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MASS STORAGE DEVICES FOR COMPUTERS SERVICING - VINTAGE RADIO - COMPUTERS - AMATEUR RADIO - PROJECTS The aerodynamics ol model aircraft * VOICE OPERATED SWITCH WITH AUDIO DELAY * CW FILTER FOR RADIO AMATEURS * RF FIELD STRENGTH METER TO BUILD Registered by Australia Post. Publication No NBP 9047 Metrix 50 Series Metrix 40 Series • Exceptional All-Weather Performance • Four Year Warranty • 4000 Count Resolution • Autoranging with Manual Override • Hold & Peak Functions • True RMS AC or AC+DC • Sate to IEC348 Class 11 • Comprehensive Display with Analog ,Bar-Graph • 5000 Count Digital Display • Patented Live-TrendrM Mode Shows Instant Values • Storage of Up To 5 Different Readings • Surveillance Mode • Models with dBs and Frequency to 500kHz from$195 From $275 TQp1jii~ From the home of the Mercedes Benz and BMW comes Metrix - Europe's Favourite Multimeters Metrix MX573 Metrix MX1200S & MX200 Clamp-On • True Analog and Digital • True RMS ac • 25kHz Bandwidth for Vac • Auto-Polarity Switching • Taut Band Linear Scale Analog Movement • 2000 Count Digital LCD Display • Power Measurements • Current Ranges to 200A/100A • Frequency to 1kHz • Resolution as low as 10mA • Analog Output $595 $770 Also ask about the MX545 Series anc MX579 Benchtop Multimeters and a Wide Range of Probes & Accessories ELMEASCO Instruments Ply.Ltd. Australia's Leading Test & Measuring Instrument Company NEW SOUTH WALES 18 Hilly Street, MORTLAKE PO.Box 30, CONCORD NSW 2137 Tel • (02) 736 2888 Telex • AA25887 Fax • (02) 736 3005 VICTORIA 12 Maroondah Highway, RINGWOOD P.O Box 623, RINGWOOD VIC 3134 Tel• (03} 879 2322 Telex • AA30418 Fax : (03) 879 4310 QUEENSLAND 192 Evans Road, SALISBURY P.O.Box 274 SALISBURY OLD 4107 Tel• (07) 875 1444 Fax • (07) 277 3753 SOUTH AUSTRALIA 241 Churchill Road , PROSPECT P.O.Box 154 PROSPECT SA 5082 Tel • (08) 344 9000 Telex : AA87519 Fax : (08) 269 5411 W. AUSTRALIA 32 Teddington Road , VICTORIA PARK, W.A. 6100 Tel • (09) 470 1855 Fax• (09) 470 3173 Prices quoted do not include Sales Tax and are subject/a change without notice APRIL 1990 FEATURES 6 Servicing Your Microwave Oven by Leo Simpson Simple jobs that you can do yourself 68 Taking The BASF CD Challenge by Leo Simpson WITH THIS LOW COST field strength meter, you can adjust antennas to resonance & align transmitters for maximum output. Construction starts on page 20. Can chrome tape sound as good as compact disc? 83 High Density Data Storage from Philips A promising new technique PROJECTS TO BUILD 20 Relative Field Strength Meter by Ralph Holland Lets you adjust antennas and align transmitters 28 Build A VOX With Delayed Audio by Darren Yates Don't chop off the first syllable 46 Dual Tracking :!: 50V Power Supply by Greg Swain New switchmode design delivers up to 1.7 A 72 16-Channel Mixing Desk, Pt.3 by John LOOKING FOR A dual trucking power supply that can really deliver the goods? This design can provide up to ± 50V DC at currents up to 1.7A. Details page 46. Clarke Assembling the PC boards SPECIAL COLUMNS 16 Vintage Radio by John Hill Finding receivers from the 1920s 36 Computer Bits by Jennifer Bonnitcha Mass storage devices - bigger than Ben Hur 60 Serviceman's Log by the TV serviceman It's an ill wind ... , as they say 88 Remote Control by Bob Young Model aircraft aerodynamics x':s:: < ~ ~' •" - ~% ~ /' 0 • r:;.,,.: ,:,r-.-, t \ •~5-~ IT'S AN ILL WIND that blows nobody any good, us they say. The serviceman was very busy this month and it wus ull due to wind! - see page 60. 94 Amateur Radio by Garry Cratt Active CW filter for weak signal reception DEPARTMENTS 2 Publisher's Letter 4 Mailbag 40 Circuit Notebook 66 Back Issues 97 Product Showcase 100 Ask Silicon Chip 101 Notes & Errata 102 Subscription Page 103 Market Centre MOST VOICE OPERATED relay circuits chop off the first syllable of speech but not this unit. It features an in-built audio delay so that all the speech signal passes through. See page 28. APRIL 1990 1 SILICON CHIP 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 (02) 982 9553 Regular Contributors Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill Jennifer Bonnitcha, B.A. Bob Young Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 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, Rozelle, NSW 2039 . Printing: Macquarie Publications Ltd , Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: currently $42 per year ( 1 2 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 . Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP PUBLISHER'S LETTER Myths and • microwave ovens One of the boon appliances in today's household is the microwave oven. Not only does it do a much quicker job of cooking but it saves quite a lot of energy in the process. Strangely enough though, there are quite a few people who will have nothing to do with food cooked in a microwave oven because it has been somehow "polluted" by the process. While it is easy enough to pour scorn on such attitudes, it is partly a result of confusion and disillusion with science and technology. After all, how many times in the past has a new technology been praised as being a wonderful advance and then years later, we have learned that it has some very nasty and long-lasting environmental side effects. Some examples: atomic energy, supertankers, most pesticides and weedicides, many drugs, asbestos, most mineral extraction and refining processes, PCBs (poly chlorinated biphenyls) - the list is endless. However, just because many new technologies do have side-effects which must be carefully controlled, we should not swear off them all; particularly not such a benign product as a microwave oven. It is a simple product with positive benefits for the environment and for personal health. Food cooked in a microwave oven retains much more of its vitamins than food cooked in any other way. This applies particularly to vegetables. And cooking food in a microwave oven saves quite a lot of energy since virtually only the food itself is heated, not the container, or a large quantity of water, or the surrounding air and so on. And there is another practical benefit to using a microwave oven a lot less washing up of pots and pans. That means you save time and hot water - another saving in energy. Does that mean that there are absolutely no side effects to microwave ovens? Well, there are two that I can think of. Microwave energy is dangerous if you are exposed to it. That is why there are complex interlocks and a special microwave proof seal on the door. That is also why the door glass has a fine metal mesh in it - to prevent microwave energy from passing through. There is also a high voltage power supply inside which could be quite lethal if it was touched. But provided a microwave oven has not been tampered with in any way, it is no more dangerous and in fact less dangerous than another potentially lethal domestic appliance - your colour TV set. It too can emit radiation if it's defective, and it also has a very high voltage power supply inside. But nobody swears off watching television for those reasons. Nor should anyone avoid eating food cooked in a microwave oven because of vague fears about radiation or pollution. Eat and enjoy. Leo Simpson . NRCCESS COMMUNICATIONS PTY LTO MS-101 9-Band Shortwave Receiver Ideal for Travellers: • Miniature size. • Complete with personal stereo headphones. • Includes short wave listening guide. • Great " leather look" carry case. • AM broadcast and FM stereo coverage. Cat # C6000 $119.00 • Optional AC adaptor Cat # T0321 $19.95 ATS·803A Portable Communications Receiver: • Continuous coverage from 150KHz to 30MHz. • AM/CW/SSB, Inbuilt RF gain control, BFO. • PLL synthesised tuning, LCD display. • Scanning, 14 memories, AM broadcast & FM stereo coverage, 12 short wave bands. Cat # C5020 $299.00 • Optional AC adaptor Cat # T0941 $24.95 ATS-802 Synthesised Shortwave Receiver: • Continuous shortwave coverage 5.8MHz to 15.5 MHz. • 25 memories. • Auto timer functions. • Up/down tuning control in SKHz steps. • AM broadcast and FM stereo coverage. Cat # C6028 $199.00 • Optional AC adaptor Cat # T0630 $24.95 SG-796 9-Band Economy Shortwave Receiver: • 6 short wave bands. • AM broadcast. • FM stereo. • Protective carry pouch and shortwave guide. Cat # C6020 $79.00 • Optional AC adaptor Cat # T0320 $19.95 •- ii'. SG-792AL: • Similar to SG-796 above, but includes 6 shortwave bands, VHF air band and long wave band. Cat # C6025 579.00 • Optional AC adaptor Cat # T0320 $19.95 MS-102: • Slightly larger than MS-101 but with 10 short wave bands. Cat # C6010 $119.00 • Optional AC adaptor Cat # T0321 $19.95 SHORTWAVE, UHF, CB, SCANNERS, MARINE Road Runner RR-477 Compact Hand-Held UHF Transceiver: • Scanning, lock out, Hi-Lo power controls. • Programmable repeater operation . • Optional tone squelch available. • Back-lit LCD display. • Maximum legal 5 watt output. • Includes rechargeable ni-cad battery. Cat # C5047 $599.00 Available Accessories: a) Speaker microphone Cat # C5050 $49.50 b) Drop in desk charger (including fast and slow charge rates) Cat # C5052 $129.00 c) Glass-mount hall wave antenna no holes to drih! Cat # 1<3095 $79.00 d) Mobile transceiver adaptor - adapts you r RR-477 to mobile configuration . Includes full mounting hardware ideal for use with a) & c) above. Road Runner AR-880 Hand-Held Scanner: • Scan , search, lock-out. hold, delay functions. • Frequency coverage 60MHz-90MHz, 138MHz-174MHz, 406MHz-525MHz, B30MHz-950MHz. • Selectivity: 7.5KHz at 6dB. • Audio output : 120mW. • Size: 140mm (H) x 55mm (W) x 44mm (D) . Road Runner Cat # C5020 $399.00 40-Channel • Optional AC adaptor 27MHz AM CB: 2 • Up/down push Cat # T0620 $19.95 button channel control. • Easy to read red LED channel display. • Miniature size suits installation in modern vehicles. • Maximum legal power output. Cat # C5100 $79.00 SPECIAL INTRODUCTORY OFFER - SAVE $10.00 i~~X Cat # C5054 $129.00 e) Spare 10.8 voll, S00mA ni-cad battery. Cat # 1<3090 $69.00 f) Communications headsel Cat # K5060 $49.00 g) Vax-unit - allows handsfree ope ration using headset f) above ----~: - -_. -;; -~· ~ ~ ~ ~ ~ : ---..,,.____~----- Cat # C5055 $69.00 h) Trickle charge AC adaptor Cat# T0120 $19.95 Seamaster International VHF Marine Transceiver: • High/Low power switch. • Scan. priority, dual watch, up/down channel control. • Auto seaphone compatible. • 54 transmit and 57 receive channels. • DOTC Approval # 274B0090. Cat # C7000 $299.00 SPECIAL INTRODUCTORY OFFER Auto Seaphone Microphone: (to'suit above) : Cat # C7005 $159.00 Wired to suit C7005 transceiver. Seamaster VHF Marine Antenna: • Includes 4-way polycarbonate UV stabilised base and coaxial cable. • Weather-proof fibreglass radome. • Ground independent half-wave design. Cat # K3162 $69.00 Mobile Scanner AR-950: • Suits mobile or desk-top installation. • Frequency coverage : 60MHz-90MHz, 118MHz-174MHz 430MHz-512MHz, 830MHz-950MHz. • Search increments: SKHz, 10KHz, 12.SKHz. 25KHz, 30KHz. • Search, scan, priority, lock-out, delay/hold, AM/FM functions. • Supplied with 2 antennas for optimum UHF and VHF reception . • Inbuilt 20d8 local/DX attenuator. Cat # C5015 $499.00 • Optional AC adaptor Cat # T1230 $24.95 MAILBAG Circuit for video monitors now available I remember a Publisher's Letter some months ago when Mr Simpson was calling on suppliers of electronic items (in particular a computer monitor) to make available a circuit diagram. In response to this , Electronics Solutions has made available circuit diagrams for all its monitors at a cost of $10.00 each. Unfortunately, we cannot make circuit diagrams available for our motherboards and other products as in most cases they consist of VLSI chips which have been surface mounted for greater reliability, and in this 'throw-away-society' are virtually un-repairable. Ian Hardwick Electronic Solutions Pty Ltd Gladesville, NSW Modifications to the Studio 200 power amplifier I felt I could not resist your offer to comment on contributor A.K. of Chatswood's "audible improvements" to the Studio 200 Stereo Power Amplifier, as written up in the January issue. Reading it made me think back to a piece of engineering advice divulged to me by an earnest audiophile back in 1959 at a time when I was busy constructing the latest in "ultra-linear" valve amplifiers. "The secret of obtaining the best sound from an amplifier", this gentleman confided, "is to use only mica coupling condensers; they give you a nice crisp tone". I knew enough at the time to take his well-meant advice with a particle of brine extract but out of curiosity, asked why this should be so. It transpired that this fellow associated the quality of a sheet of mica with clarity in musical reproduction. Apparently electrons whizzing around in his amplifiers managed to retain their purity better with mica capacitors then they would if they had to pass through soggy old wax and paper dialectrics. No doubt every time this enthusiast experienced pleasure from his records he was 4 SILICON CHIP reassured of the correctness of his discovery. A rare and extreme case of self delusion I hear you say'? Well in 1959 audio engineering circles it probably was but not, I am sad to say, 30 years later. Coincident to the current growth of Uri Geller disciples, devotees of magic crystals, astrology, phrenology, numerology and so forth, there has sprung up a corresponding 'New Age' breed of audio gurus. These self-proclaimed authorities have seemingly discovered characteristics of audio frequency oscillations, both acoustic and electronic, that defy analysis by the most sophisticated of technical equipment. Luckily for them they appear to have evolved a pair of auditory receptors which obsolete all past texts on hearing and are able to detect these previously imperceptible phenomena. Or so it would appear. This select breed of auditory connoisseurs are able to perceive the appalling consequences resulting from the smallest fraction of pick-up tracking error, meagre amounts of phase shift or musical degradation due to knots in your mains lead (no kidding). We are warned that all audio connecting cables should be treated with extreme suspicion and you might as well be listening to an Edison phonograph as use an inferior type. Never fear however, there are now scores of latter-day snake oil merchants flooding the market with cures for newly discovered audio ailments. By supplying a vast range of complexly formulated "interconnects", the " musicality" of those ever so fussy electrons that are ultimately responsible for our audio pleasures are significantly enhanced. Or so we are assured as we merrily part with our hard earned dollars. The trouble is that the theories published in an attempt to justify such goods, both by manufacturer and many 'underground' hifi journals, are so outlandish and full of vague pseudo-scientific nonsense that a genuinely informed electronics engineer would not know where to begin debating them. I suspect many wouldn't even try when confronted with statements like "conventional SILICON CHIP, PO Box 139 Collaroy Beach 2097. cables run out of breath coping with digital sound". It would be like arguing with the president of the Flat Earth Society. Revealing, like child fellow in the fairy tale, that "the emperor has no clothes" would not be enough to sway these zealots. C. Slater Fairy Meadow, NSW Analysing the mods to the Studio 200 I thought I would risk the frustrations of the word processor, especially since you have invited readers to have their say. I am adding my 20c worth to the discussion of the modification of the Studio 200 amplifier as it appeared in the January issue. The fact that A.K. has taken the trouble to experiment I feel is good because it shows enthusiasm and an inquiring mind. However, I am inclined to be a bit sceptical about his approach, and especially about the way he evaluates the outcome of the pro-. posed modifications. I shall deal with the latter point first. The human ear is a horribly imprecise detector, "designed" to work over a very large range of frequencies and input levels. Its amplitude response and its frequency response are both logarithmic and it generally exhibits poor resolution. To make matters worse, its frequency response is strongly dependent upon level, and therefore its ability to accurately resolve sound levels depends upon frequency. This is why some people have loudness controls on their hifi amplifiers, to make some correction for this unfortunate state of affairs. The fact that our hearing is imprecise is borne out by the fact that we can be quite tolerant of harmonic distortion (up to 20% can sound acceptable), while at the same time we. are quite intolerant of intermodulation distortion (usually more than 1 % is unacceptable), although both are indications of the same imperfections in the music system. Another pointer in this direction is the story told (in the Sydney Morning Herald Pink Guide) of an attempt made to have a bunch of "golden ears" distinguish between some CD players of varying price. To me, the really interesting outcome of the trial was that the players all had to have their outputs adjusted to less than 0.5dB (5% of output voltage) of each other, otherwise the loudest one sounded like the best one (a trick I have seen used by a hifi salesman to sell what he wanted, not what the customer wanted). Once this matching of levels was done those with the "golden ears" could not distinguish one player from another just by listening to them. Another point to consider is the fact that all the information picked up by our ears is processed by our brains so that the subjective effect is under the influence of other factors. Add to this the fact that our memory of music is quite poor when it comes down to fine detail, which is why auditioning of hifi gear should be done by comparing one piece with another (A-B testing), and it should be clear that evaluating any hifi equipment solely on subjective performance is pretty pointless. I know from experience that how a certain piece of music sounds and how much I enjoy it can change from one playing to another, and when you build your own amplifier it will mostly sound best when you power it up for the first time and it works, then you give it some stick (pump up the loudness) and you know nothing could sound better! At this point perhaps I should return to the issue of the circuit modifications. A.K. makes no attempt to quantify or tabulate any measurable differences the modifications might produce, quite probably due to lack of suitable and generally expensive equipment (A.K. has my sympathies on this point). In light of my foregoing mumblings I must state categorically that I cannot accept that "the sound was sweeter" as anything more than a subjective assessment by A.K. and of no technical merit whatsoever in trying to evaluate any beneficial differences that the modifications might have produced. My apologies to A.K. To the technical side of things: I presume that the collector currents of the first stage (Q2 & Q3) remain unchanged in A.K.'s modified amplifier at about 860µA, so i'E will be around 30Q. By adding the 150Q emitter resistors, the gain of the first stage has been reduced by a factor of 6 (30n/(30Q + 150Q) = 1/6). By replacing the current mirror (D3, Q6 plus resistors) in the output of the second stage (Q4 and Q5), the gain of this stage has been halved and consequently the AC current in this stage must be doubled to achieve the same output voltage. This means that the second stage produces more distortion as it has to operate over a larger portion of its (non-linear) input/ output curve (transfer function). Also the fixed current source (Q6) of A.K. 's design has asymmetrical drive capabilities; ie, it can sink (probably) more than twice its quiescent current but it can only source a current equal to its quiescent current. What effect this will have I am unable to tell exactly from the comfort of my word processor but I cannot see it as an improvement on the pushpull arrangement of the current mirror load. So with these modifications to the first two stages, A.K. has probably increased the amount of distortion generated by the amplifier and at the same time reduced the open loop gain of the amplifier by a factor of 12 (6 in the first stage and 2 in the second) which reduces the amplifier's ability to reduce distortion through feedback. This is not the direction one would take to improve the performance of the amplifier. As to the suggestion that the apparent improvement in sound may be due to supply rejection (1st column, page 102), my reaction is also sceptical on the grounds that Q15 "measures" the voltage between Q4's collector and the positive rail, and if anything will probably degrade the supply rejection. I hasten to add that I have not analysed this aspect of the circuit and I am talking from gut feeling here. There is however some merit in A.K's .modifications, notably the attempt to match transistors. Unfortunately A.K. matches for hFE and I feel that a better approach would be to match VBE· According to Taylorl (p32), "matching of the collector currents .. . is essential to obtain the lowest distortion". Further, Taylor shows (in a graph on p31) that for an input sinewave amplitude of 2mV peak, a long tailed pair (such as Q2, Q3 and Q4, Q5 are) with only 20% mismatch in collector current produces about 0.2% harmonic distortion, while a long tailed pair with 0.6% mismatch in collector currents produces less than 0.02% harmonic distortion, an improvement of more than 10 times. This effect is reduced at higher input levels. Peter Baxandall2 has also contributed much on the topic of amplifier distortion, although he does not often refer to the long tailed, pair. So what does VBE have to do with collector current? If, for example, the second stage of the amplifier (eg, Q4 & Q5) has an input offset voltage of lO0mV, then the collector currents of the first stage will be mismatched by about 5% (1.95V/1.85V). If the collector resistors are also mismatched, the collector currents of Q2 and Q3 will be mismatched by a similar amount. Furthermore A.K's unusual feedback circuit around the first and second stages using Ql, Q15, LED 1 etc does nothing to balance the collector currents of Q4 and Q5. In fact, what that circuit does is match the collector current of Q4 to that of Q14 and to match the collector current of Q5 to that of Q6. Therefore, matching of collector currents in the second ·stage, and hence the second stage's contribution to the overall distortion of the amplifier, will depend mostly on the VBE match of Q6 and Q14. Although A.K. recommends matching the hpE 's of these two transistors, it will have little or no impact on the collector current mismatch. I could probably prattle on for pages more but really I have said enough. Thank you for publishing the item and for giving us the opportunity to comment. A.K. should be acknowledged for his contribution and should not feel discouraged from further experimentation. Phil Denniss Dept. of Plasma Physics University of Sydney References: (1). Eric F. Taylor, "Distortion in Low Noise Amplifiers", Pt.1, pp28-32 , Wireless World, August 1977. (2). Peter J. Baxandall, "Audio Power Amplifier Design", Wireless World, January 1978 to February 1979. APRIL 1990 5 Simple service tips for your • nncrowave oven Most people take their microwave oven for granted and never do anything to ensure that it is always working at top efficiency. In this article, we detail some routine jobs which will help you to get the most from your microwave oven. By LEO SIMPSON Why should you have to do anything to a microwave oven? After all, modern electronic appliances are very reliable and so you may feel well justified in not touching anything on your microwave oven, apart from giving it the occasional wipe over. The problem is that simple cleaning is not good enough. Essentially a microwave oven is just a big unfiltered DC power supply feeding a magnetron. And a magnetron can be regarded as a big thermionic valve which pumps microwave energy into the oven. Whenever the microwave is actually cooking THIS PHOTO CLEARLY SHOWS the difference between Pozidrive (left) and Philips head screwdrivers. The Pozidrive has extra flutes between the blades. 6 SILICON CHIP something, the magnetron is dissipating quite a lot of heat and that is removed by a ventilation fan. You can hear that fan running when you are using the oven. For that fan to work properly, all the vents in the rear and base of the oven cabinet need to be kept clear. If your oven has been in use for several years, you will probably find that these vents are clogged with grease and dust. It's easy to understand how the dust gets there - it is pulled though the oven by the fan - but how does the grease get there? It comes from the food being cooked in the oven. The ventilation fan which cools the magnetron also removes steam and fumes from food cooking in the oven. All these fumes are pulled right through the oven and vented out the back. So if you cook a lot of fatty foods and the food is not covered with some sort of plastic film then not only will grease be deposited inside the oven itself, it will also be deposited inside the enclosure at the rear and sides of the oven. Mix this grease with dust and you will find a pretty daggy mess in the vents of your oven. The problem is likely to be worse with ovens that are permanently installed in kitchen cabinetry, although ovens which sit on bench tops can be pretty messy too. So every few years or so, it is a good idea to clean all this mess out of the vents. This is best done with a vacuum cleaner, using the brush nozzle fitting. You can do most of this basic cleaning job without having to gain access to the cabinet. To do the job properly, though, you need to remove the outside casing of the oven. WHILE YOU HAVE THE OVEN casing off, it is a good idea to remove and clean the interior lights and the glass window. Dry them thoroughly before re-installing them. Now it might seem obvious, but the power plug must be disconnected from the power point before you even think of removing the screws. Microwave ovens contain a large high voltage transformer and capacitor inside. If you accidentally came in contact with live wires to these units, it could very easily be fatal. So disconnent the power plug from the power point. screwdriver which doesn't fit properly. In an extreme case, if the screws are very tight, you might damage the heads so badly that it won't be possible to remove them. We don't want that, do we? How do you tell a Pozidriv screw from a Phillips head screw? Our photographs show the difference. Unfortunately though, they don't tell the whole story. Crosshead screws from some Asian sources may look like Phillips head types but a Pozidriv screwdriver will be a better fit. Most hardware stores these days stock Pozidriv screwdrivers, along with their Phillips head types. Those made by Stanley have blue handles while their Phillips head drivers have green handles. The size to fit the cabinet screws of most ovens.are Phillips point 1 or 2 or Pozidriv point 2 or 3. For a comprehensive article on the many diverse screws and screwdrivers in use today, see "Screws & Screwdrivers: What You Need to Know" in the November 1988 issue of SILICON CHIP. Having removed the casing from the oven, you are likely to find more dust and grease inside. This should all be cleaned off as well as possible. But while you are doing that, make sure you don't disturb any of the wiring. Cleaning the lights To remove the screws from the casing of the oven, you need the correct screwdriver. Most likely, the screws will be a crosshead design but a Phillips head driver will not necessarily be a proper fit. They might need a Pozidriv (pronounced "pozzy drive") screwdriver instead. Because the screws are likely to be very tight, you are likely to damage the heads if you use a Many microwave ovens have interior lights although these are not in the oven itself. They shine through perforations in the oven wall and are further isolated by a layer of glass. As time goes on, you will find that these lights become more and more ineffective, particularly in microwave/convection ovens. Ultimately, you won't be able to see anything inside the oven, even though the lights are on. What happens is that grease circulating around the oven is progressively baked onto the lamps and onto both sides of the glass. This happens even in the most fastidious households so that even if the oven itself is kept spotlessly clean, the globes and glass will still have a coating of baked on gunk. COCKROACHES CAN CAUSE big problems in microwave ovens. The dark patch indicates where a cockroach has urinated on the PC edge connector, leading to erratic keyboard operation. A CLEAN-UP WITH A TOOTHBRUSH and some methylated spirits was all that was needed to cure the erratic keyboard operation. A squirt with silicone water repellant completed the repair. Use the right screwdriver A PRIL 1990 7 SUSPECT THE THERMISTOR IF the cooling fan runs continuously. It's easily removed for replacement by unplugging the leads and undoing two self-tapping screws. THE VENTILATION SLOTS in the back of the cabinet should be cleaned regularly so that the oven's cooling fan can work effectively. This is best done using a vacuum cleaner with a brush fitting. While it is usually possible to change the lamps from a compartment on the side of the oven, it is not possible to remove and clean the glass, unless the oven casing is removed as we have just described. Once you have the casing off it usually is an easy matter to remove the whole bracket which supports the lamps and glass. Be careful when removing the screws that you don't let the glass fall out and break. Give the glass and bulbs a thorough cleaning and dry them off before reinstalling them. fortunately, the place which is often the cosiest for a cockroach is just behind the vacuum fluorescent digital display or behind the keyboard. Sometimes they die there and that can spell a problem for the electronics. If the clock display on your microwave oven starts to dimly light segments which are not supposed to be lit or the keyboard starts behaving erratically, the most likely suspect is a dead c9ckroach. Inevitably, the cockroach will have urinated on the printed circuit board and the resultant leakage will cause the erratic behaviour of the keyboard or clock display. If left too long, this problem can also lead to severe corrosion on the printed circuit board tracks. The oven in our photos had this problem and the cure was to thoroughly clean the affected area of the board with a toothbrush and methylated spirits. If you have a can of CRC 226 or similar silicone water repellant, it is a good idea to give the affected area a squirt or two to seal it. This will help avoid a re-occurence of any "ghosting" of the clock display. One point to be watched in disassembling the oven's control electronics is to make sure that you note the position of every screw and cable connector. You will find that a variety of different screw threads and screw lengths will be used and it is almost impossible to keep track of where each screw goes. So make notes as you go. Better still, get a piece of white styrofoam and stick each screw into it as you go, and note where it came from. Removing the cockies Another prob!P.m which even the most fastidious households can suffer is cockroaches. And these little beasties love microwave ovens. Why? Because they have nice litte niches which are warm and cosy. Un- Thermistor replacement BE SURE TO NOTE the position of every screw and cable connector when disassembling your oven. Check that the power plug is disconnected from the wall before you begin work. 8 SILICON CHIP The oven in our photos, a combination convection/microwave type, has also had a recurring fault with the temperature thermistor which controls the fan. It monitors the temperature of the cooling air and causes the fan to run until the oven cools down. When the thermistor fails, the fan runs continuously. The cure is simply to replace the thermistor, as shown in one of the photos. Lightning protection Before we conclude, we should say something about lightning protection. Because microwave ovens are usually permanently powered and they contain sensitive electronic components, they are . particularly prone to damage during thunderstorms. This is due to high transient voltages caused by nearby lightning strikes. Now most microwave ovens these days incorporate surge protection components and these will be sacrificed if a voltage surge occurs. The problem is, if such damage occurs the microwave will not work afterwards. It will have to be repaired at a cost of somewhere between $50 and $100 and perhaps a lot more if the damage has gone further than the surge protection components. Many areas of Australia have had very severe thunderstorms in the last few months and if the present trend continues, we are likely to have many more. Therefore, if a thunderstorm is coming your way, it is a good idea to disconnect your microwave oven (and any other electronic equipment such as VCRs, computers and TV sets). Sure, the surge protection components will work but why put them at risk? For the same reason, if you are going away for the weekend or a longer period, disconnect your microwave oven and any other electronic equipment. ONCE THE CASING HAS been removed, it is a good idea to vacuum out the interior of the oven to remove dust and foreign bodies. Take care that you don't damage any parts or wiring during this process. ANTRIM That way, you don't have to worry about thunderstorms while you are away. For more reading on the subject of lightning damage to electronic equipment, see this month's article in the Serviceman and an article entitled "Lightning! How To Protect Your Electronic Equipment" in the February 1989 issue of SILICON CHIP. ~ TOROIDAL TRANSFORMERS General Construction OUTER INSU LA TIO N - OUTER WI NDI NG - WI NDING QUALITY TOROIDAL POWER TR ANSFOR ME RS, MANUFACTURED IN U.K. NOW AVA ILABLE EX-STOCK AT REALISTIC PRICES. INSUL AT ION - INNER W INDING - CO RE: INSULA TIO N TAX PAID PRICES 15VA 30VA 50VA SOVA 120VA 160VA 225VA 300VA 500VA 625VA 1- 9 32.80 36.00 38.50 41 .75 44.95 55.70 62.00 72 .80 100.00 112.00 Enquiries from resellers and OEMs welcome. Quantity prices and data sheets available on request. Distributed in Australia by Harbuch Electronics Pty Ltd , 90 George St., HORNSBY, NSW, 2077 Phone (02)476-5854 Fa x (02)476-3231 APRIL 1990 9 EASTER SPECIALS Vary Latest IC TachnolOJY Optical Motion Detector HURRY, WHILE STOCKS LAST! Walkabout Wadio Why build yourself an AM radio? Just for the fun of it! This portable radio kit puts the life back into AM reception. cat K-2720SA --VE-a=VE=R=-;$.;1iii"0I Use as part of an alarm or as a door minder, etc. A special optical IC actually detects movement by chan~e in light ,, level. Two modes - guide' for sensing movement, and 'search' Cat K-2121 for be_am cutting operation. Self-SAVE OVER contained (battery operated). s149s _ 2495 $15I $ NEW KITS SOON TO BE RELEASED! Converter For The 144 - 148MHz Band Here it is - Our first innovative converter module, now making it possible for you to receive the 2m amateur band on a 50-54MHz receiver, and it easily -incorporates into our 6m FM receiver (K-6005)! It even lets you monitor the 144-148MHz band -Changing bands is simply a matter of flicking a switch! And talk about saving money!!! The Converter not only saves you the cost of another box (an expensive item nowadays!), but it works out much cheaper than having two separate recievers for each band! Short-form kit with PCB and components. 1111------•--r Cat K-6006 -<at> March'90 The Thinking Man's Battery Charger! New & clever 6/12 volt SLA (sealed lead acid) battery charger! Apart from having four LED indicators and five switchable charge rates, there's something quite unique about it; it continuously monitors the ba~ery voltage, and then a~to~atically adjusts the charge rate to suit! Unfortunately, most existing battery chargers do not charge a You'll be suprised at how a unit this compact, can be so amazingly battery at the correct current OR the correct voltage. Furthermore, highly-efficient! The new:t,50V, 1.5 AMPS Dual-Tracking Power Supply I they continually belt current into the battery, whether it's fully Kit is capable of delivering OVER 130 watts at substantial current, charged or not {doing considerable damage to the batteries & greatly making It useful for testing your amplifiers! You'll even find it handy shortening their service life) and don't provide an 'end-of-charge' for very low voltage or modern single cell operated circuits, and quite conditionf Our charger however, maintains the battery at a constant invaluable for most laboratory applications. Full-form kit, complete float voltage once it has been fully recharged. This means it can with case, transformer, front-panel label and all neccessary remain connected to the battery indefinitely and still keep it in peak components. Top features! condition! Short rorm kit with all components, hardware and front eat K-3465 =-~!Ck Apr'II . panel label. Case (H-2812) & Transformer (M-2000) not included. 90 fB:JiJI'. Af!i Cat K-3220 Dual Tracking Power Supply fJf!/1'i.· ~ O>XPRESS PHONE & MAIL ORDERS PHONE ORDERS Outside Sydney: 'Local Call Fee Only' (008) 22 6610 Sydney Customers and Enquiries: (02) 888 2105 Fax: (02) 805 1986. MAIL ORDERS: DS XPRESS, P.O. Box 321, Nth Ryde NSW 2113 March '90 PLEASE CONTACT YOUR NEAREST DICK SMITH ELECTRONICS STORE FOR THE PRICE AND AVAILABILITY. VGA Multi-Scanning Colour Monitor rr~ c._ !___~- Extremely versitile multi-scanning monitor with analogue and digital inputs - suits CGA, HGC, EGA, VGA. Resolution: 800 x 600 Band width : 35 MHz H. Freq : 15-36 KHz V. Freq : 45-90 Hz IBM AT Compatible 80286 Motherboard ~~~ Building your own computer or upgrading the old one? Our new 12MHz motherboard is the way to go for the ultimate computing · power. DRAM not included. Just take a look .. . • Expandable to 1Mb using 256K chips • Expandable to 4Mb using 1Mb DRAM chips • Keyboard or hardware selectable 8112MHz operation • Six 16-Bit and Two 8-Bit expansion slots • Selectable for RAM speed - 80 or 100 nanosecond • Selectable from Owait states on read operations (with 80 nanosecond RAM) • Socketed for 80287 Co-processor • Performance - 13. 7 using Norton S.I. • Battery backed real time clock on board • AMI Bios ROM 's included • OK RAM supplied _., s999 VGA Graphics Adaptor Cat X-2410 Perfect for AutoCAD, games, text, paint programs, graphics, charts, desktop -publishing! Fits any IBM Compatible (XT or AT). Includes utilities for emulation of EGA, Hercules and CGA. With an astounding array of graphics modes! Comes with drivers and manual. 8 Bit Version . $249 CatX-2018 XT Prototype Card Buy Both For Only $999! A veroboard on an XT compatible expansion card. Complete with interrupt and memory addressing circuits already installed to enable easier construction of more advanced project ideas. With comprehensive manual. Add $50 for 16 Bit VGA Adaptor. Cat X-2019 Cat X-2034 The Speech Thing 'Speech Thing' is a complete hardware and software package which adds sound capability to your PC. Converts text, either from keyboard or ASCII files, to high quality speech. Installation is as easy as plugging Speech Thing into the parallel port - and it doesn't interfere with its operation . Can be used in conjunction with the 'Voice Master' (X-2038) to sample and ed it digital sounds. Cat X-2036 sagg Cat X-1002 $ 14 9 s149 Disk Drive Power Splitter Cabla ',s a _ 0 0 ° RS232 Loopback Tester RS-232 Serial Jumper Box 25 pin male and 25 pin female connectors. With jumper pads and wires which allow permanent soldering for RS-232 connections. ~·;;:5. A great idea! The 'Y' adaptor allows you to connect two disk drive to one power connector. Spills a 4-line Molex male into two females. $ Used for diagnostic testing of RS232 circuits. The tester consists of 4 LED's which monitor lines 2 to 3, 4 to 5, 6 to 20 and 15 to 17. Acts as a data verifier by sending data back to the transmission device. Includes male to female DB25 connectors. .. .. ~ ~====:f 1 695 Cat X-2604 3.5" Disk Drive Power Adaptor Cabla For IBM PC/XT/AT and Compatible Computers • Allows connection of standard 3.5" disk drives to the IBM PC/ XT/AT or comp. pwr. supplies. $695 Cat X-2605 Floppy IDC Universal Data Cable A floppy drive data cable which is fitted with both Ed9e and DIL socket connectors. Facilities the easy fitting of both 5.25" and 3.5" floppy di'ik drives. Cat X-2651 s1995 $1 995 Cat X-2606 Disk Notchar Gives you extra disk space on your Apple II or CAT computer. The disk notching tool allows you to use both sides of a disk in a single sided disk drive. Easy to ~!~x-3so4 ,____ sg 95 ~ Anti Static Wrist Strap A must for wh en installing expansion cards or changing memory chips. Stray static charges can destroy chips in an instant With adjustable fastening , coiled ground lead and high value series resistor for added safety. Cat X-2042 $1495 3-Way Switch Boxes A great idea! The switch box allows switching of a common input or output to any one of three other devices. All lines are switched. Ideal for sharing a printer or modem with ------------ -- --- . more than one computer or connecting several printers to one Centronics port. 25 Pin with DB25 Connectors. Cat X-3575 36 Pin with Centronics Connectors. Cat X-3576 LCD Multimeter Cap/ Transistor Checker sgg Not just the usual voltage, current and resistance ranges - through it'll certainly got those - it also checks capacitors (2 ranges, up to a whopping 20uF) PLUS transistors and diodes. And even more: It's got an audible continuity checker. Plus other features - such as automatic zero of all ranges, high surge voltage protection, automatic overrange indication, high current measurement (1 0AC & DC) etc. etc ~ makes this the one about everything with! Looks like you'll have to check it out! d stock Cat a-1500 sav8 $20 Safety Yellow 3.5 Digit with Tr, Diode & Continuity, plus Battery Checking IPMMl 1!..·-□ •-.,-=;',a ~_!~ i - , ijl ~'. lltot~;:•• .i llff ..•-t1 . iai ZI 0 ®{f-,,~ _,:® ~i'-· ~ ., : ~ M:tl'i5Mi5H s7 9 95 At last! Someone's got away from basic black or basic grey in a multimeter! This one has all the usual ranges, including current to 10A and resistance to 200 megs, but it also has a continuity checker with a fast 1OOms response time, a diode and transistor checker, plus a battery checker - it tests under actual load conditions. It takes a sinqle 9V battery (and tells you if it's low) and comes complete with a flipdown handle that doubles as a stand . L1mlt 9 Multimeter with Bargraph & Frequency '1 -----.. I ! cat a-152s I ,., "cl'JM vrn ll!!:i!________ - Universal Panel Maiers cat a-2200 Features: Single supply rail (9V) Low supply current (2mA max) High accuracy (.01% 2 digits) Auto zeroing and overrange inbuilt Meter size : 71 x 46 x 21mm Cat Q-2045 s5995 Cat T-4505 .• ----==ex,===, ~-, Push-Action Screwdriver Sat Features clockwise, anti-clockwise and fixed direction selection. Comes complete with 6 x 4mm flat heads, nos. 1 & 2 Phillips heads plus hole reamers (2 & 2.8mm). All bits are conveniently stored in the handle. - ~--E MAJOR DlCK SMITH AUTHORISED STOCKISTS: N.S.W.: ARMIOALE: New England Elec troni cs 711655 BALLINA: Ballina Electronics 867022 BOWAAL: F.R.H. Electrical 611861 BROKEN HILL: Hobbies& Etcctronics 884098COFFS HARBOUR: Coffs Harbou r Electronrcs 525684 OENILIQUIN: Dern E!cctronics 813672 OUBBO: Chris's Hi F1 828711 FORSTER: Forste r Village Electronics 545006GLEN INNES: John Sornmer lad Electr onics 323661 GRAFTON: Repairs and Spares 421911 GRIFFITH: M1a tron1cs 624534 INVEAELL: lnvcrell Elcc 1ronics 221821 LEETON : Lecton Aud1 otronics 532800 LISMORE : Dc cro E!cctrornc Services 214137 MOREE: Moree Electronics 523458 MUOGEE: Head wa rc 723895 NARAABAI: Na mor Comp uter Servi ce 923274 NOWAA: Nowra 2 ~~~~r;~cic2~3~ WTe;~~ ~:Cf~~;~css s~~dG~~Sl~iG~rX: ~h~~,~ ~ 1 - - -Electr onics 216558 VASS: Warmington Electrica l 261 l 16 VIC: BAIANSOALE: LH & LM Crawford 525677 MILOUAA: Pullman Auto Pro 232882 MOAWELL: Morwef! Electronics 346133 SHEPPARTON: Andrew Guyatl Electr onics 219497 WARANAMBOOL: Marr!rorncs 629870 QLO: AYR: Della Electrix 831566 BUNDABERG: Bob Etk,n Etcctr on,cs 721785 MACKAY: Stevens Electronics 511723 MARYBOROUGH: Keller Ele ctron ics 214559 PIALBA: Keller Elect ronics 283 749 TAS: BURNIE: El ectronic City 314760 OEVONPORT: A.I.Elcc tron1 cs 248322 SA: MT GAMBIER: Hutchcsson's Com muni ca 11on Centre 250400 POAT LINCOLN : Bass hams TV & Com puter World 822788 WHYALLA: Eyre Etcctr on1cs 454764 WA: ALBANY: Micro Elec !r on1cs 412077 BUNBURY: Micro Electronics 216222 GEAALDTON : Batavia Lighting & Elec tri cal 211966 KAARATHA : Daves Osc11r on1 c 854836 MANDUAAH : Mrc ro Electr onics 581 2206 t,ii~7n~;~~~~t;~4 1 :1~~i~~!:t~:6~t~ $1695 Designed to suit the above panel meters. Comes with shunt resistors from 1.1 to 1,000,000 ohms, resistance wire and instructions. $195 Cat 0-2046 T-Bar Magnetic Screwdriver The T-bar handle. Lets you get plenty of grip. Comes with 6 magnetic bits - 2 Phillips heads. 2 flat blades and 2 Torx bits. Bits are stored in handy plastic holder. Ca~T g;5 • ! ;;z:: $995 Screwdriver Bit Set Includes a ¼" magnetic bit holder, 2 Phillips heads, nos. 1 & 2, 2 flat blades (4.5 & 7mm), and 2 Pozidriv bits, nos. 1 & 2. Cat T-4518 - s2195 Shunt Pack sges , ,, Cat T-4512 .. Dimensions: Scale Area - 96 x 82mm Mounting: Hole Required: - 65mm Bolt Holes - 64mm x 80mm centres CatC-2065 Cat T-4500 ~ Large A fully insulated, screwdriver set with 6 bits and magnetic heads. With 4.5 & 6mm flat blades, Phillips heads nos. 1 & 2 and Pozidriv heads nos. 1 & 2. 5 Bit Screwdriver Small Dimensions: Scale Area - 55 x30mm Overall - 55 x 52mm Mounting: hotd Required 45mm Bolt Holes - 38mm square A quality 5-piece screwdriver set which is fully insulated and actually holds the screws. Comes with 3 flat blades - 5 x 150, 4 x 125 and 3 x 125mm, and 2 Phillips heads nos. 1 & 2. •u= y Comes with 3 flat blades (1.2 x 6, 6.5 & 7mm) and 2 Phillips heads (nos. 1 & 2). All bits fit neatly in the handle for easy storage and carrying. e $30'• Universal 1OOuA panel meters that can be easily adapted for just about any situation -Volts, Amps, mA ... anything! There's two sizes to choose from so you can match all your equipment. Magnetic Screwdriver Sal s2595 $14 9 3.5 Digit LCD Panel Matar lnsul-Holding Screwdriver Sal ~ Just look all these function ... • Automatic overload indication • High surge voltage protection (1.5KV -3KV) • Capacitance measurement • Diode and continuity • Transistor hFE test • Frequency measurement • Has bargraph 58V 'Full Scale' of 200mV or 2V (user selectable) and a super high input impedance (100 megaohms) mal<es adaption to a range of applications very simple. The meter can be seff mounted - includes a mounting bezel. save $5! cat0-1445Llmited Stock Call-4395 Includes Trans, Continuity & Capacitance. A fantastic all rounder for hobbyists, technician and service people alike. Both digital and bargraph displays give you the best of both worlds. Large 30 position rotary dial for function and range selection makes it quick and ~ to use. - - - - - -. . $395 The Hot Canaries! Touch Lamp Dimmer Extension For Touch Lamp A novelty kit for the beginner or hobbyist who likes to have some fun. Kit produces sounds of 2 singing birds. Comes complete in full form and with all components including front panel label, case, battery holder, speaker and IC sockets. This unit can turn your light on and off or dim them just by touching the decorative plate. Unit is intended for dimming incandescent lamps rated from 25 watts up to a total of 300 watts. Cat K-3530 Cat K-3001 Do you have a two-way switch in your home and would like them replaced with touch dimmers? We have just the thing for you . An extension touch plate is connected in parallel to the K-3001 main unit, so that you can switch your lights on and off or dim them remotely. ~1/!t&,~ ED'JJ 5-1/1[,{tj,' Feb '90 H'J}dll I Cat K-3002 §..1/ltf,{tj~ ~J'JJ · s24ss s14ss Zaner Diode Tester A handy device that's essential for the· service bench or the hobbyist. Allows you to identify all those diodes where the markings have rubbed off. You get a direct readout, in volts, of the Zener voltage of 400mW and 1W Zeners from 3.3 to 50 volts (2 ranges). Supplied with prepunched front panel. Cat K-3051 Ell Aug '87 s39ss The DSE Variable Power Supply Kit Simple FM Transmitter For The 2Mland Ideal for the service man, hobbyist, amateur, student etc. - everyone should have one. Simple to construct. The first in a great new series of easy to build projects for the amateur radio enthusiast. The solid state NBFM transmitter module produces over 1 Watt at 144MHz. The oscillator frequency, around 24MHz, is multiplied in two stages, first a tripler ... then a doubler to 144MHz. The resulting signal is amplified through several stages before being fed to an antenna. Short form kit contains components and PCB. Cat K-6010 <at>Nov'89 Fe1tu11s: • Variable 1.5 Volts to 15 Volts DC • All necessary parts supplied included plug pack • 500mA continuous • Pre-punched silk screen front panel • Overload protection • Housed in attractive compact case • No mains wirinQ required • No drilling required£). Cat K-3200 July '89 ~ Sophisticatsd SBcurity For Your Homs Alarm/ Alarm Phone Dialler Designed by Dick Smith Electronics research and development department! Phone diallers are a great idea but, until now, they've been prohibitively expensive. So here it is! The phone dialler that is not only inexpensive and easy to install but can be fitted to just about any home alarm system with a 5V-25V output (bell/strobe output). Look what it does ... All you do is program a telephone number into the Phone and it rings you (and emits a tone) to tell you your alarm has been triggered. If you're away from home (on holidays, etc.), you can phone home and the Alarm Dialler will tell if your alarm has sounded. That means peace of mind no matter where you are. NOTE - no permit is in force authorising the connection of this unit to a public telecommunication network. featullS • Comes with pushbutton Telephone • Plug Pack included • Battery back-up capability (battery not included) • With pre-punched front panel and case • Fits most alarm systems (with 5-25V output) • Test facility • Trip LED Cat K-8300 Easily Affordablsl - July '89 s799s ~J!J;i!.L~ ~!fJ'JJ- Sep '89 s59so s39ss Bike Alarm An effective Motorcycle Alarm designed for maximum security at a reasonable price! Easy to build and install - even if you don't know much about electronics! Features LED alarm indicator, auto reset and provision for external sensor switches (mercury switch supplied). Connect it to your existing horn or to a siren. Suits all 12V systems, can be armed by toggle or keyswitch (Latter Not Supplied) and it's mounted in a ~ - compact Zippy Box. Comes complete with Micro Siren . _ Cat K-3249 $ 46 SS - Vehicle Exhaust Monitor This unit can be installed in your vehicle and will detect any carbon monoxide gases which may seep through into the cabin from your vehicles exhaust. Driver will be alerted either by a flashing led or an audible alarm. Cat K-4610 ~J.!l!f!}~ July '89 ~!i,'JJ . s59so w··= =====~ 0 " ~ l , I UWJST/'"DtilJT0 11 o - .. ., 3 WHO FRAMED THE EASTER BUNNY? HIGH PERFORMANCE LOW COST 19" Zip Rack 420 Series The unique interlocking assembly system using black corner connectors provides a self-aligning, rigid frame. Front and rear face riveting option for extra strength when required. Ready to assemble. 6 rack sizes. Optional covers. Low cost. RACK RACK CODE SIZE HEIGHT O/A COVER SET PRICE CODE PRICE H2380 H2382 H2384 H2386 H2388 H2390 358MM 625MM 893MM 1158MM 1425MM 1870MM $129 $139 $149 $179 $199 $259 H2381 H2383 H2385 H2387 H2389 H2391 $59 $69 $89 $119 $139 $159 6U 12U 18U 24U 30U 40U 'Horwood' Instrument Cases K& WInstrument Cases Favourites of hobbyists and professionals around the world - Horwood cases feature removable front and rear panels, lids and front-mounted handles to make them look really professional. These sturdy cases are made with aluminium bases, steel top covers with hammer tone finish and recessed, satin finished front panels. Available in many sizes: H2453 H2454 H2455 H2456 H2457 8x4x6" 8x4x8" 8x4x10" 8x4x12" 8x4x17" $39.95 $42.95 $45.95 $49.95 $56.00 H2462 H2463 H2464 H2465 H2466 9x3x6" 9x3x8" 9x3x10" 9x3x12" 9x3x17" $36.95 $39.95 $42.95 $45.95 $49.95 Dimple feet pressed into base: H2802 150 x 52 x 100mm. $12.95 Bolt-on plastic feet (nuts & bolts incl.): H2804 100 x 77 x 130mm $13.95 H2806 200 x 65 x 130mm $15.95 Slotted vents in top & end panels. Bolt-on plastic feet (nuts & bolts incl.): H2808 255 x 77 x 155mm $18.95 H2810 255 x 150 x 155mm $25.95 H2812 305 x 90 x 200mm $25.95 H2814 305 x 200 x 165mm $29.95 DIC Utilux/Molex Nylon Pin And Socket Connectors Used throughout the world for a wide range of applications from appliances, television and electronic games to business machines and computers, Utilex/Molex pin and socket connectors have long been considered a standard of the connector industry. Both plug and socket halves are supplied in each pack, complete with terminals. Our crimp terminals are for wire to wire applications, where the terminals wilr be crimped directly to the wires. The solder tail versions (P-5100) are made to be inserted into the connector and then soldered directly to the P.C. board. P-5103 ~~ P-5105 P-5112 0 P-5109 000 000 000 0 0 0 000 000 000 · ~~ 1. 2. 3. 4. 5. 6. 7. P5100 P5102 P5103 P5105 P5106 P5109 P5112 Mu.A■ps. 6 male/6 female 2 way 3 way 4 way 6 way 9 way 12 way 12 12 12 9 .. 9 9 7.5 Price $2.95 $1.95 $2.50 $2.75 $3.50 $4.25 $4.50 Cllew Red Gin/Red Red/CLR Red Green Yellow ~nge Green Yellow ~nge Green Yellow Green Yellow SECURITY AUDIO COMPUTERS For indoor use. Colour: natural:- For outdoor use. Colour: black :- H1974 100 x 2.5 MM PKT 100 $5.115 H1976 200 x 2.5 MM PKT 100 $8.115 H1978 300 x 3.5 MM PKT 100 $14.95 H19ao 100 x 2.5 MM PKT 100 $41.95 H1982 200 x 2.5 MM PKT 100 $9.95 H1984 300 x 3.5 MM PKT 100 $15.95 This range of cable ties is a development of the standard range combining all their advantages and strength with the additional feature of a moulded-in fixing head. The tie can be secured to a panel using no extra components other than a single bolt. H1986110 x 2.5 MM PKT 100 $22.95 H1988 160 x 3.5 MM PKT100 $24.95 H1990 215 x 4.6 MM PKT 100 $26.95 Genuine US~GAfrFA(tTape But you'll find a million and one uses for GAFFA tape around the home, workshop ... anywhere! You'll find a great range now at your nearest Dick Smith Electronics store. Heavy D1ty Black/Silver Sticks to almost anything and anywhere. Easy to remove, long wearing. 25 Metre Roll. Black Cat N-1400 $9.95 40 Metre Roll. Black Cat N-1405 $15.95 25 Metre Silver CatN-1410 $9.95 DelighHul Lads Red PHONES Standard cable ties are one-piece mouldings in tough, flexible nylon 66, immensely strong and virtually indestructible. The non-return Cam-action locking device ensures that the tie will neither slacken nor come off. 000 Plating:This brass alloy material is tin plated prior to forming and will meet most applications. Resistance:MV voltage drop per amp, +/- 10% 1st engagement 3.0, 10th engagement 3.1. High Voltage Test:Withstands 1500 volts RMS applied between adjacent terminals for 60 seconds mounted in ail housings. Current Rating:Amperage rating up to 12 amps on some sizes. (See below) """' ""' P-5_100 Ordering Information Cat. Ne. Cll"Cllls Cable Ties Sin Cal NI. 5mm diam 5mm diam 5mm diam 3mm diam 3mm diam 3mm diam 3mm diam 5mm diam 5mm diam 5mm diam 5mm diam 2x5mm 2x 5mm 2x 5mm 10mm diam 10mm diam 10mm diam Z-4000 Z-4070 Z-4075 Z-40TT Z-4079 Z-4081 Z-4083 Z-4085 Z-4087 Z-4089 Z-4091 Z-4093 Z-4095 Z-4097 Z-4060 Z-4061 Z-4062 l'rtcl EA 1.95 -~ $1.75 .35c .35c .35c .35C .50c .soc .50c .50c .ooc .ooe .ooc -~ -~ .95C l'rtcl 10., 1.85 -~ $1.65 .30c .30c 30c .30c .45c .45' .45' .45' .55c .55c .55c -~ --~ ~ 25 50 40 40 40 40 40 40 40 40 40 40 40 30 30 30 5 1.7 2.1 2.1 2.1 2.0 2.1 2.1 2.0 2.1 2.1 2.1 2.1 2.8 2.8 2.8 1.2mCd 200mCd 3.5mCd 5.0mCd 5.0mCd 7.0mCd 4.0mCd 6.0mCd 6.0mCd 9.0mCd 1.2mCd 1.2mCd 1.2mCd 10mCd 12mCd 12mCd Flashi~ Two Co our High Intensity Premium Quality Premium Quality Premium Quality Premium Quality Premium Quality Premium Quality Premium Quality Premium Quality Reel. Prem. Qual. Reel. Prem. Qual. Reel. Prem. Oual. High ln19nsity Premium Quality Premium Quality • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 3871444 • Campbelltown 27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Kotara 56 2092 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde 878 3855 • Parramatta 689 2188 • Penrith 32 3400 • Railway Square 211 3777 • Sydney City 267 9111•Tamworth661711 • Wollongong283800• ACT• Fyshwick8O4944• VIC• Ballarat315433 • Belmont438522• Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 and 246 Bourke St 639 0396 • Richmond 428 1614 • Ringwood 879 5338 • Springvale 547 0522 • QLD • Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Red bank 288 5599 • Rockhampton 27 9644 • Southport 32 9033 • Toowoomba 38 4300• Townsville 72 5722 • Underwood 341 0844 • SA• Adelaide City 223 4122 • Beverley 34 7 1900 • Elizabeth 255 6099• Enfield 2606088 • St. Marys 277 8977 • WA• Cannington 451 8666• Fremantle 335 9733 • Raine Sq 481 3261 • Midland 250 1460 • Perth City 328 6944 • TAS • Hobart 31 0800 • NT • Stuart Park 81 1977 ORDER BY PHONE OUTSIDE SYDNEY (008) 22"10 Free Call Sydney Area 188 2105 The Largest Australian Electronics Retailer! 63 Stores Across Australia VINTAGE RADIO By JOHN HILL • Finding receivers from the 1920s Radio receivers from the 1920s are very collectable items but are now becoming hard to find. However, there are still a few treasures to be found out there if one is in the right place at the right time. The term "vintage radio", as far as I am concerned, refers to old valve-type radio receivers. In covering this subject so far, the radios I have chosen to write about have mainly been from the 1930s and 40s era. This period of time produced some interesting and well made receivers and these sets would make up the bulk of most collections. The period prior to 1930 is another matter. Radios made back in that particular era would have to be referred to as truly antique radios for they belong to another world. The year 1923 saw the beginning of broadcasting in Australia and the surge of interest it created was astonishing to say the least. The receivers used in the mid 1920s were unique because they were in vogue only for a very short period of time. Once the mains operated superheterodyne receiver became established in the late 1920s and early 30s, the old style battery operated reaction sets with their harsh sounding horn speakers quickly fell from favour - and no wonder! However, when it comes to collecting; it is these old sets from the This Amplion cone speaker was the latest thing in the late 1920s. Unfortunately it no longer works and needs repairing. 1920s that are the really collectable ones. Despite their age, the problems associated with operating battery receivers and the scarcity of old triode valves, any set that pre-dates 1930 is a collector's gem and is worth having regardless as to whether it is in working order or not. The trouble is, very few of these old receivers have survived the purges of the rubbish tip brigade. They are not only almost impossible to find but if they are found they will cost quite a few hundred dollars a piece. What's more, there is every likelihood that the set will not work and has been separated from its original loudspeaker. Antique shops A typical mid 1920s radio receiver. This unrestored 5-valve neutrodyne is a home-made effort, built by the late George Irvin about 64 years ago. 16 SILICON CHIP One occasionally sees an old radio or an old speaker in an antique shop, but nearly always as separate items. Rarely do two matching units stay together. A Celestion cone speaker. The tone of these speakers was supposed to improve with age - a claim that is difficult to substantiate. Many months ago I made the comment in this column that it pays to let others know of your interests as this can alert a whole army of people who will contact you if they find something interesting. In my case, all of my friends, relatives and acquaintances keep a look out for me. In addition to this, public displays of my collection have also lead to some interesting finds. My $2 neutrodyne Only a few months ago I received a phone call regarding an auction sale. There was supposed to be an old speaker amongst the goods being auctioned, so off I went with great enthusiasm. A dozen old triodes in usable condition is always a good find but these even came in an old Browning Drake coil kit box. The information was correct lot 107 was a large Brown horn speaker of about 1926 vintage. Looking around I found that lot 63 also held a bit of interest for me it was the receiver that originally went with the Brown horn. The receiver was a five valve neutrodyne TRF with three tuning dials on the front panel. Unfortunately, the front panel was made of three ply which had become wet at some time and the layers of ply had separated. Otherwise, the set was complete, valves and all. "What am I offered for lot 63?" the auctioneer asked. "Will anyone offer me $20?" "Will anyone offer me $10?" "Will anyone make an offer?" "Two dollars", was my reply. As there were no further bids, I purchased my TRF receiver for the said amount. Lot 63 also included a substantial wooden box containing a lady's handbag and five one gallon cans for which I was offered a dollar, thus making the old five valver the best buy I ever have made. To cut a long story short; the horn speaker attracted a few more bidders and I was run up to $14 before it was mine. Considering the fact that the speaker was in working order and the flare was not dented, I felt that I did fairly well at that particular auction. It is a matter of being in the right place at the right time and having a few friends who will pass the message on when they see something of interest. TRF Radiola This 4-gang brass tuning capacitor is from an old TRF receiver. The unit was obtained complete with a gear driven dial mechanism (at right hand end). Once, my wife received a phone call regarding an old radio and took down the details in my absence. The caller's neighbour had recently seen one of my vintage radio displays and had passed the information over the side fence that I was interested in buying old radios. Usually such phone calls lead to a "Little Nipper" or the like with a cracked cabinet and missing knobs, but not this time. APRIL 1990 17 These three matching dials are off an old TRF receiver. Items such as these can help rebuild incomplete or damaged receivers. More miscellaneous bits and pieces from the past. Included are tuning capacitors, headphones, various coils and a horn speaker. This particular receiver was a 4-valve Radiola, a TRF set of 1930 vintage. Although the set was a bit shabby and not in working order, it was complete and restorable. It is also mains operated which makes it a more attractive proposition than the battery operated sets of the mid 1920s. The old Radiola also had a more expensive price tag than the neutrodyne mentioned earlier and it cost me $50. Every time I buy a genuine antique radio, I always get the feeling that it must be the last one I will 18 SILICON CHIP ever find. If you have spent any time looking for radios from the 1920s, then you will know the feeling I am talking about. Most of these early receivers have either been dumped at the tip or adorn someone else's collection. But no matter how disheartening the task may be, keep looking, for there are still a few out there to be found. Deceased estate Only last week I received a phone call from a small country town approximately 250km away which just goes to show how the word gets This large unrestored table model Radiola is of 1929-30 vintage and shows the trend at the time to bring receivers and loudspeakers together in the one cabinet. Receivers from the pre-1930 era are very collectable items. around. It was about a quantity of radios and radio parts from a deceased estate. On inspecting the radios I can only say that I was pleasantly surprised. Walking into the room where they were I immediately noticed four mid 1920s receivers on a dusty shelf with a large Amplion speaker (early cone type) sitting on the largest of them. It is indeed hard not to get excited and show too much enthusiasm when inspecting such treasures. Apart from the old radios, there were heaps of useful radio parts, plus other miscellaneous bits and pieces. A cardboard box of old triode valves looked particularly interesting, as did several larger boxes of valves of more common varieties. There was also a set of three matching dials from an early receiver, as well as half a dozen other early dials. Other items that caught my eye were a four gang brass tuning capacitor from some old TRF set and an Emmco "B" battery eliminator that appeared to be in good working order. There were also many smaller items such as high voltage capacitors, wire-wound resistors, dial lamps, valve sockets, rolls of cotton covered wire, Bakelite coil formers, rheostats and wire wound potentiometers - all the things a vintage Resurreetion Radio The original vintage wireless specialists Our skilled technicians offer QUALITY repairs & restoration . We have a large stock of bakelite and timber radios fully restored and for sale. Valves, high voltage capacitors and other specialised parts available. Another unrestored "coffin" type wireless from the 1920s. This particular TRF set can tune in six different wave bands and would have been a high class receiver in its day. It is a 5-valve battery set made in Australia by Udisco. radio enthusiast can eventually find a use for. All this equipment had belonged to George Irvin, an 82-year old who had spent his younger days experimenting with radio. It was fairly obvious that he had thrown nothing away during his lifetime. Apparently, he had one of the first radio receivers in the district, a 5-valve set which he built himself. This Brown horn speaker was bought at auction for $14. Although the paintwork has become shabby, the speaker is not damaged and is in good working order. It was a real treasure chest for someone like myself but I was disappointed to discover that I could only tender for the radios and parts and would be notified if mine was the successful bid. It is this type of treasure trove that is becoming more difficult to find. Perhaps in another 10 years or less, all the old guys with these old radios will have all passed on and the supply will suddenly dry up. In today's throwaway society where Mr Average shifts his abode every eight years, things like antique radios do not survive that type of lifestyle. Anyway, I am pleased to relate that my tender for the old radios was accepted. Possibly, it was the only one? Now those antique receivers are part of my collection and that also includes all those useful bits and pieces. No doubt some future vintage radio story will deal with some of the restoration work on these ancient radios. Although radio receivers from the mid 1920s are not very listenable with their metallic sounding horn speakers, this type of material is extremely collectable. A few sets from this era, together with their odd looking speakers, will give an interesting balance to any vintage radio collection. ~ SPECIAL - this month only: . 630V Polycaps 0.1 and 0.22µF $1.00 ea. .033 and .047 µF 0-75c ea .. 01 and .022µF 0-50c ea. Plus p&p. WANTED - valves, radios, etc., purchased for cash. Call in to our showroom at: 51 Chapel Street, Windsor, Vic 3181 PO Box 1116 Telephone: (03) 529 5639 ACTIVE SHORT WAVE ANTENNA TECHNIKIT AT4SW (SEE SC JAN '90) 't COMPLETE KIT $59 BUILT and TESTED $119 (BATTERIES INC) CASE $10 LOOP ANTENNA 0 TECHNIKIT PX1 COMPLETE KIT $44 BUILT and TESTED $69 (SEE SC JUNE 89) Improved signal strength & signal quality in a portable tunable antenna. PACKING & POSTAGE IN AUSTRALIA INCLUDED IN PRICES QUOTED. WRITE OR RING FOR BROCHURES ORDERS ACCEPTED ANYTIME PAYMENTS BY BANKCARD, VISA, MASTERCARD, CHEQUE or MONEYORDER TRADE ENQUIRIES WELCOME JILOA PTY LTD (TECHNIKIT DIVISION) P.O. BOX 73, GLENHUNTL Y, VIC 3163 Phone (03) 571 6303 APRIL 1990 19 Relative Field Strength Meter With this low cost field strength meter you can adjust antennas to resonance, align transmitters for maximum output and calculate the half-power points of circuits. It will even let you measure the relative strengths of audio signals. By RALPH HOLLAND quency. A convenient way to perform measurements and make adjustments to an antenna system is to place the Field Strength Meter where a noticeable reading is obtained and vary the frequency of the transmitter. The relative strengths can be plotted against frequency and used as an indication of the adjustments that need to be performed to obtain the desired resonant frequency. In the case of a dipole antenna, the elements can be shortened if the resonant frequency (maximum field strength) occurs at too low a frequency. Conversely, the elements can be lengthened if the resonant frequency is too high. Fig.2 shows a typical frequency response plot from an antenna, for a frequency range either side of resonance. Point B on the curve is When most people think of tuning antennas, they think of using an SWR meter. But there is a better way - use a field strength meter. It can give a better indication of resonance, provided the meter is sited correctly. Fig.1 shows a typical test situation. The field strength meter is placed in direct sight of and at least two wavelengths away from the antenna. An effort should be made to keep the meter away from the transmitter and feed system (coax) in order to avoid false indications which may be caused by stray radiation when standing waves are present in the antenna feed system. If a transmitter is operated into an antenna, the field strength surrounding the antenna will be at a maximum when the antenna system is resonant at the transmitting fre- □ 0 0 the resonant frequency. The range of frequencies between A and C on the curve is the - 3dB (half power) bandwidth. The simple field strength meter lets you do these frequency plots quite easily, provided you know or can measure the transmitter frequency. Most transmitters these days use phase-locked loop circuitry and so (J/) 0 A Fig.1: typical test set-up. The field strength meter should be at least two wavelengths away from the transmitting antenna. 20 SILICON CHIP B C FREQUENCY Fig.2: typical frequency response plot from an antenna. Point B on the curve is the resonant frequency. TO TRANSMITTER TO 52!! DUMMY LOAD 4. ~:--===::::::::::::::;-~ .11.. Fig.3: directional coupler arrangement for directly monitoring a transmitter output. TO TRANSMITTER TO DUMMY <at> ~ Fig.4: non-directional resistive coupler. The transmitter is typically adjusted for maximum output in the centre of the operating hand. for any channel setting on a CB or amateur transmitter, you will know the frequency very precisely. There's no need for a frequency meter. Transmitter adjustment To adjust a transmitter for maximum power, the field strength meter can be coupled to its output. The coupling can be via the normal transmitter antenna and radiated field, or preferably by operating the transmitter into a non-reactive dummy load and coupling system. Since adjustments can take some time, q.ummy load operation is highly desirable as it will eliminate interference to other users of the test frequency. There are two straightforward techniques of coupling to the output of a transmitter. Fig.3 employs a directional coupler while Fig.4 shows a non-directional resistive coupler. Before making transmitter adjustments, you need to know the design bandwidth and operating characteristics of the transmitter. The adjustments are a compromise between several parameters and they often interact with each other. A typical compromise is to adjust the transmitter for maximum output in the centre of the operating band. This will be indicated by the maximum field strength on the meter. If a newly constructed transmitter is to be adjusted, it is often necessary to align the transmitter right through the power amplifer chain. To do this, the field strength meter can be coupled with a loop or directly via a capacitor, to make ad- 680() S1 ANTENNA 1 0-:-1 .01 ZERO . .I + VR1 10k LIN 4.7k .01 8 EOC .,. VIEWED FROM BELOW SIMPLE FIELD STRENGTH METER Fig.5: the circuit uses diodes D1 & D2 and their associated 10k!2 resistors in bridge configuration. The bridge output drives differential amplifier stage Q1 & Q2, which in turn drives the meter. justments to the lower power sections. The input impedance of the meter is around 5k0 which is reasonably high, but any initial adjustments should be re-done with the meter coupled to successively higher power stages as the meter will still present substantial loading on the tuned circuits. PARTS LIST 1 PC board, code 04103901, 95 x 50mm 1 50µA meter movement 1 plastic utility box, 1 60 x 95 x 56mm (OSE Cat. H-2851 or similar) 1 1.5V O cell 1 1.5V O cell holder (Jaycar Cat. PH-9218 or similar) 2 knobs to suit pots 1 RCA panel socket 1 RCA plug 2 1N914 silicon diodes (01, 02) 2 BC549 NPN transistors (01, 02) 4 1on ¼ W 5 % resistors 2 6800 ¼ W 1 % resistors 1 1 OkO linear potentiometer (VR1) 1 1 kO linear potentiometer with switch (VR2, S 1 ) 1 1µF metallised polyester capacitor (greencap) 3 .01 µF metallised polyester or ceramic capacitors Miscellaneous Short length of coax cable, hookup wire, solder, adhesive (to secure O cell holder). Design parameters To be a general purpose instrument, a field strength meter should be as broadband as possible. I have measured the lower 3dB cutoff point as 35Hz and have operated the meter. at over 400MHz, so that means the circuit is pretty broadband! The circuit should also be sensitive. Fitted with a suitable pickup, the unit decribed here will respond to a 1 watt 144MHz transmitter feeding a quarter wave antenna from over 10 meters away. The prototype field strength APRIL 1990 21 Fig.6: the parts layout & wiring diagram. An RCA panel-mounting socket is used for the output connector and is wired to the PC board via a short length of coaxial cable. current through QZ is reduced by an equivalent amount. Thus, the average voltage at the collector of Ql will be higher than that at the collector of 02. This causes current to pass through potentiometer VRZ and the associated meter Ml, and thus provide an indication of the input signal amplitude. When pot VRZ is adjusted so that its wiper connects directly to the collector of QZ, the circuit is in its most sensitive condition. Winding the pot back the other way reduces the sensitivity so that the circuit can handle quite large signals. The current drain of the circuit is around 1 milliamp, so a D-size cell should last for several years. Construction Most of the components · are mounted on a small printed circuit board measuring 95 x 50mm (coded 04103901). This has been designed to ensure that stray capacitance and inductance is balanced on both sides of the bridge. The board is also designed to mount in the slots of the specified plastic utility case. All component leads should be dressed and kept as short as possible, according to good practice for The PC board slots into a plastic utility case & has been designed to ensure that stray capacitance and inductance is balanced on both sides of the bridge. meter was mounted in a standard plastic instrument case, together with a small meter and two knobs - one for sensitivity and the other for zeroing the meter. It runs from a 1.5V battery. Circuit operation The circuit is shown in Fig.5. It is effectively a bridge circuit consisting of diodes Dl and DZ and the four associated lOkO resistors. The bridge is initially balanced by potentiometer VRl and the degree of unbalance is indicated by the meter Ml which is driven by a differential amplifier consisting of transistors Ql and QZ. It works as follows. Dl and DZ are high speed silicon 22 SILICON CHIP diodes and these are biased on slightly at about 30 microamps, which has the effect of improving their sensitivity. When the bridge is balanced, by setting VR3, the voltage at the collectors of Ql and QZ will be exactly equal and so no current will flow through the lkO potentiometer VRZ or the 50µA meter, Ml. When a signal is picked up by the antenna, it is coupled via the lµF capacitor to the anode of Dl. This diode then conducts on positive cycles of the input waveform and this raises the average voltage at the base of Ql. This causes the current through Ql to increase and since it is a differential amplifier with a common emitter resistor, the This is the full-size pattern for the PC board. ... The battery holder must be positioned so that it sits between the pots & the meter when the lid is closed. RF circuitry. No special order is necessary to assemble the components onto the board but take care to orient the transistors and diodes correctly. You will have to cut a suitable hole for the meter in the lid of the case, as well as drill holes for the two potentiometers and the RCA panel socket. The D cell holder for the battery can be glued to the bottom of the case before all the wiring is completed. Note that the battery holder will have to be positioned in the case so that it sits between the meter and the pots when the lid is installed. Using the meter To use the field strength meter, you will need to connect an antenna to the RCA socket. This can be a short length of stiff copper wire soldered to an RCA plug. Rotate the sensitivity control to about half setting and then adjust the zero control to zero the meter. Now key your transmitter and check that the meter deflects. Maximum pickup will be obtained when the field strength meter's antenna is parallel to the transmitter anten- + 1.5V Fig.7: these two simple circuits can be used to select matched diodes & transistors. The transistors should be selected for matched collector/emitter voltages. na; ie, both oriented in the same direction. Remember though, when an antenna is being tested for resonance, the field strength meter should be at least two wavelengths away (at the operating frequency). You can maximise the pickup of the field strength meter by cutting its antenna pickup lead so that it is resonant at the frequency of interest. If you like, you can make up several plug-in antennas, each with a different resonant frequency. Minimising drift If you want to minimise drift in the circuit you can select the transistors and diodes so that they are matched. The circuits of Fig.7 will enable you to do this. When selecting diodes, pick those which have the closest possible match in their voltage drop, which will be about 400mV. Similarly, when picking the transistors, pick a pair which have the closest possible collector emitter voltage drop when measured in the suggested circuit of Fig.7. ~ APRIL 1990 23 YL,/\ ~i t:::.Lt:::.'-.., [ HU l\1 1\...,~ ,Jf"\ I V f"\ n LL L \.., I n v 1'lll\.., .;) ,Jf"\ I V Mn L L L I..., I n V l 'I I V..:>-.Jf"\ J VMI'\ L L I.. I.J I r, v YCAR FLECTRONICS JAYCAR ELECTRONICSJAYCAR YCAR ELECTRONICS JAYCAR ELECTRONICSJAYCAR YCAR ELECTRO NICS JAYCAR ELECTRON ICSJAYCAR YCAR 1:L[C !RONICS JAYCA R ELECTRON ICSJAYCAR ELECTRG .. - ELECmc [LEC111 C El Fcmc EL[C I RC ELECTl1C ELECTRC EL[Cmc [l [ CTl1C EL[CTnC [ l [CfRC EL~cmc EL[CTRC EL[ClRC ELEC l:.LECTRC [l[ClfK EL[CTRC 1:1.rcrnc 1:Lrcmc LLLCTRC 1'11 1\,.., ,J,.J/'"\ I l...,/'"\ I \ LLLV I , , v , ~ • vvv,, 1 v r\ 1 I L L LV 1 1 \ ~ l 'O I V>JU/'"\I VI ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR \1 I L L LV 11 ,...., , ~ ...... ,JU,, , ....,, H \ LLL "-' I I ,...., , ~,...,, ............,, 1 ....,, \I I ......... ~ t , . ...... . ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCA R ELECTRot ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRot ELECTRO NICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRO!' ELECTRONICSJAYCAR ELECTRO NICSJAYCA R ELECTRONICSJA YCA f1 ELECTROr STUDIO SERIES HALF OCTAVE EQUALISER Ref: Silicon Chip Sept 1989 Complet'ely new stereo equaliser has a performance equal to or better than the finest commercial models. The half octave freq. are: 28, 39, SS, 78, 110, t 56 220,319,440 625, 880, 1.25k, 1.75k, 2.Sk, 3.5k, 7k, 10k t 4k, and20kHz. 20 sliders for each channel. $349 Cat. KC-5055 me ECONOMY MAINS FILTER FI Ferne VERSATILE SUB-WOOFER ADAPTOR FUC I IK Ref: EA Oct 1989 Ref: EA May 1989 [LECTRC Incorporates our bargain PCB mount filter network together with Incorporates active low-pass filter with variable cutt-off El F-Crnc 2 varistors and a fuse mounted on a PCB. Short form kit designed frequency and dual phase outputs for running a stereo amp in ELECfRC to be mounted inside equipment. PC board size 78 x 67mm. Ref: Silicon Chip June 1989 bridge configuration. The kit includes PCB, box, front panel l:Ll:Clf1C Cat. KA-1722 Turn your lights on and off and and all components. Plug pack 12V AC Cat. MP-3020 $16 95 ELFCrRC dim them just by touching a required. ELfCHK decorative plate. Kit includes FI [CTRC Cat. KA-1717 PCB, HPM wallplale and all FI f CTRC components. [LECTRC Cat. KC-5052 El.ECmc ELFCrnc ELFCTRC ELECTRC Ref: Silicon Chip March 1990 ELI cmc Comprehensive battery charger for GEL batteries. Charges LUC1f1C Ref: Silicon Chip Nov 1989 both 6 & 12 volt batteries. Charging rates: · 1.2Ah (250mA); ELLCmc 2.SAh (520mA); 4.SAh (900mA); 6Ah (1.2A); 15Ah (3A). An excellent way to learn about EIEClf1C electronics and the result will be Charges our range of GEL batteries. Includes PCB and all ELlCTRC a quality analogue multimeter you board components. No box or front panel. Transformer not ELECTRC can use for years. Ideal for supplied: 1.2Ah-4.5Ah use MM-2008 $18.95 or 6Ah-15Ah ELECmo educational areas, schools, etc. use MM-2000 $37.95. ELECmc The unit is partially assembled Cat. KC-5071 ELLCIRO with some soldering required. ELEC111O This 20kV/ohm unit has ELECTRO everything included including ELECTRO Ref: Silicon Chip July 1989 ELECTRO leads/probes and battery. Includes PCB, silver decorator ELECTRO Cat. KC-5058 plate and all specified components. ELECfRO Cat. KC-5053 EL[Crno Ecmo ELlCTRO El rcrno ELECmo ELECmo ELECTRO Ref: Silicon Chip Dec 1989 u rcrno Can record your own voice, sound or music. Uses 4 separate Ref: Silicon Chip November 1989 FI FCTllO RAM chips that can store 4 x 30 second messages or ganged A gentle breeze from your ceiling fan rather than a gale! ELFcmo together for 2 minutes. Kit includes PCB and all components. Full range control from fast to slow. Includes partially FIFCmo Speaker, mic insert and box not included. built Speediwatt module, wall mounting block and all ELEClRO Cat. KC-5072 components to connect to your existing fan control EIECfRO inductor. EL~CTRO EL.Lerno El FCTRO ELFClRO ELECTl1O Ref: EA Sept. 1989 FU crno Automatic discharger used in EL[Crno conjunction with KA-1718 Ref: EA July 1989 ELECTRO Ref: Silicon Chip October 1989 NiCad charger. Kit includes It can charge single cells or cells in series up to 9V. Once ELECmo Provides communication between rider and pillion or riders PCB, box, front panel and the battery is charged the unit automatically switches to EIECmo on separate bikes. The unit is a 2-way radio system which all specified components. trickle charge until you switch off. Kit includes PCB, box, E:l.lC111O allows you to communicate with more than one rider at a It is powered by the charger fronty panel and all components. You will need battery ELECTRO time. 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GOOt nAII 50mA · 4 AA 6 0Llm'1H . 6C m~ checks and appear in the advert (we're human tool) l: l [ClllO !; C& O ),2Ah 1211mA Ll [CTRO Please don't blarre the store managers or staff, they ELECTflO Ref EAAugust1989 cannot control a dock strike or a lost PCB artwork from [I f Cl llO Use your IBM or compatible on your TV. Kit is a low-cost a magazine to the PCB manufacturer for a new kit. or fix ELlCTRO RGBI to PAL video encoder and RF modulator. IBM or an error that appeared in print. r 1 rcrno compatible must be fitted with CGA (colour graphics If you are about to drive across town to pick up an El l-CfRO adaptor). Kit includes PCB, box, RF modulator, advertised item, why not play it safe and call the store EU: CfllO 9D plug and all components. Optional power supply parts first - just in case. Ell Cl RO not supplied . Cat. 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FOR TOUCH LAMP DIMMER n $29.95 $69 $34.95 $14.95 CONTROLLER FOR CEILING FANS IGITAL VOICE RECORDER $125 $ 16.95 FM RADIO INTERCOM FOR MOTORBIKES $69.95 NiCad DISCHARGER AUTOMATIC NiCad CHARGER $27.95 $42.50 ., , • ,, ,, _ •• BI TO PAL ENCODER/ MODULATOR $39.95 lr"An r1 rr"Tnn•u,...r,, I AV/"'l\n r r r r- Tn r"\"- ll r"C" I AVr>An C l r,... T n r'\,. 11 ,... t'.' I AVr>An Cl c: r,Tn l""l ld l r"C' I AVrAn C: I t:ro T n f""l ldl,... C" I AVr-An C l C/"'Ti)/"\" l l f"'C' 11,, vr-An C l c r-TO/'\ h. 11,...C' I AV/"' A O e t Cf"T[')f"\ ,. 11/"' C' I AVf"'/\D C l C'f"' T Of"H, :vcAFi IYCAR 1YCAR IYCAR Ei:Eci-FioNics:iAvcAFi Ei:Eci-FioNics:i:O:vc:.:R ELEci-i:ioNics:ilivc:...R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR . j:,.:.;,c:,.:ri Ei:i:'ci-rio, ELEcTRoN1csJ!ivcAR mci-i:ioNics:i:O:vclii:i Ei:Eci-i:ioNics:ilivc:.:Fi Ei:Eci-FioNics:iAvcAFi Ei:Eci-FioNics ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR 1:LECTROI ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICsJAYCAR ELECTRO! ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICs JAYCAR EL[CTROI "!fflffl!ffl!ffl!ffl!fflffl!ffl!ffl!fflffl!fflffl!ffl!ffl!fflfflffl!fflffl!ffl!ffl!ffl:!!fflffl!ffl~!!ffl!:~ffl!!:!!jsl. ·RELECTRO! J ,R ELEC1ROI ,R El ECTROI ,R ELECTRO! ,R ELECTRO! 1R ELECTRO! IA ELECTRO! R ELECTRO! R ELECrno1 R El ECTROI R EIYCTROI R ELECTRO! \ R ELECTRO! R ELECrnOI \ R ELECTRO/ R [ LECTROI R ELECTRO! R ELECrROI R ELEcmo1 R FlfCTROI R ELECTl,01 R ELECTRO! \R ELLCTROI R ELECTRO! R EL~crno1 R ELECTRO! R ELF·crno1 R ELF CTROI R ELECTRO! R ELEC7 110I R ELECTRO! R ELECTRO! R ELECTRO! R ELECTRO! R ELrcrno1 R ELECTRO! R ELECTl101 R [L[CTROI R ELECTRO! R ELECTRO! R ELECTl101 R ELl:CTl101 RELEC I ROI R ELECmOI R EL[Cmo1 R ELECTRO! R ELECTRO! = = = = = = = = = = = = ~ ? J (:R El lCll101 R EL~CTl101 , R ELECTRO! R EL[CTROI · R ELECTf101 \R ELECTRO! R ELECTRO! R ELl:ClROI R ELECTRO! R [ L[CTROI R ELECTRO! REU:CTROI R ELEClROI R EL[CTl101 R ELECTRO! R ELECTflOI RELECIROI 11 EU, CTl101 R ELECTRO! R ELECTl101 R EL[Cfl101 R ELECTRO! R ELECTRO! R ELECTRO! R ELECTf10I R ELLCT l10I 0.005% Distortion R ELECTRO! Many features: phono in/out. aux input, loudness, bass, R ELECTRO! treble & midrange con trol+ provision for tone defeat R ELECrno1 switc h. Requires ±15V 200mA p/s). Size 203x 106x40(H)mm R ELFCTROI Cat. AA-0315 R ELECTRO! R ELLCTl101 R ELECTRO! WAS $84.95 R EL[CTROI R ELl.:ClROI R ELECTRO! R ELECfROI R ELECmo1 R ELECTRO! AR EL[CTROI R ELECTRO! R ELECTRO! ,.------------R ELECTRO! AR ELFCTROI R EL[CTROI R ELEClROI Jaycar will purchase your surplus stocks of components R ELECTRO! PRO SERIES 1 POWER AMP · 140 WATTS RMS PER CHANNEL Ref: EA Dec 1989/Jan 1990 NEW • upgraded design - now gives 140W rms channel into 8 ohms. Dual toroidal transformers supplied. Cat. KA-1725 $599 MASSIVE 12 & 16 CHANNEL AUDIO MIXERS Ref: Silicon Chip Feb/March/April 1990 FULL 16 CHANNEL MIXER Cat. KC-5065 $1399 Ref: Silicon Chip Feb 1990 This kit generates the sound of two birds singing and chirping, starting slowly and building up to both birds in full song. The kit is housed in a jiffy box and comes complete with PCB, speaker and all electronic components. Cat. KC-5062 $24.95 12 CHANNEL PANEL KIT Cat. KC-5064 $999 CONSOLE CHASSIS/POWER SUPPLY Cat. KC-5070 $239 ea INPUT PREAMP BOARD Cat. KC-5066 $65 ea EQUALISER/METER BOARD Cat. KC-5067 $65 ea FOLDBACK/EFFECTS BOARD Cat. KC-5068 $39 It consists of a fused cigarette lighter plug with 2 metres of heavy duty cable to a 1.8mm DC plug. Fuse is 3A. Fused cig. lighter plug is $2.95 on its own. Limited quantity. Cat. PL-2008 ONLY $1.95 ea A complete preamp and high power amp - with power supply electronics and loudspeaker protector in the one package. All that you need to connect is a power transformer and a signal source. Transformer to suit Cat. MM-2015 $69.50. Cat. AA-0310 10+ $1.50 ea Was $169.95 KNOB PACK Another Jaycar surplus deal! We have a quantity of Japanese Sato brand knobs. some lovely aluminium, some black and aluminium and some are just black. We also have a quantity of Rean knobs with different coloured caps. The Sato knobs are imperial and the Rean metric. This pack will include a minimum of 50 knobs - generally more. The majority will be Rean knobs - with caps. and the remainder Sato. The Rean knobs are worth about$1.20each and the Sato up to $2 each. We figure there is about $60 worth of itt vouRS FOR 0 YC. YC YC $10 ON ''Y I. SAVE $25 NOW $59.95 SAVE $40 NOW $129.95 Limited Quantity TURN YOUR SURPLUS STOCK INTO CASH!! " •W 'ff,t-~i; · ' ' ~:~!~;i~fili~;!fii~~=~~~ ~m~m~i ROUTLEYNOW ON (02) 747 2022 RE ll CTl10I R [LECTROI R ELECTRO! EL[CTROI L~;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;._~;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;._.;________________.;_~R '!CAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTl10NICSJAYCAR YCAR. ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAll ELECTRO! [LECl llOI ELl:CTROI ELECTRO! ~s~~ ~~~s!~~~1s~~~~s~~ ~~~S;~~~1s~~~s~~ ~~~s!~~~ 1 s~~~s~~ ~~~s!~?~is~~~~s~~ ~~~s~~?~i~~~~~~~ ~~~~~? ~l ~~~~~A~ ~L~C:! ~ONICSJAYCAR ELECTRON ICS J~~~~~ ~L~~~~?i . . . . . . . ,,.,._...,...,,,, <J1 :AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR :AR ELECTRONICSJAYCAR ELECTRONIC&JAYCAR ELECTRO NICSJAYCAR :AR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR :AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR AR ELECT AR ELECT AR ELECT AR ELECT AR ELECT AR ELECT 8/30 replacement AR ELECT Power Handling 120 watts rms AR ELECT . Resonant Freq. 31 Hz AR ELECT , Freq. Range to • 4kHz AR ELECTI Sensitivity 95dB AR ELECT I Oms 1.73 AR ELECT ! Oes 0.47 AR ELECT Oto 0.37 AR ELECT I Vas BOl ~R ELECT! Cat. CW-2110 AR ELECT ! WAS $99.50 ea AR ELECT.I AR ELECTI AR ELECT AR ELECT AR ELECT,, AR ELECTII AR [LECTI AR ELECT!, I\R ELECT! I\R ELECT!' I\R ELECT!' .\A ELECT!' I\R ELECT!' Get your speakers off the floor. these are made from !\A ELECT!' aluminium anodised black, and are suitable for most ".A ELECT!' speakers. They are supplied with castors and spi kes (for ".R ELECT!' carpel) and adhesive pads for wooden floors. Speakers I\RELECTI sit off the floor approx 250mm (with castors). The width I\R ELECT!' is adjustable from 148mm (ID) for small speakers to \R ELECT! 250mm (ID ) for large speakers. Depth is about 225mm. \R ELECT! Supplied in pairs \R ELECTf Cat CS-2700 \R ELECT!' \RELECH' \R ELECTf· IA ELECTf \R ELECTI \R ELEcn : \R ELECTI \R ELECTI \R ELECTf \R ELECTf' 1R ELECTF 1R ELECTF ,R ELECTF 1RELECTF 1R ELECTF ,R ELECTF ,R ELECTF ,R ELECTf ,A ELECTF ,R ELECTF ,RELECTF ,R ELECTF ,R ELECTF • 5/sec sampling .R ELECTF • Data hold ,R ELECTF • Frequency counter .A ELECTF • Diode conti nuity .R ELECTF See catalogue for .R ELECTF full details .R ELECTF Cat OM-1 500 .R ELECTF .R ELECTF .R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF A ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF A ELECTF Don't pay $499 • $700 R ELECTF See catalog ue for fu ll specs R ELECTF Cat. OT-2332 'l ELECTFi 'l ELECTG 'lELECTn1 ELECTR MAGNAVOX SMV SELLOUT SAVE $24.50 NOW $75ea SPEAKER STANDS $49.95 TRUE RMS AUTORANGING 3. 75 DIGIT METEX $169.50 ELECTRONICSJAYCAR ELECTRON IC&JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONIC&JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR JC-250 1 O" WOOFER SELLOUT Black square frame grey polypropylene cone. It requires a seale enclosure of 70 litres. Resonant Freq. 28Hz 75watts rms Power ~andling 45-4500Hz Freq. Response Oma 3.54 Oes 0.85 Oto 0.68 Vas 170 Cat. CW-21 20 WAS $64.95 " ' L.L.L.<J,, ,v,~•vu v n , vr.11 LLL'-', nvr'II'-'• ELECTRONICSJAYCAR ELECTRON ICS JAYCAR ELECTRONIC ELECTRON ICSJAYCAR ELECTRON ICS JAYCAR ELECTRONIC: ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC: ELECTRON ICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC: lilEtSp";;n";;-sPEAKERS ' I •• High Power High Quality I I See • Dualcatalogue Impedance for full specs. I 6 " woofer I 4/8 ohm BOW rms Cat. CW-2140 $69 I 8" woofer 4/8 ohm 120W rms Cat. CW-2142 $99 10" woofer SAVE $20 NOW $44.95 4/8 ohm 160Wrms Cat CW-2143 $149 12" woofer 4/8 ohm 200W rms Cat. CW-2145 $179 Dome midrange MOTOROLA KSN 1141A PIEZO TWEETER 400W RMS Brand new Motorola Powerline horn.Includes a protection circui t internally which allows the new horn to handle 400W rms. It uses a miniature light bulb and a PTC resistor. Under extreme high power surges, the PTC opens up allowing the speaker to conti nue to play at a somewhat compressed power level. The resulting product is virtually blow-out proof. Repl aces the KSN102SA. See catalogue for specs. 3 year warranty. Cat. CT-191 2 4/8 ohm Cat. CM-2090 $4 7 ■ 50 Dome tweeter 4/8 ohm Cat. CT-2010 $29 ■ SO $37.95 3 YEAR GUARANTEE 3. 75 DIGIT 4000 COUNT · 39 RANGE SCREWDRIVERS • Inductance • Ca paci ta nee • Frequency • Temperature • Peak hold • logic See catal ogue for full details Cat OM-1 475 Cat. Type TD-2015 Slot Blade length 50mm Tip 3mm TD-2016 Slot 75mm 4mm TD-2017 Slot TD-2018 Slot 100mm 5mm 100mm 6mm TD-2022 Phil 75mm Osmall TD-2023 Phil TD-2024 Phil 100mm 100mm 1 med 1 large TD-2012 Posi 75mm 3/1 6" TD-2010 Posi 100mm 1/ 4" New for 1990. A ran ge of quality Chrome Vanadium screwdrivers suitable for the hobbyist and electronics technician. There are 4 slotted, 3 Phillips and 2 Posidriver types . $179 Price $1.95 $2.40 $2.95 $3.95 $2.20 $3.50 $3.95 $3.65 $3.95 1.3GHz FREQUENCY COUNTER --------------- $399 '1ELECTR '1 ELECTR '1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR \YCAREL . ,--- -------. - ALARM PANEL TELEPHONE DIALLER Connect to virtually any home/business alarm panel. It has buil t-in microphone which rec ords a 16 second message by you and when the alarm is triggered will send the message to up to four different numbers, or any combination of the same. Su itable for tone and pulse systems. Also suitable as an alerting system for the elderly and sick. Easy to connect to both alarm system (N/C terminal ) and telephone (2 wires). Requires 12V DC· from alarm panel. We have seen this product for $249 in other electronic ca talogues. Cat. LA-51 90 SAVE $70 ~~g~~ ~~-·~-•.. •.-•. ..• -.....• -• ·•· •. ·•- •;-,., 1YCAR ELECTRONICS ,YCAR .ELECTRONICS ,YCAR ELECTRON ICS ,YCAR ELECTRONICS .YCAR ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ONLY $179 0■.l _l. ,!.10!1 !,1·!•·•·,.■., _1! 1! ,!l!l.,;■,!!! . , .,.-1!1, •· '-·'-1111! . .. ! , 1 -• ·.c• c l!l 0 11!1 , ,l-,'>J !!!l.II!·,1111 ·, -,1!1 ·0 11!1 ._,., 1!1 , .•, 11 -,,lh.l!llllLllLL!I!-!'v■,lllnlllull1 ·'!1"·1'(■.,-'>J!lll!!'Mllli\ll.. , ,·101!1 !1 ,.,.1,!,1! 1'-!1■LC0 l! l!1111!,.,-,!-l0!l··•·~·•v■~l-! I!Ill"■'v■nlll,■,L■L■L■v■,,lllavlll,l,,■ ll vl..;c! l■-A!.I!,-1v■ ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR CTRC c v ,'!l! -.; r,1111 · c1·111:..111111 G111 , n!·'!111 · -,~'1·1111 ·<..'-s., !l~;.,!..!Ij'!!' -(.l!! :,~~Nllli:III L.l:!'l! :c.1!1,!'!!;,!0!!! !' •,\J!!! iLIIICI> JI'!!l j.\'!! Yll!l ..,Alll>~ n '-" :L~E-g ;~g ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El ECTRONICSJAYCAR ELECTRONICSJAYCAf1 ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRC ELECTRONICSJAYCAR ELECTAONICSJAYCAR ELECTAC ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRC ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRC FI ECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRC YCAH YCAR YCAR YCAR YCAR tLtC I HONICSJAYCAH ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR tU: ClHONICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR 8 PIECE ELECTRIC INSULATED SCREWDRIVER SET This set consists of 8 screwdrivers which are fully insulated right down to the tip of the blade. Each screwdriver will handle 1000 volts. Slotted Blade Length Tip diameter 75mm 2.5mm 100mm 4mm 125mm 5mm 150mm 6mm Phillips 75mm 2.5mm Size 0 100mm 4mm Size 1 150mm 6mm Size 2 Slotted 100mm 4mm 100-SOOVelectric tester Cat TD-2008 _,!!'!l!li""'!'ffl"""'~•g;n mmm --il-!!!l\.,il\s11- - ! B "'. fiii.ilil.,,.e;;.s """'"' - $19.95 Another Jaycar direct import All disks are supplied with envelope, index labels and writeprotect tabs. Remember, these disks might be cheap but they are good quality. We are so impressed by the quality we are happy to offer a lifetime guarantee. 51/4" OSDO 48TPI DOUBLE SIDED/DOUBLE DENSITY Cat. XC-4730 $6.50 for 10 5 1/4" DSHO 96TPI DOUBLE SIDED/HIGH DENSITY Cat XC-4732 $15.95 for 10 SAVE $3 31/'l' MF2DD 135TPI DOUBLE SIDED/DOUBLE DENSITY Cat. XC-4736 $16.95 for 1 0 SAVE $10 FORMAT TO 1 .4Mb! lfyourcomputerhasthenewfonnat sizing then you can store up to 1.4Mb on the one disc. ,,N JI:. $49.95 WAS Cat.XC-4738 NOW $34.95 ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECJAYCAR ELEC ELECJAYCAR ELEC ELECJAYCAR ELEc· ELECJAYCAR ELEC. ELECJAYCAR ELEC. : ELEc· : ELEc· I ELEc· I ELEC I ELEC I ELEC I ELEc· IELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC Conver! your normal hand operaled window wi nders lo power windows. They are really easy lo I ELEC connecl, simply remove lhe manual handle, choose lhe correcl adaplor and connecl lhe molar I ELEC drive. The screw lhe drive lo lhe door. A melal brackel is supplied which mounls inside lhe door for I ELEC added slrenglh. All cables for connecling are supplied. Driver unil has a second swilch which I ELEC controls passengers window. Also included is a special relay which shuls the molar down when lhe IELEC window is complelely up or down. which saves wear and tea r on lhe molar. There is even a I ELEC courlesy lighl buillin which is connecled to the door pin swilch and ligh ls up when the door is I ELEC open. Colour is grey. I ELEC Kit includes - 2 window winders, relay, 4 metal adaptors which cover mosl cars, complele wiring I ELEC harness and full wiring instruclions. I ELEC BRAND NEW MODEL I ELEC Cat. LR-8812 I ELEc· I ELEC I ELEC. IELEC I ELEC I ELEc· IELEC IELEC I ELEC. I ELEC I ELEC I ELEC I ELEC I ELEC I ELEC. I ELEC. I ELEC I ELEC" I ELEc· Cat WAS NOW SAVE I ELEC. Playmaster 60/60 I ELEC Amp (standard version) KA-1 650 $329 $289 $40 I ELEC" RTTY Encoder KM-3016 $32.50 $19.95 $12.55 I ELEC Ultrafidelity Preamp KM-3030 $359 $279 $80 ! ELEC : ELEc· Soldering Iron ! ELEC Temp Control KE-4725 $39.50 $29.50 $10 : ELEC. Telephone Intercom KE-4731 $49.95 $39.95 $10 : ELEc· $3.95 Modem End File Ind KC-5024 $9.95 $6 : ELEC : ELEc· KC-5044 Car Safety Lights $29.95 $21.95 $8 : ELEC. Octave Equaliser : ELEC KM-3064 Module $59.95 $39.95 $20 : ELEC : ELEC : ELEC : ELEC" : ELEC : ELEC I ELEC IELEC I ELEC I ELEC I ELEC ELEC ELEc · MAIL ORDERS POST & PACKING MAIL ORDER VIA ELEC P.O. Box 185 Concord 2137 ELEC $10 - $24.99 $ 3.75 HOTLINE (02) 747 1888 ELEC $25 - $49.99 $ 4.50 ROAD FREIGHT ANYWHERE ELEC. FOR ORDERS ONLY $50 - $99.99 $ 6.50 IN AUSTRALIA lup lo 20kg) ELEC TOLLFREE (008) 022 888 OVER $100 $800 S13.50 ELEc· ELEC GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799ELEC B:l'ilf: $239 · ', QUALITY DISCS AT UNREAL PRICES 10 x 31/Z' MF2HD ELECTRONICSJA YCAR El ECTRONICS ELECTRON ICSJAYCA R ELECTRONI CS ELECTRONI CSJAYCAR ELECTRONICS ELECTRONICSJA YCAR ELECTRONICS ELECTRON ICSJAYCAR ELECTRONICS ~-' SAVE HEAPS WITH JAYCAR'S DISCONTINUED KIT SALE 1r 1 \\ (MasterCard.) \~ SYDNEY - CITY PARRAMATTA CONCORD VISA :s JAYCA HURSTVILLE 117 YorkS l.(0 21267 1614 · Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Church St (Cnr Victoria Rd) I02) 683 3377 Mon-Fri 9 · 5.30 Thurs 8.30 pm· Sat 9 • 4pm 115 Parramatta Rd (02) 745 3077 · Mon-Fri 8.30- 5.30 · Sat 8-30 - 12 121 Forest Rd (02) 570 7000Mon-Fri 9. 5.30 Thurs 8.30 pm_ Sat 9. 4 BURANDA OLD MELBOURNE-CITY SPRINGVALE VIC ADELAIDE SA • - - Mon-Fri 9 - 5.30 Sat 9 - 4pm 144LoganRd(07)3930777Mon-Fri 9 _5.30 Thurs 8.30 _Sat 9 _12 Shop 2. 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9- 12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon- Fri 9 - 5.30 Fri 8.30- Sat 9- 2 190 Wright Street (Cnr Selby Street) (08) 231 7355 Mon-Fri 9-5.30 Fri 8.30- Sa t 9- 12 ::(Ee· ELEC ELEc· ~LLEEcc: : LEc· : LEc· : LEc· · E : L c· : LEc· :S JAYCA _ t======================================================~!LEC" :s :s :s :s JAYCA. . ~LECl JAYCAR ELECTR ONICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRO NI CSJAYCAR ELECTRONI CSJAYCAR ELECTRONICS JAYCAR ELECl jAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRONI CSJAYCAR ELECTRON ICSJAYCAR ELECTRO NI CSJAYCAR ELECTRONICSJA YCAR ELECTRO NI CS JA YCAR ELECl JAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRON ICSJAYCAR ELECTRO NICSJAYCAR EL[CTRONI CSJAYCA R ELECTRONICS JAYCAR ELECl :~ ~~:,S~~ ~~~S!~~~!S~~~ :,S~~ ~~~S!~~~!S~~:,S~~ ~~§S!~~~!S~~ !S~~ §~§S! ~?~!S~~~!S~~ §L§S~~?~I S~~~~~~ §L~~ ~~()Nl~~AY~A~ §L§~!~()NICSJAYCAR EL§C!~ON ICS ~~ !S~~ §~§S! Build a VOX with delayed audio What's the biggest problem with VOX (voice operated relay) circuits? They chop off the first syllable of speech every time they operate. This circuit doesn't. It passes the speech signal through an electronic delay circuit so that when the relay operates, all the signal goes through. Design by DARREN YATES Ever since voice operated relay circuits were invented, they have been chopping off the first syllable of speech signals. It is inevitable. There is always a short delay in any circuit which senses a rapidly rising signal but the big problem is the finite operating time of the relay. Typically, the small relay used in VOX circuits will take 10 milli28 SILICON CHIP seconds to close, after it has been energised. This is quite a long time as far as speech is concerned and it means that the first syllable, or at least the first consonant, is missed, never to be heard of again. This applies whether the vox circuit is used to operate a cassette recorder or a transceiver. The solution to this problem has been known almost as long as vox circuits have been around: put in an acoustic delay. That way, the relay switches the delayed audio signal. Since the acoustic delay is longer than the relay closing time, the whole signal passes through. The general scheme is shown in Fig.1. There is a microphone to pick up the speech and a preamplifier to amplify the microphone signal, which is then fed to the VOX circuit and the delay. The VOX circuit drives a relay which operates a cassette recorder or sets a transceiver into the transmit mode. The acoustic delay is provided by a bucket brigade device made by Matsushita. In this circuit, it provides a time delay of around 17 milliseconds, so instead of the relay closing 10 or so milliseconds after speech has commenced, it closes about 7 milliseconds before speech AUDIO DELAY ~OUTPUT .,. MICROPHONE MICROPHONE PREAMPLIFIER I RELAY .,. Fig.1: basic scheme for a VOX with delayed audio. The output from the microphone preamplifier feeds an audio delay circuit and also triggers the VOX circuit. If the audio delay is longer than the relay closing time, the entire signal passes through. FROM PREAMPLIFIER 3RD ORDER 3kHz LOW-PASS FILTER 17mS DELAY 3RD ORDER 3kHz LOW-PASS ALTER OUTPUT CLOCK fc = 15.7kHz Fig.2: the audio delay circuit consists of two 3rd order low pass filters and a bucket brigade device which provides a 17ms delay. The bucket brigade device is clocked at 15.7kHz. appears at the output socket. The circuit The circuit diagram is shown in Fig.3. To use the unit, it is normally placed in between the microphone and the device that is to be operated by the relay; ie, a cassette recorder or transceiver. The VOX OUT socket is linked to the "remote" of the recorder or the PTT (press to talk) switch of the transceiver and the audio output is taken to the input of the recorder or transceiver. Looking at the circuit diagram, the microphone is connected to the MIG INPUT socket. This socket is wired to short the input of the preamplifier when the microphone is removed. The preamp stage of the circuit is IC1a, a FET-input op amp connected as a non inverting amplifier. Its gain is variable between unity and 100 by the tookn sensitivity control, VR1. ICta's output is fed to a filter stage comprising IC1 b and the vox section comprising IC2a and IC2b. For the vox section, the signal from the preamp is fed through a O. tµF capacitor into the inverting input of op amp IC2a, which is wired as a Schmitt trigger. The inverting input, pin 2, is biased via the 22k0 resistor while the non in- Specifications Signal Delay Clock Frequency Frequency Response Maximum Output Signal Maximum Input Sensitivity Harmonic Distortion Signal To Noise Ratio 16.4 milliseconds 15.?kHz 1 00Hz to 3kHz within ± 3dB 800mV RMS 0. 7mV RMS (to actuate relay) (0 .5% at 250mV and 1kHz ( 1 .5% at 800mV and 1kHz - 66dB unweighted with respect to 500mV RMS at the output verting input, pin 3, is biased from a voltage divider consisting of the 120k0 resistor from pin 1 and the tkn resistor to OV . When the output signal of ICta exceeds about 200mV peak to peak, the output of the Schmitt trigger is toggled between the supply rails, producing a square wave of about 20 volts peak to peak. This square wave signal has the same frequency as the input signal from the microphone. The square wave output is AC coupled to a voltage doubler involving diodes D4 and D5. The DC voltage developed is stored in a O. tµF capacitor connected to pin 5 of IC2b which is connected to work as a non-inverting comparator. When the voltage at pin 5 is low, the ouput of IC2b is low. When the voltage at pin 5 is high (ie, above the + 3.75V threshold set by the 33k0 and 15kn resistors at pin 6), the output of IC2b is high and this turns on transistor Qt which drives the relay. The "attack" and "release" time of the vox circuit is set by the components at pin 5 of IC2b. The attack time is a function of the O.lµF capacitor and the associated charging resistance made up of diodes D4 and D5 and the output impedance of IC2a. Since this total impedance is quite low, the attack time is very fast (less than a millisecond). Since the Schmitt trigger signal will cease as soon as the person pauses between words, a defined "release" time is needed to prevent the relay from dropping out during these short breaks. This is provided by the 560k0 resistor at pin 5 of IC2b. This sets the release time at around 200-300 milliseconds. This stops the relay from chattering rapidly on and off during normal speech. As well as driving the relay, Qt drives LED 1 via a 2.2k0 resistor so you can see when the relay is operating. Diode D6 protects Qt against spikes from the relay coil when it is de-energised. Diode D5 protects the base of the transistor from being pulled below 0. 7 volts by the output of comparator IC2b. Now we'll look at the acoustic delay section of the circuit. The block diagram of Fig.2 will help in APRIL 1990 29 This scope photo shows an input signal at 820Hz (top) and the output signal from the bucket brigade device before the clock signal is filtered out (pin 13). The input frequency was chosen to be an exact sub-multiple of the 15. 7kHz clock frequency so that both traces would be stationary. understanding how it works. The heart of the circuit is the MN3004 512-stage bucket brigade device (BBD). This can be thought of as a series of 512 switches and capacitors. The input signal to the BBD is chopped into small samples at a rate determined by the clock To keep hum to a minimum, a ground plane is installed beneath the PC board and connected to circuit earth. The PC board is stood off the groundplane using 6mm spacers. 30 SILICON CHIP A feature of the MN3004 bucket brigade device is the facility to cancel out the clock signal. This is made possible by two in-phase outputs with out-of-phase clock signals. This scope photo shows the outputs at pins 13 & 14 when no audio signal is present. Note that the 15.7kHz clock signals are exactly out of phase. frequency. These small voltage samples are then shuffled through the 512 stages until they appear at the other end, to be reconstituted as a delayed version of the input signal. Just how much delay there is depends on the number of stages, in this case 512, and half the period of the clock signal. The lower the frequency of the clock signal. the longer will be the delay. There is a practical limit and that is set by the desired frequency response of the circuit. This must be limited to less than half the clock frequency otherwise an audibly unpleasant effect called "aliasing" will occur. In this circuit, we wanted to maximise the delay but could put up with a fairly limited frequency response since it is intended for speech. Therefore, we used a clock frequency of 15.7kHz which gives a delay of 16.4 milliseconds. In theory, a clock frequency (or sampling frequency) of 15.7kHz should result in an audio frequency tit response to about 7kHz, just as the compact disc sampling frequency of 44. lkHz allows an audio frequency response to 20kHz. However, to achieve that result, you need complex "brick wall" filters which give very savage filtering above the cut off frequency. Our circuit has easy to make third order filters so we have had to settle for a frequency response to about 3kHz which is adequate for speech signals. Also essential to the operation of the circuit is the 2-phase clock generator, the MN3101. As well as providing the clock signals, it also provides bias signals to the MN3004. An important aspect of the MN3004 is its clock cancelling feature. It has two outputs, pins 13 & 14, both of which produce an inphase audio signal but which have out-of-phase residual clock signal components. When these two outputs are mixed together, the audio signals are added while the clock signal components are largely cancelled out. One of the photos accompanying this article shows the two outputs of the MN3004, with no signal present and with the out-of-phase clock components. ' ~ + I• ► "'[ ~Q ....::, ~ "' 0 z "' ....::, ~ ;! ~ "'!fE !a I > J;-il· ,-..=" ~ ~~ + ,. > N + f-1•· ... ~ + f-t•· ~ ,-.. ~ ..; ,n "'"' + ;,: ,-.. > + I• ~ ,-..=" 0 ~~ H•· <Q ,n ,-..=" J-1•· = ~~ H•· = ~ 0 ;! ~ ... ~ ... ,. - ><t ..J ... '--'"' -z ..,g 0 =?~ w "' •· :a :E H•· 0 :c I- ;= ~ = 0 N ~ ~ ~ 0 0 J. ;! ,n ~ N N >< ~ ~ ; -~ 0 0 Delay circuit details The output from the preamp, ICla, is fed to IClb which is connected as a third order, unity gain low pass filter to attenuate frequencies above 3kHz at the rate of 18dB/octave. Its output signal is fed to the input of the bucket brigade device, IC3. The delayed outputs at pins 13 & 14 are mixed via 4.7k0 resistors and the associated lOkO trimpot, VRZ. The trimpot is there to adjust the clock signal components to a minimum. Signals from the wiper of VR 1 are fed to IClc, which is a third order filter identical to the input filter (IClb), except that it has a =-g 2!i - ~ .... O>- I· ;!: 0 > I I• I ~ = I-.!•· "'~~"' N N ~ + + ~ I ~ J. I -~ o=" o> + H•· o=" o> -~ .... -~ ::, 0 a,O >;! 0 ;!: HI• 'a 15 .,__;,:H•· ...· > ~ g "' N 0 NO "'"";: g I· Fig.3 (right): ICla is the microphone preamp and this feeds filter circuit IClb and a VOX section consisting of IC2a, IC2b & Ql. IC3 is the bucket brigade device, IC4 the 2-phase clock & IClc the output filter. lf I• .... ~ N 0 "';i: -o ;;; c~ c.. ! ~~ 5:5 1ljc.. 0 >< ~~: - ~ff§ ~ APRIL 1990 31 small amount of gain to make up the signal loss occuring in the BBD. The result is a clean audio signal that has been delayed by 16.4ms. The 2-phase clock, IC4, has its frequency determined by the components on pins 5, 6 and 7. The two clock phases appear at pins 2 and 4, and are fed into pins 2 and 12 of IC3. Power supply The rear panel carries the power socket, power on/off switch & the delayed audio output socket (VOX OUT). Power for the unit is derived from a 12V AC plugpack supply. PARTS LIST 1 PCB, code SC061 04901 , 140 x 122mm 1 front panel label, 143 x 54mm 1 plastic case, 150 x 160 x 65mm, Jaycar Cat. HB-5913 1 knob 2 6.35mm phono sockets 1 6 .35mm phono socket with shorting contacts 2 5mm LED bezels 1 SPOT mini PCB relay (Jaycar Cat. SY-4060) 1 2. 1mm DC power socket 1 SPST switch 4 PC pins 1 1 2V AC plugpack 4 6mm spacers, non threaded 1 single sided blank PCB, 140 x 122mm (for ground plane) 4 16mm x 4G self tapping screws 1 14-pin IC socket (optional) 1 8-pin IC socket (optional) Semiconductors 1 LF34 7 quad FET input op amp (IC1) 1 TL072 dual FET input op amp (IC2) 1 MN3004 bucket brigade delay (IC3) 1 MN3101 BBD clock IC (IC4) 1 7812 positive 12V regulator 1 7912 negative 12V regulator 6 1 N4002 silicon diodes (D1-D6) 32 SILICON CHIP The power supply is derived from a 12 volt AC plugpack, which feeds two half-wave rectifiers, D1 & D2. The rectifier outputs are then filtered by the lOOOµF and 470µF electrolytic capacitors. This results in smoothed DC supplies of about ± 17V which are then regulated to ± 12V by 7815 and 7915 3-terminal regulators. Their outputs are further bypassed by lOOµF capacitors. Power indication is provided by LED 1 which is mounted on the front panel. 1 BC338 NPN transistor (01) 2 5mm red LEDs (LED1 , LED2) Construction Capacitors 1 1 OOOµF 25VW PC electrolytic 1 4 70µF 25VW PC electrolytic 4 1OOµF 16VW PC electrolytic 4 4 7 µF 25VW PC electrolytic 2 4. 7 µF 16VW PC electrolytic 1 1µF 50VW PC electrolytic 8 0 .1µF metallised polyester (greencap) 2 .0056µF metallised polyester 2 .0033µF metallised polyester 2 470pF ceramic 2 1 OOpF ceramic vox are mounted on a PC board Potentiometers 1 1 OOkO log potentiometer 1 1 OkO miniature vertical trimpot Resistors (0.25W, 1 560k0 1 1 50k0 1 120k0 6 100k0 1 43k0 1 % 1 39k0 1 33k0 1 27k0 1 24k0 1 % 5%) 2 22k0 3 1 5k0 1 12k0 1 9 .1 kO 1 % 1 8 .2k0 2 4 . 7k0 2 2.2k0 2 1 kO 1 2200 Miscellaneous Hookup wire, shielded audio cable, solder, nuts, washers . Most of the components for the measuring 141 x 12 2mm (code SC06104901}. This is housed in a standard instrument case measuring 150mm wide, 160mm deep and 70mm high. Before commencing assembly, carefully check the PCB pattern for shorts or breaks in the copper tracks, which should be corrected at this stage. Fig.4 shows the wiring details. Start by installing the PC stakes on the PC board. Once this has been done, you can install the wire links and the resistors. We suggest you use a digital multimeter to check each resistor value as it is installed. Be sure that the polarised components are correctly oriented on the PCB. These parts include the electrolytic capacitors, diodes, the transistor and the ICs. Mount the ICs on the board last of all. We used IC sockets for IC3 and IC4 but they are optional. We have provided for two different relay pinouts on the board so no matter which one you use, there will be some holes vacant. The relay we used is a Jaycar model, Cat SY-4060. Equivalents are available from other suppliers. Fig.4: watch component orientation when wiring up the PCB & check that the microphone socket has shorting contacts. o7 ,.... C a, ,q- ,.... 0 (0 C (.) en 0 Fig.5: here is an actual size artwork for the PC board. APRIL 1990 33 Vox with delayed audio - ctd normal speech causes the transmit LED to turn on and stay on during the brief pauses that occur between words - in normal speech. To test the audio section, feed the output into an amplifier and speak through the microphone. You should hear your voice coming through loud and clear. Don't expect to hear the actual delay between the time you speak and the time you hear it from the loudspeaker. Rather, your speech will have a slight echo to it. And turning up the gain will not produce acoustic howl. If you have an oscilloscope, adjust VR2 so that the signal at its wiper has minimum clock signal. This will result in the best signal to noise ratio. ~ , r1-- :::::, • ll.. z () !::: • :E :E en z <I: > a: 1-- > The PCB & groundplane assembly is secured using four self-tapping screws which go into integral plastic pillars in the bottom of the case. Use shielded cable to wire the microphone socket to the PC board. Once the board assembly has been completed, check it for correct installation of all the components. You can now connect the 12V AC plugpack to the circuit. Check the DC voltages around the circuit with respect to one of the PC stakes which is at 0V. You should find + 12V present at pin 4 of ICl, pin 8 of IC2, pin 1 of IC3, pin 1 of IC4 and the collector of Ql. For the negative rail, - 12V should be present at pin 11 of IC1 and pin 4 of IC2. The PC board can now be installed in the case. To keep hum and noise to a minimum, a ground plane needs to be installed underneath the PC board. This can be made from sheet steel, aluminium or from 34 SILICON CHIP PC board copper laminate which is what we used. Whatever material is used, it must be electrically connected to the earth track of the PC board. With copper laminate, this is easy - just solder a wire to it. With this done, the two boards can be mounted in the case. Use 4-gauge 16mm-long self tapping screws and 6mm spacers. The screws go into the integral pillars in the bottom of the case. When all the wiring is complete, you can switch on and check the voltages again. Testing Now plug in a microphone and adjust the sensitivity control so that 1-- • > j:: en z w en a: • <C ...J w C J: - ~ == >< > 0 w 3: 1-- 0 :::::, ll.. ll.. • 1-:::::, 0 0 c :::::, <I: L Fig.6: this artwork can be used as a template for drilling the front panel. 3.5 " D.S.D.D. COMPUTER DISKS David Reid Electronits PKT 10 , , NOW ONLY $19.95 ,. BULK PURCHASE / (100 DISKS) FOR $140.00 . DB-25 PLUG to CENTRONICS PLUG 1.8MTR LONG LAST CHANCE AT THIS PRICE NOW ONLY $8.00 ea two heads and the butane gas torch itself. • Insulated handles with spring return. 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You go to a mass storage device such as a CD-ROM or WORM drive. These can store huge amounts of data but they don't replace hard discs. Remember the celebrations in 1988 - Australia's Bicentennial of European settlement? One can only wonder what the computer world will turn on for the PC's 10th birthday in 1991. When IBM unveiled the original PC, a major selling point was the fact that it was "personal". At last the frustrating hours of waiting for elf 4 1 time on a mainframe terminal were at an end for there, sitting proudly on your desk, was a gleaming monochrome PC with two floppy disc drives and a massive 256K of memory. It was computing heaven - freedom to do what you want, when you want and for as long as you like! Little more than a decade later, ' This 5.25-inch CD-ROM drive is made by Philips. A CD-ROM can typically store 660Mb of data or about 300,000 pages of text. 36 SILICON CHIP bigger the standalone PC is almost a thing of the past. The growing prominence of computer networks in the workplace is slowly taking the "personal" out of personal computing. The circle is complete once again everyone's data is gathered together on a hard disc rather than scattered over many different discs. But each user can still have information like call lists and other personal data stored on diskettes. With so much important information stored in one place, the importance of regular and reliable backups must not be underestimated. The skill of the person overseeing the network is also of considerable importance. So many users and so much information. In the standalone world, most users typically have a hard disc with around 20Mb of storage capacity. For the home or small business user, any thoughts of using a CD-ROM drive are laughable. When the CD-ROM is part of a network however, it starts to make much more sense. When you talk about optical storage technology, CD-ROM is the oldest. Generally it is used for publishing large amounts of information - such as dictionaries, encyclopaedias and databases - that don't require constant updating. Applications have progressed, however, from general reference material to more specialised data. Which is just as well since the major limitation of the CD-ROM is that it is a read only device. You can't update it or store new data on it. typically stores 1Gb (Gigabyte or 1000 megabytes) per side although Sony recently released a 30cm disc providing 6Gb of storage. The 35.5cm disc usually stores over 3Gb per side. Aside from the variations in disc formats, media types, recording techniques and rotation methods, WORM drives are usually made up of opaque recording material between two clear plastic plates. Philips' latest CD-ROM is the CM201. CD-ROM is a read-only device and is ideal for large databases that don't require constant updating. Philips and Sony have defined the standard for CD-ROM discs. This means all suppliers use the same protocols when creating their discs and all players can read the discs. The compact disc contains digitised data which can be audio, computer data or a combination of both. One CD-ROM can hold 660 to 680Mb of data - the equivalent of about 300,000 double-spaced pages of text. So much data on such a small device! Microsoft's Programmer's Library is delivered on CDROM and contains information on OS/2, MS DOS, Windows, networks and PC hardware. The disc has the MS-DOS encyclopaedia together with references to C, Macro Assembler, Basic, Pascal and Fortran, Peter Norton's Programmer's Guide to the IBM PC and PS/2, QuickC Programming, Advanced OS/2 Programming, volumes one to four of the Microsoft Systems Journal, 15Mb of sample code for use in your own programs and a whole lot more. CD-ROM drives will certainly become more appealing given the increasing size of operating systems and applications software. Computing requirements for realistic visual images on disc will pro- bably also increase demand for the discs. WORM drives To date though, the optical or WORM (Write Once Read Many) drive has provided the most practical answer to mass storage requirements. Access times for optical drives remain well behind those for the more familiar magnetic drives. WORM drives use lasers to record data at a very high density on a removable disc. Compared to CD-ROM, WORM drives are less prevalent. The drives themselves may be either standalone or organised in a kind of "juke-box" arrangement with a number of discs and an autochanger. Applications requiring permanent storage such as medical and taxation records, engineering drawings and plans, financial and insurance records, to name just a few, are the prime uses for WORM drives. WORM drives can use 13.3cm (5.25-inch), 25cm, 30cm and 35.5cm discs, while the CD-ROM has been more or less standardised to 120mm. Storage capacity on the 5.25-inch WORM varies from 300Mb to 600Mb per side. The 30cm disc A high powered laser is focused through the plastic plate to burn holes in one only of the WORM's recording material, to store the data bits. To access the other side of the disc, typically you need to remove the cartridge and turn it over, just like your trusty old record player. The data bits are read back when the laser focuses a lower power beam on the media. Usually, data written on one vendor's WORM drive is not readable on another, whereas CD-ROM has the advantage of being able to play any disc on any reader. Technologically, WORM is just behind the compact disc. Although you can write your own data to a WORM disc, you can't then change what is written. Laser video discs Laser video discs are ideal for storing large numbers of photographic images. Visitors to the IBM stand at Brisbane's Expo 88 would have seen the laser video disc in full flight. The archival value of the video disc system is considerable since alterations can be made onscreen to copies of the stored image. Images can be made clearer, reconstructed or changed without affecting the original photograph. A laser video disc can store in analog format a combination of stills and video images (up to 108,000 images on a 30cm disc). Laser video disc quality is considerably better than the conventional television image. Each disc is protected by an acrylic seal, like the compact disc. Thus, there is little likelihood of damage from mechanical wear and tear, like the magnetic medium, nor is there the possibility of magnetic interference. APRIL 1990 37 Designed by Philips, this cartridge-loading device protects the CD-ROM from direct handling. Also, because the data is sealed into the optical disc, it is less likely to be corrupted than other media during use. Erasable optical discs Erasable optical discs are the latest players on the mass storage scene. Rewritable magneto-optical (MO) disc drives use the 5.25-inch form and store up to 650Mb of data on optical media protected by a removable cartridge. The disc spins at around 3600rps, making it comparable to the traditional hard disc. However, access times tend to be somewhat slower. Magnetic hard discs still have a significant speed advantage and the $10,000 price tag for an erasable optical disc drive means they are not for the faint-hearted. The erasable optical disc, like the WORM disc, is made up of recording material between plastic discs. The discs work by magnetic orientation. At room temperature, recording material on a "blank" disc has a uniform magnetic orientation. However, when the temperature is raised significantly, you can alter the material magnetically. The Next Month in Silicon Chip The Mozzie QRP Transceiver This nifty little transceiver is an unconventional design. It is suitable for Morse and RTTY and puts out as much as 800 milliwatts at 3.5MHz from its internal battery pack. And it's nice and clean spuriae are less than -40dB. PLUS: Bonus 180-Page Dick Smith Catalog 38 SILICON CHIP drive head uses a laser to heat the target area and reverse the orientation. Once the material returns to room temperature, the reverse magnetic orientation remains. Thus, the varying magnetic orientations of the disc represent the data bits. Erasable optical discs are therefore ideal for backups since you can remove and re-use them. Erasing then rewriting the data requires one pass of the drive head to heat the target area and apply a uniform magnetic orientation. The second pass actually writes the new data. Data is read when the drive focuses a laser beam on the recording surface to determine the polarity of the surface, since reflected light changes according to the magnetic orientation of the disc. Again like the WORM drive, the erasable optical disc can only access one side of the disc at a time. It was not so long ago that 20Mb hard discs were "de rigeur" in the office environment. Even now, 20Mb to 40Mb is still adequate for most applications. Nor is hard development standing still. IBM has already demonstrated an experimental hard disc drive which stores a gigabit (one billion bits) of information on a single square inch of disc surface! Magnetic tape drives Throughout all this technological change, the magnetic tape drive is still the lowest-cost method of storing vast amounts of material. It is cheap to buy, high capacity, relatively easy to keep and catalog and simple to operate. The main disadvantage is the sequential nature of the tape. Waiting for a file right at the end of a large magnetic tape is not fun and certainly not recommended for the impatient. Tape backup systems, like backup to floppy disc, generally provide the facility to selectively backup and restore individual files, rather than the entire contents of a hard disc. The tape is usually housed in either a cassette or cartridge. However, it is subject to magnetic interference and is not everlasting. For long term record storage you really need a WORM or erasable optical drive. 1§:;l II ROBBER STOPPERS" I FAMOUS 'ROKONET' PIR DETECTOR Features Include: • 15 x 15m coverage, 105 degree angle. * Full SMD Technology • Fully Computerised Quality Control system • Low noise, high sensitivity twin element pyroelectric • Extra High RF immunity • Very compact, low profile • Silent relay • Flat wall & corner mounting WAS $119.00 E36-4M 4 SECTOR ALARM PANEL Famous IEI brand 4 sector alarmPanel. Designed and manufactured in Australia for the Alarm Industry. One of the most popular Alarm Panels on the market! Features include:• Adjustable entry delay• Exit delay of 90 seconds • Automatic test mode • Can select 'Home' or 'Away' modes· 24 Hour Panic status· 24 Hour Tamper circuit • Built-in power supply and 1.9 Amp back-up battery • Welded steel cabinet plus MANY OTHER FEATURES! ~ WAS $349 3 NOW S69.95 Features include: • EEPROM • Local siren test • Keypad programmable • Two year warranty • Watch-dog timer circuit • Auto test facility • Built-in siren driver • Partial (arming) facility • 4 Wire keypad • 8 E.O.L. supervised zones • 15 User codes • Up to 4 Remote keypads • One button arming Probably the most advanced Panel of it's type. This Panel is fully programmable by the user and can be programmed to suit the requirements of any situation. Includes: Remote Keypad, 12V 6.5Ah Rechargeable battery+ power supply $16.95 BLUE STROBE LIGHT High intensity flashing light for alarm systems. $32.95 • s279 ACCESSORIES DAS-208L 8 SECTOR ALARM PANEL WEATHERPROOF HORN SPEAKERS 10WATT NOW HORN COVER & TAMPER SWITCH ...................$24.95 FLUSH REEDS ..........$7.95 SURFACE REEDS .... S7.95 EMERGENCY SWITCH ..................... $4.95 12V BAK SMOKE DETECTOR ....... ......$99.00 All of our Alarm equipment is of the highest quality 120 d812V PIEZO SIREN $26.95 ALARM PANEL TELEPHONE DIALLER TWO-TONE PIEZO SIREN $199 In-built microphone and recording system allows any 16 second message to be automatically sent to up-to four different numbers. - Designed to connect up to any alarm panel or security system - Individual numbers or all four can be called - Designed for both tone and pulse type dialling systems High efficiency 11 0dB 12V DC 200mA. Two tone pulsating signal. Dimensions: 85mm diam. 50mm height. NOW$22.95 :=:::::::::::::=:::::::::::=:rn::::=:::::::::=:=:=:=:=:i:::=:i:=:::=::::::::i:r::::::::::::::::1in:im.t1~:::11:i~:::;n~:::11■.r:::1i,1:::~1:::11,~1■<at>::::::::::::::::::::::::::::]:::::::::1:::::::::i:::::::::::::::::::::::f:::::::::::i:::::]:::::::: ....... ~ ......_ _ I ADELAIDE · h S CHRISTIES BEACH 203 Wng t t. 24 Beach Rd. Ph:(08)212 5505 382 3366 .___ _ _ _ _ _ _ _ _ ___, LONSDALE ENFIELD 5 Somerset Gire. 445 Main Nth. BRIGHTON FINDON 500a Brighton Rd. 127 Findon Rd. 377 0512 347 1188 MAIL & PHONE ORDERS Rd. Delivery charge of $8.00 for packag ~Y mail or_up-to 3K by up to ~ 0kg 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. Pulse width modulated signal expander Here's the complementary circuit for the PWM signal compressor published in the March 1990 issue of SILICON CHIP. The PWM signal expander works in virtually id~ntical fashion to the compressor circuit but with one important difference: CMOS switch IC3a is no longer in the feedback network of IC2c. Instead, it is now in series with IC2c's inverting (pin 9) input and thus forms part of the input resistance. What happens is that as the input signal level increases, the mark space ratio on pin 3 of ICl increases and so IC3a is closed for longer periods. This reduces the resistance at the inverting input of IC2c and thus increases the gain of the op amp. Conversely, as the signal level decreases, the gain of IC2c goes down. By using both circuits, it would be possible to create a dbx-style dynamic noise reduction system Low-cost alarm status indicator If you have a burglar alarm, this simple circuit will tell you whether or not it has been triggered, even if power to the alarm is subsequently removed. For example, it could indicate that a thief has attempted a break-in while you have been away or that the alarm is false triggering and annoying your neighbours. The circuit is based on a 7555 CMOS timer and uses a super capacitor as a power back-up. It can be triggered using either positive or negative going alarm output signals. Positive-going inputs are used to turn on Ql while negative going inputs are used to forward bias Dl. 40 SILICON CHIP +9V 4.7k 1 +10 _ ._,__.__. .,. EXPANDED OUTPUT 1 that could improve the signal-tonoise ratio of a cassette deck or older VCR by 10-15dB. In use, the signal to be recorded is first fed through the compressor. Then, on playback, the signal is fed through the expander which restores the dynamic range. Darren Yates, French's Forest, NSW. ($30) S1 v+ s~s .,. 0.1 10J ov+ u I.,. 01 1N914 02 1N4001 C1 .047-3F SUPER CAP I + 03 1N914 1M 0.1 S2 RESET I IC1 LM7555 Sl .,. 100k .,. .,. Power for the circuit is derived from an external DC supply via a 5-volt 3-terminal regulator. Normally, the trigger input (pin 2) of ICl is held high via a lMO resistor and so pin 3 is low. .,. .,. 01l If the alarm generates a positivegoing output, Ql turns on and pulls pin 2 low via a 0.lµF capacitor. Pin 3 of ICl now switches high and so FET Q2 will turn on and activate LED 1 if the momentary action 27k 27k ,___ _ _ _,___,o I OUT ANO SUPPLY •c COMP 2.7k 01 02 1.6k +1NPUT • 03 PN3643 43k -INPUT • 43k 1M 1M . .,. * 4.3k 100k 0.1 . • TRIM FOR CORRECT GAIN * ADJUST FOR CORRECT GAIN ANO OFFSET 820() . Single supply instrumentation amplifier This circuit is for a singlesupply amplifier with current output and an input voltage range that includes negative voltages. The amplifier was originally designed to buffer a high impedance microwave detector and to amplify the signal to a suitable level to be sent down .a 10-metre long coaxial cable. It is used in a hostile RF environment Status switch is now pressed. The circuit remains in this state (ie, pin 3 high) until pin 6 is pulled high by pressing the Reset switch. Similarly, if the alarm has a lowgoing output, pin 2 is pulled low by D1 and the 0.lµF capacitor. Backup power for the circuit is provided by super capacitor Cl. This can have a value anywhere between .047 and 3 Farads. Steve Calder, Parramatta, NSW. ($35) and has been carefully designed to avoid earth loops. The input stage consists of a pair of FETs (Ql & Q2} and a dual op amp (ICl} connected as a differential input/differential output amplifier. The output of this differential amplifier is converted to a single ended output by IC3 which is a Burr-Brown INA105 precision op amp. IC3 in turn drives Q3 to provide a current source output. IC2a and VN10 provide a constant current source for the differential pair (Ql & Q2} while IC2b functions as a gain stage and provides the supply to the differential input and output pairs. Note that the INA105 is necessary to achieve a CMRR of lO0dB. Unfortunately, the basic DC performance of the amplifier is almost totally determined by Ql and Q2, and FETs can be notoriously poor in this aspect of their performance. Even so, the linearity of the circuit is quite good over the common mode range of ± 500mV. Phil Denniss, University of Sydney, NSW. ($45) Handy hint Do you have trouble with tangled leads from your power supply to your prototyping breadboard? This is a particular problem when you are using positive and negative supply rails and so have three leads. One way to solve it is to use a length of light duty 3-core mains flex, preferably the older type with red, black and green leads. Cut off a suitable length, say 60cm or thereabouts and strip and tin (with solder) the leads at each end. Then red is naturally the positive lead, black is negative and green is 0V or earth. APRIL 1990 41 LOOK at the really great bargains we've got for you this month! Prices are SLASHED on the 240V/DC Plug Packs, Ferro Fluid Dome Tweeters, Lelon quality capacitors and much, much morel Get In EARLY to avoid disappointment! You can trust ALTRON ICS to supply the most up-to-date products at the lowest prices - Australian made whenever possible - and deliver them to you overnight. If you missed our catalogue In February EA phone now TOLL FREE 008 999 007 for a free copy. TELECOM ISOLATION TRANSFORMER SALE M 11 oo soon : soon NORMALLv $13.95, SAVE UP TO $5.oo EACH THIS MONTH. BE QUICK! >"-< THIS MONTH ONLY Jack O'Donnell Managing Director .. ·.,:-. ', L;bt;~h D~a,··T~ace20MHz . ,: ' · .C.• . '· , ,. ·:-:;:::::::::::::::::::::::::::::::."{7 :::::.••{ 1/:::,..::::::::::::::::::-:-:.. HEADPHONES CRO With Component T~~~~r ••• •• • •• •• • •• •••• · •• •• .. • •••• • •••·•·•·",",C"·•· • m•••;.•,.•.:•' : • · •;.:.-.y •.•••w, • •y y.'"."·"·Y-' ' ' ·" . •, { $1 O.oo EACH OR, 2s OR MORE $8.oo EACH , Why pay $400 or more for a David Clark set? AVIATORS HEADSET WITH OIL FILLED EAR CUSHIONS .. e • High pcrfonnance, noiae • ttcnu . arph-•· • Noise canccu· . •tuia Cu.sbioncd head "'8 Dll<rophonc , pcrf<mn&ncc • s:ad~ Super ~dy • Groat last a~ifc' _proks11ona1 pilot', trcatrncnr. • Include., tune wi~ n::aaonable hcad.,ct will tandard lllra'aftjacb C90100NLY · $189.00 1;; DESCRlmON: This model ii a dual -trace 20MHz Oscilloscope using high bd~tm:ss CRT. ·ca1 Jifien ha.., high 1CD1itivity of 5mV/l)iv and th:, fn:qucncy chara"im: 1511c 1<:,POIIJC .,, verb. moo-::roll off exceeding 20MHz. 11z special circuit is designed so ~ta single c o ~ t or the s ts in er out of the actual circuit board can easily be tcsttd. rcqu~~g no power to drive the ~ display ibows c:omponcnt faulta, compotznt value, characterut1e1 and teats componcntl -"' ~ ~~- ~ NAolwtroanvlal/aoble from cs ea/ers > > ) ;~is: . Component Tcstc:. Wide bandwidth & high scnliti~ity • Very low power . consumption• High 1C111itivity X-Y mode. Zaxil (intcnzuty modulation)• Front panel clcctncal trace rotator• Rgualtcd power supply for greater accun.cy. Q 0155 LABTECH DUAL TRACE CRO $799 PLUS 2 OFF Q 017510:1 PROBE KITS $99.90 PAIR SAVE $100 THIS MONTH PAY ONLY $799 THE SET Reaietor Inaulatioo. breakdown can in electrical wiring and appliance, can be determined with this dual range nzgohm mct,r, Ideal for c:Jzcking ' imulatiOD in trmlfonD:n, Typical component test at■t~• pattern• . Digital Circuit Capacitor Zener Diode appU.a.ncca:, automotive gencratc:w1 and altcmatcr1, bOllX wiring etc. Breakdown can bcmcuuredateither500V or 1000V depending on the 1ituation. Perfect ror workvan, toolbox or work bench. -- K 2555 wit~!~;~!~!~:.~~:::::.,., . . >l!~!!il !II Audio Frequency Generator . d voltage PLUS a convenient and s1rT"4>le to ,... All the normal ranges of current, res,stance an . t t t . f' e PLUS trans,s or es er. use capacitance meter ,n ive rang_ , . . multimeter from the Labtech range: Check the features of this top quahty d1g1~l 200 Ohm • Capacitanoe: 5 ranges, 200pF • Continuity test • Buzzer sound: less t an ,,. 204pF • Transistor Tesler. DC Current AC Voltage AC Current .. -20db, -4Ddb and fine adjuat Q 1540 Normally $299 This month $249.00 < ii SPECIFICATIONS: Frequency Range: 10<:A< -lSOMHz in 6 ranges RF Output level: IOOmV RMS Accuracy+/· 3% Modulallon: Internal (30% dcplh). !kHz• &11:mal. 50Hz • 20Hz • Cry,tal Ioclced oscillator Q 1550 Normally $299.00 This Month $249.00 Save $S0.00 ) :) } \ ,,., ooov 0.2, 2.0, 20, 200 , 1 200uA, 2mA, 20mA. 200mA, 2A. 10A O2 2 20 200, 750V 200uA, 2;.,,A, 20mA, 200mA, 2A, 10A Reelatance 200, 2k, 20k 200k 2M,_20M. . Display: 3 112 digit LCD, 0.5". h~h "!'nh polarny and LO-Bat indication • Over range tnd1cat1on Maximum common mode volt~ge: SOOV peak Power gy alkaline or carbon-zinc battery Dimen~lona: 170 • 87 • 42mm, Weight: 350grams Speciflc:etlona: Input impedance: 10M on 11;11 ranges Nornmal mode noi• rejection: 46dB at 60Hz ·(1 k unbalanced) Common mode noise rejection: 100dB at 60Hz Overloade protection: 1OOOV DC or peak on all ranges Response time: less than 1 second. DC Voltage In testing audio circuitry it ia uca:aury to have an accurate audio signal 10urc:c. h e'Yml allows you to test 45SkHz IF >tage1! SPECIACATIONS: Frequency Range 1 DHz • 1 MHz +I• 3% +2 Hz Accuracy Sine/Square Output Waveform11 Sine: BV RMS Output level Square: ,ov p.p $79.QQ a 1085 USUALLV $139.00 EXTRA SPECIAL '.'Nffiiifii~!;!~iB!~~bb':§~~~!i; ~;~J~~~~~~ff~;;;i66;,~' •>:I0 INVERTERSINVERTERSINVERTERSINVERTERSINVERTERS POWERHOUSE 600W Get 240V AC Mains Power from your battery with these handy Inverter kit sets Many co111blnatlons to choose from: (Seo HA Doc'87) This inw- hu the capacity to produce 600 watU of maim power which will nm a f.anwtic ·· Operatc1 from 12V Car Bartcry 1 Auto Start draws power from array of appliance1. Ideally suited to running power tools, lighting (including tluroo) electric motcra and much more. It can be used either u a ponable or a permanent fixture. • Manual or Auto Start f.acilitics • Low bartcry your bat!ery DDly when appliance ii plugged in md •tumcd e11• ic, battery can be left pormancndy «>11n1:c:lled if requin>d. • Voltage Regulated • Current Ri:gulalled • Cun-out Overload unit solf " ait-out. Kit version K 6770 $425.00 Fully built and tested 12V Input K 6774 $525.00 24V Input K 6775 $525.00 limim Complete Kit K 6750 $279.00 Fully built and tested K 6755 $379.00 100'5 OF USES AT HOME AND AWAY 1 GHz Digital Frequency Meter {See Silicon Chip Nov '87, Jan '88) Thie euperb 1GHz Frequency Meter will out perform meny other inetrument• twice it• price. was $299.00 NOW$249.00 SAVE $50.00 . K 2515 Features include:• Professionally machined and screen-printed red perspex front panel • Easy lo assemble • Brighi Hewlett Packard 8 digit display • Electronic switch latching • High performance IC's • High Quallty components. Specification•: Operational Modes: Period frequency to 100MHz freq. to 1GHz freq . Range: 100Hz lo 1GHz {1.7GHz typical) in lrequency mode; 10Hz to 2.5MHz (5MHz typical) in period mode. Gating times: 0.01, 0.1, 1.0 and 10 seconds (10MHz and 100MHz ranges); 0.128, 1.28, 12.8 and 128 seconds (1GHz range). E•m• tta coet hunderde of timee over in cleaning connectora, PCB'•, awltchea, jewellery, glaeeea, watchee, drafting pen•, etc. Awsrded the Good Product Deeign Award for CETDC in 1987 Pin Point ULTRASONIC CLEANER WIii even clean your teeth! Woo 't 1ct1tch a damage - Ulel ordinary tap water and cn:atc1 -milliooa of 1upcr-pcnctr1tU'l3 bubbles. Hoopital u,,u ,how that Ultruonic cleaning produce, better resultJ safer than conwnticmal a:tbodl. Jn Just 3 minutes you wtll be amazed at the dlff'erence! A 0100 TOP VALUE NORMALLY $199.00, ONLY $174.00 THIS MONTH .. .. . . .. . PHONEORDER TOLL FREE ALTRONICS 008 999 007 \ff), ; ;; ici iiiili~iiRDEBitim!,iS EEl'A~t.BSNi;§;gg;:~~9 0011,i\'~1'.~' TY 1 ; 1J;;;~~::t::;:~;1 · · OURDffiECT IMPORT P RICE LESS DIA...-V $100! 240V/DC PLUG PACKS Pocket Sized Personal Audio Signal Generator WAS THIS MONTH t,U001 sV DC M900212VOC M9004 9VOC M 9020 12V AC 300mA 300mA 300mA 300mA $15.95 $15,95 $15.95 $16.95 $12,00 $12.00 $12.00 $10,00 Ou~e the finest portabel audio oscillator have ever seen . Range switch and multiply enable selectron to 46 preset frequencies from 20Hz to 150kHz, eg 20Hz, 28Hz, 32Hz, etc. Sine Wave and Square Wave output. Output control -20db to Odb Internal 9V battery a 1542 Oscillator M 9030 5 •MP WAS $32.9 6/7 519112 - 1,,. 0 $99.00 THIS MONTH $25.0 SAVE$7.95 ~~r.E.577.Z'-"',· ·"··-7:-"•·•'"y< ·"'•· """"<'"+;"" .;>"""" .;.;.; I ....:·r ERROFLUID DOME • \ < 1!'::'!:J!!ts . SAVE ON THESE LARGE •·. TopcndqualityataVERYr,,uonablepncc. VALUE CAPACITORS C 3012 Normally $29.50 each, LELON QUALITY Now $15.00 AT ALTRONICS LOW Save $14.50 PRICES Buy four for $50.00 Desk Mounted Lamp M . agn,tier TWIN RANGE LED TACHO (S .. ETI Aug '80) .·. :♦'i' -: ~t--a--/ ·- - ,._ .. •--~¥'r·/ WAS NOW 63V RB $4.70 $3.50 25V RB $2 .75 $2.00 16VAXIAL S1 .50 S1.0D R 5716 3.300uF 50VAXIAL S4.95 U .00 R &74010.000uF IOOV RP $29.50 $20.00 C/1-'··~· · >'. . . .· . .·••: &¥k;z,· -•-¥rHt.rne;~ ,i,--.~// / 0-1OOORPM/0/10,000RPM Passive Infra-Red This unit is suitable for I, 2, 3, 4, 6 and 8 cylinder vehicle,, both 2 1trok<: and 4 stroke. Fully compatible with conventional CDI and transistorized igniticn system1. Includes protection circuitry to prevent noix and high voltage spikcl from the points and the coil circuit damaging the elcctronica. Display flu~, when ovcr•rcvving OCCW'I. Only requires 3 connections to the clecirlcal system. CEILING SPEAKERS KIT Lite Guard K 4324 Normally $32.00 This month even more fantastic value at only $20.00. SAVE $12.00! That's an incredible 37.5% off! Floodlight Control • Howolten have you thoughtthere could be a prowler outside your door? Install a Ute Guard & (once armed) any "gueat" will be floodlil when detected by Ihle highly aenaltlve Infra-Red Detector. SpeclllaUons: • All weather operation • Operation Time, l-20minJ • Senslll•IIJ: 1l1 • 50', 30 bcllllU e Almeble e Switching Capablllt1: 500W max. incandollCCDt • Operation Modes: OFF, AIJfO, TI!ST, MANUAL, ON. ss3so was $135.00 SPECIAL ONLY $99.00SAVE •45V 2A Dual Tracking Power Supply . (See Silicon Chip Feb '110) • The ideal high grade extension speakers for the games room, den, study, workshop, back verandah, kitchen or wherever else you want quality sound. Kit include. everything you need. right down to the acnwa. Ceiling mounting can actually enhance the sound so that the 4", 15Watt drivers that comprise the heart of the system really sound stunning/ Kit Includes: 2 x Redford C 0626 drivers, 2 x C 0810 grilles, 1 x A 2300 60W stereo volume controller, 2 x 20M rolls speaker wire and mounting screws. C 0988 899.00 eautifully packaged, they make the perfect house warming gl~ This NEW dual tracking ~ r supply is a must for your workbench. The !WO rails track exactly wrth each other on any voltage and precise voltage IS obtained wrth the mullt-turn rotary control. It also has a clear display and meter movement, a dropout indicator and load ON/OFF swrtch. Housed in a medium sized instrument case with a silver anodised and pre-punched and screened front panel. I FEATURES : $ • Housed in a tough "ABS" instrument case e Floatingground • Load sw~ch K 3375 II 149 'l ..· ··•··•·. .•· ······/..•.••.•.• • •u••• ••H t •••·>•••>><••· · ···· ··· · •· ·•·•. •·NiC~cls Telephone Extention Bell Automatic Charger for INSTALLED IN MINUTES. Connects via P 0995 double adapter to telephone line at existing wall socket. Double adapter accepts both telephone and extension bell, which is supplied with a 10 meter lead. NOT SUITABLE FOR COMMANDER PHONE SYSTEMS. (See EA July '89) les from your nlcads G t 100's more recharge eye tly charging nlcad cells e II known that correc Its now we their service life. . greatly extends . fully automatic N1Cad Here Is a bi s charger that ena e battery rates as appro· differing charge AA C D cells or priate for A_AA, · once cells in sen~s up to ;d .the unit I the batt~ry sly~;~~he~ to trickle automatica1 · ff charge until you switch it o . P 0996 'v K 1550 $29.so Hot Canaries - The Electronic Canary (Silicon Chip Feb'90) Get that atmosphere of tranquility that only birds can give. The realism of this project is remarkable. Sounds for all the world like two trilling canaries. $39.so • Battery powered M 9020 (Plug-Pack Extra) $16.95 $25.95 K 1130 Bel Express 3 Radar Detector Detects X, Kand the new Ka Photo Radar Band. ThB n11w Industry standard! Expr11ss 3 contains thB lat11st BBi br11akthrough. lmagB RB/ectlon TBchnology for KA band Photo Radar d11tectlon and twice the X and K band s11nsltlvlty of ordinary superhet radar detectors. Fully equipped, Express 3 has no 9qual. Preprogrammed Features ■ NORMALLY $699.00 SAVE $100! A1540 Special introductory price $5 9 9 .00 Bel Express 3 - acclaimed the leader In Canada and USA - now available in Australia from Altronic. ■ ■ ■ . . . .. Instant On/Pulsed Warning: Encountering radar of this nature results In a warning sequence consisting of a series of quick "beeps" (unlike X, Kor Ka alerts) followed by the audio alert that corresponds to the type of radar received. Rashid VASS Rejection: Automatic rejection of signal received from collision warning systems which operate on the same frequency as police radar (K Band). Automatic K/Ka Band Override: Express 3 instantly alerts to the presence of Kor Ka Band radar when the FSA mode is engaged. Automatic Test Sequence: · Each time power is engaged, Express 3 will sound a single group of X, K, Ka and instant On/Pulsed alerts indicating ~ is ready to process police radar. e BANKCARD e VISA e MASTERCARD e PHONE TOLL FREE 008 999 007 e NEXT DAY JETSERVICE DELIVERY Country clients please allow an additional 48-72 hours MORE ALTRC,NICS DEAL~RS WANTED If you have a Retail Shop, you could increase your income significantly by becoming an Altronics Dealer, Phone Chris Campbell (09) 328 2199 for Details. 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Stirling Street Exchange Perth W.A.6000 AL TRON ICS RESELLERS Chances are there is an Altro nics Reseller right near you - check this list or phone us fo r details of the nearest dealer. Please 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 Expre11 Mall and Phone Order S.rvlce • for the coot of a local call, Bankcard, Vita or Matercard holder, can phone order for Hme day de1patch. Blue Ribbon Dealero are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg $8 over 1Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post Allow approx 9 days from day you post order to whe n you receive goods OVERNIGHT JETSERVICE Up to 3 Kg is $8.00 • 3Kg to 5Kg is $20.00 - We process your order the day received and despatch via. Overnight Jetaervlce Courier for delivery next day Country areas please allow additional 24-48 hours. HEAVY HEAVY SERVICE - Al l orders of 10Kgs or more must travel Express Road • Please allow 7 days for delivery. $12.00 to 10Kgs. $15.00 over 10Kgs. INSURANCE -As with virtually every other Australian supplier. we send goods at consignees risk. Should you 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 - Ban~card. Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight Jetaervlce we deliver next day. COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communicat ion s 713344 GERALDTON Bird Electronics 641631 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521500 Farmer Electronics 522388 DARWIN Ventronics 480030 ACT CANBERRA Bennett Commercial Electronics 805359 VICTORIA CITY All Electronic Components 6623506 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 CAPALABAKingsway Electronics 3902399 WOODRIDGE David Hall Electronics 8082777 COUNTRY BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724459 MACKAY Phi ltronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 TOOWOOMBA Hunts Elec tro nics ■ 329677 TOWNSVILLE Solex ■ 7724466 MAROOCHYDOREMals Electronics 436119 SA CITY 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 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 COUNTRY COFFS HARBOUR Coifs Habour Electronics 525684GOSFORD Tomorrows Electronics 247246 GRAFTON East Coast Electronic 431250 NEWCASTLE Novocastrian Elect.Supplies 6213 58 RAYMOND TE'IRACE Alback Electron ics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 WAGGA WAGGA Phillips Electronics 216558 W.A PHONE0ROER ..TOLL FREE .Al...TRONICS 008 > 999 007 Dual tracking ± 50V power supply Looking for a dual tracking power supply that can really deliver the goods? This switchmode design can provide up to ± 50V DC and features a LED dropout indicator and short circuit protection. By JOHN CLARKE & GREG SWAIN There are many situations where you need a high voltage dual tracking power supply. For example, this design could be used to power prototype audio amplifiers or high voltage op amp circuits, or it could be used in any application requiring a high voltage rail of up to 100V (eg, for servicing some TV sets). Perhaps the most important feature of the design is its tracking positive and negative DC outputs. These are adjustable from 0V to ± 50V (ie, the supply can deliver up to 100V DC) and are fully protected against short circuits and voltages generated by external loads. By contrast, most other currently available dual tracking power supplies only go to about ± 20V or perhaps ± 30V. 46 SILICON CHIP Another important feature is the output current capability. Take a look at Fig, 1. This shows the maximum load current for output voltages between 0 and 100V (ie, 0 to ± 50V). As shown, the maximum current is 1. 7A between 0V and ± 43.5V. After that, the output current capability is reduced but the supply can still deliver 1A at ± 50V (ie, 100V). The line and load regulation figures are very good. On the prototype, the line regulation was within ± 5mV of a given output voltage setting for mains voltages between 220V AC to 260V AC. The load regulation is within 500mV at ± 50V for an output current 1A (ie, 1 % ). The ripple output, which consists of 100Hz and other noise superimposed on the DC rails, is less than 3mV p-p for all load currents up to 1.7 A. A LED indicator on the front panel lights when the output ripple exceeds 5mV p-p. This indicates that the supply rails are beginning to drop out of regulation. Front panel hardware There are just three basic controls on the front panel: a Power ON/OFF switch, a Load switch and a 10-turn Voltage Adjust pot. The 10-turn pot makes it easy to adjust the output voltage to precisely the value you want. A conventional pot would be much too coarse in this position, so don't be tempted to save a few bucks. Th€! Load switch is a handy facility. It allows you to switch power to the load without having to switch the supply itself on or off. In operation, the Load switch simply switches the output rails to the positive and negative output terminals. Also on the front panel are a power on/off LED indicator, the aforementioned Dropout LED indicator, and four binding post output terminals (plus, minus, 0V and Specifications 10011 Type Dual tracking with switchmode preregulators for high efficiency Output Voltage 0 to ±50V Output Current 1.7A from Oto 87V; 1.5A at 91V; 1A at 1 OOV Tracking Accuracy Within ±1 % Load Regulation Better than 500mV at ±50V and 1 A Line Regulation Better than ± 5mV for mains voltages from 220-260VAC Ripple output Less than 3mV p-p at full load Protection Fully protected against output short circuits and forward and reverse voltages connected to the output; fuse protection for the power transformer GND). The rear panel carries a large finned heatsink, the mains cord entry and a panel-mount fuse holder. In practice, you can use the power supply in several different ways. You can use it to provide balanced positive and negative rails; you can take the output from between the positive and negative output terminals to obtain up to 100V DC output; or you can use it to obtain a single supply rail. Because the circuit is fully floating [ie, not tied to mains earth), the output can be referenced to earth by tying either the positive, negative or 0V terminals to the GND terminal. Our last dual tracking power supply was described in the 1.7 Fig.2: basic adjustable positive regulator circuit. The LM317 maintains a constant 1.25V between its OUT and ADJ terminals, which means that 12.5mA flows through the 1000 resistor and VR1 at all times. \ 1.5 I\ 0.5 I I 10 20 I 30 I 40 I I 50 60 I 70 I I 80 90 OUTPUT -1.25V REFERENCE January 1988 issue of SILICON CHIP. That unit was capable of supplying 0 to ± 18.5V at about 1-amp and was based on adjustable positive and negative 3-terminal regulators [the LM317 and the LM337). Our new design also uses LM317 and LM337 3-terminal regulators but there is quite a bit more to it than that as we shall see. Let's first take a brief look at how these devices work. Fig.2 shows an adjustable positive regulator circuit based on an LM317. Capacitor Cl is used to filter the DC input to the regulator, while potentiometer VR4 adjusts the output voltage. In operation, the LM317 produces a nominal 1.25V between its adjust [ADJ) terminal and the output [OUT) terminal. The 1000 resistor between these terminals thus has Design considerations +1.25V C1 100 OUTPUT VOLTAGE Fig.1: maximum output current vs. output voltage. The supply can deliver 1.7A for outputs up to 87V and 1A at 100V (ie, ± 50V). 1.25V across it which means that 12.5mA flows through VRl at all times When VRl is set to on, the output voltage [ie, at the OUT terminal) sits 1.25V above point A. This point is set at - 1.25V by a - 1.25V reference circuit, and so the output sits at 0V with minimum VRl. As the resistance of VRl increases, the voltage on the ADJ terminal is " jacked up" and so the output voltage also increases. OK, so what do we have to do to obtain a high voltage, high current dual tracking supply? Unfortunately, you can't just use high voltage regulators and substitute a bigger transformer, bigger heatsink and larger filter capacitors. The problem is that as the power dissipation in the device increases, its temperature also increases and the device shuts itself down by current limiting. This means that the amount of current that you can obtain using the circuit of Fig.2 is severely limited at low output voltages due to the high voltage developed across the regulator. Pre-regulator circuit Fig.3 shows how we solved this problem by employing a switchmode pre-regulator circuit ahead of the 3-terminal regulator. The pre-regulator acts to minimise the input voltage to the regulator and thus reduces power dissipation for a given voltage and current setting. The result of this scheme is that the regulator can supply heaps more current. It also means that we can now use the cheaper lowvoltage 3-terminal regulators inA PRIL 1990 47 REGULATOR L1 01 100n Cl JUUL PULSE WIDTH MODULATED SIGNAL stead of the more expensive high voltage units. Now take a closer look at Fig.3. Qt, D5, Lt and C2 form a basic switchmode circuit. What happens is that Qt is switched on and off rapidly by a pulse waveform into its base. If the pulse waveform has a short duty cycle (ie, the transistor is off most of the time), very short current pulses will be fed to 11 and the resultant DC voltage across C2 will be low. Conversely, if the duty cycle is high, the transistor will be on most of the time and the DC voltage across C2 will be high. By switching Qt on and off to control the output voltage, its power dissipation is low and the overall circuit efficiency is high. D5 protects Qt against the inductive kickback from 11 when the transistor switches off. So the voltage at the input of the regulator is controlled simply by adjusting Qt 's duty cycle. The switching pulses to Qt 's base are provided by a high gain er- VT /\ /\ V[/I'<iVMK ror amplifier circuit consisting of IC3c, IC2b and Q3. This circuit monitors the voltage across the regulator and then generates a pulse width modulated (PWM) feedback signal at the output of comparator IC2b. This signal then switches Q3 which in turn controls Qt. As shown in Fig.3, the inverting input of op amp IC3c is fed from a voltage divider network consisting of ZD7, R2 and R3. This network is connected between the regulator input and OV. Similarly, the noninverting input is fed from voltage divider network R4 and R5 which is connected between the regulator output and OV. Because equivalent values are used for the resistors in each divider network (ie, R2 = R4 & R3 = R5), the inputs to IC3c are equal only when the regulator's input is 4.7V greater than its output. This 4.7V differential is necessary to compensate for the 4. 7V drop introduced by ZD7 in one of the divider networks. IC3c thus effectively monitors the L<T/\/\ "'I nf VP-1...____.~ . _ _ _ _ _ . ~ ~ r (a) HIGH VOLTAGE (b) LOW VOLT AGE Fig,4: how the error voltage VE and the triangle waveform VT interact. The higher the error voltages, the wider the voltage pulses (Vp) produced at the output of IC2b. 48 SILICON CHIP Fig,3: adding a preregulator circuit drastically reduces the power dissipation in the LM317 for a given output. IC3c monitors the voltage across the regulator & produces a DC error voltage which is fed to IC2b. IC2b compares this error voltage with a constant triangular waveform and produces a pulse width modulated (PWM) signal to drive transistors Q3 & Qt. voltage across the 3-terminal regulator and generates an appropriate error voltage (VE), If the voltage across the regulator begins to fall below 4.7V, the error voltage goes up. If the voltage across the regulator begins to rise, the error voltage goes down. This error voltage is applied to the non-inverting input of IC2b where it is compared with a triangular waveform applied to IC2b's inverting input. This triangular waveform (VT) is derived from an oscillator circuit (not shown in Fig.3). Since IC2b is wired as a comparator its output can only be high or low, so when VE is above VT the output will be high and when VE is below VT, the output will be low. The interaction of VE and VT via IC2b is shown in Fig.4. Fig.4(a) shows that when VE is high (ie, the voltage across the regulator is beginning to fall), the output from IC2b is a series of fairly wide pulses (Vp). Thus, Q3 and therefore Qt will be pulsed on for fairly long periods of time and this will increase the pre-regulator output voltage. Similarly, if VE is low as in Fig.4b, the output from IC2b will consist of a series of narrow pulses and Qt 's duty cycle will be low. What this all means is that Q 1 is pulsed on and off at exactly the correct rate to give the required input voltage to the regulator. If the voltage across the regulator begins to move in either direction away from 4.7V, the pulse signal at the output of IC2b automatically adjusts to switch Ql on for longer or shorter periods as required. Circuit details Now take a look at Fig.5 which shows all the circuit details. While this may appear daunting at first sight, all the circuit elements in Fig.3 can be directly related to Fig.5. The main difference between these two diagrams is that Fig.5 also includes all the circuitry necessary for the negative supply rail. Its pre-regulator circuit operates in a similar fashion to that used for the positive rail but uses a PNP driver transistor (Q4) and an NPN switching transistor [Q2). IC3b is the error amplifier for the negative rail, IC2a the comparator, Q4 the driver transistor, Q2 the The supply is easy to wire but you should take extra care with the mains wiring. Use a cord-grip grommet to secure the mains cord and sleeve the switch and fuse terminals with heatshrink tubing. The finned heatsink on the rear panel ensures adequate cooling for the power devices. main switching transistor, and L2 the inductor. The output of this pre-regulator circuit drives an LM337 negative 3-terminal regulator. Power for the circuit is derived from a 160VA toroidal transformer with an B0V centre-tapped secondary winding. This drives bridge rectifier Dl-D4 which, combined with the four l000µF filter capacitors, gives ± 60V DC rails. Short circuit protection for the transformer is provided by a 250mA fuse in the mains active lead and a 2A fuse in each leg of the secondary winding. The ± 60V rails are connected directly to the emitters of switching transistors Ql and Q2. These are BD650 and BD649 Darlington devices which have a collector to emitter voltage rating of 100V and require only about 12mA of base current to deliver 3A. In addition to the ± 60V rails, there are five other supply rails in the circuit: ± 30V, ± 15V and + 12V. These supply rails are derived using zener diodes ZD1-ZD5. The ± 15V rails feed dual comparator IC2 and quad op amp IC3, while the ± 30V rails feed IC4, a high voltage op amp. The + 12V APRIL 1990 49 F2 2A F1 25 0mA +60V +30V _ _ _,......+.... 15.,.v_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _..,..._ _ _ _ +15V pm A N 39k 1000 63VW E + 1000 + - 63VW _ TRIANGULAR WAVEFORM +l 2V GENERATOR 10k 24 0VAC ltl 7555 1W -15V 1M + ZD1 LM336 -2.5 J - A 100k COMPARATOR 100k 1.Bk E +15V A POWER LE01 10k 10k 04 BC640 330 63VW A X 1M OV OUTPUT SET VR1 10k 1000 63VW + 1000 + _ 63VW - -15V 2.7k -1.2V OFFSET AMPLIFIER 10k ERROR SIGNAL 06 BY229 10k -15V ,w -30V :t50V, 1.5A DUAL TRACKING POWER SUPPLY BC546,BC556 VIEWED FROM BELOW rail is used to power ICl. ICl is the triangle waveform generator. It consists of a CMOS 7555 timer which runs at 10kHz. This frequency is set by the 15k0 and 4 7k0 resistors and by the .0015µF capacitor on pins 6 and 2. 50 SILICON CHIP Because the circuit is wired in astable mode, the .0015µF capacitor repeatedly charges to 2/3Vcc and discharges to 1/3Vcc (Vee = the 7555 supply rail). Th_e resulting triangular waveform developed across the capacitor is then fed to pins 2 and 6 of IC2a and IC2b via 10k0 isolating resistors. These stages compare the triangle waveform with the error signals from IC3c and IC3b to produce the pulsed waveforms to drive Q3 and Q4 as described previously. + - 2.2M DROPOUT LED2 15k 4x 1N4148 LOAD LM317T IN OUT S2a +0-50V ~ ADJ 100n ZD7 4cio1.:w j 100 63VW 100k . - 22k 1% 15k 39k 15k ERROR SIGNAL 470 50VW SET 50V OUT VR2 10k 330 63VW 03 BC639 10 50VW BP • A 010 1N4002 METER CAL VR3 20k E 100k 2.7k 2.7k -15V DV +15V 2.7k 2.7k +3DV GNO 100k J, CASE + 10k 100k 0-SOV \ 470 sovw + 15k 011 1N4002 100 63VW + _ 22k l¾ 15k 012 1N4002 L4 LOAD 0-0 S2b -0-SOV LM337T LH4 : 33T. 0.5mm ENCU ON NEOSIO 17-732-22 TOROID 013 1N4002 A CMOS 7555 timer must be used for ICl, by the way. Don't substitute a standard 555 timer, as this will impose discharge spikes on the supply line and disrupt the operation of the switchmode circuitry. ICZa and ICZb are part of an Fig.5: the final circuit uses the parts depicted in Fig.3 to derive the positive rail, while the negative rail is derived using an LM337 negative regulator and a similar switching pre-regulator arrangement. IC4 ensures that the negative rail tracks the positive rail. LM393 dual op amp package. These have open collector outputs which means that pins 1 and 7 can switch to the - 15V supply. Because of this, diode D7 is included to prevent the base of Q3 from being pulled APRIL 1990 51 I. ± SOV 1.SA DUAL TRACKING PC • DROPOUT • POWER VOLTAGE ADJUST • • L This artwork can be used as a drilling template for the front panel. The meter is supplied with its own mounting template. negative when pin 7 of IC2b goes low. The 10k0 resistor between Q3's base and the OV rail ensures that the transistor completely switches off. No diode is necessary for IC2a, since its output will only go to OV. This is by virtue of the 10kn pullup resistor connected to the OV rail. Offset amplifier IC3a provides the - 1.25V offset voltage for the LM317 regulator. This op amp is connected as an inverter, with feedback via the 2.7k0 resistor connected between pins 1 and 2. Its non-inverting input is connected to OV via a 1.BkO resistor, while the inverting input samples the voltage from ZD1 via trimpot VRl. ZD1 is an LM336 precision 2.5V reference diode. IC3a simply inverts and attenuates this reference to provide the nominal - 1.25V offset voltage which is applied to the bottom of voltage adjust pot VR4; ie, IC3a operates with a gain of - 0.5 . In practice, VR1 is adjusted so that the output voltage is at OV when VR4 is at minimum setting. Kick start circuit The circuit shown in Fig.3 won't start up when power is initially applied. The problem is, Ql cannot switch on and charge C2 until a pulse signal appears at the output of IC2b. And this pulse signal can52 SILICON CHIP not be generated until IC3c generates an error voltage which in turn cannot be generated until voltage appears at the input to the regulator. So we have a classic catch 22 situation - Ql cannot be pulsed on to give an output because there is no output in the first place. The way around this dilemma is to "kick start" the circuit by fitting 100k0 resistors between the supply rails and the inverting inputs of error amplifiers IC3b and IC3c. Take a look at IC3c on Fig.5. It has a 100k0 resistor fitted between pin 9 and the - 15V rail. Now, when power is applied, pin 9 is initially pulled to - 15V and so a large error voltage appears at the output (pin 8). IC2b thus produces a pulse waveform with a high duty cycle and so Ql quickly charges the 330µF capacitor on the regulator input to the required voltage. As the voltage to the regulator input rises, the voltage on pin 9 of IC3c also rises and so the error voltage decreases and the circuit quickly stabilises. The negative rail pre-regulator is kick started in similar fashion by using a lOOkn resistor to pull pin 6 of IC3b to + 15V. As well as providing the kick start facility, the 100kn resistors also have the effect of increasing the input/output differential applied to the 3-terminal regulators. This is because the resistors provide an additional voltage offset at the inverting inputs of the error amplifiers. As a result, the circuit of Fig.5 stabilises when the differential voltage across the regulators is 8V instead of 4. 7V as is the case for Fig.3. Voltage adjustment VR4 provides the output voltage adjustment for the positive supply rail. This is wired in parallel with a series pair consisting of trimpot VR2 and a 15k0 resistor. VR2 sets the maximum output voltage and is adjusted to give exactly ± 50V out when VR4 is at maximum setting. OK, so the output of the positive regulator is adjusted using VR4 but what about the negative regulator'? It doesn't have a potentiometer on its ADJ terminal but uses a voltage tracking circuit consisting of IC4, D14, D15, Q5 and Q6 instead. IC4 is an LM344 high voltage op amp while Q5, Q6, D14 and D15 form an output buffer stage to provide the necessary lOmA drive to the LM337. Q5 and Q6 drive the ADJ terminal of the LM337 via two 1.2k0 resistors in series. Because a current of 10.4mA flows through the 1200 resistor between the OUT and ADJ terminals, it follows that the voltage across the two 1.2kn resistors is 25V. This allows IC4 ,weR SUPPLY 7 • LOAD • ON GND • • ov + _J and its buffer stage to drive the ADJ terminal of the 1M337 to - 48.75V in spite of the fact that the negative supply rail to the op amp is only -30V. In practice, the output of the op amp buffer stage (ie, the junction of the two 330 resistors) swings between about + 26.25V and - 23.75V to provide the full O to - 50V range of the negative supply output. So how does the circuit work? The idea behind the op amp circuit is to provide a mirror of the voltage on the positive supply rail. IC4, its output buffer stage Q5 and Q6, and the 1M337 regulator can all be regarded as a power op amp. This op amp can be regarded as an inverter with a gain of minus one, set by the 22k0 resistor to the positive output rail and a second 22k0 resistor connected to the negative output rail. Thus, if the positive output rail is at + 50V, the negative rail will automatically be at - 50V. 13 and its associated 470µF capacitor filter the output from the positive regulator while 14 and another 470µF capacitor filter the negative regulator output. These two filter networks remove any residual switchmode ripple due to radiation from the pre-regulators into the positive and negative output supply lines. The output voltage of the supply is monitored by a lmA FSD meter PARTS LIST 1 PCB, code SC04104901, 167 x 126mm 1 plastic instrument case, 260 x 1,90 x 80mm (Altronics Cat. H-0482 2 aluminium panels to suit case (Altronics Cat. H-0488) 1 front panel label, 255 x 73mm 1 80V 2A centre-tapped toroidal mains transformer (Altronics Cat. M-3075 or equivalent) 1 heatsink, 110 x 33 x 72mm (Altronics Cat. H-0560 or equivalent) 1 pushbutton mains switch with plastic body 4 Neosid 17 · 732-22 toroids (Altronics Cat. L-511 0) 1 DPDT toggle switch 1 red binding post 1 black binding post 1 white binding post 1 green binding post 1 panel-mounting 3AG fuse holder 4 PC-mounting 3AG fuse clips 1 250mA 3AG fuse 2 2A 3AG fuses 3 solder lugs 1 mains cord grip grommet 1 3-way mains terminal strip 1 mains lead & plug 1 MU52E 1 mA panel meter with 0·50V scale (Altronics Cat. 0-0538) 1 5k0 1 0-turn potentiometer 1 20k0 horizontal trimpot 2 1 OkO horizontal trim pots 4 T0-220 mica washers and insulating bushes 1 95 x 125mm metal plate 3 300mm lengths of heavy duty hookup wire (red, green, blue) 4 250mm lengths of medium duty hookup wire (red, yellow, brown, white) 1 500mm length of green/yellow mains earth wire 500mm length of brown mains active wire 4 1-metre lengths of 0.8mm enamelled copper wire Semiconductors 1 LM31 7T positive adjustable 3-terminal regulator LM337T negative adjustable 3-terminal regulator 1 7555 CMOS timer (IC1) (do not substitute a 555) 1 LM393 dual comparator (IC2) 1 LF34 7 , TL07 4 quad op amp (IC3) LM344H high voltage op amp (IC4) - (available from Geoff Wood Electronics) 1 BD650 PNP Darlington transistor (01) BD649 NPN Darlington transistor (02) 1 BC639 NPN transistor (03) 1 BC640 PNP transistor (04) 1 BC546 NPN transistor (05) 1 BC556 PNP transistor (06) 1 LM336 -2.5V reference diode (ZD1) 4 15V 1 W zener diodes (ZD2-ZD5) 1 1 2V 400mW zener diode (ZD6) 2 4 . 7V 400mW zener diodes (ZD7,ZD8) 4 1 N5404 3A diodes (D1 -D4) 2 BY229, MUR1550 fast recovery diodes (D5,D6) 7 1 N41 48 diodes (D7 ,D14,D15,D16-D19) 6 1 N4002 1 A diodes (D8-D13) 2 5mm red LEDs (LED1 ,LED2) Capacitors 4 1 OOOµF 63VW PC electrolytic 2 470µF 50VW PC electrolytic 2 330µF 63VW PC electrolytic 2 1 OOµF 63VW PC electrolytic 2 1 OµF 50VW non-polarised PC electrolytic 1 0 .15µF 1 OOV metallised polyester 1 0.1 µF 100V metallised polyester 1 .0015µF metallised polyester 1 22pF ceramic Resistors (0.25W, 1 2 .2MO 2 2 1MO 5 6 1 OOkO 1 1 47k0 1 2 39k0 2 2 22k0 1 % 1 8 1 5k~ 2 9 10k0 1 1 1 OkO 1 W 1 2 6.8k0 2 1 4.7k0 5%) 4.7k0 1W 2 .7k0 1.8k0 1.2k0 1.2k0 0.5W 1 kO 5600 5W 1200 1000 330 Miscellaneous Screws , nuts, star washers, heatshrink tubing, solder etc. APRIL 1990 53 The 3-terminal regulators and switching transistors are bolted to (but electrically isolated from) the rear panel (see Fig.7). Their mounting bolts are also used to secure the finned heatsink. (with a 50V scale) connected across the positive and negative rails via a 39kn resistor and trimpot VR3. Diodes DB, D9, D10, Dll, D12 and D13 protect the regulators from reverse voltages which may be generated by capacitive or inductive loads connected across the outputs. Drop-out indicator When the regulators are working as designed, the ripple voltage superimposed on the DC rails will be very low. However, if the current drain is higher than the regulator can supply while still maintaining about BV between its input and output terminals, the ripple voltage will suddenly become quite high and the output voltage will fall. IC3d detects the onset of this condition and flashes a warning LED indicator. This op amp is wired as an inverting amplifier and monitors both the positive and negative regulators via 15kf2 resistors and a 0.15µF capacitor. The amplified ripple at the output of IC3d is fed to a full wave re.ctifier consisting of diodes D16-D19. When the ripple on one of the regulator outputs exceeds about 30mV, the output of IC3d swings sufficiently 54 SILICON CHIP high and low to drive LED 2 via the rectifier circuit. Construction The ± 50V 1.5A Dual Tracking Power Supply is housed in a standard plastic instrument case measuring 260 x 170 x 80mm. Most of the components are mounted on a PCB coded SC 04104901, while the transformer is mounted on a metal baseplate measuring 95 x 125mm. Metal front and rear panels are also used to provide power supply earthing and heatsinking for the 3-terminal regulators and Darlington switching transistors. In addition, a large finned heatsink is mounted on the rear panel to ensure adequate cooling for the power devices. Fig.6 shows the wiring details. Start construction with assembly of the PCB. Install PC pins at all external wiring points first, then install the fuse clips, wire links, resistors and trimpots. The two 5W resistors should be installed 1-Zmm proud of the PCB so that air can circulate under them for cooling. Next, install the semiconductors on the PC board. Make sure that each device is correctly oriented before soldering it in place. Note in particular that diodes D5 and D6 (BY229) face in opposite directions. Zener diodes ZD2-ZD4 should be mounted with a small loop in one end to provide stress relief under changing temperature conditions. IC4 (LM334H) is in a round metal TO-5 package. You will have to align its 1-4 leads and its 5-8 leads as shown in Fig.6 so that the leads fit the PCB. The tab on the bodv of the IC is adjacent to pin 8. Note that IC3 faces in the opposite direction to ICl and IC2. Ql, Q2 and the two 3-terminal regulators should all be mounted at full lead length and with their metal tabs facing away from the PCB. Make sure that you don't mix these devices up - you will run into big trouble if you do. Construction of the PCB can now be completed by installing the capacitors and making up and fitting the inductors. All the inductors (Ll-L4) are the same and consist of 33 turns of 0.5mm enamelled copper wire on a Neosid 17-732-22 toroid. You will need about 1 metre of wire for each coil. The best procedure is to first slide the toroid half way along the wire, then wind 16 ½ turns using one end of the wire. The remaining 16½ turns can then be wound using the other end and the completed inductor dipped in epoxy resin (eg, Araldite). This will prevent the windings from coming loose and also reduce the winding buzz from Ll and L2. Clean and tin the leads before installing L1 and L2 on the PCB (L3 and L4 are left till later). Drilling the case The case can now be drilled to take the various items of hardware. Most kits will be supplied with a pre-drilled front panel but if you're working from scratch, you will have to use the published artwork (or a self-adhesive label) as a drilling template. If you have a selfadhesive label, it's best to affix this to the front panel before drilling. Drill small pilot holes initially, then carefully ream out each hole to the correct size. The meter cutout can be made by drilling a series of small holes just inside the circumference of the marked circle and then filing the resultant cutout CORD GRIP GROMMET METAL REAR PANEL Q E~niH Al _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __j - (GREEEN/ ) MOUNTING PLATE A EJ\RTH POWER TRANSFORMER <at> © ~½ S1 LUG 470uF A~ LED1 LE02 METAL FRONT PANEL Fig.6: take care to ensure that all polarised parts are installed with correct polarity on the PC board. You can use medium-duty cable to wire up the meter, Voltage Adjust pot and the LEDs but the remaining wiring must be run using heavy-duty (23 x 0.2mm) cable. APRIL 1990 55 ;#"' ii This close-up view is of one inductors on the PC board. Wind the turns on tightly and dip the finished inductor in epoxy adhesive (eg, Araldite) to stop winding buzz before mounting it in position. The bottom CRO trace shows the triangular waveform produced at pin 6 of 555 timer IC1 and applied to the inverting inputs of IC2a and IC2b. The top trace shows the waveform on the collector of switching transistor Ql. to a smooth circle. The meter is supplied with its own mounting template. On the rear panel, you will need to drill holes to accept the mains fuse (Fl ], the cord grip grommet and the earth lug. Fig.6 shows the locations of these holes. You will also have to drill holes to accept the mounting bolts for the 3-terminal regulators and switching transistors. These same mounting bolts are also u:sed to secure the finned heatsink. The locations of these holes can be determined by mounting the PCB on the integral standoffs inside the case and sliding the rear panel into position. Bend the leads of the power devices so that their tabs sit flat against the panel, then check that the heatsink can be positioned so that the mounting holes will go between the fins. Adjust the power devices as necessary to achieve this, then mark the locations of the holes. This done, drill one hole and bolt the heatsink in position. The remaining holes can then be drilled at the appropriate locations from the heatsink side. That way, there's no danger of a hole running into a fin. Carefully deburr all holes on the inside surface of the panel and smear heatsink compound on the mating surface of the heatsink. Once drilling is completed, the various items of hardware can be mounted on the front and rear 56 SILICON CHIP panels. Note that the black anodising on the panels can form a good insulator so scrape this away from around the mounting holes for the earth lugs to ensure a good contact. The earth lug on the front panel is secured by one of the meter mounting screws. The power devices must all be electrically isolated from the rear panel using mica washers and insulating bushes. Fig.7 shows the mounting details for each device. As before, smear the mounting surfaces of these devices with heatsink compound before sliding the panel into position and installing the heatsink and mounting screws. When the devices have all been MICA WASHER \ SCREW ! ~ J PCB l METAL REAR PANEL ' FINNED HEATSINK Fig.7: mounting details for the switching transistors and 3-terminal regulators. The metal tab of each device must be electrically isolated from the rear panel. secured, switch your multimeter to a low ohms range and check that the metal tabs of the power devices are all isolated from the metal panel. If you encounter a short, clear the problem before proceeding further. Transformer mounting The transformer mounting plate can now be drilled to accept the transformer, mains terminal block, earth lug and mounting screws. Fig.6 shows the location of all these parts. Note that one of the mounting screws (at back right] is not shown in Fig.6 but you can see where it goes from the photographs. You will also have to drill corresponding holes to accept the four mounting screws in the base of the case. Check that everything fits in the case before marking out these holes. If the mounting plate is too far forward, the transformer will foul the meter. The remaining hardware can now be installed in the case and the wiring completed. Medium-duty hook-up wire can be used to connect the meter, potentiometer and the two LEDs but the remaining wiring must be run using heavy-duty insulated cable (eg, 23 x 0.2mm]. This includes the wiring to the output terminals and to the load switch (S2). Inductors 13 and 14 and their two associated 470µ,F capacitors are mounted adjacent to the Load 0 NOG 0 The PC board is coded SC 04104901 and measures 167 x 126mm. switch to ensure maximum reduction of switching hash. Use epoxy resin to glue the capacitors to the front panel so that they are not just supported by their leads. 13 and 14 can then be supported by gluing them to the ends of the capacitors. The 3-core mains cord is clamped to the rear panel using a cord grip grommet but first strip back the outer insulation by about 60mm. Connect the active (brown) and neutral (blue) leads directly to the terminal block as shown in Fig.6, and solder the earth lead (green/ yellow) to the adjacent solder lug. The remaining wiring can then be run to the mains fuse, power switch, front and rear panel earth lugs, and to the GND terminal using 240V AC cable. Sleeve the mains switch with plastic heatshrink tubing to avoid the possibility of accidental shock. In fact, it's a good idea to sleeve the switch terminals first, and then sleeve the whole of the switch body up to the mounting nut. Note that we have specified a mains switch with a plastic body and actuator. Don't use a miniature toggle switch here. If you substitute a switch with a metal body, make sure that it is correctly earthed to the front panel. Switching on Before switching on, wind the Voltage Adjust pot (VR4) to minimum setting and set VRl, VR2 and VR3 to mid-range. With that done, you can apply power and check the supply rails. Check that the unregulated voltages to the emitters of Ql and Q2 are at ± 60V, and check that the ± 30V, ± 15V, + 12V and + 2.5V rails are all present. Now connect your digital multi- meter across the positive and negative output terminals and check that the positive and negative output voltages increase as the Voltage Adjust pot is wound up. Check also that the two rails track each other within ± 1 % (by measuring between each rail and OV). If you want the tracking closer than that, you will need to pad one of the 22k!l 1 % resistors. If everything is OK, wind the Voltage Adjust pot back to its minimum setting, connect your DMM between the positive and OV output terminals, and adjust VRl so that the DMM reads OV. This done, wind the Voltage Adjust pot up to maximum setting and adjust VR2· for a reading of 50V. Finally, adjust VR3 so that the front panel meter reads 50V. All that remains is to secure the lid of the case and your new power supply is ready for work. ~ APRIL 1990 57 JerernY Smith's . BOlRD SOlUllOMS MOTHERBOARDS 10MHz XTM/Board, OK RAM Baby 286 M/Board, 20MHz/0K Baby 286 M/Board, all-in-1 OK Baby 286 M/Board, 12MHz OK Half-size 286 M/Board, with 1MB M1000 M2000 M2010 M2020 RAM M2030 Baby 386 M/Board, 33MHz OK M3000 Baby 386SX M/Board, 20MHz 0KM3010 Baby 286 12MHz (1MB) OK RAM M2040 I 695.00 2795.00 995.00 399.00 CHIPS 1M RAM Chip - 100nS 29300 1M RAM Chip - 80nS 29380 256K RAM Chip - 100nS 29400 256K RAM Chip - sons 29480 8087-2, 8MHz Co-Processor 29500 80287, 6MHz Co-Processor 29510 80287, 8MHz Co-Processor 29520 80287, 10MHz Co-Processor 29530 4 X 256K RAM Chip, 1oons 29200 4 X 64K RAM Chip, 120nS -for VGA card 29212 64K RAM Chip- 120nS 29112 29000 NEC V20 Chip NEC V20 Chip, 10MHz 29010 NEC V30 Chip, 10MHz 29020 64K RAM Chip - 100nS 29210 I 149.00 695.00 545.00 499.00 Hard, NEC 5.25in 179MB 18mS ESDI D8050 Hard, NEC 5.25in 380MB 18mS ESDI D8060 Hard, NEC 5.25in 760MB 16mS ESDI D8070 Hard, NEC 5.25in 380MB 18mS SCSI D8080 Hard, NEC 5.25in 760MB 16mS SCSI D8090 Hard, Kalok 20MB 40mS 29.95 32.95 8.95 9.75 275.00 315.00 450.00 499.00 32.95 12.00 4.95 24.95 39.95 49.95 5.45 DISK DRIVES Floppy, YE-Data 360K D5500 Floppy, YE-Data, 720K/1.44M D3000 Floppy, D3000 Plus Frame D3010 Floppy, YE-Data, 1.2MB D5510 Hard, NEC 42MB, 28mS 3.5in D8000 Hard, D8000 plus Frame D8010 Hard, NEC 42MB 22ms AT BUS 3.5in D8020 Hard, NEC 3.5in 134MB 23mS ESDI D8030 Hard, NEC 3.5in 134MB 23mS SCSI D8040 145.00 175.00 199.00 175.00 745.00 775.00 795.00 1595.00 MONITORS 1995.00 Monitor, 14in TTL, Amber Monitor, 14in TTL, Green Monitor, 14in TTL, Paper White Monitor, 14in EGA Monitor, 14in VGA Monitor, 14in Multisync Monitor, NEC 14in Multisync 3D 3995.00 5995.00 4195.00 6195.00 399.00 ROCTEC EXTERNAL FLOPPY DISK DRIVES For Amiga 500, 1000, 2000, 3.5in 880K For Amiga 500, 1000, 2000, 5.25in 360/880K For Commodore PC1, 5.25in 3601720K 40/80 track For Atari ST series, 3.5in 720K For Atari ST series, 5.25in 3601720K 40/80 track For Amstrad PC1512/1640, 3.5in 720K For IBM XT, 3.5in 720K XT For IBM AT, 3.5in 1.44MB For IBM XT, 5.25in 360K For IBM AT, 5.25in 1.2MB For TOSHIBA laptop series, 5.25in 360K For TOSHIBA laptop series, 5.25in 1.2MB 199.00 199.00 199.00 599.00 749.00 899.00 1275.00 MICRO CHANNEL Dual Sync Adaptor, PS/2 Comp. MC1000 349.00 2MB RAM Card for PS/2, OK RAM MC1010 349.00 8MB RAM Card for PS/2, OK RAM MC1020 599.00 249.00 299.00 1/0 CARDS 299.00 299.00 Multi 1/0 Card XT only 11000 Multi 1/0 Card, 2 Ports all 4 drive 11010 types supported Parallel Printer Card 11020 Serial PortCard X 1 11030 Serial PortCard X 2 11040 1/0 Plus Card - XT Only 11050 Serial/Parallel Card - XT/AT 11060 2 Serial, 2 Parallel, AT 11070 Games, Parallel Printer, Serial Card, 'XT'& 'AT' 11080 Multi-Serial Card, 4P-AT 11090 299.00 269.00 299.00 329.00 299.00 329.00 349.00 399.00 MICE & JOYSTICKS Joystick Logitech Mouse, 2 button serial Logitech Mouse, 2 button serial + PaintS/V'v Logitech Bus Mouse, 2 button + Paint S/W Mouse Mat M4000 M4010 M4020 M4030 M4040 M4050 M4060 J1000 J1010 29.95 99.00 J1020 140.00 J1030 J1040 150.00 7.50 129.00 149.00 29.95 55.00 79.00 99.00 55.00 75.00 99.00 245.00 VIDEO CARDS VGA Card, 800 x 600 VGA Card, 1024 x 768 Magic Combo CGA Card EGA Card, with Hercules Mode Mono Hercules Card, 16MHz operation + Parallel Port V1000 V1010 V1020 V1030 349.00 449.00 129.00 249.00 V1040 115.00 1795.00 HELP! We made a boo-boo•••YOU REAP THE BENEFIT! HELP! We're overstocked: we bought too many of these famous brand 286 Motherboardsand the bank manager is not at all happy. Help us out of our embarrasing overstock and help yourself to a $150 saving. That's right -while stocks last, $150 off normal! HELP! HELP! HELP! HELP! • Half size, 12MHz boards - ready to run just right for updating your old XT slug into an AT performer. • lncludies 1MB RAM on board. That's right - 1MB memory at no extra charge. • Strictly this month only, or while current warehouse stocks last. Hurry! NORMALLY M;:;is545 ONLY STRICTLY WHILE STOCKS LAST! an April Fool's joke: are always this low! POWER SUPPLIES 150W PSU, Circu it Board 150W Switching PSU - XT 200W Switch PSU - Baby AT 200W PSU, Baby AT, L Type 220W Switching PSU - AT 200W PSU With Battery Backup 150W PSU Cap. 220nF/200V I P1500 P1510 P2000 P2010 P2200 85.00 124.00 149.00 149.00 175.00 695.00 R1500 2.95 KEYBOARDS 84 Key Keyboard XT/AT 101 Key Keyboard, XT/Ar 101 Key Keyboard + TrackBall K1000 95.00 K1010 115.00 K1020 199.00 I RAM CARDS I DISK CONTROLLER CARDS RAM Card, OK RAM, XT only R1000 99.00 2MB RAM Cd , OK LIM/EEMS AT R1010 265.00 2MB RAM Cd , OK LIM/EEMS XT R1020 245.00 6MB RAM Card, -OK RAM R1030 295.00 Floppy Disk Card, 4 Ports 1.2M/360K, 720K/1.44M E1010 Floppy Disk Card Disk Cont 4 port, 2In 2Ex or 4In ESDI Hard Disk Cont Card - AT ESDI HOD/FOO Card - AT Hard Disk Cont, 1:1 lnt. AT HDD/FDD Cont, 1:1 lnt. AT Hard Disk Cont,1 :1lnt. RLL, AT HDD/FDD Cont, 1:1 int, RLL, AT SCSI Card for AT Hard Disk Controller, XT Hard Disk Controller, RLL-XT I I E1000 55.00 E1030 E1040 E1050 E1060 E1070 E1080 E1090 E1100 E1110 E1120 99.00 130.00 349.00 399.00 225.00 249.00 249.00 275.00 249.00 125.00 145.00 C1000 C1010 C1020 C1030 125.00 249.00 275.00 99.00 CASES Hinged, Baby AT Hinged Baby AT w/200W PSU Slimline 'XT' or 'AT' with PSU 3.5in Hard Disk Ext. + Cable 5,25in Floppy Disk Ext. + Cable 5.25in Full Height Ext. + Cable 5.25in Mount for 3.5in Drive Baby Tower Case AT Baby Tower Case+ 200W PSU Tower for 6 Dev., Swit. at Top C1090 Tower for 6 Devices, + 200W PSU Switches at top C1110 Tower for 6 Devices, Switches in Middle C1120 Tower for 6 Devices,+ 200W PSU, Switches in middle C1130 Case, hinged XT C1140 I Microtronics Micro Electronics Hobbies And Electronics Whitsunday Decor Newtronics Coifs Harbour Electronics Deni Electronics Al Electronics John Sommerlad Electronics lnverell Computer Bits Leaton Audiotronics Cycle & Sound Decro Electronics Steven 's Electronics Keller Electronics Morwell Electronics Hutchesson's Communic. Outback Electronics Headware Nambour Electronics Namoi Computers Bassham 's TV & Computer Brad's Electronics Suf?erSolex Ph1llip's Electronics Maartronics Windsor Communications PRODUCTS 449.00 299.00 499.00 95.00 INTERFACE CARDS 48 Line 1/0 Card F1000 Serial RS-422 Adaptor F1010 Industrial 1/0 Card F1020 Universal Wire-wrap Card F1030 Dual Serial RS-422 Card F1040 80286 Speed-up Card F1050 IEEE 488 Interface Card F1060 IEEE 488 Interface Card- National Compatible F1070 A-0/D-A Converter, 12 bit, 1 Ch. F1080 A-0/0-A Converter, 12 bit, 2 Ch. F1090 Clock Card - XT F1100 EPROM Writer Card F1110 Games Card - 'XT'& 'AT' F1120 110.00 135.00 445.00 125.00 195.00 495.00 299.00 549.00 199.00 449.00 50.00 245.00 35.00 NETWORK BK Ethernet 8 bit with 'T' Adaptor 16K Ethernet 16 bit with 'T' Adaptor Ethernet 50 Ohm Terminator Thin Ethernet Cable, 25 feet Thin Ethernet Cable, 50 feet Thin Ethernet Cable, 75 feet Auto Boot ROM for NEE1 Auto Boot ROM for NEE2 Workstation, 12MHz Diskless, with 1MB RAM MAJOR AUTHORISED DEALERS Adelaide Albany Broken Hill Cannonvale Charlestown Coifs Harbour Deniliquin Devenport Glen Innes lnverell Leeton Lightning Ridge LIsmore Mackay Maryborough Morwell Mount Gambier Mt Isa Mudgee Nambour Narrabri Port Lincoln Taree Tcwnsville Wagga Wagga Warnambool Windsor NEW N1000 399.00 N1010 N1020 N1030 N1040 N1050 N1060 N1070 449.00 12.75 35.00 49.00 62.00 35.00 35.00 N2000 2495.00 SEAGATE 5-1/4in HALF HEIGHT DRIVES 20MB 70ms RLL inc XT contr. D8200 20MB 65ms RLL inc XT contr. D8210 30MB 65ms MFM inc XT contr. D8220 40MB 70ms MFM inc XT contr. D8230 40MB 40ms RLL D8240 40MB 28ms RLL D8250 65MB 40ms RLL D8260 65MB 28ms RLL D8270 20MB 40ms MFM D8300 20MB 28ms MFM D8310 30MB 40ms MFM D8320 30MB 28ms MFM D8330 30MB 40ms RLL D8350 30MB 28ms RLL D8360 49MB 40ms RLL D8370 49MB 28ms RLL D8380 42MB 24ms Voice Coil D8390 SCSI HDD/FDD AT E1105 Full Size Hinged AT Case C1005 2 Ser. 1 Parallel AT board 11080 1 Ser. 2 Parallel XT/AT board 11100 Chip Set 11090 Chip Set & Cable suit 11040 11041 200 Watt PSU Suit Tower Case P2020 200 Watt PSU Suit Baby Tower Case P2030 4MB Fast Card Suit 20MHz +SX R1040 80387SX 16MHz Co-Processor 29540 64K 100ns RAM Chip 29210 SIMM Module, 1MB sons 29680 499.00 529.00 579.00 625.00 649.00 699.00 739.00 799.00 429.00 479.00 599.00 649.00 549.00 599.00 649.00 699.00 749.00 275.00 175.00 99.00 65.00 $ 29.95 175.00 149.00 299.00 995.00 5.45 395.00 CA LL FOR COMPLETE S YSTEM PRICES • 14 Day money-back 2121799 412077 884 908 466 898 439 600 525 684 813 672 248 322 323 661 223 769 532 081 290 579 214137 511 723 214559 346133 250 400 433 475 723 895 411 604 923 274 822 788 526 603 724 466 216 558 629 870 775 935 NEW DEALERS REQUIRED IN ALL AREAS: PLEASE CALL OR FAX FOR DETAILS • • • • • • • • • guarantee (except software) 3 month warranty on all our products Mail orders are our speciality! Freight on small items is $9.00 Insurance $1 .00 per $100 of order value All price INCLUDE sales tax We accept Visa, Bankcard, Mastercard and Post Office COD Call for our latest price list Special prices apply until April 30, 1990 - or while stocks last! Leasing facilities available: just ask! Jeremy Smith 's BOARD SOLUTIONS PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 5222 It's an ill wind... , as they say "It's an ill wind that blows nobody any good", according to the popular saying. Well, this was a real wind that came close to qualifying. The only person to benefit was yours tr1:1ly and then mainly because it gave me a story to write. It happened in the early hours of a Saturday morning. It was a particularly violent local squall some suggest it was a willy-willy and it did a fair amount of minor damage to trees and houses. Its best - or worst - effort was to lift an iron roof off a house, then carry one large sheet of iron across a road and into an 1 lkV high tension line. That was bad enough - for the llkV line - but it made contact with the 240V line underneath it at the same time. It was probably only a fleeting contact because the sheet finished up further down the road, but that kind of mix-up doesn't have to last for long to have serious results. And this is the story of those results as I saw them. (Incidentally, the mention of brand names should not be taken as any indication of vulnerability, or otherwise, of that brand. There is no obvious pattern). The first I knew of the incident was when I opened the shop that Saturday morning. The phone rang and it was one of my regular customers, with the gist of what I have just related, plus a tale of wocl concerning his own appliances. It was quite a list. He has two t ~"'a-.... . ~- .. ~~ l..lGH1"Nl~G SlM?L-'( "DOESN'1'° K.NOvJ THE. 'f<UL..E:S 60 SILICON CHIP cc>o 6fO~- ,; video recorders (a National NV-370 and an AW A AV-14 ), two TV sets (a Sanyo CTP 5604 and an unknown brand), two clocks, a National microwave oven and two small motors driving fish-tank circulation pumps. Out of that lot, only one TV set had survived - the one whose brand I can't remember. Then to cap it all, the TV distribution amplifier in his home unit block had copped it. In greater detail, both video recorders had suffered open circuit power transformer primaries but no other damage. Repairs were more or less routine. The Sanyo TV set had suffered a similar fate, in this case to a small transformer used to provide 6.3V for the picture tube heater. This transformer is also used to pre-heat the picture tube when the set is turned off and so is connected permanently across the mains while the remainder of the set is disconnected. In the OFF condition, one set of switch contacts opens the 24ov line to the set proper, while the second set opens the heater circuit but are bridged with a power diode (a more effective device than a wasteful dropping resistor). The microwave oven had not suffered any really serious damage at all. This model houses its surge protection components - varistors, fuses, etc - in a single package and this had done its job well, sacrificing itself to protect the rest of the device. The replacement package is relatively inexpensive and so that problem was easily solved. As for the two clocks - well, the motor windings were open in both cases and they were a write off. The fish-tank motors were low voltage devices, run from a transformer, and this latter had lost its primary also. I referred him to the local pet shop to seek a replacement transformer. All of which added up to a pretty sordid story of destruction and financial loss. But it was only the beginning. Other customers from the home-unit block began arriving shortly after, with similar problems, along with others from the same area. And they kept coming; not just for that day but for days and, in some cases, weeks after. Apparently some had been on holidays; others simply hadn't had occasion to use a particular appliance. SILICON CHIP BINDERS * High quality * Hold up to 14 issues * 80mm internal width * Gold printed with SILICON CHIP logo on spine The mains supply All this aroused my curiosity to the point where I made some further enquiries about the area involved. As I hinted earlier, the violence was restricted to a very limited area; an area somewhat isolated from other housing. And it was isolated in another sense electrically. The whole area consists of two streets and a cul-de-sac, and this is serviced exclusively by one modest size substation. As a result, relatively few homes were affected; it could have been much worse. It could also have been worse had it happened during the day or evening, when many more appliances would have been on line. My final count, including the above, was eight ovens, six video recorders, one TV set, four electric clocks, a Philips battery/mains radio, the home-unit TV distribution amplifier and the fish-tank transformer. And since several colleagues also service this area, the total count would have been much higher. At first glance it may seem surprising that there were not more TV sets involved, but this is probably because they would be switched off at that time, and most sets feature a double pole mains switch which would provide a high degree of isolation. In this regard the situation would appear to differ from that of a lightning strike, where the voltage could be much higher high enough to jump across a set of switch contacts. The video recorders involved · were of three brands: National AVAILABLE NOW These beautifully made binders protect your copies of SILICON CHIP. In distinctive two-tone green high-quality vinyl specially selected for SILICON CHIP, and with heavy board covers, each binder holds a year's issues (the 14 issues of Vol.1 or the 12 issues of Vol.2). It will look great on your bookshelf. -------------------~-Yes! Please send me _ _ _ _ SILICON CHIP binder(s) at $A 11.95 pl us $A3 p&p each (NZ p&p $A6). Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ __ (PLEASE PRINT) Street_ _ __ _ __ _ __ _ __ _ _ __ __ _ _ __ Suburb/town _ _ _ _ _ _ __ _ _ _ _ Postcode _ _ _ _ __ Enclosed is my cheque/money order for $ _ _ _ _ or please debit my □ Bankcard □ Visa Card □ MasterCard Signature _ _ __ _ _ __ _ _ _ _ Card expiry date_ ~ -- ~-----------------------~ APRIL 1990 61 SERVICEMAN'S LOG -CTD Panasonic, AW A and Rank NEC. And they all suffered the same fate - an open circuit power transformer primary. But rather interestingly, in most cases the mains fuses were still intact. Also in most cases, that was the only damage. The exception was the National Panasonic NVG-7, in which two !Cs in the servo circuits had also been destroyed. Oven faults & repairs The ovens presented a more varied batch of faults. With the exception of the first customer's oven, already dealt with - and which used a mechanical timer - they all featured touch pad microprocessor control. Such units normally use two power transformers; a heavy duty one supplying the magnetron and associated circuitry, and a light duty one supplying the microprocessor and clock. In all cases the heavy duty transformer and associated components survived. Modern oven circuitry switches the magnetron on or off in the primary of the heavy duty transformer, so this would be open on at least one leg when not in use. On the other hand, only one of the light duty transformers survived. In addition, there were varying degrees of other damage. In two cases, the board had suffered minor damage in the form of vapourised copper tracks feeding the small transformer primary, plus complete destruction of the protective varistors and fuses across the mains. The copper tracks were very thin and I suspect that this was deliberate, as a form of protection. There was no other damage and it was a simple job to bridge these tracks and fit new varistors etc. Not so two other boards. Both had suffered damaged tracks in several places, with one suffering much more damage than the other. The varistors had been sacrificed in both cases but strangely, the transformer on the badly damaged board had survived. The price of replacement boards has been quite high in the past; so high that most customers elected to add a few 62 SILICON CHIP dollars to the repair price and buy a new oven! On this basis I decided to try a spot of cannibalising - taking the good transformer from the badly damaged board and fitting it to the less damaged one, in the hope that a few repairs to this might get it going again. It was a simple job but it didn't work out. I suspect that some of the !Cs had also been damaged. So the next step was to confirm the price of replacement boards and quote the customers accordingly. And this turned out to be the brightest spot of the whole operation. The price of boards had dropped dramatically; in some cases to one third of the previous figures. On this basis there was no point in trying to salvage anything; I simply ordered new boards, fitted them, and had two more (reasonably) satisfied customers. The remainder of the ovens fell into the simplest category; open circuit transformer primary and destruction of the varistor/fuse protection network. Straight out component replacement was all that was needed to get them back into operation. TETIA TV TIP Sony KV-1830AS (early version, before S/N 300,001) Symptom: No picture until set thoroughly warmed up (about 1 0 minutes). Luminance could be forced through by raising screen voltage, but there was no sign of colour. Cure: Fault turned out to be an inductor in the collector of the 7 .8kHz amplifier transistor, 0309. The coil was open circuit when cold but came good as it warmed up. (The fault explains the "no colour" but not the "no luminance", thus making a very confusing problem). TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. The distribution amplifier in the home unit had suffered a similar fate; open circuit transformer primary. Again a routine replacement was all that was needed. The Philips radio set was quite dead, and the transformer primary was open. Whether there had been any other damage was not immediately apparent but since it was also designed for battery operation, I was able to rustle up an appropriate voltage source and check it out that way. It worked perfectly, so only a transformer is needed. A proper replacement is not immediately available and I might have to improvise. The main problem is physical compatibility but I'm sure I'll find something. Vulnerable appliances Summing up, the first point to make is that the most vulnerable appliances are those which, by reason of their intended function, are connected directly across the mains at all times. Video recorders and microwave ovens fall into this category. TV sets, on the other hand, are relatively safe unless actually in use. And if that point seems so obvious that it didn't need to be made, I did so because I wanted to emphasise one I made earlier: the difference between a voltage surge of this kind and one due to a lightning strike. It would appear that, even at 1lkV, most appliance switches are still effective, at least in the short term, even though one would not deliberately invoke such a risk. On the other hand, long experience indicates that when lightning strikes, nothing is safe; lightning simply doesn't know the rules. To some extent, this point may seem academic but I have found that it is a good thought to keep in mind when the customer asks, "Why?", or "Why the video recorder and not the TV set?", and so on. The other point to discuss concerns the effectiveness, or otherwise, of the varistor type protective networks. Do they work, or are they just a gimmick? Based on the above incidents, I have no doubts that they are wor- thwhile. Granted, most appliances were damaged in spite of these precautions but I strongly suspect that the damage could have been a good deal worse in most cases had they not been present. But there is one important point to note; the varistor is no better than the fuse which goes with it. In fact, its job in life is to blow that fuse at the first hint of trouble, and it can only do that if the fuse rating has been carefully selected. Granted, fuse ratings are always a compromise but the varistor makes possible a much more realistic compromise. More to the point, if you have to replace such a fuse, make sure that it is exactly as the maker specified it, and not just in current rating. And so ends the saga of the ill wind, the roofing iron, and the 1 lk V power lines. Here's hoping they tie the roofs down tighter next time. Red in the face Now, for a change of pace, here's something quite different. It is an incident that happened to a friend who, while in no sense a professional, is a very keen TV hobbyist. Professionally, before retirement, he was a commercial airline captain and his main hobbies are amateur radio and TV. He takes his hobbies very seriously, taking several TV trade courses over the years, including one at the commencement of colour. And he has built himself a couple of colour sets, AUDIO TRANSFORMED based on commercial modules; no mean feat by any standards. The truth is that he would undoubtedly make a first class serviceman, yet he has never ventured into this field. It is purely a hobby and when neighbours approach him for help he invariably refers them to me. However, his family is a different matter and when his married daughter's set failed recently, a mayday call went out for "Dad" to come to the rescue. The set is a Kriesler 59-3 and while a little long in the tooth, has given good service over the years. Such faults as did occur were minor until about two years ago, when it was realised that the picture tube - an A66-500X - was on the way out. So my friend removed the tube, took it across town to a well known tube rebuilding firm, and purchased a replacement. Then he fitted the new tube, converged it, grey scaled it, and brought the set back to as-new performance. And this is no simple job; even removing and replacing the tube is a major TV TEST EQUIPMENT (AUSTRALIAN MADE) SHORTED TURNS TESTER Built in meter to check EHT transformers including split diode type, yokes and drive transformers. $78.00 + $3.00 p&p HI-VOLTAGE PROBE Built in meter reads positive or negative 0-50kV. For checking TVs, microwave ovens. $84.00 + $5.00 p&p. j4' FOR PROFESSIONAL, OEM OR AMATEUR l:l roadcast qua lity a u d io transform e rs ex-stock More than 70 standard types ava il ab le Fast proto t y ping service for n o n-sta nd a rd t y pe s Co mpre hensive data av ailable o n requ es t Lo cally manufac tu red Compe titively priced HARBUCH ELECTRONICS PTY LTD 90 G eo rge S t.. HOR NS BY :--/SW 20 77 Pho ne <02 1476-585 4 j TELE-TEST TUBE TESTER & REJUVENATOR Removes cathode grid shorts & rejuvenates picture tube . Suitable for all colour tubes. 12 months warranty. $420.00 + p&p. NEW PRODUCT DEGAUSSING WAND: A must lor all workshops. Efficient design, strong magnetic field, low heat, double insulated with momentary on/off. $75.00 + $1 0 p&p. ALSO TUNER REPAIRS FROM $17.00. Cheque, Money Order, Bankcard or MasterCard Y.V.TuNERs) 216 Canterbury Road, Revesby, NSW 2212. Phone (02) 77 4 1154 APRIL 1990 63 SERVICEMAN'S LOG -CTD ''"' . . - •.. •. . .. ~ ~SSUME. -rH~T . 1H~ \NE.\J\1Aa~ V\~TtOI'\, -E.VE:.N ON GOOD 'ROADS_, WAS SUF~lCIE.NT"''TO 1)\SL.0~ 1\-\E. FO'RE-lG~ 'P~'RTIC.,<-€ FROM "ffiE: GUN o physical task, having to be done from the front of the cabinet. All went well until a few weeks ago when the screen suddenly went brilliant red, with no sign of a picture. That initiated the call for help. A check revealed that the set would come up normally when first switched on, run for a few minutes, and then the red gun would turn hard on, swamping the image completely. Initial checks My friend's immediate reaction was to suspect an intermittent breakdown in the red driver transistor (TR506}. These do break down and produce these symptoms, and not only in the red circuit, of course. One way to check this is by opening the plug and socket on the main board - PL506 and SK506 which disconnects all three cathodes from their driver transistors. All three collector voltages will rise but by approximately the same amount if the transistors are intact. If one is substantially lower, then breakdown or leakage would be suspected. My friend did this and all the in64 SILICON CHIP dications were that the transistor was not at fault. So what did that leave? A short in the picture tube red gun was the horrible thought that came to his mind, and he voiced this fear when he sought my advice. I had to agree that this was a very real possibility but cautioned him about being too hasty. The leads from PL506 run to the neck board and there are a couple of traps here. One is the protective spark gaps across the tube elements, which have been known to fail and create all the symptoms of a faulty tube. Another is the tube socket, which can also break down or leak and create similar symptoms. Thus encouraged, my friend returned to the fray but as I learned later, the news was not good. He pulled the neck board/socket combination, which brought the red collector voltage back to normal, leaving the picture tube as the only suspect. So he and the family resigned themselves to the cost of a new tube. At the same time, he was surpris- ed at this turn of events because he knew from me that the firm concerned has a very high reputation, their rebuilt tubes being virtually as good as new. But the fact had to be faced so he pulled the tube out, loaded it in his car and took it across town - a lengthy journey to the factory. The tube was out of warranty but was still valuable and, in any case, he wanted final confirmation that it was faulty. So imagine his mixed feelings when, after the most exhaustive testing, the technician could find no sign of a breakdown and in addition, pronounced the tube as having better than 90% emission . Good news & bad It was a good news/bad news situation; the good news was that there was no picture tube fault the bad news that there appeared to be a weird fault in the set which had beaten him. So, back at the ranch, he set to and refitted the tube. Then he switched on and prepared to do battle with the mystery fault. What battle? What fault? Nothing wrong with the set; working perfectly. And it has continued to work perfectly for the past several weeks, right up to the time of writing. The answer? It's only a guess but we both came up with the same idea. In short, the fault in the tube had been real enough but the journey to the factory had cleared it. And in support of this theory is the manner in which the tube was transported. Normally he would have used its original carton, with it sitting in the same position as in the set. But the carton had long since been recycled, so my friend used a large foam rubber cushion which he put in the boot of the car, then sat the tube on it face down, and packed it with blankets and other cushions. As I mentioned, it was a fairly long trip and we assume that the inevitable vibration of the vehicle was sufficient to dislodge the foreign particle from the gun. As I say, it's only a guess but what other explanation is there? Unless time reveals something, I'm afraid we're stuck with it. ~ WOOD FOR CHIPS . WOOD FOR C ~ SerialTest serial data analysis on your PC ~·i we carry a full range Cable Mounting This is an MS-DOS software and Female Austr1/i1n Style . Mafe cabling package which enables $6.95 All Telecom Approved 3 pm $6.95 technicians and engineers to $13.95 PT1 Plug $4.95 4 P!n $8.95 perform serial data comms analysis. PT2 In-line.socket $5.45 5 pm . . $10.95 $18.95 It offers sopllisticated problem TEL2 Dual adaptor - one plug to Ch~ssts Mounting solving facilities at a fraction of the $8.95 two sockets for answering machine 3 pin L. profile $5.95 cost of dedicated hardware systems. someone made a boo-boo and we n/a extra phone etc. $9.95 3 P!n V~rt Holes $5.95 SerialTest provides a window onto put an extra zero on our order. Now $8.95 TEL3 Dual adaptor - In-line socket 3 P!n DIag Holes $5.95 RS232 lines operating either as a you can benefit. These are quality n/a to plug/socket adaptor with 10m 4 P!n V~rt Holes $7 .95 passive observer or actively sending CTS brand with seal over actuators $12.95 cable between. $18.95 4 P!n D!ag Holes n/a data or control signals to simulate to prevent soldering/cleaning $17.95 TEL18 Extension Lead - 15m long in 5 pm DIag Holes $8.95_ either at DTE or DCE device. Triggers contamination. 10 way only $3.30 handy storage reel $34.95 240~ 3pm Types 5A rating can be defined based on error each or 10 for $10.00! US Style ln-Lm~ $14.95 $14.95 conditions or data to initiate or Modular PC Mounting Sockets Chassis $10.95 $11 .95 terminate monitoring sequences. PT14 4 way/4 wire $2.45 Black Marviplate construction with PT16 6 way/6 wire $2.45 aluminium front and rear panels. PT18 8 way/8 wire $4.45 Supplied with handles. Modular Plugs H0461 153x102x203 $29.95 PT44 4 way/4 wire $2.95 H0463 254x102x203 $30.95 PT64 6 way/4 wire $2.95 H0465 203x76x228 $26.50 PT66 6 way/6 wire $3.95 Now stocking a full range from 0.1n H0468 305x76x228 $34.50 PT88 8 way/8 wire $7.95 to 3.9k. All 65c each Accessories --TEL9 6 way/4 wire extension cable DC Voltage from 200mV to 500V 1Sm long $5.95 AC Voltage from 2V to 500V TEL14C 4way/4 wire curly cable for Resistance from 200n to 20Mn keyboards, handsets etc plug to plug AC/DC Current to 200mA No need to tum your head to read . $5.95 Diode Test 2V 18821 Hithl lrht \lllllr cirloice wi th the urou ke,p • nd pr-en IDITEll), or press the this multimeter. The read out is right Continuity firs t letterof7r choice . ThelESCJkey111,rbenedtouitthe11trw, , PT7 6 way/ 4 wire joiner $3.95 check to 2kn there in the probe! Telephone Cable Logic Testing to 1MHz and 1µs • Handles baud rates up to Auto and manual ranging, 3.5 digit TEL104 4 conductor suits PT44, 115.2kbaud. large 14mm LCD display - all in a PT64 65c/m t • View each bvte in ASCII or handy probe. Logic testing function TEL 106 6 conductor suits PT66 EBCDIC, decoded to hex, decimal, ~ for CMOSmL. Data Hold button, $1.00/m binary or octal Diode test, Continuity buzzer. TEL108 8 conductor suits PT88 • Writes captured data directly to Display shows all functions ... ~-· $1.50/m disk to allow maximum capture Protected to 250V · buffer All this for just • CRC checksum calculations • Auto-configuration to any of the comms ports 1 to 4 C') • Time -stamping (absolute and Black Utility Boxes :t: 2metre 1OA power leads with relative) including delta time All plastic. Snap together without straight IEC socket only $6.95 Operates from 5 to 14Vdc (12V/1A calculations screws. Removable front and rear Also available with 3pin, 6A IEC right • Split line DTE over DCE display nom). No load speeds up to panels. UB10 has cooling vents angled socket $16.95 18000rpm! Supplied with 1mm drill $395 plus sales tax UB10 93x135x47 $8.95 IEC extension leads with IEC 3pin bit, grinder and engraving bit. Three Send $10 for a demo disk, UB11 186x125x50 $6.95 line plug and line socket $13.95 interchangeable collets 1, 2, 2.3mm. refundable on purchase. Pl,stic/Aluminium Utility Boxes Monitor power plug allows you lo OrderME12 $29.95 Quality, beige coloured, screws plug monitor into PC and switch c..,, together. Removable aluminium end both on and off together. plates. PCB ribs. Rubber feet Contains 3 precision knives and 6 L2298 $6.35 Simple way to check 25 pin "D" UB14 140x110x46 $19.95 blades in heavy duty storage case Series RS232 inputs, outputs and UB16 170x158x54 $24.95 with magnetic blade holder. cables. No external power. Utility Baxa Surgically sharp blade in various Connecting leads with in line plug Black ABS with PCB mounting ribs. shapes. Aluminium handles with and socket between computer and Screw lid safety locking collar. peripheral. 10 Tricolour LEDs UB4P 83x54x28 $2.75 Order HT23 $18.95 monitor standard activities. 2 spare UB3P 130x68x41 $3.55 LEDs for additional functions. 24 DIP UB1 P 150x90x50 $5.25 switches to reconfigure lines and Free standing with huge 115mm UB2P 195x113x60 $6.95 circuits. Spring terminals for (4.5inch) lens. Folds flat for storage. New type with screw holes for patching into anr of the 24 active Order MG2 $13.95 securing PCBs lines for externa monitoring or UB6 83x54x28 $5.95 testing. A must for any computer UBS 130x68x41 $7.95 technician - will save hours m Heavy duty cast iron base. Dual coil Plastic/Aluminium Freestanding getting systems running for just No excuse now for not fitting a construction suits most irons. Box ~ $99.95 mouse to your PC! Suits IBM PC/XT Sponge pad for tip cleaning. C' Silver grey with aluminium front & AT and compatibles. 500mm/sec C) Order SIS3 $19.95 panel. Screws together with screw C) tracking speed with 200dpi .,, holes for PCB. Rubber feet Bench Type resolution. Requires system with ) UB19 1.40x110x46 $8.95 0-SA disk drive, 128k RAM, RS232 $159.6D Lightweight metal construction with :r· Metal Utility Bax 0-7A interface and PC-DOS or MS-DOS. $187.3D Teflon tip 195mm long. Replaceable Professional looking for larger Supplied with Mouse driver software 0-13A $314.6D tips Order HT1 $16.95 projects. Cooling vents. Assembles Panel Mounting and cable with 25pin connector. Large~ heavy duty model 210mm to top with seH tapping screws 0-1.2A $97.7D Three button, heavy steel ball for long. urder HT3 . $32.95 UB22 149x133x73 $9.95 0-2.SA $122.1D accurate positioning. All for $59.95 ~ $59. 95 RS 32 Breakout Box ariacs 229 Burns Bay Road, (Corner Beatrice St.) INC INNsw Lane Cove West, N.S.W. P.O. Box 671 , Lane Cove N.S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. PENROSE ~ Mai l Orders add $5.00 to cover postal charges. i~ 0U.DESV1\.LE TO Next day delivery in Sydney add $5.00. i BA~ All prices INCLUDE sales tax. . Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED Silicon Chip BACK COPIES February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems; Door Minder Alarm; Low Ohms Adaptor for Multimeters; Line Isolation Unit for Phone Patch; Electronics In The Jaguar XJ40; Easy Tips on Headphone Repair. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Endless Loop Tape Player; Build Your Own Light Box; New Life for RadioCassette Players; Old-Time Crystal Radio. April 1988: Walkaround Throttle for Model Railroads, Pt.1 ; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players; What is Negative Feedback, Pt.1; Mobile ·Antennas for the VHF & UHF Bands. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm; Walkaround Throttle for Model Railroads, Pt.2; Designing and Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data . June 1988: Stereo Control Preamplifier (uses LM833), Pt.1 ; Breakerless Ignition For Cars Using Hall Effect Pickups; Mega-Fast Nicad Battery Charger; Automatic Light Controller Uses PIA Detector; RF Sniffer Probe & Preamplifier; What is Negative Feedback, Pt.2. July 1988: Stereo Control Preamplifier, Pt.2; Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show , Pt.1; Tone Burst Source for Amplifier Headroom Testing; National Semiconductor LM833 Op Amp Data; What is Negative Feedback, Pt.3. August 1988: Building a Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter (uses OP-27), Pt.1; Discolight Light Show, Pt .2; Getting the Most Out of Nicad Batteries; Data on Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Switchmode Charger for 1 2V Gel Batteries; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice; Motorola MC34018 Speakerphone IC Data; National Semiconductor LM 1 2 150W Op Amp Data & Applications; What is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (uses Rohm BA 1404); High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting a CB Radio To The 28MHz Band; Electronics & Brock's BMW Blaster; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding a Headset To the Speakerphone; How To Quieten the Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs) , Pt.1 ; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Use this handy form to order your back copies ~ I----------------------------------□ □ □ Please send me a back issue for: February 1988 March 1988 April 1988 •--7 I [1 May 1 988 0 July 1 988 □ December 1 988 August 1 988 □ September 1 988 I 0 June 1 988 0 November 1 988 □ D October 1 988 □ January 1989 □ February 1 989 I I D March 1989 11 April 1989 □ May 1989 □ Ju-ne 1989 □ July 1989 0 August 1989 □ □ October 1989 □ November 1989 □ December □ D February 1 990 □ March 1 990 I I I 1 1 I I I I I I I January 1 990 September 1989 1 989 Enclosed is my cheque/money order for $ ______ or please debit my D Bankcard D Visa Card ~-r----r----.--, -~--D MasterCard Card No . J Price: $A5.00 each (includes postage). Overseas orders add Signature _ __ _ _ _ _ _ _ _ _ _ Card expiry date._~~$A 1.00 per issue for postage. NZ & PNG orders are sent by Name,_________________________ air mail. (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ PO BOX 139 COLLAROY BEACH NSW 2097 Suburb/town, _ _ _ _ _ _ _ _ _ _ _ _ Postcode._ _ _ _ OR FAX: (02) 982 9553 -~~~I II I ~~~~~ II l I ~------------------~-------------------~- 66 SILICON CHIP Receivers ; Electronics & Holden's New V6 Engine; Why Diesel Electrics Killed Off Steam ; Index to Volume 1. January 1989: Line •Filter for Computers; Ultrasonic Proximity Detector for Cars; Simple Computer Sound Repeater; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How to Service Car Cassette Players; The Goalkeeper Gatling Gun ; Massive Diesel Electrics In the USA. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher for Model Railways (uses LM3909); Build a Simple VHF FM Monitor (uses MC3362). Pt. 1 ; Lightning & Electronic Appliances ; Using Comparators to Detect & Measure. March 1989: LED Message Board , Pt. 1 ; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor for CD Players; Map Reader for Trip Calculations ; Amateur VHF FM Monitor, Pt.2 ; Signetics NE572 Compandor IC Data; Electronics for Everyone - Resistors . April 1989: Auxiliary Brake Light Flasher; ·Electronics for Everyone : What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2 ; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC ; Simple Stub Filter For Suppressing TV Interference; LED Message Board , Pt.3; Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586) ; Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; LED Message Board, Pt.3; Coherent CW - a New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (uses TGS81 2 Gas Sensor) ; Extension For the Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electrics; Facts On the PhaxSwitch - Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1 ; Garbage Reminder - A ? ·day Programmable Timer; Introduction to Stepper Motors; GaAsFet Preamplifier For the 2-Metre Band; Modern 3 ·Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (uses MC13024 and TX7376P) Pt.1 ; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089) ; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (uses LMC669); A Guide to Hard Disc Drives . October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (uses BA 1404 and TDA7000) Pt.1; GaAsFet Preamplifier for Amateur TV; 1 Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc in the PC; A Look at Australian Monorails. November 1989_: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options ; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs) ; UHF Remote Switch ; Balanced Input & Output Stages; National Semiconductor °LM831 Low Voltage Amplifier IC Data & Applications ; Install a Clock Card In Your PC ; Index to Volume 2. January 1990: Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs ; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV; Speed Controller For Ceiling Fans . February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2 ; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/ 1 2V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; Digital Waveform Generation Using a PC; The Controls On A Model Aircraft. Note: November 1987, December 1987 &' January 1 988 are now sold out. Problems? ... and you don't have our NEW 1990/91 148 pp.ge electronic parts and accessories catalogue ... Its our latest TRADE catalogue for the consumer ARISTA ... Your one.-stop problem solver. ... Stylus .. . .. .Plugs, Jacks and Sockets ... ... Batteries ... ... Cable ... .. .Tools and Technical Aids .. . ... Plug and Power Packs ... ...Car/Auto Accessories .. . ... Boxed Hi Fi Speakers .. . ... Raw Replacement Speakers ... ... Speaker Accessories .. . ... Telephones and Intercom .. . ... Public Address Accessories .. . ...Security and Alarm Accessories .. . .. .TV/Video/Antenna Accesories .. . ... Videocam Accessories ... · ... Audio Accessories ... .. .Headphones ... ...Computer Accessories ... .. .Microphone Accessories ... ... Mixers, Amplifiers, Equalizers .. . Just about anything you want. .. Get your catalogue complete with "Recommended Retail Prices" free from your local ARISTA dealer or send $2.50 P & H and your return address to: ARISTI\ ELECTRONICS PTV LTD PO BOX 191, LIDCOMBE, NSW, 2141 APRIL 1990 67 Can chrome tape sound as good as CDs? Taking the BASF CD challenge Over the next few months in shopping malls, record bars and at major sporting events, Australians will be challenged to identify whether music is coming from a BASF chromium dioxide audio tape or a CD. BASF reckon you won't be able to hear the difference. By LEO SIMPSON Not only do BASF reckon that their chrome tape is "damn close to CD" but they also state that their chrome tape is "99.9% noise-free". Such claims seem outrageous, don't they? After all, everyone knows that CDs and CD players have a much greater signal to noise ratio and available dynamic range than cassette players. CDs also have lower distortion, better frequency response and much lower wow and flutter. BASF still reckon that few people will be able to tell the difference when they listen to the set-up they will have in shopping malls and record bars. Essentially, the equipment rack you will see uses standard Pioneer hifi equipment - a CD player, a 3-head stereo cassette deck with Dolby C noise reduction and a stereo amplifier which drives several sets of headphones. At the top of the rack is a unit made by BASF which switches the · output signals from the CD player and the tape deck to the inputs of the stereo amplifier. It does this in a random fashion so that you listen to 10 12-second segments of music. You then have to identify, as you listen, whether the music is coming from the CD player or the tape deck. The tape deck is recording the signal from the CD player and the output is taken from its playback head. Thus it is quite easy to pick when the music is switched because there is a time delay of abuut 0.3 seconds between the CD signal and the tape playback signal. Picking the moment when the signal is switched is no problem at all; picking which is which is a lot harder. Most people, after they 've marked the score sheet, get less than five out of 10 right. Dolby C noise reduction When these two Sydney Kings basketballers took the BASF CD Challenge, they could not tell the difference. Depending on the type of music being played and the noise level of the surroundings, it can be very difficult. Few people achieve a score of better than 5 out of 10. 68 SILICON CHIP The tricky part is the use of Dolby C noise reduction in the tape deck. BASF make the point that compact discs are rarely recorded with a dynamic range of more than 70dB and that most hifi cassette decks with Dolby C can achieve a signalto-noise ratio of 70dB or better. Hence, as far as signal-to-noise ratios are concerned, there is less difference between CDs and cassettes than you might think. The other trick is in the selection of the music used for the test. If the program is classical music, it tends to be easier to pick the difference than with most popular vocal recordings which have relatively little 40 . 1 -,~ 30 .,.,r - ·- _,. f ., ~ f -" L V I I I' . ~ 10 ,,IIT _J\ ,, - -., -- - I ~, ~ ." " .. -""LI. " . ,. -,-,. \ ~ 'I.Tllo . - - I \ -•• ,n "' ,.,. _,. , . ' - Hz 50 100 200 dynamic range. The other point to be noted is that the venue where these "CD challenges" are taken is not the best for serious music listening. Shopping malls are notoriously noisy places so, even when listening on headphones, trying to pick differences in sound quality is very difficult. Most people are likely to conclude that the differences are non-existent, which is just what BASF wants them to think. Is it valid though? With a lot of recorded music on CDs, the answer is yes - because it has not been critically recorded with the very best sound quality in mind. However, if the same comparison is carried out in a quiet room with good loudspeakers and the very best that CDs can offer, few hifi enthusiasts with keen hearing will have any problems picking the difference between CDs and BASF chrome cassettes simultaneously recording with Dolby C. If the test was done using dbx noise reduction, it would be quite a lot more difficult. Incidentally, while most hifi cassette decks these days have both Dolby B and C noise reduction, most car players, Walkman-style players and "ghetto blasters" don't even have Dolby B. 500 ,,,..,. I I - & .,, • l;ll 2000 l'ln y ' lo T I \ IN Ill ..I 'Y .. ., T T I ~ .. I . " .... L -T -r,, I \ \ \ I l. ' \ \ I ~-'l. 1000 - - -- "' I •- 0 20 JY I - •• I .. . "' "\ \ I I.I I , .. I I ~ ,- ~ ft -,, ,, ,,.... ,, . -. lr'I J ,. "' T [7 V ,,_. /\ I ,,. r IW ,J V ,. .,r ,r, 20 - _. . & .,, f 5000 10000 ' 20000 The cornerstone of the BASF CD Challenge is the use of Dolby C noise reduction. These curves show the difference in high frequency noise attenuation between Dolby B and C. Dolby C can give a signal/noise ratio of 70dB or better. What is the point? Why has BASF gone to the trouble of running the CD challenge? Well, as you might expect, it is a marketing exercise designed to draw attention to its new Chrome Maxima II cassette. This has a redesigned housing which is claimed to be more rigid and to give better tape azimuth for minimum high frequency losses. The housing is also claimed to be less likely to distort when subjected to the high temperatures in cars. At the same time, the tape formulation has been improved to give a greater dynamic range, which is where the statement " 99.9% noise free" comes from. BASF quote a signal to noise ratio of 60. 5dB without noise reduction. When you convert this to a straight ratio, it gives a figure of .0009441 or as BASF states, better than 99. 9% noise free. What do you think? ~ BASF's new Chrome Maxima II uses a high precision shell which gives better tape azimuth and is less likely to distort at high temperatures. The tape is a double layer type with high coercivity for greater signal range. APRIL 1990 69 ...,.. AUSTRALIA'S CHEAPEST DISKS! 1-9 1MB • &Ons 4164-15 4164-12 4164-10 41256-15 41256·12 41256-10 41256-08 4464-10 10+ $24.95 $22.95 $2.95 $2.75 $3.95 $3.50 $5.95 $5.50 $4.50 $4.25 $4.75 $4.50 $5.95 $5.50 $5.95 $5.75 $11.95 $10.95 - - -• - GENUINE INTEL CHIPS 8087•3 8087-2 8087•1 80287-6 80287•8 80287-10 80387-16 8038720 80387•25 (4 .77MHZ) (&MHZ) (10MHZ) (6MHZ) (&MHZ) (10MHZ) (16MHZ) (20MHZ) (25MHZ) $175 $265 $395 $295 $395 $495 $795 $895 $1.095 -~ I l L.u...:....Ll.ll..L...ll.l.Lll...::::r: ~► Ill:·· :,::1 1 1\ L.1.Lw II :\i,':'i\\'Si ,: : ~et I _)\.._:._ ~ . t .::,____.__.,a:\ i "NO BRANO" DISKS Now you can buy absolute top quality disks that are also the cheapest in Australia! 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Pause, Reset, Clear Screen xr X12022 ............. only $109 DESCRIPTION (ALL PRICES PER BOX OF 10 DISKS) 1-9 BOXES 3 1/2" 1S/2D ....... ;....... $37.95 3 1/2" 2S/2D ............... $36.95 3 1/2" 2S/HD .............. $74.95 5 1/4" 1S/2D............... $20.95 5 1/4" 2S/2D ...............$24.95 5 1/4" 2S/4D ............... $75.95 5 1/4" 2S/HD ..............$32.95 10+ BOXES $35.95 $34.95 $72.95 $19.95 $23.95 $70.95 $31.95 Teflon* Coated (All PRICES PER BOX OF 10 DISKS) 51/4" DS/DD C12522 .......................................$34 5 /14" High Density C12523 .................................$64.95 deflection dot type black matrix. Standard persistence phosphor. Active Dlaplay Area : 240mm x 180mm Resolution : 64 Colour:720dots(H) x 350 lines 16 Colour:640dots(H) x 200 lines Quality monitor■ without the price tag! Dlsplay Tube: 14 Inch 90' deflection 0.39mm Dot ■ trio pitch. Dark face ■c'"n . Plloaphor: P22 Reaolution :640 dote (horizontal) 240 line (vertical) X14526 ..................... $395 to delivery! • 8 Slot motherboard • 12 months warranty! • 1SOW power supply 640K RAM TURBO COMPATIBLE COMPUTER WITH 40 Mi BYTE HARD DISK : & single 360K \I.C. H.D.. ....$1 .575 & dual 360K \I.C. H.D.... .....$1 .725 • Super high resolution: 200 D.P.I. (0.12mm/dot) • Silicon rubber coated ball • Optical rotary encoder X19952 .......... .. ...... $74.95 WITTY MOUSE HOrtlor■ nl money! • Final assembling and testing in Australia! • Fast TURBO Motherboard • AT' style keyboard • Tested by us for 24 hours prior MICROSOFT' COMPATIBLE! • Auto-selection and auto· transfer between mouse system system PC mouse mode and Microsoft serial mouse mode • Microsott Serial Mouse and Mouse System compatible • Super high tracking speed: 600mm/sec X14527 ..................... $595 RITRON CGA COLOUR MONITORS prices. We're sure you 'll agree they're exceptional value for WITH 20 M/BYTE HARD DISK: & single 360K Disk Drlve .. $1 .295 & dual 360K Disk Drives .. .$1 .395 QUICK MOUSE Display Tube: 14 inch 90' Check these features and our 2 x 360K Disk Drives. Multifunction Card. Colour Graphics. Disk Controller. 1 Serial. Parallel Port (Clock) ................. .......$895 X14528 .................... $895 RITRON EGA COLOUR MONITORS IBM* XT* 640K RAM TURBO COMPATIBLE COMPUTER • Three buttons, user definable • Silicone coate<! steel ball • High resolution movement of 195 dots/Inch. Smaller table space and less hand movement required • Optical rotary encoder • Max. tracking speed: 200misec • Mouse resident firmware • Size: 116 x 66 x 34mm • Mouse Driver Software included. allowing you lo install with all popular software packages. Also Included Is the handy Pop-up menu software that allows the user to integrate the mouse with the keyboard. DOS. and other popular software packages X19950 ....................... $59 BABY AT* COMPATIBLE COMPUTER! 2M/B RAM $1,695 • Final assembling and testing In Australia! • 4 M1By1e Main Board. 2 M/By1e · fitted • Switch able 81.10/12 MHz • 1.2 M/By1e Floppy Disk Drive • 80286 CPU • Colour Graphics Display Card • 8 Slots • Floppy & Hard Disk Controller • Printer Card and RS232 • Keyboard • 200W Power Supply • Manual • 6 Months Warranty • Size: 360(W) x 175(H) x 405(D)mm With 20 M/By1e Hard Dlsk.$1.995 With 40 M/By1e \I.C . H.D.. .. $2.195 With 80 M/By1e Hard Dlsk.$2.795 IBM•CARDS EPSON PRINTERS G7 CGA/ MGP X18007 ... ... ...... .. .. .......$95 LX400 .............. $349 LXSS0 .............. $475 LO500 .............. $f>9~ LOSS0 .......... .... $996 LO1050 ......... $1,395 MGP X18003 ....................... $89 HEGA EGA X18070 ............... ......$169 VGA 256K X18071 ........... ...... .. .. $199 VGA 512k X18072 ............ ...... ... $299 FOR OTHER EPSON PRINTERS PLEASE CALL FOR BEST PRICESII P.C ACCESSORIES MAGIC STAGE A working bench for your Mouse. •High qulllity ABS plastic and anti•static rubberised top •Stationary holder •Includes pull•out shelf for Mouse •Dimensions : 280 x 260 x 25mm • Fits over keyboard C21080 ................. $24.95 RS232 X18026 .................... ... $39 DISK BOXES ' DISK STORAGE UNITS • 80, x 3 1 2·· • Lockable C16038 .... ........... ... $16.95 • 40 x 3 1 2 ··. Lockable C16035 .......... ...... .. $14.95 • 40 x 3 1 2 ·· ·· Eclipse " C16040 ................... .$8.99 • 120 x 3 1 2 ··- Lockable RS232 & Clock X18028 ....................... $49 C16039 ... ............ ... $21 .95 Clock X18024 ................ .......$39 C16025 ..... ....... ... .. .$14.95 Printer X18017 .................. ..... $29 C16042 ...... .............. $9.95 Games X18019 ............ ........... $29 Multi-function X18040 ....................... $99 Multi 1/0 X18045 .............. .. .......$99 2 M/Byte Ram X18052 ............ .... ..... $225 3M/Byte Ram X18056 ..................... $275 Serial /Parallel /Games X18151 .....................$115 Floppy Disk Drive X18005 ....................... $52 4 Way Drive Controller 360K/ 720K/ 1.2M/ 1.44 X18006 ............ .........$129 XT* Hard DiskController X18060 ... ,................. $129 JOYSTICKS • 50 x 5 114 ··• Lockable • 100 x 5 1•4 ····Eclipse .. MINI VACUUM CLEANER 10 MHz XT* TURBO MOTHERBOARD Increase the performance of you sluggish XT' approximately tour times with this super fast motherboard. • 8088·2 running at 1O MHz, no wait state • Turbo/ Normal selectable • 640K • 8 Expansion slots • 4 Channel OMA • Keyboard port Excluding RAM X18032 ... .. ................ $179 Including RAM X18033 .......... ........ ...$350 APPLE* COMPATIBLE Ideal tor games or word processing. Fits most 6502 ""compatible"" computers. C14200.................. $39.95 APPLE* UE & IIC SERIES COMPATIBLE These joysticks have adaptor connectors to suit the Apple II. lie, lie and II+ computers. Features Include selectable ""spring centring"" or ""free floating"" . Electrical trim adjustments on both axis. 360' cursor control and dual lire buttons. C14201 ................ .. $:19.95 • 120 x 5 1,4 ··. Lockable Cl 6028 ................. .$19.95 C21087 .... .... ...... ... $14.95 MELBOURNE : 48 A·s eckett St Phon e : (0 3) 663 6 151 NORTHCOTE : 4 25 High St. Phone : (03) 489 8866 TOWER COMPUTER CASING state Without RAM X18103 ... ..... .. ........$1 ,195 Including 2 M/Byte RAM X18107 ... ...............$1,625 :r :1:e SYDNEY: 74 Parramatta Rd . Stanmo re 2048 Ph one (0 2) 519 31 34 Fax (02) 519 3868 C21065 .............. ....$14.95 • 80286-12 Microprocessor • Hardware and software switchable • Socket tor 80287 numeric data co-processor •64K ROM • Phoeni x 8105 or Award • 8 Expansion slots 386 MAIN BOARD • 5 114·· Cl 2555 ........$5.95 All sales tax exempt orders and wholesale inquiries to: • Atlaches to the top of your monitor • Put your copy right where you need ii spring clip to hold paper • Velcro at mount tor easy removal (WITHOUT MEMORY) • Intel 80386 CPU (20 MHz) • Socket tor 80387 Math co• processor • 32-bil Memory BUS system • Built-in speaker attachment • Battery backup for CMOS configuration table and real time clock • Keyboard controller and attachment • 7 Channel OMA • 1,; Level interrupts • 3 Programmable timers • 8 System expansion I/O slots: 5 with a 36 pin and a 62 pin expansion slots / 2 with only the 62 pin expansion slot 1 1 with two 62 pin expansion slots (32 bit BUS) ...... . Cl 2560 .... ... $5.95 ROD IRVING ELECTRONICS GRIP CLIP COPY HOLDER • 6/12 MHz system clock with zero wait state. 12 MHz, 1 wait JOYSTICK FOR IBM* C14205.................. $39.95 • 100 x 5 1.4 ". Lockable Cl 6020 .................. $15.95 BABY AT* MOTHERBOARD Excluding Ram X18202 .. ...................$375 Including 2M/Byte Ram X18201 .....................$795 Features selectable '"spring centring" or "free floating". Electrical trim adjustments on both axis. 360 degree cursor control Use it to clean : • Computer keyboards • Printers • Video recorders , Computer circuit boards HEAD CLEANER DISKS It only takes a minute amount of dust. dirt or magnetic oxide particles on your drive heads to cause problems : errors, downtime or an expensive service call . Regular use of a head cleaner will keep your drive free of trouble causing dirt and help kieep your system up and running . these disk cl,;.aners are simple to use, and include cleaning solution and iristructions. 1·9 • 3 1•2· COPY HOLDER (YU-H32) • Adjustable arms alfows easy positioning • Copy area 9 112·· x 11". • Sliding line guide • Clamp mounting Remount your computer to give it that professional look. • Accepts XT, AT, Baby AT and 386 boards • Horizontal full height hard disk drive mounting • Room tor 2 x3 112·· and 2 x 5 114·· floppy drives • Full height HOD plus tan mo1Jnt , Size : 155(W: x 600(H) x 500(0) X11105 ................. .... $250 RITRONICS W HOLESA LE : 56 Re nver Road . Clayton . Phone :\03 ) 54 3 2 166 (3 lines) Fa x: (03) 543 2648 ORDER HOTLINE 008 33 5757 (TOLL FREE) STR ICTLY O RDERS O NLY LOCAL ORDERS & INQUIRES (03) 5431an C21062 ..... .. ...... ..... $39.95 EXTERNAL PS/2* COMPATIBLE 51 /4" DISK DRIVES Capacity: 360K Track/Disk : 40 MTBF: Greater 10,000 hours MTTR : 30 min. or less • External 37 pin connector COPY HOLDER (YU-H33) MAIL ORDER & CORRESPONDENCE : P.O . Box 620. CLAYTON 3168 Order Hotline : 00 8 33 5757 (Toii lree. strictly orders only) lnqu,nes : (03) 543 7877 Tele x : AA 151 938 Fa x: (03) 543 2648 cable • Copy area 9 112·· x 11". • Sliding line guide • Flot metal· base • Internal 40 pin adaptor cable for PS/2 models p,.'1~ • 40 pin card edge 'o oO , Installation Guide ~~ C21060 ............. .. ... $39.95 C11907 ..... ... ............. $245 POSTAGE RATES : $1 - $9.99 .... .... .. ... ....... ..... $2.00 $10 • $24.99 ......... ... ........ . $3.00 $25 • $49.99 .. ... .... .. ..........$4.00 $50 - $99.99 .................. FREE $100 + .. ................ ......... FREE The above poslage rates are for bas,c pos1age only. Road Fre,gnt. bulky and lrag ,ie items will be charged al differenl rates . Errors and omissions excepted . Pnces and spec1ilcat1ons subIec1 to change . IBM· PC' l(f' AT· a,e ,99,s1e,81J 1,~em•n,,s ot 1n1ern;111,on1.1 8,1 s,ness Millch, ,.es ·Apple ,s a •eg,ste• ed 1• ad1 ma, ~ 1otion · ,s a , e9 ,s1 ered iradema,i. ol 0uP0"1 ·o.,.o,.hn •e9 ,s 1e ,ed ■ ree 16-Channel Mixing Desk, Pt.3 In this third article on our new 16-Channel Mixing Desk, we present details of construction. All told, there are 2 3 circuit boards to be assembled: 16 preamplifier boards, 2 effects boards, 4 equaliser/VU boards and one board for the power supply. By JOHN CLARKE & LEO SIMPSON This mixer is a very big unit to assemble and so it is wise to proceed slowly and carefully. Don't barge in and start assembling all 16 preamplifier boards at once. If you do it that way, you are likely to duplicate your mistakes 16 times. To avoid that sort of debacle, we suggest you first assemble and test one of each of the boards. That way, you will presumably make mistakes only once. Furthermore, we suggest that every board is assembled and tested before it is mounted on the mixer panel. This will avoid the frustration of removing any defect board for repair. If you have a power supply which can deliver ± 15V, you can test the preamplifier and effects boards. To test the 5-band equaliser/VU boards you will need an additional power supply which can deliver + 5V. If you don't have power supplies with this capability, you will need to assemble the mixer power supply before any board testing can be done. The LEDs on the equaliser/VU meter hoards are aligned by mounting them on a jig and then gluing a 105 x 3mm strip of aluminium to them. The LED leads are then soldered to Molex pins on the PC hoard. 72 SILICON CHIP Therefore, our suggested assembly procedure is this: assemble one of each of the boards, including the power supply board. You can then complete the power supply and use it to test each of the three signal boards so far assembled. That done, learn by your mistakes and proceed to assemble and test the remaining 19 boards. Ideally, to do the testing you will need a digital multimeter. An audio oscillator is essential for verifying the boost and cut of the equaliser controls and the response of the VU meters. Now let's assume that you have the required power supply and so can go straight to assembling the signal boards. Assembling a preamplifier board The first step in assembling any board is to carefully inspect it for defects. Are all the holes correctly drilled? Are there any shorts between tracks or any breaks? If there are any defects, they should be corrected before proceeding further. This done, insert the PC pins at each end of the board. These are essential for making connections to the boards. Check the component overlay diagram of Fig.6 to see the number of PC pins required. There are 13 PC pins at the selector switch (S1) end of the board, including two for LED 21. At the other end of the board, there are 11 PC pins. Next, install the small polarised components: the three diodes (Dl, D2 & D3) and the two transistors (Ql & Q2). By installing these polarised components at this early stage, into an uncluttered board, it is easier to see that they are correctly inserted. Using the same thinking, bung in the electrolytic INPUT ATTENUATOR VR1 TREBLE VR4 10kHz VR18 BALANCED LINE OUTPUT (TO CH1 OUTPUT SOCKET) MIO VR3 J.5kHz VR17 1kHz VR16 PAN VAS 240Hz VR15 EFFECTS VAT 60Hz VR14 FOLDBACK VAS 0 ~ ~ 2 3 .,"' TO CH2 HEADPHONE OUTPUT a ~ CH1 BUS TO INPUT 2, S2 • al cl i= CH2 BUS TO INPUT 2, S2 EFFECTS BUS TO INPUT 2, S2 FADER VR6 0 0 Fig.6 at left shows the parts layout for a preamplifier PCB while Fig.7 (above) is the parts layout for an equaliser/VU board. APRIL 1990 73 TABLE 1: CAPACITOR CODES Value D D D D D D D D D D D D D D D D D D D D D D D 22pF 33pF 39pF 100pF 150pF 220pF 330pF 560pF .0012µF .0015µF .0027µF .0047µF .0058µF .01µF .012µF .015µF .018µF .022µF .047µF .082µF 0 .1µF 0 .18µF 0.22µF Alt Value IEC Code EIA Code (10%) 1.2nF 1.5nF 2.7nF 4.7nF 5.6nF 10nF 12nF 15nF 18nF 22nF 47nF 82nF 100nf 180nF 220nF 22p 33p 39p 100p 150p 220p 330p 560p 1n2 1n5 2n7 4n7 5n6 10n 12n 15n 18n 22n 47n 82n 100n 180n 220n 22K 33K 39K 101K 151K 221K 331K 561K 122K 152K 272K 472K 562K 103K 123K 153K 183K 223K 473K 823K 104K 184K 224K capacitors now. There are 8 in all. Make sure they go in the right way .a round. Next come the links and resistors. The links are easy. Cut them to length out of tinned copper wire and solder them in. Resistors are next. Use your digital multimeter to check each value before it is installed. Remember that the 1 % resistors will have 5 colour bands and the last (tolerance} band is brown. The capacitors are next to be installed. These can be labelled in a variety of ways, so we have listed the IEC and EIA codes for all the non-electrolytic capacitors in the mixer. So before installing each capacitor, check its coding against Table 1. The trimpot and the 5 ICs are next. Note that all five ICs are oriented in the same direction; ie, the dimple faces up to the end where the two 33µF capacitors are. The overload LED (LED 21} is soldered to two PC stakes at the end of the board. Its leads should be bent at rightangles close to the LED 74 SILICON CHIP body and soldered to PC stakes so that the LED stands 19.5mm above the PCB. By the way, our prototype preamp boards had the overload LED fitted to flying leads, as you can see from the photo published last month. Subsequently, we modified the boards so that flying leads weren't necessary. Potentiometers Before installing the 7 pots, their shafts should be cut to a length of 10mm. File any burrs off the shafts so that the knobs will go on easily, when they are finally fitted. The locating tabs on each pot should be bent as in the photo so they do not foul when the board is ultimately installed onto the mixer control panel. Solder in each of the pots and then clip off their lugs which protrude from the copper side of the board. This will prevent the leads from shorting to the pot bodies on the adjacent board (when they' re mounted on the mixer panel}. Finally, check your work careful- ly against the component diagram of Fig.6 and the circuit diagram of Fig.2 , published last month. You should then proceed to the section on testing or to the next board to be assembled. Assembling an equaliser/VU board Again, check the board carefully for missed holes and any etching defects before installing any components. Note that this board has one end cut at an angle to ensure clearance from the chassis when it is in place. The component overlay diagram for this board is shown in Fig.7. From here on in, follow the same general order of assembly that we suggested for the preamplifier board above. That means PC pins first, then diodes (D4, D5 , D6 and D7}, transistors (Q3, Q4} and electrolytic capacitors. Check that each of these components is in the right way around before proceeding further. Next, install the links and resistors, capacitors and ICs. Note that IC9, IClO, ICll and IC12 are oriented differently from the rest of the ICs on this board. All five pot shafts should be cut to 10mm length and cleaned up with a file before they are soldered into the board. Clip off the pot terminals where they protrude from the copper side of the board. Installing the LEDs One job that does need to be done carefully is installation of the 20 LEDs. They all need to be precisely in line otherwise they will not look good when they are installed in the mixer panel. There is no easy way to ensure this so we suggest you make a jig as shown in Fig.8. The jig consists of a wood block with a couple of strips of aluminium screwed to it, together with layer of electrical insulation tape, sticky side up (or you could use double sided tape}. The idea is to line up the 20 LEDs in the jig and then glue a 3mm wide strip of aluminium 105mm long to one side with epoxy adhesive. That way, all the LEDs are held precisely in line before being installed on the board. Note particularly that the LEDs must all be laid down precisely in WOOD BLOCK ALUMINIUM STRIP 102mm \ / ~ e -~~------~~~~~~~~___.____.____.___ ALUMINIUM STRIP 3mm WI OE GLUED TO LEDS INSULATION TAPE CLAMPED UNDER ALUMINIUM STRIP (STICKY SIDE UP) I \ WOOD BLOCK t LED LEADS Fig.8: this simple jig can be used to precisely align the LEDs on the equaliser/VU boards. The LEDs are all be laid down with the same orientation (anodes to the right) and then glued to an aluminium strip. the same way, with the anode and cathode leads as shown in the lower diagram of Fig.8. After the epoxy adhesive has set, the leads of each LED should be bent at right angles close to the body. The next step is to solder the 40-way Molex strip into the board. That done, clip off the top section of the Molex strip so that you have 40 individual Molex clips on the board. The strip of LEDs is soldered to the clips. When finished, each LED should appear as shown in Fig.9. Assembling an effects board Having read the article to this point, you can see the general procedure for assembling the two ef- LED / ![ , BENO CLO SE TO LED MOLE X PIN c ! =:=:=:=:::::P::;:C :/ B::::::=:> Fig.9: when the adhesive has set, the LED leads are bent at right angles and soldered to Molex clips on the PC board. fects boards. Only three ICs need to be installed and they are all oriented in the same direction. Follow the component overlay diagram of Fig.10. Power supply board To wire up this board, follow the This is the jig we used to align the LEDs. They are held in position by the sticky surface of the insulation tape. Note that the longer anode leads are to the right. component overlay diagram of Fig.11. Whack in the PC pins first, then the tinned copper wire links and diodes. Electrolytic capacitors are next, followed by the 3-terminal regulators. Make absolutely sure that you install the capacitors the right way around otherwise they are likely to seriously overheat and perhaps even spew out their insides when power is applied. Each of the regulators is attached to a small heatsink, which is retained by a screw and nut to the printed circuit board. Completing the power supply When the boards are ready for testing, you will need to assemble the power supply into the chassis. One of the first steps in this process is to add an 8VAC winding to the toroidal transformer. This will need to be done with at least the first batch of transformers supplied by Jaycar Electronics. Adding a winding to a conventional power transformer is a major task but with a toroidal transformer, as specified for the mixer, it is fairly straightforward. All that has to be done is to wind on 70 turns of 0.5mm tinned copper wire. To do this, you will need about 10 metres of wire. The idea is to thread the wire through the centre of the toroid and make sure that each turn is tight and not likely to rattle around. The 70 turns should be as evenly spaced as possible around the toroid, to After the aluminium strip has been glued in position, the LED assembly can be clamped using a second block of wood until the glue dries. APRIL 1990 75 MORE DEALS TO MAKE THE High performance AT/386Hard Disk/Floppy Disk Controllers Universal Wirewrap Card CAT IF'054 This universal wirewrap card is ideal for engineers and other technical people developing hardware add-ons for IBM PC/XT/AT/386 or compatibles The card provides a complete built-in data bus, address bus and VO !me buffer circuit. It incorporates a universal address decoding chip (0-3FF, step 8 or 16) and a D25 female connector. Buffering of the inputs and outputs makes damage to the PC's bus from faults on the card impossible. The wire-wrap area is 4000 holes which are plated through for easy prototyping work The card is built to a very high standard and can withstand heavy use. 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LAGC25M, CAT, LAGC25F ONLY$9.75 Modem cable 25 pin plug to 25 pin socket. All pmsare wired stra ight through Hardware Control CAT.LACSP25 graphics card adaptor. 9 pin to 15 pin adaptor enables multisync monitors to plug into the 15 pin analog output of VGA graphics cards. ONLY $9.75 each AMERE$9.75 CAT. LACM9 Modem ca ble 9 pin socket CAT. LANULL Null Modem Adaptor Modem Cables - 2 Metres CAT LACM9 CAT LACM25 'Type 0 Compute t End 25 Pm Female Mu<iAm Comput.P.1 •mci2S pUl •md 25 Pll l fl nci 9 pm :-·1-m1a!H nml+-i 1 femalH I $9.75 each 2 3 19 20 568 ?t1nte1 ?nntei End 9 ?in En<l 25 ?m Female Male 3 _ __ • Suits all parallel printers • Crossover switch • 36 pin centronics connectors ONLY$39.95 RS-232 Break-OutBox ...,,,,,,¼~.~~..., CAT LAAB Used totestand _ _ _ re-wire RS-232 interfaces ONLY $29.95 Serial Printer Cables- 3 Metres xon/x off Hardware Control CATLACSPX25 CATLACSPX9 Type2 Typel Comµute1 End 25 P::1 P11mei End 25 Pin M a!P. 3 Modem end 2r} pm r.m l~ . 2 Compute! End 9 P1:-. 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All pins straig ht through CAT.DCAHF to 25 µ,n plug . The aµproria te pi ns are connected (TXD to Tl<D, RX Lo RX ctc ) ,, 9 pin socket . to 25 pin plugThe .-~ ~·' appropriate . pins connect internally to . allow for matching of senal equipment usmga mixture of 9 pin and 25 pin connectors (eg. a 9 pin serial connector on a serial mouse to a 25 pin serial port on a PC). Serial Printer Cables ONLY $175 SAVE $50 Gr0c1L fo r faull plug to 25 pin socket. EXTRA SPECIAL!!! DISK BOX WITH 100 DISKETTES CAT.DCAH Modem Accessories Data Switches CATACDS21 CAT. LA9F25M CAT DCAH (HDD) or CAT DCA HJ-' (H OD & F'DD) Speed up the disk performance of your AT or 386 machine by a factor of around 2:1 with these fast cachmg disk controllers. 1:1 sector interleaving, using the latest Western Digital 1006 chip set greatly increases performance with most drives . Adaptors CAT. LA9M25F 9 pin ONLY $15. 75 each SAVE$100 USE:: 9 (OR 10) lNl RE CABLES ONLY $19.90 $15. 75each CALL US NOW FOR OUR GREAT CATALOGUE WITH ALL OUR PRODUCTS LISTED! OPPOSITION HATE OUR GUTS! BABY AT CASE + POWER SUPPLY CATCAATBP MULTISYNC MONITOR + VGA Save 40% on 2 Serial/1 parallel Port Card CAT !OPS2 Need more ports on your PC? T his compact half slot card comes complete wit h 2 serial and 1 parallel pow er and all the connectors, plus a 9 pi n to 25 pin DB adaptrn cable for the serial port. CARD CAT A CMM & CAT. VC0B00 This compact PC/AT case features a flip-top lid and facilities for expansion for up to 8 slot mother boards. The i nternal drive mounting tray will accept up to 3 half height 5¼ hard or floppy drives. LEDs and switches for Reset/Turbo/Power are provided . A keylock and key are also provided. Dimensions are: 360mm(W) x 165mm(H) x400mm(D) Normally $85 Limited stock: ONLY$45, SAVE$25! ! The cards provide complete register level compatibility with the IBM Video Graphics Array standard (VGA), w hile being backwards compatible with EGA. CGA 0 nd Hercules Graphics/MDA monochrome standards. The VC1024 is fitted with an additional 256K of display memory for up to 1024 x 768 pixel resolution. Prices the competition can't match!! 12MHz 0-wait state Normally $1,298 11half-size" AT Only $995, SAVE $303 motherboard Great Deal with TheTurboXT Motherboard CAT MB1600 Includes a heavy duty 200W AT Power Supply. Limited Stock Save $246 on 12MHz ONLY $175, SAVE $74 0-wait-state Baby-Size" AT Motherboard 11 Monitor Madness!!! 14" EGA MONITOR + EGA CARD CATACMEGA & CAT.VCEGA The ACMEGA is a full EGA colour monitor, providing both text and graphics display with all EGA and EGA compatible graphics cards. It features a 0.31mm dot pitch tube with anti-reflective coating . A tilt and swivel stand is provided This high perfonnance AT motherboard features ultra-fast performance and a full 8 slot expansion bus. It is switchable to 6, 8, 10 and 12MHz and can accept 256K , 512K, 640K or 1MB of memory on t he motherboard. The range of speeds allows slower memory to be used when available. The design uses the powerful CHIPS & TECHNOLOGY chip set (12 5MHz version) for very high performance and reliability. It outperforms other 12MHz designs by a wide margi n. Normally $848, now only $675. SAVE $173 Normal price $595. But while current stocks last: only $349 Magic Combo" 11 Mono/Colour Graphics Card + High-Resolution Monochrome Monitor CAT VCCOMBO/CAT ACMA This is the video card and monitor to suit all occasions I The Magic Combo Card dnves both your old CGA colour monitor and this blil~ant new monochrome monitor to the two most popular standards. 1. Colour Graphics Adaptor (CGA) standard. When usmg the TTL monochrome monitor, grey tones are used to simulate colours. 2. Monochrome Display adaptor with Hercules graphics (720 x 348 pixels) w hen dnving it as a TTL monochrome monitor. Now you don't need to put up with gritty CGA graphics for your text - switch to high quality 720 x 348 pixel MDA/hercules. Nor do you have to m iss out on all the games software because you can't run CGA graphics. You get the best of both worlds with the Magic Combo. Normally$328, nowonly$275. SAVE $53 per oimance motherboard has a full 6 expansion slots (5x16 bit, 1x8 bit) and a full 1MB of sons memory for maximum performance - 13.7 on Nortons SI rating ! 8 or 12MHz operation is keyboard selectable. The small size of t he board makes it ideal for replacement in both XTs and slower ATs. The mounting holes match those of both XT and AT machines Normally $495 plus $295 for 1MB of RAM. Sale Price $495 complete, SAVE $295!! The MB1600 is an IBM PC/XT compatible motherboard . It measures only 8½'' x 9" T he board runs at 10 M Hz or 4.77MHz, providing complete compatibility with the IBM standard . Eight 62 pin edge con nectors are also mounted to the board. The VO channel is bussed across the eight expansion slots. The heart of the M B1600 is an 8088-3 microprocessor. The system board supports both ROM/EPROM and R/W memory. It has space for 32K x 1 and SK x 1 of ROM or EPROM . A full 640K of high speed RAM can be fitted on the motherboard . NORMALLY $149 ONLY $99, SAVE $50 with V20 chip $109 Only while stocks last!! ................................. ipg~ I! ~~:: ;:~: : : ■ ~ ---••••-••-•-••• Fax (02) 906 5222 We accept Bankcard, Mastercard & VISA Mail orders our specialty. Freight on smaller items is now $9.00 + $2.50 P&P • All prices include sales tax • All products carry a 14 day money back guarantee (software and hard d isks excepted) • All products carry a full 3 month warranty • All cards come with full documentation • Ring for quantity discounts and tax free prices Owing to technical advances products we supply may in some cases vary from those pictured. In all cases they are guaranteed to pe rform to an equal or higher standard . ................................. "' . ~+---....lEFFEfJ:u;ETURN (TO 1-8 SOCKET) EFFECTS RETURN VR9 EFFECTS SEND OUTPUT (TO 1-8 SOCKET) PAN VR1O FOLDBACK LINE OUTPUT (TO 1-8 SOCKET) EFFECTS SEND VR11 FOLDBACK VR12 TO 1-8 FO ov ---./ TO 1 8 EFFECTS 8 TO CH2 EQUALISER CH2/CH4 +15V -15V EFFECTS POWER BUS TO CH1 EQUALISER PCB --•-CH3 I I I CH4 9-16 EFFECTS BUS ~ 9-16 FOLDBACK BUS 2CH/4CH SWITCH 1 TO 9-16 EFFECTS PCB Fig.10: parts layout for the two effects boards. Don't forget the link on the PC board that runs beneath the bottom two pots (VR11 & VR12). The ICs are all oriented in the same direction. assure a neat job. When you have finished winding on the turns, they should be well secured by winding electrical insulation tape over them. The two ends of the finished winding should then be stripped of enamel and tinned with your soldering iron. Fit a length of plastic sleeving over each winding end and secure it to the toroid with another few turns of insulation tape. Installing the transformer Before installing the transformer or any hardware in the chassis, it is a good idea to fit some solid rubber feet to the underside, to avoid scratching your workbench or table. The transformer is mounted directly on78 SILICON CHIP to the chassis using the hardware supplied with it. This consists of a long bolt which runs up through the centre of the toroid, to retain it with a large washer plate. A large rubber washer is fitted to either side of the transformer, to mount it compliantly yet firmly. Having mounted the transformer, fit the mains cord and associated wiring, according to the layout shown in Fig.11. Follow the diagram carefully to avoid mistakes. The mains cord must be secured with a cordgrip grommet so that it is firmly anchored. Leave 15cm or so free so that the three wires (Brown - Active, Blue - Neutral and Green/Yellow - Earth) can be stripped and terminated. The Active and Neutral wires are terminated to the power switch (S3). On the other side of the switch, the Active wire goes to one side of the fuseholder. The transformer primary is then terminated to the fuseholder and to the Neutral side of the power switch. The earth wire is connected to the chassis via an earth lug which is secured with a screw, nut and star washer. It is preferable to fit shrinkable sleeving over the fuseholder and power switch wiring, to make it safe from accidental contact. When the mains section of the wiring is complete, it is necessary to identify the start and finish of each of the two 15V secondary windings. Join the green and blue secondary wires and then make sure that none of the secondary wires are touching the chassis; then switch on the mains power. Set your multimeter to measure 30V AC and check the voltage between the red and brown secondary windings. It should be 30VAC or thereabouts. If it is zero, disconnect the green and blue wires, join the red to the green and measure the voltage between the blue and brown. This effectively reverses the phase of one of the windings. Disconnect the mains plug from the mains and continue with assembly of the power supply. The power supply board should be mounted on the chassis with four 6mm spacers, screws, nuts and lockwashers. That done, connect the transformer to the power supply PCB. Checking the power supply Now switch on power and check the output supply rails for + 15V, - 15V and + 5V. With these correct, you are ready to check the signal boards. To test each signal board, you will need an audio signal oscillator and a digital multimeter. If you have access to an oscilloscope and perhaps an AC millivoltmeter, so much the better. In our experience, any problems found on the PCBs are most likely to be incorrectly placed or incorrectly oriented components or shorts between PC tracks. It is seldom that !Cs are found to be faulty, unless Fig.11: parts layout & wiring diagram for the power supply. The completed power supply can be used to test the other boards before installing them in the chassis. 0 HEATSINK TO BAR DISPLAY BUS HEATSINK NEUTRAL (BLUE) POWER TRANSFORMER COROGRIP GROMMET \ AINS © EARTH LUG APRIL 1990 79 PARTS LIST FOR 16-CHANNEL MIXER Input Channel Boards (16 required} 1 PCB, code SC01102903 1 3mm red LED and bezel (LED 21) 25 PC stakes Semiconductors 3 LM833 dual op amps (IC1, IC2, IC3) 1 CA3140 op amp (IC4) 1 7555 CMOS timer (IC5) 1 BC338 NPN transistor (01) 1 BC328 PNP transistor (02) 3 1 N914, 1 N4148 diodes (D1, D2, D3) Capacitors 1 330µF 16VW PC electrolytic 2 1 OOµF 16VW PC electrolytic 2 33µF 1 OVW PC electrolytic 2 6.8µF 16VW PC electrolytic 1 3.3µF 16VW axial electrolytic 1 2.2µF 16VW axial electrolytic 2 1µF 1 6VW PC electrolytic 6 0 .1µF monolithic ceramic 1 .01 5µF metallised polyester 1 .012µF metallised polyester 1 .01 µF metallised polyester 1 .0027 metallised polyester 1 .001 5 metallised polyester 1 330pF ceramic 1 220pF ceramic 3 1 50pF ceramic 1 1OOpF ceramic 1 39pF ceramic Resistors (¼W, 1 470k0 2 220k0 1 4 7k0 3 33k0 4 15k0 2 12k0 10 1 OkO 1 10k0 1 % 2 6.8k0 2 2k0 1 % 5%) 1 1.8k0 1% 1 1 .5k0 1 1 .2k0 1 % 2 1k0 3 1 kO 1 % 1 6800 1 5600 1 % 1 4700 1 % 1 1500 1 1000 the supply rails have been inadvertently reversed. Testing a preamplifier board Before applying any power, you will need to wire in the main slider (VR6) and connect a link between the two PC pins marked "X" on the diagram of Fig.6. In this condition, 80 SILICON CHIP 1 910 1 % 1 680 2 330 1 130 1 % 2 4. 70 Potentiometers 3 1 OOkO linear PCB mount pots 3 1 OkO log PCB mount pots 1 1 OkO linear PCB mount pot 1 1 OkO log slider pot 1 1Ok miniature horizontal trimpot Chassis hardware 1 XLR 3-pin chassis mount female socket 1 3-pole 3 position rotary switch (S1) 1 4-pole 2 position miniature toggle switch (S2) 1 6. 5mm insulated panel mount stereo socket 7 small knobs to suit pots: 1 green, 1 blue, 3 grey, 1 red, 1 white Effects Boards (2 required} 1 PCB, SC01102901 3 6.5mm insulated mono panel sockets 4 knobs to suit pots: 1 red, 1 green, 1 white, 1 yellow 20 PC stakes Semiconductors 3 LM833 dual op amps (IC6, IC?, IC8) Capacitors 2 1 OOµF 16VW PC electrolytic 2 4 7 µF 1 6VW PC electrolytic 2 4. 7µF 16VW PC electrolytic 1 2 .2µF 16VW PC electrolytic 5 1µF 1 6VW PC electrolytic 2 0.1 µF monolithic ceramic 3 220pF ceramic 4 1 50pF ceramic 2 39pF ceramic ICla will be set in the microphone balanced mode and will have a gain of 10 [by virtue of the 10kn resistor between its pins 1 and 2). Apply power to the circuit and check the voltages. You should find + 15V present at pin 8 of ICl, IC2 and IC3, at pin 7 of IC4, and pins 4 & 8 of IC5. You should find - 15V Resistors ( ¼ W, 5%) 3 6.8k0 2 1 OOkO 3 47k0 3 2.2k0 2 39k0 6 1kO 1 22k0 2 330 4 15k0 Potentiometers 3 1 OkO log PCB mount pots 1 1 OkO linear PCB mount pot Equaliser & Meter Boards (4 required} 1 PCB, code SC01102902 1 XLR 3-pin male plug 1 stereo 6. 5mm panel socket 5 grey knobs to suit pots 1 40-way Molex strip 22 PC stakes Semiconductors 3 LM833 dual op amps (IC9, IC10, IC11) 4 TL071 op amps (IC13, IC16, IC18, IC19) 1 CA3140 op amp (IC17) 1 TL07 4 quad op amp (IC12) 2 LM3915 logarithmic LED drivers (IC14, IC15) 1 7555 CMOS timer (IC20) 1 4066 CMOS quad gate (IC21) 1 BC338 NPN transistor (03) 1 BC328 PNP transistor (04) 4 1 N4148, 1 N914 signal diodes (D4, D5, D6, D7) 20 red rectangular LEDs (LED 1 to LED 20) Capacitors 2 1OOµF 16VW PC electrolytic 2 4 7 µF 1 6VW PC electrolytic 9 1OµF 1 6VW PC electrolytic 2 4 .7 µF 16VW PC electrolytic 4 1µF 1 6VW PC electrolytic 1 0.22µF metallised polyester 1 0.18µF metallised polyester 2 0 .1µF monolithic ceramic 1 .082µF metallised polyester 1 .04 7µF metallised polyester 1 .022µF metallised polyester present at pin 4 of ICl, IC2 and IC3. OV should be at pin 4 of IC4 and pin 1 of IC5. In addition, the voltage at pins 1 and 7 of ICl, IC2 and IC3 should be very close to OV, say within ± 20mV. If you find any deviation from these voltages, you should switch off and check your work carefully 1 .018µF metallised polyester 1 .01 µF metallised polyester 1 .0056µF metallised polyester 1 .004 7 µF metallised polyester 1 .0012µF metallised polyester 1 560pF ceramic 1 220pF ceramic 1 1 50pF ceramic 2 33pF ceramic 1 22pF ceramic Resistors (1.4W, 5%) 8 1OOkO 3 2.2k0 1 75k0 2 2k0 1% 1 68k0 4 1 kO 1 62k0 1 % 3 1kO 1 % 2 47k0 5 9100 1 36k0 1% 1 9100 1% 1 30k0 1 % 1 6800 1 22k0 2 6800 1% 9 10k0 1 680 1 6.8k0 4 330 2 4 .7k0 1 4.70 2 3.9k0 Potentiometers 5 1 OOkO linear PCB pots 2 1 OOkO miniature vertical trimpots 1 1Ok{} log slider pot 1 1 OkO miniature vertical trimpot Power Supply 1 PCB, code SC01102904 1 30V centre tapped 80V A toroidal mains transformer with 8V 1 A winding 1 illuminated DPDT 240VAC rocker switch (S3) 1 3AG panel fuse holder 1 250mA slow blow 3AG fuse 1 mains cord and plug 1 cord grip grommet 3 T0-220 heatsinks (Jaycar Cat. HH-8508) 1 solder lug 1 screw, nut and star washer to suit above 4 6mm standoffs 4 screws and nuts to suit above 3 screws and nuts for regulators 14 PC stakes Semiconductors 8 1 N4004 1 A diodes (D8 to D15) 1 7805 5V 3-terminal regulator 1 7815 15V 3-terminal regulator 1 7915 -15V 3-terminal regulator Capacitors 4 2500µF 25VW axial electrolytic 2 2500µF 16VW axial electrolytic 3 1 OµF 16VW PC electrolytic 3 1µF 25VW PC electrolytic Additional Chassis Hardware 2 insulated 6.5mm stereo panel sockets 5 large rubber feet Wire 2 metres tinned copper wire 10 metres 0.8mm enamelled copper 1 metre grey 24 x 0.2mm hookup wire 5.5 metres black 24 x 0.2mm hookup wire 6 metres red 24 x 0.2mm hookup wire 9 metres green 24 x 0.2mm hookup wire 6 metres blue 24 x 0.2mm hookup wire 3.5 metres yellow 24 x 0.2mm hookup wire 0.5 metres 19 x 0.193mm figure-8 polarised wire 1 O metres single core shielded wire 7 metres twin shielded wire Miscellaneous Thermal grease for heatsinks, cable ties, heatshrink tubing for mains switch and fuse holder. Made here in Austrara? Polystryrene Capacitors - 1 0pF to 1mF Voltage Range 63VDCW to 10,000 VDCW Tolerance - 0.25% to 10% Allied Capacitors A ustra/ia manufactures capacitors to the specification of the customers using high quality, imported polystyrene and aluminium foil with a tolerance of 1 micron. Our capacitors are manufactured to the system of Total Quality Control. We can provide Just In Time delivery if required, together with a Certificate of Conformance if requested. Specific values between 10pF and 1uF are no more expensive than standard value components. You can now design circuits to use a single capacitor rather than a number in parallel or series to achieve a desired value . Personalised labelling is available at no extra cost. Your component code or name can be built into the capacitor. Minill'!um runs of only 25 allow you to specify a particular value for a prototype run. Delivery lead time for short runs is 3 to 4 working days, and for longer runs is less than 2 weeks. We are also able to produce capacitor styles for applications such as dual mount, end filled and mini style capacitors. Call us now on: before proceeding further. Now apply a signal of about lOOmV at lkHz to the input; ie, PCpin 1 (ground) and pin 2 (signal active). Use the circuit diagram (Fig.2) and the overlay diagram (Fig.6) to aid in checking the signal flow through the circuit. With lOOmV RMS applied to the input, the lkHz signal at pin 1 of ICla should be close to 1 volt RMS. At pin 7 of IClb, the signal should be 2 volts RMS with the attenuator, VRl, set fully anticlockwise. Now reduce the lkHz input signal to lOmV RMS and wind the attentuator VRl fully clockwise, to give maximum gain. The signal at pin 7 (02) 938 4690 ALLIED CAPACITORS AUSTRALIA PO Box 740 Brookvale, NSW 2100 APRIL 1990 81 of signal on the foldback and effects bus outputs and the operation of the relevant controls, VR5 and VR7. Operation of the bass control can be tested by applying a signal at around 40Hz and then checking for boost and cut and the extremes of rotation of VR2. To test the midrange control, VR3, apply a signal of around 700Hz while the treble control, VR4, can be checked at lOkHz. Testing the effects PCB The pots on the two effects boards are angled slightly so that the bottom edge of the board clears the chassis. should now be close 10 volts RMS. Now wind VR 1 fully anticlockwise and increase the input signal back to 100mV RMS, which should give 2 volts RMS at pin 7 of IC1 and also at pin 1 of IC2a, provided the three equaliser controls, VRZ, VR3 and VR4, are all at mid setting. The same voltage output should also appear at pin 1 of IC3a and at the headphone output (via the 680 resistor). All these test results should also be obtained if you apply the input signal to PC pin 3, to check the noninverting input of IC1a. Adjusting the peak detector The peak detector is adjusted by varying the TRIM 1 trimpot associated with IC3. With an input signal of 100mV applied, you should be able to get the peak detector LED to light by winding up the input attenuator VR1 or the main attenuator VR6, depending on the setting of the TRIM 1 trimpot. Our suggestion for setting the peak detector is to adjust the attenuators (VR1 and VR6) until the signal level at pin 7 of ICZ is 8.5 volts RMS. You then adjust TRIM 1 until the LED just lights. Alternatively, if you have access to an oscilloscope, you can adjust the attenuators until the signal at pin 7 of ICZ is just on the verge of clipping. You then adjust TRIM 1 until the LED just lights. Check for the presence of signal on the Channel1/Channel2 buses and operate the Pan control VR8 to vary the signal between the two buses. Also check for the presence ·'-·••11;. ;r.~~~~:.1;: 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. 82 SILICON CHIP Connect the supply rails to the board, apply power and check the voltages. You should find + 15V present at pin 8 of IC6, IC7 and IC8. You should find - 15V present at pin 4 of IC6, IC7 and IC8. In addition, the voltage at pins 1 and 7 of these three ICs should be very close to 0V, say within ± Z0mV. If you find any deviation from these voltages, you should switch off and check your work carefully before proceeding further. Apply a 100mV RMS signal at 1kHz to the effects return input and measure the signal at pin 7 of IC6 which should also be lO0mV RMS, as expected from a unity gain stage. Rotate the effects return control VR9 fully clockwise and measure the signal at pin 1. It should be 400mV RMS. Check for the presence of signal on the Channel 1 and Channel 2 bus pins and see that the pan control, VR10, varies the signal on these buses. Now feed a 50mV RMS signal to the effects bus pin. The signal at pin 1 of IC7a should be 886mV RMS. Wind up the master Effects Send control, VR 11, and a signal of 6.9 volts RMS should be present at pin 7 of IC7. Similarly, apply a 50mV RMS signal to the foldback bus PC pin. The signal at pin 1 of IC8 should again be 886mV. Wind up the master foldback control, VR12, and a signal of 6.9 volts RMS should be present at pin 7 of IC8. Next month we will complete the discription of the mixer by presenting the test procedure for the equaliser/VU meter boards and then the wiring and assembly procedure for the mixer panel and chassis. ~ High density data storage: a possible new technique This is a pure science story which may be extremely important in the future or it may have no relevance at all. Up to now, the only practical way to create extremely small surface features has been with photo-etching techniques. Now there is another way. Using a tungsten needle in a vacuum, two Philips scientists have been able to create a pattern of minute pits in silicon with a density which is around ten thousand times higher than on today's compact discs. This discovery, by Dr Evert van Loenen and Mr Dick Dijkkamp of the Philips Research Laboratories in the Netherlands, may lead to the possiblity in the future of performing higher-precision operations on technologically important chip materials, such as silicon. The possibility of creating pits in silicon with a tungsten needle was discovered during experiments with a Scanning Tunnelling Microscope (STM). This instrument essentially consists of an extremely sharp needle which is held in a vacuum at several atomic spacings, ie, around half a nanometre (one nanometre is a millionth of a millimetre), above a surface. When a voltage is applied between the needle and the surface, electrons pass across this very small gap. The needle is mounted on a scanner of piezoelectric material, which expands or shrinks under the in- The left picture shows rows of pits in silicon with a diameter of 10 nanometres and a depth of 0.6 nanometres. It can be clearly seen that the silicon has been pushed away in the centre of the pit and that it has been raised slightly at the edges. The picture at right shows fine lines drawn in a silicon surface. Note the natural ordering of the silicon atoms in the background. fluence of an electric voltage which is applied to it. By keeping the current strength constant, the distance between needle and surface also remains constant and the needle can accurately follow bumps and pits on the surface. The movements of the needle are registered with a computer and the resulting "relief map" is displayed on a screen. In this way, it is possible to inspect the surface very precisely. Variations in height as small as one hundredth of a nanometre can be made visible. As the needle is made so sharp that there is ultimately just a single atom at the tip, it is possible to observe individual atoms. Work on observing surfaces was soon followed by the manipulation of surfaces with the aid of the STM electron current. With higher current strengths it proved possible, for instance, to locally melt or otherwise deform surfaces of soft metals. Unfortunately, the minute pits and bumps made in this way did not turn out to be stable. Atoms from the environment migrated to the damaged places, generally causing the pits and bumps to change in shape again fairly quickly. However, Dr van Loenen and Mr Dijkkamp have succeeded in making stable ultra-minute pits in the hard semiconductor material silicon in a vacuum, simply by pushing the needle into the surface. Their results were recently published in the scientific journal Applied Physics Letters. First they positioned the STM needle over a required location. Then they carefully pressed the needle several tenths of a nanometre into the surface, while the electronic circuit controlling the distance from the surface was briefly switched off. After switcontinued on page 99 APRIL 1990 83 •• - · . . . .... - ~ - •. ,~, · · - - · •. - · w, ~ ............ . , , ..., , ~ , _,,.,,...,,, ...,, .. , ._.,_ ._ ...,,, ,...,,.,....,...,..,, ., , ,._,,, , , .._.__._,._,,, ,.....,,.,,,._,.......,,..., , ,._,,...1, .__.__ ......., 1nv, ·o...,\Jvr'\ 1 vr1n LLLV I nu1'1111...,0,,.1/"\ 1v/"\n C LCVI nvr"11,..,;::, R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR RELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR .R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEClHONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR .R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR .R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR fl.E'CTRONICSJAYCAR FI ECTRONICSJAYCAR 'LECTR< · ;m \t~g~~ :LECTR ,LECTR !t~gi= ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYc..;AH l:::Ll:::CI HONIC::i JAYCAR JAYCAR JAYCAR JAYCAR .JAYCAR ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS r N~w::~AY~J\lj :t<•Ts f~iij :~~:~,~~~ :: ± 50V (0 - 1 00V) 1 .5A Dual Trac k ing Po w er Supply Kit Ref: Silicon Chip April ·go This magnificent switch mode type laboratory power supply has great professional features but costs around 1/2 of inferior built up units. This kit features high efficiency toroid power transformer. professional high resolution 10-turn wire wound voltage control potentiometer. latest I.C. technology, excellent line load regulation. low ripple voltage, apart from a smart plastic case! (for more information see specs belowj. The Jaycar kit is complete down to the last nut and screw as well as all hard-to-get I.C.'s. ,LECTR ,LECTR :LECTR Cat No. KC-5073 ,LECTR ' LECTR Specifications ,LECTR Type: ,LECTR Output Voltage: ,LECTR Output Current: ,LECTR Tracking Accuracy: ,LECTR Load Regulation: ,LECTR Line Regulation: :LECTR Ripple output: cLECTR Protection: :LECTR :LECTR '=. ,LECTR \ :: UCTR $229 Dual tracking with switch mode pre-regulators for high efficiency 0 to+/-50V 1.7A from Oto 87V; 1.5Aat91V; 1Aat 100V Better than 30mV Better than 500mV at +/-Vand 1A Better than +/-5mV for mains voltages from 220-261N AC Less than 3mV p-p at full load Fully protected against output short circuits and forward and reverse voltages connected to the output fuse protection for the power transformer. :(''2=~~=~~~~~===~~~~~~~===========~J?['J:Jfil~~=====;;:z:==~~====mz EXPERIMENTORS PLUG lt!g~~ • , ~~~Ii!~~~:A~J~3A~I~~ a~~~tPceeo~2!1R Ya~!t~o~l~~u~!f~he PACK BARGAIN :LECTR ,LECTR ,LECTR ,LECT ,LECT first bit of speech! This clever project uses an acoustic delay to prevent the common fault in all but the most expensive VOX circuits - the 10mS or so of that is lost by relay operating time. It may not sound much but it is very annoying and a long time in speech terms. This kit is supplied by Jaycar in a short form. i.e. without case. front panel. plug adaptor etc. This saves you over $20 on the price otherwise. as we believe most of these projects will be built into other equipment anyway. All other parts (including all PCB parts) included. :;: ,:_ :,: .· Only $59.95 ea1. KC-5074 Specifications Signal delay: 16.4 miliseconds • Clock frequency: 15.7kHz • Frequency response: 100Hz to 43kHz within (pm) 3dB • Maximum output signal : 800mV RMS • Maximum input sensitivity: 0.7mV RMS (to actuate relay) • Harmonic Distortion: <0.5% at 250mVand 1kHz <1.5% at BO0mV and 1kHz • Signal to noise ratio: (ms) 66dB unweighted with respect to SO0mV RMS at the output ,LEcT \t~gi \t~g !tig~ If IC SOCKET MADNESS : LECT :LECT ' LECT /· ) / Solder Type J l t~gi : LECT X : LECT \ : LECT \ 20 Pin normally 48\', each Now 16 for $2 Save $5.68 Cat No. PI 6504 28 Pin normally 70\! each Now 14 for $2 Save $7.80 Cat No. PI 6507 (t~gi : 40 Pin normally 70~ each , LECT :\ Now 10 for $2 Save $5 ····· Cat No. PI 6508 \ t~gi ] : LECT ~t~g : LECT : LECT )LLEECci : LECT : LECT : LECT : LECT : LECT : LECT ~t~g = : LECT : LECT : LECT : LECT :: LECl LECT it~g , LECT ,LECT , LECT ,LECT : LECT , LECT : LECT : LECT ' LECT : LECT : LECT : LECT :LECT ' LECT :LECT :LECT :LECT ,LECT Machine Pi n Type 16 Pin normally $1.50 each Now 3 for $2 Save $2.50 Cat No. PI 6456 18 Pin normally $1.65 each Now 4 for $2 Save $4.60 Cat No. PI 6458 20 Pin normally $1.90 each Now 3 for $2 Save $3.70 Cat No. PI 6460 22 Pin normally $2 each ~;"N!f~[ ~~62 24 Pin normally $2.30 each Now 3 for $2 Save $4.90 Cat No. PI 6464 28 Pin normally $2.60 each Now 4 for $2 Save $8.40 Cat No. PI 6466 40 Pin normally $3.25 each Now 3 for $2 Save $7.75 Cat No. PI 6468 Don't miss this one. Primary- 220V 50hz (will work OK on 240V) lead length 1.8mt long - bare ends ( no 240V plug supplied). - 16V AC at B00mA • 9V AC at 1.5AMP Lead length 1.7mt long terminated in a strange pi ug Supplied in a maxi box style. Measures 75 (W) x 85 (L) x 60 (Hlmm 1-9 $5.95 10-49 $5.50 50-99 $4.95 100 +$4.50 Cat No. MA 2618 Save $6 )\;),:==================================~t:f:~================;;:j (? Custom Make Your Own Soeaker Crossovers Now you can design your own 6 or 12 (or more) d~}octave high, low or bandpass filters to custom make a crossover system exactly to fit yourneeds! (SEE PAGE 23 -1990 CATALOGUE FOR FULL DETAILS) INDUCTORS Inductors (L) OCR Wire Dia Core Cat. No Price 0.22mH 0.3W 0.8mm Air LF-1310 $3.95 0.33mH 0.37W 0.8mm Air LF-131 2 $425 0.39mH 0.41W 0.8mm Air LF-1 314 $4.50 0.47mH 0.47W 0.8mm Air LF-1316 $4.50 0.56mH 0.5'Nv 0.8mm Air LF-1318 $4.75 0.82mH 0.66W 0.8mm Air LF-1320 $5.50 1.0mH 0.74W 0.8mm Air LF-1322 $6.50 1.8mH 1.05W 0.8mm Air LF-1326 $7.95 2.7mH 1.31W 0.8mm Air LF-1330 $8.95 3.0mH 1.3fNV 0.8mm Air LF-1332 $9.50 9.0mH 0.95W 0.8mm Bar LF-1340 $9.50 Fora Ohm Hz L1 mH Cl mF L2 mH C2mF L3mH C3mF 100 18.0 100.0 9.0 100.0 250 4.0* 100.0 7.0* 47.0 4.0* 47.0 500 2.0* 47.0 3.0 33.0 3.0 33.0 750 1.47* 33.0 2.0 22.0 2.0 22.0 1000 1.0 22.0 1.47* 150* 1.0 15.0* 2000 0.47 10.0 0.82 100 0.47 10.0 3000 0.33 6.8 0.47 6.8 0.33 6.8 4000 0.22 4.7 0.39 4.7 0.22 4.7 5000 0.195* 4.4* 3.0 3.3 0.195* 3.3 *For these values it will be necessary to use standard values in series or parallel. e.g. L3 for 100Hz is 2 x 9mH inductors in parallel; L3 for 250Hz is a 3.0mH & 1.0mH in series. etc. The same will apply (to a lesser extent) with some capacitor values. e.g. Cl for 5000Hz is 2 x 2.2mF caps in parallel. NOTE: If your application is for 4 ohm systems instead of8 ohm. HALVE inductance values and DOUBLE capacitance values. Power: All inductors shown have the wire gauge capacity to handle at least 100 watts rms with very little copper loss. =' ";:Z::Z:8lZ8lZ:Z::Z::Z:8lZ8lill:Z::Z::Z:8lZ8lill:Z::Z::Z:8lill8lill:Z::Z:8lZ8lill:Z::Z:8lZ:Z::Z::Z:8lZ8lill:Z::Z::Z:8lill:Z::Z::Z::Z:I:Z_Z_ I:_ J:_I:_Z_ Z_ :I_Z_I:_ Z_ Z_I:_z~ :z:m::;f :;;;, ~ Mic Input Impedance ~: ~~~ ~~~ Cat. AM-4206 6 Input Microphone Mixer This microphone mixer is housed in a standard 19' rack mount box and operates directly from 240V AC. It has 6 inputs. 4 low impedance (600 ohm) and 2 high impedance (50k ohm). Each channel has its own volume control with a master volume control as well. It also incorporates a master bass and treble control. Microphone connections are on the rear panel via 6.5mm sockets. There is a high and low impedance output. Low Level Output High Level Output Frequency Response Distortion Power Supply Dimensions 3mV 0.3V 20 · 20kHz Below 0.3% 240V AC Panel Height44mm x 150(0) x 330(W) at rear mm $ 1 49.50 :)::,:."""'""""""""'""""""""'"""'=""'""'="""""'"""'"""""'""'om:"""""'""'""'°'"""""'""'""""""""'""'""""""""'"""°""""'""'"""""'""'"""'"""""'""'""""""""'""'"""""'""'""'""""4 :LECT LECT , :;::'.;'.i'.:~:: ::::;: ::: :::::::::::::::::'.::.:.~ ~;;;·;;;:; ~~~'.:;;;;'.;:;;::_;;:;:;;:;:_;;:;:;__:::;__~:;;;;i:~::_;;;:'.'.;;i'.:'.'.;'.: ~~-- ,,,_,,. __,,. -· .. , ____ .. -· . ___ .._ ... ___ :LECTRONICSSJAYCAR ELECTRONICS JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR :LECTRONICSSJAYCAR ELECTRONICS JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR :LECTRONICSSJAYCAR ELECTRONICS JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR :LECTRON ICSSJAYCAR ELECTRONICS JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEOTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR TRONICSJ TRONICSJ ELECTRONICSJ ELECTRONICSJ ELECTRONICSJ ELECTRONICSJ ,JJ-'I, 1 VM.M c Lcv I nvr1,111..,,~f-\ r 1uM n c:Lcv I n u1'1 1V.:>,J/-\ TvMn C L CV I MVl'41Vi:>.JM YVMH t:.LC.L. I HUI\I IL,.:>...IA Y\..-AH t:Lt.L, I HVNIV.:>JA YVAH t:Lt:\., I HUNIL.:tJA YL,AH t:U:L, I HU I\I IL,~JA TL.AH t:Lt:L. I HUl\lll,~JA f'A_YCAR JA YCAR ELECTRONICSJAYCAR JAYCAR ELECTRONICSJAYCAA JA YCAR ELECTRONICSJAYCAR JAYCAR ELECTRONICSJAYCAR JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAA ELECTAONICSJAYCAA ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON\CSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEC ELECTRONICSJAYCAR ELECTRONICEJAYCAA ELECTRONICSJAYCAR ELECTRON ICE JAYCAR ELECTRONICSJAYCAR ELECTRONICEJAYCAR ELECTRONICSJAYCAR ELECTRONICcJAYCAR ELECTRONICSJAYCAR ELECTRONIC, JAYCAR ELECTAONICSJA Y'A YCAR ELEC ELECTRON ICSJAY1AYCAR ELEC ELECTRONICSJAY'AYCAR ELEC ELECTRONICSJAY AYCAR ELEC ELECTRONICSJA YAYCAR ELEC ELEC ELEC FULL DETAILS SEE PAGE 61 -1990 JAYCAR CATALOGUE ELEC ELEC Just imagine a security/alarm system that does not need wires to connect the PIRs, window/door reed switches, personal remote control and optional ELEC remote keypad. The only wiring required is to connect to a horn speaker. ELEC ELEC ELEC ELEC ELEC ELEC ELEC ELEC COMPLETE SYSTEM includes ELEC 1 x Control Panel ELEC 1 x Passive Infra Red Detector/Transmitter ELEC 1 x Door/Window Reed Switch/Transmitter ELEC 1 x Hand Held Remote Control/Transmitter ELEC 1 x Horn Speaker - 10 watt/wired ELEC FLEC 1 x 240V AC adaptor ELEC 1 x 1.2Ah Back-up Battery ELEC 1 x Set of batteries far all transmitters ELEC ELEC Cat. lA-5200 ELEC ELEC ELEC OPTIONAL EXTRAS ELEC • Wireless Remote • Hand Held Remote • Door/Window Reed • Wireless Passive ELEC Control • Wireless Infra Red Detector Keypad Switch - Wireless ELEC Cat. IA-5205 $149 Cat. lA-5215 $129 Cat. IA-5208 $59 Cat. IA-5210 $69 ELEC ELEC ELEC ELEC ELEC We are proud to announce that CB radio and accessoELEC WEATHERPROOF/WATER RESISTANT/SHOCKPROOF ries have been reintroduced to our 1990 line-up. The ELEC This torch is supplied with a Krypton globe, which is 70% brighter than a standard globe. Krypton globes products chosen and shown here have been extensively ELEC don't draw heavy current like halogen globes so your baneries last much longer. evaluated and represent outstanding value for money. ELEC This torch takes 3-D cells and gives a brilliant light. D cells not supplied. SEE PAGES 68/69 -1990 CATALOGUE FOR FULL RANGE ELEC Replacement Krypton gl ooos Cat SL-2712 2 pcs $2.95. ELEC Cat. ST-3022 ELEC ELEC ELEC ELEC ELEC Cat. DC-2000 (Not illustrated) ELEC ELEC ELEC ELEC ELEC ELEC ELEC ELEC ELEC The BIG brother to our 2-AA torch. This torch measures a massive 440mm long and has a Krypton Long Cat. DC-2010 (Not illustrated) ELEC Reach Beam glooo which is 70% brighter than normal torches. ELEC It's waterproof and shockproof and has a durable anodised abrasion resistant finish with a non-slip knurled ELEC grip. This torch will last a lifetime. ELEC The American originals of this product sell for about $90. Direct import from Asia saves you over 50%. ELEC Spare globe supplied in tail cap. Spare Krypton globe available- 6 volt Cat. SL-2716 $1.50 each. ELEC Cat. ST-3025 i ELEC ELEC ELEC ELEC ELEC Cat. DC-2015 ELEC ELEC ELEC ELEC ELEC • Find a positive lead under the dash easily , ELEC • Check the charge in the battery ELEC • Check if high voltage is present in spark plug leads i ELEC If you have ever tri ed to wire an accessory to your car, you will know how difficult it is to find a positive , ELEC cable easily. This product will do this in moments. Simply insert the tool over the cable and it will pierce it ELEC with a needle. With the alligator clip attached to each it will immediately tell you if there is 12 volts there. ELEC You can also check to see what charge the battery is holding and if high voltage is present in the spark plug , ELEC leads. ELEC Cat. QP-2245 ELEC ELEC ELEC Top loaded whip Cat. DC-2060 ELEC ELEC ELEC UHF Wireless Security System NEW UHF 303MHz Microprocessor Control Wireless Security Alarm System • ONLY $599 • Back into CB Radio! Krypton Power Rubber Torch • 3D Cells ONLY $6.95 AM 40 Channel Budget Model PEARCE-SIMPSON SUPER LYNX Mklll $89.95 AM 40 Channel Full Feature PEARCE-SIMPSON SUPER COUGAR Mkll 5-D Cell Machined Aircraft Grade Aluminium Flashlight $129 Full Feature AM/SSB 40 Channel CB PEARCE-SIMPSON SUPER CHEETAH Mklll GRABBER' $19.95 Bulbs • Low Voltage A must for the serious ca·er! Cat. OM-1600 $29.95 ~~g1= ~ ~ ALL PEARCE-SIMPSON CB RADIOS have a ONE YEAR WARRANTY. not 3 months like most of the others. Each and every unit is thoroughly te st cd IN AUSTRALIA before despatch. AYCAR EL . AYCAR ELECTRONICS JAYCAR AYCAR ELECTRONICS JAYCAR AYCAR ELECTRONICS JAYCAR AYCAR ELECTRONICS JAYCAR This is the same as the 'firefly' lighting you saw all over the over the original system we sold in 1988. The cable simply and a slide clip arrangement holds the bulb firmly. 10 BULBS/BASES CatSL-2800 $12.95 CABLE TO SUITcatws-110s55~ metre POWER SUPPLY 1 AMP TRANSFORMER Cat. MM-2002 (up to 25 globes) $10.95 2 AMP TRANSFORMER Cat. MM-2004 (up to 50 globes) $16 .95 , B1cErntennarv. , ELEc ELEC ELEC ELEC ELEC ELEC ~t~~ ~t~~ ~ :"'y;:'.'),,, SEE PAGE 10 -1990 CATALOGUE FOR FULL DETAILS . ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ~LECTRONICSJAYC:A~ §l§C!~ONICSJAYCA~ §L§C~ONICSJAYCAR ELEC i ~t~~ ELEC gi=g CTRC ELECTRONICSJAYCAR ELECTRC ELECTRONICSJAYCAR ELECTRC ELECTRONICSJAYCAR ELECTRC ELECTRONICSJAYCAR ELECTRC LECTRONIC~JAYCAR ELECTRONICSJA' JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS LECTRONIC~JAYCAR ELECTRONICSJA' JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ' LECTRONICSJAYCAR ELECTRONICSJA' JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS LECTRONICSJAYCAR ELECTRONICSJA' JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS LECTRONICSJAYCAR ELECTRONICSJ\' JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS . 1_ECTRC .. LECTRC LECTRC _ECTRC _ECTRC To use simply insert into power point or onto points where voltage is present. At last! A driver set incorporating those obscure shaped heads! _ECTRC Measures AC Volts 110 - 380 Have you ever needed recently to service an electric tool? Chances are you would not have _ECTRC DC Volts 150 • 500 been aele to do so because the screws holding the appliance together had strange shaped _ECTRC There are three lamps which indicate the voltage present. These are at 110VAC. 150VDC heads. _ECTRC and 22r:NAC. 300VDC and 380VAC. 500VDC. Well now you can with our 30 piece driver set I This set contains all the driver bits you are _ECTRC Unit has dual insulated probes for safety. Ideal for industrial machinery where various EVER likely to encounter. (See below). Basic to the set is an 8 112· Chrome-Vanadium driver _ECTRC voltage levels may be present. which will accept any of the 28 hardened steel bits supplied. They are held into the socket _ECTRC Cat OP-2240 of the driver by a small magnet - so you can use the driver in any.position. The screw _ECTRC together hollow handle will hold several tips so you don't have to take the whole set with _ECTRC you into the field. There is a tip here to suit almost any screw/nut you may come across. _ECTRC _ECTRC Here's what you get: _ECTRC • 5 slotted bits 0-1, 3-4. 5-6. 8-10. 12 _ECTRC • 5 hex bits 3/32'. 5/64·. 7/64·. 1/8·. 9/64. _ECTRC • 4 Philips bits No O. 1. 2 & 3 _ECTRC • 4 square recess bits No O. 1. 2 & 3 _ECTAC • 6 Torx bits T10. T20. T25. T30. T40 _ECTRC • 2 Pozidrive bits No 1 & 2 _ECTRC • 1 x 1/4. drive socket adaptor The kit shown below contains a motor with press-fit brass cog. gearbox housing. 3mm x _ECTRC • 1 x 1/4. drive hex bit holder 110mm steel driveshaft. 2 intermediate shafts. 7 gearwheels and 6 nylon bushes. _ECTRC And it's all housed in a sealable tough plastic case. The motor will run from a source of 1.5 - 4.5 volts DC and depending on load consume _ECTRC Cat. TD-2000 between 200 - 800mA A typical gearbox arrangement is shown in the exploded drawing. _ECTRC YG-2712 with 25mm motor with high torque and oilite bearings. All components (apart from _ECTRC the motor) are UK or French made. _ECTRC Cat. YG-2712 REDUCTION TABLE YG-2712 _ECTRC No 1.SV 3V 4.SV _ECTRC of gears _ECTRC _ECTRC 6 5blHforSlott•d•c••w• 5 _ECTRC 0 4 _ECTRC _ECTRC 3 ~ ,~ ~ ~ _ECTRC 2 ~ 5/fl4 ° 3132 • 7164 . _ECTRC 1 _ECTRC t I~ _ECTRC _ECTRC ~ ~ LECTRC e blU to• To,.- "- 1cr•w• LECTRC j ¥¥1 LECTRC [ r.iw\ =#ii ~ T10 LECTRC LECTRC LECTRC LECTRC LECTRC LECTRC CREATE YOUR OWN CLIMATE IN YOUR LECTAC LECTRC OFFICE OR HOME This set consists of B screwdrivers which are fully insulated right down to the tip of the blade. LECTRC Features Each screwdriver will handle 1000 volts. if required. and may save the users life. Specifications LECTRC • Cutout switch when water runs out Ideal for anyone who works with 240V AC constantly. There are 4 slotted screwdrivers. 3 • 40watts LECTRC • Generous 6.75 litre water tank Phillips and one electric tester 100 - 500V. Screwdrivers have Chrome Vanadium steel blades • 240V AC power source LECTRC • Ultra quiet operation with black tips and are all hardened. A quality screwdriver set for hobbyists. electricians. etc. • Humidity control 30 - 90% LECTRC • Adjustable intensity control • Dimensions 375(L) x 150(W) x 290{H)mm LECTRC Slotted Blade length Tip Diameter • Adjustable humidity control Cat. YH-5500 LECTRC 75mm 2.5mm • Air filter included LECTRC 100mm 4mm • Humidifies up to 4.000 cubic feet LECTRC 125mm 5mm LECTRC 150mm 6mm WAS LECTRC 75mm 2.5mm Size 0 Phillips LECTRC 100mm 4mm Size 1 SELLING LECTRC 150mm 6mm Size2 LECTRC 100mm 4mm 100-SOOV electric Slotted LECTRC tester LECTRC Cat. TD-200B LECTRC LECTRO LECTRO _ECTRO LECTRO LECTRO LECTRO LECTRO LECTRO LECTRO LECTRO LECTRO LECTRO LECTRO $9.95 $19.95 .• $18.95 CD' ;. .... !i EF~ <at>••,••••••~m••~ t ~ --: l ®···a~·~ ~ ~~) 8 Piece Electric Insulated Screwdriver Set Ultrasonic Air Humidifier FOR $149 in 1986 $19.95 NOW ONLY $109.50 JAYCAR ELECTflONICS JAYCAf1 ELECTRON ICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRi ELECTRONICSJA YCAR ELECrn ELECTRONICSJAYCAR ELECrn ELECTRONICSJAYCAR ELECTR1 ELECTRONICSJAYCAR ELECTR1 ELEC ELEC ELEC ELEC At last. a reasonably priced 16 drawer parts cabinet. Designed to hold all your 'bits & pieces':• ELEC resistors, capacitors, semiconductors, drill bits. nuts & bolts. nails. etc. ELEC The unit is grey with clear drawers. There are key holes in the rear for easy wall mounting. ELEC Drawers have a stopper so when pulled This fantastic 3 1/2 digit meter is actually easier to use than a conventi onal hand-held unit. ELEC The readout is in the body of the 'probe' itself so you don"t have to avert YQUr eyes to get a out they won't come all the way out ELEC circuit reading. The unit has most of the features of conventional meters as well! spilling your components. Each drawer ELEC Logic Probe Bonus. This TTL/CMOS compatible feature will test logic 'HI' or logic 'LO'. The will accept up to 3 plastic dividers which E LEC circuit is protected to 250V. All electrical symbols are shown in the large 142mm x 18mm) E LEC can divide the drawer into 2, 3 or 4 window. ELEC separate compartments. 16 drawer Cat. OM-1420 ELEC dividers are supplied. ELEC Drawer size 1l~L) x SOIW) x 34ID)rnrn ELEC Total size 185{H) x 2421W) x 124ID)rnrn ELEC ELEC Cat. HB-6320 ELEC ELEC E LEC R ELEC R ELEC R ELEC R ELEC R ELEC R ELEC ELEC Light duty precision ELEC knife with safety E LEC cap. Ideal for fine The latest in battery testers. Consists of a very ELEC angle cuts, etching, Up until now these have cost a fortune! fl exible piece of plastic with a conductive strip on ELEC hollowing, scoring, FEATURES the rear. Simply place over the battery terminals and EL EC scraping, scribing, the indicator will show if the battery is good, • CMOS SAFE conductive ELEC stripping and reasonable or bad. Re-usable. Every desk drawer. plastic ELEC tri rnrning. workshop, toolbox needs at least one. And at Lhe • Exclusive bent pin alignment R ELEC Four jaw chucking price who cares. guide in handle. 8 to 40 pins ELEC method of blade • One hand opera lion 5 different designs available. E LEC retention. Cat. SB-2350 ELEC Cat. HG-9955 ELEC ELEC ELEC E LEC E LEC ELEC ELEC Considering the price. we were most impressed at how well this unit works. ELEC It has an ABS plastic body with strong suction. Unit is very easily cleaned. corning apart in the ELEC centre. in moments. Spare tips are available and are very reasonably priced. CatTH-1808 ELEC Tota l length inc. tip 195mm Repl acement tip !Teflon) ELEC Cat. TH· 1860 Cat. TH-1861 ELEC Replacemen t Blades ELEC Packet 5 ELEC Cat. HG-9956 ELEC ELEC Was $3.95 Cat. TH-1810 ELEC ELEC ELEC ELEC ELEC ELEC Replacement Blades ELEC Cat. TH-1814 Packet 5 ELEC Another new addition to our range of products for 1990. Cat. HG-9957 ELEC This desolder tool is made of lightweight metal and has the strongest suction we·ve ever seen ELEC in this type of tool. Features include• constant vacuum force maintained throughout action• Was $3.95 ELEC one hand operation • designed for long life • automatically cleans itself with each action • ELEC very little recoil • small size ELEC Measures only 137mm with the plunger pushed in. A quality product. Cat. TH-1816 ELEC Cat. TH· 1862 Replacement tip !Tefl on) E LEC Cat.TH-1863 ELEC ELEC ELEC Deceptively simple looking device. One ELEC piece metal construction. 8 • 40 pins. ELEC ELEC Cat. TH-1818 E LEC ELEC ELEC ELEC ELEC ELEC MAIL ORDER VIA ELEC HEAD OFFICE P.O. Box 185 Concord2137 ELEC 888 ELEC •· • 115 Parramatta Road Concord 2137 J~L~ :~~: :~: ELEC Telephone (02) 747 2022 $50 .$99 _99 $ 6.50 1 ELEC ; ; ~ , F_A_c_s_1_M_1_L_E_1_0_2_1_1_44_0_1_6_1-=r=oL=L=FR=E=E=1=oo=s=,0=22=s=ss=~ov,::E::.:_R:,:$l,::::oo:.__ ___:$8'..o:::.o ELEC :.: ELEC GORE HILL 188 Pacific Hwy ICnr Bellevue Ave) 102) 439 4799• ELEC • Mon-Fri 9 • 5.30 Sat 9 • 4pm ELEC 117 York St.102) 267 1614 • ELEC 144 Logan Rd 107) 393 0777 • BURANDA OLD Mon-Fri 8.30 • 5.30Thurs 8.30 pm• Sat 9 • 12 ELEC ' Mon-Fri 9 • 5.30 Thurs 8.30 • Sat 9 - 12 355 Church St ICnr Victoria Rd) 102) 683 3377 ELEC Shop 2. 45 A'Beckett St City 103) 663 2030 MELBOURNE-CITY Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 · 4pm , ELEC Mon-Fri 9 • 5.30 Fri 8.30- Sat 9 • 12 ELEC 1 15 ParrarnaLLa Rd 102) 745 3077 • CONCORD 887-889 Springvale Road Mulgrave 103) 547 1022 SPRINGVALE VIC ELEC Mon-Fri 8.30 - 5.30 - Sat 8.30 • 12 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 - 2 ELEC 121 Forest Rd 102) 570 7000 HURSTVILLE 190 Wright Street ICnr Selby Street) IDB) 231 7355 ELEC AD ELAIDE S.A. 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This month we continue with a discussion on aerodynamics. Coping with the interaction between axes has been the prime mover in the quest for computerised model encoders, but the story does not end there. Other reasons include overcoming non linearity in electronic components, non linearity in airframes, convenience, the good old fashioned (or is it new fashioned) love of "gingerbread", and the dreaded sales gimmick. The importance of this last factor must not be underestimated in the development of sophisticated equipment. At the very heart of aerodynamics lie several very simple mathematical statements and Newton's three laws of motion: The fuselage of the Grumman Panther provides about 30% of the total lift which means that the centre of gravity must be located forward of the leading edge of the wing to produce a controllable model. 88 SILCON CHIP (1). Bernoulli's Theorem. This states quite simply that the sum of the static and dynamic pressures in air must remain a constant. This is the factor that makes flight possible. (2). The "Velocity Squared" factor. This simply means that if you travel twice as fast you will generate four times as much force; four times as fast, 16 times the force. All of the major forces in aerodynamics have a velocity squared component: lift, drag, kinetic energy, centrifugal and centripetal forces. This is the factor that makes high speed flight difficult and expensive. (3). Newton's First Law. This states that if a body is in equilibrium it tends to remain so. All of the forces acting on that body are in balance and there is no tendency for it to change state or accelerate or decelerate in any direction. (4). Newton's Second Law. This states that the force required to br- ing about a change of state in the motion of any body is directly related to the mass of that body. Mass is not the same as weight. Weight is the force of gravity applied to a mass here on Earth. On Mars the weight would be less but the mass remains the same. (5). Newton's Third Law. The third law of motion establishes that action and reaction are equal and opposite. A model in level flight, which is not climbing, diving, accelerating, decelerating or turning, may be said to be in equilibrium. Thus, lift equals weight and thrust equals drag (see Fig.1). Any change in one of these factors will cause a change in state. Thus, a change in thrust will cause acceleration until the increase in drag brings the system back into equilibrium. Control interaction It is here that we first begin to see the highly interactive nature of the aircraft and the usefulness of the computer encoder. An increase in thrust will increase speed which will increase lift which will either make the aircraft climb or call for Fig.1: these diagrams show the forces acting on an aircraft in (a) level flight; (b) gliding; (c) climbing; (d) diving; (e) vertical climb; and (f) • vertical dive. When the aircraft is flying straight and level, the lift equals the weight and the thrust equals the drag. LIFT TOTAL LIFT= TOTAL WEIGHT TOTAL THRUST = TOTAL DRAG FLIGHT PATH DRAG THRUST WEIGHT (a) POWER MODEL IN LEVEL FLIGHT LIFT = WEIGHT x COSINEC\' 0 DRAG = WEIGHT x SINEO'" TOTAL AIR REACTION WEIGHT WEIGHT COMPONENT OPPOSING LIFT (b) GLIDING THRUST LIFT = WEIGHT X COSINEU0 ORAG + (WEIGHT x SINEU = THRUST WEIGHT 0 ) WEIGHT (c) CLIMBING DRAG ORAG LIFT the pilot to alter the elevator trim to maintain level flight. A computer coupled to the throttle could automatically apply the correct amount of down elevator trim required to maintain level flight, thereby making the flyer 's life just that much easier. There is a ea tch here, however. What if the pilot wants to climb and the increase of thrust was applied to achieve just that? No problem, for the control stick still has ample overriding movement for the pilot to apply the correct amount of up elevator trim required for the climb. In this example, we merely encounter the big problem with all computerised devices. They are just dumb machines which must be given every instruction very carefully indeed. I am never very happy about electronic gimmickry in any field. The real art in any endeavour is mastering the manual dexterity required to wring the very best out of · your machine. The prime example of this situation is the electronic organ. Where does playing the electronic organ stop and playing a CD begin? Certainly they are great fun but do they really teach you anything of real substance in the end? ANGLE OF DIVEC\'' DRAG = THRUST + W.SINEO'' LIFT = w.cosa· WEIGHT WEIGHT (d) DIVING DRAG THRUST DRAG = THRUST + WEIGHT LIFT= 0 THRUST = WEIGHT + ORAG LIFT= 0 ANGLE OF DIVEC\' 0 = 90° 0 ANGLE OF CLIMB // = 90' WEIGHT WEIGHT DRAG WEIGHT + DRAG (e) VERTICAL CLIMB THRUST WEIGHT + THRUST (n VERTICAL DIVE Model helicopters The best example I ever experienced was in regard to flying aerobatics. When I was in Pennsylvania in 1971 I saw the first public demonstration of model helicopters, by Dieter Schluter and a friend, who not content with flying one helicopter, flew TWO in formation. I was stunned and knew I just had to have one of these fascinating toys. I subsequently purchased one of Oki's (the Japanese licence builder of the Schluter helicopter) Kalt Huey Cobras and in due course was taught to fly helicopters by Oki himself. This was in 1972 and I APRIL 1990 89 F·Low SEPARATION LOW PRESSURE -----------==== OEc:c~~TES c'") HIGH P R E S S ~ ~ IJow. '-.J ;yW.q FLOW ACCELERATES Sf! THE ORIGIN OF LIFT STALLING Fig.2: a wing generates lift because air flowing over the top surface is made to take a longer route. It thus flows faster than the air taking the shorter route below and this creates a pressure differential. Fig.4: when a wing is in a stalled condition, the air no longer follows a streamlined path and the flow separates from the wing. This creates a great deal of drag and also drastically reduces the lift. CD 0.32 o· I I - I ORDINARY ANGLES OF FLIGHT 15 ' I I I I 0.24 ,.._ i ~, ,.._ ~l O.F., t:: ::l l1 0.2 Ii z w "' 51 i ~I ~ 0.16 "' ~I 0.12 0.4 .08 / 0.2 .04 0 .___.,__~_ _...___ -4 · o· 4• __.__ __,__--'--'_ __. 5• 12 · 16 ° 20 · __,.. ........ SILICON CHIP ~I "" :;;1 / I I 0 - 4· o· 4• 8' 12 · 15 • 20 ° ANGLE OF ATTACK Fig.3: this graph plots the lift of a wing against the angle of attack. Note that lift falls away rapidly for angles of attack greater than 15°, at which point the wing is in a stalled condition. 90 / 1~::1 I ANGLE OF ATTACK believe that I was one of the first to achieve solo status on helicopters in this country. Oki was a wild man and we flew that helicopter inside my factory and over the roof. As a grand finale, Oki flew it at the Easter show in 1973 and during that show he also flew a Jet Rang.er around the Clock Tower at the Showground. I was his caller that day and he kept asking me was it time to turn yet. It was the longest pylon course I have ever called on, as the chopper was half a mile away before he finally turned. I had these awful visions of it running smack into the tower as it is very difficult to judge perspective at those distances. However, he made it safely and the crowd roared. I made myself scarce. Now the real point is that for about two years I was totally engrossed in flying helicopters and this was in the days before they had I I 0.8 15 u I --i I 0.28 Fig.5: drag coefficient vs. angle of attack. Note how the drag coefficient increases rapidly for angles of attack greater than about 8°. The stalling angle is 15°, at which point the aircraft falls like a stone. gyros on the tail rotor. This meant I had to learn to coordinate my left thumb, as the tail rotor on a model helicopter needs constant attention, as indeed do all the controls. This is why model helicopters need such large flight batteries. When I returned to pattern flying I was suddenly a good flyer. Slow rolls, 4-point and 8-point rolls, indeed all manoeuvres that I had had great difficulty with previously, were suddenly a breeze and a friend asked on seeing me fly for the first time in many years, "where did you learn to fly like that?" It took me awhile to realise that the dexterity developed while flying helicopters was vital to my aerobatic flying. The key was the use of the left thumb which is pivotal to good rolling manoeuvres and which prior to 1972 was useless to me. I tend to feel that modern helicopter flyers miss out on this training, using gyros as they do and special helicopter encoders fitted with all kinds of mixing programs and gadgets. The same trend is developing in model aircraft with programmable manoeuvres being built into radio transmitters. Is this real flying? Here there is room for endless debate. The aerofoil However, to return to the beginning. From Bernoulli's Theorem comes the basis of the curved lifting surface or aerofoil. Fig.2 illustrates this quite clearly. In order for the split airstreams flowing over the aerofoil shown to arrive simultaneously at the trailing edge, as they must, the upper stream speeds up because it is following a longer path and for the opposite reason, the lower stream slows down. This results in an increase in dynamic pressure and a reduction of the static pressure on the upper wing surface and an increase in static pressure and a reduction of the dynamic pressure on the lower surface. The result is a nett upward force which follows the formula below: L = ½p.V 2 .S.C1 For level flight then: L = total weight of the aircraft; p = air density; V = velocity; S = lifting surface area. The term S can include fuselage and tailplane lift and C1 is the coeffici~t of lift of either the wing, tailplane or complete airframe, depending upon which unit is under examination. It is an expression of the ability of the surface to create lift. Thus, a body with a C1 of 1.3 will generate more lift than a body with a C1 of 0.8. Note also that C1 is dependent upon the angle of attack for its final value (see Fig.3). The concept of the fuselage providing lift may come as a surprise to some but I have seen figures as high as 30% of the lift coming from the fuselage. The Grumman Panther, a 1950's fighter, gave a figure similar to this and anyone who builds a model of this fighter is in for an awful surprise if he locates the centre of gravity more rearward than 3cm in front of the leading edge of the wing. (Normally it would be 3-Scm behind the leading edge). I did and found out to my horror that fuselage lift played a major role in determining the location of the centre of gravity on that particular aircraft. As stated previously, an aircraft is a highly interactive device. Fig.3 shows the relationship of the angle of attack to the lift coefficient, C1, Note here that C1 is the coefficient of lift of the practical surface while C1 is that of the wing section as determined in wind tunnel testing. The two are not the same for reasons too complex to explain in this series of articles. Note that C1 increases to about 12° then begins to level off until at about 15° the lift falls away rapidly. At this point the wing is said to be in a stalled condition. Fig.4 shows the airflow separation over a stalled wing. In effect, the air can no longer follow a streamlined path and breaks down into a turbulent flow. At this point virtually all lift is lost and the aircraft falls like a stone. Fig.5 shows the drag coefficient of the wing section at all angles of attack. Note the rapid increase in drag from about S 0 onwards. Fig.6 shows the relationship between lift and drag and is a most important graph. Note that the curve peaks at 4° and so this is the most efficient angle for this particular section to operate at. The LID ratio is a most important relationship as we shall soon see. WANT A REALLY LOUD SIREN FOR YOUR ALARM? Then have a look at this READY MADE and TESTED UNIT. All you need is a 6· 14V supply and add a horn speaker to obtain an output of 110-125dB. NOW THAT'S LOUD! As used in a well-known , expensive commercial siren that costs over $70.00. High power bridge design. Comes with circuit and instructions. ONLY $11.80 ea Metal horn speaker to suit $13.50 Grab some while you can at this giveaway price. LASER TUBES Wanted to make a LASER but could never afford it? THEN DON'T MISS THIS FANTASTIC OFFER Use them for Discos, Experimenting , Surveying , Security, Special Effects in Entertainment, etc. Model 08 Tube (0.5-0.SmW) is available for ONLY $129.90 Increasing lift From the above formulas, it is obvious that an increase in any of the factors involved will give an increase in total lift but, as we have already seen, by far the most effective is an increase in speed (because it follows a square law). The others must not be underestimated however, for on a hot day the subsequent reduction in air density will affect take off performance quite noticeably, through both loss of engine performance and lift. Now there is a point here which is vital to the safety of any aircraft, full size or model. Notice that total lift depends upon C1 for one of its components. As C1 is dependent upon the angle of attack for its final value, in practice what can happen is as follows. On a hot day, air density falls and engine power falls, so we have a double reduction in the total lift available for take off. The most important is loss of engine power which results in loss of forward speed and the old vz reduction in lift. Thus the pilot (full size or model) has only one immediate fix at his disposal. This is to increase lift by increasing the angle of attack, by pulling back harder on the elevator control than usual. Here the pilot of an underpowered aircraft can begin a very destructive chain of events. An increase in angle of attack results in an increase in drag as well as lift (Fig.5). At angles above S 0 on our sample section, this increase is very rapid indeed. Also Available: 1·2mW Laser Heads (Model 20) $199.00 3-4mW Laser Heads (Model 40) $249.00 Some lubes are HALF their normal price! COMPLETE LASER KIT Based on Model 05 LASER Tube , this unit includes 240V power supply, all the hardware, plans and instructions, so you can make a complete LASER. 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By this time the pilot is watching with horror the rapid approach of the boundary fence and is bending the elevator stick in an effort to call for more lift. All he will get is more drag. At this point he is in the "drag bucket" and in very serious trouble. If he does not stall the aircraft, he will fly into the fence or trees. The prudent pilot knows when to abort a take off. 14 Loss of engine power A really dangerous situation arises in a twin engine aircraft which loses one engine just after take off. All of the above factors are valid but to these must be added a further drag increase in the form of asymmetric drag. This arises because the thrust line is suddenly moved off centre towards the active engine. The result is an immediate turn in the direction of the dead engine. Countering this turn calls for large applications of rudder which puts the entire airframe in a yaw and increases the drag on every component of the airframe. One safety rule to keep in mind here is never turn into the dead engine, always turn away from the dead engine. It is very easy for the forces generated in a turn into the dead engine to exceed the control forces available for recovery. The result will be a spiral dive and a certain crash. Flying twin engined models is a tricky business and calls for some study into the problems involved. There is a further compounding factor in this scenario. The propeller is only another aerofoil subject to the same LID formula. In model aircraft, the pitch of the prop (angle of attack) is fixed. Thus it is designed to operate at the best forward speed (when flying straight and level). As the forward speed of the aircraft increases in a dive there is an effective reduction in 92 SILICON CHIP the pitch and a subsequent loss of thrust. If the aircraft slows down, as is the case at take off, the pitch angle is usually too high and therefore the prop operates inefficiently and loads the motor heavily. For this reason, full size aircraft use variable pitch propellers. The pitch angle can be matched to the forward speed. Any aircraft with a fixed pitch prop that is caught in the above "drag bucket" scenario is in double trouble. The wing drag and prop drag will load the motor and the prop will not develop anything like full thrust. Sometimes the only way out of this situation is to trade every centimetre of height available for forward speed by diving, thus unloading the prop and motor and reducing the angle of attack of the airframe. This calls for a cool head and steady hand, but one centimetre of altitude is all that is required to keep the aircraft flying. Once the speed begins to build, thrust and lift will increase and drag will reduce. This is easy for a model pilot safely on the ground but unnerving for a full size pilot who knows full well that a mistake will see him thump into the ground with a force related to the square of the increased velocity achieved in the dive. Also in the foregoing, we arrived at a mathematical analysis of a very serious argument in aerodynamics. There is and always has been a tendency for people to underpower aircraft, particularly in the model field. There are many reasons for this, including cost and lack of suitable engines, but one reason often put forward is that overpowered aircraft are dangerous. This may be so but underpowered aircraft are lethal. There are many situations in which any degradation of any of the above factors can be made good by a small increase in velocity. This increase is so easily obtained if sufficient reserve power is available. You do not have to use full power but it is nice to have it if needed. The big problem with this approach is that it is very easy to o· 4• 15' I I I I I I 12 ( 10 II " ~ I I \ I I '\ \i ;;iz ... C I .I... I ;;i~ ~, i\ "'~ ....., c:, ;;;!f :E I I I I D -4' I 4' a· 12' 16' ANGLE OF ATTACK Fig.5: the graph shows the lift to drag ratio for increasing angles of attack. Note that the curve peaks at 4° and so this the most efficient angle to operate at. become caught in an upward power/weight spiral, particularly in view of the fact that the v2 component gives rise to increased forces which must be taken into account in the aircraft structure. Compromise, always compromise. Unfortunately, the formula for drag also follows a similar square law and the maths involved are as follows: D = ½p.V 2 .S.Co As before, p = air density, V = velocity, S = the same surface area as used in the lift calculation, and Co is the drag coefficient of the body under examination. Basically, Co is an expression of the "aerodynamic cleanness" of the body in question. The interactive relationship between lift, drag and thrust have some interesting ramifications. If we wish to travel twice as fast we must use four times as much power. We will, however, have an increase in engine weight. This in turn will require an increase in structural strength (and thus weight) to hold this engine in place and to cope with the increased aerodynamic and "G" forces generated by the higher speed. These interactions will be examined in detail next month. ~ 20' NOW OPEN SHERIDAN ELECTRONICS BLACKTOWN YES WE HA VE SERVED SYDNEY FOR 20 YEARS AND ARE NOW HERE TO SERVE THE WEST DON 'T PAY MORE. COMPARE OUR PRICE AND SAVE. 10 % OFF ALL STOCK - ALL YEAR STATIC RAMS 2114 $1.00ea 4116$1 .70 6116·1 $4.50 6264 $6.00ea 62256-80 $19.95 DRAMS 41 64· 1 5 $2.00ea 41256-12 $6.00ea 41 464-1 $7 .00ea RECHARGEABLE SOLDERING IRON CABLES ALL REDUCED! Centronics - Plug to Plug Centronics - Plug to Socket Centronics - RS232 Socket IBM Printer Cable ALL ONLY $8.50 AUDIO VIDEO TRANSMITTER Dept. of Communications Approved No need to run long Cables REDUCED· FRO M $89.95 TO $75.00 Arista Brand Heats up in 25 sec . 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Trading Hours: Mon-Frl . . . . . . . 9am-5.30pm Sat . ...... . .. . 9.30am-1pm ALSO AT: 286 Cleveland Street, Surry Hills NSW 2010 NOTE: We accept Bankcard, Mastercard and Visa. However, we cannot give quantity discounts on credit card purchases or accoun t orders . Minimum for account orders is $15 exclusive of postage and pa ckin g. All prices Include Salos Tax. All prices quoted are for th is month only or until stocks last AMATEUR RADIO By GARRY CRATT, VK2YBX Active CW filter for weak signal reception This simple circuit will clean-up those difficult to read CW signals. It provides active bandpass filtering and tone decoding of the incoming signal, and then regenerates the signal using an oscillator. Considerable concentration is required by both experienced and inexperienced CW operators when called upon to copy a wea~ signal affected by strong background noise. This in turn can lead to fatigue and may result in errors. By using this active filter, the ease of reception of weak CW signals is substantially improved. Active filters have long been used to improve the readability of weak CW signals but they still depend to a large degree upon receiver tuning, as the "beat" signal must fall within the narrow filter passband. This type of filter is most useful when the receiver being used has neither AF (audio frequency) or IF (intermediate frequency) filtering designed for dedicated CW reception. The design presented here is slightly more complicated in that it comprises two stages of active bandpass filtering, each having a slightly different centre frequency. This combination provides an adequate passband (400Hz or so) and rapid rolloff, in this case around 20dB per octave. We could have used a single high Q bandpass filter but this would have given a very narrow bandwidth, making it difficult to use. Fig .1 shows the combine d response of the bandpass filters while Fig.2 is a block diagram of the Active CW Filter. As shown, one bandpass filter is centred on 1.15kHz and the other on 1.35kHz. The output from the filter stages is then fed to a PLL tone detector. When a valid tone is detected, the PLL "keys" (ie, switches on) an audio oscillator to regenerate the signal. Circuit details All the parts for the Active CW Filter are mounted on a small PC board. We used PC stakes to terminate the external wiring connections. 94 SILICON CHIP Now take a look at Fig.3 which shows all the circuit details. The bandpass filters are two stages of an LM1458 op amp (ICla & IClb) and these provide an overall gain of around 40dB. Bias for the non-inverting inputs of the op amps is provided by a voltage divider consisting of two 22k0 resistors connected across the supply, while the 47kn and 470 resistors form an input attenuator which ensures that the filter is not overdriven. The output of the filter (pin 7 of IC1 b) is fed to pin 3 of ICZ via a 47kQ resistor and 1µ,F capacitor. IC2 is an LM567 phase locked loop tone decoder, commonly used in +10 \ -10 i -2U I\ J V / -40 / -50 -60 100 \ I -30 Fig.1: this graph shows the combined response of the two bandpass filters. The response is centred on 1.2kHz and the passband is about 400Hz. / 400 200 600 \ 2k 1k I\ 4k I\ 6k 10k HERTZ INPUT 1.15kHz 1.35kHz BPF BPF PLL TONE DETECTOR LPF AUDIO OSCILLATOR OUTPUT Fig.2: block diagram of the Active CW Filter. The output from the bandpass filter stages is decoded by a PLL tone detector which then switches an audio oscillator to regenerate the signal. telephone circuits for decoding signalling tones. When a valid tone (ie, a 1.ZkHz signal) is received, the PLL locks on and pin 8 switches low. VRl, in conjunction with the 2.7k0 resistor and O.lµF capacitor, sets the centre frequency of the tone decoder. In practice, VRl is set to give a centre frequency of 1.2kHz. The O. lµF capacitor on pin 2 sets the bandwidth (ie, the locking range) of the tone d.:::coder to about 130Hz. This narrow locking range prevents two adjacent signals from activating the unit. The output of the LM567 (pin 8) drives PNP transistor Ql, a BC557 which operates as a DC switch. This in turn controls phase shift oscillator stage IC3. When pin 8 of IC2 switches low, Ql turns on and supplies power to pin 7 of IC3 and also bias to pin 3 via two 33k0 resistors. IC3 is an LF351 BIFET amplifier and this generates a reasonably pure audio tone which the operator can listen to directly with a set of high impedance headphones. VRZ adjusts the oscillator for minimum distortion. Construction The circuit is built up on a small PC board coded SC 06204901 and measuring 106 x 66mm. Fig.4 shows the parts layout. You can install the ---------------------<11-----+9V PARTS LIST 47k 5 1 1 2 1 1 ON/OFF + 9 V - - - - - - - - - - + - - -......-------o>---o+9V 022I. 10 16VW .,. + - 33k 01 BC557 C IC2 LM567 VR1 10k O.ll .,. 2.2 + 16VW+ B 01+ 1~. , 1 "~' "'!"' EOC VIEWED FROM BELOW VR2 470k + F-o OUTPUT ~ 33k .,. -t ACTIVE CW FILTER Fig.3: the circuit uses IC1a & IC1b as the bandpass filters and these feed tone decoder stage IC2. When a valid tone is detected, pin 8 of IC2 goes low and turns on Q1 and phase oscillator stage IC3. PC board, code SC 06204901, 106 x 66mm PC stakes battery snap connector SPOT toggle switch RCA output sockets 1OkQ trim pot (VR 1 ) 4 70kQ trimpot (VR2) Semiconductors 1 LM1458 op amp (IC1) 1 LM567 tone decoder (IC2) 1 LF351 op amp (IC3) 1 BC557 PNP transistor (01) Capacitors 2 1 OµF 16VW electrolytic 1 2.2µF 16VW electrolytic 2 1µF 1 6VW electrolytic 1 0.47µF metallised polyester 2 0 . 1- µF metallised polyester 1 .022µF metallised polyester 3 .01 µF metallised polyester 4 .0033µF metallised polyester Resistors (0 .25W, 1 470k0 3 1 390k0 1 2 47k0 1 3 33k0 1 2 22k0 1 5%) 5.6k0 4. 7k0 3.3kQ 2. 7kQ 470 APRIL 1990 95 D.DAUNER ELECTRONIC COMPONENTS WE STOCK A WIDE RANGE OF ELECTRONIC PARTS • i-_,_______. 0 . 47k --.✓ GND INPUT Fig.4: here's how to install the parts on the PCB. The finished board can be housed in a plastic jiffy box and powered from a 9V DC plugpack or from batteries. -----.----7 rXo z.., - a,a-- 0 ! I oooa.; ~-0? Jo L Fig.5: here is a full-size artwork for the PC board. parts in any order you wish bu~ be sure to install the ICs, transistor and electrolytic capacitors with correct polarity. you will need a digital multimeter (to monitor the voltage on pin 8 of IC2) and either an audio oscillator or a frequency meter. The first job is to set the centre frequency of IC2. Adjustments If you have an audio oscillator, apply a 1.2kHz signal to the input and adjust VRl until pin 8 switches low. Note the setting on VR 1, then continue to rotate the trimpot until pin 8 switches high. Set VRl to the midpoint of these two settings. Alternatively, if you have a frequency meter, you can set the centre frequency of IC2 by monitoring pin 5. Make the measurement with the probe in the xlO position and adjust VRl to give a reading of 1.2kHz. Check the completed PC board carefully for possible errors before applying power. To adjust the unit, CAPACITOR CODES D D D D D 96 IEC No Value 1 2 1 3 4 470n 0.47µ,F 100n 0 .1µ,F .022µ,F 22n .01 µ,F 10n .0033µ,F 3n3 SILICON CHIP EIA 474 104 223 103 332 for Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST Quartz in filter 10.9MHz 6kHz BW. $12.50 US Filter capacitor 4/.tF 3kV. . $15.00 Electromagnetic Airpump for Aquarium ........ . . . ... . .. $9.00 Timer Motor 240VAC 6RPH. . $6.00 Come and see. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Caltex Service Station In Blrdwood Road) Phone 724 6982 TRADING HOURS: Monday to Friday 9.00 a.m. to 4.00 p.m. Saturday from 9.00 a.m. to 12.00 noon. Now, whenever a 1.2kHz tone is applied to the input, IC3 should generate a new tone at the output. This can be monitored using a pair of headphones. Adjust VR2 so that the output has minimum distortion content. Using the CW filter The entire project could be housed in a plastic jiffy box and run from either a DC plugpack or batteries (9V). There are no controls to operate other than the ON/OFF switch. To use low impedance headphones, it will be necessary to add a simple attenuator to the output of the audio oscillator. This can take the form of a lkO potentiometer wired as a voltage divider. The filter can be driven from the headphone or "record" output of most receivers. In fact by using the record output, which allows the receiver loudspeaker to operate in the normal fashion, it is possible to make an instant comparison between filtered and unfiltered audio. You'll be amazed at the results! ~ I PRODUCT SHOWCASE I struments Pty Ltd, PO Box 30, Concord, NSW 2137. Phone (02) 736 2888 . Automatic printer switch Disc drive, printer & board tester If you have a need to service any microprocessor based equipment, you will be well aware that there is a dearth of suitable test equipment. But before you cut your throat on that next difficult repair on a PC peripheral, consider the multiple capability of the Electrotest MT-1000. It can be used to test and troubleshoot floppy and hard disc drives, SCSI devices, all sorts of printers [including lasers), 8-bit microprocessor boards, plotters, modems, communications ports and cables. The system is module based [two are shown in the photo) so that you don't have to buy a really large system - just the modules you need for your application. There is a substantial manual with each module so that comprehensive testing can be performed. Our photo shows the 8-bit microprocessor tester but a 16-bit tester is also available. For further information and a demonstration of the Electrotest MT1000, contact Elmeasco In- Electric hot-air gun for heatshrink tubing Most enthusiasts use a hair dryer for fitting heatshrink sleeving but with some sleeving a hair dryer is not hot enough. This Arlec hot air gun has a 1600W output with two temperature ranges of 400°C and 600°C. It has a pistol-like grip with switchable settings and comes with operating instructions, ready for use. It should produce more than enough heat for even the thickest tubing. And it is quiet, so it won't disturb other people. The price is $59.50 from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385. Sick off swapping leads from one computer to another to use the printer? Then use this AutoSwitch from Rod Irving Electronics. It allows two computers to use the one printer and has automatic switching no need to mess around with software controls. It has LED indication for each computer and is easy to install and use. The unit is available with either Centronics parallel or RS-232C serial interfacing and comes with a user's manual. At $79.95, the AutoSwitch will save a lot of time fiddling around with printer cables. It's available from Rod Irving Electronics, 74 Parrama tta Rd, Stanmore, NSW 2048. Phone (02) 519 3134 or Melbourne (03) 663 6151. APRIL 1990 97 alarm option, parallel and serial interfaces, data logging functions and chart annotation capability. For further information, contact Elmeasco Instruments Pty Ltd, PO Box 30, Concord, NSW 2137. Phone (02) 736 2888. Pen recorders from Elmeasco Switchmode supplies for Eurocard rack systems Disc filing system holds 120 discs Elmeasco Instruments Pty Ltd has recently been appointed agents for the Rikadenki range of programmable pen recorders which have a very good reputation. Pictured is the Rikadenki HR 1300', a vertical format recorder which is ideal for continuous recording for prolonged periods. As with other recorders in the Rikadenki range, it is fully programmable for up to 24 channels and has a liquid crystal menu display for fast setups. Recording and storage bandwidth is from DC to 20kHz. All units in the range feature an **GREAT VALUE AND TECHNOLOGY ** PRODUCT OF THE MONTH .. . PC FAX with TSR SW ONLY $399.00 Featured EA Nov, Dec '89 CONTINUED SAVINGS ON ... XT-1000 SYSTEM 12MHz V20 . . . . . . . $699.00 AT-4000 SYSTEM 12MHz 512K 101 KBD 200W PS etc . . .. $999.00 VGA MONITOR 0.31 for 800x600 ... $599.00 EC-F/HDD FDD/HDD CONTROLLER 1 : 1 . $169.69 COMPUTER PRODUCTS ... XT1 000 MOTHERBOARD V20, 12MHz, Skts 1M RAM . .$ 127 AT-4000 MOTHERBOARD 12MHz 80286 AT u/g for XT . . . . $349 AT-8000 MB 25MHz 80386 . $1399 ECI VGA-16 EGA, CGA, HGA modes Card 800x600x16 Res. $279 AWARD POST TEST CARD . . $802 2S+P+G $85; FDC $97.25; 101 KBD $88.43; CASE & 200W PS $189; XT/AT CLK $49.95. protection which prevents maximum current being taken from all outputs when the total supplied power rating exceeds 110% of maximum rating. The mean time between failures (MTBF) is more than 40,000 hours with a typical load at 25°C. For more information, contact Amtex Electronics Pty Ltd, 13 Avon Road, North Ryde, NSW 2113. Phone (02) 805 0844. Amtex Electronics has a range of switchmode power supplies for installation in Eurocard rack systems. The series includes single, double and triple DC output supplies with power ratings ranging from 45 to 100W. Each supply is based on a l00kHz Mosfet forward converter design and they can be run from either 90 to 130VAC or 180 to 260V AC. All the supplies have overload Instead of having your floppy discs strewn all over your desk, why not tidy up your act with this storage filing system from Rod Irving Electronics. The Diskette File is made from sturdy plastic and has key-operated locks for security. It also comes with labels and 10 dividers for separating your discs into selected categories. At only $19.95 , there's little excuse not to have one. They're available from Rod Irving Electronics, 74 Parramatta Rd, Stanmore, NSW 2048. Phone (02) 519 3134 or Melbourne (03) 663 6151. MODEMS ... ECI-FAX CARD for XT/ AT Aust Made. . . $399 EC-2400S V22 bisN22/V21 External Modem . $399 EC-2400P V22 bis/V22/V21 Internal Modem for PC .... . .. $299 DRAM ... 512K Kit 18x256Kx1-10. .$72 ·-2M Kit 18x1Mx1-10. $299 QUALITY DISKETTES . . . (Pkt of 10, 100% error free, Utime Gtee) 5¼" DSDD . $5.99 51/," DSHD. $14.40 31/," DSDD. $14.36 3½" DSHD . . . . $33.00 P&P $8.50 - PRICES INCLUDE SALES TAX PRICES SUBJECT TO CHANGE WITHOUT NOTICE 26 Boron St, Sumner Park, Brisbane, Old 407 4. Ph: (07) 376 2955 Fax: (07) 376 3286 SYDNEY Ph: (02) 555 7659 Fax: (02) 818 2949 98 SILICON CHIP Crimping tool for coaxial connectors This heavy duty crimping tool is designed to crimp four different sizes of coaxial crimp type connectors. It has moulded rubber handles and has a pressure adjustment for precise crimping. It comes with instructions on the packaging and is currently priced at $69.95. The tool is available from David Reid Electronics, 127 York St, Sydney, NSW 2000. Phone (02) 267 1385. Solid state dual potentiometer Low cost VGA graphics card Electronic Solutions has a new VGA graphics card which they claim to be around 40% of the normal retail price. Designated ES VGA plus, it has a 16-bit bus for high speed processing and can run up to 1024 x 768 pixel resolution. The unit is IBM VGA compatible and, by fitting the full 512K RAM, it can produce 16 colours at maximum resolution. Many of the most popular software packages such as AutoCAD, Lotus, PageMaker and WordPerfect can also be made to run at higher resolution using this card. In normal VGA mode, it can provide 256 colours out of a palette of 256,000. It has three text display options up to 132 x 60 characters and can be used with analog, digital and multisync monitors. It is priced at $499 plus sales tax. For further information, contact Electronic Solutions, 5 Waltham Street, Artarmon, NSW 2064. Phone (02) 906 6666. Miniature changeover mercury switch Guaranteed to perform up to 1 billion operations at their rated load, these new changeover mercury switches are sealed in a glass envelope only 15mm long and 2.5mm in diameter. Rated to switch 1A and up to 350V DC, the units will carry a current of up to 3A. Open-contact insulation is guaranteed at 1000V AC. The maximum switching frequency is lOOHz and the magnetic sensitivity is from 35 to 60 ampereturns. For more details, contact IRH Components, 32 Parramatta Rd, Lidcombe, NSW 2141. Phone (02) 648 5455. New data storage technique ching on the circuit again they moved the needle to the location for the next pin-prick. They then examined the result using the STM. To their surprise, the two researchers were able to use the same needle. In this way, they were able to create pits with a diameter of about 10 nanometres and a depth of 0.6 nanometres without any appreciable distance between them. By overlapping the indentations, it is also possible to make extremely fine tracks and even to write microscopically small letters. "If you work it out, you come to the conclusion that it would be The Dallas Semiconductor DS1267 Digital Potentiometer is a software-controlled dual 256position potentiometer. It can be used as a dual pot or the two sections can be series connected to produce a potentiometer with 512 positions. In addition, an unlimited number of potentiometers can be daisy-chained and controlled with only three signal wires. The digital equivalent of the wiper arm is controlled by feeding an 8-bit word to an on-chip register which is stored in a read/write memory, allowing the position to read back. The wiper position can be set directly: no need to sequentially pass through the intermediate settings. Once the setting has been made, there is no activity in the chip to induce noise. The D51267 digital potentiometer is available in 10k0, 50k0 and 100k0 versions. For further information on this series, contact IRH Components, 32 Parramatta Rd, Lidcombe, NSW 2141. Phone (02) 648 5455. Helium/neon laser tubes from page 83 possible to fit ten thousand pits into the space taken up by one pit on one of today's compact discs," says Dr van Loenen. ''Whether or not this would serve a purpose remains to be seen." "Just as important as the size is the speed with which you can write and read out the pits. What is more, the structures must also remain stable outside the vacuum. A great deal more research must therefore be carried out to ascertain whether these pin pricks can be usefully employed in practical applications. Which all goes to show how small a pin prick can be, doesn't it? ~ Oatley Electronics has three low power laser tubes currently available: a 0.5-0.8mW unit (Model 05), a 1-2mW laser head (Model 20), and a 3-4mW unit (Model 40). Also available is a collimator lens assembly which can be used to maintain a small beam diameter at long distances. A power supply unit will also be avaiable for all tubes. Prices start form $129.90. Contact Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. APRfL 1990 99 ASK SWCON CHIP Got a technical problem'? Can't understa!)d 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. Offset voltage problem with the Studio 200 pre amplifier I have been meaning to write to you for a long time now regarding the Studio 200 stereo control unit published in the June and July 1988 issues of SILICON CHIP. When it was published I was so intrigued with the circuit based on three ICs plus a headphone amplifier that I have built 5 versions. They all worked extremely well except that in each case the DC offsets of ICs 1, 2 & 3 are at 70, 250 & 50mV respectively, or thereabouts. Only IC4 gets under the 10mV suggested in the article. Can you throw any light on this? (D.G., Julatten, Qld}. • Your control unit circuits are working perfectly. We should not have specified a figure of ± lOmV for the offset voltages. In fact, a little analysis will show what the expected figures will be. For example, in the RIAA stage (IC4}, the DC offset voltage due to the unequal input bias resistances will be around 50mV for a typical op amp and around 1OOmV or so for a worst case, so your 70mV for IC1 is not unexpected. Similarly, for IC2, the DC gain is around 5.7. The input offset voltage could be as much as 10mV and the Needs transformer for cartrid1e player I Ull trying to fuui a replao• nut trU:ifol'l',Qtr for a tria\d's 1-irack. lteali.snc Til-MZ oar. tridt• ta}" recerd•r. A. you know, tlt•se v,ere marketed 'by Ta:ady. I h•ve bM• in touch witb tlaeir service centre but they were uuble to h•lp. I the circuit dria,nm. but I CQJI.Ot d.etel'111liB.e the nc,oa- uve 100 SILICON CHIP input offset due to unequal bias resistances could be as much as lOOmV (1 microamp multiplied by 100k0}. Multiply the total of 110mV or thereabouts by the gain of 5.7 and the worst you could measure would be just over plus or minus 600 millivolts. By the same sort of analysis, you could expect to find a worst case output offset for IC3 of around ± 100 millivolts. IC4 should have a worst case output offset of ± 7mV. So all the figures you have measured are less than could be expected in worst case situations. None of these figures have any audible affect on the performance of the circuit. How to stop blowing expensive lamps I recently bought a Datek ER-4 circuit board photo etching kit which uses the pos-neg system. This requires the use of a 500W 3200-3400° Kelvin photolamp which costs around $50.00. The lamps are specified to last 6 hours, however they promptly blow after about 6 minutes of on/off operation [usually while they are running}. This makes the home etching hob by a little expensive. Could you tell me of an alternative exposure method, or if a voltage spike protection unit incor- Mrf volta,o. It appu,rs to be 0.24V with an IV tap. II you follow the path of th8 8V ta.p it appears to feed a 11uaib• of m- clcator la-,. ud also feed.a • <lode whiclt IIIOl'D!t&OW procfu.oN 14 nltis. I -woald he Vfff F•taful if yOlll could · kelp ae select a suit.Ne NJUC881411lt. {A. Sterl-,, 4 Rowe AY.ue. Lumea, N8W 2110). • We had a look at ill• circuit diagram you'Ylll "'1i in but we porating a high quality double pole switch could be the answer. The bulbs are an Edison screw type fitting. (T.T., Mt. Eliza, Vic}. • As far as we know, there is no alternative to a high power lamp to expose Datek boards. So what you really need is a soft-start for the lamp, to reduce the damaging inrush current when the filament is cold. We have not published a softstart circuit but you could improvise one with a dimmer such as the Speedi-Watt first described in the December 1987 issue of SILICON CHIP [and featured just recently in the "Speed Controller for Ceiling Fans" in the January 1990 issue}. This kit is currently available from Jaycar stores. To use the Speedi-Watt as a softstart ci.rcuit, you have two options. First, you could arrange for the Speedi-Watt dimmer to run the lamp filament at red-heat [ie, barely glowing}. Then, when you wanted full brilliance, you merely turn up the dimmer control. The problem with this arrangement is that since the Speedi-Watt has been primarily designed as a fan controller, it gives maximum brilliance at switch-on and then clockwise rotation of the control reduces the brilliance. That being the case, it would be better to remove the switchpot from the board entirely and set the caa't work out what ta• tra:asfenner voltages are fr•• it. Ju1t how has the trauforaer failed? If Out priBua.ry has failed. yeu cu. -.ertil• tu Melllmdary with 24V AC u.d ii-. .,..MU"e the volta,a at tu tap. ,...PI You cwld then possibly 1Uk1t a c1s.oi.cie from o:rte of tke curr•tly avwble multitap tra:uftnaer1. W • have a:ts. puhli&Jled. ycmr full u11ue ud add.Nit !JI case eu of our road.en can ats:sist yem. Speakerphone in New Zealand First. could you tell me where I could get some close tolerance capacitors suitable for an RLC bridge? These would need to be 1 % or better. Also I would like to know where to obtain an edgereading meter of 200-400µA FSD. I would like to build the Speakerphone described in the September 1988 issue of SILICON CHIP but I am unsure of the connections to the New Zealand Telecom network. Does anyone know how to do this? Lastly, how about a stereo FM receiver to go with the FM transmitter in the October 1988 issue? This would save a lot as wireless headphones are expensive. (I.B., Palmerston North, NZ). • You can order close tolerance capacitors from Allied Capacitors, PO Box 740, Brookvale, NSW 2100. Phone minimum lamp brilliance with trimpot VRl. You could then use a mains rated toggle switch to short the dimmer out and apply full voltage to the lamp. Which ever way you do it, by maintaining the filament at red heat before applying full voltage, you will greatly reduce the initial surge current which can literally blow a weak lamp filament apart. Switching mains voltages with the remote switch I am interested in building the UHF receiver which appeared in the December issue, as it appears to be the answer to a long standing problem that I have had. If I go out at night, I usually leave the two outside lights on, which are two paraflood 150W flood.lamps. Quite apart from the tremendous waste of electricity, the lights are only there to serve as a means of finding my way around the back yard, without breaking my neck! 612 938 4690 (that's the international number, if phoning from New Zealand). 250µA edge reading meters are available from Altronics in Perth at $6.95, plus postage and packing. Phone 618 328 1599. Alternatively, Dick Smith Electronics has a 500µA edge reading meter which you should be able to get from DSE stores in New Zealand. As far as we know, Telecom standards in New Zealand are very similar to those in Australia except that domestic installations use a 3-wire scheme with one of the wires carrying the ring voltage. If you look inside your telephone you should see a circuit diagram which will enable you to identify the three wires and therefore the one carrying the ring voltage. The other two wires go to the Speakerphone. We don't see a portable FM stereo tuner as a viable project since W alkman-style receivers complete with headphones can be purchased quite cheaply. At one stage, I had considered the idea of having a second switch in a weatherproof enclosure and mounted to a metal post, wired up as a 2-way switch. To do that, it would have been necessary to dig up the yard, lay conduits and bring cables up into the roof space and then down to the first switch. The UHF receiver appears to be the ultimate and easiest solution to my problems. In fact , it would probably work out a whole lot cheaper as well but there are a few things I would like to know first before I consider building it up as a project. There are several spaces where I could locate the receiver: in the roof space, on the wall next to the existing light switch, or under the eaves of the house. Our house is quite old and it has an iron roof and I thought perhaps that this could upset the efficiency of the receiver. I have a preference for mounting it next to the light switch, as wiring would be far easier and it is no great hassle to provide a 12V DC supply for the receiver. I had intended to wire the relay output in parallel with the existing switch, perhaps by means of a special 240V AC outlet made for special types of applications and having a round earth pin to prevent other appliances from being' inadvertently plugged into it. It would also provide an easy way of removing the mains from the receiver should I need to work on it. The two floodlamps would draw about 1.2A so I would prefer to use a relay with a contact rating of at least 5A 240V AC. The distance from where the transmitter would be operated to where I would prefer to mount the receiver would be about 10-12 metres. Would it be possible to atta ch a small whip antenna to the receiver in lieu of a dangling piece of wire? Naturally, I would make absolutely certain that the 240V AC side of things is adequately isolated and that all wiring is firmly attached. A cable grommet could be used to secure a length of twin double insulated cable from the relay contacts to the switch. I would appreciate your views on the subject, particula rly as to the best place to locate the receiver with regards to wiring it up. (N.B., Canterbury, NSW). • Any of your suggested schemes would be OK, although your idea of mounting the receiver next to the existing light switch would probably be the most convenient. A range of 10-12 metres is well within the capabilities of the unit and, yes, you can use a small whip antenna instead of a "dangling wire". Because you are bringing mains voltages inside the case, it will be necessary to securely earth all exposed metal parts to ensure safety. These include the front panel and all mounting screws. Alternatively, you could substitute a plastic lid fo r the front panel and use nylon screws to mount the PCBs. Notes & Errata The formula given for parallel resonance on page 102 of the March 1990 issue is incorrect. The equation should have read: F = 1/21rj[c. A PRIL 1990 101 Don't miss a single issue 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. Here's what to look for in each issue: * Constructional Projects For The Enthusiast * Amateur Radio: Theory & Projects * The Serviceman's Log * Computer Bits: Getting The Most From Your PC * Vintage Radio: A Suf>scr·L Toda (02) 982 9553 Send the coupon with your Credit Card details. 24 Hours, 7 Days a week. y by filliu 9 out aud IQajJ· sub IQ!' this - ____s_c_..._•,::P~t:io::u~, coupoq Fascinating Hobby 24 Hour Fax Service lue r------------------- - --Freepost * Subscription Co u pon D Renewal D New subscription Start in, _ _ _ _ _ __ Name._ _ _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ __ (PLEASE PRINT) Subscription Hotline Telephone (02) 982 3935 9am-5pm Mon-Fri and quote your Bankcard, Visa Card or Master.Card No. and expiry date. 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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. MEMORY CHIPS Prices at Februari, 1 st, 1990 Speed 120ns 100ns BOns Chip type Prices (excluding tax) SIMMS (MACS) (IBM) SIPPS DIP PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS ZIP 2 3 5 4 9 9 8 9 x 256 x 1Mb x 1 Mb x 1Mb HP PS2 9 x 256 9 x 1Mb 7 8 9 10 11 12 13 14 15 ($7.00) 40.00 128.00 122.00 165.00 48.00 132.00 130.00 - 44.00 132.00 52.00 136.00 12.70 13.80 4.10 4.25 2.50 13.40 14.60 4.40 4.60 2.70 18.00 5.00 18.00 - 20.00 411000 (1 Mb) 414256 (1Mb) 41256 41464 (256) 4164 3.50 414256 (1Mb) 41256 411000 (1 Mb) 4400 (4Mb) 4.00 16.00 Sales Tax 20% 6 - 2.30 Overnight delivery 150.00 Credtt cards welcome DISCOUNTS FOR DEALERS Phone for pricing on 70ns. 80ns. PS2 , Compaq, and NTX PELHAM Tel (02) 427 0011 - Fax (02) 428 5460 16 ($7.40) 17 ($7.80) 18 ($8.20) 19 ($8.60) 20 ($9 .00) 21 ($9.40) 22 ($980) 23 ($10.20) 24 ($10.60) 25 ($11.00) FIX-A-KIT Name .. .... .. ........ ..... ..... ..... ............... ....... ... ... ......... ... ... ....... ... ...... ........ ... ...... ...... . Street ............. .. .. .... .... .. .. ... . Postcode Suburb/Town Enclosed is my cheque or money order for$ .... Bankcard O Visa Card D MasterCard . .... or please debit my 0 Card No I Signature ........ .. ..... .. I ................ .. ........ .. ........ Card expiry date ....... / ..... .. / ...... .. ANTIQUE RADIO ANTIQUE RADIO RESTORATIONS. Your one-stop electronic repair shop. Specialising in restoring vintage radios including chassis rewiring, quality new parts, valves, valve sockets, speakers, transformers, cabinet restoration. Quality secondhand radio dials & parts for most brands & models. About 400 radios in stock for restoration & parts. Every restored wireless is covered by a 2-year warranty on parts & service. French polishing of timber cabinets available. Vintage car radios in valve & transistor types available for restoration . Repairs done on tape decks, amplifiers, TVs & videos. Open Sat. 10am-5pm; Sun . 12.30-5pm. 109 Cann St, Bass Hill, NSW 2197 . Phone (02) 645 3173 BH or (02) 726 1613 AH. FOR SALE USED EPROMS, 5 MIXED for $6 .00 plus $2.00 p&p. Used 27MHz remote control crystals $1 .00 each plus $1 .50 p&p any quanity. Many other products available. Send SAE for detailed list. Electronic Toy Services, PO Box 491, Noarlunga Centre, SA, 5168. Phone (08) 382 8919 . PROJECT PCBs. Talk to the outside world . ETl-1643 PC 1/ 0 card , PC 1 6ADC 1 6-channel 8-bit. Both $39.95 each. Rear bracket & DB25 cable $16 . 6502, 6809 , Z-80 mini- $15 PER HOUR LABOUR NO CHARGE FOR KITS THAT CAN'T BE REPAIRED 3 MONTHS WARRANTY ON REPAIRS CONSTRUCTION AVAILABLE HYCAL INSTRUMENTS DESIGN, MANUFACTURE, REPAIR OF ELECTRONIC EQUIPMENT (02) 633 5897 processor with 2 x PIA, RAM , ROM, expansion bus $49.95. Intel 8039/48/49 with wire wrap area B&T $199. Digi-125 125W power amplifier PCB $4.95 . P&P $2.00. PC Computers, 36 Regent St, Kensington , SA 5068. NEW SERVICE - PARTS location and supply. Want just that part of a kit or just a hard to find part? We will find and supply them for you . No search fees. Send SSAE with requirements to Part Search, PO Box 491, Noarlunga Centre, SA 5168 . Phone (08) 382 8919 . SATFAX: NOAA, METEOR & GMS weather satellite picture receiving program for IBM XT/AT. Displays in 64 colours. Needs EGA colour monitor & card and "Weather Fax" PC card. $45 plus $3 postage. RADFAX2: HF WEATHER FAX, Morse & RTTY receiving program for IBM XT/AT. Needs CGA, SSB HF, FSK/tone decoder. Also "RF2HERC" & APRIL 1990 103 r~------------·---------, BINDERS & SUBSCRIPTION COUPON To: Freepost 25, Silicon Chip Publications, PO Box 139 Collaroy Beach, NSW 2097, Australia. NO POST AGE STAMP REQUIRED IN AUSTRALIA. □ Startin, _ _ _ _ _ _ __ □ New subscription □ Please send me _ ___ SILICON CHIP binder(s) at $A11.95 plus $A3 p&p each (NZ p&p $A6). Renewal Name _ _ _ __ _ __ _ _ _ __ _ _ _ _ _ __ _ __ (PLEASE PRINT) Street._ _ _ __ __ _ _ _ _ _ __ _ _ _ _ _ _ _ __ Suburb/town, _ _ _ _ _ _ _ _ _ _ __ Postcode _ _ _ _ __ 1 year ( 12 issues) □ $A42 Australia 2 years (24 issues) □ $A84 NZ & PNG (airmail) □ $A65 □ $A130 Overseas surface mail □ $A62 □ $A130 Overseas airmail □ $A 1 20 □ $A240 Enclosed is my cheque/money order for $ _ __ _ or please debit my 1J Bankcard □ Visa Card □ MasterCard Card No. I~ ____L_.____i_.____L_._,I IL_---'--_,.___._I_] I~ ____L_.____L_.____L_._jl IL_ _ J L __JL__JL_...J Signature _ __ __ _ _ _ _ __ _ Card expiry date_~-- L _______________________ J "RF2EGA" , same as RADFAX2 but suitable for Hercules & EGA cards respectively . $35 plus $3 postage. All programs are on 5.25-inch 360K or 3 .5-inch disc & include full documentation. Only from M. Delahunty, 42 Villiers St, New Farm, Old 4005. Phone (07) 358 2785. TOSHIBA T3100 CO-PROCESSOR kit. This piggy-pack board enables the fitting of an 80287-8 to the early T-3100. Two types available, solder in & plug in. Solder version $250.00. Plug-in version $375.00. Import Technologies (07) 372 5138. LOGIC ANALYSER. Gould Instruments K40 stand alone analyser. Eight nonvolatile memories, 7 -inch CRT, 4 x 2K sample memories, 2 x 16-channel, probes up to 100MHz, asynchronous capture. Weighs 7.7kg. $1345.00. Import Technologies (07) 372 5138 . EPSON PS0 PORTABLE battery rechargeable 80-column printer. Serial interface . Very compact & light. 1.1kg . Uses normal or thermal paper. $175. Import Technologies (07) 372 5138 . 104 SILICON CHIP TOSHIBA LCD SCREEN. Originally to suit T1500 desktop. 240 x 180mm, 640 x 200 pixels. Uses 5V supply & TTL drive signals. Suit experimenter. $150. Import Technologies (07) 372 5138 . PUBLIC DOMAIN & shareware software for IBM & compatibles. Catalog disc $4.00 on 5.25-inch 360K or 3.5-inch 720K disc . Also TVREPAIR.TXT which covers faults in most popular brands. It can save hours of work . Just $29 inc. p/post. Martins Television Service, PO Box 1013, Taree , NSW 2430. BELT KITS FOR VCRs. Please supply brand & model number & $12.00 for each kit required. Prompt dispatch assured. James Cotterill, PO Box 44, Farrer, ACT 2607. BUILD A LOW-COST 280 microcontroller development system. Uses any PC/XT/AT/386 or Z80 system as the host computer. Fast PC machine language cross assembler included . Super fast load to target system via parallel printer port; eg, 8K ROM file in Advertising Index Access Communications ..... .... 3 Allied Capacitors .... .. ... ..... .. .. 81 Altronics ....... ........ .... ..... 42-45 Arista ..... ... .. ... ..... ....... .. ... .. . 67 Board Solutions .... ... ....... 58,59 Dauner Electronics ............ .. 96 David Reid Electronics ... ....... 35 Dick Smith Electronics ..... 1 0-1 5 Electronic Solutions ..... ... 76, 77 Elmeasco ...... ..... .......... ..... IFC Energy Control ....... .. ... ..... ... 98 Force Electronics ..... .... .... ... 39 Geoff Wood Electronics ... ..... 65 Harbuch Electronics ... ...... . 9,63 Hycal Instruments ...... ..... ... 1 03 Jaycar Electronics ......... . 24-27 84-87 Jiloa .... .. ...... ............ ... ... ..... 19 J.V. Tuners ... ..... ......... ........ 63 Oatley Electronics ..... .......... 99 PC Marketplace .. ..... ........ ... IBC Philips ......................... .... OBC Pelham ............. ................ 103 RCS Radio ............... ... .. ...... 82 Resurrection Radio ............ .. 1 9 Rod Irving Electronics ... .. 70, 71 Sheridan Electronics ..... ....... 93 Silicon Chip Binders ... .... ... ... 61 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 For£, St, Welshpool, WA 6106 . Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. 3 seconds on standard 4 .77MHz PC . Battery back-up on target system. For more info, send a 41 c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . WANTED CPM PULSAR LITTLE BIG Board in working condition. Phone Peter (02) 449 1558 (A.H). SERVICE MANUAL for Palec Model valve tester . Phone Garry (045) 78 1359. COMPUTER PART# SIZE AMIGA AMIGA AMIGA AMSTRAD ATARI D2930 D2932 D2938 D2904 D2916 02918 D2946 D2948 D2950 D2952 D2970 D2972 ATARI IBM IBM IBM IBM TOSHIBA TOSHIBA r 3.5" 5.25" 3.5" 3.5" 3.5" 5.25" 3.5" 3.5" 5.25" 5.25" 5.25" 5.25" COMMENTS CAPACITY 880K 360/880K 880K 720K 720K 360/720K 720K 1.4MB 360K 1.2MB 360K 1.2MB PRICE WITH ON/OFF SWITCH WITH ON/OFF SWITCH INTERNAL KIT FOR A2000 FOR PC1512/1640 WITH POWER SUPPLY SWITCHABLE, WITH POWER SUPPLY WITH ADAPTER INTERFACE & CABLE WITH ADAPTER INTERFACE & CABLE WITH ADAPTER INTERFACE & CABLE WITH ADAPTER INTERFACE & CABLE SUIT TOSHIBA LAPTOP SUIT TOSHIBA LAPTOP 249.00 299.00 229.00 269.00 269.00 299.00 299.00 329.00 299.00 329.00 349.00 399.00 c,rEc!f.1JIF${MJtfjclJseFc,ALsANixuu.~r'411,yroA11lua nt$}ff{ei1x,xtty1J1:tE • c COLOUR GRAPHICS ADAPTER FOR IBM PC/XT/AT Toe M5752 is a colour graphics adapter card capable of operating with either IBM RGB or composite monochrome monitors and features the following: • Parallel printer port • Text modes: 40 x 25 or 80 x 25 • Graphic modes; 320 x· 200 or 640 x 200 • Light pen interface • Includes composite video monitor adapter • Manual included Ms1s2 - XT1MB 12MHzTURBO MOTHERBOARD • V20 processor• Can be expanded to 256k, 512k, 640kor 1mb • Uses combinations of 414256, 41464 and 41256 • 4. 77 or 12MHz hardware or keyboard selectable operation• Front panel LED indicators supported • Eight expansion slots • Legal BIOS ROMs included • 8087 maths co-processor capability • Norton Sl rating of 2.5 • Size 8.5" x 8.5" e Weight 1.1 lbs M5500- XT 1MB 12MHz TURBO MOTHERBOARD WAS $115.00 NOW $69 WAS $129 NOW $110 YOU SAVE! 84 KEY KEYBOARD- GREEN SCREEN MONITOR-TTL - HIGH RESOLUTION AMERICAN/MEXICAN MANUFACTURE A qualay product by a major American company. These would normally sell for $200 to $300 but we have a limaed amount of stock available 14" flat {ONLY 200 UNITS) screen, including tilt/swivel base. Extremely high quality Memorex brand. LIMITED STOCK AT $125.00 EACH this month only $69.00 AT(16 BIT) HARD/FLOPPY/DISK CONTROLLER Will control 2 x ST 506 lntertace hard drives AND 2 x Floppy drives; 360k/720k/1.2M/1.44M. DEALER ENQUIRIES WELCOME Normally sells for $245, this month we offer 50 only at $145.00 YOU SAVE $100 Have you seen our catalogue? Write or phone today for your FREE copy. PERSONAL COMPUTER MARKETPLACE Ptylt d PHONE (02) 418 6711 FAX (02) 418 6713 Mail Order Address: P.O. Box 1100 Lane Cove NSW2066 FREIGHT CHARGES Include $10 with order for all normal items - heavy items, e.g. monitors add $15. 14 day money back guarantee Order by phone (use credit card), by fax or by mail. Unless insurance is declined it will be charged at 1% of total purchase. This is for your protection. WHERE SERVICE /S THE DIFFERENCE