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AUSTRALll(S DYNAMIC ~ ELECTRONICS MAGAZINE~ 1.5\J TO 9\J oc coN\JERTER Build it & replace t~ose expensiVe gV batterres with 1.5V cells F\X\NG \J\NTAGE RA0\0 RECENERS Unfamiliar with valve radio receivers? Here are a few tips to get you started THE MUS\CAL \NSlRUMENT O\G\TAL \NTERF ACE A look at the ~ntertace that links musical inst-ruments together 0 ICOM Count on us! a corn's impressive range of receivers lets you listen to more frequencies, across the band and around the world. Starting with one of the smallest rece ivers ever produced, the IC-Rl covers l 00kHz - 1300MHz (2 - 905MHz guaranteed), with AM, FM and W ide FM modes, Dual Frequency Selection and 100 memories. The IC-R 72 receives 30kHz - 30MHz ( 100 kHZ - 30 MHz guaran teed) in SSB, AM and CW modes and comes with numerous impressive features, including lcom's DDS System to improve Carri er to Noise Ratio characteristics an d optional FM mode. IC-R9000 With an lcom receiver, the world is as wide as your band The mobile IC-Rl 00 is packed with powerfu l featu res, and covers the l 00kHz - 1800 MHz (500 kHz - 1800 MHz guaranteed) range in AM, FM, wide FM modes with multi-fu nction scanning and 100 memories with 20 scan edge channels. While the IC-R7100 covers from 25 - 2000 MHz in SSB, AM, FM, wide FM modes, optional TV and FM stereo adaptor , wi th 900 memory IC-R7"100 channels, sophisticated timer funct ions and multiple scan functions. T he top of the range IC-R9000 expands your listening hori zons, covering 100 kHz - 1999.8 MHz in all modes and featu ring lcom's un ique CRT display, intelligent scan functions and an amazing 1000 memory chan nels, in a un it that IC-R"100 delivers superb h igh frequency stability, even in the G Hz range. So tune in to the ones that professional listeners use, from the wide range of lcom wide band receivers. For furth er in fo rmation ca ll free on (008 ) 338 9 15 or write to Reply Paid 1009 lcom Australia Pty Ltd P. 0 . Box 11 62 Windsor Victoria 3 18 1 IC-R"1 Telephone (03) 529 75 82 A.C.N . 006 092 575 /COM Australia's warranty is only a/iplicable w produw /)l(rchased from their authorised Australian Dealers. IC-R72 L. L. BROW ADVERTISING 3907 Vo/.5, No.8. August 1992 FEATURES THIS SLA BATTERY charger automatically charges either 6V or 12V SLA butteries at any one of six current settings. Find out how to build it by turning to page 22. 16 The Musical Instrument Digital Interface by Michael Hawkins Linking electronic musical instruments together 82 The Story Of Electrical Energy, Pt.19 by Bryan Maher Electric traction schemes in Sydney ' PRO~CTSTOBUliD 22 Build An Automatic SLA Battery Charger by Darren Yates Charges 6V or 12V batteries & has six current settings 36 Miniature 1.5V To 9V DC Converter by Darren Yates Build this & save on those expensive 9V batteries 62 Dummy Load Box For Large Audio Amplifiers by Leo Simpson Handles up to lOOOW per channel into 4-ohms 68 The lnterphone Digital Telephone Exchange by Jeff Monegal It operates automatically & handles up to 10 stations SPECIAL COLUMNS SMALLER THAN a 9V battery, . this 1.5V to 9V converter project uses just three electronic components. Build it & save money by replacing those 9V batteries with more cost-efficient 1.5V cells. Details page 36. 6 Vintage Radio by John Hill Troubleshooting vintage radio receivers 38 Amateur Radio by Garry Cratt Review: Kenwood's TS-450S HF transceiver 40 Serviceman's Log by the TV Serviceman How I ended up in the sync 58 Remote Control by Bob Young Internal combustion engines for model aircraft DEPARTMENTS 2 Publisher's Letter 5 Mailbag 14 Circuit Notebook 53 Product Showcase 88 Back Issues 90 Ask Silicon Chip 93 Order Form 94 Market Centre 96 Advertising Index FANCY AN AUTOMATIC telephone exchange for your home? This unit can handle up to 10 stations & allows calls to be transferred or put on hold. It also functions as a multi-station intercom with full duplex communications. See page 68. AUGUST 1992 1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) PUBLISHER'S L:E'I*I'ER 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 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 The Pay TV farce: where to from here? Now that the Senate has sent the proposed Pay TV legislation back to the drawing board, there is time for people in the electronics and broadcasting industry to assess what it could mean for the future of the industry over the next 10 years. Initial reactions were that the 1-year start to be given to the first licence holder would not be anywhere near enough. In fact, the danger was that, had the legislation passed, nobody would have bid for the first licence and the Federal Government would have been left with egg on its face. Potential entrants into this field would need to commit hundreds of millions of dollars and to say that they will then have a year's grace before the race is open to established media operators is like giving a 20-metre start to an untrained athlete against a marathon runner like Robert de Castella or Steve Monaghetti. A start of 3-5 years would seem to be much more reasonable. Where the Government did make a good decision was in not confining Pay TV to satellite transmissions. There seems no good reason why it should not be eventually available via optical fibre. Sending the Pay TV signals via the same optical fibres which are increasingly carrying phone, fax and other data signals would make a great deal of sense. Significantly too, if Telecom's optical fibre network ultimately became the major Pay TV medium, then a great part of the considerable investment needed would stay in Australia and would be used to develop our growing expertise in this field rather than being spent on imported technology. And do we really want millions of satellite dishes pointing at the sky? Apart from the aesthetics of the matter, each house sprouting a satellite dish will also be a beacon to thieves as satellite receivers become the latest easily "fenced" commodity. How much more discreet would Pay TV be if it came in via the same cable that brings your phone service. Another advantage would be that the signal coming via optical fibres will not be affected by weather conditions. · Consider also that satellites do not last forever and when they stop transmitting there is nothing for it except to send up another enormously expensive replacement. The optical fibre transmission network, on the other hand, will continue to grow and will be subject to continuous enhancement. Perhaps the Senate has done everyone a big favour. Now is the time to stop and consider whether we would all be better off waiting a few years until Pay TV can run via optical fibres. Leo Simpson : ·• -: : :-· Record Cleaning Brush BLUE Led's ■ ■ ■ That's Right I BLUE LED's I 5.25" D.S.D.D. $38.00 per 100 ■ 5.25" D.S.H.D. $68.00 per 100 ■ 3.5" D.S.D.D. $70.00 per 100 ■ 3.5" D.S.H.D. $150.00 per 100 ~· ·•:;;;•· · Diskettes Buy in Bulk and Save I ■ Reverse Voltage: 5.0V. =~1~~i~:~~~h~~t~~~o deg. ■ Available in 3mm and 5mm case. ■ Case Colour: water-clear. ~~ ~~ rc:::::ziz=i;.;~ '. V,!__ ~ - - ~ 3mm Part No.: L-934BC (BLUE) 1 to 9: $3.95ea. 10+ $3.55ea. 50+ $3.20ea. 100+ $3.00ea. 5mm Part No.: L-53BC (BLUE) 1 to 9: $3.95ea. 10+ $3.55ea. 50+ $3.20ea. 100+ $3.00ea. From $38.00/100 iiiii Tape Head Demagnetiser =:::,----,,Je Luminous Intensity <at> 20mA: 7mcd (mm.). 14mcd (typ.) Forward Voltage: 2.7V (min.). 3.0V (typ.). 3.5V (max.) <at> 20mA. DMM02 Digital Pocket Multimeter z ■ Auto Ranging ■ 3.5 digit LCD display • AC/DC volts ■ AC/DC amps up to 10A ■ Ohms range ■ 20mA & 200mA range ■ Manual ranging ■ Data Hold ■ Continuity Beeper ■ Memory function ■ Includes Test Leads ~ -ffl (A) [II co co ■ :■ 0, APS-305 Power Supply 0 - 30 volt DC adjustable 0 - 5 amps DC adjustable Fully Built. Not a Kit. Limited Stock's Only $199.00 _ _ ___.._ my-power 200 inverter A mini power station that fits in the palm of your hand I ½!~e • 1 ■ 12V DC to 240V ~~ AC 50Hz inverter 140W (cont.), 200W (peak), 400W (surge) , Overload. Under voltage prot ection ■ Size: 50 x 135 x 75mm ■ 12 months warranty. ■ ■ was $199.00 I I Battery Packs LAB 4 External battery pecks tor We/kmen & Discmen. The LAB 4 has four full function test instruments BH22W Holds 2 x ·c· size batteries · 3 volt output. Output lead with 1. 1.3, 2.1, 2.5mm DC plugs was 4.95 Now $1.00 · •·•·•C::U II Now $180.00 ■ 4 in 1 Work Station DC POWER SUPPLY Triple Output; 5V, 15V, 0-50V With the MESSAGE STOPPER you can now II leave your answering machine on and not have to worry I It will also prevent "barge-in" f rom ;~ ,; 16$ ; ;_~;n a call is in progress. ~ David Reid 127 York St, SYDNEY 2000 ~ Electronics P.O. Box Q103,SYDNEY 2000 A.C.N . 001-372-372 Ph: (02) 267 1385 Fax: (02) 261 8905 Postal Charges $5 - $25 ......... $4.00 $26 · $50 ...... $6 .00 $51 - $100 ..... $7.00 $101 - $499 .. $9.00 $500 • ............ FREEi ,-----------------, 1 1 1r1ilill1■r1 r11■11&ri1I1i1 :Fax/Modem: llll llllll:liil I by Comma Corp. I :I -~ ? $349.00 :I I I ., . . . . . .. ... ~ .. ~'t'~'t~ I I I I I I I I I I I I I I I I Send/Receive faxes from your PC Yourfaxescannowbesentdirectly fromyourPCwithouthavingtoprint them first. You can view incoming faxes on-screen and print them using a standard dot matrix printer. Justthinkofthetime/papersavings. , The Comma Fax/Modem is a 9600 high speed send/receive fax and is also a full 2400 baud V22N22bis modem. This will allow you to communicate with other PC users or Bulletin boards just about anywhere around the world. Comma Corp. products carry an exclusive 15 month warranty. Extensive communication and fax software included. Versions for Windows and Macintosh also available. The Comma Corp. Fax/Modem is a TR29 Class 2 product. Class 2 ls the current international standard for fax/modems, this type of equipment is faster and can operate in background mode. Class 2 Fax/Modems also look after difficult timing issues that leave your PC free for other tasks while your fax operate.sin background. For minimal effects on your PC choose Class 2. Mail Order Service $10.00 P&P per unit. r ■iiiiiiiiiiiiiiil ~ ~ PO Box 1100 Lane Cove NSW 2066 1 - Level 1, 465 Pacific Hwy, Artarmon NSW 2064 Telep_h~ne 02-418 6711 Facs1m1le 02-418 6713 _i IZ] • · I I I I I I I I I I I I I I I I ~-----------------F IAN J. TRUSCOTT'S ELECTRONIC WORLD &..commaCorporationPty Lim;ted 30 Lacey Street, Croydon, 3136. Phone (03) 723 3344; Fax: (03) 725 9443 Now also at: 200 Smith Street, Collingwood. Phone (03) 419 2808 Mail & Credit Card Orders Welcome *** SAVE ON OUR AUGUST SPECIALS *** Exclusive to SILICON CHIP readers: *The Portasol Professional Soldering Iron* Normally $79.95. This month Cordless, Refillable Butane Gas-Power'd Soldering Tool Kit $67 .50 Safety Stand Hot Knife *PLCC Extractor Tool* PLCC Extractor prevents damage: this new J-lead IC remover has a dual action to protect fragi le PLCC packages when being extracted from carriers. First, its two steel fingers are inserted at diagonal corners of the package. Then , as hand pressure is applied, the steel fingers lock under the PLCC body. Finally, as further hand pressure is applied, the steel fingers apply a balanced upward pull to remove the package without damage. Normally $22.95. This month $17 .95 Cleaning Sponge Blow Torch accessory Ask about our great range of kits & TV antennas 4 SILI CON CHIP Hot Blower accessory MAILBAG Wants an exhaust gas analyser I have been hoping for some time that you would publish an Exhaust Gas Analyser and the letter from S. L., North Balwyn, Victoria on page 91 of the May 1992 issue prompts me to write. Surely the calibrating problems can be overcome. Having had my car converted to gas, this would be a very handy piece of equipment. Maybe some other readers can come up with some ideas re calibrating. Bob Cliff, St. Clair, NSW. Failsafe operation of thermostatic fan Regarding the letter from P. Bradstock in the June 1992 issue of SILICON CHIP concerning a thermostatic switch for a car radiator fan, I would point out that the use of normally closed relay contacts would not make the arrangement fail-safe. It could reduce the risk of adverse consequences from failure but is not immune to (for instance) punch-through in the output transistor, which would hold the relay permanently operated and so disable the fan. On balance though, it appears to be a good idea. The editorial comment tries to rule it out on what I regard as unfair grounds. In this circuit, inversion can be obtained without using a separate inverter. All that is necessary is to replace the output transistor by a PNP type with emitter and collector connections interchanged so as to obtain emitter-follower action. This has the hidden benefit of obviating the need for a diode shunt on the relay coil, since at turn-off the follower drains away the inductive energy stored in the relay coil even more effectively than a protective diode. E. Wormald, Florey, ACT. Digital control for model locos Your current articles on the model railway controller are of interest. However, I would be more interested in a SILICON CHIP, PO Box 139, Collaroy Beach 2097. project relating to digital control for locomotives and control functions, using addressable messages. Currently, Marklin offer a comprehensive and very expensive system, and an Australian company markets a similar system. Enthusiasts with a computer and a reasonably priced locomotive addressable decoder/driver could make a much less expensive entry to the next generation of train controllers. Your comments please? J. H. Ferrett, Holland Park West, Qld. Comment: We agree that a control system involving a locomotive decoder/driver would be a good project. However, there is a big problem in that the only suitable IC decoder, the NE544, has been discontinued. Until we come up with a suitable circuit replacement, such a project cannot be considered. nous types, do not care whether the re-inserted carrier is a square wave or a sinewave, as the demodulator performs a switching or sampling process. I am aware that Philips has been using this technique for at least seven years. I would also like to add my two cents worth to the current debate on a microprocessor-based project. It would prove educational and possibly would be more versatile and adaptable than a PC. It would give a good insight into the hardware and operation of PCs, especially from a practical point of view. I for one could use a brush up on microprocessors. The IR Remote Control for Model Railways looks like another great project. I look forward to reading SILICON CHIP for many years to come. P. Maljevac, OTC Sydney. Many PAL TV sets use an 8.86MHz crystal Information wanted on the Commodore 64 I thought it was time to drop you guys at SILICON CHIP a line but this time it's directed to the Serviceman's Log. Perhaps it should be passed on to him. He is puzzled as to the use of a 8.86MHz crystal for the chroma subcarrier oscillator - that is, if you have not already explained why this crystal frequency is used. When using a 4.43MHz oscillator to obtain the 90° phase difference for the carriers of the B-Y and R-Y demodulators, an LC network is usually used. With an 8.86MHz oscillator, the oscillator's output is divided by two using flipflops to obtain the 4.43MHz carrier but one of the flipflops is a positive edge triggered device while the other is a negative edge triggered device. This results in two square waves at 4.43MHz which have a 90° phase difference between them ready to be applied to the B-Y and R-Y demodulators. Quite nifty eh! This produces an accurate and very stable 90° phase shift, and flipflops are easily fabricated on LSI chips. The demodulators, usually synchro- I have been collecting SILICON CHIP magazine since May 1991. Because of the broad range of material, I thought that possibly you or your readers could assist me. My problem is to obtain literature concerning the Commodore 64. For a period of time I have been experimenting with an assembler to move away from the slow BASIC. In particular, I have been trying to set up communications between my computer and disc drive. However, because of the difficulty in obtaining literature, I am gradually becoming discouraged. Since January 1989, I have sent letters and faxes to numerous companies but they have not been able to help me. I also recently obtained a book from Prentice Hall which, unfortunately, did not cover the topic in as much detail as I would like. Additionally, I contacted Commodore USA and Sams Publishers USA. To date, they have not replied. Can anybody help? D. C. Rose, 96 Ferguson St, Midvale, WA. AUGUST 1992 5 VINTAGE RADIO By JOHN HILL Troubleshooting vintage radio receivers - the basic techniques There are few tasks more daunting to a new and inexperienced radio collector than the repair of a receiver that does not work. If one is unfamiliar with valve radio repairs, finding a fault can be quite difficult. Here are a few tips to get you started on vintage radio repairs. Many vintage radio collectors are totally divorced from the electronics trade and often have little or no knowledge of the workings of a radio, whether it be valve or otherwise. Many such enthusiasts simply collect their treasures, clean them up so that they look nice and display them. If a set happens to be in working order, it is a special prize. However, even if it does go, there is a good chance that it will not work for very long before something breaks down and the set no longer functions. This month's Vintage Radio column presents a simple troubleshooting chart (Table 1) and discusses some of the problems associated with fault finding. The chart contains a list of problems (or symptoms) and the pos- sible reasons for them. The chart does not contain every conceivable fault or remedy but most of the common ones are covered fairly well. Multiple faults A neglected 50-year old radio can be a mess of problems and there is often more than a single fault to find and repair. For example, a partial short circuit in a high voltage capacitor may not stop a receiver from working but the leakage problem can overload other components. Items such as valves, resistors, loudspeaker field coils and high tension chokes are vulnerable to overloading of this nature. It is, therefore, pointless to replace the overloaded component without also replacing the component that caused the problem in the first place. One of the most potentially destructive faults for the vintage radio enthusiast is an open circuit speaker transformer (see Table 1). It should be carefully checked before the set is turned on. Failure to apply HT to the plate of the output valve will cause the screen to carry excess current and to run red hot - a valuable warning sign but one which may come too late. The red hot screen can release (occluded) gas, making the valve gassy and useless. Most valves can withstand this abuse for brief periods but a few suffer instant destruction. The type 59 valve was notorious for this weakness and there may be others. This was tragic enough in the days when these valves were popular but at least they could easily be replaced. Another very common fault listed in Table 1 is weak and (often) distorted audio. This was almost always due to the first audio stage screen resistor - usually 1.5MQ- going high in value, typically to several megohms. The high value resistors of those days (ie, anything above lMQ) were notoriously unreliable. Paper capacitors _ ___,_ _....,__ _ _ ___,_+3V 22k .001 --■---411--PROBE ,___ _ _ _ _ _ _ _ _ _ _ ovEARTH CLIP B EOc VIEWED FROM BELOW 6 SILICON CHIP Fig. 1: the signal injector circuit uses two transistors wired as an astahle multivibrator. It produces a 2kHz tone that is rich in harmonics up to 20MHz. At the risk of repeating myself, I will say again what I have said quite a few times in the past. Faulty paper capacitors are the cause of a great deal of trouble in old valve radios. These ancient capacitors are unreliable and are the direct cause of many problems. In fact, they can be so troublesome that I feel justified in discarding all of them. That's · right! Total replacement of the paper capacitors is part of my routine restoration procedure. By do- RESURRECTION RADIO Vintage Wireless Specialists A simple signal injector can be built around two common NPN transistors. This unit operates from a 3V supply which is provided by two penlight batteries. Repairs - Restoration - Sales 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 capacitance is better than one of the more basic types. The signal injector When using the signal injector, the earth clip is connected to the chassis and the probe is connected to the control grid of the valve being tested. A signal injector can quickly locate a faulty stage in a radio receiver. ing this, one can eliminate about half of the common problems that would otherwise be encountered when restoring a valve receiver. Total capacitor replacement (using modern polyester types) also minimises the likelihood of future capacitor breakdowns and makes the set more reliable than it may have been when new. If your wallet dictates that you restore with restraint, then at least replace those paper capacitors that have some measurable voltage potential across them - particularly where high voltage potentials are involved. However, vintage radio repairs often involve more than just replacing a few suspect capacitors. There are many other things that can go wrong and stop a receiver from working. To trace these faults requires more than a troubleshooting chart. Some basic tools and instruments are also needed. Two very useful instruments are a multimeter and a signal injector. Little needs to be said about multimeters other than that you only get what you pay for. A meter that has a good ohms range and can measure A signal injector is another very useful piece of test equipment and can be made up quite cheaply for only a few dollars. Fig.1 shows the circuit details of such a device, while one of the photos shows the constructed item. An injector is used as follows: first, attach the earth clip to the receiver chassis, then switch on the injector and place the probe on the grid pin of the output valve. If the output section is OK, the injector signal will be heard through the loudspeaker. If the signal is not heard, then there is a fault somewhere in the output stage. In such a case, the problem could b_e a defective valve, a faulty coupling capacitor, a corroded valve socket connection, an open output transformer, no high tension at the valve socket, a dry solder joint, a speaker plug not making contact or faulty wiring inside the speaker plug. On the other hand, if the output stage tests OK, then one must go back AUGUST 1992 7 Protect your valuable issues Silicon Chip Binders 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 upto 14issues& 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 _ _ _ _ _ _ Illa _ _ _ _ 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_ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ P/code_ __ ·-----------· 8 SILICON CHIP The author's signal injector was built into a convenient cabinet that once housed a low-cost burglar alarm. to the preceding valve and again place output a little but is a small price to the probe (ie, inject the signal) on the pay for protecting the transistors. control grid. If that stage is working, The advantage of a signal injector is sound will again be heard through the that it will quickly locate the defecloudspeaker (it should be louder than tive section of a malfunctioning rebefore) and you then move back an- . ceiver. Once a particular stage beother valve until the faulty stage is comes suspect, it then narrows down isolated. the search by a considerable margin. A signal injector will not indicate If you don't have a signal injector, the exact cause or location of a fault removing a valve while the set is opbut it will indicate where you should erating usually produces a loud look. If a signal injector is designed "click" in the speaker as the high tenproperly, it will deliver a signal that sion is disconnected from the valve. produces an audible sound in the A click accompanying the removal of loudspeaker no matter what part of an output valve would be a reasonthe set the signal is fed into. This able indication that the valve and the signal should be heard regardless as loudspeaker are operating and that to whether it is injected into an audio the fault lies elsewhere. Shorting out or a radio frequency (RF) stage of the the grid with a clip lead may also receiver. It should even be heard from produce similar results. the aerial terminal, if the set is funcCompiling a troubleshooting chart tioning normally. is a difficult exercise, as it is impossible to cover every conceivable situaPrecautions tion. Valves can have internal faults, Care should be taken when using transformers can have open windings, the injector probe. It is unwise to in- and dry solder joints can be difficult discriminately place the probe any- to find. Dry contacts such as those in where, unless the injector output is adequately protected. Touching any high tension connection could damWARNING! age the transistors. Protection is normally provided by Dangerous voltages are present means of a small capacitor in the probe in valve radio sets so always exlead. The original injector circuit ercise due caution when troubleshown used a .0lµF capacitor in this shooting. In particular, take care role, which was too large for high with the power supply and high voltage (valve radio) use. Consetension (HT) circuitry in the set. quently, any high tension contact Note also that some vintage repromptly wrecked the transistors. Receivers were AC/DC models with placing this capacitor with a value of no power transformer and these .00lµF solved the problem and made should be left strictly alone unless the signal injector more suitable for you know precisely what you are valve work. doing. The smaller capacitor restricts the _TABLE 1 Possible Cause Symptom · PCB and SCHEMATIC CAD No power; nothing lights up Faulty mains plug connection; faulty on/off switch; open circuit power transformer primary; disconnected mains wiring inside set. ..... . Receiver lights up but does not work Faulty HT winding on power transformer; faulty valve; open circuit winding in aerial coil, oscillator coil and/or IF transformer; open circuit winding in field coil or HT choke; burnt out resistor; shorted high-voltage capacitor; faulty valve socket or speaker plug connection; missing parts; disconnected wiring; short circuit caused by perished insulation. . Receiver works but is noisy Troublesome dry solder joint; dirty socket or switch connections; faulty valve (tapping may pinpoint); faulty components (resistors, capacitors, etc). Severe oscillation (receiver squeals) Faulty decoupling or bypass capacitor; ineffective valve shield; faulty valve (usually in RF stages); wrong valve. Motorboating Open grid or cathode circuit (usually in audio section); faulty valve; faulty second filter capacitor. Distortion Faulty coupling capacitor to output valve; incorrect grid bias; gassy output valve. Hum Inadequate filtering of high tension; stray coupling from AC source to grid lead; short between valve cathode & heater; unshielded audio leads; gassy or faulty rectifier valve; filament resistor in early output valves; faulty electrolytic capacitor. Pronounced hum Shorting electrolytic capacitor; internal fault in rectifier valve; shorted field coil or HT choke. Intermittent loud/soft volume Faulty coupling capacitor on output valve; valve with loose internal elements; faulty connection (eg, valve socket or solder joint); faulty screen grid bypass capacitor Static like noises when tuning Tuner plates scraping; faulty earth connection on moveable plates. Set crackles or makes frying sounds Faulty connection or component on HT line; faulty valve (tapping may pinpoint) ; badly worn volume control. Very soft volume Worn out valves; low HT voltage; incorrect valve types; leaky high-voltage capacitors; alignment problems; open circuit audio-coupling capacitor; high value screen resistor on first audio valve. Low high tension Weak rectifier valve; damaged or faulty power transformer; wrong primary tapping selected on power transformer; incorrect loudspeakar (ie, wrong field coil impedance); faulty valve. . -· ···· ·-- ··· · -"::t ·= m.li!.m ·- TV IF AMPLIFIER - . . : )r. • • ........ ....... -::. ~ i ---- ------------ .______ ___________ __ J C•nitifl4♦ EASY-PC • Runs on PC/XT/ AT/286/386 with Hercules, CGA, EGA or VGA. • Design Single sided, Double sided and Multilayer boards • Provides Surface Mount support • Standard output includes Dot Matrix/Laser/Inkjet printers, Pen Plotters, Photo-plotters and NC Drill Double spotting Incorrect alignment. • Award winning EASY-PC is in use in over 12,000 installations in 70 Countries World-Wide Overheated choke or field coil Excessive HT current caused by faulty HT component, probably an electrolytic capacitor. • Not Copy Protected Rectifier anodes glow red hot Direct short on HT line (eg, electrolytics in HT filter short circuit). Output valve screen grid glows red hot Open circuit anode on output valve (probably open circuit output transformer). Note: this can damage the output valve. No shortwave reception Dirty wave-change switch contacts; leaky paper capacitors; resistors gone high in RF stages; low HT voltage; weak frequency changer valve. • Superbly Easy to use Options: • 1000 piece Schematic symbol library • Surface Mount symbol library • Gerber Import facility For full info 'phone, fax or write: valve sockets, wave change switches and some tone controls are just waiting to give trouble and often do. The list could go on and on. Hence the accompanying chart lists mainly common problems and has been compiled for the benefit of the novice. Remember, a good vintage radio res- toration should result in the set looking and working as it did when it was new. Restoring a vintage receiver so that it looks as new can be a difficult and time-consuming task in some instances, but there's no reason why it cannot function as new. Hopefully, my troubleshooting chart will help you in this regard. SC BTC PO BOX432 GARBUTT 4814 QLD. PH (077) 21 5299 FAX (077) 21 5930 AUGUST 1992 9 Phone Your Order To Us Toll Free We guarantee our Jetservice Courier will deliver to your door faster than any other Australian supplier (including that local supplier just up the road). If we fail, I'll give you your money back plus $5.00 for your inconvenience. Digital High Performance Signal Generator Kit 252.8 ' ' 'i (SC July '90) This Digital Sine/ Square Wave Generator uses high speed CMOS \Cs and a digital filter IC to produce sine and square waves over the frequency range from 0.1Hz to 500kHz. It also features a 4-digit frequency readout and an output level control. This inverter is ideally suited tor powering low wattage mains appliances from a car battery. Ideal for camping , boating etc. Typically, it can be used to power an electric shaver, e lectric blanket electric ca n opener or a 40W light bulb. Output frequency can be either crystal locked at 50Hz or variable over a small range via internal trimpot. When 240V is available this inverter can be used to recharge ca r batter~.(: 2547 Normally $~.00 Now $125.oo The Discolite flashes party lights on and Discolite Chaser & off in beat with music 4 light channels• Forward reverse and auto- reversing Colour Organ Kit chaser patterns • Strobe function • Alternating light patterns • Music modulation available on chaser and strobe• Inbuilt microphone for beat triggering or audio modulation of lights • Front panel_ LEDs mimic light display • Altron1cs Kit pre-punched and silk screened. $90.oo Ad ------~~"!"'"------,,.,,,:-:-----1 me Colour To Your Next Party. Great For Parties, Shop Dl1play1 and Special Lighting Effects Unit sharpens picture detail, and can actually improve the quality of a copy by amplifying the top end of the video signal Specifications. Signal to noise ratio 1 ft?:t~ rf~z ~ t~~i:~i~~n;~~';,"ioano"~ cut plus and minus 6.3db • Gain 0db • Input impedance 68 Ohms Complete kit supplied with silk screened front panel ,Q"'. K 5825 Normally $,n:.:50 $35 ._oo.,,..__________-1 CreeC h er Car Al arm S (EA Aug '86) .N_,o..w_,___ $49.50 t K4360 ■ Deafening 100db Modulated Tone Now· our top selling Car Alarm Kit. Two Sensor inputs - Normally open and normally closed enable simple connection to door, bon net, boot light, switches etc. Automatic Charger for NiCads Kit Here is a fully automatic NiCad battery charger that enables differing charge rates as appropriate for AAA, AA , C, D cells or cells in series up to 9V. Requires M 9020 12V AC PI ug Pack $16.95 eatures: • Fully unched and creened case • ariable c harge te • Variable mer • Flexible and s,mp isual display of charge mode • Ni a not be over charged. (SC May '90) K K 6705 Normally $7"'.00 Now Highly Accurate 4Digit Capacitance Meter Kit K 5805 Normally $ ~.50 $129.oo Now This video amp can greatly improve picture stability and eradicate shimmer, screen swim etc . Two outputs, normal and inverted . Ideal for VCR users. Tired of a grainy or snowy picture? Connect this amp internally to your TV and presto, the improvement is fantastic! (Documentation is quite detailed on connection to TV sets). For computers and videos with low video output. 5850 Normally $).?'so Now $ 15.oo Digital Voice Recorder Kit K (SC Dec '89) This Digital Recorder delivers astonishing reproduction of voice and/ or music without any moving parts. Here is a digital voice recorder that can store 4 different signals, voice, sound or a music source of up to 30 seconds each or or.a recording of up to 2 minutes. Typlcal appllcatlona Include: • Alarm system messages • Sales messages for customers put 'on hold'• Experimental telephone answering mach ine • Door Station announcer• Talking displays for shops• Emergency warning message announcement • Operation instructor for machinery etc • Countless other applications where voice or music is required • $100's cheaper than imported digital recorders• Includes instrument case ~nd all components. This attractive 4-digit capacita nce meter is designed for the workshop or laboratory. It can measure capacitance from 1pF up to 9999uF in seven ranges with ali accuracy of better tha n +/-1%, +/1 digit. 2524 Normally $1)'9 95 Now $99.oo FM Stereo Transmitter Kit K (SC Oct '88) Turn Your CD Player Into a Mini FM Transmitter. Simply connect your CD player or any other source to the mini mitter which converts the audio signal to an FM signal. This FM signa l then can be tuned in via any FM radio . Great for listening to your favourite CD while was hing the car, mowing the lawn or doing the vac uuming etc, without blasting the neighbours. Powered by single 1.5V pen lite battery. Single IC circuit. Simple to build and construct. K 1120 Normally$ .50 Now $35.oo Fluoro Inverter Kit Voice Operated Relay Kit ( EA Apri I '82) Th is versat ile Vox circuit i~ triggered whe never a noise or sound is made causing a relay to close Think of the uses: • Controlling tape recorders • Slide projectors• Elimina te the need for a press to talk button on transmitters • Turn on external porch lights • Paging systems• Hands free intercom switchover • Reaction sensitivity and " On Time " are fully variable K (SC July '89) Thi s charge r is designed to operate from a 12V battery. It can cnarge nicad battery packs from 6-12V at up to 6A, or you custom wire the circuit to charge battery packs up to 30V at a reduced current. In operation the circuit will recharge a typical nicad racing pack in about 20 minutes. Featurea, • Fast charge rate • Switch selectable voltage setting in 1.2V steps from 6V-12V • Fully punched and screened front panel • State of the art digital circuitry. 1660 Normally $1~oo $35.95 6360 (20W/40W Version) $43.95 K 6350 (16W Ve rsion) 12V Gell Cell Charger Kit K This kit enables you to build a high power DC• in verte r suitable for driving fluorescent lights from a 12V source typically a car battery. Ideal for use in camping or boating . Now $99.oo Stereo 50 + SOW . Midi-Style Amplifier Kit (SC Feb and March '92) the features of commercial units K 5790 Normally $~95 Now $69.oo ,......,,, . Audio Frequency Generator Playmaster Pro Series One 200W Mosfet Module Kit (EA Dec '89) This amplifier modu le has all the same high specs as the " Stereo Pro Series One", but in short form i.e.: One mono module - no power supply or case. Fantastic fo r use in J ukeboxes , am plifie r racks (m ulti-amplifier setups) discos etc. See above for specifications. I a 1540 , .00 Now $349 Spaclflcatlona: Frequency Range: 100kH - 150MHz in 6 ranges RF Output Level: 100mV rms Accuracy: +/-3% Modulation: • Internal (30% depth): 1kHz• External: 50Hz-20kHz • Crystal Locked Oscillator oo Now $25O.oo .,_a 1550 Normally $~.00 Now $225.oo Amazing Value on Deleted UHF Alarm This UHF system contains one receiver and 3 wireless reed switches for doors and wirrdows etc . The main controller simply plugs into 240V , the remote, reed switches are attached to your door/ window frames and presto, the alarm is installed! Simple push button operation , 4 dig it user selectable on/ off code, built-in siren makes this unit a pleasure to instal l and use. Includes 12V 1.2Ah backup battery and 9V batteries for remote reed switches. Because there is no wiring required, there is no need to drill holes in the wa H or ce il ing, mak ing th is un it just great for re nted fla ts or un its, or for those who don't want the trouble and hass le of a w ired system . Also idea l for boats, caravans , the shed, garage or granny flat. Take the unit with you if you move - no wasted time and money. AMAZING VALUE SB 5260 Normally 00 WELL BELOW COST! SORRY NOT AVAILABLE Now only $249.oo 0 FROM AL TRON IC DEALERS 000• - NO BACK ORDERS 0\G i\O(\ 0 ON LY WHILE STOCKS LAST! . i(\\0110 Wireless Door <il'_ \(\\ Reed Switch e""c\(\cll· $§(4 This amaz in g nel/v mode l feah..:res just about everything you cou ld imagine! Mu ltifunction key ri ng remote control w ill arm a11d disarm alarm (and activate cent ral locking if fitted) , chirp the horn, turn on car head lights, panic and even open the boot (if actuator fitted) . One remote can contrc l two alarms . Other features include: Starter inhibit , valet mode, central locking interface, flashes car indicators when tripped. auto reset plus much more!· s 5230 S 5231 Cl:249.oo ;replacement Remote Control $48.50 ••wt44itilt4•);il4;t<at>i UHF Microprocessor Controlled Wireless Security System Apart from the flawless operation of the system one of the great features is its application with rented or leased premises - let's face it . money spent on installing a wired system in your home or office, factory , etc is irrevocably lost when you move on . With this system you simply take it with you . Ultra high -tech and push button operation makes this unit a breeze to install and operate. Features 6 sectors plus 2 x 24 hour fire and tamper circuits. The S 5240 system includes main controller, 1 Passive Infra Red Movement Detector, 1 window or door Reed switch , wired siren , power supply , back -up rechargeable battery, and a special personal remote . A ll sensors are radio tra nsmitters wh ich means no wiring is neccessary (except for the plug pack and siren) . The whole systern is codP.s so it can not be interfered with and can be changed any time by tn e ow ne r. Each ind ividua l senso r can be eas ily set to operate C'n any sector. The main contrc; 1er .. ti li zes latest EEPROM techno logy which means things like select ing user on / off codes, isolating sectors are a breeze. Includes a myriad of other amazing features. too many to mention. Wireless Remote Keypad Call AL TRON/CS today lor a lree colour brouchure. S $1.,'.36'.'00 Compiete 1y1tem lncl udea: 1 x Control Panel ; : 1x 1x 1x 1x 1x 5255 External Siren c 2015 $1~ 6~5;/f ::ii~n~~a/r~~JJ;~~~o;g;:~;;i\\~; Hand Held remote Control/ Transmitter Ho rn Speake r - ·i 0 watUwired 240V AC adapto r 1.2Ah Back-up Battery Set of batteries for all transmitters ~ow Now $11.95 · Door/ Window Reed Switch & Transmitter S 5247 $7~ Now $63.95 .00 _________ _________________ Normally $3~ New High-Tech Remote Car Alarm - With provision for internal d external modulation. 'Speclflcatlona: i Frequency: i 10Hz- 1MHz jAccuracy: : +/ -3% + 2 Hz i output l waveforma: i Sine/ Square l Output Level: · Sine: 8V rms Square: 10V P-P Output Attenuator: -20dB, -40dB and fine adjust 5170 Normally $~00 $79 .oo ,,,...,.,,...."<_> This professional quality Public Address Amplifier offers performance equal to better than commercial units, at about half the price . Amplifiers using 100V line outputs are used extensivel y in everyd ay situations where numerous speakers and tong output lines are employed. ideally suited for Halls, Churches , Clubs and even temporary setups. Inputs: 2 ba lanced mics (3 Pin XLR connectors) 2 Auxi ll iaries (RCA connectors) Outputs: 4 Ohm, 8 Ohm or 100V li ne. Power Output: 125W RMS ir.to 4 Ohms, 90W AMS into 8 Ohms, 120W RMS into 100V line Frequency Response: 30Hz to 30kHz $ Harmonic Distortion: Less than 0 .3% from 20Hz to 20kHz K 5020 Normally ~ 5115 $49.s5 This Month Only (SC Nov '88) High Performance Low Nolte P.A. Amplifier This great module features moderate power output at low harmonic distortion . Simple to build and compact in size this unit makes a great replacement modu le for yo u r o ld HiFi or buy two and make your own stereo amplifier. K Add Some Life To Your Next Party Designed by Austra lian Electronics Monthly. Flashes in time to your music. Will also work as normal strobe. Exclusively custom ised by Altronics into our H 0480 Instrument Case, making construction a breeze and improving stability and overall appearance. Includes silk screened panel. Two tube option available which boosts lighting output. 120 Watt Public Address Amplifier Kit SOW Mosfet Module Kit K Beat Triggered Strobe Kit (AEM Ju ly '85) This fantastic new amp has all costing hundreds of dollars more using tip 142/ 147 transistors it is capable of producing a total producing a total of 50 Watts per channel RMS. Into 8 Ohlns makes an ideal replacement midi unit. Performance: Output Power: 55W into 8 Ohms 80 watts 4 Ohms Harmonic dl1tortlon: typically less 0.05% $114.95 A 2040 Featurea: . . • Digital LED frequency readout display • FET FM front end for high image reIect1on • Phase-linear ceramic filters are incorporated in both AM and FM IF section• Phaselock loop (PLL) IC for FM multiplex stage• Dimensi on s: (W x H x D) 435 x 60 x 232mm • Weight: 3kgs. 12" Guitar Speaker 50 Walla RMS, 100 Walla Max. Attention all guitarists and keyboard musicians.This fine USA designed speaker is supplied :1s standard equipment to the world famous brand name series Guitar Amps. • Impedance: 8 Ohm • Sensitivity: 101 dB/W (0.5m) • Weight: 2400gm C 3102 Normally $ ~.00 Now $79.oo 100mm Super Carbon Fibre Speakers These amazing little speakers will impress you and your friends. Carbon Fibre is a new high tech material from which these speaker cones are made. Complimented with Barrium ferrite magnets the results are simply amazing. 8 and 16 ohm versions available makes multi speaker installations a breeze. Weatherproof design makes them ideal for car doors and boats! Normally $%95 C 0641 8 Ohm · 00 C 0643 16 Ohm This Month . That 's Half Price! $2 or $40.oo pr Sensational Dome Tweeter Ferro Fluid cooled voice coil 60 watts power capability. Silky~ smooth frequency response 1.5kHz to 20kHz . Wide angle dispersion. ln comparative tests we rate this fantastic new Dome Tweeter superior to the VIFA D19! (which costs $45 or moreJ . Incredible low price. C 3016 Normally $ Now .OO $30 Famous Vifa 5" Woofer have a huge surplus o a C13WG-08-08 woofer ese quality drivers offer h performance in both rted and sealed enclosur ceptionally smooth respon 5kHz. Careful design and ing rubber surround make tain an amazing 50 watts labicity. Fantastic replace nstruction speaker. 3110 Normally $~.00 N $$$ _ 12v Outpul S••~or a Myriad of Electronic• Save heaps with this deleted line of 12.6V CT, 150mA transformers. Great for any number of electron ic projects etc. Buy 10 and save! MA2851 Normally ~ Now $5.30 ea, or 10 up $3.75 ea $6lt, This Month $539.oo This stereo amp la Ideal for background/foreground appllcallons. Fantastic for restaurants, ■ hops, dl1c0'1, aerobics, PA sound 1y1tem1 and home. • 90 watts RMS per channel • 2 large power meter indicators • XLR socket for speaker terminal • Output relay to eliminate turn-on and off transients Vifa Speaker Kits Famous Altronics Inverters These kits use quality Vita speakers made in Denmark and specially engineered enclosures for optimal performance. Black wood grain veneer make them ideal for any decor and situation. These two way models include high grade crossovers, speaker terminals and removable front grille. Simple co nstruction with only basic too ls and skill required . These kits are complete a~d include speaker cloth, damping material , grille clips, speaker term ina ls, screws and parts. Outstanding performance for the fraction of the cost of commercial equivalents . Get 240V AC from your car, truck or boat battery . The Altronics range includes an inverter for nearly every application . Fantastic for camping, boating, farms and anywhere else 240V AC isn't available. Each size inverter is available in kit form or fully built and tested. The 300 and 600 Watt Inverters now feature new improved circuitry using multiple mosfet outputs making th em even more reliable with a genuine 300 or 600 watt continuous power rating. Our latest model, the 1200 Watt Powerhouse offers excellent value for money and performance. It features crystal locked circuitry and a massive 2400 watt power surge making it ideal for small fridges , vacuum cleane rs , power tools etc. Any model an absolute necessity where 240V isn 't available. Call Altronlcs today for more information on freecall 008 999 007 . VIFA SA-50 2 Way Bookshelf System, 50 Watts RMS Normally 300 Watt $279 $379 K 6750 Kit Version K 6755 Built-up $3~oo pr Now Only $299.oo pr . . • VAILABLE . NOT A EALERS 1 so~~\LTR0~ ~R~cES FR AT THES VIFA SA- 100 2 Way, 100 Watts RMS Normally $7~o Now Only $699.oo pr Stereo Extension Ceiling ' Speaker Kit Want a set of high grade extension speakers for the back patio, games room, den, workshop, kitchen? Well here at Altronics we have put together this great kit which includes speakers, grilles, cable, screws and even a wall mounted volume controller. The speakers are our high quality 4" C 0626 dual cone drivers. w ith stylish white grilles - ideal for mounting in the cei ling. Volume contro l mounts in standard electri ca l wall box and includes 6 volume settings as well as off . Includes 2 x 20m c;:_able. 1 C 0988 Normally $~00 , Now Only $69.oo T 2450 $ 3 9 .50 Winner of the Taiwan Good Design Award Now you can solder anywhere with this new gas soldering iron. Feature, • See through gas chamber (no more guessing how much gas is left!) • Built in ignition cap• Uses standard butane gas • Comes wit h safety bench stand• Supplied with 2mm soldering tip and blow torch tip• Adjustable temperature from 400°C to 1200' C • Can be easily refilled with standard butane lighter gas • Replacement tips are less than half p ri ce of some other brands! REPLACEMENT TIPS • ALL $4.95 ea T 2451 Replacement 1mm Conical Tip T 2452 Replacement 2mm Conical Tip T 2453 Replacement 3mm Conical Tip T 2454 Replacement 3mm Chisel Tip 40MHz Dual Trace Oscilloscope A superb oscilloscope for technicians and engineers wo rking on projects where other instruments would be stretched beyond their capabilit ies . Where precise meas"urements of computers, CD's, digital videos, RF applications, high speed digital , and other high speed equipment is a must. Wllh Features Like: • Delayed sweep for partial waveform expan sion • Channel 1 signal output for use with a frequency counter • CH2 polarity inversion switch • Vertical deflection magnification , X5 • Switchable chopping frequency• Scale illuminating system • 8 Intensity co ntrol for bright, magnified waveforms• Variable hold-off for observation of waveforms with complex periods • Single sweep mode for one time o r other suddenly occuring events• Sweep mag nificat ion, X 10 • Signal delay line for accurate view of high frequency pulse leading edge• Trigger preset function. ITT 2455 Replacement Exhaust Port 2456 Hot Knife Tip T 2458 Blow Torch Tip T 2457 Hot Blower Tip $10.95 T 2448 Weller Butane Gas Refill $6.95 Top quality blank panel clearout. All stock must go at these crazy prices. Stock is limited with definately no back orders at these prices. High quality computer fans ideal for power supplies, amplifiers, computers etc. Reliable _ Sunnon brand. Full range available for almost any application . 240V Models 24V DC Model F 1020 80mm' $22.25 F 1040 120mm ' $23.90 F 1030 120mm' $24.25 12V DC Model F 1050 80mm' $17.50 2 unit - All $8.00 3 Unit - Finger Guards .,,,,,,.. ] :Rack Shelves F 1022 80mm $2 F 1032 120mm .45 Sturdy Spotlight Relay Includes two seperate 30 Amp relays with individual fuses . Great for car headlights. spotlights etc. s 4335 Normally $1 ~O This Month Only $9.95 PCB Mount RCA Sockets 3 rows of stereo (left and right) sockets. High quality. Bargain price. PA 0235 Normally $3;1l(> This month only $1.50 Rack frame 4U Black Panel set for H 5304 Rack frame 6U Black Panel set for H 5306 Rack frame 12U Black Panel set for H 5312 Rack frame 18U Black Panel set for H 5318 Rack frame 30U Black Panel set for H 5330 Rack frame 38U Black Pane l set for H 5338 $125 $44 $135 $49 $152 $80 $170 $99 $205 $143 $242 $175 Just In Stock - 'Universal Wacki Bracket' Yet another Altronics innovation, proudly designed and made in Australia. These great new speaker mount brackets simply screw onto the wall and speaker allowing a universal 50° angle of adjustment. Suitable for speakers up to 5kg . No special tools required . Available in white or black. A must for any extension speaker . H 8010 White H 8012 9 1ack $39.95 pair Proudly Made In Australia ---------------------'----------------------■ Super Large Instrument Cases Maaslve 355 x 250 x 122 mm • Designed to house amplifiers, inverters, power supplies, micro-processor equipment, etc • Mounting posts provided for PCB's, transformers• Vented for efficient air-flo~ cool ing • Extra tough, super finish front and rear panels. H 0490 Grey Case, H 0491 Black Case, H 0492 Blue Case Normall y 5 Now $29.95 4LTrlOnlC.) 174 Roe St. Perth W .A. 6000 Phone (09) 328 1599 PHO NE TOLL FREE 008 999 007 MAIL ORDERS C/ - P.O. Box 8350 Stirling Street PERTH W.A. 6849 STANDARD DELIVERY & PACKING CHARGE $3.50 to 500gms, $5.50 500gms - 1Kg . $8 1Kg-5Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 9 days from day you post order_ to when you receive goods . OVERNIGHT JETSERVICE Up to 3Kg is $10.00, 3Kg to 5Kg 1s $23.00-We process your order the day received and despatch via. Overnight Jetaervlce Courier for delivery ne-.;t day Country areas please allow additional 24-48 hours . ' -~ _ , ) H 5352 2 Unit (88mm) Normally $~95 Now $39.95 Now H 5304 H 5305 H 5306 H 5307 H 5312 H 5313 H 5318 H 5319 H 5330 H 5331 · H 5338 H 5339 . Enables rac_k ~ • .. mounting of tuners, --= videos, G.D. players , ampl ifiers etc. which normally can't be rack mounted. Suppl ied in flat pack form - easily assembled in minutes. Available in black only. Now $125 $44 $135 $49 $152 $80 $170 $99 $205 $143 $242 ~175 ~ -- ~ Suitable for home or commercial use, these fantastic rack frames are durable strong, good looking, light weight and easy to assemble. The frames are available in either Natural Anodised aluminium or Black Powder Coat aluminium and the side panels in Electric Blue or Black Powder Coat finish . Ideal for use in home Hi-fi systems , Professional Audio installations , Band Gigs, Computer Patch panel etc. Two colours to choose from: Proudly Made Frames: Natural Anodised or Black Powder Coat In Aus tralia Panels: Electric Blue or Black Powder Coat. Rack frame 4U Nat Panel set for H 5204 Rack frame 6U Nat. Panel set for H 5206 Rack frame 12U Nat. Panel set for H 5212 Rack frame 18U Nat. Panel set for H 5218 Rack frame 30U Nat. Panel set for H 5230 Rack frame 38U Nat. Panel set for H 5238. ~- -- - ---------__,. , ~ Australian Designed and Manufactured Professional Series Modular Rack Frames H 5204 -H 5205 H 5206 H 5207 H 5212 H 5213 H 5218 H 5219 H 5230 H 5231 H 5238 H 5239 All $12.95 H 0423 Natural Aluminium H 0433 Grey H 5353 3 Unit (132mm) Normally $4ef95 Now $39.95 H 5354 4 Unit (176mm) Normally $~95 Now $45.95 Universal Battery Chargers As a result of a bulk scoop purchase, we are able to offer to you these fantastic universal Ni-Cad battery cha rgers at a more than ridiculous price! It will charge any combination of up to 4 of AAA. AA, C or D size batteries al one time plus a 9V. Features a LED indication to show each battery has made an electrical contact. Also has an added bonus _. · of a battery tester - - 50°/o function. Hurry . Stocks limited. Definately no Sr backorders. ,.~f M 8010 Normally $3~5 This Month Only $19.95 Digital & Analogue Com bi nation ,.-.·-·r--iiii ·· - -- -Multi meter This fantasti c meter gives you the accu racy of a digital as well as the ease of an !~a\~~~el~e;:,~r~ctri~r~~ts test. AC and DC vo ltage resistance continu ity etc and many other fea ture s you would only expect on r,1uch more expensive meters a 1090 Normally $1%50 This month on ly $129.oo HEAVY HEAVY SERVICE - All c,,ders of 10Kgs or more rr,ust travel Express Read Please al!ow 7 days for delivery. $12.00 to 10Kgs. $15 .00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk . Should you requirl:! comprehensive insurance cover against loss or damage please add $1 .00 per $100 of o rder value (minimum charge $1) . When phone o rder ing please request "Insu ranc e". TOLL FREE PHONE ORDER - Bankcard, Visa, Mastercard Holders can phor,e oroer toll free up to 6pm Eastern Standard Time . Remember with our OvernlghtJetaervlce we deliver next day . AL TRON ICS RESELLErlS Chances are there is an A:tronic Resell er right near you - check this list or phone us for details o f the nearest de-:1.ler. Blue Ribbon Dealers are high!ighted with a ■ These dealers generally carry a comp rehensive rar ge ui Altronic rroducts and kits or will order any requ1 red 1terr. for you . WA COUNTRY ALBANY BP Electronics ■ (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097 ) 216222 ESPERANCE Esperance Communications (090 ) 713344 MANDURAH Lance Rock Retravision (09) 535 1246 PORT HEDLAND Ivan Tomek Electronics (091 ) 732531 ROCKINGHAM TV Joe's (09) 5271806 NT ALICE SPRINGS Farmer Electronics (089; 522388 DARWIN Ve ntro nics (089) 853 622 VIC All Electronic Components (03 ) 6623506 TECS (03 ) 67064 14 BORONIA Ray Cross Electronics ■ (03) 7622422 CHELTENHAM Talking Electronics (03) 5842386 COLLINGWOOD Truscott Electronics (03 ) 4198208 CROYDON Truscott Electronics ■ (03) 7233860 FOOTSCRAY G.B. Telespares (03) 3179100 PRESTON Preston Electron ics ■ (03) 4840191 COUNTRY BAIRNSDALE LH & LM Crawford (051 ) 525677 BALLARAT Ballarat Elect ron ics (053 ) 311947 MILDURA McWilliam Electronics (050) 236410 O L D Delsound PL ■ (07) 8396155 WEST END B.A.S . Audiotron1cs (07) 8447566 WOODRIDGE David Hall Electronics ■ (07 ) 8082777 COUNTRY GLADSTONE Gladstone Electronic Services (C/9) 724459. Electron ic Enterprises (079) 726660 MAROOCHYDORE MAL.S Electronics ■ (074) 436119 MARYBOROUGH Keller Electron ics (071) 214559 NAM BOUR Nambocr Electronics (07 4) 411966 PI ALBA Keller Electronics (071) 283749 ROCKHAMPTON Access Electronics (East St.) (079) 221058 TOOWOOMBA Hunts Electronics (076) 3296"l7 TOWNSVILLE Super Solex ■ (077) 724466 SA Force Electronics ■ (08) 2125505 BRIGHTON Force Electron ics ■ (08) 37705 12 CHRISTIE$ BEACH Force Electronics ■ (08) 3823366 FINDON Fcrce E l ectron i cs ■ (08) 3471 i88 HOLDEN H ILL Force Electronics ■ (08) 2617088 LONSDALE Force Electronics ■ (06 ) 3260901 ENFIELD Aztronics ■ (08) 3496340 COUNTRY WHY ALLA Eyre Electronics (086) 454764 TAS HOBART George Harvey• (002) 342233 LAUNCESTON George Harvey ■ (003) 316533 NSW David Reid Electronics ■ (02) 267·1385 REVESBY Revesby Electroni cs (02) 7922295 SMITHFIELD Chantronics (02) 6097218 COUNTRY COFFS HARBOUR Coifs Habour Electronics (066) 525684 NEWCASTLE Novocast rian Elect .Supplies (049) 621358 WARNERS BAY Vilec Distnbutors (049) 489405 WINDSOR M & E Elect . and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620. Vimcom Electronics (042) 28 4400 WOY WOY Alphatran Electronics (0 43) 434919 CIRCUIT NOTEBOOK 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. vcc 6 6 VR2-VR9 8x47k 13 14 02 BC548 15 4 15 11 IC4 4051 10 ·1 10 9 IC3 4510 MONOSTABLE ANO INVERTER 12 5 GATED ASTABLE OSCILLATOR 4 22k BCD COUNTER 0.1 Musical chime generator When triggered, this circuit will play a tune of eight notes and then repeat the tune any number of times. It has been found to be useful for local alarm situations and is preferable to mechanical buzzers. The soothing tune is much more pleasant than a harsh buzz, the only problem being the space required by the loudspeaker. IC1 is a 555 configured as a monostable oscillator with a period of about 10 seconds. This is the total time the tune will be played and can be varied to suit using trimpot VR1. The pulse output from the 555 appears at pin 3 and is inverted by Ql and fed to pin 6 (the INHIBIT input) of IC4, as well as to a gated oscillator consisting ofIC2a and IC2b. IC2b feeds clock pulses to IC3, a 4510 BCD counter. The clock fre quency from the astable oscillator determines the speed at which the tune is played; increasing the frequency will speed up the tempo. IC3 then drives IC4 via its BCD outputs but with the fourth output tied to its RESET pin, since only three digits are necessary. 12VDC to 240VAC inverter for small appliances If you need a low-power (up to a few watts) 12V DC to 240VAC inverter, then take a look at this circuit. It's based on ICl which is a TDA2030 14W audio amplifier wired here as a square-wave oscillator. It drives the primary of a step-up transformer via a 4700µF capacitor. The layout is not critical but note that the TDA2030 should be mounted on a large heatsink to keep it cool. The 22µF capacitor should be a bipolar unit. T. Van der Burg, Christchurch, NZ. ($10) 14 SrLrcoN CHTP IC4 is a 1-of-8 analog switch, the outputs of which are connected via trimpots VR2-VR9 into a tone generation oscillator consisting of NOR gates IC2c and IC2d. Thus, the frequency of the tone oscillator is directly controlled by IC4 and the eight trim pots (VR2VR9) . The oscillator output then feeds a complementary emitter follower consisting of transistors Ql and Q2. These transistors do not require any quiescent bias voltage since the output signal is a square wave. Steven Merrifield, Heidelberg, Vic. ($20) +o-----a>----------. 100k 100k w 1 3 5 2200 25VW + 101!_~ 0.1 The circuit for this low-power 12VDC to 240VAC inverter is based on a TDA2030 audio amplifier module. . . . - - - - - - - - - - - . . . . __ _ _ _ _ +12V High performance drill speed controller This speed control circuit is intended for use with 12V DC PC drills which draw several amps. The circuit was derived from the "Walkaround Throttle for Model Railroads" which was published in the April 1988 issue of SILICON CHIP and more recently as part of the "Infrared Remote Control for Model Trains". It is suitable for controlling any permanent magnet 12V DC motor drawing up to 5A. ICld is the ramp generator and is connected to produce a sawtooth waveform running at about Z00Hz. This waveform is applied to the inverting input of IClb which is connected as a comparator. ICla is connected as a voltage follower/buffer to feed the speed control voltage from potentiometer VRl to the non-inverting input ofIClb. If the speed voltage setting is high, it interacts with the ramp waveform so that the output of comparator ICl b produces a Z00Hz pulse train with a high duty cycle (ie, on for most of the time). Conversely, if the speed setting is low, the pulse train will have a low duty cycle (ie, off for most of the time). The output of IClb is inverted by Ql and then fed to Darlington transistor QZ which drives the motor. Transistor Q3 and op amp IClc provide feedback and thus improve the speed regulation of the circuit. IClc monitors the motor back-EMF during the pulse off-times and this voltage is fed to the ramp generator circuit. This raises or lowers the ramp +20V 2.2k +12V 100k 1k .01+ F1 3A OUT 4700 + 0.1: 10 +12V 0.1 .,. voltage applied to comparator ICl b. Thus, any tendency for the motor speed to fall will have the effect of lowering the ramp voltage and thus increasing the duty cycle of the pulses applied to the motor. Q3 prevents any Simple lap timer for slot cars This circuit was designed to enable a calculator/stopwatch to be used as a timer for a slot car drag strip. The calculator used in the prototype has a mode select .,. switch to select the lap timer function, a start/stop switch to time the lap, and a reset switch to zero the counter for the next run. It was found that taking any of them high enabled the respective function. A 556 dual timer and two CdS light sensors were used to create two lightactivated Schmitt triggers. These start and stop the stopwatch when two light +20V motor voltage being applied to IClc during the pulse on time by virtue of being switched on when an output pulse is present. Geoff Monegal, Condell Park, NSW. ($15) 10 IC1b beams are broken by the car as it passes. Switching is by a 5V reed relay which has its output contacts soldered across the start/ stop switch on the stopwatch board. The light sources are not shown but two focussing 2.4V torch globes were used (one at the start and the other at the finish line). The globes and CdS sensors (eg, ORP12 or DSCD0l) are mounted in tubes 25mm long to eliminate interference from ambient light. The two 5kQ trimpots give adequate adjustment cif sensitivity. Greg Armstrong, Carrum Downs, Vic. ($15) AUGUST 1992 15 A By MICHAEL HAWKINS LTHOUGH MIDI HAS BEEN around for nearly 10 years, few people really understand it and certainly most don't know its full capabilities or its inadequacies. I'm going talk about the grass roots of MIDI, particularly with a view to eventually building your own MIDI gear. But first let's get a misunderstanding out of the way concerning the use of the term "midi". Unfortunately, Japanese manufacturers have used the term midi to describe the smaller rack mounting hifi systems which have proliferated over the last few years. They are called midi because they are mid-sized. Midi hifi gear has nothing to do with the MIDI equipment used by musicians. Now having got that out of the way, let's have a quick look at where we were 10 years ago. Before MIDI Up until about 1980, music synthesisers were based around analog technology; ie, the way they made noises was by using a voltage controlled oscillator (VCO). The oscillator would feed into a voltage controlled amplifier (VCA) and then into a voltage controlled filter (VCF). There would be a few envelope generators that provided the control voltages for the VCA and VCF and the keyboard would provide the control voltage for the oscillator. These instruments were generally mono; ie, you could only hit one note at a time. They had a few sockets on the back called CV and CV gate (or something similar). CV stands for control voltage and it allowed you to control the keyboard from another keyboard or sequencer. The control voltage was The Musical Instrument Digital Interface The purpose of this article is to introduce and explain the technical aspects of MIDI which stands for Musical Instrument Digital Interface. This is used by virtually everyr recording outfit, from million dollar operations right down to the humble busker. 16 SILICON CHIP D KEYBOAI\D SYNTHESIZER 00 - ~_J-"J~:: 1111~1rn11~1m~1i1~1~~1I1i L__I PERSON~.M~MPUTER ~THWWJGH-l~i~ OUT MIDI INTERFACE KEYBOARDLESS SYNTHESIZER MODULE ORUM 1'"1~"" Ml1911 c::::::J HHB O I rnmm c::::::J 'AUDIO I AUOIO I MIDI OUT I THROUGH ,--- -- - -- - - -- - - - - _ _ _ . OUT .---- - - ---- - ---------- ---- -EFFECTS OUT __._ t MIXING OESK 0 0 0 0 0 0 0 0 0 'o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 lo 0 0 0 0 0 0 0 0 0 0 0 L __._ _ __ _ __ t I 0 0 0 0 MIDI r--- -~TH=R= OU~G--;HI O tA~~IO C::=J O O _, AUOIO OUT a c:, MIOI ..,1;,;.N_ _ _ _....1 EFFECTS UNIT ~B 0 0 0 0 0 0 0 0 0 0 fri+tlll t t 0 0 0 90 o, MULTITRACK TAPE RECORDER 0 0 0 0 0 0 0 O 0 I I I I I I I 0 Fig.1: this diagram shows just some of the equipment which can be hooked together and synchronised via the MIDI bus. Not shown here are MID] samplers and tone generators. 1-volt per octave. The range was 10 volts so you could play notes across 10octaves. For the technology at the time, this was quite good and many people used this sort of gear with fantastic results. However, to build up a large number of notes with a few different instrument sounds required an awesome array of equipment and you needed to understand all the technology fairly well. Just prior to 1980 though, synthesisers started appearing with polyphonic capability; ie , you could play more than one note at a time (usually eight). With miniaturisation, all the VCOs, VCAs and VCFs could be packed into smaller spaces, allowing one instrument to contain many such circuits. The only problem here was that the CV gate system only allowed you to control one note externally. It became apparent that some sort of interface was going to be required to allow lots of notes to be controlled at once. A few attempts were made by individual manufacturers to introduce different interfaces but none of them took off, mainly because they did not address all the problems of reproducing music. Some of those problems were: (1) you should be able to change a synthesiser's sound remotely; and (2) you should be able to synchronise drum machines and sequencers and tape machines to each other. Up until 1983, the industry generally remained confused. In 1983, the International MIDI Association (originally made up of a conglomerate of representatives from cooperating instrument manufacturers) released the MIDI specification 1.0. i This non-profit organisation had defined a standard for the interfacing of electronic music devices based on digital communication techniques. Due to the fact that most devices had microprocessors in them already, it was reasonably easy to integrate MIDI into machines and so , within a year, all major manufacturers had begun supporting MIDI. Within another • i:· ,,!inl!'l'SIOII llll ( A small MIDI interface card for the expansion socket of any PC/XT/AT system and the right software allow musicians to do things that were unheard of just a few years ago. The Miracle keyboard which we reviewed in the December 1991 can be part of a comprehensive MIDI system linked to your computer. AUGUST 1992 17 One of the most rewarding pieces of MIDI equipment a musician can use is the sampler. The Akai SHOO is a popular instrument which gives CD quality sound with 44.lkHz 16-bit sampling. Sound waveforms can be sampled, viewed on the screen and modified at will. The unit can have up to 32 megabytes of memory and extensive sound libraries are available. It even has a SCSI port for an external hard disc drive. year, virtually all other interfaces had been dropped. One significant feature of MIDI was that it wasn't restricted to just turning notes on and off. It has various modes and levels of control, thus allowing virtually any type of music gear to be attached. Let's digress and have a quick look at what can be attached and done with the technology around today. A typical home studio These days, you can have your own home studio, with every piece of gear connected via MIDI - including your personal computer. You might have a keyboard, a sound module, a PC, a few effects units, a drum machine, a mixer and a multi-track tape recorder. Loaded onto your PC will be a sequencer package that will allow you to control every piece of gear to varying levels. For example, you would have corn- 18 SILICON CHIP plete control of the keyboard, the sound module, the effects units, the drum machine, and partial control of the mixer depending on how much MIDI is implemented into it. And you could probably synchronise the tape recorder to the drum machine and the PC. Therefore, you could compose and play your music, recording one instrument at a time on the PC. While the PC replays your first instrument, you record a second one, and this process is repeated until you have all the instruments recorded. You then set up the effects units with just the right reverb , echo and chorus that you want and record those settings on the PC. Finally, you can set up the mixer with just the right EQ (equalisation) and volume levels before recording the whole thing on the tape recorder, which in future will be able to synchronise the PC to itself so that you can change, add or delete whatever material you wish. Furthermore, all the settings, mixing levels, echo, chorus, music , etc will be recorded on the PC as a file that can be saved to disc. This can be sent to someone else via modem or the music score printed on a standard printer. Let's briefly define the purpose of each device I have just mentioned in the last paragraph, along with a synopsis of the kind of controls that each unit is likely to have. Keyboard: has a piano type keyboard, generates sounds, has many controls over the sounds produced, pitch bend, transpose. Sound Module: same functions as a keyboard but does not have a piano keyboard. It uses MIDI to allow other keyboards to make it produce sounds. Has the same control over the sounds produced, either through a panel of switches etc, or via MIDI. Effects Unit: a device which takes the audio outputs from other sound generating equipment and alters the sound using delay or filtering. Usually, the effects produced will be reverb (makes the sound sound like a concert hall) or echo. Other effects are phasing, flangeing, chorus (sounds like more than one instrument), or even harmonising. Has control over Today's MIDI keyboards offer a wealth of facilities for the innovative musician. This 61-note model DX711 D/FD from Yamaha has 64 voice memories, 32 performance memories, liquid crystal and LED alphanumeric displays and a 720Kb floppy disc drive for data storage. A. : ll1lf!!f,If,,11 ' I l\,,\\,\\,,\\\ ttU>.lfi,11' - - - - ------ ---- --~- 1 .· =;.,.,...,,.,,·_,· __ 1_-···~...-..i-·•----,..,....._·_1_, . - ¥• . • "--• This Kawai MIDI keyboard is shown together with a MIDI interface card and a number of software packages including the Musicator, which runs on 286 machines or higher. It turns the PC into a 16-track sequencer but also will record in real time from a MIDI keyboard and transcribe it into sheet form. delay times, sweep times and many others. Drum Machine: a unit that produces percussive sounds. Usually can be programmed to repeat drum patterns. Has controls over virtually every aspect of percussive sound generation. Can be started and stopped manually or via MIDI. Can also be synchronised to other equipment via MIDI. Mixer: takes the audio outputs from any device (ie, instruments, microphones, effects units, etc) and combines them into a few outputs suitable for recording on tape. Has control of EQ (tone), volume and level of effects. Some recent mixers are able to be controlled via MIDI. Sequencer: either a dedicated device or part of a personal computer that allows a music score to be recorded as digital codes (not as actual audio sounds) and be altered, replayed and stored digitally. Has control over virtually all aspects of music composition, depending on the type of sequencer. Information going into or out of a sequencer will usually be MIDI. Can be synchronised to other equipment via MIDI. not unlike the modem port found on PCs (although it's a current loop). Each MIDI device will normally have a MIDI In port and a MIDI Out port and maybe a MIDI Thru port. These are 5-pin DIN sockets which only use two pins. Whatever is received at a MIDI In port is always immediately repeated at a MIDI Thru port. So Thru ports are useful for cascading devices with only one control device. • ,._...,,,___r---1- - ·.- f The MIDI Out port simply transmits MIDI information that originates from that particular piece of gear. However, most devices have a facility called "Soft Thru" which allows you to repeat at the MIDI Out port whatever is received at the MIDI In port and transmit all the information originating from the device as well. There are three basic types of information transmitted down MIDI. Let's have a look at each group. Channel voice messages One main area of confusion with MIDI is exactly how each instrument is "spoken to" via MIDI. Just how does MIDI at the lowest level So what actually is MIDI from the hardware side of things and from the lowest level of software? MIDI is an asynchronous (serial) 5mA current loop interface, running at 31,250 bits per second. It transmits eight bits with one start bit and one stop bit. Basically it's a fast serial link One of the most common MIDI instruments you are likely to see in any musical combo is a drum machine such as this Akai MPC60 II which is an integrated sequencer and drum sampler. · AUGUST 1992 19 Want more instruments in your combo? The Roland RA90 Realime Arranger offers one way to get them. It is a MIDI peripheral unit which adds backup instruments as well as providing the facilities of a digital drum machine. one instrument know to play a note while all other devices remain quiet? Quite simply, each device attached to MIDI is assigned a channel from 1 to 16. Every channel voice message carries along with it a channel number, 1-16 (but actually sent as 0-F hex). Channel voice messages can be divided into two sets of commands. Voice messages turn notes on or off and the mode messages alter parameters on the designated instrument. For example, mode messages change an instrument's sound (violin to distorted guitar) and pitch bend (for those sliding guitar notes), and alter the touch sensitivity of an instrument (the difference between when your cat runs up your piano or your pet elephant). Channel voice messages could be argued as being the most important commands sent through MIDI simply because they are the commands that actually make instruments play music. System messages System messages are acted upon by all attached equipment; that is, system messages don't have a channel number sent with them. And you guessed it, they can be divided into a few categories: Common, Exclusive and Real-Time. There are only four Common messages. One sets the position of a song before it starts to play. Song select tells all attached devices what song to use. Tune request is rarely ever used (I have never seen it) and instructs Analog Synthesisers to tune themselves. The last command is the EOX ("End of System Exclusive") which leads us to System Exclusive Messages. Exclusive messages are manufacturer dependent commands. Each exclusive message starts with an organisation identification number. Then follows a limitless string of data which must be terminated by the EOX command. System exclusive data ·can be used for anything the manufacturer wishes. Often, it's used to transmit entire blocks of data used by an instrument to create new sounds to replace or alter the original ones programmed in. It can also be used to control manufacturer specific capabilities. Real-time messages are used to synchronise drum machines, sequencers and personal computers together so that they all play their pre-recorded YAMAHXS MIDI WIND INSTRUMENT MIDI keyboards and stringed instruments are fairly commonplace but have you heard of a MIDI wind instrument? The Yamaha WX7 Wind MIDI controller allows wind instrument players to directly play the most advanced synthesisers and tone generators available. There are sensors for breath pressure and lip pressure to provide the control facilities. · 20 SILICON CHIP tunes, beats, etc, in time. There are start, stop and continue commands. These three commands allow all instruments to be started or stopped at exactly the same moment and continue lets you continue from where you last stopped. Finally, there is the time clock command which is sent down MIDI at the rate of 24 clocks per quarter note. This is the command that actually keeps instruments in time with each other. Only one instrument at a time should send time codes, otherwise there will be time codes going everywhere and resulting instrument confusion en masse. The start, stop and continue commands, however, can be sent by any machine. There is one more real-time message called System Reset. It is rarely used (my peepers haven't ever seen it used) and should preferably not be used unless something has gone haywire. Its purpose is to reset every attached machine back to the state of first being turned on. Channel Mode Messages MIDI has four modes of operation available that are dependent on two variables, OMNI on/off and POLY on/ off. Generally, channel mode messages are sent when MIDI is first fired up and sent by the master sequencer or PC. There are two other uses for channel mode messages. One is an All Notes Off command, which is used to make sure all notes are turned off in an instrument. The other is to allow local control of an instrument to be turned on and off. Local control can be turned off so that the instrument only responds to MIDI note events and does not play notes if keys are hit at the particular instrument. But, when a key is hit, its MIDI note on and Note Off command will still be sent down MIDI, allowing other devices to respond or record the event. Well, that's probably enough technical jargon in one article but it should be enough to give the concept of MIDI - the musical instrument digital interface. To sum up, it is an 8-bit serial data system running at 31,250 bits per second. It is similar in some aspects to the serial data transfer system used in remote control of model cars and aeroplanes. The difference is that while a remote control system will have different channels devoted to SILICON CHIP AUSTRALIA'S BRIGHTEST ELECTRONICS MAGAZINE Three good reasons why you should subscribe to SILICON CHIP 1. You get a 12.5% discount on the newsstand cover price. Last year, we had to increase the cover price of the magazine because of rising costs but we have held the subscription to the old price so you get the benefit. Understanding The World Of CB Radl<> , ' • _. f T - 1 S!RVICINO-VMAOE AAl)JO •·• (.::(')jVffl'IJTEJt$ -AMAtWII RA,DtQ ., .• PllO,ja;T,s TO 1UJ1W 2. You'll never miss an issue. Sometimes it can be very hard to 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 plastic to make sure of that. 3• Get a discount on the binder too. You '11 want to store and protect your issues of SILICON CHIP so when you take out a subscription you get a further 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 from the start. Interested in these savings and benefits? Just fill in the coupon on page 92 and send it with your remittance. Or telephone (02) 979 5644 & quote your credit card number; or fax the details to (02) 979 6503. You'll be glad you did. Why not do it today? I hope to see you as a supporter soon. Leo Simpson, Publisher control of throttle, flaps and so on, the MIDI system has different channels devoted to different instruments. In a few month's time, I 'hope to present a simple way for you to get involved with MIDI music. That's the best way to understand the system. See you then. SC AUGUST 1992 21 · 1.2A {6Ah) 2A Build this 6/12V SLA battery charger This upgraded version of the March 1990 SLA battery charger is both cheaper & easier to build than the original unit. It automatically charges either 6V or 12V SLA batteries at any one of six current settings. By DARREN YATES As with most batteries, it is important that SLA (sealed lead acid) batteries be correctly charged. Incorrect charging procedures can cause considerable damage to a battery's internal structure and can reduce its service life. Unfortunately, most car battery chargers are not suitable for use with SLA batteries and will almost always result in overcharging. This SLA battery charger is a far better alternative. It can be used with both 6V and 12V batteries and automatically adjusts its charging rate to suit the condition of the battery. Like the original version, it's based on the Unitrode UC3906 intelligent battery 22 SILICON CHIP charger IC which monitors the battery and automatically switches to one of three charging modes. Because the battery voltage is continuously monitored and the charging current adjusted accordingly, this charger can be permanently connected to the battery if required. The unit maintains the battery at a constant "float voltage" once it has been fully recharged. A 6-way rotary switch on the front panel of the unit is used to set the maximum charging current to match the battery capacity. All the common battery capacities are catered for, as follows: 1.2, 2.5, 4.5, 6, 10 & 15Ah. The maximum charge currents for these settings are 250mA, 500mA, 900mA, 1.2A, 2A and 3A, respectively. Note that the charge currents provided are at the rate of C/5, where C is the battery capacity in amp-hours. If you have a battery which does not quite match one of the batteries listed, it doesn't matter-just select the nearest setting. For example, if you have a 1Ah battery, select the 1.2Ah rate. There's only one other control on the front panel and that's the 6/12V selector switch. The power on/off switch is located on the rear panel. The front panel of the unit also has three LEDs to indicate which of the three possible charging modes is currently in operation. These charging modes are MAIN (red), TRICKLE (yellow) and FLOAT (green) . We'll explain these three modes a little later on. Another very worthwhile feature of the unit is that it is output short circuit proof. After all, you don't want the unit "blowing up" just because the battery clip leads touch each other. Nor can the unit be damaged by re- SINK 16 verse connected batteries (except for blowing an internal fuse). SOURCE 15 COMPENSATION 14 +VIN Upgraded features Although the March 1990 SLA battery charger was a very successful unit, the amount of internal wiring caused problems for some readers. In particular, readers experienced problems wiring up the 4-pole voltage selector switch. Some constructors also experienced problems with inconsistent operation of the LED indicators. The charger would operate normall y but the TRICKLE or FLOAT indicator LED would refuse to light. The cure is simple: just replace the TL074 op amp with an LM324. Our main goal with the new unit was to make it much easier to build. This has been achieved in two ways: (1) by simplifying the mechanical construction; and (2) by simplifying the switch wiring. The list of new features and improvements is as follows: • the sheet metal case has been re. placed with a cheaper and smaller plastic instrument case; • a cheaper and smaller 60VA power transformer has been substituted for the original 108VA unit; • three of the four 5W resistors have been eliminated from the circuit, thus reducing heat dissipation; • a 3A current meter has been added to indicate the charging current; • a 6A PC-mounting power diode has been used instead of a stud-mounting diode; • CMOS logic switching has been added so that an SPDT toggle switch can be used for voltage selection instead of the previous 4-pole rotary switch. • An extra current range (2A) has been added to cater for 10Ah batteries. 1----41>-013 VOLTAGE SENSE C/L 40--U---I , I C/S OUT 1 0 - - - - - - - - , CIS+ I I Jo---•+' 25mV C/S - 20----1 + I I I 1-----012 CHARGE ENABLE VREF VREF 2.3V AT 25"C -3.9mV/"r. GROUND 60--+---- .,. 9 OVER-CHARGE INDICATE POWER 7 INDICATE OVEn.GHARGE 8 TERMINAL UC3906 Fig.1: internal circuit of the UC3906 intelligent battery charger IC. It monitors the battery voltage and automatically switches to one of three charging modes: trickle, main charge or float . _J _______________ _ INPUT SUPPLY VOLTAGE r----EE - - - - : : - - - - - . . . : - VDC C CHARGE VOLTAGE -=--~~VF_ A - ---------------CHARGE CURRENT I --------- ------IT STATE LEVEL OUTPUT oc INDICATE OUTPUT The UC3906 IC The heart of this project is the UC3906 intelligent SLA battery charger IC from the Unitrode Corporation. As we mentioned back in March 1990, it is a tricky IC to work with and is easily damaged. However, with a little care, it works very well. Fig.1 shows the basic internal structure of the IC. It contains five op amps which monitor the battery and current settings and control the driver circuitry to determine the charging rate. What makes this IC unique is its - - - - - - 011 TRICKLE BIAS VREF +VIN 5 0 - - - - DC TERMINATE INPUT (C/S OUT) ·::~ I I Off ~~ STATE 1 , I I I I ---t--- . -t---_1 ~ I - _ _ _ _.___I I STATE 2 _ ____ j ,, STATE 3 . . _ , _ _ I- • I STATE 1 Fig.2: these graphs show the voltage & curre)lt waveforms for the various charge states. If the battery is flat, it is trickle charged at current IT until voltage VT is reached. The circuit then switches over to main charge (point B) & finally to float charge when the overcharge voltage (Vod is reached (point C). specially-designed internal voltage reference. This sits at 2.3V at 25°C but has a negative temperature coefficient of -3.9mV/°C. This means that as the temperature rises, its voltage reduces by 3. 9m V/°C and this closely matches AUGUST 1992 23 PARTS LIST Semiconductors 1 PC board, code SC14109921, 225 x 124mm 1 front panel label, 245 x 73mm 1 0-3A meter scale 1 plastic instrument case, 262 x 190 x 82mm 1 M-2165 60VA transformer (Altronics Cat. M-2165) 1 SPST mains panel switch 1 M205 bayonet fuse holder 2 M205 PC mount fuse clips 1 5A M205 fuse 1 500mA M205 fuse 1 cordgrip grommet 1 TO-220 mounting kit (mica washer & plastic bush) 1 2-pole 6-position rotary switch 1 SPST toggle switch 1 MU-45 50µA FSD panel meter 1 red 4mm binding post 1 black 4mm binding post 2 solder lugs 1 2-way mains terminal block 1 21 mm x 6.4mm shaft Collett knob 3 5mm LED bezels 1 3-core mains power cord with moulded 3-pin plug 1 0.5m length of 10-core rainbow cable 1 300mm length of heavy-duty figure-8 cable 1 5kQ 5mm trimpot (VR1) 3 15 x 4mm machine screws & nuts (for power transformer & earth lugs) 2 15 x 3mm machine screws & nut (for bridge rectifier & mains terminal block) 1 10 x 3mm machine screw & nut (for 01) 5 No.6 self-tapping screws Hookup wire, solder, heatsink compound, tinned copper wire for links, heatshrink tubing. the temperature coefficient of an SLA battery. This thermal tracking is important because it ensures that the battery is always charged to the correct voltage, regardless of temperature. In particular, it avoids overcharging and possible damage to the battery in cold weather. The UC3906 also contains the logic which is used to switch the charger from one state to another, as well as operating the LED indicators. Fig.2 shows the voltage and current wave- forms for the three possible charging states: MAIN, TRICKLE and FLOAT. Take a look at the graphs for the charge voltage and the charge current. If the battery voltage is below VT (in this circuit, 10.5V for the 12V range), the UC3906 switches to the trickle state (IT) and charges up the battery at about 30mA. This is done to prevent damage to an overly-flat battery. When the battery voltage reaches 10.5V (point B in Fig.2), the "charge enable" comparator inside the UC3906 24 SILICO N CHI P 1 UC3906N intelligent SLA battery charger IC (IC1) 1 LM324N quad op amp (IC2) 1 CMOS 4066 quad analog switch (IC3) 1 TIP126 Darlington power transistor (01) 1 BC547 NPN transistor (02) 1 15W 1W zener diode (ZD 1) 1 3.3V 400mW zener diode (ZD2) 1 PW04 400V 6A bridge rectifier (BR1) 1 PX6007 or R250H 6A rectifier diode (01) 1 5mm red LED (LED1) 1 5mm yellow LED (LED2) 1 5mm green LED (LED3) Capacitors 1 4700µF 25VW electrolytic 2 0.1 µF 63VW MKT polyester 1 .022µF 63VW MKT polyester Resistors (0.25W, 1%) 1 560kQ 1 360kQ 1 220kQ 1 180k.Q 1 110kQ 4100kQ 1 91kQ 1 82kQ 1 47kQ 2 22kQ 118kQ 6 10kQ 1 8.2kQ 1 6.8kQ 1 4.?kQ 1 3.9kQ 51kQ 1 680Q 2 390Q 1 330Q 1 0.22Q 5W Miscellaneous switches the charger into the "main charge" state. As can be seen from the charge current graph, it jumps up to the maximum current level. In practice, this level will depend on the setting of the "charge current" switch set (ie, from 250mA to 3A). What happens now is that the battery voltage steadily rises towards a maximum of 14.6V. However, the charge current begins to decrease when it reaches 95% of this voltage. This is shown as point C in Fig.2. By the time the battery voltage reaches 14.6V or the "overcharge" voltage, the charge current has tapered off to about 120mA (point D) and the charger switches into the "float" state. What happens now is that it switches off momentarily and allows the battery voltage to drop to 13.8V. When a voltage of 13.8V (point E) is reached, the charger then supplies about l00mA of current to maintain this voltage indefinitely, or until a load is placed across the battery. If a load is connected, the battery voltage drops. Once it reaches about 13.ZV (or 10% below 14.6V), the charger kicks back into "overcharge" mode and supplies its main charge current to the load. A similar sequence of events occurs when a 6V battery is charged. Voltage selection is achieved simply by changing the bias settings to the op amps inside the UC3906. Load current If the load current is less than the selected charge current range, the charger will supply the required current but both the MAIN and FLOAT LEDs will light. This indicates that the battery is not being significantly depleted and that the charger is able to handle the load. Conversely, if the load current is higher than the current range, the charger will switch into the main charge mode and light the MAIN LED only. This indicates that the charger is now supp1ying its maximum current to the load and that the battery is also snaring some of the demand. For example, if the charge current switch is set to 1.2A and the load draws 2.5A, the charger will light the MAIN LED only. If the load is less than 1.2A, both the MAIN and FLOAT LEDs will light up. Once the load is removed, the charger will automatically resume '11 like the feeling of our new tligital troubleshooting scope. ~~ ~ 0. ~ i Q..r;J~i:,;:: ·- I - ! ~ ~EJ··· -a ....... ,!J . . . ! -. ' Now there's a 100 MHz digital scope that handles just like analog. instantly to the slightest control change. Digital oscilloscopes have certain advantages that are hard to overlook. But for troubleshooting, many engineers still prefer analog scopes. Simply because they like the way they handle. But when it comes to troubleshooting, the HP 54600's digital performance leaves analog and hybrid scopes far behind. At millisecond sweep speeds, the display doesn't even flicker. Low-rep-rate signals are easy to see without a hood. The HP 54600 changes that. It looks like a 100 MHz analog scope. All primary functions are controlled directly with dedicated knobs. And itfeels like one. The display responds It has all the advantages that only a true digital scope can provide. Like storage, high accuracY, pretrigger viewing, hard copy output, and programming. And since it's one . of HP's basic instruments the HP 54600 gives you all this performance at a very affordable price. So if you like the feel of analog control, you'll like the way our new digital scope handles troubleshooting. To find out more call the Customer Information Centre on 008 033 821 or Melbourne 272 2555. rJ,'n9 ~/!II HEWLETT PACKARD A Better Way. Just rete·ased: the HP 54602A scope with bandwidth up to 250MHz JIVTHTMl25/A ! ...-----------------------------<11----------~-v+ 100k 100k Z01~ 15V 1W VR1 5k 4700 + 25VWr BR1 PW04 F2 5A llATTERY 01I 680(1 180k + 16 V+ 15 10k 11 15V 4A 12 -:- IC1 UC3906N .0221 'i 18k _ ___,.___ V+ F1 500mA 10k 13 240VAC A N E 14 10 V+ ~ 560k 1k B IC3c EOc VIEWED FROM BELOW BCE LED3 FLOAT GREEN -:- K 12V 6V 47k .,. -:- A 10k ~K .,. 6/12V SLA BATTERY CHARGER 22k -;- Fig.3: although based on ICl, the circuit also uses IC2a-c to drive the indicator LEDs and IC3 to switch resistors in & out of circuit for voltage range selection. IC2d forms part of the selector circuit for the three lower current ranges. charging the battery, depending on its condition. It's this flexibility that makes this charger unique - it can be left on the battery indefinitely and will look after it under all conditions. Circuit details Now take a look at Fig.3 which shows the full circuit details. Two other !Cs are used in addition to the UC3906 (ICl). These are an LM324N quad op amp (IC2) and a 4066 quad analog switch (IC3) which performs most of the functions of the 26 SILICO N CHTP voltage selection switch in the previous circuit. Power for the circuit comes from the mains and is applied to transformer Tl via switch S1 and a 500mA fuse. The 15VAC secondary of the transformer then feeds bridge rectifier BRl and a 4700µF filter capacitor to give about 21V DC. This DC supply rail is applied to pins 3 and 5 of !Cl and to the emitter of Darlington transistor Ql via a 0.220 5W resistor. The 0.22Q 5W resistor forms part of the current limiting circuitry. Meter Ml monitors the current through this resistor, with VRl used to calibrate the meter for a full scale reading of 3A. Transistor Ql (TIP126) acts as the main pass element of the circuit. It is controlled by the drive current from pin 16 ofICl. Q1 's collector then feeds diode Dl which protects the UC3906 from damage if a battery is connected to the output while no power is applied to the circuit. Diode D2 and the 5A fuse in series with the positive output terminal protect the circuit if a battery is connected the wrong way around. If a battery is wrongly connected, D2 con- Most of the parts, including the large power transformer, are mounted on a single PC board. Take care with the mains wiring & sleeve all exposed terminals with plastic tubing to prevent accidental electric shock. ducts heavily and blows the' 5A inline fuse. Current selection The maximum charge current is set by the 0.22n 5W current sensing resistor and the 250m V reference source at pin 4 of IC1 (see Fig.1). The voltage developed across the 0.22Q sense resistor is compared with the voltage at pin 4 and the current through it is then adjusted accordingly by IC1. There are two modes by which this current sensing and control take place. The first mode applies to the 1.2A, 2A and 3A settings and in these cases, switch S2 taps off the voltage developed across the 0.22Q resistor, via a voltage divider consisting of the 8.2kQ, 4.7kQ and 10kQ resistors. With the 1.2A setting for example, S2 taps off the full voltage developed across the 0.22n resistor; ie, 250mV/0.22ll For the 2A range, switch S2 selects the voltage at the junction of the 10kQ and 4. 7kQ resistors. Since the voltage between pins 4 and 5 is limited to 250mV, the voltage developed across the 0.22n resistor will be higher, at around 443mV; ie, (250mV/(8.2kQ + 4.7kQ)) x (8.2kQ + 4.7kQ + 10kQ). Similarly, when the 3A range is selected, the voltage developed across the 0.22n resistor is around 698mV. Since the maximum current provided by the charger passes through the sense resistor, this resistor cannot be too large otherwise__ there will be too much voltage loss and too much power dissipated. On the other hand, the resistor cannot be too small, otherwise the voltage developed across it for the low current ranges will not be enough. That was the dilemma we faced in the original design and so the sense resistor was much larger. In this new design, we have tricked the circuit into "seeing" a much larger sense resistor than is really there, when the ranges below 1.2A are selected. This is accomplished by op amp IC2d and its associated resistor string. This op amp acts like a current sink and it reduces the voltage which must be developed across the 0.22Q resistor for a given charging current. For example, when the 500mA current range is selected, only 110mV will be developed across the 0.220 sense resistor. However, pin 4 of IC1 is fed with 250mV because IC2d and the tapped resistor string provide the remaining 140mV. A similar process occurs for the 250mA and 900mA ranges. So by using IC2d, we've been able to do away with three of the 5W resistors from the original design. Voltage selection The charging voltage is selected by switching parallel resistors in or out AUGUST 1992 27 ----- -------- EARTH TO ~NEL 0 0 ~;wr,a&1nw::ca .an. ~; O! ~ •il ' ~ VR1 l::I POWER TRANSFORMER BATTERY Fig.4: use heavy-duty cable when wiring up the output terminals & note that D1 the 0.22n 5W resistor are mounted proud of the board to allow the air to circulate beneath them for cooling. Qt is bolted to the rear panel (see Fig.6). & of circuit to obtain the correct bias levels for pins 12 and 13 of ICl. Switching of the resistors is accomplished by 4066 analog switches, in IC3. 28 SILICON CHIP For a 12V battery, the unit is set to change state at the following battery voltages: trickle voltage= 10.5V; overcharge voltage= 14.6V; and float voltage= 13.8V. For a 6V battery, the relevant voltages are: trickle voltage = 5 .1 V; overcharge voltage = 7.2V; and float voltage = 6.5V. To select the 6V range, IC3a and IC3c are closed and IC3b and IC3d are opened. When the 12V range is selected, the analog switches are re- RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 No. 1 4 1 2 6 1 5 2 Value 560kO 360kO 220kO 180kO 110kO 100kO 91kO 82kO 47kO 22kO 18kO 10kO 8.2kO 6.8kO 4.7kO 3.9kO 1kO 6800 3900 · 3300 0.22O5W versed. Transistor QZ provides an outof-phase signal so that the switches can be made to work alternately from a single pole switch (S3). The circuit works like this. When S3 is closed to select the 6V range, pins 6 & 13 are pulled high and IC3a & IC3c turn on. IC3a connects a 1 l0kO resistor in parallel with the' 180kO resistor on pin 12 of ICl, while IC3c connects a 360kO resistor in parallel with the 560kO resistor between pins 10 & 13. At the same time, transistor QZ turns on and pulls pins 5 & 12 of IC3 low, thus turning IC3b & IC3d off. Conversely, when S3 is opened, pins 6 & 13 ofIC3 are at 0V and so switches IC3a & IC3c are turned off. QZ also turns off which means that switches IC3b & IC3d are now turned on. IC3b connects a 91kO resistor in parallel with the 18kO resistor between pins 12 & 13 ofICl, while IC3d connects a 220kQ resistor in parallel with the 47kO resistor on pin 13. Op amps IC2a, IC2b & IC2c are used to drive the indicator LEDs. IC2a is driven by pin 1, the current sense output. When pin 1 goes low, the output of ICZa (pin 14) goes high and turns on LED 1 to indicate that the 4-Band Code (1%) 5-Band Code (1%) green blue yellow brown orange blue yellow brown red red yellow brown brown grey yellow brown brown brown yellow brown brown black yellow brown white brown orange brown grey red orange brown yellow violet orange brown red red orange brown brown grey orange brown brown black orange brown grey red red brown blue grey red brown yellow violet red brown orange white red brown brown black red brown blue grey brown brown orange white brown brown orange orange brown brown not applicable green blue black orange brown orange blue black orange brown red red black orange brown brown grey black orange brown brown brown black orange brown brown black black orange brown white brown black red brown grey red black red brown yellow violet black red brown red red black red brown brown grey black red brown brown black black red brown grey red black brown brown blue grey black brown brown yellow violet black brown brown or... ;ige white black brown brown brown black black brown brown blue grey black black brown orange white black black brown orange orange black black brown not applicable charger is delivering full charge. ICZb drives TRICKLE charge indicator LED 2. When ICl is in trickle charge mode, current is supplied from pin 11 to the battery via a 6800 resistor. While this is happening, the voltage on pin 11, and hence on pin 5 of IC2b, is above the reference voltage on pin 6 and thus pin 7 switches high and lights LED 2 to indicate that the charger is in TRICKLE mode. ICZc is driven from pin 10 (the state level control) ofICl. Pin 10 goes high at the end of the main charging period and turns on FLOAT indicator LED 3 via ICZc. Trickle current The trickle current is set by the 6800 resistor between the output and pin 11 to approximately 30mA, although this figure is not critical. In any event, pin 11 cannot supply any more than 40mA maximum. Practical example Let's consider what happens when a 12V battery that has discharged to 8V is connected to the charger. Initially, the circuit senses that the battery voltage is below 10.5V and this switches pin 11 to the supply voltage so that the battery trickle charges at about 30mA. At the same time, IC2b switches its output high and lights the TRICKLE indicator LED (LED 2). Once the 10.5V threshold is reached, the enable comparator in ICl is turned off and the internal blocking diode keeps the voltage at pin 11 of ICl at the battery voltage. This pulls the non-inverting input ofICZb below its inverting input and so LED 2 now turns off. Series pass transistor Ql now turns on and feeds the selected charge current to the battery. This causes the current sense amplifier to turn on, which pulls pin 1 low. This low is coupled into pin 8 of ICl and also into the inverting input of IC2a. The output of IC2a now goes high arrd turns LED 1 on. The battery continues charging until the voltage nears 14.6V. ICl then begins to throttle back the charge current until it drops to about 120mA, this being set by ICl's internal 25mV source and the 0.220 resistor. When the Voc overcharge voltage (14.6V) is reached, the current sense AUGUST 1992 29 comparator output goes low, thus switching off its transistor and pulling the overcharge terminal (pin 8) high. This also pulls the non-inverting input ofIC2a high and turns LED 1 off again. If you look at Fig.2, you will see that the state level output goes high at this point as well. In the circuit, this results in pin 10 ofICl going from 0V to about 2.ZV, as set by its associated resistors. This output is fed directly into pin 10 ofIC2c which switches its output (pin 8) high and thus turns on .:;:=-~~i1 0 LED 3. ~ ICl also now turns off pass transistor Ql, allowing the battery voltage to drop naturally from 14.6V to 13.BV. Once this level is reached, Ql is allowed to pass about 90mA of current to keep the battery at this voltage indefinitely. The .022µF capacitor between pin 12 and ground removes any tendency for the circuit to oscillate slowly between charge states. If an external load drawing greater than 90mA (approx.) is applied to the battery at this stage, the battery voltage drops until it reaches 95% of 13.BV, or 13.1 V. The voltage amplifier and current limit comparator now set the driver circuitry to deliver the maximum selected current to the load. When the load is subsequently removed, the charger automatically selects the correct charge state according to the battery condition. w w :::r: Construction A Most of the components, including the power transformer, fit on a PC board which is coded SC14109921 (225 x 124mm). Before mounting any of the parts, carefully check the board for shorts or breaks in the tracks. If you find any, use a dash of solder or a sharp artwork knife as appropriate to fix the problem. Fig.4 shows the PC board assembly. Install the wire links first, followed by the resistors, diodes and zener diodes. Note that the resistors should all be 1 % types. Check each resistor with your multimeter before installing it on the board and don't confuse the two zener diodes. Diode Dl and the 5W resistor should be mounted about 5mm above the board to allow the air to circulate for cooling. The capacitors, trimpot VRl and the fuse clips can now be installed. u <[ 30 SILICON CHIP a P O SC14109921 Cl! w _J a.. Cl! w :E 0 Cl! □ u... (I) z: <[ Cl! t- Q SILICON CHIP 1992 Fig.5: this is the full-size etching pattern for the PC board. Be sure to orient the fuse clips correctly but don't snap the fuse in just yet. A 16-pin IC socket can be used for the UC3906 IC (optional), while the other two ICs can be soldered directly We Only Skimped OnThe Price. Introducing The Fluke Series 10. Fluke quality: Made in the USA by Fluke , with the same rugged reliability that's made us the world leader in digital multi meters. Count on hard-working high performanceand a two-year warranty to back it up. Large, easy-to-read display: 4000 count digital readout. Actual size: Easy to carry, easy to use. New! Min/Max record with relative time stamp and Continuity Capture™: Makes intermittent problems easier to find. Records highs and lows- and "time stamps" when they occurred. In continuity mode , opens or shorts as brief as 250 µs are captured and displayed. New! V Chek'": For fast accurate checks on power sources and supplies, set your meter on V Chekand let it do the rest. V Chek will determine continuity/ohms; if voltage is present, it will automatically change modes to measure AC or DC volts, whichever is detected. For most initial troubleshooting checks, here's the only setting you need to make. I I For high performance at Fluke's lowest price, get your hands on the new Series 10. Stop by your local Fluke distributor and feel what a powerful difference the right multimeter makes-at the right price. For a free product brochure , contact your local Fluke distributor today. Autoranging with manual option: Your choice, depending on your situation. Sleep Mode: Shuts itself off if you forgei, extending long battery life even further. ~ New! Slide switch~ few pushbuttons co:~o1 all functions: Designed for true one-hand operation. Capacitance: Autoranging from .001 µF to 9999 µF. No need to carry a dedicated capacitance meter. Fluke 10 4000 count digital display 1.5% basic de volts accuracy 2. 9% basic ac volts accu racy 1.5% basic ohms accu racy Fast contin uity beeper Diode Te st Sleep Mode Two -year wa rranty . ~ .Fast, accurate tests· and measurements: AC and DC voltage measurements to 600 volts, oh ms to 40 MQ; audible continuity test; and diode test. Fluke 11 V Che k1" Capacitance. .001 to 9999 ~F 4000 count digital display 0.9% basic de volts accuracy 1.9% basic ac volts accuracy 0.9% basic ohms accuracy Fa~t continuity beepe r Diode Test Slee p Mode Two-yea r war ranty Fluke 12 V Che k"·' Min/Max recording wi th relative time stamp Continuity Capture "·' Capacitance, .001 to 9999 ~F 4000 count digital display 0.9% basic de volts acc uracy 1. 9% basic ac volts acc uracy 0.9% basic ohms acc uracy Fast continuity beeper Diode Test Slee p Mode Two-year warranty Optional holster with tilt-stand available. Safety-a Fluke standard: Designed to meet UL 1244, IEC 1010, CSA and VDE safety requirements; extensive overload protection built in. New! TL75 Hard Point™ Test Leads: Comfort grip with extra strong tips for extended service life. The New Series 10. A Small Price For A Fluke. Audible Continuity: To perform fast continuity checks, just listen for the beep; no need to watch the display. F L UKE AND PH I L I PS T H E T &M A L L I ANCE For further information contact: Philips Scientific & Industrial. Tel: (02) 888 0416 FLUKE ® Light-duty hook-up wire can be used to connect the front panel switches, LEDs and the meter but be careful not to transpose any of the connections. Note that the PC board was modified slightly after the photographs were taken. to the board. Note that the ICs all face in the same direction. The two transistors can also be installed at this stage. Mount Ql at full lead length so that it can later be bolted to the rear panel for heatsinking (see Fig.6) . Case assembly The next step is to mount all the front panel hardware. If the front panel has not been supplied pre-drilled, it will require holes for the switches, LED bezels, output terminals and the meter. It's best to use the front panel label as a drilling template for these holes. Carefully attach the label to the panel, then drill pilot holes at the points indicated and ream them to size. The meter is supplied with a drilling template for the large cutout required. This cutout can be made by drilling a series of small holes around the inside perimeter of the marked circle and then knocking out the hole and filing it to a smooth finish. The meter requires a new scale to be attached and this should be supplied with the kit. To install the new scale, first unclip the front plastic cover and remove the two meter scale screws. This done , remove the old scale by sliding it under the meter 32 SILICON CHIP pointer, then attach the new scale and refit the cover. The metal rear panel can now be drilled to accept the bridge rectifier mounting screw, fuse Fl, the earth lug mounting screw, switch S1 and the mains cordgrip grommet. The exact location of these components is not critical and can be gleaned from Fig.4. A mounting hole is also necessary for transistor Ql and this should be marked out by temporarily install- INSULATING MICA WASHER . ,~JI SCREW r llllllll(3 -----CASE ' T0220 DEVICE Fig.6: mounting details for the TIP126 Darlington transistor (Q1}. Check that the rear panel mounting area is smooth & smear all mating surfaces with heatsink compound before bolting the assembly together. ing the PC board and the rear panel in the case. A square cutout is required for switch S1 and, as for the meter, this can be made by drilling a series of small holes and then knocking out the centre piece. File the cutout to a smooth finish but be careful not to make it too big. Final wiring Once all the holes have been drilled, mount the hardware items on the front and rear panels and bolt the transformer and mains terminal block to the PC board. The 12-position rotary switch is converted to a 6-position switch by removR1g the nut from the threaded boss and changing the position of the locking ring (located at the front of the switch). Fig.4 shows the chassis wiring details. You can use light duty hook-up wire for most of the connections but note that heavy duty cable must be used between the PC board and the output terminals. The wiring to the rotary switch and_LEDs can be run using rainbow cable (note: LED 2 is oriented in the opposite direction to the other two LEDs). The mains cord enters through the rear panel and is clamped using the cordgrip grommet. Terminate the Active (brown) and Neutral (blue) leads to the mains terminal block as shown, and solder the Earth (green/ yellow) to one of the earth solder lugs on the rear panel. The transformer metalwork is earthed by a lead that runs from the rear panel to a large solder lug that's secured by one of the transformer mounting nuts. Use mains-rated cable for the connections to the power switch (S1) and to the fusefolder (Fl). These connections should be sheathed in heatshrink tubing to guard against accidental contact with the mains. Don't connect the transformer secondary to the bridge rectifier just yet - we 'll come to that shortly. At this stage, the PC board should be secured to the matching standoffs on the bottom of the case and transistor Ql bolted to the rear panel. Fig.6 shows how Ql is insulated from the rear panel using a mica washer and insulating bush. Check that the mounting area is smooth and smear all mating surfaces with heatsink compound before bolting the assembly together. Finally, use your multimeter to confirm that there is no connection between the metal panel and the transistor tab. The transformer secondary voltage should now be checked to ensure that it is correct before it is connected to the bridge rectifier. Wire in the C-F connection on the transformer as shown in Fig.4, then install a 500mA fuse in the mains fusefolder and switch on. You should get a reading of 15-17VAC across the transformer secondary (ie, between points B & D). If not, switch off and check the transformer wiring. As a final check, measure the voltage across the capacitor when the FLOAT LED is alight. You should get a reading of 13.8V (approx.) when the 12V range is selected and 6.9V (approx.) when the 6V range is selected. Note that these figures may vary slightly due to component tolerances. Switching on Meter calibration Assuming that everything is OK, connect the transformer secondary to the bridge, set VRl to mid-range and re-apply power. The FLOAT LED should immediately come on and you should be able to measure about 24V DC across the 4700µF capacitor (ie, between the + and - terminals of the bridge rectifier). If either of these things do not occur, switch off immediately and check for wiring errors. If all is well, set the charger to 12V and 250mA, and connect a 220 resistor across the output terminals. This should cause the TRICKLE LED to light. The TRICKLE LED should go out and the FLOAT LED should come back on again when the resistor is disconnected. Finally, VRl should be adjusted to accurately calibrate the meter. To do this, connect a battery to the charger (preferably lOAh or 15Ah) and connect your multimeter in series with one of the leads to monitor the current. Set the current range, apply power and adjust VRl so that the reading O.Jl the charger's meter matches that on the multimeter when the MAIN LED is lit. If the battery is already fully charged (ie, the FLOAT LED comes on), connect a load to discharge the battery until the MAIN LED comes on. The charger will then supply the maximum selected current to the battery, thus allowing you to accurately adjust VRl. SC 0 .L CLASS-2.5 You can now afford a satellite TV system MU·45 For many years you have probably looked at satellite TV systems and thought "one day". You can now purchase the following K-band system from only: Fig. 7: this artwork is used to replace the existing meter scale. The old scale is removed by unclipping the front plastic cover & undoing two screws. $995.00 Here's what you get: *A 1.6-metre prime focus dish antenna, complete with all the mounting hardware. Now set the charger to 6V and connect a 100 resistor across the output terminals. As before, the TRICKLE LED should light and then go out again when the resistor is disconnected. You can now simulate a battery by connecting a 4700µF (or larger) electrolytic capacitor across the output terminals, together with a parallel 2. 2k0 bleed resistor. When the charger is turned on (250mA current range selected), the TRICKLE LED should light for a few seconds, after which the unit should rapidly cycle first to the MAIN LED and finally to the FLOAT *or better). One super low-noise LNB (1.4dB *magnetic One Ku-band feedhorn and a signal polariser. * 30 metres of low-loss coaxial cable with a single pair control line. * lnfrared remote control satellite receiver with selectable IF & audio bandwidth, polarity & digital readout. Your receiver is pre-programmed to the popular AUSSAT transponders via the internal EEPROM memory. This unit is also suitable for Cband applications. LED. Call, fax or write to: 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 & Pay TV hardware. I I II -----------· Name. ...................................... ........ I I II I Address ...... .. .... .. .... ..... ........... ..... .... I I ........................... P/code ................ II Phone ............ ...... .. .......................... I I I II I I ACN 002174 478 01/92 ~-----------~ AUGUST 1992 33 Stereo PreAmplifier with Magnatic Mic. Amplilier $20.00 Speaker Protector Stereo .. $22.00 35W PURE CLASS A Main Power Amplifier Mono . $64. 00 Dynamic Noise Reducti on System . $39.00 120W+120WDC LOW TIM Pre-Amp & Power Amp . . . .. .... .. ........... .. .... .. $1 19.00 80W+80W Pure DC Stereo Power Amp . .. ................... $109.00 NF-CR BI-FET Pre-Amplifier (with 3 way tone control) .. $72.00 State OfThe Art Full Complimentary Symmetry FET Stereo Pre-Amplifier ..... .... $159.00 60W+60WOCL DC Pre-Main & Stereo Amplifier . $99 .00 100W Dynamic Class A Main Power Amplifier Mono .. $79.00 Stereo Tone Control Amplifier . $15.00 Complete Speaker Protector Stereo . . $19.00 100W PURE CLASS A, Fully Symmetrical Power Amplifier Mono . . $79.00 250W(BTL 320W) All FET, Dual Differential, Symmetrical Stereo DC Final Amplifier .. . .. ............... $199.00 40W x 2 IC Low Voltage Amplifier . $33.00 BTL 200W or 60W+60W Stereo, Super LOW TIM Power Amp. wi th Speaker Protector $87.00 120WMOSFET Super Low TIM Power Amplifier Mono $69.00 Stereo All FET Pre-Amplifier with 5 Band SEA Equalifier $94.00 All FET, BTL 200W, Stereo 80W+80W Fully Symmetrical Super Low TIM Power Amplifier .. $124.00 $69.00 SOW RMS. 8 ohm PURE CLASS A Power Amplifier Mono High Precision Sound Control Switch . Sound or Touch Switch Control lnfrared Remote Control Unit Multipurpose Melody Gene Multipurpose Melody Gene Multipurpose Melody Gene Compact Electronic ~·-· Mini Timing Swi tch Mini Electronic Org $19.00 $24.00 $44.00 $17.00 $17.00 $19.00 $15.00 $15.00 $12.00 HUGE RANGE OF KITS FOR YOU TO CHOOSE AND SAVE YOUR$$$ PHONE OR WRITE TO US FOR A COPY OF PRICE LISTS S020t S0202 S0203 S0204 S0205 S0206 S0207 S0208 S0209 GENERAL S0101 Battery Fluorescent Light Driver .. $19.00 S0102 DC-DC 12Vto +/-35V or +/-50V 6A Max High Power FET Booster Transformer ..... $120.00 INVERTERS S0001 0-SOV3A High Precision Power Supply with Short Circuit Break & Overload Protector .. $42.00 S0002 0- 15VSA Regulated DC Power Supply . $37.00 S0003 0-25V 10A Professional High Efficiency Regulator . .. $84.00 S0004 0-30V 3A Regulated DC Power Supply .. $37.00 S0005 0-20V 20A Professional Regulated Power Supply with Full Protection Circuit ....... $134.00 S0006 0-30V 20A Professional Heavy-Duty Regulator with Full Protection .. . ..... .......... .. . $149.00 S0007 +/- 0-35V 2.5A Dual Regulated Power Supply . $48.00 S0008 0-30V 10A Professional Heavy-Duty Regulated Power Supply with $84.00 Protector Circuit S0009 0-SOV 6A High Effeciency, Cut-Off &Auto-Reset, Electronic-Protected, $89.00 Regulated Power Supply POWER SUPPLIES S0320 S0317 S0318 S0319 S0315 S0316 S0301 S0302 S0303 S0304 S0305 S0306 S0307 S0308 S0309 S0310 S0311 S0312 S0313 S0314 ASSEMBLED & TESTED KITS AMPLIFIERS FUN, LEARN & SAVE $$$$$ A-ONE ELECTRONIC KITS •- .,_,.,. ,,.,,.,. • , ' "' , ,~ ·J;f ~--';, ---..,~, -,., :-_, -,., ~~ .;. .-, 0 ..,, •".I?',, ·•• . ·••A .~>·. ~.'. \t: l.ii# ~"If,•" ;-cc- ~ ,-'fulj~,.,,,., . ·. r,.... • FUNCTION CAT No. M0203 CTI C87A 1 $144.00 .l • 2Hz-200KHz (5 Ranges) • Sine, Triangle, Square Wave • 1% Typical at 1KHz ' . · GENERATOR • 10 Ranges, fully Automatic with Range Hold. • Full Scale Value From 99.9pF to 99.9mF. • Accuracy 0.5% +/- 0.5pF +/-1 Digit. AUTORANGING CAPACITANCE METER 0 , .. - -- ··- -· - ·-,, CTI C89A • 10Hz-60MHz Two Ranges • 0-9999999 Counts • 25mV RMS Sensitivity CATNo.I0017 UNIVERSAL COUNTER 144.00 CTIC86A • 2CH Input, auto selection. • Dual Decimal Points Indication • 0.1 Second Gate Time ri-r~~HWtlq·.. $95.00 t) ()_ ()-. l) CAT No. l0008 . wuuwwwuu mnnnr,nnn CAT. No. 10014 550 M Hz FREQ U ENCY C OUNTE R TS : 6.6V(MAX) : 5ms-5Dms · AC 240V at 50Hz : Wide 360mm,(14.2in.) Deplh t22mm,(4.82in.) Height 53mm,(2.10in.) EDM-82 Surround sound output Voltage Delay time Power Dimensions M0106 EDM-70H 3 .5 Di g it Pocket Size DMM M 0107 EDM-72B 8.5 Di g it DMM w / Cap M 0101 EDM-162 3 .5 Digit , ? Fu ne. A utorange M0103 EDM-1133 B ar Grap h, 8Fun c. A utorange M0104 EDM-1155 B ar Gra ph , 12 Fu nc. Aut orange M0105 EDM-1177 B ar Grap h , 14 Fun c . A uto ran ge AUTORANGING DMM $212.50 $154.50 $112.50 $92.50 $73.50 $53.90 V DC 400mV to 1000V, 5 ranges 100µ.V max resolution , ± 0.5 % V AC 400mV to 750V, 5 ranges 100µ.V max resolution, ± 1.2% A DC 4mA to 20A, 4 ranges 1µ.A max resolution, ± 1% A AC 4mA to 20A, 4 rang es 1µ.A max resolution, ± 1.5% Ohm 400ohm to 40Mohm , 6 ranges 0.1ohm max resoluti on , ± 1% • 3 ¾ Di git , BIG LCD Di spl ay • 12 Functions DC V, AC V, DC A, AC A and Ohm Frequency counter 1Hz to 4MH z (auto) Capacitance 4n F (1pF) to 40µ. F Diode foreard voltag e test Transistor hFE test Audib le continu ity Logic level test Peak Hold CAT No. M 0102 ..) 161.50 3 3/4 DIGIV Dl\'IM SPECI FICATIONS & ELECTRICAL CHARACTERISTI CS: FREQUENCY RESPONSE : 20Hz-20KHz+l- 5dB T. H.O. (Front channel) . 0.05% 20Hz- 20KHz T.H.D. (Rear channel) <0.25% Input signal voltage : 0.1V-3.5V(MAX) Front channel output vollage : 0.1V-3.5V(MAX) Input impedance 47K ohms $199.00 CTI C 550A ECONOMICAL BENCH-TOP INSTR • .,zy •⇒ - '.. ."'·"""., ·-- $239 SM-333 surround sound processor employs the most updated integrated circuits as its heart. It is also equipped with a (DNA) Dynamic Noise Reductor systems IC made by "National Semiconductor" to particularly filter out the annoying noise that is commonly found on tapes or CD disks; therefore (DNA) system is suitable for and has outstanding performance on different video types, CD, LO, or Dolby Surround encoding disks and tapes, etc. In addition, there is six low noise operating amplifi ers and all in one board design, no other external connections connect to the main board besides the power line, hence that makes the internal noise reduced to its minimum level, as well enabling , SM-333 to produce ultimate live performance effect. SM -333 VIDEO/AUDIO SURROUND SOUND PROCESSOR $79.00 $109.00 100 watts into 8 ohms 125 watts into 4 ohm s 10Hzto100KHz Less th an 0 .008 % Better than 80 dB 1V 35 to 45 VDC <at>3 amp . $119.00 80 watts per c h an nel into 8 ohm s Less than 0.05 % at rated power Less than 0 .05 % at rated power DCto200 KHz, - OdB ,-3dB, <at>1 watt 30 VAC x 2 <at>6 am p. MAIL ORDERS WELCOME: CHEQUE, MONEY ORDER, BANKCARD, MASTERCARD, VISA OR AMERICAN EXPRESS. PHONE OR WRITE TO US FOR A COPY OF PRICE LISTS Power output 120 Wr.m. s. per c h annel into 4 o hm load 72 Wr.m.s. per c hannel into 8 ohm load Frequency re sponse 10to 20KHz Total harmonic disto rti on : Less than .01 % Tone control Ba se: ± 12 dB, Mid: ± 8 dB, Trebl e: ± 8 dB Sensitiv ity Phono input , 3 mv into 4 7 K. Line,0.3 V into 4 7 K. S ignal to noise ratio 86dB Power requirement 40VDC 0' 6amp The TA-800 MKII is a co mplete pre and mai n stereo power amplifier. It has provision for input progra m source switching , a phono pre-ampl ifi er stage with RIM equalization , three-b and ton e co ntrols, built- in power supply rectifier and filter and a speaker protection c ircuit. It only nee ds to be installed in a su itable housing and the add it ion of a power transformer in order to make it operational. CAT No. 5 0305 SPECIFICATIONS 120W + 120W LOW TIM P R E- MAIN A M PLIFIER Power output Total harmonic d istortion Intermodul ati on distortio n Fre quency res p o nse Power re qu irem ent s Modern circuit design uti lizes full comple mentary power output and differential cascode input st age. DC coup ling provides superb transient response. A special output circuit guards against short circ uits and overload operation. CATNo.50306 SPECIFICATIONS 80W + 80W PURE DC STEREO MAIN POWER AMPLIFIER Frequency re sponse Total harm o nic di stortion Signal to no ise rati o Sensitivity Power req uirem ent s Power output This well designed and stable amplifier features DC coupling throughout and a fully complementary symmetry circuit topology. It operates in class A at low and medium levels and gradually sh ifts to cl ass AB operation at high levels. A pair of these amplifiers provide 200 watts of super high fidelity sound reproduction. CAT No. 50310 ~ SPECIFICATIONS 100W DYNAMIC CLASS A MAIN POWER AMPLIFIER an PURE CLASS A POWER AMPLIFIER Dual differential fully symmetrical circui try. Overload and short circuit pro tection. Constant temperature compensation. Built-in speaker protector. Extra large 250W power transistors MS273, MS274 fo r output3. Extrem ely low square wave distort ion at 20-20KHz. Dynamic frequen cy response: 10-30KHz. Compact and integral design for easy installat ion. $149.00 ;•••·•1 . • ordinary 12Vamplifiers, making treble clearer and bass more dynamic. • Suitable for all integrated amplifiers, car HiFi & 300W max. Stereo amplifiers. • Efficiency of up to 85% eliminates insufficient power problem for converter. • DC input: 12V (Batt ery). • DC output selectable: ±35Vor ±50V (6A) max. • Six 30A power MOS FETs used for high speed 20KHz switching CAT No. S0102 300W DC TO DC HIGH POWER FET BOOSTER TRANSFORMER • Professional reg ulator provides high stability, high reliability and extrem ely low ripple. • With overload signal. current cut-o ff protect ion, current limitin g protecti on, circuit selection and LED indicators, it is su itable for many • • < ; _/ • • "'\ A .- ~ .,._:I'• ·.·' ·, : different appl ications. ... ... ...,:I --.. ♦ • The precisely designed electronic protection circuit works faster, sa fer and is more dura ble than fuses. .._ .'!I\ d ' • Output current selectable 5A, 10A, 15A, 20A, plus protection mode ~ ' selector. • The system incorporates four 30A Schottky barrier diodes and filter capacitance of 36000µF as well as eight power transi stors for regu lati on ou tput, providing safety and reliability. • The 1 kg, 12" heat sinks provide sufficient cool ing. • Integral and compact design. CHARACTERISTICS: CAT No. 50006 0 - 30V 20A PROFESSIONAL HEAVY DUTY REGULATOR WITH FULL PROTECTION • Use specialised regulators for voltage regulation, enchancing stabil ity and reliability and reducing ripples to a minimum. • Current cut -off or cu rrent limiting protection can be chosen to suit different applica tions. • Precisely desig ned elect ronic protecti on circuit works faster, safer and longer th an fuse. • Selectable output current system: 5A, 10A, 15A & 20A. • The system incorporates two 30A Schottky barrier diodes and fil ter capacitance of 27200µ F. The heat sinks employed in rectifi cation circuit ensure high effi ciency and high reliab ility. It can operate immediately with connection to a tra,isformen. • 12" kg heavy duty slot heat sink for cooling, six 200W power transitors for output. CH ARACTER ISTICS: CAT No. S0O0S 0-20V, 20A PROFESSIONAL REGULATOR WITH FULL PROTECTION CIRCUIT • • • • • • • • CAT No. S0320 50W R.M.5. Build this miniature 1.5V to 9V DC converter This tiny project allows you to replace those expensive 9V batteries with more cost-efficient 1.5V cells. It uses only three components and is smaller than the 9V battery it replaces. By DARREN YATES Back in November 1990, we published our smallest project ever. It used just three electronic components and allowed a 1.5V cell to replace a more expensive 9V battery. You could use any type of 1.5V cell as well either AA, C, D, N or AAA. Of course, the bigger the cell, the longer it lasted. There was just one drawback - the unit was larger than a 9V battery which meant that it could not be fitted inside the device to be powered. This revised unit overcomes that problem by using a much smaller toroid core and a revised PC board. It now measures just 17 x 43 x 16mm which means that it will fit comfortably inside a 9V battery compartment. The new toroid core is cheaper than the original unit too, which means that the new unit costs a few dollars less than the previous version. Circuit diagram Fig.1 shows what's inside the TL- 496, while Fig.2 shows the circuit details. At the heart of the circuit is ICl which is a TL496CP switching inverter. We gave a detailed explanation of how this IC works in the No- PARTS LIST 1 PC board, code SC11111921, 42x 17mm 1 Neosid 17-732-22 toroid core, 14.8 (OD) x 8 (ID) x 6.35mm (H) 1 1.SV battery holder to suit battery 1 AA, C or D-size battery 2 metres of 0.63mm enamelled copper wire. Semiconductors 1 TL496 DC converter (IC1) Capacitors 1 220µF 16VW PC electrolytic vember 1990 issue, so we'll just briefly cover the circuit operation here. Inside ICl is an oscillator that drives_ a switching transistor at a rate that depends on the load current. The higher the load current, the higher the switching frequency, which can be anywhere from a few Hertz up to 2kHz. This internal transistor alternately switches the current through inductor L1 on and off. When the transistor is on, current flows and energy is stored in the inductor. When the transistor turns off, the voltage across Ll rises and the inductor dumps its stored energy into the 220µF capacitor. An internal feedback and voltage regulator circuit ensure that the output is maintained at 9V. The maximum output current which can be drawn from the circuit is about 40mA. At this current, a typical 9V battery would not last long at all. By contrast, a 1.5V alkaline D-cell will last for about 20 hours, despite the considerably higher input current required. Note that because the circuit steps the voltage up six times (from 1.5V to 9V) and because the circuit is not 100% efficient, the current consumed goes up by a factor of twelve (eg, if the load current is 2mA, the input current is 25mA). Putting it another way, the circuit T INPUT (4) 9V SERIES REGULATOR 2C INPUT (3V) (~) SWITCHING VOLTAGE REGULATOR CONTROL lC INPUT (1.5V) (3) GNO (5) - - - - - (6) SWITCH GND (7) Fig.1: block diagram of the TL496 switching converter IC. It uses a.variable-frequency oscillator to drive a switching transistor. 36 SILICON CHIP g QUALITY NO BRAND DISKETTES =l,;1= 3 1C 2 SW IC1 Tl496 2C 5.25" 5.25" 3.5" 3.5" OUT B GND GND 7 5 +9V 220 + 16VW OUTPUT _ _ _ _ _ _...,._ _ _ _ _oov Fig.3: install the parts on the PC board as shown here. The inductor (Ll) consists of 60 turns (approx.) of 0.63mm ECW on a small toroid core. L1 : &OT, 0.63mm ENCU ON 17ll32/22 NEOSIO POWDERED IRON TOROID 1.SV TO 9V DC CONVERTER Fig.2: in addition to the IC, the final circuit uses an inductor, a single capacitor & a 1.5V battery. The circuit can also be powered from a 3V supply, in which case the connection to pin 3 is deleted. Fig.4: the etching pattern for the PC board measures just 42 x 17mm. DSDD DSHD DSDD DSHD $4.70 $8.95 $8.50 $16.95 II I *************** JAPANESE BRAND -~':--1/ +·- /;";,{ FLOPPY DRIVES <:,.-- SUPER ~ 3.5" 1.44M $99.00 7- SPECI~~ 5.25" 1.2M $125.00 "h~\~"""' 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 27C1001 ..... $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 *** * ** *** ** *** * is about 50% efficient, since the input current goes up by a factor of twelve, not six. Even so, it is still cheaper to use the converter than a 9V battery. , <~'~!!!~~~ , ?~ ~ TABLE 1 Load Current Input Current no load 50uA Construction 0.1mA 1mA The PC board for this project is coded SC11111921 and measures 42 x 17mm. Fig.3 shows the assembly details. The inductor consists of two layers of 0.63mm diameter enamelled copper wire (ECW) . To wind the inductor, first take a 2-metre length of wire and thread it half-way through the toroid core. The first layer is now wound using one end of the wire, followed by the second layer using the other end. Keep the turns tight and as closely spaced together as possible. There should be about 60 turns total, although the exact figure is not critical. Clean and tin the ends of the leads carefully before soldering the inductor to the board. The external leads to the 1.5V battery can be wired to a suitable 1.5V battery holder. When the assembly is corpplete, install the battery and measure the output voltage from the board. It should be very close to 9V. Exercise extreme caution if you intend soldering a battery snap connector to the output terminals, to mate with an existing snap connector. In this case, you will have to connect the red lead to the negative(-) terminal of the board and the black lead to the positive (+)terminal to ensure correct 0.SmA 6mA 1mA 12mA 2mA 25mA SmA 65mA 10mA 134mA 20mA 250mA 40mA 460mA polarity at the battery snap terminals. Alternatively, you can use output terminals that have been salvaged from a discarded 9V battery. Check the output polarity carefully with your multimeter before connecting the project to any equipment. Depending on your situation, you can use either an AA, C or D-size battery with the circuit. Table 1 shows the expected input currents for loads ranging from 0. lmA to 40mA, A Dsize cell will last longer than AA or C cells, especially for high input currents, while alkaline cells will last longer than carbon zinc types, Finally, you can modify the unit so that it functions as a 3V to 9V converter by cutting the track to pin 3 of the TL496. This will not make the circuit any more efficient but, because the input current is halved, will approximately double battery life: 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 REGULATDRS 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 W04 ................ $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 ~ )iY TRANSISTDRS BC547/8/9 ........ $0.15 BC557/8/9 ........ $0. 15 8D139 ....... $0.45 8D140 .............. $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 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 AUGUST 1992 37 AMATEUR RADIO BY GARRY CRATT, VK2YBX Kenwood's TS-450S HF transceiver Recently, we were given the opportunity to review Kenwood's latest HF transceiver offering, the TS-450S. Despite a front panel that boasts some 50 controls, it proved to be easy to drive. Once the TS-450S had been delivered to our lab, it quickly became obvious that significant advances had been made in HF transceiver design since last we peered into such a unit. This transceiver, whilst capable of delivering 100 watts, is remarkably compact in size, measuring 280 x 340 x 107mm and weighing in at just 6.3kg. As Kenwood themselves state, this transceiver is an ideal candidate for DX-peditions where weight is at a premium. However, considering that the receiver draws 2A at 13.8V, provision of a power supply of adequate endurance and capacity is quite im- Below: this photo shows just some of the accessories available for the Kenwood TS-450S. The PS-53 power supply is capable of delivering 22.5A, a necessity in order to obtain the full 100-watt output of the TS-450S. Also available is the TS-450SAT, a model with an inbuilt automatic antenna tuner. 38 SILICON CHIP portant and should be taken into account by those contemplating mobile or portable operations. It took just 15 minutes with the instruction manual for us to work out the basic controls, thus allowing us to fire up the receiver and listen to activity on the various bands. As we soon discovered, one of its most useful features is the ability of the synthesiser to operate in 1Hz steps! This function is controlled from the front panel and allows either 1Hz or 10Hz increments to be selected for SSE operation. For AM or FM operation, the synthesiser step is set to 100Hz increments, giving l0kHz of coverage per revolution of the tuning knob on SSE and 50kHz for AM and FM operation. Combined with the added features of IF SHIFT and an adjustable audio NOTCH (400-2600Hz), the small synthesiser steps make it easy to tune two adjacent channel SSE signals and resolve either one. In fact, we also tried this feature on the time standard signals which appear at 10.00MHz on AM, with similar results. One other sophisticated, yet essential feature, considering the congestion of the HF bands, is the ability of the user to select different bandwidth IF filters for various modes of operation. For SSE, there is a choice of 6kHz, 2.4kHz and 500Hz, the last two being plug-in options. For CW and AM operation, the filter choices are 12kHz, 6kHz, 2.4kHz and 500Hz. The receiver uses triple conversion, having intermediate frequencies at 8.83MHz and 455kHz, and the filters at both these frequencies can be switched to select the most suitable IF bandwidth. If the 2.4kHz position is selected for both 8.83MHz and 455kHz, the combined effect of both filters results in a bandwidth of 2.2kHz. Of course, the receiver section also caters for some of the more exotic transmission modes, such as FSK and packet(AFSK). In fact, there is a dedicated socket on the rear panel of the transceiver for direct connection of either an RTTY terminal or TNC. Both FSK shift and receive tone are user selectable via the user accessible "function selection programming menu", as are 42 other receive and transmit parameters, including CW pitch, RIT increments, frequency steps for both VFOs, numeric keypad disable, data transfer between radios, The complex front panel of the Kenwood TS-450S makes it quite daunting to look at but the unit turned out to be quite straightforward to drive. It offers state of the art technology. memory channel write protect, memory split frequency operation and transmit inhibit. There is also a socket, located on the side of the transceiver, for direct connection to the optional "IF-232C" RS -232 interface, which allows 25 functions to be controlled via a personal computer. The SCAN function can be used to either scan the entire 500kHz to 30MHz band, or to scan the 100 memory channels. By selecting the FINE mode, scanning is incremented in lOHz steps. We found the receiver section easy to operate, although the main tuning knob lacked the customary dimple for locating the tuning digit. Nevertheless, with adjustable dial drag'and direct frequency entry via the front panel keyboard, we were soon accustomed to rapidly changing from one HF band to another. The UP and DOWN tuning controls can be programmed to increment the tuning range in either 1MHz or 500kHz steps in conjunction with the "lMHz" key, or in the normal tuning mode, they step between the nine amateur HF bands: 160m, 80m, 40m, 30m, 20m, 17m, 15m, 12m and 10m. There are also two different noise blankers fitted to the transceiver, one for short duration pulse noise and the other for "woodpecker" type radar noise interference. Our test unit also had the optional voice module (VS-2) fitted. When the "voice" button is depressed, a synthesised voice indicates the frequency to which the receiver is tuned. There is also provision to connect Kenwood's "Digital Signal Processor" DSP-100, an external signal processor for both transmit and receive use. This makes use of several multi pole active filters and 16-bit D/ A and AID converters which give waveshape restoration, thereby providing superior performance. We plan to review this unit in a subsequent issue. To evaluate the transmitter, we ran the usual bench tests for transmitter harmonics, output power, FM deviation, frequency accuracy and spurious radiation. Transmitter harmonics were well suppressed, almost to the level required by the new DOTAC commercial specification, ECR 235. However, conducted spurious signals were quite noticeable at 100MHz with harmonics up to 500MHz sometimes approaching -60dBm (quite a significant level). These changed as the various bands were selected, leading us to believe that they are related to the microprocessor control circuits. Frequency accuracy was well within the specified limits. At 29MHz, we recorded a frequency error of 136Hz, better than twice the accuracy quoted, and the FM deviation limiting worked well to keep the maximum deviation below ±5kHz. Current drain at maximum power reached 21A, something to be considered when selecting a suitable power supply. As 25% of the rear panel of the transceiver is dedicated to the PA heatsink, maintaining an adequate temperature for the transmitter should present no problem, provided suffi- cient clearance is allowed for air circulation. Overall, we were very impressed with the TS-450S. The transceiver offers state of the art technology in a compact size and at an affordable price. The 95-page instruction manual covered all aspects of the operation and contained easy-to-read circuit and block diagrams of the transceiver. We did lift the lid to see if the unit was field serviceable and found that all components, and often their functions, were silk-screened onto the PC boards, indicating a thorough ap proach to the transceiver's design. Some components are surface mounted which would require specialised repair equipment. However, considering the service facilities offered by Kenwood, that aspect should be well covered. There is a comprehensive range of accessories for the TS-450S, including External Antenna Tuner (AT-300), Data Transfer Cable (E30-3047-05), VS2 Voice Synthesiser, Digital Signal Processor (DSP-100), IF 232C RS-232 Interface, TU-8 Tone Unit, AT-450 Automatic Antenna Tuner, SP-23 External Speaker and a range of eight IF filters . There is also range of communications headphones, RF filters and various hand and desk microphones. Recommended retail price of the Kenwoo'd TS-450S is $2204. For further information, contact Kenwood Electronics Australia Pty Ltd, 8 Figtree Drive, Australia Centre, Homebush, NSW 2140. Footnote: all transmitter tests were carried out under the terms and conditions of the author's DOTAC experimental license. SC AUGUST 1992 39 SERVICEMAN'S LOG How I ended up in the sync This month, I have a story about an apparently easy job that turned into a monster. I also have a follow up story on a Sharp VCR that I wrote about some months ago. My role as Dr Frankenstein concerns a General 48cm colour TV set, model GC-202. The owner brought it in early one morning, described the problem, and indicated that he needed it rather urgently. How soon could I fix it? In fact, I was snowed under and explained that I might not be able to tackle it for a few days. Although disappointed, he accepted this philosophically and decided to leave it anyway, so I said I'd tackle it earlier if I could. His description of the fault suggested picture pulling, as probably caused by hum in the horizontal system. On this basis, I assumed that it should be relatively simple and so I put it to one side without even bothering to switch it on. Now it so happened that I had a more than usually successful day. I FRACARRO SAVES ••. ... more than $10. from every UHF television antenna you buy. -~ i----:.c-------. • - - - -· --"-- - Fracarro's 4PUN for better performance from weak UHF signals. Peter C. Lacey Services Pty. Ltd. P.O. Bo x 678 (74Fulton Rd.) Mount Eliza 3930 Tel:03 787 2077 Fax:(03) 787 3460 ACN006893438 40 STLICO N CH f P quickly knocked over several jobs which I had originally expected to be difficult and, by about 4 o'clock, had made quite an inroad into the backlog. It was still too early to knock off but too late to tackle anything nasty, so I decided to finish the day on something easy. And what better than the General which the owner needed urgently? Sure enough, when I switched it on, it came up with a classic hum pattern. It was pulling madly although it appeared to be normal in all other respects (brightness, contrast, colour and sync). I also checked the scan width, which can sometimes provide a further clue, but this was normal. The first setback My first bet was the main filter capacitor C408, a 330µF 200V electrolytic following the bridge rectifier, so I simply clipped another high value unit across it. And that was the first setback; it had no effect whatsoever. Oh well, it was worth a try. I moved on to the regulator transistor, TR701 , measuring voltages around it. The voltage from the main rectifier, applied to the collector, is shown as 146V, while the voltage at the emitter, which becomes the main HT rail, is shown as 128V. In fact, the collector voltage was closer to 156V but I wasn't worried by this small difference. But when I measured the emitter voltage, I knew that there was something wrong. It was also at 156V - an impossible situation if everything is working properly. But of course it wasn't; the regulator transistor had obviously gone short circuit and I really didn't have to test it to confirm this. At this stage, I needed to make another routine check. The focus control pots in these particular sets are rather notorious for failure. They can go open circuit, the moving contact can go high resistance to the track, or sometimes they can just fail mechanically. Sure enough, when I tried rotating the shaft, it simply spun in my fingers; it wasn't coupled to anything! Well, that looked like it - a new regulator transistor and a new focus control pot and we would be back in business. I had replacements for both on hand and fitting them was routine. It had been a simple job after all and I was well ahead on the day. It's not fixed Until I switched the set on, that is. Then I was in real trouble. I had sound and I had a raster but I had only a faint video image - just enough to tell me that I also had no sync. As anyone who has experienced this situation will testify, it is a most disturbing one. It is much worse than simply being confronted with a set with such symptoms. Quite apart from being totally unexpected, it immediately suggests that it is something careless one has done which has created a fault far more serious than the original. I tried to recall anything I might have done to create the problem but without success - at least then. Eventually, I did think of something but more of that later. Right now, I had to start troubleshooting all over again. A logical deduction from the symptoms was that the loss of video luminance and loss of sync were one and the same fault. There had to be a fault somewhere in the video IF or video chain which was wrecking the luminance signal. Unfortunately, the only circuit I have of this set is a much copied one which is extremely poor. I can follow it using a jeweller's loupe and a lot of imagination but it would be quite circuit is virtually identical with the GC-202 and the IF module is totally interchangeable. So what quicker and easier way to check the suspect module than by replacing it with known good one? If it worked, I could even leave it in place as a quick cure. Unfortunately, it wasn't going to be that easy. All I learned was that it wasn't the module, because the replacement made no difference. So what now? The tuner? This seemed to be a long shot, since I still had sound, but stranger things have happened. And how best to check it? I thought for a moment that I might substitute the tuner from the junked set but a closer look at the mechanics involved discouraged me - it would be a much bigger job than swapping the IF LOS module. 0 So I turned to a piece of test gear left over from the monochrome era but which I still use occasionally. It consists of a standard VHF tuner .' \ t?'. ·• .. mounted in a box with \. I.\ ·, ·. I\ d, ~ ,/ its own small power -~ h. • I supply, so that it can -s-r ·s-,E:? WPt~ be quickly substituted .,-o J:).??\..'< A 'ROU"'f\NE: for a suspect tuner. This \/O\.-"'f'AGS C.t-\e:C.'tC::oo~ ; ,; -'· was quickly hitched up and a test pattern fed pointless to reproduce it. So I will sync/video bOard. This provided a in. Alas, still no joy; the signal out have to describe the circuit as best I convenient access point for the CRO. was exactly as before. I made the connection, fed a colour can and hope that the reader can folThat really set me back. Why, when bar pattern into the antenna, and both the tuner and IF module were low it. My first step was a routine voltage checked the output. It's rather hard to known to be OK, could I not get a describe the resulting signal but it signal through them? check. The signal path supply rai1 sits at 18V and I traced this on the circuit wasn't good. There was very little inand the chassis, making sure that it dication of the luminance signal or of The next suspect was correct to all points. This was no normal sync pulses. The only place I could turn to for Anyway, the implication seemed inspiration was the next board in the simple task, because the circuit shows very few voltages. Having done that, I obvious - there was probably a fault chain (the sync/video board), the reaturned my attention to the video sig- somewhere ahead of this check point, soning being that something on it was nal path. either in the IF module or even in the loading the video circuit. This board The main video chain is contained tuner. Of the two, I plumped for the IF carries the 2nd and 3rd video amplifiin one module; a single board in a module. ers, the sync separator, the noise gate, metal box. This board carries the 1st At this point, I need to digress and the red, green and blue output video IF amplifier transistor (TRl); briefly. In these notes, back in January stages. It also carries the brightness the 2nd video IF amplifier and AGC 1989, I described how a General GC- and contrast control circuitry. gate (ICl); the 3rd video IF amplifier 181 had suffered a picture tube imOnce _again, I decided to substitute stage (transistor TR2); the video de- plosion, incurring mechanical dam- the board from the junked set but tector; the 1st video amplifier transis- age to the cabinet and chassis in the halfway through the exercise, I realtor (TR3); and, finally, IC3, which is process. And the economics of the ised that it was not totally compatthe sound IF amplifier and detector. situation were such that the owner ible. The suspect board used a 3-pin So where could I check for video elected to write it off, giving it to me plug (P201) to connect to the brightsignal? The video signal comes out of to salvage anything I wanted. ness control (J201), while the contrast this module via pin 7 of a plug and It was too good to send to the tip, so control was mounted on the board socket assembly, J412, and from there it has been languishing in my junk and protruded from the rear of the goes to pin 3 of plug P407 on the pile ever since. More to the point, the cabinet. \ \.I!~\,;,::~- ~ I ... ~li1 /,~ :,·. A UGUST 1992 41 now and I was running late for tea. Oh well, Mrs Serviceman is used to this kind of thing. SERVICEMAN'S LOG - CTD Who dunnit? .- Qt.-1> ,s"i-U• •• V'-K ISPO"-A o. ""'«..\. -(. e;T"c.. r ----·· s . -:~-"' ) i -;;;---(' ~ -·-a..· ~ ? .. <... 'RE::S \'DUE: \>J~~ 'P~E.-n""( N\UC.K'-f A.T ~\~'S-r... i\.-'\S The substitute board used a 5-pin plug, to allow the contrast control to be mounted on the front panel. After some head scratching, I lashed up a set of patch leads which allowed the substitute board to work, albeit with maximum brightness. Progress at last As it turned out, the lack of brightness control didn't matter because I now had a normal picture - the fault was on the original sync/video board. This was confirmed by the CRO pattern, which was now showing normal staircase and sync pulses. And so I went back to the faulty sync/video board. The video signal enters on pin 3 and goes in two directions. One path is to the 2nd video amplifier (TR201), while the other is to the noise gate stage (TR208) and thence to the sync separator stage (TR209). I tried the video amplifier 42 SILICON CHIP first, pulling TR201 out and checking it. It checked OK but, more to the point, when I tried the set with this transistor removed, the fault was still evident on pin 7 of the video IF board. I replaced TR201 and set off in the other direction, to TR208. I pulled this transistor out and, immediately, the waveform at pin 7 jumped back to normal. When I checked TR208, it showed a short from collector to base. I fitted a new transistor and tried again. Problem solved? Not really; half solved would be more like it. The CRO now indicated a normal luminance signal but still no sync pulses. I could hardly wait to pull out TR209 and test it. It was open circuit, both base to collector and base to emitter. A new transistor brought everything back to normal and restored a first-class picture. But the job had taken much longer than I had expected. It was dark by But why did it happen? Thinking it over, I can recall only one possible cause. It was when I was checking the regulator transistor and found the same 156V on both collector and emitter. Access to the emitter connection is awkward and, although the probe on the meter lead is insulated as close as possible to the tip, I did observe a small spark as I manoeuvred the probe. And it could only have been from the emitter, at 156V, to chassis. So was that it? It seems a long shot but it's the only explanation I can offer. Anyway it was all a nasty experience. The only bright spot was first thing next morning when the owner turned up unexpectedly. There was a special program he wanted to watch and he had decided to take the set, fault and all, and bring it back later. Imagine his surprise when I told him that it was fixed. So he went on his way, happy as Larry, without any idea of how I finished up in the sync. (The price I paid for being late for tea was that I found myself stuck with the washing up. I will refrain from labouring the point about sinks). The Sharp VCR And now to the VCR story. Last March, I described a fault in a Sharp VC-9300X, involving a capstan shaft which had seized in its bearing due to some "gummy" substance. I cleaned the shaft and bearing and the machine went back to the customer. However, a couple of months later, it was back on the bench with the same problem. This time, the diagnosis was easy but I was surprised that my previous effort had failed and, in fact, that there had ever been oil in the system. I was under the impression that these machines used socalled oiless phosphor bearings. Anyway, I tackled the problem with more vigour this time. With the capstan shaft removed I set the machine up so that I could spray cleaning fluid into the bearing every few hours. I did this over the next couple of days. The cleaning fluid was Caltex Aqua Tee, described as "a drying and penetrating spray", aimed mainly at the marine market, but which I use a lot in the workshop. So I kept spraying it into the bearing, with a folded tissue underneath to catch the residue. This residue was pretty murky at first but eventually came clean. I then relubricated the bearing with CRCZ-26 and put everything back together. As before, everything worked fine but, having been caught once, I wasn't going to make a song and dance about it until it had stood the test of time. Well, now I am cautiously optimistic because when the machine came back recently for another fault, all was well with the capstan. But that is all by the way. The real story concerns the reason it was back in the shop. The owner's complaint was that recording was unreliable although playback of previously recorded tapes was OK. More specifically, it would sometimes produce a good result while at other times it appeared as if the heads were very dirty. In fact, he had brought in a new tape with a sample of the fault. To my mind, it looked exactly like a fouled h ead problem. I put the machine through a series of recording and playback functions, TETIA TV TIP Sharp DV4884 TV set Symptom: no on-screen display. The set works perfectly but the on-screen display which advises channel number or control settings cannot be called. Cure: the vertical sync pulse into the character generator chip is missing. This could be. a loose plug and socket or a dry joint. H and V sync pulses are necessary to allow the chip to output coherent signals. TETIA TV Tip is supplied by the Tasmanian branch of the Electronic Technician's Institute ofAustralia. Contact Jim Lawler, 16 Adina St, Geilston Bay 7015. using my own tapes, but couldn't fault it. Eventually, for want of a better idea, I gave it a clean-up, put it through another set of record/playback cycles (without result), and gave it back to the customer. But I wasn't very confi- AUSTRALIAN MADE TV TEST EQUIPMENT 10% discount on all test equipment. 15% discount on two or more items. SHORTED TURNS TESTER Built-in meter to check EHT transformers including split diode type, yokes and drive transformers. $78.00 + $4.00 p&p dent an d warned him accordingly. Sure enough, he was back in a few days and I tried another tack. How old were his tapes? Most of them pretty old, he admitted. I suggested he bring some in for me to check an d the next day he brought in four tapes, one relatively new, the other three quite old. I rejected tw o immediately, put one in the too-hard basket, and used the fourth one for further tests. Meanwh ile the custom er went off and bought a new set of tapes. The risk with worn tapes is that they not only foul the heads on a more or less permanent basis, necessitating professional cleaning, but that they can also cause short term fai lure. A scrap of oxide can foul a head for anything fro m a few secon ds to several minutes, then be swept clear and let everything return to normal. Initially, I suspected som ething like this , since the symptoms can be similar to an intermittent electrical fault. But subsequent testing an d observation convinced me that, if it was, it was not the only problem ; there just had to be an electrical fault. For one thing, the fault was now ANTRIM TOROIDAL TRANSFORMERS HIGH-VOLTAGE PROBE Built-in meter reads positive or nega- _,,. live voltages from 0-50kV. For check- ' ing EHT and other HT voltages. $98.00 + $5.00 p&p a DEGAUSSING WAND 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 REMOTE CONTROL TESTER Designed to test infrared or ultrasonic control units. Supplied with extension infrared detector lead. Output is via a LED and piezo speaker. $84.00 + $4.00 p&p ~-~~~ ~ 2~ TUNER REPAIRS ~ From $19 exchange plus post & pack Cheque, Money Order, Visa, Bankcard or Mastercard 216 Canterbury Rd, Revesby, NSW 2212, Australia. Phone (02) 774 1154 Fax (02) 774 1154 • • • • Now made in Austral ia Standard range 15VA to 2kVA Large ex-stock· quantities available Competitive pricing available for OEMs & resellers • Simply the best transformers all round HARBUCH ELECTRONICS PTV LTD 90 George St, Hornsby, NSW 2077. Phone (02) 476 5854 Fax (02) 476 3231 AUGUST 1992 43 ' VIDEO joints and hope for the best. I hooked up the CRO to monitor pin 11, pushed in a 3-hour tape, and set the machine running. Granted, it was hardly practical for me to sit with my eyes glued to the CRO for hours at a time but at least I could keep a close watch on it while I did other jobs. After I been through this ritual several times, I was convinced that the signal was reaching pin 11 at all times. Several breaks had occurred on the tapes but I had not observed one failure on the CRO, even though some breaks had been 15 minutes long. The next logical step was to fire up the CRO's second channel and monitor both pin 11 and pin 8 together. And I was particularly careful to clip the CRO leads directly onto the IC legs rather than to nearby circuitry. This produced a real breakthrough; it wasn't long before I glanced at the CRO and found that there was no signal out on pin 8, although it was still solid on pin 11. H£A0 Missing voltages Fig.1: the relevant circuitry in the Sharp VC-9300. IC201 is at the top, Q205 to its right and IC301 beneath it. The video head plug is at bottom left. Note the heavier lines which run to the plug - these were colour coded on the original circuit to indicate playback & record paths. occurring relatively frequently on known good tapes. More importantly, it was occurring only in the record mode. On the law of probabilities, this didn't add up. I had played one ofmy own 3-hour test tapes right through several times and it never faltered. But when I took a known good tape and made a 3-hour recording, the fault showed up in several spots. I noted these positions on the counter, then put the tape in another machine and made new recordings over these spots. These recordings were perfect, so it wasn't damaged tape. The signal path At this stage, I turned to the manual to trace the record signal path and check likely trouble spots. The relevant part of the circuit is shown in Fig.1 and the main components are IC201 at the top and IC301 below it. To the left of IC301 is a 7-pin socket which connects to the lead from the video heads. In the original circuit, some paths 44 SILICON CHIP around IC301 are colour coded blue for playback and orange for record. These cannot be reproduced here but I think the reader will be able to follow my description. Among other things, IC201 generates the necessary FM signal for the video record function. This signal emerges from pin 9 of IC201 and is fed via filter unit FL201, transistor Q205 and level control pot R310 to pin 11 ofIC301. It then passes through the recording amplifier in IC301, comes out on pin 8, and goes to the aforementioned 7-pin socket. The rest of the IC performs the switching functions. I decided that this was as good a place as any to monitor the record signal. In all such cases, one has to start somewhere in order to determine in which direction the fault lies. And there was another reason. I had checked the soldered joints to the IC pins and was somewhat suspicious of pins 11 & 12 on IC301. Butl couldn't be sure and I wanted prove it if I could, rather than simply remake the Why? It could be the IC of course but what about my suspicions regarding the joints to pins 11 & 12. And what about the voltages on the IC pins? The circuit shows two sets of voltages: an upper set for the playback mode and a lower set (enclosed in brackets) for the record mode. And, in the record mode, pin 8 is marked 5.6V, pin 11 as 4V, and pin 12 as 11.2V. This latter is the supply voltage for the IC. These three voltages were now missing. I measured 0V on pin 8, 0V on pin 11 and ov,on pin 12, even though I traced the 11.2V right up to the pin 12 connection. But there was nothing on this pin itself - nothing, that is, until I pressed the probe hard against the pin and pushed it into the solder connection, whereupon everything came good. So that was it; a dry joint to the IC pin. It was easyily fixed, of course, and I remade all 12 pin connections while I was about it. No sense in tempting fate or giving Murphy an even break. And that wrapped it up. It is now nearly two months since the machine went back to its owner and a recent check confirmed that there has been no further sign of trouble. So it looks as though I have finally cured the capstan fault and fixed a nasty intermittent into the bargain. SC >NICS JAYCAR INICS JAYCAR >NICS JAYCAR >NICS JAYCAR >NICS JAYCAR >NI CS JAY .ECTRON . ECTRON .ECTRON .ECTRO'\ . ECTRQ['. . ECTR01' .ECTRON .ECTRON ECTRON . ECTRON .FCTRON . 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The HP 4263A allows users of passive components to make low frequency transformer measurements easily. It also provides high through- put and fast electrolytic capacitor testing capabilities. With Option 001 for transformer measurements, the operator can avoid lengthy manual calculations and awkward test setups when evaluating low frequency transformers. Option 001 allows users to perform and display transformer parameters automatically, such as mutual inductance, turns ratio and DC resistance. Degaussing tool for TVs & monitors While all colour TV sets have inbuilt degaussing coils, most computer colour monitors apparently do not. This means that if they do develop a purity problem, there is no way of correcting it short of sending it away for service. We have observed that quite a few colour monitors do have a purity problem. The result of this can be easily seen if you display a white screen - it will have blotches of red, blue or green. The cure is to thoroughly degauss (ie, demagnetise) the monitor with this portable degaussing tool which produces a powerful AC magnetic field. You wave it around the face of the picture tube, according to the instructions and the job is done. The price of the degaussing tool is $75 including tax (plus $10 postage and packing) from J. V. Tuners, 216 Canterbury Rd, Revesby, NSW 2212. Phone (02) 774 1154. Because it's designed for fast electrolytic capacitor testing, capacitor manufacturers can integrate the HP 4263A LCR meter into automated test environments where high speed and reliable electrolytic capacitor testing is critical. The HP 4263A also has internal DC biasing. Other key features include a basic accuracy of 0.1 % , 5-digit resolution for 15 measurement parameters, Kelvin correction and open/short/load correction. These corrections minimise errors caused by fixture, cable and switch parasitics, and ensure instrument accuracy at 0, 1, 2 and 4metre cable lengths. For further information, contact Test & Measurement, Business Communications, Hewlett Packard Australia Limited, 31-41 Joseph St, Blackburn, Vic 3130. Phone (03) 272 2869. Microcontroller has 512 bytes of RAM The 83C528 microcontroller from Philips Semiconductors is one of the first 80C51-compatible microcontrollers to feature 32Kb of ROM and 512 bytes of on-chip RAM. Togetherwith the 32Kb ofon-chip ROM, the extra RAM capacity allows the 83C528 to run compiled application programs written in high-level languages such as PL/M and C. The 512-byte RAM also provides enough space for context switching, especially with regard to stack enhancements in internal memory. The stack enhancement capability also gives advantages when using a highlevel language such as C. Another feature of the 83C528 is a watchdog timer (WDT) with its own AUGUST 1992 53 Scrambler for 2-way radio Imark Communications Pty Ltd has released the Integrated Digital Security Protocall (IDSP) Voice Security System for use with most FM-AM-SSB 2-way radios. The new IDSP operates by "scrambling" your voice into an unintelligible signal before transmitting it using your standard radio. Obviously, other radios will be able to hear the signal but would not be able to understand the conversation. When this signal is received by the companion 2-way radio, the signal is decoded and heard from the speaker as a normal intelligible voice conversation. The new IDSP is not a voice inversion type scrambler which can be decoded and understood quite easily. The ISDP is also not compatible with the previous DIGISCRAM. IDSP is a high-security digital time and frequency domain type scrambler. There are a total of nearly 26 million code combinations, of which each IDSP module can be programmed for one receive code identity and 99 transmit code identities. Naturally, all transceivers within a system must have the same precode setting to operate and conversely, if they have an incorrect code setting, they will not be able to decode the signal. Transceivers not fitted with a DIGISCRAM will not be able to decode the scrambled ·signal. on-chip oscillator. This configuration makes it possible to run the WDT during power-down mode and to wake the 83C528 up from power down mode when a WDT overflow occurs. The microcontroller can also be woken up by an external interrupt, allowing it to continue program execution from the status of the last program instruction executed before it entered the power down mode. Fabricated in an advanced lµm CMOS process, the 83C528 operates at clock frequencies as high as 24MHz. EPROM and one time-programmable (OTP) versions are also available. For further information, contact Philips Components, 34 Waterloo Rd, North Ryde 2113. Phone (02) 805 4455. Smart 1GHz counter fromDSE The model Q-1314 Period/Frequency Counter from Dick Smith Electronics is packed with unique features which make it ideal for anyone working in the signal spectrum from subsonics to UHF. In the frequency domain , the instrument will measure 54 SILICON CHIP The new IDSP now includes Digital Selective Calling, with provision to flash a "called indicator light", and an audible "alert tone" which sounds through the speaker for a preset time. With Sawtron transceivers, the last two numbers can be encoded, thus providing 99 calling combinations. A Group Call facility is provided to allow group broadcasts ifrequired. Additionally, an auxiliary alarm output is available to activate a further alarm such as the vehicle horn or a flashing light. Further details can be obtained from the manufacturers, Imark Communications Pty Ltd, Unit 2, 75 Mark St, North Melbourne, Vic 3051. Phone (03) 329 5433. . The standard timebase is a 10MHz crystal exhibiting 1ppm/month ageing and 10ppm drift over a 10-40°C temperature range. The counter is priced at $499 and is available from all Dick Smith Electronics stores. from 0.1Hz to 1GHz. Period measurements range from 10ns to 10 seconds. The counter can sense low frequency signals and automatically switch to period measurement mode while in frequency display mode. This allows subsonic and audio frequencies to be measured in a fraction of a second. Other features include continuously variable gating, from 60ms to 10s, auto or manual trigger threshold, and switchable input sensitivity and bandwidth. On the low frequency range , input impedance is 1Mn and sensitivity is better than 25mV up to 80MHz. For the high frequency range, input impedance is 50Q and input sensitivity is better than 20mV to 650MHz and 55mV to 1GHz. Interlink high speed modems Interlink Electronics has released enhanced versions of their highly successful IQ12345, Base 12345 and Fastbit II modems. Designated the IQ6, Base 6 and Fastbit IIbis models, they incorporate V.32bis mode and can provide full duplex data transfer up to 14,400bps. The top of the range Interlink IQ6 is priced at $1194 (including sales tax), the Base 6 at $799 and the Fastbit IIbis at $680. The IQ12345 and Base 12345 models have been reduced by $100 to $1094 and $699 respectively. The Fastbit II model sells at $580. For further information, contact Marilyn Bayfield, Interlink Electronics, 118-122 Queens St, Woollahra 2025. Phone (02) 362 4344. Key chain battery analyser Electronics Workbench® Do you always have an assortment of dry cells lying about in drawers and junk boxes and you are never sure whether they are good or bad? Some people check 9V batteries by applying the "tongue test" but that is not really a good idea and anyhow, it doesn't work with normal dry cells, unless you have a funny shaped tongue. A far better idea is to get hold of one of these handy battery checkers which will do double duty as a key ring. It has three LEDs to tell whether the cell is fresh, OK or weak. It stops the guesswork. It is available from all Rod Irving Electronics stores at just $4.95. Multi-element UHF TV antenna for bands 4 & 5 / I ,,/\ / I ,-r /< ~;:)~./ ::/,, ·, · ,,.-' ~ \ The electronics lab in a computer! A simple, intuitive and very powerful teaching tool, Electronics Workbench lets students and hobbyists design and test both analog and digital electronic circuits, without the delays and expense of a laboratory . THREE VERSIONS • Professional Version: EGNVGA colour display; unlimited components • Personal Plus Version: Monochrome display; unlimited components • Personal Version: Monochrome display; limited to 20 components per 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 formu la to logic gates • Customisable hypertext help system ... EMONA INSTRUMENTS NSW ......................... (02) 519 3933 VIC ............... .. ........... (03) 889 0427 QLD .......................... (07) 397 7427 DISTRIBUTORS Perth .... .......................... (09) 244 2777 Adelaide .. . . ... . ... .. ..... (08) 362 7548 Hobart ........................... (002) 34 2233 // /,,-:</::/;:;,,:, , EmonaLAB4 ,,,'~- F_our instruments in one package! ;_:~J;>>-" This UHF TV antenna has a quoted gain of 13dB, which is about what you would expect from an 11 to 12element Yagi. It comes in completely disassembled form in a compact carton and is reasonably straightforward to assemble provided you are competent in these matters (the instructions are quite scanty). Rated as covering UHF bands 4 and 5, the antenna is now available at $49.50 from all Jaycar Electronics stores. The LAB4 has four full function test instruments: ■ with neatly laid out and labelled front panel controls. Also, the LAB4 is compact and only takes up a small space, compared to four bench-top instruments. DC POWER SUPPLY Triple output; 5V, 15V, 0-50V Blue LEDs now available from David Reid Looking for that special touch for your latest project? How about using a blue light emitting diode? David Reid Electronics currently has them on sale at $3.95 each and with discounts for quantities of 10 and above. The blue LEDs are available in 3mm and 5mm sizes, with a clear plastic lens. Luminous intensity is typically 14 millicandelas at a forward current of 20mA - they are not very bright and they have a fairly narrow viewing angle of 30 degrees. Forward voltage is typically 3V or ■ DIGITAL MULTIMETER Full function, auto-ranging ■ FUNCTION GENERATOR 0.02Hz-2MHz, with SWEEP ■ • FREQUENCY COUNTER 1Hz-100MHz input range INDEPENDENT INSTRUMENTS Each instrument in the LAB4 is completely independent and can be s-.vitched ON or OFF as required. The LAB4 has only one 240V mains input, saving on multiple power points. Each instrument is clearly defined EMONA INSTRUMENTS NSW ......................... (02) 519 3933 VIC ............................ (03) 889 0427 QLD ........... :.............. (07) 397 7427 DISTRIBUTORS Perth .. ...... .. .............. ... (09) 244 2777 Adelaide ..... ...... .. ......... (08) 362 7548 Hobart .. .. .. ........ .. ... (002) 34 2233 AUGUST 1992 55 3.5V maximum; ie, almost twice that of a conventional red LED. Rush in for your blue LEDs to David · Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385 100MHz digital storage oscilloscope The Model 3100D 100MHz 2-channel DSO (digital storage oscilloscope) from Leader Electronics incorporates an extensive range of features. All front panel settings and functions can be remotely controlled via its GPIB interface and measurement data sent to external devices such as a hard copy printer. Waveforms, range settings and cursor measurement values displayed on the scope's CRT can be fed to a plotter via its HP-GL interface. Completing its suitability for automatic testing is a go/no-go facility which allows pass/fail tests to be made on automated inspection lines. The 3100D has a maximum sampling rate of 40MS/s at 100MHz bandwidth. A reference memory with battery back-up allows up to four waveforms to be stored, and the waveform currently being measured can be displayed simulta!1eously with a stored ; waveform for easy comparison. Both vertical and horizontal axes have autoranging, and a waveform parameter function enables automatic measurement and display of such values as peak-to-peak voltage, risetime and fall time. A delayed sweep function allows high sampling of an arbitrary part of the waveform after the trigger point. The sampled waveform can be expanded horizontally up to 100 times and a peak-to-peak auto trigger level function enables easy triggering on very small to large signals. In addition, smoothing and averaging functions greatly reduce high frequency components on a stored waveform and reduce noise levels on periodic signals respectively. For further information, contact AWA Distribution, 112-118 Talavera Rd, North Ryde, NSW 2113. Phone (02) 888 9000. Plug-in solar battery charger ___________ \. Test instrument kits from A-One A-One Electronics has a range of test instrument kits which will appeal to enthusiasts and technicians alike. We have seen four fully assembled kits and they are designed to a good standard, as these photos show, with metal cases and good quality front panels. Pictured is an 8-digit 550MHz frequency counter and audio function generator. Also in the range is a 4-digit capacitance meter, colour TV pattern generator and a high performance signal generator. Interested? Why not take a look at the full range. You can see them at A-One Electronics Pty Ltd, 432 Kent St, Sydney, NSW 2000. Phone (02) 267 4819. Do you have a seldom used car or van which sits out in the sun all day? Why not put the sun to work and keep the battery in good charge. Just sit this panel up on the vehicle's dashboard and plug it into the cigarette lighter socket. With a few hours' sun each day, it will keep the battery fully charged and ready to go. No doubt it could also be pressed into use for the same task on a boat, whether it is in the water or sitting on a trailer. The solar battery charger retails for $29.95 and is available from all Rod Irving Electronics stores. SC Telecom would like to help you develop it. Telecom Australia wants to encourage entrepreneurs and inventors working on ideas relevant to telecommunications and related fields in Australia. That's what the Telecom Product Development Fund is all about. Already the Fund has supported the ideas of people from many local companies. Companies like Almos Systems from Perth, Security Domain from Sydney, Mosaic Electronics from Brisbane and Teletech from Melbourne. These were ideas that might otherwise have languished or been lost to other countries. Many of the ideas which have been supported are also adding to Telecom's efficiency and effectiveness and, in some cases, are earning valuable export dollars. Any company or individual looking for an opportunity to get their ideas up and running should contact Telecom soon. Not only is financial help available for viable ideas, but Telecom can also provide support with technical and marketing know-how. If you'd like to know more about the Telecom Product Development Fund, call Telecom's Technical Liaison Office on 008 033 673 or send in the attached coupon. = Telecom Australia r-----------------, I I I I I I I I I I I I I I Please send me an information package NAME COMPANY ADDRESS POSTCODE L Send to: Manager Telecom Product Development Fund PO Box 249, Clayton, Victoria 3168 _________________ ... ccoso;sc Australian and O verse.is Tekcommuni<..·ations Corpora tion l.imited /\.CN . 051 775 556 I REMOTE CONTROL BY BOB YOUNG Internal combustion engines for model aircraft The subject of this month's column was prompted by a reader's letter enquiring about the possibility of converting a glow plug model aircraft engine to operate on petrol. Inevitably, as part of the conversion, the reader wants a design for an ignition system to complete the conversion. Why would you want to do such a conversion? The reader, Leon Burkamshaw, of Coffs Harbour, NSW, is quite succinct when he states that the cost for methanol-based fuel is becoming prohibitive. He is right. The short answer is to his query is "yes but with some difficulty and great care". However, I am not renowned for my short answers so sit back while I endeavour to fully explain this subject. First though, I will give a brief This is particularly true of 4-stroke motors which can run too hot when fuelled by petrol. This excess heat can cause severe damage to the valves and head. And, as a secondary effect, the spark plug element can begin to glow under the heat and compression and cause severe pre-ignition, with attendant problems to the conrod and bearings. While fuel prices are important, so is safety and petrol is a very explosive "Anyone attempting to convert a modern motor to petrol ignition is advised to proceed with caution as there are vast differences between motors designed for methanol and petrol fuels". explanation and a word of warning on operating petrol motors. Anyone attempting to convert a modern motor to petrol ignition is advised to proceed with caution, as there are vast differences between motors designed for methanol and petrol fuels. The main areas of difference are in compression ratios, timing and carburation; in other words, in virtually every area of the motor design. 58 SILICON CHIP chemical when compared to methanol. Handling methanol is a fairly laid back business and in over 40 years of hanging around methanol powered models, I have rarely seen a model catch fire and I have never seen anybody seriously burnt in an accident. Some of the fuel additives are, however, · very toxic when inhaled and great care is called for when using all chemicals. Nitro-benzene was a very . popular additive in my early years and was particularly dangerous. Fortunately, it is rarely used these days. I must add here that one should never run motors or fly indoors and for those who think I am mad for even suggesting it, I once flew a helicopter inside my factory and nearly gassed myself. To go one better, a friend of mine once flew a helicopter in his hotel room and suddenly found himself and his helicopter on the footpath outside the hotel; along with all of his luggage! Fuel dangers On a more series note, there was an article in an American modelling magazine some time ago, written by an American modeller who was also a trained military aviator. He had a methanol fuel-can fitted with an electric pump explode and catch fire under his face. He was immediatelv engulfed in flame from the chest up. His survival training had taught him never to breathe in until the flames went out if caught in this situation, as otherwise one's lungs and throat can be badly seared. He survived to write the story. An untrained person may not have been so lucky so please be careful, even when using methanol based fuels. As a personal idiosyncrasy, I will not use an electric fuel pump. I realize that such accidents are rare but they do happen. The situation with petrol is potentially much more dangerous. Again, I have not heard of any accidents in the modelling field but stories abound in general society of the dangers of petrol. Carrying petrol in a. model box Speed Control Still Coming This month, I must apologise to those who have been eagerly awaiting the speed control construction article. Judging by the response to the speed control series, there are many more interested in this subject than I first anticipated. Unfortunately, pressure of work has prevented me from devoti ng the amount of time necessary to complete such a complex project. And here I must point out that I am quite surprised at just how complex this project has become. When Leo Simpson first asked me to do a construction article on a simple speed controller, I had exactly the type of circuit I wanted in mind. Leo applied only one constraint - that the design was to be based on commonly available components. The NE544 servo amplifi er ch ip is no longer current and other chips can suffer the same fate at any moment, so I considered this a reasonable request. It did, however, introduce containing batteries is just not on and it should always be contained in a well sealed can, painted red and clearly marked PETROL - INFLAMMABLE. Tanks should be fi lled in such a way as to prevent spillages an d the motor sh ould not be started over any area where a spillage has occurred. Even a small spark from a glow battery or starter battery can start a petrol fire and the really wise will carry a small powder fire extinguisher in their flight box as a matter of course. I might add that electric fuel pumps and petrol sounds a really dangerous combination to me. Thus endeth today's sermon . Motor types The motors most commonly employed in models fall largely into two categories: single cylinder 2-stroke and single cylinder 4-stroke. But, in keeping with all fie lds of modern human endeavour, the recent technological revolution has resulted in a proliferation of very expensive multicylinder motors. These days , it ap pears that the sky is the limit in regards to cost, with radios selling for some unexpected complications. This constraint also had a second and less obvious consequence in that it 'also precludes a microprocessor based system on the grounds that the software also becomes a single source component and therefore difficult to obtain . But because the speed control ler lends itself so well to a micro-based system, I have finall y managed to twist Leo's arm into a painful enough position for him to agree to let me do a second construction article at a later date on a more specialised unit. The good news is that as a result of the enormous amount of work put into analysing the prevailing speed contro l design philosophy, we have come up with a very interesting new wrin kle to the design approach, again using readily available corn: ponents. Prototypes are currently under construction for testi ng and more will follow shortly, so stay tuned . up to $2000 and multi-cylinder engines and the n ew gas turbines exceeding even that figure. Prices of this order were unheard of in th_e late 1960s but th ey do give the manufacturers a chan ce to recover costs so that they can develop .newer and even more specialised units. The two categories may be broken down again into three sub-categories: Diesel, Glow Plug and Spark Ignition. Each type has its own advantages and disadvantages and each has its own particular set of design rules, all of which are too complex for a full analysis in a column such as this. There are , however, many books covering engine theory and operation for those interested in this fi eld. The names "4 -s tro ke" and " 2stroke" derive from the number of basic operations required to complete one cycle of operation. In a 4~stroke motor, there are inlet and exhaust valves to enable the fuel mixture to get into the cylinder and the exhaust to get out. In a 2-stroke motor, by contrast, there are no valves and the crankcase is used to transfer the mixture into the cylinder and to scavenge SOLDER HEATSHRINK TUBING Big savings on quality 60/40 1in/Lead, resin-cored solder. Perteet tor electronics. Long lasting 1/2 kilogram rolls. Diameter 0.56mm was $23.50 NOW $14.50 0.71mm was $22.88 NOW $13.50 1.0mm was $21.00 NOW $11.50 16mm was $19.25 NOW $12.00 Upon application of heat, this tubing shrinks to approximately half normal size· and our prices have shrunk to approximately half normal size!! Per metre: , 1.6mm was $1.95 NOW $1.20 2.5mm was $2.95 NOW $1.50 3.5mm was $3.45 NOW $1.BO 4.8mm was $3.65 NOW $1.90 6.4mm was $4.75 NOW $2.40 9.5mm was $5.25 NOW $2.70 12.7mm was $5.85 NOW $3.00 OR - try one of our handy packs of assorted sizes. Only $6.50. SPEAKERS 5" round 8 ohm tweeter (as used in some Pirn-.,er systems) 2 for $7.00 5" round 4 ollm 2 wan general ~rpose. Ideal for the test bench $3.00 SIEMENS MAINS FILTER MINI VICE Filter "noisy· and "dirty" mains power with this high quality self contained unit 115/250VAC, 4A, 50/60H, . Simply add varistor (V275LA20 $1.50) for spike protection. Save time and improve solder ~ ints. Order qwckly • only 30 left! ONLY ~8.95 ONLY $15.95 Ever wanted a third hand when soldering connectors etc.. . ? Try Thisll Plastic bodied, suction mounted base. wide jawed. lightweight vice. ASSORTED GOODIES were NOW . $1.95 $ .50 .... $1.75 $1.00 $11.95 $3.00pr. $ .28 $ .1 0 or $3.50/ 50 220uF 25V RT electro. Cap.. . .55 .20 220uF 35V electro. cap. .70 .30 HJ Kohm 4W resistor. . .60 .10 270 ohm SW resistor. .78 .20 2.2 Kohm 6W resistor" .80 .15 33 Kohm 6W resistor. . .80 .15 82 ohm 7w resistor. . . . . .. .. .. .. . . . . .85 .25 120 ohm 7W resistor. .85 .25 560 ohm 7W resistor . . .85 .25 2.7 Kohm 7W resistor . . . .85 .25 1-3.5 pF trimmer capacitor .82 .20 1.4-5.5 pF trimmer capacitor . . .82 .20 2·27 pF trimmer capacitor . . . .82 .20 4-40 pF trimmer capacitor. .82 .20 5·60 pF trimmer capacitor . . . .82 .20 5.5-6.5 pF trimmer capacitor .... . . . .82 .20 CM3052 35A 200V bridge rectifier . . . 8.50 2.50 78 15K (+ )ve 15v T0-3 Voltage Reg . . . . 5.40 7915K (-)ve 15v T0-3 Voltage reg . .. . .40 11.00 I.OD 1Ok LOG. 45mm travel slide slide pot . . .60 .50 1M linear VCU rotary pot. . . 1.85 .75 SOOK linear VCU rotaiy pot .. 1.85 .75 089 plugs (solder) . . D89 covers (plastic). . . . . 25KHz ultrasonic trans./rec .. 1u1 50V RB electro cap. . REIAY MADNESSII Siemens V23030 A1012 A104. Flat, 4-change over, 4-12 VDC, 50ohm, 2A, 250 VAC. Were $32.50 NOW ONLY $5.00 SiemensV21354 00426 F104. Cradlerelay, 2 changeover 18-40 VDC, 2450 ohm, 10A 250 VAC. Were $17.60 NOW$4.00 Siemens V23027 80006 A101 . PCB mount, single change over, 17·40 VDC, 1200 ohm, 8A, 250 VAC. Were $10.40 OW$4.00 Lynnks LD21 OH. DPDT, PCB mount, 12 VDC, 1500hrl\ 1OA, 250 VAC. As used in many kitsets. Were $11.85 NOW $4.50 NEC MR71C·12. SPOT, PCBmount. 12VDC, 285 ohm, 10A, 250 VAC. As used in many kitsets. Were $8.00 NOW $3.00 SUPER CAP A huge 0.1 Farad (100,000 uF) CABLE TIES capacitor rated at 5.SvDC. . . Great for energy storage for PanciJ1t 94x2.4mm Cab~ ties. memories, etc. Black or white. $1.50 per 100 were $2.52 NOW50C CATALOGUE APOLOGY Our sincere apologies to all our customers awaiting copies of our catalogue We are having to endure a systems error at our typesetter He 1s 1nstalhng a new system and production should be finished shortly MAJOR CREDIT CARDS/CHEQUES WELCOME Orders under $50 · $4,00 P&P - Orders over $50 · $6.00 P&P ALL ELECTRONIC COMPONENTS 11 8· 1ZZ Lonsdale Street, Melbourne Vic. 3000 Telephone: (03) 662 3506 Fax: (03) 663 3822 A UGU ST 1992 59 Protect your valuable issues MODEL AIRCRAFT ENGINES - CTD Silicon Chip Binders the exhaust products out. The all important factor in any engine is the timing of these operations and much energy has been expended on developing better methods of timing. In keeping with all technological achievements, the early beginnings were very quaint and somewhat primitive but the fundamentals were there. Glow plug motors 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 uo 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 r----------1 Enclosed is my cheque/money order for $_ _ _ or please debit my II I I II O Bankcard O Visa O Mastercard Card No: Card Expiry Date __/__ Signature _ _ _ _ _ __ _ __ Name _ _ _ _ _ _ _ _ __ _ II Address- - - - I _______ P/code_ __ 1,, _ _ _ _ _ _ _ _ _ _ _ .. 60 SILICON CHIP The invention of the modern glow plug model motor is attributed to an American engine enthusiast, Ray Arden, and the idea swept the world, pushing the diesel and spark ignition motors into the background. Here it seems was a great new idea, yet the Wright Brothers flew at Kittyhawk with a glow motor of their own design. The old adage of "there is nothing new under the Sun" still holds it appears. The method of generating the ignition is the next most important factor. Diesel motors use a self-ignition process which relies on the heat generated in the compression process to raise the fuel/air mixture to flash point. Diesel motors used in model work have a sub-piston fitted above the piston and a screw on top of the cylinder head to adjl.).st the compression ratio whilst the motor is running. The compression is reduced for starting and then increased for maximum revs. They are very difficult to throttle effectively and do not run well at low speeds. Fuel is commonly a mixture of ether, kerosene and castor oil. The piston/cylinder seal must be good. Glow plug ignition is again a selfignition process, in which a glow plug which consists of a wire element, usually made of platinum, supplies the ignition. To start this type of motor, the plug is raised to bright red heat by connecting a battery across the element. Once the motor begins to run, the platinum wire element will continue to glow under the heat from compression and the chemical effects of the methanol fuel. At this point, the battery is disconnected and the motor will continue to run. As in the diesel motor, the piston/cylinder seal must be good which these days means piston rings. · If there is a noticeable drop in en- gine revs when the battery is removed, the plug is "too cold" and a hotter plug must be fitted. What this means is that a more active element must be fitted for that compression ratio. The art of motor tuning is very subtle and such things as plugs, porting and fuels make a very big difference to engine performance. These motors throttle extremely well and are very popular in R/C work as a result. The fuel is usually methanol and castor oil with extra oxygen supplied sometimes in the form of nitro-methane. Glow fuels make excellent paint strippers and many paint jobs have been destroyed completely because the model was not fuel proofed or the incorrect paint was used in the first place. Spark ignition And now to get to the question which started this article. Spark ignition is the oldest form of model engine, the first engines being petrol powered "gas jobs". And very quaint they were. The compression ratio in these motors is usually much lower and the spark is supplied by a true spark plug as used in cars. This plug is connected to a coil, condenser and a set of points and the spark ignites the fuel -air mixture. Because of the lower compression ratio, the piston/cylinder seal does not need to be as good as for glow plug motors. A good bright spark cures a lot of the ills encountered in model motors, such as worn pistons and cylinders. The early motors did not throttle well, however, and a 2-speed set of points was often fitted, to provide spark advancing and retarding. Modern spark ignition motors are now fitted with electronic engine management systems and many of the old ills are now cured. The fuels used are most commonly petrol and mineral oil but methanol-based fuels can be used. Once again though, the dreaded space restriction brings us to the end of this month's column and we must await next month's issue for a more detailed analysis of the ins and outs of modern spark ignition and 4-stroke engines. SC A very small telescopic monocular IA viewer. The assembled scope has high quality military grade optics, and employs a prefocussed IR image converter tube. This tube has a useful response from 600-1300 nM, thus also making it useful when working with IR LEDs, and IR laser systems. The scope has provision for a coaxial E.H.T. connection, and is supplied with a power supply kit, that features a ready assembled inverter on a small PCB. The power supply easil y fits into a small plastic case, and can be fitted with $269 fr~c~:~~I~ i~l~~:iuv"ti~!?' At a very small (Item No. We can also supply the same monocular viewer with its original power supply. Powered by a sing le 1.5V C type battery. In this case all that is needed is connecting the scope to the power supply unit via a coaxial cab le, which is also supplied. (Item No. 0122) VISIBLE LASER DIODE POINTER-PEN LARGE LCD DISPLA V MODULE - These are brand new units, main body has a diameter of 58mm and a height of 25mm. Will operate from 5V, has 7.5 deg. steps, coil resistance 6.6 ohm and it is a two phase type. Six wires. ONLY Brand new large Hitachi LM215XB display, as used in some laptop computers. Yellow-green LCD reflective type, 480 X 128 dot display, effective display area of 242 X 69 mm, has 14 LSI ICs mounted on the rear of the PCB. Includes four pages of data sheets. Limited stock at a small th 1 ::a~ ~a~u~ eir ea. $39 SINGLE CHIP MICRO COMPUTER 12V OPERA TED LASER WITH A KIT SUPPLY (Item No. 0132) Save by making your own 12V laser inverter kit. This combination includes a He-Ne visible red laser tube and one 12V universal laser power supply kit - Mkll. This inverter features easy construction since the transformer is already assembled and will drive all the 0.2-15mW tubes efficiently. Universal 12V supply plus a used 2-3mW tube or head sgg $12 ea . (Item No. 0140) Small PCB assembly containing two ICs, one of which is a Music generator (7910 CF). The other IC is probably a power amplifier (NECCTM701D). Apply 3-12V across two of connector pins to obtain music from one of the IC pins. This information and a circuit diagram is provided. s4 One extra tube or head $30 extra. Only with initial purchase. (Item No. 0105X) ea. Item No. 0146 Universal Supply Kit plus a new 1mW tube $129 (Item No. 0105) Suit teachers, doctors, businessmen, and other professionals. Improve and enhance all you r presentations. Not a kit, but a complete , commercial pen sized laser pointer at an incredible price! ON SPECIAL AT $180 Small pen sized body. Runs on two small AAA battery. Battery life: 2-10 hours. Visible 5mW red (670nM) laser. Projects a visible red spot at more than 50 metres. As used for medical treatment by doctors and acupuncturists. (Item No. 0101) These brand units are supplied in their original packing. T hey are an option for backlighting Citizen LCD colour TVs. The screen glows a brilliant white co lour when the unit is powered from a 6V battery. Draws approximately 50 mA. The screen and the inverter PCD can be separated. Could be used as the basis of a solar. powered sign, e.g. house number. Effective screen size is 38 X 50 mm. The inverter PCB can be also used for powering backlighting strips on LCD displays. ea. s 12 (Item No. 0144) In the form of a telephone display. Based on an NEC uPD7503G single chip micro computer. Apply power to the unit and the display will show date and time (Xtal controlled oscillator on board) but this is only a small part of the micro computer's featuces: 4 bit single chip micro computer, 4 bit parallel ALU, 8 bit serial interface, 4096 X 8 bit words of ROM , 224 X 4 bit words of RAM, 23 general purpose 1/0 lines, 24 line segment outputs and 4 lines common outputs for driving LCDs, instruction set enables direct memory addressing, can be battery operated (3.5-6V), extremely low battery consumption: less than 1mA whi lst operating, less than 10uA in standby. Connection to the phone display can be made by simply pushing wires into the socket provided. One complete 15 page set of instructions on the uPD7503G and a circuit diagram of the phone display will be provided with each order for one or more of the phone displays. $ ONLY ea. OR 5 lor $60 (Item No. 0133) 15 Universal Supply Kit plus a new 5mW tube $189 (Item ~o. 0106) A mixture of no less than 15 switches: 5 off modern 3A panel mounted mains rated switches, 5 off modern 16A panel mounted mains rated switches, and a mixture no less than 5 rotary switches: small and large. That's a total of 15 New switches worth at least five tim_es our s 16 total price of FOR THE COLJ..ECTION Item No. 0150 LARGE ROT AR't SWITCHES Universal Supply Kit plus a new 10mW tube $299 (Item 0107) LARGE COMPUTER FANS Powerful ball bearing mains powered fans. 220V/0.13A, 173mm diameter by 60mm deep. Thermally protected , . finger guard included. removed from new equipment. • Item No. 01 S2 sg·go $89 Contains mainly 8 modern ferrite transformers which are very easy to dissamble and rewind. Ferrite halves are clipped together and no adhesives are used between them or in coil winding. There are fou r identical small transformers and four identical larger transformers. The transformers can be rewound .for use in 5 ~~~:.r\~~!~~~~~c~· 5 Item No. 0147 ea. SOLAR PANEL GIVEAWAY Brand New high quality US made, amorphous I I i':,:;!n~f~~~pf£t ~ 150 X 2.5mm. In normal su nlight they deliver a full 1 Watt whilst charging 6V-8V batteries! Can be connected in series. in parallel , or series/ parallel , to increase the voltage, and/or current capacity. For example, in average sunlight, two of these panels connected in series will deliver approximately 150mA of charging current, into a floating 12V (14V) battery: 2 Watts! Four panels can be connected in series parallel to deliver 300mA into a floating battery: 4 Watts' Compare the prices! All the panels have a weather protection film on rear, and the terminating clips are provided. B These large rotary switches have "snap in" action and all are rated at mains voltages, or higher. They have at least three positions and are have currents ratings from 10-35A. Great for high power mains, and antenna switching. s15 ONLY ea. Item No. 0151 LASER GUNSIGHT Small black anodised metal body. Removable pressure switch. Vertical and horizontal adjustments. Battery life more than 10 hours continuous. SmW 670nM class IIIA laser. Range is about 150m, some would claim three times more. Shock tested to 20009. One year warranty. ON SPECIAL AT $249 Price includes one rifle or pistol mount (Item No. 0108) This precision collimator assembly was removed from working laser printers. but is supplied with an extra Brand New laser diode to suit. It produ ces a beam that can be focussed to a fine dot or line. Barely visible, 780 nM/5mW. We also supply a PCB components and instructions kit. for a suitable digital driver circuit that can be used to complete the laser transmitter. Suitable for co mmunications, data links, perimeter protection. bar code reading. medical. etc. Limited stocks. $10 INCREDIBLE PRICING: or 10 for $85 (Item No. 0130) ea. ONLY (Item No. 0111) We can also supply a si milar kit which is based on an unmounted collimating lens which will need to be supported in front of the laser diode. This kit includes a brand new 5mW/780nM IR laser diode, a suitable heat sink. a co llimating lens, a driver ki t (PCB and com ponents) and the instructions. ONLY $45 Note that if either of lhe above lasers are coupled with a suitable rece iver (E.A. April 91) a perimeter protection or data link with a range of a few ki lometres should be possible. We tried it over 300 metres, with no problems! We may stock a kit for the receiver which would include the instru ctions. in July 92. Approximate price S20 for the PCB, all on -board co mponents. and a suitable re lay. DANGER! LASERS ARE NOT FOR KIDS A dummy load box for large audio amplifiers Checking the power output of a large audio amplifier is not a trivial exercise. A stereo amplifier rated at around 500-1000 watts per channel will need to be tested into 8, 4 and 2-ohm loads, as well as requiring a 1-hour soak at 33% of its rated power. The load box described here meets this need. By LEO SIMPSON Since we do quite a lot of testing of audio amplifiers from time to time, we often have need of a load box which is able to dissipate a lot of power. We set a target rating of 1000 watts per channel with load impedances of 8, 4 and 2Q. And while amplifiers rated to deliver 1000 watts per channel into 80 are not commonplace, many amplifiers will deliver quite 62 SILICON CHIP surprising amounts of power into 20 loads for short periods. You might ask why it should be necessary to test power output into 20 since the vast majority of loudspeakers have a nominal impedance of either 80 or 4Q. The answer is threefold. First, if two 40 loudspeaker systems are connected in parallel, the resulting load impedance will be nominally 20 and that is what the amplifier has to drive. Second, the impedance of some 40 loudspeakers may dip down to as low as 20 at some frequencies. Third, many amplifier manufacturers make a big point about how much current their amplifiers can deliver. The specification for amplifier resistive loads can be found in IHF-A202, published by The Institute of High Fidelity, Inc, New York, in 1978. To quote the relevant section: "The resistor shall not have more than 10% Above: a high power load box requires a big case and plenty of forced air ventilation. This case measures 540mm wide, 210mm high and 350mm deep. It was salvaged from an obsolete computer. reactive component at any frequency up to five times the highest test frequency and shall be capable of continuously dissipating the full output of the amplifier while maintaining its resistance within 1 % of its rated value". Temperature problems While it may not be immediately apparent, that is a very stringent specification . While it may be reasonably easy to obtain a resistor with a tolerance of 1 % , getting it to maintain that tolerance while dissipating a lot of power is quite another matter. Most large wirewound resistors will operate with a surface temperature of up to 300°C if they are run at full power without fan cooling. Clearly, you can't afford to have the resistors run up to those temperatures, otherwise their temperature coefficient will ensure that the resistance is well above (or maybe below) its nominal value. Interestingly, the temperature coefficient of wirewound resistors can be positive or negative or maybe both; ie, positive for lower temperatures and negative for higher temperatures. So the first problem is to ensure that the load resistors maintain their value within that ±1 % range up to the full power rating. That means extensive cooling and derating; ie, not running the resistors at their full power rating in order to keep their surface temperatures down. When you think about it, a total rating of 2000 watts is This view shows the internal wiring to the four relays and the 12V regulated supply which energises their coils. in the same league as domestic electric radiators and they get red hot! Even fan forced radiators pump out hot air, so their internal elements run at quite an elevated temperature. Reactive component The other problem is the requirement that the reactive component of the load resistance does not exceed 10% of the nominal value up to five times the highest test frequency. What this part of the specification is saying is that the inductance must not be too high. But because power resistors are "wirewound", they naturally have inductance and sometimes quite a lot of it, relative to their nominal resistance. Typically, the highest audio frequency used for power testing (as opposed to frequency response testing Below: this view shows how the banks of jug elements were mounted on brass rods. The three fans can just be seen behind the elements. "J}ii '··•· liJ. - : :,t9 -•· . AUGUST 1992 63 I A 4n ~ RL1a C 1kW RIGHT CHANNEL RL2a ~ 4Q RL 1b 1kW LE.FT CHANNEL RL2b A~ c-.bo s2a MONITOR 8 ~ o---1o S2b Fig.1: four relays are used to perform the load switching. One resistor bank is used in each channel for 4Q loads, while two resistor banks are connected in parallel in each channel for 2Q loads & in series in each channel for an loads. which is usually done at low power) is 20kHz. Therefore, five times the highest test frequency is lO0kHz and at this frequency the load resistor must have a reactive component not more than 10% of the nominal value; ie, no more than o.zn for the zn range, 0.4Q for the 4Q range and 0.8Q for the 8Q range. So the maximum inductance for the zn range should be no more than 0.3 microhenries; for the 4Q range, no more than 6.4 microhenries; and for the sn range, no more than 1.3 microhenries. These are extremely low values of inductance because even if the resistors had no inductance at all, the inductance of connecting wires would still be considerable. For example, the inductance of a single 1-metre length of 2mm-diameter wire in free space is around 1.2 microhenries. If the wire is curved or near magnetic material such as steel, that inductance can be quite a lot higher. It _ is possible to obtain resistors rated up to 250 watts under forced air cooling conditions, or up to 500 watts or more with water cooling. However these are usually only available with a tolerance of 5%. You can obtain, to special order, non-inductively wound 64 SILICON CHIP resistors with similar ratings and value of tolerance although they are very pricey. For custom wound non-inductive resistors with 1 % tolerance , the price goes through the roof. In fact, for a stereo load box with a rating of 1000 watts per channel in the three load impedances listed above, we were looking at a cost of several thousand dollars and that was just for the resistors. There had to be another way. Our approach was to use a variation of an old idea - the humble jug element. In the past, we have used tapped combinations of jug elements to provide dummy loads for amplifiers. Naturally, they have to be immersed in a bucket of water but they work well. The only problem is that with a high power amplifier, the water soon boils. That presents a real hazard, especially if the bucket is kicked over, as happened on one occasion in our workshop! How to cool it Having decided on using paralleled jug elements, we next had to addres~ the question of cooling. We ruled out water cooling right at the outset because that would mean a substantial tank together with a radiator core and fan. So that left oil cooling or forced air cooling. We ruled out oil cooling because a substantial tank and a finned radiator would again be required. So forced air cooling was chosen by default. We then had to decide how much power a single jug element could dissipate. Our method was to feed current through a single jug element in still air and measure its temperature rise and resistance shift. With SOW being dissipated, the element became moderately hot but stayed below red heat, although the wire began to discolour (ie, turn blue) after 5 minutes or so. For this temperature rise, which we estimated at less than 200°C, the resistance shift was less than 1 % which is right on the button as far as the aforementioned IHF specification is concerned. Based on that, we decided that each jug element should be able to dissipate 100W if forced air cooling was used. Typical jug elements have a resistance of around 36-39Q. That is quite convenient because with 10 jug elements in parallel, we could then obtain a resistance of close to 4Q which would be able to dissipate 1000 watts. Four such resistor banks would be required and the resultant 4Q resistors would be switched in parallel or series to give zn or 8Q. The resistor banks would need to be switched simultaneously for each channel and give a selection of no load, sn, 4Q or zn. Relay switching And this brings us to the next problem. How to do the switching? The currents and voltages involved are quite high. For example, an amplifier delivering 1000 watts into an 8Q load will put out close to 90V RMS. The same amplifier could be expected to deliver at least 40A continuously into zn loads (before fuses blow) and possibly a great deal more on a pulse power test. There isn't any multi-pole rotary switch (that we know of) which can handle the voltages and currents involved. That left us with relays or multi-pole circuit breakers. Ultimately, we decided to use relays, each with two sets of changeover contacts rated at 240VAC and lOA. These have more than adequate ratings as far as the likely applied volt- Starring KT OAT KT 386SX-20 KT 386-25 KT 386-33 KT 486-33 KT 386 NOTEBOOK * * * * • New Costumes • All Australian Support Cast Our Promoter is seeking Dealers wishing to present this talented new range of PC Performers to the Australian Public. Don't miss your opportunity to book your place in this ever expanding dealer network. ,. KT TECHNOLOGY ~~~~m~ iu~1~::~ ~ ~~~~evard, Port Melbourne 3207 Tel: (03) 646 5755 Fax: (03) 646 7997 \ \ The resistor banks were mounted in a rectangular tunnel fabricated from sheet aluminium. Three high-capacity computer fans mounted at the back switch on & provide forced air ventilation when ever a load is selected. Even when running at high power, the exhaust air is cool. ages are concerned but are underrated as far as amplifier current capability tests are concerned. We think that they will do the job but when testing big amplifiers we will have to reduce the signal level before switching ranges, so that they don't have to switch those high currents. The relays are energised from a regulated 12V DC supply derived from the 240VAC mains. The relay switching is arranged so that the loads cannot be connected unless the 240VAC mains is switched on. This ensures that the three fans always run when the loads are connected - we don't want a meltdown while testing a big amplifier. 66 SILICO N CHIP The three fans are 120mm computer fans, each rated at 105 cubic feet per minute. Together, they pull quite a draft. The mains voltage to the fans is reduced to 220VAC which gives a slight reduction in noise while not appreciably reducing the draft. Method of assembly You can see the result of our work in the accompanying photographs. The load box is housed in a large plastic case salvaged from an old computer (from the days when 8-inch floppy drives were standard). This is fitted with perforated steel at the front and the three fans at the back. The small control panel at the front accommodates the substantial binding post terminals for both channels and a rotary switch which controls the internal relays. Forty jug elements were connected in four banks of 10. Their brass connecting wires were removed and they were mounted on 3 70mm lengths of 1/8-inch threaded brass rod. The start and finish of each jug element was soldered to the brass rod. The resulting resistor banks were then suspended in a rectangular tunnel fabricated from sheet aluminium. The brass rod connections to each element were isolated from the sheet metal sides using a sheet of rigid fibreglass suitably drilled. Four relays, wired as shown in the circuit ofFig. l, do the load switching. One resistor bank is used in each channel for the 4Q load condition. For the ZQ load condition, two resistor banks are connected in parallel in each channel, while for the 8Q load condition, the same resistor banks are connected in series. In effect then, the load box could handle 2000 watts per channel while in the ZQ and 8Q load condition, and 1000 watts per channel while in the 4Q condition. However, we think it will rarely be used at powers of 1000W let alone 2000W. Note that the relays provide for disconnection of the loads at each extreme setting of the rotary switch. This is handy when doing measurements such as damping factor and in testing for stability. Switch 2 enables external monitoring equipment, such as a noise and distortion meter, to be connected to the left or right channels of the amplifier under test. And how close did we come in meeting those resistance and inductance conditions described at the start of this article? All three load settings give cold resistance values within 5% of the nominal values and they come closer as the temperature rises. The inductance results were as follows: 0.8 microhenries on the ZQ range; 1.19 microhenries on the 4Q range; and 1. 76 microhenries on the 8Q range. These figures are a little higher than indicated in the IHF specification if Z0kHz is used as the highest power test frequency, although in practice this should not have a significant effect. SC FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS. .. Digital Voice Recorder Kit Back Again SerialTest PC-based Protocol Analyser & Data Line Monitor ~ :i: <..) ct e § Cl ~ :i: <..) ct e § $ NC.t;, ~ The new version of Serialtest turns ANY PC into a full-featured serial data protocol analyzer - even laptop and notebook computers - for both synchronous and async data. Serialtest unleashes the power of your PC for data communicatior,s testing with a simple, user-friendly interface and eirner' The new Com Probe plugs in to your printer port. With Serialtest and your PC, there is no longer any need to buy or rent expensive, dedicated protocol analyzers. The Serialtest package includ es Serialtest software and Frontline·s RS-232 Com Probe™ adapter. The Com Probe connects to your computer via the parallel printer port (no need for plug-in cards) and allows Seriaftest to work with both synchronous and asynchronous devices. Serialtest's monitor mode shows you exactly what information is flowing between any two serial devices - both data bytes and control signals Source mode allows you to interacfively simulate either the DTE side or DCE side of the communications link. Serialtest Async is similar to Serialtest, but is limited to async-only testing. The package includes Serialtest Async software and custom cabling which wo rks in conjunction with the serial ports on your PC. Anyone who works with serial data communication needs Serialtest. Field service engineers and system integrators will appreciate the portability and ease-ofuse. Communication specialists and network supervisors will enjoy the power and flexibility. No matter what the industry, Serialtest will prove to be an indispensable tool. SerialTest Sync/Async with Comprobe $2480.00 (ex tax) $2536.00 (inc taxL Plug Pack $24.95. Allow $15 P&P SerialTest Async is still $480.00. Demo disk $10.00 refunded on purchase Look at ALL these features Protocols: Async, SDLC, Sync, X.25, HDLC, SNA _Data Capture: data bytes, control signals, and error conditions. . Capture data to RAM and directly to disk with no capture file size limit. Data Display: Frame/Packet level.· one decoded frame/packet per line. Byte level: split-line DTE over DCE or mixed using reverse video for DCE. Characters displayed in hex, ASCII, EBCDIC, or Baudot. Nonprintable characters displayed using hex, mnemonics, graphics, or dots. Captured data can be searched; search patterns can include wildcard characters. Control Signal Display: Live breakout box includes timing diagrams and counters. Captured control signal transitions can be viewed in relation to captured data bytes using timing diagrams. Timestamplng: Absolute or relative display of event time. Delta time and effective data rate calculations. Triggers: Character strings, control signals, and error conditions can be used to activate and deactivate data capture. String triggers can .include wildcard characters. Device Emulation: Transmit data entered from the keyboard, Serialtest capture files, or any DOS file. Modify control signals. Use hardware and software flow control including user-defined XON/XOFF characters. Configuration Management: Name and save an unlimited number of configurations. User Interfaces: Pop-up menus and context-sensitive help allow new users to be up and running quickly. Command line options can be used to fl./fther simplify operation. ~ ~ ct e § Cl ~ :i: <..) ct e § Cl ~ :i: <..) ct itCl ~ 8.30am to 5.00pm Mon to Fri. 8.00am to 12 noon Saturday. :::.. Mail Orders add $5.00 min to cover postal charges. ~ Next day delivery in Sydney add $8.00. 5:: 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. 8 $ see Silicon Chip Feb 92. Records up to 512 seconds of speech in up to 4 separate messages. $135. Optional case $20 and plug pack $18 .00. Add $10 p&p. Soldering Irons & Spare Parts ~~- We are now stocking a full range of Scope soldering irons and accessories. Ideal for maintenance workshops and production lines. Take your pick from - Superscope Maintenance and repair iron with manual temperature control for medium to heavy duty solderin8 • 20W to 1O W adjustable • Adjustable 200° to 500°C • 5 seconds to reach 20°c • Low 4V sup ply • Automatic switch-off Miniscope The pencil iron with real power. Manual contro l of temperature while soldering. Suits light to medium duty work • 1OW to 70W adjustable • Adjustable 200° to 500°C • 5 seconds to reach 20°c • Easy owner maintenance • Low 4V supply • Automatic switch-off ET&OL &OW 24V Soldering System New Electronic Workbench The Electronics Lab you keep in your PC! YES you can now build, simu late and test Analog and Digital Circuits without laying you r hands on a single componenti It's so easy with Electronics Workbench®. Do it all with the mouse drag new parts from the parts bin, drop them onto the breadboard and click to run wires. Editing circuits is easy as wires are re-routed automatically. It's much faster than building rea l circuits. No faulty parts! It's the result of 1Oyears innovation and thousands of students, hobbyists and engineers have been using theWorkbench since its introduction in 1988. Analog Module Includes '• Comprehensive parts bin includes opamps, zeners , transistors etc • Function Generator with sine, square, triangle etc • Oscilloscope with dual trace, int/ext trigger, nanosecond timebase upto 999MHz • Bode Plotter for frequency responses and _phase shift (-200 to +200dB) • SPICE Simulation plus transient and steady-state simulation Digital Module includes • Comprehensive parts bin with gates, flipflop s, half adders, displays etc • Word Generator up to 16x8-bits • Logic Analyser with 8 channels , int/ext trigger • Logic Converter converts between gate, truth table and boolean Professional version has inhanced colour interface, supports maths coprocessor. Requires IBM AT or PS/2 with 286 or greater, hard disk, 640kB RAM , Microsoft mouse, EGA/VGA and DOS 3.0 . $429 .00 Personal Plus Version is monochrome. Requires PC/XT/AT or PS/2 , 2 floppies or hard disk, 512kB RAM , Microsoft mouse, CGA/EGA/VGA/Hercules graphis adaptor and DOS 3.0 or greater. $299.20 • Infinitely adjustable 200°c to 470°C • Illuminated temperature readout monitors actual tip temperature • Select tip temperature required See the review in Electronics Australia • Zero voltage switchning for maximum March 92component safety "Electronics Workbench is certainly the • 60W of back-up power- 30W pencil easiest simulator I've ever used" option Peter Philips • Burn-proof flexible lead Sco_p_e Irons SCOPE-ET60L-1 60W Adiustable w/- Disp 225.40 SCOPE-MINISCOPE MINISCOPE Handpiece (needs PSU) 55 .60 SCOPIE-PH20-5PK 5 Piece Hobby Pack 41 .95 Power Supply Unit SCOPE-PSU 63 .55 SCOPE-STAND General Purpose Stand 14.20 SCOPE-SUPERSCOPE SUPERSCOPE Handpiece (needs PSU) 50.30 Spares for Superscope SCOPE-SK2-01 A SS Tip 6.4mm Dual Flat 1.50 SCOPE-SK2-0IB SS Tip 3.2mm Conical 1.50 SCOPE-SK2-02 SS Stainless Barrel 8.95 SCOPE-SK2-03 SS Element 1.50 SCOPE-SK2-04 SS Bead Retaining Nut 0.40 SCOPE-SK2-05 SS Ceramic Bead 0.20 SCOPE-SK2-06 SS Push Rod 7.70 SCOPE-SK2-06A SS Push Rod Assembly 10.20 SCOPE-SK2-07 SS Return Spring 1.20 SCOPE-SK2-08 SS Flexible Lead 10 .70 SCOPE-SK2-09 SS Bakelite Lock Nut 3.25 SCOPE-SK2-10 SS Brass Nut 2.80 SCOPE-SK2-11 A SS Handle Body Only 7.15 SCOPE-SK2-12 SS Switch Ring 3,60 SCOPE-SK2-13 SS Rubber Grip 0.95 SCOPE-SK2-14 SS Grommet Spring 1.85 SCOPE-SK2-15 SS Grommet Nut 3.60 SCOPE-SK2-11 B SS Complete Handle 20.30 Ultrasonic Cleaner NEW SC-7000 DeSoldering Tool Why pay up to $200? Ideal for PCB and computer parts, jewellery, Now with 1DOW ceram ic heater. Work on watches, dentures etc! up to 12 layer boards. Special antistatic We still have them tor just $150!! housing. Optional surface mount kit $482.50 ex tax $579.00 inc tax Geoff Wood Electronics Pty Ltd (inc in N SW) 8 CJ Cj lJ ~ ~ 8 c:J Cj lJ ~ ~ 8 c:J Cj lJ 2'ti 9) ~ 8 Cj lJ 2 'ti 9) ~ 8 Cj lJ ~ ~ 8 c:J Cj lJ 2 'ti r 8 c:J Cj lJ 2 'ti r 8 c:J Cj lJ (') ;J;; ~ 8 c:J Cj lJ ~ 8 c:J Cj lJ (') 229 Burns Bay Road,, Lane Cove West N SW ;J;; (Corner Beatrice Street) ;g Mail Orders to - P O Box 671, Lane Cove N S W 2066 ' Telephone : (02) 428 4111 Fax : (02) 428 5198 8~ c:J • HOW I E • BUSY HONE Build the Interphone: a 10-station exchange for your home Do you have a lot of phones in your home? Would you like to have all the features of an automatic switchboard like a Telecom Commander system? The system presented here provides many of the features of a Commander system but at only a fraction of the cost. By JEFF MONEGAL 68 SILICON CHIP These days, few people are content to have just one or two telephones in their home. They want one in each bedroom, one in the kitchen, one in the garage and, in fact, they probably would like one in most rooms of the house. This may be desirable but four or five phones is probably the limit as far as a normal installation is concerned otherwise reliability may be prejudiced. And with all those phones in the household, wouldn't it be nice to use them as a multi-station intercom? With the Interphone you can have this feature and quite a lot more besides. The main features of the unit are listed in an accompanying panel. If you were to have a Commander system installed in your home, it would cost you many thousands of dollars. You can have an Interphone system with all the features listed in the panel for around $300 to $400 in kit form. Before we proceed any further, we should clarify a couple of terms which often cause confusion in articles about telephones. The terms are "off hook" and "on hook". When a phone is "off hook" it is actually connected to the phone lines. Similarly, when a phone is "on hook" it is disconnected from the phone lines. Now let's talk about how the Interphone is used. You can have as many as 10 extensions or remote stations. Each of these stations has its own identification number, from 0-9. To use the intercom feature, simply pick up the phone and the busy LED will start to flash on all stations. You then press the number of the wanted extension for at least one second. The ringer of the wanted extension will then sound and will continue to sound for as long as you hold down the relevant button on your handset or until the extension is answered. You then have 2-way communication. Unlike standard intercoms, both parties can talk at the same time. This is full duplex communication and is great if two people want to yell insults at each other at the same time. To make an outside call, you pick up any of the extensions and press' the # button. The switching unit detects the tone associated with this button and connects the outside line to the system. You hear a dial tone and use the phone as normal. To answer an incoming call, just pick up the phone and press the# button again. You will be connected to the line and the incoming caller. Transferring calls If, after answering an incoming call, the caller wants to talk to someone else you can place them on hold by pressing the* button on your handset. You then use the system as an intercom to call another extension and tell them that a call is waiting. You then hang up your phone. Yo_u r spouse (son, daughter, etc) then presses the# button to talk to the outside caller. A caller can only remain on hold The Interphone is built into a large plastic case, with rows of sockets for the various extensions mounted on the rear panel. The base station board is on the left, while two remote station boards are stacked to the right. Each remote 'station board services three extensions. for about 30 seconds before a signal is sent to all stations which sounds the ringer. That way, you cannot accidentally forget about a caller on hold. You must then take the caller off hold and if you wish place them back on hold. Ring tones The "ringer" associated with this project indicates three different conditions. With an incoming call, the ringer has the familiar telephone ring cadence. Features • Up to 10 tone phones can be connected. • Make calls from any station. • Answer calls from any station . • Transfer an answered call to any other station. • All stations can talk to each other (intercom mode). • An outside caller can be put on hold while you talk to another station on the intercom. • Phone off hook indication at all stations. • Full isolation from phone lines using a Telecom-approved isolation transformer. If a caller has been on hold for 30 seconds, then the ringer will sound for one long ring until the caller is taken off hold. If someone is paging an extension, then the ringer will sound for as long as the calling station has their button pressed. Any standard tone phone can be connected to the Interphone but your local telephone exchange must have DTMF tone dialling. Most exchanges in Australia now have tone dialling available even though a lot of modern phones may still be using pulse dialling. How do you know if your exchange has DTMF (stands for dual tone, multi frequency) dialling available? The first way to tell is to lift up your phone. If the dial tone is a tone and not the old familiar "brrr" of pulse exchanges, you have no problems. Second, even if you're presently not using tone dialling it is highly likely that your local exchange has it. To get your phone changed over, all you do ·is ring your local Telecom office and ask to have it changed over. You then have to switch your phone from pulse to tone dialling (via a switch under the handset). As a bonus, you will then have much faster dialling and connection of called numbers. All wiring from the Interphone to AUGUST 1992 69 You can build as many remote station boards as you like & stack them one above the other to give the required number of extensions (10 maximum). The remote stations decode the intercom control tones & provide the ringer facilities. extensions involves running standard 4-core telephone cable around the home. A standard tone phone must be connected at all times to the incoming phone lines and the Interphone is connected in parallel with it. All the extensions are then connected to the Interphone. By having a phone directly connected to the incoming lines, you will always have a telephone service during blackouts - the Interphone needs a mains power supply to work. However, the directly connected telephone will not have the ability to talk to the extensions, put calls on hold or transfer calls. How it works The circuit ,for the Interphone is broken into two sections - base station and remote station. There can be as many as 10 remote stations although they will all be built into the same case as the base station board. Now let's look at the circuit of the base station which is shown in Fig.1. This circuit provides isolation for the incoming phone lines, power supplies, internal exchange facilities and so on. At the top lefthand corner of the circuit you can see the incoming phone line pair. This is connected to a bridge rectifier and also to IC5 (at bottom of circuit). IC5 is used as a ring voltage detector. When the ring voltage of around 90VAC appears across the incoming 70 · SILICON CHIP line it feeds the internal LED of IC5 via a 100kQ resistor and O. lµF capacitor. Diode Dl 1 ensures that the LED is not reverse biased by the ring voltage. Thus, when ring voltage is present, the output at pin 4 of IC5 is a square wave at the frequency of the ring voltage. This is filtered to produce a DC signal at pin 13 ofIC4d and when this signal is present, pin 11 goes high and this sounds the ringer on all extensions. More on this later. Whenever a button on any extension phone is pressed, a DTMF tone appears on the internal line (adjacent to transformer Tl on Fig.1). This is clipped to an amplitude of ±0.6V by diodes D5 and D6 and fed to pin 7 of ICl which is DTMF tone decoder chip. It produces a BCD code at its outputs which are fed to IC2 , a 4028 1-of-10 decoder. a Unconventional decoding The outputs from ICl are not connected to IC2 in the conventional sequence, however. This has been done to allow IC2, which will normally only decode states 0-9, to give an output when BCD codes outside the normal 0-9 are present. The decoded output from ICl for the # button on a standard tone phone would be seen by IC2 as 1010 (decimal 12) which IC2 cannot decode. The same occurs for the * button. Its BCD code from ICl is 1011 (decimal 11) which again is outside the limit of IC2. Connecting IC2 and ICl with one of the BCD lines out of sequence allows the circuit to decode the * button and # button codes. Other codes are ignored by ICl and IC2. When IC2 is fed the BCD code for the # button, its Q9 output, pin 5, goes high. This sets flipflop IC3b, taking its pin 13 high. Q3 now turns on, energising relay RLY2 which connects the incoming phone line to the primary of isolating transformer Tl. Line current is now drawn from the phone line and the telephone exchange will interpret that as a phone off hook. A dial tone will now be heard from the handset and calls can be made in the normal manner. When any phone extension is lifted off hook the OFF HOOK line goes high. This causes pin 11 of IC6d to go low. This prevents anything from happening in the circuit until the phone is placed back on the hook. The OFF HOOK line goes low again and about one second later pin 11 of IC6d goes high. This results in a short positive pulse being fed to the reset pin of flipflop IC3b. Q3 then turns off, releasing relay RLY2 and disconnecting the phone line. What this means is that by placing the extension phone back on the hook you effectively hang up the phone in the normal manner. Line on hold If an outside call is in progress and the * button is pressed, another tone is placed on the internal line which is also decoded by ICl and IC2. This time, pin 4 of IC2 will go high. This sets flipflop IC3a, turning on transistor Q2 and relay RLYl This connects transistor Ql and its associated components across the incoming phone line and disconnects transformer Tl. Transistor Ql draws current from the phone line and maintains the "off hook" condition. The Interphone is now in intercom Fig.1 (right): the base station circuitry provides isolation for the incoming phone lines and includes the power supplies and logic circuitry for the internal exchange facilities & so on. IC1 and IC2 decode the # and buttons which control the hold, transfer & intercom facilities. * -..i ... N co co ..... -J (/) C: 0 > C: PHONE LI NE ~K uu 10k • • IGO 47k ECB ·-w. + 10 ..:- ; +5V -- INTERNAL LINE +5V B EOc -:- .,. *) 05l • VIEWED FROM BELOW ,rr;.::r··1 I 01 -,I XTALJc, INTERPHONE BASE STATION 011 1N914 012 1N914 ~ I T1 .,,,h 10 01 BC548 ., 06\. I / : . +5V + 14 1 113 0 D7 1N4004 I • _ 2 09 15 03 15 02 oo~14 01 1000 T '""°f 0.1 f .,. IN[ V+ !.- . 100k +5v--4F .,. IC2 4028 100t 11 O 12 C ~ (f) A 13 B J..!! OFF HOOK LINE OUT RING SIGNAL 12VAC FROM PLUG-PACK -:- IC1 MC145436 47! :I 101 16 10 ◄ -:- 0.1 100k 08 1N4004 V+ .,. 1 ~ +5 V J 10..: 7 I J: +5V 470 35VWJ +5V 013~ 1N914':t' RLY1 ~. ------rt +5V -:- I 01j POWER~ LED3 K A. 470il TO ALL BUSY LEDS K A + 470'2 LINE SEIZED LED2 I ----~ 03 BC548 "~t 470il +5V--- 010 1N4004 1 -----------------<11------- - -----------, + S V 0 - - - - - - - -...... 16 10 IC9 MC145436 +50V 0.1 INTERNAL LINE IC10 ,4028 + 2.2k 1W 10k 220pFJ . .4 021 020 .,. PHONE 12 10k .,. 100k -r .,. 10k .,. 022 1N914 .,. STATION SET OFF HOOK 1k 120k +50V 22k RING 82k 10k 023 1N914 .,. 0.1! INTERPHONE REMOTE STATION Fig.2: this remote station circuitry must be duplicated for each extension phone. IC9 & IC10 decode the control tones but note that only one of the 10 outputs from IC10 is used on each remote station board. mode and you can page any of the other extensions simply by pressing the corresponding numeric button on the phone you are using. This will cause their ringer to sound. They pick up the phone and talk to you. If they now press their # button, ICl and ICZ will again decode this and take the caller off hold and connect the new extension to the outside line. Whenever a caller is placed on hold, pin 2 offlipflop IC3a is low. Diode D9 is now forward biased which prevents flipflop IC3b from being reset if all phones are placed on hook. This means that if a caller is on hold, then you cannot disconnect the caller simply by replacing all phones. When pin 2 of IC3a goes low (incoming caller placed on hold), diode D12 is reverse biased which allows the lO0µF capacitor associated with IC6b to discharge. This takes about 30 seconds after which pin 4 of IC6b goes high. The Schmitt trigger oscilla72 SILICON CHIP tor built around IC6a now runs at a frequency of about lHz. This is fed through IC6c and IC4d and causes the ringer on all extensions to sound in 1second bursts, indicating that a caller is still on hold. Any extensions can then take the caller off hold by press- ing the # button and talking to the caller. IC4b, IC4a and diode D9 reset flip flops IC3a and IC3b when power is first applied. This is highly desirable since without this feature, the circuit could either pick up the outside line or ring all extensions when power was first applied and this could be in the middle ,Q_f the night, after a blackout! DC rails WARNING! In order to comply with the Telecommunications Act, we draw the reader's attention to the following: "This customer equipment has no AUSTEL permit and may be dangerous or damage a telecommunications network. Connection to a telecommunications network is an offence under section 253 of the Telecommunications Act 1991 and may attract a maximum fine of $12,000". Power for the circuit comes from a 12V plugpack transformer. This feeds halfwave rectifiers D7 and Dl 7, and their associated filter capacitors. Both of these rectifiers produce about 18V DC unregulated and the supply associated with D17 then feeds a 7805 regulator to produce 5V DC. The 5V rail powers all the CMOS circuitry while the unregulated supply feeds the relays. Diodes Dl4, D15 & D16, in conjunction with two 470µF capacitors and one lO00µF capacitor, form a voltage tripler. This produces a little over SONY. SONY. 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DOS 3.1 or above hard disk drive. Recommended VGA Monitor-& VGA adapter Mouse *Requires VGA (For PS2 MCA 1/F card add $320) PACKAGE CONTENTS Sony external drive model CDU 7205U (which supports CD Rom mode 1 & 2 & Audio combined CD) Sony bus.interface card (half card value $180) Software Collection (as detailed) PELHAM PTY LTD 1st Floor, 100 Yarrara Road , Pennant Hills 2120 Ph (02) 980 6988 Fax (02) 980 6991 AMATEUR RADIO EQUIPMENT KENWOOD ELECTRONICS AUSTRALIA PTY. LTD. P.O. BOX 504, 8 FIGTREE DIVE, AUSTRALIA CENTRE, HOMEBUSH, N.S.W. 2140, AUSTRALIA. (A.C .N . 00 1 499 074) . 50V DC which is used to run all the extension phones in the system. By this means, all the extension phones are powered by the plugpack supply and not by the incoming phone lines. Remote stations Let us now discuss the remote station circuitry which is shown in Fig.2. One remote station is needed for each extension phone and you can have as many as 10 extensions. The limit of 10 is set by the 4028 1-of-10 decoder used in each remote station .board. Our prototype, by the way, is built with six remote stations, three to a PC board. Each remote station board has the job of decoding intercom tones , sending control tones and providing the ringing facilities (via a buzzer). IC9 and IClO decode any tones found on the line but only one of the 10 outputs of ICl0 is used on each remote station board. This is the nominated number for that extensi_on. For example, if button 5 is pressed on any extension phone, then pin 6 of ICl0 ·on every remote station board will go high. However, only one remote station is designated as station number . 5, via a linking option on the board. When a remote station detects its number, the lOµF capacitor associated with diode D22 charges up via a 120kQ resistor (from the decoded output of IClO). After about one second, pin 10 of IC8c will go high. This enables a Schmitt trigger oscillator based on ICl la which gates oscillator ICl lc on and off via IG11b. The output of ICl lc is buffered by ICl ld which then drives Q6 and Q7 and thence the buzzer. This provides the ringer for each extension. We should note that standard tone phones do have their own ringer but this requires a high AC voltage which the Interphone circuitry does not provide - hence the need for separate ringer circuitry. Q7 is supplied from the 50V DC rail, in order to provide a high drive voltage to the buzzer. Before we leave this part of the circuit, we should explain the reason for the one second delay provided by the lOµF capacitor at pin 13 of IC8d. This delay is necessary because if it was not there , then when the digits of a phone number were being pressed to dial out, the ringer would sound on each extension, corresponding to the digits being pressed. PARTS LIST Base station 1 large instrument case, Altronics Cat. H-0490 1 PO board, 130mm x 80mm 1 12VAC 500mA plugpack transformer 1 600Q isolation transformer (T1 ); Altronics Cat. M-1000 or equiv. 2 12V miniature relays 4 100kQ 1 82kQ 2 47kQ 610kQ 31kQ 3 470Q 2100Q Miscellaneous Hookup wire, phone sockets, solder, screws, nuts. Remote station Semiconductors 1 MC145436 DTMF decoder (IC1) 1 4028 BCD to decimal decoder (IC2) 1 4013 D flipflop (IC3) 1 4001 quad NOR gate (IC4) 1 4N28 optocoupler (IC5) 2 4093 quad NANO Schmitt trigger (IC6,IC7) 1 7805 3-terminal 5V regulator 3 BC548 transistors (01 ,02,03) 1 BD140 transistor (04) 5 1N914, 1N4148 signal diodes (D5, D6, D9, D11-D13) 11 1N4004 power diodes (D1 -D4, D7, D8, 'D10, D14-D17) 1 5mm orange LED (LED1) 2 5mm green LED (LED2,4) 1 5mm red LED (LED3) 1 3.58MHz crystal ,(Xtal1) Capacitors 2 1000µF 16VW electrolytic 1 1000µF 63VW electrolytic 2 470µF 35VW electrolytic 1 100µF 16VW electrolytic 4 10µF 16VW electrolytic 1 4.7µF 16VW electrolytic 2 1µF 16VW electrolytic 1 1µF 250VAC metallised polycarbonate 7 0.1 µF monolithic 1 220pF ceramic Resistors (0.25W, 5%) 3 1MQ 1 2.2kQ IC8a and IC8b detect when the extension phone is off the hook. When the phone is on hook, the voltage at pins 1 & 2 of IC8 is clamped at about +5.6V. When the phone is taken off hook, the voltage at the junction of the 2.2kQ and l00kQ resistors will fall to a low value and so pin 3 of IC8a will go high, which causes pin 4 of IC8b to go low and turn on transistor 1 PC board, 115 x 77mm 1 DTMF phone (tone phone) 1 100kQ trim pot Semiconductors 1 4001 quad NOR gate (IC8) 1 MC145436 DTMF decoder (IC9) 1 4028 BCD to decimal decoder (IC10) 1 4093 quad Schmitt trigger (IC11) 1 3.58MHz crystal (Xtal2) 6 1N914, 1N4148 diodes (D18,D19,D20,D21,D22,D23) 1 BC558 transistor (05) 1 BC548 transistor (06) 1 BD140 transistor (07) 1 red or green LED (Busy LED) Capacitors 1 10µF 16VW electrolytic 1 4.7µF 16VW electrolytic 2 1µF 16VW electrolytic 2 0.1 µF monolithic 1 220pF ceramic Resistors (0.25W 5%) 1 1MQ 410kQ 1 120kQ 1 6.8kQ 2 100kQ 1 4.7kQ 1 82kQ 1 2.2kQ 1W 1 47kQ 1 1kQ 2 22kQ Miscellaneous Phone sockets, hook up wire, screws, nuts, solder, etc. Q5. This causes the OFF HOOK voltage line to go high. This line is fed back to the Base Station board (Fig.1) where it is detected, as discussed earlier. This causes the Busy LED at all extensions to light. Next month, we will complete the description of the Interphone with the assembly and installation procedures. SC A UGUST 1992 75 AUSTRALIAN MADE ANTENNAE All Antennae Include • 75ohm Balun • PVC power coated aluminium boom • 3 year guarantee • UV resistant plaatlc insulators • Water reaisteant plastic balun caaing • Support off mast available. VHF Channels 0·11 UHF Channels 28·36 Suitable for prime.good signal reception area. This antenna is used for installation on houses, flats and, because of installation simplicity, on caravans and boats. 5ELEMENTS L 15020........ $44.95 ASRIGN~ Included with this antenna is a gutter grip mast and 8 metres of twin feeder cable. Suitable for good signal reception areas. Ideal tor houses, flats and caravans. Horizontal or vertical mounting is provided. 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Simply play the disc or cassette and tune In the signal on the FM tuner. Can also be used with radio headphones. • Mono or Stereo signals can be received. ANALOGUE WORKHORSE • Fuse and Diode protection •hFE measurements O • 1000 ( By x 10 range) ~ Mirror scale tor more accurate reading. RANGES • DC Voltage : O • .1, 0.5, 2.5, 10, 50, 250, 1ooov. (20k ohm/v) • AC Voltage: O - 10, 50. 250, 500V, 1000V (BkohmN) DC Current: 0·0.05, (50uA) 2.5, 25, 250m A • Resistance: 0·2K, 20K, 2M 20M ohm • Load Current : 0•150uA, 15mA, 150mA • Load Voltage:0•3V • Volume Level: ·10· + 22dB. + . 62dB • DC Current Ampl ification Factor: (hFE) 0·1000 ACCURACY • DC Voltage & Current: Within +/·3% t.s • Resistance: Within ::/· 3% Of arc. • Battery: 1.5V (um•3) 2pcs. 9V (oo6p) 1 pc • Fuse: o.5A, 50 x 20mm • Diode: 4148 x 2 • C.C: 0.04uff x 50V • Size: 147 x 99 x 57mm • Weight: 400g approximately LOGIC PROBES ANALOGUE / DIGITAL MULTIMETER 22 ELEMENTS VHF Channels 0-11 UHF Channels 28·36 (AS 20) UHF Channels 36·69 (AS 20/5) Suitable for medium signal reception areas with Improved VHF gain. 13 ELEMENTS L 10970..........$99.45 LOGIC PROBES 011020 ..............$59.95 AS 60 UV ~ O12105 ..........••........•... 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D . . $795 TTL PRINTER........ ..$89 6M AT EX/EXP... . .. ..... $325 FAX CARD ...........:::':.-::-:··· ...........$595 4PORT SERIAL CARD ............... ...... $199 2 WAY FOO CONT (360) .................. .$39 RS/232 SERIAL CARD ..... ............ ....$39 EPROM CMOSEPROM 2716 ... $11.75 2732 ... $9.00 2764 ... $6.95 27128.$7.50 27256.$9.00 27C32 .... $14.95 27C64 .... $5.50 27C128 .. $7.50 27C256 .. $9.00 27C512 ..$11.50 Matrix, 180 Cps Draft 30 Cps NLO, Pull Tra c tor C2 2074 ....................$365 FX·850 80 Col. 9 Pin Dot Matrix, 264 Cps Draft 54 Cps NLO Push Tractor Smart Park Feature .................. .............. $750 FX· 1050 136 Col. 9 Pin Dot Matrix, 264 Cps Draft, 54 Cps NLO. Push Troclor, Standard,Pu!Ul Trac tor Smart Park LQ• 1070 136 Col, 24 Pin Dot 0; LQ•400 80 Col, 24 Pin Dot Matrix, 180 Cps Draft, 60 NLO Pull Tractor C22070 ..................... $439 - LQ•S70 80 Col, 24 Pin Dot Matrix, 252 Cps Drstt, 84 cps, NLO Scalable Fonts 8 to 32 points, i 1 LO Fonts 360 x 360 DPI, Top, Rear, Bottom and Front paper feed paths, Convertable Puah/Pull Tractor. Smart Park Feature. ................................ ... .. $925 SQ-850 80 Col, 24 Nozzel ink jet, 600 Cps Draft, 198 Cps LO, Push Tractor, Smart Park f e ature. $55 Feature .................................. $ 1095 C22054 ................. .. $249 Matrix, 240 Cps Draft 48 Cps NLO, Push Tractor, Smart Park Feature 100+ $48 $15 $185 LQ•860 80 Col, 24Pin Do1 Matri x· 295 Cps Dra tt, 98 CPS LO. Colour LX·400 80 Col. 9 Pin Dot LX·850 80 Col. 9 Pin Dot 1-9 10-99 41256-08 .. ... $2 .95 $2.75 44256-08 ..... $7.95 $7.75 44256-07 ..... $8.95 $8.50 SIMMS 1-9 10-24 25+ 1M X 9· 70 $65 $59 $55 256K-ao $21 $19 $17 4M X 9-80 $239 $219 $199 SIPP$ 1M x 9-00 $79 $69 $59 - S·. ~ LO 100 80 Col, 24 Pin Dot Matrix 200 Cpa Draft, 72 LO, Friction paper · feed, 6 resident fonts, Very compact C22070 ................................$475 ~ · -----.::: · · OPI, Top, Rear, Bottom, and Front Paper Feedpaths, Convertable Push/Pull Tractor ................... ........ .. ......... $ TT5 " ' . ~ LQ• 1170 136 Col, 24 Pin Doi Matrix, 350 Cps Draft, 110 Cps y 1/ _j}y NLO, Scal able Fonts, 8 to 32 point, 11 LO Fonts, 360 x 360 · DPI, Top, Rear, Bottom, and .................................. $575 Front Paper Feedpaths, LQ•870 80 Col, 24 Pin Dot Matrix,330 Cps Drof~ 110 Cps NLO, Scalable Fonls, 8 to 32 points, 11LO Fonte, ........................................ $1,149 Convertah,e Push/Pull Tr ac tor LQ• 1060 136 Col, 24Pin Doi Matrix' 292 Cps Draft. 98 Cpa LO, Colour 360 x 360 OPI , Top, Rear, Bottom, & Front paper Feed paths Convertable Puah/Pull illiilli■ ....................... ............. $1,225 Matri x, 252 Cps Orafl, 84 Cps NLO, Scalable Fonts, 8 to 32 point, 11 LO Fonts, 360 x 360 Standard.Push Tractor, Smart Park l=eature. ............................................ $1 ,395 Tractor. ...................................... $895 LQ•2550 136 Col, 24Pin Dot Matrix' 400 Cps Drott, 133 LO Colour Standard.Push Tractor, Smart I ROD IRVING ELECTRONICS Pty. Ltd. ~.~'.~.~~~'..~.'.~:.................. $2,049 ACN.005428437 HEAD OFFICE: 56 RENVER RD, CLAYTON. PH : (03) 543 2166. FAX (03) 543 2648 CITY 48 A'BECKETT ST. MELBOURNE. PH. 663 6151 I 6391640. FAX: 639 1641, OAKLEIGH: 240C HUNTINGDALE 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 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 The•poetag• rate■ arw bulc po1ta91 only up to :~lty ~•: :gr:lgh~ 11,nw wt• be chorgod at clttorwnl r••• ~· .J... , _.. 'tj-n. I \\ 41 t. imi\1. TOLL FREE MAIL ORDER HOTLINE: 008 33 5757 OKILASER IT'S LOWEST PRICE EVER! 400 It's the cheapest it has ever been! The famous OKI LASER 400 Laser printer at only $1299! Reliable and compact, It fits neatly Into the smallest of offices. Highly reliable due to its latest LED imaging technology. The OL400 offers excellent print quality, superior paper handling, and a variety of fonts which rivals some of the more expensive laser printers on the market -.. 5 year warranty on LED system head. . . , No moving parts (LED SYSTEM HEAD) recycles its own toner! Approx. 1.8 t per $1095 Ex Tax Double your disk storage with .... DR DOS 6.0 The most advanced, fully DOS-compatible operating system available today. lt'a everything you need to run your DOS, Windows, and networking applications faster. Maximize hard disk performance, keep your system and Data secure, and make your PC easier to use. Only $1299 perlormane<1 so you can get more work done In leaa time. Its optional automatic file compreaaion feature potentially doubles your hard disk storage sp11e<1. MEMORYMAX: movea DR DOS buffers, drivers, TSRs and networking software outside the 640K memory area, leaving more memory for your DOS, Network and Windows applications. THIS MONTHS PRICE ••.•...• $89. 00 DISKMAX : Improves your PC's overall SOUND BLASTER 2 with FREE MINI SPEAKERS The sound blaster II is the ultimate sound board th,.t easily plugs into any slot In your IBM, PC, XT, AT, 386, etc. TEXT• TO SPEECH SYNTHESIZER • 11 VOICE FM MUSIC SYNTHES IZ ER • DIGITIZED VOICE OUTPUT WITH 4KHz TO 44,1KHz SAMPLING RATE • DIGITIZED VOICE INhJT (8 BIT ANALOGUE TO DIGITAL CONVEF:SION) • BUILT•IN MIDI INTERFACE FO'l CONNECTING MUSICAL INSTRUMENT. • BUILT•IN JOYSTICK PORT • BUILT•IN STEREO POWER AMPLIFIER SOUND BLASTER PRO MORE THAN JUST - LISTENING EXPERIENCE! THE SOUND BLASTER PRO CARD EASILY INSTALLS INTO YOUR IBM PC/AT AND 100% COMPATIBLES . (266 AND HIGHER RECOMMENDED) PACKAGE INCLUDES: • SOUND BLASTER PRO CARD • RCA AUDIO CABLE • 5.23" AND 3.5" DISKETTES • VOICE EDITOR 11 • SBTALKER (TEXT-TO·SPEECH SOFTWARE) • FM INTELLIGENT ORGAN SOFTWARE • CD MUSIC PLAYER • MMPLAY PRESENTER • DOS DRIVERS AND WINDOWS DLL • SB MIDI - A MIDI FILE DRIVER SOUND BLASTER PRO V2 MORE THAN JUST - LISTENING EXPERIENCE I THE SOUND BLASTER PRO CARD EASILY INSTALLS INTO YOUR IBM PC/AT AND 100% COMPATIBLES. (286 AND HIGHER RECOMMENDED) • BUILT•IN STEREO POWER AMPLIFIER BUNDLED SOFTWARE INCLUDES · SBTALKER FOR READING ASCII FILES & DR SBAITSO VOXKIT•VOICE DEVELOPMENT TOOLKIT FOR RECORDING SOUNDS TALKING PARROT MIMICS YOUR SPEECH FM INTELLIGENT ORGAN - CREATES ORCHESTRA LIKE MUSIC USING YOUR PC KEYBOARD AS INPUT. JUKEBOX - A WINDOWS THREE APPLICATIONS. X18012 ................ $199.00 SOUND BLASTER 2 with 256 COLOUR SPACE QUEST1 x1so1s •••• $229 • SBSIM - A SB STANDARD PROGRAMMING TOOL SYSTEM REQUIREMENT • IBM PC/AT OR 100% 286 ANO HIGHER COMPATIBLES (286 AND HIGHER RECOMMENDED) • MINIMUM 512KB RAM • DOS 3.0 OR HIGHER • EGA OR VGA l;-/GA RECOMMENDED) COMP,\ntJLE X18021 ........$369.00 • MMPLAY PRESENTER • DOS DRIVERS AND WINDOWS DLL • SB MIDI -A MIDI FILE DRIVER • SBSIM • A SB STANDARD PROGRAMMING TOOL PACKAGE INCLUDES : • SOUND BLASTER PRO CARD • RCA AUDIO CABLE • MIDI CABLES • 5.23" AND 3 .5" DISKETTES • SP PRO MIDI SEQUENCER SOFlWARE • VOICE EDITOR II • SBTALKER (TEXT-TO•SPEECH SOFTWARE) • FM INTELLIGENT ORGAN SOFTWARE • CO MUSIC PLAYER SYSTEM REQUIREMENT • IBM PC/AT OR 100% 288 AND HIGHER COMPATIBLES (286 AND HIGHER RECOMMENDED) • MINIMUM 512KB RAM • DOS 3.0 OR HIGHER • EGA OR VGA (VOA RECOMMENDED) CD-ROM PACKAGE t.lCROSOFT WINDOWS 3.1 (with Multimedia extensions) - Full Implementation of Microsoft Windows 3.1, 10 t.t, of help data, multimedia acceHorlea Including Music Box, Sound Recorder, Juke Box and more. This CD-ROM Drive provides a total solution• with a low coat entry into the revolutionary multimedia Information technology. A key component in the Multimedia Upgrade Kit, It hH a mas• atorage necessary to run the data~ntensive multim~is application. CDROM drive will also lit Into any 5.25" half-height drive bay on yo.., IBM compatible (XTa not compatible) FEATURES: • Includes S.iund Blaster Pro (ahort version) • CD quality sound (you can even play normal audio CD's) • Ability to display photographic Images & motion video (requires VGA display) • Audio jacks for quality sound through your own speaker aystem630 Mb of data on one compact disc • Full compliance with multimedia extensions 1.0 • Front mounted stereo headphone jack and volume control MICROSOfT® WINDCM'3'" X17050 ........$449.00 t.lCROSOFT BOOKSHELF- A complete referene<1 library with a n ~ · Encyclopedla, Thesaurus, Atlaa, Quotations, Book of Facts, ' ' · ·, ·· Dictionary and Columbia Dictionary of Quotations. • ,· . ~ ~ CREA nvE·s SOUNDS- Superb muelc and sound effects. , Includes audio Clips, 29 compositions In 4 formats and up to 111 aound effects. ', r .~ . . · .. • ·•. ,./ i,, '.' X17060a.a•$979.00 '. • ,.,,..!. ... 3 year warranty! RITRON QUALITY ;:::::;:;·,:::::i/ /'"'"''':::::':;:::;:::::;:;::::: ~ ~ i ~ ~ ~:::,; ;x:; ~ I. RITRON • •: ADD PRICE TO BASE SYSTEM COST. j 512K VGA CARD •• $50 I :;==,c:: SOFTWARE INCLUDED. $1299 TAX INC. :,,,lllJ/ j :::•: EXTRA RAM Genuine 80386SX-16 CPU 1 MEG RAM EXP TO 8 MEG AuSlralian, Fully Upgradable 21Mhz LANDMARK SPEED TEST DR DOS . 60 1.2M JAPANESE F.D.D. 512K VGA CARD supplied with 40M HARD DISK DRIVE, every system. 101 EXTENDED "CLICK" KEYBOARD MINI CASE & 200W POWER SUPPLY DOS 5 $50 extra SUPA VGA COLOUR MONITOR 1024x768 Res 0.28"DP SERIAL PARALLEL GAMES PORTS 3 YEAR PARTS & LABOUR WARRANTY IBM' COMPATIBLESPREADSHEET, WORDPROCESSOR & DATABASESOFTWARE $1,379 INCLUDED. • SHAREWARE SOFTWARE ASSEMBLED & TESTED TNACX. 1 ) ) ( } / / ) { ) ) $1,169 TAX EX ,.•.. ,- - - - - - - - - - - - - -;-.:--~--~~::- ....•t-== ---....:.---"'-----------""""""""""'"""...................'"""""'i $1099 RITRON EXECUTIVE ~•• • • • ·• • • •~~§--.§?' Genuine Australian, Fully Upgradable DR DOS 6.0 supplied with every syatem. DOS 5 $50 extra 80386SX 25M CPU 1 MEG RAM EXP TO 8 MEG 31 Mhz LANDMARK SPEED TEST 1.2M JAP F.D.D. 512K VGA CARD 40M HARD DISK DRIVE, 101 EXTENDED "CLICK'" KEYBOARD MINI CASE & 20/JW POWER SUPPLY SUPA VGA COLOUR MONITOR 1024 x 768 Rea 0.28" D.P SERIAL PARALLEL GAMES PORTS 3 YEAR PARTS & LABOUR WARRANTY IBM' COMPATIBLE SPREADSHEET, WORDPROCESSOR & DATABASESOFTWARE INCLUDED. $1 399 ' $1179 RITRON EXECUTIVE ~~~§rt~~~ 1 MEG add .. $65 2 MEG add .. $130 WINDOWS 3.00.$69 WINDOWS 3.1.$179 SOUND CARDS SOUND COMMANDER ... ... ............... $149 THUNDER BOARD .................. .... .... $199 SOUNDBLASTER II ............. ... ... ... ... $229 SOUNDBLASTER PRO ..................... $369 FLOPTICAL DRIVE add .. ....... .......... $849 21 M/BYTE DISC TO SUIT...... .. ....... $39 CD ROM DRIVE ..................... .......... $599 IN AUSTRAUA. TAX EX. RITRON 'SHAREWARESOFTWARE ASSEMBLED .S TESTED IN AUSTRAUA. lM VGA CARD .. $150 } TO CHANGE A 85M HARD DRIVE TO A ) 126M HD add $175 105M HD .. $105 . 200m HD add $575 180M HD .. $475 WJ~ /.t~ 80286-16 CPU Genuine 1 MEG RAM EXPANDABLE TO4 MEG Australian, Fully / 21 Mhz LANDMARK SPEED TEST Upgradable \ .. 1.2M JAPANESE BRAND F.D.D DR DOS 6.0 \ 40M HARD DISK DRIVE 28ms ACCESS supplied with :::: 101 EXTENDED "CLICK" KEYBOARD every system. } JAPANESE KEYBOARD SWITCHES DOS 5 $50 extra ;:: MINI CASE & 200W POWER SUPPLY - - - - - ~ 1-:: SUPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28" DP :'· 2 SERIAL, PARALLEL, GAME PORTS . 3 YEAR PARTS & LABOUR WARRANTY 512K VGA CARD. IBM' COMPATIBLE SPREADSHEET, WORDPROCESSOR & DATABASE ;:;:::::,:::::::,::,://i::::: TAX INC. TAXEX :D 80386-33 CPU 64K CACHE ON BOARD ..........,.Ge_n_u_in_e_-. MEMORY 1 MEG RAM EXP TO 16 MEG Australian, Fully 57Mhz LANDMARK SPEED TEST Upgradable 40 MEG HARD DISK DR DOS 6.0 1.2M JAPANESE BRAND F.D.D supplied with 101 EXTENDED "CLICK" KEYBOARD every system. SERIAL PARALLEL GAMES PORT DOS 5 $50 extra MINI CASE & 200W POWER SUPPLY SUPA VGA COLOUR MONITOR (1024 x 768 Rea) 0.28" DP 512K VGA CARD (256 COLOURS) IBM' COMPATIBLE 3 YEAR PARTS & LABOUR WARRANTY SPEADSHEET, WORDPROCESSOR & DATABASE SOFTWAREINCLUDED. 'SHAREWARE SOFTWARE $1 649 ASSEMBLED & TESTED IN AUSTRALIA • ' $1,399 TAX INC. TAX EX t === -=-=~==--=~:"-'"------""-"'-=""-"""'-",i RITRON EXECUTIVE ~ l3~§,t§s>9 :: 80386-40 CPU 64K CACHE ON BOARD : 1 MEG RAM EXP TO 16 MEG i 65 Mhz LANDMARK SPEED TEST •·· 40 MEG HARD DISK 12ms ACCESS TIME -::. 1.2M JAPANESE BRAND F.D.D ·'· 101 EXTENDED "CLICK" KEYBOARD MINI CASE & 20/JW POWER SUPPLY SERIAL, PARALLEL, GAMES PORTS 512K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28" DP 3 YEAR PARTS & LABOUR WARRANTY SPEADSHEET, WORDPROCESSOR & DATABASE SOFTWARE INCLUDED. 'SHAREWARE SOFTWARE ASSEMBLED & TESTED IN AUSTRALIA. $1,679 ~:t $1,399 TAXEX. WITH 200 MEG DRIVE $2,254 TAX INC. $1,895 TAX EX. • Genuine 80486SX-20 CPU Australian, Fully 1 MEG RAM EXP TO 32 MEG Upgradable 75Mhz LANDMARK SPEED TEST DR DOS6.0 40 MEG HARD DISK supplied with 1.2M JAPANESE BRAND F.D.D every system. 101 EXTENDED "CLICK" KEYBOARD DOS 5 $50 extra MINI CASE & 20/JW POWER SUPPLY 3 YEAR PARTS & LABOUR WARRANTY SERIAL, PARALLEL, GAMES PORTS, 1MEG VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Res) 0.28" DP SPEADSHEET, WORD PROCESSOR & DATABASE SOFTWARE INCLUDED. •SHAREWARE SOFTWARE Genuine Au stralian, Fully Upgradable DR DOS6.0 supplied with every system. DOS 5 $50 extra ASSEMBLED & TESTED IN AUSTRALIA. $1 7 9 9 ' TAX INC. WITH 200 MEG DRIVE $2,374 TAX INC. $1,999 TAXEX. $2,299 $1,949 WITH 200 MEG DRIVE TAXINC. TAXEX. ROD IRVING ELECTRONICS Est. 1977. MAIL ORDER HOTLINE: 008 33 57 57. ORDER FAX LINE: (03) 543 4871 ENQUIRES (03) 543 7877 HEAD OFFICE: 56 RENVER RD, CLAYTON. PH: (03) 543 2166. FAX (03) 543 2648 CITY 48 A'BECKETT ST. MELBOURNE. PH. (03) 639 1640. FAX: 639 1641. OAKLEIGH: 240C HUNTINGDALE RD, OAKLEIGH. PH: (03) 562 8939 FAX: (03) 562 8940 NORTHCOTE 425 HIGH ST. NORTHCOTE, PH. 489 8866. FAX: 489 8131. SYDNEY:74 PARRAMATTA RD, STANMORE. PH: (02) 519 3134. FAX: (02) 516 5024 BLUESTAR COMPUTERS: MELBOURNE: 271 MAROONDAH HWY, RINGWOOD, PHONE: (03) 870 1800 FAX: (03) 879 3027 SYDNEY: 115 -117 PARRAMATTA RD CONCORD. PH: (02) 744 5526 FAX: (02) 744 5405 $2,874 $2,399 TAXINC TAXEX FREIGHT CHARGE BASED ON 35KG COMPUTER SYSTEM $2,795 TAXEX. All sales tax exempt orders to :RI TRON ICS WHOLESALE 56 Renver Rd, Clayton, Victori a . Melb-Metro.$12.00 Vic country•... $19.00 Sydney....... $17.00 NSW country.$39.00 Adelaide ..... $17.00 S.A country.-$39.00 Bribane ...... $24.00 OLD country.$55.00 Canberra •••• $18.00 W.A country.. $74.00 Oarwin. ....... $40.00 Insurance :• Perth .....•••••• $31.00 $1 / $100 Value. Taamania....$53.00 Ph: (03) 543 2166 Fax: (03) 543 2648 MAIL ORDER & CORRESPONDENCE P.O BOX 620, CLAYTON, VICTORIA. 3168. Errora & ommlaeona excepted. Pricea & apeclflcatlona .,bfect to change. •reM, PC, XT, AT, are reglatered trademartc a of lntem atfonal BualneH Machlnee. PRICES AT AUS $• US $0.74 ~F== ~F== QUALITY 3mm LEDS 1-8 10-111 100+ """~ ,,.~ 1-8 Z1014'l(R) $0.15 Z10141(G).. S0.20 Z10143(Y). $0.20 Z1014S(O) .. $0.20 10-98 S0.12 S0.18 S0.18 S0.18 100+ S0.10 S0.15 S0.15 S0.15 QUALITY 5mm LEDS BNC PANEL SOCKET 1·8 10+ 100+ P10516 $2.50 $2.25 $1.50 BNC CRIMP PLUG 1.e 10-88 100+ P10530 $3.95 $3. 75 $3.00 ~) BNC SOLDERLESS TWIST ON PLUG Z10150(R). $0.15 $0.12 $0.10 Z10151 (G). $0.25 S0.20 $0.18 Z10152(Y).. $0.25 S0.20 $0.18 ------ FLASHING LEDS RED 5mm 1-9 10+ Z.1 0159 $1.10 $1.00 -== These pin• are not gold plated so they are much cheaper. They are suitable to; wire wrapping and flt holes of 1mm (0.04") diameter. Two types are available. Single aided and Double aided. -~ ...--b DOUBLE SIDED Packet of 20 Hl 1680 .................$3.95 Packet of 100 H11681 ..•......••..... $18.95 Packet of 500 H11682 .......•.....•..$85.95 1.9 10+ 100+ RED 20e 15e 12e GREEN 20e 15e 12e YELLOW 20e 15e 12e ORANGE 20e 15e 12e 1.9 10-88 100+ P10962 $3.50 $2.95 $2.50 """ ' i:JS .,. , 1.9 10-88 100+ CANNON TYPE 3 PIN CHASSIS FEMALE 1-9 10-99 100+ WIRE WRAP IC SOCKETS TheN qualHy 3 levol wire wrap sockots aro tin plated phosphor bronze. P10579 Spin $1.50 $1.40 P10580 14pin $1.85 $1.70 P1058516pin $1.95 $1.80 P10587 18pln $1.95 $1.80 P10590 20pin $2.95 $2.75 P10592 22pin $2.95 $2.70 P10594 24pin $3.95 $3.50 P10596 28pln $3.95 $3.50 P10598 40pin $4.95 $4.50 c:::, CANNON TYPE 3 PIN LINE MALE COMPUTER CABLES • She eonduclor ■h leldN computer lnlet11c. cable. W12670 • CIC& 6 con. 1-9M 10M+ 100M+ $1.30M $1.1 0M $1.00M W12672 • CIC9 9 con. 1-8 M 10M+ 1-9M 10M+ j,nnnm WIRE WRAP IC SOCKETS These qualHy 3 level wire wrap sockets are tin plated phosphor bronze. P10579 Spin $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 40pln $4.95 $4.50 100M+ $1.60M $1.50M $1.20M W12674 • CIC12 12 con. 1•IIM 10M+ 100M+ $2.50M $2.20M $1.90M W12676 • CIC16 16 con. 1.11M 10M+ 100M+ $3.SOM $3.20M $2.50M W12678 • CIC25 25 con. 100M+ $3.90M $3.40M $3.00M ELECTRET MIC INSERTS With pin• for N ■ y board ln....Uon. C10170 1-8 10-98 100+ $1.20 $1.00 $0.90 Packet of 20 H11690................$3.50 Packet of 100 H11691 .....•......... $17.95 ULTRASONIC TRANDUCERS Designed to transmit at 40kHz (L 19990) & recieve at 40kHz (L19991) withup to 20V 1/P on the transmitter. These unite can•t be heard ao are ideal for TV remote controls. water level dectectors, burglar alarma, motion c:=::r-o SINGLE SIDED C MOSFET ..__ _ sP_E_c_IA_L_s_ RECTANGULAR LEDS ( IC SOCKETS ) CANNON TYPE 3 PIN LINE FEMALE ,-._;..;.------, We have a great range of penel meters at great priceal 010500 MU45 0·1mA $9.95 010502 MU45 50/50UA $9.95 010504 MU45 0-100\IA $9.95 010533 MU52E 0•5uA $12.95 010538 MU65 0-50uA $12.95 010540 MU65 0•1mA $12.95 010550 MU650-100UA$12.95 010560 MU650-20V $12.95 dectectors & information carriers as they can be either pulsed or used in a continuous wave mode. Transmitter 1·9 10+ L19990•.•..•• $2.95 $1.95 Receiver L1999t ....... $2.95 IDC PLUGS & SOCKETS WOW I FROM $1.00 D TYPE IDC PLUGS 1..S 10+ 100+ • DE9P Spin plug P12166 $1.50 $1.20 $1.00 • DA15P 15pln plug P12168 $1.50 $1.20 $1.00 • 0825P 25 pin plug P12170 $4.50 $3.95 $3.50 -- DTYPE IDCSOCKETS 1-8 10+ 100+ • DE9S 9 pin eocket P12167 $1.50 $1.20 $1.00 • DA15S 15 pin eocket P12168 $1.50 $1.20 $1.00 • 0B2SS 15 p,n eocket P12171 $4.50 $3.95 $3.50 VOLTAGE REGULATORS BARGAINS DeecrtpUon 1-8 1 O+ 7805UC 7812UC 7815UC 7905UC 7912UC 7915UC 78L05 78L12 LM324 555 741 $0.50 $0.50 $0.50 $0.60 $0.60 $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 IDC CENTRONICS 36 WAY PLUG & SOCKET 1·9 10+ • Plug P12200 $3.95 $3.00 • Socket P12201 $3.95 $3.00 DB25 CONNECTOR SPECIALS P10880 DE9P P1088.5 DE9S P10891 DA15S P10892 DA15C P10895 DA15S P10902 DB25C P10904 DB25P P10905 DB25S 1·9 10+ $1 .00 $0.80 $1.00 $0.70 $1.00 $0.70 $1.00 $0.90 $1.00 $0.80 $1.00 $0.80 $1.00 $0.80 $1.00 $0.80 ECONOMY TRANSFORMER 1·8 10+ 2155 240V 6-15V 1A 1112155 ......... $8.95 $7.95 2156 24'lV 6-15V A2 M12156 .•...• $13.95 $12.95 2851 240V 12•6V CT 250rnA M12851 ......... $4.95 •• $4.50 66 72 240V 15 30vc 1A lapped M16672 ........$12.95 $11.95 CR__) 12VDC FANS 80 X 80 X 25.4mm 12V DC. 1.7 Watt 0.14 Amp T12469 .••••••••••.•.• $18.95 10+ fans. only $17.95 FANS QualHy fans for use In power amps, computer hotspot cooling otc. Anywhoro you nood plenty of air. 240V 4 518.. T12461 ..$16.95 115V 4 518.. T12463.. $16.95 240V 3112.. T12465 .. $16.95 115V 3 1/2.. T12467.. $16.95 10+ fan ■ (mixed) Only S14.95. NEW SWITCH BOXES 100+ $2.95 9 PIN D SWITCH BOXES $2.95 2 WAY............... $59.95 ~ 4 WAY..•••••••..•••. $69.95 ~ MONITOR & KEYBOARD SWITCH BOXES only $69.50 ) _, ~ 2SJ49 2SJ56 2SK134 2SK176 C 1-9 $9.50 $10.00 $8.50 $9.50 10+ $8.00 $9.50 $8.00 • 1/4" NUT DRIVER • 3/16" NUT DRIVER • 3 CLAW PARTS RETRIVER/EXTRACTOR •TWEEZERS • T10, T15 TORQUE SCREWDRIVER • #1 PHILLIPS SCREWDRIVER • 3/16" FLAT SCREWDRIVER • IC EXTRACTOR • IC INSERTER, 14-16 PIN 1c•1 • #0 PHILLIPS SCREWDRIVER • 1/8" FLAT SCREWDRIVER • VINYL ZIPPER CASE TOGGLE SWITCHES $8.90 NICADS ) ~ Save a fortune on expensive throw away batteries with these quality Nicada and Rechargeral Size M •somAH 1~8 10+ $2.95 $2. 75 SlzeC 12AH $9.95 $9.50 SlzeD 12AH $9.95 $9.50 WIRELESS MICROPHONE 100+ $2.50 $8.95 1; .- . $8.95 PS2 CONNECTORS .. Tuneable:92-104MHz Freq response: 5015k Hz. Range: over 300 feet In open field. A 10450...•...... $24.95 HEATSINK COMPOUND VGA MONTOR AD A.l.'I.QR DB·SP FEMALE TO HD•15P MALE .X15670•..•..........••.......... $14.95 MOUSE ADAPTOR DB·9PMINI DIN 9P PLUG X15672 ................•..••......$14.95 Heatsink compound is applied to the base and mounting studs of transistors & diodes. It maintains a positive heateink seal that Improves heat transfer from the device to the heateink, thus increasing overall efficiency. H11800 .. 10g.•. $2.00 H11810.150g. $29.95 .:J FJ.~~ ENCAPSULATED SOLAR CELL MODULE 0.45V 200mA SOLAR BICYCLE WARNING LIGHT AND BATTERY CHARGER. for 2 'AA' size batteries 219056 ..................$19.95 SOX 18mm Pack of 4 These are Ideal for almple aolar experimemta. Can be connected with other aolar cell•. 219001 ....................$2.95 • ~SOLAR MOTOR KIT This la a great starter kit conaiatlng of a 0.9V 400mA solar cell and a email motor with a 48" wlra. Graat for beginner or just the curioual 219040 ................$9.95 Learn what solar power la and how to build your own solar ayatem. With thla graat kit you can make an electrical circuit. Learn how to lncraase voltage, learn how to Increase currant, learn how to make a aolar panel, use aolar power to produce the energy for a radio, calculator battery charger or 1.5V CHaatta player 219.22.95 ___ --''-- SOLAR WOODEN MODELS Build great little aolar powered wooden models with Ihle kill Thera are 3 different model• to chooaa from a helicopter with working motor, Nroplane with working motor and gramophone that playa music. Each kit contalna a aet of precut plywood, PVA cement, aaaembly lnatructlon sheet, aol ■r cell module, mualcal IC or email DC motor, wire and Hnd pap«. 219044 Aeroplane.....••....$19,95 219046 Gralnophone ......$1 ~,95 219048 Hellcopter...........$19.95 MOUNTING HARDWARE L-SHAPED CORNER BRACKETS H11860 ...................$4.95 SOLAR MUSICAL KEYCHAIN WITH LIGHT. Never lose your keya again with thla clever little device. The solar powered keychaln with light will let you find where you left your keys where you left them juat by listening to music. The aolar powered light will alwaya let you find that Illusive keyhole In the dark. A very handy Idea and all run on FREE powerl I BONDED HEATSINKS IDEAL FOR HOT IC'S Length 32mm H10668 ...............••......•.$2.95 Length 19mm H10670 .........................$2.50 • Double Insulated Input: 240 Volt 50Hz 2AMP Rating: 2 Mins on - 30Minsoff Field Strength: 4700 AT Made in Australia T12316 ..................$98.95 rJ 219060 ...................$4.95 \ I; SOLAR CAR BATTERY CHARGER Never worry about your car battery going flat when left without being used over a prolonged period of time. Simply place the aolar power unit on your daah or near a window In your garage and plug It Into your car cigarette lighter. The unit conelata of solar cella In a houalng with 1 rnetra of cable and cigarette lighter plug. 219054..................$29.95 Colour: Multi. Reel alze: 100m 12 conductor flat rainbow cable. Each 1.2mm diameter cora la colour coded and can be easily eeparated. Conductor• 12 x 7 atranda/0.12mm •••••• PVC: Each with 1.2mm dia. CB MIC HOLDER Designed for CB and other communication microphonea. • S~rew mounting • Mounting alot allows mic to be quickly removed or reheld. KEYCHAIN B_ATTERY ANALYZER FOR TESTING ALL SIZES OF BATTERIES 219062...................$4.95 ................................$1.95 Ideal for Joining wlrea and cablea together •12 amp • Sia: 0.5-1 .Smm • Gauge: 22-16 100Pcs ..........................$14.95 •20 amp• Sia: 1.5-2.Smm • Gauge: 16-14 100Pcs •............$15.45 •SO amp • Sia" 2.5-6.0mm • Gauge: 12-10 100Pcs.............$15.95 TTTT INSULATED STAPLES 12V 16V(max) 18V lsc 1200mA (max) 1500mA Z19038 ................$299.00 25 ....•..•...............$1.95 DISK LABELS (To fit 3.5.. disks) c21022 Oty. 25 ........••••..•........ $1.95 id==j[D= ] Set of SO hexagonal nuta designed for securing lnline chaaala computer .. D.. connectora. Fila moat standard size hardware aupplied with 9, 1S, 19, 23 and 25 .. D.. lype male and female computer connectora. (To fit 5.25.. disks) c21021 Oty. 25 labela & 25 wrile Pack of 50 ..............$7.95 protecta ••••••••••••••••• $1.95 For apaaker cable and other figure eight cable. • Takea cable with a maximum width of 5 mm. Pack of 100..........................$4.50 DISK LABELS & WRITE PROTECTS ~1 75OHM 3WAY SPUTTER Splits UHFNHF/FM algnala. • Input: 1 x 75 ohm screw terminala. • Output: 2 x 75 ohm acrew terminals (4dB) 1 x 75 ohm with AC power paaa (BdB) • Bandwidth: 5-890MHz ' I I INTEL A-4 COPY PAPER BOGMSWHITE RECOMMENDED FOR HIGH SPEED COPIERS/LASER PRINTERS. ALSO AVAILABL IN RECYCLED PAPER CO-PROCCESSORS ····························· ·········$7. ................................$7.95 CRIMP CONNECTORS • NYLON 12V. Voc16V(max)18V lsc 400mA (max) S00mA Z19028 ..............$99.00 DISK 1:NVELOPES Protect your 5.25.. dlaka from duet with theee dlak envelopes C21020 Oty . MOUNTING HARDWARE RIBBON CABLE 12V Voc 16V (max) 18V lsc B00mA (max) 1000mA Z19036 .•• ••........ •.. $199.00 SOLAR BATTERY CHARGER FOR 'AA' SIZE BATTERIES 219050..................$12.95 ARLEC DEGAUSSING WAND for colour TV • Cat No. U21841 U21851 U21854 U21855 Type 287XL 387DX 387SX·16 387SX-25 3.5" HARD DRIVE MOUNTING KIT 2 Universial -brackets with acrewa to mount 3.5.. hard drives Into computer cuea X19971 ••• •••••.••••••••••••••••••.••• $9.95 The Story of Electrical Energy, Pt.19 Electricity for electric traction came to Sydney over a century ago. In the early days, all electric power was DC and much of it came from the Ultimo power station. By BRYAN MAHER After a disastrous start in 1861 with George Train's horse-drawn trams in Pitt Street in 1879, Sydney substituted steam tram locomotives to haul passenger cars in city streets. The steam tramway depot at Randwick, then called the Locomotive Workshop, was in fact a part of the Railway De82 SILICON CHIP partment. There, at the corner of Randwick and Darley Roads , is where our story begins. On 22nd May 1886, the New South Wales Railways opened a cable tramline from Milson's Point ferry wharf. It ran 2.4km up the hill to Ridge Street, where the steam driven winding en- gine was located. Seven years later, it was extended 1200 metres to Crows Nest. A similar service on the city side in 1894 encompassed King Street, Queens Square, College and William Streets, King's Cross, and terminated in Ocean Avenue, Edgecliff. This 4km line was powered by a steam engine at Rushcutters Bay. In 1895, the Public Works Department saw Ridge Street and Rushcutters Bay as the nuclei of future electric tram systems. Thus, these short-lived cable lines were vital to our story. First electric traction The first electric traction in Australia was a trial trip by a Julien accumulator tramcar on the Sydney to This is one of the three experimental electric tramcars used in Sydney from Randwick to Waverley from November 1890 to August 1892. It carried 26 passengers. Each axle was initially driven by a 550V 10HP (7 .5kW) high speed DC motor through double reduction gears. (Photo from SRA/UTA archives). Botany steam tram lines on 1st June 1888. The rechargeable battery proved too expensive for a permanent system, however. The first powered system was the demonstration tram provided by the Thompson Houston Electric Co. of Boston, USA. It ran at the' Melbourne Exhibition from 1st August 1888 until 11 March the next year. After that, the machinery was sold to a development company which operated the tram as a land sales incentive on the Box Hill to Doncaster (Melbourne suburbs) line in 1889. This ceased running after seven years, leaving Victoria without a service for another decade. Facing page: taken in 1899, this photo shows one of the original steam driven generators in the Ultimo power station. Primarily installed to power Sydney's electric trams, the system underwent major expansion over many years to eventually supply most of Sydney's demands for power. By that same year, 1889, Sydneysiders had grown tired of the dirt, noise, cinders and smoke from their steam engines. Subsequent to the visit by a Randwick engineer to the United States, the first Sydney electric trams ran on Sunday afternoon 15th November, 1890. Heavy passenger traffic was carried the next day, it being a public holiday. This experimental service was planned to run on the existing crosscountry Waverley to Coogee steamtram tracks. But the railway commissioners voted only 5000 pounds for the project, sufficient only to electrify the Rand wick Workshops to Waverley section via Randwick and Frenchmans Roads. This 3.3kmroutehadgradesof5.5% and curves of 33-metre radius. The overhead trolley wire was suspended from poles, with four different types of timbers - ironbark, turpentine, grey and blue gum - being used to assess the most suitable. All rails were bonded to an 0-gauge buried copper conductor running throughout the route. Three 26-passenger cars were 1 provided by the Thompson Houston Company, each a four-wheeler C Class. Each axle was initially driven by a 550 volt 10 horsepower (7.5kW) high speed DC motor through double reduction gears. Carbon brushes, as patented by C. V. Depoele in 1888, were used. Later, 25hp (19kW) motors were substituted. The driver and the equipment were in a very exposed position. The original flat face controller was mounted under the floor, operated from either end by a chained sprocket mechanism. Series-parallel resistance starting was used even then. All under-floor switchgear was later replaced by rainproof direct drum controllers mounted at both ends. In this type, copper strips mounted on avertical rotating spider assembly contacted sprung fingers connected to starting resistances. To stop the car the driver could "plug" the motors ie, switcp. them into low power reverse or he could apply the hand brake. (True regenerative braking came many decades later). The Thompson Houston F30 motors, each weighing 896kg, were primitive. On a 550V DC supply and running at 1000 RPM, they consumed 25 amperes. The armatures were surface wound and the gears, field coils, cornAUGUST 1992 83 This drawing shows the details of the 4-wheel base used on Sydney's first electric trams. The motors were of completely open construction and used double reduction gears. mutators and live brush gear were all exposed to road dirt and wet weather, causing numerous breakdowns . Power came from the Randwick workshops where an Armington Sims 120hp (90kW) steam engine was direct coupled to a Thompson Houston shunt wound DC generator. At 300 RPM, this 60kW machine was supposed to generate 550 volts but because the steam supply was insufficient, it never put out more than 500 volts at best, leaving the trams underpowered. Though these first three cars gave good experience to the engineers, their problems and running costs caused suspension of service in August 1892. In its eight months of running, this first electric service carried 132,240 paying passengers! Eventually, in 1893, the generating plant and cars were transferred to Ridge Street, North Sydney where they initiated the Military Road run. A trial electric tram attempt was also made at Rushcutters Bay. Electric lighting Electric lighting had been used in Sydney many years before the first traction experiments. One solitary arc lamp at the Observatory lit up the sky on 11 June 1863 for the Prince's visit. The next occasion was in 1878 when the hurried construction of the Exhibition Building saw the builders working at night under temporary electric arc lamps. The first permanent installation was at Eveleigh railway sheds in June 1882. Three Edison bipolar DC generators 84 SILICON CHIP and some Brush arc lighting machines were driven by two Westinghouse single acting steam engines. Line shafts and long flat belt drives were state of the art in those days. The generators powered brilliant arc lamps with two carbon electrodes. This new Eveleigh plant illuminated the loco sheds and surrounds, the extensive Darling Harbour goods yards, and Sydney's original railway terminal station which was Redfern. Out in the west, Clyde railway yards were lit in 1896 using Brockie-Pell type arc lamps. These were powered by a 30kW bipolar Crompton series machine generating 3000 volts DC. All the arc lamps were connected in one big series circuit in which 6.6 amps circulated. (Much later, the arc lamps were replaced by 6.6 amp incandescent lamps). Also at Clyde was a 6kW 110 volt machine made by the Mather and Platt company. The success of this venture prompted the building in the same year of the first electricity transmission line in the state. This ran from the Clyde generators to Flemington stockyards (now the site of the Sydney markets). Early staff In January 1891, the entire staff of the railways electric lighting section consisted of three men and a boy, accommodateJ in an old railway van parked in Sydney yard. In that same year, Mr P. B. Elwell was appointed Railways Electrical Engineer. Given charge of all lighting equipment plus the Randwick enterprise, this man went on to design and direct much of Sydney's early electrical development. His original little section mushroomed into the huge Railway Electrical Branch of which he became first Chief Electrical Engineer. Rushcutters Bay power house Initially, the New South Wales Public Works Department proposed a tramway electric power station on the shores of Rushcutters Bay. Coal was to be brought in by barge on the harbour. The government's plan was to electrify the King Street cable tram line using the existing depot at the Bay as the power station. They had similar plans for another electric power house at Ridge Street. Mr Elwell had other ideas and proposed a much larger central power station to be built in Harris Street, Ultimo, between William Henry and Macarthur Streets. Rail transport for coal supply and ash disposal was already available via the existing Darling Harbour goods yard and there was ample land for expansion. Mr Elwell selected a 4.5-acre site for the planned power station and tram car sheds. This land was purchased for the princely sum 7727 pounds 12 shillings and 11 pence. However, the authority for this action came in a rather devious way. The Public Works Department had recommended in 1896 that the George and Harris Street tramlines be electrified but that the power house be at Rushcutters Bay. Attempts to change the Public Works plan would require, by law, further long drawn out investigations by committees. But the Rail- Another view of Ultimo power house, taken in 1899. This shows the classic construction of those early machines and the extensive switchboard which occupied most of the 30-metre wide north wall. The platform was elevated 4.27 metres above the floor, thus giving the operator a clear view of all machinery way Commissioners, unfettered by any such regulation, were legally able to proceed immediately. So they did, invoking their choice of the Ultimo site. Mr Elwell envisioned far more than· the electrification of just a few streets. He and his successors foresaw the whole of Sydney being served by fast, clean electric trams. And furthermore, Ultimo was closer (than Rushcutters Bay) to the centre of the existing tramway network. That was important to minimise feeder length. Long lines at 600V DC, the only technology available at the time , would be plagued by serious voltage drop problems. Initially, Ultimo was seen as a 20,000hp (15MW) station. Sadly, Mr Elwell died in September 1899 before his dream was fulfilled. But he was ably succeeded by his deputy Mr 0. W. Brain. The speed of construction in those days was amazing, especially by today's standards. On the 16th November 1896, Parliament voted 150,000 pounds towards the electrification of tramlines. Three weeks previously, the Railway Commissioners were given authority to provide electric traction on all present and future lines. By June 1898, the site for the power station was excavated, tenders for machinery accepted and the chimney construction well advanced. First test run On 22nd November, 1899, the power station was built and running, and the first test run of an electric tramcar through Harris and George streets was successful. During the following week, members of Parliament rode on the cars and the power station was completed and opened for inspection. Nine days later, Sydney celebrated the official opening with ceremony and fanfare . Prior to that, on 12th July 1897, a tender was accepted from Kingsway Co of Sydney, representing General Electric of USA, for the supply of four complete steam engines with direct coupled 550V DC generators. The original specification of 800kW each was raised to 850kW at 600V at GE's suggestion. The first four Ultimo machines were 2-cylinder double expansion double acting horizontal steam engines. After the steam did its expanding in the large 660mm-diameter high pressure cylinder, it passed to the even larger low pressure cylinder. Though the steam was then at lower pressure, because of the huge 1219mm diameter of the low pressure cylinder, both cylinders did equal work. In each ep.gine, the two cylinders were mounted parallel to one another, a construction known as cross-compounding. Piston rods, slides and connecting rods delivered the power to two cranks on a single crankshaft. Between the cranks were mounted the enormous flywheel and the generator armature, both pressed and keyed onto the shaft. The engines develop ed 1212hp (905kW) when running at 100 RPM. At this speed, the 6.1 metre diameter 45-tonne flywheel was fairly flying around with nearly 20 megajoules of stored rotational energy - the "spinning reserve" . The engines were manufactured by E. P. Allis and ComAUG UST 1992 85 This strange looking contraption helped early Sydney trams up the steep hill from Balmain wharf. This was a dummy truck which was pushed downhill by trams. It was connected to a heavy counterweight truck which ran on rails underne_ath the road. The heavy counterweight then gave assistance to the trams when they climbed back up the hill. pany (later Allis Chalmers) of Milwaukee, USA. Huge for their time, the 12-pole 850kW generators were a fascinating sight. The twelve sets of brush gear around the commutator were adjustable for minimum sparking under the 1545 amperes full load current. The armatures were enormous, being 2.75 metres (9ft) in diameter. Two governors were fitted to each engine. One was belt-driven and was a low speed centrifugal type. This controller adjusted the steam valve, to maintain shaft speed between 98 and 102 RPM at any load. However should the belt break or slip off, all control would be lost. Therefore a second regulator, driven at high speed by eccentrics on the main shaft, would shut off all steam if the shaft speed exceeded 105 RPM. These centrifugal controls were after the 1849 designs ofT. H. Corliss of the USA - designs which were progressively improved by the inventor and the Reynolds company. Electrical switchgear The first switchboard gallery was a massive assembly of fireproof insulating slate panels mounted on steel 86 SILICON CHIP frames . Occupying most of the 30metre wide north wall of the engine house, the platform was elevated 4.27 metres above the engine room floor, giving the operator a clear view of all machinery. The Cedar timber handrails and the white-tiled walls and floor attested to the artistic flair of the designers. Five large panels in the centre of the switchboard contained one section for each generator plus a summation panel. Each generator board held a dynamic ammeter, a magnetic blowout circuit breaker, hand-operated switches and a recording ammeter, each rated at 2000 amperes. Other panels controlled batteries, lighting, and 10 outgoing 600V DC distribution feeders. Voltmeters showed the generated potentials. All this switchgear, supplied hy H. H. Kingsway and Co of Sydney, wc1s hand operated by staff who became accustomed to working and walking close to live 600 volt equipment. The original Ultimo boilers were a world apart from today's monsters. Fourteen "Colonial" horizontal firetube boilers were arranged in two batteries of seven. These were manufactured by G.& C. Hoskins of Sydney. Coal, delivered by railway hoppers, was dumped into a bin from which wheelbarrows and handcarts on small rails delivered the fuel to the boiler room. Firemen hand shovelled the coal into the furnace in the same manner as would a steam loco fireman. With no windows provided, the boiler room was a very hot, dirty, exhausting workplace. Ash handling was an horrific occupation in the ash tunnel below the boilers. Sweating men heaved the red hot ashes into trucks for disposal and broke up clinker with iron bars which caused hot ash to fly. Burns to the face and arms were common. Exit steam from the engines condensed to water in cylindrical condensers cooled by salt water. This was pumped 305 metres from Darling Harbour in two conduits, each a metre diameter. Each centrifugal pump was driven by a 4-pole 600V DC motor, an advanced feature for that time. The 30hp (22kW) motor driven pumps could shift 150 litres of water per second. Boiler feed water, distilled from the town supply, was pumped into the boilers by two 3-cylinder plunger pumps, each driven by a 19kW electric motor, with an emergency steam driven pump on standby. Today, all this seems easy but in 1898 it was state of the art technology. The electric tram system expanded rapidly. By mid July 1900, there were 50km of electrified tram tracks in Sydney, including both sides of the harbour. To supply the system with 600V DC, positive and negative feeder cables fanned out to all electrified lines. The positive feeders joined to the sectionalized overhead trolley wires. The grounded negative (more properly "zero") cables were connected to the running rails, all of which were bonded together. In the city underground, feeder cables were laid in Callender-Webber bitumen casing under the footpaths of Liverpool Street and between tracks in George Street. Junctions were made in brick or cast iron pits which gave trouble because of water entry. The cables were manufactured by Callender & Co of England and insulated by vulcanised bitumen! A small fraction of the power for the North Shore line was generated initially at the Ridge Street engine house. But for the most part, Ultimo This early bipolar generator is similar to those used before Ultimo power station was built. This particular unit is on view in Sydney's Powerhouse Museum and has its armature missing, provided the current. Three underground 600V DC cables ran from the . power station to Dawes Point, From there, the current was carried to Milsons Point via a submarine cable laid on the harbour floor. The cables then ran as aerials to Ridge street to feed the whole North Shore system as it existed in 1900. Balmain tram Sydney was a notoriously difficult place for tram traction, with the worst grades and curves near the harbour. So steep was the drop down to the ferry wharf at Balmain that for retardation the trams pushed a counterweighted dummy truck down the hill to the wharf. The counterweight was a second heavy truck on narrow gauge tracks in a tunnel below the road, the two trucks joined by a towline running around a pulley at the top of the hill. To return up the hill, assistance was provided by the counterweight running downhill in the tunnel. Fast expansion Meanwhile, at Ultimo power station, engine generator sets 1 and 3 were tested in September 1899 before flooring and lagging were completed. Two months later, on 8th December 1899, with passengers using the George and Harris streets tram service, Ultimo power house was one of the wonders of Sydney. Indeed nothing in the whole continent surpassed it in size, power and engineering flair. In 1899, only one generator was required to supply the load. But by mid-March 1900, just three months later, two machines were needed. So fast did the electrification of tramlines progress that one year from opening three machines were needed to supply the peak hour load. Immediately the planning of massive extensions to Ultimo power house commenced, ushering in the age of alternating current (AC). Ultimo was enlarged many times over its 66-year working lifetime, eventually growing into a huge 80 megawatt installation. Its charm was that at one time or another, Ultimo contained almost every power generation technology that has ever been invented. Today, Sydneysiders know it as the Powerhouse Museum. Acknowledgements Grateful thanks for photographs donated by SRA Archives and the Trustees- of the Sydney Museum of Applied Arts and Sciences. Acknowledgements to Don Godden et al in "Ultimo Power House; Report on its History and Technology"; also to Victor Poljanski, Troy Thomas, Ken McCarthy in "Trolley Wire", Arthur Perry, John Keating, P. Smythe, P. Tweedie, J. Brearley and Public Works Department of NSW. SC AUGUST 1992 87 Silicon Chip tronics 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: Electronic 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. BACK ISSUES July 1988: Stereo Control Preamplifier, Pt.2 ; Fitting A Fuel Cut-Off Solenoid To Your Car; Booster For TV & FM Signals ; The Discolight Light Show, Pt.1 ; Tone Burst Source For Amplifier 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. Octobe~ 1988: Stereo FM Transmitter (Uses Rohm 8A1404); 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; SSB 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; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher For Model Railways (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; 32Band Graphic Equaliser, Pt.1; Stereo Compressor For CD Players; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Map reader For Trip Calculations; Electronics For Everyone -Resistors. April 1989: Auxiliary Brake Light Flasher; Elec- June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586) ; Passive Loop Antenna For AM Radios ; Build A Universal Temperature 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. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; Alarm-Triggered 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 BA1404 & TDA7000) Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC . November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); 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. J ----------------------------------- ----, Use this handy form to order your back issues Please send me a back issue for: October 1988 O November 1988 O March 1989 o April 1989 O September 1989 O October 1989 O February 1990 o March 1990 0 July 1990 O August 1990 O December 1990 0 January 1991 0 May 1991 0 June 1991 o October 1991 O November 1991 O March 1992 0 April 1992 o 0 O 0 O 0 0 O 0 0 0 July 1988 December 1988 May 1989 November 1989 April 1990 September 1990 February 1991 July 1991 December 1991 May 1992 O O O O 0 O O O O O August 1988 January 1989 June 1989 December 1989 May 1990 October 1990 March 1991 August 1991 January 1992 June 1992 Enclosed is my cheque/money order for $___or please debit my: O Bankcard Card No. Signature _____________ Card expiry date_ _ /_ _ O Visa Card 0 O 0 O 0 O 0 O O 0 September 1988 February 1989 July 1989 January 1990 June 1990 November 1990 April 1991 September 1991 February 1992 July 1992 O Master Card $5.00 each (includes p&p). Overseas orders add $1 each for postage. NZ orders are sent air mail. Street _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ __ Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROV BEACH NSW 2097 Suburb/town _ _ _ _ _ _ __ ______ Postcode _ _ _ _ __ Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 6503. Name _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _ _ _ _ _ _ __ I I I I I I I I I I I I I I I I 1 L--------------------------------------- -•-88 SIUCON CHI!' 11 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. Low-Cost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics ; Simple 6Metre Amateur Transmitter. You r PC, Pt.1 ; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape - A Game Of Skill; Wiper Pulser For Rear Windows ; Versatile 4Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; The Great Green CD Pen Controversy; Index To Volume 3. 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 . 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. December 1991 : TV Transmitter For VCRs With UHF Modulators; Build An lnfrared Light Beam Relay; Compact Solid-State Laser Pointer; Colour TV Pattern Generator, Pt.2; Windows 3 & The Dreaded Unrecoverable Application Error; Index To volume Volume 4. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt. 2; Using The UC3906 SLA Battery Charger IC. February 1991 : Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights ; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2 ; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. 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. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception ; How To Find Vintage Radio Receivers From The 1920s. March 1991: Remote Controll er 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. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier; 12VDC/240VAC 40-Watt Inverter; Adjustable 0-45V 8A Power Supply, Pt.2; The Mobile Telephone Revolution; Designing A Model Speed Controller. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors ; The Mazzie CW Transceiver; Waveform Generation Using A PC, Pt.3 ; 16Channel Mi xing Desk, Pt.4; What To Do When Your Computer Goes Bung , Pt.1. 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. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1 ; Thermostatic Switch For Car Radiator Fans ; Telephone Call Timer; Updating The Resistor/ Capacitor Scene; Coping With Damaged Computer Directories. 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. June 1990: 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 ; LowCost Dual Power Supply; Inside A Coal Burning Power Station ; What To Do When Your Computer Goes Bung, Pt.3; Weather Fax Frequencies. 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 ; LowCost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound 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: How To Connect Two TV Sets To One VCR ; A Really Snazzy Egg Timer; 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. April 1992: lnfrared Remote Control For Model Railroads ; Differential Input Buffer For CROs ; Studio Twin Fifty Stereo Amplifier, Pt.2 ; Understanding Computer Memory; Switching Frequencies in Model Speed Controllers; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom ; LowCost Electronic Doorbell; Battery Eliminator For Personal Players; lnfrared Remote Control For Model Railroads, Pt.2; A Look At Large Screen High Resolution Monitors ; OS2 Is Really Here. July 1991: Battery Discharge Pacer For Electric Vehicles; CD Error Analyser, Pt.1; Loudspeaker Protector For Stereo Amplifiers; 4Channel Lighting Desk, Pt.2 ; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; PEP Monitor For Transceivers June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; lnfrared Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter (includes optional control unit for telescope drives) ; What's New In Oscilloscopes? ; A Look At Hard Disc Drives ; Video Editing On The Small Screen . August 1991: Build A1 Digital Tachometer; Masthead Amplifier For T V & FM; PC Voice Recorder; Error Analyser For CD Players, Pt.2; Turiing In To Satellite TV, Pt.3 ; Installing Windows On Your PC ; Step-By-Step Vintage Radio Repairs. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Ott-Hook Timer For Telephones; Multi-Station Headset Intercom, Pt.2; Understanding The World Of CB Radio; Electronics-Workbench For Home Or Lab. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1 ; Build A Fax/Modem For Your Computer; The Basics Of AID & DIA Conversion; Windows 3 Swapfiles , Program Groups & Icons; How Glass-Mount Antennas Work. PLEASE NOTE: All issues from November 1987 to June 1988 plus the August 1989 issue are now sold out. All other issues are presently in stock. For readers wanting articles from soldout 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. October 1991: Build A Talking Voltmeter For AUG UST 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. Oscillator problem in TV pattern generator I have recently completed two projects and struck minor problems with both of them. I have overcome all of these but I would invite your comment as to the correctness of the solution. In the DTMF Decoder, described in the May 1991 issue, I found that, if the tone signal was large enough to cause clipping at D7 and DB, the valid code LED went out. This means that the input must be adjusted to between the threshold level and the onset of clipping. As phone transmission levels vary over a large range, I find this a real problem. The second problem I had was that I could not access the stored condition ofICs 5, 6 & 7 until I changed the value of the .0ZZµF capacitor and l0kQ resistor connected to pin 11 of ICld to 0. lµF and lZkQ I also built the Colour TV Pattern Generator featured in the November and December 1991 issues. On completion of the project it worked first pop. However, after a number of switch on/switch off cycles, two problems showed up. The first was that at switch on the pattern would break up into bits and pieces (monochrome). A check with the scope revealed that the 4MHz crystal oscillator was jumping in frequency to 32MHz. After experimenting with the values of the 82pF and 33pF capacitors, I found the complete solution was to change the l0MQ resistor to 5MQ The second problem showed up when the mains voltage fell from 235V to 220V. At this voltage, a hum bar appeared on the screen of the monitor. On checking the output of the supplied plugpack, I found that it had dropped so low that, after rectification, the 12V regulator had lost control. I had on hand a transformer rated at 230/lZV at 40VA, which I substituted for the plugpack. This restored the rectified DC to about 14V and eliminated the hum bar. It would seem that the output from a plugpack falls rapidly at inputs lower than 230V. (J. D., Thames, NZ). • We have had no complaints regarding the variability of the tone signal as far as the DTMF Decoder is concerned and we would expect the circuit to be reasonably tolerant in this respect. It may be that conditions are more variable in New Zealand than in Australia. Your modifications would appear to be quite satisfactory, especially so since they enabled you to make the unit work. We have not had any complaints along the lines you set out regarding the Pattern Generator, although your change to the circuit to stop the 4MHz crystal jumping in frequency is quite legitimate. As far as the plugpack transformer is concerned, we did specify a 12V unit rated at 500mA. The smaller types rated at 300mA have insufficient regulation. Digital recordings for guitar tutorials Running the steam simulator from 6V Some time back, I made the SteamSound Simulator described in the April 1991 issue of SILICON CHIP magazine. I used the speaker that appeared later in the Mk. 2 version in October 1991 and used a 12V supply from a rechargeable battery made up from cheap 2.4V batteries purchased from Jaycar. Using my own PC board, I was able to fit the electronics into a Bemo HO scale goods van and connect this up to a fo llowing goods van with the 12V rechargeable supply. This setup works very well and sounds very good. It was done this way because I like the steam noise while the loco is stationary. My question is can the first circuit design or the Mk.2 design be 90 SILICON CHIP altered to operate at a lower voltage; eg, 6V or even lower? Battery life does not matter as I use rechargeable batteries. This reduced voltage would allow me to reduce the battery weight which is very important with small locomotives pulling the weight of the train. (S. H., Woonona, NSW). • Unfortunately, it is not possible to run this circuit at 6V because the noise generator part of the circuit requires at least 9-l0V to produce any noise at all. If you wanted to operate at 6V this would be the most critical part of the circuit and you would have to use another device, such as a lower voltage zener diode, and then use more amplification to get sufficient noise signal. It is something we have not tried and so quite a lot of work would be required to achieve a satisfactory result. The Digital Voice Recorder described in the February 1992 issue looks to be a great project with hours of fun to be gained. However, can any modifications be made to adjust the speed of playback, as I presume no change in pitch will occur (it being a digital recorder) if the playback speed is adjusted. As a musician trying to learn fast and sometimes complicated guitar lead breaks and guitar runs, the digital voice recorder could be used to record a particular passage of music and then played back at a slower speed with no loss of pitch. Commercial units are available for this purpose, but obviously this project - if the modification can be made - would be much more enjoyable because I would be building it myself. Obviously this unit would not be as good as the commercially available units because there is no way of filtering (unless you guys can do that as well) unwanted musical instruments that sometimes accompany a lead break. Of course, any musical instrument player and not just the guitar player would benefit. (H. C., Mt Gambier, SA). • You cannot change the speed of playback without changing the pitch. Nor can we see how any recording system can change speed without changing pitch, unless it is a MIDI based system in which case you would be storing sequences and not analog signals. Resurrecting a SpeediWatt light dimmer A few years ago, I built a SpeediWatt dimmer as .described in your article of December, 1987. It has given faithful service until recently,when it stubbornly refused to lower the output voltage level. Removed from the PC board, the Triac's resistance between the Al and A2 terminals measured 0. Hl I assume that it should be infinite with its gate open. It measures about 14H1 between the gate and Al or A2. Unfortunately, I can't find a listing for the AC03F Triac in any of my several parts catalogs, so I have no information about its specs. Hence I ask if there's a likely supplier, or if there's a more readily-available substitute for it. (G. L., Redfern, NSW). • The fact that the Triac is triggered by an ST2 Diac means than you can substitute just about any Triac. Try an SC141D or a BT137F, both of which are readily available. Using the phone patch with UHF CB radio I am very interested in building the Phone Patch for amateurs, as described in the January 1990 issue of SILICON CHIP, together with the associated line isolation unit. I would like to know if it is legal to use these devices on the UHF citizen band. As a farm manager, it would be very convenient if I could make a phone call from the paddock to check on the arrival of stock trucks, order animal health products and various other uses, but I could not justify the expense of a mobile phone, which are very unreliable in this area anyhow. I realise that these calls would be broadcast to all and sundry but they Problem with the multi-sector alarm I have a problem with my burglar alarm and I would be grateful if ypur people could put me on the right track to solve it. I decided to build the Multi-Sector Home Burglar Alarm, from the June 1990 issue, the Alarm Power Supply with Battery Back-up (September 1990), and the Burglar Alarm Keypad and Combination Lock from the July 1990 issue. · On completion, each unit operated OK to your test procedures and after installing the completed units together with a transformer and a battery into an aluminium cabinet, I decided to connect up the keypad, arm the system on the workbench and check each individual function on a daily basis for a week. On the initial check, all functions operated OK except the mains power failure check which proved a disaster! I had switched the AC off and on about six times whilst listening to the relay working when I noticed that the red LED on the keypad was out. The alarm was disarmed. I continued to switch would be non-private conversations anyway, so it wouldn't really matter. My problem is that there is quite often no-one at the base station to operate the phone patch. What I need is a circuit similar to that used in answering machines, which could switch on the phone patch by using a code sent by a tone controller via the remote transceiver, unhook the phone and dial the phone number using the same device. I envisage that it would be possible to use a similar circuit as used by modern "memory type" telephones to dial the number or use a cheap modem. (P.A., Bunnan, NSW). • The Phone Patch project can only be legally operated by licensed amateurs. It would not be legal for use with CB equipment. It would also be difficult to make the Phone Patch remote controlled, particularly as you would need it to dial the numbers. We are am sorry that we cannot suggest an electronic solution to this problem. Perhaps a practical solution the AC off and on another three times and the LED lit again, rearming the alarm. On rechecking this many times, the number of off/on switchings required before the LED light went out varied from one to 23, while three to six switchings were required to light the LED again. The keypad showed the same false triggering problem when checked using each of two other regulated power supplies. I replaced the two transistors, two capacitors, the relay and the two ICs of the keypad with new components, checking for false triggering after each substitution. I also placed additional 0. lµF capacitors across the supply pins of each IC, all to no avail. I would greatly appreciate your comments on my frustrating problem. (J. W., Nunawading, Vic). • It seems most likely that the cause of the false triggering lies in the keypad circuitry. Make sure that the keypad circuitry and wiring is well away from the mains wiring and also try increasing the 0. lµF bypass capacitor on the 12V supply rail on the keypad board to l0µF. would be to arrange to have someone who is always at home, maybe on another farm, to make any calls for you. You could call them on the CB and then they could make phone enquiries for you. Amiga 500 - help required I desperately need you to do a project, kit or "Circuit Notebook" on analog inputs/relay outputs for the very popular Amiga 500 hobby come puter. There have been recent offerings for IBM and PC compatibles but these are_too expensive. Fast operation is not required. The required specifications are as follows: 8 (or 16) analog inputs, 0-5V DC, 4 (or 8) relay outputs, plus simple software for a hobby weather station, solar house, or house security; logging of parameters every 15 minutes maximum, simple control, and graphics to give 24 hour, weekly, monthly, AUGUST 1992 91 More inputs needed on burglar alarm I have a problem with regards to the Multi-Sector Burglar Alarm described in the June 1990 issue of SILICON CHIP. My previous alarm consisted of microswitches on doors and windows (connected to relays). If a window is opened, a switch closes and this activates a relay and siren. When I armed this circuit and a window had been left open, this would trigger immediately and let me know that there was something wrong. With the Multi-Sector Burglar Alarm, if switches are connected in series so that all switches are closed when windows are closed, and if I break this circuit, it will trigger the alarm as normal. If I accidentally leave a window open (ie, a switch is opened) and I arm yearly, graphs etc. Alternatively, could I appeal for readers' ideas? (D. G., Jabiru, NT). • This sounds like a pretty good description for a project. Do any of our readers have such a unit under development or ready to go? Solar charger wimps out at low voltages I am writing in response to your article on the Solar Battery Charger, in the November 1991 issue of SILICON CHIP. This appeared to be an ex- the system, the LEDs will revert to normal, indicating that all is well. This problem can be overcome by checking each window before arming but a concern is that if a wire is broken between the input and first switch, I may never know until I check each window individually. A similar problem occurs when switches are connected in parallel. Could you please advise me if this is normal, or have I a fault within the system, or are there any changes I have to make to give me an indication of a fault or window left open when the alarm is armed. (F. P., Bedford, WA). • Essentially, there is no way around this problem unless you use one input for each switch. Checking to see that all windows are closed before you switch on the alarm is a much cheaper way. cellent project, especially as it should enable a 12V lead acid battery to continue charging under weak sunlight and partly cloudy conditions by boosting the output voltage. However, on constructing the kit I soon found that when it is used with a low-powered (1W) panel, it is far too inefficient. More charging current would be supplied by disconnecting the regulator and connecting the panel directly to the battery via a diode. The system may work with a large wattage panel (lower internal resistance) but the extra quiescent current r-----1,-.......- +12V Relay output for car reversing alarm The Car Reversing Alarm described in the January 1989 issue was a handy circuit but I would like to use it to operate a relay as well as producing the audible alarm. How do I do it? (M. Z., Cabramatta, NSW). • Adding the bits to drive a relay is simple. You only require a BC337 transistor, a z.zkn resistor, a 1N4002 diode and a 12V relay. They are wired as shown in Fig.1, with the 2.2kn base resistor con92 SILICON CHIP D3 1N4002 IR\tv drawn by the regulator under low sunlight conditions causes an excessive reduction in solar panel output voltage to the point where the regulator drops out of oscillation and closes down the output. A large current is drawn as the voltage approaches 4V. When the solar panel is connected directly to a 12.5V battery via a diode, the relatively high internal resistance of the panel is connected directly across a 12.5V low-resistance load. The higher internal resistance acts as a current regulator and maintains the solar cell voltage around 12V. In practice, this arrangement gives useful charging current to the battery equal to approximately half the short-circuit current of the panel under low sunlight conditions. With the regulator in circuit, the unit's internal quiescent current rises so much under low sunlight conditions that it looks like a short circuit to the panel, with the resultant short circuit current being totally dissipated in the regulator. When connected to a 12V car battery, the regulator draws an excessive internal current as the solar panel voltage falls towards 6V. As the input voltage is reduced towards 5V (using a variable power supply in place if the panel), the regulator dissipates nearly 1A fqr an output charge to the battery of merely 50mA. It appears that at low voltages the regulator's oscillator stops and it goes into a short circuit mode. Have you had any feedback on this from other constructors and are there any errors in the published circuit apart from the error in the number of turns on the choke? Your comments would be appreciated as maybe there is a fault with the IC, although the unit does operate satisfactorily on higher input voltages with a resistive load. (A. F., Blaxland, NSW). 10k Q1 BC337 Fig.1: use this circuit to add a relay output to the Car Reversing Alarm. The 10kn resistor & .047µF capacitor are existing components. necting to the pin 2 output of ICZc in the original circuit. • We have not performed checks of the circuit on a low output solar panel. It is quite possible that the circuit becomes inefficient at very low input voltages but then a normal solar panel would not be able to produce any output ifit was directly connected via a diode to a battery under these conditions. We have not had any other feedback from constructors and there are no errors in the published circuit apart from that concerning the number of turns on the inductor. SC ORDER FORM BACK ISSUES* MONTH MONTH YEAR YEAR MONTH YEAR MONTH YEAR *Back issues are $AS each (incl. postage). Overseas orders add $A 1 per issue for postage. BINDERS 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 D New subscription - month to start D Renewal - Sub. No. r---- -- -- - ---7 D RATES {please tick one) 2 years (24 issues) Australia D $A84 Australia with binder(s) * 0 $A105 NZ & PNG (airmail) D D D $A130 Overseas surface mail Overseas airmail I I I I I I I I I I Gift subscription~ 1 year (12 issues) D D $A42 $A65 $A130 0 0 $A240 D $A120 $A53 $A65 *1 binder with 1-year subscription; 2 binders with 2-year subscription I I YOUR DETAILS Your Name (PLEASE PRINT) Address Daytime telephone number Postcode or please debit my Enclosed is my cheque/money order $ D Bankcard Card No. D Visa Card D GIFT SUBSCRIPTION DETAILS Month to start Message Gift for: Name I I I I I I I I I I ~ (PLEAS E PRINT) I Street I I I I Suburb/town I I I Postcode I State I IL _ _ _ _ _ _ _ _ _ _ _ _ ...JI Signature Master Card I I I I II I I I II I I I II I I I I Phone (02) 979 5644 Fax (02) 979 6503 9am-5pm Mon-Fri. 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 A UG UST 1992 93 ...__TCENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. r-------------------------, CLASSIFIED ADVERTISING RATES : Advertising rates for this page: Classified ads: $10.00 for up to 15 words plus 40 cents for each additional word. Display ads (casual rate): $20 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. I I 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) I I I I m~. I I I I I I I I ANTIQUE RADIO 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. Second hand 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. Open Sat. 10am-5pm; Sun. 12.30-Spm. 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613 AH. FOR SALE Enclosed is my cheque/money order for $_ _ _ _ or please debit my o Bankcard O Visa Card O Master Card Card No. Signature,_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _-'/_ __ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ _ _ __ XI I I I I I I I I I L-------------------------J 94 SILICON CHIP WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" $35 is a high resolution, shortwave fax, Morse & RTTY receiving program. Suitable for CGA, EGA, VGA and Hercules cards (state which). Needs SSB HF radio & Radfax decoder. *** "SATFAX" $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus "WEATHER FAX" PC card . *** "MAXISAT" $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Old 4005. Phone (07) 358 2785. 8051 MICRO-COMPUTER PROTOTYPING PCB $30 - similar to my ROMLoader EA Jan 92. Provision for 8255 PPI, 9346 EEPROM, 2k-32k SRAM, 2k- 32k EPROM, MAX232, DIP switches & expansion header. Send A4 SAE for article. Tantau, PO Box 206, Gordon 2072. A 4Mb SIMM can now be used in my Printer Buffer kit, and my PC printer MEMORY EXPANSION PRICES AT JULY 1ST, 1992 SIMM 1Mbx9 80ns 1Mbx8 100ns 1Mbx8 80ns 4Mbx9 80ns 4Mbx8 80ns 256x9 80ns (FOR SIP ADD $1) TOSHIBA T1000SE 2Mb T2000SX 4Mb T1600 2Mb T31 000SX 2Mb T3200SX 2Mb T3200 3Mb T5200 2Mb T2000SX 8Mb T44/6400 4Mb $48 $42 $45 $180 $160 $16 $155 $275 $140 $135 $135 $230 $150 $525 $330 DRAM-DIP 41100080 256 X 4 80 4125680 1Mbx4 80Z 1Mb x 4 80S $540 $5.60 $2.00 $24.00 $24.00 DRIVES 3½ PANAS 1.44 $78 S'GATE IDE 64/16 $365 S'GATE IDE 42/28 $325 S'GATE IDE 108/16$475 S'GATE IDE 130/16$530 CO-PROCESSORS 387/33/40 $235/$280 387/20/25 $210/$215 sx 20/25 $155/$170 287/10/20 $95/$100 Safes Tax 20%. Overnight Delivery. Credit Cards Welcome. PELHAM Tel (02) 980 6988 Fax (02) 980 699 r Plans Kits and PCBs UNIDEN SCANNERS DON'T PAY MORE! 100W Valve Amp PCB ............................................... $30 Valve Amp PSU PCB ................................................. $25 Universal PSU (±5/±12V) Dual Supply ...................... $10 Digi 125 100W amp/pair........... .. .......... $10 ETI 1623 PIA for PCs ............................................ $40 Max 1/0 Board ............................................................ $40 Max Kit ............................................. $169 LM380 3.5 amp PCB .................................. .. ............. $7 AEM 35W amp kit .......... ......................... . $20 ETI Audio Toolkit PCB...... ... $10 AGC Amp PCB .................. ...................... $7 Z-80 Miniprocessor PCB... .. ....................... $50 6502 Miniprocessor PCB ........... .. ........ $50 6809 Miniprocessor PCB .................. $50 8048/8049 Developers board complete B& T .. ,........ $199 IBM PC Prototype PCB .............................................. $50 EPROM Programmer ........................... $299 ESL-1 Electrostatic speaker kiVpair inc manual ...... $899 ESL-1 Assembly Manual ...................................... ... $50 50XL RRP $299.95. Our price $211 10 memories, Lo-Hi VHF, UHF 1 OOXL T RRP $449.95. Our price $409 100 memories, Lo-Hi VHF, Air, UHF 200XLT RRP $549.95. Our Price $477 200 memories , Lo-Hi VHF, Air, UHF, 800 MHz CB, SCANNERS MARINE For more information, write to: TopCom Communications, Reply Paid 336 (no stamp) PO Box 336, Greensborough 3088. \.. Phone (03) 883 9535. Fax (03) 432 0716. ~ FIX-A-KIT KIT REPAIR & CONSTRUCTION TRANSFORMER REWINDS ALL TYPES OF TRANSFORMER REWINDS TRANSFORMER REWINDS ~eply Paid No.2, PO Box 438, Singleton, NSW 2330. Ph: (065) 761291. Fax: (065) 761003. port driven ZB0 Micro Development board has a Basic Interpreter. Short form kit prices include postage. Buffer $52, ZB0 Dev. $76. For more information, send a 45c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. Phone (03) 338 6286. SWITCHED MODE POWER SUPPLIES: compact enclosed ex-Telecom supplies. Dimensions 300 x 90 x 180mm. Unregulated input 30-50V, regulated output of 12V<at> 6A or 12V<at> BA or 5V <at> 40A. Three different units. Limited stocks <at> $28 ea. P+P $7 (heavy!). Specify type when ordering (item No. 0145). * MUSIC ON HOLD PCB: small PCB assembly based on a 7910 CF music generator IC. Apply 312V across two of connector pins to obtain music from one of the IC pins. Basic information and a circuit diagram 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION , " TECHNICAL ASSISTANCE HVCAL ELECTRONICS Design, Manufacture & Repair of Electronic Equipment (02) 633 5477 P.C. Computers (08) 332 6513 36 Regent St, Kensington SA. KIT REPAIRS Kits repaired from all magazines. Switchmode power supplies repaired. Design work from start to finish. Computer software consultancy. Ring any time 9am-9pm Mon-Sun EEM ELECTRONICS is provided. $4 ea (item No. 0146). * MICROSWITCH COLLECTION: a mixture of no less than 10 small and large, new, mil-spec microswitches. $6 for the collection (item No. 0148). * MAINS RATED RELAYS: four separate SPST switches (24A) actuated by a mainsrated solenoid. $10 ea (item No. 0128). We also have some SPOT mains relays which will switch up to 10A AC. These are fully enclosed in an attractive clear plastic housing. $12 ea (item No. 0149). * LARGE ROTARY SWITCHES: these large rotary switches have- "snap in" action and all are rated at mains voltages or higher. They have at least three positions and have currents ratings from 10-35A. Great for high power mains and antenna switching. Only $15 ea (item No. 0151 ). * LARGE FANS: powerful ball bearing mains powered fans, 220V/0.13A, WANTED: YOUR CIRCUIT & DESIGN IDEAS Do you have a good idea languishing in the ol' brain cells. If so, why not sketch it out, write a brief description of. its operation & send it to us. Provided your idea is workable & original, we'll publish it in Circuit Notebook & you'll make some money. We'll pay up to $60 for a really good circuit but don't make them too big please. So transfer your idea to paper & send it to Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097. 10 Bouverie Place, Epping, Vic 3076 Phone (03) 401 1393 WANTED DISTORTION TEST SETwanted. Must be auto-nulling and in good condition with the instruction manuals. Can be Audio Precision, Sound Technology 170x, Hewlett Packard 339 or equivalent standard. If you have one to sell, please contact Leo Simpson on (02) 979 5644 with details and price. 173mm diameter by 60mm deep. Thermally protected, finger guard included, removed from new equipment. $9.90 (item No. 0152). * TEMPERATURE CONTROLLERS: mechanical temperature switches, designed for switching air conditioning (heating/cooling) systems directly. Adjustable temperature controls and mains-rated switches, can control currents of at least BA directly. Most are rated for typical ambient ranges but some higher temperature types are also available. All come with specifications. $35 ea (item No. 0152). * PRESSURE AND TEMPERATURE GAUGES: brand new, large mil-spec gauges. Overall diameter approx AUGUST 1992 95 r-------------------------, SILICON CHIP BINDERS l These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers and are made from a distinctive 2tone green vinyl that will look great on your bookshelf. Advertising Index Adi lam Electronics ...... ......... .. OBC Altronics ... ........ ..... ..... .... ...... . 10-13 All Electronic Components .. ...... 59 Antique Radio Restorations ....... 94 A-One Electronics ................ 34,35 Av-Comm .............. .. .. ....... .. .. ...... 33 * High quality. AWA Distribution ...................... IBC * Hold up to 14 issues Breakthrough Computers ........... . 9 Comma Corporation ..... .. ............. 4 * 80mm internal width. * SILICON CHIP logo printed in gold- David Reid Electronics .. .............. 3 EEM Electronics ............. ...... ..... 95 coloured lettering on spine & cover. Electronic World .......... .. ........... ... 4 Emona Instruments ................... 55 Yes! Please send me _ _ _ SILICON CHIP binder(s) at $A11.95 plus $A3 p&p each (NZ $A6 p&p). Enclosed is my cheque/money order for $_ _ _ _ or please debit my o Bankcard D Visa Card D Master Card Geoff Wood Electronics ............. 67 Harbuch Electronics .................. 43 Hewlett Packard ... ... ..... ... .. ........ 25 Hycal Instruments ............. ......... 95 lcom Australia .... ...................... IFC Jaycar Electronics ...... .... ... ... 45-52 Card No. J.V. Tuners .......... ... .. ... ............... 43 Name _ __ _ _ _ __ _ _ _ __ _ _ _ _ _ _ _ __ _ Kenwood Electronics .... ...... .. ..... 74 KT Technology ... .............. .. ........ 65 Oatley Electronics ................ 61,95 Street _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ __ Pelham ............................ .... . 73,95 Suburb/town _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ _ _ __ Peter C. Lacey Services .. .. ........ 40 Philips Test & Measurement ...... 31 Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _~/_ __ PC Computers ....................... .... 95 SILICON CHIP PUBLICATIONS PO Box 139, Collaroy Beach, NSW 2097, Australia. Phone (02) 979 5644 Fax: (02) 979 6503. L-------------------------J RCS Radio ..... .. ......................... 96 Reserve Electronics .................... 4 Resurrection Radio ..... ... ... .. ...... ... 7 Rod Irving Electronics .......... 76-81 Silicon Chip Binders ............. 60,96 TECS Electronics & Computers. 37 130mm. Pressure gauge reads from 016 bar, temperature gauge reads from 20-80°C and has a remote sensor attached to a 2-metre lead. Pressure gauge $32 (item No. 0153A) . Temperature gauge $29 (item No. 0153B). * MAINS SWITCHES: large 3-pole 20A/ 500V switches as used to switch machinery $18 ea.* UHF REMOTE CONTROL BARGAIN: one single channel receiver PCB and all on-board components kit as per EA April 1989 and two complete transmitter kits (include cases and the battery). Yes, one receiver and two transmitters for an incredible total price of $39.90. Two months only, at this special Market Centre bargain searcher's price. Major cards accepted with phone and fax orders. Certified p&pAustralia $5, NZ (airmail $10. Oatley 96 SILICON CHIP Electronics, PO Box 89, Oatley, 2223 NSW. Phone (02) 579 49485. Fax (02) 570 7910. Telecom Australia ...................... 57 Transformer Rewinds ................ 95 TopCom Communications ......... 95 PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. ACS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 • 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. LEADER Putting Affordable Reliability First The first 4-in-1 measuring instrument hel~you do more with less effort. A leader our Model 300 packs all the in every measurement functions you normally require Way in this one compact, portable unit. Its 30 MS/s, 10MHz bandwidth, 2-channel DSO and full-feature 3.5 digit DMM let you conveniently view waveform and DMM reading together on the large LCD screen . In its 8-channel logic scope mode, you can perform timing analysis of digital signals with ease. And when you can't be there, it even becomes a data logger, storing repetitive DMM readings on memory card for later output to printer. Packed with user-friendly features, the Model 300 is extremely versatile, yet easy to use . No other instrument can offer so much in one compact package. · For full specification details, contact: AWA Distribution _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ SYDNEY' Ph, (02) 888 9000 Fax, (02) 888 9310 MELBOURNE, Ph, (03) 693 3322 Fax, (03) 690 3094 BRISBANE, Ph, (07) 844 1631 Fax, (07) 844 8738 ADELAIDE, Ph, /08) 272 2366 Foxe (08) 274 1685 PERTH, Ph, (09) 244 2884 Fax, (09) 244 2766 LAUNCESTON, Ph, (003) 27 3566 Faxc (003) 27 3987