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- - Lightning: protecting your electronic appliances· l~S1S' SERVICING - HIFI - ElEC1R\\"\C~MiM;l;M•][· Build this low cost loudspeaker system , LED flasher for model railways Uses a single IC and is easy to build Simple beta tester For easy checking of transistors ,,~ ;. I : Plus - The Original & Best TV Serviceman, Vintage Radio, The Way I See It, Amateur Radio i :l;l•![iliJi-11 Harmony Perfect Image loudspeaker Cutec stereo power amplifier Monitor PC pure silver speaker cable ~-:-: ; - - --Fi _. _. __. .....JI .....JI ~ __. __. .....JI ~ __, __, .....JI .....JI .....JI __, .....I _J ___,I _ . __,, _. _. .....JI ,-I __. _. _. .....JI .....JI .....JI __. __. __. ....I FEBRUARY 1 989 FEATURES 4 Lightning & Electronic Appliances by Leo Simpson LIGHTNING CAN DO a lot of damage to your electronic appliances. Our article on page 4 outlines the dangers. How to safeguard against damage 26 Cutec Z-2000 Stereo Power Amplifier by Leo Simpson Rugged design has very high music power output 28 Using Comparators To Detect & Measure by J. Axelson How to use op amps to monitor real world conditions 74 The Evolution of Electric Railways by Bryan Maher Pt.16: The search for cost efficiency 82 The Technology Letters, Pt.3 by Richard Kopf An Aussie goes to America PROJECTS TO BUILD THIS EASY-TO-BUILD instrument lets you check transistors for gain and identify their leads. Construction starts on page 20. 20 Transistor Beta Tester by Malcolm Young Checks gain & identifies leads 37 Minstrel 2-30 Loudspeaker System by Leo Simpson Build this budget system for good sound 52 LED Flasher For Model Railways by Malcolm Young Uses a single IC & is easy to build SPECIAL COLUMNS 10 Vintage Radio by John Hill Restoring plastic & bakelite cabinets 50 Amateur Radio by Garry Cratt : r}~Jk OUR TV SERVICEMAN had to sneak up on the faults this month. His story starts on page 58. Build a simple VHF FM monitor 58 Serviceman's Log by the original TV serviceman A Sharp in Pye clothing 66 The Way I See It by Neville Williams Jump start your new car & blow up the electronics! DEPARTMENTS 2 Publisher's Letter 3 Mailbag 36 Bookshelf 44 Circuit Notebook 64 Subscription Page 86 92 94 95 96 Product Showcase Ask Silicon Chip Notes & Errata Back Issues Market Centre ,_.._.. , LOOKING FOR A GOOD pair of loudspeakers that won't break the _b ank? You can put this system together for just $269. Details page 37. FEBRUARY1989 1 SILICON CHIP PUBUSHER'S LE'I-IER Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann · Lightning: more dangerous than you think Regular Contributors Neville Williams, FIREE, VK2XV Bryan. Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill David Whitby Photography Bob Donaldson Everyone acknowledges that lightning is spectacular and dangerous but during thunderstorms most people carry on their normal activities as if nothing is happening. Because our electricity supplies are so rarely interrupted during thunderstorms these days, because the lights rarely even flicker, we take it for granted that everything is as normal. But during an electrical storm everything is definitely not normal. The amount of energy released during a typical thunderstorm beggars the imagination. And there are indications that thunderstorms are becoming even more severe than used to be the case. If you talk to people in the power transmission or broadcasting industries they can tell lots of stories of installations which were designed to withstand severe lightning strikes and yet have been destroyed. The trouble is that not a lot is known about lightning - how it develops, where it might strike and what damage it might do. So even though electricity supplies and radio and TV broadcasts are rarely interrupted and the phone service keeps going, that is not to say they are not severely effected during thunderstorms. This is why we have published the article on the effects of lightning . on electronic appliances this month. It had become obvious to us that people just did not realise the risk to their appliapces, particularly those such as microwave ovens and VCRs. They are big casualties during thunderstorms. So turn 'em off and disconnect 'em during storms. 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. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd , Waterloo, NSW 2017 . Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rate: currently $42 per year ( 12 issues) inside Australia. For overseas rates, refer to 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. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097 . Phone (02) 982 3935. ISSN 1030-2662 * Recommended and maximum Australian price only. 2 SILICON CHIP 1 Since this article was prepared the stories are now starting to come out about the large numbers of facsimile machines that were damaged during the' severe thunderstorms in Sydney during December. These stories reinforce the message. It seems that telephone lines are much more vulnerable to lightning induced voltage surges than are power lines. So if you have equipment connected to both the phone lines and mains supply it is doubly important that you disconnect it during thunderstorms . In fact, next time there is a severe electrical storm make sure that you do go around your household and disconnect all the appliances as suggested in this month's article. Then turn off your lights, go to the nearest window and look up at the sky. The electrical performance is likely to be far more spectacular than anything on TV at the same time. Leo Simpson MAILBAG 120W PA amplifier Congratulations on your magazine; it has lots of interesting projects. I am making the 120W Mosfet amplifier published in the November 1988 issue and have noted a couple of incorrect items. First, the lkQ resistor is missing from the parts list. Second, the line-to-speaker matching transformer on page 17 is drawn incorrectly; the wattage would increase as the primary winding is decreased. Actually, the primary winding is not normally tapped. The full primary winding is used to preserve the maximum inductance, giving good frequency response and inductance, and the secondary winding is tapped. Also the maximum current drawn from the power supply is not stated. Is the power supply shown man enough for two amps? I worked most of my life as a radio engineer, the last 15 years at Bang & Olufsen (UK) Ltd, Gloucester, England. If anyone would like advice on problems with B&O equipment and would like service manuals, I would be glad to help, if postage was paid. S. Farrant 8 Toona Gardens Edgewater, WA 6027 Comment: another reader has already drawn our attention to the wrong labelling of the diagram for line output operation. His letter was published in these pages last month. The suggested power supply employs a 300VA (ie, 300 watt) toroidal power transformer, a 35-amp bridge rectifier and a total of 16,000µF of capacitance. It is considerably over-designed for the job but will give very good regulation. Thanks also for your offer on B&O equipment. We have published your address for the benefit of readers. Likes traditional electronics magazines I would like to add my congratulations for a fine magazine and for completing the first volume. I have collected electronics magazines for about 20 years but had stopped in recent times when they no longer seemed to cater for my interests. It is good to see a return to the "traditional" style of electronics magazine and you can be assured of my continued support. I have no real criticisms of the magazine but would venture a request for more articles dealing with. specific devices and useful circuits to show how these could be used. Keep up the good work. You are doing fine. C. Wilkes Lakemba, NSW Oscillation problems in FM transmitter I constructed the FM transmitter described in the October 1988 issue of SILICON CHIP but could not get it to oscillate. I was puzzled by your use of F16 ferrite cores in the inductors (this is a high permeability ferrite useful to about 15MHz if my memory serves me correctly) so I changed them to the higher frequency lower permeability F29 slugs. Lo and behold it sprang into oscillation and was tuneable from 88 to 108MHz. I then noticed some spurious sidebands in the output of the transmitter. Some probing with an oscilloscope showed that there was a low level oscillation of about 2MHz on one of the audio input pins of the IC. Soldering in a lO0pF capacitor from each of the audio input pins stopped that. The FM stereo transmitter now works quite well. I am sure the specification of F16 slugs was an error as a colleague who purchased a kit had exactly the same problems as I did. Perhaps you could publish my modifications to assist other constructors. R. Dannecker Rockhampton, Qld Comment: we refer you to Notes & Errata on this project published in the December issue on page 96. If the .01µF capacitor on pin 12 is replaced with .001µF, it should work properly. It is true that F16 slugs have higher permeability and are generally used at frequencies below 15MHz. However, our specifying them for this application was not an error. They do work. F29 slugs could also be made to work but the number of turns might have to be varied and the Q of the coil would undoubtedly be different. We checked the inputs of our prototype for any sign of spurious signals SILICON CHIP, PO Box 139, Collaroy Beach 2097. but could find none. Your addition of 100pF capacitors will degrade the 50µs pre-emphasis. We wonder whether the signals you observed were peculiar to your locality or caused by your method of measurement. Or did you have a CD player connected at the time? Many CD players have sampling artefacts, at the 44.1kHz rate, running well up into the megahertz region and this could be what you are observing. TV protection circuits cause problems The letter from R. Palmer (SILICON CHIP, November 1988) opens a Pandora's Box of problems for ordinary electronic servicemen. I have to agree with Mr Palmer that the ideal situation is to find the cause of the trouble and fix it. The difficulty is that most customers are unwilling to pay for the time necessary to find and fix these troubles. The August article related to a problem common to one model of Hitachi/GE television. A similar fault occurs in one of the Rank Arena models. The problem applies particularly to a form of protection circuit added to these models to protect against an anticipated fault, but removed from later, similar chassis because either the fault didn't eventuate or the protection circuit proved too unreliable. Mr Palmer specifies C722 in the Hitachi/GE chassis as the cause of trouble. I agree that this capacitor is sometimes found to be low value or even open circuit. But if it is not faulty, then· what? The fact that the manufacturers chose to delete the particular protection circuit from later versions of the chassis seems to indicate that it is reasonably safe to delete it from the earlier versions, providing that all other parts of the chassis are working within design limits. I wish Mr Palmer well but I fear he will have many call-backs in those cases where the trouble is not just a fault in C722 but also an over-design in an otherwise unnecessary "protection" circuit. Jim Lawler Hobart, Tasmania FEBRUARY19B9 3 ■ HOW TO PROTECT YOUR ELECTRONIC EQUIPMENT Every year thousands of thunderstorms occur in Australia but most of them pass without note. But they can cause untold damage to electronic equipment - damage which runs into millions of dollars. Some of this damage is virtually unavoidable but you can avoid most of the risk to your own equipment. By LEO SIMPSON Virtually everyone acknowledges that lightning is spectacular and dangerous. It is especially dangerous to people who are exposed in open, flat areas. Every year several people are either killed or hospitalised by lightning strikes. And it does damage to large buildings and other man-made structures, not to mention the countless trees that are destroyed by direct strikes and the starting of lots of bush fires. These risks of thunderstorms arewell known and accepted by everyone. Not so well known are the risks of damage to electronic equipment. The fact is, after every large thunderstorm over a metropolitan area, lots of TVs, VCRs and many other appliances go in for service. The repairs are for damage which occurred during the thunderstorm even though the owners may not have realised it. For a TV set or VCR the risk of damage due to lightning comes from two sources. The most obvious one is via the antenna. Even though the antenna may not be directly hit [direct strikes on antennas are rare), the intense static discharge from a nearby strike can be enough to blow all the semiconductor components in the tuner. And while these components may only be worth a few dollars in themselves, the resulting repair bill can easily run to more than $100. A more common source of damage to VCRs and TVs is via the mains supply. Because the electrical supply grid is hit so often during thunderstorms, high surge voltages are unavoidable. It is these brief surges which do the damage. Often the damage is immediate and the TV or VCR stops working straight away. But in many cases the appliance keeps working and may not fail for a few hours, a few days or even weeks afterwards. The sort of faults which occur due to surge voltages on the mains supply are, naturally enough, usually in the power supply. They involve switchmode transistors, switching diodes and other associated components. The major power consuming component in a TV chassis, the horizontal output transistor, can also be damaged. How can components be damaged in lightning induced surges and not fail straight away? It is quite simple really. The very brief surge voltage over-stresses the component and thereafter its leakage current is higher than it should be even though it may keep working for the moment. Ultimately, the leakage current rises to the point where the component fails completely and a repair job is called for . It is unlikely that such repairs are thought of as being caused by thunderstorms but they are. Just how many repairs are caused by brief voltage surges on the mains supply is unknown but it is likely to be quite high. When you think about it, electronic equipment is very reliable once it has passed through its initial "burn-in" period. After that it tends to have very low failure rates so any major failures in semiconductors must be regarded as probably being due to an unusual surge voltage. In VCRs, power supply components are frequently damaged and ironically, those that are damaged are intended to protect the circuitry against high voltage surges. But the very fact that these components are sacrificed means that fuses are blown and a trip to the service centre is necessary. Again, the components involved may not be in themselves very expensive but the overall repair bill can amount to quite a lot by the time labour charges are figured in. And you have to add to that the inconvenience of not having the TV or VCR for a week or more. [Interestingly, the coming of summer always brings a rash of TV failures. Partly these are due to thunderstorms but high humidity also plays havoc with TV sets, particularly in the high voltage horizonFEBRUARY 1989 5 A graphic demonstration of the destructive power of lightning. On December 9, 1988, the transmitter building for Sydney radio station 2KY was struck by lightning and the subsequent fire destroyed the building. Photo by Bob Tregea. tal sweep circuitry and in the EHT (extra high tension) circuitry. Humidity causes current leakage and leakage leads to failures). Refrigerators and microwave ovens In the days before TVs and VCRs, the appliances most likely to be damaged by passing thunderstorms were refrigerators. Because they are always connected to the mains and always turned on, they were and are at high risk. These days, refrigerators are still commonly damaged by high voltage surges caused by lightning but they now tend to be over-shadowed by the newer and more fragile electronic appliances. Another expensive appliance which is at risk during thunderstorms is the microwave oven. As with refrigerators and VCRs, these are usually connected to the mains and switched on, 24 hours a day. They can't help but be damaged. Frequently the damage is to the power transformer and to the 6 SILICON CHIP microprocessor control circuitry. In many microwave ovens though, it is often the surge voltage protection components which go. These will be blackened or ruptured by the high voltage surge and fuses will be blown. The net result though is a trip to the service centre. You can easily pay $100 or more for routine repairs. Computers and modems While the domestic appliances listed above are the most common casualties of thunderstorms, the damage caused to computers and modems can be equally if not more expensive. Often the gear is out of service for longer too. Computers and modems can cop damage from two directions: from the power lines and from the phone lines. And when a modem is damaged from a high voltage surge via the phone lines or power lines, the computer is often a casualty too. Even if a computer is not damaged during a thunderstorm, peripheral components such as video monitors and printers can still expire, for the same reasons as set out previously. Filters and surge protection circuitry can be a help in this regard but with the double whammy of surges from mains and phone lines, computer systems are especially at risk. Facsimile machines If you have a facsimile machine in your home or business it is even more at risk than your computer, if only for the fact that it is usually left running 24 hours a day. Make no mistake, the biggest reason for service to fax machines is for damage due to voltage surges on the mains or via the phone lines. Fax machines are often regarded as temperamental machines. If they are it is partly because they are working in a tough environment. It goes without saying that they are not cheap to repair . Frequently, if a fax machine goes in for repair, the whole motherboard is replaced. Motherboards are usually not repaired because it is too time- consuming to do so - they are packed with surface mount components. Other equipment which is connected both to the mains and phone lines is also at risk. Under this heading come telephone answering machines and call diverters, mains powered wireless telephones and burglar alarms. Amateur and CB equipment Amateur radio operators have always recognised that their equipment is at risk during thunderstorms. This applies to installations which have large antenna arrays. Such arrays, if they have been installed properly, will be correctly earthed and will have lightning arrestors or spark gaps on the antenna lead-ins but even so they are still at risk. Citizens band radios are also at risk although their antennas are usually nowhere near as big as those used for amateur radio operation. What you can do to protect your equipment Let's not beat about the bush. There is only one foolproof way to protect your appliances during a thunderstorm and that is to disconnect them completely. Don't just switch them off you must physically disconnect them. Remember that most TVs and VCRs are still operating even when they are nominally switched off. And even if your TV is switched off and consuming no power, it is not disconnected as far as a high voltage surge is concerned. If lightning strikes a power line, substation or pole transformer, even quite some distance away, the resulting voltage surge on the mains supply can easily be several thousand volts or much more. Such a surge may only last a few microseconds but in that time it can cause a lot of damage. In the face of a surge of several thousand volts with a very fast risetime, the power switch in your TV is no barrier at all. The high voltage can easily jump across the switch, burn out tracks on the printed circuit board and do untold other damage whether the ap- Oddities of Lightning Damage There is no predicting the damage that lightning can do. The currents and magnetic fields generated by a major bolt of lightning can be extremely intense. Currents in a really big strike can exceed 50,000 amps and the strike can last for more than a second. Such extreme currents and the related high voltages can induce very high voltages in nearby metal structures even when they are some distance from the strike. It is quite common for electronic doorbells and burglar alarms to be triggered during thunderstorms - pliance is switched on or not. Having disconnected the appliance from the mains remember to disconnect the antenna lead too because it can damage the front ends of both the TV and the VCR. The same applies to your hifi equipment. Disconnect it from both the mains and antenna, if you have an FM antenna. Protective routine If you live in an area which experiences severe thunderstorms, or the thunderstorm you are experiencing is notably wild, you should go around your house, from room to room, disconnecting all the appliances. If you have a computer, modem, fax machine or phone answering machine, don't forget to disconnect the phone lines too. Pushbutton phones are liable to damage too and if you purchased them you are liable for any repairs, not Telecom. Disconnecting the phone during a thunderstorm has another advantage which may not be obvious. It stops anyone from ringing you. It is quite unnerving if you feel compelled to answer a ringing phone during a thundertstorm (and who doesn't). Telecom rightly warns against using the phone during a thunderstorm but the party at the other end may not know that there is a storm in your area. Disconnecting the phone stops that dillemma. the cause is high static voltages or induced voltages during a strike. And the high magnetic fields can cause damage to TVs even though they are completely disconnected from both the mains and antenna. We know of cases where the shadowmasks of colour TV receivers have been heavily magnetised and required subsequent external de-gaussing (demagnetising) before they could give a recognisable picture. Such cases must be regarded as extremely rare but they do show the extreme energy of lightning. Now we won't maJ<e any secret of the fact that having to disconnect everything during a storm is a pain. Switching on everything after the storm and resetting the clocks in your VCR, microwave oven, clock radios and so on is an even bigger pain. Is it really worth it? Without a doubt it is. It is a foolproof method of protection. Barring a direct strike on your home, it is highly unlikely that any damage can occur to an appliance which is completely disconnected (although we will give one instance which can occur). Cracking it hardy You may feel that the process of disconnecting every appliance in your home during a thunderstom and then powering everything up afterwards is just not worth the trouble. And you may be right. However, a number of · TV servicemen and service organisations we talked to in preparation for this article agreed that lightninginduced surges do undoubtedly result in a great many repairs to electronic equipment. If you feel that you can withstand the relatively low risk of damage to your appliances, then well and good. But remember that by using the "disconnect routine" during severe thunderstorms you will undoubtedly avoid the inconvenience of having equipment in for repair. Even if you don't do it for all apFEBRUARY 1989 7 Lightning: protecting your appliances And that brings us to lightning protection itself. We don't intend to go into the aspects of protecting buildings and structures from lightning. That is a complete subject in itself. Suffice to say that all large and exposed buildings and structures must have good lightning protection otherwise the risk of damage can be very high. In rural areas which have a high incidence of thunderstorms, individual homes should also have lightning protection. In metropolitan areas, there is no doubt that the electrical power grid itself gives quite considerable protection to smaller buildings and homes. And typically, it is struck hundreds or thousands of times every year in Australian cities. TV antennas This photo inside 2KY's transmitter building shows the aftermath of the fire started by lightning. The building also housed the transmitter for 2EA and this was destroyed too. Photo by Bob Tregea. pliances it is worth doing for major units such as computers, microwave ovens, TV and VCRs. Insurance claims There is a bright side to this subject too. If you are unlucky enough to have an appliance damaged during a thunderstorm, it may be possible to claim the repair cost on your home contents insurance policy. Many contents policies do have clauses involving lightning damage. To make a claim, the damage must clearly be identified as having been due to lightning. To give the claim some weight, the service organisation or repairman would have to make a statement to the effect that the repair was for lightning damage. If you want really strong evidence (some insurance companies are not the most willing payers) and the damage is graphic, take a Polaroid photo. Remember though that many lightning induced failures may not 8 SILICON CHIP be easily identified as being due to a thunderstorm. This is especially the case if the component fails days or weeks after the storm. Other means of protection Yes, you can use surge protected power outlets to protect your major appliances. These may contain metal oxide Varistors (MOVs) or gas filled spark arrestors and they can give a high level of protection. But they can only protect those appliances that are connected directly to them. They will not protect equipment against voltage surges or discharges on the phone lines or on TV antenna leads. So surge protectors are not foolproof. In the case of a severe voltage surge on the mains they themselves can be destroyed and the equipment they are connected too can still be damaged. At least one manufacturer, Click Industries Pty Ltd, recognises this fact , and includes $5000 free insurance with its Surgebuster protector. But while most Australian homes probably don't need a lightning protection installation, their external TV antennas are another matter, particularly if a high mast is involved. These should be earthed, if not as direct lightning protection then at least for static protection. The recommended method is outlined in the relevant Australian Standard, AS 1417.1 1987 [Receiving Antennas for Radio and Television in the Frequency Range 30MHz to 1GHz; Part 1- Construction and Installation). Briefly, the method involves earthing the antenna mast by a copper wire of 2.5 square mm cross-section. The wire should be connected to a copper clad steel earth stake via the most direct route. If wire other than copper is used, it should have equivalent current carrying capability. The reason for earthing the antenna is so that it does not present a hazard to the building it is mounted on or to its occupants. In our experience, very few antenna installations are earthed in this manner, even though most are professionally installed. These days, it is even more important for antennas to be earthed because there is no direct earth path via the antenna socket on VCRs or TVs. Nor are these appliances themselves earthed because they are mostly double insulated. ~ NOW SAVE EVEN MORE ON THESE OUTSTANDING MODEMS Avtek, the longest established Australian modem manufacturer, now gives you a chance to get even better value when you buy. Just check the features and the prices of Avtek and you'll see why it's the modem chosen by more and more PC users. More compact and reliable than most and suitable for data transfer between PCs, on-line services, E-mail and all videotex facilities like VIATEL (Model 123 only). Available as a standalone RS232 model or as a plug-in true ½ card for IBM PCs and compatibles. Specifications: Data Standards CCITTV.21 (300/300 baud full duplex). Data rates - CCITTV.23 (1200/75 baud). AN/DEAL F1Rsr MODEM! A fuUy automatic operation, HAYES-compatible smart modem. Choose from 3 models (internal or external) model 21/23 300/300, 1200/75 12 300/300, 1200/1200 123 300/300, 1200/1200, 1200/75 $ 325 325 399 A highly reliable data communicator at a budget price. The compactly designed Minimodem II is supplied complete with Telecom-approved, pushbutton phone. PHONE NOW FOR FAST DELIVERY PH: (02) 888 5333 All Avtek modems are sold complete with power supply, instructions and telephone connections. Designed and built in Australia, service and technical support for modems is available direct from Avtek Data communcations. MAIL ORDERS WELCOME. AVTEK, P.O. BOX 651, LANE COVE 2066. 30-DAV. NO-QUESTIONS-ASKED, MONEY-BACK GUARANTEE. 89] 'fTEK ATA COMMUNICATIONS (A Member of the NetComm Group of Companies) ltro:rrmtrrfil\\\. SEND COUPON TODAY! Name: _ _ _ _ _ _ __ _ _ __ Address: _ _ _ _ _ _ _ _ _ __ _ Name on Credit Card: _ _ _ _ _ _ __ Credit Card No: _ _ _ Expiry Date:_/_/_ Please rush me Qty Model internal/external price Post to Sub-total$ Avtek Data Add freight$ Communications, P.O. Box 651, Lane Cove TOTAL THIS ORDER$ 2066. 10.00 AV005 VINTAGE RADIO By JOHN HILL Restoring vintage radio cabinets No matter how well an old valve radio is restored in the electronics department, the effort is wasted if a similar effort isn't put into the cabinet. The overall appearance of a set will depend on what the cabinet looks like and every attempt should be made to restore this to its former glory. Vintage radio cabinets fit into two categories: (1) those made of natural materials such as wood; and (2) those made of synthetic materials like Bakelite and plastic. The restoration procedure is quite different for these two categories so they will be dealt with separately. In this month's column, I will discuss the treatment for synthetic cabinets and leave the timber cabinets for next month. As far as I'm concerned, Bakelite and the so-called plastic (thermoplastic) cabinets can be lumped together under the one heading of "plastics". But the difference between the two regarding serviceability is considerable to say the least. Bakelite has been around since the early days of radio and first came into service around 1920. Bakelite is a strong, durable and Plastic radio cabinets, as used with this Radiola, are often badly scratched but can usually be successfully restored by sanding and polishing. The acrylic dial can be polished to look like new with a fine abrasive paste. 10 SILICON CHIP relatively stable material that has many excellent properties including that of being a good insulator of electricity. Used for relatively small jobs initially, Bakelite was used for radio cabinets from the early 1930s to about the mid-1950s. It wasn't until the late 1940s that cheaper plastic cabinets began to take the place of Bakelite. The passing of time is a good test for the durability of materials and time has proven that Bakelite will endure, whereas plastic generally does not. Most plastic cabinets from the post war period have virtually disintegrated with age. They frequently crack and distort and in some cases, totally self-destruct. On the other hand, many Bakelite cabinets from the 1930s era are still in quite good condition. Only a You can use "Brasso" to polish Bakelite or plastic radio cabinets but, for this work, car polish is even more effective. Clean the cabinet thoroughly before polishing and remove scratches using wet and dry abrasive paper. Vintage Radio Kits & Parts ORPHEUS *RADIO* This stylish old receiver was made by Mullard. Its Bakelite cabinet was in excellent condition and has been restored so that it now looks brand new. Suppliers of • • • • • VALVES RADIO KITS CAPACITORS RESISTORS BOOKS, ETC. Please send for our free catalogue ORPHEUS RADIO RSD B98 BALLARAT VICTORIA 3352 Ph. (053) 34 2513. Fax (053) 31 3412 FIX-A-KIT Kit Repairs - $1 5 per hour. Normal Rate - $30 per hour. No charge for kits that can't be repaired. 3 month Warranty on repairs. Construction - fixed or hourly rate. 1 2 Month Warranty on Manufactured Kits. This neat little Stromberg Carlson is another receiver that used a strong, yet attractive Bakelite cabinet. A toothbrush is useful for cleaning those hard-toget-at nooks and crannies. drop or some other similar shock treatment is likely to damage a Bakelite cabinet. Restoration Despite the obvious differences between plastic and Bakelite, the restoration procedure is the same for both types. Let's go through the procedure step by step. The first step in restoring a cabinet is to remove all detachable fittings; eg, dials, dial mechanisms, brackets etc. Nothing is more annoying than to skin a knuckle on some sharp protruding object that could have been easily removed. Next is a thorough clean-up and the best way to do this is to scrub the whole cabinet in a tub of hot soapy water. A nail brush and a toothbrush are handy tools for this job as they can reach into obscure corners and grooves where dirt and Custom Designing, Manufacturing, Large or Small Quantitites. HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment. (02) 633 5897 (02) 92 6309 Fax (02) 925 0840 FEBRUARY1989 11 llltlll The cabinet of thls 1937 model Airzone was cracked in three places due to rough treatment but was repaired satisfactorily using super glue. These receivers used a rather complicated dial mechanism. grime have collected over the years. After cleaning and drying, inspect the cabinet for cracks. Whether plastic or Bakelite, many old cabinets will have cracks in them which should be repaired if the spread of the crack is to be checked. Super glue is a good remedy for cracks and a bead of glue run along the inside of the cabinet will usually give a satisfactory repair. Make sure that the crack has dried out This old Radiolette receiver was made in 1937. Its cabinet is made of Bakelite and is in excellent condition despite its age. Bakelite is a very durable material and lasts much longer than plastic which was introduced in the late 1940s. and is not full of water before applying any glue, though. The next job is to remove any deep scratches from the outside surface. This is best done using medium grade wet and dry abrasive paper, followed by a finer grade to smooth things over. Wetting the paper gives the best results. Although sanding will remove the scratches and produce a smooth finish, these smoothed areas can contrast quite noticeably with the RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 4-HOUR TURNAROUND SERVICE 12 SILICON CHIP rest of the cabinet. This can be particularly apparent with some Bakelite cabinets, especially those that have a slightly rippled surface texture. The simple remedy for this problem is to sand the whole cabinet. It may make the job more time consuming but the overall result will be better. Polishing At this stage of the proceedings, the cabinet is ready for polishing. In previous columns I have suggested that "Brasso" metal polish is highly suitable for this job and so it is. However, I have since found that automotive cutting and polishing compounds are even more effective. These special abrasive pastes have a little more bite in them than "Brasso" and they not only cut well but also have a built-in polish. But regardless of the polishing agent used, there is no escaping the hard work required to complete the job. A good surface finish can only result from a considerable amount of rubbing. In particular, special attention must be given to all those awkward nooks and crannies such as grooves decorative scrolls and the like. Once again, an old toothbrush does an excellent job of these otherwise inaccessible tricky bits. Those with good workshop facilities at their disposal may prefer to use a fabric buff on their cabinets which could save a bit of time and effort. But be careful. Some plastics, particularly acrylics, have relatively low melting points and the heat generated by too much pressure on the buff can quickly gouge a deep hole into the surface of the cabinet. Don't forget to also clean and polish any parts that go with the cabinet such as control knobs, detachable speaker grills and dial escutcheons. Control knobs in particular can be difficult to clean thoroughly, as dirt and grime can clog up their fluted edges. A scriber point run through each groove will quickly remove the accumulation of 40-50 years of dirt and rubbish. Once again, Bakelite knobs are usually reusable and polish up like new. Plastic knobs, on the other hand, are not so durable and like plastic cabinets, tend to selfdestruct. One common trouble with pushon plastic knobs is that when they are pulled off the pot shaft, they often come apart, leaving the imier section of the knob still attached. I recall one set that had all four knobs snap off when I tried to remove them. A squirt of WD40 or the like will help with knob removal but if those knobs have been made of cheap plastic, there is still a good chance of them ending up in two pieces. Speaker cloth While that just about covers most aspects of cabinet restoration, this story would not be complete without some comment on speaker fabrics. No matter how well the cabinet is restored, the job will look pretty poor if the dirty, torn, moth- Polystyrene capacitors YES Made here in Australia? YES Made Special to Type? YES Where From? Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors. Why design circuitry which requires additional components to achieve a specific capacitance ; we can wind exactly the capacitance you need to match your design criteria within the ranges of 1 OpF to 1µF and up to 10,000VDC. Capacitors are manufactured to 0.25%, 0 .5%, 1 .0%, 2 .0%, 2.5%, 5%, 10% and 20% and are priced according to tolerance . All capacitors are tested to 2.5 times the rated voltage. --.--------------, Interested? Call us now on: 102J 938 4690 I Yes, I am interested in your capacitors. I I Please post me details of the following values: I I ...,... voc . ' . voc . .. , ... voc .. ., . voc OR Cut out and post this coupon to I Name (Please print) Post Office Box 740 _ ~_r_o_~_v_a_~_._N_.s_._w_._2_1_0_0_ __ · : Address 1_~~~~~-~~~~~~J eaten speaker fabric is not replaced. Unfortunately, suitable speaker fabrics are now quite difficult to obtain for vintage radio restoration. No fabric made today has any resemblance to that used in radios 40-50 years ago. Hardly anything comes even close to the original materials. Instead, one has to make do with curtain materials and old evening dresses from the opportunity shop and even then they are not what is really required. If a new modern fabric is used on an old radio it either looks out of place or is too clean and new looking for the age of the receiver. Believe me, choosing a suitable speaker fabric is one of the most difficult aspects of vintage radio restoration. In many cases it is better to use a serviceable piece of material from another old radio. For example, the torn fabric from a large console set may have a u_sable corner that could fit a smaller mantle model. If the cloth is a bit grubby or faded, it can often be reversed and it will look OK in many instances. No matter what, re-using old speaker fabrics frequently produces a far more realistic restoration than would a piece of new and unsuitable material. When all is said and done, no-one really expects to see a 50-year old radio in as-new condition. Most people would expect a restored radio to be clean, tidy and well preserved - but not necessarily looking brand new. If the set is really old (50 years or more), a good piece of second hand material will look far better than something new and spotlessly clean. Incidentally, if any reader knows of a supplier who has some old speaker fabric, I would greatly appreciate hearing from him. In conclusion, restoring a radio cabinet is not a difficult task but it can be time-consuming if the job is to be done properly. However, this time is well spent since the appeal of an old radio will very much depend on its final appearance. ~ FEBRUARY 1989 13 ALL 'YOUR ELECTRICIANS' REQUIREMENTS Just. in case you hadn't noticed(!) over the past few monthB we've greatly increased our range of Electricians' and Contrai:tore' requirements: cables, outlets, boxes, eoo 800. Now you can get your bits and _pieces at the same placll you get your bits and pieces! Twin Flat "Switch" Cable JUST A SMALL SELECTION insulation (not red and black) for use in switch wiring (ie ceiling rose down to switch, etc). White cable avoids mixup of neutral and switched wires. cat W- 2063 Power Twin & Earth - Heavier 1/1. 78 conductors for general purpose power circuit usage. Twin insulated conductors plus earth. rated at 25A. Cat W-2062 Light , ! .111.13 conductors in red and tir/';/' black insulation, with earth wire, for general purpose lighting circuit usage. Rated at 1OA. Gat W-2060 ( , 1 yellow insulation. For all general purpose earth wire usaae (also makes a great aerial wire for radio use!) cat W-301 o 1'°/mor $12511oom roll 7O•tm or $6O/100m roll • ed1t1on Antenna Handbook from the •• small size m a transformer? Vou antennas Update Now! Cat B-2208 want a toroidal And If you want a 1;,j~~a~s2v2Agpl~~u~g~\~" one' wmd1ngs Ideal for audio amplifiers Cat M 1 2 t3ftll!I .:,-- '° R d" a IO H dbook Was $69.95 Theory an ~ Hundreds of mods, adaptions, tips etc to get the most from the EPROMs used in most CB's. If you're into CB: 1 95 17 ge~~7 i-~~J A great one for the Aussie amateurwork • Ideal reference . . NOW ' for getting that elusive amateur licence! s5995 ' ~39:S 80 to 480MHz IN "Universal" Panel Meters ~~;!.~~!!~~~!for the amateur, VHF listener or st ~! s;w~ and up to ~~~:a~~~u1 250W rated. Cat 0-4315 '129 Larger 96 x 82mm movement, 96 x 49mm scale. cat 0-2065 ~~~~ts~:'~~ cat D-4434 • 1OOkHz to 1SOMHz/6 ranges • 3% Accuracy • Sine and Square Wave Output cata-1312 IT'S A GAS! MARINE RADIOS ■■■ $ AU~ I. Butane Powered Tools AV~ mean you can go anywhere! Portasol: Save money by buying at Dick Smith Electronics. Save worry by knowing you're protected. And, quite possibly, save a life! The original and best non-electric Silver brazingsoldering wherever& you want. Or even decorative woodwork, etc. ~~~~, to use - MC610 VHF Seaphone Approved ~ _ , Got some connections to make? Make'em safe and sure with these multi-pin connectors. As used in computers, automotive industry, Space Shuttles .. . they're everywhere! Assemble-it-yourself system, plug is captive to socket unless released. Your choice of pins, too: /1 2-WAY ea f,;,/~ Ca!P-5102$1 75 ~,:!~~25~ {JI 4-WAY ea, P-s 104 1250 ea 6-WAY rid / ) Cat P-5106 , ea ~ 295 12-WAY~, ;,,,, Cat P-5112 The ultimate for close in-shore boating. VHF has 55 channels, is reliable and normally monitored 24 hours a day! AND you can make phone calls direct from your boat. Fit one to your boat before you go out again! Cat D-1 720 $ ,\ : / · :,',;,, s3a5ea _,,.. '.' , ·✓ 9 $30FF 3 9 SUPPRESSORS - ~!,~~riao $1 4 95 Butane Gas: Broadbander Base scanner antenna that won't break the budget. 65 to 520MHz coverage at less than $50 - it's a bargain! Cat 0-4432 95 Pressurised tin of Butane gas to refill your Portasol or Blowtorch. With appropriate nozzles. Cat N-1081 75 OHM (CO-AX) TYPE Great for extensions & vcr's. Cat P-2030 Our Transistor Dip Meter is ideal for the ham shack, test bench or lab, and has a 1.5 to 250MHz range with 6 colour coded plug-in coils. Essential test gear! Cat 0-1335 s139 Lux Meter ~ -0° 0 No - it's not for soap flakes. Direct read-out of fight $129 C-2050 C-2052 C-2054 C-2060 C-2062 Bin TWINCONE IBAX020) C-2080 Bin TWIN VOICE (8JX) C-2082 CONNECTORS ~;~;~!s Melal 750hm Line Socket Wanna Dippa? 0 0 ' l "I, 12mWOOFER (12W) 10,n WOOFER (6J) Bin WOOFER (BW) 5inMIDRANGE(RM120) 4in MIDRANGE (C10M21) NOW $49.95 $39.95 $29.95 $11,95 $9.95 $19.95 $24.95 Everyone knows Dick Smith EIBctronics is the place to go for your new TV antenna. But what about the bite and piecBB? The plugs &, sookete? The splitters? The wall outlate? The cable? And everything elae in the TV field? Hers are just a few to whet your appetites! $249 pay twice as much? Cat 0-1400 (i)m WAS $54.95 $44.95 $34.95 $16.95 $14.95 $24.95 $29.95 brilliantlY.. T one s49 AF Generator I~ ~ ~~:,~:;i;~;: ~~~~~~ r~, Economy RF Generator ~ Blowtorch: '1495 They're back! Our famous audio & RF sig gens are back after some time being out of production. ~:e~~~~e a! t~~C~2k~~xW~e0nwt~~~ ~:rka~~~~~~h e can-1310 bases, covers 70 to 525MHz (receive spopk MORE TEST GEAR! Audio & RF Generators • 10Hz to lMHz/6 ranges • <0.5% distortion ~~toYa~gerated Suits standard size outlets, switch plates, etc - perfect for mounting proud of wall or other surface where inset mounting cannot be achieved (eg brick!) cat P-5531 to Qrab some for replacements , standard cig lighter butane and recharges in seconds. Get more from your scanner than those little whips can give you! Mobile antenna fits all standard Universal Meter Shunt Pack $229 g s495 ~°tciJ1~~~~1t~n:e~ Mobile Scanner Antenna lOOUA MU65 Universal Movement Just add the shunt or multiplier you want to make the meter you want. Includes instructions. cat 0-2046 -. Mounting Block Standard a r c h i t r a v ~ mount light switch, ~ SPOT with looping terminal, rated at ~ • 10A., (While they last - we re shortly • _chan_ging to _ ind1v1dual switch ~ $275 ~~tc~~s:lates) .. ARRL Internationally known as one of Data Book ;grua1r:;~~f~~ Single Light Switch UTILUX: 10 OFF $5 OFF i~~'n :v~1\~;~~~~~i~rery THE MULTITOROIOALS regardless of size' Be quick JI G U A IIQ1 V What low noise, high capacity and fflH ftH .. ' :A buildmgnew systems whatever' WAY the best references you can get on CB EPROM ~ldealfor"lateron" fitting of points, switches, etc to ~~ri~n~g~~~~\rom th f t · t et~ 5530 wall. Cat p. Don't to11at: we also have a great nnge of mains plugs & sockets, fittings, etc for flexible cords. AND Ille flexible conll A BIT OF HEAVY READING! Not a lightweight, this one the new 15th , ,o 1295 110/m or $9Ot100m roll Standard 7/0.67 copper earth wire, with green/ Multistrand cable consisting of 7/0.50 conductors, in insulated flat format with no earth. Rated at 15A. Cat W-206t Wall Board Clips o,' I I general purpose outlets on one standard size plate. As used e-v-e-r-y w-h-e-r-e! Cat P-5560 $ Insulated Earth Cable ~ l /mor$95/100mroll Twin Flat ' 1 '1 95/m or $175t100m roll 1 21 Dual GPO: Twin switched 1/1.13 cable (rated at 10A) with red and white Twin & Earth - • • Switches, Outlets, Etc: ~ t, •l'•ea WALL OUTLET PLATES "Snap in" System - buy the wall or architrave plate you want, and snap in the outlet insert required - 75 Male/Female Coax Joiner ohm, 300 ohm or even "F" (professional) type! When you need a sex change! Cat P-2070 large Wall Plate •1 ea 40 m (same size as power point}. cat p. 2050 s250 Small Architrave Plate (Same 1 Metal 750hm Line Plug As above, but the other end! Cat P-2020 ., . •1•• ea ~ size as light switch) cat P-2052 Coax Cable Joiner Guess what this is for? Cat P-2075 ., .. ea Sl 75 Inserts: 300 Ohm Cat P-2056 750hm Cat P-2055 "2"" '2"" ~~; ~Yf6ss 300 OHM (RIBBON) TYPE Skirting Board type 300 Ohm outlet. Cat P-2081 s195 300 Ohm Plug to suit above - crimp type. Cat P-2082 s120 300 Ohm Cable Joiner (plug and socket 300 Ohm Plug to suit Cat P-20B6 Cat P-2084 system, solderless) above - solderless type . s195 s150 COAX CABLE 300 OHM RIBBON W-2081 75c/m W-2070 30c/ffl N- available at IIO atom: • NSW • Albury 218399• Bank1town Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • Campbelltown (046)27 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gostord 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Squiue 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Warringah Mall 905 0441 • Wollongong 28 3800 •ACT• Fyshwick 804944 •VIC• Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankaton 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 1614 • Ringwood 879 5338 • ~~!:W'=b;:: O~~~ ~s:: CitJ 223 4122 • BeverleJ 347 1900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 • WA ~rc!cn::::;:~ ~~ ~:f.Lfo~~r;,-;:~; iJ~~ ~~o!!~;~:~~~5JJ • 2 5 +~,,;n~:rem;J~e7gg~ • Aclel ■kle • Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 • NT • Stuart Part< 811977 NOW AVAILABLE AT ALL STORES - OR CALL TOLL FREE: (008) 22 6610 FOR HOME DELIVERY! Our range of DATAK products has proved enormously successful: small wonder, this quality product, made in the USA, makes virtually every aspect of PCB making a breeze. Below are just some of the DATAK products - try them! Etch Resist Pen Dry Transfers DATAK PCB designing and Remember the pen we used to sell? We stopped selling it when we found out the resist was a deadly poison (others still sell it!). The DATAK etch resist pen is a non-nasty, highly effective way to make one-off PCB's. cat N-5180 $495 Datak Burnishing Tool: You'll need one of these if you're at all serious about making PCB's. Cat N-5715 s1095 DATAK make some great transfers. To whet your appetite (no, Lucretia, you don't eat them) here are two. SAMPLER ASSORTMENT, containing 17 different sheets. A great starter pack. $ Cat N-5766 199S 141111 Datak Contact Frame: Eventually, you'll get a PCB that's RS. Fix it with Cricuit Fix Kit. Pure Copper traces & do nuts with adhesive backing, readY. to repair a PCB or modify a new one. Great for developers too. Cat N-5900 s3995 You could spend hundreds of dollars on a hands-free phone. Or you could build this kit. Simple, effective - and cheap! Use in conjunction with existing phone for full two-way hands-free conversation. Cat K-3100 Masthead Amplifier TITLES, LABELS, NUMBERS, ETC: NOTE: l'llwlr su"1! llll iocllllld. Mixer/Preamp Module Perfect for band use - or any general purpose mixing application. 4 inputs allow virtually unlimited choices: guitar, mic, organ, line inputs, etc. with each input fully adjustable for gain and impedence. Also includes bass, treble and "presence" control. Drives any of above amplfiier modules directly, and uses same power spply. Cat K-3036 Similar to above, five shee1li to pack, with letter/number sheet. Black (Gat N-5755) White (Gal N-5756) Mini Mixer Here's a great beginners project - with specs that make it good enough for serious use. 4 input mixer suits mics, guitar, etc very simple to make. Cat K-30.S Test & lndusbial Equipment s299s Completing the set: 5 sheets for CRO's, meters, analysers, etc etc. Yep, you'll need one of these Also includes letter/number sheet. too. If you're serious, that is. Black (Cat N-5757) White (Cat N-5758) Beats the old sheet'o glass and two books routine anytime. Cat ALL ABOVE SETS: N-5710 i Discolight sS9a DIAL MARKINGS, SCALES, PATTERNS, PANEL & METER \'lllfo EN11ANCER lt. .. ~"C:£ $ Video Enhancer 165 If the sound of your VCR is crook what about the video! Especially when you're making copies of tapes (yes, the ones you shot yourself of course).Make sure you don't lose detail when dubbing : use the EA video enhancer. Very simple to use: all control is via one knob. And unlike most enhancers, you can cut as well as boost (ideal for softening harsh pictures). Cat K-3463 s4995 Variable Power Supply: 30V/1A Resist Ihese Bargains? Unlikely! s99 Ideal for laboratory, amateur/experimenter or technician use. Adjustable up to 30 volts at up to 1A- very handy! Includes full metering and overload protection. Cat K-3475 DATAK quality resist products to make your PCB making a breeze. They re also refills for the DATAK PCB kit Developer Resist Filter N-5905 N-5907 N-5711 $18.95 Move over, Musicolor: Discolite is here. It's the latest in colour organs, with chaser, audio chaser, etc etc. You want a light show? Discolite is what you want! Cat K-3150 I ; Marks & Switch Patterns s4995 Crook TV signal? Build your own masthead amplifier and fi x it! Very simple to build comes complete with all hardware, power supply, etc. Easy one night project. Cat K-5800 i. &t $11.95 Hands-Free Phone making material - exclusive to Dick ' - - - - - - - - Smith Electronics. You've asked for them: an economic range of tapes, pads, lettering and so on for designing PCB patterns, marking panels and so on. Here they are! A great range of wording ready for your front panel or other marking TARGETS & REGISTERS applications. Dry transfer lettering: •• . • simply rub over them with a containing 40 different pcb & suitable burnisher (such as a ball crosshatr regIstratIon marks for point pen) precIsIon alignment. · 5795 caI N-ss20 Audio, TV & Hi Fi Five sheets containing titles for the UNIVERSAL OIL above applications plus one letter/ number sheet. Available in Black PAmRNS, allowing you to (Cal N-5753) or White (Gal N-5754) make any Oil pattern up to 40 leads. 48 in pack. cat N-5768 Amateur Radio & TV 1 Datak Circuit Rx It Kit: THE BEST OF '88! $10.95 Pos/Neg Rim Refills Photo-sensitive polyester film suitable for laying out PCB patterns in pas or neg format. 6 sheets 125 x 150mm. · Cat N-5705 1GHz DFM for under S300: complete! s1395 MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: :=. ~~=~:;~~i~s ~ = H:C:o~r E~~:~~~s i1 Jm ----------,■ 7 I i t : =:e~~rec~:~n~t~~ E!j~~~c! H~ • DIIIN: Chris's Hi-Fi 82 8711 • Font.: Forster Village Electronics 54 5006 • Glen 1-: John Sommerlad Electronics 32 3661 •6r1ffhll: Miatronics 62 4534 • ll!Wlnll: Lyn Willing Electronics 221821 • wmore: Decro 21 4137 • Mofet: Moree Electronics 52 3458 • ~ : Headware 72 3895 • Nowra: Nowra Electronics 21 4979 • Wavp: Phillips Electronics 21 6558 •VIC• Morwetl: Morwell Electronics 34 6133 • Sfllppartoa: Phillips Electronics Pty. Ltd. 21 9497 • Warmambool: Marrtronics 62 9870 • QLD • lklndallerg: Bob Elkin Electronics 721785 • Kilpuy: Holmes Today Electronics 621658 • Kawana: Splitec 94 7349 • Mactcay: Stevens Electronics 5t 1723 • Mlr1'anltlll: Keller Electronics 21 4559 •SA• Mt Galillier: Hutchessons Communications Centre 25 0400 • WA •Albany: Micro Electronics 41 Glnldtoo: Batavia lighting & Electrical 23 1842 •Kmtlla: Dave's Oscitronics 85 4836 • TAS • Oovonport: A.I. Electronics & Hobbies 24 8322 20n • Yes it's true. A 1GHz (that's 1000MHz just in case!) digital frequency counter with typical sensi tivity of around 20mV - and even more, it's delightfully simple to build! cat K-3437 YAESU V Yaesu's Budget FT747GX: Everything you need without the frills! Yaesu recognised the fact that amateur transceivers were getting out of the reach of the average person. So they did something about it: The FT? 47GX. A full 100 W with all amateur bands between 1.8 and 30MHz SSB, CW, AM and optional FM; receiver is 100kHz to 29.9999MHz continuous. If you're looking for value along with performance, there's simply not a better rig than the FT747GX; anywhere! Cat D-2930 IDEAL FIRST RIG! 5 1349 FT•211 RH FT-290Mkll 2M portabiltiy, versatility and performance at its best, The Yaesu FT-290Mkll is just what you need for real amateur value! Features include All Mode (LSD, USB, CW & FM), 10 memories, 2.5W output, twin VFO's and much more. Cat D-2875 s975 FBA-8 optional Batt Holder Cat D-2876 FT-690RII $675 45W 2M Mobile Transceiver with mic, mounting bracket. Cat D-3493 Plus bonus 5/8 wavelength antenna Cat D-4207 (Save $15) Portability Plus/ 54995 Broad Band VHF/UHF Discone Antenna Use it for transmitting and receiving! Save $40 on this high quality, Japanese made, broad band · discone antenna that covers scanning, 2M, 70cm, UHF CB ... the lot. 3dB gain and less than 1.5:1 SWR between 80 & 480MHz! Sensational value at this astounding low price. Cat D-4315 899 Was $169 also available 5 Only S129 150W (FM) max power rating And the ultimate HF/VHF/UHF transceiver: FT767GX With bonus microphone! Combine the best features of the renowned FT-757GX with the FT-726 and what do you have? The all band FT767GX. DC to light (well, almost) covering all HF, VHF and UHF bands up to and including 70cm! Sure, the FT767GX isn't cheap. In any sense of the word! It has all the features and p~rformance you'd want from your amateur station - because it is a complete amateur station - in one! Cat D-2935 Save over $300 off Catalogue price s4595 • Every amateur band between 160m and 70cm! • A complete amateur station in one handy package! • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • Campbelltown /046)27 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City . - - - - - - - - - 267 9111 • Tamworth 66 1711 • Warringah Mall 905 0441 • Wollongong 28 3800 • ACT • Fyshwick 80 4944 • VIC • Balla rat 315433 • Bendigo 43 0388• Box Hill 890 0699 • Dandenong 794 9377• East Brlghton592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 1614 • Ringwood 8795338 • Springvale5470522 •OLD• Brisbane City 229 9377• Buranda 391 6233• Caims 311 515 • Cherrnside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300• Townsville 725722 • Underwood 341 0844 •SA• Adelaide City 2321200 • Beverley 3471900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 But communications from Dick Smith Electronics let you do all the things you dreamed about when you were a kid. Rsducsd to sag Now you get extra value from the amazing DSE AM CB! It's easy to operate and comes with maximum legal power, all 40 channels, microphone, mounting hardware and a great low price to boot. Cat D-1200 Power & Performance! 5W 6 Channel Marine A hand-held transceiver with all the power and performance of a fixed model! The Uniden AX55 is fitted with all 6 marine channels and you can also use it for CB (just fit the appropriate crystals). A superb transceiver at a bargain price! Cat D-1125 Was$189Now $169 Deluxe AM CB Al ABudget Price! The compact Maxon AM CB is a favourite among CBer's for quality, reliability and value! With all 40 AM channels, maximum power and superb performance. Complete with mic and mounting hardware. Cat D-1450 Just ~ Extra $99 Range With SSB CB If most of your boating is by the coast - here's the one to buy! The Uniden Barracuda AM/SSB Marine Transceiver with an impressive range of features including 10 AM and 10 USB channels an9 the one-touch Emergency Channel 88 switch. Cat D-1714 Va/us/ s2 79 55 Channel VHF Marine With SBBphons Compatibility! A truly classic transceiver from Uniden the MC610. Outstanding value and an astounding array of features. With all 55 international frequencies, 1W/25W power saver switch, instant emergency channel 16 selection .. .it's superb! Cat D-1720 ,• - - - - - - - - - - - - -- -- - - - - NSW• Albury218399• BankstownSquare 7074888• 8Iacktown6717722• BondiJunction3871444• Campbelltown (046}27 2199 • Chatawood Chaae 411 1955 • Chutlora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Homlby 477 6633 • Liv«pool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcaatle 61 1896 • North Ryde 88 3855 • Pan~matta 689 2188• Penrith (047)32 3400• Railway Square 211 3777 • Sydney City 267 9111•Tamworth681711 • Wamngah Malt 905 0441 • Wollongong 28 3800 • ACT• Fyahwiclt 80 4944 • VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Dandenong 794 9377 • Eaat B~hton 592 2366 • EMendon 379 7444 • Foobcray 689 2055 3 4 ;:;_-:;•~~"5~~ • Redbank 288 5599 • Aockhampton 27 9644 • Southport .a2 9863 • Toowoomba 38 4300 • Townnile 72 5722 • Underwood 341 0844 •SA• Adelaide City 232 1200 • Bffertey 3471900 •St.Marya 277 8977 • Ellubeth 255 6099 ~~0 Fremantle335 9733 • North Perth 328 6944 • Perth ctt, 481 3261 • TAS 0 8 ORDER BY P.,_Q,.f TOLL FREE (001) 22 8110 FOR DSXprea 24 HOUR DESPATCH 0 ::=~~ o~~~ :a'tt~i~:_~~ ~1fyM~:09~~; •~,!!~6 ~=i~ :~s;,:-;.~• 15,1/ft,66 • g:~ ;:Jf!"~1«:n!2%1~6Ji/.'g~~:~~~; You've seen the reports in the newspapers: burglary is on the increase. Everyone knows someone who's been robbed! It's a fact: after a lull of a couple of months, break-ins are increasing at an alarming rate. Burglars are getting smarter and more brazen. Haven't been broken into yet? Don't be too complacent! Your place could be the next on the burglar's 'hit list' - particularly if it isn't protected. These days, you need the peace of mind that only a good security system can give. And the best security system is the one you install yourself. LED status indicators tell you what's happening. Our new Alarm Control Unit is perfect for the home, office, factory ... anywhere. Fully professional quality (it's actually based on a commercial module) but so simple for the home handyman to install. Do it yourself and save a fortune AND you'll be the only one who knows the details of your own system & wiring! • MAINS ON • LOW 8ATlERV • HOM E Heavy duty steel case with in-built tamper protection. SECURITY CENTRE L-5140 4 individually controllable sectors for maximum versatility. Key-lock switched for maximum security. • 0 --1--------9 Inbuilt battery charger for your standby battery (fits inside case). Mains power supply included. ~ " ~ -----t-- Advancad circuitry minimises false alarms, fully complies with noise pollution regulations. Siren oscillator built in suits standard horn speakers no expansive sirens to buyl Constant 12V output for PIR's and other accessories PLUS switched 12V (alarm) output for strobes, alarm diallers, etc. Cat L-5140 $ 199 Manufactured exclusively for Don't let your place be next on the list! And ta complete your system ... Vibration Sensor Easy to install, detects vibration and shock in windows, doors, ceiling, etc. With adjustable sensitivity. Cat L-5250 Only lntramd Detector ... s595 Security Lights A fantastic idea for entrance ways, verandahs, etc. Features two spot lights which are turned on when movement is sensed. Lights can be set at any angle for maximum coverage. Lamps not included. Cat L-5335 s7 Passive lnfrared Detector ~ · .~ The best, most versatile sensors you can get for your alarm - and this one's value plus! Covers an area 6m x 6m. Comes with mounting bracket. Cat L-5009 sag I . Heat Sensor Why not make sure you don't burn down? Your alarm can look after that, too with this · ,,,.~~"'---.heat sensor! Triggers at 135 degrees F. Cat L-5254 s1795 Magnetic Reed Switches The most reliable, yet simple form of window/door protection. Surface tvoe (suit aluminium windows etc). Set of magnet and switch. Cat L-5210 . Horn Speaker Individual Switch cat L-s215 S2 95 Individual Magnet cat L-s214 S1 95 --~,,/ Concealed lvpe Suit wooden doors~ frames etc. Magnet & Switch. Cat L-5212 Snecial Switch Sel for roller tilt doors. Cat L-5227 ss95 Window Foil An effective part of your alarm system and also a visible deterrent. $ 32m roll adhesive foil. Cat L-5200 Foil terminal blocks. Cat L-5205 Pressure Mat Hides under carpet: if it's walked on, it goes off. Put in doorway or hall for optimum protection. cat L-5270 s2495 Horn Cover M Strobe Lamp Blue flashing light warns if your alarm has - _ been triggered - even after the horn stops. Cat L-6000 ' ' ' ~ "· s2495 With inbuilt tamper protection, stops them disabling your alarm speaker. Catl-5300 Q a 1495 roll s1 ea s1395 Economy Horn Speaker gives ear-piercing wail to almost wake the dead! Cat C-2705 ~ s3995 /k 95c /m j/L Connecting Cable Various types to suit every application, 4 Core: Suits detection devices needing power or horn sp-eakers with tamper protection, etc. Cat w-2100 .. 4 Core Phone Cable Similar to above, but small diameter. Suits. permanent installation (not flexible). Cat W-2120 Other types of cable: (Fig. 8, multicore, etc always in stock). 75c0 /m Emergency Button Gell-Cell Batteries Just in case! Prowlers, peepers, snowdroppers ... one push of the button and it scares the daylights out of them! Cat L-5285 Rechargeable batteries for back-up use. Various sizes available (depending on capacity required) but general purpose 12V, 2.6Ah is ideal for l-5140 panel. Cat S-3320 s395 • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • Campbelltown (046)27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 6118.9 6 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Warringah Mall 905 0441 • Wollongong 28 3800 •ACT• Fyshwick 80 4944 •VIC• Ballarat315433 • Bendigo43 0388 • Box Hill 890 0699 • Dandenong 794 9377• East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 1614 • Ringwood 8795338 • Springvale 547 0522 • QLD • Brisbane City 229 9377 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide City 223 4122 • Beverley 3471900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 • WA • Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 • NT • Stuart Park 81 1977 OR ORDER BY PHONE (TOLL FREE) 008 22 6610 FOR 24 HOUR FROM DSXpress - DELIVERED DIRECT TO YOUR DOOR. Measure Tran The Beta Tester is easy to use. You just connect up the transistor, select NPN or PNP, press the pushbutton, and rotate the knob clockwise until the LED goes out. You can measure the gain of any bipolar transistor with this simple Beta Tester. Just connect a transistor, push the button and rotate the knob until the LED goes out. Then read the transistor's Beta off the scale. That's all there is to it. No meter is required and it can he built for around $20. By MALCOLM YOUNG & LEO SIMPSON Nobody likes putting dud transistors into circuit. If you can, it is always a good idea to check your transistors before using them. With this easy-to-use tester it is but a moment's work to check each transistor. By doing so you eliminate one source of uncertainty from . your work - you know that the transistors are OK. Even if you are fairly certain that you don't have any dud transistors there are times when you will want to measure their Beta (DC gain). Some circuits call for transistors with a minimum gain figure and these are easily checked with this Beta Tester. Other circuits call for transistors to be matched to within a certain tolerance, say within ± 5%. Again, this is a snack to do with the Beta Tester. If you are building an audio power amplifier you will get lower crossover distortion, and therefore better sound, if you can match the 20 SILICON CHIP driver and output transistors closely. If you are building a stereo amplifier you will have at least two pairs of driver and output transistors. By using our Beta Tester you can "mix-n-match" the devices for best overall performance. Finally, you can use the Beta Tester to identify the leads of unknown transistors - where the labelling might have been rubbed off or the type number is unknown to you. We set out the method for doing this in a panel accompanying this article. OK. So there you have a number of good reasons to build this handy unit for your electronics workbench. Once you build it up you'll wonder how you ever managed without it. Long battery life The Beta Tester is housed in a compact plastic utility box measuring 130 x 68 x 43mm. Its controls are simple. There is a momentary contact pushbutton which applies power to the circuit while you do the test. This means that the circuit will not flatten the battery because you've forgotten to turn it off. So the battery should last a long time. In addition, there is a slide switch to select NPN or PNP transistors and a knob with a scale graduated from 5 to 500 - the Beta scale. Using the Tester is simple. Rotate the knob fully anticlockwise, connect the three flying leads to the transistor and select the NPN or PNP setting of the slide switch. Now press the pushbutton and the LED (light emitting diode) will light up. Rotate the knob until the LED just goes out. The pointer of the knob will then indicate the Beta of the transistor on the scale. The Beta Tester uses a 2.BkHz signal to test the gain of transistors; it is not just a simple DC gain test. The circuit There is nothing fancy about the circuit components; just one 555 timer IC and a few transistors. However, a closer look will show that there are a number of clever aspects to the circuit (see Fig.1). Fig.1 can be split into four sections: an oscillator, an amplifier, a detector and a comparator. and match transistors Vlith this: sistor Beta Tester pin 2 and a square wave with an amplitude of close to 9 volts peak at pin 3. The frequency of oscillation is about 2.BkHz. There are two advantages of using the 555 oscillator circuit described here, instead of the more usual arrangement. It uses at least one less resistor and it gives an almost exact 50% duty cycle square wave without any need for adjustment or careful selection of the timing resistors. The square wave output from pin 3 is then fed via a tkn resistor and clipped by two diodes, D1 and D2, to give a waveform with an amplitude of 1.2 volts peak. This waveform is then coupled via a O. tµF capacitor to the amplifier stage. This uses the transistor under test, in a simple common emitter amplifier stage. IC1, a 555 timer, is the oscillator stage. Instead of the usual freerunning oscillator configuration with a capacitor being charged from the positive supply rail, this circuit has the .033µF capacitor being charged from the output, pin 3, via a 68k0 resistor. In more detail, IC1 works as follows. The .033µF capacitor is connected between the junction of pins 2 and 6 (connected together) and OV. The capacitor is charged and discharged via the 68k0 resistor connected to pin 3. At switch-on, the voltage at pins 2 and 6 will be OV and the output at pin 3 will be high; ie, close to + 9V. The capacitor will now charge towards 6V (ie, 2/3Vcc). When it reaches that point, the output at pin 3 will switch to OV and the capacitor will then discharge towards + 3V (ie, 1/3Vcc). The output at pin 3 will then switch to + 9V again and the charging cycle will recommence. The result of this cycling will be a sawtooth waveform with an amplitude of 3 volts peak to peak at Common emitter amplifier To explain further, a "common emitter" amplifier is one where the transistor's emitter is common to both the input and output of the amplifier. In its most simple form, the emitter is connected to "ground" which may be the negative or positive rail of the circuit. The input signal is then applied between the transistor's base and ground while the output signal is taken between collector and ground. In our circuit, the emitter of the transistor under test is connected to OV while its collector goes to the + 9V rail via a 1.5kn resistor. DC bias is fed from the collector to the base of the 'Ji'UT (transistor under test) via two series tMn resistors. This describes the connections for an NPN transistor. NPN/PNP selection If the TUT is a PNP type, slide switch S2 swaps the connections to the collector and emitter so that the emitter goes to + 9V while the collector goes to OV. Otherwise the circuit stays the same. The 2.BkHz signal from the 555 oscillator is fed via a 22kn resistor and 2Mn linear potentiometer (wired as a variable resistor) to the base of the TUT. The 2.8kHz signal 0.1 o.1I "l .,. 1M NPN T gy: 0.1 ..L. IC1 555 D1 B .0022I .,. 02 .,.. ELJc VIEWED FROM BELOW ~- NPN .,. .,. .,. 1 TRANSISTOR BETA TESTER Fig.1: a 2.BkHz oscillator (IC1) is used to pulse the base of the transistor under test (TUT). This signal is then amplified by the TUT which drives class-B detector stage Qt. When the positive voltage swings on Q1's base exceed 1.BV, Qt, Q2 and Q3 conduct and the LED lights. FEBRUARY1989 21 parator function. If the positive swings of the 2.BkHz signal fed to the base of Ql are not 1.BV or more, then Ql and Q2 will not conduct, Q3 will not be turned on and the LED won't light. So these transistors perform an important signal level monitoring function - they won't operate if the signal is not big enough. The test function All the parts, including the switch, are mounted on a small PCB. Make sure that the parts are installed so that they do not protrude above the mounting surface of the switch. Three PC pins are used to anchor the pot lugs. is then amplified by the TUT and then fed to the following detector stage via a O.lµF capacitor. Qt, D3 and D4 make up the signal detector stage. Qt acts as a class-B detector. It has no DC bias to its base and it conducts for positive swings of the 2.BkHz signal. Negative swings of the signal are clipped by D3, to protect the base of Qt. In effect, Qt acts as an emitter follower for positive swings of the 2.BkHz signal and does not conduct at all for negative swings. This is why it is called a class-B detector - because it only conducts for half the signal waveform. The detected signal appearing at the emitter of Qt is fed via diode D4 and stored in a O. lµF capacitor. This filtered voltage then turns on NPN transistor Q2 which then turns on PNP transistor Q3 and the LED. Ql, D4 and Q2 perform a corn- In the Beta test procedure described at the start of this article, potentiometer VRl is first set fully anticlockwise which corresponds to its minimum resistance condition (since it is wired as a variable resistor). This means that the maximum amount of 2.BkHz signal is fed to the base of the TUT (transistor under test) and so, providing it is actually working, it can't fail to have a big signal at its collector. This signal will be fed through to Ql and the other transistors and so the LED will inevitably be glowing. Now, to find the Beta of the TUT, we rotate VRl clockwise and this increases its resistance. This progressively reduces the signal to the TUT until, at some point, the signal at its collector will drop below 1.BV peak, or thereabouts. At this point, the LED will go out. The Beta of the transistor under test can then be read off the scale surrounding the potentiometer knob. Fig.2 (left): mount the LED so that the top of its lens is about 15mm above the board surface and don't forget the wire link under S2 on the copper side of the PCB. Note also that all the polyester capacitors should be bent parallel with the PCB. Fig.3 (right) shows the full size board pattern. 22 SILICON CHIP How to Test Unknown Transistors Most of us have come across transistors of the unknown and unmarked variety which usually get relegated to the junk box. The versatility of this instrument can be increased with a certain amount of operator skill and patience. Transistors can at least be identified as NPN or PNP and their Beta measured. With the aid of a data book you might go further and classify transistors into similar groups with a little trial and error. The procedure for such a task begins with identifying the tran_sistor leads. Set the Beta knob to minimum as before and clip the test leads to the transistor terminals. Test the transistor on both PNP and NPN settings and swap the leads systematically until the LED remains on. There are six different ways to connect the Tester to the transistor and two different transistor types (NPN or PNP). This means that, at worst, you will require 1 2 tests to find the particular pin out for a particular transistor (or discover the bl--dy thing doesn't work!). This task is reduced if you remember a number of ground rules. If you turn a small signal transistor upside down as shown in Fig.4, they all have their leads in a straight line or triangle arrangement. Further, as shown in Fig.4, their leads will be C(ollector), B(ase), E(mitter) from right to left in most cases and B(ase), C(ollector), E(mitter) for the remainder. Fig.6: for TO-3 style transistors, the case is the collector while the emitter and base leads are as shown. VIEWED FRDM BELOW Collector, Emitter as shown in Fig.5 . And for larger power transistors such as those in metal TO-3 cases (2N3055, etc), the case is the collector terminal and the base and emitter leads are as shown in Fig .6 . Reverse gain Fig.4: possible lead connections for small signal transistors. With the majority of common small signal transistors (such as BC547, BC557) the base lead is in the middle. For small power transistors in the plastic encapsulations, such as TO-220 and TO-202, the leads usually (but not always) run Base, Fig.5: the most common lead configuration for TO-220 & TO-202 transistors. BCE Once the pin . configuration is discovered then i_ t is simply a matter of turning up the gain control until the LED goes out. Note that there is still a possibility that the collector and emitter leads are reversed even though you have obtained a believable measurement. This is because bipolar transistors have a reverseactive mode of operation as opposed to the normal forward mode of operation . The reverse gain of a transistor is always very much smaller than the forward gain. So take the highest Beta result in figuring out whether a transistor is a NPN or PNP type . Some transistors will have a gain of more than 500, such as some BC548s, BC549s, BC559s etc. Some of these transistors can have a Beta of up to 900 which is well beyond the range of our simple Tester. However, you can still verify that these high gain transistors are working. If the LED lights, they are OK. Self-monitor function Interestingly, the circuit has its own self monitoring function which tells you that it is working properly and that the battery is not flat. Push the NPN/PNP slide button to the NPN setting and then push the button. Regardless of whether there is a transistor under test or not the LED should light momentarily. This happens because when power is first applied, the 1.5k0 resistor connected to the + 9V rail (for the NPN condition) charges the An insulated wire link must be installed on the copper side of the PCB between two of the slide switch terminals (see Fig.2). The completed PCB assembly is secured to the lid of the case using locking nuts on the pot and pushbutton switch collars. FEBRUARY1989 23 PARTS LIST 1 plastic utility box, 130 x 68 x 43mm (Altronics H-0153 or equivalent) 1 PCB, code SC04102891 , 72 x 61mm 1 9V battery, Eveready 21 6 or equivalent 1 snap connector to suit battery 1 clamp to suit battery 1 pointer knob, 30 to 35mm in diameter 3 alligator clips 3 PC pins 1 DPDT slide switch plus mounting screws (DSE S-2040, Jaycar SS-0821) 1 momentary contact pushbutton switch (DSE S-1102, Jaycar SP-0710, Altronics S-11 02) 0.1µF capacitor connected to the base of Ql. This causes a short pulse of more than 6V to occur at the emitter of Ql. So D4 conducts, as does Q2 and Q3 and the LED flashes briefly. This self test function does not work in the PNP mode because the 1.5k0 resistor is connected to the OV line. On the other hand, if you have an NPN transistor under test and the LED will not flash or light at all, then the transistor under test probably has a short between base and collector. r C + Semiconductors 1 1 2 4 555 timer IC BC558 PNP transistor BC548 NPN transistors 1N4148, 1N914 signal diodes 1 5mm red LED Capacitors 5 O. 1µF metallised polyester (greencap) 1 .033µF greencap Resistors (0.25W, 5%) 2 x 1MO, 1 x 68k!:l, 1 x 22k!:l, 1 x 1 OkO, 2 x 4 . 7k0, 1 x 2.2k0, 1 x 1.5k0, 2 x 1 kO, 1 x 2MO linear potentiometer Miscellaneous Insulated hookup wire, solder Power for the circuit is provided by a 9V battery which can be an Eveready Energiser type 5 2 2 alkaline battery for long life or an Eveready 916 carbon zinc type which will have a lower initial cost. Either way, we estimate that the battery should last a year or more with normal use. Construction As already noted, our Beta Tester is housed in a compact plastic utility box measuring 130 x 68 x 43mm (Altronics Cat H-0153 or equivalent). All the circuit,ry is B mounted on a printed circuit board measuring 72 x 61mm (code SC04102891}. Construction of the Beta Tester is relatively straightforward but before you turn on the soldering iron you should inspect the PC board to ensure the tracks are all etched properly and that there are no open circuits or shorts between tracks. You can check this by carefully comparing your PC board pattern with the artwork included in this article. Make sure that all the holes are drilled out too. Enlarge the hole for pushbutton switch Sl by first drilling a pilot hole of around 1-2mm. The hole for S1 should be around 8mm. The mounting holes for the lugs of the slide switch S2 should also be enlarged to 2.8mm (7/64 inches). . Three PC pins are used for the connections to the 2MO potentiometer VR 1. These should be mounted first as these are inevitably the hardest components to mount. Install all the low profile components next; ie, the resistors and the diodes. The slide switch we used is a particular panel mount type, Altronics Cat. S-2035 or Jaycar SS-0821. You can also use the Dick Smith Electronics type S-2040. Whichever switch is used, make sure that its lugs will fit into the PC board. Note that there is an insulated wire link on the copper side of the board 7 E + + D PNP 100 NPN TEST + L _J Fig.7: here is a full size reproduction of the front panel artwork. 24 SILICON CHIP under this switch. The momentary contact pushbutton switch we used is readily available. You can use Dick Smith Cat. S-1102, Altronics S-1060 or Jaycar SP-0710. The capacitors must be installed so that their height above the board does not exceed 10mm since the entire PC board assembly is mounted to the lid of the case using the fittings of S1 , SZ and VRl. Similarly, the transistors should be mounted so that their overall height does not exceed 10mm. Mount the LED, a 5mm red type, so that the top of its lens is about 15mm above the board surface. This will allow the LED to protrude from the front panel by the required amount. Wire in a snap connector for a 9V battery. Three test leads need to be fitted to the board but they should be left off until after it has been tested and installed on the lid of the case. This side-on view shows how the PCB is secured to the lid of the case using locking nuts on the pot and pushbutton switch collars. What is Beta? There are a number of ways of testing the gain of a transistor. The most common method is to connect the transistor in a commonemitter amplifier arrangement as shown in Fig.8. A fixed current is fed into the base and the resulting current into the collector terminal is measured. The ratio of the collector current to the base current is then the DC forward gain of the transistor. It is commonly known as DC current gain , hFE or DC Beta. Most digital multimeters with a Beta measuring facility perform the above test. They use a base current of typically 1 OµA and they measure the collector current directly. Our Beta Tester uses an AC signal of 2.8kHz to measure AC Beta, which is also commonly METER T I I ..L.. I I ...L.. Fig.8: the common emitter configuration for an NPN transistor. referred to as the "small signal current gain" or hte· Again a small AC current is fed into the base of the transistor and AC current in the collector is then measured. The ratio between the two is the AC Beta. In practice, the AC Beta of a transistor is generally slightly less than the DC Beta. AC Beta also decreases as the signal frequency increases Checking it out Check your soldering and installation of the components carefully. Compare the board with the PC component diagram of Fig.2. Now connect the battery and switch S2 to NPN. When you depress the test button, the LED should briefly flash, as described above. This tests Ql to Q3 but does not test the 555 timer, ICl. To test ICl, connect a short jumper lead between pin 3 (the junction of the lkn and 68k0 resistors] and the junction of the 22k0 resistor and VRl. Connect another jumper lead between the base and collector lead connections for the TUT. Connecting the two jumper leads couples the 2.BkHz signal from !Cl to the input of Ql, via VRl and a O.lµF capacitor. Now, with the pushbutton pressed and VRl fully anticlockwise, the LED should light. Rotating VRl clockwise by about 30 degrees will then put out the LED. The Tester is now ready to be placed into the plastic case. Attach the front panel artwork to the lid of the case and drill out the holes where marked. If you are building from a kitset it is likely that the front panel will be supplied screen printed and drilled so these steps won't be necessary. Now you need to make up three flying leads; these will be the transistor test leads. Use three different colours of insulated hookup wire, preferably of the multistrand extra flexible type. We suggest red for the collector lead, black for the emitter lead and white for the base lead. Cut the three leads about 150mm long and solder an alligator clip to one end of each. Fit each alligator clip with an insulating boot. The leads should then be poked through the appropriate holes in the front panel and then soldered to their respective points on the PC board. Secure the battery in the base of the case to stop it from rattling around. You can use a piece of double sided foam backed tape for this purpose. Alternatively, for a more secure job, make up a battery clamp from scrap aluminium. Connect up the battery snap, attach the lid assembly to the case and you are in business. ~ FEBRUARY1989 25 HIFIREVIEW Cutec Z-2000 stereo power amplifier Cutec is a new name to the high fidelity market but it is one we will probably see a lot more of in the future. As one of their first products, they have produced the Z-2000 stereo power amplifier, a rugged unit with very high music power. Cutec call their amplifier a "digital power amplifier" although this is really a misnomer since there is no digital circuitry in the unit. Presumably they mean that it is fully compatible with digital audio sources such as compact disc and DAT machines (when and if the latter become available). Which brings us to the question, what criteria does an amplifier have to meet in order to be considered compatible with digital sources? The answer must be that it does not cause significant degradation of the sound quality provided by digital sources. To do that, it must put out a lot of power, have a wide frequency response, very high signal to noise ratio and very low distortion. Arguably, the Cutec Z-2000 aims to meet these criteria. It is a large and rugged unit in a black rackstyle case. It measures 437mm wide, 153mm high and 398mm deep, including the front handles, rubber feet and rear terminals. A rack mounting kit is available if desired. Mass is just 15kg. Controls Being a power amplifier, the Z-2000 is practically devoid of controls. On the front panel, it has separate volume controls for the left and right channels, a large onoff switch and a number of status indicators. On the rear panel, it has a pair of RCA sockets which are paralleled by 6.5mm jack sockets. The output terminals are shrouded binding posts which will present no problems with heavy duty cables. There is also a recessed slide switch for selecting normal stereo or bridged mono operation. Inside, the Z-2000 appears to have all the hallmarks of a classic stereo power amplifier - large fully shielded power transformer, lots of power supply capacitance, and the two power amplifier circuit boards symmetrically arranged either side of the power transformer. A particular feature is the use of large herringbone style heatsinks which must be particularly efficient since they have such a large surface area. We've seen these heatsinks used in a number of high power amplifiers and they appear to be very effective. We'd love to know how they are manufactured; they appear to start out as an extrusion which is then "upset" in a shaper machine to form the very fine fins. Specifications The Cutec Z-2000 stereo power amplifier looks conventional enough but it can deliver up to 625 watts per channel of dynamic power into 40 loads. 26 SILICON CHIP As the specifications show, this is a big power amplifier. This is not so much in the continuous power ratings, although these are very respectable, but in the dynamic power output which is a measure of the amplifier's capacity to deliver very high power for short periods, say for several hundred milliseconds. As far as dynamic power is concerned, the Cutec Z-2000 is one of the new breed of power amplifiers which vary their supply rails to cope with instantaneous power demands. In this way it can deliver high power without having to cope with the high standing power dissipation of an amplifier with high voltage supply rails. (For the full background on the subject of dynamic power and headroom, see the articles in the July 1988 issue of SILICON CHIP}. We had no trouble in confirming the amplifier's specifications for 80 and 40 loads, as far as continuous power and rated harmonic distortion were concerned. As far as 20 loads were concerned, we had to "pass", as our loads weren't up to the task. To measure the dynamic power, we used the standard IHF signal which consists of a 20 millisecond toneburst of lkHz at a repetition rate of two pulses per second. We were able to achieve figures which were very close to those specified in the accompanying panel for 80 loads while the result for 40 loads was comfortably ahead of the maker's claims at 625 watts. Compared with conventional power amplifiers, these results for dynamic power are huge. As far as headroom is concerned (the US IHF method for expressing dynamic power, see July 1988 SILICON CHIP}, the result is + 4.5dB for 80 loads and + 4.7dB for 40 loads. These are very respectable results for an amplifier in this price range. For the bridged mode, both channels of the amplifier drive one load in push-pull mode. This nominally gives twice the power of a single channel although normally the manufacturer puts a restriction on how low the load impedance can be. In this case though, the Z-2000 is rated for both 80 and 40 loads, with 20 being permissible although the manufacturer does not recommend testing at this value. No matter. We confirmed the figures into 40 and 80 loads. We weren't able to do a dynamic power test in bridge mode though because our test set-up doesn't allow it. On the basis of the other tests though, we have no doubt that Inside the Cutec Z-2000 amplifier. Note the large power transformer and 80,000J.tF of filter capacitance. The herringbone heatsinks work very well. the maker's claims would be validated. Signal to noise ratio figures were very good. We tested for both unweighted (20Hz to 20kHz) and Aweighted figures. We achieved 105dB unweighted (worst case) and 115dB A-weighted with respect to 140 watts into 80 loads. These are very good figures. As you can see then, the Z-2000 had no trouble delivering the goods. It is a very powerful, very quiet amplifier. It is also rugged and able to withstand intentional abuse such as shorting the speakers at full drive. We can recommend it for anyone interested in upgrading their system. Recommended retail price of the Cutec Z-2000 is $1159. For further information and the name of your nearest dealer, contact Arista Electronics Pty Ltd, 5 7 Vore Street, Silverwater, NSW 2141. Phone (02) 6483488. ~ Specifications Power output (stereo mode) Load Continuous mode 80 140 watts RMS x 2 40 210 watts RMS x 2 20 250 watts RMS x 2 Dynamic power 450 watts x 2 570 watts x 2 690 watts x 2 Power output (bridged mono mode) 80 400 watts RMS 40 625 watts RMS 1000 watts 1250 watts Rated harmonic distortion Intermodulation distortion Input sensitivity Input impedance Signal to noise ratio Damping factor Slew rate (.02% (.03% 0. 7 volts RMS 50k0 ) 11 0 dB A-weighted ) 120 80V/µsec FEBRUARY1989 27 Using Comparators to Detect and Measure OUTPUT 3 14 OUTPUT 4 13 INPUT GNO 2 3- LM339 1 3 OUTPUT OUTPUT 2 1 V+ 5 INPUT INPUT INPUT INPUT 1- 1+ 2- 2+ Fig.1: the LM339 contains four independent comparators and can operate from single or dual voltage power supplies. Discover how to use op amps to monitor real-world conditions. By JAN AXELSON Comparators are among the easiest op amp circuits to use. Unlike other op amps, whose outputs vary linearly in response to some input, the outputs of comparators switch between just two voltage levels, depending on the relative voltages at their inputs. A comparator is really quite similar to a toggle switch. When the toggle, or lever, is raised slowly (in a linear fashion), the switch will suddenly snap to the on position. There's no in-between state! Likewise, as the toggle is lowered, the inner switch mechanism will suddenly flip to the off position. The comparison stops here though, because comparator circuits are much more flexible than ordinary toggle switches. Comparators are ideal for voltage monitoring in test or alarm circuits. Any condition, such as temperature or light, that can be sensed as a voltage can be monitored with a comparator. Besides using comparators in simple voltage-detecting circuits, you can use a pair of comparators to detect whether an input falls within a range of voltages; or you can use a series of comparators to control a bargraph display, for a good-looking and more precise indication of signal levels. The circuits that follow are typical examples of comparators in action. They can be used to guide you in choosing and using comparators to fit your own circuit needs. What's special about comparators? Although some op amps are specifically designated comparators, in many cases a general-purpose op amp can also serve the same purpose. The main limitation is that op amps often include phase and frequency compensation for better closed-loop stability. Since comparator circuits operate open-loop (without negative feedback), they don't need this compensation and respond faster without it. 28 SILICON CHIP Most of the examples in this article use the low-cost and readily available LM339 IC, which contains four independent comparators on one chip. Fig.1 shows the LM339 chip's pinouts. The chip can be powered from a single supply ranging from 2-36 volts DC or from dual supplies from ± 1 to ± 18 volts DC). Supply current requirements are less than one milliampere (lmA) which is low enough to allow battery-powered operation. Comparator basics Fig.2 shows a basic comparator circuit using the LM339. The voltage to be sensed (Vinl is connected to the non-inverting ( +} input (pin 5), while the reference, or trip point, voltage (V rerl is applied to the inverting ( - } input (pin 4). The comparator's operation is straightforward: when Vin is greater than Vref, V 0ut (at pin 2) goes high. Conversely, when Vin is less than Vref, V 0ut goes low. ....-------+9V Rl 1k Fig.2: in this basic comparator circuit, Vout goes high when Vin is greater than Vref· The reference voltage (Vref) determines the comparator's toggle point. Fig.3 illustrates the comparator's response (Voutl as Vin is varied with respect to V ref· For inverting operation (ie, Vout high when Vin is less than Vref), all we have to do is swap Vref and Vin at the comparator's pin connections in Fig.2. The reference is now connected to the + input while Vin TIME (a) + VOLTS Voull:::====------------~====-..TIME (b) Fig.3: this diagram shows the relationship between the input and output voltages for the comparator represented in Fig.2. The upper graph (A) shows the inputs to the comparator's + and - inputs while the lower graph (B) shows the circuit's output response. R2 390{! +9V--+-------~Niltr--. Rl 10k 2 (a) 8 .,. Rl 390{! +9v--.....-~~--, (b) (c) Fig.4: here are three ways of using a light-emitting diode (LED) to indicate the electrical output state of a comparator. pull-up resistor Rl, and the collector current through Ql lights the LED. When Vin is less than V ref, pin 2 is low and Ql is cut off, turning the LED off. Resistor RZ limits the current through the LED. The circuit in Fig.4b is similar to Fig.4a but this time the comparator controls a PNP transistor. When pin 2 goes low, Ql turns on and lights the LED, giving the opposite effect of the NPN circuit in Fig.4a. Fig.4c shows yet another option for connecting a LED. Typical current-sink capability of the LM339 is 16 milliamperes. This is enough current to light a highefficiency LED directly, without using a driver transistor. The circuits in Fig.4 are shown using one of the four identical comparators in the LM339. In these and the circuits that follow , the inputs to unused comparators on the chip should be tied to ground. The power supply rails should be connected at pins 3 (positive) and 12 (ground) as shown in Fig.2. Achieving snap action The circuits shown so far all have limitations. If Yin has noise riding on it, the output may chatter high and low as Vin approaches V ref· A slowly changing input may also caus'e the output to oscillate as Vin nears the trip voltage. Adding a little positive feedback can take care of both of those problems. Fig.5 shows a temperature-monitoring circuit with positive feedback via resistor R6. The trip voltage is set with potentiometer R4 . The sensed voltage is taken from a voltage divider containing a thermistor (temperature-dependent resistor) and resistor RZ. As the temperature of thermistor Rl increases, its resistance decreases because it has a negative temperature coefficient. The·resulting drop in the network's resistance increases the current through RZ, raising the voltage at pin 4 of the LM339. Here's how the positive feedback works. When the output at pin 2 is high, a small part of the output voltage feeds back through R6 to pin 5. This raises the voltage at pin 5 so that it is slightly higher than the level set by R4. When rising temperatures subsequently cause pin 4 to go higher than pin 5, pin 2 goes low, buzzer BZl is energised, and the voltage at pin 5 drops , this time to a level slightly lower than that previously set by R4. The buzzer thus remains on until the temperature falls enough so that pin 4 is less than pin 5 aga in. r-----------.----..--+9V Rl THERMISTOR PIEZO BUZZER 10k AT 25 ° C goes to the - input. V 0 ut will now be high when Vin is less than V ref and will switch low when Vin exceeds Vref· A light emitting diode (LED) provides a simple indicator of a comparator's output state. The circuits in Fig.4 show several ways of interfacing a LED to a comparator's output. In Fig.4a, when Vin is greater than Vref, pin 2 goes high, transistor Ql turns on through .,. R6 1M Fig.5: in this circuit, a piezoelectric buzzer sounds at and above a temperature selected by potentiometer R4. Positive feedback through R6 ensures that the buzzer snaps on decisively at the trip voltage. FEBRUARY1989 29 ..-----------+-------+9V Because the turn-on voltage is higher than the turn-off voltage, the buzzer snaps on decisively at the desired temperature and remains on until the temperature drops. How much feedback? The feedback resistor (R6 in Fig.5) is usually chosen to be much larger than the input resistor (R5). Its precise value isn't critical but the smaller it is, the greater will be the difference between the turn-on and turn-off trip voltages. Although you can calculate the effects of the feedback mathematically, for basic alarm circuits like this it's often just as easy to set the trip point by experimentation. You simply bring Rl to the desired alarm temperature and adjust R4 so that the buzzer just turns on. As shown, the difference between the trip points in Fig.5 is around 400 millivolts. Positive feedback is also useful in relay-control circuits. Fig.6 shows a light-sensing circuit that controls a relay. The light sensor, R2, is a cadmium-sulphide light dependent resistor; its resistance decreases as the light level increases. As the light level goes up, pin 4 is progressively pulled lower by the decreasing resistance of the light dependent resistor. When its voltage is less than the voltage on pin 5, pin 2 goes high and turns on Ql, activating relay RLYl. Resistor R6 makes sure that RLYl turns on and stays on until the light level has fallen by a preset amount (as determined by the value of feedback resistor R6). .,.. Fig.7: this single-ended comparator circuit can be used to measure voltages that would otherwise exceed the comparator's input voltage rating. single-ended configuration, Vref is proportional (but not equal) to the trip voltage of Vin· If R2 is made much larger than R3, the voltage at pin 5 will remain well within the differential input rating, even with very large input voltages. For example, in Fig.7, if Vref is set at - lV, the trip voltage at Vin is + lOOV! One important limitation of the single-ended configuration is that Vref must be of the opposite polarity from the trip voltage. In the circuit shown in Fig. 7, Vref is always negative, so the trip voltage will always be positive. Germanium diode Dl protects the comparator by limiting negative voltage inputs to - 0.3V. Creating a window What if you want to determine if a voltage falls between an upper and a lower limit? A window detector is the answer and the LM339, with its multiple comparators and open-collector outputs, is ideal for that use. In Fig.8, the thermistor/resistor voltage divider of R4 and R5 connects to the - input of one comparator and the + input of another. The trip points for the comparators are taken from another voltage divider made up of Rl, R2 and R3. Because the outputs of the LM339 have open (uncommitted) collectors, they can be connected together as shown, and a low output on either one will pull their combined outputs low. When Vin falls between Vref-high and Vref-low, the outputs of both comparators go high and turn on LED Monitoring large voltages An important characteristic of comparator devices is their differential input voltage rating. This is the maximum voltage difference allowed between the + and - inputs of the device for correct operation. Many comparators, including the LM339, can handle input differences nearly as large as the difference between their positive and negative supply pins. If you need to monitor voltages larger than the input rating allows, a voltage divider can be used to derive a proportion of the total voltage. Alternatively, a singleend.e d comparator like the one, shown in Fig.7 can be used. Here, Vin and Vref connect through resistors R2 and R3 respectively to the + input of the comparator, while the - input is grounded through Rl. In the r----.----f-----..----+-~+9V R4 NTC THERMISTOR 10k AT 25 ' C R6 10k r--------------+----+------+9V 01 R7 10k 1N914 .____ I RLY1 Vin C i::::: R2 CdS PHOTO-RESISTOR R5 .,. .,. 10k R6 20k Fig.6: light dependent resistor R2 is used here to sense the light level. When the light rises above a preset level, as se_t by potentiometer R4, the output of the comparator switches high and turns on transistor Ql and the relay. 30 LM339 ~ SILICON CHIP .,. Fig.8: this window detector circuit lets the experimenter know when the detected temperature is within a pre-selected range. Resistors Rl, R2 and R3 set the comparator trip points and thus determine the upper and lower limits. +9v_..._......_ _ _ _ _ _ _ _ _ __ 1. But if Vin is greater than V ref-high or less than Vref-low, the output goes low and LED 1 is off. The LED is on only when the temperature is within the window set by resistor network Rl, RZ and R3. Fig.9 is similar but different - it's an out-of-window detector. In this circuit, the output of the bottom comparator goes high when the temperature is too high, lighting LED 2 [red). Similarly, the output of the top comparator goes high and lights LED 1 [green) when the temperature is too low. When the temperature falls within the window, both comparator outputs are low and the light-emitting diodes are off. REGULATED VOLTAGE SOURCE R3 1.2V 1.2k R4 Sk Bargraph display The final example [Fig.10} is a light meter with bargraph output. The circuit design has been made easier by using an LM3915 bargraph driver IC which contains a series of 10 comparators. The - input of each comparator connects to the buffered input voltage and the + inputs connect along a 10-resistor voltage divider network. This divider network biases each of the non-inverting outputs to a different level. The top of the resistor string [pin 6) is connected to a regulated voltage which can be varied by potentiometer R4. This means that the output of the top comparator only switches low when the voltage from the buffer amplifier exceeds the voltage on pin 6. The previous LEDs in the series are turned on in 3dB steps in response to a rising input signal on pin 5. This pin connects via a ZOkO resistor to ther buffer amplifier. To use the LM3915, you need only add a sensing circuit and connect the comparator outputs to a bargraph display or a succession of 10 light-emitting diodes. In Fig.10, the input at pin 5 of ICl is taken from a voltage divider made up of Rl [a cadmium-sulphide photo-resistor) and RZ. Each comparator inside ICl compares the buffered input voltage to its reference and turns its LED on or off, as appropriate. The R7 390H +9V--+----.----+----YN,.---. R1 20k R4 10k R2 10k IC1 LM3915 +9V R1 CdS PHOTORESISTOR .,. Fig.10: the LM3915 IC contains a series of 10 comparators and can be used to drive a bargraph display. In this circuit, the number of LEDs lit in the display varies with the light level sensed by photoresistor Rl. number of LEDs that light thus varies with the light level at Rl. Resistor R3 sets the current in each of the light emitting diodes at 10 milliamperes (lOmA), while potentiometer R4 varies the full scale [ie, all LEDs on) input voltage between 1.2V and 7V. Leaving pin 9 of ICl unconnected will change the display from a bargraph to a single-dot display. In that mode, only one LED is lit at a time [which saves on battery power). The position of the LED indicates the signal level and thus the light intensity. Now it's your turn R3 20k RS HTC THERMISTOR ' 10k AT 25°C Fig.9: an out-of-window comparator detector circuit. When the temperature is too high, the output of the bottom comparator goes high and lights LED 2 (red). Conversely, when the temperature is too low, the output of the top comparator goes high and lights LED 1 (green). Comparators are circuit building blocks that are both easy to use and adaptable to many circuit situations. By carefully studying the circuits presented in this article, you should be able to adapt them to your own specialised requirements. le This article first appeared in Hands -On Electronics, USA (August 1988); reprinted with permission. FEBRUARY1989 31 VIFASpeaker Kits PRICE SENSATION!!! We all know how fantastic the VIFA speaker system SA-series speaker units sound. It would not be an exaggeration to say that they generally pe,form as well as built equivalents that cost twice as much! Despite this, Jaycar is constantly trying to further reduce prices for the customers' benefit. We are now proud to announce MASSIVE PRICE REDUCTIONS on the entire range of VIFA SA-Series HI-FI speaker kits. Check out the savings below, but hurry! These prices can only last while the Aussie dollar is strong - and that can change overnight. SA-70 SA-50 5" Woofer/Dome Tweeter 2-Way bookshelf kit with cabinets and crossovers. 30W RMS power handling. Price savings are for speaker and cabinet buy only. See our catalogue for full details, or call into any Jaycar store for a demonstration. (Demo speakers are not at Concord) Cabinet size: 210D x 170W x 260Hmm Cat. CS-2460/CB-2452 . 8" Woofer/Dome Tweeter (Sealed cabinet) 2-Way kit complete with crossovers and cabinets. 70W RMS power handling. Cabinet size: 250D x 260W x 490Hmm Cat. CS-2471/CB-2472 SAVE SAVE $30 $50 ONLY $369 APAIR ONLY$449 APAIR SA-130 SA-100 • • 8" Woofer/Dome Tweeter (Bass reflex) 2-Way kit complete with crossovers and cabinets. 1 00W RMS power handling. • ONLY $669 A PAIR • • • 3-Way Reflex Complete with crossovers and cabinets. 130WRMS power handling. Cabinet size 368D x 300W x 940Hmm Cat. CS-2485/CB-2467 SAVE Cabinet size: 338D x 290W x 640Hm' Cat. CS-2460/CB-2482 SAVE $100 10" Woofer $200 • ONLY $999 APAIR ' JAYCAR - BEST FOR QUALITY, BEST FOR BARGAINS not er surp us stoc pure ase. The quality Is first class, the only problem Is the colour. It would have been totally In vogue In the 1950's or 60's, but It's not really suited to the loungerooms of the SO's. II you have speakers In the rumpus room, garage, boys room etc., that require cloth then this cloth Is Ideal._ Oh, we haven't told you about the colour yeti 'It Is also Ideal II you REALLY want to be MEGA trendy l STYLE 1 Gold with black strips at about 1 1/2" Intervals. Size S' x 1 ml Cat. CF-2768 $3.95 SA VE $10 STYLE 2 Gold with gold reflective pieces through It. Size 3' x 1mt. Cat, CF-2757 $2.95 SA VE $7 STYLE 3 11'1 1 bit more down to 11rth. 11'1 brown with red, ack and grNn fleck. Size 3' X 1ml, Cat. CF-2758 $3.95 - - Size 40mm x 40mm. Cat. HH-3100 I As used with the,Slllcon Chip speakerproject. Headset, I phone microphone with lead and plug. Mini size I 3.5mm ultra lightweight. Cat. AA-2018 I 10 for $1 for $8 <CONTACT CONNECTOR BARGAIN ,• F16.9s f Easy to use automatic connectors. Slrrply wrap around the existing wire and new wire and aqueeze. NORMALLY $1.25 for 4 or 31 oa .i . I SPEAKER(Two atyles supplied In pack) rI PACK 15 for $1 .95 (only 13e Cat. HP-1207 1 PHONE Ref: Silicon Chip Sept 11188 PACK 100 for $10 (only10eaa)Cat.HP-" 1208 • I that High quallty hand• free telephone adaptor workl extremely well, I former Full kit Including box, panel, laollllng trana• and 111 p1rt1. Unb1llevablt 11r apllttlng 120dB. 12 volt 300mA, I Cat, KC-5040 Normally 1211,115 I ,,.----~~~~ ...-1 Llmlt1d quantity Brand new mini mlc lnHrt, I avIllabl1 for ld11I for 111 thOII mlnlIturl11d clrcultl, ....... I Operlllng Voltage 1.5 to 15V 00 I $19.95 Current Oonaump. 0.5mA or I•• (8V aupply) (:i Frequency Range 40•10,000Hz I SAVE$10 Output lmpedan01 Same u load r11!1tIn ea) _, omnld lrectlon■I , I.} SAVE$6 - HANDS FREE TELEPHONE HEADSET L - . ::, • . . ; :· =--=-=·::::-= :.J (150 ohm• 5k ohm) Senaltlvlty 88dB :!:3dB SIN Ratio More than 40dB Cat, AM-4008 ' $2.20 f you're tired of locking 11 that mantle clock read ing ten pall one (and It'• not), why not fix It! It Nill take you about 10 mlnutea with one of our clock modul11, have four typea, Juat remove lh• old mechanlam, throw It In the bin and replace It with an accurate quartz cryetal movementl even have onoe that play the old faahloned tune (W11tmln11er Chime) and then chime the hour, Aleo Ide■! for making your own cu1tom clock face. w, Size: 3,5mm x 8mm dla, w, STANDARD MOVEMENT • Very oompaot 58 x 58 x 15mm • Powered by 1•AA battery • Supplied with 3 dlfftrant H II ol handa Cat. XC•0100 Inm~ll~1tll mm•. I $12.95 Another•urptu• •coop purchsH. PENDULUM MOVEMENT/QUARTZ CLOCK Ideal clock meohanl1m replacement for a ,mall pendulum cl or create your own pendulum. • 3 1111 of hand1 aupplled • U111 1·AA battery Cat. XC-0103 1 $16.95 MELODY CLOCK MOVEMENT TAG TANTALUM BARGAIN We have aboU1 20,000 pea of a 4. 7uF 16V tag tantalum made In West Germany. Normally worth 75e each. Grab yourself a bargain. -·- ··· ··-··- · · · .... · Cat. RZ-6636 10 for$2 100for $15 1000for$110 12 VOLT ILLUMINATED BEZELS ThHI b1zel1 look Identical to the expen1lve rectangular lllumlnI11d 1wltch11 for car alarm, , except that there 11 no 1wltch, Quality Europaan brand Arrow Hart, Normally worth $15 each. Complete with globe. Yellow Cat. SL-2870 Orange Cat. SL-2871 Blue Cat. SL-2872 Green Cat. SL-2873 I I ONLY $3.95 ea MAGNIFYING GLASS Magntty the savings you make by buying at Jaycarl Also good for checking small corrponents as well. Every toolbox should have one. Lens 35mm dla., handle 40mm long. Cat. QM-3500 (DOM not magnify our prices eithtK I) JAYCAR Nol FOR EX-STOCK KITS 120 WAIT PA/ . GUITARAMP MODULE KIT - - KA-1109 KA-1115 KA-1116 KA-1117 KA-1119 KA-1220 KA-1230 KA-1390 KA-1392 KA-1428 KA-1430 KA-1505 KA-1506 KA-1508 KA-1522 KA-1535 KA-1550 KA-1556 KA-1500 KA-1574 KA-1582 KA-1595 KA-1598 KA-1610 KA-1630 KA-1635 KA-1636 KA-1650 KA-1652 KA-1660 KA-1670 KA-1675 KA-1677 KA-1681 KA-1682 KA-1683 KA-1688 KA-1689 KA-1690 KA-1691 KA-1692 KA-1693 KA-1694 KA-1695 KA-1696 KA-1697 KA-1698 KA-1699 KA-1700 KA-1701 KA-1702 KA-1703 KA-1704 KA-1705 KA-1706 KA-1707 KA-1708 KM-3015 KM-3030 KM-3040 KM-3042 KM-3050 Electric Fence 300W amp module 300W power supply 300W speaker protector Transistor tester Signal tracer Zener diode tester Freq. counter 50MHz Prescaler 500MHz Function generator Vocal cancelltir TAl Hau effect Transistor asst Ignition i~t~ ~~,~~r~~~~ ~~~~;~!~arm Ultra sonic move det. Railmaster controller 30V 1A power supply Houseaiarm DiRlJal capacitance meter 40 inverter 121230V 300W inverter 121230V 12V lamp flasher AMlfM stereo tuner AMlfM remote control Playrnaster 60/60 Bluep1int 60/60 Electric fence Light saver Screecher car alarm Audio oscillator (metered) 3 band short wave radio Dual track power supply Battery monitor Electronic strobosoope Exp. power supply DI box TV colour bar/pattern gen Voice operated relay Metronome VolVcontinuity test AC/DC Millivoltrnet"' Econ. Temp probe DMM Utility timer Tran, FET, Zener test Bench amp- signal trace Pow"' transistor tester RF detector r,.ooe 50MHz Dig req meter Line Filter FM Receiver Stroboscopic Tuner Cheap capacitance meter Powermate 2 Supertimer Listeninj post Ultrafid ity preamp Dual ~ed modem ~ synthesiser khorseamp 23.50 $119.95 $105.00 $23.50 $21.50 $27.95 $16.95 $169.50 $46.50 $129.50 $24.95 $44.95 $42.50 $29.95 $115.00 $23.50 $89.50 $34.95 $109.95 $89.50 $169.00 $85.00 $99.95 $249.00 $12.95 $599.00 $99.50 $329.00 $369.00 $59.50 $15.99 $34.95 $165.00 $79.50 $129.95 $14.95 $13.95 $26.95 $39.95 $159.00 $24.95 $19.95 $29.95 $46.50 $19.95 $21.95 $55.00 $39.95 $22.95 $13.50 $99.00 $39.95 $55.00 $47.50 $16.95 $109.00 $59.00 $39.95 $359.00 $169.00 $43.50 $35.00 KM-3056 KM-3061 KM-3063 KM-3064 KM-3065 KM-3067 KM-3068 KE-4014 KE-4023 KE-4029 KE-4033 KE-4050 KE-4052 KE-4048 KE-4200 KE-4204 KE-4220 KE-4405 KE-4666 KE-4690 KE-4698 KE-4711 KE-4722 KE-4724 KE-4725 KE-4728 KE-4729 KE-4730 KE-4733 KC-5010 KC-5012 KC-5013 KC-5015 KC-5016 KC-5017 KC-5019 KC-5021 KC-5023 KC-5027 KC-5028 KC-5029 KC-5031 KC-5032 KC-5033 KC-5034 KC-5035 KC-5036 KC-5037 KC-5038 KC-5039 KC-5040 KC-5041 KC-5042 KC-5043 KC-5044 KC-5045 KJ-6502 KJ-6504 KJ-6505 KJ-6531 KJ-6535 KJ-6655 KJ-7000 100WmodulelessMFets Microphone preamp Uo satellite deooder Octave EQ mod AS true 232intertace NiCadchar~ FMmlnder g Mixer preamp Si~nal Spkr protector Ni ad battery charger Temperature probe ETl480 SOW amp module ETl480 1oow amp mod ETl480 power supl)iy 5000 power amp 5000 1/3 octave equaliser ETl499 1fiJN Mosfet amp ETl581±1-15V power sup RS232 Centronios intern ETl342 CDI 4 sector house alarm Mini FM transmitter RS232 Commodore Parametric equaliser Solder Iron temp control Ring tone customiser Guitar preamp Solar gen p/supply Active Crossover Capacitance meter Car radio fFwer suppy 1GHz Dig Freq meter Telephonerin~er Speed conrol dimmer 24 to 12V converter 100W amp module Protector car alarm Low ohms adapt DMM Ph meter Train controller CD H/phoneamp Optical tacho D,scolit,1 SbJdio 2 Preamp Remote 1or Car Alarm Plasma discharge Wireless doorbell TX Wireless doorbell RX Universal power supply Vader Voice ~kerphone ini Mill"' Knttrider LEDs 12 PA/Guitar amp Car Safety ~hts Poor Mans asma Syntom drum synth 8 channel mixer Console Psupply above 28011/3 octave Eq. 201010 band stereo Eq. Hall Effect Trigger kit Red light flasher $79.50 $36.95 $55.00 $59.95 $27.95 $24.95 $11.95 $39.50 $22.50 $14.95 $32.95 $27.50 $34.50 $29.50 $499.00 $219.00 $109.50 $27.50 $32.50 $79.50 $29.95 $9.95 $16.95 $23.50 $39.50 $29.95 $45.00 $12.95 $39.95 $27.95 $28.95 $299.00 $19.95 $18.95 $59.00 $38.95 $79.50 $29.95 $49.95 $89.00 $24.95 $49.95 $159.50 $229.00 $79.50 $129.50 $16.95 $42.50 $12.95 $19.95 $89.00 $29.95 $17.95 $72.50 $29.95 $49.50 $42.50 $595.00 $119.00 $239.00 $169.00 $99.95 $19.95 I I I Ref: SIiicon Chip November 1988 This rugged Mosfe1 amp module Is designed specttlcally to drive a 100V line transformer for PA. It can also be used for guitar and stereo amps. Short form kit. PC board and all corrponen1s supplied, Including Mosfets., No power supply parts or heatslnk Included In kit. Heatslnk extra Cat. HH-8550 $22.95 I Cat. KC-5043 (kit) I $72.50 _ I I I I I I I I I I I I L _______ _J KNIGHTRIDER" LED SCANNER KIT I Ref: SI/Icon Chip November 1988 Provides the scanning effect same as on kit car in Knightrlder TV program. Use for burglar alarm applications, novelty applications on kids toys, etc. PC board and all components supplied. Cat. KC-5042 But he tells us that he has been working with Silicon Chip on the great new e· 2-way speaker kit that appears (definltelyl) In this month's issue. It's a fantastic speaker system for the price - $269 complete with cabinets, crossovers and speakers that have Theile-Small specifications. (Whatever that meansl) I I of Ithe case has two screw holes for easy mounting. Slide handles also take label I I cards, which are also supplied. I Size: 137(0) x 97(W) x 85(H)mm. I Colour: Beige I 7 Cat. HB-6305 I MINIMl"~i:A~lllEl~LABLE I I WAS $5.95 I BA-1404 Trans IC 38MHz Mini Crystal I NOW ONLY $3 95 I r - - - - - - - - $29.95 ~a~L::='~-~C.::_R~2~$~ _J L - - - - - - :.. _J SIMPLE PC -DRIVEN FUNCTION GENERATOR KIT Ref: EA January 89 Here's a simple and low cost llttle unit which lets you use your Personal Computer to generate signals with almost any conoeivable wave-form. It hooks up to the computer via a standard Centronics-type parallel printer port, making It corrpatible with almost any kind of computer. Cat. KA-1709 going to sell for before I heard them. They sounded like some expensive English speakers that an old ex-boyfriend had. Being a Yuppy he had plenty of money and spent a fortune on those speakers. I thought the same as those English ones but when the Boss told me the prioe - I nearly fell over backwards ... 1SAVE $2 , 1 girls In the Kit dept. will will have plenty I A two drawer case with 3 removable plastic I ofThework making this kit up. That's for sure. I Insert boxes In the lower drawer. These are I Ideal to remove from the drawer to find that another note, "Beepo" Is our new I elusive nut or resistor, without taking out I On continuity tester from EA Feb. (sorry about the complete drawer. Side and bottom the dreadful pun). It's a great little gadget I keying allows you to use just a few or to I that will check all sorts of circuit conditions I build a whole wall of drawers as your parts I In a circuit. The tone the beeper tells you expansion dictates. Flange on the rear of Ref: Silicon Chip October 1988 This fantastic project enables you to transmit a signal IN STEREO over the FM band. The range Is limited to about 20 metres or so, so It's not a nuisance to anyone else. It uses a single 1.5V AA (penlight) oell which lasts for ages. Just Imagine I You can listen to your CD player on your FM headphone reoelver while washing your earl You can play your Walkman CD player over your car stereo - no wires I The posslbllltles are endless! Set up your own micro FM Radio Station! The Jaycar kit of this project includes the hard to get Rohm BA1404 chip and the CORRECT 38kHZ crystal • even harder to get I All other specified I SPECIAL IC AND CRYSTAL FOR ONLY Once again the Boss INSISTED that I listen to them personally with him. after knock-off . time of course. No 0/T just B&C which at least is my favorite drink! ~ I honestly did not know how much they were I ~~~s:C~s~\uded as well. Hi Guys Firstly I had better get my BOOB (oopsl) I mean BOO BOO, out of the way. I told you In last month's column about the new 33-band Graphic Equaliser. I said that It would appear in the Feb. (I.e. this) issue. Stop looklngl It's in the March Issue. It's also 32-band, not 33. So the boss spanked me twloel Speaking about the Boss, he's more or less behaving himsell lately. Thal Is compared to Deoember and January. we even see him in here at work from time to time. $17.95 • Interlocking Parts • Drawers KIT'S COLUMN $49.95 what's going on. A winner! I can hear the girls groaning now. Sorry, I have to run. (The Boss keeps me flt.) We have some other great kits released this month too, so please, pretty please, check our ads. You won't be sorry! In the meantime, keep your Iron hotl Kit Ifft TURN YOUR SURPLUS STOCK INTO CASH!! Jaycar will purchase your surplus stocks of components and equipment CALL GARY JOHNSTON OR BRUCE ROUTLEY (02) 747 2022 Dear Customers, Jaycar has already introduced you to the easy and economical way to buy resistors and greencaps. Now you can purchase ceramics in packs, so, you'll never run out of one again. Eight, easy to buy, low cost packs which represent a considerable saving over buying individual parts. At 1~ each ceramic, you figure out the savings. Each pack contains 1O of each value and packs cover the complete range from 1pF to 0. 1uF. Values (10 of each) 1pF, 1.2, 1.5, 1.8, 2.2, 2.7 Values (10 of each) 330pF, 390,470,560,680,820 Sometimes the products we advertise are so popular they rvn out 'Mlhin a few days. At other times unforessM circumstances might hold up shipments so that sdvertissd Jines are not in the stores by the tim• the advtJff app6Brs. And, very occasionlM/y, an t1"or may slip throvgh our cht,eks and appear in the sdvsrt (we're hvman too). I I I Total 60 pcs Cat. RC-5390 $6.95 Total 60 pcs Cat. RC-5395 $6.95 Values (10 of each) 3.3pF, 3.9, 4.7, 5.6, 6.8, 8.2 Values (10 of each) .OOuF, .0022, .0033, .0047, .0056, .0068 ITotal 60 pcs Cat. RC-5391 $6.95 Total 60 pcs Cat. RC-5396 $6.95 Values (10 of each) 10pF, 12, 15, 18, 22, 27 Values (10 of each) .0082uF, .01, .022, .033, .047, . 1 I Total 60 pcs Cat. RC-5392 $6.95 Total 60 pcs Cat. RC-5397 $7.50 I Values (10 of each) 33pF, 39, 47, 56, 68, 82 Total 60 pcs Cat. RC-5393 $6.95 I Values (10 of each) 100pF, 120, 150,180,220,270 ~ a l 60 pcs Cat. RC-5394 Please don't l:iame the store managBr or staff, l>ey cannot cont'ol a dock stike or a lost PCB 8"NOrlf. from a magazine to the PCB m11nufacturer for a new kit, or Ix an error that appewed Jn print If you are about to drive across to'M'I to pick up an sdvertiHd Item.why not play It safe and calf thB store first ~ just in case. $6.95 ----------, - - - - PCB TERMINAL STRIP BARGAIN 1/2 PRICE MOLEX PINS BARGAIN BAGS BACK AGAIN! Another surplus stock buy. These are a high quality black thermoplastic PCB terminal strip. As used by the alarm industry. Available in 4 way and 10 way. Units are supplied unassembled - i.e. you have to screw the screws in. Normal Price 10+ 100+ 4 way $2.50 $1 .50 $1.30 Cat. HM-3204 1Oway $4.95 $2.00 $1.80 $ 1.50 Cat. HM-3205 Bigger than ever. Contains between 2.5 and 3kg of an amazing range of brand new goodies. No two bags are Identical and every bag represenis great value. P & P extra $5 due to heavy weight. No 7 day return. BELOW WHOLESALE PRICE These have been selling for $4.50 for 100. We now have available a new style and can offer thPm at 1/2 the previous price. r . Pl-6541 ONLY $2.25 for pack 100 STILL ONLY $12.95 Cat. XB-9000 ~wAYRcA'soCKITTBAR.oMN -----~I SMOKELESS ASHTRAY I In this day and age, cigarette smoking is becoming socially unacceptable. This product will help the poor old smoker by removing all smoke from a cigarette srtting in the ashtray. It works like this:Swrtch the unrt on, and rt will just srt there in the off mode. When you "light up" simply tap the ashtray and it turns on and rusn for 10 minutes before going back to the standby mode. The unit has a silent motor wh ich draws the smoke inside and through activated charcoallayers to purify the air. Operates on 2-C sizebattories or a 3V DC power source. The ashtray section (where the cigarette srts) is made from Melamine and just lttts out to empty and clean. Size: 125mm x 125mm x 75mm. Cat. YX-2930 Our import manager made a big booboo. Instead of ordering our standard style he ordered one with an extra hole in the centre for more rigid mounting. So, they don, fit any of our panel cutouts for kits. So, ff you haven't cut your panel for a 6 way RCA socket yet• these are Ideal. I •Q O • Q 6~~~1;~~~;:rrm x 22mm. Q O O I NOWONLY S0~ea I 10+65iea • .•.• I S[OPE•FRQNT•MEtA.LcA·t11NEt$ AVAI LABLE IN 3 SIZES: project. Size 1: ONLY$14.95 150mm(W) x 103mm(D) x 70rrm(Rear height) x 35mm(Front height) Cat. HB-6080 $11.95each IOplus $10.95each Size 2: 200mm(W) x 150mm(D) x 70mm(Rear height) x 35mm(Front height) $14.95each Cat. HB-6081 Size 3: 10plus $13.95each 265mm(W) x 200mm(D) x 82rrm(Rear height) x 32mm(Front height) Cat. HB-6082 $ 18.95each 10plus $17.50each __.,\\- _ ~ ~ l ;y:- :, .,,,,,- to be quick! At this low price of $39.95 they can't fast much longer. ■ VISA $39.95 SYDNEY - CITY PARRAMATTA I - -: - -~,CONCORD !!MasterCard. L .- HURSTVILLE u•• i••·••> •·· Jaycar is proud to announce a range of three direct import, attractive powdercote finish, slope-front boxes, made of 18guage steel wrth large, non-slip rubber feet already mounted. These boxes are held together with countersunk screws and their excellent qualrty would compliment any fine Massive SCOOP PURCHASE of quality Japanese-made (OX Antenna Co.) high-gain UHF antenna (CH2B-63). This 14 element unit incredible front to back gain and would be suitable for "fringe" UHF areas. (Gain 7.5 · 11.Sdb depending on actual frequency). The boom measures 1.2metres long and is fitted with a diagonal support strut for extra ruggedness. Not only that, this antenna is fitted with a 300175ohm weather proof balun as standard/ (You can use either 300ohm or 75ohm co-ax.) This antenna is priced about 50% below its rrue retail value. They are running out fast so you need s 11 __________________ _II INORMAILY~~ ..._ UHF ANTENNA Cat.LT-2176 0 N L Y I . 117 York SL (02) 2671614 · Mon-Fri 8.30 • 5.30 Thurs 8.30 pm • Sat 9 - 12 GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799. Mon-Fri 9. 5.30 Sat 9. 4pm 355 Church Sl'(Cnr. Vicloria Rd) (02) 683 3377 Mon-Fri 9 · 5.30 Thurs 8.30 pm · Sat 9 · 2pm BURANDAQLD 144 Logan Rd (07) 393 0777 . Mon-Fri 9 · 5.30 Thurs 8.30 • Sat 9 -12 11 5 Parramatta Rd (02) 745 3077 . Mon-Fri 8.30. 5.30. Sa t 8.30 . 12 MELBOURNE-CITY Shop 2, 45 A'Beckett St City (03) 663 2030 Mon-Fri 9. 5.30 Fri 8.30 • Sat 9. 12 121 Forest Rd (02) 570 7000. Mon-Fri 9 · 5.30 Thurs 8.30 pm • Sal 9 - 12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9. 5.30 Fri 8.30. Sat 9. 2 BOOKSHELF How to use test equipment Meters and Scopes: How to use Test Equipment. By Robert J. Traister. Published 1988 by Tab Books Inc, Blue Ridge Summit, Pa, USA. Soft covers, 131 x 210mm, 312 pages. ISBN O 8306 2826 6. Most electronics enthusiasts will have some type of test instrument stacked away in their den. One of these items will inevitably be a multimeter with at least the ability to measure AC and DC voltage and resistance. The question is, do you know how to use it to best advantage and would you be better off with more test equipment? This book is aimed primarily at the beginner to electronics and it begins by discussing the origins of modern science and measurement. It proceeds to explain basic physical quantities such as voltage, current, resistance, etc and then gives brief descriptions of electronic components. Even though this book was published in 1988, a lot of the material is of much earlier vintage. Analog equipment is predominantly featured and much of it is now well and truly obsolete. In fact, if we had 36 SILICON CHIP reviewed this book in the early seventies we would have regarded it as being reasonably up to date. Now, it is passe. There is a section on how to use your multimeter but this isn't much more informative than the instruction book supplied with most meters. The section on oscilloscopes is not much better though it does tell you how they basically work. It gives the now rarely used method of comparing phase or frequency difference using Lissajous figures which may be useful if you only have a single trace scope. The information concerning dual trace oscilloscopes is brief but OK if you really don't know how to use one. The last chapters concern RF equipment such as SWR and field strength meters but again what the author has to say has no real value unless you are a complete novice. As you will have concluded, this book is disappointing. If you are real beginner thirsting for knowledge, by all means have a look at it. But be aware that it is pretty old hat now. Our copy came from Dick Smith Electronics (Cat No B-5000). It is priced at 19. 95. Experimenting with EPROMs Experiments with EPROMs, by David Prochnow. Published 1988 by TAB Books Inc, Blue Ridge Summit, Pa, USA. Soft covers, 188 x 234mm, 230 pages. ISBN 0 8306 2962 9. Price $21.95. There are very few books around on the subject of EPROMs while there are large numbers devoted to the software and hardware aspects of computers. This probably reflects the fact that most computer enthusiasts are not really involved in the practical aspects of electronics and therefore feel no need to delve into EPROMs. For those that do though, "Experiments with EPROMs" will be welcome. At first the text appears to be aimed at a very elementary level as it explains topics such as the binary number system and commonly used codes. Further on though, the author assumes a higher level of knowledge as the code systems are explained in a fairly vague manner. The frequent use of unexplained acronyms in the text is likely to be a little confusing to the novice too, although a glossary is provided at the back of the book. The sections on digital logic and integrated circuit fabrication are quite informative although they are brief so a general background on the technology can be quickly attained. A sizable proportion of the book contains information on various memories and support chips. This is reasonably up to date and forms a useful reference on what is currently available. The book actually performs two functions. As well as giving useful background information on read only memories (ROMs) of various sorts, it presents 15 projects which involve EPROMs in one way or another. The list of projects is as follows: Boole's Box, Keyboard Encoder, Bit Smasher, Bit Smasher II, EPROgraMmer, EPROgraMmer II, continued on page 91 By LEO SIMPSON Build the Minstrel 2-30 Loudspeakers Hands up all those who want a new set of loudspeakers but can't afford the prices for imported models. Well you can all put your hands down now because this 2-way system is a real bargain. continued next page The key components of the Minstrel 2-30 system are the 200mm woofer (left), a 25mm aluminium dome tweeter (right) and a 2-way crossover network. Let's face it, many people would like to update their speakers to something newer but price is a big consideration. This is especially the case if you purchased a rack or midi system and now want to upgrade the speakers. Some of, the speakers supplied with the cheaper rack systems really do let the side down as far as sound quality is concerned. So now we are able to present a decent sized 2-way loudspeaker system with an all-up price of $269 for a pair. That price includes all the parts you need to build two complete loudspeaker enclosures. Not bad,huh? We've called the new loudspeaker system the "Minstrel 2-30" - "Minstrel" because it makes music and "2-30" because it is a 2-way system with an enclosure volume of just over 30 litres. The enclosure is a completely 38 SILICON CHIP sealed unit which means there is no messing about with vents or ports - just two loudspeakers on the front baffle and that is that. The enclosure is very well finished too, and is every bit as good as you would expect from commercial loudspeakers purchased from a hifi dealer. You can obtain this high standard of finish easily because the cabinets are so easy to assemble - no woodworking tools are required. The' cabinets are finished in black with a simulated wood grain. The matching grille cloth frame is covered in black fabric and is held securely in place with plastic clips. At the rear of the cabinet a recessed panel has two spring loaded terminals for easy connection to the loudspeaker leads. Two loudspeaker drive units in each enclosure cover the full audio spectrum; hence the term " 2-way". The low frequencies, up to 3kHz, are covered by the woofer. This has a nominal diameter of 200mm (8 inches) and is conventional in construction. It has a pressed steel chassis and uses a large ceramic magnet. The heavy paper cone has a generous synthetic rubber roll surround and a large centre dust cover. The voice coil diameter is 25mm. Free-air cone resonance is close to 45Hz. The matching tweeter is a 25mm aluminium dome unit with a protective grille over the front. It handles all the audio frequencies from 3kHz up to the limit of audibility. Crossover network To couple the woofer and tweeter together we have designed a fairly complex crossover network. Or, putting it in perspective, it's a fot more complicated than the crossover networks found in many comme::cial loudspeakers costing a great deal more than the Minstrel 2-30. We didn't do this because we're keen on complex networks but because the ultimate sound quality of any loudspeaker probably depends more on the crossover network than the basic quality of the drivers. Our crossover network is shown in Fig, 1. It rolls off the signal to the woofer for frequencies above 3kHz at a rate of 12dB/octave. Similarly, it rolls off the signal to the tweeter for frequencies below 3kHz. To get a slope of 12dB/octave, you need an LC section for both the tweeter and the woofer. For the woofer the relevant inductor is Ll and the relevant capacitor is Cl. For the tweeter, the equivalent components are LZ and C2. If we ignore the other components for the moment we can easily see how the crossover network functions. In a very simple crossover network a single inductor feeds the woofer and a capacitor feeds the tweeter. As the signal frequency rises, the impedance of the inductor starts becoming significant until, at the nominal crossover frequency, its value is equal to the impedance of the woofer. So the power level in the woof er is reduced by half and this is known as the - 3dB point. Below the crossover frequency virtually all the audio power is fed to the woofer. The opposite happens with the tweeter and associated capacitor. As the frequency rises the impedance of the capacitor reduces until, at the crossover frequency, it is equal to the impedance of the tweeter. Again, this gives "half power" into the tweeter. Above the crossover frequency, virtually all the power is fed to the tweeter. With this simple type of crossover network the attenuation slope (ie, the rate of signal rolloff) is - 6dB per octave. The crossover used in the Minstrel can't simply be regarded as two 6dB/octave networks combined for each driver. It's more +0---------------, C2 L1 540µH 4.7 L2 600µH 7.2fl 5W SEE TEXT Fig.1: the Minstrel 2-30 crossover network. L1 and the 5.2µF capacitor roll off the signal to the woofer at 12dB per octave for frequencies above 3kHz. Similarly, L2 and the 4.7µF capacitor roll off signals to the tweeter at a 12dB rate for frequencies below 3kHz. ~ 30 s I I 20 10 0 I - 20 J/ ' --- - ... 100 lk 10k complex than that and takes the form known as a constant resistance parallel network. The term "constant resistance" refers to the fact that the crossover network presents a virtually constant impedance to the amplifier over the whole range of frequencies. This is desirable for the amplifier as it means that its performance will not vary according to the load impedance. The term "parallel" refers to the fact that the woofer and tweeter networks are effectively in parallel. Both the tweeter and woofer networks are matched so that Ro2 = (L/C)/2 In the case of the woofer, Ro is 7.20 and for the tweeter Ro is 80. Impedance equalisation 40 1 The tweeter handles all the audio frequencies above 3kHz. It is secured to the baffle using four small wood screws or self tappers. 20 FREQUENCY (Hz) Fig.2: the impedance of the Minstrel 2·30s is virtually constant between 100Hz and 20kHz. Below 100Hz it rises steeply to a peak of 3812 at 65Hz which corresponds to the low frequency resonance of the system. k To make sure that the crossover network works as it should, it is necessary to have "impedance equalisation" for the woofer. This is provided by the 7. 20 resistor and 16.BµF capacitor connected in parallel with the woofer. What these components do is to effectively cancel out the inductance of the woofer's voice coil so that it does indeed present a resistance of 7.20 to the crossover network. If impedance equalisation was not included the gradual rise in impedance with frequency, due to the voice coil inductance, would degrade the attenuation slope of the crossover. The net result of this is that the woofer would be getting more high frequency signal than it should. Because all woofers tend to FEBRUARY1989 39 A . : ---e I IPI SECTION ON AA HOLES : I : 71 DIA C: 111 DIA COUNTER IORED 208 DIA 4 DEEP ON OUTIIDE become quite peaky above their rated frequency range the sound quality would thereby be degraded. Impedance equalisation is not necessary for the tweeter but because it is more efficient than the woofer, some signal attenuation is required. In fact, we provided about 3.6dB of attenuation which is more than the nominal efficiencies would seem to require but which we felt gave best overall balance between tweeter and woofer. The attenuation is provided by the 2.70 and 150 resistors associated with the tweeter. Fig.2 shows the result of the crossover network in the Minstrel 2-30. As can be seen the impedance is virtually constant between 100Hz and 20kHz. Below 100Hz the impedance rises steeply to a max40 SILICON CHIP ALL PANELi 1U TIICK PARTICLE BOARD ALL DIMENSIONS IN MILLIMETRES Flg.3: for those who want to make their own cabinets, this diagram shows all the relevant dimensions. These dimensions can be varied somewhat, provided that the enclosure volume is not varied by more than ± 10%. Don't use material less than 16,5mm thick. imum of 380 at 65Hz. This corresponds to the low frequency resonance of the system which is a result of the interaction of the enclosure with the woofer cone. We designed a printed circuit board for the crossover network, as shown in Fig.5 but as it happens, a fully assembled crossover network will be available by the time this issue goes on sale. The prototypes of this assembled network arrived too late to be photographed for this issue but they are well made units with large air-cored inductors, bipolar capacitors and wirewound resistors. The sealed loudspeaker enclos- ure has been designed according to Thiele-Small principles to give a smooth bass response down to below 60Hz. This is a good compromise between bass response and box volume. Combine this with the relatively high efficiency for the system (95dB at 1 watt at 0.5 metre) and you have the makings of quite a potent little system. When we finally had a pair of the final prototypes going, the overall sound quality was quite gratifying. The overall balance between bass and treble is very good and the bass response will be more than adequate for most people's tastes. The treble is smooth and extended without any tendency to "spit" as sometimes happens with inferior tweeters. Power handling is good too and the Minstrel 2-30 will comfortably handle the full power output of stereo amplifiers rated up to 50 or 60 watts per channel, on normal program material. Combine that with the efficiency noted above and a pair of Minstrel 2-30s have the capacity to produce lots of good quality sound in average to large listening rooms. (That's a polite way of saying that they're deafening when you turn the wick up). BAFFLE Where to buy the kits The Minstrel 2-30s have been a cooperative project between Jaycar Electronics and SILICON CHIP. Jaycar have been able to produce a keenly priced kit which will appeal to many buyers. As noted above, the total price is $269 for a pair, with all parts included. If you wish to build the enclosures, the price for the four drivers, two crossovers and all other necessary bits and pieces is $149. The cabinets are also available separately at $129 for a pair in kit form. They will be available from all Jaycar stores. Building the Minstrel 2-30s For those people who used to make their own speaker cabinets (read: your's truly), building the Minstrels just seems too easy. No woodworking skills are required and the tools needed are very basic - a screwdriver is about all you'll need. Of course that doesn't mean that you can't make your own cabinets from scratch. The diagram of Fig.3 gives the major dimensions of the ea binet. Both the baffle and the rear panel are rebated into the wraparound sides, top and bottom panels. If you like, the need for routing can be eliminated by the use of cleats. The enclosure dimensions have been selected partly for efficient cutting from large sheets. These dimensions may be varied though, provided the internal volume does not change by more than ± 10%. We have specified 16.5mm particle SIDE I SIDE GLUE ALL MITRED EDGES AND BAFFLE GROOVE. INSERT BAFFLE IN GROOVE AND WRAP SIIES AND BOTTOM AROUND BAFFLE Fig.4: cabinet assembly details. Make sure that the woofer hole is at the bottom and that the T-nuts (used to secure the woofer screws) are inside the enclosure when it is folded up. board as a mm1mum thickness material but there is no reason why thicker material could not be used to advantage. For most people though, the idea of building cabinets will be a no-no. Unless you are skilled in carpentry, obtaining an airtight cabinet with a good looking finish is no easy task. If you fall into this large majority of people, buying the cabinet kits is a good proposition. Out with the Aquadhere Virtually all you need to put the cabinets together is a bottle of PVA (polyvinyl acetate) glue such as Selleys Aquadhere. You don't need large sash clamps although there is nothing to stop you using them if you have access to such handy tools. Instead of clamps you will need a roll of masking tape or packaging tape which can be purchased from your local hardware or stationery outlet. The cabinet kits are supplied with all holes cut. All you need to do is to assemble and glue them together - a one step process. Fig.4 illustrates how the cabinet goes together. The base, sides and top are supplied as one long strip of timber which has been routed so that it will "hinge" at three points, corresponding to the two top corners of the cabinet and one of the base corners. The "hinge" is the simulated veneer and so you have to handle it carefully to avoid tearing. In effect, the long hinged section is wrapped around the baffle and rear panels. The glue is run into all the joint sections before assembly so that assembly is just one step. FEBRUARY1989 41 • L1 0 • .....,=- C1 I I C1 4.7µF ~~ ,:g, C: . u.. • :~ . J FROM AMPLIFIER --- + • I--- ---- WOOFER • C2 4.7~F + • 150 5W -------- TWEETER ____, ' *MOUNTED ON COPPER SIDE OF BOARD Fig.5: parts layout on the printed circuit board for the SILICON CHIP version of the crossover network. If you want to make your own crossover, you can order the coils from Nelson Components, 66 Blackbutt Avenue, Lugarno, NSW 2210. Phone (02) 53 9684. Note the 560 resistor which is mounted on the copper side of the board. Inductor L1 was secured to the hoard using super glue, while L2 is secured by a thick wire strap which runs through the centre of the plastic former and has both ends soldered to the board. The commercial version looks quite different although the circuit is the same. 42 SILICON CHIP Before beginning assembly, there are a few holes to be drilled in the baffle and rear panel. It is more convenient to drill these now rather than have to do it afterwards. The recessed terminal panel is secured using four small roundhead woodscrews (or self tappers} so 2mm holes should be drilled for these. You can use one of the terminal panels as a drilling guide. Don't drill the holes all the way through - 10mm deep will be sufficient. The crossover network is screwed to the inside of the rear panel, just below the terminal panel. It is secured using two 15mm-long 10-gauge self tappers. Again, don't drill the holes all the way through the panel. On the baffle the tweeter is secured using four small wood screws or self tappers. The woofer uses four 25mm 3/16-inch Whitworth roundhead screws secured into T-nuts (which are on the inside of the baffle}. The four T nuts require 1/4-inch holes to be drilled. (At the time of writing we could not be sure whether the baffles will be supplied drilled with these holes}. The T-nuts should be driven into the rear baffle before the enclosure is assembled. With all the drilling completed, you can proceed to glue the enclosures together. The procedure is as follows. Lay out the continuous side piece on a flat surface such as a large table or floor (preferably carpeted}. The three fold joints should be flexed as little as possible. Now run a fillet of PVA glue into each of the three V-cuts for the corners and into the rebated channels for the baffle and the rear panel. The baffle (front panel} is now fitted into the channel of what will become the base panel (of the hinged side piece}. Make sure that the woofer hole is at the bottom and that the T-nuts will be inside the enclosure when folded up. Now, while holding the baffle vertical with respect to the base panel, insert the rear panel into its channel in the base panel. Again, make sure that the rear panel is in the right way, with the holes for the crossover network at the bottom. The next step is to carefully wrap the sides around the two vertical panels, making sure that no stress is placed on the three corner joints. With the enclosure now folded up completely, the final corner is held in place with strips of masking tape or packaging tape. Pull these strips on as tight as you can, so that the final corner joint is as tight as possible. Don't worry if some of the glue oozes out of the various joints. It can be wiped off easily. If it gets on the vinyl simulated grain it can be easily peeled off when it is dry. Leave the assembly for at least an hour to make sure it is really dry. If the humidity is low the glue will dry much quicker than this but if the weather is wet and humid, it can take a lot longer to dry. In any case, you can leave the masking tape on the enclosure while further assembly is taking place. Before the crossover network is screwed into place three pairs of wires need to be soldered to it. This can be standard figure-8 flex. Use Close-up view of the recessed terminal panel. To ensure an airtight seal, run a bead of silicone sealer around the mounting flange. about 200mm for the connections from the crossover to the rear panel connector and about 400mm each for the woofer and tweeter connections. Incidentally, the crossover network diagram of Fig.1 shows a 7.20 resistor in the impedance equaliser, a value which is not available. The value fitted in the crossover will be 8.20. To bring it close to the correct SC01102891 .:.I Fig.6: this full-size reproduction of the PC artwork is for those readers who wish to make their own crossover networks. value, solder a 560 1W resistor across it. Now screw the crossover network to the inside of the rear panel. Dangle the wires for the rear terminals out the back and solder them to the terminals, then screw the the terminal panel into place. Similiarly, feed the tweeter leads out through the small hole in the baffle and solder them to the tweeter lugs. Make sure that the polarity of the tweeter and woofer connections are correct. Fig.1 shows the tweeter reversed in polarity with respect to the woofer. This is as it should be. Before mounting the woof er, place the BAF (bonded acetate fibre) filling inside the enclosure. A piece 1 metre x 1 metre will be sufficient for two enclosures. All you have to do is cut the supplied piece in half and place it loosely inside each enclosure. This done, solder the crossover wires to the woofer and screw it into place. Each of the four roundhead screws for the woofer should have a washer under the head. This is to stop the screw heads from pulling through the woofer frame. Do not over-tighten the screws otherwise the frame could be distorted. To ensure that the woofer frame· seals properly to the baffle opening, it is a good idea to run a thin bead of silicone sealer around the baffle rebate. Do the same for the tweeter. You are now ready to do a quick listening test. Connect the speaker system to your stereo system and listen to a music signal. Make sure that both the tweeter and woofer are working. Turn up the volume and bass and then run the cupped palm of your hand around all the joins of the cabinet to test for leaks. None should be apparent. Finally, the grille cloth frame has to be fitted. We understand that this will be supplied with the grille cloth already fitted. It is then simply a matter of fitting the grille frame clips into the frame and the four matching sockets into the corners of the baffle. The grille cloth frame now clips firmly into place. And that' s it. For $269 you have a pair of bargain-priced loudspeakers. Connect them to your system and settle back to enjoy the music. ft FEBRUARY1989 43 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. Simple binary encoded keypad Here is a circuit to enable you to build your own custom keypads. This circuit gives a binary output and a control line to indicate when a key has been pushed. The diode array has been arranged so that whenever a key is pushed the appropriate data line or data lines are excited, giving a unique 4-bit code for that key. For example, when the S6 button is pressed, two diodes will conduct to pull the Dl and DZ lines high. This will give a 4-bit binary code of 0110 which corresponds to the decimal number 6. The keypad can be easily extended by adding additional diodes and data lines. If you look closely at the diode arrangement corresponding to each key, you will notice that the diodes appear in the array where a '1' would appear in a particular binary code. The exclusive OR gate arrangement on the right of the circuit controls the 'valid key' line. When any single key is pushed, one input of the associated exclusive OR gate is pulled high while the other input remains low. So if SB is pushed, the output of IC2d will go high and pull one of the inputs of the following gate (IC3a) high. IC3a's other input will still be low so IC3a's output will go high. In turn, IC3a will pull one input of IC3b high and so its output will go high. Thus, the high output from IC2d will ultimately be shuffled through to the output of IC3c which becomes the 'valid key' line. When no key or two keys are pushed the valid key line remains 44 SILICON CHIP +sv +5V ~ ..!!... ..E.. ..£. -------000 IC1-IC3 :,4030 . , _ - - - + - - - - - - - 0 0 1 4-BIT OUTPUT 20x1N4148 ~---+---""T"------002 CODE ~---+---""'7"---+------003 4.7k 4.7k inactive although if an odd number of keys is pressed the valid key line does go high. However, in this situation a nonsense code is passed onto the data lines. More elaborate circuitry would avoid this situation but 4.7k 4.7k this will complicate what essentially is a simple device. The exclusive OR gates are specified as CD4030 but the CD4070 is an identical device as far as we can tell. TTL equivalents may be used if you are going to interface this keypad with a computer. -----+2•15V 1Ok -----------32.768kHz 1M TO CRYSTAL-~"---....:.i 555 1M 32.768kHz WATCH CRYSTAL 7555 ~'h LK1 LK2 ------v+ 15 STAGE BINARY DIVIDER 1Hz Fig.2: this alternative scheme shows how pin 7 can be used to drive the crystal. LK3 t~ Fig.1: basic circuit for a 7555 oscillator using a 32kHz watch crystal. The linking options are for calibration. Crystal oscillator using a CMOS 555 This simple oscillator circuit (Fig.1) uses a 32kHz watch crystal and has a number of advantages over the usual biased TTL or CMOS inverter circuit. The CMOS version of the 555 timer (ie, 7555 or TLC555) will drive heavier loads and offers better stability and more reliable starting, even with inferior crystals. Alternative override for car safety light This circuit replaces the automatic override facility in the Car Safety Light circuit published in the November 1988 issue of SILICON CHIP. It has the advantage of using only one LDR to detect both daylight and approaching traffic. During daylight hours the input pins 1, 5 and 6 of ICl will be held high by the voltage divider network formed by the LDR and the 4 7k0 resistor. Because the LDR is exposed to light, its resistance will be low. The output of ICla will be forced low and so the lO0µF capacitor will have negligible voltage across it. The remainder of the circuit is therefore effectively disabled. At night, when the LDR is in darkness, its resistance will be high, so that the voltage at pins 1, 5 OUTPUT For applications where heavy output loading is likely to affect the stability of the oscillator, pin 7 can be used as an open drain output instead of using pin 3. Pin 7 is capable of sinking up to 100 milliamps. As an alternative, pin 7 can drive the crystal provided it has a 10k0 pullup resistor, as shown in Fig.2. 32.768kHz watch crystals are usually parallel resonant, with a nominal shunt capacitance of +12V Fig.3: this alternative override circuit uses just one LDR to detect daylight and approaching traffic. and 6 will be low. The output of ICla will be high and this will allow the lO0µF capacitor to be slowly charged via the associated lMO resistor. 12.5pF. The capacitance associated with pins 2 and 6, together with the associated wiring, can be expected to be about lOpF. Extra capacitance will lower the frequency of the crystal oscillation and vice versa. One or two of the three links, associated with the crystal, are used for calibration. Commence calibration with link LKl in place. If the crystal frequency is too high, solder in link LK3 which connects the l0pF trimmer capacitor in parallel with the crystal. If the frequency is too low, remove link LKl and connect LK2, which connects the trimmer in series with the crystal. The suggested trimmer is an air-spaced porcelain type which can be obtained from Jaycar. Steve Payor, Kogarah Bay, NSW. ($20) If the LDR is now exposed to light, say from car headlights, pin 1 will go high and the output of ICl b will go low. The lO0µF capacitor will slowly discharge and disable the circuit if the LDR is constantly exposed to light for around 40 seconds. This is the time for the capacitor to discharge to the lower threshold of the Schmitt trigger. Note that if your car is parked along a well used thoroughfare, the circuit may be permanently disabled for long periods. The output is also disabled when the ignition switch is activated. This is achieved by using the BC547 transistor to short pin 1 to ground. Note that the lO0µF capacitor must be either a tantalum or low leakage electrolytic (Elna RB-LL or equivalent). Peter van Schaik, Gilgai, NSW. ($15) FEBRUARY1989 45 < < iiiiiiiiiii iiii iiiii iiiiiiiijij. iiji iii iii :~ :~ <>: ilif 4LTROnlCl 1989 ELECTRONIC COMPONENTS CATALOGUE YOURS FREE With This Month's Electronics Australia Magazine OR Send $1 to cover P & P To Altronlcs, P.O. Box 8350 Perth mall Exchange W.A. 6000 Silicon Chip Readers ring Us Toll Free Right Now On 008 999 007 And We Will Post You One Absolutely Free I Altronics Staff are all keen Electronics Enthusiasts - just like yourself - so when you need a little technical help, give us a call • Quality Products at direct import prices • Save up to 50% on our competitors prices • Overnight delivery Australia wide• Bankcard phone order service to 8pm Monday-Friday 111 •, FOR THE VERY QUICK! Here are some incredible bargains. We suggest you phone order now to reserve yours. Please check inside our Catalogue for full specifications on these items . Special prices are available on current stocks only, sorry no back orders, strictly "lst come - 1st served". 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Ideal Hi Fi extension speaker. ii .iIII •1 C 2000 Output Current: 2A Normall y $69.95 NOW $45 M 9050 Normally $16.50 THIS MONTH $7 .so 20+ $6.oo •• -: •.•.·.·.·-:-:-:-:-::::::::::::::::::.::.::.:=.=:.::.,.'.,.'.:.,.:.,.:.,.:.,,'.', '. ,' ',',', ', ,' ,' ,' .' ','.,'',', ',',','·,',',.',.',.',',.',',.',.'., .', ',.'., '·,',.·,·_.,, :, ,:,., ,:.,,,,:,.,,:,.,::',.',,',.',,'., ', '.,': l,.1:, :,,:,;,,:.,..:: ~.: u•: tnrrntrtrnrrnr Design Award Winner Awarded the Good Product Design Award for CETDC in 1987. This fantastic Ultrasonic cleaner can earn its cost a hundred times over in cleaning Computer Connectors, PCB's, Switches, Relays, Jewellery, Glasses, Watches etc. How Does It Work? The Pin Point Ultrasonic Cleaner uses a transducer generator to produce millions of activated microscopic cleansing bubbles, which blow dirt, grease & grime off surfaces, and deep into cracks and hoies. This personal ultrasonic cleaner won't scratch precious jewellery or glass. Comparison studies made by hospitals, commercial businesses and Industry show ultrasonic cleaning proves better and safer than any conventional method. But don't take our word for It. Teat the Pin Pol"nt Ultrasonic cleaner yourself. Pop your dirty watches, glasaes, connectors etc. Into the cleaners stainless steel basin, add a cup of tap water, and three minutes later see the difference. The results are Instantly revealing. IPICll'ICATIONI Power Supply : 240V 50Hz Power Con1umptlon : 300mA Frequency : 40 +/-2KHz Dlmen1lon1: 224 x 114 x 124mm Capacity: 570ml Weight : 1kg Body Materlal: ABS Plastic Tank Materlal : Stainless Steel (SUS 304) On/Off: 3 Minute Auto Timer. * Amazing Price Breakthrough * Free $50 Probe Set Thi•., !'~~i~!•{=,,~:~= 0 ~ -.. ::ror:t= 1 I' ili~~iiiii~ll~~:~I!~Ei§l1 ::~!~~~~~~~~~J~ir:,;t~~J~~~c~~a::i~~~-~~n:~~~~\~Y~~~cJ":/ff ~esign :~~~~~;~n~~:~~fel~~~~:f~~~\~~~~ug,;::~tdh~~~u;~~~?~rit~~~~free separation circuit forquick measurements of video signals • A convenient X-Y operation mod a allows phase difference measurements between two waveforms. It!II :::::1 ,:,:,:=::\Qi ·······························= I M/Director I Country Clients Please Allow Additional 48-72 Hours ~-------------------------------~ Ultra High Power Capacity Polypropylene Ba•• Drivers Save 25% This Month 12" (300mm) Model 100 Watts continuous input 150 Watts intermittent input lmpedanca 8 Ohm Sen1ltlvlty 93db Weight 3620gm 99 C 3070 300 Watt Inverter With Auto Start $ Normally S139 15" (375mm) Model 120 Watts continuous input 200 Watts intermittent input 1 C 3075 :111:1::!:111:!:11:iil:lIiii ii:t :~~:v~rl~g~Ohml ~ 49 J!\\\IJ\J!;;::J::jl\\ll!:::::!:J:\:: · Normally $_179 . . ,;,,,::::::','::::?O)/,:/,,:·our all new "Black" polyprop cone Bass Drivers exh1b1t quite astonishing 0 i:::::::::1:1:::i:i::1:::::::::::::: i~~ir:~~s~~r~:er~~~g~~~e f('''''ti4f ·· best value we know of - Anywhere. The real exciting new, 11 we have the ,,,,,,,,,;,;,;,;,;,;,;,,.,...,.,:; top 1■ lllng 12 and 15 inch model, at low dl1count prlc■1 thl1 month - but be ~~:f~~~~~~~~g~~h~~ ~:~i~i~:1~~~~~~~~~~he .\\l\l\l\l\i\\\\\\_\\_:J_:1_1_·,:_·,:_: _:_._i,\_i,\_\,l_\.l\_l\_l\_\ quick stocks are O limuiterd. Top ~Ii\-=·=·· ::r:::jJ;gj: ·.· ·1 we. Selling Professional Stereo Console Mixer Power House 600W Inverter (See EA Dec'87) A must for farming, camping, mining, boating, remote settlements and wherever else 240V power isn't available. Featur■1: Strong custom steel chassis • Industrial grade power coat finish• Can be configured to operate off either 12Vand 24V DC• Very little internal wi"ring • Manual or Auto start facilities• Low battery cut out• Compact Toroid transformer. _ K 6770 KIT VERSION '<at>Hi\,,,, s425 ·:ll\IIIIIIIII:::i! Fully Built ""-s, ., K 6774 12V INPUT K 6775 24V INPUT s525 Electronics Australia and Silicon Chip Magazine Projects. A 2570 Normally $499 This Month S449 Save $50 This Month Our sophisticated 'NEW' Audio Mixing Console is ideal for'live' recording • PA mixing • Fantastic Tape recordings • Even Stereo/Mono VCR tilr recording. A truly professional deck that features separate R/ l 5 band graphic equalisers• Echo and Peak LED level indicators• Talkover facility • Separate H/ Phone level control • Patch switch bank • Individual microphone, Phono 1 Phone 2, Aux/L ine 1, Aux/line 2, and Master slide level controls. Blend up to two magnetic or crystal turntables, two tape decks or tuners and two microphones all at once!! SPECIFIC,\TIONS: ··.,,,,,,.......... ;,,:;,;;;,;,;,,:::"':' .'::: ,,,,;,;,;,;,;,;,; • Input Mic 1-0.SmV 600 Ohms Mic 2-0.SmV- 600 Ohms Mic 2-0.SmV 600 Ohms (low -imp.) 2.5mV 10K Ohms (low imp.) Phono 1 & 2 (Mag) 3mV SOK Ohms Phone 1 & 2 (Cry) 150mV 100K Ohms Tape/Tuner 1 & 2 150mV 100K Ohms • Equall1■ r 5 frequency bands-60Hz, 250Hz, 1KHz, 4KHz, 12KHz-Boost Cut range-plus or minus 12db <at> Centre frequency. • Output 1.5V/0.775V (Selectable) • Frequency R ■1pon1■ 20Hz to 20KHz plus or minus 1db • Dl1tortlon Less than 0.05% • S/N Ratio More than 50db //,?:::::::::: ,:,:,: : :,: : ~~~~g§~~Ji ~J'~io~~~~~:co~r~r:J:iaEyc~l~-gi,~~~~~e;.;!!i~~!~~ T;::~::!.!".:::r -~ ':)]It':':':':':',:,' Why • Toroid? :~!!~r~~~~J:~Y:~~~~~~•: : :~: : ~:. :::1:::!::::::::r, ./?.fi}(f by compact equipment. ,;;::\:i!i::1iiiiiiiiiiili; : g~e~~~{f~~t~::~~::::::~:::.ervative !\;[I:lt]:;:Ji • Simple, quick single bolt mounting . Dlmen1lon1 and Weight 180 VA ModelI110 Diam. 45mm H. 1.8Kgs Leads 200mm .·.·.·.)ilfr('(' . ,. . 300 VA Model• 125 Diam. 45mm H. 25Kgs Leads 200mm Ii 180 Watt Models 300 Watt Models\\\':"', S65 10 up S62 Cat.No. M 3050 M 3055 M 3060 M 3065 M 3070 M 3075 SEC.V 12 + 12 18 • 18 25 • 25 30 + 30 35 • 35 40 • 40 ea S79 Cat.No. M 3085 M 3086 M 3088 M 3090 M 3092 M 3100 10 up S75 ea · · · SEC.V 12 • 12 18 • 18 25 • 25 30 + 30 35 • 35 40 • 40 ~~~~~~;~~,..-~~=~ This professional quality public address amplifier offers performance equal to or better than commercial units at about half the price. Ideally suited for halls, churches, clubs and even temporary setups. Inputs 2 balanced mic with 3 Pin XLR connectors.: 2 auxiliary suitable for direct connection to C.D. tuner etc. Outputs 4 Ohm, 8 Ohm or 100V line output configuration. K5020 s499 Save $200 Or More On Commercial PA Amps RF Detector Probe (See EA May'88) This simple RF probe is ideally suited fault finding and trouble-shooting in AM radios. Feeds directly in the input of an audio amp. Requires external supply. Ideally suited for use with the K 2100 Bench Amp. K 2565 Power Transistor Tester (See EA May'88) Hand select transistor for power output stages. This tester has been designed specifically fo,r bipolar transistor with a continuous collector rating of at least one amp. Super simple operation allows for testing of current gain and Vbe of all popular power transistors. Suitable for both N.P.N and P.N.P. types. • s·12.oo LED Light The House Number Identify Your House - Build The LED Light. (See SIiicon Chip Oct'88) The LED light makes your house easily recognisable at night by illuminating your house number. Great for people visiting, easy for taxis and emergency services to locate you at night. Any number can be configured including Alphanumeric combinations. Automatic operation works only at night. Automatic switch off approx. 4.5 hrs. 64 LEDS supplied . K 1960 s59.es Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) Colin Fobister 437 4077 Perth 09 328 2199 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 AL TRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. PIHH Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don't forget our ExpreH Mall and Phone Order Service - for the coat of a local c■ II, Bankcard, Via■ or Mnterc■ rd hold ■ra c■ n phone order for a■ me day despatch. =:=:):() •:•:•:::::'\: .?=:~? ···1= I :JIit: I STANDARD DELIVERY I PACKING CHARGE $4.00 lo 1lg $7 over 1 KgAUSTAALIA WIDE" - We process your order the day received· and· despatch via. Australia Post. Allow approx 7 days from day you post order to when you receive goods $7 ..00 OVERNIGHT JETSERVIC.E - We process your order the day received and despatch via. Overnight Jeta■ rvlc■ Courter for delivery next day Country areas please allow additional 24-48 hours. Weight limit 3Kgs (3Kgs covers 95% of Orders). $10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDER - Bankcard.Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight Jeta■rvlc■ we deliver next day. WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K .B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521713 Farmer Electronic; 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOURNE Winscott Trading 6995740 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Delsound P/ L 8396155 SUBURBAN CAPALABA David Hall Electronics 3902399 FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 SA CIT'Y Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 56997 70 SMITHFIELD Chantronics 6097218 COUNTRY COFFS HARBOUR Coffs Habour Electronics 525684 NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect .Supplies ■ 621358 NOWRA Ewing ==?JC/ i\l\l~~)l~l {ii: I ~~.:;~:~~~~:;;;;;::~~;'; AMATEUR RADIO By GARRY CRATT, VK2YBX Build this simple VHF FM monitor receiver Need a spare VHF receiver for monitoring the local repeater? How about a dedicated unit for foxhunting, or a radio direction finding receiver? If the answer to any of these question is yes, then this may be the project for you. A few hours of construction time is all it takes to build this little unit. The heart of the receiver is a new integrated circuit from Motorola, the MC3362. Unlike many previous "single chip receivers" (such as the CA3089), this new integrated circuit provides all receiver functions from the antenna input to the audio preamp output. It is a low power dual conversion design with low power drain, excellent sensitivity, and good image rejection in narrow band voice and data link applications. Dual conversion A dual 'Conversion receiver is an extension of the basic superheterodyne principle. A normal RF lnpul to 200 MHz Vee . . - - - . . - From PLL Phase f--:i_ 5 0 pF a._______ __. 10 245 MHz Detector 001 -:22t----~ 0 41 µH 21t---+--~ Ceramic Filter - c - - - - - l 5 455 kHz rt---=Ceram,c FIiter tO 7 MHz Lp ep Fig.1: this diagram from the Motorola applications data shows how the MC3362 is used in a typical PLL frequency synthesised receiver. 50 SILICON CHIP superhet has one local oscillator which is "heterodyned" or mixed with the incoming signal to produce an intermediate frequency which is then amplified and demodulated. This is referred to as single conversion and the intermediate frequency is typically at 10.7MHz for FM receivers or 455kHz (or 450kHz) for most AM receivers. By contrast, a dual conversion receiver has two local oscillators. The first one beats with the incoming signal to produce an intermediate frequency (IF) of 10.7MHz. This is amplified in the first IF stage and then mixed with the second local oscillator which operates at 10.245MHz. This produces the second intermediate frequency of 455kHz (ie, 10.7MHz 10.245MHz = 455kHz). Dual conversion receivers with this arrangement are commonly used for narrow band FM reception. By "narrowband" we are referring to the fact that normal broadcast FM has a deviation of ± 75kHz and a total channel bandwidth of 150kHz. This is wideband FM. For the amateur bands and commercial use, narrowband FM normally refers to a much smaller frequency deviation, such as ± 5kHz. This can vary though, for amateur operations, depending on which band is in use. This will be the subject of a future article. Using the chip Fig.1 shows a typical application of the MC3362 in a circuit from Motorola's application literature. It shows the incoming signal fed from ANTENNA RF AMPLlflER 8FR91 2ND IF 455kHz 1ST IF 10.7MHz 1ST LOCAL OSCILLATOR LIMITER L 2ND Dr LOCAL 10.245MHz OSCILLATOR -t QUAD DETECTOR LM386 AUDIO AMPLIFIER SPEAKER MC3362 Fig.2: block diagram of the receiver to be described in next month's issue. A simple RF amplifier stage precedes the MC3362's input while the output drives a single-IC audio amplifier stage to provide loudspeaker volume. the antenna via a matching network and .0lµF capacitor to pin 1 of the MC3362. This is the input to the first mixer. The first local oscillator can be run using a free running LC tank, or as a VCO using PLL (phase lock loop) synthesis. With variable tuning, a range of 4MHz is available using the internal varicap at pin 23. Alternatively, for single channel use, the local oscillator can be driven from an external crystal oscillator. A buffered output of the first local oscillator is available at pin 20. The Motorola data sheet says that the local oscillator can be run as high as 170MHz which means that, in this configuration, the highest receiver frequency we could cover would be around 160 MHz. As the chip itself was designed as a cordless telephone receiver for the US market (49MHz), the design lends itself immediately to either a 6-metre or a 2-met.r e receiver for amateur use. A 10. 7MHz crystal or ceramic filter connected between pins 17, 18 and 19 sets the bandwidth for the first IF stage where the signal is amplified before being fed to the second local oscillator. The second local oscillator is a common base Colpitts type which is typically run at 10.245MHz under crystal control. A buffered output is available at pin 2. Pins 2 and 3 are interchangeable. The mixers are double balanced to reduce spurious responses. The first and second mixers have conversion gains of 18dB and 22dB respectively and the mixer gain does not vary with changes in the supply voltage. For both conversions, the mixer impedances and pin layout are designed to allow the user to employ low cost, readily available ceramic filters. Sensitivity is quite high. The input level for 20dB (S + N)/N is 0. 7µ V at 50MHz. The 455kHz IF is filtered and fed to the limiter input, at pin 7. The limiter has a 10µ V sensitivity for - 3dB limiting, flat to 1MHz. The output of the limiter is internally connected to the quadrature detector which includes an internal quadrature capacitor. A parallel LC tank is connected externally from pin 12 to Vee. In addition, a 68k0 shunt resistor is included which determines the peak separation of the quadrature detector. A smaller value will increase the spacing and linearity but decrease recovered audio output and sensitivity. For data communications, the recovered audio output from pin 13 can be connected to an internal comparator between pins 14 and 15. FSK (frequency shift keyed) data rates of 2000 to 35,000 baud are detectable. The hysteresis of the internal comparator can be varied by connecting a high value resistor from pin 14 to pin 15. Values below 120k0 are not recommended as the input signal cannot overcome the hysteresis. A meter drive circuit at pin 10 detects input signal level by monitoring the limiting of the limiter stages. It can be used to trip a carrier detect circuit, pin 11, at a particular input level. Our receiver Veiru-· olp Cnntrnl -. 22 151 LO Tank I I 21 1st LO hnk I 20 1sl LO Output 19 1st Mo,et Ou1put 18 2nd M1aer Input L,m,te, Decoupling l 1m 1ter Decoupling l 7 2nd Mixer lnpul 16 VEE Fig.3: the MC3362 is virtually a complete narrowband FM receiver on a single chip. Our receiver circuit uses a number of variations c:in the theme suggested by Motorola. The block diagram for the receiver is shown in Fig.2. It shows the main functions of the MC3362 which is preceded with a single BFR91 RF amplifier stage. Our design uses a 10.7MHz crystal filter, although a ceramic unit could be used at the expense of adjacent channel rejection. Following the MC3362 we used an LM386 as an audio amplifier to provide sufficient drive to a small speaker. Next month we will present the full circuit of this receiver, configured for the 2-metre amateur band. A printed circuit pattern and constructional information will be included. ~ FEBRUARY1989 51 A rotating light is often mounted on the leading locomotive of US trains as a safety device. In this photo, it can be clearly seen on top of the crew cabin. Low-power flasher for model railways All around the world's railways, guards' vans are disappearing. In their place, battery operated flashers are being mounted on the end wagon of long trains. Here we present a project to simulate those units. And we present a different version to simulate the strobe light mounted on some American locomotives. By MALCOLM YOUNG In most states of Australia, we call them "guards' vans". In most countries of Europe they are referred to as "brake vans" while in America and South Australia they are referred to as cabooses. Whatever they are called, they are steadily disappearing from the world's railways and being replaced with battery operated flashers which are usually mounted on the coupler on the end of the last wagon. 52 SILICON CHIP As such, they are a safety device to indicate the end of the train. In America, such devices are known as "end of train" indicators. In Australia, they are commonly referred to as BOGs; short for " battery operated guard". In practice, these train safety devices are not much different from the battery operated traffic beacons placed on the barriers around road excavations. The lamp has a lens about 15cm in diameter and it flashes at around once a second or thereabouts. Locomotive flasher As one of the photos in this article shows, the leading locomotive on American trains often has a rotating light mounted on the cab, again as a safety device. Naturally then, keen railway modellers will want to simulate these modern developments and they can with the flasher circuits presented here. Both the BOG and the locomotive flasher circuits are based on the National Semiconductor LM3909 Led flasher/oscillator. This readily available device has been around for about 15 years now and is the ideal device for this application. The beauty of the LM3909 is that it will easily flash a light emitting diode even when it is powered from a 1.5V cell which is practically flat. Furthermore, the LM3909 is such an efficient device that it works at an extremely low current drain, typically around 0.5 milliamps . PARTS LIST Locomotive flasher 1 PCB, code SC09102891, 20 x 25mm 1 LM3909 integrated circuit 1 W04 400V miniature bridge rectifier 1 3mm or smaller diameter yellow or orange LED 1 .047 Farad 5V super capacitor 1 4 7 µ,F 16VW electrolytic capacitor 1 1 kn 1 / 4 W resistor BOG Flasher 1 PCB as above, or small piece of Veroboard 1 LM3909 integrated circuit 1 4 7 µ,F 1 6V electrolytic capacitor 1 3mm or smaller diameter red LED 1 1.5V AA-size carbon zinc or alkaline cell 1 AA size 1-cell holder (Tandy Cat. 270-401) 1 subminiature panel mount slide switch, Jaycar Cat. SS-0852 or DSE Cat. S-2010 . Miscellaneous Superglue, solder, hookup wire. The BOG circuit Our circuit for the "battery operated guard" is taken directly from the National Semiconductor applications literature for the LM3909 - see Fig.1. Besides the LM3909, it uses just three components: a light emitting diode, a 47µ,F capacitor and a 1.5V cell. You couldn't have a much simpler circuit than that. Well the circuit is simple enough to build up but explaining the operation of the LM3909 is anything but simple. Basically what it does it is to charge up the reservoir capacitor to about 1.2V. Then it effectively connects the charged 47 µ,F capacitor in series with the 1.5V battery and uses the 2.7V combination to briefly flash the LED. Thus, the LM3909 powered from a 1.5V cell can easily drive LEDs even though they typically require 1.6V to conduct. Green and yellow LEDs need more voltage; 2.2V or more. For a more detailed explanation of the internal operation of the What could be simpler? The battery operated guard circuit uses just one IC, a capacitor and a light emitting diode (LED) - plus a switch and 1.5V dry cell. The flashing LED of the BOG circuit is mounted just above the coupler on the end of the last wagon. This photo shows how we installed the battery operated guard components on the bed of a HO wagon. Both the cell holder and slide switch are glued in position. The switch actuator protrudes through a slot cut in the bottom of the wagon. S1 1.5Vf - - - - - - - - - - - - - - - - s1 - - - - - - - - ~ _,. 0 , 6 LED1 LM3909 2 END-OF-TRAIN FLASHER Fig.1: the circuit for the battery operated guard. The LED flash rate is about twice a second. 0 SINGLE CELL HOLDER ~ WAG ON BED Fig.2: here's how to install the battery operated guard circuit on the wagon bed. You can make the cuts in the Veroboard pattern using a large drill. FEBRUARY1989 53 TO TRACK 47000 5VW + - LOCOMOTIVE FLASHER Fig.3: the locomotive flasher derives its power from the track. The bridge rectifer takes care of AC or reverse-polarity DC voltage on the track, while the 4. 7V zener diode limits the supply voltage to the LM3909. I TO TRACK F -5."1,_ _ , I I ~ ::=:.. .JI K LED1 A Fig.4: parts layout for the locomotive flasher. All parts except for the lk!1 resistor are polarised so be sure to install them the right way around. SC09102891 LM3909 see the panel accompanying this article. The locomotive flasher Fig.5: here is a full size pattern for the PCB. The locomotive version of the circuit is shown in Fig.3. While the BOG circuit above runs from a single 1.5V cell, the locomotive ver- This is the fully assembled locomotive flasher circuit, prior to installation in the locomotive. Note that the zener diode and resistor are mounted end-on to conserve space. The handed end of the zener diode denotes the cathode lead. 54 SILICON CHIP We used a 3mm LED and mounted it through a close-fitting hole in the roof of the cabin. sion of this flasher gets its power from the tracks or more precisely, from the wires to the motor in the locomotive. The circuit therefore needs to cope with negative or positive rail voltages (depending on whether the loco is going forward or in reverse). It also needs to cope with a variety of train controllers which may supply smooth DC up to 12V, unsmoothed DC of up to 20 volts peak, low voltage AC up to 12VAC (in the case of Marklin models and some other Continental brands), or pulse width modulated DC as in the case of the Railpower which was published in the April and May 1988 issues of SILICON CHIP. In all these cases, the supply voltage can be expected to vary widely. Normally, there will be some minimum voltage of 2V or more always present on the track, at which the loco will not move. Above this voltage the loco will begin to move and in normal operation 4V or more can be expected across the tracks. To cope with these conditions, the locomotive flasher has a bridge rectifier and a 4. 7V zener diode. The bridge rectifier takes care of low voltage AC or DC of either polarity while the zener diode protects the LM3909 against voltages of more than 5V. Current through the zener diode is limited to a safe value by the 1kn resistor. Super cap The cunning part of the locomotive flasher is the inclusion of a .047 Farad (47,000µF) 5V super capacitor made by NEC of Japan. Normally intended for memory backup use in computers, VCRs and FM tuners (for storing the station settings), the supercap is used here simply as a large reservoir capacitor, albeit in a very small package. So while the 4. 7V zener diode protects the circuit (and the supercap) against the higher track voltages, the supercap lets the circuit continue to operate more or less normally when the track voltage drops to low values or the loco is on a section of track which is temporarily unenergised. In the latter condition, the supercap will power the flasher circuit for about five minutes or more, which could be a considerable boost to model realism. After all, normally when power is removed from a model loco, it is completely dead. With the flasher in operation, it looks active even though it is not moving. Construction Because these two circuits use so few components there are a number of different approaches to construction. For the locomotive flasher we have produced a small printed circuit board measuring 35 x 20mm (Code SC09102891). This accommodates all the circuit components and can be comfortably fitted into typical HO scale (1:87) American diesel electric locomotives. Assembling the board is easy. The specified W04 bridge rectifier is available from Dick Smith Electronics (Cat. Z-3304) while the .047 Farad supercap is available from Jaycar (Cat. RU-6700). The 4.7V zener diode may be a 400mW or 1W rated type. Both the zener diode and 1kn resistor are stood "on end" Yes, it fits! We slid the circuit board for the locomotive flasher into a vacant space behind the leading bogie but other arrangements can be used. The power supply leads are connected across the motor. to minimise the space they occupy on the board. The LED is wired to the board using two short lengths of light duty hookup wire or a length of 2-way rainbow cable. Make sure that the LED is correctly oriented before wiring it into circuit. In general the longer wire on the LED is the anode (positive connection). Similarly, it is important to ensure that the 4 7µF electrolytic capacitor and the 0.047F supercap are connected with correct polarity. On the 47µF capacitor the negative connection is easily identified with the black strip down one side which is often associated with a minus sign. On the supercap, no minus signs are present but there are a couple of black lines down one side to in- dicate the negative connection. The negative pin is also slightly longer than the positive pin. When construction is complete, connect the circuit up to a variable DC supply. The circuit should work down to at least 2.5 volts. Alternatively, if you don't have access to a variable supply, you can use two 1.5V cells in series. A few seconds after the supply is connected the LED should begin to flash. The rate of flashing does vary according to the supply voltage. If the supply is above 6 volts (ie, biasing the zener diode fully on) the LED will continue to flash for at least five minutes after the supply is disconnected. Installation In the loco in the photos, we inFEBRUARY 198~ 55 How the LM3909 Works The LM3909 has been specifically designed to flash LEDs from a supply of 1.5V or less although it will operate on supplies up to 6V. It will work in other applications too although most of these revolve around its ability to work efficiently as an oscillator from low voltage supplies. Fig.6 shows the internal circuitry of the LM3909 plus the external components needed for it to work as a LED flasher. It is reproduced from National Semiconductor data. Here's how it works. When power is first applied, the 300µF capacitor connected between pins 2 and 8 has no stored charge (ie, the voltage across it is zero), 04 is biased on and 01 is off. The 300µF capacitor then begins to charge via the two 4000 resistors and via the internal resistance selected by pins 8 or 1 . In the case depicted in Fig. 6, the internal resistance selected is 3k0. As the capacitor charges, the voltage at pin 8 falls . Hence the emitter voltage of 01 also falls while its base voltage remains largely constant. After about one second, the voltage between the base and emitter of 01 exceeds O. 6 volts and so O 1 turns on. 04 then turns off, as its base voltage is forced low. When 01 turns on, it turns on 02 and 03 which pulls pin 2 and hence the positive side of the capacitor down to OV. This means that the negative side of the capacitor will be forced down to about -1 .2V. Since the LED is connected between pins 6 and 8, it now has 1.5V + 1.2V from the 300µF capacitor applied to it. The resulting pulse of current, as the 300µF capacitor discharges, causes the LED to flash briefly. The discharge current is limited by the internal 1 20 resistor in series with pin 6. stalled the circuit board vertically within the body. It fitted in easily. The supply to the board should be taken from across the motor, using light and flexible leads. A close fitting hole needs to be drilled in the roof of the cabin, to take the LED. We used a 3mm LED which is really a little large to be of correct size for HO scale. A number of manufacturers such as HewlettPackard produce 2mm LEDs in red, orange, yellow and green. These would be much closer to correct scale. To our knowledge though, these are not generally stocked by retailers but we understand David Reid Electronics [phone (02) 267 1385) will obtain stocks if demand warrants it. The flasher circuit could probably also be fitted into N scale (1:160) locos although somewhat 56 SILICON CHIP LM3909 _..,,..,.,.:3--___.1w2n~-----------i'5::.._.+1.5v LED 03 1---- Fig.6: basic schematic of the LM3909 IC. The external capacitor is charged to about 1.2V and then connected in series with the battery to give 2. 7V to flash the LED. The whole cycle then recommences with 01 turning off and 04 turning on , to allow the 300µF capacitor to recharge . Note: this explanation is not the whole story as the circuit of Fig .6 is a schematic only; it does not show all the internal componentry of the LM3909 . Instead of the explanation above, the LM3909 could be. regarded as a bistable pair; ie, 01 and 04 with positive feedback applied around the circuit by the 300µF capacitor. Either way, the circuit does oscillate and the LED flashes at about once a second. more ingenuity would have to be employed. BOG construction The BOG flasher circuit could be built on the printed circuit board or assembled onto a small piece of Veroboard as shown in our photos. We powered the unit from a standard 1.5V AA cell mounted in a onecell holder (Tandy Cat. 270-401). This was glued to the bed of a HO wagon. A slide switch is mounted (glued) so that its actuator pokes through the underside of the wagon, so that it can be easily turned off and on but is barely visible. This circuit could also be easily mounted in an N-scale wagon although you would need to use an AAA size 1.5V cell. The circuit could also be made a great deal more compact by dispensing with the Veroboard and wiring the LED and 47 µF capacitor directly to the LM3909 IC. In fact , by using this approach and powering the circuit from a silver oxide or mercury button cell (as used in cameras, watches and some calculators), it may be possible to fit the flasher into a Z-scale (1:220) wagon. Incidentally, we have specified the 47 µF capacitor with a 16V rating. This may seem a little over the top since the supply voltage is only 1.5V in the case of the BOG circuit and no more than 4. 7V in the case of the loco version. However , unless your parts retailer has old stock it is unlikely that you will be able to buy electrolytic capacitors with a voltage rating of less than 16VW (VW means " volts working") or even 25VW. That's the way they make them these days. ~ ~ DAVID REID W ~ ..,_................,.. ELECTRONICS PTY. LTD. ~ !FLUKE'® ~ For the electronics th t en usiaS ~..... ~ ~ COMPUTER BREADBOARDS GENDER CHANGERS ~~ ~ THE NEW FLUKE 80 SERIES DIGIT AL/ ANALOG MULTIMETERS. FLUKE 83, FLUKE 85, & FLUKE 87 08-25 MALE to 08·9 MALE 08-25 MALE to 08-9 FEMALE . 08-25 FEMALE to D8-9 MALE . D8-25 FEMALE to D8·9 FEMALE .. 08-9 MALE to D8·9 MALE . . . . . D8·9 FEMALE to D8·9 FEMALE . D8·25 MALE to D8-2 5 MALE ..... 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CRO $1 .90 LM383 7 WATT AUDIO PWR-AMP $4.25 8255 PPI $7.95 8250 ASYNCH COMM ELEMENT $20.00 LM833 DUAL AUDIO OP-AMP D!KIKUSW JAPANESE TECHNOLOGY 2 YEAR WARRANTY 5 127 York St, Sydney 2000 00 BUSINESS HOURS INCLUDES 2 PROBES MAIL ORDERS WELCOME ~~~ i)~20 -,- -~- ~ ~ rd ----=---..--- - ~ A Sharp in Pye clothing What's in a name? So goes the popular adage and the implication is: not much. Even the Bard was moved to suggest that "a rose by any other name would smell as sweet". Maybe so, but a TV chassis made under one name and sold under another can smell sour indeed if the original name is not immediately apparent. This story started when one of my regular customers called into the shop and announced that his TV set had finally packed it in. This was no surprise really because he had been complaining for some time that it was "getting a bit cranky", although the fault never seemed to be definite enough to justify his bringing the set in. Now it had stopped completely so at least I would have something tangible to look for. When he brought the set in it turned out to be a 34cm Pye Model 14G4. This was a set which, as far as I could recall, I had not encountered before. What was more, I doubted whether I had a manual for it and a search through my Pye manuals confirmed this, the closest one being for a Pye 14G 1. This didn't help much. The 14G1 is actually a Toshiba chassis which was also marketed under the Precedent label. More to the point, it was obviously nothing like the set in front of me. There was little doubt in my mind that the chassis had come from another manufacturer but, for the life of me, I couldn't identify it. Stop laughing Such a situation can be serious. If the fault is relatively simple it is sometimes possible to muddle through on the basis of one's general knowledge. But if it's a sticky one, it may be wiser to knock it back before becoming involved. 58 SILICON CHIP Time is money and such sets are best left to someone who has more experience with that particular model. But I wasn't going to give up immediately. I decided to give the set a quick once over for anything obvious and, if this showed promise, approach some of my colleages in the hope that I could borrow a manual. Time enough to panic when all else failed, I reckoned. In the meantime, I felt sure that I should be able to recognise the chassis, if only I could tap into the right memory bank. Hopefully, working on the chassis might provide a clue. A preliminary check revealed an immediate reason why the set would not work - both mains fuses, 2A delay types, were blown. From here I moved to the power TETIA TV TIP National CP2000 Symptom: Hum bars. Vertical lines in the picture waver from side to side and sometimes black patches can be seen at the edges of the screen . Only 1V difference between collector of TR806 and TP-S1, instead of 8V. TR851 (2SC64 7) leaky or short circuited. Cure: Replace TR851 and also TR806 (2SC582), 0814 (EQB01-15) and 0812 (SV04) . Any or all of these components can break down under load and destroy TR851 . supply, a fairly conventional arrangement consisting of a bridge rectifier, main filter capacitor and a 2SC2365 chopper-cum-regulator transistor. The latter was an obvious suspect and sure enough, it was a top-quality short circuit. Based on experience, my next suspect was the horizontal output transistor, a 2SD869. Right again. Which was all very gratifying up to a point but gave little indication as to what had caused all this; which transistor had failed first and taken out the other one? I decided to replace both transistors, then sneak up on the set and try to find any other faults without doing any more damage. I replaced the chopper transistor with a 2SD380 and the horizontal output transistor with a 2SD898. Sneaking up With two new fuses in place it was time to start my sneaking up procedure. I connected the set to a Variac and gradually increased the input voltage while monitoring what was fairly obviously the main HT rail. Nothing happened - good or bad. There was no sign of any HT voltage, nor were there any signs of distress at a moderate input voltage. But there was obviously another fault lurking somewhere. A resistance check between the HT rail and chassis confirmed my suspicions - a dead short. But where? Now I really did need a circuit; the idea of trying to track down a short of this kind, on a rail which would undoubtedly wander all over the place, did not appeal one little bit. Then suddenly the memory bank came good; the chassis I was looking at was a Sharp. With spirits revived I began searching through my Sharp manuals, hoping that I might have the right one and that I . : i ~m • I l!U , 7. ~ l oo - . 0 . Q) --- .... Having made that deduction, checking the zener (ZD702} was largely a formality and explained the HT rail-to-chassis short. It also suggested a likely sequence of events. My bet is that the chopper transistor failed first and the zener made the supreme sacrifice as a result - but not before the horizontal output transistor had also succumbed. That much established I simply lifted the zener and started from scratch again with the Variac . This time I was rewarded with a rail voltage and some signs of life, in the form of a raster. Well, that was something but there was no sign of a picture and no sound. Also, the raster was very bright, with visible flyback lines and some evidence of hum. The brightness control also appeared to be inoperative. Other damage ... wrn-1-rwo t\lE-W FUS&S IN 'PL.AGe::, l'T' VJ~S -r1N\~ -ro ~A~ M"< SNe:AK\NG UP ?ROCEl>~~ would be able to recognise it if I did. It so happens that, some time ago, a colleague retired from his business and I was able to buy a stack of manuals from him at a very modest price. This now paid off handsomely. The first clue was the photograph on the cover, even though this was not necessarily conclusive. But what was conclusive was a notation above it, in my colleague's handwriting, "Pye 14G4". With the circuit in front of me, everything made a lot more sense. I had done everything right so far, including picking the HT rail, which I now learned operated at 115V. More importantly I was reminded of a design trick used on many Sharp models; that of fitting a sacrificial zener diode between the HT rail and chassis to protect the rest of the set · in the event of a voltage regulator failure in the power supply. (This is not the only protective circuit in this set}. The zener is normally rated about 10V above the rail voltage and, in the event of a minor overload, will simply load the rail and hold the voltage down. But there is very little protective resistance in its circuit and a major fault will cause it to break down permanently. All the evidence suggested that there had been a major fault. The circuit is such that a shorted chopper transistor will put the full bridge rectifier voltage, some 300V plus, on the HT rail; more than double its intended value. And that could do a lot of damage. All in all, the situation didn't look too good. With no picture or sound I began speculating on what other damage the excessive rail voltage may have caused, particularly to the front end components such as the tuner, the IF signal processing IC (!201}, and the video signal processing IC (!401}. This latter includes the brightness control circuit. I searched through my stock of !Cs and to my surprise found that I had both the 1201 unit (0062CE} and the !401 unit (0118CE} in stock. I had apparently bought them at some time for a now long-forgotten job but had never used them. Well, at least it would not be hard to provide replacements if further checking supported such a move. But I had no intention of taking such a drastic step at this stage. To begin with, I was more concerned with the excessive screen brightness. The neck board of this set carries an adjustment called a "screen" control. This consists of a pot, R878, which varies the G2 voltage on the picture tube. It is used as an auxiliary brightness control during setting up procedures. On an impulse I wound this control back as far as it would go. It had some effect but not much. Then I had another inspiration; I wound back the bias controls - R851 , FEBRUARY1989 59 2SAIO 15fYl/ 2SA 10291CI uf u, J.lc•12 R43t 22oP a 47K J 0 406 v.:.,8 TO·H2/ R422\ , R426 5K(8) ; · Jl.. LU I 911,c;,mus I ~ 50M (8) R42S 10K (A) s•101 MAINS ~ LU -~ POWER 240v QACCL30vl!CEZZ TO-HI TO Fig.I: power supply and horizontal output circuitry for the Pye 14G4. The chopper transistor (Q701) failed and took out several other components with it. The neck board is supplied from point H2 at the bottom of the circuit (ie, from the HT rail via ZD702). R856 and R863 - on the red, green and blue driver transistors (Q850, Q851 and Q852). This reduced the brightness much more effectively, even though I wasn't sure just what this was supposed to prove. In fact, it proved something very important because a closer look at the screen revealed that I now had a faint picture. Perhaps "proved" was too strong a word but it at least suggested that my fears about damage to front end components were groundless. Thus encouraged, I began a more detailed examination of the neck board operating conditions and it didn't take long to establish that the collectors of the three driver transistors (red, green and blue) had no voltage on them. Small wonder that the screen was excessively bright. These collectors are fed from the 60 SILICON CHIP 115V HT rail via a 100 safety resistor, R725, which connects to a line marked "HZ" (shown at the bottom of the circuit). This resistor was open circuit and replacing it brought the picture tube operating conditions back to normal. Of course, I had to reset the screen and bias pots back to near their original settings because the screen was now much too dark. (I subsequently did a complete grey scale adjustment). This left the lack of sound as the only remaining problem although I had no inkling of what solving this would entail. The sound section is contained in IC 1301 (0096CE) and my first move was to check the supply voltage to this IC, which is supposed to be 12.BV applied to pin 10. In fact, it was zero. This voltage is derived from the secondary wind- ing of the power supply transformer, T701, via diode D706 and filter capacitor C716. I checked across the filter capacitor but there was no voltage there either. I checked the diode and it was OK. There is also a safety resistor, R719, in the circuit and this checked OK. By this time, there was little left to suspect other than a lack of voltage across the transformer winding and this proved to be the case. But why? The winding was intact so why wouldn't it produce voltage? (you'll never guess the answer). One thing was obvious - there was something very silly going on in the power supply. As well as the lack of secondary voltage, there were two other symptoms: a quite obvious hum pattern on the screen (which I mentioned earlier) and, I now mode at the correct voltage by courtesy of the Variac (which meant that there was no voltage regulation). Had I paid more attention to the setting of the Variac, I might have woken up sooner. It also explained why there was no voltage across the secondary winding; there was only DC flowing in the primary instead of the chopped current from the chopper transistor. I fitted another 2SD380 - they are not cheap, by the way - refitted Q702, Q703 and ZD702, tidied everything up and tried again. I paid more attention to both the input voltage from the Variac and the behaviour of the HT rail this time and was gratified to note that the latter pegged at 115V as the input approached 240V. What's more, it remained constant as I simulated a typical range of mains voltage variation. And, of course, the sound came good, thus bringing the set virtually back to normal. As I mentioned earlier, it needed a grey scale adjustment and I found that the volume control was horribly noisy and had to be replaced. Otherwise, that was it. The set has now been running for several weeks and hasn't missed a beat. So that was another happy ending but that's about the only part of it that was happy. I don't want too many more like that. I WAS N\~e. CONc£RI\JE:D WITI-1 TH£. From the Apple Isle E:XCE.SSIV~ SG~E.E.N ~RIGH1tJE.SSoo• To change the pace, realised, a total lack of regulation within the supply. It was sitting on 115V simply because I had adjusted the Variac to produce this voltage. Regulator checks I switched the set off and began a systematic check of all the components involved in the regulator section. I pulled out transistors Q702 and Q703 and these checked OK. While they were out I checked some half dozen diodes and a zener diode in this section, along with the various resistors, but found nothing. That seemed to leave only the capacitors, since the chopper transistor (Q701) had already been replaced. Nevertheless, on a hunch, I checked the transistor again. And would you believe it, it was a dead short. How or why I don't know. The only explanation I can offer is that it failed when I first attempted to energise the HT rail, before I discovered that zener ZD702 had broken down (which is surprising because I advanced the Variac only marginally before I realised that there was unlikely to be any HT voltage). Still, this discovery explained a lot of things. As I mentioned earlier, a shorted chopper transistor in this set puts the bridge rectifier DC voltage directly on the HT rail, so the set had been operating in this here are three shorter stories from my colleague, J. L., in the Apple Isle. They emphasise the variety of problems a serviceman is expected deal with. Here's how he tells it. A customer brought in a Teac stereo amplifier, complaining that it continually blew fuses. In more detail, it had occasionally blown one of its two fuses for no obvious reason. But recently it blew both and now would not work at all. A quick examination showed that one fuse was identified on the board as a 3.15A 2AG type and the other as a 4A 2AG type. The reason for the difference was not clear because both seemed to be associated with the DC supply. I guessed that they might protect two FEBRUARY1989 61 SERVICEMAN'S LOG separate rails - the output stage guitar amplifier. The guitar faults and the rest of the works. were obvious and easy to fix but the I put the job aside until I could amp problem took a little ingenuity get a circuit or service manual. This to sort out. proved to be a lengthy exercise but Both guitars were suffering from eventually I had both. And five the same fault. The 6.5mm phono minutes later I knew all about this output sockets had been forcibly particular amplifier and its history. torn from their bodies and one of This amplifier was a Teac A-515 them had taken the tone control pot 38W per channel model. Teac also with it. made a 25W model, the A-313, usI understand that this is a coming the same circuit board. The mon problem. Young musicians try larger unit requires two 4A fuses in to emulate the on-stage antics of the feed lines to the bridge rectifier. their rock-and-roll heroes and a The smaller one uses 3.15A fuses in 2-metre lead will not stretch to this position. And rather than over- · three metres without something givprint different boards for each ing way. Either the plug comes off model, Teac printed the one board the lead or the socket comes out of to suit both types. the guitar. It seems that, in this amplifier, a One of these guitars had been in fuse had failed and it just happened for the same repair some time ago to be the one in the holder marked and I had made a new mounting 3.15A. It was replaced, not with plate for the socket from a heavier another 4A type but with a 3.15A plastic sheet than used on the type as marked on the board. original. The students had still Of course, this didn't last all that managed to break it so this time I long and was soon replaced with made a plate from 1.5mm-thick yet another 3.15A fuse. This ac- aluminium sheet. They won't break counted for the history of fuse that in a hurry. failures. The amplifier was reported to be When I examined the board more "distorting", though I couldn't closely, I found that the fuse holder understand how anyone would hear marked for a 3.15A fuse also had a that in the complex signals it was tiny rectangle alongside with the being asked to process. number A-313 inside it. The other I connected one of the guitars fuse, the 4A one, had a similar symand strummed a few chords. The bol marked A-515. output at workshop level sounded It could be argued that these quite clean. But then, who ever markings are adequate but this pre- heard of a rock guitarist playing at supposes the knowledge that there workshop level? So I wound up the are two similar model amplifiers, wick to loud, then to very loud, then using the same circuit board with to glass-shattering level - and different fuses. I didn't know that, finally I heard it. nor did the owner or whoever I wasn't quite sure what it was replaced the fuse on those previous but it sounded very like something occasions. Not a really creditable loose inside the amplifier cabinet. arrangement, is it? What I needed was a steady, high The reason for the failure of both level tone that would keep the rattle fuses was simply that the power going while I searched for the amplifier IC, an STK465, had source. My audio oscillator providshorted internally. A replacement ed a suitable signal and I soon had IC put the amp back into first class lO0Hz bouncing around the shack condition. And I scratched the and rattling even the books on the misleading fuse rating from the cirshelves. But it didn't rattle the amp. cuit board. That mistake won't hapSo I ran the oscillator up towards pen again. lkHz. Then I found it. At about School work 250Hz the cabinet back began to vibrate so strongly that it disapThe local high school sent up a peared into a black blurr. When I couple of electric guitars and a 62 SILICON CHIP looked more carefully, I found that each of the 16 screws holding the back was undone by about half turn. That bit was easy to solve. I continued to crank up the frequency and at about 800Hz there was another strong, noisy vibration. This time it was one of the tone controls on the front panel. It had come loose and the lock nut was free on the shaft. This was a little harder to secure but it was eventually done and the high school can now start next term with a distortionless rock band. a Customer problems I wish customers could be more accurate in their description of TV faults but I suppose that's hoping for too much. I've just spent the best part of a week going backwards and forwards to an old Precedent that was supposed to be suffering from erratic fine tuning. In fact, fine tuning was only incidental to the real fault. The customer rang one evening and said that her picture had gone all wriggly, then had bent in the middle and finally dissolved into masses of dots. I asked her if the other channel was also affected. She hadn't even looked at that before asking for help. She had to leave the phone to check. Back on the phone, she said the other channel was OK but her favourite program was still all dotty. Would I come and have a look at it? I suggested that it sounded like a fine tuning problem which she could probably fix herself. I told her what to do and to ring me back only if that would not fix the trouble. I heard no more that evening, and it was later the next day tbat she rang to say that "the fine tuning fixed the fault last night but now it's back again and this time the fine tuning won't work. What's more, both channels are the same now! " There was nothing I could do but put her on the list for a visit the next day. When I finally fronted the set, the owner rather shamefacedly appologised because the set had been perfect since the previous morning. It was displaying quite a good wpoD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR C NEW VARIABLE TRANSFORMERS NEW - National Semiconductor Data Books ~ ~ O;: 0 ~ Cl 0 ~ The latest editions (1988) just received. Hurry because they never lastl Interface contains all you could possibly require on. 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Approximately 412mm Wide x 80mm High x 370mm Deep UPS-350, 350 Watts Square Wave $754.00 UPS-501, 500 Watts Square Wave $841.00 HSG-0052 2 x 36- 0.1 in wire wrap 2 x 30 • 0.1 in wire wrap 1 x 48 • 0.1in wire wrap 2 x 50 · 0.125in PCB 2 x 40 · 0.125in WIW 2 x 40 • 0.125in RIA PCB 1 x 8 • 0.156in Solder 1 x 1O• 0.156in Solder 1 x 15 • 0.156in Solder 2 x 43 • 0.156in WIW 0-250V 0-2.52A$118.00 ew o w ---..-- - -0° Heavy Duty Connector Wooay won't tell us how he does it but here's another super connector special. • 24 Pin polarised plugs and sockets. • Chassis Mounting. • Genuine gold plated contacts. • Full 5 amp rating. v_w_,_,_ ,. ,.;; _ .._ • .;;.11_111.,.. , ' ' . ~ ~ .... - Dimensions Panel Cutout 65mm x 20mm Mounting Holes M3 clearance on 73mm centres Plugs Sockets Height 81 .8mm 81.8mm Width 22.2mm 22.2mm Depth 24.6mm 22.7mm You could pay over $25.00 each for these little beauties, but Geoff said to clear them at a measly unit price of $9.50 But, as they say on the box, that's not all I C65.M 6.5mm Panel Mount Mono Socket were $1 .40 now $0.50 PCB Mount "D" Connector• D-15-PLG-RA Metal Shell were $4.00 now $2.00 D-25-PLG-STR Metal Shell were $4.50 now $2.00 only $17.50 Now $7.30 $6.35 $8.00 $4.00 $15.95 $15.95 $15.95 $2.40 $3.75 $4.65 $17.05 $8.00 $7.50 $7.50 $1.20 $1 .90 $2.40 $8.50 Others claim to be No 1 in semis(or is that no-one) but we a// know it's Wood for Chips, so we have taken the axe to this selection of semiconductor specials. If he keeps giving stuff away like this the accountant will take the axe to Woody, so better get in for your chop now. 2N2160 Unijunction was $1.10 now only $0.65 2N2904A PNP 60V 600mA was $1.45 now only $0.70 2N4403 PNP 40V 600mA was $0.30 now 10 for $1.50 2N5401 PNP GPA was $1.90 now only $0.50 2N5485 NFET 25V 10mA was $0.80 now only $0.40 2N5550 NPN GPA was $0.30 now only $0.15 BD646 PNP D/ton 60V was $1 .40 now only $1.00 LM311 H TO5 Comparator was $0.55 now 10 for $1.00 MRF208 RF 225MHz 10W was $3.50 now only $1.50 PN3565 NPN 30V 150mA was $0.25 now 10 for $1.00 PN3566 NPN 60V 150mA was $0.25 now 10 for $1.00 PN3567 NPN aov 150mA was $0.25 now 10 for $1.00 PN3569 NPN 60V 150mA was $0.25 now 10 for $1.00 PN3641 NPN 60V SOOmA was $0.25 now 10 for $1.00 PN3642 NPN 60V 500mA was $0.25 now 10 for $1 .00 TSB3055 NPN 60V 15A was $3.00 now only $1.00 Three Super Semiconductor S ecials 2 6706 NPN T092+ 45V was $1 .00 now 10 for $2.00 2N6710 NPN T092+ aov was $1.10 now 10 for $4.00 PN3643 NPN 60V SO0mA was $0 .25 now 100 for $6.00 GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road , (Corner Beatrice St.) iNc IN Nsw Lane Cove West , N.S.W. P. 0. Box 671, Lane Cove N.S.W. 2066 Telephone: (02) 4271676, Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add S5.00 to cover postal charges . Next day delivery in Sydney add $5.00. Were $14.60 $12.70 CHIPS, CHIPS, CHIPS u, 0 NE~ VARIABLF POW RES PRN-553 Series • 320W Continuous • 640W 15 minutes • 1280W 4 minutes • 800V DC 750V RMS 33 ohm $166.20 Other resistance values from . 1 ohm to 300 ohm available on short delivery. PRN-800 Serles • 640W Continuous • 1280W 15 minutes e aoov DC 750V RMS 106 ohm $174.90 Other resistance values from 0.5 ohm to 500 ohm available on short delivery. EDGE CONNECTORS We have previously advertised the closed version of these transformers, but we now stock the panel mount variety in two sizes. Other sizes up to 26A are available to special order on short lead times. HSG-0022 0-250V 0-1.2A $94.00 "'"ROSE All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED ~ a .,, C, a :l) 2 j Don't miss a single issue r ~ ! Electronlc house number :J· Convert a CB radio IF YOU'RE THE KIND OF READER that can't wait to get the next copy of SILICON CHIP, then why not have the magazine delivered direct to your door? Each month, we'll bring you the best and brightest electronics magazine in the business, put together by Australia's most experienced team. 1for I amateur use l FM&·element antenna Matchbox crystal sat * Constructional Projects for the Enthusiast * Garry Amateur Radio by Cratt * The Serviceman's Log * The Way I See It * Hifi Features & Reviews HIii review: Yamaha's brllllant new CD player Plue - lho Orlglntl l I H I TV I Ol'V ICtn11n, Vlntllo• Aodlc, The W•v I Sn II, !ho ! volutlon cl Elt ctrlo Aollwoye 0 da 1' JI,,,,,,, Jf •111,,,, ~::t •11d Po11 FREEPOST * SUBSCRIPTION COUPON D D New subscription Renewal Start in _ _ _ _ _ __ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ __ (PLEASE PRINT) Street_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ Postcode_ __ 1 year (12 issues) D $A42 2 years (24 issues) D $A84 NZ & PNG (airmail) D $A65 Overseas surface mail D $A62 D $A120 D $A130 D $A130 D $A240 Australia Overseas airmail Enclosed is my cheque/money order for $ _ _ _ or please debit my D Bankcard Card No. I D Visa Card D MasterCard I I I I I I I I I I I I I I I I Signature _ _ _ _ _ _ _ _ Card expiry date__ /_ / _ _ Subscription Hotline We can accept your subscription order by telephone. Just ring us on (02) 982 3935 and quote your Bankcard or Visa Card number and the expiry date. I I I I I I I I I I I I Detach and mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 • No postage stamp required in Australia. I I I I I X I ~-------------------- - - ----- - --- ---- - -~ 64 SILICON CHIP -- e •- • ~~-- 0 I CONN~CT'E-t> ON& OF 11-1~ 6U\~'R.~ 8t St'RUN\H\E:'0 ~ ~ CHORDS oo• picture, except for some worminess in the yellows. This is usually seen in sets that are tuned almost into sound bars. This seemed to confirm my feeling that it was a fine tuning problem, though I had yet to see the full-blown symptoms as described by the owner. I tried fine tuning the set but nothing happened. Then I noticed that the AFC switch was on so it was no wonder that the fine tuning wouldn't work. With the AFC switch off, I tried again and this time it worked. As luck would have it, I tuned deeper into sound and as the picture broke up the owner cried, "That's it! Thafs what it did the other night!" Adjusting the fine tuning "the other night" had apparently cured the fault. I asked her if the AFC switch had been on or off when she tried to tune the set. She couldn't remember but thought it had been on. If that had been the case, how was she was able to tune the set? In the circumstances all that I could do was to carefully retune the set, then advise her to call me if the trouble recurred. She was back on the phone that evening. The next day and the day after that were repeats of the first one more or less perfect pictures, with only slight maladjustment of the fine tuning. In the end, I decided that the only way to come to grips with this fault was to run the set in my workshop. It could sit there for days if necessary and I would be on hand when the symptoms reappeared. And so a few days later I delivered a loan set and collected the villain. The loan set turned in a first class picture which removed any doubt that the customer's antenna system might have been contributing to the fault. Next morning I positioned the set on the bench and set it to channel 2. This was the customer's usual channel so it was the one most likely to show up the symptoms. Again, the fine tuning seemed to be slightly out but it responded to adjustment. I couldn't work out why it was just a little different every day and always in the same direction. The way things were going, we would eventually run out of adjustment! Still, the set had been running for only about two hours when the real cause of the trouble was revealed. Although I was working on another job at the time, I just happened to look in the right direction when the Precedent decided to play up. First, the colour disappeared. Then vertical lines in the picture started to weave from side to side. Finally, the whole picture collapsed into diagonal lines as the horizontal hold lost its grip. So that was the real symptom loss of horizontal sync - and not tuning drift . Of course, the customer couldn't tell the difference between the sound bars I had created while testing and loss of horizontal sync. Once I had seen the fault, I found that I could easily provoke it by tapping the chassis in the vicinity of one of the auxiliary boards, the video IF module. These Precedent sets use a Toshiba model C8.10 chassis which is well known for its dry joints on both the mother board and the plug-in modules. They use double sided boards with numerous pin-throughs which are notorious for bad solder joints. In this case, the dry joints were on the video IF module (FM-106) in the vicinity of the video detector (IC-102). The result was a crushing of the video output which reduced the amplitude of the horizontal sync pulses. Also, the video detector provides the control voltage for the AFC module, so the fault had to have some affect on the fine tuning. Fixing the fault was easy, once I had seen it. A few minutes work with a hot iron on the IF module cleared up the trouble. But like most intermittent faults, it wouldn't show up during the brief periods I could spend in the customer's home. And of course, the customer's description didn't help a bit! ~ FEB RUA RY1989 65 THE WAY I SEE IT By NEVILLE WILLIAMS Jump start your new car and blow up the electronics! In October and November, according to a Victorian reader, I exaggerated the vulnerability of fly-hywire technology hut paid too little attention to the problems of electronic management systems in modern cars. They are especially at risk, he says, when jump-starting a car which has a flat battery. Most SILICON CHIP readers would relate more readily to everyday problems in the family car, particularly a new one, than to arguments a bout the control system of an aircraft in which they may never get to fly. But to make life easy, I present the letter as written and discuss the subjects in the same order. Here's what the reader has to say: Dear Neville, I feel a bit uneasy about the views expressed about the A-320 in the October and November issues of SILICON CHIP. Accordingly, I have copied for your perusal an article from "Electronic Engineering" for July 1988 relating to this aircraft and others to come. It shows the other side of the coin. After reading it, I hope you won't look too much at the gloomy side of new technology in aircraft design. While I agree that an aircraft can be shot down by a bolt of lightning, I believe that flying in a modern aircraft is still much safer than driving around in the new cars of today. They are lighter (they use thinner metal) and are less reliable electrically. I have heard stories recently of the 66 SILICON CHIP electronics being completely destroyed by jump-starting a modern car which has a flat battery. This, I would add, with the batteries connected the right way around. It surely indicates very poor design on the part of manufacturers, in not adequately protecting the electronics from the voltages and situations that one can encounter in a family car in the course of everyday use. A major electronics failure can be both expensive and time consuming, because it may completely disable the car. Maybe you could prepare an article on the do's and don'ts of a modern car and its electrics. I trust that you will find the enclosure helpful. You may not have had access to it prior to writing your article. W. K. (Ascot Vale, Vic). Thank you, W. K., for the article, which I had not previously seen. Despite the July 1988 dateline, it would almost certainly have been set up and printed well before the A-320 crash on June 26. For the author, Pierre Baud, President of the Flight Division of Airbus Industrie, it must have been an agonising experience for an article extolling the design of the A-320 to coincide with such a public crash during an exhibition flight; more than that, to hear worldwide speculation that the crash may well have been due to a catastrophic failure of the much publicised FBW (fly by wire) control system. Baud's article emphasises the care taken with its design and the high order of redundancy provided as a precaution against possible equipment failure - although it probably doesn't go beyond what one would expect, anyway, in such a new and commercially important aircraft. There is no way that I can do justice here to Baud's 4-page article but the following brief summary will give readers some idea of its content: • FBW control, in analog form, has been in use in the Concorde since 1969 and to a limited extent in digital form in earlier models of the Airbus since 1983/4. • With a response time of not more than 5ms in some functions, the computers can intervene to protect the aircraft against stalling, excessive speed, unduly violent manoeuvres and the effects of windshear - a phenomenon that has been a key factor in several major accidents in the past ten years. • The FBW system in the A-320 relies on five main computers, of which any one of four can fly the plane independently of the others, largely obviating the risk of hardware failure. • At the same time, the risk of coincident software failure is minimised by the deliberate use of dissimilar processors and dissimilar processor languages in paired computers. Meet the "Oscilloclast" By way of a complete change of subject, I would like to pick up again the theme in the last issue: pre-occupation with the supposedly therapeutic qualities of electricity. I had intended to leave it to readers to comment further but, as it turned out, I came across an article on yet another " revolutionary" discovery: an electrical procedure, also from the early 1920s that might well have given last month's Dr Rogers and his " Neurophonometer" cum "Kiro-Vox" a run tor the American " get well" dollar. Under the heading " The Electronic Reaction of Abrams ", it was the subject of a series of articles in Pearson 's Magazine (New York) which described it as " the most revolutionary discovery of the age - the Abrams method of diagnosis and treatment" . Dr Albert Abrams, it appears, had established a clinic in San Francisco "to which hundreds of physicians from all over the United States were sending specimens of the blood of patients so that the Abrams method of diagnosis could be applied to them ". The report continued: "each blood specimen is placed in turn in an electrical device invented by Dr Abrams and the vibratory rate is read oft by varying a rheostat the readings indicating whether a disease is present in the patient, • All computers are normally ac. tive at all times, some actually flying the aircraft, the others fully updated and on instant standby. Constant input/status self-checking alerts each FBW computer separately to any inconsistency and possible fault. • In the unlikely event of progressive computer system failure, a design philosophy of "graceful degradation" transfers control logically to the pilots. This initially involves the "wire" facility but, in an extreme emergency, transfers direct control of the mechanical tail and rudder trim. • The aircraft has been the sub- the nature of the disease, its locality and its history" . "When the disease has been determined , a course of treatment is prescribed using another invention of the doctor's - called the Oscil/oclast - which is said to be capable of breaking up ordinary alternating current into various vibrations" . The basic idea, apparently, was in some way to subject the patient to electrical impulses at the frequency of the disease (?) and thereby destroy it. I quote: "Ascertain the vibratory rate of the disease, ascertain what current will cancel that reaction, and then pour into the body a current at that rate , and you destroy the activity of the germs". In between those last two quotes were observations attributed to Upton Sinclair, "the great American novelist" (?) and a Dr W. G. Doern of Milwaukee, ne ith er of whom contribute anything meaningful to the text. Even Dr Abrams is a bit vague about his so-called "discovery of the age " . Again I quote : " Dr Abrams makes a guess as to why the same vibratory rate destroys the disease activity. He tells how once he saw Caruso at a dinner party tap a wine glass and determine the musical note at which it vibrated, and then sing the note at the glass and shatter it to fragments .. . Dr Abrams believes ject of exhaustive flight testing, such that it satisfies all international airworthiness authorities. The segregation and shielding of FBW cables has proved effective against" exposure to deliberate high RF fields from radars, etc and simulated lightning strikes. It's a reassuring article but the undeniable fact is that the aircraft did crash and burn in a very public manner at the Mulhouse Airport on the Franco-Swiss border. It was little short of a miracle that only three persons were killed out of the 140-odd passengers on board. It is also true that the crash occurred in circumstances that sug- that this is what happens to the disease germs ... that which was a disease germ becomes something else". By way of a further illustration , he quotes the transubstantiation of elements (uranium /radium/lead) and suggests: "that by means of a current, he can change the atoms of a cancer into the atoms of something else ". Skipping a few more paragraphs, I came upon a couple more quotable statements, one reassuring, the other interesting: " Asked if the applied vibrations might not injure living tissue, he answers that there is nothing in the normal body which yields the same vibratory rate as disease" and : "Dr Abrams has ascertained that pain has a certain vibratory rate , and if you have a pain , he can locate it; also, he found the vibratory rate which cancels pain and has taken the Oscilloclast to a dentist's room and demonstrated to several dentists that work, otherwise agonising , could be done practically without sensation". Strange, isn't it, that such a marvellous device should have disappeared without trace . Especially as $50 ,000 is said to have been pledged to promote its use in a childrens ' clinic by the good doctor "who happens by rare good fortune to have been a man of independent means ." gested either pilot error or an aberration in the computerised control system, rather than a mechanical failure in the aircraft itself. Moreover, allegations by the French Airline Pilots Union of an official cover-up and argument about the conduct of the inquiry seemed to point to the electronics. What's his real concern? Having read and re-read W. K.'s letter, I am still not clear as to the reason for his unease about the views expressed in the October issue. Was it because I did not specifically lay the blame on pilot error or did he construe the entire FEBRUARY1989 67 THE WAY I SEE IT - CTD article as an opportunistic and thinly veiled attack on the Airbus philosophy? In fact, the article on fly-by-wire and the electromagnetic environment was planned in early June and was nearing completion when the Airbus crashed. I simply added a couple of pars mentioning the crash and speculation about the cause, qualified by the remark "the matter may possibly have been clarified before you get to read this .. ." As it transpired, the official report blaming pilot error was published about a month after the crash but rather than start pulling finished pages around at that late stage, it was decided to let the qualification run as it was. The remainder of the article was simply an open-ended discussion of the conflict between critical electronic equipment and the electronic environment. I posed the question as to whether the problems really had been resolved as completely as some would imagine. It proceeds to the proposition that, for critical electromagnetically vulnerable links, our thinking should perhaps be towards the use of fibre-optic technology rather than metallic cables. The November article continued the theme, prompted by a fortuitous episode of Quantum on ABC TV. It explained the problems that NASA had experienced with lightning discharges and detailed their current research in that area. The statement about the frequency of lightning strikes on aircraft in American skies was Professor Krider's, not mine. What I personally described as the "odd-ball scenario" of technologists working towards disparate objectives is surely self-evident. No, I am not anti-technology or anti-aircraft. I, too, can relax aloft with a greater sense of content than when negotiating endless curves on a lohg car journey. I agree that lightning strikes rarely damage conventional aircraft but it would be nice to be assured that FBW planes would be no more vulnerable in the same situation. Electronics in cars As for electronics in motor cars, that's another story, in more ways than one. Says W. K.: "I have heard stories recently of the electronics being completely destroyed by jump starting a modern car that has a flat battery. This, I would add, with the batteries connected the right way around". I, too, have heard such stories but seeking confirmation or otherwise, I rang a friend connected with the NRMA (the National Road Motorists' Association in NSW). "Yes" , he said, "electronics can be destroyed in that situation" and, while he didn't profess to know all the answers, he was certainly familiar with the problem. First off, he suggested, don't take too much notice of claims that the jump leads were correctly connected. Reversing the polarity is probably the single most effective way of wrecking the electronics but someone who has just been guilty of doing that is often loath to admit it. The next most effective way, he said, is to jump start the engine with correct polarity, then immediately remove the jump leads and rev the motor madly to assure all and sundry that it really is running! A flat battery, he explained, cannot be relied upon to smooth the load spikes, especially if someone races the motor immediately after starting. Up go the spike voltages and "phut" goes one or more of the devices in the black box. He made the further point that excessive voltage is by no means a new problem. In other days, it has damaged indicator light globes and the odd clock or radio that has been left across the supply. But while annoying, such items are scarcely in the same class as an engine management computer. For how long, then, should one leave the jump leads connected? "For not less than five minutes", he said. "By that time, an otherwise good battery should be active enough to cope - especially if you're on the spot to double-check the voltage". He went on to say that, while a near worn-out battery was problem enough, they also had to be very careful with a good battery that had been flattened by leaving the lights on overnight or in an airport parking lot. "They get really flat", he said, "and sometimes take a fair while to reactivate". Open-circuit batteries I gather NRMA repairmen have to be particularly cautious about batteries which may have developed an internal open circuit. An open-circuit battery provides no protection at all against spikes and over-voltage from the alternator and exposes the system to damage immediately the jump lead is disconnected. If a battery shows little or no voltage at all across the terminals on a sensitive meter "it's a case of getting a replacement battery or a tow truck''! One aspect I omitted to check with him was the possible effect of a "crook" battery connection - the corroded clamp or the rusty chassis bolt that stalls the starter motor. It might also expose the system to spikes or over-voltage from the alternator but I would expect the "won't-start" problem to show up first. Reversing the polarity of jumper leads is probably the single most effective way of wrecking a car's electronics but the guilty are often loath to admit it 68 SILICON CHIP Electronic devices other than in-car computers can also be vulnerable & expensive. These include 2-way radio systems and in-car telephones How extensive or how expensive the damage may be to an electronic control system depends on the nature and the number of separate "computers" in the particular vehicle. The truth probably is that computer breakdowns are never cheap; it's just that some are more expensive than others. One parting point made by my informant was that, these days, electronic devices other than in-car computers can be vulnerable and expensive. As a precautionary measure, when dealing with battery problems, he recommends pulling the fuses supplying 2-way radio systems and in-car telephones. I'd be surprised if other SILICON CHIP read.e rs don't have a few corn- ments to add to the above. That brings me back to W.K.'s proposition: "It surely indicates very poor design, on the part of manufacturers, in not adequately protecting the electronics from the voltages and situations that one can expect and encounter in a family car in the course of everyday use". It surely does, which is exactly what we had in mind on page 39 of the October issue. Thankfully, some of the early problems are being sorted out but there are still a few to go. The pity of it is that the weaknesses had to be identified the hard way. My expressed hope was simply that it wouldn't be like that in the aircraft industry, where a great deal more is at stake. Harking back to that, it's ironic that the A-320 crash should have been due, not to any failure in the electronic control system, but to a couple of pilots who would appear to have taken more notice of the chips on their shoulders than those in the FBW equipment. I quote from a report, as published: "The crew contemptuously dismissed warnings emitted by the computers, the pilot saying several times: knock that one off, it's getting on my nerves". As I write, the first of the new A-320 "Skystars" has just landed in Sydney. One would sincerely hope that our own pilots will not be quite as nonchalant! It CONTACT INTERNATIONAL PO BOX 390 COW ANDILLA, SA 5033. 2/283 BURBRIDGE ROAD, BROOKLYN PARK, SA. MAIL ORDER MAIL ORDER COMPUTER PERIPHERALS 00027 MULTI 1/0 CARO + FOC . 00372 PRINTER CARO. 00390 TOWER COMPUTER CASE + OISPLA Y 00387 XT CASE + LOCK . D0245 COPYHOLDEA D/TOP, ADJIARM D0260 DISK STORAGE BOX , 100 x 5¼ " D0100 DISK STORAGE BOX, 80 x 3.5" D0282 JOYSTICK FOR XT/AT D0392 KEYBOARD, 101 KEYS . D0350 MONITOR LEAD IEC PLUG TO SKT . D0012 XT MIBOARD 8 MHZ, 0 RAM D0297 GENIUS MOUSE GM6+ .. D0342 MOUSE PAD . D0040 AT MOTHERBOARD, 12 MHZ, 0 RAM D0359 ATIXT CASE, RESET + KEY , F/TOP . KEYBOARD WITH MOUSE . PRINTER RIBBONS D0419 BROTHER 1509 RIBBON . 00420 BROTHER 1724 RIBBON 00427 COMMODORE CP80 RIBBON 00450 EPSON EX80011000 RIBBON . OVER 80 TYPES AVAILABLE PHONE: (08) 231 2202 FAX: (08) 352 1449 RETAIL 80.00 26.95 325.00 80.00 22.95 11.00 10.50 19.00 89.95 3.99 119.95 95.00 4.50 499.00 59.95 199.95 14.95 14.95 10.50 12.95 I THIS MONTH'S SUPER SPECIAL* MAIL ORDER COMPUTERS " GOLD PLATED LEADS 00005 XT TURBO , 1OMHZ, 640K , 2 x 36K FOO , 101 KEYBOARD , FLIP LIO CASE, LED SPEED DISPLAY 1125.00 D0001 SHERRY AT 512K, 1 x 1.2M FOO, 101 KEY/BOARD, EXPANDABLE TO 1MB, 611 OMHZ , CGA CARD , SERIAL/PARALLEL PORTS . 1895.00 SHERR Y EGA COLOUR MONITER 695.00 640 X 350 SCANNERS D0237 HS3000 SCANNER . CARETS OCR SOFTWARE .. . 379.95 269.95 MUSIC CARD D0145 MUSIC CARD - See Produc1 showcase sec1ion JAN 89 . 350.00 WOOS 7 LEAD GOLD W0064 LEAD GOLD W0029 LEAD GOLD MALE . W0042 LEAD GOLD MALE W0207 LEAD GOLD MALES BNC MALE TO MALE . BNC MALE TO RCA MALE RCA MALE TO 3.5mm 5.95 5.50 3.00 RCA MALE TO RCA 3.50 RCA MALE TO 2 RCA 3.95 COMPUTER POWER SUPPLIES D0057 D0061 D0060 D0058 D0358 150 150 200 200 220 WATT FOR XT . WATT FOR XT SQUARE . WATT COMPACT FOR AT WATT STANDARD FOR AT WATT FOR TOWER COMPUTER 89.95 89.95 145.00 119.95 169.95 CONTACT US FOR HARD TD GET ITEMS. MANY OTHER PRODUCTS AVAILABLE. SEND FOR FREE PRICE LIST. BROCHURES AND FULL SPECIFICATIONS FOR "AT" COMPUTER AVAILABLE UPON REOUEST. ALL PRICES INCLUDE SALES TAX PRICES VALID WHILST STOCKS LAST ···············································································································. * D0528 XT CASE, TURBO LED DISPLAY $79.95 * PLASMA DISPLAY $159.00 Mall Order Postage Less than $50 ............................... $3.50 $50 • $99 ...................................... $4.50 $100 • $250 .................................. $7 ,00 Above $250 ................................ $1 o.oo HeaVy Items adds extra WHOLESALE ENQUIRIES WELCOME 0 BANKCARD O MASTERCARD O VISA EXPIRY DATE Card No ................ ... ...... .... .. ................ . Signature: ................................................. ..... ................. . (Note: unsigned credk card mall orders cannot be accepted) Name: ........................................................................... . Address: ................................................................. .... ... . • IBM is reg. trade mark of International Business Machines ............. ....................................... Postcode: ........... ....... . • XT, AT and Atari are registered trade names __ (Please_allow14DAYS_fornormalmallandbankclearancedelays) JAYCAR NO. 1 FOR NEW ECONOMY DIGITAL MULTIMETER (With everything!) This really is the all singing, all dancing DMM. Jaycar's direct import saves you money again. (Stock due mid-Feb.) Just look at the features * Frequency Counter * Temperature Measurement • Transistor Tester * Capacitance Tester • Diode Tester * Continuity Buzzer * Data Hold Currens * 20 Amp • 28 Ranges Cat. OM-1450 ONLY 1 , 1 \ \ ' $169.00 LOOKATTHEFEATURES ~:.::~ • 34 ranges• 3.5 digit LCD display • High Impact yellow case • Small size - only 133 x 70 x 30mm • 10 amp AC and DC. DCV under 1% worst case · • Diode tester • Continuity buzzer • Frequency counter 10Hz - 200kHz • Built-in 20MHz logic probe • Capacitance tester 1pF - 20uF • Tilting bail • Safety test leads • One hand operation with unique feature where probes can mount Into either side of the case. • 3 month warranty / / ONLY $10 ~1/, DIGITAL ' MULTIMETER (With almost everything) A Jaycar exclusive direct import. Save a massive $50 over similarly equipped units. Lowest Price Jaycar Digital Multimeter f.'✓ ~R Another Jaycar exclusive direct import. Digital Multimeter at an Analog price!! • 3.5 digit LCD display • 20 ranges • Diode checker • DC 10 amp, 1000V, 0-20M ohm, etc. • 1500 hour battery life • One hand operation with unique feature where probes can mount into either side of the case • Tilting bail • Safety test leads • 3 month warranty Cat. QM-1410 ONLY $5,9.95 DIGITAL ~ MULTIMETER, Cat. OM-1400 ~· 9 SAVE $50 AND EXCITING PRODUCTS 8" (200nm) PLASMA LAMP The most beautiful thing we have ever seen. Just imagine, a beautiful plasma display in your own home for under $2001 Watch as the red glowing element in the centre of the 200mm glass sphere projects beautiful blue lightning outwards to the inner surface of the ball where it magically changes back to crimson. This event occurs simultaneously at least 50-100 times all over the inside of the sphere and is constantly in motion. It is truly beautiful to watch. The intensity of the display can be controlled by a slider pot mounted on the attractive base. In addition you can trigger the performance by means of a sensitive sound aC'.ivated circuit. The entire unit comes wrth its own dedicated pcwer supply and is packaged in an attractive gift carton. This beautiful instrument will give countless hours of pleasure and relaxation and is truly unique. Cat. XP-1000 PERSONAL DATABANK/ CALCULATOR UNDER $40 PIEZO REVERSING BUZZER This personal databank will store your telephone numbers as well as being a pccket calculator. The databank has 2K memory which is t ,936 characters which will accommodate more than 100 names and telephone nuni:lers. It measures only 88 x 57 x 4mm thick, about the same size as a credit card. It also has a special securrty code, so those private phone numbers can1 be retrieved by anyone but Extremely loud ( 11 Sdb) piezo buzzer which is rncunted on a metal angle bracket. Ideal as a reversing war ning on vehicles or just an intermittent beeper. Draws 100mA. We tested this against the sonalert we used to sell at $9.95 and found that this one is MUCH louder. Size 58mm diam x 38mm deep plus bracket 50mm. These would normally be worth about $18.00 Cat. AB-3443 Special at $9.95 NATIONAL CMOS LOGIC DATABOOK • Auto power off • Edit feature • 1o digit calculator • Includes battery We have seen these for as much as $79.95. But wrth our direct importing we can otter them at about 1/2 that price Cat.OM-7200 BACK AGAIN ONLY $39.95 Once again we have stocks of this fabulous databook. Components covered in the book include: • 74HCQQ series * 4000 series •74COO series CMOS application notea and surface mount MachinedAin-Tdfi..(jrnde Ahnniniwn Aashlight solderless terminals. Included lug terminals, cable joiners, an block. These normally cost bet normal price for these parts w LIMITED QUANTITY Cat. HP-1210 °"Tio ONLY$10 50 ONLY $9.95 :::r~:~:~ :~o:!~ !~n~~oe;:::~it:~/= i/:~n: ~~:P 1 s8:,~~ey~: phone, you'd better be quick. Only $5.00 each and we'll even include lhe artide on how to fix them. ii they're faulty. (The telephone plug alone is WOfth $4 , let alone the keypad .. cable, mic. speaker etc.,) No seven day return on this bargain . 95 Cat. BN-4004 What an excellent product! It measures 145mm long and runs off 2 - AA batteries. It is 70 times brighter than a normal torch and the beam is adjustable from spot to beam, and it's waterproof and shockproof. Durable anodised abrasion resistant finish, wrth a non slip knurled grip. This torch will last a lifetime. Small enough to fit inside a car glovebox or handbag. It can also be used as a lantern. Unscrew the top and the bulb A Vf!lfy large telephone importer!vvholesa/er came to Jaycar, ..: ~ ·•·.···• ,·•: ..... - · is exposed to give 360° light. They had a dilemma. Whenever they get a one piece phone ._'. · \. back from a large department store, with a note on it S,ctying ·~,... # ::~. We have seen these torches for $19. "Faulty", they immediately replace it. They don't even check to · •: • •·~ We have direct imported them and can offer them for see if ii is acb.Jally faulty or not We are sure that a good ·, <=. ~ • \ the amazing price of only $9.95. Cat. ST-3000 percentage hsve nothing wrong 'Nith them , bot the majority 'Nill : ,. \ Spare bulbs available for only $1.50 (Cat. ST-3002) h_ave some !ault. or a small problem . Ele_ctronics Australia h~ve a ·. ·":\ .,:·; : · 0 pa$ ges. 1 9 . e KEY FOB TRANSMITTER SELLOUT Refer our catalogue page 124 Transmttters which once formed pM of our RXITX set, but we don't have any more receivers left. Transmitter key measures 60x34x14mm. Cat. LR-8814 Buy a couple of spares. >:-~· ~~~~~~~~~~~~~~~~~~~~ TURN YOUR SURPLUS STOCK $5• OOe aCh INTO CASH!! Cat. YT•7000 Jaycar will purchase your surplus stocks of components and equipment CALL GARY JOHNSTON OR BRUCE ROUTLEY (02) 747 2022 WAS$27.95 NOW$10.DD SAVE $17.95 ULTRA THIN SHIELDED CABLE Oualrty English made shielded cable wrth a total diameter of 1mm. Ideal for screened wiring in small spaces. Packet 5 metres Cat. WB-2310 ONLY$2.50 5" SPEAKER SALE lbis is your chance to save big bucks on the ETl5000 and 2801 graphic equalisers. See ow- catalogue for full details. Both units are ba.c;ically the same except that the 2801 has connon connectors and a power supply for 240V operation. The 5000 requires 15V, usually derived from the 5000 Amp. T I ONLY $14.95 ~ 5 watt power handling, widerange speaker. Cat. AS-3020 8 ohm : ONLY$3.95 2801 EQUALISER CAT. KJ-6531 I Forget those old mercury thermometers. This new digital I 10+ $3.65 ea thermometer will read in both Celsius and Fahrenheit. I range 32°-43°, Farenheit range 89.6°-109.4°. Also WAS $239 NOW $149 SA VE $90 I Celsius 1~a includes buzzer alarm. We have seen these in other I catalogues for as much as $29.95. Jaycars direct Ell 5000 EQUALISER CAT. KE-4204 in-porting cuts out the middleman and you SAVE ':~', MONEY. WAS $219 NOW $129 SAVE $90 IIt.....:..: __ __ _ _ _ _ _ _j r.at._ OM-6300 ONLY $14.95 .. ,;;~;~~:•J~~~~~ uP TO AN AMAZING $200 I e,' / ; HUNG CHANG 20MHz CRO • Front panel trace rotater• TV video sync filter • Z axis (intensity modulation)• High sensitivity X-Y mode • Regulated power supply circuit SPECIFICATIONS Effective Display Area 8 x 10 div (1 div = 10mm) VERTICAL CH-A, CH-B, DUAL, ADD (CH-B can Operating Modes be inverted) Alter; 0.2ufs - 0.5ms/div. Chop ; 1ms Dual Modes 0.5s/div CHOP frequency 200kHz approximately Deflection Factor 5mV/div 20V/div ±3%, 12 ranges in 1-2-5 step with fine control DC; DC - 20MHz (-3dB), AC; Bandwidth 10Hz - 20MHz (-3dB) Rise Time Less than 17ns Overshoot Less than 3% 1M ohm ±5%, 20pF ±3pF Input lrrpedance HORIZONTAL NORMAL and AUTO Sweep Modes Time Base 0.2ufs - 0.5s/div ±3%, 20 ranges in 1-2-5 step with fine control 5 times (5x MAG) Sweep Magnifier Linearity 3% TRIGGERING INTERNAL; 1 div or better for 20Hz Sensitivity 20MHz (Triggerable to more than 30MHz). EXTERNAL; 1Vp-p or better for DC - 20MHz (Triggerable to more than 30MHz) INT, CH-A, CH-B, LINE and EXT Source Slope Positive and negative, co ntinously variable with level conlrol PULL AUTO for free-run COMPONENT TESTER Component Tester Max AC 9V at the terminal with no load. Max current 2mA when the terminal is shorted. (Internal resistance is 4.7k ohm) CRO-NORMALLY$899 NOWONLY$719SAVE$180 Cat. OC-1900 PROBES(IWQ)NORMALLY$99 Cat. OC-1902 NOWONLY$79for2SAVE$20 '4164 64K MEMORY BARGAIJV I 200ns variety Cat.ZZ-8420 I Normally $4.95 : __Now Only $2.95 each __ I 41256 RAM I I : I jYes, we have stock of this unbelievably I I hard-to-get part. I I 256K RAM, 150ns Cat. ZZ-8453 I L $27!~e~ _ ~u~$~!!_0.::_a~ Here's what you get: Cat. TD-2000 $19. 95 .. ~, · ~ .:..·· • · JAY D IMP I VERBATIM DISCS AT UNREAL PRICES JAYCAR No.1 FOR DISCS Compare our prices with your normal supplier Description 1-9 Boxes 10+ Boxes 3.5" 1S/2D $39.95 $37.95 Cat. XC-4720 3.5" 2S/2D $46.95 $43.95 Cat. XC-4721 3.5" 2S/HD $99.00 $89.00 Cat. XC-4722 5.25" 1Si2D $22.00 $21.00 Cat. XC-4725 $26.00 $24.00 $41.00 $39.95 - _J At last! A driver set incorporating those obscure shaped heads! Have you ever needed to service an electric tool? Chances are you would not have been able to do so because the screws holding the appliance together had strange shaped heads. Well now you can with our 30 piece driver setl This set contains all the driver bits you are EVER likely to encounter (See Below). Basic to the set is an 8 1/2" Chrome'-Vanadium driver wh ich will accept any of the 28 hardened steel bits supplied . All held in the socket by a small magnet - so you can use It in any position . The screwtogether hol low handle wil l hold several tips so you don1 have to take the whole set with you into the field. There is a tip here to suit almost any screw/nut you may come across. •, Slotted Bits 0-1, 3-4, 5-6, 8-10, 12 • 5 Hex Bits 3/32", 5/64", 7/64", 1/8", 9/64" • 4 Philips Bits No . 0, 1, 2 & 3 • 4 Square Recess Bits No. 0, 1, 2 & 3 • 6 Torx Bits T10, T15, T20, T25, T30, T40 • 2 Pozidrive Bits No. 1 & 2 • 1 x 1/4" Drive Socket Adaptor • 1 x 1/4" Drive Hex Bit Holder And its all housed in a sealable tough plastic case. ~~ At last. A reasonalbly priced portalble gas soldering iron that can double as a small welder or heater with an optional tip. Save $10 over other gas soldering irons. • Use anywhere • Uses standard butane gas fuel • Temperature adjustable - equivalent to 10-60 watts • Soldering up to 400°C • Welding up to 1300°C (Optional tip) • Use for heat shrinking (Optional tip) • Refills in seconds • Up to 60 minutes continuous use • Reasonably priced replacement tips • Includes one 1mm soldering tip Cat. TS-1410 O N LV $9.95 TS-1413 0 N LY $9 .95 Welder Tip Cat. TS-1411 Spare soldering tip 1mm Cat. • • • FANTASTIC NEW KITS FOR '89 MINSTRAL 2/30 SPEAKER KIT Refer Silicon Chip Feb 89 Jaycar and Silicon Chip proudly present the first in a series of quality, economical speaker kits. These popular bookshelf type speakers will handle 60W RMS! AND They perform extremely well, showing a good overall balance between speakers and a very flat response through the tonal range . Just look at these features: * high efficiency - 96db - 7Watt/7meter * pre:built crossovers with aircore chokes * small size - 490(H) x 303(W) x 290(D)mm * Recessed push terminals on rear * quality black cabinets with removable grills $1 49 ■ 0Q Cabinets $129.00 Speakers cat. cS-2540 Cat. CS-2542 If purchased together only$269.00 complete PCB SHORTS LOCATOR Refer EA Feb 89 This kit will allow you to use anu analog RGB colour video monitor as a CGA colour monitor for your IBM PC or corrpatible. Kit includes PCB. box. panel. D sockets and plug and all specnied components. Cat. KA-17t' 49.95 Refer EA Feb 89 This simple krt will help you locate shorted tracks on printed circuit boards by means of a varying audio tone. It's easily built and much cheaper thao commercial units. Cat. KA-1712 r----------, BETA TESTER 1 MAINS.MUZZLER 1 I I I I Refer Silicon Chip Jan 89 A line filter kit for your computer which incorporates an effective fi lter for mains borne interference and a varistor to clip dangerous spike vollages. Krt includes PCB, box (HB5446) 4 mains sockets and all specrt ied components. Cat. KC-5046 Refer Silicon Chip Feb 89 Great NEW krt. Will measure the gain of a transistor, test NPN, PNP and power transistors, PLUS, by trial-and- error, you can identify BCE on an unmarked device. Kit includes PCB , box and all specnied components. I I I I I $18.95 I L - - - - - - - - - - .J Cat.KC-5047 $55.00 :m -~ _M~~~. _ HEAD OFFICE $22.95 BEEPO CONTINUITY TESTER Refer EA Feb 89 This all-singing, all-dancing continuity tester krt features three audio tones, operation over six decades of resistance, auto-polarity reversal, and an ambient current so low, it needs no ON/OFF switch . Krt includes PCB, box and all specnied components. Batteries extra (Cat. SB-2369 $4.35for2Alkaline) $19 95 ~c_a_t._K_A_-1_1_10_ _ _ _ _ _ _ • _ _ _ _ _ _ __ _ __ _ _ MAIL ORDERS 137 POST & PACKING 7 18 f i t rr_f:_i_i_i_~~_ti_~:_(~_(:_~a_;_:c_:._~c_:_: _:__ _ _ _ _~_l_R:_~_i_~-~-~_f_1i_1_::_0_~_:~_:a_a___li_t_s_rn_o_l_!i_9J_i_ i_tl_l_!o_ ~ VISA MAIL ORDER VIA YOUR "1"' _ - ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY-CITY 11 7YorkSt.(02) 2671 61 4 Mon- f ri 8 30 . 5.30 Thurs 8 30 pm - Sat 9 - 12 GORE HILL t 88 Pacil1c Hwy (Cnr . Bellevue Ave)(02) 439 4799 Mon-f n 9 · 5.30 Sat 9 - 4pm PARRAMATTA 355 Church St (Cnr Vic toria Rd) (02) 683 3377 Mon-fri 9 • 5.30 Tburs 8.30 pm • Sa t 9 - 2pm BURANDAQLD 144 Log an Rd (07) 393 0777 • Mon-fri 9 - 5.30 Thurs 8.30 . Sa t 9 . 12 CONCORD 115 Parrama tt a Rd (02) 745 3077 Mon-fr, 8.30 - 5.30 . Sat 8.30 - 12 MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030 \1 on -fri 9 • 5.30 fn 8 30 • Sat 9 . 12 HURSTVILLE 12t forest Rd (0 2) 570 7000 Mon-fn 9 • 5 30 Thurs 8.30 pm · Sa t 9 · 12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 547 t022 Nr Cnr. Dandenong Road Mon-fr, 9 - 5 30 f r, 8 30 Sat 9 • 2 MasterCard. ~ $ UNIT FREIGHT TRAINS earn big money for railway companies. This sulphur unit train in Canada is pulled by two 2.24MW (3000hp) EMD SD40-2 locomotives. The two locos have been coupled together back-to-back. THE EVOLUTION OF ELECTRIC RAILWAYS By BRYAN MAHER US roilrood companies face fierce competition from rood, air, sea and other ruilroud companies. To stay in business, they demand locomotives which combine high pulling power with low fuel and maintenance costs. Most Australians would not appreciate the magnitude of the American railroad systems. They collectively form by far the greatest rail system on the face of the Earth. As.early as the 1900-1910 period, the US railroads were using locomotives larger, heavier and more powerful than anything ever built in Australia or England right up to the present day. PT.16: THE SEARCH FOR COST-EFFICIENCY 74 SILICON CHIP Here we regard the one rail route between Sydney and Melbourne as the norm. Why would we want more? But in America, between any two large cities, you may find up to four separate rail systems owned by four different private companies, competing tooth-and-nail for the customer dollar. Today, in a world where most passenger trains run at a financial loss, the American freight rail business is alive and well, and profitable to boot. But such is private competition that only the most costefficient railroad companies can even stay afloat. To make profits (and every private company must or go under) means ruthless cutting of costs. Today's modern diesel electric locomotives haul more tonnes while using less diesel fuel per tonnekilometre than ever before. The travelling public Compared with the heady years around 1929-1930, the latest statistics show that while Americans now travel 2,823 billion person-kilometres per year compared with 350,500 million in 1929, the railroad passenger train share of the public carrier market has dropped from 77% to a poor 4%. When statistics include private automobiles we find that cars now carry 83 % of the total traffic, airlines 14% and passenger rail a mere 0.65%. Freight traffic Over the same period, total freight business in the United States has increased from 971,800 million tonne-kilometres to today's 3,989,728 million. In 1929 railroads carried 727,680 million tonnekilometres of freight loadings, which has increased to more than double today at 1,497,600 million. But of the total freight market, so much today goes by road trucks, oil pipelines, river and canal vessels (in that order) that freight rail has only managed to capture 37.5% of the business, well down from the glorious 74.9% they once had. Cost-effective trains Many once-great US railroads have now sadly disappeared in ·~ -/4;,., ._ _ ~":.,__,-.-.-~_,.._ l:f- ,"·- ~ GENERAL ELECTRIC MADE BIG strides in the American locomotive market during the 1960s with its U-258 diesel electric loco. These were commonly , referred to as "U-boats" and set the style for 20 years. bankruptcy or have been absorbed by larger neighbouring systems. The thousands of private railroad companies which once existed are now condensed into 608 surviving organisations. Almost entirely of standard gauge, the various railroads commonly rent locomotives and track rights from each other, while one freight wagon might circulate around the whole country over many companies' lines to reach its destination. The survival of the fittest railroad company demands that the loco-motives do the following: (1). Haul heavier loads than the competitor. (2). Use less fuel in so doing. (3). Arrive at the destination sooner. (4). Run longer without engine change. (5). Require less turnaround time for refueling and cleaning. (6). Rarely need workshop attention. (7). Be easier to strip and rebuild when major overhaul is needed. To accept larger and heavier locomotives and wagons, the track beds, bridges and the rail itself have been made stronger. In eastern Australia, the heaviest rail used is 53kg/m (107lb/yd) with some 29.8kg/m (60lb/yd) relics of 1906 vintage still surviving on branch lines. By contrast, American Class 1 railroads use mostly 67.5kg/m (136lb/yd) rail, with more than a thousand kilometres laid with 77.4kg/m (156lb/yd) metals. The heavier rail used in the US allows permissible axle loadings as high as 33 tonnes per axle, compared to eastern Australia's limit of 25 tonnes. Preferred loadings In every country, all railroads would like to have " unit train loadings"; ie, complete trains of the same type wagons carrying the same commodity. Prime examples are the long coal trains of NSW and Queensland, the wheat trains running from mid-western NSW to the seaports of Newcastle and Sydney, or the huge iron ore trains of Western Australia. FEBRUARY1989 75 Alco remained in the picture for years as a manufacturer of diesel electric locomotives and diesel engines for export overseas. In Australia, their diesel engines will be found in many locomotives manufactured in Newcastle or Sydney. The 1.5MW (2000hp) NSW SRA 80 class made by Comeng of Granville in 1978-80 is an example. But in contrast to the pre-war days when they built more locomotives than the competition, today Alco does not even appear in the loco inventories of some of the largest US railroads. Lima MAIN BEARING - CRANKS AT 180'/ THIS SKETCH SHOWS THE arrangement of cylinders used in the Fairbanks-Morse opposed piston diesel engine. These were originally used in marine applications but were successfully adapted to locomotive use. In the USA, some railroads, such as the Norfolk and Western, carry coal almost exclusively. Qf all American rail freight carried in 1984, 40% or 567 million tonnes was bulk coal. This has led to some startling developments in train length and the locomotives used. Enter the new breed From about 1950, with the demise of steam, all railroads could purchase diesel electric locomotives from amongst the three or four remaining manufacturers. The EMD plant at La Grange in suburban Chicago, Illinois looked like permanently capturing the market but they still had two or three competitors: Alco, FairbanksMorse and General Electric. Famous older manufacturers like Lima and Baldwin were fading away. Alco The American Locomotive Company, Alco, at Schenectady, had 76 SILICON CHIP production diesel electric locomotives for sale before 1942 and sold them in the US and other countries. Some of their diesel electric production was notable and included designs rated up 4.lMW (5500hp) as noted last month. In 1941, Alco produced their first real road switcher diesel locomotive, the model RSl. Also in 1940 they developed their 1.5MW (2000hp) model DL109 high speed passenger diesel electric loco which used an Alco diesel engine and General Electric DC generator, motors and control gear. These two-unit machines also hauled many a freight train, though their diesel engine was heavier than that of their competitors. More than seven railroads bought DL109s, including the New York, New Haven and Hartford Railroad. The latter railroad purchased twenty in the first two years. Hartford called them the 700 class and they were used between New York and New England. Then there was Lima, a locomotive construction company of Lima, Ohio, who in the 1942-1945 period still built steam engines exclusively while their competitors were producing more diesel electric than steam. Some of their notable steam designs included the Texas class 2-10-4s built in 1925 for the Texas and Pacific Railroad. These were quite large at 208 tonnes with 38.4 tonnes (84,600lbs) tractive effort. Lima also were responsible for some odd types, like the small 84 tonne 0-4-4-0 Shay locomotives built for the Dayton, Ohio power station in 1908. Regretably, Lima ceased steam loco construction in 1949 and by 1954 had given up locomotive construction completely. General Electric In the 1940s and 1950s the demise of many rich and famous locomotive manufacturing shops was a sign of the times to come. The General Electric Company, with their wide experience in electric locomotive production since the 1920s, had less trouble in turning to mainline diesel electric manufacture than did factories like Baldwin [a name synonomous with the latest, greatest and best in steam locomotive manufacture for 120 years). The General Electric Company [USA) had been building electric locomotives from 1920, even before EMD began. The most famous American electric locomotive of all, the · 3.5MW (4 700hp) Pennsylvania Railroad THIS THREE-UNIT LOCOMOTIVE was the Fairbanks-Morse answer to EMD. The railing along the top of the leading locomotive is for a radio antenna. Fairbanks-Morse could not compete with EMD and ceased locomotive manufacture in 1964. "' LOCOMOTIVE MANUFACTURE INVOLVES a lot of heavy engineering. This photo shows a brand new EMD SD40 locomotive being lowered onto its bogies. The big diesel engine can be clearly seen through the open doors. model GGl of 1934 (designed and built in Pensy's Altoona workshops), used a lot of General Electric motors , control gear and expertise. They had a 2-Co-Co-2 wheel arrangement with twelve 292kW (400hp) traction motors (two driving each axle). The traction motors were mounted in the body (a method GE have used to advantage in some modern electric locos). The GGl class (see SILICON CHIP Nov. 1987, page 6) lasted in highspeed express service for a record 50 years . Though Westinghouse provided electrical equipment for some of the later production, GE gained valuable early experience in this eminently successful design. Their early experience together with GE's worldwide financial power and diversity, and their continuous deep investment in heavy electrical equipment research, accounts for GE being the only major competitor against EMD in today's world of diesel electric locomotive manufacture. GE is not as committed to "off the shelf" locomotive selling as EMD, yet both realize the necessity of providing a range of models for all sizes of railroads. After all it had been GE who in 1924 produced the USA's first ever diesel electric locomotive, a little 224kW (300 horsepower) Bo-Bo yard switcher. That was actually a great year in diesel electric loco history. The world's first export of a diesel electric loco took place (Mallesta & Sodermanlands, exported from Sweden) and Brown Boveri with Fiat produced Italy's first diesel electric railway locomotive. At one time in association with Alco, GE brought out their first diesel electric passenger loco late in the 1930s. Breaking their FEBRUARY1989 77 tenance workshops found the opposed piston engine design was expensive to maintain. Fairbanks Morse ceased locomotive manufacture in 1964. Electro-Motive Division (EMD) THIS PHOTO SHOWS THE turbocharged 2-stroke V20 EMD-645 diesel engine, as used in the SD-45 locomotive. The engine delivers 2.7MW (3600hp) and stands about two metres high. It has now been superseded by the 16-cylinder 710 series which delivers even more power (2.97MW or 3980hp) but has lower maintenance costs. The main alternator is at the rear of the engine. association with Alco in 1953, GE then completely reorganised its diesel electric locomotive thinking and its manufacturing facility. By the early 1960s, GE was going all out as a locomotive producer. They then unveiled their model U25B diesel electric freight loco, a technologically advanced unit that set the style for the following 20 years. Fairbanks-Morse The dark horse manufacturer was a newcomer in 1944 to locomotive construction, Fairbanks Morse. This company had produced highly successful diesel engines of the "opposed pistons" type design. Their engines were well proven, having been used widely in US submarines and smaller ships during the war. The "opposed piston" engine has two pistons per cylinder but there is no cylinder head. Fuel combustion takes place in the space between the two pistons. On the power stroke both pistons move apart, travelling in opposite directions but both are linked by connecting rods to the one crankshaft. Very large versions of this engine 78 SILICON CHIP design also appeared in Australia in 25,000-tonne (and larger} freight ships, the cylinders being up to four metres long. Such ships were regular visitors to Newcastle (NSW} harbour during World War 2, carrying silver-lead ore residue from Port Pirie smelters. Other versions of the opposed piston design also appeared in stationary engines in some dieseldriven AC power stations in western NSW in the Condobolin area. Using a compact version of their engine coupled to a DC generator, Fairbanks Morse in 1944 brought out two 746kW (l000hp} switcher locomotives, which were sold to Milwaukee Railroad. Then in 1950, Fairbanks Morse released their triple unit high speed express diesel electric locomotive known as the "C Liners". This was purchased by the Pennsylvania Railroad and others. More conventional single unit diesel electrics followed. The last design produced by the Fairbanks Morse company was the 1.8MW (2400hp} Co-Co "Trainmaster" which sold to Jersey Central Railroad and others. Though powerful and reliable, the main- In 1941, General Motors Corporation established their ElectroMotive Division at La Grange, Chicago, Illinois. Electromotive soon became known to the world as EMD which today makes most of the diesel electric locomotives (89 % of American production one year}. Even when other manufacturers outside the USA produce locos, often the diesel engine is an EMD product. In the early 1980s, EMD achieved great success with its 2.24MW (3000hp} models SD40 and SD40-2 Co-Co diesel electric locomotives, which were widely adopted by the "Class 1" railroads. The SD40 uses the EMD V16 model 16-645E3 turbo-charged diesel engine which drives an alternator. Large silicon diodes rectify the AC generated to drive the six axle-hung series DC traction motors. Geared to the driving axles through a 16:61 ratio, the motors achieve a tractive effort of 37.6 tonnes (83,000lbs} at 18 km/hr. SD40s and SD40-2s are found all over the USA and Canada. The 16-cylinder engine was well received by the maintenance shops. Santa Fe by 1986 had purchased 204 of this model, while in the same period Conrail bought 275. EMD's SD45 diesel electrics Back in 1967 the record for the largest train stood at 47,000 tonnes. This train consisted of 500 coal wagons and was 8.8km long. For this huge haulage task, the Norfolk and Western Railway used six 2.69MW (3600hp} SD45 locos made by EMD. Six SD45s, each weighing 177 tonnes, together exert a total tractive effort of 226 tonnes (498,000 lbs}. To avoid breaking the headend drawgear and couplings, three locomotives were pulling at the head end and three more were positioned in mid-train and radio controlled. TWO EMO-BUILT GP38 DIESEL-ELECTRICS are shown here at the head of a train rounding Horseshoe Curve, Altoona, Pennsylvania. These locos are each rated at 1.49MW (2000hp) and use a Bo-Bo wheel arrangement. An SD45 loco uses a 20-cylinder tur ho-charged two-stroke type 20-645E3 diesel engine. Each cylinder has a capacity of 645 cubic inches (10.57 litres) so the total engine capacity is 211.4 litres. This mighty engine is direct coupled to an AR 1 0B4 type multi-pole alternator. The alternator and associated silicon rectifiers provide over 5000 amps to feed the six D77 series DC traction motors. Each motor is axlehung and drives its axle via a 15:62 ratio reduction gear, giving a maximum rated speed of 104km/h (65mph]. Maximum tractive effort of the SD45 is 3 7. 7 tonnes (83,000lbs]. Brake equipment includes engine air and handbrake, train air brakes, and "extended range tapered dynamic brake" (ie, blended with the train air brakes according to train speed]. Under dynamic braking, the traction motors (with their field coils supplied from the rectifiers] act as DC generators with the electrical power so generated dissipated in a low-resistance high-power braking resistor, which is forced-air cooled. Locomotive diagnostics Modern US railroads face a continuous shortage of the highly skilled tradesmen needed to maintain the sophisticated mechanical and electrical plant carried by their locomotives. The real cost of a locomotive breakdown - including the cost of upsetting the timetable, the inevitable delays and possibly track blockage - is so critical that microprocessor-controlled event recorders and system diagnostic analysers have been installed in many locos. The class SD45-2 locomotives may contain a digital 2-channel pulse electronic recording system as an optional extra. Any locomotives so equipped can halt at a testing stand and plug into a computer. In a few moments this can read all the data from the onboard microprocessor's memory, analyse, summarise and print out a prognosis of future mechanical and electrical reliability. It can also issue warnings of potential or imminent breakdown. These high speed test procedures can be performed by semi-skilled employees, leaving the fully skilled tradesmen for essential duties in the maintenance shops. With computer testing growing in importance, more and more locomotive functions are now being continually tested and recorded. Engine functions recorded include rpm, fuel usage, compression ratios, bearing temperatures and supercharger air compression. Also monitored are electrical measurements of alternator voltage, current, power and excitation; traction motor voltage, current, power, speed and temperature; train speed; and whether the train is under traction or braking. From these, the computer can completely analyse the locomotive's condition and the driver's skill. From figures of individual traction motor voltage, current and speed can be deduced history of wheel slip, wheel skid, weight transfer between axles in a motor bogie, traction power transfer and braking effort transfer. These axle-to-axle weight and power transfer figures can in turn be used to evaluate the success or failure of motor bogie design and to FEBRUARY1989 79 engine capacity is therefore 186 litres. Power output of the new EMD engine is 2.97 megawatts (3980hp) which is substantially more than the 2.69MW [3600hp) produced by the 20-cylinder engine in the SD45. Interestingly, the SD60 is also slightly lighter than the SD45. Note that the very important factors "power per locomotive tonne" and " train tonne-kilometres run per dollar spent" [on fuel and maintenance) are the crux of today's locomotive selling. By the way, all these EMD SD series locomotives are of the Co-Co 6-axle wheel arrangement. General Electric locos THIS DIAGRAM SHOWS A CROSS-SECTION of the General Motors EMD 645 series engine which came in VB, V12, V16 and V20 versions. The angle between the cylinder banks is 45°. indicate unevenness in the track. By no means are all locomotives so fully equipped in self-analysis gear but the trend is growing. Up to eight digital channels of multiplexed data are presently used in the latest locomotives. SD45 sales Even with all their achievements, the EMD model SD45 and SD45-2 diesel electric locomotives have not sold well. The problem has been the higher maintenance cost of a 20-cylinder engine compared to that required by a 16-cylinder engine of about equal power. Realising this, EMD subsequently 80 SILICON CHIP produced the 2.61MW (3500hp) V16 SD50 locomotive in 1980. The smaller number of cylinders and improved economy has resulted in good sales for this model. The SD60 Several years later, in 1984, EMD upped the ante with the bigger engined SD60. This loco is 21.6 metres long and weighs 177 tonnes. The SD60 still uses a turbocharged 16-cylinder engine but it has bigger bores and is designated the 16-710G3. Again, the 710 denotes the cylinder capacity in cubic inches so each cylinder has a displacement of 11.63 litres. Total GE has replied admirably to EMD's challenge by producing a high-power range of diesel electric locomotives: the model C30 of 2.24MW (3000hp), the model C32 of 2.39MW (3200hp), and the model C36 of 2.76MW (3700hp). Of these, the model C32-8 is geared for the highest tractive effort - 49 tonnes (108,000lbs). All three models and variations thereon use the Co-Co wheel arrangement and either a 12-cylinder or 16-cylinder diesel engine. Comparison of the loco manufacturers' market acceptance may be judged by a typical railroad's locomotive inventory. On the Conrail Railroad's list we see 852 road freight diesel electrics from the EMD stable, and 403 similar units from GE. No other manufacturer appears on the list. This indicates today's American locomotive scene, with just two manufacturers remaining in the American marketplace and all the rest virtually gone. No longer do American railroads use a dozen small diesel electric locos on a 3000 or 4000 tonne train, nor are they inclined to use the enormous double-engine units described last month. Rather you would see from one to six of the most modern high-efficiency diesel electric units described above hauling any US freight train, grossing from 5000 to 50,000 tonnes. Next month we will look into the present state of passenger traffic in the USA. ~ A AMATEUR LINE-UP m z VHF UHF Kenwood's amateur ·lineup for 1988 incorporates the latest developments in communications technology. Superior front end specifications are accompanied by the latest developments in transmitter design. Automatic antenna tuning and advanced digital & microprocessor technology make these the easiest to operate Kenwoods ever. Personal computer control is available on several models. HF TH-215A TH-415A FM Handheld ll'anscelvers. Transmitters : Frequency Range: 144148MHz (TH-215) 430440MHz (TH-415). Output: 5W/0.5W (Hi/ low). Receiver: 141 163MHz (TH-215) 430440MHz. Scan modes include band , memory and programmable band scans with 3 scan stop modes. Power requirements: 7.2-16V/ 2.0Ama•. TR-751A TR-851A All-mode ll'anscelvers. Frequency Range: TR-751 A: 144 148MHz TR-851A: 430-440MHz Tran smitter: SSB/CW/FM modes. Output: 25W Receiver sensitivity: less than 0.11uV (TR-851A) Features include: Auto-mode selection. dual digital VFOs. 1O memories plus "COM" channel. Optional Digital Channel Link System. Power req.: 13.BV ±15% 7.5A max HF ER MISC. STATION MONITOR SM-220 Based on a wide. frequency range oscilloscope, it combines a two tone generator , a wide variety of waveform observing capabilities. HF LINEAR AMPLIFIER TH-25A TH-45A FM Handheld ll'ansceivers. Frequency range: TH-25: 144148MHz TH-45: 430440MHz. Output: 5W. TS-940S Rec eiver sensitivity: less than 0.16uV (TR-25). 14 multi-function memories, memory scan and band scan. Powe r req .: 6.0-16VDC/ 1.2A max Competition Quality HF ll'anscelver. Transmitter: SSB, CW, AM, FM and FSK. 160- 10 metres bands. Output 250W PEP. Automatic antenna tuner. Receiver: 150kHz30MHz continuous. 40 memories, programmable and band sc an s. Power requirement: 240VAC, 50/ 60Hz TM-721A Dual band FM Transceiver with across band duplex. New for 1988, with dual watch, selectable full duplex cross band operation, automatic band change, 30 memory channels. Tran smitter: Frequency Range: 144- 148MHz/430440MHz. Output 45W (VHF) 35W (UHF) Receiver sensitivity: 0. 16uV (UHF). RECEIVERS Compact HF ll'anscelver. Transmitter: SSB/CW/FM/AFSK. 160-10 metre bands. Outpu t 200W PEP. Optional automatic antenna tuner. Receiver: 100kHz-30MHz continuous. Power requ irement: 1216VDC/20A max. 1.8-S0MHz :.- -w,+~·c,~~-- !ffe · ' !!!, ,. ~ - - ...~ '"""""' ~ ~,.,_,_,.,..,.. ~ '- ~ A class AB 2 grounded-grid linear amplilier. Covers 160-1 Orn for SSB. CW and RTTY modes. Drive Power: BOW for full output. RF Input Powe r: 2,000W PEP fSSB). ANTENNA TUNER TS-711A TS-811A TS-440S .::_ TL922 , ' ,. TS-680S High performance HF & 6 metre Transceiver. Transmitter: SSB/CW, AM and FM mod es. 160-6 metre bands. Output 1DOW PEP ( 16010m) 10W (6m). Receiver: 500kH z30MHz continuous. fv\emory scan/ band scan. Power req .: 12-16VDCi 20A max . All-mode ll'anscelvers. Transmitters: modes SSB/CW/FM. Freq uency range: TS-711: 144-148MHz TS-811 : 430-440MHz. Output: 25W. Receiver sensitivity: less than 0.2uV (TS-811). Features include: 40 multi-function memories, programmable band scan and memory scan plus programmable memory channel lockout. Power req .: 240VAC. 13.BV DC/8.0A max. TM-221 TM-421 FM Mobile Transceivers. Transmitters: Frequency . range 144. 148MHz (TR221) 430-440MHz (TR421). Output: 45W (TM -221) 35W (TM-42 1). Low power switch to 5W. Receiver: Frequency Range 130173.995MHz (TR-221) 438449.995MHz (TR421). Sensi tivity: less than 0. 16uV. Power requirements: 13.BVDC ± 15%/9.5A max. KENWOOD ELECTRONICS AUSTRALIA PTY. LTD. 4E WOODCOCK PLACE, LANE COVE, SYDNEY, N.S.W., 2066. Ph. (02) 4281455. YOUR AUTHORISED KENWOOD DEALER, BELOW, WILL GUARANTEE SATISFACTION: Fu rther, beware of dealers not listed in th is advertisement who are selJing Kenwood communications equipment . 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NSW: Sydney, Emtronics (02) 211 0988 ; Parramatta, Captain Communications (02 ) 633 4333 ; lnverell, Reg Stockman Communications (067) 22 1303; Cessnock, Robe rtson Electron ics (049) 90 7908; Wollongong, Macelec Pty. Ltd. (042) 29 1455; Port Macquarie, DX Eng ineering (065) 84 9922: Lismore, Frank Boundy (066) 86 2145; ACT : O'Connor. Alex Johnson (062) 47 91 25; VIC: Moorabbin . Measure-Tech Su ppl ies Pty. Ltd. (03)553 4566 ; Melbourne, Emtronics (03) 670 0330; Ballarat, Brian Stares (053) 39 2808 Bendigo, Sumner Electronics (054) 43 1977 TAS: Hobart, Watsons Wireless (002) 34 4303; Launceston, Marine & Communication (003) 31 2711, Burnie, VK. Electron ics (004 ) 31 7733 OLD: Albion, Mitchell Radio Co. (07) 357 6830; Brisbane, Emtronics (07) 394 2555 SA & NT: Port Adelaide, International Communic ations Systems Pty Ltd (08) 47 3688 WA : Victoria Park, Willis Electronics (09) 4 70 1118; Ferndale, Bay Radio (09) 451 3561; Osborne Park, Ford Electron ics (09) 242 1766 11December 197New England the U.S. of A. Merry Christmas, Dickie and a happy New Year. Come to think of it, it'll probably be your Labour Day by the time this letter arrives. You're probably surprised that I've come to America. So am I! Before I finished the Middle East contract, one of the few good blokes there said he could ensure that I got a green card and a job in the US. We came o tay at his family home in the midwest for a few weeks while the paperwork was sorted out. I worked for a short time at a 500-watt country-and-western radio station on the sly. My first day there, fixing all manner of gear, was enlivened by an irate ex-DJ. The owner-manager had sacked him but neglected to provide termination pay. This bloke turned up in the foyer, screaming his head off. Old Irving heard him, called the police, and did not come out of his office until they arrived to remove the bloke. They were really apologetic but said the law was on Irving's side. Rubber cheque I found out myself how close Irving was with a dollar, o my first pay clieque bounced! The bank account was made good two days later but by then I had decided to drop him in it. I told the morning DJ that I would not be in the next day to run up the transmitter. DJ grinned and said that he was capable of doing it himself - but that he would not be able to get into the building, would he? Late that night, I returned to the station and slid my letter of resigna- By RICHARD KOPF ers 82 SILICON CHIP tion under the front door. Ha, ha! The DJ phoned me the next morning said he waited until about 6:30am before finding a phone box to call Irving. Although the owner was not radiotelephone licensed, he came in and got the station on air, anyway. In the eight days I worked there, I had a look at the station logs. Some 25 engineers' signatures appeared in just over four years' entries. Furthermore, the station was not even legal. The station licence renewal Had been posted three months late but the copy was not on the wall. The licence that was there had well and truly expired. Hidden amplifier I'd noticed some splatter in offair monitoring but all my meter readings said everything was normal. Then I was told that Irving had a 10dB line amplifier hidden under the floor between the final output on the patch panel and the input to the rig. Ancient modulation! Apparently, Irving thought more push would give him wider coverage! I heard later that the irate DJ sent a file to the FCC but nothing ever came of it. Whoever said a broadcast licence was a licence to steal had the truth of the matter. If my first experience in broadcasting in the US was weird it was but a mild introduction to the real job awaiting me here. Bob, the bloke who got me into this, was of- fered a job by a friend. We came up to find the real situation; a TV station being run by management, as the union staff had walked out! I accepted the job contingent on being assigned to a videotape position. Two days after I arrived, they ordered me to the transmitter. I objected. "It's only while we're short handed," they explained. Like a fool, I agreed to go. Six weeks later, I was still there. By now, I had found out the true state of affairs at W ... never mind! At least, I know now that no-one can point the bone at Australia about union problems. The labour relations situation here looked like World War III compared to the industrial actions I've seen in Oz in the past. First of all, the local bargaining unit had decided to include the onair personnel, along with engineering and technical production staff. Not the usual sort of situation, you will agree. The station management naturally refused. Wildcat strike The union called a wildcat strike; the company responded with a lockout. Neither side obviously took the contract seriously - it precluded both of these actions. A 24-hour picket line went up. Unfortunately, the local unemployment office was on the ground floor of the building where the studios were located. A small riot started between the blokes coming to pick up their weekly cheques and the strikers. The cops were called. The local union reps claimed the company would go down the tubes if they tried to run it themselves. It took no time at all to prove this to the management and the viewing audience. So they started hiring new staff. Everyone they picked = o"o . (Jo· • •• It> NO'rlC.E.t> SON\~ S-A.A1Te-'R \tJ OFF-~rR N\ONrrORttJ6o•• was either between jobs or from non-union stations in the deep south. Bob and I were initially told that there had been industrial unrest but we were little-prepared for going on-shift in commando-style raids. More than once, we had a couple of blokes cause a diversion while we thundered the wrong way up a one-way street in a Pontiac VB. A squeal of brakes and the passenger scurried across the footpath toward the side entry, key in hand. Once he was safe, the driver made a quick getaway. Walking into master control the first time did not give us confidence. Various modules on extender boards protruded from the racks. Access panels stood against the walls, having been removed from major pieces of equipment apparently some time ago, as the cobwebs testified. Half the time, videotape was on a to-second roll and, more often than not, the picture was not locked when it went to air. Audio levels were all over the ·place. Continuity wasn't! Sometimes, the booth announcer was reading one piece of copy and an unrelated visual accompanied it. A voice-over promo for the 6 o'clock news with a "Living Bra" slide is something to consider, believe me! And, Dick, I hate to say it, but you would probably guess that this sort of station is what gave NTSC the label of "Never Twice the Same Colour" . When I finally did get into studio work - after threatening to quit I pulled a subcarrier reference cable into the VTR area and solved the phase problem once and for all. The studio supervisor was amazed that it made things easy . He was a curious fellow. I should mention that he'd been one of the few staff engineers that refused to go out on strike. His reward was a $15 a week pay rise and a title! He tried to teach me how to set up the headwheel servo, saying that "the supplier has screwed up again" and sent a refurbished HW panel out of spec. After a mechanical FEBRUARY1989 83 THE TECHNOLOGY LETTERS - CTD maladjustment, which I tried to tell him was wrong, he slipped it into the machine, powered up and straight away cut the alignment tape in two. "If you're so darn smart," he said when I snickered, "you do it." So, while he was splicing the alignment tape, I did just that. As you know, old son, one has to balance the mechanical adjustments and match the servo "centre" to it, for both manual and automatic control. I tried to explain this gently to him but he wanted no advice from a subordinate. A necktie party The next laugh was over the necktie incident. Management had decided all studio staff should dress "appropriately" so as not to offend the sensibilities of clients having commercials cut there. Everyone objected to the idea but management, in the guise of one studio supervisor, was adamant. Two days after the rule, SS was lounging by that VTR mentioned earlier. Someone had not closed the headwheel cover and the machine was on remote, with the next syndicated program up. A bloke said something, SS turned to answer him, and the tip of his necktie fell into the machine, just as the tape rolled. I never knew a headwheel motor had so much torque. It managed to pull half the tie through the vacuum guide before the machine died. Scratch one new headwheel panel, one syndicated tape, one necktie and one rule. A few days after that, SS was standing by the same machine. The tape rolled. His shirt somehow got caught up between the capstan and the pressure roller. Scratch one commercial tape. You've worked commercial TV in the US, Dick, but all the regional stations can't be this bad, surely? They decided we needed a rotating roster, so someone came up with a three week schedule. There were eight sign-on shifts in a row, starting on Sunday, then three days off, then seven late shifts and three more days off. Then, the cycle began again. Of course, it was not unusual to sign off at about 2am, so the three days off before the Sunday morning start at 6am seemed pretty short. We did get penalty rates, or what passes for it in the US. Anyone that tried such a stunt in Australia would go broke pretty quick. Percussive maintenance Although I did not like being stuck out at the transmitter when I first started, it was a straight night shift. My first shift, though, was nearly my last. The senior bloke was sitting there, sipping his coffee, when he jumped up and grabbed a four-by-two. I leapt out of reach but he was not after me. It seems the rig had an intermittent which he was able to cure with a large, technical tap. He bashed the frame of the modulator and lo! - the audio power came back up. Usually. Well, this timber modulatormodulator got plenty of use until a field engineer turned up to put things right. He was still there three days later. As he started to do his preliminary checks the first night, I warned him of one thing I had discovered: the precision CRO wasn't. The regular bloke had not gotten the signal he expected one time, so he adjusted the calibrator and vertical amps to the "standard" studio signal! I take my hat off to this field engineer - he solved the mysterious power loss problem. After exhausting every electronic test known to man, he went back to the fundamentals. The problem was the silvered "finger" seal of the RF cabinet. Apparently, it had oxidised so much that its conductivity was changing and detuning the cavity. One good poke with the four-by-two overcame the poor contact, for a time. I would not recommend this as a long-term answer, though. There was one bit of fun at the transmitter one night. Seems the union goons drove by and saw a strange car parked near the driveway. They decided it was a "scab" and intended to trash the car. As they got out and walked up, the car took off. They gave chase and forced it off the road. The I ~~VE-1< K~e:w P. '. 84 SILICON CHIP HEAt>WH~~L- N\0-C-OR \-\~"D so N\OC.H -rOR.QO& •oo driver turned out to be a regional union rep. Studio work Once I got into studio VTR work, I wondered why I had wanted it. There were four machines. A syndicated tape show ending with four tape commercials, followed by another tape program (with a 27-second opening), again followed by four tape commercials, really makes one adept at instant set-up and reel changes - especially if one has to record the closed circuit network bearer at the same time. Generally, there was never enough time to dub a commercial reel so separates were the order of the day. The trick was to cue things in advance, lift the tape out of the guides, and remove both feed and takeup reels as a stack. A quick turnaround like this usually went to air clean but it took several minutes to sort out the aftermath. Tail-out spots had to be rewound, empty reels picked up from where they'd been flung, etc. At certain periods, the VTR man was also responsible for telecine, too! In your spare time, you had to edit a feature VTR reel for the news department. Three live local newscasts a day, with different material in each, was normal. Nothing had prepared me for the chaos of the baseball season, though. That was the only time we made up a commercial reel, machines permitting. It was a oneman operation, with no production aids or computerised consoles just the electronic edit module option and a talent for cueing and for hitting the button to allow for the six-tenths of a second lag. Summer relief Another thing I was not prepared for was the American way of senior engineers taking holidays, seemingly all at the same time - in the summer. The answer to this, of course, is the "summer relief" engineer. We got one fellow , a schoolteacher in real life, who apparently- worked cheap. He had worked for other stations during previous summers. Our second fill-in was an offer management could not refuse: a warm body at no cost! Seems the US Navy had a plan to convince its sailors to "re-up" (re-enlist) by showing them the perils of civilian life. They placed blokes near the end of their enlistment in an allied continued on page 91 FEBR UA RY1989 85 I PRODUCT SHOWCASE I Digital frequency monitor for receivers and transceivers Captain Communications has released a digital frequency monitor for most older receivers and transceivers operating in the HF and VHF bands. Called the FC-200, the monitor gives a 5-digit readout which will make tuning much easier and more precise. Unlike conventional frequency meters, the FC-200 can read both the frequency of the transmitted signal as well as the received signal. This is managed by a down conversion system based on the receiver's local oscillator and by subtracting 455kHz. It is simply connected between the antenna input and the transceiver by PL259 connectors. The frequency range is covered in two switchable ranges, from lkHz to 54MHz and from 50MHz to 250MHz. The input impedance is lM!l shunted by 20pF. Rated temperature range is from 0° to 40°. For further information contact Captain Communications at 28 Parkes Street, Parramatta, NSW 2150. Phone (02) 633 4333. Lightning protection for phone equipment' This month's article on lightning highlights the vulnerability of telephone equipment. One solution is to unplug such equipment during lightning storms but this has the obvious disadvantage of preventing the equipment from working and then you must remember to connect again. To help cope with this problem, ABE Computers has a device that protects against high voltage spikes on the telephone line. Called the "Telephone Safety Device" or TSD, it incorporates a gas arrestor which shorts any excessive spike voltages to an attached ground wire. Testing has been carried out at the high voltage laboratory at Monash University and the results of these tests are available upon request. The TSD is priced at $39.50 and comes with a 2-year guarantee. Further information can be obtained from ABE Computers, 24 Burwood Highway, Burwood, Vic. 3125. Phone 288 2144. Stereo mixing console from Altronics Uninterruptible power supply Power interruptions can cause enormous problems for personal computers. Now Amtex has produced an uninterruptible power supply which takes the place of the standard switchmode power supply fitted to IBM PC AT,'PS/2 and 386 compatible computers. Called the UPSA 4280-2, it will maintain power for 5 to 8 minutes, depending on the load requirements. When power does fail, the unit maintains the computer but sounds an alarm to warn the user to save data and close down. An optional hardware and software package allows for automatic shutdown. This would be v~ry handy if the power failed while the user was not present. Of Mosfet design, the UPSA 4280"2 delivers up to 230 watts of DC for the system mqther86 SILICON CHIP !Vi'*~ .] ·--~ 1!.,.,.,.,, .. board and peripherals and has an 80 watt 50/60Hz output to power a monochrome or colour monitor. The circuit design includes surge voltage, overvoltage and over-current protection, and an EMI filter. Its builtin maintenance-free battery automatically recharges fully within 8 hours. For further information, contact Amtex Electronics, 13 Avon Road, North Ryde, NSW 2113. Phone (02) 805 0844. Many cassette decks these days lack even the most basic mixing facilities and those that do have mixing often leave much to be desired. The solution is not to look for another cassette deck but to consider a separate stereo mixer. The A-2570 stereo mixer console from Altronics could be the ideal solution. It can be rack mounted, used on a desktop or built into a large console. It offers mixing facilities for two microphones, two phono inputs and two line inputs which could be a tape player or CD player. A five band graphic equaliser is included and there is provision for external echo and repeat facilities. Normally priced at $499, the Low-cost pushbutton circuit breaker Digital clamp meters measure voltage and resistance These new digital clamp meters from Sanwa feature a 3-digit liquid crystal display and AC current and voltage measurements can be made over the frequency range from 40Hz to lkHz. The low ohms range is convenient for measuring continuity of wiring and transformers or for checking diodes. The deluxe model DCM-20AD measures both DC and AC current while the DCM-20A measures AC only. The deluxe model has a data hold function and an analog output which may be connected to an oscilloscope or recorder. Both clamp meters sample at a rate of three times/second and can withstand a voltage of 2500VAC for one minute between circuit and outer case or circuit and core. For further information contact Anitech, 1-5 Carter Street, Lidcombe, NSW 2141. Phone (02) 648 1711. A-2570 is presently available at $449 from Altronics, 17 4 Roe Street, Perth, WA 6000. Phone (09) 328 2199 or toll free (008) 999 007. Low cost 20MHz AT motherboards Electronic Solutions has recently released a new range of fast AT motherboards using the latest Chips & Technology NEAT chipset. The boards come in a range of speeds from 12MHz with zero waitstate up to 20MHz. All but the 12MHz board come standard with 1 megabyte of RAM, expandable to 4 megabytes [on the motherboard). The boards are switchable to lower speeds, making it possible to use existing slower peripherals and memory. Depending upon the system's slowest peripheral and the maximum speed of a particular model, the board can run at either 8, 10, 12, 16 or 20MHz. This low cost circuit breaker comes in 5, 10, 15 and 20 amp versions and is rated for up to 50V DC and 250VAC. It is a quality item and is listed by the Underwriters Laboratories USA. All versions are identical in appearance and have spade lugs for connection into circuit. They are priced at $4.50 from Altronics of Perth. You can order them on their toll-free line (008) 999 007. Like all Electronic Solutions products, these motherboards carry a 3-month warranty and a 14-day money back guarantee. For further information and pricing contact Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 427 4422. High per£ormance cermet trimmers The VRN 780 series is a range of square cermet single turn potentiometers featuring sealed O-ring construction and miniature PC mounting case. The unit is only 9.5mm square and is available in resistance values ranging from 100 to 2MO. Power rating is 0.5 watts at 85° Celsius. The VN-780 devices are available in three different low profile packages in both horizontal and vertical mounts. Further information can be obtained from IRH components, 32 Parramatta Road, Lidcombe, NSW 2141; or 80 Mokoia Road, Birkenhead, New Zealand. FEBRUARY1989 87 New disk controller gives format compatiblity Electronic Solutions now has a floppy disk controller that can work with any mix of up to four 5.25-inch or 3.5-inch floppy drives including 360K 5.25-inch, 1.2M 5.25-inch, 720K 3.5-inch and 1.44M 3.5-inch disc formats. The controller allows for two internal and two external floppies or just four internal floppies. It works with all PC XTs, ATs and 386 PCs. All signal and power cabling is provided, including two daisy chain cables and power cables, both ready to plug into 5.25-inch and 3.5-inch drives. If you need to mount a 3.5-inch drive in place of a 5.25-inch drive, Electronic Solutions can supply a suitable tray and power cable. For external mounting, they have a range of cases and cables. Further information on this disk controller can be obtained from Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02} 427 4422. ously - distress channel 16 and any two other channels. The IC-Ml 1 also features multiple scan modes: Dial Scan for all channel monitoring, Memory Scan to monitor only the 24 user memories, plus Dual Watch and Tri Watch. Top mounted controls and a large, clear LCD digital readout make the IC-Ml 1 ideal for beltmounted portable operation (see picture}. The lcom IC-Ml 1 VHF marine handheld is approved by the Department of Transport and Communications and is available now at your nearest authorised lcom dealer. For more information, or the name of your local authorised learn dealer, contact lcom Australia, 7 Duke Street, Windsor, Vic. 3181. Or phone toll-free on (008) 33 8915. Short form catalog jrh , ' . . Tr:x,\~ INSTRUMENTS : BIIB . ([l) _,,,._ ,3fJI Amphenol ,t} "-' t..<."!-1m-'.t,1.,.~ <at>Bishop Bunmann SPECTRf\:.SfWP 'J~ !3ATO ~ ··· ~~v. One for the rough times When the going at sea gets rough, !corn's handheld VHF marine transceiver will be ready for any emergency situation. Icom's latest release, the IC-Mll, has one button access to the channel 16 emergency frequency. This unit has been designed to withstand the most severe conditions, featuring splash resistant and dustproof rubber seals on all casings and switches, and a strong front and rear metal frame enclosing the electronics. The compact IC-Ml 1 is preprogrammed with all possible VHF marine channels for immediate use in any port world-wide. The 24 user memories can store your preferred operating frequencies at the touch of a button, or clear and rewrite 88 SILICON CHIP The IC-M11: one button access to the channel 16 emergency frequency and 24 user memories. memories in an instant. With 5 watts of output power and a sensitive receiver, the IC-Mll is capable of "long distance" contacts. Icom's Dual Watch and new Tri Watch functions let you monitor two or three channels simultane- People interested in being able to buy quality electronic components can now obtain a short form catalog with a wide range of components from an Adelaide supplier, Electronic Components and Equipment Pty Ltd. Among some of the major brand names listed are Amphenol connectors and cables, Bishop Graphics drafting materials, Eddystone aluminium diecast boxes, IRH resistors and potentiometers, Rifa capacitors and DC/DC converters, Royel soldering equipment and Texas Instruments semiconductors. You can obtain one of these catalogs by contacting Electronic Components and Equipment Pty Ltd, 30-40 Hurtle Square, Adelaide, SA 5000. Phone (08) 232 0001. - - --~ (~ -=---- ~-__ _:,~ . =~., f<i :- : _ --'' SPECIALS! Quality, Safely and Pelformance! FEATURES: • Super quick heat up coupled with faster thermal recovery permits high quality soldering at lower tip temperature • Built in ceramic heater sensor maintains temperatures within 0·5°C of the setting • Soldering iron grip is heat insulated for operator comfort • The soldering iron is low voltage 24V, and is completely isolated from the A.C.1ine by an insulated transformer . • A full wave zero crossing switch system is utilized to turn heater element ON and OFF • The soldering tip is connected to earth ground SPECIFICATIONS PowerConsumptionAC100, 110, 120, 240V-60W. Output 24V -=========- KITS -====QUALITY 3mm LEDS 48 ~es'::C::1~~ur~.;~1~~~~~e g~~ohm (480°C) Leak Voltage under 0·6mV (between tip and ground) Weight 1·5Kg without cord and iron stand ... ......... .. ......... .. .. $195 PORTABLE 16 DRAWER CABINET • Overall size: 270(L) x 160(W) x 165(H)mm • Drawer size: 142(L) x 56(W) x 31 (H)mm • Metal case, clear plastic drawers • Carry strap • Stackable or wall mountable ...... $19.95 H10085 . Cat. Q 11272 ...... $34.50 115V 45,a " Cat. T12463 Cat. T12465 Cat. T12467 $12.95 $12.95 $12.95 $12.95 10+ fans (mixed) only $11.95each FAN GUARDS TO SUIT Cat. T12471 $3.95 Cat. T12475 $3.95 45/a" 3½" ·;\\\ni\\l · .. METEX M-3650 MULTIMETER 20A, 3'f.> digit frequency counter multimeter with capacitance meter and transistor tester. This spectacular, rugged and compact DMM has a bright yellow high impact plastic case. It features a frequency counter (to 200kHz), diode and transistor test, continuity (with buzzer), capacitance meter, up to 20 amp current measurement and comprehensive AC/DC voltage, current and resistance ranges . CHECK THESE FEATURES .... • Push-button ON/OFF switch. • Audible continuity test • Single function, 30 position easy to use rotary switch for FUNCTION and RANGE selection. • Transistor test • Diode test • Quality probes • 1k" High contrast LCD. • Full overload protection e20Amp • Built in tilting bail • Capacitance meter • Instruction manual 091550 . Normally $165 Special, only $129 NICADS! Save a fortune on expensive throw away batteries with these quality Nicads and Rechargers! Size Desc. 1·9 10+ 100+ AA 450 mA.H. $2.95 $2.75 $2.50 C 1.2 A.H. $9.95 $9.50 $8.95 D 1.2 A.H. $9.95 $9.50 $8.95 'J . QUALITY 5mm LEDS Cat. No. Col. 100+ $0.06 $0.10 $0.10 1-9 10+ Z10150 Red $0.08 $0.07 Z10151 Grn $0.15 $0.12 Z10152 Ora $0.15 $0.12 . IEC PLUG 3 pin, female line plug. 250V, 6A P10251 ..... ........... $2.95 RAM CHIPS! Description 1-9 4164-12 . $6.95 41256-12 .. ...... $24.95 AEM DUAL SPEED MODEM KIT Th e ultimate kit modem featuring 1200/300 baud, case and prepunched front panel. (AEM 4600 Dec '85) Cat.K34600 .......... $169 10plus $6.50 $23.95 121240V 40W INVERTER GENUINE INTEL CHIPS! 8087-3 (4.77MHz) .... $245 8087•2 (8MHz) ..... $350 8087·1 (10MHz) $475 80287-6 (6MHz) ................ $375 80287-8 (8MHz) ................ $555 80287-10 (10MHz) ....... $690 80387-16 (16MHz) .... ........ $995 80387-20 (20MHz) $1460 80387-25 (25MHz) ....... $1860 This 12 240V inverter can be used to power up mains appliances rated up to 40W, or to vary the speed of a turntable. As a bonus, it will also work backwards as a trickle charger to top up the battery when the power is on. (EA May'82) 821V5 di "NO BRAND" DISKS Now you can buy absolute top quality disks that are probably the cheapest in Australia! They even come with a lifetime warranty! So why pay 2-3 times the price for the same quality? Packs of 10, 2S/2D without boxes, or brand name, just their white paper jacket, and index labels. (5¼" disks includes write protects). tOO+DISKS Most microcomputers worth owning have an 'RS232' connector, or port, through which serial communications (inpuVoutput) is cond ucted. It is a convention that, for listing on a printer, the BASIC LUST or LPRINT command assumes a printer is connected to the RS232 port. Problem is, serial interface printers are more expensive than parallel 'Centronics' interface printers . Save money by building this interface. (ETI Jan.'84) ETI 675 Cat.K46750 ..... ... $39.50 1.000+DISKS 5¼" HIGH DENSITY $21 Add excitement to parties, card nights and discos with EAs Musicolor IV light show. This is the latest in the famous line of musieolors and it offers features such as four channel "color organ " plus four channel light chaser, front panel LED display, internal microphone, single sensitivity control plus opto-coupled switching for increased safety. (EAAug.'81)81MC8 (PRICE PER 10 DISKS) Cat.K81080 ........... $115 $21 ea IOO+DISKS 1,000+OISKS $20°" $19ea (ALL PRICES PER 10 DISKS) 3½" 2S/2D DISKS Suitable for IBM, PS/2, Macintosh, Atari, etc. 10+ 100+ 9P 9S 9C 15P 15S 15C 25P 25S 25C $0.60 $0.60 $0.50 $0.65 $0.65 $0.60 $0.60 $0.65 $0.60 $0.50 $0 .50 $0.40 $0.60 $0.60 $0 .50 $0.50 $0.60 $0.50 $0.70 $0.70 $0.60 $0. 70 $0.70 $0.70 $0.70 $0.75 $0.70 DB25CRIMP SPECIALS! Type 1-9 10+ 100+ Female$2.95 $2.50 $1 .95 Male.... $2.95 $2.50 $1.95 ...... :r··:1~:e ··_--. ··. . " . . . . . RODIRVING ELEaRONICS All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE, 56 Renver Road, Clayton. Phone: (03) 543 2166 (3 lines) Fax: (03) 543 2648 SYDNEY: 74 Parramatta Rd. Stanmore. 2048. Phone (02) 519 3134 Fax (02) 519 3868 MELBOURNE: 48 A'Beckett St. Phone (03) 663 6151 NORTHCOTE: 425 High St. Phone (03) 489 8866 CLAYTON: 56 Renver Rd. Phone (03) 543 7877 MAIL ORDER & CORRESPONDENCE: P.O. Box 620, CLAYTON 3168 Order Hotline : 008 33 5757 (Toll free, strictly orders only) Inquiries: (03) 543 7877 Telex: AA 151938 Fax: (03) 543 2648 MICROBEE SERIAL-TO-PARALLEL INTERFACE MUSICOLOR IV I0+DISKS $5.50 l.~I (ALL PRICES PER 10 DISKS) (DOUBLE SIDED) Low dual cone, wide range . 200mm (Bin.). Ideal for public address, background music, etc. Tremendous Value at these prices! .. Cat.C12000 1~ 10+ Cat.K82050 ....... . $69.95 5¼" 2S/2D DISKS $6·9508 $6·75°8 $6·5008 P.A. SPEAKERS • 8087CHIPS I0+DISKS $5.95 Cat.K83500 ........ $37.95 $59.95 Quality, new fans for use in power amps, computers, hotspot cooling etc. Anywhere you need plenty of air! 240V 31,2 " 115V 3 1,2·· 100+ $0.10 $0.12 $0.12 $0.12 MCM 511000P-10 DUAL IN-LINE BRAND NEW FANS 240V 45/a" Cat. T12461 10 + $0.12 $0.15 $0.15 $0.15 1 MEG DRAM ■ LOGIC PROBE Features 20MHZ memory. TTU CMOS operation. Cal. No. Col. 1-9 Z10140 Red $0.15 Z10141 Grn $0.20 Z10143 Ylw $0.20 Z10145 Ora $0.20 LISTENING POST KIT This device attaches between the audio output of a shortwave receiver and the input port of a computer. It allows decoding and printing out of morse code , radioteletype (RTTY) and facsimile (FAX) pictures using the computer. It has been designed from readi ly available parts. Details for writing the software program are included. (AEM 3500, July '85) TYPE 1·9 ORDER HOnJNE 008335757 fTOLLFREEJ STRICTLY ORDERS ONLY LOCAL ORDERS & INQUIRIES (03)5437&n POSTAGE RATES: ... $2.00 $1 - $9.99 $10 - $24.99 ... ...... .. ... .. ... $3.00 ... $4.00 $25 - $49.99 ..... $5.00 $50 - $99.99 $100 plus ........ $7.50 The above postage rates are for basic postage only. Road Freight, bulky and fragile items will be charged at different rates . Errors and omissions excepted. Prices and specifications subject to change. xr. IBM' . PC' . Ar. are reg1stereo1rac1emark so1 lnternat10nal Business Machines •Apple rs a registered trademarl< 'Denotes registered 1radmarl<s ol thelf respective owners [Eel VISA Dual band transceiver What do QSK CW, "talking on the twin pair " (using the telephone) and lcom' s new IC-3210A have in common? Answer - they all let you hold a real conversation without having to wait for the button to drop. The all new IC-3210A dual band VHF-UHF mobile is a full duplex transceiver which allows transmission on one band and simultaneous r eception on another band·. The IC-3210A has a frequency range covering (Tx) 144-148MHz and 430-44 0MHz, (Rx) 138174MHz and 430-440MHz, and two sets of 20 memory channels, one for each band, storing frequency, offset and tone data. The IC-3210A has excellent scanning facilities which can be set to scan from band edge to band edge or between preset Sports Handycam has splash resistant case While Video-8 camcorders may be light and highly flexible they are hardly the sort of product you would be willing to expose to salt and sand at the beachside. Recognising this fact, Sony has just released their CCD-SP5 Video 8 Sports Handycam, a high performance go-anywhere Camcorder with lots of useful features. The most notable feature is its splash resistant camera body which allows the user to use the SP5 in potentially harsh conditions such as surf, sand, snow and 90 SILICON CHIP limits, over all memory channels in sequence, or through only the memory channels relevant to a particular band. Rated power is 25 watts on two metres and 70cm, generated by a custom designed final amplifier power module. Sensitivity is less than 0.18µV for 12dB SINAD. Other features of the IC-3210A include a bright colour LCD display, instant input frequency check via the front-panel monitor switch , a nd programmable deserts. The camera weighs 1.8kg including battery and Video-8 format cassette, making it the most versatile lightweight unit on the market today. Other major features of the SP5 include a variable speed electronic shutter with noiseless still, slow and frame-by-frame playback. The shutter has 5 settings from 1/5oth to 114000th of a second. Quick and easy editing while recording is achievable by simply pushing the edit search button back and forth to search for the scene you wish to remove and setting the zero memory to the end of the unwanted scene. The recording stops automatically when that point is reached. The unit also has good sound reproduction using the AFM hifi recording system. The SP5 is fitted with a 6X power zoom lens (with macro facility for close-ups), making it suitable for any videoing activity such as recording sailboarding, surfing or waterskiing. The Sports Handycam has the normal 3-hour recording capability of all Video-8 Camcorders. A 2-page priority watch on the call channel or any other memory channel. You can add Pocket Beep with the optional UT-40 Tone Squelch Unit to use the IC-3210A as a mobile pager. It sounds a 30 second alarm when the correct tone frequency is received. Check out the Icom IC-3210A at your nearest authorised Icom dealer or contact Icom Australia Pty Ltd, 7 Duke Street, Windsor, Vic. 3181. Phone (03) 529 7582 or toll free on (008) 338915. digital superimposer allows any image, illustration, or handwritten title to be easily superimposed onto video. Direct playback can be obtained through the viewfinder on location or by direct connection to any television. The CCD-SP5 has a suggested retail price of $4,199.00 and is available from your local Sony dealer. High voltage screwdriver set . ~~!Li . ._, ri . •• • •• . ~ - . ~~~fi,• 1 This set of screwdrivers is rated for use on voltages up to 1000VAC. Both the handles and shafts are encased in bright red plastic. Two Phillips head and four flat blade drivers are included plus a driver with an inbuilt neon. For further information, contact Bowthorpe Australia, 105 Cawarra Road, Caringbah, NSW 2229. Phone (02) 525 2133. 12V tester from Dick Smith Electronics "Spannungs-prufer" it says on the bubble pack and a lot of other German type words so we were in trouble with this product, or so we thought. Luckily all the instructions on the back of the pack are in English as is the labelling on the device itself. It is a handy automotive voltage tester which will test your battery and identify live wires ( + 12V) and high voltage in the ignition system. y OU can get your own Spannungs-prufer from all Dick Smith Electronics stores at just $7.95. Heavy duty joy stick for computer games Are you one of these gorillahanded over-enthusiastic players who can virtually rip apart a joystick in the heat of a game? Now Dick Smith Electronics have a heavy duty joystick (Cat X-3831) which is claimed to be built to the same standards as those used in amusement machine parlours. Recommended price is $49.95 and the unit comes with a 3-year warranty. The technology letters occupation and continued to pay their salary. Employers loved the idea. At ohe point, we were calling the place " Make-Good City". One Saturday, Teach got out of sequence - we got game rights from the home game channel, took half of their regional spots, and the other half were to be ours. We tried to tell him he was goofed up but the co-ordinator has the final say. The following Monday, however, he heard more from the chief engineer than he had bargained for. He departed, clutching his final pay cheque in his grubby fist and muttering about the unfairness of management. I got hauled in on account of the sailor's foul-up. On the Sunday, he had been poking around the racks and managed to blow some fuses. When the off-air monitor in VTR went dark, I heard a scream. I ran in, determined we had a severe problem and intended to patch around it. To my dismay, all the labels on the patch panels were missing! The schoolteacher was screaming at me to do something; the sailor was crying that it wasn't his fault; the transmitter bloke was on the intercom, yelling that the link had Bookshelf - ctd from page 85 dropped out. I said a few wellchosen rude words to all, then tried to remember what was where. It took me about five minutes but I patched around until I got our late movie back to air, then proceeded to rectify (pun!) the power situation. Just as I got my first cup of coffee on Monday afternoon, the SS summoned me to the CE's office. The grin faded from the weasel's face, though, when I mentioned the denuded patch panel. The CE had been unaware of this and SS excused it by saying that he had started to draw up new labels the Friday before but his technical pen had run out of ink ... As I write, most of the strikers have drifted off to other jobs. The arbitrators were called in, an election was required, and existing personnel also had to vote on whether to reinstate the union shop. The company won - by one vote! But they were required to take back anyone who wanted his job back. Now they are overstaffed and trying to get the excess people to leave of their own accord. As I'd like to see some more of America, you'll probably hear from me another place, another time. Warmest regards, Colin. le ctd from page 36 Three-Line Burner, ABeEP I, EPROM Program Tester, ROM Drive, Speech Synthesiser, Music Synthesiser, Message Centre, 4-Watt Eraser, 8-Watt Eraser. The Boole's Box is basically a logic state indicator for common logic ICs. Not too many people would be interested in building it although the concept is interesting. More useful is the Keyboard Encoder although again not many are likely to build it. The two Bit Smasher projects are very simple EPROM programmers using DIP switches for the Data and Address lines. The two versions of EPROgraMmer are programmers intended to be connected to the parallel port of a computer. The Three-Line Burner is a further version using a UART (Universal Asynchronous Receiver/Trans- mitter) for serial connection to a computer. The ABeEP is a programmer intended for use with an Apple Ile computer. The Message Centre is an EPROMbased keyboard encoder. All the other projects are more or less selfexplanatory although none of the projects listed are well explained. You would need a high level of practical knowledge to get any of the projects to work. The remaining sections of the book discuss commercial EPROM equipment and the Heath programmer/eraser kits. On the whole then, "Experiments with EPROMs" is a useful text if you want to know more about EPROMs although it does assume a good level of practical knowledge. Our copy came from Dick Smith Electronics (Cat. B-5001). le FEBRUARY1989 91 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. More loudness from the Speakerphone I recently built your Hands-Free Speakerphone as described in the October 1988 issue of SILICON CHIP and found that it works extremely well. I had a suitable 80 loudspeaker and so used an 180 series resistor (to provide the specified 220 load). However, I found that when a quietly spoken person was on the other end of the line, the loudspeaker volume was slightly lacking. After experimenting with a couple of lower value series resistors, I eventually bridged this resistor out altogether and found that the increase in volume was quite significant and hence cured my problem. Also is it possible to add a pot into the circuit to increase the transmit volume? As with any telephone, occasionally the distant Wants circuit for Weldon radio Congratulations on your first twelve months of publication. Keep up the good work. Although I am happy with the magazine as is (I have been buying electronic magazines for 3 2 years and still find it an interesting hobby), I think you need a brickbat for not producing cheap easy-to-build projects for newcomers to the hobby. These include both young people and retired people looking for something to fill in their spare time. I have spent many years in the Scout organisation with boys from 8 to 16 years of age. Many of these boys wanted to get into electronics but found it hard through lack of suitable projects. The main projects I get asked for are simple radio receivers and small amplifiers. I find the ZN414 radio a good starter pro92 SILICON CHIP party complains of insufficient volume - whether they are slightly deaf or the phone line is bad, I don't know. If a small pot could be added to the circuit and mounted on the back panel perhaps it would be a worthwhile improvement. (W. A., Kirwan, Qld). • Your comments regarding the speaker are interesting although we are not sure whether the lower than specified load will prejudice the performance on loud signals. The IC is short circuit protected so there will be no problems on that score. According to the Motorola data, the microphone sensitivity may be adjusted by varying the 2k0 microphone bias resistor although we don't think this would lead to any really worthwhile increase. There is no way of externally varying the gain of the microphone amplifier. ject for these people. Anyway, enough of that. I am restoring a 1933 Weldon radio, Model No. BC834A, made by Block & Gerber Ltd of Sydney. The valve lineup is 57, 58, 2A6, 2A5 & 280. I would appreciate it if you could publish a few lines asking if readers can help with a circuit diagram for it. The vintage radio series in your magazine is great reading. I have been restoring radios for about ten years and now have a good collection. (E. Gill, 249 Sawtell Road, Toormina, NSW 2452). • Thanks for your comments. We agree that newcomers need easy to build circuits but there is a limit to the number of simple radio projects which can be published. As you can see, we've published your address so that any reader who has a circuit of the Weldon radio can write to you directly. On the other hand, Motorola state that the nominal gain of the transmit attenuator is inversely proportion to RTX, the resistance connected to pin 2. This is shown in the data on the MC34018 published on pages 58 and 59 of the September issue. Examination of the data indicates that the transmit gain should be maximised by reducing the resistor at pin 2 to 30k0. This can be easily achieved by shunting the existing 91k0 resistor with 47k0. Converting a CB radio to 28MHz In the October 1988 issue of SILICON CHIP you had a very good article on converting a CB radio to the 28MHz amateur band. We are building the suggested circuit and have got to the stage of placing the components on the board but have come to a full stop with C4, the 330pF capacitor. Where is it on the board? (0. C., Wilston, Qld). • The capacitor in question, C4, is between Qt and C6. If you trace out the pattern on the component overlay diagram on page 85 of the October article, you can confirm this for yourself. Queries on the December issue I have just read the December 1988 issue and found it enjoyable as usual. However, I wish to note a few points which may have been oversights. First, in the caption on page 77 for the NSW 900-class rail motors, you ref er to them as being diesel-electric. To my knowledge these are diesel hydraulic. Second, on page 28, on the circuit for the 120 watt public address amplifier, the switch for the microphone socket is shown with normally closed contacts. This appears to be an error. Finally, your Circuit Notebook 1k 01 BC337 TO POINTS 4.7k TO POINTS Fig.1: basic impulse tachometer circuit. It's operation is explained in the text. Tacho connection for high energy ignition I have built and installed two examples of the high energy ignition system described in the May 1988 issue of SILICON CHIP with excellent results. However, the tachometer on the 1969 Nissan Skyline will not work when the high energy ignition is fitted. There is no meter deflection at all, regardless of engine speed. The tachometer connection is taken from the negative side of the coil. Can you help me with an explanation of why this has occurred and give a suggestion as to how it can be fixed? (R. F., Curtin, ACT). • We assume that your tachometer is what used to be known as an "impulse tachometer". The circuit was similar to that in Fig.1. It uses a zener diode to clip the high voltage pulses from the points. The clipped pulses are ihen differentiated by a series capacitor and fed to a bridge rectifier and meter. Even if your tacho does not use this general configuration, the principle of its operation will be broadly similar pages show a number of battery charger circuits using the LM317 adjustable 3-terminal regulators. These are OK as far as .they go but there could be a problem if the batteries remain connected while the mains supply is not present. The batteries will attempt to discharge back via the regulators and possibly cause damage. The manufacturers normally recom- ~ +12V VIA IGNmON SWITCH TACHOMETER 1000 ------------► CHASSIS Fig.2: this circuit can be used to drive an impulse tacho when electronic ignition is used. to this scheme. The fact that your tachometer will not respond to the high energy ignition system suggests that it relies on the slower rise time of conventional ignition systems, as set by the points capacitor. Perhaps the primary resonance, after each spark has extinguished, also plays a part in driving the tachometer circuit. With transistor ignition systems which have no capacitor to slow down the coil rise time, the pulse fed to the tacho circuit would be a great deal shorter. After being clipped it would have little remaining energy to drive the tacho. Also lacking in the high energy ignition system, as far as a tachometer is concerned, is any primary resonance. This is prevented because the spark duration is fixed at one millisecond arid so no coil energy is wasted in primary resonance. What is the solution? It is not possible to modify the high energy ignition circuit to drive your tacho and, as we see it, there is little point in modifying the tacho to work with the new mend protection diodes for these circumstances. (A. L., Narrabeen, NSW). • A check with the author has shown that the 900 class rail motors are diesel hydraulic and we agree with your comment on the jack socket switch for the 120W PA amplifier. With the switch contacts closed, the circuit can only work in the unbalanced mode. ignition system. If you took the latter course, it probably wouldn't work with conventional ignition and that would not be desirable if you wished to sell the car in original form. With that in mind, the most practical approach would seem to involve another circuit to generate pulses for the tacho. Our suggested circuit is shown in Fig.2. This uses the primary winding of a small mains transformer, type PF 2851 as made by Ferguson, or equivalent. This is driven with an MJE340 transistor (Q2). The coil voltage is limited by the .033µ.F capacitor connected between collector and emitter of Q2. Q2 is driven by Ql which merely inverts the signal from the points. While we have bench-tested this circuit we have not been able to see if it will correctly drive the tacho circuit described above. Still, the circuit concept will provide the basis of a tacho driver. In the meantime, perhaps other readers have faced this problem and have worked out a solution. If so, we'd like to hear from them. As far as the battery charger circuits are concerned, National Semiconductor recommends the use of protective diodes where the output capacitance is more than 25µ.F and the output voltage is more than 25 volts. Certainly a battery constitutes an output capacitance of more than 25µ.F but the voltage is not a problem. However, if you think about how FEBRUARY1989 93 Fun & games with the FM subcarrier adaptor I recently built your FM subcarrier adaptor as described in the January 1988 issue of SILICON CHIP. I decided to use it with an old Philips AM-FM portable radio and feed the output signal to a separate amplifier. I tuned the radio to 90.1MHz which is public station 2NBC, knowing that they run a Greek program on their subcarrier. I had no circuit diagram for the Philips radio but after I spotted the FM demodulator I started poking around for the signal. Within about 5 minutes I picked up the signal and it did sound quite good. I was actually thrilled at the discovery. After using the adaptor for awhile, and having set the two pots (VR1 and VR2) for best out- the circuits operate, there really isn't a problem. Any tendency for the battery to discharge via the LM317 will be counteracted by the rectifier(s) at the input to the circuit. These will be reverse biased in this situation so negligible current can flow back through the regulator in either circuit. Where diode protection for 3-terminal regulators is really a necessity is where the output load is inductive and may generate large spike voltages. Our dual tracking power supply, published in the January 1988 issue, included protection diodes for the regulators for this reason. Starving for info on nicad batteries Being an avid reader of SILICON CHIP, I was wondering if you could do a series of articles covering all facets of nicad cells. I recently acquired some nicads and a charger and found my thirst for knowledge on these little suckers won't stop. Trying to feed this thirst with textbooks leads to a dead end. 94 SILICON CHIP put, I decided to try the adaptor in my car stereo which is a very modern Eurovox. This time I thought it would be very easy to pick up the subcarrier signal since I have the full circuit diagram of the unit. I pulled it out of the car, took the covers off, laid the circuit diagrams out on the bench and started looking for the signal. But after about 4 hours of frustration, I had no luck. I seem to pick up the subcarrier at pin 11 of IC603 or either side of R634, as well as some other points on the board, but it is very distorted and adjusting the pots on the adaptor achieves nothing. I am mystified. The normal signal as received from the FM stations is very good and the subcarrier as received from the portable radio is good and strong. I have enclosed the circuit in the hope that you can tell me where the signal might be Even though I know it takes current to charge the nicads, what voltage does it take to charge 1.2V or even 7.2V nicads? I would like to design my own special chargers that trickle feed and maybe charge my cordless drill from my van battery while I'm working. I'm sure I'm not the only one who could make good use of this knowledge. (J. P., Magill, SA). • We published a good background article on nickel cadmium batteries in our August 1988 issue and an article on a fast nickel cadmium charger in the June issue. And in the December issue, in the Circuit Notebook pages, we had a simple nickel cadmium charger. Both of these circuits could be run from a 12V car battery. If you need them, we have back copies of all these issues available at $5 each, postage included. picked up. I enjoy your magazine very much and have purchased every issue since you started. I think it is a down to earth magazine and the projects are very practical and enjoyable. (P. T., Canterbury, NSW). • That circuit of yours is certainly inscrutable and we don't have any data on the devices used which would be a help. However, the block diagram shows IC601 as containing the FM detector so we would expect the wanted signal to be present at pin 8 of IC601 (ie, the output). In any case, since the input of the subcarrier adaptor has quite a high impedance (more than tok!l) you could take a wander lead from the input and touch on every pin of the likely ICs in your radio. The chances of doing any damage are very remote and you should pick up the signal quickly without problems. modore C-128. So far all the units I have come across of the homebuilt type are designed for Z80 based computers like the Microbee. Has your magazine published a suitable circuit for my Commodore? I am most interested in a circuit that will program chips up to and including 27256 Eproms. (G. C., Karrinyup, WA). • Sorry, but we can't help you on that one. Any readers know of some suitable circuit for the Commodore? Courses in amateur radio Do you know of a place where one can undertake a course in amateur radio operation? (B. C., Avalon, NSW). • We suggest you contact the Wireless Institute of Australia, 109 Wigram Road, Parramatta, NSW 2150. Phone (02) 689 2417. Eprom programmer for Commodore C-128 Notes & Errata I am hoping to burn some Eproms for myself in the near future and have been trying to find an Eprom programmer to work with my Com- Fish Bite Detector, September 1988: all the diodes are shown reversed on the wiring diagram. The circuit diagram is correct. Silicon Chip Back Issues Issue Highlights November 1987: Car Stereo in Your Home; 1 GHz Frequency Meter; Capacitance Adapter for DMMs. December 1987: 100W Power Amplifier Module ; Passive lnfrared Sensor for Burglar Alarms; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter. January 1988: 4~ wtie UHF Antenna; D.u~ i19\li1'.ier Supply; . Custom Pl$Gl-'P'f~ ubcarrier Adapter for ~ s. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems; Simple Door Minder. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Low Cost Function Generator ; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm . June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; Automatic Light Controller ; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show. August 1988: Plasma Display ; Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries . September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; Switchmode Charger for 1 2V Gel Batteries; Vader Voice. October 1988: Stereo FM Transmitter; High Performance FM Antenna; LedLight House Number; Matchbox Crystal Set. November 1988: 120W PA Amplifier Module; Poor Man's Plasma Display; Car Safety Light; How to Quieten the Fan in Your Computer. December 1988: 120W PA Amplifier; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Receivers. January 1989: Line Filter for Computers; Proximity Detector for Cars ; Computer Sound Repeater; How to Service Car Cassette Players. BACK ISSUES ORDER FORM Please send me a back issue for : D March 1988 D August 1988 D April 1988 D November 1987 D May 1988 D October 1988 D December 1987 D February 1 988 D June 1988 D July 1988 D December 1988 D Sept.1988 D November 1988 Jan. 1989 □ Enclosed is my cheque/money order for $ ______ or please debit my D Bankcard D Visa Card D MasterCard Card No ___.___.____,____,_____,__---'------'-------'--'___J___JL__L.,_.J__.J__J____J Price: $A5 .00 each (includes postage). Overseas orders add $A 1 .00 per issue for postage. Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_/___)_ _ NZ & PNG orders are sent by Name _________________________ air mail. (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS Stree..___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ PO BOX 139 COLLAROY BEACH Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode____ NSW 2097 '-I ~-------------------------------------J FEBRUARY1989 95 T CEN'l Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising Index Advertising rates for this page: Classified ads - $7 .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. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put'one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds , PO Box 139, Collaroy Beach, NSW 2097. Allied Capacitors .. ..... .. .. ..... .. 1 3 Altronics .............. .. .... .. .. 46-49 Arista Electronics ...... ... ... .... IBC Avtek .............. ..................... 9 Ballarat Electronic Supplies ... 11 Contact International .. ....... ... 69 David Reid Electronics .... ..... . 5 7 Dick Smith Electronics .... . 14-1 9 Elmeasco ...... ............. ... .... IFC Geoff Wood Electronics ..... .. . 63 Hycal Instruments ................ 11 Jaycar Electronics .. .. .. .... 32-35 70-73 Kenwood Australia ... .. .... ...... 81 RCS Radio ............. .. ........... 1 2 Rod Irving Electronics ........... 89 Temple Smith Aust. .. ..... .... OBC PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7 00) 16 ($7.40) 17 ($7.80) 18 ($820) 19 ($8.60) 20 ($900) 21 ($9.40) 22 ($9.80) 23 ($10 20) 24 ($10.60) 25 ($11.00) 26 ($11.40) 27 ($11.80) 28 ($12 20) 29 ($12.60) 30 ($1300) 31 ($13.40) 32 ($13.80) 33 ($14.20) 34 ($14.60) 35 ($15.00) Name ......... ... .. ... .. ..... ... .. ... ..... ........ ............. ... . Address Suburb/Town Postcode Enclosed is my cneque or money order for $ Bankcard D Visa Card D MasterCard . . . . . or please debit my PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 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 . D Card No I I l I Signature ...... ....... .... ...... . FOR SALE BUILD YOUR OWN LED Moving Message board. $75 for a 4-character display experimenter's short form kit and $150 for 16 characters . Includes Intel MOS II Micro Development System with three disc drives. Very good condition with original manuals, circuits and many extras. Make an offer. Ron (02) 428 6491 (business). 96 SILICON CHIP I ...... ... Card expiry date ...... ./ .... .. ../. .... .. . PC boards, EPROM and full instructions to complete the project to a professional standard. Loaded from Centronics printer port or PC/XT keyboard. Equivalent commercial units start at around $1000. For more info send a 39c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. RADFAX 2: HI-RES RADIO facsimilie , Morse and RTTY program for IBM PC/XT on 360K 5.25-inch floppy plus full documentation . Need CGA. SSB HF FSK/tone decoder. Has re-align, autostart, view, magnify, save, print. Also "RF2HERC" same as above but suitable for Hercules card and "RF2EGA" for EGA card (640 x 350 mode). Programs are $30 each plus $3 postage. Only from Michael Delahunty, 42 Villiers Street, New Farm, Old 4005. Phone (07) 358 2785. BOOKS & PLANS LOW SPEED GENERATORS for windmills, water turbines, steam engines. The definitive book: "The Homebuilt Dynamo" (1987) , 182 pages, 8 .5" x 12", hardback. Generator design and construction with ceramic magnets. Complete plans, 268 photographs, step-by-step construction details. $A85 .00 postpaid airmail (brochure $A5.00 refundable). Todd-Forbes Publishing, 627 West Coast Road, Oratia, Auckland . Can you spot the eight features on this scope that you won·t find on o es? eckin e specs on low cost scopes can get a bit repetitive Yes, they all have 20MHz bandwidth and Yes, they've all got 6 " rectangular screens. Some have 1m V max sensitivity. So what's different about the New Goldstar OS7020? 1. Variable Sweep Control incorporating x10 Magnifier Simply adjust the sweep to give a suitable trace then pull control for a x1 o magnified image. 2.Uncal Warning Lights When the timebase or input controls are not in their calibrated positions you'll see a warning light - handy if you're taking measurements. 3.Triggered LED If the input level is sufficient to trigger the OS7020, then this LED is illuminated. Saves a lot of time fiddling when you're not certain that you've got proper triggering. 4. TV-V & TV-H Triggering These switches are a further aid to triggering and are particulrly useful for the TV service technician. Also enquire about the OS7040 scope. 40MHz/1mV with delayed sweep. $1380 inc tax with 2 probes. $1150 ex tax with 2 probes Gotta Gatta GoldStarSupported & Serviced Australia-wide by Elmeasco Instruments Pty Ltd Dealer enquiries welcome. Call (02) 736 2243 Recommended prices only 5. Trigger Hold-Off Another aid to triggering - use this control to delay the sweep on complex waveforms 6. Professional Tilt Handle. Many manufacturers take a short cut and give you a cheap carry strap. Not so on the Goldstar OS7020; you get a professional multi-position tilt handle. 7. 1mV maximum Sensitivity Use the built-in x5 magnifier to get 1mV/div maximum sensitivity. 8. Made by GoldStar Your guarantee of quality. The OS7020 is designed and built in Goldstar's own factory . Many of the parts are specially made by GoldStar. That's why we can offer a one year warranty and extra features at no extra .cost! Check these prices ! $888 inc tax complete with two high quality switchable probe kits $740 ex tax with probes You 've Gotta Getta Goldstar Scope from : A.C.T. John Pope Electrical 80 6576 • J Blackwood & Sons 80 5235 • George Brown 80 4355 N.S.W. George Brown 519 5855 Newcastle 69 6399 • Ames Agency 699 4524 • J Blackwood & Sons • Auto-Catt Industries 545 1322 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ma_celec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply (049) 62 1358 • Ob1at Pty Ltd 698 4776 • David Reid 2671385 • Digitel 709 6511 • Geoff Wood 427 1676 N.TERRITORY J Blackwood &Son (089) 84 4255. 52 1788 • Thew &McCann (089) 84 4999 QUEENSLAND Auslec 854 1661 • George Brown 252 3876 • St Lucia Electronics 52 7466 • L.E.Boughen 369 1277 • B.A.S. Audiotronics 844 7566 • Colourview Wholesale 275 3188 • E.C.Q. Electronics 376 5677 • The Electronics Shop (075) 32 3632 • Thompson Instruments (Cairns) (070)51 2404 • Solex (Townsville)(077) 72 4466 • Xanthos Electrical (079) 27 8952 S.AUSTRALIA George Brown 212 3111 • J Blackwood & Sons 46 0391 TASMANIA George Harvey (003) 31 6533 (002) 34 2233 Y!QIQfilA Radio Parts 329 7888 • George Brow_n Electronics Group 878 8111 • G.B. Telespares 328 4301 • J Blackwood & Sons 542 4321 • The Electronic Components Shop 670 6474 • A.W.M. Electrical Wholesalers • Factory Controls (052) 78 8222 • Mektronics Co 690 4593 • Truscotl Electronics 723 3094 W AUSTRALIA Atkins Carlyle 481 1233 • Dobbie Instruments 478 1366 • George Brown 362 1044 PAPUA NEW GUINEA TE (P.N.G.) Pt Moresby 25 6322 Lae 42 6246