax cable between the modulator RF OUT terminal and the transmitter INPUT terminal (see Fig.1). This lead must be fitted with a PAL plug at one end and a PAL socket at the other. Finally, connect the antennas and switch the modulator TEST switch down for video modulation. Apply power and play a tape through the VCR. Provided the transmit switch is set to ON, you should now receive the VCR program on the remote TV set. Note that the two antennas should be aimed directly at each other for maximum effect. If it doesn't work, check your connections and the supply voltage to the OM350 ICs and the modulator by measuring the voltage across ZDl. You should get a reading of 12V. If not, check the orientation of ZDl. SC DYNAMIC RAMS 4164-10 ........... $3.25 41464-08 ....... $2.75 41256-08 ......... $2. 75 414256-08 ....... $7.95 411000-08 ...... : $7.95 256KSIM,SIP. $23.50 IM,SIM,SIP .... $79.00 4M SIM.SIP. $335.00 REGULATORS 7805T .............. $0.50 7812T .......... $0.50 7815T ... ........... $0.50 7905T .... .......... $0.60 7912T .............. $0.60 7915T .............. $0.60 317T .. .............. $1.50 337T ................ $2.10 723 .................. $0.80 DIODES IN4148 ............ $0.04 IN914 .............. $0.05 IN4004 ............ $0.08 IN4007 .. $0.10 IN5404 .. ... .. .. ... $0.20 IN5408 .. ... ....... $0.25 BRIDGES WD4 ...... .......... $0.50 BR64 .............. $1.50 BR104 .. $2.50 BR254 .... $3.50 BR354 ..... $3.95 LEDS 5mm RED ........ $0.15 5mm Green ..... $0.25 5mm Yellow .... $0.25 TRANSISTORS BC547/8/9 ........ $0.15 BC557/8/9 ........ $0.15 BD139 ........... ... $0.45 B0140 ............. . $0.45 TIP31C ............. $0.80 TIP32C ............. $0.80 MJ15003 ........ $6.50 MJ15004 ......... $6.50 · MJ2955 ... ... ..... $2.50 2N3055 .......... .. $1.50 LINEAR & SPECIAL FUNCTION 1488 ..... ... ... ..... $0.50 1489 ................ $0.50 8250 ................ $7.50 82C450 .......... $17.50 16C450 .......... $18.00 16C550 .......... $29.50 XR2206 ............ $8.50 ICL7106 ......... $14.00 324 .................. $0.75 339 ... ... . $0.50 358 ....... $0.90 555 . ..... $0.45 741 .......... ....... . $0.55 FREE PRICE LIST UPON REQUEST . .·' ♦' I .// · s%OFF . . ;· ALL ORDERS ''f. " -_IF YOU MENTION~ "1;,· 111,~.~ IECS ELECTRONICS & COMPUTER SUPPLIERS 289 LATROBE ST MELBOURNE, VICTORIA 3000 PHONE: (03) 602 3499 FAX (03) 670 6006 MAIL ORDER HOTLINE: (008) 33 5901 ALL MAJOR CREDIT CARDS WELCOME POSTAGE RATES $1.00-$9.99 ......... $3.00 $10.00-$24.99 ..... $3.50 $25.00-$49.99 ..... $4.50 $50.00-$99.99 .. .. $5.50 $100.00-$199.00 $6.00 $200.00+ ............. FREE MARCH 1992 21 Studio Twin Fifty Stereo Amplifier Looking for a new compact stereo amplifier to replace your ageing clunker? Or perhaps you are looking to upgrade the amplifier on your midi system. Either way, this new stereo amplifier will deliver the goods and give you sound quality equivalent to amplifiers costing hundreds of dollars more. By LEO SIMPSON & BOB FLYNN As the name suggests, this new amplifier gives a high standard of performance, especially so since it is quite a compact design. It uses the new "Plastic Power" stereo power amplifier module described in the February 1992 issue, together with a stereo preamplifier which is very similar in features to the Studio 200 Stereo Control Unit published in the June and July 1988 issues of SILICON CHIP. Our approach to the design and 22 SILICON CHIP presentation of this new amplifier has been to take the middle road. It is not a spartan, no-frills, no-expense spared design but nor is it laden with every feature you could possibly want and most likely never use. Hence, the new Studio Twin Fifty has all the features that most users will want but still includes some design features that dyed-in-the-wool audiophiles would regard as mandatory. For example, while everyone would like to see a headphone socket on an amplifier (some no-compromise designs lack this feature), many hifi enthusiasts would not be keen on the idea of having the speakers switched when the headphones are in use. Relays or headphone socket switching are regarded as undesirable because it can introduce unpredictable contact resistances into the amplifier/loudspeaker circuit. Our approach has been to provide a separate ultra-low distortion amplifier just to drive the headphones. This has the benefit of eliminating relays and any need to switch the speaker signals. But we're getting a little ahead of ourselves in telling the story of this new amplifier which has been under development for the previous six months. Features The new Studio Twin Fifty Amplifier is housed in a midi-sized case. It could be mounted under a midi-sized rack hifi system or together with other free-standing units such as a compact disc player and cassette deck. Overall dimensions of the amplifier are 360mm wide x 95mm high x 360mm deep, including knobs, rubber feet and rear projections. As can be seen from the photos, the Studio Twin Fifty Amplifier has the usual line-up of controls found on most mid to high-priced amplifiers : bass, treble, balance, input selector, tape monitor switch, tone defeat switch and volume control. It also has a stereo/mono switch, headphone socket and power switch. The circuitry of the preamplifier section has been greatly simplified compared to amplifiers produced a few years ago and uses just four low cost dual op amps (this includes those used in the stereo headphone amplifier). The overall performance of the preamplifier section of the new amplifier is superior to some really highcost stereo control units which can cost thousands of dollars. The Studio Twin Fifty is particularly quiet on both the high inputs and phono inputs. On the phono inputs, with a typical magnetic cartridge fitted, the signal-to-noise ratio is -83dB with respect to an input signal of lOmV at lkHz, with a noise bandwidth from 20Hz to 20kHz (ie, an unweighted measurement). This improves to -88dB with A-weighting. On the high-level inputs, the signal to noise ratio is 99dB with the same noise bandwidth. This is as good as many CD players. A-weighting, as ' .. - .. · . .. , -· ., - - .., . Main Features * 50 watts per channel with both channel driven into 8-ohm loads. * Very low noise on phono and line level inputs - comparable with many CO players. * Up to seven stereo program sources can be connected. * Tape monitor loop. * Separate ultra-low distortion stereo headphone amplifier. * Headphone socket disables signals to stereo power amplifier. * Stereo/mono switch. * Tone defeat switch. * Easy to build construction using three separate printed circuit board assemblies. * Estimated cost: $350. used by most hifi manufacturers, improves the figures by about 2 or 3dB. Inputs & outputs The Studio Twin Fifty caters for six pairs of inputs and it also has a tape monitor loop for the connection of inputs and outputs from a cassette recorder. This means that you can connect up to seven program sources. The Selector switch is labelled as follows: Phono, CD, Tuner, VCR, Aux 1 and Aux 2. The rear panel has an array of 16 RCA sockets to provide for all these inputs and outputs. There is also a set of four spring-loaded terminals for the loudspeaker connections. Push-on push-off switches are used for the tape monitor, tone defeat and stereo/mono switches. These have accompanying symbols on the front panel which show their settings. As already noted, the headphone socket has an inbuilt switch to disconnect the signals to the power amplifiers when headphones are in use. This stops you from unwittingly blasting your speakers when you are wearing headphones. The headphone amplifier has the potential to deliver more than adequate drive so that even insensitive headphones can be driven to painful levels (not that you should do this if you value your ears). With 32-ohm phones, the drive can exceed lO0mW while for 8-ohm phones the drive capability is more than 40m W. The Studio Twin 50 Amplifier uses this 50-watt/channel stereo power module, as described in the previous issue. It uses four big plastic Darlington transistors in each channel to give a rugged, compact design that incorporates full protection. MARCH 1992 23 RIAA PREAMPLIFIER 'PH0N0 u-----t MONITOR S2 SOURCE-TAPE CDO>-------...'t) TUNERO------on VCR0>-------0 n AUX1O,___ _ _ _ _,,,- J SOURCE S1 VOLUME VR2 TONE CONTROLS SPEAKER MONO AUX20>--------'- 1AJlu-----------J TW:Eu-------------J ~tMgfE t -;EREO OTHER CHANNEL Fig.1: the circuit features of the new stereo amplifier are illustrated in this block diagram. To keep things simple, only one channel is shown. The second channel uses exactly the same circuitry. Note the use of a separate headphone amplifier to drive the headphones. Interestingly, listening via a set of closed headphones is the only way that most hifi enthusiasts will ever be able to experience the full dynamic range of compact discs. Most listening rooms have quite a lot of background noise and this tends to mask the really quiet signals on compact discs. Unfortunately though, the headphone outputs on some commercial amplifiers are not as quiet as the main amplifier outputs (some have quite high hum levels via the headphone outputs). So not only are the amplifier outputs not as quiet as they should be, as we noted above, but the headphone outputs are even worse. By contrast, with the Studio Twin Fifty Amplifier, you really do get phenomenally low background noise, on both the headphone and the main amplifier outputs. of the auxiliary inputs. Inside the chassis, the circuitry is accommodated on three printed circuit board assemblies and the power transformer is a toroidal type, giving low hum radiation. Omissions Block diagram To keep the unit reasonably simple and inexpensive, we have omitted a couple of features that are found on some amplifiers and control units. First, as already mentioned, there is no speaker switching. Second, we have not provided for moving coil cartridges. Indeed, some readers may regard the phono inputs as unnecessary since vinyl records are now virtually unobtainable except from some specialist stores. Third, we have not provided for dubbing and monitoring between two cassette decks. Tape dubbing in one direction is possible though, if the outputs of one deck are fed into a pair Now let's have look at the circuit features which are illustrated in the block diagram of Fig.1. This shows one channel only, to keep matters simple. Remember that all circuit functions are duplicated in the second channel. The same goes for the main circuit diagram of Fig.2. S1 is the 6-position Selector switch. It selects the input signal and its wiper feeds the tape output as well as the following Tape Monitor switch SZ. This selects the signal from S1 or from the cassette deck connected to the Tape In inputs. The signal then goes to S3, the stereo/mono switch, which shorts the two channel signals together The rear panel carries eight pairs of RCA sockets. These accept up to seven program sources as well as providing stereo output signals for a cassette recorder. The loudspeaker terminals are located to the left of the fuseholder. 24 SILICON CHIP to obtain the mono function. When the mono function is switched in by S3, the left and right channels of the selected program source will load each other (as far as the difference signals are concerned). To avoid any degradation in signal quality due to this effect, there are 1kn resistors between S1 and S2 and in the "Tape In" signal path to S2. Following S3, the signal is fed to the volume control and then to a noninverting op amp stage with a gain of 4.1. From there, the signal goes to the unity gain feedback tone control stage, which can be taken out of the circuit by the Tone Defeat switch, S4. After S4, the signal goes to the balance control and then to S5 which is integral with the headphone socket. It normally feeds the tone control stage's signal to the following stereo power amplifier. When a headphone jack plug is inserted into the socket, S5 switches the signal to the headphone amplifier instead. Circuit description The complete circuit diagram (for one channel) is shown in Fig.2. The four op amps are depicted as ICla, ICZa, IC3a & IC4a. The pin numbers for op amps IClb, ICZb, IC3b & IC4b in the second channel are shown in brackets on the circuit. ICla is the phono preamplifier and equalisation stage. It takes the low level signal from a moving magnet cartridge (typically a signal of a few millivolts) and applies a gain of 56, at the median frequency of lkHz. Higher frequencies get less gain while lower frequencies get considerably more, as shown in the accompanying equalisation curve of Fig.3. To be specific, a 100Hz signal has a boost of 13.1 ldB while a 10kHz signal has a cut of 13.75dB. The phono signal is fed directly from the input socket via a small inductor, a 1son resistor and a 47µF bipolar capacitor to the non-inverting input, pin 3, of ICla. The inductor, series resistor and shunt 150pF capacitor form a filter circuit to remove RF interference signals which might be picked up by the phono leads. The 150pF capacitor is also important because it provides capacitive loading of the magnetic cartridge. Most moving magnet (MM) cartridges operate best with about 200-400pF of shunt capacitance. The 150pF capacitance Specifications Output Power 47 watts into 8-ohm loads, both channels driven; 70 watts per channel into 4-ohm loads, both channels driven. 55 watts per channel into 8-ohm loads or 80 watts per channel into 4-ohm loads, with one channel driven. Frequency Response Phono inputs: RIAA/IEC ±0.5dB from 20Hz to 20kHz High level inputs: within ±1dB from 10Hz to 20kHz; -2.4dB at 50kHz (measured at one watt into 8 ohms). Total Harmonic Distortion Typically less than .05%, 20Hz to 20kHz, at rated output level for any input or output. Signal-to-Noise Ratio Phono (moving magnet): 83dB unweighted (20Hz to 20kHz) with respect to 10mV input signal at 1kHz and rated output with 1kn resistive input termination; 88dB A-weighted with respect to 10mV input signal at 1kHz and rated output, with 1kn resistive input termination. High level inputs (CD, Tuner, etc): 99dB unweighted (20Hz to 20kHz) or better, with respect to rated output (with volume at maximum) with Tone Defeat switch in or out; 101 dB A-weighted, with respect to rated output (with volume at maximum) with Tone Defeat switch in or out. Separation Between Channels -51 dB at 10kHz; -67dB at 1kHz; and -82dB at 100Hz with respect to rated output and with undriven channel input loaded with a 1kn resistor. Input Sensitivity Phono inputs at 1kHz: High level inputs: Input impedance (phono): Input impedance (CD, etc): Overload capacity (phono): 4.3mV 235mV 50kn shunted by 150pF 50kn 1S0mV at 1kHz Headphone Output 40 milliwatts into an headphones; 100 milliwatts into 32n headphones. Tone Controls Bass: ±1 0dB at 100Hz Treble: ±12dB at 10kHz Phase With tone controls defeated, non-inverting (ie, zero phase shift) from phono to main output; non-inverting from high level inputs to main outputs. Noninverting from all inputs to Tape Out. With tone controls in circuit, inverting from phono and high level inputs to main outputs (ie, 180° phase shift). Protection SA fuses plus RDE245A Polyswitches Damping Factor >50 (for an loads) in the control unit, plus the usual 200pF or so of cable capacitance for the pickup leads will therefore provide an optimum shunt capacitance. Stability Unconditional For its part, the 47µF bipolar capacitor is far larger than it needs to be, as far as bass signal coupling is concerned. But having a large capacitor MARCH 1992 25 N ;; ::r:: n :z: 0 0 c=::: (f) Cl) CD PHONO r L2 100k 10k - 15V +15V ' * PHILIPS 4312-020-367<at> 100k 47 *' ,,.,,, \i,i)(I I..I ' o- ·1 ' 100:, BP'+ 47k ' I +15V I I BCOB • E • • C VIEWED FROM BELOW ECB BF-.80139 PLASTIC1 SIDE OTHER CHANNEL I I I I BCE TIP- 01 POWER AMPLIFIER ~ ~ JHEADPHONES I S5a HEAOPHONEO / AMPLIFIER / AUX 2 k ~ t 47 .,: 16VW+ 1k .033 04 50011 SET CURRENT VR1 22k 4 + l i ~ TJ 100ll$ 1.6V ! +15V STUDIO TWIN 50 AMPLIFIER I t 1 C 2xBC556 , 03 BC556 4. 7k;f 2.2V 4.7kJ: 2.2V C ·c 1' 02 STEREO OTHER CHANNEL ~ S3a M°f~ODE r1t MONITOR S2a SOURCE-TAPE 68pF l ? + 0.22! 0.1 } 37.2V ♦ h'f + .... 37.2V ~ u B .01 t 1 0.22l F2 SA SA Fl 0.22:r 0.22,I OUT-IN 33pF O -38 5V 6.BuH Ll 0+3B 5V -15V +15V + OUTPUT Fig.2 (left): this diagram shows the circuitry for one channel of the new Studio Twin Fifty Amplifier. The total semiconductor complement is four low noise dual op amps, 26 transistors, 10 diodes, one bridge rectifier and two 3-terminal regulators. means that the op amp "sees" a very low impedance source at low frequencies (ie, the DC resistance of the magnetic cartridge coils) and this helps keep low frequency noise, generated by the input loading resistors, to a minimum. RIAAIIEC equalisation The RIAA equalisation is provided by the feedback components between pins 6 and 7. These equalisation components provide the standard time constants of 3180µs (50Hz), 318µs (500Hz) and 75µs (2122Hz). The phono preamplifier also adds in the IEC recommendation for a roll-off below Z0Hz (7950µs) . This is provided by the 0.33µF output coupling capacitor in conjunction with the load represented by the 50kQ volume control, together with other low frequency rolloffs in the circuit. One of these roll-offs (at around 4Hz) is caused by the lO0µF capacitor in series with the 390Q resistor. The 390Q resistor sets the maximum AC gain at very low frequencies while the lO0µF capacitor ensures that the DC gain is unity. This means that any +20 i-,;--- 20Hz (795Dµs)~ ...... / 1/1/ ~ +10 ' / I/ - PROPOSED IEC ,.... -..' input offset voltages are not amplified (by more than one) which would inevitably cause trouble with unsymmetrical clipping and premature overload in the preamplifier. By the way, the feedback capacitors (.0047µF and .015µF) in the RIAA network should be 2.5% or 5% tolerance if you are to achieve equalisation within ±0.5dB of the RIAA/IEC standard. As noted above, the signal from the phono preamplifier is coupled via S1 and S2 to the volume control. From there, the signal goes via a 1µF capacitor to non-inverting op amp ICZa. The feedback around this stage is set by the 4.7kQ and 1.5kn resistors to give a gain of 4.1 times. The input (pin 5) of ICZa has a series 1kQ resistor acting as an "RF stopper" to prevent the possibility of strong RF signals (from local radio or TV transmitters) being detected inside the op amp. The 330pF capacitor across the 4. 7kQ resistor also provides high frequency roll-off above 100kHz to ensure low sensitivity to RF signals and to ensure stability of the stage. towards the input side of IC3a (ie, setting the controls for boost) increases the gain for frequencies above 2kHz for the treble control and below 300Hz for the bass control. The reverse happens when the tone controls are rotated in the opposite direction. This has the effect of increasing the negative feedback at treble and/or bass frequencies and the effect is treble or bass "cut". The amount of treble boost and cut provided by IC3a is limited by the 3.9kQ resistors on either side of the 25kQ treble pot. Similarly, the amount of bass boost and cut is limited by the 22kQ resistors on either side of the 100kQ bass control pot. Note how S4a, the Tone Defeat switch, bypasses the circuitry associated with IC3a. Its output feeds the balance control via a 6.8µF capacitor. The 6.8µF capacitor is there to block any DC offset voltage at the output of IC3a from being fed to the input of the stereo power amplifier. It also stops DC from appearing across the balance control pot, which could otherwise become noisy. Tone controls Headphone amplifier Besides providing gain, ICZa acts as a low impedance source to drive tone control stage IC3a. This has the tone controls connected in the negative feedback network. When the bass and treble controls are centred (ie, in their "flat" settings), the gain of the stage is unity over the frequency range up to at least 50kHz. Winding the bass or treble controls Following the Balance control is S5a which is inside the headphone socket. This diverts the signal from the Balance control to the headphone amplifier which consists ofIC4a combined with transistors Q12 and Q13. The two transistors are there to boost the output current capability of the TL072 op amp. They are slightly forward-biased (to keep cross-over disFig.3: the RIAA compensation curve for the new preamplifier incorporates the IEC modification to roll off the response below 20Hz. This has the effect of removing low frequency noise, as well as the rumble on records. 50Hz (318Dµs) . "'" / ' I").. t--... '\I'. / I'\ I/ I) 500Hz (318µs) 2.12DkHz (75µs) "i,.. "-- ,,,I r---....' r-...' ~ N -10 "' ~ '\. -20 I I 2 10 100 1k " I "\ I HERTZ 10k 20k MARCH 1992 27 4 CHANNEL LIGHT CHASER DIMMER A superb 4-channel lighting controller. It's designed to take the rigours of commercial use in theatres, discos, stage shows, etc. Powered by a 240VAC 15amp outlet with a total lamp load of 2400 or 3600 watts. The chaser can be operated automatically or manually. Complete with a fully pre-punched black case, silk screened front panel and all components. Cat K-3165 Now Only s279 DUAL TRACKING +/- 50V POWER SUPPLY Save $50 with this quality switch mode power supply. It has a variable output from 0 to 100 volts DC and a current output of 1. 7 A <at> 0-87V and 1A <at> 100V. With short circuit protection and a LED indicator for ripple exceeding 5mV p-p. Comes with a pre-punched, silkscreened, front panel. Reduced! s199 Cat K-3465 DOWN, DOWN, DOWN! Compare our original kit prices to our current kit prices and save! DESCRIPTION ORIGINAL PRICE (& YEAR) CURRENT PRICE Touch Lamp Dimmer Dimmer Extension (suit K-3001) Stereo Control Unit Transistor Tester Telephone Bell/Monitor Battery Power Supply Fast NiCad Charger Sprinkler Timer Lotto Selector Book Shelf Speaker Enclosures Car Interior Light Delay 120-150 WATT Speaker Protector Car Tune Up Adaptor Brake Lamp Flasher Vehicle Exhaust Monitor RF Attenuater Box 200 Watt HF Linear Amp HF Upgrade 40 mtrs (Suit K-6330) HF Upgrade 20 mtrs (Suit K-6330) HF Upgrade 10 mtrs (Suit K-6330) Morse RTTY Decoder Transistor Beta Tester Beepo Continuity Tester 30 Watt Stereo Amp S/Form 30 Volt Variable power supply Egg Timer 12V-100 WATT DC Converter Telephone Amp Portable AM Stereo Radi o Gel Cell Battery Charger (S/ Form) Hands Free Phone Adaptor Hot Canaries 4 Input Mixer Pre-Amp 6 mtr FM Receiver 420-450 MHZ Converter (suit K-6005) 144-148M HZ Converter $ 34.95 $ 14.95 $ 99.00 $ 46. 95 $ 19.95 $ 49.95 $ 99.95 $ 99.00 $ 59.50 $212.50 $ 24.95 $ 39.95 $ 29.95 $ 29.95 $ 59.50 $ 79.95 $379.00 $ 39.95 $ 39.95 $ 39. 95 $169.00 $ 19.95 $ 29.95 $ 99.00 $ 99.00 $ 19.95 $129.00 $ 39.95 $ 79.95 $ 69.95 $ 89.95 $ 24.95 $ 69.95 $139.00 $ 39.95 $ 49.95 19.95 8.95 49.95 $ 29.95 $ 14.95 $ 32.95 $ 49.95 $ 59.95 $ 39.95 $ 99.00 $ 14.95 $ 19.95 $ 19.95 $ 16.95 $ 39.95 $ 49.95 $199.00 $ 9.95 $ 9.95 $ 9.95 $ 79.95 $ 12.95 $ 16.95 $ 69.95 $ 59.95 $ 12.95 $ 69.95 $ 24.95 $ 59.95 $ 49.95 $ 69.95 $ 14.95 $ 49.95 $ 99.00 $ 19.95 $ 32.95 (1990) (1990) (1990) ( 1990) (1990) (1990) (1988) (1990) (1990) (1989) (1990) (1989) (1990) (1990) (1990) (1988) (1988) (1988) (1988) ( 1988) (1989) (1990) (1990) (1990) (1989) (1991) (1991) (1991) (1991) (1991) (1991) (1991) {1991) (1991) (1991) (1991) CAT NO. $ $ $ K-3001 K-3002 K-3045 K-3052 K-3102 K-3460 K-3476 K-3588 K-3700 K-4000 K-4002 K-4008 K-4400 K-4500 K-4610 K-6323 K-6331 K-6332 K-6333 K-6337 K-6339 K-7200 K-7700 K-5100 K-3475 K-3590 K-3235 K-3104 K-5200 K-3220 K-3100 K-3530 K-3036 K-6005 K-6008 K-6006 STORE LOCATIONS: If the kit you want is out of stock, ask our staff to check on it's storewide availability. In most cases our mail order service can get it for you within days. NSW • Albury 21 8399 • Bankstown Square 70l 4888 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 3871444 • CampbelltowP 27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Kotara 56 2092 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde 878 3855 • Orange 618 400 • Parramatta 689 2188 • Penrith 32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800ACT• Belconnen (06) 2531785 • Fyshwick 80 4944 VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 & 246 Bourke St 639 0396 • Richmond 4281614 • Ringwood 879 5338 • Springvale 547 0522 QLD • Brisbane City 229 9377 •Buranda 391 6233 • Cairns 311 515 • Capalaba 245 2870 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9033• Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 • SA • Adelaide City 223 4122 • Beverley 3471900 • Elizabeth 255 6099 • Enfield 260 6088 • St. Marys 277 8977 WA • Cannington 451 8666 • Fremantle 335 9733 • Perth City 481 3261 • Midland 250 1460 • Northbridge 328 6944 TAS • Hobart 31 0800 NT• Stuart Park 81 1977 ORDER BY PHONE: - SYDNEY AREA 888 22 6610 OUTSIDE SYDNEY !FREE CAUi 008 22 6610 81293/PB The Go-Anywhere Receiver It's Portable! 16 BAND SHORTWAVE RECEIVER 10 BAND PORTABLE SHORTWAVE RECEIVER The Sangean SG -789 is a neat and compact receiver with the power to pull in radio broadcasts from around the world! •Local AM/FM bands (FM stereo with optional headphones) •Receives the 8 most popular international shortwave bands •Bandspread tuning and LED tuning indicator •Superb sound reprod uction •Sockets for headphones & AC adaptor $ Cat D-2834 Listen to the world direct... Europe, Asia, America and Australia. Also covers local AM / FM stations, longwave and 13 international Shortwave bands. •Incredibly compact & portable •Large LCD screen showing major city times •With dual alarms, sleep timer & tuning indicator •Electronic band selection & volume contro ls • Pop out stand for desk use Cat D-2839 A World Of Listen,ing 45 MEMORY SHORTWAVE RECEIVER $169 7995 MULTI BAND SHORTWAVE RECEIVER Tune into the world via shortwave with the superb ATS-808 from Sangean . With 45 memories, stereo headphones and more! •External antenna socket & •AM & FM-stereo bands •16 band divisions with built-in whip antenna • Longwave: 150-519k Hz direct access buttons •Mediumwave: 520-1720kHz •Keypad, auto-scanning, •Shortwave: 1.711-29.999MHz or rotary tuning •Alarm, sleep timer & dual continuous or in 13 bands time settings •FM: 87.5-108MHz •LCD signal strength meter cat D-2829 Hear the world news as it happens via shortwave, or your local AM/FM stations. Listen to Commercial comm unications, Amateur, Marine, HF Aircraft and more. •Covers 150kHz-30MHz, 87 .5-108MHz •9 pre-set station memories •5 tuning functions including direct keypad entry •Backlit LCD frequency screen & 24hr clock •RF gain control, plus BFO for SSB reception •Battery powered or optional AC adaptor Cat D-2831 $269 - - - - - - - AUDIO CABLES - - - - - - Extremely high quality audio cables. OFC Spkr, 60 x 0.12mm conductors, Figure 8. Cat W-2013 $0.95/m OFC Spkr, 315 x 0.12mm conductors, Figure 8. Cat W-2017 $3.95/m Audio, 'MUSIFLEX' Twin Shield Pro. Cat W-2044 $2.45/ffl Audio, Super OFC Single Shielded, Cat W-2032 $1.95/m Audio, Super OFC Figure 8 Twin Shield . Cat W-2033 $3.95/m - - - - - - SURGE PROTECTORS Protect your valuable electronic equipment from dangerous voltage surges and lightning spikes with our great range of surge protectors. llf~ HPM DOUBLE ADAPTOR & SURGE PROTECTOR 111 A quality double adaptor with a bui lt in surge protector. The red indicator light tells you surge protection is activated. Simply plugs into any powerpomt. Cat M-7153 s29ss SURGE SPIKE SAFETY PLUG Protect your computer, fax machine, hi-fi and other valuable eq uipment from voltage surges and lightn ing spikes. It simply plugs into any powerpoint and automatical ly absorbs surges and spikes. With a green LED 'on' light. Cat M-7157 I 1 , l1 . \ I CENSOR PASSIVE POWER FILTER A quality multi-stage L-C filter. Designed to give affordable protection from transients for microprocessor equipment. With an attenuation bandwidth from 100KHz to 4MHz and suppression of 40dB over this range. Cat M-7185 $2995 IEC SURGE/SPIKE SAFETY CORD A cord set which continuously monitors and auto matically absorbs voltage surges and spikes. With a green LED 'on' light at both the plug and socket. Cat M-7159 s39s5 B1293/PB .01 250VAC ffi ffi 5 F3 A 1A r powEii7 I 1' 240VAC I I I I BRIDGE RECTIFIER 12 IN +3B.5V S6 5 OUT I IN +15V '--- - N 47 35VW + 100 + 16VW OV -::- CHASSIS 47 35VW - GNO 100 16VW r••15V 100 "H'tt-r 100 0.1 OUT n -·1 10 0.1 E OUT \ I I GNO + GNO + 15vwI 01 - + 1 J3:I o.1I I -15V 15V PREAMPLIFIER AND CONTROL UNIT -38.SV Fig.4: the power supply for the new Studio Twin 50 Amplifier delivers unregulated ±38.5V rails for the power amplifiers and regulated ±15V rails (via the 3-terminal regulators) for the preamplifiers and stereo headphone amplifier. tortion to a minimum) by the two diodes connected between the bases. The output current of the headphone amplifier is limited by the 15Q emitter resistors and 68Q output resistor. This provides short-circuit protection and protects the headphones against damage in the unlikely event of the amplifier being damaged (which would otherwise cause ±15V to be applied across the headphones). By the way, this headphone amplifier circuit is very similar to that used in ~4.e 16-Channel Mixer described in the Feb-May 1990 issues of SILICON CHIP. The only significant difference is that we have specified a TL072 dual op amp instead of the LM833 used elsewhere in this circuit. The reason for not using the LM833 in this circuit is that we have found it has a tendency to oscillate at around 60MHz; the TL072 does not do this. Power amplifiers As noted above, the power amplifiers are the same as featured in the stereo power module described last month. For the sake of those readers who have not seen last month's article, we repeat the circuit description here. The input signal is coupled via a lµF metallised polyester capacitor and 1.8kQ resistor to the base of Ql which together with Q2 makes up a differential pair. Q3 is a "constant current tail" which sets the current though Ql and Q2 and thus renders the amplifier largely insensitive to variations in its supply rails (otherwise known 30 SILICON CHIP as power supply rejection). Diodes Dl and D2 provide a voltage reference of about 1.2V for Q3 so that it applies a constant voltage to its 680Q emitter resistor. This sets the current through Q3 at close to lmA. This means that Ql and Q2 each operate with a collector current of about 0.5 milliamps. Signals from the collectors of Ql and Q2 drive another differential pair, Q4 and Q5, which have a "current mirror" as their load. The main advantage of the current mirror, D3 and Q6, is that it makes the second differential pair highly linear and therefore low in distortion. The output of Q5 drives a class-AB output stage consisting of Darlington transistors Q8-Q11. By class-AB we mean an amplifier which is essentially class-B (ie, each half of the output stage conducts for only half the signal) but which has a small current bias to minimise crossover distortion. The current bias in the output stage is controlled by transistor Q7 and trimpot VRl. Q7 is a Vbe multiplier, so called because the voltage between its base and emitter is multiplied by the ratio of the resistors between base and collector and base and emitter, respectively. VRl adjusts this voltage to give a voltage between the collector and emitter of Q7 of about 2 volts. In practice, it is adjusted to give an output stage current of 40 milliamps. Q7 is a BD139, a transistor normally used in amplifier driver stages and video circuits. It has a dissipation rating of 8 watts and so is only doing light duty. However, it is specified here because it gives better Vbe tracking with the output stage transistors and therefore better stability for the quiescent current. The Darlington transistors -Q8 and Ql0 and Q9 and Ql 1 - are connected as parallel pairs to share the output current. Each Darlington has a 0.47Q emitter resistor which helps ensure equal current sharing. As well, the emitter resistors improve the output stage bandwidth and the stability of the quiescent current. The value is a compromise though; bigger emitter resistors would give better stability and improved current sharing but would reduce the maximum output power capability. The lO0Q base resistors for the Darlingtons serve a number of functions. First, they reduce any tendency for the output stage to oscillate; always a possibility with emitter follower stages. Second, they limit the base current in the event of a short circuit in the output and thereby reduce the possibility of damage to the Darlingtons. Negative feedback is applied from the output stage back to the base ofQ2 · via a 22kQ resistor. This resistor, and the lkQ resistor also connected to the base of Q2 , sets the voltage gain to 23. The low frequency roll-off of the voltage gain is set by the 47µF capacitor in series with the lkQ resistor. This sets the -3dB point at about 3Hz. However, the lµF input capacitor is the main factor in the low frequency response of the amplifier and sets a -3dB point at 7Hz. The overall effect of the two time constants is a -3dB point at lOHz. The 820pF capacitor and the 1.8kQ PARTS LIST 1 steel case with 2.5mm anodised black aluminium front panel 1 60 x 60 x 290mm 3mm-thick angle aluminium heatsink 1 power transformer, 2 x 25V, 160VA (available from Harbuch, Altronics or Torrtech) 8 SOT-93 (TO-218) transistor mounting kits 2 SOT-32 (TO-126) transistor mounting kits 1 3AG panel-mounting safety fuse holder 1 1A 3AG fuse 8 20mm fuse clips 4 5A M205 20mm fuses 2 Philips 4322-021-30330 or Neosid 60-601-72 coil formers 2 Philips 4312-020-36760 ferrite wideband chokes 2 RDE245A polyswitches 1 rocker type SPST mains switch with inbuilt neon 1 2-pole 6-position rotary switch (S1) 3 2-pole push on/push off PCB mount switches (Lorlin or similar) with black knobs (S2,S3,S4) 5 22mm-dia. black anodised aluminium knobs (with index mark) 1 cordgrip grommet 1 3-way insulated terminal block 1 black binding post terminal 3 3 x 2-way RCA socket panels (Altronics Cat. No. P-0123) 1 PCB-mount 6.5mm headphone socket with integral switch (Jaycar Cat. No. PS-0180) 1 1/4-inch solid shaft coupler 1 140mm long 1/4-inch shaft (for selector switch) 4 rubber feet 2 solder lugs Cable & ties 1 3-core mains cord and moulded 3-pin plug 1 150mm length of black insulated 1mm diameter single strand cable 1 300mm length of red insulated 1mm diameter single strand cable 1 500mm length of figure-8 shielded audio cable 3 1-metre lengths of hook-up wire 1 2.5-metre length of 0.8mm enamelled copper wire 1 plastic cable tie 1 160mm length of heatshrink tubing (to fit over mains switch & wiring) PC boards & hardware 1 phono preamplifier board, code SC01103921 , 186 x 135mm 1 switch mounting board, code SC01103922, 54 x 38mm 1 tone control board, code SC01103923, 252 x 85mm 1 stereo amplifier board, code SC01102921, 80 x 233mm 43 1mm dia. PC pins 3 15mm threaded spacers 1 10mm threaded spacer 2 6mm spacers Semiconductors 3 LM833 low noise dual op amps (IC1 ,IC2,IC3) 1 TL072 FET-input op amp (IC4) 6 BC556 PNP transistors (01-03) 4 BF469 NPN transistors (04,05) 2 BF470 PNP transistors (06) 2 BD139 NPN transistors (07) 4 TIP142 NPN Darlington transistors (08,010) 4 TIP147 PNP Darlington transistors (09,011) 2 BC337 NPN transistors (012) 2 BC327 PNP transistors (013) 8 1N4148 signal diodes (D1 -DS) 1 PO4 6A bridge rectifier 1 7815 3-terminal regulator (NB: 78L 15 not suitable) 1 7915 3-terminal regulator (NB: 79L 15 not suitable) Capacitors 2 4700µF S0VW electrolytics 6 100µF 16VW PC electrolytics 2 100µF bipolar electrolytics (phono preamps) 2 47µF 35VW electrolytics (power supply) 2 47µF 16VW electrolytics (power amps) 2 47µF bipolar electrolytics (phono preamps) 2 22µF bipolar electrolytics 2 6.8µF bipolar electrolytics 4 1µF 63VW MKT polyester 2 0.33µF MKT polyester 8 0.22µF 63VW MKT polyester 2 0.15µF 10% 100VDC 10mmpitch metallised polycarbonate (Philips 2222 344 21154) 8 0.1 µF 63VW MKT polyester 2 .033µF 1O0VW MKT polyester 2 .015 MKT polyester (2.5% or 5% tolerance preferred) 2 .01 µF MKT polyester 1 .01µF or .0047µF 250VAC metallised paper 4 .0047µF MKT polyester (tone controls) 2 .0047µF MKT polyester (2.5% or 5% tolerance preferred - phone preamps) 2 820pF S0V ceramic 2 470pF S0V ceramic 2 330pF S0V ceramic 2 150pF S0V ceramic 2 68pF 100V ceramic 2 33pF S0V ceramic 2 2.2pF S0V ceramic Potentiometers 1 dual gang 100k.Q linear potentiometer, PC-mounting (VR3, bass) 1 dual gang 50k.Q log potentiometer, PC-mounting (VR2, volume) 1 dual gang 25k.Q linear potentiometer, PC-mounting (VR4, treble) 1 dual gang 10k.Q M/N potentiometer, PC-mounting (VRS, balance) 2 500.Q horizontal mount trimpots (VR1) Resistors (0.25W, 1%, 7mm body) 21M.Q 4 3.9k.Q 2 200k.Q 2 1.8k.Q 6 100k.Q 2 1.Sk.Q 2 47k.Q 101k.Q 12 22k.Q 4 680.Q 2 16k.Q 4 180.Q 2 15k.Q 2 150.Q 4 10k.Q 12 100.Q 4 5.6k.Q 2 68.Q 6 4.7k.Q 4 15.Q 2 4.7k.Q 1W 26.8.Q1W Wirewound resistors 2 270.Q 3W 10% (Philips AC03 or similar) 8 0.47.Q 3W 10% (Philips AC03) 2 560.Q SW resistors (for setting quiescent current) M ARCH 1992 31 The circuitry for the new amplifier unit is accommodated on three PC boards: one for the tone controls, one for the phono preamplifier and high level inputs, and one for the power amplifiers. To make construction easy, the control pots, pushbutton switches and headphone socket are soldered directly to the tone control board. input resistor feeding Ql form a low pass filter which rolls off frequencies above lO0kHz. The 68pF capacitor between base and collector of Q5 and the 2.ZpF capacitor between base and collector ofQZ are used to roll off the open loop gain to ensure stability with feedback applied. We have also used our standard RLC network in the output stage. A configuration originally proposed by Australian engineer Neville Thiele, it uses 6.8µH air-cored choke, a 6.8Q resistor and a 0.15µF capacitor. 32 SILICON CHIP The beauty of this network is that it effectively isolates the amplifier output stage from any nasty impedance dips which may occur at high frequencies and which could cause the amplifier to be unstable. It also has another favourable effect because it kills any RF signal pickup by long speaker leads. Power supply The power supply, as shown in Fig.4, uses a 160VA transformer with a centre-tapped 50V winding feeding a 6-amp bridge rectifier and two 4700µF 50VW electrolytic capacitors. These provide unregulated supplies of about ±38.5V (at no signal and with 240VAC mains input). The unregulated supply rails feed the two power amplifiers directly. For the small signal circuitry, the unregulated ±38.5V rails are fed via 270Q 3W resistors to 3-terminal regulators to produce balanced supply rails of ±15V. The 270£2 dropping resistors reduce the input voltage to the regulators and thereby reduce their power dissipation. That's all we have space for this month. Next month, we 'll present the construction and troubleshooting details. SC vVCXX) FOR CHIPS... vVCXX) FOR CHIPS... vVCXX) FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS...WOOD FOR CHIPS... WOOD FOR CHIPS...WOOD ~ Why pay up to $150 for a label? NEW 100 SERIES Take a close look at these APPA multi meters. Look fami liar? That's because they're sold under different brand names. It's called 'Badge Engineerinf:g~aw~~k:g~~~:u:l~~~~a~~ 6~s It. And that means you could pay a lot more than you need to. We've seen the top of the line model selling at around $150 more than our price. So you're paying that much extra just for the brand label 1 It's also an indication of how good Appa meters are that other people want to put their names on them! • Extra tough for industrial users • High energy fuse and PTC {lrotection against overloading • 0-ring ssalea case, , witch and jacks against dirt and moisture • Protective holster and tilt stand with lead storage ~ Test probes have finger shields and sleeved plugs • Thick walled ABS case and shock mounted LCD withstands 2m drop on to concrete floor • Unique rotary switch with berrylium copper contacts and gold plated pcb Look at the teatur111 • Large high contrast display The 96 and 98 have ana/og bar graphs too • Colour coded input tennin11l1 and function switch for ,a1y selling • Probe storage clips built in for easr two handed measurement, • The 96 is water resislaRce tor industrial use • Shockproof fora drop of 1.5ml • Built-in tilt stand : 'i.t1~r,:gcJ:ii'fi~-:,~, and UL 1244 standards tor ,afety • Full 12month warranty Mode/93 • 1999 count • Large 20m m high contrast LCD read out • 8 Functions - Vdc, Vac, Ade, Aac, Ohms, Diode, Frequency, Ca£acitance • 0.5 Y, de accuracy $142.80 $119.00 ex tax Ranges Vdc 200mV, 2V, 20V, 200V, 1000V Vac 200mV, 2V, 20V, 200V, 750V Ade 200uA, 2mA, 20mA, 2uOmA, 2A, 20A Aac 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200!1, 2kn, 20kn, 200kn, 2M!1, 20Mn Frequency 2kHz 20kHz, 200kHz Capacitance 2nF, 20nF, 200nF, 2µf, 0 Als~ fva ilable Model with transisto r tester in place o 2A range $142.80 $119.00 ex tax Model 103 & 105 • 4000 count • Dignal update twice/second, analog 20 times/sec • 8 Functions - Vdc, Vac, Ade, Aac, Ohms, Diode, Continuity, Frequency, Capacitance • Data hold & Relative functions • 0.5% de accuracy $298.80 $249.00 ex tax Ranges Vdc 400my, 4V, 40V, 400V, 1OOOV Vac 4V1 40v, 400V, 750V Ade 4-•00mA, 1OA Aac 4-400mA, 1OA Ohms 400!1, 4kn, 40kn, 400kn, 4M!1,40M!1 Freq_uency 1OOHz, 1kHz, 10kHz, 1OOkHz, 1MHz Capacitance 4nF, 40nF, 400nF, 4µf, 40uF Mqdi/ 105 has similar specs but With improved accuracr of 0.1% typ on Vdc and 0. 5% a 50Hz $358.80 $299.00 ex tax 93f Mode/96 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or manual selection • 6 functions - Vdc, Vac, Ade, Aac, Ohms, Diode • Water resistant • Data hold • Memory offset Ranges Vdc 200mV, 2V, 20V, 200V, 1000V Vac 200mV, 2V, 20V, 200v, 750V Ade 200uA, 2mA, 20mA, 2uOmA, 2A, 20A Aac 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200n, 2kn, 20kn, 200kn, 2Mn, 20M!1 $166.80 $139.00 ex tax APPA 35 CLAMP METER • • • • • 4000 count display Autoranging Measures fo 350A ac Conductors to 25mm diameter Measure, voltage to 750Vac, Ohms to 4011n and continuity with beeper • Large 12.5mm LCD display • Dafa Hold button • Built-in bell clip APPA 88 Low Cost Basic Multimeter ------------------... Just Released 90 SERIES Mode/98 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or manual selection • 8 Functions • Vdc, Vac, Ade, Aac, Ohms, Diode, Frequency, Capacitance • Data hold tt Memory offset Ranges Vdc 200mV, 2V, 20V, 200V, 1OOOV Vac 200mV, 2V, 20V, 200V, 750V Ade 200uA, 2mA, 20mA, 200mA, 2A, 20A Aac 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200n, 2kn, 20kn, 200kn, 2M!1, 20Mn Frequency 2kHz 20kHz, 200kHz Ca~acltance 2nF, 20nF, 200nF, 2µf, Appa 90 Carrying Cas, $14. to • 3 1/l digit display $12.20 BX lax • Autoranging Appa 90 Holster • 7 functionJ Vdc, Vac, Ade, Aac, $19.20 Ohms, Continuity $16.00 BX lax • Sing/~ handed.operation • Bu171-m belt clip . ~ ~~ • large 12.5mm LCD display • Da(a /fold button • Bu1lt-m probe holder $94.80 · $79.00 ex tax OµF Range, Vdc 400mV, 4V, 40V, 400V, 1000V Vac 400mV, 4V, 40V, 400V, 750V Ade 400µA, 4mA, 40mA, 4uOmA, 2A, 20A Aac 400uA, 4mA, 40mA, 400mA, 2A, 20A Ohms 400!1, 4kn, 40kn, 400kn, 4M!1, 40M!1 Frequency 0-4MHz autoranging, 40MHz (500mV min) Capacitance 4nF, 40nF, 400nF, 4µf, 40µf Transistor hfe 0-1000 pnp/npn Continuity 2kHz buuer, <50n Logic to 20MHz Power 011 alter 15min Appa Model 95 Check these value feature, • 3999 count high resolution display • Elevsl! functions - Vdc, Vac, Ade, Aa&, ohms, diode, /og,c, continuity, frequency, .capacitance and transistor hie • Peak hold button • Automatic power oH • 0.5% basic accuracy • Shock proof from 1.5m drop $166 .80, $139 .00 ex tax Fluke - The Ultimate in Multimeters NEW for 92! Fantastic Fluke 10/11/12. Now everyone can afford a Fluke! o Fluke 1 4000 cour.t display, 1.5% basic accuracy, sleep· mode, continuity $108 ($90 ex tax) Fluke 11 adds V-chek™ auto mode change + capacitance, 0.9% accu racy $138 ($115 ex tax) Fluke 12 adds mini max, time sta mp, continuity capture $156 ($130 ex tax) Fluke 70 Series II offer a lot more than 'Basic' Features Automatic TouchHold™• Diode Test • Audible continuity• Autoranging with manual ranging• TL75 Test Leads with Hard Pomts™• Sleep mode• For measurements to 4800V-A 70 3200 count dig ital display• 31 segment analog bar graph• 0.5% basic Vdc accuracy• 2.0% basic Vac accuracy• 0.5% basic resistance accuracy• 2000 hour battery life (alkaline) $146.00 $125 .00 ex tax 73 As 70 but 0.4% basic Vdc accuracy • 2.0% basic Vac accuracy• 1.5% basic de current accuracy (10A range only) • 0.5% basic resistance accuracy• Holster/Flex-Sta£~~.OD $175.00 ex tax 75 As 73 but with additional current range 32mA to 10A $312.DD $260.00 ex tax 77 As 75 but with improved acc uracy 0.3% basic Vdc $354.DD $295 .00 ex tax Measures volts, amps, ch ecks continuity a~d pertorms diode tests, measures frequency, duty cycle and capac itance. The minim um, maxim um and averag e valu es can be recorded simultaneously. Analog bar graph updates at 40 tim es per second and the input Alert™so unds a constant audible warning of wrong input connections. 3 Year Warranty Brief Specifications DC Voltage 400mV to 1OOOV AC Voftage 400mV to 1000V DC Cwrenl 400uA to 10A AC Current 400uA to 10A Resistance 400n to 40Mn , 40nS Other functions Continuity: threshold <20!1 Capacffance: 5nF to 5uF Frequency: 0.5Hzto >200kHz Diode Test: Displays voltage drop to 3V Duty Cycle: 0.1% to 99.9% 100ms and 1s mod e Min/Max. $478 .00 $399.00 ex tax Fluke 85 Handheld Multimeter e All Fluke 83 Features PLUS • 0.1% basic accuracy e 20kHz bandwidth $576.00 $480 .00 ex tax $214.80 $179.00 ex tax Model 76 Component Tester Does the things your multimeter doesn 't' • Capacitance 200pF to 20uf • Resistance 200!1 to 20M!1 • Transistor hfe and lceo • Diode displays Vf at 1mA • LED displays Vf at 2Ma and 1Om A • Battery tests 9V and 1.5V cells • SCR Pas&'Fail test $142.80 $119.00 ex tax Fluke 83 Handheld Multimeter • 0.3% basic accuracy • Min/Max average recording • Duty cycle, capacitance, freq uency • Zoom bar graph, xlO • Relative measurements Fluke 87 Handheld Multimeter e All Fluke 85 Features PLUS 4 1/2 digit mode 1ms peak Min/Max record ing True rm s measurements High resolution 128 segment analog pointer • Backlighting with tim e-o~~ _ 90 00 $580 .00 ex tax • • • • !FLUKE! Geoff Wood Electronics Pty Ltd <!) (inc 1n N s W) 229 Burns Bay Road, (Corner Beatrice Street), Lane Cove West N S W Mail Orders to - P O Box 671, Lane Cove N SW 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198 8.30am to 5.00pm Monday to Friday. 8.00am to 12 noon Saturday Mail Orders add $5.00 rnin to cover postal charges Next day delivery in Sydney add $5.00 All prices INCLUDE sales tax unless stated otherwise Tax Exemption Certificates accepted if the line value exceeds $10.00 BANKCARD, MASTERCARD, VISA, CHEQUES or CASH cheerfully accepted. The Story of Electrical Energy, Pt.18 Queensland - glorious one day, perfect the next. But the mouth of the Nerang River on the Gold Coast was hardly a benign place - a dangerous crossing for boats in heavy seas and a constant threat to the towns and settlements on South Stradbroke Island. This is the story of how the Broadwater, the mouth of the Nerang River, was tamed using electricity. By BRYAN MAHER 34 SILICON CHIP The south easterly swells continuously carry sand northwards along the east coat of Australia. From the regions about Coffs Harbour to Fraser Island, this northward migration averages half a million cubic metres of sand.annually. This flow tends to fill the south side of river entrances, thus forcing the river mouth gradually northwards unless a rocky outcrop is encountered. Thus, northern rivers such as the Richmond, Tweed and Nerang now flow almost to the sea before turning northwards and then running parallel to the coast for many kilometres before ◄ Left: this photo shows the extent of the sand control project. The sea walls for the river mouth can be clearly seen, together with the large trestle to the left. This carries the 10 jets which pick up the sand slurry. finally flowing into the ocean. The Nerang River at the Gold Coast, source of all canal suburbs and the Broadwater, once had its mouth far to the south. In the early 1800s, the river entered the sea at Broadbeach, the site of the present Jupiters Casino. By 1822, the river mouth had moved northwards 2.5km to the present Northcliffe surf club house. A further 20 years on, the first government maps showed the Nerang River mouth where today we find Cavill Mall, the centre of Surfers Paradise! Everything north of that spot was part of South Stradbroke Island. By 1930 the river entered the sea where today we find Sea World carpark and the bungee jumpers. The inexorable northward march of the river mouth threatened everything in its path. Holiday homes on South Stradbroke Island, where the present Seaworld Narara hotel stands, were engulfed in 193 7. The site ofMoondarewa, a small village shown on 1880 maps, is now under water. Before 1986, the Southport Bar, as the Nerang River mouth was called, was an infamous passage for pleasure boats and fishing trawlers alike. Ever changing, at all times dangerous, often violently destructive, this river entry claimed many boats and lives over the years. Boats would ride up on a wave crest at the bar only to hit bottom and capsize in the wave trough which immediately followed. Currents continuously shifted the channel, leading to many groundings, with subsequent destruction of yachts and trawlers. So certain was this inevitable gobbling-up of South Stradbroke Island that from 1968 professional engineering measurements were undertaken. The river mouth was found to move northwards at about 20-40 metres every year. That's half a metre each week. Cyclones could shift the river a few metres over night! It was predicted that the towns Curragee and What would environmentalists think of this? The large pipe at the top of this long trestle carries the sand slurry back to a holding tank on the shore. Tipplers Resort would be obliterated by the year 2050. The Delft Hydraulics Laboratory of Holland, retained by the Queensland Government, presented a report in 1976. This established parameters for stabilising the river mouth and a plan for a vast electrically powered sand pumping system. Nature could not be halted but could be guided. To stop its northward march, the river mouth could be trained by the building of solid walls out to sea each side of the channel. But any wall or groyne built at right angles to a beach causes sand buildup on the south side and beach erosion on the north. Such sand migration would eventually form a bar seaward of the river mouth. Typical examples of this occur today at the Tweed River and Ross Creek entrances. Training walls The remedy applied to the Nerang River mouth was the building of twin training walls plus continuous pumping of sand from the south to the north side. This has the following effects: (1). It prevents swamping of the south training wall by sand buildup. (2). It counteracts any tendency for seaward bar formation. (3). It preserves the sand flow to the northside beaches, stabilising their contour, sand depth and quality. This was to easier said than done! After all, we are talking about collect- ing some 660,000 tonnes, (ie, half a million cubic metres) of sand annually and pumping it approximately 1.5km north. Great quantities of electric motor power would obviously be required, more than that used by a small town. Building the walls Because South Stradbroke Island has vehicular transport from the mainland only by barge, access to the north side of the channel is inconvenient and uneconomic. For this reason, commencing September 1984, a pair of training walls 320 metres apart were built on the beach to the south of the natural channel. The southern wall protrudes out to sea 600 metres, the northern wall only 400 metres. The idea was to first build the walls where vehicle access was easy, then to remove the sand between them to form a new river channel. Finally, the natural river mouth was plugged with sand. One million tonnes of rock in boulders sized- at 4, 8 and 15 tonnes were transported from many quarries to the site. The smallest rcicks were laid on a sand core and formed the bed of the walls. Above these were placed two layers of 20-tonne concrete blocks, forming a flat topped vehicular pathway out to sea. Mobile cranes then placed rocks on both sides to form protective aprons. MARCH 1992 35 The sand slurry pump is about two metres in diameter and is driven by a 710kW motor via a step-down gearbox and variable hydraulic drive. each powered by a 560kW 3.3kV squirrel cage induction motor. When running at full load, these motors produce nearly 25kW of heat by their normal resistive and iron losses. Hence, the 4-pole Toshiba machines are self-cooled by large externally mounted shaft-driven fans. However, when the plant is not running, the motors could become quite cold, especially in rainy winter weather. Since the installation is built in a salt atmosphere right on the beach, provision must be made to keep the windings warm and dry when not running. For this purpose, an inbuilt 240V 280W heater, controlled by the plant computer, keeps the windings warm and prevents condensation. Each 560kW motor drives a Worthington high pressure centrifugal pump at 1475 RPM. These units, made at Penrith, NSW by a division of Wormald Ltd, raise the water pressure to 1400kPa. The high pressure outlet pipes from each pump contain non-return and computer operated butterfly stop valves. So the computer can run the pumps singly or together in parallel. Sand collection tonne cubes provide armouring on the seaward ends of the walls. To collect the sand on the south side of the new channel, a 490 metre long trestle was constructed out to sea on steel piles. This structure supports a system of 10 jet pumps submerged 11 metres below sea level. Along the top of this trestle runs a 380mm pipe which carries the salt water from the two high pressure pumps. Motor driven valves control the flow of high pressure water to the jet pumps. These jets, spaced at 30-metre intervals along the trestle, act as venturi pumps to collect sand stirred up in a large trench below the trestle. The resulting slurry is carried 22 metres up into a large gravity flume mounted above the trestle structure. From there , the sand slurry flows to a holding tank on the shore. Pumping the sand Slurry pump The first requirement of the sand pumping system is the supply ofhighpressure salt water. At a subsidiary site within the Broadwater, twin turbine pumps; each powered by 150kW electric motors, collect salt water. This is pumped at low pressure across the Spit to the main pump house. Inside are two high pressure pumps, Sand slurry from the holding tank is fed to a large centrifugal pump, two metres in diameter. This was made in Australia by Warman Industries. The slurry pump is driven by a 710kW 3phase induction motor, made in Japan by Toshiba. Being a 4-pole squirrel cage motor, it runs at about 1480 RPM. This is too high for the pump which How does the computer know the speed of the slurry pump? An infrared source illuminates the bolt heads on this shaft coupler and they are detected by an infrared phototransistor - crude but effective. Two layers of 15-tonne rocks, sloping at an angle of 45 degrees , form primary armouring on both sides. Outside these, 8-tonne boulders form protective side wings. These extend 10 metres on both sides. This method of construction gives protection against undermining by big seas. The slopes chosen allow wave overtopping without damage during cyclonic storms. A total of 4500 concrete cubes were used in the construction. Heavier 2536 SILICON CHIP -- - ~ Ten of these large jets are immersed in a large trench to pick up sand. Water is pumped at high pressure from the jet at the bottom and the sand/slurry mixture is taken up the larger pipe to the top of the trestle. The 10 jets move a total of 660,000 tones of sand annually. needs a variable speed drive. Therefore, a step-down gearbox and a variable hydraulic coupling are interposed between the motor and the pump. The fluid drive unit is about one metre in diameter and its output can be regulated by changing the attitude of internal oil pickup shoes. These are controlled by a hand wheel or by a motor drive operated by the plant computer. There can be considerable heating of the hydraulic oil, running into hundreds of kilowatts. The slurry output from the pump passes via a pipeline buried below the river to the north side of the channel. There the sand is dispersed by the natural action of waves onto the northside beaches. flow in cubic metres per second is measured by an electromagnetic flowmeter inserted in the pipeline. Knowing the flow rate of slurry is not sufficient as the sand/water ratio is variable. To know exactly how much sand is pumped it is necessary to also know the slurry density. This is measured by a densimeter based on the absorption by sand of gamma radiation. A very small quantity of the radioactive isotope Caesium 13 7 is mounted below the delivery pipe in a safety lead shield housing. The radioactive decay of this metal (halflife 30.3 years) results in the emission of gamma radiation and beta particles. The gamma radiation, formed into a beam by a lead collimator, passes upwards through the pipe and the slurry and then into a shielded ionisation chamber. This consists of a sealed insulated stainless steel cylinder, polarised at 700 volts and filled with Freon gas. A single insulated electrode suspended in the centre of the cylinder is connected to a charge-sensitive electronic amplifier. The gamma radiation, having passed through the steel delivery pipe and the sand slurry, ionises the Freon gas. This releases electrons which are collected by the centre electrode and fed to the amplifier. Electron currents as small as 20 picoamps are involved. From the densimeter signal, the plant computer computes the slurry density. The maximum specific gravity achieved is 1.33 compared to around 1.026 for sea water. Cathodic protection To protect submerged metal parts, a cathodic current is passed between all steel pipework and a sea electrode. The piles of the trestle are fed a DC current of 20 amperes at 20 volts. The underwater slurry delivery pipe is protected by a 1.3 amp current from a 10 volt DC supply. The whole system, from start, through the running sequence, to closing down, is under computer control. The results of this unique system are excellent. The sand pumping maintains the northside beaches in excellent condition and the sea entrance to the Nerang River is kept stable. The total cost of the project, including sundry roadwork, revegetation and navigation aids, was $50 million. This installation is the only one of its size in the world and is unique in being able to withstand and operate during cyclonic storms. Acknowledgements Grateful thanks and acknowledgement to the engineers and staff of the Department of Transport and The Coastal Protection Unit of the Department of The Environment and Heritage; to Ross Winks, Liam Farrell, P. Coughlan, D. Robinson, and Mayday Journal. SC Sandflow measurements The plant computer measures the slurry pump shaft speed by an infrared source illuminating the bolt heads of the shaft coupling. Thus the bolt heads are sensed by an infrared detector so the computer can calculate the pump revs per minute. The slurry More sand please? The whole sand pumping operation is under the control of this computer. No doubt it is well within the capabilities of a humble PC. MARCH 1992 37 AL TRONICS 24 HOUR EXPRESS DELIVERY 'Our customers are often amazed at the speed and efficiency of our Jetservice Courier delivery. Phone your order Toll Free 008 999 007 and presto we can deliver your order next working day (country areas 24-48 hours later). Our famous 14 day satisfaction money back guarantee protects your hard earned $$$'s should ever a purchase be unsuitable for your needs. I invite you to try Australia's best electronics phone order service soon.' Regards, Jack O'Donnell The All New Powerhouse 1200W Inverter This new design of Power Inverter wi ll provide 1200 Watts of power from a heavy duty 12 or 24V battery. Using the latest Mosfet output stage and toroidal transformer this inverter is efficient and will deliver high surge currents. The Powerhouse has been designed not only for rugged bullet proof operation but for ease of construction, two PCB's hold all circuitry with one inter-connecting cable. (7 wires). Thi• kit come, to you In a fully drllled, pre punched cha11l1 complete with ollk ocreened front panel. Aoaembly of the kit 11 olmpllfled ao the majority of component, mount on a olngle PCB . .Thul virtually ellmlnallng all external terminal,. Suitable for uoeo In camping, boating, llohlng, mining, remote oelllemento etc. Feature,:• Massive 1200W continuous 2400W surge will run almost anything• 12 or 24V operation selected via internal wiring • Low battery cut-out• Over temp cutout • Circuit breaker for overload protection • Auto start circuitry for standby operation • Easy to construct $ K6790 Kit Version 799.oo K6792 Fully Built Tested 12V Input $999.oo K6793 Fully Built Tested 24V Input $999.oo & & Sensational Value on Powerhouse 600W Inverters I (Fully Built & Teoted) j •• .. ,H£>owe~Hou8E.. Fealureo: • 12V or 24V DC Models available - great for _ cars, trucks, caravans etc • Compact Tonodal \ • i -~ .. :.. T<ansformer • Built In sturdy ABS case• A must for ·.• • • I farming, mining , boating, camping, remote settlements, or ~ wherever else 240V Is not ava1lablel ~ - '....u ~1, , 1 K 6774 12V Input GtNt Velue Thie Month et Only K 6775 24V Input "°" "•uoe,•c r-:;;,,_ $ Normally $625.oo 499.oo ''"'•rre, _J '_' • -- --- Highly Accurate 4-Digit Capacitance Meter It is ideal for use with incandescent globes, (note this model inverter will not run fluorescent lighting) electric shavers. small radios and some plug pack operated devices, ie charging cordless drills and (SC May '90) This attractivE> 4-digit capacitance meter is designed for the workshop or laboratory. It can measure capacitance from 1pF up to 9999uF in seven ranges with an accuracy of better than +/-1%, +/-1 d1g1t. other rechargeable battery appliances etc. K2524$119.95 Featureo: • Operates off 12V DC • Battery connection leads provided • Light weight • Uses Mosfet devices • High efficiency • Low heat dissapation K6710 $79.oo Low Voltage CutOut for Cars and Boats Colour TV Pattern Generator (SC Nov '91) l ____ .:__,. AdJu■ table Cutout Variable from 10.9V to 11.9V. lncludeo Automatic or Manual Voltage Reoet Function. I . ·.!. ,, ,~-•~"' LL---.::,;::..::;;-i This simple project allows you to monitor a doorway or a path using an infrared light beam. When someone walks through the beam , it triggers an alarm for a 1 second period. Ideal door monitor for shops or for security around home or office. Requires 12V DC plugback (M 9002). K1920 $32.s5 TV Transmitter for Digital Altimeter for Gliders and Ultralights Video Recorders ~-:i; Build this simple little device, and avoid getting caught out with a flat battery during your holidays. It simply connects into a 12V accessories power line, and shuts off the flow if the battery voltage drops to a dangerously low level. Ideal for batte!y powered camping fridges etc. Bu.ild this Infra-Red Light Beam Relay Thi• new colour TV pattern generator produce, oeven ■eparate patterno: • Checkerboard • White raster • Crosshatch • Red raster • Dot • Colour bars• Greyscale It will enable you to set your TV's (SC Sep/ Oct '91) convergence and purity for the best This compact digital altimeter can possible pictures. Requires 12V AC display altitude up to 19,990 feet with 10 plugpack M 9020 $16.95. feet resolution . Accurate to better than 3.5 percent. Operates on 9V battery. Kmo$115.oo K25ao $299.oo (SC Dec '91 This TV transmitter enables you to transmit signals from the UHF output of your VCR to a second TV set in the house without mess splitters and cables. 10 Watt Megaphone PA With Wlrele11 Remote Control 125dB siren. Visible warning by flashing headlights when the alarm system is triggered. The alarm system will be triggered by unauthorised entrance through the car doors, booth, bonnet (negative trigger inputs) or removal of the car sound unit (normally closed input to earth). Automatically resets after 60 seconds. s 5220 $99.oo !!~~?a~st~!~:~~r~!:e~: flash output at a rate approx 1 per second 12V DC 320ma Dlmenalona: 97 diam 50H . • 5455 Blue Normally $27 95 This Month $20 .00 · s5450 Red Normally $27 95 This Month $2O.oo S ~ " . II High Energy Siren Absolutely ear splitting SPL 120dB Handy brack for wall mounting etc 12V 300mA Ideal for industrial applications or alarm systems Dlmen1lona: 100mm Diam 125mm L S 5177 Normally $29 95 This Month $22.oo Economical Alarm System Kit The kit comes complete with the following components: • One Alarm Panel • One Passive lnfrared Detector (P.1.R.) • One AC Power Pack• One 8 Ohm Horn Speaker • Three pairs of Magnetic Reed Switches • One 12V/ 1.2AH Rechargeable Back Up Battery • Emergency Panic Button 100W Max Attention all gultarl and keyboard mu1lclan1. Thi• fine USA de ■ l gned 1pea II 1upplled 81 Excellent 1tandard equipment C larlty the world famou1 And brand name ■ e rle ■ Performance Guitar Amp ■. Range: Depending on conditions approx. Impedance (300Hz) Ohm, Sen1ltlvlty 300M Requires 8 x AA batteries. 94dB/W (0.5m) Voice A 1980 Normally $147.oo Weight 4000gm Magnet This Month $99.oo $299.oo Thll 1tereo 11 Ideal for background/ foreground appllcatlon1. Fan:a1tlc for re1taurant1, 1hop1, dl1co'1, aerobics, PA sound 1y1tem1 and home. • 90 watts RMS per channel minimum into 8 Ohms fro m 20 to 20,000H z with less than 0.05% THD • 2 large power meter indicators • EIA Panel with handle device • XLR socket for speaker terminal • Output relay to eliminate turn-on and off transients • Dimensions: (W x H x D) 482 x 92 x 295mm • Weight: 10.5kgs • Ideally suited to A 2210 stereo tuner. A 2040 $625 Thll Month the■e model ■ Alarm Stickers Door Strike For the Hou ■e 200mm x 75mm S Normally $1.95 5400 Ideal for security access areas, this high quality lock will fit most door jambs. Operates off either 12V AC or DC making it ideal for any type of system. This Month $1.oo ln:::n111rw:J!l For your Car 70mm x 25mm S 5410 Normally $3.95 s 4390 $39.95 This Month $3.oo Battery Operated Portable Passive InfraRed Intrusion Alarm Ward off thieve■ and lntrudera at home or when travelling This is a portable, battery operated passive infrared intrusion alarm. It employs the most advanced circuitry offering fully automatic operation and superb performance. The alarm gives over 100 squre metre protection. Feature■: • A ready to use system, no installation • Fully auto . matic operation , very user friendly • Large coverage, over 100 square metres • Portable wall mounted • Long life 9V battery operation • Battery low warning • Lightweight, compact and attractive • Recommended for home, shop, caravan or when travelling s 5305 -Normally $69.oo , . = _ - Thi■ Month Only $49.oo jo, i=....,._ Weatherproof Horn Pressure Mats thin switch mat for under car Speaker ~ Ultra mat etc. 10 Watt 8 Ohm C 2015 Normally $15.95 This Month $12.oo S 5184 Normally $29.95 ~ This Month $25.oo C 09 4 White The new versions of these models include a natty little builtin protector allowing around 100 watt input without damage to the drivers. Rugged Extruded Con1tructlon These vibration free enclosures are constructed from die extruded heavy guage aluminium and finished with incredibly durable industrial powder coat enamel. The speaker ends are sealed via gaskets and tough moulded "LURAN S" UV resistant end caps, The end result is "Good Looks" together with assured rugged durability for the Australian environment. Excellent Reproduction The drivers have been chosen for wide range, low distortion, mid range "presence" (essential for high grade vocal work) and high efficiency in general. Weather proof Construction and use of "Doped Cones". Foam plastic and cloth is sandwiched between baffle and front grill to prevent water ingress. ln1tallatlon Hardware Each speaker system is supplied with wall mounting brackets. Normally$149.oo ea, or $280.oo pair This Month Standard CB Type Microphone Low impedance Dynamic mic with curly cord (incl switch pair) . Suitable for CB's, radio transc ievers etc. Does not include plug . Froquency Re ■ po n ■e 300SKHz Impedance 500 Ohm Sen1ltlvlty -70d B C 0332 Normally $17.95 · $599.oo PA Sound Column and HI Fi Extension Maalve 100 Witt Input rating make simply Spe akers brilliant 81 exten1lon speaker■ for home, club, hot11l1 etc. $50.oo Save $99.oo Two Chann Per Chann Alarm Panel Features: • 5 Protection Circuit Loops • Independent Connections for N.C. and N.O. Sensor Switches • Arm - Disarm by Digital Access Key-Pad • Multi Station Remote Control • Warble Tone - Steady Tone Siren Driver • Adjustable Timers for Entry Delay and Siren Duration • "Latch" and "Timing" Output Relays • Remote and Local Alarm Status indication This system is easily installed by the Home Handyman. No special tools or equipment are required. Comprehensive installation instructions supplied. S 5470 Normally $349.oo Thi• Month Only C 31 02 This Month $1 5.oo $100.oo ea High Performance ALC Wireless M. . . . . (Automatic Level Compreuor) For high grade vocal entertainment • Cardio id-uni directional pic k-up pattern • Carrier frequency: 88-108MHz adjusta bl e • Field 1trength of carrier: With 50u V/ m at a distance of 15M from th e mic • Battery compliment: 1 x 9V C 0328 Normally $1 2 9 .50 This Month $99.oo Altronics Aviation Headset • High performance noise attenuating earphones • Noise caneetting microphone • Cushioned head pad • Super sturdy • Great performance • Superb, professional pilot's headset w ill last a lifetime with reasonable trea tment • Includes standard aircraft jacks. C 9070 $189.oo 1 Harris Four Channel Digital Recorder/ Announcer Amazing Nicad Battery Bargain From $2.00 All full specification premium quality. Good for up to 1000 re-charges. S 5020 AA 500 MAH S 5022 'C' 1.8 AH S 5023 'D' 4 AH 1-9 10-24 $2.95 $2.50 $8.oo $7.oo $14.oo $13.oo 25+ $2.oo $6.oo $12.oo 20MHz Logic Probe The Harris A 2100 provides 4 channels of natural speech recording and play-back. Recording time for each channel is internally selectable to 10, 15, 20 or 30 seconds. The sound quality is outstanding on the lower settings and " industrial" on the higher ranges. Channels can be used separately or linked to provide one long recording/ announcement. Facllltlea/Featurea: • Mlceophone Inputs - Balanced line, low Z, 5 Pin DIN socket (mates with Redford C 0372 desk mic) • Auxlllary Input - 100k, 0.2V sensitivity, eg for CD, tape deck, tuner, BGM line • Channel Select Pulhbuttona - A, B, C, D or all, i.e.: when activated will playback which ever is selected • Timer Switch Automatically initiates the playback of the selected channel. Intervals are 10, 20, 30 seconds, 3, 6, 12 and 30 minutes and off. Literally Dozen, of Appllcatlona: • Mualc on Hold Adviser - Over 50% of phone calls are placed on hold - use this ti me to promote your business or products • Information Gulde - Great for displays trade shows, self guided tours and even art galleries• A Security Guard - Good weather or bad, holidays and weekends, it stays on duty 24 hours a day to query and direct all personnel at siores, warehouse, plants, offices, hospitals and parking facilities. And for apartments, hotels, estates and more - whenever you wish to screen traffic • PA Syatem Feedback Ellmlnator - With the Harris announcer feedback is eliminated. Just operate on Paging Playback mode and once the announcement is recorded it will automatically page. Self resets ready for the next message. • Emergency Slgnala - And/ or security warnings can be generated automatically or at the push of a button • Advertlaement Announcer for Retell Store, - Either record your own ads or have them commercially produced - play through your PA/BGM system as often as desired with the :.,ternal timer. A 2100 Normally $799.oo This Month $599.oo a 1272 Normally $37.50 This Month $25.oo Economy Parts Case PCB Stands Screw one of these handy jigs to your workbench and instantly you have a third hand . Great for servicing, assembling PCB's, inspecting components soldered joints etc. WITH- MAGNIFIER T 1460 Available in 3 sizes H 0246 15 Way (260 x 175 x 43mm) $10 .50 Famous Labtech 20MHz Dual Trace NORMALLY $699 .oo Oscilloscope ·= - --- -- THAT's $100 OFF I ij Ideally suited to Q 0156 (2 required) . Superb quality. DC to 80 MHz. Max 600 Volts DC. Lead length approx 1.5m. aom$49.95 Auto-Ranging Multimeter with Dlgltal and Bar Graph Readouts and Memory Mode. ·,--- ---- ·-- --··· -, Just $99.oo Compares very favourably to Fluke Tm or Beckman Tm at a fraction of the cost • 42 Segment Bar Graph Display • Auto- ranging on Voltage and Resistance • Memory Mode • Low Ohm Rang e• Hold Facility • Automatically indicates negative inputs • Low Battery Indi cator • Continuity check with Buzzer Specltlcatlona: DC Voltage Ranges: 5 (200mV, 2V, 20V, 200V, 1000V) Input Impedance: 100m Ohm , 200mV Range, 10M Ohm, the other Ranges AC Voltage Range: 4 (2V, 20V, 200V, 750V) Input Impedance: 1OM Ohm DC Current Rang es: 200mA, 10A AC Current Range: 200mA, 10a Realatance Ranges: 200 Ohm, 2K ohm, 20K Ohm 200K ohm, 2M ohm, 20M Ohm General Display: 3½ digit LCD a 1075 Normally $119.oo Now Q 1077 Protective Holster $12,50 Q Carry Case 1076 Probe Set '_-!ii 0156 This Month Only $599.oo Feature ■: $9.so $5 .25 H 0248 5 Way $3 .50 (175 x 95 x 38mm) SENSATIONAL VALUE Q T 1450 H 0247 6 Way (210 x 110 x 44mm) This I• the 1992 model of our fanlaallc l.ebtech Dual Trace 20 Meg Scope. There are over 3000 now In aervlce throughout Auatral/a - Our cuatomera Include Unlveralllea, Reaeerch Eafabl/ahmenla and lnduatry The '92 model is a dual trace 20MHz oscilloscope using a high brightness CRT. The vertica l amplifiers have high sensitivity of 5mV/div and a frequency characteristic response with smooth roll off exceeding 20MHz. The TV sync. signal operator circuit is provided to ensure stable observation of video signals. Triggering is obtained by sampling the AC power waveform, external waveform or internally generated trigger. Highly recommended for Service Workbench, Dealgn Laboratory, Manufacturera, Unlverelllet and the dedicated enthulia1tlc. $14.s5 W/ OUT MAGNIFIER $12.50 $99.oo Our Top Selling 17 Range Dlgltal Multimeter for an Amazing $39.95 With qual ity and features you wou ld expect only on expensive meters the Q 1056 represents excellent va lue for money. i Speclflcatlona: DC Voltage: Ranges 2-2000V AC Voltage: Ranges 200V, 500V DC Current: Ranges 200mA, to 10A Realatance: 5 Ranges 200 Ohm, to 2M Ohm Diode Teet: Test Current 1.0mA Test Voltage 3.2V Max Battery Teat: Ranges 1.5V, 9V Loaded Current: 1.5V 100mA, 9V 6mA a1os6 Normally $49 .95 $39.95 This Month Q 1057 Carry Case to Suit $12.50 TESTMA Te 308 TRANSFORMER SALE Save Up To 30% Customers please note - All A/Ironies Mains Transformers are now wound on segregated nylon 66 flam., retardant bobbins. Models M 2851 - M 2855 and PCB Transforme rs M 7112 - M 7130 are fitted with primary thermal fuses. All comply to the latest (and very stringent) Australian Standard Code AS 3108 Toriod Power Transformers ALL MAINS TRANSFORMERS PRIMARIES 240V SPECIFICATIONS LISTED REFER TO SECONDARY WINDINGS Dimensions and Weight Multipurpose SOVA SOVA Models 160VA Models 300VA Models 500VA Modelo 9, 12, 15, 18, 21, 24, Volts at SOVA output M 2165 Normally $26.50 This Month $2O .oo SOVA Multipurpose 100VA Normally All $49.95 Now $45.oo ea 12, 15, 24, 27, 30, Volts at 100VA output Model M 2170 Normally $29 95 This Month $22.oo M 3020 Multipurpose 120VA M 3025 M 3030 M 3035 M 3040 12, 15, 24, 27 , 30, Volts at 120VA output. M 2175 Normally $39.95 This Month $30 .00 SEC.V 12+12 18+18 25+25 30+30 35+55 300VA 160VA Normally All $65 00 M 2851 12.6V CT 150mA M 2852 12.6V CT 300mA M 2853 12.6V CT 500mA M 2854 24V CT 150mA M 2855 30V CT 150mA M 2154 12V, 15V, 18V 1 Amp M 2155 6V3, 7V5, 8V5 Normally 1-9 ea 10+ ea $7.30 $7.65 $8.20 $7 .65 $7.65 $11.00 $6.00 $5.00 $6.00 $5.00 $6.00 $5.00 $6.00 $5.00 $6.00 $5.00 $9.00 $8.00 $9.00 $8.00 $15.00 $13.00 $15.00 $13.00 9V5, 12V6, 15V 1 Amp M 2156 6, 9, 12, 15V 2 Amps $10.95 $17.95 M 6672 15, 17V5, 20, 1 Amp $16.50 24, 25V5, 30V 1 VA PCB Mount Mains T ransformers From $8.00 Model SEC. M7112 M 7115 M 7118 M 7 124 M 7130 6+6 7.5+7.5 9+9 12 12 15:15 T 1 •••• Now $60.oo ea Model M 3055 M 3060 M 3065 M 3075 M 3080 Normally All $89.95 Normally All $129.oo Now$80.oo ea Now $110.oo ea Model M 3085 M 3086 M 3088 M 3090 M 3092 M 3100 SEC. V 18+18 25+25 30+30 40+40 45+45 M 3105 Telecom Type Line Isolating Transformer Impedance: 600 Ohm line/600 Ohm equipment Tuma Ratio: 1 :1 · Normally $13.95 ~~ sec 1 sec 2 Audio FUSE Microphone Type Primary: 200 Ohm Secondary: SOK Ohm 1-9 10+ $1O.oo $ 9 .oo Bridging loolatlng Type Used for coupling audio modules. Prevents earth loops, hums etc. Essential coupling device where DC isolating is required. Nominal Impedance ratio: 10K: 10K (1:1) 28mm 2'0V ilZrJ f"\,.Q.Q._r] , ,Omm ll 15mm I • • • SEC.V 12+12 18+18 25+25 30+30 35+55 40+40 45+45 M 0702 Normally $34 .95 M 0701 Normally $34.95 Normally All $12.95 This Month $1O.oo ea Or buy 10 or more for $8.oo each. This Month $ 2 5 .oo Thi• Month $25.oo HEAVY HEAVY SERVICE- All orders of 10Kgso r more must travel Express Road - Please allow 7 days for delivery . $12.00 to 10Kgs . $15.00 over 10Kg s. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk . Shoul d you require com preh ensive insurance cover aga inst loss o r damag e pleas e add $1.00 per $100 of orde r valu e (minimum charge $1 ). When ph one 174 Roe S1 . Perth W.A. 6000 Ph one (09) 328 t 599 PHONE TOLL FREE 008 999 007 MAIL ORDERS C/ - P.O. Box 8350 Stirling Street PERTH W.A 6849 STANDARD DELIVERY & PACKING CHARGE $5 .50 to 1Kg. $8 1Kg-5Kg AUSTRAL IA WIDE - We pro cess y our o rd er the day receive d and despa tch via . Aus tra lia Post . Allow approx 9 days from day you post ord er to when you receive goods. OVERNIGHT JETSERVICE Up to 3Kg ,s $10.00, 3Kg to 5Kg is $23 .00 - We process your order the day rece ived and despatch via. Overnight Jetservlce Courier for delivery next day Country areas please allow add iti on al 24-48 hours. ordering please request " Insurance" TOLL FREE PHONE ORDER - Ban kcard, Visa, Mastercard Ho lders can phone order toll free up to 6pm Eastern Standa rd Time . Rem ember with our Overnight Jetservlce we deliver next day . AL TRON!CS RESELLERS Ch ances are there is an Altronic Reseller right near you - ch eck this list or phone us for details of the nearest dealer. Blue Ribbon Dealers are highlighted with a ■ These dealers gene ra lly carry a comprehens ive range of Altronic products and k its or will order any requ ired item fo r you · Wl..t. COUNTRY ALBANY BP Electronics• (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 216222 ESPE.RANCE Esperance Communications (090) 713344 KALGOORLIE Todays Electroni cs ■ (090) 215212 MANDURAH Lance Rock Retravision (09) 5351246 Micro Electronics (09) 5812206 PORT HEDLAND Ivan Tomek Electronics (091) 732531 ROCKINGHAM TV Joe's (09) 5271806 NT ALICE SPRINGS Farmer Electronics (089) 522388 DARWIN Ventronics (089) 853 622 VIC All Electronic Components (03) 6623506 BORONIA Ray Cross Electronics • (03) 7622422 CHELTENHAM Talking Electronics (03) 5842386 CROYDON Truscott Electronics • (03) 7233860 PRESTON Preston Electronics • (03) 4840191 COU NTRY BAIRNS DALE LH & LM Crawford (05 1) 525677 BALLAR AT Ballarat Electronics (053) 311947 BENDIGO KC Johnson ■ (054) 4114 11 MILDURA McWilliam Electronics (050) 236410 OLD Delsound PL • (07) 8396155 WEST END BAS . Audiotronics (07) 8447566 WOODRIDGE David Hall Electronics ■ (07) 8082777 MAROOCHYDORE MALS Electronics ■ (074) 436119 MARY BOROUGH Keller Electronics (071 ) 214559 NAMBOUR NambourElectronics (074) 411966 PIALBA Keller Electronics (07 1) 283749 ROCKHAMl'TON Access Electronics (East St .) (079) 221058 TOO WOO MBA Hunts Electronics (076) 329677 TOWNSV ILLE Super Solex ■ (077) 724466 SAForce Electronics ■ (08) 2125505 BRIGHTON Force Electronics ■ (08) 3770512 CHRISTIES BEACH Force Electronics ■ (08) 3823366 FINDON Force Electronics ■ (08) 3471188 HOLDEN HILL Force Electronics• (08) 2617088 LONSDALE Force Electronics • (08) 3260901 ENFIELD Aztronics ■ (08) 3496340 COUNTRY WHYALLA Eyre Electronics (086) 454764 TAS HOBART George Harvey ■ (002) 342233 LAUNCESTON George Harvey• (003) 316533 NSWDavid Reid E lectronics ■ (02) 2671385SMITHFIELD Chantronics (02) 6097218COUNTRY COFFS HARBOUR Coifs Habour Electronics (066) 525684 NEWCASTLE Novocastrian Elect.Supplies (049) 621358 WARNERS BAY Vi lec Distributors (049) 489405 WINDSOR M & E Elect . and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620, Vimcom Electronics (042) 284400. By JOHN CLARKE THERMO FOR CAR Has the thermostat failed on your electric radiator fan? This electronic thermostat can r eplace it and can be adjusted to switch on at a temperature to suit your particular vehicle. Electric radiator fans are excellent for cooling th e w ater in a car radiator. Unlike most belt driven fans , they are on ly sw itched on when cooling is required and so they are very energy efficient. If used to replace an engine driven fan , the resu lt is an increase in available engine p ower, reduced fuel consumption an d lower engine n oise. Oth er benefits include increased water pump bearing an d fan belt life. Given these facts, it's n o won der that many peop le with older cars h ave replaced th eir original engin e-driven fa n w ith an electric fan. Most late42 SILICON CHIP model vehicles now use electric fans as standard , as do all cars with eastw est engines. If air-conditioning is fitted to the vehicle, a second electric fan is usually fitted in front of the radiator and this operates whenever the air-conditioning is turned on. So why would you want to build this Thermostat Switch? There are two reasons. First, you may have installed an electric fan cooling system in your vehicle and the thermostat has subsequently gone faulty. Perhaps you've overcome this problem by shorting out the thermostat, since obtaining a replacement for many brands is virtually impossible. The problem with this scheme is that the fan now runs all the time and so provides too much cooling. That means less performance, longer warmup times and increased fuel consumption. The SILICON CHIP Thermostat Switch will ensure that the fan cuts in and out only as required, so that the engine always operates at the correct temperature for peak efficiency. The second reason for building this project is so that it can be used with a secondhand fan obtained from a wrecker. Often, the thermostats associated with such units are missing or faulty. An advantage of this unit is that it operates with greater accuracy than conventional thermostats and it can easily be adjusted to cut in at a temperature to suit the engine. The SILICON CHIP Thermostat Switch uses a commercially available temperature switch sender unit (available from K-Mart) which is mounted in the radiator. This sensor changes its resistance with the radiator fluid temperature. When th e resistance drops below a critical point, the Thermostat Switch switches on the fan. It then turns it off again when the sensor resistance increases (ie, when the coolant temperature goes down) but has a degree of inbuilt hysteresis to ensure that the fan does not "hunt". Circuit details Refer now to Fig.1 for the circuit details. An interesting aspect of the STATIC SWITCH RADIATOR FANS +12V F R O M O - - - - - - i l - - - - - - - - -IGNITION - -- - F1 RATING TO SUIT FAN +12V----c.-...c>----, - - - - - - - ~ D1 1N4002 ---------1 - 390ll 390\l ,w ,con 5W OR OUT 410n 7 IC1 5 COMP MC3334P INPUT POWER SENSE GND GND 4.7k 27Dn SE~SE B R1 510ll TEMPERATURE SENDER AUTO PACE TS6178 OR SIMILAR 0.1 0.1 1oon 0.1 0.1 5W ,oon FAN ON TEMPERATURE VR1 20011 0.1 5W 0 0 B GNDTO~-+-------~t----tl-----e-----t1---- VEHICLE CHASSIS - -- ---------~ DIVIDER VIEWED FROM BELOW CURRENT SENSE THERMOSTAT SWITCH FOR AUTOMOTIVE ELECTRIC FANS Fig.1: the circuit is based on a commercial temperature sensor (TS6178) & an MC3334P ignition chip. When the radiator temperature increases, the sensor pulls the base ofQ2 low via Q1 which is wired as a diode. Q2's collector tp.us goes high & triggers ICl which switches its pin 7 output high & turns on the fan motor via Q3. design is that it's based on a Motorola MC3334P automotive ignition chip (IC1). Apart from that, it uses only three transistors and a few minor components to complete the circuit. ICl was used for several reasons. First, this IC is rated for operation up to 125°C which makes it suitable for automotive applications. Second, the IC has a comparator input which switches the output at pin 7 from a high to a low and a low to a high over a precise voltage range. IC1 also has a sense input which can be used to monitor the current drawn by the fan. If the fan current becomes excessive, then ICl starts turning transistor Q3 off to limit the current through it to a safe value. Finally, the MC3334P is designed to withstand the high voltage transients found on automotive supply lines. The end result is a very reliable circuit. Sensor input The temperature sensor is a standard commerciai unit designed for radiator mounting. It has a negative temperature coefficient which means that its resistance decreases with increasing temperature. At about 100°C, its resistance is about 40Q and this increases to about zson at 2s c. One side of the sensor is connected to the vehicle chassis, while the signal output is connected to the emitter of transistor Ql. Zener diode ZD1 provides a 4. 7V reference voltage which is derived 0 from the +12V rail via two parallel 390Q resistors. The thermal coefficient of this zener diode is close to zero which means that the voltage across it remains relatively constant over a wide temperature range. This fixed 4.7V rail is the supply for the collector resistors of both Ql & QZ. Ql is actually connected as a diode and is included to provide temperature compensation for QZ. In operation, Ql 's base-emitter voltage matches that of QZ's. If Ql's baseemitter voltage increases (due to an increase in temperature), then QZ's similarly increases and the voltage between their emitters remains the same. This temperature compensation is important if we are to obtain reliable MARCH 1992 43 <at> 03 l0.1 5W 0.1 5W ~ 0 0 Q ~-- SHAKE-PROOF WASHER TO CHASSIS Fig.2: install Qt & Q2 so that they are touching each other & mount the 5W resistors slightly proud of the board so that the air can circulate around it. All wiring from the board should be run using 4mm auto cable to ensure an adequate current rating. switching of the fan at a given radiator temperature. It eliminates changes to the trigger point due to ambient temperature variations. In operation, the current through the 4700 resistor, Ql and the temperature sensor sets the voltage at the base of transistor QZ. This voltage is then amplified by QZ which operates as a common emitter amplifier. VRl allows adjustment of the quiescent voltage on QZ's collector and thus sets the trigger point. When the resistance of the temperature sensor goes down (ie, when the water temperature goes up) , it pulls the voltage on QZ's base down and thus its collector voltage goes up . This voltage is fed to the pin 5 comparator input of ICl via a 22kQ resistor and decoupled with a 0. lµF capacitor. The threshold voltage of the comparator is 1.8V on a rising voltage and 1.5V on a falling voltage. This means that the output at pin 7 of ICl goes high when pin 5 rises above 1.8V and low when pin 5 drops below 1.5V. ICl thus provides the necessary hysteresis so that the fan doesn't continually switch on and off at a single trigger point. Pin 7 of ICl is an open collector output and thus has a lO0Q pullup resistor which also supplies current to the base of transistor Q3, a power Darlington. When pin 7 is low, the base of Q3 is pulled directly to ground and Q3 and the fan are off. Conversely, when pin 7 goes high, Q3 turns on and switches on the fan motor, either directly or via relay RLYl. I __ soLDER LUG I ~ CASE ~ Q -._INSULATING BUSHES / ' I SHAKE-PROOF ~--•-WASHERS ~ ., ~---NUTS Fig.3: the MJ10012 Darlington power transistor (Q3) must be isolated from the case using insulating bushes & a mica washer. Smear both sides of the mica washer with heatsink compound before bolting the assembly together. Current limiting is provided by using the pin 8 sense input to monitor the current through Q3. It does this by sampling the voltage developed across the two parallel 0. lQ 5W resistors (via a voltage divider network). This sense input has a nominal threshold of 150mV but it can be anywhere in the range from 120-190mV. When the current through Q3 produces a voltage on pin 8 that exceeds its threshold value, the voltage on the pin 7 output ofICl is reduced. This in turn "throttles" back Q3 to limit the current through it to a safe value. The gain of this control is set by the 4. 7kQ RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 44 No. Value 4-Band Code (1%) 5-Band Code (1%) 1 22kQ 4.7kQ 1.SkQ 510Q 470Q 390Q 270Q 100Q 100Q SW 0.1Q5W red red orange brown yellow violet orange brown brown green orange brown green brown brown brown yellow violet brown brown orange white brown brown red violet brown brown brown black brown brown not applicable not applicable red red black red brown yellow violet black red brown brown green black red brown green brown black black brown yellow violet black black brown orange white black black brown red violet black black brown brown black black black brown not applicable not applicable 1 3 2 2 SILICON CHIP ol SC05204921 0 Fig.4: check your PC board carefully against this full-size pattern before mounting any of the parts, to ensure that there are no defects. resistor between pins 7 & 8. The range over which this current limit can occur is from 5.65-9.57 A, depending on the actual threshold of the pin 8 input. If required, the current threshold can be increased by removing Rl (510Q) ifit is at the lower limit of about 6A but more on this later. The current limit feature is important because the normal starting current for the fan motor can exceed Q3's 10A rating. With current limiting in circuit, the fan motor will start more slowly and take slightly longer to get up to speed before then running normally (assuming direct drive). · Whether you use a relay to drive the fan or drive the fan directly from Q3 depends on the current drawn by the fan. If the fan current is greater than about 6A, then you should activate the fan motor via a relay. This is covered later in the installation procedure. Power for IC1 is supplied via a 390Q resistor and decoupled using a 0. lµF capacitor. This RC network provides sufficient transient suppression to prevent damage to the IC. Construction The Thermostat Switch circuit is assembled on a PC board coded SC05204921 and measuring 100 x 55mm. This is housed in a metal diecast case which also provides the necessary heatsinking for the output transistor (Q3). Fig.2 shows the assembly details. Begin construction by installing PC stakes at the external wiring points , followed by the resistors, capacitors and the IC. Mount the 5W resistors about 2mm above the board surface to allow the air to circulate around them for cooling. Make sure that the IC is oriented correctly before soldering it into place. Install the zener diode (ZD1) and the trimpot next. Note that the zener diode should be mounted with a loop in its cathode lead to provide temperature and shock stress relief (see photo). Mount the trimpot with the adjusting screw positioned as shown on Fig.2. The two BC33 7 transistors are mounted facing one another. Bend the transistor leads slightly so that the top edges of the transistors touch each other. This will ensure that they are run at a similar temperature. Work can now begin on the diecast case. Begin by placing the PC board inside the case and marking out its four mounting holes. You also have to drill a hole in one end of the case for the cord grip grommet plus another hole in one side for the earth connection assembly. The switching transistor (Q3) is bolted to the other side of the case using a standard TO-3 insulating kit (mica washer plus insulating bushes). Use the mica washer to mark out the hole positions, then drill the holes and carefully deburr them so that the mounting surface is perfectly smooth. The PC board can now be mounted PARTS LIST 1 PC board, code SC05204921, 100 x 55mm 1 metal diecast case, 121 x 66 x 39mm 1 temperature switch sender unit (Auto Pace TS6178 from K-Mart, or similar) 1 tapered nut for sender unit, suitable for radiator mounting (available from radiator repair specialists) 1 200Q top adjust multi-turn trimpot (Bourns 3296W or equivalent) 1 cordgrip grommet 4 6mm plated brass standoffs 4 TO-3 transistor insulating bushes 1 TO-3 mica washer 1 TO-3 transistor cover 5 PC stakes 3 solder lugs 3 9 x 3mm machine screws 4 12 x 3mm machine screws 7 3mm nuts 7 3mm spring washers 7 3mm flat washers Semiconductors 1 MC3334P ignition chip (IC1) 2 BC337 NPN transistors (01 ,02) 1 MJ1001210A Darlington (03) 1 4.7V 1W zener diode (ZD1) Capacitors 4 0.1 µF 63VW metallised polyester Resistors (0.5W, 1%) 1 22kQ 2 390Q 1W 1 4.7kQ 1 270Q 1 1.5kQ 2 100Q 1 510Q 1 100Q 5W 1 470Q 2 0.1Q 5W 1 390Q Miscellaneous Heavy duty hookup wire, solder, heatsink compound. in the case on the 6mm standoffs and the earth connection assembly installed. Use spring or star washers under the nuts to prevent the screws from coming loose. This done, smear both sides of the mica washer with heatsink compound and bolt the power transistor to the case as shown M ARCH 1992 45 To mount the temperature sensor, you have to drill a hole in the bottom of the radiator tank to accept the mounting nut. This nut has a spigot & is soldered to the tank using 50/50 plumber's solder. The temperature sensor is then screwed into position & connected to the Thermostat Switch via a lead. in Fig.3. As before , use washers under the nuts and tighten the screws firmly to secure the transistor. Note that plastic bushes are used to insulate the emitter and collector leads from the case, as well as the mounting bolts. A solder lug is fitted to one of the mounting bolts and is used to terminate the lead from the fan motor (or from the relay). Once the transistor is mounted in position, use your multimeter to confirm that its collector is indeed isolated from the case. The various wiring connections can now be run using heavy-duty hookup wire. Don't use light-duty cable; it may not be able to handle the currents involved. The ground lead connects between the solder lug on the case and the ground terminal on the PC board. Make the three external leads long enough to reach the fan, the +12V automotive rail (via a fuse) and the temperature sensor. These three leads 46 SILICON CHIP should be sheathed together in plastic tubing and secured to the case by the cordgrip grommet. Installation The Thermostat Switch should be mounted in a convenient position in the engine bay where there is sufficient air circulation to provide a degree of cooling. We fitted the prototype with angle brackets so that it could be screwed to the side of the engine bay. The temperature sender unit is mounted at the bottom of the radiator tank. This job requires draining the radiator fluid and removing the radiator. A hole is then drilled in the bottom radiator tank to accept the nut for the temperature sender. This nut has a spigot which is inserted into the tank and soldered using 50/50 plumber's solder or preferably silver solder. If you do not feel confident about this procedure, a radiator repair shop will be able do it for you at reasonable cost. Once the job is done, re-install the radiator, screw in the temperature switch sensor and refill the radiator. Now for the final wiring. Whether you can drive the fan motor directly via Q3 or via a relay depends on the current drawn by the fan. Most fans used with 1.6-litre engines or smaller can be driven directly from Q3 without a relay. If two fans are used or the fan draws more than 5A continuous (check the fan rating), then a relay will be required (see Fig.1). Make sure that the relay contacts are rated to take the required current. Note that a diode should be placed across the relay coil to quench any voltage spikes when the coil is switched off. A fuse should be installed between the +12V supply rail and the fan motor regardless as to whether a relay is used or not. This will prevent a fire if the fan jams or if there is a short in the wiring. All wiring should be done using automotive connectors to ensure a professional job. The +12V supply to the Thermostat Switch should be derived via the ignition switch, while the supply to the fan motor (or relay) is derived from the unswitched side of the fusebox (again via a suitable fuse; eg, 10A or 15A). The lead to the temperature sender is terminated using an eyelet connector, nut and spring washer. You should also check that the earth side of the temperature sender is connected to chassis using your multimeter. If it isn't, you will have to earth the radia- . tor to the chassis. The Thermostat Switch is now ready for testing. Switch on the ignition without starting the engine and check that there is a +12V supply to the circuit. The fan should now start if you short the temperature sensor to chassis. Check that the fan runs in the correct direction, so that it blows air into the radiator. If the Thermostat Switch controls the fan directly rather than via a relay, you should now check that the current sensing circuit is set up correctly. To do this, connect your multimeter across one of the 0. H2 resistors and check the voltage across it when the fan is just starting and then when it is running at full speed. If the voltage is less than 300mV at Protect your valuable issues Silicon Chip Binders After mounting the Darlington power transistor, use your multimeter to confirm that its metal case has been correctly isolated from chassis. The transistor should be fitted with a plastic cover to prevent accidental short circuits. start-up and then decreases as the fan gets up to speed, remove Rl (510Q) from the circuit using a pair of side cutters. If the start-up voltage is greater than 300mV, then leave the resistor in circuit. If the fan subsequently does not run at full speed, then ICl is probably current limiting. In this case, you should use the Thermostat Switch to activate the fan motor via a relay. Now run the engine until it reaches its normal operating temperature and adjust VRl until the fan just switches on. At this point, turn VRl anticlockwise by one turn (the fan should turn off). The fan should now come on again when the engine has heated up to a temperature above normal. Now watch the temperature gauge and check that the fan switches off again just before the engine cools to normal temperature. After that, it's simply a matter of making further adjustments as necessary after driving the vehicle. Note that VRl must be set so that the fan always switches off slightly above the normal engine temperature. If you don't do this, the fan just runs continuously after the engine has warmed up. SC These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a distinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. * High quality * Hold up to 14 issues * 80mm internal width * SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11 .95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. Use this handy form l ----------Enclosed is my cheque/money order for $_ _ _ or please debit my O Bankcard O Visa O Mastercard Card No: Card Expiry Date __/__ Signature _ _ _ _ _ __ _ __ Name _ _ _ __ _ _ _ __ _ Address _ _ _ __ _ _ _ __ The Thermostat Switch can be mounted in any convenient location in the engine bay. Don't forget the connection to chassis. . ___________. _ _ __ _ _ _ P/code_ __ MARCH 1992 47 ,H \R \H '.1.rl l.H \R r l H, HI NIG'> ELFCTR ",IC, tc "l::C11' Jl,IC :, t._t-1..., l ·, J''.!l,~ r.Lt:Cl HO\lC~ H.cC 111•)'-,C,c, ,IAYCAR H rC I Rll1\1(,/:, ,AYGAR FLECTR01'1C:-, .JAYl~AH l::Ll::C fHO!'.!Cb JAYGAH l::Ll::C I RO'JICS JA• GAH LLl::G I HO"<!Gb JAY, AR 'LbCTRUNIC', JAY 'Ii JA, CAR ELECTRO'iiC', JA', CAR [LECTRO'lf(.., JA, CAH llc_CTRONICS JAYC,,H t.LcC 1 HO'< Cs JA C:Af1 ,. cicC 1'lONICS JAY Af , f ,;JHO',IC, I\ c R JA, CAH clc Cl HONIC:, A, ,;AR ELECTRCNIC~ ,AYCAR FLECTRONICS JA>'CAR ELECTRO'JICS JAYCAH f L, CT9CI JI( , A v, Af· • · r, TRV·.IG ,f JATl,AH 1:-Ll:::l, I HUN ll,::, JA r LAH clt'"l, I HON IG::, JA, CAR tlf:-CTHOt-JICS JATCAR t U C1hONICS :A 1 CAn t L ...::TPOf~IC JA 1 Af, JA r'CAH C.L!....Cl HONIC'l JA r CAH i::.Ll:.Cl HON IC,-, ..;AYCAR ELFCTHON ICS JAYCAR [l[Cl fiONICS .1A'1CAR ~UC' HONIC,.) JATGAh JA ,c,;1< t , ~ L CTn0\1C' f _t_, TF~O'«C· t, f Cl ROl'.ICr JA CAR tl tCTRONIGc, ,JA CAR ELECTRONICS JAYCAR ELECTRONICS JA', CAR cl CTRONIG', ,;,-, ,.;Afl l"t.'.. l10N,V ,H !::Ll::CT 1 ,R tclf·C' \R t.Lr:crr \R LLf('T ,p ELF T ,R F ~: T \R I ,,Cl \R elf l . ,R ,·1FCT ,H EllCT . ( :.i::_ H .:.r1 . , :..n ' { ..:..~ -I !. L~ C TI ,LECll· EL.FCT FLECT E:LtCT fLFCTHmJIC' ELECTllOl ,!C., ELECTRONICS ELECTRuN ICS l EIECTBONICS l l l l l l l l ;., ,A,r:;,H J,\, C-:AR JAYC-:AR JAYCAR 1 ff FG R0'11r:s F cFC-:TF<O'JIC ELECTflOt-.lCS ELECTRONICS IA Y C A □ F I FCI □ ONlrS IAtCMl ,;.:, i,R ,JAY CAR JAYCAR h F CTRO:-JIC . NIC-:S IA\CAR F Le CTHOI\ICc J/, YCAH cL~C l RONI('> IA\ CAH ELECTRO'<ICS JA\ CAR FU CTHOl,IC , AYCAR t LlCTRONICS JAVCAR E~FCTRON ICS JAYCAR ELECTRONICS JAYCAR ELECTRO'JICS JA '!CAR El I Cl RONICS JAYCAf1 E Lf C' RONICS .JAY CAR ELECTRONICS JAYCAR lltCTRONICS JAYCAR ELECrno,1cs JAYCAR ELECTnONICS JAYCAR ELEC~RONICS1JAYCAR I OYCAR El Fr..T.B.QhHrC:: L:lYCOD r1 i=:CIDOh ll C' l j \CQP kl h-croo~ 1cc 111.,·coo c , c c ro o~ ,c, 101·coo r, rc..,.oo,11c<' FI FCTR f rr ELECTRONICS r, Tf<OI EL FCTRONICS A, CAH E Ll'CT RO' FLECTRONICS JAYCAH ELECTRO! 111.,·c!'I □ c, CCTClf'\h.dCC ,. n I r CJPO' ::cs JIL JIC < JI( JI( Jll 'j~~CAf1 E.~E.C: r1CNICS J/;~c;\HELECTRO ~I CS :11vcARcL!c CTR ONICS JAYC AR lcLtCTRO\JICS JAY CAR ELECTRON ICS JAYCAH ELECTRONICS JAYCAR ELECTRON ICS JAYCAR ELECTHON Ic:; J AYC Ar JAYGIIH Ji•vCAH 11\ , ,AR JA', ;AH .I L L,.:;1 HGcl ll,::, r '...t-C l H01' ICci t Lt-C I f10NICS cLcC THONIC:; JAYCAH J1\YCAR JAYC AH JAYCAl1 tLt-G I HU:" u, FI ,'r 1F10NICS clf-CTHUN IC:; cLEC TRO NICS JAY CAR JAYC AR JAYC AR JAYC AR l:LECT RONICS ELECTR ONICS c LECTR ONICS ELECTR ONICS JAYCAH JAYCAR JAY C AR JAYCAR ELE C TRO\JIC:; ELECTRO\JICS ELECTRO\JICS ELECTRON ICS JAYCAR JAYCAR JAYCAR JAYCAR ELECTRON ICS ELECTRON ICS ELECTRON ICS ELECTRONICS JA YCAR JAYCAR JAYCAR J AYCAR ELEC TRONICS ELEClRON ICS ELECTRONICS ELECTRON ICS JAYCAR JAYCAR JA YCAR JAYCAR ELECTRON ICS ELECTRON ICS ELECTRONICS ELECTRON ICS JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONIC S ELECTRONICS ELECTRONICS ELECTRON ICS l:""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'="""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""'"""':::;i SS JA YCAF J/\ YC /\F NEW KIT - 40 WATT INVERTER KIT S JAYC /\I The Best Passive Infra-Red Detector We've Ever seen .=Li::C" ELEC'" ELEC ::~ EC C:::...ECEcEC FLEC' ELEC ELC:C " ELEC ';- E.L, _l c' EL.'C EL:cr· E- r · ELE cLEC LE CLE< EL~-· cl:' :cLECE'LC:C ' ELEC t:L!="- We have made yet another scoop purchase of an extremely high quality 'National' (Panasonic) Japanese PIR. Quite frankly we have never seen a PIR buill as well. To give you an example. the first amplifier stage trom !he Pyroolectric elemenl is actually buill righl behind the elemenl and housed in a shielded box. This maxim ises the signal to noise ratio and helps reduce tatse triggering. Three lens conliguralions are otfered: 1) Ceiling mount, 360° coverage. This is !he only unit Iha! we know that can do this. t:~~c ELEC ELEC EL::r· t=L.f_(..; ELEC"' ELEC' EL:=CELEC =L:=::CELEC ELcC t:LEC.. - L::v cL=cl=c·EL~C ~L..:. ,. E_FC ::1_:::c::'....cc- S JAY CAf 'l JAY C Af ' VCA f NEW KIT - Adjustable 0 -45V at S J/\YC/\I S J AYCA I S JAYCAI S .IAYCA I S ,I AYCA, S J AYC/1, .f J ,r If If 99 S J /\YCA I B Amp Power Supply Kit $99 Ref SC Jan/Feb 1992 Do you need a really big power supply? One that's big enough to do awaywilh car batteries on your workbench? Well, this is tor you! It's oulpul is adjustable from045V DC and ii can deliver currents up lo 8 amps. Features current limiting, current overload indicator, separate voltage and current me te ring, 13.8Voulpul switch selling and utilising the lalest switch mode design. Kil comes complete with instrument case, toroidal translormer, punched and screened tront and rear panels and all specified components. Cal LA-5030 3) Wall/ceiling mounl, wide angle (80°) up to 16 melre range. Ideal corner mount unit, covers an enormous area. $99 Cal LA-5032 Each uni! comes wilh comprehensive instructions, NG Tamper Circuit, N.0./N.C. alarm output. Power requirement 6-18V DC or AC. Range sensitivity is adjustable which is in keeping with the professionalism ot the unit. These units were used by professional installers tor major building securities. They are not cheap 'toy· PIR's. SCOOP PURCHASE on quality Ferguson 9V DC 300mA plug pack. Ref SC Feb 1992 This compact 40W inverter can drive low power appliances such as shavers trom a 12V ballery. II is Ideal tor use when camping In areas where 240V AC supply Is unavailable, or as par! ol a small solar power installation. Kil comes complete with punched and silk screened tronl panel and all specified componenls. The Jaycar versi on will in actual lact deliver around 60watts. Cal KC-5108 $ $149.50 CatLA-5028 2) Wall/ceiling mount long range. Wil l delect intruders up to 30 meters away, wilh a narrow beam angle. Ideal for hallways, looki ng down rows ot shelving, etc. EcEC S JA'r CAI JAYCA: JI\YCA J 1\YCA JA YCA JN'!'C/\ ., .:> JAYCA . , ,JAYCA ·~ JAYC A S S S _; ., S -, 1\YC,\ $399 CELLULAR PHONE BATTERIES & BATTERY ELIMINATORS Cal KC-5109 HEAVY DUTY HOT LINE FILTER Supplied with 1.5 meters ot cable and lerminales to bare ends. We only have a small quanlity of these and al !his price they won't Ias! long. Be quick! Cal MP-3005 Huge 20 Amp current capacity11 Ideal for high power amplifiers in car audio systems. Virlually eliminates ignition noise via !he positive lead to battery. Complete with capacitor and wiring instructions. Inductance 0.5MH. $10.95 / 1 O+ $9.85 CalAA-3075 Ill Battery Ellmlnators When you are in your car. use your cars power and save your lelephones balleries. Simply slide the ballery pack oul of ttie phone and replace ii wilh the Eliminator. it has a curly cord allached with acigarette lighler plug. B atteries Why not keep a 2nd ballery charged up tor your cellular phone. Youj usl don't know when you may need ii. NEC P300 SERIES Battery Eliminator Cat MP-3116 ;cc- i:c::v FLEC ELEC cLECeLE.: • ELEC re EC , u,c 1 , ELEC' EcEC, E"EC l ELECl ELECl ElcC' EL=r, cLE • S S ;; S .s S .>i $79.95 :s :t.; :0 ~:~6 ~ .JAYC/• ,JAYC 1i J/IYCrJA YCf. ,J/1 , CA J IIYCA ,Jl\ , Cf. .JAYC/ ,JA't"Ci 1Arc; AUDIO SWITCH BOX ~: ~~~,g~ :S .11\YC/ ml ONLV $49.95 I ELEC ' ELEC JA', CA JA CA 1AvCA . .,WCA J/1.. YCA If your amplifier has not got enough inputs, then !his swilch ••· fa'ce willsolveyourproblems. There ---are manycomponenls available now tor HiFi systems including tuner, cassette ~ deck or 2, VCR, CD player Slereo TV, DAT, laser disk elc .. Mos! amplifiers don't have enough inpuls. This audio swilch box has 3 sels ot RCA sockels on the rear tor any three ot lhe above, and one set tor the oulput to the amp. This output lead is supplied with the swilch (2 RCA to 2RCA plugs). There is more inpul on the switch and ils tor awalkman. So, now you can play your walkman through your Hi Fi slereo with a minimumot tuss. The connection lead tor !his is also supplied (3.5m plug to 3.5m plug - stereo). The selector switch has push buttons and once the unit is wired up, all components can be lett connected. Requires no power. Size 138(L) x 29(H) x 39 (D)mm. CalAC-1660 ,~ .,A ,c 1 ;, 1;, , c; :s IAYC, NOVATEL PTR-800 SERIES ·1 MOTOROLA MICRO TAC PT FLIP 500 Battery EI imi nato r cat SB-2312 3110 ,,, . Cat MP-311 2 $59. 95 Cat MP- $ _ 59 95 • ' '~, • iLI HEAD OFFICE SYDNEY· CITY ..:C asterCard. -- VISA PARRAMATTA RHODES BANKSTDWN GORE HILL :~t :~~:~~ $ 4.50 $50- $99.99 OVER $100 $ 6.50 $ 8.00 1 1 ', .,\ v e;, J,\'r(, ;~ :•, c, JA .. , .,;, ., 1,\, c :· ,,.-, Gi l 1 :, •;, 'r; '> ,.,, • ,, .IA·,c, :•, .i,wc, (6V200mA) POST & PACKl~~ 75 1,, ,, A ' (,/ CatSB-2310 6 Leeds Street Rhodes 2138 Telephone (02) 743 5222 FAX (02)743 2066 YCI (.t IA , c, , ., . ;,, .II\ YC $99. 95 $79 95 i iAm :~,s ,JA·-, JI\ ·1 Batter Pack Y Battery Pack :;, Battery E1m nator ,LEC'j;:..:;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;~;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;,.iiimi.;...;.;_~·;_;;. .-:-...;;;;.__ _ _ _ _ _ _ _ _ _ _ __ _ ~~~g S !:-> S S S :s ~lf,YC/ !::.LEC", ~~~g S J AYCA S JAYCA S ,J A\ CA S JAY CA S JAYCA S J1\'1C/\ S J,\ YC/1 S .l,\YC/1 S JAYC.A S .IAYC/1 S JAYC,i S aAYCA Battery Pack (6V 700mA) CatSB-2316 $14. 95 $59.95 MOTOROLA 9800/9500 XL Battery Eliminator catMP•3114 $59.95 Battery Pack CatSB-2314$89.95 E-Ec· E.... EC t-. J AYCAF ,JAYC/lf JA YC Af JA YC Af MAIL ORDERS MAIL ORDER VIA _:;,l.1~ ,iI ,( '. 1J' :i ::~:~; P.O. Box 185 Concord 2137 FREE CALL_ FOR ORDERS ONLY ROAD FREIGHT ANYWHERE IN (008) 022 888 AUSTRALIA (up to 20kg) $13.50 HOTLINE (0 2) 743 6144 144 Logan Rd (07) 393 0777 117 York SI. (02) 2671614 BURANDA QLD Mon-Fri 8.30 - 5.30 Thurs 8.30pm - Sat 9-1 355 Church St (Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 9- 5.30 Thurs 8.30pm - Sal 9 - 4pm Sunday 10am- 4pm 6 Leeds SI (02) 743 5222 Mon-Fri 9- 5.30 363 Hume Hwy Cnr Meredith St (02) 709 2822 Mon-Fri 9- 5.30 Thurs 8.30pm - Sal 9 - 4 - Sun 10 - 4pm 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4pm Mon-Fri 9 - 5.30 Thurs 8.30 - Sal 9 - 4 COBURG VIC 266 Sydney Rd (03) 3841811 Mon-Fri 9- 5.30 Fri 8.30 - Sat 9 - 4 MELBOURNE CITY Shop 2, 45 A'Beckell St Cily (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sal 9 - 2 SPRINGVALE VIC 887-889 Springvale Rd Mulgrave (03) 5471022 Nr Cnr. Dandenong Rd Mon-Fri 9-5.30 Fri 8.30 - Sal 9 - 2 ADELAIDE SA 190 Wrighl St (Cnr. Selby SI) (08) 231 7355 Mon-Fri 9- 5.30 Fri 8.30 - Sal 9 -12 ' .,:::: ~; •, JA . (,1 ~ :~; 2'. :!;~::~: c, , j;.; t'. ;~ JA , , 1A , J,1 , c, c, ~ ~~ ~~; 0 Ji'\Yc, , JA' c, ~ :::~ .JAY c, , AYC , g; ~ ('.i...: •.,_,,,-,-- .,..,...,.,.,,..,---,--,,--,-,--.,..,...,.,.,..,..,,..-,-,,,.,,,-,-,--.,.,....,.,,..,,,,,,.-,--,--,--,--,-..,.,,..,.,,,,..,---,--,-,---------------- - - - - - - - - - - - U~,J/1. YC , 1.. ,U,t1 rLll, I HU ,m ..,;:, J ,U,Y L, ,U,H t:.Lt:.L, HUl'lll, ~ JAYCAH tLtL, I HUNlt.,;::, .J AYL,AH t-Lt.L, I HUJ\,tl.,;~ JAYL,Arl t:.Lt:L, HUl\l 1t., ;::, .JKYl.,/"\M C..L L V i"'IU 1-..1v u -.Jt\ tVM" r Lt 1.., 1 t-; u1~1vS J AY C, ~ICS .JJ-•Yl,,U, J r-Lt-L, I HU·,,m _,:-, ,I-\ .. c~ JIIYCAR ELfCTRO \J ICS JAYCAR ELF'CTRONICS aAYC AR ELE CTRONI CS JAYCAR f lf'CTRONICS JAYCAR ELECTRON ICS JAYCAR ELECTRON ICS JAYCAR ElfCTRONICS JA YCAR lLECTRON ICS JA YC , JI CS J A <CAR ELEC TRON ICS JAY C AR ELEC TRO NICS JAY CAR ELECTRONICS JAYCAR fLECTRON ICS JA YC AR ELECTRON ICS JAY CAR t-Lt-CTRONICS JAY CAR flfCTRONICS JAYCAR f LrC rROt-.lC S JA YC, ~:2~ ~~~2~~ ~~~2!~~~12~ ~~~2~~ ~~~2!~~~12~ ~~~2~~ ~ ~~2!~~~12~ ~~~2~~ ~ I ~2~~~~ 1 2~ ~~~2~~ ~L~2~~~~ 12~ ~~~2~~ ~~~2~~~~12~ J~~2~~ ~~~2~~~~12~ •'.~~2~: :~~2~~~~12~ JAY~, I AMATEUR RADIO 1 BY GARRY CRATT, VK2YBX The AR-1500 & AR-2800: more goodies for scanner enthusiasts The features built into scanning receivers continue to increase so that even the most blase reviewer becomes agog. It's hard to know what the designers will think of next. Here we look at the AR-1500 and AR-2800 scanning receivers fromAOR. Last May, we reviewed the AR-2500 multimode scanning receiver, a full featured mobile or desktop unit which sells for around $1000. Now the maker of that unit, AOR in Japan, has released two new models, a handheld unit and a mobile scanning receiver. They offer full frequency coverage, multimode operation and easy pro- gramming, all at reduced cost to the user. Both units feature 1000-channel memory capacity, full frequency coverage from 500kHz to 1300MHz, an inbuilt input attenuator, and SSE reception through the use of a BFO. Amateur operators will therefore find that both units have a place in the "shack", for use as general-purpose receivers AR-1500 handheld unit The handheld unit, the AR-1500, is the size of a typical VHF or UHF handheld transceiver, and measures 55 x 152 x 40mm, making it pocketsized indeed. This is the first handheld scanning receiver that we have seen which is capable of covering the HF bands. As can be seen from the a,ccompanying photo, the unit is controlled by the user through a 25-button keypad on the front of the unit, and six controls on the top. The BFO, input attenuation, volume, squelch, and manual frequency functions are operated using conventional rotary controls. The keypad is divided into two operational areas: the command section and the numeric data section. The numeric data keys are used to enter receiver frequencies, search limits, memory channel numbers and scan memories etc, while the command keys determine the mode of operation of the receiver. In addition to the standard scanner functions such as search and scan, the AR-1500 offers reception in FM, AM, SSE and wideband FM modes, and allows the user to program channel increments The AR-2800 is suitable for mobile operation. It has almost the same specifications as the handheld AR1500 with the important addition of AUDIO SCAN. This feature automatically re-enables the scan function if the receiver stops for more than a few seconds on an unmodulated carrier. 50 SILICON CHIP frequencies from 144-148MHz, or over any other range, can be searched for activity. Frequencies located in this manner can be stored in a scan memory position for future reference. The AR-1500 is easy to program, has an LCD which is easy to read and can be backlit for low light applications, and has quite respectable sensitivity (0.5µV for VHF and UHF bands). Like all scanners of this type, performance is limited by the flexible antenna supplied. However, connecting an external discone antenna via the BNC antenna socket really makes a big difference to the performance. HF reception was also quite reasonable using a discone antenna. The unit has a scan/search speed of 20 channels per second and produces lO0mW of audio output, which we consider too low for mobile use. The AR-1500 is controlled by a 25button keypad on the front of the unit & six controls on the top. The receiver has 1000 memories, covers from 500kHz to 1300MHz, & operates on FM, AM, SSB & wideband FM. between 5kHz and 1MHz. The receiver can also be instructed to stop scanning or searching once an active channel is located, or to continue scanning after a 2-second delay. It is also possible to lock out any memory channel, and also to monitor any nominated frequency, using the PRIORITY mode, while searching or scanning other banks of frequencies. The receiver memories are arranged in 10 banks of 100 channels and any of these channels can be nominated as the priority channel. This allows groups of frequencies to be allocated to the same memory bank. Thus, all 2-metre repeater frequencies could be entered into a particular memory bank and all UHF repeater frequencies into another. Scanner enthusiasts might also like to collect all frequencies used by a particular service (eg, airband, etc) into a single bank. Apart from the 10 scan banks (where user selected frequencies are stored), there are also 10 search banks. These banks allow the user to search between two frequency limits. Thus, all AR-2800 For enthusiasts who prefer mobile operation, the AR~2800 may be just the answer. This unit has basically the same specifications as the AR1500, with one important addition AUDIO SCAN. This function is used when unmodulated carriers are found in either search or scan operation. Normally, a scanning receiver without audio scan will stop on an unmodulated carrier until it is manually reset by the user. The AR-2800 overcomes this problem, as the audio scan feature automatically re-enables the search or scan function after a few seconds of reception of an unmodulated signal. For mobile use, this is quite a valuable feature. We also found the frequency stability of the unit to be very good. This is an important quality when selecting a receiver for SCPC satellite reception. The unit is supplied with a DC power cord, mounting bracket, AC adaptor, desk stand, and surprisingly easy to read instructions, considering the country of origin. In summary, the AR-1500 and AR2800 offer good value for money and are somewhat easier to use (and less expensive) than the AR-2500 scanner we reviewed last year. They are priced at approximately $800 (incl. tax). This price includes the AC charger and the nicad batteries supplied with the AR1500. Both units are imported by Access Communications and are available from Dick Smith Electronics. SC A IN plastic case, pushbutton sMtch, tettEms ,rd battery holders and of oourse too la9er di:x:lereEd. Blaythro \OJ reed to ma<e a HGH QU.AJJlY LASER DIODE a-e 12" U\M:RSl'J... LASffi ~ aFR..Y /qf. Erd lWJ RD l.A.':ffi Tl.8:S: Cre 1rrW U:a, m::I a-e l"tj1 cµty 3'Tw 8:Ml\S - 11..te. Tu, 1LJ::ea ae um b.i t-e.e pn; di>~ 0J>Al'NlcID lhl ~ ssl te 931'8 m p,- ar WiJ1 a:fs, b.i ts rrcm 'tO.J o>N a--o::EE lO E£9.ffiID\MlH lWJ 71--E 3vWTL.8:S l\6100 CNc 1rrWtte. m::1 CNcarw a= a= R::NTTR.a:aGJ\60-iT , FffiA lDT/ll FFCE a= $145 lLE!3 ll-'AT'SA Bt>A:Wsl I NINI INRIA 1B NICHJVIWER As per EA Oct 91 Issue. A very ,rnal carplete l<lt that Includes a lens a IR tube and an eyepiece. These were removed from rew, end nee,- reN Gerrrm rjglt -...sb1 equpment. SfT'ple to oonstruct. The kit Is ro,; St.Pp/loo with a Hgh qualty miltay Dra,;s mi-/ 20'nA from a 9V battery. Not oni-/ at the LOWEST PRICE OFFERED, but we hcude a Rff R..TER. ~· A us , but guaranteed ARGON LASER HEAD. It needs fen cooling, 2V at 25A tor too fl~ent, and 11 OJ at about 8A for the tube. All this to produce rrae tt-B1 1rorw al B...LE BEAM II We provide a ample rn,,,a- suAC>Y circuit , and we w ill suggest suppliers of a suitable ta:rcidal tra,sbmer, Creek scpplles befae orderrg, at a, RW-15. L.MfTED STCICK. ll'#RA RED BINOCUUIR VEWBI Hg, qualty, t-emet mcunt ex-military binocular IR VE11V91'.S..fpcwerecbya sroie 1 ,5v battery, Paci<ed In or~lna flbreolass carry case . l.mted qcmtlty at a, I\CREDB..E PRCE al: ONLY $649 I\Cf1EDB.E FHCEOF: $800 $299.00 Includes too IR tube, lens, eyepiece, electrmlcs l<lt a 75rrm ra.rd R plastic filter end the case kit. Kit No. $149 FatreNr;p:,J-ea::lmi-f A t'Q1 quallty, motay ga::ie, deep Infra red (R) filter. Fa medium end high power hcmdescmt spdi;j)ts a,d floodlights. Appra>dmately 13:lrm diEmetef ,rd 6mm thick. High temperature Pyrex-Glas base material. Excellent for night surveillance equipment! Wa:l<s wel with IR VE\/V91'S ird oome IAcJeo equprmnt. On SPECII\L at $55 GUSSPIISMS Prec1srn 11as9 i:r\9111 asse<Tdles. Were a:'r;j,dy used 1o fa:m a persccpe In a tank l.r. MV\llltlon system . Their ~na pica would ha-e been a-ourd 1CXXJ dolla-sl The two glass prisms can be removed from toolr holding asserrbies. Mae a ri\11 qualty perlscqJe er use n optlca systems . A must fo- persms Interested In h~h qualty cµlcs. $19 hlii LCD IISPlAY MODIIES qualty, ri\11 cmtrast , ap'1mJrmrc Lal display modules Surface mounted control circuitry Is hducled. 5v op9lll!la, ,rd very bN '{XJNff =-sun~. nbmatb'l hcl.Jded. Offered at a very S'T18I fractm al their Brird reN roo \ace: m 16 era-acter by 2 roo:Jue (16 x 2), wth tackll11tno:.. """""" " """"'$22,50 24 Cra-acter by 2 m cisp<lf module (24 X 2), wth tacklli1tno:.. .. .............$35.CXl 16 Cra-acter by 2 Ire dlspay roo:Jue (16 x 2), wltrout tacki111tno: . . .. .........$16.CXl 24 Cra-acter by 2 Ire dlspay roo:Jule (24 x 2), wltrout ~ t n g: ' ".$27 ,(X) Bacld\titro n1.erter l<lt 1s a1so - - $15 Some of the above items are in LIMITED SUPPLY ANY OR AS MANY ITE MS FROM THIS LIST DELIVERED BY SKVROAD EXPRESS TO YOUR DOOR : $10 OATLEY E;LECTRONICS PO BOX 89, OATLEY, NSW 2223 Telephone: (02) 579 4985 Fax: (02) 570 791 O Certified p&p: S6 in Aust. NZ (Airmail): $10 Melbourne Distributor: Electronics World (03) 723 3860 or (03) 723 3094 MARCH 1992 51 COMPUTER BITS BY JENNIFER BONNITCHA How to cope with damaged directories & file allocation errors Continuing on with troubleshooting tips for your PC, this month we look at problems such as non-DOS discs, damaged directories, allocation errors and invalid clusters. Each disc used by DOS must first be subdivided into tracks and sectors. You can think of tracks as a series of concentric circles covering the disc surface (Fig. l). The tracks are numbered from the outer edge to the inner edge as track 0, track 1, track 2 and so on. Additionally, discs with more than one side have their sides numbered, starting with 0, then side 1. Finally, tracks are divided like pie slices into sectors, starting with sector 1, then sector 2 and so on. Typically, sectors have a storage capacity of 512 bytes. You can work out disc capacity with the following formulas: (1) No. bytes per sector x No. sectors per track= no. bytes per track; (2) No. bytes per track x total no. tracks = disc storage capacity Sector 7 Sector 3 Fig.1: how a computer disc is divided into tracks & sectors by the FORMAT procedure. SILICON CHIP Disc formatting Tracks and sectors are constructed during the disc FORMAT procedure, which also places a copy of the DOS boot record in sector 1, track 0, side 0. This record has a table containing information about the disc and machine language code that loads two system files into memory. Format also constructs the File Allocation Table (FAT) and the file directory. The file directory is just like a table of contents for a disc. Every file on the disc has a corresponding entry in the disc's file directory; each entry is composed of 32 bytes which in turn are partitioned into 8 fields. Finally, each of these 8 fields contains information used by DOS in file management, such as a file's name, extension, time and date stamp, starting cluster, etc. File allocation table Sector 8 Sector 1 52 Hard discs consist of one or more platters, each with two surfaces. These platters are also divided into tracks and the tracks into sectors. All tracks with the same radius form a cylinder through the platters. Note, however, that the layout of hard drives varies according to the manufacturer and disc capacity. While the disc directory tells you which files are present on a disc, the FAT tells DOS where a file's contents are actually located. DOS divides each file's contents into clusters which are numbered according to their physical location on the disc. The first cluster starts with the sector immediately following the last sector of the file directory; the second cluster follows the first and so on. An invalid entry for the FAT is a cluster number that points to a non-existent cluster on the disc. The entry is either 1 (which is invalid since DOS starts with entry 2 on the disc) or a number higher than the number of clusters for the disc. Without the FAT, DOS would be unable to access any files. It is so important to the running of your computer that a second copy is stored on each disc. Should you experience an Invalid Cluster message while running CHKDSK, you can be reasonably sure it is the result of an unexpected system shutdown or a poorly behaved program. You can expect to see one of two messages from CHKDSK if this is the case: <filename> First cluster number is invalid, entry truncated; or <filename> has invalid cluster, file truncated In the first case, the starting cluster number in the file's directory entry doesn 't make any sense since DOS doesn't know where the file's chain is in the FAT. The second message indicates corruption in the FAT file chain at the point of the invalid cluster. In either case, DOS determines that the file's entry in the file directory indicates that the file is larger than the amount of disc space allocated for it in the FAT. The errors typically occur during an update operation, so you could try using a backup of the fil e (which will be out-of-date but intact), or you could try recovering the file . You have some chance of manual repair, provided you do not use CHKDSK/F. The IF switch in this instance truncates the file at the invalid cluster number so that its size matches the allocation specified by the FAT. The part of the file beyond the invalid cluster is then lost. Recovery, while not impossible requires some luck and a good knowledge of both DOS and the FAT. If you are desperate, try a disc-sector editor such as the Norton Utilities and follow the associated instructions. The general idea is to change the wayward entry to point to the next cluster of the disc. More orphans CHKDSK may report orphaned and invalid clusters within the FAT. Usually the orphaned clusters belong to the file whose FAT chain is broken. You should run CHKDSK/F and convert the lost chains/clusters to files then examine each of the files created by the procedure. If the information is worth saving, use the copy command: COPY <filename>+FILE000l .CHK+FILE0000.CHK [d:}<filename> IB The /B switch causes COPY to treat the file(s) as a binary file. If a file is to be copied, this switch tells COPY to copy the entire file based on the size stored in the file directory. If the file is to be a copy, the switch tells.COPY not to place an end-of-file marker at the end of the file. Examine the result of your file concatenation command then delete the CHK files created by CHKDSK, together with the originally suspect file. Should you get a message indicating an invalid starting cluster, DOS has lost track of the entire FAT chain(s) for the file. Chances are good that the chains still exist on the disc. Once again run CHKDSK/F to truncate the file and generate a series of CHK files containing the orphaned clusters. Once again examine each of the CHK files and try to piece together the file. Allocation errors Inconsistencies between the file size in the directory entry and the number of clusters allocated to the file in the FAT produce the following message: <filename> Allocation error for file, size adjusted As a general rule, the file's information has been successfully written to the disc; the problem is simply that the file size in the directory entry is too large or small. Although serious problems seldom occur as a result of this procedure, you may find some extra information at the end of the file in question. Possibly some information may be deleted which will cause the program using the file to object. Finally, ensure that the allocation error is for a file. Should CHKDSK report this error for a directory, you may be in serious trouble. A good starting point once again is the Norton Utilities' Disk Doctor. The program is menudriven and easier to understand than CHKDSK; it will diagnose and repair many logical and some physical disc problems. While there are certainly other programs which will help with these problems (MACE Utilities, PC Tools, etc), Norton Utilities is my personal favourite. Any one of the utilities is a good investment for all computer users. Non-DOS discs From time to time, you may receive the following message, even when you have previously used a disc: Probable non-DOS disk Continue (YIN)? CHKDSK checks each disc to make sure it is a DOS disc , since it has the capability to alter the information contained therein. By examining the first two entries of the FAT (where the media ID is stored) and the second sector of the disc, CHKDSK can determine the disc's status. If the media ID byte is invalid, CHKDSK reports a potential nonDOS disc. In this situation, it's possible that the disc is either unformatted or has been formatted under a different operating system. If you get this message periodically, you may have a program or hardware problem which mangles the FAT. Once again the disc editor can repair the damage - compare the two copies of the FAT, then correct the media ID byte and write the sector back to the disc. Directory errors All subdirectories have two entries placed when the directory is created - the "." (dot) and" .. " (double dot).· The single dot entry designates the parent of the current directory while the double dot is the current directory. Should CHKDSK report that the "." or " .. " entry has a bad attribute (or link or size), the first or second subdirectory entry is defective. The only DOS attribute usually set to ON for a subdirectory is the directory attribute. If CHKDSK reports a bad link, the starting cluster number for the directory is incorrect. Badly behaved programs can cause the special subdirectory entries to have problems with their file attributes, size or FAT linkage. Run CHKDSK/F to repair most of the above problems, provided the parent directory is undamaged. If the parent should happen to be damaged, CHKDSK will display more warning messages. You may get the following: Processing cannot continue Unrecoverable error in directory Convert directory to file (YIN)? The first message indicates that the disc structure may be so badly damaged that CHKDSK is confused. Respond "N" then try re-booting DOS and run the command again. If you continue to get the message, try to back-up the disc then run CHKDSK/F and convert the subdirectory to a file. However, in converting the subdirectory to a file, all files in this and subsequent subdirectories will become orphaned clusters. You could try to rebuild the files you did not back-up or delete the subdirectory and files , then use a previous back-up. SC MARCH 1992 53 SERVICEMAN'S LOG VCR tape transport problems I suppose that it's inevitable that a device like a video recorder, with its complex tape transport system, would have more than its fair share of mechanical "funnies". Some day, no doubt, we will have all electrical recording systems, with no moving parts and no need for service. (Oh yeah!) In the meantime, from the real world, here are a couple of VCR stories involving transport problems. The first was a Sharp VC-9300X from one of my regular customers. It came in with the stated fault that it would -load a tape but refuse to play it. Transport problems can take many forms and the word "play" is often used quite loosely by some customers. Sometimes they mean it literally and sometimes they mean that the tape will load but not rewind (ie, if the tape is partly used when loaded) . Or they can mean that it will load but not fast forward , or that it will load, start to play, and then foul up and chew the tape. Getting the true picture can call for some tact. Fortunately, there was no real confusion in this case. The owner's description was correct; it would load but not play. However, it could fast forward and rewind normally. A visual check with the covers removed showed that it was attempting to function in the play mode but was forming a loop of tape. Idler wheel assembly Most transport problems, including those mentioned above, can be traced to the idler wheel assembly; an arrangement which, with minor variations, is used on most machines. So, when trouble strikes, it is always replaced as a routine first step. Even if it proves not to be the trouble, it is a worthwhile service for any machine more than a few years old since the component cost is quite low. The loop of tape is a classic symptom. If the idler mechanism fails and deprives the take-up reel of drive, the loop of tape forms until the take-up reel sensor informs the microproces- TETIA TV TIP AWA C620 (G chassis) Symptom: screen shows a small, bright raster, with all four sides curved inwards. There is no sign of convergence on the screen. The bottom edge of the picture shows severe vertical foldup and the whole picture is covered with flyback lines. Cure: In spite of the complex nature of the symptoms, the fault is quite simple. It is caused by the loss of 54 SILICON CHIP the 150V rail. The usual reason for the loss of this rail is that D575 (UF2) goes short circuit and takes out safety resistor R581 (4.?Q 0.5W fusible). A DYX55/600 makes a good substitute for UF-2. TETIA TV Tip is supplied by the Tasmanian branch of the Electronic Technician's Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, 7015. sor that the take-up reel is not moving, at which point the system shuts down. And so I changed the idler wheel, noting as I did that the old one was looking rather tatty and really needed changing anyway. I also went over the system with the torque gauge. The fast forward and rewind torques read 800gm plus, which was well within tolerance, as was the take-up reel torque in the play mode at around 175gm. But all this was cold consolation when I tried the machine again and it behaved exactly as before. It was only then that I took a closer look at what was happening and, in particular, at the exact nature of the tape loop. And what I saw was something which, in theory, couldn't really happen; the tape loop was forming ahead of the capstan. This should not happen because there is nothing to propel the tape at this point in the transport system. Nothing in theory, that is. What in fact was happening was that the capstan mechanism had failed and the tape was being propelled by friction from the drum. So why had the capstan failed? The most likely possibility would normally be a broken capstan belt but this was clearly not the case. What's more, if it had been simply slipping, there should have at least been some propulsion, however erratic. Well, the short answer was that the capstan shaft had completely seized in it's bearing. The capstan shaft and flywheel assembly is held in place by a thrust bearing on the underside of the flywheel. This in turn is mounted on a short bar held by a couple of screws. Removing the screws and the bar allowed the capstan assembly to be gently worked free in the bearing and then withdrawn. The best way to describe the shaft · was that it was "gummy"; apparently as a result of the original lubrication having dried out. This is the first time I] -. - J.. G .. Cc • 0 g;i......., • .___ MOS, 1"'MN~'PORT 'PROB>LE:.MS ;.._,CAN Bt:: "'1""-RACt;:.1) ,-o fHE:: \t)LE'.-1<- W\-\E.E:L ~'SSE.t•l\"BL'Y ------P..'S USE:P ON MOST t-1\f:\C'r\lNE.S~•• I have encountered anything like this and just why it should have happened is something of a puzzle. Was it the original lubricant but which, for some reason, was incorrect (did someone used the wrong oilcan)? Or had someone been there before me and used the first lubricant that came handy? Fortunately, there had been no actual damage to the shaft or bearing. I cleaned them up, re-lubricated them, and put everything back together. And that was all it needed; everything functioned like new and the machine was returned to the customer. That was several months ago now and there has been no word from the owner since. Another Sharp The second machine was another Sharp, a VC-782X, which came in quite recently. In this case, the fault was quite erratic and much more subtle. This particular VCR belonged to one of my long-standing customers, although the machine had not been serviced for about four years. The lady of the house dropped it in and gave a fairly detailed description of the fault. According to her, the machine would play normally for most of the time but every so often it would go into what she described as the "pause" mode. And to back up this description, she had brought in a tape on which this fault appeared. At the first opportunity I connected the machine to a monitor and played the customer's tape. It ran for about an hour before anything happened and then it was so fleeting that one rieeded to be quite alert to notice it. In fact, all that I could be sure of was that there was a glitch of some kind in the sound. I continued playing the tape and, towards the end, it was misbehaving quite frequently. Sometimes it was quite brief; similar to the effect described above. At other times it was much longer; it would pause for two or three seconds , five seconds, and close to 10 seconds on one occasion, but never longer than this. During these longer periods, when I had time to look at the screen, there was a stationary image, with noise bars and some jitter and, of course, no sound. Two aspects of the problem had me stumped at this stage. By what mechanism could such an effect be recorded on the tape, as the customer had implied. Indeed, was the fault really in the record mode, or was it only present during playback? In an effort to clarify this point, I took the customer's tape and put it in a known good machine, selecting the last part of the tape where the fault had been the most obvious. Unfortunately, the results were, as they say, inconclusive. There were still some glitches but they were not as frequent as in the previous run. Nor could I be sure that they all occurred in the same parts of the tape, which made things rather confusing. One problem with tests of this kind is that it is seldom practical to sit down in front of the monitor and give it one's undivided attention for several hours at a time. In real life, such tests have to be made while routine jobs are being handled. But had I been able to give the setup my undivided attention, I may well have learned something more about the fault and tracked it down sooner. But that's with the benefit of hindsight. As it was, it did seem that the fault was common to both the record and replay modes. At this stage, I decided to try one more trick. I turned the customer's machine on again and loaded it with a known good tape of my own. Well, I thought it was a good idea but, after three hours without so much as a flicker or a click, I was more confused then ever. In desperation, I rewound the tape and ran it again. And at last I achieved some kind of result; after another two hours ofrunning (a total of five in all), it suddenly went into fault condition, coming up with several pauses, one after the other. It was relatively severe in terms of frequency, although the effect was quite brief - only a few seconds - in each case. Our loss i your gain Fracarro's ESVU2. The really low loss VHF/ UHF mixer with areasonable price tag. Peter C. Lacey Services Pty. Ltd. P.O. Box 678 (74Fulton Ad.} Mount Eliza 3930 Tel:03 787 2077 Fax:(03) 787 3460 ACN006893438 MARCH 1992 55 Video Recorder Faults Well, th at confirmed that the trouble could occur in th e replay mode, while my previous checks had indicated that it could also occur in the record mode. And of all the functions which were common to both, the transport system was the most likely suspect. But an other thought had emerged from all these tests; it w as possible that the fault was temp erature conscious an d appeared only after th e machine had been running for som e time. But w hat was it? As already mentione d , my favourite susp ect is th e idler wh eel, although I was h ard put to rationalise this with all the observed symptoms. Nevertheless, I decided to ch ange it; after fo ur years, a new one wouldn't go amiss. Which is what I did . I th en ran th e known good tape through it again an d it behaved perfectly - as it did a second time , and a third time, and a fourth time. In all, it ran perfectly for close to 12 hours , from when I started in the workshop early in th e morning until I gave it away in th e late evening. Had I fix ed it? I would have liked to have thought so but I wasn't prepared to believe that on such evi den ce . So I put the machine through anoth er sequence of tests , this time alternately recording and replaying th e tape on a 3-hour basis. And the prolonged running did eventually pay off; the fault returned. But this time I was a ju mp ahead; I had removed the bottom cover an d turned th e machine on it's side so that I could observe its beh aviour from both the top and the bottom. So when it started to play up this tim e, I was ready. And I soon had the answer; by observing th e flywheel I cou ld see that the cap stan was stopp ing briefl y whenever the fault occurred . Well, that was a major breakthrough, even if I still h ad to find out exactly why. My first suspect was the capstan motor; did it have an intermittent fault? I managed to get my finger onto it, so that I could feel it running. An d that cleared it; it was still running when the system baulked , with th e belt slipping on the pulley. That left only one possibility in my book. I pulled the capstan/flywh eel 56 SILICON CH I P assembly out of its bearing and examined it closely. And there was th e faint brown stain signifying the same gummy substance that I had found in th e other Sharp machin e s everal months previously. Only this time it wasn 't bad enough the stop the shaft permanently; just briefly and , I suspect, when the temperature rose after prolonged use and th e metal expanded. And n ow, w ith hindsight, the symptoms I h ad observed began to make sense - not that this was much use now, although it might help in the future . But had I been able to give the screen my undivided attention, I would have seen that there were two quite diffe rent effects . Wh en the capstan jammed in the record mode, several seconds of recording would be lost, causing a jump in both m ovement and sound on playback, exactly the same as the effect caused by chopping several frames out of a p iece of film. It was quite fleeting and I only ever observed the sound discontinuity; by the time I looked to the screen, it was all over. In fact, depending on just where this happened in the program, it could even sometimes go unnoticed. But when the capstan jammed in the replay mode, the effect w as quite different. We now had a froz en frame, exactly as in the pause mode and, of course, n o sound. So it w as all very easy to explain in hindsight. But they were very deceptive symptoms at first en counter. Letter from NZ And n ow, for a change of scene but not the subject - here are some comments prompted by a letter from a reader, Mr K. M. of Silverstream, New Zealand. It is reproduced - in slightly edited form -in the accompanying pan el. I suggest that you read it first. There w ere three other pages accompanying this letter. One was a copy of a letter to the service company, complaining bitterly about the failure of the company to provide adequate service and solve the problem. The oth er two - amounting to a little over one A4 page of typed material were copies of the machine's fault The attached fault record and my response to a service com pany here in NZ details a number of problems I have had with my video recorder. Would you consider forwarding it to the Serviceman, perhaps for any comments he may care to make. (He may ignore it, or use it in the column if of any use) . I ran out of time on the last fault (intermittently failing to load) and I feel let down by the particular service company, who virtually ignored al l the information I provided them and didn't adopt the right approach , or make any real effort to locate the fault, or substitute any parts! I have regularly admired the SILICON CHIP serviceman 's perseverance on "the dreaded intermittent" and, "sure as eggs", the fault on my machi ne wi ll be back! I neither expect a "free fix", or a "remote fix", but the Serviceman probably knows off the top of his head the likely causes (ie, parts which could be swapped or substituted) of the fail ing to load fault, or possibly the whole series of faults. The faults may make the basis of a segment in the column, if the Serviceman knows what may cause such a sequence of faults. The machine has always had the intermittent quirk of sometimes not recording on timer record. Probably it didn't load and the micro shut it down . K. M., Silverstream, New Zealand. h istory which went to the service company. Unfortunately, space does not permit reproducing all this but I will comment on extracts from it as I proceed. Mr K. M. 's probl ems ar e best divided , initially, into two categories : the purely technical problems, on which h e has asked m e t o comment , and the problems w ith the service . organisation. Let's look at the technical problems first . The machine is a National/ Panasonic NV-85 0 video recorder. This particular model first appeared about eight years ago and was one of the first with stereo sound recording. I am happy to offer any advice or suggestions which I can but, as can b e appreciated, at this distance that is all they can ever be. If they h elp, that's fine. The machine appears to have suffered from three separate faults. The first, according to K. M. , has always been present; an intermittent failure to record in the timer mode. The second apparently occurred after a mains supply failure and was traced , by K. M., to low 5V and 12V rails. The 5V failure was traced, in turn, to an open circuit ¼ W fusible resistor, R1001, in the 14V rail, which supplies the 5V rail. Failure of the 12V rail presents something of a mystery; and in more ways than one. For a start, there are two 12V rails in this model, both derived from the same 18V unregulated rail but otherw ise quite separate. It is not clear from K. M.'s letter which of these two was involved. More importantly, th e cause of failure ap pears not to have been found; it apparently came good spontaneously after an ohmmeter check for a short circuit. K. M. suggests that the ohmmeter voltage performed some kind of "bootstrap" function. The third fault , and the one for which the machine was submitted for service, was intermittent failure to load a tape. For a number ofreasons, I will comment on this fault first. K. M. made a number of observations regarding it, which he set out in the screed to the service company. I quote in part: "The loading cycle commences OK , with the tape extracted and wrapped around the drum. However, the capstan roller, which is operated (held) by a spring but released by a mechanism driven by the lower loading motor, does not engage the tape and capstan. The problem appears to occur when the machine is w arm. "I replaced the capstan belt, with no effect. My pick would be to replace the load motor belt but I don't have one. In fact, I replaced this about tw o years ago". Well, that is a n ear perfect description of a classic fault. An d, ironically, it is almost certainly due to a belt failure - the very belt that hasn't been ch anged. The condition of this belt is quite critical; it needs only a small deterioration in order to produce exactly those symptoms. In sh ort, if a machine turned up on my bench with those sym ptoms, the first thing I would do would be to change the belts. And I used the plural there deliberately; I would order a complete set of belts and replace the lot. Th ere is n o room for mucking about w ith belts; once on e gives signs of trouble, th ey sh oul d all be changed. The material cost is small - relative to any service charge - an d it might as well be don e wh ile the machine is open. And it minimises the risk of another failure in a few months time. I ch ose to comment on that fault firs t for a couple of reasons. One was simply because it appeared to be the one with the most obvious explanation. Another reason was that K. M. advanced the theory that the fai lure to record on timer was due to a failure to load. I don't totally subscribe to this theory - although it can't be ruled out - but if it is valid, then replacing AUSTRALI AN MADE TV TEST EQUIPMENT 10% discount on all test equipment. 15% discount on two or more items. Built-in meter to check EHT transformers including split diode type, yokes and drive transformers. $78.00 + $4.00 p&p TOROIDAL TRANSFORMERS Built-in meter reads positive or negative voltages from 0-S0kV. For checking EHT and other HT voltages. $98.00 + $5.00 p&p Strong magnetic field. Double insulated for your safety with momentary switch operation. 240V AC 2.2 amps. As important as a soldering iron! $75.00 + $10.00 p&p Designed to test infrared or ultrasonic " contro l units. Supplied with extension infrared detector lead. Output is via a LED and piezo speaker. $84.00 + $4.00 p&p _,, ,.__.---~ = ~ _-::,::--,-'7:·--J'J'+-"v"' -~ 2 TUNER REPAIRS ~ pFf~;1p!~; ~xpc~~~ge -~ Cheque, Money Order, Visa, Bankcard or Mastercard 216 Canterbury Rd, Revesby, NSW 2212, Australia. Phone (02) 774 11 54 Fax (02) 774 1154 • • • • Now made in Australia Standard range ~ SVA to 2kVA Large ex-stock quantities available Competitive pricing available fo r OEM s & resellers • Simply the best transformers all round HARBUCH ELECTRONICS PTY LTD 90 George St, Hornsby, NSW 2077. Phone (02) 476 5854 Fax (02) 476 3231 MARC H 1992 57 SERVICEMAN'S LOG - CTD the belts may kill two birds with the one stone. So what is my theory about the timer mode recording failures? My first suspect would be an intermittent - probably a dry joint - on the timer board or the timer operations board. The timer board is on the right hand side of the machine, immediately behind the clock, lying flat under the main cover, and readily accessible. The timer operations board is on the front of the machine and carries the clock display. Having said that, I must concede that finding the actual fault is not likely to be easy. But that would be the first place to look. That brings us to the original power supply failure. Once again, the failure of R1001 is a classic fault. Another common offender in this area is Cl 101, a 3300µF 16VW electrolytic on one of the 12V rails. C1103, another 3300µF electro, rated at 25V, on the 18V rail can also give problems. In view of the rather dubious cure of the 12V rail failure in this power supply, I would suspect that Cl 101 might be intermittent (I am doubtful about the "bootstrap' theory). Well, those are the three faults, dealt with as best I can on an individual basis. Of course, I could be wrong; but those are the best suggestions I can offer at this distance. I hope they help. The service company So much, then, for the technical problems. What about K. M. 's other problem; the quality of service provided by the service company? This is even more difficult to evalu- 58 SILICON CHIP ate, at this distance, the more so because I have heard only K. M. 's side of the story. Nevertheless, his complaints would seem to justify some comments, at least of a general nature. It would be unfair to identify the company concerned, although a colleague who visits relatives in NZ, tells me that they are a large organisation, with several branches throughout the country. So what exactly is K. M. complaining about? As he sums it up in his letter to SILICON CHIP, "I feel let down by the particular service company, who virtually ignored all the information I provided for them, and didn't adopt the right approach or make any real effort to locate the fault or substitute any parts!" In greater detail, it appears that K. M. submitted the machine and, as he puts it, "had gone to some trouble to detail not only the current fault (it intermittently wouldn't load) but also previous faults which had recently occurred" (the above-mentioned two pages of fault history). He complains that, in spite of this, he had to ring the company to explain the nature of the fault and that the booking clerk wanted to reduce the complaint to one or two words; suggesting "no colour". Several days later, he rang and asked to speak to the technician but he was not available. He rang again three days later but; again, he was not available. The technician was finally contacted another two days later and reported that he had been running tapes through it regularly but could find no fault. At this K. M. protested that this was no way to find a loading fault and suggested that it be put through a series of loading sequences. This the technician agreed to do. Two days later, he again contacted the technician who told him that he had been unable to create the fault. So K. M. elected to take the machine back. The firm then submitted an account for $33.00. And that is, of necessity, a condensed but, I fee l, fair summary of the situation. What went wrong? So what went wrong? Lack of communication , basically. And who was to blame? Both parties, to some extent, but the major offender was the service company. They are suffering from an attitude which has been with us for almost as long as there have been servicemen but which I had hoped was dying out. Unfortunately, my colleagues assure me that it is well and truly alive and kicking. I refer to the isolation syndrome; the barrier which such organisations erect, doubtless on their accountants' advice , between the customer and the technicians. It is apparently based on the concept that nothing must be allowed to interrupt the smooth flow of production line servicing. So the customer is greete d by a non-technical booking clerk, arined with a set of stock phrases which are supposed to cover all the likely faults that a piece of electronic equipment is prone to. There is no provision for the multitude of way-out, never-heard-of-before, faults which, as any serviceman will confirm , are par for the course. And the word "intermittent" has never been heard of, or is too hard to spell. Hence the ridiculous situation where the booking clerk wanted to classify K. M.'s problem as "no colour", when this was as far from fact as it could be. Accountants & ivory towers But this is something which the accountants , in their ivory towers, cannot appreciate. Suggest to them that they should employ someone with some technical knowledge as a booking clerk and they would scream , "too expensive. Can't afford it." The truth is, they can't afford not to if they value their reputation. This sort of communications barrier is the main cause of ineffective service , misunderstandings , customer complaints , and, ultimately, protests to the Consumer Affairs Bureau - to say nothing of the w ord-ofmouth publicity which can be so damaging. And this is where the one-man organisation , with its sympathetic, face-to-face approach to his customers , leaves them for dead. OK, so much for the company's faults. What di d K. M. do wrong? I think he tried too hard. Probably in anticipation of the problem I've just discussed, he tried to make sure that he presented every fault detail, past and present. And I suspect it was too much; that the technician had difficulty in differentiating between past and present faults and finally tossed the whole screed to one side. Granted, a well run organisation should have been able to cope. But they didn't. And, finally, I feel that the technician should have been prepared, and been allowed, to pursue the fault for longer than two days, after it was clear exactly what he was looking for. I would certainly want longer than that. And that's about all I can say, looking at it from this distance. SC Electronics Workbench® • C . 0: ..... :_ ' 0 ii i. ;. - ---, - - -- '., ].,.: I• - - ~ T~, ..... . . [!;] =~--'_-,_:-~ _;.. ........ _ _ ___, I : .I j uU" N" c. j - --"------------ , 0 , 606606 66 "'"" r:;;-_ Build and simulate both analog and digital circuits, complete with simulated instruments on your computer! FEATURES • Quick and simple circuit entry • Digital and Analog Modules included, complete with all components • Simulated instruments: dual trace scope , spectrum analyser, function generator, multimeter, digital word generator and logic analyser • Complete control over all component values and parameters • Print: circuit schematics, parts list, instrument readings, macros • Logic conversion -truth table to Boolean formula to logic gates • Customisable hypertext help system THREE VERSIONS • Professional Version: EGA/VGA colou r display ; unlimited components • Personal Plus Version: Monochrome display ; unlimited components • Personal Version : Monochrome display ; limited to 20 ----------------I YES ■ ~ want_ELECTRONICS WORKBENCH m my computer Professional Version $429 Personal Plus Version Personal Version $299 $149 Plus $7 Delivery Enclosed is my cheque/money order for $_ __ __ or Please debit my Ca rd No.I O Bankcard O Mastercard IIIIIIIIIIIIIIII Signature _ _ _ _ _ __ _ Expiry Date _ _ /_ _ Name _ _ _ _ _ _ __ _ _ __ _ __ __ Street _ _ _ _ _ __ __ __ _ __ _ _ _ Suburb/Town _ __ _ _ _ _ _ Postcode _ __ _ Send to: Emona Instruments, PO Box 15, Camperdown, NSW 2050. ·-----------------~ Tel: (02) 519 3933 Fax: (02) 550 1378 MA RCH 1992 59 The Shooter can program most NMOS, CMOS and HMOS EPROMs. The built-in serial port operates at up to 2400 baud. Fast algorithms combined with its compact size make this programmer ideal for use in personal projects or field service applications. For more information, contact Mark Breznik at Emona Instruments, 86 Parramatta Road, Camperdown , NSW 2000. Phone (02) 519 3933. Protect your computer from surges & spikes Intelligent 4-port serial card The PE-514A 4-port adapter provides asynchronous serial communication ports (RS232C}, which link a computer to peripheral devices such as modems, serial printers, plotters and mice. The interface is a DTE type with male DB25 sockets. The four ports are individually addressable by any IBM PC/XT, PC/ AT, PC/386 or compatible operating under DOS or any other multi-user system such as PC-MOS/386, Concurrent DOS, XENIX/UNIX or PICK. Under DOS 3.3, the ports can be addressed as COM1, COM2, COM3 and COM4. The regular BIOS in most machines only allows baud rates up to 9600 but software included with the card extends the baud rate to 19,200. Using SCO XENIX version V2 .2. 1 or later, drivers are included that can be i used directly with the card. The XENIX drivers can address up to eight serial ports, so two cards can be used with different addresses to provide eight ports. The adapter is fully address and interrupt selectable. The driver software takes over communication between the CPU and each port. All device drivers are included and the manual gives full instructions for installation on different systems. For more information, contact Rod Irving Electronics, 74 Parramatta Road, Stanmore, NSW 2048. Phone (02) 519 3134. Low-cost, stand-alone EPROM programmer Logical Devices of the US has released the Shooter, a low-cost stand-alone EPROM programmer with 512Kb of internal RAM. It is capable of programming all popular single voltage EPROMs from the 2716 through to the 27512, including 'A' and CMOS versions. An optional adapter allows the programming of 8751/ 87C51 micros. In stand-alone mode, the user can directly copy and verify EPROMs via three control switches and LED status indicators. When connected to an MSDOS compatible computer or dumb terminal, the user has full function 60 SILICON CHIP This computer protector saves computers, fax machines, video and hifi equipment, PABX telephone systems and other high-tech microprocessor based equipment from damaging power spikes and surges. It is about the same size as a normal double power point and plugs directly into a 240VAC power socket. The protector incorporates four levels of protection: a primary RFI filter, a secondary RFI filter, surge voltage limiting varistor circuitry and an earth line choke. It is available in 3, 6 and 10-amp output sizes and has a completely sealed outer casing. For more information, contact Westinghouse Brake and Signal Company, Stephenson St, Spotswood, Vic 3015. Phone (03) 391 1300. New data acquisition cards for PC's control including RAM edit, blank check, checksum, up and down load, offset and file transfer format. Formats cover Intel hex, Motorola hex, ASCII hex or binary file formats. National Instruments Australia has released four new data acquisition boards for PC-ATs or higher. The ATDSP2200 is a high performance DSP accelerator board with high-accuracy delta-sigma modulating ADCs and DACs. The card features a dedicated high-speed numerical computation 'engine' that can perform scientific calculations faster than the generalpurpose 80X86 processor on the PC. The AT-A2150 is a four channel board that uses delta-sigma modulating ADCs to provide high accuracy analog inputs with extremely low Upgrade your PC to MS-DOS 5 noise and low differential non linearity. Two versions are available, one designed for general audio-frequency measurements and the other targeted at speech and voice band measurement applications . The AT-AO-6 and AT-AO-10 are two high performance analog output cards that differ only in the number of DACs featured . The AT-AO-6 has six highspeed multiplying DACs and the ATAO-10has10. NI-DAO DOS and NI-DAO Windows software drivers are included free with each of these boards. For more information, contact Tony O'Donnell at National Instruments Australia, 1 Colin Ave, Park Orchards, Melbourne, Vic 3114. Phone (03) 879 9422. Enhancements to HP's ProbeView software Now you can upgrade any PCconipatible machine that has DOS 2.11 or higher to DOS 5, with no effort at all. In the past. DOS has been a total mystery to many people. This latest version has an improved shell with on-line help to explain functions that are normally found daunting. DOS is now loaded into extended memory, leaving more conventional memory available for large applications, such as spreadsheet programs and data management systems. It also lets you load things like network software, drivers and TSRs (terminate and stay resident programs) into the upper memory area on a PC with an 80386 or higher processor. DOS 5 now includes functions like 'undelete', 'quick format' and 'unformat' which were previously only found in applications such as Pnlhe\'lew• Qu.t.\fu !f'&lo ~!):;Msd . C"OIIINf CTU,I) f!r~beUAl: -;! 1001: ~ e y M~..:.::_~ ··~ U~r Cretted~dl:_:C-C--CCC---- I Na me l hpspdle HP has enhanced its ProbeView software to add echo-test capabilities to the HP 4990S LanProbe networkanalysis system for local area network (LAN) management. The enhancement permits echoloopback tests for all nodes on a segment. This allows network administrators to test remotely for node activity and to measure network responsiveness . Operators can now find out when things go down before users do and problems can be fi xed before they become serious. The protocols that the echo-test capability uses include ICMP echo , 802 .2, DECnet, Novell 802 .3 and Novell Ethernet 11. One or all of the test protocols can be used. Test-response information is shown on the segment map as node colour changes. Nodes that change in echocapabil ity status turn from green to red, alerting managers when important nodes such as file servers or gateways become inactive. The HP 4990S LanProbe networkanalysis system comprises the HP 4991 A Lan Probe segment monitor, f:i1>t1....!S~ .. ~ ... Nortons Utilities. A task swapping capability ends the time consuming quit-load-quit-load routine and a command-line history and editor reduces keystrokes and lets you browse through previously used commands. The DOS 5 upgrade is available from Rod Irving Electronics, 74 Parramatta Road, Stanmore NSW, 2048.Phone(02)5193134. j :-0i«&nn1lft.l-:;::=:-;-; TestPt :oto<o!s:--:=== = === CJ'if,J ~;,.f : C! .NCN'!: lltf':lt.emetj :. . 0£.l!mne:I CfP ; C NovclljtlO:l'. )J • 21 ICMP Echo Ner... ml f"· ~ · lies u.: spo n.de<l prtW11nfy the HP 4990A ProbeView software and the optional HP 4992A Nodelocator. The LanProbe segment monitor attaches to the end of an Ethernet segment and monitors all network traffic. Attachment can be directly to a th in or thick coaxial cable, or through an external transceiver to a fibre-optic or twisted-pair cable. Network data is transferred through an RS-232C connection, Ethernet adapter or modem connection to a PC running the Probe View software. For more information, contact Cate Rejman, Test & Measurement, Hewlett-Packard Australia, 31-41 Joseph St, Blackburn , Vic 3130. Phone (03) 272 2869. SC Computer Watchdog & 48-line 1/0 Card: $318.00 • Provides 48 TTL inputs or outputs. • On -board watchdog (PC fails, dog will hardware reset the bus) • Useful for unatte nded computers so that if th ey stop you can have the watchdog independently reset your PC. • Fully addressable & programmable by the user (even in Basic). • eg, Turn ON/OFF devices in your home, office, workshop, industry. • Address & examples of software or hardware su pplied . 24-lnput Opto-lsolator Board: $229.00 • 24 opto-coupled inputs . • Either transistor pull-down or current loop input. • Pin compatible with 1/0 Watchdog Card (optional leads available) • High voltage isolation. • Provides immunity from EMI, RFI & earth loops. • 16-output & 8-input board also avai lable. AC/DC Interface Card .................... $185.00 Relay Board With 8 Relays ............ $259.00 Temperature Board (4 Inputs) ...... $189.00 PO Box 628 Willoughby, NSW 2068. Phone (02) 809 1083 Fax (02) 808 1432 MARCH 1992 61 Keep your phone bills low with the TELEPHONE CALL This project helps you keep track of the time while you make those expensive overseas phone calls. It times for up to 19 minutes and provides four warning beeps during the last 12 seconds of each minute. By DARREN YATES How often have you lost track of the time while making an overseas phone call? No doubt , you haven't worried about it at the time - until the next phone bill came in, that is! For example, making overseas (IDD) calls can get quite expensive if you lose track of the time. Not only that, but you also'get charged a full minute's worth for every part minute that you use. 62 SILICON CHIP Thus, if you make an IDD call that lasts for three minutes and five seconds, you get charged for four minutes. That's because IDD calls are always rounded up to the next minute for billing, which means that you can wind u p paying an extra cou ple of dollars for just a few seconds. Our Telephone Call Timer can save you or your business big m oney. It keeps track of the time for you - for up to 19 minutes - and it gives four warning beeps 12 seconds before the end of every minute. It then lights one or more LEDs to indicate the elapsed time since the start of the phone call. That way you don 't end up paying for the minute you don't use. Alternatively, by using the timer, you can keep talking until the next minute is almost up to make sure you get your money's worth. The timer uses only common components, many of which you'll probably already have lying around in your junkbox. To keep the cost down, it uses a series of LEDs to indicate the elapsed time instead of the normal?segment LED displays. There are 10 LEDs in all, with each unit LED lighting in turn to indicate the elapsed time during the first nine minutes of the call. RING OF TEN COUNTER IC3 ALARM TONE IC5 Fig.1: block diagram of the Telephone Call Timer. Clock signals from 3-second timer ICl are first divided by two & then fed to decade counters IC3 & IC4 wired in cascade. IC3 activates the alarm tone circuitry, while IC4 & IC2b drive the LEDs to indicate elapsed time. a: w :E j:: ..I ..I <( u After that, the 10-minute LED lights and remains lit for the next nine minutes as the other LEDs again light in turn. An advantage of this unit is that it doesn't require any connection to the telephone line. That does away with the need for isolation transformers, interfacing circuitry and connecting sockets. All you have to do is switch the unit on the moment the called party answers the phone. w z 0 ::c c. w w ..I I- Block diagram Refer now to Fig.1 which is a block diagram of the Telephone Call Timer. Clock signals for the circuit are provided by timer stage . . .YN,.......1-----''f\-.......~u....l1, TIMER 0 ci '-' ,. ..J '-' ICl. This provides a square wave output with a period of three seconds. This output is then fed to a divide-by-2 circuit (IC2a) which increases the period to six seconds. The output from IC2a is fed to a decade counter with decoded outputs (IC3). This stage is used to activate the warning tone alarm (IC5), while its divide-by-10 output gives us a square wave with a period of one minute. This square wave output is then fed into another decade counter (IC4) whose outputs go high in turn after every minute. We use these outputs to drive the LED display. The divide-by-10 output from IC4 is another square wave with a period this time of 10 minutes. It is fed into :;; a: ci '-' ;::: 0 ., Fig.2 (right): the circuit uses 7555 timer IC1 to generate the clock signal. NANO gates IC5a & IC5b make up the tone oscillator. This oscillator is activated for four 3second periods during the last 12 seconds of each minute & drives complementary transistor pair Ql & Q2 via a 33kQ resistor. MARCH 1992 63 ®~~u , - - - - - - - - - - - - - - - - - - -- ·02- ~~ 0} ®fLPD [~~~ 2"'" ·, " ® ""si: ,®~®~®~ """" LED1·9 LE010(!) (!) WG) G) G) G) G) G) CD Fig.3: the parts can be installed on the PC board in virtually any order but make sure that the link wires are straight to avoid short circuits. Install the two electrolytic capacitors so that they can be bent over to lie flat against the board. IC2b , which is another divide-by-2 circuit, and this in turn drives the 10minute display LED. As you can see, the accuracy of the circuit relies on the 3-second timer, so you must get that as close to correct as possible. Circuit diagram Fig.2 shows the complete circuit details . IC1 (7555) is a CMOS version of the popular 555 timer and is wired here in the astable configuration. The 4.7MQ and 3.3MQ resistors, the 2MQ trimpot (VR1) and the 0.33µF capacitor set the timing period When the trimpot is adjusted correctly, the output at pin 3 of IC1 is a square wave with a 3-second period as described previously. The advantage of using the CMOS version of the 555 is that it allows us to use much higher resistor values in the timing circuit and h ence a low value capacitor to get the required time delay. The output at pin 3 is fed into pin 11 of IC2a, which is one half of a CMOS 4013 dual-D flipflop. Because the Q-bar output is connected back into the D input, it forms a toggle flipflop which simply divides the clock frequency by two. The output is taken from the Q output (pin 13) and is a square wave with a period of six seconds. This output is now fed into the clock input (pin 14) of IC3 which is the first of the two 4017 decade 64 SILICON CHIP counters . Among other things, this IC provides the required outputs to activate the 12-second warning circuit. Here's how it's done: outputs 8 and 9, which correspond to the 48-second and 54-second marks of each minute , are used to drive diodes D3 & D4. These diodes, together with the associated lOkQ pull-down resistor, form an OR gate. The output from this OR gate is then fed into the cathode of diode D2. D1, D2 and the associated lO0kQ pull-up resistor form a simple AND gate. D3 & D4 drive one input of this AND gate, while pin 3 of IC1 drives the other. The output of the AND gate (ie, the anodes of D1 & D2) is high only when both inputs are high. This only occurs each time pin 3 of IC1 goes high during the last 12 seconds of each minute (ie, from the 48-second mark onwards). Because IC1 has a 3-second period, it follows that the output of the AND gate (and thus pin 13 of IC5a) goes high and low four times during the last 12 seconds of each minute. This signal is used to gate the alarm oscillator on and off to provide the four warning tones. The alarm oscillator is made up using NAND gates IC5a & IC5b, which are wired together in a conventional manner. The associated 4 7kQ resistor and .015µF capacitor set the oscillator frequency. The resulting square wave output appears at pin 10 and drives complementary transistor pair Q1 & Q2 via a 33kQ resistor. Q1 & Q2 in turn drive a miniature 8-ohm loudspeaker via a lOµF capacitor. Note that no quiescent bas e biasing has been provided for the transistors; nor is it necessary, since they are only being fed with a square wave signal. So much for the alarm tones. We'll now return to the main timing part of the circuit and find out how the LED indicators work. The divide-by-10 output (CO) from IC3 (pin 12) is fed to the clock input of the second decade counter, IC4 . Because IC3 's output has a period of 60 seconds, IC4 's 1-9 decoded outputs go high in turn at the end of each successive minute to light the relevant LED indicator. When a count of 10 is reached, the divide-by-10 output (pin 12) goes high and clocks divide-by-2 stage IC2b. IC2b 's Q-bar output thus switches high and drives LED 10 (the 10-minute indicator) via a 3.3kQ current limiting resistor. Because it is now latched by IC2b, LED 10 now remains on while IC4 cycles through the next nine counts, with LEDs 1-9 again switching on in turn at the end of each minute. After 19 minutes, both LED 9 & LED 10 will be on and this is the longest practical time for the Telephone Call Timer. After 20 minutes, IC2b is clocked again and LED 10 turns off. To ensure that the circuit is correctly reset at switch-on, IC2b 's Set input is momentarily pulled high by an RC timing network. This initially sets IC2b's Q-bar output low and thus ensures that LED 10 is off. Counters IC3 & IC4 are reset at switch-on by similar RC timing networks connected to their Reset inputs (pin 15). Power for the circuit is derived from a 9V battery via on/off switch S1 and is decoupled using a lO0µF capacitor. Alternatively, you can delete the battery and use a DC plugpack supply. Construction All of the parts , including the miniature foudspeaker, are mounted on a small PC board, codeSC12104921 (110 x82mm). Before starting construction, check the PC board carefully for any shorts or breaks in the copper tracks. If you find any, use an artwork knife or a dash of solder as appropriate to repair the problem. PARTS LIST 1 PC board, code SC12104921, 110 x 82mm 1 plastic utility case, 150 x 90 x 50mm 1 adhesive front-panel label 1 miniature toggle switch (S1 ) 1 battery clip 1 9V battery 4 10mm-long plastic standoffs 1 25mm-dia. miniature 8-ohm loudspeaker 1 2MQ horizontal-mount trimpot (VR1) The miniature loudspeaker is mounted directly on the PC board using short lengths of tinned copper wire. Power comes from a 9V battery but there's no reason why you couldn't use a DC plugpack supply instead. When you sure that the board is OK, check that the horizontal trimpot (VRl) fits snugly into its mounting holes. If the holes are too small, enlarge them slightly so that the trimpot does fit. Fig.3 shows how the parts are mounted on the PC board. You can begin construction by installing the wire links. Make sure that they are all nice and straight so they don't end up shorting each other out. You can CAPACITOR CODES Value IEC Code EIA Code 0.33µF 0.1µF 0.015µF 330n 100n 15n 334 104 153 straighten the link wire if necessary by first clamping one end in a vyce and then pulling on the other end with a pair of pliers. Once all the links are in, you can install the resistors and trimpot VRl. Table 1 shows the resistor colour codes. It's also a good idea to check each value with your multimeter as it is installed, just to make sure. The polyester capacitors can be installed next, followed by the two electrolytics. Bend the leads of the electrolytics at right angles to their bodies so that they lie flat against the board and check their polarity carefully before soldering them into position. The diodes, transistors and ICs can now all be installed. Make sure that you don't mix up the two transistors since one is an NPN device and the · other is a PNP (see Fig.2 for pinouts). Semiconductors 1 7555 CMOS timer (IC1) 1 4013 dual-D flipflop (IC2) 2 4017 decade counters (IC3,IC4) 1 4011 quad NANO gate (IC5) 1 BC337 NPN transistor (01) 1 BC327 PNP transistor 4 1N914 diodes (D1-D4) 10 red LEDs (LED 1-10) Capacitors 1 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.33µF MKT polyester 4 0.1 µF MKT polyester 1 .015µF MKT polyester Resistors (0.25W 1 4.7MQ (5%) 1 3.3MQ (5%) 4 100kQ 1 47kQ or 0.5W, 1%) 1 33kQ 4 10kQ 10 3.3kQ Miscellaneous Hook-up wire, foam rubber to secure battery, machine screws and nuts, tinned copper wire (for links). Note: 0.25W 5% resistors can be used in this project. TABLE 1: RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 No. 4 1 4 10 Value 4-Band Code (1%) 5-Band Code (1%) 4.7MQ 5% 3.3MQ 5% 100kQ 47kQ 33kQ 10kQ 3.3kQ yellow violet green gold orange orange green gold brown black yellow brown yellow violet orange brown orange orange orange brown brown black orange brown orange orange red brown yellow violet black yellow brown orange orange black yellow brown brown black black orange brown yellow violet black red brown orange orange black red brown brown black black red brown orange orange black brown brown MABCH 1992 65 the sound escape from the loudspeaker. Begin by attaching the adhesive label to the front panel (ie, to the case lid), then (working from the front) drill 3mm holes for the loudspeaker and at the P.C-board mounting points. The holes for the LEDs are best made by first drilling small pilot holes and then slowly reaming them out until the LEDs are a snug fit. This done, mount the LEDs with their cathode leads adjacent to the edge of the PC board, then secure the board to the front panel using screws, nuts and spacers. Fig.2 shows how to identify the LED leads. The cathode lead is the shorter of the two . The LEDs can now be gently pushed through the front panel holes and checked for correct orientation before finally being soldered. Don't worry if the LEDs don't perfectly line up with the hole positions. Just bend their leads slightly so that they go in. The PC board can now be removed from the front panel so that the supply wiring can be installed. The battery clip negative lead goes directly to the PC board, while the positive lead goes to one of the outer switch terminals. A short length of hook-up wire is then used to connect the switch centre terminal (wiper) to the positive supply terminal on the board. ..-< (\J °' 'Sj- C) ..-< (\J ..-< 0 ~_! _Qj ...._l_~_~_?_!_).~_ Fig.4: this is the full-size etching pattern for the PC board. Check your board against this pattern for defects before mounting any of the parts. Pin 1 of each IC is identified by the adjacent notch at one end of the plastic body. The loudspeaker used in the prototype is a miniature 25mm type (available from Jaycar Electronics), although other speakers could also no doubt be used. The best way to install it is to first solder a couple of link wires to its terminals and then solder the other ends of these links directly to the board (see photos). Installing the LEDs Before you install the LEDs, you need to drill all the necessary holes in the front panel. In addition to the mounting holes for the 10 LEDs, there are four mounting holes for the PC board plus a number of holes to let TELEPHONE CALL TIMER + 4 warning tones will sound 10 seconds before end of each minute + + + MINUTES 12 3 4 5 + + + + .10 + 67 8 9 • ••••••• •• Fig.5: this full-size artwork can be used as a drilling template for the front panel. The holes for the 10 LEDs are best made by first drilling small pilot holes and then slowly reaming them out until the LEDs are a snug fit. 66 SILICON C HIP You can now afford a satellite TV system For many years you have probably looked at satellite TV systems and thought "one day". You can now purchase the following K-band system for on ly: $995.00 Here's what you get: * A 1.8-metre prime focus dish antenna,. complete with al l the mounting hardware. * One super low-noise LNB (1.4d8 or better) . *magnetic One Ku -band feedhorn and a signal polariser. * metres of low-loss coaxial cable with a single pair control line. *receiver lnfrared remote control satellite with selectable IF audio 30 & bandwidth, polarity & digital readout. The PC board is mounted on the lid of the case & secured on 10mm spacers using screws, nuts & lockwashers. Note the circular pattern of holes drilled in the lid to allow the sound from the loudspeaker to escape. The on/off switch can be mounted on the front panel or on the side of the case, depending on your personal preference. Testing To test the unit, connect the 9V battery and wire your multimeter in series with the positive supply lead (you can do this simply by connecting the multimeter across the open switch terminals). Check that the current consumption is about 2-3mA when no LEDs are lit. If it is much more than this, switch off immediately and check for incorrect parts placement and orientation. If the current consumption is in the ballpark, switch the project off by disconnecting the multimeter. You should hear a low level squeak from the speaker about two seconds later. At this stage, you're ready to adjust the timing oscillator. To do this, start the timer and check the time taken for LED 1 to come on. Adjust VRl as necessary so that LED 1 comes on after exactly one minute, then remount the PC board and secure the lid to the case. Your receiver is pre-programmed to the popular AUSSAT transponders via the interna l EEPROM memory. This unit is also suitable for C-band applications. You're now ready to start timing those long-distance phone calls. Troubleshooting Call, fax or write to: If it doesn't work, you can quickly track down the faulty stage using your multimeter. The first step is to check that the +9V rail is present on the supply pins of the five !Cs. If this is OK, use your multimeter to check that pin 3 of !Cl successively switches high at 3-second intervals. Similarly, pin 13 ofIC2a should switch high at 6-second intervals, pin 12 of IC3 at 60-second intervals, and pin 12 of IC4 at 600-second intervals. If any of the LEDs fails to light while the others work OK, it is probably connected the wrong way around. Finally, if the LEDs all work OK but you don't get any sound from the loudspeaker, check diodes Dl-D4, IC5 and Ql & Q2. The cathodes of D3 & D4 should go high for the last 12 seconds of each minute, during which the anodes of Dl & D2 should switch high and low four times. If you strike problems here, the most likely cause is an incorrectly oriented ilia&. ~ AV-COMM PTY LTD PO BOX 386, NORTHBRIDGE NSW 2063. Phone (02) 949 7417 Fax (02) 949 7095 All items are available separately. Ask about our C-band LNBs, NTSCto-PAL converters, video time date generators, FM 2 & EPAL & Pay TV hardware. I I II ----------Name .. .. .......................................... I I II I Address ....................... ................... I I ........................... P/code ................ II Phone..................... ....................... . I I I II I I ., YES GARRY, please send me more information on K-band satellite systems. ___________ ,. 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Top, Rear, Bottom, and Front Paper Feedpalhs, Convenable Push/Pull Tractor ........................................ $1,149 LQ• 1060 136 Cpl, 24Pin Dot Matrix" 292 Cps Draft, 98 Cps LO, Colour Standard,Push Tractor, Smart Park Feature. • ACN.005428437 HEAD OFFICE: 56 RENVER RD, CLAYTON. PH: (03) 543 2166. FAX (03) 543 2648 CITY 48 A 'BECKETT ST. MELBOURNE. PH. 663 635116391640. FAX: 6391641. OAKLEIGH: 240C HUNTING DALE RD, OAKLEIGH. PH : 562 8939 NORTHCOTE 425 HIGH ST. NORTHCOTE, PH. 489 8866. FAX: 489 8131. SYDNEY:74 PARRAMATTA RD, STANMORE. PH: (02) 519 3134. FAX: (02) 519 3868 BLUESTAR COMPUTERS: 271 MAROONDAH HWY. RINGWOOD. PH: (03) 8701800 ·. ......................................... $TT5 ' . ..................................$575 - ............................................$1,395 Postage rates $1 • $9.99-.... $3.00 $10 • $24.99.. $3.50 $25. $49.99.. $4.50 $50 • $99.99•• $6.00 $100 • $199... $7.00 $200 • $500... FREE $500 PLUS .. FREE Th•• pootago rale• ara bHIC poot&go only up to :~~y ~o::g':.lgh~ IIOnw wil be chorgod ot c l - t •••• TO LL FREE MAIL ORDER HOTLINE: 008 33 5757 Updating the resistor & From this month onwards, we are changing the way we specify resistors and capacitors in the parts lists for SILICON CHIP projects. No longer will we be specifying greencaps or resistors with 5% tolerance. By LEO SIMPSON The ubiquitous greencap, otherwise known as a 100V dipped metallised polyester capacitor, has had a good run. It has been used in Australia for around 25 years, an exceptionally long time for any electronic component to be in current use. Over the last few years, and particularly in the last six months or so, we at SILICON CHIP have been changing over to the newer potted encapsulation types with a 5mm lead spacing (pitch) . While they are generally smaller than greencaps, their main advantage is the fact that they have a consistent lead spacing of 5mm. Greencaps, by contrast, have a spacing which varies widely between different manufacturers for a given capacitance and voltage rating, and also over a wide range from the smallest to the largest value in the range. Differing lead spacing presents a problem when a PC board has been designed to take a particular size of capacitor. The leads for greencaps also tend to be rather flimsy so that the capacitor can be bent over from side to side, eventually resulting in broken leads. With more of our PC boards being designed on CAD systems, we wanted to standardise the lead spacing for polyester capacitors - and what better way to do it than to specify a range of capacitors which already comes with a standard lead spacing of 5mm. MKT capacitors Usually referred to as MKT capacitors, these units can be fully described as metallised polyethylene terephthalate film capacitors potted with epoxy resin in a moulded plastic case and with 5mm lead spacing. The capacitor element itself may be of stacked metallised film construction or wound film with sprayed metal ends to give low residual inductance. The latter construction technique is the same as used for greencap capacitors. Strictly speaking, most MKT capacitors are specified with a lead spacing of 5.08mm which is equivalent to 2110th of an inch and in line with the 1/10th-inch grid used in CAD packages for PC board layout. Still, the difference between 5mm and 5.08mm is hardly worth arguing about for most applications, even including those where boards are to be loaded by automatic component insertion. While these MKT capacitors may be new to many of our readers, they have been available for quite a while. Philips, for example, has had its MKT range available for seven years (original catalog listing is December 1984). The beauty of these MKT capacitors is that they are so widely available from different manufacturers and one manufacturer's range is physically directly compatible with any other manufacturer's. They are made and distributed in Australia by a number of suppliers, as listed below: (1) Adilam Electronics - Wima MKS range; (2) Crusader Electronic Components Pty Ltd -Arcotronics MKT range; (3) Mayer Kreig - Roederstein MKT range; (4) Philips - MKT 2222 370 series; (5) Siemens Ltd - MKT range; (6) VSI Promark Electronics Pty Ltd - Samhwa EB range. Different manufacturers use different colours for the plastic case although this may also vary, depending on whether the dielectric is polyester (ie, polyethylene terephthalate), polypropylene or polycarbonate. For example, the Philips MKT range is light blue, the Arcotronics MKT range is white and the Wima MKS range (from Adilam) is red. Voltage rating Unlike greencaps, MKT capacitors come with a fixed 5mm lead spacing, thus simplifying the design of PC boards. They come in a number of colours, depending on the manufacturer, & are generally rated at 63VDC or 100VDC. 70 SILICON CHIP Depending on the capacitance and manufacturer, the voltage rating will be 63V DC or 100V DC but can also be 50V DC for some of the larger values. In most applications, the voltage rat- capacitor scene MKT capacitors are usually smaller than equivalent-value greencaps & this makes it possible to fit more circuitry into a given space. The lead pitch of an MKT capacitor is always 5mm, regardless of value or manufacturer. ing will not be important since the supply voltage in the vast majority of SILICON CHIP circuits is less than 50 volts. In those applications where the voltage rating is critical, we will naturally specify the correct value. The way of printing the capacitor value, tolerance and voltage rating also varies from brand to brand. For example, Philips use the IEC code for the value but also use the EIA letter code for the tolerance. Thus, a .OlµF capacitor with a tolerance of ±10% will be labelled 10n K. To cover this situation, we will continue to publish listings which give each capacitor value in both the IEC and EIA codes. A number of kitset and retail outlets we have spoken to have indicated that they already stock or will be stocking the full MKT range. At present, they are a little more expensive than equivalent greencap capacitors but as they come into more general use, we expect that they will become as cheap as greencaps and will eventually displace them altogether. What if you presently have a big stock of greencaps? Naturally, you will still be able to use them in most projects although they will not fit the PC boards precisely as will the 5mm lead spaced MKT capacitors. It will also be possible to substitute metallised polycarbonate or metallised polypropylene MKT-style capacitors where these are available and the others are in short supply. Resistors The other change we need to talk about regards the specifying of resistors for SILICON CHIP projects. Up to the present, we have specified most resistors as 0.25-watt 5% tolerance. This has really ignored the fact that resistors now available with a 0.5watt rating are no larger than was the case for a 0.25-watt rating. In fact, there is a fair chance that some of the resistors now being purchased over the counter as 0.25-watt units are actually 0.5-watt units. How can you tell? You can't. You have to take the word of your supplier. As an example of just how tiny resistors have become, consider the Philips MRS16T or SFR16T metal film resistors. These were specified in the Steamsound Simulator project featured in the October 1991 issue of SILICON CHIP. These have a body length of only 3.7mm which is about half the normal 0.25-watt size but they have a dissipation rating of 0.4 watts. The Philips SFR25 and MRS25 metal film resistors have a body length of 7mm and yet have a dissipation rating of 0.6 watts. Part of the reason they have such a high rating is that they are designed to dissipate much of their heat via the leads and thence via the copper pattern of the PC board. Clearly then, specifying 0.25 and 0.5-watt resistors is a little archaic when we could just standardise on the small 0.5-watt resistors. For some time too, we have been specifying a mixture of 1 % and 5% tolerance resistors and we have been publishing tables of colour codes for both tolerances. We think that the time is right to now standardise on 1 % resistors and forget about 5% types entirely, even though they are adequate for many applications. Hence, from now on, the vast majority of resistors we will specify for our projects will be 0.25 or 0.5-watt 1 % 7mm body metal film types. For resistors above 1MQ though, the tolerance of 5% will still apply. This will enable kitset suppliers and parts retailers to gradually rationalise their resistor stocks from four separate ranges (0.25W & 0.5W, 1 % & 5%) into one range - 0.5-watt, 1 % 7mm body metal film. At least one kitset supplier, Jaycar Electronics, has indicated that they intend to rationalise their resistor stock along the lines indicated. We assume that others will follow. There remains the question of the 4-band and 5-band resistor colour codes. At present, retailers have stocks of 1 % resistors with both 4-band and 5-band codes. To reduce confusion as much as possible, we will continue to publish 4-band and 5-band codes for the resistor values we specify. However, whereas before we would give a 4-band code for 5% tolerance resistors (the last colour always being gold), we will now give the 4-band code for 1 % tolerance resistors (the last colour band always being brown). We also suggest, as we have for some time, that resistors always be checked for value by measuring them with your digital multimeter. We must emphasise that we are not trying to dictate what parts retailers can stock. Ultimately the buying public will decide that. However, by taking the above approach with MKT capacitors and 1 % resistors, we are attempting to do our part to keep electronics enthusiasts in Australia as upto-date as possible. SC MARCH 1992 71 VINTAGE RADIO By JOHN HILL A look at valve substitutions Contrary to popular belief, valves for domestic radio receivers are fairly easy to come by. Collectors usually have numerous types on hand and valves can still be bought from various vintage radio suppliers, either here in Australia or overseas. However, that statement only applies to the more common types. When one turns back the clock to the 1920s and early 1930s, then valve availability is not very good at all. Although some odd and obscure types can be procured from various sources, most early radio valves are hard to find and expensive to buy. What's more, secondhand valves are often the only ones available or affordable. Domestic radios went "electric" from about 1927 onwards. Prior to that, they were battery operated al- most without exception. The popular receivers of those early AC days were of the TRF (tuned radio frequency) type, although the superhet was rapidly gaining on them. AC valves were still in the developmental stage at that time and were subject to numerous changes. Not only was it early days for indirectly heated cathodes but a proliferation of new valve types was about to take place, with the development of many revolutionary valves only a year or so down the track. It was an interesting and exciting time for radio. Many early AC valves had very short production runs before they were superseded by better designs. It is these odd valve types that may have been in vogue for only 12 months or so that are the hard ones to find today - simply because there were never many of them made in the first place. On the other hand, more common valve types such as the 5Y3, 6A8, 607, 6B6 and 6V6 (a popular line-up for many 5-valve superhets) were used extensively for at least 15 years . Whether new or secondhand, such valves must be easier to obtain than a valve that was superseded almost immediately it went into service. Directly heated cathodes Although the majority of early AC valves were designed with indirectly heated cathodes, some retained their battery valve ancestry and had directly heated cathodes in the form of a heavy, oxide-coated filament. In most instances, these direct heated types were confined to rectifiers and output valves such as the 80, 45, 47, 2A3, etc. Obtaining a cathode connection on a directly heated cathode requires that a centre-tapped resistor be connected across the valve filament, or that the filament be fed from a separate transformer winding having a centre tap. The cathode connection is made to the centre tap. This arrangement is necessary to minimise mains hum. Valve substitution A TRF chassis from the early 1930s. Receivers of this type often used AC valves such as types 24, 35, 47 & 80. These are all 2.5V valves except for the 80 which is a 5V type. 72 SILICON CHIP When restoring an old radio receiver, one often finds that some of the valves are either missing or in '"!eed of replacement. If the restorer . has the necessary valves, he is indeed fortunate. If he hasn't, then he must find a suitable substitute if the set is to work again. The substitution of unobtainable valves with more common types will solve most problems the vintage radio restorer may encounter. However, an old receiver with more modern valves doesn't quite look the part and there is nothing quite like having the right replacements. But if the choice is either an inoperative receiver or one that works, then the latter is the better alternative. This brings us to the purpose of this month's Vintage Radio column the substitution of valves now long forgotten and unobtainable. TRF receivers Around 1930, a number ofTRF and regenerative receivers used the following valves apart from the 80 rectifier: 24, 24A, 27, 35, 45 and 47. All were 2.5 volt valves. Other receivers could have used European type valves with 4V heaters. Such valves may have been E442, E415, E424 and C443. One often confusing aspect of early American valves is that a 45 output valve, for example, may be marked 245, 345 or with some other numerical prefix which apparently identifies the manufacturer. As far as the valve type is concerned, the first digit is ignored and the valve is referred to as a type 45. The 24 and the 24A type valves can be considered as being the same apart from the fact that the 24A has a faster warm up time. Many early AC valves had quite prolonged warm-up periods. A few early AC valves (from left): 24, 26, 27, 35, 51 and E406. Table 1 lists equivalent & possible substitute types for these & a wide range of other types. The rapid warm-up feature was developed to suit the direct coupling audio system, which enjoyed a (mercifully) brief popularity. A complex bias arrangement allowed the output valve grid to be connected directly to the driver valve plate but suffered from the complication that the output valve was deprived of bias while the driver stage was warming up. The type 24A was designed to overcome this problem. There are also physical differences in the appearance of these two valves, with the 24A looking the more modern of the two. The older 24 has the bulbous glass envelope that characterised many early valves. The shape alone is good reason for wanting origi- These type 57 & 58 radio frequency pentodes can be used to replace the older type 24 & 35 valves respectively. A new valve socket and minor wiring changes are all that are required. The 57 can also be used in other ways - see text. nal replacements. A valve shield, whether needed or not, will help disguise a ring-in valve. The 24 and 24A are radio frequency tetrodes and were used in many TRF and regenerative detector receivers in the very early 1930s. The 24A is still available new from local suppliers and at the time of writing costs around $10 . If a suitable replacement cannot be found, a 57, 6C6 or 6J7 could get one out of trouble. The 57 is a 2.5V radio frequency pentacle and would require a different valve socket and slight wiring modifications. A 6C6 or 6J7 replacement would also require a 6.3V transformer for the valve heater. The 35 is a close relative to the 24, The 2A3 (right) can be used as a substitute for the 45, the main drawback being its more modern appearance. Output triodes were quite popular during the early 1930s. MARCH 1992 73 FIG.1: VALVE SUBSTITUTION CHART VALVE EQUIVALENT POSSIBLE SUBST. VALVE EQUIVALENT POSSIBLE SUBST. 2A3 45 687 687S 6G8, 688 2A5 42, 6F6 688 6G8* 2A6 75, 686, 6S07 68A6 EF93 2A7 6A7, 6A8 68D7 E8C80-81 287 687,688 6C6 24 24A 57 6D6 24A 24 57 6F6 26 6J7, 6SJ7 78 27, 56 ,57 6G8 688* 27 56 57 6H6 E834 35 51 57*, 58 6J7 42 6J8 42 41 6K7 6U7 45 2A3 6K8 6J8, ECH33-35 47 2A5 6M5 EL80 57*, 58 6N8 E8F80, 6AD8 85 607 686, 6S07 6SK7* 41 51 35 55 6U7, 6K7 6V6, 6AG6 , EL33 6U7*, 6K7*, 6SJ7 ECH33-35 6K8,6A8 6A8 56 27 57 6SJ7 57 58* 6C6, 6J7 6S07 58 57* 6D6, 6U7 6U7 2A5 6V6 6F6, EL33, 6AG6 686, 6SO7 EL33 6V6, 6F6, 6AG6 59 75 78 6D6 6A7 6K8, 6J8, ECH33-35 E8F80, 6N8 6AG6 6K7 6U7, 6K7 6A8 6A8 6AD8 686,607 280 80 80S,83V 80 280 80S,83V 5Y3 5V4,5Z4 ECH80 5V4 5Z4,5Y3 6AQ5 EL90 6V4 EZ80 6AV6 6AQ6, E8C91 6X4 EZ90 686 607 6X5 EZ2, EZ35 6AN7 6V6, EL33 RECTIFIERS 6S07 Note 1: valves listed under "equivalent" should interchange without modification. Those listed under "possible substitute" may requ ire a valve socket change, a different heater voltage and alterations to some component values before they will work properly. Note 2: * sharp & remote cut-off types may not interchange satisfactorily in some cases. being a variable mu version. It is also available new for approximately the same price as the 24A. A defunct 35 can be replaced with a 58, 6D6 or 6U7 which would also require a valve socket change and small wiring modifications. If using a 6D6 or 6U7 as a replacement, a 6.3V heater transformer is again required. The 27 triode was used extensively in early AC receivers and was employed as a detector or first audio stage in most instances. It was also used as an oscillator in some old superhets. 74 SILICON CHIP A type 56 can be substituted for the 27 and will plug into the existing socket without modifications. A 57 connected as a triode can also be substituted (screen, suppressor and plate all tied together), although in this case a socket change is required. A direct-heated output triode such as the old 45 can be replaced with other similar valves, the 2A3 being the most logical choice. Failing this, many triode-connected output pentodes could be suitable replacements. A 2A5 would be convenient because of its 2.5V heater. There is no convenient equivalent for a 47 output pentode and perhaps the best way out of this problem is to substitute a 2A5 once again. A valve socket change would be all that is necessary and the 2A5 should perform better than the original output valve. Another 2.5V valve of interest is the 59, a valve which is occasionally found in the output stage of some early 1930s superhets. The 59 is an unusual valve in that it has two heaters instead of one. This odd construction characteristic has a distinct ad- RESURRECTION RADIO Vintage Wireless Specialists This photograph shows a 280 (left) and an 80. The shape of the glass envelope alone makes the older valve far more appealing. vantage in that the valve continues to operate reasonably well should one heater element burn out. Once more, the good old 2A5 is the logical substitute for a defunct 59 and requires nothing more than a socket change. The old 26 (a very early AC triode) is a difficult one to replace. This particular valve is likely to show up in some of those pressed steel TRFs of American manufacture. As far as AC valves are concerned, the 26 is a bit of an orphan for it has a 1.5V directly heated cathode. This valve was an attempt to use a directly-heated cathode in the audio driver stage, as well as the output stage. The low voltage, high current, A 6.3V heater transformer makes it easy to convert a set from 2.5V to 6.3V operation. The heater transformer supplies the 6.3V valves while the original transformer continues to supply the rectifier filaments and high tension. heavy duty filament was designed to have maximum thermal storage, to minimise fluctuations in cathode emission at mains frequency. As far as is known, it was the only such attempt and appeared only briefly. It is not uncommon to find the 1.5V 26 lined up with 2.5V valves and a 5V rectifier. Finding a replacement power transformer for such a set can be a problem. Unfortunately, there is no equivalent or even a close substitute for a 26. If you are stuck with this one, the best way out of the problem is to fit a 2.5V triode such as a 27 or 56, or a triode connected 5 7. This will require a new valve socket and the heater will have to be connected to the 2.5V winding of the power transformer, assuming it can carry the extra load (up to 1.75A in the case of a 27). Although many of the early superhets used valves similar to those used in TRF receivers, the more common types encountered are as follows: 55, 57, 58 , 59, 2A5, 2A6, 2A7 and 2B7. Many of these 2.5V valves carried on through to the octal series and if, for example, a replacement for a type 58 cannot be found, a 6D6 or 6U7 is exactly the same valve apart from having a different heater voltage and base configuration. European valves Those previously mentioned European valves present a few headaches and may have to be replaced with Repairs - Restoration - Sates Our skilled technicians offer QUALITY repairs and restoration . We also have a large stock of bakelite and timber radios fully restored and for SALE. Parts are available for the enthusiast, including over 900 valve types, high voltage capacitors, transformers, dial glasses, knobs, grille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalog. WANTED: Valves, Radios, etc. Purchased for CASH Call in to our showroom at: 51 Chapel Street (PO Box 1116), Windsor, Vic 3181_ Telephone: (03) 529 5639 Our first full catalogue of our huge range of electronic components and kitsets is nearing completion and will soon be delivered to those requesting a copy - FREE! To secure your copy, please fill in the coupon (or copy details), send together with 3 x 45<!: stamps for postage and we'll send a catalogue, hot off the press! You'll also receive updates, bonus offers, specials, etc. during the year AND each month until June you will be in the draw for a free SCOPE PH20 soldering iron! Q W/ Please send me a FREE catalogue I have enclosed stamps for postage ~c Name: . . .. Address .. . Postcode . \ ALL ELECTRONIC COMPONENTS ft 118 -122 Lonsdale Street . Melbourne. V,c. 3000 Telephone. (03) 662 3506 Fax (03) 663 3822 MARCH 1992 75 There is no direct equivalent for a 47 output pentode. However, a socket change and a 2A5 will do the job just as well. appropriate 2.5V valves. The conversion will need to include a voltage dropping resistor to reduce the 4V heater supply to 2.5V. If valves other than the 2.5V series are used (eg, 6.3V), then a separate heater transformer will have to be installed to supply the higher voltage. Equivalents vs. substitutes One point that should be remembered is that very few valves have direct equivalents. An equivalent can be interchanged without modification, whereas a substitute may require a socket change, a different heater voltage, or changes to the circuit. This latter requirement may take the form of a screen or cathode resistor with a different value to the original, or additional wiring to convert a A pair of 26s. The one on the right is of more recent manufacture and lacks the visual appeal of the original version with its bulbous glass envelope. pentacle valve to a triode. A substitute output valve may require a different output transformer. Also, some substitute valves may overload the power transformer; eg, if a 3amp rectifier is used to replace a 2amp unit. There are many ways of getting out of valve trouble and a study of Fig.1 may help solve a particular valve substitution problem. Although it may not be a complete list of suitable replacements, they are ones I have tried or have learned about from other sources. Fig.1 also includes substitutes additional to those earlier types discussed in the text. Odd heater voltages Finally, a few thoughts about providing odd heater voltages for replaceA type 24 and its improved version the 24A. The more modern looking 24A has a faster warm-up time but apart from that they're virtually identical. 76 SILICON CHIP ment valves. If a mains-type transformer is not readily available, or is unduly large and difficult to mount, it is worthwhile considering the auto transformer. The auto transformer is a single winding, with tappings for appropriate voltages. Typical would be a single winding tapped at 2.5V and 6.3V. The 2.5V tap could be connected to an existing 2.5V heater supply, while 6.3V would be available at the other tap. Construction is quite simple, no mains connection is involved, and most enthusiasts could wind their own. An old speaker transformer core, with the air gap removed, is ideal. Use heavy gauge wire, 18 or 16 SWG, and work to a design figure of between five and 10 turns per volt. Tappings are made in the form of a small twisted loop. The transformer will, of course, step down as well as step up. Two words that vintage radio restorers should be familiar with are substitution and improvisation. Finding suitable replacement valves for old receivers is just part of the "fun" of vintage repairs. Working out suitable replacement valves is not usually difficult, although this approach is often unacceptable to the purist who insists that the radios in his collection be original. However, tracking down the origi- . nal parts in not always practicable and we often have to make do with other arrangements. SC BOOKSHELF A stimulating text on analog design Analog Electronic Design. Principles & Practice of Creative Design, by Jonathon Scott. Published 1991 by Prentice Hall Australia. Soft covers, 170 x 235mm, 554 pages. ISBN O 13 033192 9. $46.95. In case you don't know it, analog electronics is about to enjoy a revival and not in the area where you might think. Analog has been in retreat for many years with the advent of digital recording, digital signal processing and so on. But now with the advent of "neural networks", the latest technique in computing, after fuzzy logic, analog is set to make a comeback. And that means this book on the subject is very timely. Of course, analog enthusiasts would retort that analog never really was dead and that to truly understand the trickier aspects of digital design, you need to know analog principles thoroughly. Writing as one who is an analog person first and foremost, I naturally agree. The author of this book is also a keen analog (and audio) enthusiast. Those who used to read "Electronics Today" in the 70s will well remember the name of Jonathon Scott. If you are wondering what happened to him, he is alive and well in the halls of Academe. He is manager of the Sydney Microwave Design Resource Centre and a senior lecturer at the School of Electrical Engineering, University of Sydney. (A number of other writers from the heyday of "Electronics Today" are also comfortably ensconced in university research or teaching positions - good luck to them) . This text is not at all like regular electronics courses which have a certain predictability about them as they move from the basics to the more advanced concepts. And although the author states this text originated "from a final university course on electronics given to generalist electronic engineers", I rather think of it as a supplement to more conventional texts be- cause of its unorthodox approach. Indeed, Jonathon appears more to be pushing a philosophy of electronic design rather than just teaching principles, most of which he assumes the reader is already aware of. Furthermore , the author would seem to prefer posing design conundrums than actually giving the answers and analyses. He is obviously trying to get the reader to think. In some cases though, the reader is bound not to have the answers and will have to do some research to find them. For my part, if a question is posed in a text, I prefer it to give the answer, even if not straight away. Principles & Practice of Creative Design Jonathan Scott I have already indicated that this book is unorthodox and you can get some of idea of this by a look at the contents of each chapter. Chapter 1 , entitled "The Start", is really an extended preface and outlines the author's approach and philosophy. It also outlines all the electronics concepts that Jonathon Scott assumes that the reader will be familiar with. It is a pretty forbidding list and one which would put all but genius level graduate engineers in the reject bin if they were being tested at a job interview. Still, it does give the reader a standard to aim for. Chapter 2 is titled "Discussion of Components" and briefly talks about things like resistors, capacitors, transmission lines and waveguides, BJTs and Mosfets and so on. It talks about their characteristics and fabrication . Chapter 3 is on "Circuit Prototyping and Documentation" and mainly discusses the various ways you can build prototypes; eg, rat's nest, matrix board and protoboards. Chapter 4 is on "Active Device Configurations" and covers common emitter, collector and base arrangements, cascades, current mirrors and so on. Chapter 6 is on "Distortion" and is one that the author would be very familiar. Indeed, he covers it well. Chapter 7 is on "Multipliers and Mixers", Chapter 8 is on "Discriminators", and Chapter 9 is on "Phase Lock Loops". I won't list all the chapters, however, as there are 20 in all, with the last topic being "Noise". In each chapter, the author really seems to be , attempting to highlight the tricky aspects of the topic rather than to give a broad overview. Jonathon Scott's writing experience at ETI magazine has held him in good stead as his style is light and entertaining, a far cry from some of the dull texts which used to be the norm in engineering courses. But how to summarise this unusual text? If you are well advanced in a university electronics degree, then it certainly provides plenty of food fo r thought. That appears to be the author's prime intention. Otherwise, if you are keen on analog techniques but with little formal training, you might be better staying away from this book as it can be annoying in its posing of questions or exercises without indicating what the answers are. It cannot be regarded as a reference book for most of the topics it covers because it assumes too much background knowledge on the part of the reader. Our review copy came direct from the publisher, Prentice Hall Australia. Phone (02) 905 7934. SC MARCH 1992 77 REMOTE CONTROL BY BOB YOUNG Voltage losses in speed controllers Following last month's article introducing the topic of speed controllers for electric motors, we present more figures on motor performance and voltage losses in typical FET circuits. Having looked at the performance of some commercial controllers last month, let us now look at the figures for an unloaded motor running in both directions and driving directly from short leads (no speed controller), to establish some sort of additional benchmark-refer to Table 1. The columns in the table are as follow: Vs = Battery Voltage at the terminals; Vm = Voltage at motor terminals; Is = Instantaneous start up current in amps; Ir = Sustained running current in amps. Table 1 last month - see page 71. In Table 1 below, we are losing 0.02 volts with no speed controller in circuit and a lower current. The 2-digit resolution of the meter, and the fact that the batteries were losing their charge as we measured, made accurate measurements very difficult to achieve but the general thrust of the problem is there. Does this mean that Australian automotive wire is at least twice the resistance of what appeared to be a lighter American wire? On the face of things, it certainly seems so. TABLE 1 Comments Vs Vm Is lr 12.47 12.45 17.80 2.64 Anti-clockwise direction & timing. No load. 12.44 12.42 19.56 1.92 Clockwise, incorrect rotation & timing. No load. The interwiring was 75mm of 10A automotive cable. The small anomalies in the figures are due to the resolution of the digital meter and the use of two separate battery packs. I am at a loss to explain these figures as they are nothing like what I would have expected. Unfortunately, I did not have the facilities to measure the unloaded RPM but at least we have some guide as to current and voltage drop in the leads, the latter being 0.02 volts across 0.0075 76 ohms. Here we have 10-amp automotive cable giving almost twice .the resistance of the wire and speed controller in the Novak installation listed in 78 SILICON CHIP As I said earlier, beware the power of the milliohm. To compound the problem, I would have expected the motor to run at a higher current when running clockwise than in the correctly timed anticlockwise rotation. This was not the case and I would be very interested in retiming this motor at some later date. Paralleled FETs To further illustrate the point, Table 2 lists some system losses with the prototype speed controller fitted. This table was compiled very early in the development of the speed controller and shows the effect of paral- leling FETs to reduce the "ON" resistance of the switching network. If you will recall, in an earlier column I stated that the number of FETs to be used and what type would be decided as a result of this work. Incidentally, although it is not a good idea to parallel bipolar transistors, FETs are just the opposite and it is quite in order to parallel these devices. These figures were taken using 10 x 1.8Ah cells, 10 x 4 Masters propeller and the standard-wind Kyosho 360ST motor, as tested above. This motor was timed to run anticlockwise and was fitted with a 2.5:1 gearbox, the interwiring again being the poor quality 10A automotive cable. Due to the fitting of the gearbox, the motor had to be run in reverse. Column 1 shows the number ofFETs fitted to the speed controller. Vd represents the system losses calculated by subtracting the voltage across the motor from the battery voltage measured under load. These losses include wiring harness resistance, voltage drop across the FETs, contact resistance and meter shunt. The leads in this case were quite long. Two things become very obvious from a quick glance at Table 2. Firstly, the results are not very good at all. Secondly, the FETs are the major source of losses. There is, however, a law of diminishing returns in regard to adding additional FETs to reduce the "ON" resistance. At some point the cost and weight of the additional FETs will outweigh the gains. This is in keeping with Ohm's Law. The same applies to wire thickness. Adding copper beyond the optimum point will add considerable weight for only very insignificant gains. It appears that a better approach here is to use high quality cable, probably This model shows that electric flight can be applied to quite large models. This model of an Australian Air Force Caribou has a wing span of 2.4 metres. It was built a few years ago by David Masterton who also built a model of a B-36 bomber which had six electric engines. test equipm ent cable or some equally high quality cable. Insufficient gate drive As th e FETs used were IRFZ44s and these have one of the lowest "ON" resistances in th e range of readily available FETs (28mQ), there was obviously a problem somewhere in the FET drive circuitry. Measurement of the Gate voltage showed only 7.73V. It is obvious th at this is not enough drive voltage to push the FETs into saturation. As a result of these tests, I decid<:Jd to change th e voltage doubler driving the FET gates to a voltage tripler. This resulted in an increase in Gate drive voltage from 7.73V to 12.21V. The results of this are sh own in Table 3. All other test parameters remain u n changed . Table 3 shows a substantial increase in RPM for a reduction in the number of FETs and FET heating when compared to Table 2. Note also that there TABLE 2 No. Vd l(A) RPM 1 0.62V 12.6A 7100 2 0.42V 12.4A 7200 3 0.38V 14.0A 7600 4 0.33V 14.2A 7800 is still a substantial loss in the interwiring. In the first item on Table 3, we have lost 0.63V (46 mQ) across the wiring which was deliberately made very light. In line 2 of Table 3, there is only a 0.15V (llmQ) loss but it still seems high to my mind. Mind you, there is a 100A meter shunt in this circuit and the wiring harness is longer than that used in a model , but it does illustrate the point in regard to wiring. Do not just grab the nearest piece of wire, even if it does look thick enough. There is little pointin spending $12.50 on each FET if you are going to lose more voltage across a 5-cent piece of wire. Alternative FETs Incidentally, there are a number of very useful FETs which cost a lot less than the IRFZ44 and deliver almost the same p erformance. One in particular which I have been testing gives an ON resistance of just 23mQ. Six of these in parallel will give us the required 4mQ ON resistance required to match the commercial units . More on these in a future issue. Comments There is also no fus eFET very hot holder in this circuit but fusi ng is a must, particuFETs hot larly for aircraft. This is another potential source FETs warm of unwanted milliohms FETs OK and fo r this reason the finished design will feature a PCB track fuse option, to reduce bulk and parasitic resistance. Table 4 gives a final set of figures, to illustrate problems of a completely different type. These figures were taken with a prototype speed control fitted with two FETs only; this time using a Leisure 05 Stock motor driving an 8 x 4 propeller on a direct drive. In th e figures of Table 4, we see the usual problems of insufficient FETs and voltage drop in the interwiring, resulting in a total of 0.74 volts. However, look at the battery voltage under load. Wh y is it so low and why is the voltage drop much higher than usual? The answer here lies in the much higher running current of 25 amps. The direct propeller driver provides a much greater load and thus the armature RPM is lower than the geared version , resulting in the higher current. The low battery voltage is an indication of poor quality batteries. These were sold to us as high current 1.8Ah batteries. When I cut the pack open to find what brand and type they were, I found that they were just simply labelled "Japan: (no brand, no type number). Do not forget that these figures w ill all change in flight as the propeller unloads. I have gone into a great deal of detail in the foregoing material to drive home the point that in high current electric motor applications you cannot just grab the n earest piece of wire , battery and motor. Great care must be exercised if you intend to get the best from your system. Th e one lesson which stands tall from th e rest is do not underestimate the power of the milliohm. As stated earlier, there is great scope in electrics for careful system design and the whole thing can become very absorbing indeed. However, having outlined the foregoing shortcomings , I must say that , all things con sidered, the system shows a lot of promise. By the time I have finished with the development work and installed all six FETs, we will have a good cheap controller with performance comparable to some of the commercial units. Dangers of electric props One last point for tyro electric fans (I love this pun). Do not get casual about the dangers of using electric M ARCH 1992 79 ~ ~ - - The electronics magazine for the enthusiast Four good reasons why you should subscribe to SILICON CHIP 1. You get a 12.5% discount on the newsstand cover price. Recently, we ha d to increase the cover price of the magazine because of r ising costs but we have held the subscription to the old price so you get the benefit. 2 • You'll never miss an issue. Sometimes it can be very hard t o find SILICON CHIP in the newsagents because it sells out early or gets buried under other magazines. By taking out a subscription you don't have to search for it - it arrives in your letter box in mint condition. We wrap it in tough pla stic to make sur e of that. 3• Get a discount on t he binder too. You'll want t o store and protect your issues of SILICON CHIP so when you take out a subscription you get a fur ther discount on the binder. By taking out a 2-year subscription and buying two binders at the same time, you get even bigger savings. And we despatch the binder(s) with your first issue so you have it right fr om t he start. 4 • From time to time, we will have special promotions and offers in t he magazine, like the Bose Lifestyle compet ition featured in the September to December 1990 issues. When you are a subscriber you are automatically eligible for these and you get the chance to benefit. Interested in these savings and benefits? Just fill in the coupon on the following page and send it with your remittance. You'll be glad you did. Why not do it today? I hope to see you as a supporter soon. Leo Simpson, Publisher Just fill in the order form on page 93 ~ 80 SILICON CHIP JUNK MAIL Most magazines sell their subscriber lists to mail order companies, to earn extra income. Be assured that we will not do this. Your privacy will be respected and you will not be deluged with unwanted mail. MAGAZINE BINDERS Speciafly designed binders for SILICON CHIP are always available. Made with a distinctive high quality 2-tone vinyl, you can obtain them at a discount when you take out or renew your subscription . The price details are on the coupon overleaf. TABLE 3 No. RPM l(A) Vd Protect your valuable issues Comments 2 0.77V 13.7A 7200 0.14 V across FET S/D pins. Thin Fig.8 speaker cable used for interwiring. 2 0.3V 14.2A 8000 0.15V across FET S/D pins. 1OA automotive cable used for interwiring. FETs warm motors, particularly with propellers. In more than 30 years of power flying with internal combustion motors, I had very few accidents because I treated those propellers with great respect. However, I did not treat the electric driven propeller with the same respect - at first. In my first week of electric experimenting, I had two nasty accidents. One involved a gearbox which I damaged by switching on the power without adequately securing the motor. As a result, the propeller hit a nearby object and cracked the gearbox housing. This was repaired with superglue and seemed OK - that is, until the aluminium strap holding down the motor began to stretch. At this point, the propeller, which had not been balanced, began to shake the motor and the gearbox disintegrated and the propeller and drive shaft went hurtling around the workshop. It gave me a hell of a fright. The second accident was more serious and occurred when I accidentally connected the positive lead of the motor directly to the positive battery terminal instead of the positive speed controller lead. At this time , the speed controller was switched off but the battery terminal was live and the motor burst into life. I was standing in front of the motor with my wrist just inside the propeller arc. The tip of the propeller hit my metal watch band and skidded off into the flesh of my wrist, slashing it across the arteries. If it had not have hit the watchband first, I may have ended up in hospital that day. As it was, I had a bruised wrist and a cut which drew blood. I saw a friend of mine do the same thing with a 60-size IC motor and he was not so lucky. He did end up in hospital. So the rules are simple. Polish off the flash on plastic propellers, balance them properly, and never work in line with the propeller or with your hands inside the prop arc. It's also a good idea to always switch off the power to both the battery and the speed controller. And finally, because they are only electric motors, do not get casual. They deliver every bit as much power as an internal combustion motor and are just as dangerous. Design features So here we are at the end of another column. As a result of the foregoing work, the design of the completed controller is now beginning to firm up. A brief summary of the major points is now in order. Firstly, the design calls for a simple and cheap controller, which will give forward only speed control. Secondly, all components are to be readily available. This precludes my favourite servo amplifier chip, the NE544 which is now obsolete. Thus, we will be using standard op amps as the active elements. Other features will include a ZkHz switching rate , a voltage tripler for operation from a low cell count, provision for up to six FETs, a PCB track fuse option, and finally a dynamic braking option. All of this will be in surface mount technology.· Thanks to ABC Models at Bexley, Hobbyworld at Hurstville and Moore Park Model in Armidale for the help given in preparing these articles. sc Silicon Chip Binders These beautifully-made binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a distinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. * High quality * Hold up to 14 issues * 80mm internal width *gold-coloured lettering logo printed in on spine & SILICON CHIP cover Price: $A 11.95 plus $3 p&p each (NZ $6 p&p). Send your order to : Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. Use this handy form l ----------Enclosed is my cheque/money order for $_ _ _ or please debit my O Bankcard O Visa O Mastercard Card No: Card Expiry Date __/__ Signature _ _ _ _ __ _ _ _ _ TABLE 4 lr Name _ _ _ _ _ _ _ _ _ __ Vs Vm Is 12.7 12.7 12.0 2.60 No load, no speed controller, 75mm of 1OA auto cable 8.44 7.70 50.0 25.0 Comments 10,800RPM on an 8x4 propellor, with two FETs Address_ _ _ _ _ _ _ _ __ _ _ _ _ __ _ P/code _ _ _ ·-----------· MARC H 1992 81 141 0 .... .... $1 .g5 141E ....... • $2.95 142E or Teccor ooeL Trlac .$2 .25 1460 ........ $2.85 1510 ........ $2.95 038 or CR100-6 ..... $0.90 06D Equiv. Tag 403DE ...... $1 .50 122D .......... $2 .50 22E .......... $1.95 2646 ..... .... $1 .gs 6027 ........ $1 .20 Utldil!il ······$ .... $1 .00 2219 ......... $0.90 2369 ..... .... $1 .00 2646 ........ . $1 .95 21l04 ......... $1.10 3019 .. ....... $1 .90 3055 .. .•..... $2 .00 356 3 .. ....... $0 .35 3564 ..... .... $0 .30 3566 ......... $0 .30 3569 ......... $0 .30 3638 ......... $0 .30 3641 ........ . $0 .30 3642 ......... $0 .30 3643 ......... $0.30 3644 ......... $0 .30 3645 .. ..... $0 .30 3771 . $6 .96 3772 ......... $5 .70 377 3 ..... .... $7 .95 381L ...... $1 .50 3866 ..•...... $2 .95 3904 ..... ,... $1 .00 3906 ......... $1 .00 4033 ......... $2 .20 4258 .. $0 .40 4356 .... $0 .50 4360 ...... ·• $1 .50 4342 ......... $1 .50 4401 .. ....... $0 .30 442 7 ..... .... $3 .90 5484 ......... $1 .50 5088 ........ $1.00 508L ...... $1.00 5401 .... . $0 .35 5458 ........ . $0 .90 5459 .. ..... $1 .00 5485 ... $1.15 5486 .. $1 .30 6027 ..... .... $1 .20 6125 ........ . $1 .90 D350 ........ $6 .95 J4L ........ $9 .9 5 J56 ....... .. $14 .50 K134 ......... $9 .95 K176 ....... $14 .50 :M•Nil .UAME BCS49 ........... $0 .15 BC550 ........... $0.30 BC556 ... ........$0 .30 BC557 ...........$0.15 RC558 ...........$0.15 BCS!Q .... .. .. .. .$0.15 Bcs3g···········So · 80 BC640........... $0.80 B0139 ...... ..... $0 .90 B0140 ........... $0 .90 BD237 ........... $0 .90 B0238 ........... $0 .90 BD650 ........... $l . 96 BD649 ........... $1.65 BD647 ... ........ $l.80 B0681 ........... $2.00 B0682 ........... $2.00 BF115 ........... $1 .00 BF180 ........... $l .20 BF199 ........... $0.60 BF245A ......... $1.95 BF489 ........... $l .20 BF470 ...........$1 .20 BFY50 ........... $1.50 BFYgo ........... $3.00 BU208A ... ..... $4 .90 BU326A ....... . $4 .95 BUX80 .......... $5 .95 BU806 ........... $7.95 MFE131 ........ $2.90 MFE3001 .... .. $!1.90 MJ10012 .... ... $5 .95 MJ 802 . .... $7.80 MJ15003 .... $!1 .50 MJ15004 .. $9.70 MJ15024 ....... $!1 .60 MJ 2955 ......... $2 .95 MJ4502 ......... $8 .50 MJE340 ......... $2 .00 MJE350 .... ..... $2 .50 MJE2955 .. .. .. $4 .90 MJE3055 ....... $3 .90 MJE13007 ..... $4 .95 MJE13009 ..... $9 .95 MPF131 ... $2.90 MPSAOS ... $1 .00 MPSA13 ........ $0.50 MPSA42 ........ $0 .80 MPSA43 .. $0 .60 MPSA9 3 ........ $0 .50 MPF102 ........ $0 .90 MPF109 ........ $0 .90 MPSU56 ........ $1 .75 PN 100 ........... $0. 25 PN200 ... ·· $0 .25 TIP31B .......... $1 .00 TIP31C ....... ... $1 .20 TIP32B .......... $l .OO TIP32C .......... $1 .20 TIP41A .......... $1 .90 TIP41C .......... $2.00 TIP42A .. ...... .. $1 .90 TIP42C .. ..... $2 .00 TIP49 .... ······· $1 .90 TIP50·.. ..... $2 .20 TIP 53 ...... $2 .50 TIP112 ... ...... $2.50 TIP 115 ........ ... $2 .50 TIP 117 ........... $2 .50 TIP 120 .......... $2 .90 TIP122 ..... ..... $1.95 TIP125 ....... ... $2 .90 TIP127 ........ .. $ 1.95 TIP147 .... ...... $4 .95 TIP 295 5 ........ $2 .25 TIP3055 ........ $1 .95 2illilf KBPC2504 400V............. $ 5.5 o KBPC2510 lOOOV............ $ 7.3 5 ll.A.Me KBPC3504 .,,,,,..._ _ 400V... . ... $6 .SO KBPC3506 600V. . ... $6 .75 KBPC3510 _"""_ _ _ _ 1000V.... ..... $8 A O t!iPiW1'"1 it? AC128 .... ....... $2.95 BC107 ...... ..... $0 .80 BC 1 08 ........... $0.80 ••--.■ ec109 ...........$0 .80 BC212 ......... .. $0 .30 BC318 ...........$0.30 BC327 ...........$0 .30 BC 328 ........... $0 .30 BC337 .... .. ... ..$0.40 ec338 ........... ,o..to &C548 ........... $ 0.30 BC547 ...........$0.15 8C548.,........ .. $0 .15 llV.. $0.25 12V.. $0.25 13V.. $0 .25 15V..$0 .25 16V .$0 .25 18V .$0 .25 20V .$0 .25 22V .$0 .25 24V .$0.25 27V .$0.25 30V .$0 .25 33V .$0 .25 36V $0 .25 ■!J.111 1W ZENER DIODE Description ........ $ 1N4728 3V3 ..$0.35 1N4729 3V6 .. $0.35 1N4730 3V9 .. $0.35 1N4731 4V3 .. $0.35 1N4732 4V7 ..$0 .35 1N4733 5V1 ..$ 0.35 1N4734 5V6 ..$0.35 1N4735 6V2 ..$0.35 1N4736 6V8 .. $0 .35 1N4737 7V5 .. $0 .35 1N4738 8V2 .. $0 .35 1N4739 9V1 ..$0 .35 1N4740 10V ..$0 .35 1N474111V .. $0 .3 5 1N474212V .. $0 .35 1N473313V .. $0 .35 1N47441 5V ..$0.35 1N4745A 16V$0.35 1N474618V ..$0 .35 1N4747 20V ..$0 .35 1N4748 22V ..$0 .35 1N4749 24V ..$0 .35 1N4750 27V .. $0 .35 1N4751 30V .. $0 .35 1N4752 33V ..$0 .35 1N4753 36V ..$0 .35 1N4761 75V ..$0 .80 1:1.j~M SW ZENER DIODE Cescrlptlon ......... $ 1N5339B 5V6$1 .50 1N5342B 6V8$1 .50 1N5349B 12V$1 .50 1N5358 15V$1 .50 1N5361 27V $1 .50 1N5359 24V $1 .50 1N5363 30V $1 .50 1N5372 62V $1.50 Mrl;ff-i(·Jf~ Oescnpti on ....... $ 1MHz ............ $6 .00 1.8432MHz ....$7 .SO 2MHz ..... .......$3 .00 2.4576 MHz ...$2 .00 JMHz .............$4.90 3.57954MHz ..$3 .00 4.00 M Hz .......$3 .00 4. 19430MHz ..$3 .00 4 .433618MHz$2 .00 4.44 MHz .......$2 .00 4.9562 MHz ...$3 .00 5MHz .............$2 .00 6 MHz ............$2 .00 6.144 MHt ..... $3 .00 KBPC607 1000V .. ...... .... $2 .7S - - - - - KBP= 400V............. $3 .50 KBPC1007 1ooov... ........ S4 .5 o 1N962A 1N759A 1N954A 1N965B 1N966B 1N967B 1N968B 1N9698 1N9708 1N971B 1N9728 IN973B 1N974B .Description .. S, 1N4002 200V .$0 .10 1 N4004 400V .$0 .10 , N4007,cnov .$0 .20 .u.Me Description . $ 1 N5401 50V .. $0 .40 1 N5404 400V $0 .40 1 N54081 OOOV$0 .65 GERMANIUM DIODE Description ........ $ OA47 OA90 OA 91 OA95 .......... $l .50 ...........$0.75 ............ $0 .75 ........ $0. 75 1 N746A 3V3 .$0.25 1 N747A 3V6 .$0.25 1 N748A 3V9 .$0 .25 1N749A 4V3 .$0 .25 1 N750A 4V7 .$0.25 1N751A 5V1 .$0 .25 1 N752A 5V8 .$0.25 1 N753A 8V2 .$0.25 1N754A 8V8 .$0.25 1 N755A 7V8 .$0.25 1 N758A 8V2 .$0 .28 1N787A 9Vl .$0.25 1N758A 10V .10.25 8.00 MHz ...... .$3.00 8.86723MHz .. $3 .00 10 MHz .. :...... $2 .00 11 MHz .......... $3 .00 12.00 MHz ..... $3.00 14.318 MHz ... $2 .00 15 MHz .......... $2 .00 16.00 MHz .... .$3 .00 20.00 MHz ..... $2 .00 24 MHz .......... $3 .00 48MHz ........... $2 .00 32.768KHz .... $2 .00 ■rDl!llf Description ............ $ 74HC00 ......... $0.75 74HC02 .........$0 .75 74HC04 .........$0 .7 5 74HC08 ......... $0 .75 74HC10 ....... ..$0 .75 74HC11 ....... .. $0 .75 74HC14 .........$1 .60 74HC30 ......... $0 .60 74HC32 ......... $0.80 74HC42 ........ $0.90 74HC74 .........$1 .10 74HC85 ......... $1AO 74HC86 .........$1 .10 74HC123 ........ 1 .40 74HC132 .......$1 .25 74HC138 ... .... suo 74HC157 ..... .. S1 .25 74HC151 .. .....$2.25 74HC184 .......$2 .25 74HC174 ....... $1 .40 74HC244 ....... $2.00 74HC245 .......$2 .50 74HC273 ....... $2.75 74HC367 ....... $1 .85 74HC373 ....... $1.80 74HC393 ....... $2. 75 74HC4040 .. ... $l .65 74HC4060 ..... $3 .95 74HC4066 ..... $1 . 70 M1il!t1\'1'1'f Description .. ..... $ lhti1dit1 Description ....... •.. $ 74504... ......... $l.20 74S08......... ... $l .50 74S30............$1.00 74S32 ............$l .OO 74S132 .......... $3.50 74S133 .......... $l .20 74S138 .......... $2.50 745139 .......... $3.30 74S174 .......... $3.50 SifiMitl 4000 .............. $0 .75 4001 .............. 45 Descnpt1on ..... ..... $ 4002 .............•$0 . 85 74F00 ............$0.25 4 0 06 .............. $1 .55 74F04 ............$0.25 4007 .............. $0 .45 74F32 ............$0.25 4008 .............. $1.70 74F74 ............$0.25 4 009 ...... ... ..... $0 .90 74F109 .......... $0.50 4 0 10 .............. $0 .90 74F138 .......... $l .OO 4011 ·············· $0.45 74F151 .......... $1.20 4012 ......... ..... $0 .45 74F153 .......... $l .20 4 01 3 .............. $0 .70 74F157 ..........$1 .20 4014 .............. Sl .OO 74F194 .......... $2.41 4015 ... ........... $0.90 74F244 .......... $3.·r,; 4018 .............. $0.70 4017 ··········· ···'1 .35 4018 ......... .....$0.50 Descnpt1on........ $ 4019 .............. $0.SO 74L500 ......... $0.30 4020 ..............$1.40 74LS01 ......... $0.60 4021 .............. $1 .50 74 LS02 ....... $0.60 4022 .............. $1 .45 74 LS03 ..... .... $0.60 4 023 .............. $0 .45 74LS04 ......... $0. 75 4 024 ..... ..$l .60 74LS05 ......... $0. 75 4025 ·············· $0 .45 74LS08 ......... $0 .60 4026 .............. $1 . 10 74L510 .. $0.30 4027 ............. $0.85 74 LS 11 .......... $0. 75 4028 ........... ... $1 . 15 74LS13 ......... $0.90 4029 .............. $1 .50 74LS14 ......... $0.75 4030 ... ........... 50 74LS15 ......... $0.80 4033 ..... . ... $2 .75 74LS20 ......... $0.90 4038 ... $2 .2S 74LS21 ......... $0.90 4040 ... $1.20 74LS27 ......... $0.90 4042 .. . ..... $1.50 74L530 .........$0.30 4043 .............. $l .20 74LS32 ......... $0.60 4044 ...... ........ $1 .25 74LS379 ....... $0. 70 4045 ...... ........ $4 .90 74LS38 ...... ... $0.80 4046 ........ ..... $1 .00 74LS42 ......... $l .20 4047 ............. $1 .90 74LS47 ......... $1.80 4049 ....... $0 .60 74LS48 ......... $1 .80 4050 .......... ... $0 .60 74LS74 ......... $0.40 4 051 .............. $1.20 74LS75 ......... $1 .20 4052 ..... ... ..... $1 .20 74LS76 ......... $1.00 4053 ... .. $l .20 74LS85 ......... $0.85 4060 .... $2 .50 74LS86 ......... $0.60 4066 .... $0 . 90 74LS90 ......... $1 .20 4068 .. . ... $0.50 74LS92 ......... $1.20 4069. ....... $0 .50 74LS93 ......... $1.50 4 070 . ............ $0 .SO 74LS95 ......... $1 .20 4071 ............ $0 .50 74LS107 ....... $0.90 4073 .... $0 .50 74LS109 ....... $0.90 4075 ..... .. ..$0.50 74L S 112 ........ $0.70 4076 .. ........... $1 .90 74LS123 ....... $1 .30 40n .............$0 .50 74LS125 ....... $1.00 4076 .. . .......... $0 .50 74LS126 ....... $1 .00 4081 ········· .... $0 .50 . 74 LS132 ....... $1.00 4082 ............. $0 .50 74LS138 ....... $0.80 4093 .... · ... $0 . 90 74LS139 ....... $0.80 4098 .. ........... $1 .90 74LS145 ....... $1 .50 45104 ......... ... $7 .25 74 LS147 ....... $2.50 4503 .............. $1 .30 74 LS151 ....... $1.20 4510 .............. $l .40 74LS153 ....... $1.00 4511 ...... ........ $1 .45 74LS155 ....... $0.50 4512 .............. $l .40 74LS156 ....... $1 .50 4514 ··· ····••····· $2 .60 74LS157 ....... $1 .20 4515 .. ······ ' 1· 90 74L5158 .... .. . $1 .00 4516 ....... ...... $1 .60 74LS160 ....... $1 .50 4518 ........ $1 .50 74LS161 ..... .. $1 .00 4520 ............. $1.00 74LS162 ........$0 .50 4522 . ... $l .90 74LS163 ....... $1.10 4526 ............. $1.00 74LS164 ....... $1 .40 4528 ............. $l .95 74 LS155 ....... $1 .20 4532 ..... $2.65 4536 ... $6.50 74LS166 ....... $1.25 74LS168 ....... $2. 10 4538 ...... ... . ... $1 .20 4543 .. ....... .... $2 .SO 74LS174 ....... $1 .20 74LS175 ....... $0.70 4556 ............. $1 .25 74LS181 ....... $4.00 4584 ........... ... $1 .00 74L5191 ....... $1.20 40014 ......... ... $1.50 40175 ............ $2 .00 74LS193 ....... $1 .20 74LS195 .... ... $0.SO 74 LS196 ....... $1.20 74LS221 .......$2.00 74LS240 .... ... $ 1.40 Oescnpt,on ...... $ 74LS241 ....... $0.95 74COO ........... $1.00 74LS243 ....... $1.10 74C04 ······ ·•··· $1.00 74LS244 0•• •••• $2.20 74C08 ...... ..... $1.00 74LS245 ....... $2.95 74 C14 .... $1 .75 74LS257 ....... $1 .20 74C74 ...........$1.00 74L5258 ....... $1 .20 74C86 .... $1 .50 74LS259 ....... $2.25 74C90 ........... $2 .50 74 LS266 ....... $0.70 74C192 ......... $3.50 74LS273 .... ... $1.00 74C221 ·········$3.95 .74 LS323 ..... .. $8.50 74C244 ......... $3 .95 74LS352 ....... $2.20 74C373 ... .... .. $8 .911 74LS361 ....... $1 .00 74C9011 .... ..... $2 .90 74LS3111 ....... 11 .00 74C922 .......$14 .98 74LS387 ....... $1.00 74C928 .... .. .$13.911 74LS373 ....... $2.00 74C948 ....... $24.50 74LS374 .... ... $2.00 74LS375 ....... $1 .00 so. lfltlWl\t1 so. 14lili 74LS393 .......$1.00 74LS629 ....... $5 .95 74LS540 ....... $1.00 .LM393 ....... .... ..$0.60 .LM394CH ....... $7.9 5 .LM395T........... $9.9S LM395K .......... $7 .95 LM3 96K..... ... $16 .50 LM399H .......... $7 .50 Descripti on... ..... $ LM711 .... ......... $1.20 7400 ..... ..... ... .$0 .80 LM725 ............ $7.50 7402 ............. .$1.00 LM733. .... $1 .50 7403 ..............$1 .00 LM741............ $0 .60 7404 ..............$0 .30 LM747 ............ $1 .5 0 7406 ..............$0 .40 LM748 ............ $1.1 0 7407 ....... ....... $0.50 LM759 ............. $3 .90 7408 .......... .... $1.00 LM833 ........... $2.10 7409 .............. $1.00 LM1830 ......... $4 .90 7410 .............. $1 .20 LM : 871N ...... .. $7.50 7414 ..............s1.5 o LM1872N ... ..... $8 .60 7416 ........ ..... .$0 .50 LM1886 ........... $9 .10 7430 .............. $1 .00 LM2907•14 ..... $3 .50 7432 ........ ..... .$1 .00 LM2907-8 ....... $5 .10 7438 .............. $0 .80 LM2917· 14 ..... $2 .50 7442 .............. $1 .50 LM2917·8 ....... $4 .80 7445 ............ $1.00 LM3900 .... ...... $0.80 . 7446 .. . ... $1 .20 LM3909 ..... · .$2.50 7447 .............. $1 .75 LM391 1...... .. $3 .95 7473 .............. $1 .20 LM3914 ......... $2 .90 7474 .. .... ........ $0 .40 .LM3915 ........... $2 .90 7475 ... ....... ... ., 1.20 .LM3999Z ....... $5.95 7476 ..... ......... $l. 50 .LM 4250.. . .. $2 .4 5. 7483 ............. .$1 .10 .LM11CN .......... $4 .95 7490 .............. $1 .20 LM1 3600 ......... $ 2.70 7493 .. ... ......... $l .2 5 LMC555 ... $1.2 5 74121 ...... ...... $1.55 MAX232/ICC232 74123 ············$0 .50 HMC232 ........ $11 .95 74125 ······ ······$1 .00 OM350 .......... $21 .00 74126 ............ $1 .00 MC1408L8 ...... $7 .50 74150 ........... .$1 .90 MC1458 .......... $1 .20 74154 ............ $2 .50 MC1488 .......... $0.60 74157 ............ $1 .30 74161 ............ $1 .20 . MC1489 .......... $0 .60 MC1496 ... $2 .50 74154 ............ $1 .20 MC3334P........ $6 .95 74177 ... $1 .95 MC34018P ...... $8 .95 74193 ... ......... $1 .50 MOC3021 ........ $l .95 741 95 ............ $1.00 NE555 .. ........... $0 .5 o 741 97 ............ $1 .20 NE556 ............ $0 .95 74283 ............ $2 .45 NE558 .......... ... $6 .50 74290 ············$0 .90 .NE554 ............. $ 7.00 NE566 ...... $2 .9 o NE567 .... $2 .00 Description .. ......... $ NE570 .... $9.95 DAC0800 ....... $4. 95 NE571 .... $6.95 DAC0808 ... . .... $4 .90 NE572 .......... $1' .20 AOC0800CN .. $29 .95 .INS8250N ... $18 .10 ADC0803 ... ... $13 .50 .TA7205P........ $2.95 ADC0804 ......... $7 .95 TDA1024 .... .... $3 .90 ADC0808 ....... $13 .00 TEA 1002 ....... $17 .50 AOC0820LCN .$27 .95 TL054 ............. $2 .10 DAC0832 ......... $7 .95 TL071/ LF351 . $1.20 OAC1020 ....... $16 .28 TL072/ LF353 . $1.60 11C90 ......... ... $16.50 TL074/ LF347 . $1.40 DAC1220 ....... $22 .95 TL081 ....... ....... $1 .90 DAC1408 ......... $l.OO TL082 .... ·· $2 .20 .AD590J ......... $ 12.95 TL084 ............ . $l .5 0 UA710CN ....... $1 .00 UA739 .............$2 .75 :uP08288 .... $16.50 Ntidil'tl 1\P'KJ·p•p Description ... ....... $ 2114 ......... ....... $5.20 2716 .............. $1 2.50 .. 2732·200........ $8 .25 2764-250........ $8 .95 27126 ....... ., .. ::; $8 .00 27256•2S0 ....... $9 .50 27512-250 .... .$14 .9S 27•1MEG ....... $29.50 · 27C64-200NS . $8.95 27C128 ........ . $12 .50 27C2561 2SONS ........... $15.SO 27CS12 ......... $22 .50 27C 1 MEG .... $34 .50 4116 16K ........ $3.9 S 4164· 10 .. ........ $4 .95 4464•10 .......... $5 .50 4464•08 ......... .. $5 .90 41256·10 .... ..... $4 .95 41256·08 ......... $S .50 44256·10 ....... $ 13.9S 44256·08 ....... $9.00. 44256•07 ....... $15 .95 6116 ........ $5 .50 6264LP ·10 .. $19 .95 62256LP· 10 .. $39 .95 1M·10 ......... $9.00 1M·08 ...... ...... $9.00 - D escnpl1on . S 256 X 9·80 .. $24.00 1 M X 9 -80 ... $89.00 1M x 9•70 ... $99 .D0 fjl k -,1v11 -11 ■ 111 ■ Description ........ $ 256 K x ll-60 $24. 00 1M X 9-80 .... $89.00 1M X 9•70 ....•$99.00 111t1WIW! Descnpt1on .......... S 6502A ........... $16 .96 6522A ........... $15 .95 6802....... s7 .oo 6809 ...... ..... ... $17 .00 6821 ................ $5 .SO 6845 ... ............. $9 .95 6850 ....... $3 .50 7910 $29.95 8035N•6 .......... $6.90 8039 ................ $9.90 8060 ......... $8 .00 8085.A ......... $16 .50 8088 ............. $12.50 . Descnption .... ... S: XR2208 ...... ... .. $9.95 ICL7106 ........ $15 .95 .AY·3· 1015 ..... $11 .95 . XR2209 ........... $6 .90 ICM7216B ..... $~.50 XR2211 ........... $7 .95 LF13741 ......... $0 .80 .AY·3·8910 .. ... $19.95 .AY·5·8116 ..... $14 .50 XR2216 ........... $5.90 NS18450 .... ." $26. 98 CA3028 ......... $3.95 XR2240 ........... $6.95 S3530 .......... $24.95 CA3086 .. $1.20 XR2243 ........... $5.95 SP0256 ....... $21.95 CA3130E ........ $2 .90 26LS30 .......... $2 .00 . TR1863 .......... . $8 .90 V20A ........... $35.95 CA3130T......... $3.95 26LS31 ........... $2 .00 V20 .............. $29.95 CA3140E ..... ... .$1 .30 26LS32 ........... $2 .00 W02123 ........ $29 .95 5534AN ........... $ 3 .95 CA3140T......... $2.95 CTS256A ...... $45 .50 . 8155 ................ $8.95 XR8038 ...... ..... $7.50 Z80A CTC ...... $8 .50 OM2502 ........ $13.50 8156 ............... .ss.5 o LF347 ........ ... .. $l .40 81LS95 ........... $1.00 Z80B CPU .... $13.50 Z80A CPU ....... $5.75 LF351 N.......... $l .20 81LS96 ........... $2 .75 LF353 .. , .......... $l .5 0 8216 .............. $3 .00 Z60A PIO ........ $4.SO LF356N .......... . $1.50 8237 .............. $14.50 Z80A SIO..... $14.50 LF357 ............. $2 .95 8255 ................ $6 .90 5o LF398 ........... · $5 .9 o 8279 .............. LM301H ... ..... $1.50 8830 ·············· $6.95 8 087·3 ....... $189 .00 LM301 N.......... $0 .50 95H9 o ......... ..s10.5o 8087-2 ....... $279.00 LM302H ........ · $6.50 9667 ........ ...... $0.90 8087-1 ....... $379.00 LM305H .......... $1.50. 966 8 .............. $2.95 80287·6 ..... $249 .00 LM307CN ....... $1. 50 80267•8 ..... $379 .00 LM308 ... . ··· $0 .SO 80287· 10 ... $459.00 LM309K. .... $2 .95 80387-16 ....$695 .50 LM310N .......... $4.95 . 80387·20 ..... $795 .00 LM311 ........... $1.00 . 80387-25 ... $895 .00 LM324 ............. $1 .20 80387•39 .... $995 .00 LM331 ...... .. ... ..$6.00. LM339 ............. $0 .6'l · LM348 ............ $1.00 • Description......... $ LM 317T. .... ...... $2 .50 LM317KC ........ $5.50 LM320K12 ...... $1 .40 LM320K·05..... $3 .00 LM320T•5 ....... $1 .40 LM 323K ......... $9 .SO LM326 ............ $5 .50 LM329DZ ....... $0 .90 LM334Z ........ .. $1.70 LM335Z .......... $2 .50 LM336Z·2 .5V.. $2 .9S LM336Z5 .0V... $2 .95 LM337T. ......... $2 .90 LM337KC ..... $12 .50 LM 338K $9 .45 LM340T•5.. $0 .90 LM340KC ·5 ..... $2 .9S LM340T·5 ...... $0 .90 LM340KC·5 .... $2.95 LM340T· 12 ..... $0 .90 LM340T·1 8 .... $2 .00 LM340T•15 ..... $0 .90 LM340KC·12 .. $4 .95 LM350T.......... $8.40 LM3501( ........ $11 .50 LM378 .. ........ . .$6 .9 5 TL494 .......... ·· $4 .90 LM723CH ...... $1.50 LM723CN ....... $0 .95 78H GK ............ $9 .SO 78P05GC ..... $14 .50 7805 ......... .... $0 .75 78L12 ...... $0 .75 78L 15 .............. $0.75 79LOS............. $1 .20 7QL12... .. $1 .20 79L15 .............. $1 .20 LM396K ......... $16 .50 8:011~1 Description ...... $ 76489 .. . ... $12 .50 ICL7660 ... $6 .90 VN88AF.......... $S.95 MM5369 ......... $4 .95 Description .......... $ 3 mm LEDS Rod ........... ...... $0.20 Graen ............ $0 .30 Yellow ............. $0 .30 Orange ........... $0 .30 5mm LEDS Ro d ................ $0. 20 Gretn ..... ........ $0 .30. Yollow .......... ... $0.30 Orange ........... $0.30 l\1!!Mtl u. LM349 ............ $2 .95 LM358 ... .......... $l .40 LM361 ....... ..... $4 .95 LM380N• 14 ..... $1.95 LM380N-8 .. .... . $1.50 LM311 ............. $4.9S LM382 ........... .. $3.50 LM383 .......... ... $4.95 LM384 ......... .... $3.50 LM388-1 .. .... .... $1 .40 LM387 .... ......... S2.75 LM390 ............ S2.95 LM392 .. ........... $1.80 - 10mm J UMBO LEADS Rod ..... ........... . $1 .50 Grun ............. $1 .50 Orang e........... $1 .50 SUPER BRIGHT LEDS Rod ........... ..... . $1 .00 Groen ............. $1 .00 Yellow............ $1.00 5mm FLASHING LEOS Rod ............. .... $1.25 RECTANGLE LEOS Rod ................. $0 .25 Green ............ $0.30 Yollow ....... ..... $0.30 Orange ........... $0 .30 5mm RED/GREEN DUAL LEO ..... $1. 05 i Prices are 1 ·9. I 1 Q-99 : : : l~ss 10%. 100+ less 20%. L.---------~ 1 j BNC PLUGS AND SOCKETS LEDS vii w ~t== ~t== r---------------------------, 1 I 1 PICK UP YOUR NEW 1992 MAIL ORDER CATALOGUE AT ANY OF OUR ROD IRVIIIG I ELECTRONICS STORES or PHONE 008 33 5757 : FOR YOUR FREE COPY or WRITE TO PO BOX 620, I CLAYTON. MELB. VICTORIA. 3168 / Designed to transmit at BNC MALE PLUG 1-9 10-98 100+ '.:: 40kHz (L 19990) & recieve 1-9 1 - 100+ Z10140(R) $0.15 $0.12 $0.10 · at 40kHz (L19991J withup Z10141(G).. $0.20 $0.18 $0.15 to 20V 1/P on the Z1 0143(Y).. $0. 20 $0.18 $0.15 \ transmitter. These units Z10145(0).. $0.20 $0.18 $0.15 \ can't be heard so are : QUALITY 5mm LEDS •:: Ideal for TV remote Z10150(R). $0.15 $0.12 $0.10 \ controls, water level BNC PANEL SOCKET Z10151(G). $0.25 $0.20 $0.18 }: dectectors, burglar Z10152(Y) .. $0.25 $0.20 $0.18 ? alarms, motion 1-9 10+ 100+ \ dectectors & infonnation P10516 $2.50 $2.25 $1.50 } carriers aa they can be \ either pulsed or used in a •• QUALITY 3mm LEDS '"'" ~,,.., ![ l i••- - 1·9 10-99 100+ P10530 $3.95 $3.75 $3.00 ~ BNC SOLDERLESS TWIST ON PLUG CANNON PLUGS AND SOCKETS CANNON TYPE 3 PIN CHASSIS MALE 1-9 10-99 100+ P10962 $3.50 $2.95 $2.50 -=~ CANNON TYPE 3 PIN LINE FEMALE 1-9 10-99 100+ P10964 $3.95 $3.50 $2.90 a CHASSIS FEMALE 10-98 100+ P10966 $4.95 $4.50 $3.50 c:::::i 1O0M+ 1-9M 10M+ 1-9M 1ClM+ Slz.e AA 450mAH 1-9 10+ $2.95 $2. 75 SlzeC 12AH $9.95 $9.50 SlzeD 12AH $9.95 $9.50 ffi4c LOW PROFILE IC SOCKETS Save a small fortune on these "Direct Import" low profile IC sockets! PCB mounting solder tall. All tin plated phosphor bronze or borrylllum and dual wlpo for rollablllty. 1.9 10+100+ P1osso pin 15e 12e 1oe P10560 14pin 20e 18e 1Se P1osss 16pin 2oe 1ee 1se P1056718pin 30e 25e 22e P10 56 a 20pln 35~ 3De 25e P10569 22pin 35f 30e 26e P10510 24pin 3se 30e 2se :}. 1-9 10+ 100+ :\ • DE9P Spin plug P12166 $1.50 $1.20 $1 .00 /. • DA15P 1Spin plug ... P12168 $1 .50 $1.20 $1 .00 P12170 $4.50 $3.95 $3.50 :\· ): ::'. /. :;:;:" i\ D TYPE <:: t $1.00 $1.00 -- ELECTRET MIC INSERTS 1-9 10+ • Plug P12200 $3.95 $3.00 • Socket P12201 $3.95 $3.00 :·-:.. ./: . ···/::..,c,:.,~ ,. $3.50 100+ $2.95 $2.95 ...,...,...,==-~:: : :::.::):::::.:::·._'·'. ---- - -""? ) / ) ( / :>> DE9P OE9S DA15S DA15C DA 15S DB25C DB25P DB25S 1-9 $1 .00 $1.00 $1.00 $1.00 $1.00 $1.00 $1 .00 $1.00 10+ $0.80 $0.70 $0.70 $0.90 $0.80 $0.80 $0.80 $0.80 100+ IDC CENTRONICS 36 WAY PLUG & SOCKET Theso quality 3 lovel wire wrap sockets are tin plated phosphor bronzo. P105798pin $1.50 $1.40 P10580 14pin $1.85 $1.70 P1058516pin $1.95 $1.80 P10587 18pin $1.95 $1.80 P10590 20pin $2.95 $2.75 P10592 22pin $2.95 $2.70 P10594 24pin $3.95 $3.50 P10596 28pin $3.95 $3.50 P10598 40pin ·$4.95 $4.50 P10880 .. P10885 :i• P10891 \ P10892 .. ,.. P10895 P10902 P10904 P10905 JDC SOCKETS :\ 1-s 10+ :{ • DEBS 9 pin oocket · · P12161 $1.50 $1.20 f. • DA15S 15 pin oockel :\ P12169 $1.50 $1.20 (: • 0B25S 15 pin oockel (' P12111 $4.50 $3.95 ) \ DB25 CONNECTOR SPECIALS -- :-·::. • DB2SP 25 pl,1 plug P10572 21ipln 45e 35e 30e :\ P 10575 40pin 45e 40e 35e C 100M+ 100M+ > NICADS Save a fortune on expensive throw away batteries with these quality Nicads and Rechargersl 10+ 100+ RED 2oe 1se 12e GREEN 2oe 1se 12e . YELLOW 2oe 1se 12e •• ORANGE 2oe 15e 12e $2.SOM $2.20M $1.90M W12676 • CIC16 16 con. $3.50M $3.20M $2.SOM W12678 • CIC25 25 con. MONITOR & KEYBOARD SWITCH BOXES only $69.50 ~ ..... · 10M+ 4 WAY••.••••••••••.•. $69.95 ( RECTANGULAR LEDS WIRE WRAP IC SOCKETS 1·9M ( :': \ ) i 2 WAY..•....••••..... $59.95 "':::::\:.:c" ·.·.... . .....,,.,,,,............,.,~ Transmitter 1-9 10+ L19990 ••••• •• $2.95 $1 .95 CANNON TYPE 3 PIN LINE MALE $1.30M $1.lOM $1.00M W12672 • CIC9 9 con. 1-9 M 10M+ 100M+ $1.60M $1.50M $1.20M W12674 • CIC12 12 con. L---------------------------J 1111== 1-9 I I I : I I:: continuous wave mode. RED 5mm 1-9 10+ 210159 $1.10 $1.00 a CANNON TYPE 3 PIN 1-9 ------ FLASHING LEDS BNC CRIMP PLUG < ::: VOLTAGE REGULATORS BARGAINS Deecriptlon 1-9 10+ 7805UC 7812UC 7815UC 7905UC 7912UC 7915UC 78L05 78L12 LM324 555 741 $0.50 $0.50 $0.50 $0 30 $Cl.SO $0.60 $0.40 $0.40 $1.00 $0.40 $0.50 $0.45 $0.45 $0.45 $0.55 $0.55 $0.55 $0.30 $0.30 $0.90 $0.38 $0.45 ECONOMY TRAN::lFOt'IMER ! ~~ :/_ JJI:;JJll~ 1-9 10+ 2155 240V 6-15V 1A M12155 .........$8.95 $7.95 2156 240V 6-15V A2 M12156 ....... .$13.95 $ ~2.95 2851 240V 12•6V CT 250mA M12851 ......... $4.95 •• $4.50 6672 240V 15 30vc 1A lapped M16672 •.•....•$12.95 $11.95 1 1 c m::J 12V DC FANS 80 x 80 x 25.4mm 12V DC.1 .7 Watt 0.14 Amp T12469 •••• ••••.•••.••• $18.95 10+ fans, only $17.g5 FANS Oualtty fans for uso In power amps, computer hotspot cooling otc. Anywhoro you nood plonty of air. 240V 4 5/8.. T12461 ..$16.95 115V 4 5/8" T12463 ..$16.95 240V 31 /2.. T12465 .. $16.95 115V 31 /2" T12467 .. $16.95 10+ fan• (mh:ed) Only $14.95. 100+ $2.50 $8.95 We have a great range of HEATSINK panel meters at great prices! COMPOUND 010500 MU45 O•lmA $9.95 010502 MU45 50/SOuA $9 .95 010504 MU45 0-10DuA $9.95 010533 MU52E 0-SUA $12.95 010538 MU65 0-SOuA $12.95 010540 MUGS O•lmA $12.95 Heatsink compound is 01osso Muss0-1oouAs12.95 applied to the base and 010560 MU650-20V $12.95 · mounting studs of transistors & diodes. It MOSFET maintains a positive SPECIALS ,. heatsink seal that improves heat transfer from the device to the heatsink, thus ~O+ $9.50 $8.00 $10.00 $9.50 $8.50 $8.00 $9.50 $8.90 TOGGLE SWITCHES increaaing overall efficiency. H11800 .. 10g ...$2.00 H11810.150g. $29.95 WIRELESS MICROPHONE ~ Tuneable:92-104MHz Freq response: 501SkHz. Range: over 300 feet in open field. A10450 ........ ..$24.95 I PRODUCT SHOWCASE Big sound from small speakers Bose has now released the Acoustimass 3 Series II loudspeaker system. This compact system is claimed to have remarkable dynamic range and bass. The two tiny stereo imaging speakers each contain a single longthrow 65mm wide range transducer, especially designed for this purpose. At the heart of the system is the Acoustimass bass module. Shoebox sized, the bass module can be hidden anywhere in the listening room and still provides a satisfying bass response to complement the satellite speakers. Each driver is fully magnetically information, contact Mychelle Vanderburg at Bose Australia, 11 Muriel Ave, Rydalmere, NSW 2116. Phone (02) 684 1022. Central door locking for your car shielded, allowing it to be positioned near video monitors without interfering with picture performance. The Acoustimass 3 Series II is compatible with amplifiers or receivers rated from 10-100 watts per channel. It is available in either arctic white or black and retails for $879. For more Uniden mobile phone from Dick Smith Dick Smith Electronics has ai pocket-sized cellular phone that has go-anywhere capabi]ities and optional hamds-free operation fior in-car use. With features like 30number memory, dual PIN lock codes, three call timers and minute minder, the Uniden CP-5000 can keep you 'in toueh' and tell if anyone called whiie you wene away from the phone. In a handheld, conseFvation of battery power is of the utmost importance. The Uniden CP-5000 powers down automatically to conserve batteries and has capacity for 12 hours of operation in standby mode or two hours in active openation. An LCD readout sh_ows current status and signal strength. The unit comes with antenna, two batteries, charger and leather case. It.retails for $129'5 (Cat. E6040) 84 SILICON CHIP I The optioDal car mount'ing kit consists of a phone mount, haDdsfree microphone, speaker and battery charger. The car kit sells for an additional $399. Fon more informa'tdioD, visit you local Ditsk Smith Electronics store. One of the mod cons found on late model cars which is very worthwhile is central door locking. As soon as you unlock the driver's door then all the doors are open and when you lock the driver's door, all doors are locked. It makes it so much easier for you and your passengers. This power doorlock kit will upgrade any 4-door car to the 90s. The system consists of two master solenoids and two remote solenoids. The masters are intended for the front doors, whereby unlocking either of the front doors of your car will unlock all four doors. The main kit contains the four solenoid locks, the controller relay circuit, a full wiring harness and instructions to get the system running. The wiring harness is long enough to connect the four solenoids in even the biggest cars. The controller circuit may also be remote controlled with the purchase of an additional kit. The 4-door central locking kit sells for $119.50 and comes from Jaycar Electronics, 6 Leeds St, Rhodes, NSW 2138. Phone (02) 743 5222. New surge/spike protectors A pair of Australian made surge/ · spike protectors has been released onto the market by Triangle Safety. The first is a dummy plug that you fit Rechargeable lithium cells Rechar,geable lithium manganese dioxide button cells are now available from Pnemier, Batteries. These cells are ideal for memory back-up applications in portable equipment and have been designed with ex0ellent discharge eharacteristies. They offer a stable 3V outpl!l.t for most of their discharge. A single 3V rechangeable lithium coin Gell can now be used in applications where previously it was necessary to use three nicad cells, thereby improving both reliability and cost effectiveness. This new range of rechargeable lithium button cells can be charged using a simple constant voltage into the same power board that's used to power your fax machine, computer, video, or any other piece of electronic equipment that is prone to damage from dangerous voltage surges and lightning spikes. The plug u ses a semiconductor surge suppressor to automatically absorb any voltage spikes or surges. These are usually caused by loadswitching and lightning, but can also be generated by other equipment such as fluorescent lights, welders, motors , fridges, freezers, air conditioners and washing machines. The plug glows green w hen the power is on. The second product incorporates the protection plug into an extension cord, thereby protecting whatever you plug in to the lead. It also has a green charge - a full charge can be delivered in less than five hours. The cells are currently available in ea~ pacities of 20mAh and 70mAh and are fitted with printed circuit board pins for mounting. For further information, contact Premier Batteries, 9/15 Childs Rd, Chipping Norton, 2170. Phom.e (02) 755 1845. neon that glows when the power is on. For more information , contact Rod Irving Electronics, 74 Parramatta Rd , Stanmore, NSW 2048. Phone (02) 519 3134. Introducing the Prate! advantage. Protetfo r Windows': Protelfor Windows is an entirely new Printed Circuit Board design system created for Windows 3. Prate/fo r Windows brings the professionalism of Protel's proven PCB design sofware to the highly productive Windows 3 environment. New Protel users will start designing sooner and experienced users will work more efficiently than eve,: Jn 386 advanced mode, Windows 3 provides virtual memory capability, which allows advanced PCB users to design without .. restrictions on the total number of components, nets, tracks, etc. Protelfo r Windows supports the multiple document . 181 Top - □ MidB 0 - Mid 1 D Drill Guide D Drill Draw - 0.Mid 9 - □ MidlO 0 0 Midll 0 0 Mid 4 Mid 5 OMi d 6 0 Mid 7 0 0 0 - Mid 12 Mid 13 - □ Mid14 D Top fiiiBl -181 Bottom - JSolder Mas k - ' : Special Copper Tra ce Layers Visi ble D DRC Errorsl l 181 Grid 1 181 Grid 21a D Rats Nest - 181 Keep Outs Selections 181 Multi LayerD Background D - M hanical Laye rs 181 Tra ns pa rent D Dith ered Colors ech 1 ech 2 ilJ D Mech 3 D Mech 4 11!9 • • inte1face (MDI) standard. Any number offiles can be loaded at the same time , using standard Windows routines, to move information between different files or different applications. The Protel for Windows faimily consists of" Advanced PCB advanced level PCB layout - $1990. Options: Advanced Place $995, Advanced Route $995, Advanced Pack* - $3490. Select Printer IPoilSc,ipt P,inter on LPT1 : D Bottom Balch Mode 0 0 Seperete Page For Each Print Compoaile Print <at> Panels (Multiple Layers Per File) Scale P1int Scale ~ X Couection ~ YCorreclion ~ ;:;;,;====~ ,.__---:.__....,._..;....CJ ~~ ■ Technology Protel Technology Pty Ltd PO Box 204, Hobart Tasmania 7001 Phone (002) 730100 Fax (002) 730944 Tollfree 008 030 949 *Includes all 'Advanced' options. Prate! is a registered rrademark. Advanced PCB and Professional Schematic are registered trademarks of Prate! Technology Pty Ltd. Windows is a registered trademark of Microsoft C01poration Inc. MA RCH 1992 85 New double cassette deck from Yamaha Yamaha's new KX-W952 cassette deck replaces the previous KXW900 model and offers auto-reverse, Dolby B/C, HX Pro, infrared remote control and 'play trim', a feature allowing playback adjustment for the inconsistencies which can occur when playing a Dolby encoded cassette recorded on a ' different deck. This new deck uses a chassis that is claimed to eliminate chassis resonance & vibration. The unit also uses large anti-vibration feet for isolation. The unit contains two identical cassette decks housed in the one chassis. Both sections contain all features and are independent of each another. A single program can be recorded by either or both sections, or the first section can record one source while the other tapes a second source. One-touch twin recording permits simultaneous recording us- ing both decks. Other transport features include music search, random program play and intro scan. A full auto-dubbing feature combined with Yamaha's synchro-start allows the copying of both sides of a tape automatically. Random dubbing permits the copying of desired selections in any wanted order. Up to 15 selections can be made from a total of 79 on a single tape. Editing can be done via the unit's manual dubbing mode and a Dolby B tape can be re-recorded to Dolby C and vice versa. The unit retails for $999. For further information, contact Yamaha Music Australia, 17-33 Market St, South Melbourne, Vic, 3205. Phone (03) 699 2388. rather like a large fountain pen with a clear case so you can see how much butane is in the fuel reservoir. It comes with 2mm catalytic soldering tip and a small blow torch. A rotary control adjusts the flow of butane to the catalytic burner, allowing the heat output to be varied from the equivalent of a few watts to about 70W. The flint lighter is in the cap of the unit and spare flints are included. Also included is a small wire stand to enable you to rest the iron safely on your benchtop. The Iroda butane soldering iron retails for $39.95 (fuel not included). For more information, contact Altronics Distributors, 174 Roe St, Perth, WA 6000. Phone (09) 328 4459. Battery charger for camcorders World's fastest triple video AID converter Siemens has just released the SDA 9205-2, a triple 8-bit video AID converter IC. Claimed to be the world's fastest, this new device has a scanning rate of 30MHz and is intended for use with the three colour components for television. The fact that the chip permits oversampling means that external anti-alias filtering can be simplified due to internal digital filtering. Special features of the new converter include internal clamping and also separately selectable scanning data formats , in conformity with the international standard CCIR/Rec. 601/656. The chip was designed using CMOS technology and is suitable for digital image processing in PCs, television and video recorders, studio equipment and video printers. It is encapsulated in a PLCC-68 package. For more information, contact Edgar Sandy, Elec86 SILICON CI-ITP tronic Components Department, Siemens , 544 Church St, Richmond, Vic 3121. Phone (03) 420 7314. Low cost butane soldering iron Altronics has just released a new butane soldering iron that is low cost and has high heat output. It looks BatteryGuard is specifically de signed to tackle the problem caused by the memory effect in camcorder batteries. It operates by cycling the batteries to eliminate problems caused by memory effect. First, it discharges the battery at a current of 1.2 amps , down to 1V per cell, before starting · the recharge. When the battery is fully charged, a beeper sounds and the charger cuts off automatically. The unit can also be used as a tester to ascertain the battery status. It will accept most camcorder batteries, including Sony-type 6-volt, JVC-type 9.6-volt and Olympus-type 7.2-volt and equivalent. BatteryGuard retails for $59.95 and is available from Rod Irving Electronics. For more information, contact Rod Irving Electronics, 74 Parramatta Rd, Stanmore, NSW 2048. Phone (02) 519 3134. Reid Electronics, 127 York St, Sydney 2000. Phone (02) 267 1385 . Precision light sensor has digital output PLCC extractor from Scope Minute changes in light intensity can now be detected and measured with increased accuracy with the new TSL220 light-to-frequency converter from Texas Instruments. The device consists of a large-area photodiode and aBiMOS current-to-frequency converter which can be connected directly to a digital control circuit. Applications for the TSL220 include light control systems, burner flame control in heaters and solar monitoring. A single TSL220 can replace a discrete photodiode, amplifier and A/D converter. The device can also be used in photographic light meters and exposure timers, as well as to adjust display brightness to compensate for ambient light levels. It can monitor the consistency of finishes on paper, paint or other surfaces, to match colour, and to measure the light absorption or reflection by fluids in a medium. For more information, contact Rita Wong at Texas Instruments, 6-10 Talavera Rd, North Ryde , NSW 2113. Phone (02) 878 9000. SC Replacement for Eveready 276P battery This battery is just right for those devices that flatten regular 9Vbat~=l ,. teries in a matter ... ~- // of hours. It is a carbon zinc cell ' . and has a 4.3Ah capacity. It is equivalent to the Eveready 2 76P (no longer produced) which was widely used in Australian-made transistor portable radios and is still used by Telecom for their Pandora test set. It is available at $10.95 from David ·~·. "ji , .c... I Scope has just released a ]-lead IC remover especially designed for protecting fragile PLCC packages when they are being extracted from carriers. It works by first inserting the two steel fingers under the diagonal corners of the package. As the hand pressure is increased, the steel fingers apply a balanced upward pull to remove the package without damage. For more information, contact Barry McIntosh at Scope Laboratories, 3 Walton St, Airport West, Vic 3042. Phone (03) 338 1566. New watchdog has frightful hark hut no bite Do you have a problem feeding or bathing your guard dog? Well then, get rid of it and buy one of these. It is an electronic watchdog that will sense movement up to six metres away. On detecting an intruder, the electronic dog will emit realistic barking sounds, similar to that from a German Shepherd. Because it uses radar and not infrared detection, the unit can detect movement through doors or windows within its patrolled area. Adjustment of the range control determines the size of the area to be watched. A volume control alters the bark loudness. Powered by a 16V plug pack, the Hardy Dog needs to be placed about 1.5 metres above the floor for maximum sensitivity and will bark for five seconds when triggered. As long as movement continues, the 'dog' will bark. Get your Hardy Dog for $129.50 at Jaycar Electronics, 6 Leeds Street, Rhodes, NSW 2138. Phone (02) 743 5222. PRESTON ELECTRONICS 217 High Street, Preston, Melbourne Victoria 3072 (Cnr of Bell & High Street) Quantum 50-Meg SCSI Hard Drive (1 only) $295.00 Fujitsu 240V Coil Relays, DPDT 30A $9.95 ea Fujitsu 5V Relays, SPOT Subminiature 2764 Surplus Computer EPROMs, Erasable $19.95 $3.95 27128 Surplus Computer EPROMs, Erasable $4.95 27256 Surplus Computer EPROMs, Erasable $5.95 27512 Surplus Computer EPROMs, Erasable $6.95 QC-1910 Super Tiger 5MHz Oscilloscope $29.95 TEEPROM EPROM Writer Card/Cable + Software To Suit IBM-Compatible Computers $39.95 tr Mail Order Hot-Line B/Card-Mast/Card-Visa-Cheque Phone (03) 484 0191 MARCH 1992 87 July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid ; Booster For TV & FM Signals ; The Discolight Light Show, Pt.1 ; Tone Burst Source For Ampl ifier Headroom Testing ; What Is Negative Feedback, Pt.3 ; Amplifier Headroom - Is It A Con? August 1988: Building A Plasma Display; Universal Power Supply Board ; Remote Chime/Doorbell; High Performance AC Millivoltmeter, Pt.1 ; Discolight Light Show, Pt.2 ; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data; What Is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (Uses Rohm BA1404); High Performance FM Antenna ; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band ; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (Uses Mosfets) ; Poor Man 's Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten The Fan In Your Computer; Screws & Screwdrivers, What You Need To Know ; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1 ; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSS Adaptor For Shortwave Receivers ; Why Diesel Electrics Killed Off Steam ; Index to Volume 1. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; Simple Computer Sound Repeater; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LDS0 Loudspeakers. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher For Model Rai lways (uses LM3909) ; Build A Simple VHF FM Monitor (uses MC3362), Pt.1 ; Lightning & Electronic Appliances ; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor For CD Players; Map Reader For Trip Calculations ; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Electronics For Everyone Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electron ic Pools/Lotto Selector; Synthesised Tom-Tom ; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; Electronics For Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dim mer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperatu re Controller; Understanding CRO Probes ; LED Message Board, Pt. 3. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electric Locomotives. Use this handy form to order your back copies J r-------------- - ------ - ------- - - ---- -- -, Please send me a back issue for: 0 October 1988 0 November 1988 0 March 1989 0 April 1989 0 August 1989 0 September 1989 0 January 1990 0 February 1990 0 June 1990 0 July 1990 O November 1990 O December 1990 0 April 1991 0 May 1991 o September 1991 o October 1991 0 February 1992 0 0 0 O O July 1988 December 1988 May 1989 October 1989 March 1990 o August 1990 0 January 1991 0 June 1991 0 November 1991 Enclosed is my cheque/money order for $___or please debit my: Card No. II II 0 August 1988 0 January 1989 o June 1989 0 November 1989 0 April 1990 0 September 1990 O February 1991 0 July 1991 O December 1991 O Bankcard II ~~~~~- ~ - ~~~~~- ~-~~-~~- . Signature _ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _ /_ _ Name _ __ _______________________ Street _ __ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ Suburb/town ______________ Postcode _ _ _ _ __ 0 0 0 0 0 0 O 0 0 O Visa Card September 1988 February 1989 July 1989 December 1989 May 1990 October 1990 March 1991 August 1991 January 1992 O Master Card $5.00 each (includes p&p). Overseas orders add $1 each for postage. NZ orders are sent air mail. Detach and mall to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 6503 I I L-------- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ - 88 SILICON CHIP May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mozzie CW Transceiver; Waveform Generation Using A PC, Pt.3; 16-Channel Mixing Desk, Pt.4; What To Do When Your Computer Goes Bung, Pt.1. June i990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load _ Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To A Computer; What To Do When Your Computer Goes Bung, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station; What To Do When Your Computer Goes Bung, Pt.3; Weather Fax Frequencies. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-Day Programmable Timer; Introduction To Stepper Motors; GaAsFet Preamplifier For The 2-Metre Band; Modern 3Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; AlarmTriggered Telephone Dialler; High Or Low Fluid Level Detector; Simple DTMF Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (Uses BA 1404 & TDA7000) Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super-Sensitive FM Wireless Microphone; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages); UHF Remote Switch; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Install A Clock Card In Your PC; Index to Volume 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; Active Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Simple Service Tips For Your Microwave Oven; Active CW Filter For Weak Signal Reception; How To Find Vintage Radio Receivers From The 1920s. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2; What To Do When Your Computer Goes Bung, Pt.4. September 1990: Music On Hold For Your Telephone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Sur/sound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; The Bose Lifestyle Music System; Using The NE602 In Home-Brew Converter Circuits. November 1990: Low-Cost Model Train Controller; Battery Powered Laser Pointer; A Really Snazzy Egg Timer; 1.5V To 9V DC Converter; How To Connect Two TV Sets To One VCR; Introduction To Digital Electronics; Simple 6Metre Amateur Transmitter. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape -A Game Of Skill; Wiper Pulser For Rear Windows; Versatile 4-Digit Combination Lock; 5W Power Amplifier For The 6Metre Amateur Transmitter; The Great Green CD Pen Controversy; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens; Electric Vehicles - The State Of The Art. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose 1/0 Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateurs & TV; A Look At The Config.Sys & Ansi.Sys Files. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2; Playing With The Ansi.Sys File; FSK Indicator For HF Transmissions. May 1991: Build A DTMF Decoder; 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1; Setting Screen Colours On Your PC. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Electric Vehicle Transmission Options; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles; CD Error Analyser, Pt.1; Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2 ; Tuning In To Satellite TV, Pt.2; PEP Monitor For Transceivers August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Error Analyser For CD Players, Pt.2; Tuning In To Satellite TV, Pt.3 ($1000 Satellite Ground Station Reviewed); Installing Windows On Your PC; StepBy-Step Approach To Vintage Radio Repairs . September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1; Build A Fax/Modem For Your Computer; Ultrasonic Switch For Mains Appliances; The Basics Of AID & D/A Conversion; Windows 3 Swapfiles, Program Groups & Icons; How Glass-Mount Antennas Work. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSourid Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. November 1991: Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Error Analyser For CD Players Pt.3; Modifying The Windows INI Files. December 1991: TV Transmitter For VCRs With UHF Modulators; Build An lnfrared Light Beam Relay; Compact Solid-State Laser Pointer; Build A Colour TV Pattern Generator, Pt.2; The Miracle Piano Teach ing System; Windows 3 & The Dreaded Unrecoverable Application Error. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V BA Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; The GPS Satellite Navigation System. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier; 12VDC/ 240VAC 40-Watt Inverter; Adjustable 0-45V BA Power Supply, Pt.2; The Mobile Telephone Revolution; D!lsigning A Model Speed Controller,, PLEASE NOTE All issues from November 1987 to June 1988 are now sold out. All subsequent issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tearsheets) at $5.00 per article, including postage. When supplying photostat articles or back copies, we automatically supply any relevant Notes & Errata at no extra charge. MARCH 1992 89 ASK SILICON CHIP Got a technical problem? Can't understand a piece of jargon or some technical principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Active antenna still available In your January 1990 issue, you featured an active antenna for shortwave listening made by Jiloa Pty Ltd, of Glenhuntly, Victoria. I am very interested in obtaining such an antenna or something similar, as I live in a small flat with no opportunity for an external antenna. Could you please tell me whether the antenna is still manufactured or if there are alternative units on the market? (K. J., Kingston, ACT). • We have been in contact with Jiloa Pty Ltd who inform us that they have stocks of the Active Antenna for shortwave listening. Their address is PO Box 73, Glenhuntly, Vic 3163. Their phone number is (03) 587 3225. What do open collector outputs do? I have built the 4-Digit Combination Lock described in the December 1990 issue of SILICON CHIP and wish to marry it to a burglar alarm project published in another magazine. The Wants infrared remote control for model trains I am 15 and if possible I would like to build an infrared remote controlled power unit for my model train layout, but how? I have looked back through copies of the electronics magazines kept at the local library but I have found very little. However, one design seemed semihelpful. This circuit was a single-channel device, which used two 555 timers in the handpiece to give a pulse modulated carrier signal to two infrared LEDs. This was then picked up by the receiver, amplified by a uPC1373H chip and then 90 SILICON CHIP thing that has me tricked is the open collector output of the combination lock circuit. This involves a BD681 transistor (Q3) but I don't know what it actually does. Can you help me? (B. D, Forth, Tas). • Open collector outputs are fairly common in logic circuitry and are a feature of comparators such as the LM339 and bipolar logic ICs such as the 7401, 7403 & 7405 (and LS derivatives). Almost always, an open collector output employs an NPN transistor arranged so that it has no connection to the collector - hence "open collector". The collector connection is then provided by the external load which has its other side connected to a positive supply rail. So what does an open collector output do? Generally, it can be regarded simply as a switch. When turned on, it switches the collector to ground or 0V. It can be thought of as being equivalent to the door switches for car courtesy lights. When these switches operate, they connect one side of the cabin light to chassis (ie, 0V). Not all car courtesy lights work accepted by an LM56 7 PLL tone decoder chip, which in turn controlled the power to a device that was plugged into a socket provided. For the controller I have designed, five buttons are needed in the transmitter: two direction buttons , two speed buttons and a stop buttori. The receiver would take the signal in and control either the power level with eight voltage divider chains using a 4051 analog multiplexer, or the direction with a transistor bridge circuit. If using a design similar to that in the magazine, I would need to multiply everything by five. Is there any other way of achieving the same thing, such as a single chip, like the one available for the Teletext Decoder remote control unit? (C. I., in this way but most do. So what can you connect to an open collector output? In the case of integrated circuits, it is usual for an open collector output to be able to "sink" (ie, switch) only a small current, say up to 10 milliamps. This means that an open collector output in an IC is typically used to pull a logic input low (TTL or CMOS). In the case of the combination lock circuit you referred to, the BD681 can be used to either pull a burglar alarm input low or switch a relay. The circuit already incorporates a protection diode (D30) for this purpose. An equivalent to the open collector output described above is the "open drain" outputs used in CMOS logic ICs such as the 74HC03 quad 2-input NAND gate and the 74C906 and 74C907 hex buffers. Here the output device is a Mosfet with its drain having no connection. However, the output Mosfet is an N-channel device in the case of the 74HC03 and 74C906 devices and a P-channel device in the case of the 74C907. In the first two cases, the N-chan- West Chatswood, NSW). • Trouble yourself with this problem no more. As your letter arrived, we were putting the finishing . touches to a complete infrared remote controlled system for model trains. We plan to publish it in the coming April and May issues of SILICON CHIP. The design essentially adds infrared remote control to the well proven PWM controller featured in the April and May 1988 issues of SILICON CHIP. It is highly flexible and controls momentary and latched channels, as well as the train control functions. It is also possible to build as many controllers as you want, say for a large layout, and they can all operate independently. nel devices are again only able to sink a few milliamps and they may be used for voltage level translation or wiredlogic functions. Where a P-channel device is used, it can only "source" a few milliamps and it may be used to pull a circuit input high. Minimising output offset voltage I have just seen your stereo amplifier module as described in the February 1992 issue of the magazine. The design looks impressive but I note that you have made no provision for adjustment of the output offset voltage. Why haven't you done this and is it possible to add in a trimpot to do the job? (S. H., Canterbury, NSW). • Normally, the output offset DC voltage with this new amplifier can be expected to be within ±30mV. With this voltage across a nominal 8-ohm loudspeaker which will normally have a DC resistance of about 5.5 ohms, the resulting current will be about 5.5 milliamps. This current is so small that it is of no consequence either to the loudspeaker or to the amplifier output stage. Even if the input differential pair transistors were badly matched, the offset voltage at the output is not likely to exceed ±l00mV. And if this voltage was present across a nominal 8-ohm loudspeaker, the current is still only about 18 milliamps which is hardly worth worrying about. Sure the currents would be doubled if you were using 4-ohm loudspeakers but even then the DC power being dissipated in the voice coil(s) is only 5 milliwatts. Hardly a problem, is it? The only situation where amplifier DC offsets are of concern is where output transformers are involved. This is the case where an amplifier is driving a 70V or lO0V line transformer in a public address system. Or it might be driving a transformer in an electrostatic loudspeaker. Here, instead of voice coil resistances of 3-6 ohms, we are concerned with transformer primary DC resistances of 100 milliohms or less. Now, if the amplifier offset voltage is ±30mV, the current through the transformer primary becomes really significant - 300 milliamps or more. That will cause a major increase in dissipation in the amplifier's output stage and will probably lead to satura- Electronic ignition & positive chassis vehicles I have just built and installed the High Energy Ignition System as described in the April 1988 issue in my Jaguar. It goes well although now the tachometer does not work properly. Can you suggest a cure? Also, what modifications, if any, would be required to make the circuit work in a vehicle with a positive chassis? (P. W., Longueville, NSW). • Back in February 1989, we answered this question with a suggested circuit involving a smcJ.ll mains transformer driven by a transistor switching circuit. We still don't know whether the concept works as we have had no feedback from our readers. How. - - - - - . - - - - - - - - - +12v v1A ever, the circuit is shown IGNITION sw1TcH here. Give it a try. 1k We can see no reason why the High Energy Ignition System could not 4.7k TACHOMETE~ be adapted to a vehicle with a positive chassis. You would just have to TO POINTS make sure that the metal----------------CHASSIS work was connected to the positive battery conFig.I: this circuit can be used to drive an impulse tachometer when electronic ignition nection instead of to the negative line. is used. 01 02 1 o-t1-<~W.-....----''H INPUT 22 k 2xBC556 C 2.2pF IFig.2: the easiest way of adding offset adjustment to the 50W amplifier module is to connect a 200!.1 trimpot between the emitters of Qt & Q2. tion of the transformer's core. Clearly, if the amplifier module was going to be driving a transformer, an adjustment for offset voltage would be mandatory. In that case, the easiest way of adding the adjustment would be to connect a Z00Q trim pot between the emitters of Ql and QZ, with the wiper connected to the ZZkQ resistor. The accompanying modified portion of the circuit shows how this could be done. However, we are not recommending that this stereo module be used for driving transformers. It would also be physically difficult to make this modification on the PC board. But say you are a fanatic about this sort of thing and want to minimise the offset DC voltage as much as possible. The practical way to do this is to match the input transistor pair (ie, Ql & QZ) for Vbe· Vbe is the DC voltage between base and emitter and, for a silicon transistor, sits normally at around 0.6V. For our prototype amplifier, the Vbe measurements for Ql and QZ in one channel were 0.581V and 0.582V and this gave an offset voltage at the output equal to lmV; ie, the difference. Similarly, in the other channel, the Vbe voltages were 0.570V and 0.585V, giving an offset voltage of ZlmV (not quite the difference but we'll explain this in a moment). Say we had found Vbe voltages in one channel of 0.57V and 0.585V and a similar situation in the other channel. We would expect to get an output offset voltage in both channels of around +15mV or -15mV. Now, merely by swapping two of the transistors so that the 0.585V Vbe transistors were both in one channel and the 0.57V Vbe transistors were in the other channel, the offs et voltages MAHCH 1992 91 Connecting protective diodes across relays I have a question about diodes , specifically diodes such as the 1N4004 when they are used to protect electronic components from large negative voltages that occur when an inductive load such as a relay is turned off. I am a motor mechanic and because of the electronics found in modern vehicles, I was told when fitting a relay to such a vehicle that I must use what we call a protection diode which is fitted in the way I have shown in Fig.3. But in the December 1991 issue of SILICON CHIP, the circuit on page 26 (infrared light beam relay) shows two protection diodes - D5 and D6. When I saw this , I thought that would be close to zero. So by matching the Vbe of the differential pair transistors, you get close to zero offset voltage. Beta comes into the calculation too and ideally the differential pair transistors should also be matched in this regard. That is why the offset voltage in the second example was 21mV rather than 15mV - the differences in beta were affecting the result. Dicky disc drive doesn't T have been an avid fan of your magazine for some time now and I have found in the past that you have been only too willing to answer any queries which I may have had. I have a problem regarding an NEC computer, model APC-H03C, which belongs to my brother-in-law. I have only a very limited knowledge of computers, however, it would appear that the controller card is faulty, because neither disc drive will work, showing only a disc reading error every time. I have tried swapping the drives and using the other drive connections, etc, all to no avail. I have contacted NEC and other computer repairers and they all tell me that it would be impractical, if not impossible, to repair the computer. The problem is, my brother-in-law has a great deal of in- 92 SILICON CHIP + Fig.3: how a protective diode is fitted across a relay coil. perhaps I have been making a mistake by only using one diode. Have I? (F. L., Cabramatta, NSW) . • Your depiction of the normal connection of a protection relay is correct. The diode is connected across the relay so that when the relay is energised, the diode is reverse biased. Then when the relay current is switched off, the resulting negative peak voltage generated by the relay coil is harmlessly shunted by the protection diode. The reason for the additional diode in the infrared light beam relay circuit is to prevent negative voltages from appearing at pin 3 of the 555 (ICZ). This could happen in the following way. When the 555 turns off, the collapse of the magnetic field in the relay armature causes a large negative peak voltage to be generated at pin 3. This is clipped by diode D6 so that with this diode only in circuit, pin 3 would be clamped briefly at -0. 7V with respect to the 0V line. However even small negative voltages at pin 3 can cause the 555 to "latch up" and cease operation until the supply voltage is removed and then reapplied. D5 prevents the -0. 7V from appearing at pin 3 and thereby ensures normal operation. formation stored on the 8-inch discs which the computer uses and we are now unable to retrieve any of it. Is there any way that we can retrieve this information and place it on the more standard size discs using another computer, or is there anyone amongst your readers who could possibly assist with a replacement controller card? (W. H., Coombabah, Qld). • When it comes to disc drives, suspect a mechanical fault before an electronic fault . Have you tried cleaning the heads? For a machine of this age, it is likely to have been a long time since the heads were last cleaned. Failing that, try getting a quote for a repair from a local computer repair place. If that is not possible, you will need to see if you can gain access to an identical machine so that your discs can be transferred to 5.25-inch or 3.5inch floppies. microprocessor development kit over several months? Add on boards could be designed in months to come. A list of CPUs could obviously include Z80, 8088, 8051 and 6502. Many schools and colleges would benefit from a development board. A major feature I would be looking for in a kit would be the ability to be able to transfer programming code via an RS232 interface. I have spent a lot of time thinking about the subject, but a magazine such as SILICON CHIP would have greater resources. Please give this strong consideration in your kits department. (J. G., Springvale, Vic). • Based on our past experience, such a project is not likely to be supported by the kitset suppliers and with complete computers being as cheap as they are, there would be little interest from our readers. Or do readers think otherwise? Microprocessor kits wanted Notes & errata I have been working in the sales of electronic equipment for over three years. I believe that there is a real need for one or more microprocessor kits. I find that some kits that use micra's are all preprogrammed into the EPROM. You just solder the bits in and that's it. Is there any chance of a Infrared Light Beam Relay, December 1991: the A & K designations should be transposed for diode DZ on the wiring diagram. Also, the chamfer shown on the pinout diagram of the LT536 (on the main circuit) should be on the cathode (K) pin side. The position of the chamfer is shown correctly on the wiring diagram. SC IlJJJL~f)-~~ BACK ISSUES* MONTH YEAR MONTH YEAR MONTH YEAR MONTH YEAR *Back issues are $A5 each (incl. postage). Overseas orders add $A1 per issue for postage. BINDERS I Please send me _ _ SILICON CHIP binder(s) at $A14.95 each (incl. postage). Overseas orders please add $A3.00 each for postage. TOTAL PRICE $A:· ... _, , SUBSCRIPTIONS 0 Renewal - Sub. 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Please have your credit card details ready Fax the coupon with your credit card details 24 hours 7 days a week Card expiry date I Mail coupon to: Freepost 25 Silicon Chip Publications PO Box 139, Collaroy Beach 2097 No postage stamp required in Australia MARCH 1992 93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. r-------------------------, I I I I CLASSIFIED ADVERTISING RATES ANTIQUE RADIO Advertising rates for this page: Classified ads: $10.00 for up to 15 words plus 40 cents for e~ch additional word. Display ads (casual rate): $20 per column centimetre (:'v1ax. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on the form below or on a separate sheet of paper & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. ANTIQUE RADIO restorations. Your one-stop radio repair shop. Specialising in restoring vintage radios including chassis rewiring , re-condensing, quality new parts, valves, valve sockets, speakers, power & audio transformers. Secondhand radio dials & parts for most brands & models. About 400 radios in stock for sale, restoration & parts. Every restored wireless is covered by a 2year warranty on parts & labour. We restore damaged woodwork & cabinets & French polish (approx. 40 coats). Vintage car radios available for sale or restoration . Repairs done on tape decks & amplifiers. Open Sat. 10am-5pm; Sun. 12.30-5pm . 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613 AH. FOR SALE I I ·1 Enclosed is my cheque/money order for $_ __ _ 0 Bankcard 0 Visa Card or please debit my O Master Card Card No. Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _~/_ __ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Street _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ __ __ I I I I I I I XI I I I I I I I I I L-------------------------~ 94 SILICON CHIP SECURITY ALARM COMPONENTS. Commercial quality alarm panel, detectors, cable , everything for a complete alarm system . Discounted prices. 4-core alarm cable $35 per 100m. 2core alarm cable (Fig.8) $15 per 100m. PIR detectors, pulse count, $15 each. Horn speakers $12.50 each. Alarm control modules $69.50 each. Mail order service, send SAE for free price list to Security Distributors, 141 Todds Rd, Lawton, Old 4501 . Phone (07) 882 0002. WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" $35 is a high resolution, shortwave weather fax, Morse & RTTY receiving program. Needs CGA, FIX-A-KIT KIT REPAIR & CONSTRUCTION 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION TECHNICAL ASSISTANCE HVCAL ELECTRONICS Design, Manufacture & Repair of Electronic Equipment (02) 633 5477 SSB HF radio & Radfax decoder. Also "RF2HERC", "RF2EGA" & "RF2VGA", same as RADFAX2 but suitable for Hercules , EGA & VGA cards respectively. $35. *** "SATFAX" $45 is a NOAA, Meteor & GMS weather satellite picture receiving program . Uses EGA & VGA modes, needs EGA or VGA colour monitor & card, plus "WEATHER FAX" PC card. $45. *** All programs are on 5.25inch or 3.5-inch discs (state which) & include documentation . Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, 4004 Old. Phone (07) 358 2785. XT/AT HANDBOOK by Choisser & Foster. Pocket size, 92 pages. For engineers & programmers, & other serious PC/XT & PC/AT users. A collection of hardware & software facts & data on the PC-compatible family & its operating system. Latest edition. This is the one advertised by Annabooks in the US magazines Byte, Dr Dobb's Journal, etc. $20 including postage. 5 or more $15 each. Contact Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. , Prices at December 1, 1991 SIMM 1MBx9 1MBx8 4MBx 9 256 X 9 (For SIP 100ns 80ns 100ns 80ns 80ns 80ns add $1) DRAM-DIP 1MBx 1 80ns 256 X 4 100ns 80ns 41256 120ns 100ns 80ns 55 .00 57.00 48.00 53.00 225.00 16.00 6.40 6.30 6.50 1.80 2.00 2.20 PELHAM \.. COPROCESSORS 80387-DX 25 80387-SX 16 80287 10MHz 80287 To 20 173.00 142.00 95.00 156.00 FLOPPY DRIVES 3.5 Panasonic 1.44 3.5 Teac 1.44 5.25 Panasonic 1.2 80.00 86.00 92 .00 EXPANSION CARDS LS 866N 32Mb OK 240.00 AST RAM plus 8Mb . 350.00 BOCA AT plus 8Mb 250.00 INFRARED FILTER: a high-quality military grade deep infrared (IR) filter. For medium & high-power incandesce.nt spotlights & floodlights. Approximately 130mm diameter & 6mm thick. High temperature pyrex-glass base material. Excellent for night surveillance equipment. Works with IR viewers & some video equipment. On special at $5.00. Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. Fax (02) 570 7910. MINI INFRARED NIGHT VIEWER: as per EA, Oct. 1991 issue. A very small complete kit that includes a lens, an IR tube & an eyepiece. Simple to construct. The kit is now supplied with a high quality military inverter. Draws only 20mA from a 9V battery. Not only at the lowest price offered but we also include SPECIALS Sun SLC Sharp 6220 Sharp 8081 PS/2(ALL) PS/2(ALL) Mac FX/NIX Laser Printers 4Mb 1Mb 1Mb 2Mb 4Mb 4Mb 2Mb 250.00 160.00 100.00 150.00 295.00 230.00 206.00 SOCKETS Simm Sockets 30 x 1 Vert Simm Sockets 30 x 2 Ang Simm Sockets 30 x 2 Vert 1.70 3.50 3.20 Sales Tax 20%. Overnight Delivery. Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, NSW 2120. Tel (02) 980 6988 KIT REPAIRS Kits repaired from all magazines. Switchmode power supplies repaired, design work from start to finish computer software consultancy. Ring anytime 9am-9pm Mon-Sun. EEM Electronics, 10 Bouverie Place, Epping, Vic. 3076 Phone (03) 401 1393 VISIBLE LASER DIODE POINTER: Based on a small 3mW 670nm visible laser diode head. The kit includes a small plastic case , pushbutton switch, batteries & battery holders&, of course, the laser diode head. Everything you need to make a high quality laser diode pointer or a gunsight for a total price of $150. Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. Fax (02) 570 7910. 'I MEMORY EXPANSION a free filter. $299.00. Includes the IR tube, lens, eyepiece, electronics kit, a 75mm round IR plastic filter & the case. Kit No. IRNW5. Limited stock. Certified p&p Australia $5; NZ (airmail) $10. Major credit cards accepted with phone & fax orders. Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. Fax (02) 570 7910. MULTIMETERS: Philips automatic digital multimeter PM2517X with case PM9278, new condition, $350.00. Fluke 27 digital multimeter with case, new condition, $350.00. Hewlett Packard logic probe 545A, pulser probe 546A, Fax (02) 980 6991 ~ DIGI-CART DSP BOARD For 16-bit IBM compatibles. Broadcast quality 44.1 KHz/16 bit stereo audio with audio recorder software. $1599 + Tax Custom software service for applications available. PC Computers (08) 3326513 36 Regent St Kensington SA TRANSFORMER REWINDS ALL TYPES OF TRANSFORMER REWINDS TRANSFORMER REWINDS Reply Paid No.2, PO Box 438, Singleton, NSW 2330. Ph: (065) 76 1291. Fax: (065) 76 1003. as new, $300.00 each . K. S. Hickey (02) 871 6683. PCVOICE RECORDER SOFTWARE: turn your computer into an audio recorder, $25 + $3pp (VGA/EGA/CGA/ MONO). MS-DOS required. Also available: PC TALKING VOLTMETER soft- WANTED: YOUR CIRCUIT & DESIGN IDEAS Do you have a good circuit idea languishing in the ol ' brain cells? If so, why not sketch it out, write a brief description & sen9 it to us Provided your idea is workable & original, we'll publish it in Circuit Notebook & you'll make some money. You'll also help save us from the dreadful "circuit burnout" syndrome which afflicts anyone who has to generate too many circuit ideas in too short a time. We'll pay up to $60 for a really good circuit (not too big please). So transfer your circuit to paper & send it to Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097. MARCH 1992 95 r------ ---------------- --, X SILICON CHIP BINDERS Protect your valuable issues with a special binder from SILICON CHIP. Our binders feature heavy board covers, are made from a distinctive two-tone green vinyl, and have the SILICON CHIP logo printed in gold-coloured lettering on the spine and front cover. They hold up to 14 issues and will look great on your bookshelf. Price : $A 11.95 + $A3 p&p or buy a subscription and get a discount on the first binder (see the subscription order form in this issue).To order, simply fill in & mail this coupon or phone or fax your order to Silicon Chip Publications. Advertising Index Adilam Electronics .. ..... ....... ..... IFC All Electronic Components .... .... 75 Altronics .......... .. .. ....... ......... . 38-41 Antique Radio Restorations .... .. 94 Av-Comm .. .. ..... .... .. ...... ..... ... .... . 67 David Reid Electronics ...... .......... 3 Dick Smith Electronics ..... .... 28-29 EEM Electronics .. ... .... ........ ...... 95 Yes! Please send me _ _ _ SILICON CHIP binder(s) at $A11.95 plus Emona Instrum ents ....... ..... ....... 59 $A3 p&p each (NZ $A6 p&p). Geoff Wood Electronics ............ 33 Enclosed is my cheque/money order for $_ _ _ _ or please debit my Harbuch Electronics .. ... ... .. .... .... 57 D Bankcard O Visa Card Hycal Instruments ..... ....... ... ..... . 94 O Master Card lcom Australia .. .. .. .... ... .. .. .... ... OBC Card No. ~~I Jaycar Electronics ....... ... ...... 48-49 I'---'--------'-----~I I'---"--------'---~I '---I J.V. Tuners ... .. .... .. ... ...... ............ 57 L____L___J~ Oatley Electronics ..... ..... ...... 51,95 Signature_ _ _ __ __ _ _ ___ Card expiry date_ _~/_ __ Name _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Patex Systems .. ... .... ........ ... .. .... 61 PC Computers ........ ......... ........ . 95 PC Marketplace .. ... ...... ...... ... ...... 7 Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Pelham ................ .. ........ .. ... ...... . 95 Peter C. Lacey Services .... ....... 55 Suburb/town _ _ __ __ _ _ _ _ _ _ Postcode_ _ _ _ __ Philips ...... ... .. .. ..... .. .... ... .......... IBC Preston Electronics ............ ....... 87 SILICON CHIP PUBLICATIONS PO Box 139, Collaroy Beach, NSW 2097, Australia. Phone (02) 979 5644 Protel Technology .... ....... .... .. .. .. 85 RCS Radio ........................... ....... 9 Fax: (02) 979 6503. Resurrection Radio .. ... .............. 75 L-------------------------~ ware. For project published in SILICON CHIP, Oct/Nov 1991. Plugs into the printer port of any IBM PC/XT/AT/386 or compatible . Displays voltages up to ±128V on screen, takes voltage samples over time, has 8-bit accuracy to within 1%. Combines with the PCVOICE RECORDER project to give a talking voltmeter. Available on 5¼-inch 360Kb disc plus documentation and instructions for $30 plus $3pp. Send your cheque or money order to Darren Yates, PO Box 134, French's Forest, NSW 2086. WANTED AUGUST 1988 ISSUE of Roger Harrison's Austral ian Electronics Monthly. Ring Graham Welby. B.H. (047) 31 2845. A.H. (047) 58 8730. BOOK WANTED: "Electronic Design & Construction Of Alternate Energy Projects", by R. Andrew Motes. Will pay $50 for book in good condition. Call Otto (02) 728 4768. 96 SILICON CHIP Forty pages of dreams! z CD :e · Rod Irving Electronics ........... 10,11 68,69,82,83 Silicon Chip Back Issues ..... 88-89 Silicon Chip Binders ....... ........... 47 Stewart Electronics ........ ........... 96 TEcs Electronics & Computers . 21 Transformer Rewinds .. .............. 95 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. FLUKE 1, • •A ND .. ... PHILIPS - THE GLOB A L ALLIANCE IN TEST & MEASUREMENT FLUKE®• • • llr -. .,I ♦ ~ ♦ r 7 0 • e ♦ ♦ PHILIPS ♦ ,.,; S E R I E S I I We've improved on a winner If you've watted for the next generation digital multimeter technology, you've made the right choice. Now there is the new Fluke 10 Series II. We've made the world's most popular DMM's even better. At the top of the line. the new Fluke 19 and 29 blend high-performance features capacitance. frequency, a fast 63-segment bar graph, Lo-Ohms range. Smoothing'", faster ranges - and affordability. At the entry leva!, the new model 10, Fluke's lowest-priced DMM ever, delivers unparalleled fluke quality and safety. "Basics" Redefined No matter which 10 Series II you choose, you get simple. one-handed operation. High resolution. And built-in reliability. Automatic Touch Hold®- standard on every model - locks the reading on the display and signals you with a beep. Leaving you free to concentrate on your work, not on your meter. There's also fast autoranging. A quick continuity beeper. Diode test Automatic seH-test Overload protection, even in the 10 amp range. And a sleep mode that automatically powers down the meter when you forget to. Best of all, every 10 Series II is a Fluke, backed by a worldwide service network and 3-year warranty. /'~( c---=-\ Be No. 1 'th Fluke and Philips Available from the following Philips Test & Measurement distributors: ALL srAres: George Brown Group, Bestobell, Dick Smith, Petro Jee!. NSW: Obia!, Ames Agency. Ebson, David Reid , DGE Systems, Novocastrian Electronic Supply, Macalec. Vincom, Blackwoods, Emcorp, Tecnico. Tech-Fast Aus!ec. Consultant Technology, Elect.Smith Projects, Stoll Industrial Supplies. ACT: John Pope Electrical, Aeromotive Maintenance Services VIC: Radio Parts Group, Mektron!cs, Factory Controls, Blackwoods, Emcorp, Techrnco. OLD: St. Lucia Electronics, L E Boughen, Coiourview Electronics, Auslec, Thomson Instruments, Nortek, Emcorp, Mass Electronlcs. SA: Electronic Components & Equipment, AWM. NT: Blackwoods. Industrial Supplies & Switchgear. WA: Atkins Carlyle, Leda Electronics. TAS: George Harvey Electric. NEW ZEALAND: Control Tech, David Reid, Sirius Enterprises, Dick Smith Elecionics PHILIPS •