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Is radiation from power cables dangerous? S3.50 JUNE 1989 NZ $4.95 ~;TL. SERVICING - HIFI - ~ nuHu nv1111cn ~ ·n11.11n_n••••••rn SAN&eAN AR 900 Our best miniature 100 channel hand-held scanning receiver features 5 banks of 20 channels and a scan rate of 15/ sec channels including the new cell ular frequencies. All inform ation is stored in EEPROM memories which do not require battery backup . Otherfeatures include a backlit LCD display with 22 separate prompts to aid in programming and display of the channels, single memory access, scan delay, skip, hold, priority, & up/down scanning. The unit is supplied w ith 2 separate antennas and nicad batteries. Forfurther information contact your nearest communications centre. S-803A This latest state-of-the-art receiver featuring auto scanning, 14 memories, direct key access to all 12 wave ba nds, adjustable RF gain, inbuilt BFO for SSB reception, clock with alarm and sleep timer, and stereo FM capability. Complete coverage of the long wave band makes t his especially usefu l for marine and aviation enthusiasts. The unit comes complete with a range of useful accessories. For further information contact your nea rest communications centre. SAN&eAN MS-101 and MS-102 Both quality pocket-sized short wave receivers offer an almost endless number of radio broadcasts from all over the world. The quality world wide reception 1s especially useful for travellers wishing to stay in touch with home, or those interested in other cultures. Both receivers come complete with a luxurious carry case, earphones and a guide to short wave listening. Forfurther 1nformat1on contact your nearest communications centre. JUNE 1989 FEATURES 4 Understanding Oscilloscope Probes by Jonathon Gordon IT MAY LOOK SIMPLE but this loop antenna can dramatically boost AM radio signals. It's ideal for country listeners and for use in caravans. Details page 10. How they can affect your measurements 67 Sangean ATS-803A Shortwave Receiver by Garry Cratt Covers 150kHz-30MHz & receives CW, SSB & FM as well 80 The Evolution of Electric Railways by Bryan Maher Pt.20: Amtrak's monster vs. a Swiss thoroughbred PROJECTS TO BUILD 10 Passive Loop Antenna For AM Radios by Greg Swain Dramatically boosts AM radio reception 48 Build the Touch-Lamp Dimmer by Leo Simpson One touch & it's on. And you can dim up or down IS RADIATION FROM power cables dangerous? We take a look at some of the outrageous claims that are being made. Turn to page 24. 60 Universal Temperature Controller by Branco Justic Ideal for fish tanks, beer brewing & hatcheries 70 Build a LED Message Board by Don McKenzie Pt.4: building & testing the display panel SPECIAL COLUMNS 16 Vintage Radio by John Hill Collecting & restoring horn speakers 24 The Way I See It by Neville Williams Back to the stone age: down with audio, radio & AC mains! 34 Serviceman's Log by the TV serviceman Look before you leap 66 Amateur Radio by Garry Cratt Coherent CW - THIS TOUCH-LAMP dimmer circuit lets you turn your lights on & dim them at a touch. Construction starts on page 48. a new low-power transmission technique DEPARTMENTS Publisher's Letter Mailbag Circuit Notebook Product Showcase 69 Subscription Page 2 3 32 88 86 92 94 95 96 Bookshelf Ask Silicon Chip Notes & Errata Back Issues Market Centre YOU CAN BUILD this temperature controller for less than $40. It will keep the temperature of a liquid in a tank or air in an enclosure to within ± 1 °C. See page 60. JU N E 1989 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 Adver,lslng Manager Paul Buchtmann Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill David Whitby Photography . Bob Donaldson Editoriai 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 , Waterloo , NSW 2017. Printing: Masterprint Pty Ltd , Dubbo, NSW 2830 . Distribution: Network Distribution Company. Subscription rate: currently $4 2 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. ISSN 1030 -2 6 6 2 * Recommended and maximum Australian price only . 2 SILICON CHIP PUBLISHER'S U'l-l'ER Editorial content: juggling the mix isn't easy At a particular time in the production cycle of SILICON CHIP, we have to make critical decisions on the editorial content of the issue. As time goes on, we are finding these decisions quite difficult. Do we leave out a feature article so a project article will fit? Do we run a project article in one big slab rather than in several episodes? Can we afford to run more readers' letters and so on. Questions like these are difficult because we are trying to cater for such a wide range of reader interests. Each month we try to include a good range of articles but we are not sure just how they will be received by you, the reader. What we think is great may not necessarily appeal to you. We'd like to hear more reactions from you. Take for example the Passive Loop Antenna project. Superficially, this is a very simple device and you would be justified in thinking that it wouldn't do much. We reacted exactly the same way at first. I mean, it's just too simple, isn't it? But if you have an AM broadcast radio with its own loopstick antenna and you're having trouble picking up a weak station, this device works like magic. The increase in signal when the Loop is placed near the radio and tuned for maximum pickup is amazing. It's just the thing if you are staying in a caravan. Anyway, I'll not say anymore; you can read about it for yourself. The second project that we are very pleased with is the Touch-Lamp Dimmer. It uses just a single new IC from Siemens and a Triac to provide a dimmer which can be turned on and off or dimmed at a touch. It can also be programmed to provide either a "soft start" switch on or to store the selected brightness of the lamp so that when you switch on next time the lamp will be set to the same level. This is pretty fancy stuff and makes the ordinary knob type dimmer look pretty passe. Well what do you think of projects like these? We know that some readers do not buy an issue unless there is something in it that is of specific interest at the time. Later on they often regret not buying the issue because they have missed out on an article which is now vital. If you don't buy SILICON CHIP every month, we'd like to know why and what we have to do to make you a convert. Why not drop us a line? Leo Simpson SILICON CHIP, PO Box 139, Collaroy Beach 2097. MAILBAG Thanks for info on auto reverse players Just a short note to say thank you for the wonderful response to my letter back in October 1988 about autoreverse cassette player problems (see page 98). In January's edition I found a wealth of valuable information about the above-mentioned topic. There was an excellent article on servicing cassette players and, in the "Ask Silicon Chip" pages, several thoughtful and enthusiastic people also kindly put pen to paper with information which is very much appreciated. With a response like that I feel that SILICON CHIP has a big future as an electronics magazine. Ron Pankin Latrobe, Tasmania Off-hook indicators & valve radios I would like to compliment you on your magazine. I read all the Australian electronics magazines that I know of and several computer titles. SILICON CHIP gets top billing for my particular interests. I enjoy the light-heartedness and humour that you inject into both the magazine and the projects, so long as it does not detract from the seriousness of imparting knowledge. I am 36 and make a living as a selfemployed computer consultant. Electronics has been a hobby of mine since I was about 7 years old. I actually build very few projects but I use the magazines as a way of staying in touch with movements in the technical world. Being able to hold my own with hardware is also very important in my professional work. I often knock-up bits of a project to see if it works, then scrap it. I hate building things into boxes. I did build two telephone off-hook indicators. They did not work in NZ first up. My brother (a Telecom NZ employee) sussed out the problem. In NZ, the ring-tone adds up to 70 volts to the existing 50 volts on the line, so the 56 volt protection zener conducted heavily as soon as ring-tone appeared. As a result, the computer exchange thought that the phone had been answered and stopped ringing. The zener then stopped conducting but the phone had not been answered so the exchange hung the line up. We cured this problem by putting another 56 volt zener diode in series with the existing one. Strictly speaking, we should also have swapped the transistor for one with higher voltage ratings but it hasn't died yet. Changing the subject, I have a large collection of old circuit boards and 74 series ICs and suspect that I am not alone in hoarding such things. You might consider a monthly project that uses "old" parts and does something suitably trivial. When the parts are free, the number of them used is not really relevant. I also have collected 30 or more valve radios over the last two years with a view to restoration when I get time (eg, in 20 years or so). Among my acquisitions were dozens of circuit diagrams and service manuals for valve radios of widely differing complexity. While there has been the odd crystal set featured lately, no-one has featured a one or two-valve radio (remember the Hiker's One and Hiker's Two). I built a Hiker 's One about a year ago. It worked but I never did get the regeneration working properly and it lacked sensitivity. I think that you would find the valves necessary for a simple project to be still obtainable. Several firms offer tuning capacitors and you could wind your own coils. High voltage capacitors are available (albeit expensive) and ½ W resistors easily obtainable. Transformers are a little more difficult but not impossible. I know it's sacrilegious but you could always use a transistor for the audio section or even an IC. John Penney Blenheim, NZ Sound effects for model railroads I have been dabbling with model railway sound effects since transistors and miniature loudspeakers made it possible to house such systems in a model locomotive. The best I've done with an on-board sound system is a diesel engine sound similar to that described by you recently, housed in an 0-gauge locomotive. As you pointed out, a small speaker cannot reproduce the sounds realistically. I do not find the system of placing speakers around the layout very convincing and have adopted another approach which you may care to take up. The technique is to provide each driving position with heaphones through which the sounds are reproduced. Of course, this is of no use for spectators but the effect for the driver is magnificent - with very little imagination he is inside the locomotive. You could easily test this for yourself by connecting headphones to the system you have described in the December 1988 issue. Norman Cave Pascoe Vale, Vic Comment: thanks for your Jetter about your headphone system of producing loco sound effects. It sounds like a really good system and we'll give it a try at the first opportunity. Screws & screwdrivers Your article on screws and screwdrivers in the November 1988 issue told me a lot I didn't know about even though I've been working with them for more than 25 years. Already I find I have a need for a tamperproof Torx driver to repair a friend's electric drill. You refer in your article to specialist tool outlets being able to supply same. Unfortunately, tool outlets prepared to take th,ese sorts of orders are a bit thin on the ground up here in Queensland. Could you possibly let me know of a company that might be able to help? Keep up the good work. W. Adams St Lucia, Qld Comment: you can try Collier Tools (Aust) Pty Ltd, 7 Lachlan Crescent, Pebble Beach, Sandstone, Qld 4511. Phone (071) 97 5545. Alternatively, try A.B.W. Tools Pty Ltd, 54 Raynham St, Salisbury, Qld 4107. Phone (07) 275 1288. JUNE 1989 3 To effectively use an oscilloscope, you must know how the scope's probe affects the signal waveform you are measuring. Here's a rundown on how scope probes work. By JONATHAN GORDON UNDERSTANDING OSCILLOSCOPE PROBES The most common type of oscilloscope probe used by technicians is the voltage-sensing passive probe. Because passive probes are so common and used so routinely, their peculiar effect on electronic circuits is universally experienced - though very often misunderstood. Nothing can replace the kind of troubleshooting knowledge that comes from viewing different waveforms from various types of circuits, such as digital, analog and radio frequency (RF). However, understanding how an oscilloscope probe loads the circuit under ·test will give you a new troubleshooting skill that no amount of experience can equal. Fig.1 is an equivalent circuit of a typical xlO scope probe and the vertical input of the associated oscilloscope. The probe's head has a 9-megohm resistor (Rl) that is shunted by a 4-Z0pF trimmer capacitor, Cl. The shielded coaxial cable that connects the probe to the scope has a distributed capacitance, C3, of approximately 80pF. An electronic signal travels through the probe tip, the probe head and compensating network, the shielded coaxial cable, and then to the scope's input connector. The input impedance of a typical scope is 1 megohm (RZ) shunted by a Z0pF capacitance (CZ). The scope's input characteristics are often printed near the input connector. The idea of compensating a passive probe is to balance the pro- COMPENSATION C1 CAO PROBE 4-2OpF PROBE TIP \ PROBE HEAD __ l_ ---1 + COAXIAL CABLE ___\___ I I CAO INPUT I r--~~I-----q- - - - - - - r'\ -:- I C2 20pf1 R2 1M .,. FIG.1: INPUT EQUIVALENT CIRCUIT of a x10 probe and oscilloscope. The probe's head includes a 9MO resistor which is shunted by a 4-20pF trimmer capacitor {Cl) to provide compensation. 4 SILICON CHIP be impedance and the scope impedance so their time constants are equal, as shown in the following formula: RlCl = RZ(CZ + C3) If their time constants are equal, electrical waveforms will be communicated from the probe tip to the scope input without the probe adding distortion to the signal. The amplitude of the displayed pulse will merely depend on the rnsistance ratio: Vscope = (RZ/(Rl + RZ))Vinput For example, using a xlO passive probe, a lV p-p input at the probe's tip will yield a 0.1 V p-p reading on the scope's display. The resulting decade attenuation of the xl0 probe is highly desirable because it affords a greater tip resistance (10 times the 1-megohm scope input resistance) to minimise circuit loading. Once the probe has been compensated by adjusting trimmer capacitor Cl, the probe and scope input are further reduced to the equivalent circuit shown in Fig.2. Copyright 1989, Gernsback Publications. Reprinted with permission from January 1 989 Radio-Electronics. PROBE TIP \ Another compensation scheme is shown in Fig.5 which uses a 4-20pF timmer capacitor to shunt the resistor in the probe's head. Pulse waveforms Fig.2: INPUT EQUIVALENT CIRCUIT of a xl0 compensated probe as seen at the probe's tip. Any circuit under measurement will now see a single impedance at the probe's tip of 10 megohms, Rp, shunted by an 11.2pF capacitor, Cp, which is a specification that is often printed on the probe's head or compensation box. Scope probe manufacturers have been clever in the methods they use to shunt the resistor in the probe's body. For example, Fig.3 shows the inside of a Tektronix Model 6006 xlO probe. The coaxial cable's centre conductor is extended into the probe's body where it connects to a cylinder that slides over the resistor. At one end of the resistor is a shorting slug that makes contact with the cylinder. A capacitor is thus formed by the cylinder and the resistor. The probe is compensated by screwing the probe's body into the locking sleeve , which is then tightened. During that adjustment, the inner cylinder slides a varying distance over the resistor and this varies the shunt capacitance. Note that the coaxial cable 's outer conductor is connected to a second cylinder for shielding. Fig.4 shows the inside of a Tektronix Model P6105A xl0 probe. In this unit the cylindrical tubing forms a fixed shunt capacitance across the resistor. No probe adjustment can be made in the probe's body to compensate the probe assembly. Instead the assembly uses a compensation box at the connector end that houses a trimmer capacitor, C2, which is connected from the centre conductor to ground. The shunt capacitance C3 and trimmer C2 are in parallel. A common variation of this compensation arrangement uses a trimmer in the BNC plug housing for the probe. This is used by probe manufacturers such as Coline and Hitachi. In general, probes are compared by how well they transfer an electrical pulse to the oscilloscope's input without causing distortion of one kind or another. But what is the real nature of an electrical pulse? Fig.6(a) shows what a rec- tangular pulse looks like on an oscilloscope as amplitude vs. time. However, as shown in Fig.6(b), the same rectangular pulse displayed on a spectrum analyser is transformed into a chart of amplitude vs. frequency - ie, it shows what the pulse would look like if broken up into its individual sinusoidal harmonic components. As you can see, the rectangular pulse is made up of both even and odd order harmonic components. CYLINDRICAL SLEEVEE LOCKING SLEEVE ALLIGATOR GROUNDING CLIP Fig.3: THIS PROBE IS COMPENSATED by adjusting the locking sleeve. C3 COAXIAL CABLE SHUNT CAPACITANCE ·, INNE,, CONDUCTOR CYLINDRICAL SLEEVE FORMING FIXED SHUNT CAPACITOR ACROSS RESISTOR ,::;,:._/ ALLIGATOR GROUNDING CLIP FIG.4: THIS PROBE IS COMPENSATED by adjusting a trimmer capacitor housed in the compensation box at the end of the probe's cable. JUNE 1989 5 Rl COAXIAL SHIELDED CABLE 9M , I , I I I \ t \ =...._ PPOBE TIP \ TRIMMERIADJUSTMENT SCREW FIG.5: THIS PROBE IS COMPENSATED by adjusting a trimmer capacitor housed in the probe's head. w Cl :::, PULSE w PULSE Q :::, ...:i t: ~ "'"' "'"' ...... TIME (a} :,:; :,:; "' en FREQUENCY (bJ FIG.6: THE PULSE WAVEFORM in (a) shows how an oscilloscope displays an . electrical pulse as amplitude vs. time. As shown in (b ), the same pulse waveform is displayed on spectrum analyser as amplitude vs. frequency. Unlike the rectangular pulse, a perfect square wave is made up of only odd-order harmonics (that is 1, 3, 5, 7, 9, etc). For example, if a lkHz square wave is input to an oscilloscope, the lkHz fundamental (1st harmonic) sinusoid up to the 9kHz harmonic sinusoid must be reproduced without attenuation or phase shifting. As shown in Fig.7(a), the 1st' and 3rd harmonic components produce a rather poor square wave. In Fig.7(b), the square wave looks a little better when the 1st, 3rd and 5th harmonics are present. And, as shown in Fig.7(c), the square wave looks better still when the 1st to 7th odd-order harmonic components are present. The waveform will appear sufficiently square and undistorted when frequencies are present out to about the 9th harmonic sinusoid. Obviously, the shape of a square wave displayed on an oscilloscope depends on the amplitude and phase relationships of the harmonic components. To accurately reproduce an electrical pulse it would be 6 SILICON CHIP necessary to design a circuit that responds equally well to an infinite number of harmonic frequencies , so that all harmonics are included. In practice, that cannot be done so a compromise between pulse shape and circuit design must be made. Compensation Every electronics technician has recorded pulse waveform data such as risetime, width, amplitude and repetition rate, only to realise too late - that the probe wasn't compensated. Because an improperly compensated probe can distort an otherwise perfect waveform, the probe's compensation capacitor must be correctly adjusted and the test data remeasured. Let's now examine how to properly compensate a probe and, additionally, how faulty compensation can affect the measurement of pulse waveforms. Because probes should often be compensated, most scopes provide a square-wave calibration signal accessible from the front panel. There are other types of probe calibrators, such as a linefrequency calibrator, a lkHz square-wave calibrator and other more exotic types. However, they are used less often than the more convenient front-panel scope calibrators. The front-panel probe calibration signal is a lkHz repetitive square wave. A lkHz square wave is used because the sinusoidal harmonic components are very close together, so the slightest offset in the probe's frequency response will affect the amplitude and phase relationship of many harmonic components at once, resulting in a visually distorted waveform. Fig.8(a) shows a lkHz calibration signal from a properly compensated probe. Notice that the square wave is undistorted. Fig.8(b) shows the same calibration signal from an over-compensated probe. Here, the leading edge high-frequency harmonics are passed while some of the lower-frequency harmonics are slightly attenuated. Some phase shifting has also occurred. The greater the drooping effect of the waveform, the greater the degree of low-frequency harmonic attenuation and phase shifting that has occurred. Fig.8(c) shows the same calibration signal from an under compensated probe. Notice the lack of high frequency components in the leading edge of the square wave (indicated by rounding). Now let's examine the relationship between pulse shape, rise time and the capacitance of the circuit. When the driving pulse has a slow rise time, or the pulse width is comparatively wide, the stray capacitance can have a fairly high value without producing visible distortion. That's because slower rise times and greater pulse widths correspond to fewer high frequency harmonics. However, the same value of stray capacitance can become intolerable when the driving pulse has extremely fast rise times or a very narrow width. The waveshape then depends critically on the preservation of high-frequency harmonics. As more and more stray shunt capacitance is added to the circuit under test, the shunt (bypass) capacitive reactance decreases in value. Harmonic frequencies that comprise the pulse's · edge will now be shorted to ground by the lower shunt-capacitive reactance. Assume, for example, that a computer circuit is working just fine and that you want to observe the 20MHz master clock. So you connect your xl scope probe - and the whole system crashes. The clock's waveform displayed on the scope looks a little distorted. You then remove the probe from the circuit and the system immediately comes up. What happened? FUNDAMENTAL PLUS 3RD HARMONIC ' sistive attenuation ratio, the lower the probe-tip shunt capacit-ance. For example, xl, xlO and xl00 probe attenuation factors might have a 54pF, 11.2pF and 2pF tip capactance values, respectively. Continuous wave (a) FUNDAMENTAL ....I (b) (a) FUNDAMENTAL PLUS 3RD AND 5TH HARMONICS ✓-\ \ \ \ \ \ (b) (c) FIG.8: A PROPERLY COMPENSATED FUNOAMENT AL PLUS 3RD, 5TH AND 7TH HARMONICS I I I \ \ (c) FIG.7: ALL PULSE WAVEFORMS are built up from sinusoidal harmonic components. As shown in (a), the fundamental (1st harmonic) plus the 3rd harmonic create a rather distorted square wave. In (b), the 5th harmonic is added, thus creating a less distorted square wave. In (c), the 7th harmonic is added, thus minimising distortion even further. probe will display a lkHz calibration signal as a perfect square wave as shown in (a). However, in (b), when the probe is over compensated, the same lkHz signal shows lowfrequency attenuation and phase shifting as indicated by the drooping effect. As shown in (c), when the probe is under compensated, the high-frequency components are lost, as indicated by the rounded leading edge. One possible explanation is that the added shunt capacitance of the probe degraded the clock's rise time, which threw off the system timing. As shown in Fig.9, slower rise time translates into a wider pulse width. In this situation, you should try using a xlO probe instead of a xl probe because the xlO probe has a lower shunt capacitance. In general, the greater the re- When measuring a continuous signal from the output of a sinewave oscillator, the probe-tip's capacitive reactance (X_p) at the operating frequency should be considered. In Fig.10, the total probe tip impedance, designated Zp, includes the probe's resistive, capacitive and inductive elements. The capacitive and resistive elements make up most of the probe's impedance. However, some probes also include additional inductive elements that are designed into the probe itself to offset the capacitive loading. For worst case analysis, use the probe's capacitive reactance formula: Xp = 1/2-n-fC where C is the probe-tip capacitance. This value is often marked somewhere on the body of the probe. For example, the Tektronix model P6105A passive probe has a 10-megohm input resistance with a tip capacitance of 11.2pF. The Xp will equal 290 ohms at 50MHz. Depending on the impedance of the source, the probe's loading could have a major effect on the signal amplitude and possibly interfere with the operation of the circuit under test. The typical curves for probe impedance vs. frequency vary for each probe type so consult your probe's specifications. For sinewave amplitude measurements, a probe should have the highest possible impedance at the frequency of interest. Voltage derating The maximum voltage (DC and AC) that can be safely handled by a probe varies with frequency. Fig.11 shows the voltage derating curve for a Tektronix Model P6105A passive probe. The curve may be summarised by saying that the maximum voltage handling capability is JUNE 1989 7 AMPLITUDE 10M RISE TIME It= I 90 % X' 50 % I 10 ¾ \ I / 1M \ I .;;- \ ;l I\ e, I I~ -1 '' 100k ' '' = >< ~ < \ 10k ~ WIDTH WIDTH ~ ·, \zp \ 'Xp' ' , ' 1k '' I\ \, '' ' ......\ "'" TIME FIG.9: PULSE WIDTH IS MEASURED at the 50% marks on the waveform. As the circuit's shunt capacitance is increased, the rise time slows, causing the pulse to become wider. 100 .01 0.1 1 10 ~,... 100 1000 FREQUENCY I '1!Hz) FIG.10: WHEN MEASURING SINE waves, it's important to know how the probe's input impedance (Zp) changes with regard to frequency. 1000 '\ \. 100% [\ G' < 97% 'r- "' ~ ~ 100 'r-. ~ 70.7% 3dB e. w "'< :; 0 > 10 1 10 30 100 FREQUENCY I MHz) FIG.11: THE MAXIMUM VOLTAGE that a probe can handle decreases as the frequency increases. inversely proportional to the frequency. Most scope probes are supplied with their own voltagederating specification. Bandwidth Scope probes are often rated for bandwidth. It's best to use a probe that has a bandwidth equal to or higher than that of your scope. If the probe's bandwidth is less than that of the scope, then the input frequency will be limited by the probe. Fig.12 shows the response curve of a probe having a 100MHz bandwidth. By definition, bandwidth is the upper frequency where the scope's displayed voltage is down 8 SILICON CHIP 100 FREQUENCY 1MHz) FIG.12: PROBE BANDWIDTH is the point where the voltage amplitude is down 3dB from a starting reference level. 3dB from the reference frequency voltage. The formula to calculate decibels is: dB = 20 log Vout!Vin For example, if the input is a 1V p-p 100MHz sinewave, then at - 3dB the scope 's waveform will show an amplitude of only 0.707V p-p (which is an amplitude accuracy of 70.7%). For an amplitude accuracy of 90% or better, you must limit the input frequency to about 30MHz. Another useful equation shows how bandwidth is related to risetime (tr): Bandwidth = 0.35/tr From this it follows that the faster the risetime, the greater the bandwidth. For low-frequency applications (audio frequencies), you can choose a xl passive probe because it costs the least and will do the job. But be aware that the xl probe has a limited bandwidth - less than 40MHz. On the other hand, use the xlO probe for general digital, analog and RF measurements. A xlO probe has low capacitance and a bandwidth upwards to 400MHz, depending on the model and the cable length. Note also that if you are using switched probes which are the most commonly available, their stated bandwidth only applies to the x10 mode. In the direct (xl) mode, their bandwidth is much less. For example, the Coline SPlO0 probe has a rated bandwidth from DC to 100MHz in the xlO mode but its bandwidth drops to 10MHz in the xl mode. Its capacitive loading also increases from 16pF to 55pF (plus the input capacitance of the oscilloscope). Although not discussed in this article, for frequencies higher than 400MHz choose one of the active probes (FET) with a xl sensitivity. This type of probe will provide high sensitivity, low shunt capacitance and a bandwidth greater than 900MHz. Rp CP 10M 11.2pf GROUND LEAD L FIG.13: GROUND-LEAD INDUCTANCE will reduce the high-frequency response through its series-inductive reactance. RINGING ,J l\tWrG--. Grounding How often have you touched the probe tip to an IC pin only to see a waveform you know from experience isn't right? Then, after moving the probe's grounding clip from the chassis to the IC's ground pin, the scope's trace immediately shaped up and became recognisable as the waveform you've seen before. This leads us to the obvious question: how does the probe's grounding lead affect the circuit measurement? The obvious answer is that improper grounding will generally distort the waveform by allowing excess noise to be picked up. That's true but it's only part of the reason. Fig.13 shows an equivalent circuit of a passive probe connected to a voltage source. Notice the series ground-lead reactance, L, whioh represents the ground return path. Rp and Cp represent the equivalent impedance as seen at the compensated probe's tip. When measuring any signal, the series inductive reactance will be proportional to both frequency and inductance by the formula: X1 = 2-irfL The higher-frequency harmonics will therefore see a larger inductive reactance than the lower frequency harmonics. The pulse waveform displayed on the oscilloscope will show distortion and aberrations because the p-p voltages of the higher-frequency FIG.14: PULSE RINGING OCCURS when the ground-loop inductance and probe tip capacitance form a series resonant circuit that is shock-excited by a very fast rise-time pulse. harmonics have been attenuated and phase shifted across the ground-lead inductive reactance. Now let's get back to the original problem. If you move the probe's grounding clip from the chassis to the..IC itself, then the ground-loop inductance will be reduced. That allows the high-frequency harmonics to reach the scope's input, so the trace shapes up. As a rule of thumb, when making any kind of measurement - such as amplitude, rise time and pulse width - you should use the shortest grounding path possible. As shown in Fig.14, loop inductance may also manifest itself as ringing on the leading and trailing edges of the signal pulse. The ground-lead inductance and probetip capacitance form a seriesresonant circuit with only a lOMQ resistor for damping. When shockexcited by a pulse, the resonant circuit will ring with a predictable damped oscillation. For example, an 11.2pF passive probe having a 15cm ground lead will ring at about 140MHz when hit by a fast rise-time pulse. As the ringing frequency increases, it tends to fall outside the scope's passband and is highly attenuated. It's therefore desirable to try to increase the ringing frequency. To do that, use the shortest possible ground lead and the probe with the lowest shunt capacitance. It's ironic but for the reasons just mentioned, you're more likely to see ringing on an expensive high passband 300MHz scope than a low passband 20MHz scope. Mechanical properties Often, while touching or rearranging a probe or lead wire, unpredictable, confusing and nonrepeatable effects are produced on the observed waveform. That kind of problem may have more to do with the mechanical nature of the probe than anything else. If the probe's inner signalcarrying conductor is poorly shielded, then the probe's cabling will be susceptible to external electric fields. (The shielding could become frayed due to constant flexing of the cabling over many months or years of use). A poorly shielded wire can act as an antenna and pick up all types of interference such as electrical noise from fluorescent lamps, radio stations and signals generated by nearby equipment. To virtually eliminate any external field pickup, always use a probe with coaxial cable shielding of the centre conductor. As a final note, the probe tip should be clean or a poor circuit connection will result. Also, be sure to check printed circuit boards for a conformal coating which is sometimes used to guard against humidity and static. This can easily prevent an electrical connection between the probe tip and the circuit. It may be necessary to scrape off some of that coating to make a good connection to the circuit. ~ Footnote: next month, we plan to describe a practical x10 CAO probe that you can build yourself. This unit is essentially a practical version of the circuit shown in Fig.5 on page 6. JUNE 1989 9 PASSIVE LOOP ANTENNA FOR DX RECEPTION By GREG SWAIN This passive loop antenna can dramatically improve AM radio reception and is ideal for use in caravans or in remote areas where signals are very weak. It can also greatly improve wideband AM stereo reception in areas where there is a lot of mains inter£erence. A passive loop antenna is not a new device. During the early days of "wireless", this type of antenna was standard on many domestic receivers. It typically took the form of many turns of wire wound in a loop inside the case or on a large wooden cross or box frame. In the 1950s, portable valve 10 SILICON CHIP radios often had a loop antenna inside the case and they were quite effective in picking up signals. Those early passive loop antennas wound on a frame looked quite ugly but that description doesn't apply to the device presented here. The Techniloop PXl (to give it its full name) is a high-Q tunable passive loop antenna that comes with its wire loop hidden inside an attractive plastic covering. It can dramatically improve AM radio reception over long distances, both on sets fitted with ferrite rod antennas and those with external antenna connections. The Techniloop PXl will have particular appeal to country listeners, to people who stay in caravans and to DX enthusiasts. The reason we make particular mention of caravans is this. Normally, city dwellers never have a problem with weak radio stations. They just turn on the radio and all the stations they want are there. But if they go on holidays and stay in a caravan, the situation is quite different. Caravans are a very good shield against AM radio signals. Combine this with the fact that most holiday resort areas do not have a lot of radio stations and the result is that the holiday maker is in for a very quiet time. If you have never experienced this problem, just sit in a car with a portable radio and try to tune in a distant radio station. The reception will invariably be quite poor. The solution to this problem is the Techniloop. First, you tune in the station on your radio and align it for best signal pickup. You then bring the Techniloop close to the radio or sit the radio right in the loop, as shown in the photographs. Now all you have to do is carefully tune the knob on the Techniloop to get the strongest signal. When you get the maximum pickup you will find the tuning is very sharp. The increa se in signal is magic! Of course, if you are a country dweller and want to listen to distant city radio stations, particularly during the difficult daylight hours, this passive loop antenna is the only way to go. And even if you do live in the city, the Techniloop PXl can be very useful, even if you are not a DX enthusiast. If you have a wideband AM stereo tuner, city radio reception conditions can be very trying. There is a lot of " frizzle " radiated from fluorescent light fittings and power lines which can thoroughly -II ALL THE PARTS FOR the Techniloop PXl are supplied by Technikit Electronics. Not shown here is the wire loop which is supplied housed in a plastic covering and terminated with IDC connectors. spoil good radio programs. With the Techniloop PXl set up next to your tuner, the reception magically quietens and you can really enjoy the music. If we have made out that the Techniloop PXl is a universal panacea for AM reception problems that's because it virtually is. Sure, it won't give you Sydney radio stations in the Anta rctic but it really does turn poor reception into good reception. We are very enthusiastic about it. Performance It's not hard to understand why a loop antenna can be made to outperform a ferrite rod. In practice, a typical 120mm-long ferrite THE f'IRST STEP in the assembly is to clamp one end of the loop to the PCB using one of the fibreglass clamp plates. RIGHT: THE SECOND CLAMP plate is fitted by first attaching it to the PCB using two screws on one side only. You then bend the loop to form a circle, slide it under the clamp plate and install the remaining two screws. JUNE 1989 11 results in greater selectivity. So if you want to separate out two distant stations, or lift a station out of the noise, a loop antenna is the way to go. How does it compare with longwire antennas? Well, a long wire antenna may pick up more signal than a loop antenna but the signalto-noise ratio on weak signals will be worse due to broadband noise. As well, it doesn't give any increase in selectivity. The Techniloop antenna THE TWO IDC CONNECTORS are pushed into the PCB, forming loops in the cable as shown. Check to ensure that all the connector pins go through the PCB. rod will have about the same signal pickup as a 120mm diameter loop antenna. Given that the signal pickup of a loop antenna is proportional to the square of the diameter, it follows that we don't need a very big loop to outperform even the largest available ferrite rod antennas. The Techniloop antenna described here has a diameter of about 300mm. In simple terms, this means that it will pick up about 6 times as much signal as a typical 120mmlong ferrite rod. A loop antenna also has much better efficiency than a rod antenna at higher frequencies. But the main advantage of a loop antenna is a marked reduction in TUNING VC1 0-470pF I noise pickup. In many cases, the Techniloop PXl will reduce or eliminate interference due to electrical noise or other radio stations. This is because a loop antenna may be tuned to the frequency being received, a technique that also RIGHT: THE TUNING CAPACITOR and output jack socket are fitted to pre-punched holes in the side of the case. S ILICON CHIP .L. .,. PASSIVE LOOP ANTENNA FIG.1: THE TECHNILOOP PX1 is nothing nore than a simple LC tuned circuit. The coil is tapped to allow direct connection to the receiver. TWO SHORT TWIN-PAIR leads are used to connect the PCB to the tuning capacitor and to the output jack socket. 12 TO RECEIVER l1 The Techniloop PXl loop antenna is easy to use. Because it's a passive device, it doesn't require any batteries or other power. In most cases, it can be simply placed alongside the set and tuned to the correct frequency - no direct connections to the radio are required. As shown in the photographs, the loop is attached to a small control box. Inside this box is a small tuning capacitor and this can be adjusted to tune the loop anywhere over the 530-1650kHz AM broadcast band. Fig.1 shows the details - it's nothing more than a simple LC tuned circuit. L1 consists of 16 turns (one turn per layer of cable) and is in parallel with VCl which is a 470pF "polycon" variable capacitor. The two tappings on the loop are connected to a 3mm jack socket on the rear panel to allow direct connection to tuners fitted with external antenna and earth connections. Note that the tappings are only a single turn apart to provide a low impedance output. 3.5mm JACK SOCKET PCB VIEWED FROM COPPER SIDE \ [] TUNING CAPACITOR Building the kit I FIG.2: USE THIS WIRING diagram to connect up the tuning capacitor and output jack socket. The PCB is shown as viewed from the copper side. CHECK CAREFULLY TO ENSURE that you haven't swapped the leads to the tuning capacitor and the output jack socket before fitting the lid of the case. To make up the PXl passive loop antenna, you'll need a kit of parts from Technikit Electronics (see panel). This kit comes complete with all the parts, including a small printed circuit board, a case with a silk-screened panel, a tuning gang and a 16-way flat cable housed in a 30mm-wide strip of a black plastic extrusion. Both ends of the cable are terminated in 16-pin me connectors. (mC stands for "insulation displacement connector"). The loop is formed by clamping both ends of the ea ble to the PC board and then soldering in the me connectors. When this is done, the PC pattern cross-connects the starts and finishes of the cable ends to form one continuous coil. The PC pattern also provides the connections for the tuning capacitor and the tappings to the 3.5mm output jack socket. The construction steps (as shown in the photos) are as follows: (1). Clamp one end of the loop strip to the PCB using one of the fibreglass clamp plates supplied and tighten the nuts firmly. (2). Fit the second fibreglass clamp plate to the other end of the PCB and secure it on one side only using two screws. This done, bend the strip around to form a circle, slide the end under the clamp plate and install the remaining two screws. THE ASSEMBLY IS COMPLETED by laying the loop in the case grooves, then installing the lid and fitting the felt pads supplied over the screw heads. Make sure that the clamp assemblies are tight before attaching the lid. JUNE 1989 13 I TO STATION RECEIVER (VIEWED FROM ABOVE) FERRITE ROD ANTENNA FIG.3: MAXIMUM SIGNAL PICKUP is achieved when the plane of the loop faces in the direction of the station. The radio should be positioned close to the loop. PARTS LIST 1 PCB, code PX1 -7, 102 x 38mm 2 PCB clamps, 38 x 23mm 1 1 6-way cable in plastic cover, terminated with 1 6-way IDC connectors 1 · plastic case, 120 x 65 x 37mm (supplied pre-drilled and silk-screened) 1 0-4 ?0pF variable capacitor 1 knob to suit 1 3. 5mm jack socket 1 3.5mm jack plug 4 felt pads 1 1.5-metre length of 2-way cable 8 3mm x 1 0mm-long screws 8 3mm nuts Note: a full kit of parts for this project is available from Technikit Electronics, 654 Calder Hwy, Keilor, Victoria 3036 . For further details, refer to the price panel. IN SOME CASES, best performance will be obtained with the radio placed right inside the loop. Alw ays tune the radio to the station and align it for best signal pickup before introducing it to the loop. (3). Push the IDC connectors into the PCB, forming loops in the ea ble as shown, and solder the connections . Attach short leads (about 60mm long) to the PCB for connection to the tuning capacitor and output socket (see also Fig.2). (4). Fit the tuning capacitor and 3.5mm jack socket to the case. (5). Introduce the PCB assembly to the case and solder the leads to the tuning gang and jack socket. Fig.2 shows the wiring details (note: Where to buy the kit A kit of parts for this project is available from Technikit Electronics. This kit includes all parts and is supplied with a pre-drilled case and a silkscreened front panel. The 16-way cable is supplied ready-fitted inside its plastic cover and with the ends terminated in IDC connectors. Prices are as follows: Complete kit of parts ... ..... .... ... ..... .. ... ......... .. $39 .50 plus $4 .50 p&p Fully assembled & tested ....... ... .... ... ..... ........ $69 .50 plus $5 .50 p&p Payment may be made by cheque or Bankcard/Mastercard number with mail order, or by Bankcard/Mastercard number for te lephone order. Send your order to: Technikit Electronics, 654 Calder Hwy , Keilor, Victoria 3036. Phone (03) 336 7840 . Note: Techniloop is a trade name of Technikit Electronics. 14 SILICON CHIP PCB shown as viewed from copper side). (6). Install the lid on the case and test the unit by tuning to a weak station. Finally, fit the green felt pads supplied over the screw heads. Using the antenna The " close-coupling" technique is suitable for all radios that have a built-in ferrite rod antenna. You may find that the radio performs best with the Techniloop close to one end or with the radio right inside the loop. A little experimentation will show the best method. Note that the plane of the loop should face in the direction of the station (see Fig.3). Alternatively, the " direct coupling" technique should be used for tuners or receivers that have external antenn2. and earth connections. This simply involves plugging a 2-wire cable into the 3mm jack socket and making the appropriate connections to the tuner. The Techniloop PX1 should be placed away from the radio and tuned and rotated for best reception. In practice, it takes only a few moments to correctly adjust the antenna and most people quickly become adept at using it. ~ 12MHz Zero Wait-State PC 'AT' Computer, Complete on the motherboard! That's right - a complete 12MHz AT (minus video card) built right onto a "baby-sized" motherboard, only 8.5" x 13". Not only do you get superior performance (with a ll memory and disk running at processor speed) , but you save a fortune . Plus the computer is more reliable with no plug in cards to go wrong. Other features include 12MHz zero-wait-state performance - equivalent to 16MHz on most ATs ODISC (dynamic 1/0 speed control) provides superior compatibility with add-on cards OUp to 4MB can be fitted onto the motherboard - no need for memory expansion cards. Uses 256K or 1MB chips. 01\vo serial ports and one parallel port on-board 0 On-board floppy drive and integrated hard disk controller O"Award" BIOS with built-in setup. 7 channel DMA and 16 level interrupts O Realtime clock and ofl~board battery backup provided And for an introductory period, the price is: Box 426 Gladesville 2111 Phone (02 ) 427 4422 Fax (02) 427 2542 • We accept: Ban kca rd, Masterca rd & VISA. mail orders our Specia lty. • All prices include sa les tax only$495 • Note: Products may va ry in a ppearance from those pi ctured. In a ll cases th ey will perform to th e sa me or a better sta ndard . RAM prices: • All products ca rry a ful l 3 month wa rranty lO0nS high speed RAM (1MB chips) ............. $395.00 per 1MB • All card s com e with full documentation • All products ca rry a 14 day mon ey back guara ntee lsof'twa rc accepted I • Rin g fo r qu a ntity di sco un ts a nd tax free prices VINTAGE RADIO By JOHN HILL Collecting & restoring horn speakers· One of the more collectable items as far as vintage radio treasures are concerned would have to be old loudspeakers. This month, we give advice on collecting and restoring these interesting relics. Early radios had separate horn speakers which usually became lost from their respective receivers as time progressed. Occasionally, old radios and old speakers appear in antique shops as separate items but rarely ·do they stay together as a matched pair. As a result, I have half a dozen horn speakers in my collection that have long since lost their original receivers. These speakers have been acquired through a number of sources over a period of time. Horn speakers are comparatively rare and generally speaking, they are now hard to come by. Half of the speakers in my collection have come from antique dealers. Naturally, when buying from dealers, one has to pay top price, for most of these people work on a profit margin of 100% or more. On the other hand, it takes a lot of time and travelling around to locate some of these scarce items and if that time and effort is taken into account, then perhaps dealer prices are not so bad after all. When all is said and done, antique dealers are entitled to make a reasonable profit on the goods that they sell. Most antique dealers have a list of prospective customers who are interested in a multitude of different things. When one collects rare items such as horn speakers and the like, it's a good idea to be on a dealer's list. The dealer is the one with all the contacts and can give his client a call if he finds something interesting. If the client doesn't like what's on offer he is under no obligation to buy. In fact, when one takes everything into account, it must be cheaper to buy from a dealer than to spend countless hours looking for things yourself. Burnt-out windings Unfortunately, not many horn speakers work when you first come across them. They now average out at around 65 years of age and a lot of things can happen to a speaker in that period of time. The usual fault is that they burn out one of the pole piece windings and this must be rewound if the speaker is to work again. Most horn speakers were designed for use with the low-powered battery receivers of the mid-1920s era. When used as they were meant to be used, they gave very little trouble. But if they were used in other circumstances, such as with more powerful mains receivers, these ancient speakers simply could not take the strain and burnt out. Over the years, it would appear that a good many have been given this torture test and have failed miserably. Making it work again Horn speakers have an adjustment which varies the spacing between the pole pieces and the diaphragm. This adjustment affects both the tone and the volume. 16 SILICON CHIP Now some collectors don't care much whether their collection is operative or not. In some cases, if it These parts are all from a dismantled Amplion driver. The body appears to be made of moulded ebonite (hard rubber). Note the pole pieces at left. This English-made Amplion horn speaker is the best performer in the author's collection. Notice the two connecting terminals on the base. Here is a close-up view of the pole pieces. Pole piece rewinding is a very tedious job because the poles require thousands of turns of very fine wire. looks the part then that's all that matters. I'm not like that and everything in my collection is in working order. Mind you, some items work better than others but everything on display is a goer. Therefore, if I buy myself a burnt-out horn speaker, my first job is to get it working again. Dismantling a horn speaker will soon show that it is nothing more than a large headphone with a trumpet attached. All the units that I have seen are based on early headphone technology and consist of two 1000-ohm pole pieces which are bolted to a permanent magnet. The pole pieces are in close proximity to a thin metal diaphram which vibrates in accordance with the signals that pass through the coils. When inspecting the innards of a burnt out horn speaker, you'll invariably find that everything looks to be in good order. There are usually no obvious signs of damage and the only thing wrong is that the fine wire in one of the windings will have a break in it. It's worth noting that in every speaker I have repaired, only one of the windings was open. Checking for open cir- cuits with an ohmmeter will soon locate the faulty winding. The reason only one winding burns out is that the break will occur at the weakest point of the wir.dings when an overload is placP.d on the speaker. This weak spot acts as a fuse and protects the other winding before it has a chance to burn out. It is most unlikely that both windings would blow. To repair the damage, the faulty pole piece coil must be removed and rewound with a similar gauge of wire and in the same direction as the original winding. While the advice in the previous paragraph sounds simple enough, it is quite difficult to wind thousands of turns of fine wire without breaking the wire at some stage of the operation. Such a tedious rewinding job really requires the use of a winding machine of some sort, even if it is a makeshift one using a viceheld hand drill to spin the coil former. But no matter how you go about it, it is a delicate operation and far from easy. My first rewind The first horn speaker pole piece coil I rewound was an absolute JUNE 1989 17 Amp lion horns simply screwed onto the driver. Note the two-start thread not bad for 1925! disgrace to say the least. I used a slightly heavier gauge of wire than in the original and I simply wound it on by hand. As a result, I ended up with at least three joins in the wire because of breakages and a total resistance of about 200 ohms instead of the 1000 ohms of the original winding. However, I decided to see what would happen if this hideous looking hand-wound coil was put into service, so I replaced the coil in the speaker with a one-watt resistor to make up the difference in resistance. The result was a working horn speaker that was every bit as good as other units with two good windings. My next attempt was a much better effort. This time, I used the correct gauge of wire and ended up with a coil resistance of about 900 ohms. The restored speaker has now given hours of trouble-free service. I tried something different with the last horn speaker I repaired. Reflecting on my first miserable rewinding attempt, I suddenly had a great idea! What would happen if the burnt-out coil was ,simply bridg- Although unrestored, this little Brown horn loudspeaker works quite well. A repaint job will restore the speaker to as-new condition. 18 SILICON CHIP ed with a lkO 1W resistor? At the very least, it was worth a try. Just how well the speaker would work on a single pole piece was the question about to be answered. After implementing the simple repair, the old horn burst into life and worked quite well - so well in fact that I don't think I'll ever bother to rewind the offending coil. No doubt such a cheapskate repair will cause many readers to throw up their hands in horror. But before you rap me over the knuckles for suggesting such a dreadful thing, first consider this. Horn speakers are so lacking in tonal quality that there is little pleasure involved in listening to one. They sound harsh and metallic and their frequency range is very limited indeed. Bass is totally nonexistent and 10 minutes of listening is about enough for anyone. They really are awful things to listen to. What I'm getting around to is this: very few collectors would spend much time listening to their horn speakers. They are great for display purposes and it's an added bonus if they work. But no matter what you do to them they will still sound dreadful. If bypassing a burnt-out coil with a resistor gets an old horn speaker working again without additional expense, then such a simple trick must be worthy of consideration. Not all horn speakers look like horn speakers. This particular unit is of German manufacture and is housed in a decorative diecast cabinet. Amplions with a timber flare would be the ultimate collectors' items as far as horn speakers are concerned. (Photo courtesy Orpheus Radio Museum, Ballarat). Horn speaker guises As a matter of interest, not all horn speakers look like horn speakers. Many are disguised in various ways and some are specially shaped to fit into decorative cabinets and boxes. This particular type of horn speaker is ref erred to as an "internal horn speaker". But no matter how dressed up these internal horns may be, one only has to listen to know that it's a horn speaker in disguise. These ancient speakers have a characteristic harsh sound that cannot be mistaken for something else. I have also done other sneaky things to horn speakers, apart from the resistor bypass trick mentioned earlier. One of the speakers in my collection is a mismatch of two different types although not many would be aware of this fact. Only a collector who was fairly familiar with horns would pick it up. This mismatch is a combination of a Brown driver and a very fancy flare of unknown make. Collectively, the two odd parts work as well as any other horn speaker in my collection and it looks particularly good even though it is a hybrid. A lot af antiques are in fairly poor condition and most horn speakers are knocked about and in a rather sad state. I have only one, an Amplion, that was in good original condition. Usually, a 60-70 year old horn speaker has a dented flare, up to 50% of its paintwork is chipped off, and it is burnt out. Inevitably, these battle-scarred old speakers will look better after a panel beat and repaint job. Unfortunately, repainting will often cover up the maker's original name transfer. Brown and Sterling speakers, in particular, fit into this category but often the name has faded so badly it is hardly worth retaining and repainting doesn't cover up anything worthwhile. When repainting an old horn speaker, a semi-gloss surface seems a more appropriate way of finishing them. They lose some of their appeal if they are too bright and shiny. Whether horns or early cone speakers, there curios are excellent collector material and are much sort after. They make interesting displays and attract a lot of attention. However, their sound reproduction is another matter and just a few minutes of listening is enough to make one aware of how much loudspeakers have improved during the past 60 years. ~ ,--------------, I AMATEUR RADIO • Hobbyists communicating world wide using state-of-the-art e·lectronics. I I I I Are you into computers? : Like to access BBS around I the world by radio? I Interested in different forms 1 of digital communication - AMTOR - PACKET? WHY NOT BECOME A RADIO AMATEUR? Want to know more? Join the WIA - the oldest and most experienced radio society in the world - always at the forefront of radio communications for hobbyists. Receive AMATEUR RADIO, the monthly magazine for members of the WIA, full of news of DX, clubs, satellites, technical articles and lots more. Other WIA services include: • A world wide QSL card service • Weekly news broadcasts • Classes for all grades of amateur licences • Correspondence lessons available • Meetings, contests, field days • Representation for radio amateurs at Government level Learn more about the WIA and Amateur Radio Forward this coupon, or write to: WIA EXECUTIVE OFFICE P.O. BOX 300 CAULFIELD SOUTH VICTORIA 3162 I I I I I Registered address: 3/105 Hawthorn Road I Caulfield North, 3161 I Please send a WIA information package to: I I NAME: ............................................................ 1 ADDRESS: ...................................................... : This Sterling "Baby" horn speaker is one of the few in my collection that didn't require rewinding. ........................................................................ I I ................................... POSTCODE ................. I L-------------..1 E001!:a JUNE 1989 19 AA-0250 AA-0380 AA-0382 AC-1960 AS-3004 AS-3030 AS-3036 AS-3301 AM-4206 AV-6500 BS-0416 BS-0420 BS-0456 BS-045B BS-0550 BS-0602 BS-0703 BS-0714 BS-0720 BS-0730 BS-0732 BR-1120 BR-1122 BR-1132 BE-5525 CT-1908 CT-2026 HM-G065 HB-6077 HB-6305 HB-6308 HP-9522 HP-9523 HG-9912 HG -9913 HG-9914 HG-9928 HG-9936 HG-9952 KA-1503 KA-1504 KA-1505 KA-1563 KA-1645 KA-1678 KA-1688 KA-1689 KA-1703 KA-1704 KM-3016 KM-3042 KM-3048 KM-3060 KM-3062 KM-3063 KM-3067 KE-4220 KE-4678 KC-0014 KC-5017 KC-5022 KC-5045 KJ-6520 KS-8104 LT-3005 LT-3015 LT-3150 LT-3166 Stylus Pressure Gauge SOW Jaybrick 100W Jaybrick 1/4' Stereo Tape Ree Head Crystal Earpiece 2.5mm plug 6' x 2' 8 ohm 5W speaker 9' x 6' spkr Grille Magnetic Earpiece 2.5mm plug Mixer, Stereo Equal + Echo Soundtracker Audio Control Mac Program Techniques Book CProg Tech for Mac Book Understanding Microproc Book Understanding Digital Elect Book H/Book Elect Tables & Form Book Micrcicomp for Business Book Crash Course Digital Tech Book Intro to Apple Macintosh Book Fibre Optics Exp & Proj Book How to Read Schematics Book Guide Car Audio Book Amateur Radio & Elect Study Radio & ElectTheory Book Digital Logic Notes Best Wireless Weekly KSNl 135 Motorola Piezo KSN1016 Motorola Piezo Clear Styrene Utility Boxes 4pcs Black box 70x60x50mm 2 Draw Parts Drawer Component Drawer PCB 0/side thin 150 x 75mm PCB 0/side thin 150 x 150mm Bishop 24 OIL Lrg EZ6535 Bishop 28 OIL Lrg EZ6903 Bishop 40 OIL Lrg EZ6906 Bishop Target - Universal Bishop Tape 0.093' EZ3014 Bishop Edge Conn 0.156' pitch EZ6708 Siemens Hall Effect Interface Hall Effect lnterface/T Al kit TAl kit Hall Effect B'less Model R'way Li ght Controller CD Adaptor kit Elect Fence Hi Power kit Elect Stroboscope Experimenters Power Supply Line Filter - 240 volt FM Receiver kit RTTY Encoder kit Speech Synthesiser Current Sense Car Alarm Balanced Line Driver RS-True-232 Interface Vo Sat-Satellite Decoder NiCad Charger 150W MOSFET Amp· ETl499 Car Alarm - ETl340 Sulx:arrier Adaptor 24V to 12V Converter Dual Track Power Supply Poor Mans Plasma Display Fibre Optic Evaluation kit Simple AM Tuner kit 4 way 300 Ohm Splitter FM Band Reject Filter TV Antenna Ghostbuster VHF TV Antenna - Metro Price 50t $9900 $125.00 $2.00 $250 $4.95 $300 $1.25 $49900 $99.95 $29.95 $25.95 $19.95 $19.95 $34.95 $15.95 $24.95 $21.95 $19.95 $19.95 $14.95 $18.95 $18.95 $5.95 $3.95 $14.95 $24.95 $1 00 $3.00 $5.95 $5.95 $2.25 $395 $6.50 $6.50 $6.50 $6.50 $4.95 $6.50 $9.95 $9.95 $44 95 , $21.95 $18.00 $229.00 $13.95 $26.95 $39.95 $55.00 $32.50 $4350 $59.50 $995G $24.95 $55.0 $24.95 $109.50 $59.50 $22.95 $59.00 $99.95 $79.50 $49.95 $12.95 $8.95 $7 .95 $79.00 $3995 SALE PRICE 2~ $59.00 $89.50 50t $1.00 $2.00 $1 00 50t $329.00 $7500 $1200 $12.00 $10.00 $10.00 $17.95 $5.00 $1200 $10.00 $12.95 $11.95 $5.00 $11.95 $11.95 $2.95 $1.00 $9.95 $18.95 40t $1.50 $3.95 $2.95 80t $1.50 $350 $3.50 $3.50 $3.50 $2.95 $3.50 $4.95 $4.95 $29.95 $12.95 $9.95 $99.00 $7.95 $16.95 $22.95 $29.95 $17.50 $2350 $25.00 $4500 $12.50 $25.00 $12.95 $75.00 $37.50 $12.50 $26.50 $7500 $39.50 $26.95 $5.95 $4.95 $4.95 $50.00 $20.00 LT-3176 LA-5085 LA-5090 LA-5095 MF-1072 MM-1600 NA-1014 NP-1100 PS-01 25 PS-0268 PS-0347 PS-0356 PS-0866 PP-0992 PP-0993 PP-0996 PM-2700 PT-3010 PA-3597 PS-4104 Pl-6300 QC-7174 RP-3835 RP-3932 SP-0760 TS-1477 TS-1486 TS-1490 TS-1554 WA-1554 WA-1050 XW-0250 XW-0305 XM-0600 XC-4715 XC-4850 XC-4852 YT-6540 ZL-3326 ZL-3566 ZL-3710 ZL-3762 ZM-3911 ZC-4014 ZC-4501 ZC-4502 ZC -4580 ZC-4581 ZS-5012 ZS-5013 ZS-5078 ZS-5162 ZS-5875 ZS-5895 ZZ-8015 ZZ-8020 ZZ-8025 ZZ-8030 ZZ-8036 ZZ-8045 ZZ-8048 ZZ-8063 ZZ-8072 ZZ-8171 ZZ-8197 ZZ-8198 ZZ-8422 ZZ-8451 ZK-8862 ZK-8868 UHF Antenna Big Mouth Car Alarm Car Flashing Deterrent lgn Kit/Flashing Light - Car PL15/60VA Ferg T/F Audio Transformer Nickel Screening Compound Plasti Dip Liquid Coating 3.5mm Red Mono Lne Skt 6 way RCA Skt 3 Pin DIN Lne Skt 7 Pin DIN Lne Skt 370 Female Right Angle 16 way IDC Econ R/A Header 26 way IDC Econ R/A Header 50 way IDC Econ R/A Header 3 Pin Spk Line P/Skt Spk Term (2 pr) PCB Mnt Adapt. 6.5 stereo Plug/2x3.5 St Skt IEC Mains Lead L/Hand Plug 68 pin IC Skt - Leaded Tl56 Calculator Cassette Player Pot 50k 45mm Dual Slider Pot SB 250k Trigger Switch Bargain Adcola Desolder Tip Adcola Tip 3mm Chisel (CT6 & S30) Adcola Tip 3mm Chisel (CT7 & S50) Chisel Tip suit Micron Pro 20 Gold Lead 2m 2RCA - 2RCA OFC Lead 1m 2RCA - 2RCA Quartz Clock Compass Watch-Crono-Alarm. 30m Brake Lamp Flasher C20 Computer Cassette Mega modem V21. V22 Mega modem V21. V22, V23 STD Block for phones LM326 Dual Track Register NE566 Function generator UA709HC Op Amp Round CA3028 LM3911 Temperature Control 4014 8 Stage Stal Shift Reg 4501 Triple Gate 4502 Strobed Hex Inv 4580 4x4 Multi port Reg 4581 4 Bit Al11 74LS12 Triple 3 IP Nand Gt 74LS13 Dual Nand Schm/Trig 74LS78 Dual JK Flip/Flop 74LS162 BCD DCD CtrSyn Ast 7475 4 bit Latch 7495 4 Bit R/L Shift Reg Z80 AS10 4MHz ZBO AS!Ol 4MHz Z80 ASI02 4MHz Z80 ADMA 4MHz ZBO CTC 1.7MHz 6545-1 CRT Cont 6800 CPU 6845 CRT Controller CDPl822 FD 1771 Floppy Disc Cnt 81 LS97 Octal Buffer/Inv 81 LS98 Octal Buffer 4164 150nS RAM 1702 EPROM 256 x 8 13020 COAM Stereo IC MC14411 Bit Rate Gen Price $59.50 $29.95 $14 95 $3995 $47.50 $4.95 $26.95 $2495 65t $2.00 $1.00 $1.85 $11.95 $350 $3.25 $7.95 $1.50 $395 $4.95 $6.95 $14 95 $3995 $995 $5.50 $2.00 $14 .95 $5.95 $6.95 $6.50 $19.95 $35.95 $5.95 $14.95 $14.95 $1.60 $375.00 $495.00 $34 95 $5.95 $3.45 $1.25 $4.50 $5.50 $175 $1.95 $1.95 $10.50 $4.50 $1.00 soe $1.90 $125 $150 75e $14.95 $12.95 $9.95 $14.95 $2 00 $2950 $4.00 $12 00 $11.50 $39.75 S3.95 $3.90 $7 .95 $2.95 $11.95 $800 SALE PRICE $30.00 $9.95 $995 $22.95 $22.50 $200 $14.95 $14.95 10t 50t 50t 75t $2.00 $1.00 $1.00 $2.50 40t $1.25 $175 $350 $7 95 $29.95 $300 $1 00 20t $8.50 $3.20 $350 $320 $10.50 $20.00 $2.50 $6.50 $6.50 75t $200.00 $275.00 $19.95 $1.00 $1.00 30t $1.50 $2.00 40t 40t 30t $3.95 $2.00 25e 2oe 40t 30t 40t 30t $5 00 $500 $2.00 $5.00 25t $12 50 50e $500 $1.00 $18.50 $1 .20 $120 $200 $1.00 $350 $2.00 AA NiCads $3.50 ea or 4 for $12.50 Don' t waste money, buy rechargeable NiCads, 450mA Quality brand. Cat. S8-2452 4 Way PCB Terminal Block Limited quantity, surplus purchase. Solder direct to PCB and connect wires. NORMALLY $1.75 Cat. HM-3174 4~ ;~ 1 SPECIAL $1 ea HANDS FREE TELEPHONE HEADSET As used with the Sil icon Chip speakerphone project. Headset. microphone with lead and 3.5mm plug. Mini size ultra li ghtweig ht. Cat. AA-2018 $16.95 SPEAKER PHONE Ref Silicon Chip Sept 1988 High quality hands free telephone adapter that works extremeiy well. Fu ll kit incl udi ng box. panel. isolating transformer and all Cat. KC-5040 ONLY $89 1/2 AN RCA LEAD? Well. not quite. These are a stereo lead. (fig 8 shielded) with 2 RCA plugs on one end and tinned stripped leads on the other. Leads with 2 RCA plugs on both ends sell for $4.95 Cat. WA-1040 ONLY $1.95 10+ $1.75 ea ~3~~ ULTRA 171/N S~f/IELDED CABLE Quality English made shielded cable with a total diameter of 1mm. Ideal for screened wiring in small snacest ~ _ -~ Packet of 6 metres Cat. W8-2310 ~-=-~ l ONLY $2.50 , JAYCAR WILL NOT BE UNDERSOLD (on goods of the same quality) Braid PEST REPELLERS De-Solder A specially treated pi ece of braid for removing La.rt C/4al(e~ • Frequency range 30kHz to 65kHz variable • Output level 130dB • Both units include 240V adapters SINGLE TRANSDUCER ONLY $19.50 solder from a PCB . Place the braid over the solder and apply soldering iron to efficiently remove solder. 3mm wide. 5 feet long I Cat NS-3020 $2.50 Another Jaycar surplus stock purchase. UM1082 video modu lator. Operates on 12 volts. RCA jack output. Size 42 x 27 x 16mm. Cat. LM-3486 CJ Ch . + VE VIDEO IN $3.95 10+ $3.50 ea UHF TV TUNER Originally sold for $55 Cat. YS-5510 DUAL TRANSDUCER ONLY $27.50 Video Modulator Contact Connectors Simply wrap around the existing wire and new wire and squeeze. Normally 31 tea Packet of 15 Cat. HP-1207 SPECIAL PRICE $2.95 Sanyo model T1087RA Yet another fabulous scoop purchase. . A compact high quali ty tuner that operates from 526 - 814MHz [corresponding to channels 28 thru 63), and is designed for Austra li an standard reception [AS 1053 1973), and is offered at a very low price. This is a very cheap way to convert a VHF only TV to UHF (some skill may be required). See catalogue for full details. Cat. DM-1000 WAS $29.95 NOW $14.95 30 + 30 WAIT STEREO AMP Packet of 100 Cat. HP-1208 SPECIAL $12.50 MACHINED AIRCRAFT GRADE AL Ul\1INIU1\1 FLASHLI GHT What an excellent product! It measures 145mm long and runs off two AA batteries. It is 70 times bri ghter than a normal torch and the beam is adjustable from spot to beam, and it's wa terproof and shockproof. Durable anodised abrasion resistant finish, with a non slip knurled grip. This torch will last a lifetime. Small enough to fit inside a car glovebox or handbag. It can also be used as a lantern. Unscrew the top and the bulb is exposed to give 360" light. We have seen these torches for $19. We have direct imported them and can offer them for the amazing price of only $9.95. Cat. ST-3000 ro INCLUDING PREAMP! Fully buil t and tested with separate bass, treble, ba lance and volume controls. This superb amp has less than 0.1% distortion. There are inputs for microphone, phono and auxiliary (line) and all power supply components are on board. Just.connect a transformer, speakers and a signal - and away you go i Requires 36-38V AC x 2. Size 186 x 145 x 40(H)mm. , H-J.UU , Cat. AA-0300 Transformer to suit Ca t. MM-2010 $24.95 ONLY $69.95 ONLY $9.95 Sp~ bo l• as-labia Im oo I $150 l~a ~-~021 ' ({ mmfl ~ DIRECT IMPORT Light Duty H OOKUP WIRE ON 25 metre ROLLS OPEN AN ACCOUNT $3.95 per reel Jaycar is quite happy to provide ACCOUNT FACILITIES for the following: • All schools (Government and non Government) • All CAE's , Colleges, Universities, etc • All State and Commonwealth Govt. Depts. including research institutions • All mining companies • All TV and radio stations • All public i.e. "LTD" not "Pty Ltd" companies • All Pty Ltd companies must apply for an account, please ask for an account application form. ::!.-::.:~. lli Quality GOLD RCA PLUGS Now all hobbyists can afford to have a roll of each colour hook-up wire by their workbench. Quality 13/012 tinned hook-up wire on plastic spools. Red Cat WH-3000 Yellow Cat WH-:Jll04 Black Cat WH-3001 Green Cat WH-3005 Brown Cat WH-3002 Blue Cat WH-3008 Orange Cat. WH-3003 White Cat WH-3007 • 8 rolls In all for only $25.95 8 pack - Cat WH-3009 ifI _~ Don't forget Carllngford Store has moved to Parramatta 355 Church Street Phone (02) 683 3377 --· ::c·•·~'.""'r:··-•,,,·~·-~~ Similar to those used on those expensive gold audio leads Clearly marked in red or RED Cat. PP-0236 BLACK Cat. PP-023 $3.50 ea 10+ $3.20 ea SY N TOM - Drum Synthesiser Ref: Silicon Ch ip May 1989 Fantastic drum synthesiser kit that will add real depth to any performance. See the 1989 Jaycar catalogue for full details - Page 15. Cat. KJ-6502 ll $42.50 FM Stereo Transmitter "IVIINI MITTER" Ref: Silicon Chip October 1988 This fantasti c project enables you to transmit a signa l IN STEREO over the FM band. The range is limi ted to about 20 metres or so, so it's not a nu isance to anyone else. It uses a single 1.5V AA [penlight) cell which lasts for ages Just imagine! You can listen to your CO player on your FM headphone receiver whi le washing your car! You can play your Walkman CO player over your car stereo - no wires I The possi bilities are endless. The Jaycar kit of this project includes the hard to get 8A1404 chip and the CORRECT 38kH z crystal even harder to get. Al l other specified parts are included. Cat. KC-5041 ONLY $34.95 BA-1404 Trans IC Cat. ZL-3995 $8.75 - cffaS'!teclNOW $999 _.: . ... _. ,.· · ···.•.•:: ·. .. .. . ·:• '· !"';: • :--: ·,a.,./ 38MHz Mini Crystal Cat. R0-6298 $6.75 CHEAP SPEAKER PROTECTION POLYSWITCHES! ALL VIFA SPEAKER KITS SA130 WAS $1199 SPECIAL IC AND CRYSTAL FOR MINI MITTER KIT AVAILABLE SEPARATELY $6 95 for each speaker box up to 100 watts. Cat. RN-3415 Larger ones available - see catalogue - page 28 ♦ $6.95 Mixud Semiconductor Pack Brand new pack just finished. Guaranteed minimum 100 components supplied but packs generally exceed t amount. hIC's, i transistors, ~s diodes, LED's. RAM, etc. otNLv $10 ~ · ZJ 1/3 Octave Graphic Equaliser FANS Total~ !Vew rl~{flf. cfta/flft1f, au.rllo/e,,{offla/fee - 32 bMrl Two sizes available. Suitable for computers, office machinery, appliances, copying machines, power units, amplifiers, automatic vending machines, air conditioning, medical equipment, etc. FEATURES • long life - 100,000 hours at 25°C, 40,000 hours at 40°C • Operating temperature -20°C to +70°C • Can be mounted on suction side or discharge side• Wiring will not burn out even if the rotating parts are restricted. See 1989 catalogue for more details - page 134. 240V 80mm (3 1/4") FAN Cat YX-2510 In keeping with the professional nature of the product they are mounted in a standard 19', 2 unit configuration and powered directly from the mains. Naturally the Jaycar kit is supplied with all metalwork, including the state-of-the-art LM833 low noise op-amp, specially made slider controls, etc. Ref: Silicon Chip March 1989 $ FOR FULL SPECIFICATIONS SEE THE JAYCAR CATALOGUE - PAGE 6. Cat KC-5050 ONLY . .. ... .,_ ._ - $24.95 10+ $22.95 Cat YX-2514 240V 120mm (5") FAN . ,..._...,,.._ $27.50 f~~~~~~~~;~~~¥~§§§~E~~~~~~~~§5<at>~~f -o • 239 H.,, ,-. -::;;:::-::::--H:::-::::y :::_-;.::-:::;:;;._v;:,--:::;:::;v;:, --= ¥::::::::. 10+ $25.50 • ~ L.lGHTDUTY SPEAKERR.EX Ideally suited for Hi Fi systems, interc oms, etc. One conductor marked so polarity is not reversed. 14 x 0.14mm Cat WH-1702 25~ metre Cat YX-2514 ~-:::,:::.-< ........................ ........... ,.,'"' .,. .. _,.¥<,,..,_ .... _,,.,..,... SOLAR CELLS 0.45 VOLT SOLAR PANELS 2 MODEIS 6 volts <at> 240mA 12 volts <at> 120mA Connect in series or parallel. Two sizes. 0.45V 0.45V 75x45x8mm 96x65x8mm Cat ZM-9005 Cat ZM-9006 $3.95 Quality with aluminium picture framing around the edge. The cells are covered by a clear Measures 3271L)x 165IW)x 18mm thick. 6V 240mA 12V 120mA Cat ZM-9008 Cat ZM-9009 $6.50 10+ $3.75 ea 10+ $6.20 ea :,~· \ ·. ·r:-~-- ·~ ~::. BOTH $79 ea . - ,~' ...·- .-·-- . ~ - -- _;,- ·- .. . , . I :-~;.:-;._:••• r ._. Dear Customers National Linear Data & Applications Set . ~--: Sometimes the products we advertise are so popular they run out within a few days. At other times unforeseen circumstances might hold up shipments so that advertised lines are not in the stores by the time the advert appears. And, very occasionally, an error may slip through our checks and appear in the advert (we're human too). Please don't blame the store managers or staff, they cannot control a dock strike or a lost PCB artwork from a magazi ne to the PCS manufacturer for a new kit, or fix an error that appeared in print If you are about to drive across town to pick up an advertised item, why not play it safe and call the store first - just in case. Thanks. You get National linear Data books Vol 1. 2 & 3 and the ALMOST IMPOSSIBLE TO GET latest printing of National Semiconductor linear Applications. (Pl ease note that linear Applications can't be sold seperately) Cat BN-4000 Personal Datahank/Calculator This personal databank will store your telephone numbers as well as being a pocket calculator. The databank has 2k memory which is, 1,936 characters which will accommodate more than 100 names and telephone numbers. It measures only 88 x 57 x 4mm thick, about the same size as a credit card. It also has a special security code, so those private numbers can't be retrieved by anyone but you. Other features include: • Auto power off • Edit feature • 10 digit calculator • Includes battery We have seen these for as much as $79.95, but with our direct importing we can offer them for about half the price. Cat QM-7200 4 BOOKS FOR ONLY $79.95 $39.95 OMPUTERL EAD BARGAINS\ SAVE 50% on normal price Once again we have purchased a bulk shipment of HIGH QUALITY Philips brand 4-phase Unipolar Stepping Motors! The manufacturer was forced to sell this stock FAR BELOW his cost and we can pass these massive savings on to you I The motor, Philips #9904 112 06001 is a high performance bidirectional unit featuring a 7°30' step 148 steps per rev) with 40mNm max working torque. Full data is provided. INCLUDED IN THE COST is a Sprague UCN4202 4-phase stepper motor driver chip. This will drive the motor directly from logic and a nominal 12V supply. Once again full data on the chip is included. The current WHOLESALE cost of the motor ONLY from Philips is over $75 +20% sales tax i.e. around $90 You can purchase the motor and driver IC in 1-off from us for this month only $59' That makes the stepper under $50! limited Quantity Cat YM-2700 Stepper Motor and UCN 4202 chip UCN chip available separately $10 (Cat ZK-8842) Philips SM 1027 4-phase driver IC (designed especially for the motor) Cat ZK-8843 $15. Data included with SM 1027. JUNE ONLY SAVE • 25D Male to 25D Male Normally $19.95 1.Bmt Cat. Pl-0056 JUNE ONLY $9.95 • 25D Male to 250 Female Normally $19.95 JUNE ONLY $9.95 • Centronics Plug to 25D Male Normally St8.95 JUNE ONLY $9.95 $SS SAVE $10.00 1.8mt Cat. PL-0055 SAVE $10.00 1.8mt Cat. PL-0054 SAVE $9.00 ~ 10% OFF THIS PRICE PCB TERMINAL STRIP BARGAIN . -. -.. . These are high quality 10 way thermoplastic PCB terminal strip As used extensively in the alarm industry. Units are supplied unassembled i.e. you have to screw the screws in These are normally $4.95 Cat Price Cat HM-3205 • 1 ., .. . • , • _ _ "------------_) $2. 95 ea ' This Month Pkt 10 for only $10 ~ - : : I I I I I I I I I I I I • : , . - _____ , • _ _ •• - .' - _,, JAYCAR FOR QUALITY KITS KA-11 09 Electric Fence KA-1115 300W amp module KA-11 16 300W power supply KA- 1117 300W speaker protector KA-1119 Transistor tester KA-1220 Signal tracer KA-1230 Zener diode tester KA-1 390 Freq. counter 50MHz KA-1 392 Prescaler 500MHz KA- 1428 Function generator KA-1 430 Vocal cancel ler KA- 1452 Subvvoofer Amp KA- 1505 TAl Hall effect KA-1 506 Transistor asst ignition KA-1508 Touch light dimmer KA-1522 Gu itar effects 8BD KA-1535 Ignition killer KA- 1550 Deluxe car alarm KA- 1556 Ultra sonic move det. KA- 1574 30V 1Apowersupply KA- 1582 House alarm KA- 1595 Digital capaci tance meter KA-1598 40W inverter 12/230V KA- 1610 300W inverter 12/230V KA-1630 12V lamp flasher KA-1635 AM/FM stereo tuner KA-1636 AM/FM remote control KA-1650 Playmaster 60/60 KA-1652 Blueprint 60/60 KA- 1660 Electric fence KA- 1675 Screecher car alarm KA-1 677 Audio oscill ator (metered) KA-168 1 3 ba nd short wave radio $23.50 $119.95 $105.00 $23.50 $21.50 $27.95 $16.95 $169.50 $46.50 $129.50 $24.95 $134.50 $44.95 $4250 $29.95 $115.00 $23.50 $89.50 $3495 $89.50 $169.00 $85.00 $99.95 $269.00 $12.95 $599.00 $99.50 $329.00 $369.00 $59.50 $34.95 $165.00 $79.50 KA-1682 Dual track power supply KA-1683 Battery monitor KA-1690 DI box KA-1691 TV colour bar/pattern gen KA-1 692 Voice operated relay KA-1693 Metronome KA-1 694 Volt/continuity test KA-1 695 AC/DC Millivoltmeter KA-.1696 Econ. Temp probe □ MM KA-1697 Utility timer KA-1698 Tran. FET. Zener test KA-1699 Bench amp- signal trace KA-1 700 Power transis tor tester KA-1701 RF detector probe KA-1702 50MHz Dig Freq meter KA-1704 FM Receiver KA-1705 Stroboscopic Tuner KA-1706 Chea p capacitance meter KA- 1707 Powermate 2 KA- 1708 Supertimer KA-1 709 PC-driven Function Gen KA- 1710 Beepo Conti nui ty Tester KA-17 11 TTL-analog Video Convert KA- 1712 PCB Shorts Locator KA-17 14 Beat Me Metronome KA-1715 Car Brake Lamp Monitor KA- 1716 Auto Tune-up Adaptor KA-17 17 ·Subvvoofer Adaptor KM-30 15 Listening post KM-3030 Ultrafidelity preamp KM-3040 Dual speed modem KM-3042 Speech syn thesiser KM-3044 6000 Mosfet Module $129.95 $14.95 $39.95 $159.00 $24.95 $19.95 $29.95 $46.50 $19.95 $21.95 $55.00 $39.95 $22.95 $13.50 $79.00 $55.00 $47.50 $16.95 $119.00 $59.00 $49.95 $19.95 $49.95 $22.95 $29.95 $24.95 $29.95 $29.95 $39.95 $359.00 $169.00 $43.50 $1 19.00 KM-3046 Su~r Simple Modem KM-3050 Workhorse amp KM-3056 100W module less MFets KM-3061 Microphone preamp KM-3063 Uc satellite decoder KM-3064 Octave EO mod KM-3065 AS true 232 interface KM-3068 FM minder bug KE-4014 Mixer prea mp KE-4023 Signal Spkr protector KE-4029 NiCad battery charger KE-4033 Temperature probe KE-4050 ETl480 SOW amp module KE-4052 ETl480 1DOW amp mod KE-4048 ETl480 power supply KE-4200 5000 power amp KE-4666 RS232 Centronics inter/f KE-4690 ETl342 CDI KE-4698 4 sector house alarm KE-4711 Mini FM transm itter KE-4722 RS232 Commodore KE-4724 Parametric equaliser KE-4725 Solder iron temp control KE-4729 Guitar preamp KE-4730 Solar gen p/supply KE-4731 Telephone Intercom KE-4733 Ac tive Crossover KC-5010 Capacitance meter KC-5012 Car radio power supply KC-5013 1GHz Digi Freq meter KC-5015 Telephone ringer KC-501 6 Speed control/dimmer $85.00 $35.00 $79.50 $36.95 $55.00 $59.95 $27.95 $11.95 $39.50 $22.50 $14.95 $32.95 $27.50 $34.50 $29.50 $499.00 $32.50 $79.50 $2995 $9. 95 $16.95 $23.50 $39.50 $45.00 $12.95 $49.95 $39.95 $27.95 $28.95 $299.00 $19.95 $18.95 KC-5017 KC-5019 KC-5021 KC-5023 KC-5027 KC-5028 KC-5029 KC-5030 KC-5031 KC-5032 KC-5033 KC-5034 KC-5036 KC-5037 KC-5038 KC-5039 KC-5040 KC-5041 KC-5042 KC-5043 KC-5044 KC-5045 KC-5046 KC-5047 KC-5050 KJ-6502 KJ-6504 KJ-6505 KJ-6535 KJ-7000 24 to 12V converter 100Wamp module Protector car alarm Low ohms adapt □ MM Ph meter Train controller CD H/phone amp High Energy Ignition Optical tacho Disco Light Studio 200 Preamp Remote for Car Alarm Wireless doorbell TX Wireless doorbell RX Universal power supply Vader Voice Speaker phone Mini Mitter Kn ightrider LEDs 120W PA/Guitar amp Car Safety Lights Poor Mans Plasma Mains Muzzler Beta Tester 1/3 Graphic Equaliser Syntom drum synth 8 channel mixer Console Psupply above 2010 10 band stereo Eq. Red light flasher $5900 $38.95 $79.50 $29.95 $49.95 $89.00 $24.95 $49.95 $49.95 $159.50 $22900 $79.50 $16.95 $42.50 $12.95 $19.95 $89.00 $34.95 $17.95 $72.50 $29.95 $49.50 $55.00 $18.95 $239.00 $4250 $595.00 $119.00 $169.00 $19.95 /vft.et"e /et"/tJ1'itWfee, it lf(etl.faJ'-edtir l"e.fa.ft.f NEW KIT FOK JUNE 5000 POWER AMP - RebtJ/l'lf TOUCH LAMP DIMMER Ref: Silicon Chip June 1989 So new; in fact. we don't have many details on it Uses brand new Siemens chip which will hold the light level Cat KC-4200 Let's face it - if you want the best fromyour Hi Fi system and speakers you need the best cable - and Jaycar has itl Figure 8 259 strand per side - 0.003 ohms per foot and an inductance of 0.23uH per foot! With these specs you can hear lhe difference. Cat WB-1732 i~i~;;H~. KNOB PACK $4.20 per metre ·... .- Another Jaycar Surplus Deal. . We have a quantity of Japanese Sato brand knobs. some lovely alumin ium. some black and alu minium and some are just black. 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Cat KJ-6504 $595 i Illustrated with optional side panels 1~ T~ ,' &~~~' • • - ;~I ~ , HEAD OFFICE MAIL ORDERS 115 Parramatta Road Concord 2137 PO Box 185 Concord 2137 HOTLINE (02) 7471888 l 9 : Telephone (02) 747 2022 $25 $49.99 $ 4.50 Telex 72293 FOR ORDERS ONLY $50 $99.99 $ 6.50 10 0 10 00 0 ~FA:..:.:.C=S~IM~l=LE=--..!(~0~2)~7~4~4~U~7~6_7_ _ _ _T_O_L_L_F_R_E_E_~(0_ 08~)_ 02_2_8_88_ _ _v_E_R $_ _ _ _ _ s__ _ _~ MAIL ORDER VIA YOUR 'Z:r ROAD FREIGHT ANYWHERE IN AUSTRALIA $13 .50 L__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____, SYDNEY - CITY 117 York St. (02) 267 1614 · Mon-Fri 8.30 • 5.30 Thurs 8.30 pm - Sal 9 · 12 PARRAMATTA 355 Church St 1Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 9 . 5.30 Thurs 8.30 pm · Sat 9 · 4pm 115 Parramatta Rd (02) 745 3077 · [ · · ' CONCORD Mon-Fri 8.30. 5.30. Sat 8.30 · 12 'MasterCard. 121 Forest Rd (02) 570 7000 · HURSTVILLE Mon-Fri 9. 5.30 Thurs 8.30 pm · Sat 9 12 VISA :~l~ rn POST & PACKING ~~o 188 Pacific Hwy (Cnr . 8ellevueAve) (02) 439 4799 Mon-Fri 9 -5.30 Sat 9 -4pm 144 Logan Rd (07) 393 0777 BURANDA QLD Mon-Fri 9 - 5.30 Thurs 8.30. Sat 9 - 12 MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 . 5.30 Fri 8.30 - Sat 9 - 12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 -Sat 9 - 2 GORE.HILL THE WAY I SEE IT By NEVILLE WILLIAMS Back to the stone age: down with audio, radio & AC mains! If we were to overreact to the contents of an ostensibly learned paper passed on to me during the month, we might he tempted to re-think our reliance on coherent man-made electromagnetic energy of any kind and any frequency. We'd most certainly question assurances that everyday electrical/electronic activities are environmentally innocuous. Just before examining the abovementioned paper, it may be appropriate ·to acknowledge sundry other observations that have come my way since I first raised the subject of questionable electricallybased therapeutics. For the most part, they've been along the line: did you happen to see or hear about this, that or the other? Some of them had nothing to do with electricity or electronics and these I set aside, as outside my area of expertise and inappropriate for these pages, anyway. On second thoughts, I'll mention just one, brought to my notice by a lady whose husband is a regular reader of SILICON CHIP. At the request of an aging relative, she'd called in to a health food shop to buy some pills and potions. When she mentioned that they were for an elderly lady, the whitecoated attendant inquired about the latter's mental state. Assured that there was no problem, he went on.to say that they had just put into stock a new medication for treating Alzheimer's disease - the tragic loss of mental function that affects 24 SrLICO N CHIP more than one in 20 aging people. The lady wasn't impressed; nor was I. Alzheimer's disease is currently the subject of intensive research in developed countries where, within 10-20 years, it could well become the No.1 social problem in their gradually aging populations. It requires more credulity than I can muster to accept that a cure is already sitting right there on the shelf of a suburban health food shop! Crystals and whatnots But getting back to electricity and electronics, there's the matter of crystals and the extraordinary therapeutic powers attributed to them. Did I see the incident on television, some weeks ago, when a crystal was used in an apparently vain effort to save a child's life? Did I see the item in the "Sydney Morning Herald" about the professional numerologist who wears a crystal on his forehead to aid concentration when he is "discerning" Lotto numbers? Have I noticed their repeated promotion on talk shows? The answer is yes, yes and yes again, all of them making me shake my head at this outright quackery. Indeed, after putting the aforesaid numerologist's discernment to the test with hard cash, Harry Edwards, national secretary of Australian Sceptics, found good reason to be more sceptical than ever! As far as I'm concerned, crystals may look cute in certain situations and may provide the basis for a bewildering array of electronic devices but as for mystical, magical or supernatural qualities, no way! Oh yes. And did I know that a certain practitioner in a certain Sydney suburb has an impressive array of electronic instruments in his consulting rooms? No I didn't but my informant may well have chosen exactly the right adjective! Which brings me to a booklet produced by K. J. of Nelly Bay, Qld, and posted to me "with compliments" via the SILICON CHIP office. Titled: How Nature "Cures", it was endorsed "See Part 4". In it K. J. is highly critical of what he classifies as "empty boxes". Included in this group are cylinders, pyramids, pendulums and "nonsense therapy" gadgets, plus an assortment of electrical and electronic devices which may as well be empty boxes for all the good they do! However, lest I draw too much encouragement from his remarks he also rejects most other direct "healing modalities,., including conventional and homeopathic medicine, herbalism, biochemic This high-voltage transmission line passes through the north-western Sydney suburb of Carlingford. To date, there has not been a shred of evidence to suggest that such installations pose a biological hazard to anyone. salts, mineral spas and saunas, vitamins and food supplements, acupuncture, faith healing and so With the "sundry other observations" duly dealt with, we can revert to the matter referred to at the outset: the allegedly disturbing effects of electromagnetic radiation on at least some members of the community. It was raised in a letter from a reader in Carlton, NSW. I quote: and I would like to bring something to your notice. Last year, I became aware that homeopaths prescribe the taking of drops of water which has, as they say, been energised with the signature of the energy pattern contained in other therapeutic substances. The "signature", I understand, can be imparted in a few minutes in a machine which subjects it to particular electromagnetic fields. At first I treated this with great disbelief but more recently I came across an article, as enclosed, which I thought may interest you. Can you offer any more enlightenment on the subject? Incidentally, I have enjoyed SILICON CHIP from its first issue. Keep up the good work. R. M. (Carlton, NSW). Dear Mr vVilliams, Recently, in "The Way I See It", you raised the subject of the therapeutic qualities of electricity Being fairly busy at the time, I merely scanned through the enclosed 10-page article to see what it was all about. The immediate im- on. His basic philosophy is that only the body can restore itself and the proper way to "cure" disease is to remove all impediments and provide the right biological environment in which nature's own healing processes can operate. If only that was all there was to it! Electromagnetic radiation pact was a sense of incredulity which persisted when I later went through it more carefully. Prepared by Ray V. S. Choy MB BS, Jean A. Monroe MB BS and Cyril W. Smith PhD, it had all the appearance of a paper delivered to and published on behalf of a learned society: accreditation, abstract, keywords, introduction, section headings, discussion, conclusion, appendix and references. A logo on each page and the words "Clinical Ecology" suggested that as the probable title of the original publication. Identified only as Volume IV Number 3, the most recent of the listed references is another presentation by the same authors dated 1985. Seeking further information, I rang R. M. but he wasn't able to help. Photostat copies of the paper had been handed out at a meeting attended by a friend. Puzzled, the friend had shown it to R. M. who he knew to be interested in elec]UNE 1989 25 THE WAY I SEE IT - CTD tronics. Equally puzzled, R. M. had posted it on to me. The paper is entitled "Electrical Sensitivities in Allergy Patients". Abbreviated to conserve space, the accreditation of the joint authors is as follows: • Dr Ray Choy is Assistant Medical Director of the Allergy and Environmental Medicine Unit at the Lister Hospital, London; and of the Allergy and Environmental Medicine Clinic (The Sunbury Hill Clinic Ltd) Hemel Hempstead, Hertfordshire, UK. • Dr Jean A. Monro is Medical Director of the above groups. • Dr Cyril W. Smith is a Senior Lecturer, Department of Electronic and Electrical Engineering, University of Salford, UK. He has been investigating the subjective effects of electromagnetic fields for 12 years, in cooperation with Professor H. Frohlich FRS of the University of Liverpool. What's it all about? The broad thrust of the paper is summarised in the Abstract, which I quote in full: Some patients with multiple allergies complain of extreme sensitivities to atmospheric electrical conditions and to many man-made electrical, magnetic and electronic devices and systems. Experiments confirm that there are real and objective effects as well as subjective effects. The sensitivities are frequency specific rather than intensity specific. They have been observed as patient's specific frequencies from millihertz to Gigahertz and, in the most sensitive patients, at field strengths approaching the theoretical noise level limit, even in the presence of much stronger fields at other frequencies. A protocol for clinical testing has been devised based on the confrontation neutralisation technique used for chemical allergens. Neutralising frequencies can usually be found and magnetic fields at these frequencies can be used to "potentise" water for therapeutic purposes. In a given patient, the symptoms provoked electrically are similar to those provoked chemically and those provoked by the patient's environment. Electrical and chemical stimuli and neutralisation appear to be interchangeable. You're allowed to re-read the above if you didn't get the drift of it the first time through! But read on, anyway. Early in the paper, the reader is reminded of the allergic reactions that some people have to certain foods or other substances to which they may be exposed. The authors refer briefly to skin surface and intradermal tests to determine a subject's sensitivity to potential allergens, and the appropriate treatment. They emphasise the minute quantities - or high dilutions - of allergens often used in such tests. While an expert may have reason to quibble, it sounded routine enough to this medical layman. However, the reference to chemical allergens serves mainly as a back-drop to the real substance of the paper. Let me summarise the basic philosophy: Man has evolved, say the auth!lrs, in an environment which is flooded with all manner of natural electromagnetic radiations. The body itself depends on cellular and intercellular changes in electrical functions and may well use certain coherent oscillations for its own control purposes. But during the past century, various forms of highly coherent electromagnetic radiations (precise in frequency and phase) have been introduced into the environment. These may well interfere with a living system to produce abnormal reactions. I quote: "The abnormal reactions due to a (man-made) electromagnetic field stimulus are consistent with their being described as an allergicresponse in the widest usage of the term". By way of enlargement: "This paper postulates and documents that another situation also exists: namely that external electrical stimuli can initiate changes in the body's general homeostasis, including electrical. Homeostasis represents the 'normal' state of the body - in the allergic state this is perturbed and patients may become abnormally sensitive (hypersensitive) to electrical stimuli. Many of our patients give a history of hypersensitivity to a wide range of electromagnetic fields and devices in addition to their other allergic sensitivities''. The authors claim that undesirable "allergic" reactions to some frequencies can be "challenged" and neutralised by other frequencies, either by direct exposure to them or by intradermal injection of droplets of "potentised" water which carry the appropriate energy "signature", as mentioned in the abstract. Does it make sense? Setting aside, for the present, the business of potentised water, the basic proposition sounds feasible enough. Homo sapiens most certainly relies heavily on electro-chemical body functions and has had a long time to adapt to natural electromagnetic radiation and rhythms. It is also true that, over the past century, our immediate elec- During the past century, various forms of highly coherent electromagnetic radiations have been introduced into the environment. These may well interfere with a living system. 26 SILICON CHIP tromagnetic environment has been invaded by countless man-made radiations, coherent and otherwise. It is therefore not unreasonable to postulate that: • Some or many of these manmade radiations could conceivably affect the normal functioning of our bodies - our so-called "homeostasis"; • And that some people at least are unusually sensitive to particular types of radiation - as allergy sufferers are to certain substances. This does, however, tend to conflict with conventional wisdom, which holds that ordinary, everyday radiation from AC power wiring, broadcast and communications services, radar and correctly operating electronic appliances poses no measurable biological threat - presumably to anyone. In situations where people may be exposed to unusually intense electric or magnetic radiation, standards and work practices are in place which should anticipate and obviate possible harmful effects (see references to the subject in the September 1988 and January 1989 issues). What we have in the present paper is a postulation that a certain percentage of the population is hypersensitive to man-made (usually coherent) electromagnetic radiation. Furthermore, that this "allergic" reaction is not predominantly a function of field intensity but has more to do with frequency, ranging all the way from millihertz to Gigahertz. While it would be presumptuous of me to get too involved in the biological/medical aspects of the a hove proposition, it is not unreasonable for readers of SILICON CHIP to look critically at the electronic methodology on which it is based. It was in this area where some of my early reservations had their origin. I've never met millihertz! Prominent in the abstract is the term "millihertz", presumably relating to frequency phenomena so low that the repetition rate is more conveniently specified in thousandths of a cycle per second: one A "phoney" cure for baldness? According to "The Australasian Wireless Review", April 1923, the Hounslow (England) Wireless Society grabbed international attention when it solemnly declared that baldness could virtually be eliminated if everyone continued to use headphones - ignoring the growing popularity of loudspeakers. The vital difference is that the electrical waves in the headsets stimulate the scalp. Clear evidence of this is provided by the luxuriant growth of hair that characterises radio operators who wear headphones for long periods. The Hounslow Wireless Society seemed to have overlooked the fact that, in the early 1920s, most radio operators were young men, fresh out of Marconi School! millihertz would be equivalent to one thousandth part of a cycle in 1 second, or 1 cycle in 1000 seconds or 0.278 hours. Many readers may not have heard of the term "millihertz" but that doesn't mean that such a frequency can't exist. In fact, the paper lists, as one of the instruments used, a Farnell Synthesised Generator, model DSGl, with a frequency coverage from 10- 4Hz to 10 + 5. In short, a range extending from O.1 millihertz [one cycle in 2.78 hours) to lOOkHz . This is confirmed by a reference in the paper to patient S. L. who is said to have shown reactions over a frequency spectrum extending from the millihertz '' 1 cycle in 2 ¾ hours" range to the 2GHz range (of another genera tor). I must say that my mind boggles at the idea of a 1-metre "aerial" (see later reference) connected to such a generator, which could put out a few volts at most, radiating a significant electric/magnetic field as the voltage upon it changes or increments almost imperceptibly through one cycle over protracted periods of up to 2 ¾ hours. I boggle also at the notion of a subject being sufficiently relaxed for long enough periods to react either adversely or helpfully to what, over much of the millihertz range, would have to be mere segments of a single cycle; segments short enough to differ little from a sample of slowly varying (incrementing?) DC. It is of little wonder that the authors remark: "It is difficult to assess the response of patients at . sub-hertz frequencies and this is still a research exercise". No less to the point, sub-hertz phenomena have negligible relevance to everyday man-made electronic activity - even if they could be initiated in other ways. Maybe my maternal greatgrandmother enjoyed her oldfashioned rocking chair because she was unknowingly oscillating through the Earth's magnetic field at a fortuitous 333mHz (once every 3 seconds). Maybe generations of ocean travellers have suffered mal de mer because the ship has been rolling and yawing in the Earth's magnetic field at a still lower and less agreeable frequency! Signal purity? But there's another disturbing thought. I know nothing of the Farnell Synthesised Genera tor DSGl but the coverage and the name suggest that the output frequency is not generated directly but is derived (divided down?) from a much higher frequency source. Having in mind that (according to the paper) there is no physical connection to the patient and that the field strength of the test signal is well down in the noise, one cannot help but wonder what other frequency components of comparable strength may be leaking from the instrument in any one of a number of ways. The dial(s) may indicate "x" millihertz but could the subject be reacting to one or more components of a much higher order? The authors' remark about millihertz observations being "still a research effort" prompts the devil's advocate in me to suggest that a similar remark might be applicable to other aspects of their " protocol" - at least as conveyed by the paper. JU NE 1989 27 r R. F. DEVICES PTY. LTD. 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F. DEVICES PTY. LTD. SUITE 1A, 9 LYN PARADE, LURNEA, NSW 2170. X 1X 55 75 100 10 X 16 18 20 4½ DIGITS 0 OHM ADJ USTM ENT • TRANSISTOR TEST • • COUNTER QUARTZ CLOCK $169.94 same as Scope 1x 1 X / 10 X 1 X / 10 X 1 x/10x C (pF) • • 1X 10 X Ix 10 15 10 5 100 80 60 35 50 70 3 5 7 TOLL FREE: (008) 02 367 4 TELEPHONE: (02) 607 8811 FACSIMILE: (02) 607 3763 TELEX: 127948 * ALL PRICES INCLUDE SALES TAX. * ENQUIRE ABOUT OTHER QUALITY TEST EQUIPMENT. X * DISTRIBUTORS REQUIRED IN OTHER STATES. VISA Diners Club /111ema1io11al ' THE WAY I SEE IT - CTD It would seem that the total fields being created by the signal generators were not - or could not be - objectively or continuously monitored in relation to intensity or purity, or even their effective existence verified in the context of the electrical noise level. The field strength relative to the subjects appears to have been varied quite arbitrarily by relying on radiation from the 2cm long output connector, or by connecting to it a 1-metre length of wire trailing on the floor; or by the use of a small loop on the end of the ea ble in the case of a microwave generator; or by moving particular generators into a separate room 30m away, or onto a separate floor. The tests proceeded essentially on the basis of subject reaction as the frequency spectrum was progressively examined from lHz upwards. As indicated from the title and abstract, the subjects selected for detailed examination were confirmed allergy sufferers who had also complained of allergic reactions to electromagnetic radiation of various kinds. In certain cases, their apparent sensitivity threshold was well below the electromagnetic ambient from other sources - eg, less than an (estimated?) microwatt per square centimetre. electrically sensitive patients within perhaps 100 metres of the testing room .. . unless they are supervised and it is known that they can be readily neutralised" (turned off?). If that statement is to be accepted at face value, it's time we stopped arguing about mental telepathy and set about finding an environment and building a receiver that can sense the presumably electromagnetic radiations that had to be allowed for by Messrs Choy, Monro and Smith. You might also like to think about the "potentised" water mentioned in the abstract and R. M.'s letter. In what way is water modified - for up to several weeks - when it is exposed to coherent electromagnetic energy? I mean variously modified, according to the frequencies involved, so that it can, by injection or dosage, counteract hypersensitivity to other specific frequencies, or to ordinary chemical allergens. I quote: "We have challenged chemically - neutralised chemically, challenged electrically - neutralised chemically, challenged chemically Human transmitters? If you have the urge to debate any of the above, there's more to follow: According to the authors, it proved advisable to store microwave signal generators elsewhere until needed for the tests, because the passive microwave resonant cavity appeared to trigger an allergic reaction in those patients who exhibited extreme sensitivities in the microwave region. I quote: "This implies that such patients may emit radiation and hence there may also be mutual interactions between the patients, in which case they must be tested singly". And again, during the taking of case histories: · 'There should not be any other In most suburbs you can see power poles with 33kV or higher voltage lines plus the occasional pole transformer. Again, there is nothing to suggest that these are a biological hazard. neutralised electrically and challenged electrically - neutralised electrically". The authors offer certain tentative explanations and also include clinical information about a group of subject patients (3 men and 16 women) which medically qualified readers may care to study in greater detail - if you can locate a copy of the paper. In brief, the complaints extend from fatigue, depression, headaches, rhinitis, asthma and eczema, through hyperactivity and tinnitus to paroxysmal tachycardia (sudden rapid heartbeats) and colitis complaints which are often sai<l tc have emotional connotations. The most frequently blamed electrical "allergen" source is, by far, overhead high voltage transmission cables, which also happen to be the most "visible " of all electrical devices (see SILICON CHIP, January 1989, p.65}. Electrical appliances are also represented, with one woman unable to tolerate meats cooked in an electric oven. Electric typewriters, video terminals, computers and word processors receive unfavourable mention. It so happens that these same devices are often nominated by people who feel intimidated by them. Fluorescent lights, television sets and computer games are also listed as electrical allergens but no mention is made of the possibility of visual stimulation due to the flicker rate or, in the case of video equipment, the (barely) supersonic aural energy from the scanning circuits. Curiously, no one complains about tape recorders, even though they all contain a bias/erase oscillator operating in the 50-lO0kHz region. Nor for that matter, do they complain about the 19kHz subcarrier used in stereo FM broadcasts. To me, there is so much scope for "suggestibility" in all this that the postulation by Messrs Choy, Monro and Smith is best regarded as interesting and provocative, while requiring much more rigid examination with adequate checks and controls. One other point: of the 19 subjects listed, one professed to became aphonic (complete loss of continued on page 91 JU N E 1989 29 KEYBOARDS IBM PC/XT/AT COMPATIBLE KEYBOARD MOTHERBOARDS IBM PC/XT COMPATIBLE TURBO 10MHZ MOTHERBOARD -Expandable to 640K RAM using 4164, 41256 & 41464120ns chips -4.77 or 1OMHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Eight expansion bus slots -AMI BOIS ROMs included -8087-1 Math co-processor capability -Performs_at an average speed of 100% faster than the original IBM PC/XT -Norton SI rating of 2.0 -Size (12' x 8.5') -Weight (1.75Ibs) $149 IBM PC/XT TURBO 8MHZ MOTHERBOARD -Expandable to 640K RAM using 4164 and 41256, 150ns chips -4.77 or 8MHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Eight expansion bus slots -AMI BIOS ROMs included -8087-2 Math co-processor capability -Performs at an average speed of 75% faster than the original IBM PC/XT -Norton SI rating of 1.7 -Size (12" x 8.5") -Weight 1.75Ibs $139 IBM AT COMPATIBLE 12MHZ 80286 MOTHERBOARD -Expandable to 1MB RAM using 256K DRAM chips -Expandable to 4MB RAM using 1MB DRAM chips -Expandable to 2.5MB RAM using a combination of 256K and 1MB DRAM chips -8 or 12MHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Six 16-bit and two 8-bit expansion bus slots -AMI BIOS ROMs included -Zero wait state -Selectable RAM chips speed (80 or 100 nanosecond) -80287-8 Math co-processor capability -Norton SI rating of 13.7 -Size (13" c 8.75") -Weight (2.25Ibs) $499 NEAT---MOTHERBOARD $795 -Norton SI ratin of 15.6 -101 Key -Enhanced keyboard layout -Tactile touch keyswitches -12 Function keys -lluminated LED indicators for Num Lock, Caps Lock and Scroll Lock -Separate cursor pad -Low profile design -Automatically switches between PC/XT or AT -Manual included -Co lour beige (19"w x 8'd x 1.33"h) -Size -Weight (4.6Ibs) $109 84KEY $99 CASES 8088 BABY8088 BABY80286 GRAPHICS CARDS MONO PC/XT/AT $109 CGA $115 EGA $299 $99 $129 $129 POWER SUPPLIES IBM AT COMPATIBLE 200W POWER SUPPLY -Input <at>47 -400Hz (110/240V switchable) -Output +5v<at>20A, -5V<at> 0.5A, +12v<at>8A, -12v<at> 0.5A -Plug compatible connectors -Built in fan -Spee included POWER -Size (6.5"1 x 5.SS"w x 6"hl $199 POWER SUPPLY 150W $125 -Weight (6Ibs) SUPPLY 150WBABY -Size 6.25' x 6" x 6' $145 CONTROLLER CARDS 360KBll20KB/1.2MB/1.44MB FLOPPY DISK DRIVE CONTROLLER CARD FOR IBM PC/XT/AT AND COMPATIBLE COMPUTERS ~~-,. FLOPPY DISK DRIVE CONTROLLER CARD FOR IBM PC/XT AND . -Allows connection of one or two 360KB, 720KB, 1.2MB or 1.33MB floppy disk drives. Includes cable for two internal disk COMPATIBLE COMPUTERS -Run up to four 360KB disk drives -Includes cable for two internal drives -DC37S connector allows for an additional two external drives (external cable not included) -complete with manual $55 MFM HARD DISK CONTROLLER CARDS FOR IBM PC/XT/AT AND COMPATIBLE COMPUTERS -8 bit MFM hard disk controller card for the 1MB PC/XT and compatible computers. Can be used with many types of hard disk drives. Cables and documentation included. · $139 HARD DISK/FLOPPY CONTROLLER FOR IBM PC/XT AND COMPATIBLE COMPUTERS - 8 bit floppy and MFM hard disk controller for the IBM PC/XT and compatible computers . It will allow connection of up to two hard disks and two floppy 360KB drives. Cables are included to allow connection of one hard disk and two floppy disk drives. To connect a second hard disk drive an additional cable will be required. $175 HARD DISK/FLOPPY CONTROLLER FOR IBM AT AND COMPATIBLE COMPUTERS -16 bit floppy and MFM hard disk co ntroller for the IBM AT and compatible computers. It will allow connection of up to two hard disk drives and any combination of two floppy disk drives . To connect a second hard disk drive an additional cable will be required. $245 MFM HARD DISK CONTROLLER CARD FOR IBM AT AND COMPATIBLE COMPUTERS -16 bit MFM hard disk controller for the IBM AT and compatible computers. It can be used with many hard disk drives. Cables are included. $220 , Service /if the difference Over 15 years mail order experience How to order: Phone (02) 418 6711 and quote your Bankcard, Visa or Mastercard OR send you r Mail Order directly to PC Marketplace with your cheque, money order etc. (NO cash please) All prices are subject to change and will be guaranteed for present stock. Unless insurance is requested goods are sent at customers own risk. 14 Day money back guarantee except on: Semiconductors, Software, Books & Special Orders 1/0 CARDS RS232 HALF CARD FOR IBM PC/XT AND COMPATIBLE COMPUTER -Fits the difficu lt to use half card slot or any long slot -RS232 card comes with one ready to go serial port -Expandable to 2 ports by user (parts for expansion not included) -Selectable for COM1 thru COM4 -The user is able to select addresses for ports A and B as well as interrupt requests $55 -Manual included 1/0 CARD FOR PC/XT W/GMS CLCK $125 1/0 CARD 2 PORT $65 FOR AT 1/0 CARD FOR AT $125 WITH GAMES MULTI 1/0 CARD WITH MONO GA $229 MULTI 1/0 CARD $149 MEMORY CARDS 2MBYTE MEMORY EXPANSION CARD FOR IBM AT AND COMPATIBLE COMPUTERS -Utilizers (72) 41256-120ns chips for the fu11 memory capacity of 2Mbytes -Offers conventional expanded and extended memory capabi lities -Features auto-parity check -EMS compatible driver _RAM disk and print spooler software included $245 MEMORY CARD PC/XT for 640K $99 LEADS & ADAPTORS $5.95 $9.95 $5.95 $19.95 $12.50 $15.00 $19.95 $19.95 $19.95 JAPANESE DRIVES 3.5" 144M/720K Switchable between 144/720 DS/DD 3.5" Mounting $225 5.25" mounting $249 5.25" 360K Drive SOOK unformatted XT compatible $179 5.25" 720K/1.2MB Drive To 1.6MB unformatted AT compatible 5.25" 40MB Hard Drive 50MB unformatted. 28ms average seek time $695 MONITORS 12" TTL Green $179 12" TTL Amber $179 CGA 14" TTL Colour Philips 2 year guarantee. Stereo sound suits PC and Amiga $525 EGA 14" TTL Colour $649 ~m~ ~2~ $19.95 $12.50 $9.95 $19.95 $19.95 $19.95 $19.95 FOR DETAILS ON OTHER PRODUCTS PLEASE RING. BBFF D825S (socket) to D825S (socket) BBMF 0825P (plug) to D825S (socket) BBMM 0825P (plug) to 0825P (plug) These boxes wi ll allow you to design new interfaces or modify old ones. The boxes come complete with (25) 22AWG jumpers and machine tool sockets so you are sure to have a good connection. They are completely selfcontained and are available with either male-male. male-female or femalefemale D825 connector Bus mouse frees your serial port. The Bus Board installs easily in a half slot in your computer and leaves your system's serial port free for other peripherals. $149 ALL $19.95 MULTILINK RS232 TESTER AND BREAKOUT BOX Allows cable makers to configure cuttom cables. The MLA 1 will visually let you know status of lines 2,3,4,6,8,20 and 22 on the DTE and DCE side by ulitizmg red/green bi-colour LEDs. The MLA 1 provides you the signal status at a glance (four states: mark, space, clocking and off). Complete cable "breakout" and reconfiguration exists with 24 in-line switches and 54 in-line machine tool sockets. Includes handy ca rry ing case, 10 jumper wires and a device wiring chart. Cab le extends 4 inches from side of tester. Connectors; One male D825 and one female D825. With the MLA 1 you can easily see if a line is High (+6 to +25V) bright red led; High (+3 to +6V) dim red led; Low 16 to -25V) bright green led; low (-3 to 6V) dim green led; Off (-3 to +3V) led off. $49.95 SCANNER Logitech Sca nman Hand-held scanner for IBM PC/XT/AT & PS/2 and compatible computers. $399 $12.50 Floppy Cable D37 External HOD Cable 34 way HOD Cable 20 way Serial Shielded Cable M-F Serial Shielded Cab le F-F Centronics Sh ielded F-F Centronics Shie lded M-M LOGITECH BUS MOUSE -Manual included $229 Power Cable Y for disk Adaptor D9F-D25M Adaptor 3.5" power cable adaptor Serial Printer/Modem CB1 8ft Parallel Printer Cable - straight 12ft Parallel Printer Cable - stra ight 6ft Para llel Printer Cable - right angle Modem/Printer Cable Serial Cable for AT Floppy Cable 5.25" C34 Internal Floppy Cable 3.5/5.25" RS232 BREAKOUT BOXES GENDER CHANGERS MALE-MALE $9,95 FEMALE - FEMALE · $9.95 LOOPBACK TESTER $14.95 MINI TESTER $14.95 CHECK TESTER $19.95 MOUSE PAD FREIGHT CHARGES Include $10 with order for all normal items - heavy items, e.g. monitors add $15. Cleans, protects and prevents wear on you r mouse's roller ba ll. Sensitive. accurate and prevents dirt contamination. Tough non- skid neoprene backing with smooth gliding anti-static plastic coating on top surface. -Size (11 'Ix 85"w) $7 .50 PERSONAL COMPUTER MARKETPLACE Pty Ltd The new LOGITECH High Resolution Mouse is the only mouse designed expressly for today's new generation of high resolution displays, such as EGA, super EGA and VGA. The mouse is ideal for desktop pub Iishing as we lI as CAD · applications. With 320 dots per inch (dpi) resolution (compared with 100 or 200 dpi mice), the LOGITECH HiREZ covers the same area on your screen, but uses 62% less desk space to do it This saves you valuable desk space, and effort. Mouse maneuvers that used to require a sweep of the hand are now reduced to a flick of the wrist Include~ Plus Package software with mouse drivers, text editor, menu building and po int-click software (Lotus 1-2-3). -Size (38"1 x 27"w x 1.06"h -Colour light grey $179 LOGITECH MB MOUSE FOR IBM PC/XT/AT AND COMPATIBLE COMPUTERS The Logitech MB Mouse features opto-mechanical technology at acornpetitive price. This new twobutton mouse requires one male D825- pin serial port and comes with a female 0825 cable assembly. A D825 to D89 adapter (AD925) may be needed if the serial port you plan to use has a male D89 connector. The mouse comes standard with a six foot cord and features 200 dpi reso lut ion. -Colour Iight gray -Size (3.8"1 x 2.T'w x 1.06"h One year warranty $99 --....... .. ., PHONE (02) 418 6711 Mail Order Address P.O. Box 1100 Lane Cove NSW 2066 HIREZ BUS MOUSE FOR IBM PC/XT/AT/2 (MODEL 25,30) AND COMPATIBLE COMPUTERS VISA 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. NICAOS BEING CHARGED t-1 - 08 1N4002 09 1N4002 ---J...-U..ll - - - 05 1N4002 15V 1A S1b S1a D6 1N4002 100P. + E~ 33 25VW CASE LED1 Power supply for "Walkman" radios This handy circuit performs a number of functions: • it provides 3V DC to power a W alkman-style radio; • it provides a 50mA current source for charging nicad cells either from the mains or from a 12V DC supply; • it trickle charges a 12V battery while mains power is available; and • it automatically switches to the 12V battery when the mains power fails. The status of all these functions is indicated by LED indicators. X-Y light source plotter This simple circuit will produce a grid display of the direction and intensity of a light source within a 360° radius. It employs 25 LEDs laid out in an X-Y grid pattern. When a light source is detected, one LED lights to indicate the direction of the light source. Two light-dependant resistor circuits (LDRl & LDR2 and LDR3 & LDR4) are used to monitor the light-level in the X and Y directions. These two LDR circuits are 32 SILICON CHIP LE01 LED2 LED3 LED4 LED5 + MAINS POWER 12V POWER 12V CHARGING NiCad CHARGING WALKMAN POWER Refer now to the circuit diagram. With mains power applied, LED 1 lights and the 12V battery is charged via D5 and a 100 5W resistor. LED 3 is also illuminated to indicate that the battery is charging but LED 2 will be reverse biased. If the mains power fails, LED 1 goes out and the 12V battery supplies the load via D7. LED 3 is now reverse biased while LED 2 is forward biased and lights to indicate battery operation. Switch Sl selects either the "Walkman" power function or the nicad charge function. When S1 is in the position shown, power is supplied to an LM317 3-terminal arranged as voltage dividers across the supply rail. Their midpoints set the voltage on the inverting inputs of comparator stages ICla-lCld and IC2a-lC2d. If there is no light (or equal light on all the LDRs ), the inverting inputs of the comparators will all be at ½ \Tee. This means that the lower two comparators will be off in each case while the upper two comparators will be on, since their non-inverting inputs are biased in multiples of 1/5Vcc. The outputs of all the comparators are connected to XOR 33 16VW 3V 680 LED5 A regulator which is set to deliver an output of 3V. This supplies power to the radio and lights LED 5 via a 1000 resistor. If S1 is switched to the other position, S1b connects a fixed load in place of the radio. This load draws about 50mA and consists of a 680 resistor and LED 4 in series with a 1000 resistor. Sla connects the nicads in series with the regulator input so that they receive a constant 50mA charge. DB prevents the nicads from discharging if both the mains and 12V supply fail or are removed. H. Choke, Ringwood, Vic. ($25} gates IC3, IC4 and IC5. Now the output of an XOR gate is high only when its inputs are different [ie, one high and the other low). Thus, only the outputs of IC3c and IC4c will be high in equal or no light conditions, while the outputs of the remaining XOR gates will all be low. This means that transistors Q8 and Q3 will both be on and this lights th~ green LED at the centre of the grid matrix. When a light source is detected, the voltage on the noninverting inputs of each set of comparators changes. This, in 10k 24xR ED LED 10k 10k 1Dk 10k 10k 07 8C548 10k , 08 BC548 10k 09 BC548 10k 010 -:- BC548 10k .,. The circuit uses four LDRs to monitor the light level in the X and Y directions. These LURs set the voltage on the inverting inputs of comparators ICla-ICld and IC2a-lC2d and thus determine which of the XOR gate outputs switch high to drive the LED matrix. turn, shifts the high on the XOR gate outputs and thus alters the drive to the LED matrix. For example, if a strong light is detected by LDR2 the outputs of c:;omparators ICla-ICld will all be high and the output of IC5a will also be high. Thus, the red LED at centre right will turn on. A lower intensity light will turn on the LED between centre and right. Note that the LDRs should be arranged as shown on the cir- cuit, with the LDRs of each pair facing in opposite directions. The circuit can be used in games [eg, target practice) or perhaps as part of an alarm circuit. Darren Yates, French's Forest, NSW. ($30) }UN E 1989 33 Look before you leap "Look before you leap". That well worn adage might well be displayed in large letters on my workshop wall from now on. Even if I don't get around to actually printing it - and I probably won't - it will be etched in my memory for a long time to come. This all started when one of my customers turned up at the shop with a Sanyo colour TV set and a National NV300 video recorder. He pushed them across the counter and, in answer to my automatic question as to the nature of the problems, shrugged his shoulders and said, "They just don't work" . And I knew from the way he said it that any attempt to pursue the matter would be fruitless. Just why some customers adopt this attitude is hard to say. Some obviously feel unable to find the words to describe whatever signs or symptoms they have observed. Others, I suspect, have a more aggressive motivation; they are paying you to fix the device and don't feel that they should be obliged to contribute anything to the operation. Little do they realise that this at- ' 'tfr , ,. · . . -·· --- ~ ~ ~. :·.- (.?L1~\t,~3;}i&.'.-.. \ .1.) r=:.. ;x:r) s~i,;,.•.. . .... . ~c.: : ... . I~ \. , . ,\ . u--- ~{ ~ J m~rqi SOME. C\JSt"ON\E..R:S OtsV\OUSL'-( r, . F~L UNA~LE: TO FINO 11\E: WOR'DCS i'"O 'DE:.SC.1<.\~~ W\-\ ~-C-£.Ve:.:R CSlGNS o R S'<tl\'?T"OMS 11-\E."-f l-\P-.VE OD'SERV£t). ..... 34 SILICON CHI P titude can sometimes cost them a lot of money and inconvenience. Anyway, that's my whinge for the month; well, one of them! To get on with the story, the Sanyo TV set was routine. It was quite dead. The main reason for this was a failed horizontal output transistor which had taken out a safety resistor, both due in turn to a faulty power supply regulating circuit which had allowed excessive HT voltage to be . generated. That was knocked over in short order. But the video recorder was a different story. I set it up on the bench, plugged it into a monitor receiver, pushed in a test tape and pressed the play button. Nothing happened so I suppose that the customer could claim that he was right after all. The reason for the lack of action wasn't hard to find; the tyre on the play idler wheel (VXP0433) had " had it". So it looked like another routine job. Only it wasn't. While I have things set up like this I find it is a good idea to make as many tests as possible. It is surprising how often some other fault or symptom appears which one might otherwise overlook, at least initially. The first thing I did was operate the VTR/TV selector to feed the recorder's tuner into the monitor . This should normally have brought up the selected channel. And that was the first indication that there was something really wrong. All that came up was the sound, plus what appeared to be a blank video carrier; ie, a mid-grey screen, free from noise. My first reaction was to suspect that someone had been "mucking about" with the tuner presets and had detuned this channel. But a check on all the other channels produced exactly the same result, which seemed to rule out the "mucking about" theory but did not nee- ANTENNA ~~ RF IN [:] RF OUT RF OUT SPUTTER/ RF BOOSTER IN RF OUT VIDEO VCR TUNER MODULATOR VIDEO IN IF, DEMODULATION, LUMINANCE AND CHROMINANCE PROCESSING, ETC. SOUND SOUND IN SOUND VIDEO OUT OUT VIDEO PROCESSING FOR RECORDING. RECORD/PLAYBACK SWITCHING ETC. VIDEO HEADS SOUND HEAD Fig.1: block diagram showing the signal paths involved in a V~R/TV set . combination. Note that a VCR is virtually a complete TV set mmus th~ p1ch~re tube and associated deflection circuitry. For those a little rusty on this sub1ect, it may help in following the story (see text). essarily rule out a tuner fault. Another possibility was a faulty splitter amplifier, or antenna booster as it is designated on the circuit. These often suffer as a result of electrical storms and we have certainly had several of these recently. To check this I switched off the recorder via its own on/off switch but with it still powered up from the power point. If the splitter amplifier was functioning correctly, this would allow the TV receiver to function in the normal way and bring in all available channels via its own tuner. It did this, thus clearing the splitter amplifier. Well, that was one small step ahead. This still left the possibility of a faulty tuner or, more likely, a faulty modulator (designated RF converter in this unit). These are also susceptible to damage from electrical storms. So how best to check these theories? Mechanical problem I decided that this was as good a time as any to tackle the mechanical problem in the recorder. Not only would this give me time to think but, with this much of the machine functioning , I would be able to make a few more tests. So the faulty pulley was replaced, along with its mate, the idler unit (VXP0432). Then the heads, guide posts, etc were cleaned and the deck given a general once over. There were no hitches and I soon had the deck running and able to play a known good tape. But the result from the tape was the same as from the tuner; sound OK but only a blank carrier in place of the picture. Well, I reckoned that settled it as far as the tuner was concerned; it appeared to be in the clear. And, by the same token, it made the modulator the prime suspect. I normally carry one of these in stock. As I mentioned earlier, they are prone to lightning damage and I usually replace two or three during the stormy season. But I had none now, so I decided I should order one anyway, even allowing for the remote possibility that this was not the fault (although I was sure il was). The circuit setup At this point it might be a good idea to take a closer look at the broad picture of any video recorder/TV receiver setup. Fig. 1 shows the block diagram of a typical arrangement. It doesn't apply to any particular combination but, in a sense, applies to them all. Individual devices perform the various functions, such as switching, mixing, etc, in different ways but the functions themselves are essentially the same. The antenna is no longer coupled directly to the TV receiver but to the video recorder instead. Here the signal is split, half going to the TV set and half to the recorder's tuner. And to overcome the splitting losses involved, the signal is also amplified. From the recorder's tuner the signal goes to what is almost another TV set in its own right. Included in the VCR circuitry is an IF system, demodulator, luminance and chrominance processing circuits and a sync separator - in fact everything necessary to produce complete video and sound signals, albeit at a modest level. All that is missing is the picture tube, its associated deflection circuitry and the audio system. Instead, the video and audio signals are passed on to the recording processing circuits and recorded on the tape. At the same time, these signals ar.e fed to the modulator, which is really a miniature TV transmitter delivering a complete video and sound modulated carrier to a blank channel on the TV set. A choice of two output channels is normally provided, typically channels O and 1, or 3 and 4. Thus the TV set can be fed from the recorder 's tuner instead of its own. Some users take advantage of this fact to receive UHF signals on TV sets that don't have UHF tuners. In the replay mode the circuits are switched or mixed in such a way that signals from the tape modulate the carrier, and appear on the TV screen via the aforementioned blank channel. There are also various additional features, such as video and audio input and output sockets etc, for use with external gear such as cameras, other recorders etc. Now I know that my fellow servicemen may be muttering that all this is common knowledge, so why go over it. Well it is to us but not necessarily to all our readers, keen and experienced though they may be in other phases of electronics. So I thought that this was a good opportunity to bring everyone up to date and, at the same time, make this story a little easier to follow. Where was I? So where was I before I interrupted myself? Ah yes; I suspected JUNE 1989 35 2SC2206 which acts as a buffer stage (see Fig.2). There was no video here either. This stage is fed from another bufthe modulator and planned to order But the worst blow was the fact fer stage, Q3017 (2SB641), via a a replacement. Based on the above that I still had to find the fault. And 3-terminal phase compensating cirdiscussion, readers may be able to I suspected that it was going to in- cuit, FL3003. In turn, Q3017 is fed volve a fair amount of circuit tracfollow my reasoning. Since I was from pin 19 of IC3003 (AN6327). ing, both on paper and in the unit. unable to get a video modulated Note that pin 19 is fed from a switThe circuit is, of necessity, a comsignal out of the modulator from ching circuit which selects either plex document. It is spread out over two separate sources (ie, the tuner playback or record mode. many pages, most of them being or the video heads on playback), it I decided to go straight to pin 19. three or four page foldouts, and just seemed most likely that the If there was no video here, I was in modulator, being the common com- mating them mentally can require real trouble. But there was and, acquite an effort. ponent, was at fault. cording to the accompanying The logical place to start was the So the modulator was ordered waveform, it was right up to video input to the modulator where and arrived in a couple of days. Fitscratch. The same applied to the presumably, the video wasn't gain~ ting it was quite simple. There is a base of Q3017, which is virtually in. There is far too much circuitry 5-pin plug and socket carrying a 9V the same point. So where was the involved to reproduce here, apart supply rail, video, audio and video going down the drain? from the vital section, but I may chassis connections, an RCA plug Well, it was somewhere between quote some references for those of coupling it to the splitter amplifier, the base of Q3017 and the emitter my colleagues who have the and a couple of plastic clips to hold of Q3018. I made a voltage check of it in place. In a few minutes I was NV-300EN and NV340EM manuals. both transistors and, while Q3017 I trust other readers can follow the ready to go. was almost spot on, Q3018 was general idea from the text. No prizes; it didn't work. Every"funny" to say the least. I pulled it thing was exactly as before which out and checked it and it seemed was was a bit of blow and in more No video OK. And while it was out I checked ways than one. It was a blow to my The CRO confirmed that there for video at pin 3 of the phase comego for a start; I had been so sure was no video at this point (pin 3, pensating filter. No joy. that I knew what was wrong that I Video In, of modulator ENC17502 The same applied to the input of hadn't even bothered to make any page 3-15). This pin mates with pi~ this filter, pin 1, but there was norchecks to confirm the diagnosis. I'd 3, Video Out, of plug BJ7004 on the mal video on the other side of the leapt before I looked. left of the luminance and chromlkn resistor feeding this pin, which inance circuit (page 3-9). And nearis also the emitter of Q3017. Open ly two thirds of a metre away, on circuit lkO resistor? No, it was the right hand side of the circuit, is intact. the video source which is supposed Faulty filter unit? A resistance to feed it; the emitter of Q3018, a check revealed almost zero resistance between pins 1 and 3 and an open circuit from either of these to pin 2 (chassis). Since it is virtually a sealed package I could only guess as to its circuitry but I had found ;1(;, nothing to suggest that it was the Ty culprit. Nevertheless I decided to ~ disconnect it whereupon I I'/) l/ I had video at both ends of <" I ~ ~ the lkQ resistor. 1....- I -ffe. f. So what if I bypassed the C, f filter and connected the / emitter of Q3017 to the erbase of Q3018? Maybe the picture would be a bit z onkus but I should get something. i Only I didn't; there wasn't a sign of z anything on the monitor. z <: I went back to Q3018 and checked the voltages again. As I had ~ 11-100 (:, -i already observed, they were out ~\S WAS A GO i and I had initially suspected that Of'P0~UN\i"f TO __ . ~ this was due to a fault in the filter. 2. :BR.\NG E:V~'-fONE ~ j{M ... z.. Ut=> OA-f'~ooo J ✓ z SERVICEMAN'S LOG -CTD i/1// < ... so :c ,O / • ~ ~~<Z-r Fig.2: the relevant portion of the NV300 VCR circuit, showing the two buffer transistors (Q3017 and Q3018) and the phase compensator (FL3003). The video signal comes out on pin 19 of IC3003. Now that this seemed to have been cleared, I had to look further afield. The circuit actually specifies two sets of voltages - one for the record mode and one for the playback mode. In fact, the differences between the two modes are quite small, whereas the errors I had measured were much greater. More specifically, all the voltages were down but the one that stood out was the base. This was supposed to be at 1.49V for playback but in fact was less than half of this. A resistance measurement from base to chassis showed a possible reason; it was almost a dead short, around H2. But where was it? About the only circuitry left was from the base to diode D3004 and thence to C3075 (10µ,F, 16V) and the junction of a voltage divider from a 9V rail, R3095 (6.8kn) and R3096 (1.5k!1]. A run from this junction wound its way off to the left and eventually finished up at another diode, D3006 [not shown here). I lifted D3006 but the short remained. That left the 10µ,F electrolytic, C3075, as the only remaining possibility. Modern electros seldom go short circuit; the low value ones frequently dry out but to break down with only a few volts across them is rare indeed. But it was a dead short. I restored the various circuits I had disturbed, fitted a new 10µ,F capacitor and that solved the problem. In fact, it turned out to be a very nice recorder. But I was a bit browned off at myself for trying to be too smart. The answer seemed so obvious that I thought I could make it a quick one without bothering to make any checks or measurements. The point I failed to appreciate, of course, was that the modulator was not the only common factor in the video chain. Switching between playback and record was not directly ahead of the modulator but further back and involving additional common circuitry - the two buffer stages and the filter. So I came a gutser. Oh well, no real harm done, except to my ego. A crook General My next story concerns a General colour TV set, type GC207. This set is about 6 years old and I had serviced it about 12 months previously, under warranty. This was one of a few models marketed by the General Corporation which had a full 5-year warranty for labour and material. There was only a month or so left of the warranty when I serviced it on that occasion. When the customer contacted me on this latest occasion he came out with the bald and somewhat aggressive statement that "the set's the same as it was the last time you serviced it" . Obviously, he imagined that would be all I needed to know in order to recall everything about the set. I wonder if he has the faintest idea of how many sets would have passed across my bench during that time. As it was, all I could do was suggest that he bring the set in. This he agreed to do and, in the meantime, I looked up my records to bring myself up to date. The complaint from the customer then was simply that the set wasn't producing a good picture. More specifically, my records reminded me that the picture had developed a green cast plus a marginal lack of brightness. On that occasion, I had performed a grey scale adjustment and reset the sub-brightness control, a 10k!1 pot (VR305), which feeds pin 4 (pedestal clamp] of the PAL Processor IC (IC301). There is also a lMQ screen control pot (VR406) on the neck board which provides a measure of brightness control. Considering the age of the set, the need ,Y i ., ~~ -:~==~ ,,t?'c ---So W~~'R£ WA-S THe:. VlDE.0 GO\NG DOWN 1\-\E: DAAI ~? JUN E 1989 37 Fig.3: the neck board circuit of the General GC207 TV set. The major symptom appeared to be low voltage on the collectors of the R, G, B driver transistors but the fault was elsewhere. for these adjustments was not surprising. In due course the man and his wife turned up with the set. They were still in a somewhat belligerent mood, the theme being that the previous repair had not lasted very long. And although they didn't spell it out, the implication was obvious: my previous repair, under warranty, was designed to last just long enough to get the set out of warranty (just how I could have managed this remains a mystery). Of course, I couldn't refute this implication because that was all it was; I just had to wear it. But when they began complaining about the reliability of the set, in a broader sense, I was quick to point out that they had had pretty good value for money; just on 6 years of TV entertainment which had not cost them a cent until now. That quietened things down a bit. The symptoms At a more practical level I plugged the set in while they were there, as much as anything to confirm whether the symptoms appeared to be the same as before. In one sense they were, in that the picture again had a green cast and was down in brightness. But it looked a lot worse than that. While it is rather hard to define, I had a strong impression that I was looking at a sick picture tube. There was not only the lack of TETIA TV TIP Kriesler 59-03 Symptom: ( 1). Line tearing or wrig- gling verticals. (2). Small, erratic changes in overall size of picture. The tearing and wriggling only lasted for a few minutes at a time but the size changes went on continually. Cure: Replace EHT tripler. The size variations are caused by small 38 SILICON CHIP changes in output voltage from the tripler. The tearing and wriggling must come from some kind of internal arcing but this has no effect on the line drive or line output. TETIA TV Tip is supp/iec:J by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania. brightness but also a lack of contrast, a subtle but definite lack of definition, and what might be described, in non-technical terms, as "sparkle". I couldn't be sure, of course. Other things can cause similar symptoms, though not many. So I contented myself with warning the customer that this was a strong possibility but one which would have to be confirmed by further tests. This left me with an "out" if I was mistaken. Later, with the set on the bench, I still felt convinced that the image on the screen showed all the classic symptoms of a sick tube. Nevertheless, I knew I had to go through the motions of checking all other possibilities. And the first thing that came to mind was the heater voltage. The heater voltage is derived from a winding on the horizontal output transformer and, by reason of its frequency and waveform, is virtually impossible to measure correctly with an ordinary analog meter or with most digital meters. At one time, Thomas Electronics marketed a moving iron meter for this job but I use a Fluke Model 8060A digital meter which is also suitable. The heaters looked bright enough but that is hardly good enough; it needs only a small voltage loss to produce symptoms similar to those in this set, so it had to be measured. In fact, the voltage was spot on so that ruled that theory out. My next step was to measure the collector voltages of the red, green and blue driver transistors. These are mounted on the neck board and are fairly easy to get at. This produced the first surprise. They are supposed to operate at 110V but all three were down to about half this value. There were two reasons to be surprised at this. One was the fact that all three were the same and the other was that this should have substantially increased the brightness of the picture tube, by reducing the positive voltage on the picture tube cathodes and thus reducing the bias. Instead the brightness was down. These two factors indicated that the incorrect collector voltages were a symptom rather than a cause. So, instead of tracing the collector supply back to its source, as I was initially tempted to do, I made some voltage measurements around the picture tube. No G2 voltage And that was the jackpot. The screen (or G2) electrode, which normally sits at around 500V, had no voltage at all. This electrode is fed from a 900V source via a voltage divider consisting of a 330k0 resistor (R416), a 1MO pot (VR406) and a 680k0 resistor (R415) to chassis, the voltage being taken from the moving arm of VR406 (see Fig.3). The culprit wasn't hard to find; R416 [33k0) was open circuit. With that replaced things started to come good. The screen not only brightened but was excessively bright and even winding down the screen control (VR406) was not sufficient. I went back to the red, green and blue collectors and found, strangely enough, that they were now at their correct voltage. Then I remembered that I had initially turned up the sub-brightness pot (VR305) in an effort to assess the set's behaviour. Returning this to its previous setting brought the brightness back to normal. More than that, it brought the whole picture tube performance back to normal. I was now just as sure that the tube was OK as I had previously been that it was crook. Which just goes to show how easy it is to be deceived. But that's not quite the end of the story. I went through the grey scale procedure again and the end result was virtually perfect but with one strange side effect. If the screen voltage was varied via VR406, the grey scale shifted, moving to excessive green when the voltage was reduced and to a lack of green in the other direction. However, if a new voltage was selected, the grey scale could be be reset to normal. This prompted a number of questions. Was the picture tube on the way out anyway and in a manner which made it strangely sensitive to the screen voltage? And was this the reason for the original green cast or was that the first sign of the 330k0 resistor going high before passing out completely? Or was it a bit of both? And why did the lack of screen voltage pull down the collector voltages of the red, green and blue driver transistors? It seems that this could only be because of excessive cathode current but the exact mechanism escapes me. The closest I can come to an explanation is to recall how the old power pentode valves used to draw excessive screen current if they lost their plate voltage but it is not an exact parallel. Anyway, the upshot of all this was that I was able to return the set to the customer with the assurance that the picture tube was all right, at least for now. But I felt bound to warn him that the set might drift into the green again. Whether we could salvage the situation again and score a few more years out of the tube, we could only determine when [or if) it happened. ~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices Problems. ... and you don't have our .120page catalogue . .. At last . .. a TRADE catalogue for the consumer ARISTA ... your one-stop problem solver. Video plugs and sockets . .. Video extension speakers .. . Video flyleads ... Video RF interference filters . .. Video splitters ... Indoor antennas ... Video switching units . .. Down converters . . . Video speaker controllers . .. Video camera lights . . . Video tape rewinders ... Video cine adaptors ... Video head cleaners ... Video splicing kits ... Video storage cases ... Video dust covers . . . Video leads ... Scart plug leads ... Video dubbing kits ... Video headphones ... Video shotgun and wireless microphone systems .. . Pre-amplifiers with video inputs .. . Video camera stands . .. Just about anything you want. ... Try us ... NOW! _ Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ARSTK ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 JU NE 1989 39 i=o, About The Price Of Half A Chicken Breast WHAT CAN YOU BUY FOR A DOLLAR? one and a half Sunday newspapers Just under two litres of petrol Half a chicken breast About one quarter of your favourite monthly magazine OR You could pick up your very own copy of the bigger, brighter, more colourful, more informative ..... DICK SMITH ELECTRONICS 1989 CATALOGUE. It's the best dollar value you'll get all year! There's a stack of great reading, plus thousands of incredibly useful items for home, office or workshop. You'll find one at your nearest Dick Smith Electronics store - IT'S OUT NOW! Squeeze e Trigger d You'D Fix Eve It Drills! It Solders! It Screws! It's Rechargeable! Cat T-5712 See itat your nearest ing! Only $99 THREE WAYS TO STOP A THIEF.... At Dick Smith Electronics 1. Bolt Everything To the Floor there's a professional quality 2. Build A Moat & Buy A Cannon alarm system you can afford! OR 3. Install Your Own Security System! So Easy To Install! eless Five zone protection for your home that can be installed in no time - Without Wiring! It's the ideal security system for home units, apartments, etc - or where ever wiring is a problem. That's right, all you have to do is plug it in, set the code and you've got instant protection. [ With features like instant/delay modes, five zones of protection, 4 function modes, built-in speaker and provision for external speaker you get quality security in a compact unit which fits easily on bookshelf or bench. s399 Yes, it comes as a complete security package. You get the central alarm unit, a remote controller, a remote Reed switch (for door or window protection), infrared sensor (for room or entrance surveillance) and mains adaptor! Cat L-5125 ADDITIONAL UNITS AVAILABLE Remote Control Allows full control of your wire less remote sec~ritty sbstem. Jh~I remote con~roiler fits/ rh poc e or ag an a ows you se ec any O e system's functions. Even has an emergency button. cat L-5129 Window Sticker Remote ee it Remote Ideal protection for windows or doors! A magnetic Reed switch with digital coding transmitter. Incredibly easy to install, just set the security code and forget it. Cat L-51 27 lnfrared sensors are the best sensors you can get. For full room, hall or entrance protection this one offers 64 sq metre coverage and adjustable zone control. Has inbuilt transmitter. Cat L-5128 Sticks to the inside of the window or glass door so they'll know you've got an alarm system and go pick on S someone else! Cat L-531 1 WARNING THIS PROPERTY IS UNDER CONSTANT ELECTRONIC SURVEILLANCE 0 Large 245 x 270mm sign made from heavy gauge aluminium. Suitable for fi xing to wall , fence , etc. Cat L-5312 1o 95 THE ENTHUSIAST, ELECTRICIAN, EXPERIMENTER... With 27 Electronics/Electrical Formula The CASIO fx-611 Without doubt one of the most useful tools anyone working with electronics could have! With 27 of the most used electronics/ electrical formulas built-in and a programming function which allows you to input your own formula. Includes 74 scientific functions, 10 digit display, programming functions .. .. it's unbelievable. Just Look! It's all bui lt in - Resonance frequency, change in termi nal voltage in RC series circuit, time constant in RC seri es circuit, resistance, power factor, closed loop gai n, voltage gain, current gain, magnetic force, energy density stored in electrostatic field, standard electrical form ula and more! G EIDDBE.3 IDEIDEIIII DEIEID• aamam Cat V- 3828 Just s79 95 ALL NEW! COMPUTER PERIPHERALS RS-232 Multilink Adaptor A complete in-line tester/adaptor which makes complex and time consuming Serial connections a breeze. Comes with 25 pin male and 25 pin female connectors, jumper pads and wires, as well as 24 inline switches, for quick selection for any RS-232 configuration. 8 bicolour LED's tell you at a glance when you've got it right. Cat X-2654 "99 90~o ~, ii;;,,;;,_;,,,,..,; I s49s5 ~ rc~~~ei ! ~ c e?~!~r~ ar~ l ! ! ~ :r IBM PC or compatible and gives you 12 channels (Voices) stereo music output and 32 preset instruments. Plus, there's a stereo amplifier to drive speakers, headphones etc. You can define your own instruments, play background music while you work , create albums of your favourites or compose your own music. Cat X-2020 s299 'Voice Master' Sound Input Card Analogue to digital card lets you sample any sound , then vi ew and edit the wave form. If you have 'Speech Thing ' the recorded sound can then be played back. Comes with headset and software for experimenting with voice recognition. Set up to 256 different voice activated keyboard macros. Requires an 8-bit expansion slot (XT & $ AT compatible). Cat X-2038 199 'The Speech Thing' Digital Sound Synthesizer Adds sound capability to your PC! It's a full ■ $ featured 8-bit digital to analogue converter, audio amplifier and software system which is capable of creating almost any sound . Converts text to high quality speech. Just plug it in . Can be used in conjunction with r?-. =-~----· -.II'!\, the 'Voicemaster' (X-2038) to sample and ~'.\..lll! edit digltal sounds. Cat X-2036 J> Copy Images Direct To The Screen! Handy Scanner HANDY I Now you can copy any image direct to your SCANNER computer screen with the incredible Handy HS-3000 I Scanner! 105mm wide , Handy Scanner can be used with Hercules, VGA, EGA or CGA displays. Gives black and white and 3 x 32 quasi-tones. With high 400DPI resolution . Suitable for PC/XT/ AT and comp~ti~les an_ d comes complete with Desktop Publishing Editor. cat x-3825 149 • DICK__.~ _ _ _ _ _ _...,. VALUE PLUS TEST INSTRUMENTS! Auto-Ranging 3.5 Digit With FREE Protective Pouch/ With Memory! Budget Mini Multimeter An amazing little multimeter that's ideal for anyone just starting out ... or for anyone who gives their meter a hard a-:c::.,.,,.-!-.O--.::-"· 1 time. 11 ranges, 2000 ohm/volt meter that fits easily in the pocket and is perfect for general test work. DCV/ACV: 10, 50, 250 & 1000. DC: 100mA. Cat Q-1010 ONLY $17 95 Auto-ranging makes worker easier and faster - you don't have to worry about what setting you're on! This super meter also has auto-polarity PLUS high levels of overload protection on all ranges. Features include 'lo ohms' setting which limits o/c voltage for in-circuit resistance measurements, a handy buzzer which sounds at 1.9 digits, switch selectable autoranging (manual gives extended resolution, transistor check, continuity and more! Cat Q-1516 Now'99! Save $10! Multimeter It's NEW! Digital Capacitance Meter With Audible Continuity Tester. Compact and reliable with built-in buzzer for continuity testing. Even has a battery checker and 1OA DC range. Plus high sensitivity (20,000 ohms/volt), diode and fuse protection and 19 ranges plus dB. DCV: 2.5, 10, 50, 250 & 1000. ACV: 10, 50, 250 & 1000. DC (mA): 5, 50, 500 & 1A. A fantastic buy! Cat Q-1022 :· -~ .:~. :~~!<at> Now Just '2995 Hand-Held RC Oscillator Comes complete with test leads! A compact oscillator that's a must for the tool box. With 23 ranges of sine and square waves switchable between 20Hz and 1.5kHz plus x100 range. That's 46 settings in all. Continuously variable amplitude and -20dB attenuator gives you total control. Output is standard 600 ohms. Cat Q-1220 Reduced to s3995 $30 Off! Helps you care for your multimeter and keeps it free from dust, dirt, etc. Quality vinyl pouch with velcro seal. Suits Q-1516 multimeter and many other similar size meters. Cat Q-1513 Was $9.95 Only s595 Agreat Idea! Multimeter Holster Impact absorbing case to protect your multimeter that's ideal for the bench of field work. Comes complete with belt and allows you to carry your Q-1515 or Q-1516 multimeter around without it being a hassle. Cat Q-1522 s795 - 1-".r - ~ • 0 • -;.,. -~ ~ -~ '129 With Bonus Offer! Universal Panel Meters Quality universal 100uA panel meters in two popular sizes that can easily be ..:--.:.-.. adapted for just about any application - Volts, Amps. mA ...anything. Combine them with Shunt Pack (Q-2046) and .meter instrument labels (N-5751). Th~y operate over the range 100uA to 316mA and 1V to 100V. Higher currents are available by providing an appropriate resistance. ~==~~-.; Bargain Protective Pouch Was $9.95 .- ../a ·- .• - Can be used to check tolerances, sort values, select precision values, measure unmarked capacitors, select matched sets plus measure cable, switch or PCB capacitances. Ideal for the workshop, hobby bench, schools, labs .... anywhere! With 3.5 digit LCD readings over 9 ranges. Covers virtually all general usage capacitors. Battery operated, it's lightweight and comes with handy carry case and leads. Ranges: 200pF, 2nF, 20nF, 200nf, 2uF, 20uF, 200uF, 2000uF, 20,000uF. With over-range and battery low indicators, overload protection and carry case Cat Q-1222 Now SMALL MU45 With Bonus! Overall size 55 x 52mm. 45mm mounting hole required. Cat Q-2045 Sl 695 LARGE MU65 With Bonus! Overall size 96 x 82mm. 65mm mounting hole required. Cat 0-2065 s2195 Bonus Oller! With every purchase of universal Panel Meter(s) you 'll get a BONUS Shunt Pack (Q-2046) for FREE! Hurry, this offer won't last! 30W Audio o er m le Even a beginner will find this one easy to build! It would have to be the simplest (and possibly the smallest) audio power amp above a few watts ever described. Uses one common IC (National Semiconductors LM1875) and requires just 8 components on a minute printed circuit board , yet it delivers superb hi-fi performance. Comes with PCB and components only. Cat K-5002 s1&9s As Described in AEM 11/88 It's great value! Use it as a stand alone stereo control unit/preamp or match it up with your existing power amp. Either way you get a high quality stereo control unit at a fraction of the commercial price. It's easy enough to construct, even by a novice, and features the full range of controls - inputs and outputs. Rated output: 1V RMS into 10k ohms. Cat K-3045 Just $8995 This amazing little receiver can be constructed in a matter of hours and gives superb performance. A dual conversion receiver it uses the Motorola MC3362 integrated circuit, is of low-power design with excellent sensitivity, low power drain arid good · image rejection iri narrow band voice and data link applications. Cat K-6000 to Sele An inexpensive, easy to build random number selector which may well be the best investment of your life. All you do is select the game you wish to play, Pools/Lotto/Lotto 44, push the button and it selects your winning numbers for yo·u. Even has a systems select control tor systems 617/8/9/10/11/12. Comes with pre-drilled and screened front panel. 5 Cat K-3700 As described in Silicon Chip s5 9 Motorcycle Alarm An effective motorcycle alarm designed for maximum The very latest in the highly successful Playmaster series. A 30/30 watt stereo security at a great low price! Even if you know nothing amplifier that's easy to bui ld, low in cost, provides all the essential features and about electronics you can have it up and running in no offers excellent performance and superb noise and distortion specifications. time. Features include LED alarm indicator, auto reset Construction is made easy by mounting virtually all parts, including heatsinks, and provision for external sensor • on one large PCB. Short form kit comes with 2 x TDA 1514 IC's, switches. Connect it to your existing front and rear panels, transformer, PCB and instructions. horn or a siren . Suits all 12V systems Cat K-5100 As described in EA 9/88 and can be engaged by toggle or keyswitch. Comes complete with micro siren and f>•~~~~ compact Zippy Box. Small in size, simple to construct and it comes at less than half the cost of Cat K-3249 commercial units! Has 10 metre range and can be used in conjunction with your _ __________________,. existing alarm system or with optional interface (Cat K-8201) you can use it as the basis for a complete new system for your home, etc. Comes with white filter so it can be used in the daylight (not direct sunlight) or even in the car. Cat K-8200 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 One of the most popular power supplies for CB radio, amateur 1W Zeners from 3.3 to 50 volts gear etc, has now been updated and improved. The (2 ranges). Supplied with prePowermate II delivers clean , well-regulated 13.8V DC at up to punched front panel. 5amps. Comes complete with case, front panel and Cat K-3051 95 transformer. Cat K-7110 sgg Passive fra Ideal for CB or Amateur Radio! 13.SV o $119 NEW KITS SOON TO BE RELEASED ...... . s39 Teletext Decoder Mkll A wealth of information at your fingertips ... TAB results, news, stock market reports, sporting details, subtitles arid more! Watch out for the amazing T~ etext Decoder Mkll. Comes complete with remote controller, mains transformer, case and silk screened, pre~punched front panel. Cat K-6360 $299 Car Courtesy Light Delay A fantastic idea! Allows 20 second delay before the interior light turns off - enough time to find the keyhole, fasten seat belts, etc. Plus there's a dimmer control for map reading, etc and more! Easy to build , easy to install. Cat K-4002 FM Stereo Transmitter A.neat little device which allows you much more fle xibility when listening to music. The Stereo FM transmitter can be connected to your CD player , etc and you can move around the house and listen to it _via you~ W?lkman portabl~. Or you can connect your portable CD to the transmitter and then listen to It via your car radio. Cat K-5004 ~ : MITH .:r........,- ___ · -~....... • - - --.-,--~-•,....(... . ~ !!1 ~ f -~ CAT NO. K-2720 K-2721 K-3053 K-3082 K-3252 K-3415 K-3425 K-3428 K-3429 K-3433 K-3434 K-3460 K-3470 K-3471 K-3476 K-3477 K-7000 WAS KIT NAME Walkabout Wadio $1 9.95 $29.95 Motion Detector $19.95 Power Transistor Tester FI uro Starter $5.95 Deluxe Car Alarm $89.00 AM Stereo Decoder $32.95 lnfrared Remote Control Suit Teletext K-6315 $41.95 lnfrared Remote Control 240V SW $69.95 lnfrared Remote Transmitter Suit K-3428 $15.95 8 Channel I/R Remote Transmitter $49.95 8 Channel 1/R Remote Receiver $127.00 Battery Power Supply $62. 50 RF Probe Suit K-3471 $9.95 Signal Tracer/Amp $52. 50 Fast Nicad Charger $99.95 Mega-fast Charger Suit 7.2V cells $45.00 Biometal Wire Starting Kit $39.00 NOW $14.95 $24.95 $14.95 $4.95 $79.95 $19.95 $19.95 $49.95 $9.95 $39.95 $99.00 $49.95 $7.95 $39.95 $69.95 $39.95 $29.95 Walkman Amp (PCB & Instructions) $6.95 $3.95 $59.95 $39.95 VCR Sound Processor 60 Watt Mosfet Amp Module $89.95 $49.95 100 Watt Mosfet Amp Module $109.00 $59.95 $12.95 $6.95 Speaker Tweeter Suit K-4000 $39.95 $29.75 Speaker Tweeter Suit K-4000 Bookshelf Speaker Kit (everything but speakers) $196.00 $126.00 Low Cost Stereo Amp (No case & transformer) $99.95 $59.95 Infra-Red Stereo Pre-Amp $259.00 $199.00 $48.95 $39.95 Infra-Red Stereo Headphone Transmitter $48.95 $39.95 Infra-Red Stereo Headphone Receiver $32.95 $19.95 UHF/VHF Tuner Module (Pre-Built) AMATEUR/COMMUNICATIONS K-6300 K-6301 K-6306 K-6307 K-6309 K-6311 K-6313 K-6316 K-6321 K-6323 K-6326 K-6327 K-6328 K-6331 K-6339 K-6345 K-6349 UHF Transceiver UHF 40/80 Channel Upgrade (Suit K-6300) 70 cm Pre-amp 50 Watt UHF FM Power Amp UHF GaAsFet Pre-amp VHF GaAsFet Pre-amp 100 Watt 2 Mtr Linear Amp VHF Watt Meter RF Field Strength Meter RF Attenuator Box 80 Mtr Low Power Amateur CW-Tx 80 Mtr VFO Kit Suit K-6326 80 Mtr Direct Conv. Amateur Rx 100 Watt H.F. Linear Amp Morse Rtty Decoder Radio Direction Finder 100 Watt 6 Mtr Booster Amp $249.95 $12.95 $21.95 $279.00 $129 .00 $129.00 $299.00 $49 .95 $54.95 $79.95 $49.95 $39.95 $59.95 $379.00 $159.95 $149.00 $329.00 Was $19.95 sggs ow 112 Price! N ~ UHF/VHF Down Converter Your TV doesn 't have UHF? Then you 're missing all the superb programs on SBS. Here's the inexpensive way to solve the problem. This UHF/VHF converter goes together easily, covers both UHF bands 4 & 5 and is a conventional varicap unit intended for use in TV's with pushbutton station selection. And there 's no aligning or adjustments. Cat K-3236 Was $76.50 0 KITS K-2722 K-3422 K-3441 K-3443 K-3998 K-3999 K-4000 K-4001 K-4003 K-4005 K-4006 K-6051 A hi~h perfo rmance intercarrier vesti gial s·ideband modu lator intended for colour application use with TV games, VCR's, computers, graphic generators, Teletext and view data adaptors. Ensures a good grey scale, controlled chroma levels and freedom from sync compression that can cause frame and jitter problems. Operates over a wide supply range from 6V to 15V (Vee) with excellent stability against voltage changes. Designed fo r PCB insertion with 75 ohm output from standard RCA socket. Cat K-6043 $179.00 $5.95 $9.95 $179.00 $99.00 $79.00 $229.00 $29.95 $49.95 $59.95 $39.95 $29.95 $49.95 $249.00 $129.00 $89.00 $249.00 Now 5 6995 Transceiver Savs An Incredible $1001 This has to be the bargain of the decade! A high quality amateur transceiver which gives any 500kHz segment between 2 and 30MHz (80 metre module supplied). With superb specs, it comes complete with case, silk screened panel , all components and even a microphone. With LSB, USB and CW modes and power output rated at 30W PEP/15W CW. Cat K-6330 s299 Upgrade Kits 40 Metre Cat K-6332 20 Metre Cat K-6333 15 Metre Cat K-6334 10 Metre Cat K-6337 Now $1995ea Soldering Iron Temperature Controller A great device which allows you to do all your soldering work with just one iron. It's not difficult to build and gives you a fully reg ulated, ad justable temperature control soldering system using your existing iron . 240V mains operated with selectable 20-70 watts. Can be adjuste_d to suit high $ I power irons. Cat K-3479 0 Off 2 s2995 Chair/ ilt Alarm Fantastic little alarm with countless applications. As a chair alarm it helps care for your valued possession by screaming blue murder if the sitter swings back on it (the cause of death of many a favourite chair) . Can also be used as an alarm for your golf bag, bike, backpack ... anything . It's qu ite easy to bu ild , battery operated and fits neatly in the smallest available jiffy box (not supplied). Cat K-3248 $995 HURRY LIMITED STOCK ONLY! • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Campbelltown (046 )27 2199 • Chatswood Chase 4 I 1 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gostord 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • Nor1h Ryde 88 3855 • Parramatta 6892188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City 26 7 9 111 • Tamworth 66 1711 • Warringah Mall 905044 1 • Wollongong 28 3800 • ACT• Fyshwick 804944 •VIC• Ballarat 315433 • Bendigo 43 0388 • Box Hill 890 0699 • Oandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 91 44 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 16 14 • Ringwood 879 5338 • Springvale 547 0522 •OLD• Brisbane City 229 9377 • Cairns 311 51 5 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide City 223 4 122 • Beverley 347 1900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA • Cannington 451 8666 • Fremantle 335 9733 • North Perth 326 6944 • Perth City 481 326 1 • TAS • Hobart 37 0800 • NT• Stuart Park 81 1977 BUILD TOUCI and off from more than one point in a room, just like 2-way switches. You can't do that with a knob type dimmer. In fact, if you have a large room or hallway, you can dim the one set of lights via one, two or three touch plates. If one of your family members is unfortunate enough to be stricken with arthritis, it is much easier for them to turn on a light with a touch plate than with an ordinary switch. Features Are you still persevering with one of those old knob-type light dimmers? You are! Well, get onto this Touch-Lamp Dimmer. You can turn your lights on and off or dim them just by touching the decorative plate. By LEO SIMPSON Touchplate dimmers are not new; they have been around for about 6 years now but they are still new enough to be a novelty item in most homes. They do have advantages over conventional knob-type light dimmers though. First, there is no switch or knob to fumble with in the dark, just the decorative plate. With no switch and no knob involved, there are no mechanical 48 SILICON CHIP components to wear out or fail. (Mains switches do wear out, of course, often after only a few years). Second, our circuit incorporates full mains suppression so the amount of radio interference is less than from typical commercial dimmers. Third, more than one touch plate can be connected so that the lights can be dimmed or turned on The Touch-Lamp is housed behind a standard plastic grid and anodised aluminium plate from the HPM Decorator range. In fact, if you go for the gold anodised plate, it will look very similar to HPM' s own touchplate dimmer (Dimamat Cat. DRM500). Naturally, by building the Touch-Lamp Dimmer yourself, you save about half the price of the commercial version. The Touch-Lamp Dimmer is intended for dimming incandescent lamps rated from 25 watts up to a total of 300 watts (individual lamps should not be rated at more than 100 watts). It is not suitable for controlling fluorescent lights or motors of any sort. The Touch-Lamp Dimmer may be installed on walls or in standard wall-boxes (ie, HPM Cat. 140P) but cannot be installed in place of miniature architrave switches. Installation is simply of matter of disconnecting the existing light switch and wiring the Touch-Lamp Dimmer in its place. We'll talk about this in more detail later. SLB 0586 dimmer IC The circuitry of the Touch-Lamp THE 1-L P DIMMER Dimmer is quite simple and is based on a new integrated circuit from Siemens, the SLB 0586. This chip supersedes and replaces the Siemens S576 chip which had three variants: the S5 76A, B and C. The SLB 0586 is quite a complex chip but briefly, it responds to signals generated when your hand touches the decorative plate and it distinguishes between a brief touch and a longer hand contact. In response to these signals, it delivers trigger pulses to a Triac which controls the actual power fed to the incandescent lamp. To read more about the internal function of the SLB 0586 see the panel accompanying this article. employs a Triac to vary the AC power fed to the incandescent lamp. The Triac is an AC power control device which can be made to turn on at any point in each halfcycle of the 50Hz AC mains waveform. If it is turned on early in each half cycle, the power fed to the load is high. If it is turned on late in each half cycle, the power fed to the load is low. Since the Triac is a switching device, it can control quite large amounts of power while its own heat dissipation is very small. For example, if the Touch-Lamp Dimmer is feeding 250 watts to an incandescent lamp load, the power dissipation in the Triac will only be about one watt. Precisely when the Triac is turned on during each mains half cycle is determined by the timing of the Phase controlled Triac As with any other light dimmer, the Touch-Lamp Dimmer circuit trigger pulses fed to its gate electrode. Since the timing is relative to the phase of the mains waveform, this method of control is referred to as "phase control". Radio interference One big problem with Triac circuitry, as used in light dimmers, is that it generates radio inter£erence. This is because the Triac turns on extremely rapidly, within a microsecond. The fast rising current waveform is rich in harmonics and these are easily picked up by radios, expecially in the AM broadcast band. If you bring an AM portable radio close to a conventional dimmer you can hear the "buzzing" sound which is caused by the Triac switching. The buzzing is loudest when the light is at half brilliance. EXTENSIOND----- - - - - - - - - - - - - - - - - > - - -....,__ _ _ _ _....,__ _ _ _ _ _ _ _ _ _ ____,_ _ _-OA LKl ,I 1M 01 1N4148 .00b8 3 02 1N4148 1 INTEGRATOR 100 16VW _ mJ 1W 03 1N4148 VOD 8 TRIGGER.t--- - t - - - - - + - - - - i - - - - i - - t --N-+ - - t - - - - - . 5 240VAC 01 SC142-M !Cl SLB0586 4 1.™ .SYNCl - ' - - + - - - 4 . . , . _ - - - - - + - - - - - ' t - - - ' , f \ N , , - -..... VSS 120k 04 1N4007 OPTIONS: LKl - DOWN /UP DIMMING LK2 - UP/DOWN DIMMING OPEN - STORED DIMMING 250V 300W MAX. L1 : 29T, 0.63mm ENAMELLED COPPER WIRE ON NEOSIO 17/732/22 IRON DUST TORDIO TOUCH LAMP DIMMER A2 Fig.1: the heart of the circuit is the Siemens S1B0586 dimmer IC. It responds to signals generated when your hand touches the touch plate and delivers trigger pulses to Triac Qt. The Triac then controls the actual power fed to the lamp. JUNE 1989 49 The Siemens SLB 0586 Dimmer IC The SLB 0586 is a new light dimmer control IC. It triggers a Triac directly and will thereby dim a lamp to any desired level or turn it on or off in response to signals from a single sensor, the touch plate. The SLB 0586 replaces the earlier Siemens dimmer chips, the S576A, S576B and S576C. However, the new chip is not exactly compatible with the S576 family. While it has the same pinouts, it runs from a lower supply voltage and so if it was used to replace an S576, the circuit components and layout vyould have to be changed. Since the SLB 0586 replaces the S576A, B and C, it can perform the functions of these three separate chips, depending on whether its pin 2 is tied to the + 5V rail, the 0V rail (ie, pin 7) or left open circuit. When pin 2 is tied high (LK1 on the circuit diagram, Fig.1). the SLB 0586 performs the "A" function. When the lamp is turned on, it is brought up to maximum brightness within 380 milliseconds which means the lamp filament gets a "soft start". It you hold your hand on the touch plate, the lamp will start at minimum brightness and will brighten to full brightness within 4 seconds. With repeated When the light is brightest or dimmest, the buzzing will be less. In the Touch-Lamp Dimmer circuit we have included suppression components to keep this "buzzing" interference to a minimum. Now let's have a look at the circuit shown in Fig, 1. This features the SLB 0586 dimmer IC, a Triac (Ql), and a handful of other components. The touch plate is shown on the left hand side of the circuit while the Triac is on the righthand side. The Triac is connected between the mains Active lead and one side of the lamp via the 100/.lH choke. The other side of the lamp is connected to the Neutral line from the mains. The 100/.lH choke and the 0.1/.lF 250V AC capacitor (Cl) con50 SILICON CHIP dimming, the lamp is always brightened. When pin 2 is left open circuit (no connection). the SLB0856 performs the "B" function. When the lamp is turned on, it will have the brightness set at the same level as when last used. It you hold your hand on the touch plate, the lamp will brighten from the stored setting and will then dim after maximum brightness is reached. The "B" function also gives a lower minimum brightness than is achievable tor the "A" function . If pin 2 is tied low, the SLB 0586 performs the "C" function . When the lamp is turned on, it is brought to maximum brightness within 380ms (soft start) . If you hold your hand on the touch plate, the lamp will start at minimum brightness and will brighten to full brightness within 4 seconds. With repeated dimming, the direction of dimming is reversed. The "C" function also enables a lower minimum brightness than is achievable with the "A" function. For all modes, the time to go from dim to bright and dim again is 7 .6 seconds. At first reading, the "A" and "C" functions might seem identical but the ability of function "C" to more easily fine tune the level of brightness is an advantage . We recommend either the "C" Junction (link LK2) which gives stored dimming or the "B" function (no link) which gives a soft start and better control of the dimming. For convenience, we prefer the stored dimming function (B). It you are concerned about getting better life from your lamps, you may prefer to use the "soft start" function (C). Fig. 2 is a block diagram which shows the main functions of the SLB 0586 dimmer chip. It contains logic circuitry to decode whether the lamp is to be dimmed (changed in brightness level) or turned on or off. It also decodes the position of the link at pin 2 which gives the three dimming functions already mentioned . The way the SLB 0586 distinguishes signals from the sensor is as follows. First, very brief pulse signals, less than 50 milliseconds, are disregarded. This is to make the unit insensitive to short t~rm disturbances in the mains voltage. Second , tor pulse signals between 50 and 400ms, the SLB 0586 will turn the lamp on or off. Third, for pulse signals longer than 400ms, the SLB 0586 provides the dimming function. nected between the Active line and the lamp are the interference suppression components mentioned earlier. The choke and capacitor Cl form an LC filter which attenuates the RF harmonics which otherwise would be radiated by the mains wiring. Secondly, the inductance in series with the Triac stops the load current from rising too rapidly and hence generating interference. Along the bottom line of the circuit is a lkO 1W resistor, a 0, 1/.lF 250V AC capacitor (CZ) and a rectifier diode D4. In conjunction with the 100/.lF 16VW electrolytic and the 5.6V lW zener diode ZDl, these components provide a 5V supply rail for the SLB 0586 integrated circuit. The workings of the DC supply circuit are interesting for a number of reasons. First, the 5V supply is derived from the 240V AC mains with very low power dissipation. This is achieved by dropping most of mains voltage through the impedance of the 0,1/.lF 250VAC capacitor CZ. Current flow for the DC supply takes two paths. For positive halfcycles of the 50Hz mains waveform, the current flows via the 100/.lF capacitor, through diode D4, the lkO 1W resistor and then via CZ and the lamp to the Neutral line. For negative half cycles, current flows via the lamp and CZ, the lkO 1W resistor and then via the zener diode ZDl to the Active line. For positive half cycles, the Programming Input o---------- Signal Evaluation anc Recognition Types A,B,C Brightness Memory Signal Element Counter (SEC) Control Logic for Timing and Safety Log ic Comparator Extension Input Sensor Input Sync Input Sync Trigger Pulse Output Reset Output Stage PLL Cycle Counter (CC) !NT - [ 1 Fig.2: block diagram of the SLB 0586 dimmer chip. It contains logic circuitry to determine whether the lamp is to be dimmed or turned on or off. The trigger signals to the Triac can be varied between 45° (high power) to 152° (low power) in each half cycle. To be able to distinguish the length of time of pulse signals from the touch plate, the SLB 0586 has internal counter circuitry and a phase lock loop (PLL). There is also a brightness memory which is effectively another counter which is stepped up or down in response to the signals from the touch plate. The IC has three inputs to determine its response: the touch plate already mentioned, the extension input (for additional touch plates) and the sync input which synchronises the voltage controlled oscillator of the PLL to the mains frequency , 50Hz. Synchronism is necessary at all times otherwise the trigger pulses to the Triac would be incorrectly timed and so the lamp would flicker badly. All the internal circuitry works to determine whether or not the Triac receives trigger signals to turn it on . The trigger signals can be varied from between 45 ° (high power) to 152 ° (low power) in each half cycle. The length of trigger signal fed to the Triac is just over 39 micro- voltage across the lOOµF capacitor and D4 is limited to the breakdown voltage of ZDl, so that effectively, the voltage across the l00µF capacitor is limited to 5V. Note that the + 5V line of the circuit is actually the Active line of the mains. This is important because the reference line for the SLB 0586 IC is the Active line. Pin 8 of the SLB 0586 is the output of the device and it triggers the Triac. It works by "sinking" a current out of the Triac gate, via diode D3. This is the most sensitive mode of Triac triggering and hence requires the least current. Pin 4 is the sync input of ICl. It gets a small filtered sample of the 50Hz mains signal from the A2 terminal of the Triac, via a 1.5Mrl resistor. Filtering is provided by the .0068µF capacitor connected between pin 4 and the Active line. Pin 2 is the programming input. It is tied high with link LKl , or tied low with LK2 or left open circuit (no link). Programming is discussed in some detail in the accompanying panel on the SLB 0586. We think most readers will prefer to have the unit programmed so that the dimmer comes on with the lamp at the same brightness as when it was last used. To achieve this, pin 2 is left open circuit. Pin 3 is the integrator input. This is the filtered voltage for the VCO (voltage controlled oscillator) in the internal phase lock loop (PLL) of the IC. Pin 5 is perhaps the most impor- seconds. Thus the CMOS output stage of the SLB 0586 has to supply trigger current only for a very brief period in each half cycle. If power is removed from the circuit briefly, for example during a blackout of a few seconds, the SLB 0586 will remember the brightness setting of the lamp and will come baok to that level when power is restored. For long term blackouts, when power is restored, the lamp will stay off until it is turned on by the touch plate signal. tant input of all, the sensor input for the touch plate. The touch plate works in an interesting way. In effect, the touch plate is connected to the Active line of the mains supply, but via a very high impedance formed by the lMO resistor and the two 4.7Mrl resistors, all in series. The sensor input is connected to the junction of the lMO and 4.7Mrl resistors. When your hand comes into contact with the touch plate, your body capacitance shunts away the mains voltage (which is at very high impedance remember, so you are safe). This shunting away of the 50Hz signal means that pin 5 is "pulled" towards Earth (which is not even shown on the circuit). When pin 5 is pulled towards Earth, JUNE 1989 51 Fig.3: here's how to install the parts on the PC board. Do not substitute for any of the parts specified otherwise safety will be jeopardised. L1 consists of 29 turns of 0.63mm enamelled copper wire on a Neosid iron powder toroid core. METALLISED POL VESTER CAPACITORS D D No. 1 Value .0068µF .0022µF IEC 6n8 2n2 EIA 682K 222K RESISTORS D D D D D D D No. 2 1 1 1 1 1 1 Value 4.?MO 1.5MO 1MO 680k0 470k0 120k0 0.5W 1k0 1W 4-band code yellow violet green yellow* brown green green gold brown black green gold blue grey yellow gold yellow violet yellow gold brown red yellow gold brown black red gold 5-band code not applicable brown green black yellow brown brown black black yellow brown blue grey black orange brown yellow violet black orange brown not applicable not applicable * Note: the two 4.7MO 5% tolerance Philips VR37 high voltage resistors do not have a gold tolerance band - it is yellow. If the two 4. 7 MO resistors you have been supplied with do not have a light blue body ( 1 0mm long) and with yellow tolerance band, you have been supplied with the wrong type. Do not use them! it sits at several volts below the mains Active line. Since everything in the circuit is referenced to the Active line, this is enough to cause the IC to respond. For very brief signals from the touch plate, less than 50 milliseconds, the IC does not respond. This gives the circuit high immunity from mains interference. For touch plate signals between 50ms and 400ms, the IC turns the lamp on or off. In other words, if you touch the touch plate for less than half a second, the circuit will turn the lamp on or off. For longer hand contact with the touch plate, the dimmer action will take place. This is detailed in the explanatory panel on the SLB 0586. Pin 6 is the extension sensor input. It allows the use of additional touch plates or pushbuttons. The additional circuitry required for extension touch plates will be described next month. Pre-production ICs We have yet to explain the purpose of the diodes Dl and DZ. 52 SILICON CHIP The SLB 0586 was originally developed in early 1988 and lab samples were sent to dimmer manufacturers and designers during 1988. SILICON CHIP received samples in the middle of 1988 and had a circuit ready to go for the August or September 1988 issue. Subsequently though, Siemens found that their early production chips had a problem which prevented them from properly resetting after the mains power was removed (as for example, during a power blackout). We therefore had to delay presenting the project. The symptom of this problem is flickering or flashing of the lamp when the mains power is first applied (ie, correct resetting does not occur). To solve this problem, Siemens suggested the addition of diodes Dl and DZ which we have duly incorporated. These diodes are necessary for early versions of the SLB 0586 which are now available as this issue goes on sale. Later, when modified ICs go into production, diodes Dl and DZ will not be necessary, as they will be incorporated into the IC die. Therefore, for kits of this project put together after January 1990, these diodes can be left in or omitted. Kitset suppliers can be expected to omit them as a matter of course. Other points of interest Just a few other points can be made about the circuit. The first is that the DC rectifier system involving D4 and zener ZDl only works when the lamp is off. This is because when the Triac is turned on, the voltage across it is only about 1 volt which is not enough to power the DC circuit for the IC. However, the Triac turns off at the end of each half cycle and in between this time and when it turns on, during the next half cycle, power is available to the DC rectifier circuit. Second, the circuit always draws power from the mains, whether the lamp is on or off. However, since most of the voltage drop to the DC supply is across the 0. lµF Z50V AC 11 PARTS LIST 1 1 2 1 PC board , code SC 11 106891 , 72 x 56mm HPM white Decorator blank grid and Gold plate, DR770GF/WE/G 3-way insulated terminal block Neosid iron powder toroid core, 17-732-22 metre of 0 .63mm enamelled copper wire 3mm dia, 1 2mm long countersunk raised head machine screw 3mm dia. nuts 3mm washer Semiconductors Push all the parts down onto the PCB as far as they will go before soldering their leads. To stop the coil from buzzing, the wire should be wound on tightly and secured using molten candle wax. capacitor C2, which has a high reactive impedance (j31.8k0), the current drawn leads the mains voltage and so the actual true power drawn (as opposed to reactive power) is extremely small, considerably less than one watt. This will not register on a domestic watthour meter. Third, inductor L1 is wound on an iron powder toroid made by Neosid. Because it is a toroid it radiates very little interference, in contrast to inductors wound on rods which are common in commercial dimmers (or non-existent). And because the toroid is made of iron powder, it has a damping effect on the inductor. This, too, is important in reducing the amount of interference radiated by the circuit. Construction As mentioned earlier, the TouchLamp Dimmer is built behind a standard HPM blank Decorator grid and plate. We suggest white for the grid and a gold finish for the decorative plate itself. All the componentry is mounted on a small printed circuit board measuring 72 x 56mm and coded SC 11106891. The wiring layout can be seen in Fig.3. Note that the board is fairly well crammed for the most part but is more open on one corner where the two 4. 7MO resistors are mounted. These two resistors are mounted as far away as possible from the active circuitry to ensure high isolation between the touch plate and the mains. Note: the safety of this circuit can be jeopardised if you don't use the right components. Take special note of the specified components and the way they are installed. The two 4.7MO resistors are special high voltage types made by Philips, type VR3 7. They are light blue in colour and have a voltage rating of 2.5kV RMS. They are specified for your safety. Don't substitute other types. As a point of interest, VR3 7 resistors made to 5 % toletance do not have a gold band; it is yellow instead (as shown in our colour code tables). This is because metal par- 1 SC142M, BT1 37F-600 or MAC218A8FP isolated tab Triac (01) 1 Siemens SLB 0586 light dimmer IC (IC1) 1 5.6V 1 W zener diode (ZD1) 3 1 N4148 , 1 N914 small signal diodes (D1, D2, D3) 1 1 N4007 silicon diode (D4) Capacitors 1 1 OOµF 16VW PC electrolytic 2 0 .1µF 250VAC interference suppression capacitors (Wima MP3 or Philips MKT-P 2222 330) 1 .0068µF 1 OOVW metallised polyester (greencap) 1 .0022µF 1 OOVW metallised polyester (greencap) Resistors ( ¼ W, 5 % tolerance) 2 4. ?MO (Philips VR37 high voltage; do not substitute, see text) 1.5MO 1 470k0 1MO 1 120k0, 0.5W 1 1 kO, 1 W 680k0 tides would degrade the high voltage property of the resistor 's coating. Step 1: Three PC stakes are inserted into the board and soldered. These provide mounting and connection points for the 3-way insulated terminal block which can now be screwed into place. Step 2: solder in the two 0. lµF 250VAC capacitors, Cl and C2. Do not use capacitors which are not labelled 250VAC for Cl and C2. Step 3: wind the inductor Ll. J UN E 1989 53 The pen points to the two 4. 7MO Philips VR37 high-voltage resistors which are in series with the touch plate. The PC board is secured to the plastic grid plate using a 12mm-long raised head screw and two nuts (one either side of the board). 0 ,.... ,.... ,.... (.) en J!. Fig.4: above is the actual-size PC artwork. This takes 29 turns of 0.63mm enamelled copper wire . Wind it on tightly and secure it by running some molten candle wax over the winding. Strip the two ends of enamel, tin them with your soldering iron and solder the inductor to the PC board. To make the inductor mounting more rigid, use some contact adhesive or some more candle wax. Step 4: insert the diodes into cir54 SILICON CHIP cuit. Note that their polarity must be correct. The cathode of each diode (and the zener ZD1) is shown by the band at one end. Install the diodes as shown on the component diagram and make sure that you use the correct type at each location. Step 5: install the three remaining capacitors, making sure that the polarity of the 100µF capacitor is correct. The two metallised poly- ester capacitors can be marked in a number of ways, as shown in the table associated with the component overlay diagram. Step 6: install the resistors. The colour codes for 4-band (5%) and 5-band resistors (1 % ) are shown in the table associated with the component overlay diagram. The link LKl or LK2 may be inserted and soldered now, or left out, depending on how the Dimmer is to be programmed, as detailed elsewhere in this article (no link for stored dimming; LK2 for soft start and reversible dimming). Step 7: install the integrated circuit and the Triac. Note correct orientation of both these critical components. The specified Triacs are isolated tab devices which are a safer proposition than conventional Triacs with live tabs. Step 8: solder a washer or solder lug on the copper side of the board through which the touch plate screw will pass. The HPM blank plate has eight plastic lugs on which the printed board is located. One 3mm hole is drilled in the blank plate to take the touch plate screw. The hole is countersunk slightly on the dress panel side and fitted with a raised head countersunk 3mm machine screw 12mm long. It is secured tightly with one nut. A raised head screw is specified here so that is will make good electrical contact with the decorative plate when it is fitted. Step 9: fit the board to the blank grid plate. Before you do so carefully examine all your work. Are all components correct and properly located? Are all solder connections clean, with no bridges? Yes. Good. Now locate the board on the eight lugs and over the touch plate screw. Secure the board with a second nut on the touch plate screw. Make sure it is reasonably tight. Step 10: electrical check. You're The countersunk raised head screw should sit slightly proud of the grid plate surface to ensure good electrical contact with the decorative plate. almost finished at this point but don't rush it. Switch your multimeter to its highest range and measure the resistance between the Active terminal and the touch plate screw. The resistance should be close to l0MQ or there should be negligible pointer deflection if you have an analog multimeter which will not measure very high resistances. This test will ensure that there is no fault at the touch plate. If the circuit fails this test, check that the correct value resistors have been used and that there are no solder bridges or shorts on the board. Prices listed apply till August. OUR LA EST UHF REMOTE CONTROL (EA JAN 89 and APRIL 89) • • • Installation involves removing the old switch plate and replacing it with the Touch-Lamp Dimmer. Wiring involves only inserting the two switch wires into the terminal block of the PCB. Before doing this you must switch off the power at your fusebox. To ensure that you have pulled the correct fuse, try the light switch before removing it from the wall and touching its connections with a screwdriver. Once the connections are made, screw the Touch-Lamp Dimmer to the wall and re-apply power. Check that the dimmer responds correctly to hand contact on the touch plate. Once that has been established, fit the decorative plate and you are finished. After a long period of use, the Dimmer may collect dirt and an oily film on the polycarbonate plate. This can decrease the resistance between the touch plate and earth and cause false triggering. This can be fixed by a quick wipe over of the decorative plate surfaces with a clean cloth. In some cases, it may be necessary to remove the decorative plate and wipe over the whole plastic grid plate. Next month we will present the Dimmer extension circuit which will allow you to use a number of touch plates with the Touch-Lamp Dimmer. We will also show you how to wire in these additional plates and how to troubleshoot the circuit if it doesn't work. ~ High Security, Low Power Consumption. Switch and Indicator Relays. Up to 50 metre range. COMPLETE KITS TRANSMITTER & RECEIVER ONLY $49.90 Extra Transmitter Kits $17 .00 ea PASSIVE INFRARED IIE DETECTOR (EA MAY 89) • Installation Next month The decorative plate simply clips over the plastic grid plate and contacts the raised head screw. We used a gold plate but you can use any colour you like from the HPM range. LOOK AT THESE BARGAIN PRICED KITS • Uses Special Dual Element Pyroelectric Detector. Kit includes two Lenses. SPECIAL BARGAIN PRICE $34.95 Interface Components $7 .95 extra. CHANNEL UHF REMOTE CONTROL (EA NOV 88 and MARCH 89) • Package including Transmitter, Receiver and Four Channel Relay Driver, plus indicator. SPECIAL TILL END OF AUGUST $119.00 THE: MICROPHONE (EA NOV 86) • • • Profession al Quality Up to 1 V RMS Output, Drives any Amplifier, even HI-FI Line inputs. Touch Control. COMPLETE KIT $24.99 AINS MUZZLER (SC JAN 89) Short Form kit similar to the Mains Muzzler including the Torroid, 3x0.022uF/ 400V metallised polyester capacitors, 1M ohm 1 W resistor and a 275V/40joule Varistor THE PRICE? ... ONLY $7 .40 That's less than the price of the Varistor! UL ONIC MOVEMENT t TOR/ALARM • • • • High Quality Crystal Controlled Kit. Prewired Transducers. PCB & Components plus ABS Case. Relay Output. COMPLETE KIT $42.95 BANKCARD, MASTERCARD and VISA ACCEPTED WITH PHONE ORDERS. P&P FOR ANY OF THE ABOVE $2.50. OATLEY ELECTRONICS MAIL: PO Box 89, Oatley, NSW 2223 SHOP: 5 Lansdowne Pde, Oatley West. PHONE: (02) 579 4985. You can also buy some of our Kits at the following Distributors. Slightly higher prices may apply. NEWCASTLE - NOVOCASTRIAN (049) 62 1358 MELBOURNE - ELECTRONICS WORLD (03) 723 3860 WOLLONGONG - ITEC (042) 26 4044 JUNE 1989 55 ~a,, ~e•e:,e ~ eo9~ , ~ f.oe ~ e4a, ~ - .,4,ut too~ td ~ ~ ~ , 'P~~ ,N4~ ~ ~#N4,#d, 4a:e ~ k.44. ol ~·u ~---====,----~ -,---.-_-:, GUARD YOUR HOME! NEW! NEW! NEW! Pin Point ULTRASONIC CLEANER -- WIii even clean your teethl HousE GuARD ALARM SYSTEM (SccEAMarc!vApril'89) Burglaries are on the inaeue! Doean't itmalte seme toprou,ctyour home and iu contm1ll7 --------..... 10watt ·~- Megaphone/PA NoDOCd to hire PA cquipmcm and then have the bother of '°tting it up. totally portable and LOUD! Up to 800M in good condition, • pcr&,ct for the school pet mow, public meeting or sports day. HAIL THE VALUE! $99.95 A 19so "'C This euy•to-build kit aaemblct on a single PC and INCLUDES 12V 1.2AH inbuilt lead calcium back•up bot1my. :I 0 z m 0 Features Include:• Entry and exit delay• Panic alum input • Batti:ry hack•up • Line monitoring • Soft alarm Lamp start• !clltale output• Auxilliary ielay for extmw siren etc.• Key switch operation• Uses almoot any type of scmor. K 1910 $89.00 :c C MULTI SECTOR - URGLAR m MULTI SECTOR BURGLAR ALARM ALARM :c Protect your Home or Bu,lneu 11-om Intruders wllh 1h11 "State of the Art" Burglar Alarm S:,,tem Over the Jut few year,, Hou1e Break· Im have inaeucd dramatically. The ,ecoyery ralc of stolen goods is very low. Now IIIOIC thaneverbcfon:, itmalo,sextn:mcly good ICDIC to build and install this ingenious Multi• Sector Sy,1mn. 11>is unique Alarm Sy11mn incorporaa the features of the 11101Cexpenaivc commercial model ■• , ,, l••·····•• i at a &action of the p-icc. Fealures:(See EA Jan/Feb'SS or°"' 1989 Catal01ue for fuU features) Kit (I..Ha Battery Back Up) Wcm'tscratchordamagc • mes ordinary tap water andcrcazs millions of supcr•pcnell"lting bubbles. Hospital test11how that lntruon.ic cleaning produces better rcsult1 safer than convcnticmal methods. .,, In Ju,t 3 minutes you wUI be amazed at the dlll"eronco! Back Up Battery 12V 1.2AHS K1900 Awarded the Good Product Design Award for ClllDC in 1987 -I 0 Earm itl COit bunderds of times over in cleaning cooncctors, PCB',, 1witches,jcwellery, glu1e1, watches, drafting pens, etc. A 0100 TOP 5065 VALUE AT $199.00 $24.95 tli TOLL FREE BANKCARD 008 999 007 K5010 TOP VALUE AT $399 -0en a~:~~~a~~~~~ n~:e43:.;2 8 hours Companion to the Studio 200 Stereo Power Amplifier and with specifications that match, (See our 1989 Catalogue p■ gc 13) and is just u straight forward to build. • ln•built speaker prollOction • Low hum tcxoidal transformer • Professicmal looking, black satin fmillh • Low lealcagc power supply capacitors • Rugged, custom built chastis ~ DELIVERY Stereo Control Unit Great Features: m m :c 0 z e NEXT DAY JETSERVICE (See Sil icon Oiip JIIIIC/July '88) Out Performs commercial uniu costing $600.00 and more) (See SC Feb'88) Sensational Specifications! (Sec our 1989 Catalogue page 13) Yet it will only takz: the average conmuctor 6 hours to build. T/ti, will ,..U, iMpr,o JOMrf,vwl :c l> STUDIO 200 SERIES STEREO For the purists 100W per Channel Power Amplifier r r POWERFUL 6000 RPM MINI DRILL 0) FOR PCB WORK c.o c.o c.o l 2Yolt DC operation from cxtmw powerpack Tons of torque Supplied with 0.8rmn and 1.0mmchucb, PLUS 1..0mm drill bit. T 2302 WAS $21.50 Ccmtrols include: treble, bu1, balance, tape monitor switch, st.crco memo switch and. volumo con1rol. Jnpw selectable from: pbono, tuner, VCR and tape loop. ,tlt,,,,.i<:, til inclMM,ft,IIJ prof•.,io"""1 pMMclt,d •NI pri,,J,d fH6nd1. K501s SUPERIOR VALUE AT $229.00 NORMALLY THESE TWO UNITS ARE EXCELLENT VALUE AT A TOTAL OF $628.00 NOW, FOR A SHORT TIME ONLY, WE ARE OFFERING THEM BOTH FOR $550.00. YOU SA VE $78.00 0 0 Now Only $18.00 DRILL BITS for PCB work 0.8mm T2320 $1.75 1.0mm T 2325 $1.95 PHONEORDER TOLL FREE ALTRONICS 008 999 007 0 0 -.J PHONEORDER TOLL FREE ALTRONICS 008 999 007 Ultra High Power Capacity Ry exciting ,,._ Is lh•t •II o ake,. ""' •vailable at •uch • unt price for thla month - but ulck -atoca .,. limited. 15" (375mm) WOOFER Polypropylene Bass Drivers Our ALL NEW "Blad<" polyprop cone Bass Drivers exhlllt quite astonishing low register reproduction. Power ratings quoted are conservative. Not the cheapest but dellnltely the BEST VALUE we know of - ANYWHERE. Huge 120 Watts RMS Massive 200 W Max. C3075 C3070 Normally $129 Normally $99 1OOWatt RMS 1SOW Max. NOWONLY$99 ...... YOU SAVE $30 0 0 NOWONLY$89 Was$69.00 NOW ONLY $49.00 HUGESAWNGSONSPEAKERS 0, 0, 0, B"WOOFER 60Watt RMS 1 Max. co c 3060 Was $49.95 Now $39.95 SAVE $10.00 oow 0 0 1O" WOOFER ,, 60Watt RMS 100W Max. C3065 12" (300mm) WOOFER 1 61/2" WOOFER/Midrange ~ 30Watt RMS SOW Max. C 3055 WAS $29.95 . 61/2" Mid Range 30Watt RMS SOW Max. with sealed frame .~\ , NOW ONLY $24.00 . c 3045 Was $27.50 NOWYOU SAVE AT $22.00 CJ) -z (.) "'C :::c: 0 z m 0 :c ·c m :c 0 a: ~ <t ttl a: SA-70 TOP QUALITY crossovers. 3/JW RMS power handling. Cabinet size: 210D x 170Wx260Hmm C 3250 WERE $399pair 8" WOOFER/Dome Tweeter SAVE$100 NOW ONLY $299 A PAIR U. (Sealed cabinet) ..J 2-Way kit complete with crossovers and cabinets. 70W RMS power handling. e ~=i~:::~ ..J X 400Hmm C 3260 WERE $499pair ffi SA VE $100 ~ NOW ONLY $399 A PAIR <at> SA-100 z 0 J: Dome Tweeter ,· c. (Bass re/1,ex) 2-Way kit complete with crossovers and cabinets. 100W RMS power handling. Cabinet size: 338D x 29-0W x 640Hmm C3270 WERE $799pair NOW ONLY $599A PAIR SAVE$200 SA-130 10" WOOFER 3-WAY REFLEX Complete with crossovers and cabinets. 13/JWRMS power handling. Cabinet size 0 0 0) 368D x 'JlYJW x 940Hmm (0 (0 (0 C 3280 WERE $1,199pair SAVE$200 NOW ONLY $999 A PAIR CEILING SPEAKERS - KIT The ideal, high grulc extension spcala:rs for the games room, ·den, study, worbhop, back ""rsndah, kitchen- w}.:;revcr you want sound. Kil i.ncbuh~ curytl,,iag JOII right 4ow11 lo tit• •crews. Ceiling mounting can actually cnhanao the sound so that the 4 •, I SW att dri"""' that comprillc the her.rt of the sym:m really ,ound stunning! ~,/' ,,.e4 • Contents: 2x Redford c 0626 Drivers; 2 x C 0810 Grilles; 1 x Redford A 2300 60W stereo volume controller; 2 x 20M rolls speaker wire and mounting screws. * 1.,. $99.00i ~ Beautifully pockaged, they make the perfect house warming gift. PHONEORDER TOLL FREE ALTRONICS 008 999 007 0 0 ...... PHONEORDER TOLL FREE ALTRONICS 008 999 007 DIL SWITCHES Gold plated self-wiping contac:tll , ·-~ ~,., ,- . Ideal/or tu service tuluiician and hobbyist alih. Allows components to be quickly and cleanly removed wilh one hand. Comes wilh a cleaning wand. •20,000 Obm,/Volt DC 240V AC SOHz 30WJSEC Approval W/22281Euy single handed actioo!Simple cleaning action. •8,000Obm,/VdtAC •Mirror backed scale •Overload pro1"Cmd •10AmpDCc:ummtrmgc •Unique cany handle doubl .. u bench stand •19 ranges in all •mcludoo battx:ry •Sim 135 X 91 X 39mm T 12so Normally $59.95 SOLDERING STATION MICRON T2440 a 101a $39.95 Now' get one at $29.95 Electronic Temperature Controlled Temperature Selectable, Soldering Station a 101e Carry case $4.95 ECONOMY POCKET SIZED TESTER ~ \' Thi• little beauty I• all you nHd for around the hOUH Now this is really quality and versatility! or for simple kits. En• al lhu lo .., low priu ii luu pulll] of f.,,1,.,.,, • 13 ranges including; DC Volts, AC Voltl, current, resistance and dec.ibell • 20CX) Olum/Volt ,cmitivity • Overload pro1"ciCd •Mirror back scale •Uses AA bat11:ry- supplied • Complete with IHI leads and ln1tructton1 Tiny sim - 90 x 60 x 30mm (slightly larll"I' than a buoinoss card • a bit thicker tho') a 1013 0NLY $19. 0 OLD The M!Cl!.ON T2440 soldering statioo offer, the ultimate in controlled tcmpcratun:, band oddcring. Simply rotate detained rotary ,witch fn>cly to selectable fixed tcmpcratun:s of: 320'C(608"1') 350"C(662'P) T 2440 Normally $139.95 380"C(716'P) 410"C(770'1') 440"C(8'.1A"P) without c.banging heater or tip. Save $20.00 Now! 0 LY $119.95 Packed with features: S3045 S3050 S 3055 S3060 S3065 UTILITY 2Way 4Way 6Way IIWay 10Way PRICE each $1.80 $1.95 $2.25 $2.50 $2.90 EW ICE -:f, 1.80 1.20 $1.71 $1.118 .,S p ARTS CASf ~~--~ "'CJ :c ~-x:;; \\ ~ 0 z m Featuring a clear plutic lid IO you can tell contents at a glance. Simple slide lock. 41! partition combinations. Very sturdy ABS plastic. H0249WAS $23.95 NOW ONLY $18.00 SPECIAL ar-r- D SERIES CoMPUTER .,, CoNNECTORS • C"..otD Pr "'E • Temperature readout• Temperature comrol e Zero voltage switching• Ground tip• Low vdtage elemmt • Chrome plated, iron clad tip 0 :rJ C m :rJ Professional Series :rJ m m l> Get 240V AC Mains Power from your battery with these handy In verter kit sets Ci Ocpcnding on power capacity thc5c models will power: Microwave ovens, 1V octs, Hi Fi, AC lighting,, Electric drill and 1OO's of other appliance, to make your life easier. Ideal for camping, farming, mining, boating,• anywhere out of reach of the dd extcmioo cord. :rJ 0 -0z Many combinations to choose from: Powerhouse 600W lnl(erter (Soo EA Doc'87l 300 Watt Inverter Kit venim K 6770 $425.00 with Auto Start Fully built and tested 12V Input K 6774 $525.00 'JAY ffll>UI K 6775 $525.00 Ccmplete Kit K 6750 $279.00 Fully built and tested K 67 55 $379 .00 D89 P 3000 Male 9 Pin s •• ""' 1989 c ,,,,.1op. pq, 10 for fMUtl,111.iu , HUGE SAVINGS ON Professional Quality CJ) NORMALLY P 3010 Female 9 Pin P 3020 Male PCB Rt/L P 3030 Female PCB Rt/L P 3040Male PCB Mnt P 3050 Female PCB Mnt P 3090 Backshcll cov,:r $2.95 $3.25 $3.75 $4.50 $2.95 $3.95 S!.95 $ .• 1 $5 s" s ~ $20$2.~ SI.O 0 0 0) (0 (0 (0 D815 P3100Male 15Pin P 3110Fcmale 15 Pin P 3120Male PCB Rt/L P 3130 Female PCB Rt/L P 3140 Male PCB Mnt P 3150FemalcPCB Mnt P 3190 Bacbhcll cover LABTECH - 1GHz FREQUENCY COUNTER Premium Grade • Good fer up lo 1000 rcchargcs. Charge Rate 45-SOmA for AA, 2'mA for AAA _ _ _ _ _... J0-15mAfor9Vl2'mA CaLNo. 1·9 10.99 100up S 5020 AA 1.2V 500mAh $ 3.99 $ 3.25 $2.95 S 5021 AAA 1.2V 180rnAH $ 4.50 $ 3.95 $3.60 iluln,,,.,,., Extr.,,u/y hiBh •«Mracya,ul •bililJ -u lhu waifor lh• 11,l,oratory, worbhop, 1111inrsU, or tecl,nie•l college. • 8 digit, 7mm, red LED display with decimal point, gate, overflow, kHz, MHz and uS indicatioo. • Many ranges for frequency, re,ol ution and gau: time • High accuracy and stability on all scale, and r-e• • Sff our 1989 Catal011ue for the very lmpre,slve run ,peclllcallon,. a 1s30 '· $425.00 SA VE over $70.00 $3.25 $3.85 $4.35 $5.50 SI.So S!.9<: s:..~$2.00 $3.85 $4.85 $2.20 s· ., s _g s $4.95 $5.50 $4.95 $6.90 $4.95 S .i5 $.:. $3. O $4.50 $3.~ D825 P 31.00Male 25 Pin P 3210 Female 25 Pin P 3220 Male PCB Rt/L P 3230 Female PCB Rt/L P 3240 Male PCB Mnt P 3250Fcmalc PCBMnt P 3290 Backshcll cover $6.25 s $2.50 Sl HALF PRICE OR LESS PHONEORDER TOLL FREE ALTRONICS 008 999 007 0 0 ...., PHONEORDER TOLL FREE ALTRONICS 008 999 007 ~ FAN~STIC~T~LUE! . . . ,/ REGENERATIVE RADIO RECEIVER STEREO TRANSMITTER (Sec EA Jon' 88) (Sec Silicon Chip Oct'88) MEGGER METER MIN MITTER FM ~ G wiring and applian""' for insulati<m. breakdown. lruulation breakdown can be dctenniD::d by the UIC of this dual ranee megohm me•. Idcally 111ited for checking breakdown in clcarical wiring, appliancel tramConncn, Now Only $39.00 STEREO FM TRANSMITTER T•r•'JOarCD p,.,_r iltlo •MUli FM Simple, educational and fun to build. Prom the early days of radio. UJCS only 3 tramiston: but will pick up a l&rF range of statima. U1es Varicap tuning. K 1150 Usually $55.25 l'- 0 0 en en en co 0 0 en 0 _ Z 0 C:: ..... 12/240V INVERTER (Sec EAAug'85) K6705 K 1120 Normally $43.50 BEAT TRIGGERED STROBE(SeeAEMJuly'aS) Now Only $32.00 SA VE OVER 25% • ' t \ Gr..tfors"""1appli411c•s! T,.,._ill•r Coovert• CO 1igml to PM 1ignal 10 you can tune in with your Walkman or portable radio. Powered byooe UV pcnlite battery. Single IC circuit mab,s it cuy to build. 120W PUBLIC GREAT VALUE AT ONLY $89.00 u..... -.,.,,,..,.,.,,.,...,,. 0 , _1 -uu coltditio111. 6) O ..-..-w• it• •.,.u (!) o automotive gicncraton andaltr:maton etc. Breakdown can be meuwciatcithcr SOOY or IOOOV dcpcndin& m the required situation. WowW •It.ii cNUl"Kia,u or t.cl111icifuu worl: ..,., tool bo,r or worl IH11clt. REAL VALUE $79.00 K2sss ADDRESS AMPLIFIER (Sec Silicon Otip Novcmbcr'88) K5020 - Have the comfort and convenience of your hcmc appliancea: while camping; - just power them from your car batti,ry. The pn,cisc, crystal controlled output make1 it ideal for running frcqucncyacnaitive appliances such u belt drive turntables. Sec EA April/May 89 Chccksclcctrical j' •EAT "t'hJ~O.m:lito &Ti;to~,t: \ ,~=, : ..<~-"" \· $499.00 · ""O :::c 0 z m 0 :c C m 011, u •"7 Pluta in time to your muaic, er u ncmtal strobe. Exclusively customised by Altrmica Hif:/tP,,f..--11«l.owNoinA."'PliJw' :c intoourH0480lnstrumcntCuc. Includes silk SQ'CCilCd panel. Better than commercially made units that cost twice u much! Using lOOV line output, it is ideal for situatiooa requiring many speak.en: and long output lines. Great for halls, churches, clubs and outside rmctings. 0 K5790 $79.95 For Increased Power Two Tube Option K 5795 $16.50 Power Output (RMS): 125Watts into 4ohms, 90Watts into 8oluns, !20Watts into IOOV AC line. (Sec P"ll" 15 of our 1989 C.talogue for full spccs.) -f r r ,, :..J!-=======~_____:~_ _ _ : _ _ ~ - - - - - - - - - - - - - <t :c TOLL BANKCARD e NEXT DAY JETSERVICE m FREE ~ DELIVERY w m w a: LL ..J ..J ~ a: w 0 a: 0 w z 0 :c a. ~ 008 999 007 a~:~~~a~~~~~sn~:8:a~;2 hours 11·1 ,m ·;•~ . :'/ ) ii • ·:., . . t,~ ., ,...... ' • ~;_.;,:. .· · •· - -: ·-❖~ ~- . . Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) Colin Fobister (02) 437 4077 Melbc.urne (Vic/Tas Only) Brian Sorensen (03) 811 9967 Perth (WA, SA, OLD., N.T.) (09) 328 2199 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 STANDARD DELIVERY & PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 7 days from day you post order to when you receive goods $7.00 OVERNIGHT JETSERVICE - We process your order the day received ano despatch via. Overnight JetHrvlce Courter tor delivery next day Country areas please AL TRONICS RESELLERS allow additional 24-48 hours. Weight limit 3Kgs (3Kgs covers 95% of Orders). Chances are there is an Altronics Reseller right near you - check this list or phone us for $10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express details of the nearest dealer. Ple1H Note: Resellers have to pay the cost of freight and Road - Please allow 7 days for delivery. insurance and thl;'retore the prices charged by individual Dealers may vary slightly INSURANCE - As with virtually every other Australian supplier, we send goods at from this Catalogue - in many cases, however, Dealer pri ces will still represent a consignees risk. Should you require comprehensive insurance cover against loss or significant cost saving from prices charged by Altronics Competitors. damage please add 1% to order value (minimum charge $1 ). When phone ordering Don't forget our Expreu Mall and Phone Order Service - tor the coal of a local call, please request " 1nsurance" . Bankcard. Vlaa or Maatercard holden can phone order tor aama day deaoatch. TOLL FREE PHONE ORDER - Bankcard .Visa . Mastercard Holders can phone order Blue Ribbon Dealer• are highlighted with a ■ These Dealers generally carry a toll free up to 6pm Eastern Standard Time. Remember with our Overnight JetHrvlce we comprehensive range of Altronic prod11cts & kits or will order any required item tor you. deliver next day. WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperanc e Communications 713344 GERALDTON K.B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521713 Farmer Electronics 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOLIRNE Winscott Trading 6995740 SUBURBAN CHELTENhAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 723%60 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN CAPALABA David Hall Electron ics 3902399 FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Phi ltronics ■ 578855 ROCKHAMPTON Access E l ectronics (East St. ) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 SA CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Raqio T V 316171 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 CHARMHAVEN Charmhaven Electronics 043926266 SMITHFIELD Chantronics 6097218 COUNTRY COFFSHARBOUR Coifs Habour Electronics 525684 NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 .WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 PHONEORDER TOLL FREE ALTRONICS 008 999 007 l> !:i :c 0 -0z (J) 0 0 (X) (0 (0 (0 0 0 ...... Build this universal temperature controller Ever wanted to control the temperature of liquid in a tank or perhaps the air in an enclosure? This low cost controller will do just that. It will hold the temperature at any setting from near freezing to near the boiling point of water. By BRANCO JUSTIC & JEFF MONEGAL When you think about it, there are quite a few applications for a universal temperature controller. For example, you might want to control the temperature in a tropical fish tank or the temperature of etchant when making printed circuit boards. Perhaps you are a keen "home brewer" and want to make the best beer. Again, this unit will closely control the temperature of your " brew" . On the farm , it could hold the temperature of a small hatchery at a set level. We're sure readers will come up with a lot of other uses. To ensure complete safety, the 60 SILICON CHIP circuit works on low AC voltages (anywhere between 20 and 40VAC), with 32VAC shown as the nominal input on the circuit. The controller is housed in a neat black plastic case measuring 185 x 125 x 50mm. It has rounded corners and clips together. On the front panel, it has a single heater control and two LEDs, one to indicate that the desired temperature has been reached and the other to indicate· that the heater element is actually on - ie, it shows the heater element cycling on and off. There is also a 6.5mm jack socket to connect a temperature sensor which is a negative temperature coefficient (NTC) thermistor. This is placed in the medium (liquid or air) to be controlled. We'll talk about this later. On the back panel, there are two pairs of banana plug sockets. One pair is for the 32VAC input while the other is for the leads to the heating element. The required temperature setting, as determined by the front panel knob, will be controlled to within ± 1 °C, once the "Temp Correct' ' LED indicator comes on. Circuit details This temperature controller has been designed by Oatley Electronics. The circuit is perhaps a little unusual (and even overdesigned) in some aspects but uses cheap and readily available components. In fact, the full kit for this project is so cheap there would be little point in trying to buy the individual parts separately, even if you have some of them on hand. Now let's look at the circuit details. Power for the circuit comes from a 32V transformer (not supplied) which is fed to diode Dl and the 470µF capacitor Cl to produce about 45V DC. This is then fed to a regulator circuit consisting of transistor Ql, diode D2, zener diode ZD1 and .associated resistors and capacitors. ZD1 is a 15V zener which provides a constant voltage at the base of Q1, a BD679 Darlington power transistor. Ql functions as an emitter follower, producing a regulated voltage of close to 13.6V at its emitter. The 100µF capacitors C3 and C4 provide extra filtering for the DC supply to the base of Ql. D2 also helps to improve the filtering but it really is gilding the lily. Op amp IC1 is the heart of the circuit. It is connected as a high gain (x 10,000) inverting amplifier but really functions as a comparator. It compares the voltage across A negative temperature coefficient (NTC) thermistor is used as the temperature sensor. These feeds back information to the controller so that temperatures can be kept within ± 1 °C. The thermistor is housed in a plastic tube which is sealed to prevent corrosion of the leads. R12 100<:l + v - - + - - + - - - - + - - - - - - - + - - -+--"Ni~-+-- - - - - - - . - - - - - - + - - - , C7 10 + A 16VWJ C9 100 D3 1N4148 + 16VWJ: R16 56k R7 10M 02 2N2907A C C10 .01!. D4 1N4148 C5 1D .,. ':' + 16VWJ 03 ':' 2N2907A C C11 01:t T B EOC VIEWED FROM BELOW ~ EC B ,; A2 ':' D1 1N4004 .~. +v 32VAC + 31~~11~~~1 m CJ TEMPERATURE CONTROLLER + C4 + 400mW -:- J '":" Fig.1: op amp IC1 is wired as a high gain amplifier but really functions as a comparator. When the thermistor (RTtttl cools down, IC1 's pin 6 output switches low and enables oscillator IC2b via inverter IC2a. The output pulses from IC2b then trigger Triac Q4 via IC2c/Q2 and IC2d/Q3 to turn on the heater. D1, Qt and their associated components provide a regulated 13.6V supply. JUNE 1989 61 Fig.2: here's how to install the parts on the PCB and wire up the external hardware. Note the use of shielded cable for the connection to the 6.5mm jack socket. There is no need to isolate the metal tabs of Ql and Q4 from their respective heatsinks - just make sure that the heatsinks don't touch since they sit at different voltages. CAPACITORS D D D D No. 1 3 2 1 Value 0 .1µF .01 µF .001 µF 680pF IEC 1 OOn 1On 1n 680p EIA 104K 103K 102K 681K RESISTORS D D □ □ D D □ D D No. 1 1 1 2 4 2 5 3 1 Value 10MO 1MO 100k0 56k0 10k0 4 .7k0 1 kO 1000 4.70 the NTC thermistor, RTHl, with the reference voltage set by the temperature controller, VR1. When the thermistor cools down, the voltage across it increases. This causes the voltage at pin 2 to rise above that at pin 3. When this happens, IC1 's output switches low. The output line from IC1 is filtered with R8 and C6 and then fed to Schmitt trigger stage IC2a. This inverts the output from IC1 and enables oscillator stage IC2b. 62 SILICON CHIP 4-Band Code brown black blue gold brown black green gold brown black yellow gold green blue orange gold brown black orange gold yellow violet red gold brown black red gold brown black brown gold yellow violet gold gold 5-band code brown black black green brown brown black black yellow brown brown black black orange brown green blue black red brown brown black black red brown yellow violet black brown brown brown black black brown brown brown black black black brown yellow violet black silver brown IC2b is a Schmitt trigger oscillator with the frequency set by Rl 1 and C8. When its pin 2 is high (corresponding to a low output from IC1), the oscillator runs at about 500Hz. IC2a also drives the two LEDs via lkO resistors. When IC2a's output is high, the " Heater On" LED is alight and the "Temp Correct" LED is out. When IC2a's output is low, the "Temp Correct" LED lights and the "Heater On" LED goes out. The rest of the circuit is used to trigger the Triac Q4. Transistors Q2 and Q3 drive the gate of the Triac via C14, a O. lµF capacitor. Q2 "sources" current into the gate via C14 and charges it in one direction and then Q3 charges C14 in the other direction. IC2c and IC2d, together with diodes D3 and D4 and associated components, form a complementary drive circuit for Q2 and Q3 which ensures that there is a "dead time" between one The PC board is secured inside the case using machine screws and nuts. Smear the mating surfaces of Ql, Q4 and their heatsinks with heatsink compound before bolting the assemblies together and take care with component orientation. transistor turning off and the other turning on. This "dead time" is good insurance because if the two transistors happen to turn on together they will provide a direct conduction path between the positive and negative supply rails and thereby destroy themselves. Construction As mentioned previously, the Temperature Controller is housed in a dip-together plastic case. Inside is a printed circuit board which accommodates all the circuitry. After checking the board for any track defects such as shorts or open circuits, you can start the board assembly by installing the resistors, diodes and small capacitors. Make sure that the polarity of the electrolytics and diodes is correct. Now solder in QZ and Q3 and the two IC sockets. Note that the IC sockets have a slight "nick" at one end which matches the moulding of most ICs, so as to indicate correct orientation. You can now solder in Darlington transistor Ql and the Triac (Q4). Note that both these units are laid flat and mounted on U-shaped heatsinks which are each secured to the board by one screw and nut. No mica insulation is needed between the heatsink and the transistor (or Triac) which means the heatsinks are "live" at about + 45DC [for Ql) or 32VAC (for Q4}. For this reason, the two heatsinks must not touch. When you have completed the board, the two ICs can be inserted into their respective sockets and the board can then be set to one side. The case now needs to be drilled for the board mounting holes and the front and rear panels need to be drilled for the various pieces of hardware. You may also care to label the controls and this can be done with white Letraset. Now install the hardware items into the case, then install the PC board and complete the wiring. Check your work carefully against the wiring diagram. Sensor lead Now you will need to make up the sensor lead for the thermistor. For this you need a 6.5mm jack plug and a length of light duty twin flex or shielded cable. Connect the jack plug to one end of the cable and the NTC thermistor to the other. The thermistor can be protected from damage by fitting a length of heatshrink tubing over it. With all assembly complete, plug in the sensor cable and apply 32 volts AC to the input of the controller. Measure the DC voltage between the collector (centre pin) of JUNE 1989 63 PARTS LIST 1 plastic instrument case , 185 x 125 x 50mm 1 PC board, code OETC89, 102 x 85mm (available from Oatley Electronics) 1 1oon wirewound potentiometer (VR 1 ) 1 instrument knob to suit pot 1 6800 NTC thermistor (Rrn 1 ) 1 8-pin IC socket 1 1 4-pin IC socket 2 U-shaped transistor heatsi11 ks (included in kit) 1 6 . 5mm jack socket 1 6 .5mm jack plug (for thermistor cable) 4 banana jack sockets (2 red, 2 black) 4 banana plugs 2 5mm LED mounting bezels Semiconductors 1 SC151 D, E or BTl 39-600 15-amp Triac (Q4 ) 1 80679 NPN Darlington transistor (01) 2 2N2907 A NPN transistors (Q2 , Q3) 1 TL071 op amp (IC 1) 1 4093 quad Schmitt NANO gate (IC2) 1 1 N4004 silicon power diode (01) 3 1 N4 1 48 signal diodes (0 2 , 03 , 04) 1 15V 400mW zener diode (ZD1) 1 4 . 7V 400mW zener diode (ZD2) 1 5mm red LED 1 5mm green LED Capacitors 1 4 70µF 63VW electrolytic 1 1 001,tF 35VW electrolytic 2 1 OOµF 1 6VW electrolytic 1 0. 1µF disc ceramic 3 .0 1µF disc ceramics 2 .001 µF disc ceramics 1 680pF disc ceramics Resistors ( ¼ W, 1 10MO 1 1MO 1 1 OOkO 2 56k0 4 10k0 5 %) 2 4.7k0 5 1k0 3 100!2 1 4 . 7!2 Miscellaneous Hook-up wire , solder, screws , nuts, washers, heatsink compound. 64 SILICON CHIP You can use either shielded cable or light-duty twin flex to make up the sensor lead. One end of the cable goes to the thermistor leads while the other goes to a 6.5mm jack plug. where the fault lies. If you have no voltage from Q l it is likely that you have r ever se connected the zener diode, ZDl . Now check that you can get the red LED to light by rotating the control knob clockwise. Rotating it anticlockwise should extinguish the red LED and light the green LED. Heater elements The NTC thermistor looks like a ceramic capacitor but is labelled 68rl 10%. It's resistance varies with temperature. Ql and the Al terminal of Q4 [this is OV in the circuit). It should be about -t- 45V. Now measure the voltage at the emitter of Ql. It should be about + 13.6V. If these voltages are not correct check the circuit around Ql to see If you have to make up heating elements for temperature contr olling a liquid, the best approach is to use modified electric jug elements. These are cheap, come with preformed leads, and it is easy to take off resistance wire to obtain the exact ohms value you r equire. If the liquid to be heated is corrosive, the heating element should be sealed in a Teflon bag. We 'll have more to say on this topic in a future issue. ~ Where to buy the parts A complete kit of parts for this project is available from Oatley Electronics, 5 Lansdowne Parade, Oatley West, NSW 2223. Phone (02) 57 9 4985. Address all mail orders to Oatley Electronics, PO Box 89 , Oatley NSW 2223 . The kit can be purchased as follows: The complete kit, as per prototype but Without instrument case , is $29 .90 . The instrument case is $8 .00. A short form kit with the PC board , 80679 transistor and NTC thermistor is also available for $12 .00. Postage and pac king for any of these combinations is $ 2 .50. A suitable 32V 4 A transformer is also available for $26.90 plus freight. Limited numbers are available. If you have trouble getting your Temperature Controller to work , post it to Oatley Electronics at the above address. They will fix it for you at a minimum service charge . For more details, phone them on (02 ) 5 79 4985. END OF FINANCIAL YEAR CLEARANCE SALE!!! DAVID REID W ELECTRONICS PTY. LTD. DB - IBM PRINTER CABLES WITTY MOUSE C-400 SALE!! SALE!! SALE!! (J? • 1 .8mtr .... $ 9.90 • 3 .0mtr .... $27.95 • 5.0mtr .... $36.95 • IBM AT/XT compatible, disk included. • Tracking speed: 200mm/sec. • Resolution: 195 dots/inch. GENDER CHANGERS SERIES COMPUTER CONNECTORS DB-9 MALE ALL ONE DB-9 FEMALE ~ PRICE DB-9 BACKSHELL ~ $1.50 ea DB-15 MALE DB-1 5 FEMALE 100 up DB-15 BACKSHELL~ $1.00 ea DB-25 MALE save up DB-25 FEMALE " ~-' to 70% DB-25 BACKSHELL NOW ONLY $ $10.95 each 75.oo • • • • Plus receive a FREE mouse pad valued at $14.95 LABTECH 20MHz DUAL TRACE CRO with COMPONENT TESTER DB- 9M to DB -25M DB -9 F to DB -25F DB-9M to DB-25 F DB-9 F to DB -25M DIRTY POWER? NOT ANYMORE!! 6 WAY POWER BOARD MAINS FILTER • • • • Protects computer , Hi- Fi, video etc from damaging power line spikes and surges. Removes high frequency noise and tones. Overload circuit breaker. 1 0 amp/ 2400 watts. THIS MONTH ONLY $55.oo FLUKE 87 DIGITAL MULTIMETER Sensitivity: 5mV to 20V/DIV , DC to 20MHz. Sweep time: 0.2µ. sec to 0.5 sec/DIV. Modes: CH -A, CH -B, DUAL and ADD. NOW ONL v $ • • • • • • FULL 12 MONTHS WARRANTY 77 5.oo $576.oo NOW ONLY Plus this month receive a FREE softcase to suit. June bonus receive a set (2) of 1 :1, 10:1 probes FREE!! YOU SAVE OVER $200.00 This charger will accept 4-AAA , AA , C , D, and 1-9 volt rechargable batteries. Complete with test meter. NOW ONLY $32.50 A must for all who value their privacy. A simple plug-in BUG detection device for your telephone. ONLY $34_95 June bonus receive 4-AA NiCads FREE!! MINI PASSIVE INFRA-RED DETECTOR S00mA PLUGPACK This unit has 6 voltages . ie 3V , 4.5V , 6V , 7.5V , 9V and 12V. Complete with 6 different plug adaptors. GREAT FOR WA LKMANS etc. NOW ONLY $ 4.5 digit display 0 1 % DC accuracy Cap test 1 OpF-5µ.F Freq 0.5Hz-200kHz Touch hold function True RMS and more 15.00 This little unit only measures 65mm H, 45mm W , 35mm D. Distance of 15mtrs <at> 105deg range. Voltage requirements are 9 to 16 volts DC , and has NC alarm contacts . NC anti-tamper contacts both rated <at> 2 4 v DC o.5 A. was $99.00 NOW $74.50 .Jr 127 York St, Sydney 2000 Phone: (02) 267 1385Fax: (02) 261 8905 MAIL ORDERS WELCOME PO Box 0103 Sydney 2000 P+P RATES $5-$25 ....... $4 $26-$50 ...... $6 $51 over ..... $8 l •■ MasterCard. . l I AMERICIIN E>CP.AESS VISA AMATEUR RADIO By GARRY CRATT, VK2YBX Coherent CW - a new low power transmission technique C.Oherent CW is a new transmission technique capable of providing a tenfold increase in signal readability. It has been developed over the last 10 years by amateur experimenters world wide. It is basically a refinement of the oldest electronic signalling system, Morse code. To understand how coherent CW, or CCW (so named by Ray Petit W6GHM in a 1975 QST article) works, it is important to first understand the basic limitations of cw. As we know, CW has an advantage over other modes of transmission in that it occupies a narrower bandwidth. This means that, for a given transmitter power, the effective radiated power is increased when using CW as compared to other transmission modes. Just as SSB is often quoted as providing an eightfold increase in efficiency over AM due to its narrower bandwidth, the whole concept of CCW relies upon the fact that the narrower the system bandwidth used, the more efficient the use of the available power. However, this is only half the story. The timing of the signals is also very important. In general, receivers with IF filters wider than the desired signals are ineffective because they allow undesired signals and noise to be received. At 12 words per minute, a CW signal occupies about 10Hz, so that an IF filter with a bandwidth of even a few hundred hertz does nothing to improve reception. Analog high-Q filters at such narrow bandwidths are unobtainable, and a PLL filter capable of 10Hz bandwidth would take tens of seconds to lock. The ideal filter would provide a bandwidth of 10Hz and would improve receiver signalto-noise dramatically. In effect, a 1-watt signal received through a 10Hz filter is comparable to a 230-watt signal received through a 2300Hz filter. Basically, the answer to this dilemma is to design the receiver to respond to certain characteristics so that it can differentiate a signal from noise. There are three critical CW CCW Fig.1: CCW signals are sent as multiples of a basic time unit. 66 SILICON CHTP (and interrelated) characteristics: (a) precise operating frequency; (b) precise pulse length; and (c) predetermined pulse sequence . If some kind of transmitter/ receiver synchronisation was available between path "ends", it would be much easier to achieve such bandwidths (by telling the receiver filter when to expect a CW character) . Such a technique could be equally applied to RTTY, FSK and other data signalling formats. Time stations Locking the receiver and transmitter stations precisely to the same frequency can be achieved by making use of HF time and frequency standard broadcasts. There are a number of these stations around the globe such as WWV, WWVH and WWVB in the USA, JJY in Japan, CHU in Canada, and VNG in Australia. A station "master standard" can be derived from these broadcasts. The transmitter can use these signals to gener.ate a pulse of known width and phase, exactly synchronised to the standard derived from the HF time signal station. The receiver samples the received signal in intervals determined by its master oscillator (which is phase locked to the HF time standard) and is therefore "coherent" with the transmitter. By analysing a CW signal, it can be seen that it is comprised of a series of units of time which we call a "frame" (see Fig.1). By using digital techniques, it is possible to determine the exact instant that a frame begins and ends. z PADDLE OR COMPUTER IN CCW KEVER PULSE PHASE TRANSMITTER PULSE LENGTH REFERENCE FREQUENCY MASTER FREQUENCY STANDARD CCW FILTER RECEIVER REFERENCE FREQUENCY MASTER FREQUENCY STANDARD PULSE PHASE AUDIO OUT PULSE LENGTH FILTER DRIVER Fig.2: the basic CCW system. The receiving and transmitting stations are synchronised by signals received from a time and frequency station (eg, WWVB in the USA or VNG in Australia). Normally, CW dots, dashes and spaces begin at random times depending upon the operator, and thus the frame length varies to an unpredictable degree. By sending CCW so that all dots, dashes and spaces are multiples of the basic time unit, the signal will be received within predictable time frames. Now although this may sound difficult, users report that this technique is usually mastered within a short time. Naturally, the use of a keyer or computer to generate characters makes the job even easier. Fig.2 shows the basic CCW system. In order for CCW stations to communicate, it is necessary for both stations to agree in advance on the operating frequency and the frame length (normally 0.1 second) for an operating speed of 12 words per minute. Since a dot and a space each require 0.1 seconds, a string of dots at 12 WPM is a square wave having a basic frequency of 5Hz. To establish communications, a CCW station sends a sequence of dots , allowing the receiving station to acquire the signal and synchronise the IF " filter" . Once locked, the filter should remain stable for hours. There is great deal more to CCW than this short article indicates but it is clear that the technique shows a lot of potential for amateur experimentation, particularly for long distance transmissions and EME (Earth-Moon-Earth) work. Further reading on CCW (1). "Coherent CW" ; QST magazine, May & June 1981. (2). "What Is Coherent CW? "; Japanese Ham Radio Journal , January 1976. (3). "Coherent CW : Amateur Radio's New State of the Art" ; QST magazine, September 1975 (Ray Petit). (4). "Universal Frequency Standard"; Ham Radio magazine , February 1974. (5). The 1989 ARRL Handbook for Radio Amateurs (page 21-16). Sangean ATS-803A shortwave receiver There are a number of receivers available to the shortwave listener today but most are useless if you want to listen to CW or SSB transmissions on the HF bands. This receiver offers continuous coverage from 150kHz to 30MHz and as a bonus will pick up the FM broadcast band. The ATS803A is made in Taiwan and looks similar to the Sony ICF-2001 (which is now superseded) but with a number of refinements including FM stereo reception via headphones, variable RF gain control, a tuning knob and a much larger battery compartment. The cabinet is well finished in black plastic, with gold trim on the tuning knob and brushed aluminium around the LCD readout. The LCD readout has 12mm digits and is very easy to read. Below the readout is a list of the frequency ranges for the various shortwave bands. Below that again is the control panel which has 22 buttons. Five of these select the band: FM (88 to 108MHz), AM, LW (beginning at 150kHz), MW (beginning at 520kHz) and SW (beginning at 2300kHz). Tuning can be done in several ways: (1) you can punch the station frequency in directly via the pushbuttons and then hit the "execute" button; (2) you can use the Start/Stop buttons for scanning upwards from .any frequency; (3) you can use the up/down buttons or the tuning knob for manual tuning; or (4) you can call up one of 14 stored station frequencies. RF gain control For dedicated HF enthusiasts, the unit has an adjustable RF gain control, which allows the user to adjust the receiver sensitivity in cases where signal overload is a problem. The provision of a BFO (beat frequency oscillator) allows reception of single sideband (SSB) and CW signals. This feature is of particular importance for those interested in amateur, aircraft or marine HF transmissions. There is also provision for the connection of a number of accessories, including external antenna, external DC supply (9V at up to 400mA), headphones (stereo for stereo FM reception, mono for JU NE 1989 67 AMATEUR RADIO - CTD The Sangean ATS-803A receiver features fully synthesised digital tuning and provides continuous coverage from 150kHz to 30MHz in both AM and SSB modes. As a bonus, it will also pick up the FM broadcast band. shortwave reception), and a high impedance output for connection to a tape recorder. Other features include a built in digital clock with alarm (which allows the receiver to be turned on at a particular time), and a sleep timer, which turns the receiver off after a period settable between 10 and 90 minutes. The battery compartment takes 6 D-size cells and 2 AA cells for backing up the computer, so that station settings can be stored. The latter two cells are not essential to the radio's operation, which is handy if you use mains power most of the time. What we found Using the telescopic antenna on the unit, we had no problem in receiving the long wave weather beacons at Sydney, Richmond and Camden airports. These weather beacons are particularly useful for providing accurate weather information. Using the scan-UP control we scanned through the AM broadcast band to the 2MHz marine band, where most broadcasts are USB. Specifications Receiver type: dual conversion superheterodyne (LW, MW, and SW). Intermediate frequencies: AM, 55.845MHz and 450kHz; FM , 10.7MHz. IF suppression: AM, 50dB; FM, 60dB. Shortwave bands Shortwave 1: 2.30-2.50MHz Shortwave 2: 3 .20-3.40MHz Shortwave 3:. 3.90-4.00MHz Shortwave 4: 4 .75-5.06MHz Shortwave 5: 5.80-6 .20MHz 68 SILICON CHIP Shortwave 6: 7. 1 0- 7. 50M Hz Shortwave 7: 9.50-9 .90MHz Shortwave 8: 11 .65-12.05MHz Shortwave 9: 15.10-15.60MHz Shortwave 10: 17.55-17.90MHz Shortwave 11: 21 .45-21 .85MHz Shortwave 12: 25 .60-26.10MHz Note: these SW bands are selectable in sequence by repeatedly pressing the SW button. Long wave band: 1 S0kHz-281 kHz . FM band: 87.5MHz-108MHz. AM band: 150kHz-29,999kHz continuous (SSB reception using BFO) . The BFO allowed good reception of Sydney Radio on 2182kHz. Working up through the HF bands we covered shortwave 1 and 2, then the 80-metre amateur band, using the BFO for SSB and CW reception. At 5.0MHz we were able to monitor the revamped, privately operated VNG time signal, although at greatly reduced signal level compared with the original Lyndhurst site. 6677kHz provided interesting listening as many international airports broadcast current meterological conditions on this frequency. The 40, 20 and 10-metre amateur bands are also covered, although we did not hear any 10-metre activity. Towards the upper end of the receiver coverage we noticed a lack of signals, although this seemed to be due to inactivity rather than a problem with the receiver as we were able to hear an increase in background noise when we connected an external long wire antenna. FM reception was good, which is to be expected in any capital city where signal levels are high, and stereo separation was quite respectable (quoted specification is 25dB). Incidentally, stereo FM is only available via the headphones with the sound being heard in mono via the loudspeaker. Sound quality is acceptable for a communications receiver and the tone controls can give an improvement in intelligibility in difficult reception conditions. In summary, this receiver is keenly priced, a good performer, and offers features that should suit the enthusiast and dedicated shortwave listener alike. Recommended retail price is $299.00. In addition to the instruction manual, a 60-page service manual is available which contains all circuit diagrams, voltage charts, parts lists, PCB foil patterns, alignment procedures and troubleshooting flow charts. This we consider a vital factor for users not located in capital cities or close to service facilities. Our review unit was supplied by the Australian distributors, Access Communications Pty Ltd, 33 Alleyne Road, Chatswood, NSW 2067. Phone (02} 406 5311. ~ Don't miss a single issue It Electronic !~ house number ·] :I Convert a CB radio j for amateur use ~ 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. * * * * * * i 5-element ~ FM antenna Hili review: Yamaha's brilliant new CD player Constructional Projects for the Enthusiast Plus - the Original &. 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L---------- ---------------------------~ JUNE 1989 69 Part 4 Build your own LED Message Board In this final article, we show you how to build and test the display panel. We also tell you how to use the system and list the control commands that provide all the special effects. Design by DON McKENZIE As noted in previous articles, the display is made up of four printed boards, each accommodating 24 columns of LEDs (168 in all). To simplify the description, we will assume that you are going the whole hog and building a 4-board display. The procedure for building each display board (DIS5MM) is the same. Before installing any components 70 SILICON CHIP on the display board, carefully check it out on both sides for shorts or open circuit tracks. Use your multimeter to check that the ground and + 5V lines are not shorted together. It is very important to follow the correct order of assembly for the display panel. If you install components in the wrong order you will •find that others cannot be fitted. Supplied in the short form kit for the LED Message Board is a LED alignment tool. As its name implies, this is for aligning the LEDS so that they are all evenly positioned to give the professional finish that a good message board deserves. There are four holes on the perimeter of the LAD (LED alignment device) which are sized so that ½ -inch long Va-inch BSW screws can be self-tapped into them. These locate the alignment tool over the DIS5MM circuit board. Spray job The DIS5MM printed circuit board has to be sprayed black before soldering anything to it. Tape the bottom 20mm of the circuit board, where the ICs are, with a piece of masking tape and lightly spray the board with quick drying matte black paint. This is done so that reflections from the LEDs will not degrade the display. Spraying may have to be done several times. Several light, even coats are better than one heavy coat which will clog up the solder holes. It is most important that all LEDs are the same type number so that there are no inconsistencies in colour or brightness between each LED. It is also very important that the LEDs have an intensity somewhere between 7-10 mcd (millicandela) and a viewing angle of 36 degrees or greater. Most red LEDs that you would buy off the shelf would be 0.8 mcd which is totally unsuitable for the job whereas most green or orange types are 8.7 mcd (the range is very broad, starting at about 0.8 mcd and going to 350 mcd, or even higher). Do not buy high intensity LEDs as they have a typical viewing angle of only 15 degrees which is unsuitable. If your store owner cannot tell you the intensity and viewing angle of the LEDs then don't buy them as it is a murderous job to desolder all those LEDs once they are in the PCB. Typical examples of suitable LEDs are the Liton brand LTL-4223 (red), LTL-4233 (green) and LTL-4293 (orange) which all have an intensity of 8. 7 mcd and a viewing angle of 36 degrees. One last point: buy all your LEDs at once, even if at first you are go- One of the 7 x 24 LED panels. The header socket is on the copper side of the board. Note that the component side of each LED board is painted black to provide enhanced contrast and prevent reflections. ing to build just one panel. as you may not be able to get the same type again at a later date. Now comes the fun part! Starting from the left hand side of the panel insert a 7 x 7 matrix of LEDs with their ea thodes towards the bottom of the board (ie, towards the ICs). You may find that some brands of LEDs have large tangs on their legs which wont pass through the holes in the PCB. Don't worry - providing they are all the same height, it does not matter whether the LEDs are sitting flush with the circuit board or are slightly raised. Carefully position the LED alignment tool over the matrix of LEDs and lightly finger tighten some nuts onto the screws protruding on the underside of the display board to hold the tool in place. The panel can now be turned over without fear of dropping any LEDs or disturbing their position while they are soldered in place. After doing two lots of 7 x 7 LEDs, start on the righthand side of the board and that should leave just a 3 x 7 matrix in the middle to finish off the panel. The 2 x 26-pin dual row male header pins may now be soldered in but be careful as they are inserted from the solder side of the circuit board. This is because connections to and from the panel are made via headers and cables from the back of the board. Note that Jl and JZ are the only components mounted on the solder side of the board. The 24 330 ½ -watt resistors can Fig.I: a LED alignment tool (supplied with the short form kit) is used to accurately position the LEDs on the PC board. The two header sockets must be installed on the copper side of the board before the 33rl resistors are installed. J2 OUTPUT ON OTHER SIDE OF BOARD JI INPUT ON OTHER SIDE OF BOARD JUNE 1989 71 PARTS LIST FOR LED DISPLAY PANEL 1 PC board designated DIS5MM (available from Don McKenzie 1 perspex channel (available from Don McKenzie) 1 baseboard, 29 x 3.5 x 0.75-inch 2 26-way dual-row male header strips 7 1 4-pin IC sockets 1 68 5mm LEDs, all same colour and intensity Integrated circuits E1 ,E3,E5,E7 - 75492 hex inverting buffer E2,E4,E6 - 7 4LS164 serial in/parallel out shift register The four LED panels are "daisy-chained" together via the Jt and J2 header sockets on the copper side of the boards. Passive components BC1-BC6 - .01 µF ceramic capacitors R1-R24 - 330 ½W resistors Note: multiply all parts by 4 for the full 4-panel (16-character display). The Jt header on the rightmost panel is connected to the control unit via a 25-way cable terminated with a header socket and DB-25 connector. now be installed but take care to provide clearance when installing the resistors that go over the solder pins of Jl and J2. Install the 6 .OlµF ceramic bypass capacitors and the 7 sockets for the ICs, taking note of the orientation of pin 1 in each case. Now install the ICs into their respective sockets and that completes one display panel. If you are building more than one panel it will necessary to repeat the above procedure. With the panels completed, you 72 SILICON CHIP can link them together via short 26-way header cables by way of the Jl and J2 header pins. Note that when the panels are butted up next to each other with the ICs towards the bottom, the main connection from the controller will connect with Jl on the righthand side panel and will then be daisy-chained through the other panels. You can now apply the power and you should see the default ROM based test message cycling thr,ough on the display panel. Adjust the 50k0 trimpot on the interface board till you get the most stable display in both static and moving display modes. The recommended method of housing four panels is as follows: Cut a sheet of 19mm particle board as shown in the diagram and drill 16 1/s-inch holes so that the display panels can be mounted on 25mm spacers. Cut a small section away so that access can be gained to Jl on the righthand panel. If you can accurately cut this board to the dimensions shown it should fit snugly into the grey tinted acrylic housing which is available from the designer, Don McKenzie. Operator Instructions The moving message board will accept a message that can-be either a straight ASCII message or it can have some control codes (entered with the Ctrl key) embedded into the message string. These control codes will enable various attributes to be added to the message. A complete list of these attributes is included below. As noted previously, there are two ways of entering a message into the moving message board. The The LED display panel is covered by a grey Perspex channel which is suitable for all LED colours. A ready-made channel can be ordered from the designer, Don McKenzie, for $50 plus $15 p&p (see panel). 0.75" THICK PARTICLE BOARD 16x1/B" HOLES 0.4" 6.6" 6.6" CUT OUT TO SUIT CABLE 6.6" 6.6" 0.6" 118" ACRYLIC SHEET CUT TWO END CAPS TO SUIT AND GLUE AT EACH ENO Fig.2: here are the dimensions for the baseboard and the perspex channel for the display board. Note that all dimensions are shown in inches. first way is to hook up a personal computer which has a Centronics parallel printer output to the female Centronics plug on the back of the controller. Be sure to switch the front panei toggle to the computer position. Data can then be loaded into the message board by sending the data down the printer port. An easy way to do this is to use a wordprocessor or similar text editor which produces ASCII text (Wordstar is not suitable). Type your message and then embed the JU N E 1989 73 control characters depending on the way you wish your message to be displayed on the moving message board. Then just print the file as if it was going to a printer and you should see your message appear on the display. The other method is to connect an IBM PC XT or compatible type keyboard to the 5-pin DIN plug on the back of the controller. When using the keyboard method, you enter the EDIT mode by pressing HOME. This gives a static display of the first 16 characters of the current message starting at the left column and any control characters that are embedded in the message will be shown as flashing characters. The message board software supports 11 message buffers that will enable you to store up to 10 messages of your own plus the default ROM-based test message. You can select which message buffer you wish to be active by pressing one of the function keys. Fl gives you buffer 1, F2 gives buffer 2 and so on. You should see a flashing full block on the 1st character in the message. This is the display cursor. This can be moved back and forth by the keyboard cursor keys. You need to go into Insert mode for editing. The Up or Down cursor keys will jump forward to the next screen or to the prior screen, while the Home and End cursor keys will jump to the Start or Finish of the message and the cursor will be flashing on the 1st character on the lefthand side of the display. By using these keys you will be able to quickly move about the message string to do editing. The initial edit mode is the Overwrite mode which will accept any characters typed on the keyboard and overwrite them onto the existing message. This mode is indicated by a full block cursor. If the INS key is pressed to go into the edit mode, this is indicated by a flashing half-block cursor. The INS key will toggle between these edit modes and the DEL key will Delete the character shown under the current cursor irrespective of whether you are in the Insert or Overwrite mode. 74 SILICON CHIP Keyboard Commands Home: keyboard attention; stops the current display and enters Edit mode on the current buffer at the first character. ESC: run current buffer. After you are happy with your editing this will display the current message. F1·F10: selects the specified buffer tor editing. Ctrl 0: displays the ROM test message buffer. Note that this cannot be edited. Ctrl 1 to Ctrl 4: selects the number of panels that you wish to use from 1 to a maximum of 4 panels. (Note: the power up default is 4 panels). Ctrl 8: tests the type of IBM keyboard that is connected and displays this in buffer 1 0 (there are 3 types supported). Ctrl 9: copies the ROM test message into buffer 1 . Ctrl F1 to Ctrl F10: erases the specified buffer . DEL: deletes the character under the cursor. INS: toggles the insert mode on and off. END: jumps to the end of the current buffer. UP-arrow: moves to the next page. ON-arrow: moves to the previous page. RT-arrow: moves cursor right one position. LT-arrow: moves cursor left one position. Note: buffers 1 and 2 are each 2K bytes long and are also used to capture the input from the Centronics input and juggle appends etc. Therefore, anything in this buffer will be lost when sending a string via the computer. Buffers 3 to 1 0 are each 256 bytes long. Control Commands Ctrl A: this will append the new message to the old. Ctrl C: this clears the board and erases the current message from memory. Ctrl D: this will load the new message immediately; ie, will not finish current message. Ctrl Ex: this will enable the 'screen dump' filter to be changed. See note 1. Note: the above commands only apply to the Centronics input and are not applicable to keyboard input. Ctrl F: this will toggle the Flash mode ON and OFF. Ctrl Gx: this will pause and Flash the display tor "x" seconds. See notes 2 & 3. Ctrl I: this is the Tab character which is displayed as 4 spaces. When you are finished editing your message just press the ESC key and your message should start to move onto the display board. The absence of any Control character will display the new message after the last has finished its cycle. A list of the Control (Ctrl] commands that can be embedded into the text string is shown in the accompanying table. Note that each line to be displayed must have a full 16 characters of text when control characters are embedded, otherwise the display will not work correctly. If necessary, the line can be padded with spaces to make up the necessary 16 characters. Finally, note that some commands must be embedded as leading attributes while others are embedded as trailing attributes. These are listed in the table. ~ Ctrl J: this is the LF (linefeed) character which is ignored by the moving message display. Ctrl L: this is the FF (formfeed) character. See note 1 . Ctrl M: this is the CR (carriage return) character. See note 1. Ctrl N: this will show the next message as a static display after the old message is finished. Ctrl 0: this command will shoot the message one character at a time onto the screen from the right (shot on). Ctrl Px: this command will pause the display for x seconds. See notes 2 & 3. Ctrl Q: this command will clear the board by moving the display across to the right (exit stage right). Ctrl R: this command will toggle the display between large (twice normal size) and normal characters. Ctrl T: this command will display the next screen by scrolling the text down and over-writing the old screen (wipe down). Ctrl U: this command will display the next screen by scrolling the text up and over-writing the old screen (wipe up). Ctrl V: this will display the next screen by scrolling the text down, pushing the old screen as it goes (roll down). Ctrl W: this will display the next screen by scrolling the text up, pushing the old screen as it goes (roll up). Ctrl X: this will display the next screen by wiping over the old screen to the left (wipe back). Ctrl Y: this command will display the next screen by wiping over the old screen to the right (wipe forward). Ctrl Z: this is the EOF (end of file) marker and is the normal message terminator and cannot be created or overwritten while in Edit mode. Note 1 : with the Ctrl E command to enable the screen dump filter, certain characters will be translated as follows: (a) with Ctrl E0, CR and FF are ignored; spaces are as ordered. (b) with Ctrl E1, CR is translated into a Tab , FF is translated into a Tab; spaces are limited to a maximum of four spaces . Note 2: some commands require a numerical parameter to be included for a time delay in seconds: 0 = ½ second delay; 1 = 1 second, 2 = 2 seconds, up 9 seconds delay. Note 3: As the Ctrl Gx and Ctrl P commands are applicable to the entire screen they are 'trailing attributes'; ie, the message is sent first then the attribute is sent. Note 4: Ctrl T, U, V, W, X and Ctrl Y are 'leading attributes' which affect the whole screen. Note that each line to be displayed must be padded with spaces to a full 16 characters for the line to be displayed correctly. IX-A-KIT Kit Repairs - $15 per hour. Normal Rate - $30 per hour. No charge for kits that can't be repaired. 3 month Warranty on repairs . Construction - fixed or hourly 1 2 Month Warranty on Manufactured Kits. Custom Designing , Manufacturing, Large or Small Quantitites . YCAL ENTS Design, Manufacture, Repair of Electronic Equipment. (02) 633 5897 Unit 4, 62 Great Western Highway, Parramatta, NSW 2150. Trading hours: 8am to 3pm Monday to Friday. D.DAUNER ELECTRONIC NTS WE STOCK A WIDE RANGE OF ELECTRONIC PARTS • * for Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST THE FAMOUS TR-DIP METER (as featured May '89) $98.00 * CRO-VALVE 3ACP2A $45.00 * PHILIPS IR-IMAGE CONVERTER Where to buy the parts A complete set of printed circuit boards plus the programmed 2764 EPROM and full instructions are available from the designer, Don McKenzie , for $150. The specially made grey Perspex channel, suitable for all LED colours , is also available from Don McKenzie for $50 plus $1 5 for packing and postage. Write to Don McKenzie, 29 Ellesmere Crescent, Tullamarine, Victoria 3043 . All the semiconductors and other parts are readily available from parts suppliers such as Jaycar Electronics, Dick Smith Electronics, Altronics , Geoff Wood Electronics and David Reid Electronics. VALVE XX1080 $45.00 (For use in infrared sight experiment systems) Come and see. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Caltex Service Station In Birdwood Road) one 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. JUN E 1989 75 Stereo Compression for CD Players Ref: Silicon Chip March 1989 You asked for itl After many requests from readers for this projec t. here it is. This simple compressor circuit reduces the dynamic range of CD's so that you can make good recordings. Kit includes PCB. box and all specified components. (12V AC plugpack not included. Cat. MP-3020 $14 95). Cat. KC-5051 s 49 . 59 201\lllz DUAL TRACE CRO $719 (J¼ 0 ~ - - - : - : = - - -----1 OFF ALL ALARMS & ACCESSORIES 98 out of every 100 houses burgled don't have a burglar alarm I Alarming statistics arn 't they? Which category are you in' Let June At Jaycar ,--.... help make up your mind about an alarm. .., Cal. OC- 1900 SAVE $180 $ 7 99 with 2 probes SAVE s200 Quality Disks at · lfeModem Transformer Bargain St.ff Pt<-10M Another Jaycar di rect import. Would you believe - computer disks with a LIFETIME GUARANTEE for less money than you have ever had to pay before! 5 1/4" DSDD 48TPI DOUBLESIDED/DOUBLEDENSITY Nearly 1(2. price 1 A 600 ohm to 600 ohm Telecom approved unit supplied with data. Standard PCB mount. Similar to Arlec 45035. Cat. MM-1512 Cat. XC-4730 ONLY $10 $6.50 for 10 10+ $9 ea ,,....,. ·.-,···~-,-.,:····.... ,...·. ...:, 31/2" MF2DD 135TPI DOUBLESIDED/DOUBLE DENSITY Cat. XC-4736 \~c. ·.:· -..~ :;.,..J $26.95 for 10 5 1/4' DSHD 96TPI DOUBLE SIDED/HIGH DENS ITY 1989 CATALOGUE OUT NOW Cat. XC-4732 $18.95 for 10 Al l disks are supplied wi th envelope, index labels and write-protcx:t tabs. Remember, these disksight be cheap ut they arc good quali ty. We are so impressed by the quality we arc happy to offer a lifetime guarantee DIGITAL THERMOMETER D 1 Bl k R k e UXe OC OC Cabinets with Handles Forget 1.hose old mercury thermometers. This new digital thermometer wi ll measure body temperature from 32-43' C. Easy to use, simply switch on and put in mouth or under armpit. When it reaches temperature it beeps you. See catalogue for full details. Cat. OM-6300 ONLY $14 95 - -----·- ··--. . ... ...,. "?\ 16 ; "·l t:.....::...---- - · >'°'.) . •~ -) -/ - - - - - - - -- - - TJC SE' ALA NT SILAS I , n Dow Corning 738 RTV non corrosive adhesive/sealant Ideal for any sItuatIon where corrosion or high current Is a concern Will adhere to glass. painted surfaces, ceramics. etched Teflon, glass braid, silicon rubber and somP. metals and plastics. Will seal. bond, insulate nd wa terproof. · Don't pay $12.95 Cat. NM·2020, Available all stores, $1, or send $2 and we'll post you one. g~ ,_A--, ../: QUALITY AND DESIGN FUNCTIONABILITY AT A DOWN TO -(',LEARTH PRICE - A JAYCAR DIRECT IMPORT PR ODUCT j Jaycar proudly ann ou nce a range of 5 beautiful black, direct 1 - - - o - - - - - 1 1mportrackcabinets Give your equipment a real 1st class appearance All alu minium cons tructi on, removable top and bottom panels. black fi nish with • high quality brushed anodised front pa nel Handles and rubber ' feet suppl ied. along With all screws, nuts. etc . to assemble I lnd1v1dually cartoned, supplied in flat pack These cabmets rea lly . I I look the part and check out the low prices compared to other ·. I • ones A B C D E Eac h 5+ HB-5380 255 73 177 305 75 $39.50 S36.50 HB·5381 353 98 203 401 100 S49.50 S46.00 HB-5382 429 62 203 481 69 S49.50 S46.00 HB-5383 429 95 292 481 100 S65.00 S61.00 HB-5384 429 122 292 481 126 S75.00 S70.00 $9.95 NORMALLY SAVE $3 ONLY $6.95 See our ca talogue for full deta ils _ _ _ __ _ __,_111!!!=:::::..==---- -------1 Description Fil m Developer & Fixe r PCB Etch Res ista~t After many requests. it's now available. Actual Portasol brand gas Developer for Etch Res istant in a 150g can. Ideal for both Portasol gas solderin~ irons. Copying Film 125x 150x6 Cat. NA-1020 Copying Film 200x275x2 ONLY $6.50 Printing Exposure Frame PORTASOL GAS Cat. No NC-4264 NC-4266 NC-4267 NC-4270 NC-4272 NC-4280 NORMALLY S10.95 S18.95 S11.95 S17.95 S17.95 S34.95 15% OFF S9.31 S16.10 S10.16 S15.25 S15.25 S29.70 1 ~ 'J.J SCOOP PURCHASE COMPONENTS SALE! DMM's Direct import. one hand opera tion. Frequency Counter 20 ranges Capacitance Meter Diode Checker Logic Probe, Diode 10Amp Cat. OM- 1400 Yet another great factory surplus buy. They lose· you SAVE Bargain 1 $99.95 Pair of micro mini stereo speakers. Ideal for Walkman type radios. cassette players. Cat. AA-2050 #} 12 volt lluminated pushbutton switch. Green bezel. as used in expensive car alarms. (Momentary on/ off). 12V lamp suppli ed. Rectangular N 0/ N.C. contacts Normally$ 1595 ONLY $7.50 10+ $6.50 ea BELOW 1/2 PRICE NORMALLY $15.95 pair SAVE $5 ONLY $9.95 pr __ _ Cat SP-0750 ' 1/ Bargain 2 '" 8 Collet fixing instrument knob. Will accept 1/4" or 6mm pot shafts. 36mm diameter. 19mm height. Black polypropylene. Snap on cap cover with whi te F.:~~~:·: "" Cat. HK-7100 Bargain 3 Type 'J' thermocouple. Will measure from -200°C to +850°CII Supplied with 650mm va rnish impregnated glass fibre sleeving Supplied wi th full da ta. AN AMAZING $19.50 Cat ZT-9400 MS-DOS BIBLE 2nd EDITION NOW AVAILABLE The first edition was one of ou r best selling books ever ' It's been unavailable for well over 18 months. The MS-DOS operating system and its equivalent for IBM machi nes. PC-DOS, is the most.used operating system in the world. running on approxiamtely ten million machines. This revised and expanded second editi on features new material completely covering all versions of MS-DOS including the newest version 3.3. You'll appreciate the features of this new edition: • 1 • How to use all MS-DOS commands from versions 2.0 to 3.3 • Updated examples of all batch file commands • Expanded coverage of hard disks ··.. I I ..• New chapter on terminate and stay resident programs ·····... I ..... . • Complete explanation of all interrupts and functions ······... ........• Updated presentation of fil e structure and memory measurement ··· 522 pages, cover 250 x 190mm Cat. BS-0736 Still Only $39.95 Bargain 4 Piezo buzzer 3 - 20 volt. 24mm diameter. PCB mount. Pins 15mm apart. Height 17mm. Opera ting frequen cy 3800Hz. 85d8 sound pressure. $4.95 10+ $4.50 e a Cat. AB-3458 3argaln 5 Thermal cutout switches. As used in ha ir dryers. etc. Very handy. Cat. ST-3800 77°C $2 Cat. ST-3810 128°C $2 .....,.. 12V lOS PST Relay PCB mount. high quality. • ONLY $3.95 10+ $3.SO ea CASTORS Cat. HP-0838 SET OF FOUR ......... J. ~ rJ Ref S1iicon Chip Augus t 1988 Ori ginally so ld for $299 Very limi ted qua ntity is available for only S99. SAVE AN AMAZING S200 OVER ORIGINAL PRICE. C,i t. KC-5035 $99 · · ' ~·"1,1 EXTENDED TRADING HOURS!! Parramatta Gore Hill Hu rstv ill e York Street Springva le Melbourne City Buranda Old Sat till 4pm, Thu rs till 8.30pm Sa t till 4pm Thurs ti ll 8.30pm Thurs till 8.30pm Sat till ·2pm, Fri till 8.30pm Fri till 8.30pm Thurs till 8.30pm Cat. SY-4048 PLASMA DISPLAY KIT SELLOUT VERBATIM DISKS AT UNREAL PRICES NORMALLY $5 Set of 4 castors to suit speaker JUNE ONLY boxes, TV's or anything for that $3. 95 matter. Castors are mou nted on a SAVE $1 .0 5 37mm square metal bracket whichissimplyscrewedto the ~ -~ . ~ •-i ";_.'· speaker boxes. etc by 4 sel f . . tappers. (Screws not suppl ied). · ·,•. · · , Originally used on colou r TV's. . . AT LAST! Easy, Economical Cable Markers Another su rplus buy. Quality Engl ish brand wrap around clear seal markers. Consists or a sticky pa tch 72mm x 25mm wi th a wri ting surface 25 x 25mm up one end. Sticker is then wrapped around the cable. Max cable diameter 16mm. PACK OF 60 Cat. NL-4150 $4.95 Compare our prices wi th your normal supplier. 1-9 Boxes Description 35" 1S/20 Cat XC-4720 $39.95 3.5" 2S/ 2D Cat. XC-4721 $46.95 3.5" 2S/HD Cat. XC-4722 $99.00 5.25" 1S/ 20 Cat. XC-4725 $22.00 5.25" 2S/ 20 Cat. XC-4726 $26.00 5.25' 2S/ HD Cat. XC-4727 $41.00 10+ Boxes $37.95 $43.95 $89.00 $21.00 $24.0D $39.95 -• . Dummy Camera Bargain - 25% OFF We have made a great pu rchase of real istic looking dummy TV cameras. They are Aus tralian made. are supplied with adjustable swivel mounting bracket. fi xing sc rews. flashing LED circuit board and 2 flashing LED's. Also supplied is the 2 x D ce!I nylon battery holder to power the flasher circuit. Ca t. LC-5310 LIMITED QUANTITY WAS 1-4 5.9 $49.95 $42.95 10+ $39.95 NOW $37.46 $32.21--.....c..._-1,.._ _=-/L/4 $29.96 all each SALVAGE SOME CASH Turn your surplus stock into cash. . Jayca r wi ll purchase your su rplus stocks of components and equipment. CALL GARY JOHNSTON OR BRUCE ROUTLEY TODAY ON (02) 747 2022 GENUINE FM DIVERSITY WIRELESS GUITAR LINK SELLOUT Genuine NADY MODEL 201GT Guitar wireless microphone link which includes FM "True Diversity' rece iver. bodypack transmitter with high impedance input !suitable for guitar pickups, bass, sax. etc) The body pack accepts a standa rd 6.5mm plug and the audio lead acts as the antenna, neat' The body pack measures 96 x 60 x 203mm and weighs only 70 grams, it requires a 9V alka line battery. Both transmitter and receiver are crystal locked and offer 20-20,000Hz::tldB frequency respon se and 120dB lmax SPL A-weig hted) dynamic range. Output is line level 600 ohms. Minimum adverse operating range 200 feet, line-of-sight 1500 feet. Elsewhere you will pay $800+ for this system. But. while they last you will be able to get this product from us for only $3991 That's right, you will save around $400 over the normal price in Australia !Australian rec . retail $799). Ill more than one is ordered they will be supplied on separate frequencies.) N.Z. CUSTOMERS ONLY Cat DT-5020 WAS SELLING FOR $599 - NOW ONLY $399 Quality Tie Clasp Microphone AIARMPANEL TELEPHONE DIALLER Low impedance, omni-directional electret condenser. A very small microphone which cl ips on your tie. Supplied wi th 3 metres of cable to a 3.5mm pl ug. 1k ohm impeda nce. Freq. Response 40-16kHz Cat. AM-4057 • This is a marvellous product which wi ll connecto virtu ally any home/ business alarm panel. It has a bui lt in microphone wh ich records a 16 second message by you and then when the alarm is triggered will send the message to up to four different numbers. or any combina tion of the sa me. Suitable for tone and pulse systems. Also suitable as an alerting system for the elderl y or sick. Easy to connect to both alarm system IN/C terminals) and telephone 12 wires). Requires 12V DC• from alarm panel. We have seen this product for $249 in other electronic catalogues. Cat. LA-5190 ONLY SAVE $90 Metex DMM Bargain A six transistor 1/ 2 watt amp which has a two transistor tape preamp which is NAB equalised and a 4 transistor pOJWer amp. It has faci li ties to take line level inputs. It measures 1l OIL)mm x 48IW)mm. 2 required for stereo. Cat. AA-0290 Save $40 on this discontinued 3.5 di fit unit with transistor and capacitance testers included. Cat. OM-1540 WAS $129 i NOW $89 1 SAVE $40 : NORMALLY $26.95 JUNE ONLY $19.95 .,,,, SAVE $6 $159 Digital Auto Tune Up Meter Metex 4.5 Digit Multimeter Bargain Measures RPM, dwell Ion 8, 6, 5 & 4 cylinder cars). AC volts, DC volts, poin ts resistance, diode check and even ohms' Cat QM-1573 • Digital hold• 10 Amp• Transistor tester • Aud ible continu ity tester Cat. OM-1550 JUNE SPECIAL 2 for ONLY $5.90 SAVE $2 ASHTRAY WHAT A FLOP Sec 1988 catalogue for full specs We really thought this was a good product, but we were wrong. See our cata logue for fu ll detail s. 1/2 PRIC E WAS $14.95 NOW ONLY $7.50 Cat. YX-293d\ ' " LARGE SCREECHER SIREN Unbelievable ear splitting sound. 120d8 of it Operates on 12V and draws 300mA . Ideal for urglar alarms where deafening sound is ... (-required and space is not a problem. Size 11 OIW) x 851L) x 1OOIH)mm Cat. LA-5720 WAS $24.95 NOW $19.95 SAVE $5 WAS $179 NOW $139 SAVE $40 WAS $139.50 NOW $109.50 SAVE $30 IUASSl\'E SCOOP Pt:IlCIIASE Powerful 12V DC Motor! This motor, as used in automotive thermatic type /ans. has inc redible torque. It is a 'pa nca ke' style un it with a Bmrn diameter output shaft (with fla t). We have scooped up a smal lish quanti ty of these at a great price I Grab one now for an incredible $25. Worth over $6011 $25 Cat. YM-2706 Dimensions 130 !approx) dia 401approx) deep 20mmshaft lenglh 8mm output shaft 3 mounting holes tr iangularly spaced SPECS Speed 1800 RPM<at> 12V Torque 1.5kg/cm<at> 1800 RPM Power Consumplion ?OW<at> 12V Weighl 600 grams <at>105mm NEW KIT - Versatile Sub-Woofer Adaptor An other surplus stock purchase. Dua lity Japanese made with lead spac ing standard 5mm. Eapacitance 20-90pF. High quali ty. Cat. RV-57 10 SPECIAL ONLY 50~ ea a ~ l f ·l 10+40~ea Ref EA April 1989 This unit enables you to get from a stereo signal sutJ1voofer signal information. You can then feed the subwoofer signal thru a separate power amp/subwoofer speaker enclosure. It's a great way of having the space benefit of high performance book-shelf speakers with thundering bass down to 30Hzl The Jaycar kit includes all specified components, metal case and Scotchcal panel CAI KA -1717 $29.95 100 watt Mosfet Subwoofer Amp to suit. /Ref EA August 19821 Cat. KA-1452 $134.50 /power supply extra/ 100 watt 250mm Subwoofer speaker /as discussed in text/ Cat. CW-2119 $129.50 ·. Jaycar Soldering Iron I~~., Ideal for the hobbyist and ha ndyma n Our lowest price 240 vol t quality iron has a stai nless steel ba rrel. 30 watt. Cat. TS-1450 $16.95 T/4e, cfelf.ftJ.ti(llftJ.f30 PIECE ENGINEER'S DRIVER SET car alarm window stic kers. Cat KJ-7000 $19.95 DELUXE RACK CABINETS Sec catalogue for full details. All aluminium construction. Finish A Cat. HB-5411 Natural 44 Cat HB-5413 Natu1al 88 112 Cat. HB-5415 Natural Cat HB-54 10 Blac k 44 Cal. HB-5412 Blac k 88 Cat. HB-541 4 Blac k 132 B 34 57 89 34 57 89 C 38 82 126 38 82 126 Each S65 S75 $90 $65 SB5 S95 +5 $62 S71 SB5 S62 $80 $90 The black or ~alural finish cabinets are available in 44mm. 88mm or 132mm high modules. Mounting hole centres conform exactly to lntcr'lalional Racking Specifications both vertically and horizontally. P L AYMASTER 60/60 BLUEPRINT Cat. KA-1652 . ·-··-·-.- . -.2. -'"{,.~,~'- .--~: i'::i--,:::.-;:. -:~· ~'\ :::' ,;-,• !• • • ,,,. / _ _~- .$369 :l~!1 v,. HEAD OFFICE -~~~.~- ■ lllf s VISA \,'° ·V4~,• ~-......- ..--~ MAIL ORDERS 21 37 ~l - ~--- POST & PACKING 1 8 0 r_i_i_i_i_~~-i_;_t,'-(:_:,'-;_t_:4_~_:_;:_\______~_~_:_f_~_;_{_~-~-~e-~l_:_:;o_~_:_:_:B___~_!E_R_s1_oo_i_~_,_i_j_1_;_o_ _---, MAIL ORDER VIA YOUR ff ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 t'36 i:tt:~~~e Ave (02) 439 4799 · SYDNEY - CITY 117YorkSt. (02) 2671614 - GORE HILL i8:nPFarnic PARRAMATT A 355 Ctuch St 1cm. Victoria Rd) 102) 683 3371 Mon-Fri 9 . 5.30 Thurs 8.30 pm - Sat 9 - 4pm BURANDA OLD 144 Logan Rd (07) 393 0777 . Mon-Fri 9 . 5.30 Thurs 8.30 - Sat 9 - 12 CONCORD 115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sal 8.30 - 12 MELBOURNE-CITY Shop 2. 45 A'Beckett St City (03) 663 2030 121 Forest Rd (02) 570 7000Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sal 9 - 12 SPRINGVALE VIC Mon-Fri 8.30 - 5.30 Thurs 8.30 pm· Sal 9 · 12 MasterCani HURSTVILLE . Mon-Fri 9 - 5.30 Fri 8.30 • Sal 9 • 12 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sal 9 • DESIGNED IN THE EARLY 1970s, the Amtrak E60CP is the most recent but possibly the last all-American electric loco. Later American electric locos have used Swedish technology. THE EVOLUTION OF ELECTRIC RAILWAYS In this episode, we compare a very large electric loco designed in the early 1970s for Amtrak with a much smaller loco designed 10 years later by the Swiss. The Swiss loco is less than half the weight hut is more powerful than Amtrak's monster. By BRYAN MAHER Right from the start, electric locos have used series DC motors for traction. These are controlled by inserting resistances in series and/or switching the motors in series for starting, then connecting the motors in parallel when up to speed. So naturally, early electric locos ran on a DC supply. There was some use of 3-phase AC induction motors but this practice did not become widespread (see SILICON CHIP, June 1988). For 50 years then, most electric traction was based on DC systems using voltages around 650 volts, 1.5kV or 3kV. These voltages are nominal, of course, and vary with time and different track sections. For example, a 1.5kV DC system may fall to as low as 1.2kV during heavy starting conditions and may rise to as high as 1.95kV on regenerative downhill running. For longer main lines in Europe, single phase 15kV 16.6Hz AC overhead supply established a firm hold, with a 15kV to 500V transformer carried in each locomotive. The traction motors were the familiar DC series type modified to work on low frequency AC. Speed control via taps on the transformer secondary windings was simple and effective. Yf.20: AMTRAK'S MONSTER VS. A SWISS TIIOROUGHBRED 80 SILICON CHIP Equivalent locos in the USA used 11kV single phase 25Hz AC, also with series motors running on AC. (The AC/DC system of the Great Northern Railroad of USA described last month was the exception rather than the rule). Eventually, electronics finally became incorporated into railway traction. The 1950-70 period saw the introduction in Europe of static rectifiers in loco traction circuits to supply the motors with DC. France was first, using mercury arc rectifiers, but later changed to silicon rectifiers which became the universal practice. Speed control. was still via taps on the transformer secondary windings while later designs used taps on the high voltage primary, Overhead supply was 15kV 16.6Hz AC in most European countries except France where 25kV 50Hz was tried. With the motors fed from rectifiers to give DC there was no longer any reason for the continued use of a low frequency AC supply. France has been the pioneer user of the 50Hz 25kV AC system. Thyristors The 1970-80 period saw a great leap forward with the introduction of thyristors (also known as silicon controlled rectifiers or SCRs) rated at thousands of volts and thousands of amps. As well as rectifying the AC supply from the transformer, thyristors allowed more precise control of the voltage and current. The method used was the familiar "phase control" system, as applied in today's light dimmers. Early thyristors rated at thousands of amps could not switch on and off much faster than 120Hz, so series DC motors on a controlled rectified AC supply remained the norm for many years and many such locomotives were built. During the 1970s, to ease the high voltage/high current design problems, a combination of thyristor control with transformer tap changing became popular. The Amtrak E60CP An American example of this approach is the Amtrak class E60CP. In all, 26 of these electric locos ONE OF THE LATEST EXAMPLES of Swiss design, the Re 4/4 IV is a Bo-Bo type loco weighing only 80 tonnes but it is very powerful with a rating of 4960 kilowatts (6650 bhp). That's more than 1650 horsepower per axle. were purchased from General Electric on an $18m contract begun in 1973. It was this locomotive which was to be Amtrak's ultimate replacement for the GG 1 locomotives which served for more than 50 years: Ultimately though, it does not seem to have worked out that way but the General Electric designed and built loco is a massive piece of machinery. The E60CP has a high voltage transformer with two tapped primary windings which are switched in series or parallel to cope with an overhead supply of 1 lkV at 25Hz, or 12.5kV or 25kV at 60Hz. This allows the loco to run without stopping from the old 1 lkV 25Hz American lines onto a transition section of track wired at 12.5kV 60Hz, then straight onto new track sections wired at 25kV 60Hz. This technique has allowed Amtrak to electrify new ·sections of track at 25kV AC, which is fast becoming a world standard. Because DC motors running on DC (supplied by rectifiers) are used, the supply frequency change from 25Hz to 60Hz has no effect at all. Eventually all 25Hz systems can be replaced by 25kV 60Hz AC, removing the need for special power stations or frequency changing substations with their extra losses. Traction motors Each of the 6 axles of the E60CP is driven by a GE traction motor JUNE 1989 81 ANOTHER VIEW OF THE AMTRAK E60CP electric loco: weighing 176 tonnes, they are capable of travelling at speeds of up to 190km/h. These locomotives are now being rebuilt and repainted for use on secondary lines. rated at 746kW (lO00hpJ. Total power is 4476kW (6000hp). The drive to the loco axles is via a 38/68 ratio single reduction gear. The motor is axle-hung, meaning the weight of the motor hangs on roller bearings mounted on the loco axle, so the motor and train axle rise and fall together, following the track undulations. The other side of the motor, the so-called ''nose'', is suspended in a spring arrangement from the bogie chassis. With this gear ratio and 1016mm diameter driving wheels, the E60CP can exert a short term tractive effort of 34 tonnes at any speed from zero to 80km/h or 15.42 tonnes continuously up to 95km/h, reducing to 7.26 tonnes at 193km/h. The main high voltage transformer has seven secondary windings, with two groups of three windings each for traction, plus a seventh secondary for auxiliaries. As noted above, traction motor speed control is achieved by a combination of secondary taps and 82 SILICON CHIP thyristor bridges. The three motors of each bogie are connected in parallel and reversing is achieved by reversing the connections to all series fields. cars' brakes are activated. This is prevented by a WABCO braking unit which sends electrical signals to operate the air brakes simultaneously on all cars. Braking Wheel slip/slide control Blended dynamic and air brakes are used for smooth slowing from high speed and for stopping. The application of up to 50% braking by the driver is brought about by dynamic braking alone (where the traction motor fields are separately supplied and the armatures switched to braking dissipation resistors). When more than 50% braking effort is required, the dynamic braking is supplemented by compressed air brakes on both the locomotive and the train. When hauling long trains, the time taken for brake air pressure changes to travel the length of the train air line is important and could result in "concertina" effects if the front cars slow before the back Each axle of the loco carries a small alternator which generates a voltage proportional to that axle's rotational speed. The 6 voltages so generated are fed to a comparator to detect and correct wheel slip under acceleration or wheel slide under braking conditions. Auxiliaries Readers may wonder why many electric locos are as large or even larger than equivalent diesel electric units. The E60CP is a perfect example of this, being very large at 21.72 metres long, 4.46 metres high and 2.97 metres wide. It weighs no less than 176 tonnes, giving a high track loading of 30 tonnes per axle. So why are they so big and heavy? After all, they don't have a diesel engine or alternator even though those running from high voltage do carry a big step-down transformer. What more is needed? Wouldn't you expect the inside of the loco body to be virtually empty? One big requirement for passenger locos is for train heating and air-conditioning. In the E60CP that takes a lot of power in the form of a large 940kW single phase AC motor driving a 750kW 3-phase 60Hz 480V alternator. This supplies all train heating (in winter), air conditioning and cooling, lighting, cooking in the buffet and restaurant cars and other train electrical loads. Australian readers may be surprised at the sheer size of the auxiliary power supply, known as "head end power", which with the other auxiliary systems add up to more than one megawatt. This is about 117th of the main transformer capacity. But heating alone in the American sub-zero winter temperatures demands large quantities of power for a whole train. Australian trains are not faced with such severe environmental conditions. Rarely do Australian trains see snow and almost never a blizzard! Then there are essential functions that the passengers never see. In the E60CP locomotive, one 74V 15kW static rectifier supplies regulated DC power for train control and the loco's lights. These functions also have to be provided by a large battery and it too needs its own transformer and rectified supply. In an emergency, either bogie can drive the locomotive and train, as auxiliary circuit breakers are provided to allow one parallel set of three traction motors to be cut out of service. Of course the electricals must be kept cool and you need compressed air for the brakes. The air blower (for equipment cooling) and the single stage rotary air compressor with air cooler are driven by a large DC motor. Even the transformer oil must be circulated by a pump to dissipate the internally generated heat. Communications Safety demands that train dri- THIS MAIN HIGH VOLT AGE TRANSFORMER is the heaviest component in the Swiss Re 4/4 IV loco, apart from the fabricated steel chassis. Weighing about 13 tonnes, it is rated at 5.9MV A. vers keep in communication with other trains and ground staff. Therefore each driver's cab is equipped with a Motorola train intercommunication radio and a system for communication with crew and passengers. The driver is also automatically warned of train overspeed and trains can be stopped automatically if necessary by signals and ground control. Though geared for 192km/h (120mph) running, today these locomotives are often used on the short-haul trains at 144km/h (90 mph). New loco designs When it was designed in the early 70s, the E60CP would have been regarded as having the latest technology but compared with locos designed just a few years later in Europe, it is a dinosaur. Admittedly these later designs have the advantage of much improved thyristors which can operate at higher frequencies but a comparison is still startling. Swiss comparison Though Switzerland is a small country the Government railway system is second to none in the world in locomotive and coach design. Because there are three official languages - German, French and Italian - they write the name "Swiss Federal Railway" in those three languages as: Schweizerische Bundesbahen or SSB; Chemins de Fer Federaux Suisses or CFF; and Ferrovi Federali Svizzere or FSS. Hence Swiss locos may be labelled by any or all of those three sets of initials. Electric-powered since 1914, Swiss loco designs have included most possible types but their latest effort designed in 1981, the Re 4/4-IV, is remarkable in its power to size ratio. Rated at 4.960MW (6650hp), they JUN E 1989 83 3950 3950 15800 Achsfahrmasse + 201 2187 • + 201 201 • 201 2187 10700 THIS LINE DRAWING EMPHASISES just how tiny the Swiss Re 4/4 IV really is. It is only 15.8 metres long. are only 15.8 metres long and weigh a mere 80 tonnes. They are a Bo-Bo design (four powered axles) so the power per axle is extremely high at 1.24MW (1663hp). But with advanced all-thyristor motor control, radar track speed sensing and 5 % forward continuous slip control, sufficient traction is _achieved with only 20 tonnes per axle. In fact , maximum tractive effort is 30 tonnes. The designers took note of the speed and power of three earlier classes: (1). Bo-Bo-Bo class Re 6/6 rated at 7.832MW (10,500hp), weighing 120 tonnes and capable of 140km/h. 89 of these were built between 1972 and 1980. (2). The Bo-Bo class Re 4/4-II, the most numerous in Switzerland, rated at 4.7MW (6300hp), weighing 80 tonnes and capable of 140km/h. 84 SILICON CHIP 273 of this class were built up to 1985. (3). The Bo-Bo class Re 4/4-III, an 80 tonne 4.650MW (6233hp) loco of which 17 were built in 1971. For the next model, Re 4/4-IV, the designers opted for a lightweight Bo-Bo locomotive but with a top speed of 160km/h in mind. This speed is quite high considering the mountainous terrain of Switzerland. Design outline Swiss locos use a 15kV 16Hz overhead supply and so the designers chose a simple basic design. This uses a high voltage main transformer with separate secondaries and thyristors for the front and rear bogies, each with two separately excited DC traction motors. A third secondary with thyristors feeds the field windings of all motors. Speed control is therefore entirely by thyristors. Busbar connections from the transformer feed the fore and aft traction thyristor groups. These consist of two banks of thyristor assemblies, each bank fed by a 686V 1880A secondary winding. Field excitation for all four traction motors comes from a separate secondary and associated thyristors. Yet another secondary winding supplies auxiliaries. Each of the four traction motors is an 8-pole DC type with -series fields for greater starting effort, and with separately excited (shunt) fields for precise speed control. Braking Electric dynamic braking is automatically blended with the train air brakes, although the ANOTHER VIEW OF THE SWISS Re 4/4 IV which is tiny by comparison with the Amtrak E60CP but somewhat more powerful. Designed in 1981, it has full microprocessor control of all the thyristor traction circuitry. dynamic brake does most of the work, except at near stop or in emergencies. For dynamic braking, the traction thyristors are switched off and other thyristors connect the motor armatures to air-cooled braking resistors mounted within the loco ea bin alongside the traction thyristor assembly. During braking, the motor field windings are supplied as before from the separate circuit by a braking regulator. Microprocessor control Full microprocessor control is employed over the motors at all times. The microprocessor continually measures armature currents, rate of change of a rmature current and the integral of the armature current. Up to a limit, the control algorithm allows overcurrent for starting, but with safe limiting to keep the armature temperatures under control. Auxiliaries From the 990V transformer secondary (which also supplies the motor fields), supply is also taken via an harmonic filter and rectifier to a DC/ AC inverter giving 3-phase AC output at 500V, up to 65Hz, for control and auxiliary loads. Other train loads and locomotive circuits operate from a 230V supply or a smaller 36V, 60A control current circuit. An additional secondary winding on the main transformer provides for a 600kW train heating load very necessary for trains in high mountain country. Comparison with E60CP Comparisons between the Re 4/4-IV locomotive and the American E60CP show that the Swiss loco is far superior in power/weight ratio. It is also much smaller in physical size. The greatly reduced size and weight of the Re 4/4-IV compared with the American E60CP is due partly to the Swiss loco's much more modern traction control system. The American E60CP uses a bulkier transformer and busbar assembly (because its secondaries are multi-tapped), together with many large electropneumatic high current contactors. In addition, the E60CP employs a large 940kW AC motor and 750kW 3-phase alternator for train heating and airconditioning. It also ha s 6 axles and 6 traction motors in longer and heavier bogies . Overall though, the E60CP is completely overshadowed by the Swiss design. These days it is very much confined to secondary service in the USA with primary Amtrak services being provided by the Swedish designed AEM7. ~ Acknowledgements: thanks to M. Gerber et al of SBB Motive Power Works, Bern, Switzerland; to ASEA of Sweden ; to R. Clifford Black IV and K. M. Watkins of Amtrak, USA; and to General Electric USA for data, photos and drawings. JUNE 1989 85 BOOKSHELF Listening to shortwave broadcasts SAMS:,_ _ _ _ _ _ _,,__ ,,_ Shortwave Radio Listening with the Experts Shortwave Radio Listening with the Experts, edited by Gerry L. Dexter. Published 1986 by Howard W. Sams & Co, Indianapolis, Ind. USA. Soft covers, 188 x 248mm, 518 pages. ISBN O 672 22519 0. Price $25.95. I have a confession to make. Books on shortwave listening bore me to tears. Or at least they have in the past. But I have had to revise my opinion after reading this book from cover to cover. Since I really have never had the time or a receiver for shortwave listening, I have not regarded it with much interest. So it was a real surprise to come across this book. It is correctly titled "Shortwave Radio Listening with the Experts" . It has chapters on a wide variety of topics by people who really are experts in their field. No less than 25 chapters are included and they are all written by different people. In fact, each chapter is preceded by a page of info about its author, all of which adds authenticity and interest. And not only are these writers scholarly and thorough in their treatment of their chosen subject, they are also very enthusiastic so it is highly readable stuff. 86 SILICON CHIP I don't intend to list all the chapters but just those that are of particular interest. Chapter 1, entitled "Setting Up Your Shack", is predictable enough but is good info on the room you need, lighting, the desk, a range of equipment and so on. Chapter 2, on antennas, describes a number of antennas. Chapter 3 is the good oil on buying the right receiver and discusses some of the currently available models. Chapter 4 is on radio propagation and manages to treat an often boring subject in an interesting way. Chapter 5 is on recogmsmg languages and is written by a linguist. Why would you want a chapter on recognising languages? It's obvious - if you are going to listen to shortwave you're going to hear a lot of foreign languages. Knowing how to recognise them is good stuff. For me, chapter 11 is the most interesting, on the subject of over-thehorizon radars. The first of these was the Russian "Woodpecker" which was first noticed in 1976. This article gives very good background on the Woodpecker and goes on to describe other systems, including the Australian Jindalee system. The author has obviously done a lot of research and he puts it across very well. Chapter 13 is another unusual one, on the subject of "numbers stations". Apparently these are used for messages to spies around the world and their broadcasts consist only of long strings of four or five digit numbers spoken in various languages. It sounds boring but is intriguing nonetheless. Chapter 15 is on DXing FM broadcast stations and is one that would appeal to many people even though they may not own a conventional shortwave receiver . In Australia too, it is possible to receive FM signals from very long distances. There are also chapters on scanners, computers, radioteletype and tape recorders. I could go on but that should be enough to show that this is not just another book on shortwave listening. It can be recommended to anyone, whether or not they presently have any interest in the subject. At $25.95, this book is a bargain and is available from all Jaycar Electronics stores (Cat. BS-0735). All about burglar alarms ALARMS 55 Etectmnic Projects and Gircuits Alarms. 55 Electronic Projects and Circuits. By Charles D. Rakes. Published 1988 TAB Books Inc, Blue Ridge Summit, PA, USA. Soft cover, 187 x 236mm, 170 pages. ISBN 0-8306-2996-3. Price $19.95. There is more to this book than the usual car and house burglar alarms which would first come to mind. There are also battery monitors, telephone monitoring equipment and storm alarms. Many of the featured circuits are intended for the novice to tackle so don't expect anything too elaborate. A few of the suggested projects are more complicated such as the " telephone remote monitoring control system''. There are no construction details presented with any of the alarm circontinued on page 94 WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR MORE GOODIES FROM WOODIES BELLING LEE QUALITY CONNECTORS ~ ~ ~ c:c c:, lL C c:, ~ /EC Rewlreab/e Connector 3 pole reverse sex rewireable connector. Mates with L2292 appliance inlet. L2298 $6.35 141 I /EC Fused and Switched Inlet Rated <at> 6A/250V this appliance inlet, complete with integral switch and 20mm x 5mm fuse, requires a single 27.2mm x 61 mm panel cutout. Snaps in for easy mounting with 4. 75mm snap on terminations L2723 $16.75 /EC Female Chassis Socket Reverse sex 3 pole appliance outlet rated<at> 6A/250V. Mates with L2298 rewireable connector. Panel cutout 34mm x 27mm with 3.5mm holes on 40mm centres. L2292 $4.10 Chassis Mount Filter 0-Z Contacts /EC Male Chassis Socket ~ ~ Cc c:, lL C c:, ~ MADE CORDSETS /EC Appliance Cord Set Australian made, fully approved, 2 metres long. Complete with 3 pin plug. Rated<at> 240V I 10A Grey only.Straight $7.95 G c:c c:, lL C c:, ~ ~~ Fuse Holders Miniature fuseholder rated <at> 6.3A with solder terminations. Coin slot in head. Requires 12.9mm mounting hole. I""'' .·.. ~ .. L2006A $4.05 Rated <at> 6A these 4mm plugs use the Belling Lee "0-Z" contact. Contacts are silver plated phosphor bronze. Available colours black, blue, green, red, white and yellow. L37814/colour $1.90 ' ·I L2002 $3.40 4mm Fixed Socket We told you we goofed and we still have a mountain of parallel printer cables. This is your chance to take advantage of us. DB25 plug to Centromcs. During June you can still get ten for only $99.50 " Coax Connectors MORE BELLING LEE QUALITY PRODUCTS .. Panel Fuseholder - 3AG Size Finger proof, rated<at> 10A with solder terminations. Coin slot in head. Requires 12.9mm mounting hole. L2004A $8.25 \ . --· Standard Coax Free Plug Aluminium L734/PIAL $1.85 Standard Flush Mounting Coax Socket L734/S $2.00 PCB Mount Fuseholder M205 Size Standard Surface Mounting Coax Socket Enclosed fuseholder rated <at> 6.3A with coin slot in head. L2179 - 3 Pin Version $3.60 L2180 • 2 Pin Version $3.60 L604/SIAL $2.60 Open Fuseholder - M205 Size Rated<at> 6A this 4mm fixed socket has a 11-.1 mm round face. It requires a 8.2mm diameter panel cutout. Contacts are silver plated phosphor ·bronze. Available colours black, blue, green, red, white, yellow.L1413lcolour $1.10 Ten for $9.00 Ten for $9.00 Ten for $9.00 Ten for-$70.00 Ten for $80.00 Ten for $96.80 Ten for $60.00 Ten for $60.00 Huge Purchase of Printer Cables Panel Fuseholders -M205 Size . 4mm Banana Plug /EC Inlet Filter 3 pole filtered appliance inlet with 4.75mm quick connect or solder terminations. Panel cutout 28.5mm x 21mm. 3.5mm holes on 40mm centres.L2131C/S $26.50 __A_U _S_T_R _A _ L_I_ A_N__ ~ ~ Quad Line Driver Quad Line Receiver Quad Diff Receiver OMA Controller P.I.T. 2048x8 Bipolar Prom Countermmer Chip CPU 26LS31 26LS32 26LS34 8237A-5 8253-5 AM27S191 28430 28400 , .. .,~ Rated <at> 6A/250V this chassis mount filter is effective over 0400 Hz. Complete with 6.3mm Faston/solder terminations. L2140/6L $26.50 3 pole appliance inlet rated <at> 6A/250V. 2.8mm solderless/ solder terminals. Colour - black. Panel cutout 28.5mm x 21 mm with 3.5mm holes on 40mm centres . L1950A $2.50 Super Semiconductor Specials More semiconductor specials. We reckori these prices are fairly attractive but ask us for our high volume_pricing. 10 way PCB mount strips rated <at> 6.3A. They can be subdivided into lesser number of ways. On 10.16mm centres . L2222/10 $5.95 Standard Bulkhead Coax Sockets L617IN I $6.15 Heat Sinks A new low price in heat sinks. TO5/TO39 Pressed metal were $0.50 now 2 for $0.50 TO5/TO39 Cast aluminium 20mm Square, 20mm High were $1.20 now only $0.70 Open Fuseholder - 3AG Size Bridge Rectifier 12 way assembly rated <at> 7.5A. They can be subdivided into lesser number of ways. On 12.7mm centres. L1746/12 $13.25 This one is so low we can't afford to reduce it. In any case our supplier might cut of our supplies KBPC3504 400V 35A at $ 4.50 or 10 for $40 .00 GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road, (Corner Beatrice St.) iNc IN Nsw Lane Cove West, N.S.W. P.O. Box 671, Lane Cove N.S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. PENROSE 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add SS.DO.to cover postal charges. Next day delivery in Sydney add $5.00. ~ TO ~ Ol.AOESVILLE :) BfllDGE m ., All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED c I PRODUCT SHOWCASE I Weatherproof hifi loudspeaker Smart printer buffer for PC compatibles This printer buffer board for the IBM PC XT, AT or compatibles comes with 256K of installed RAM and three ports. One port is connected to the onboard female DB25 socket while another is connected via a header socket and flat cable to a male DB25 plug which could be panel mounted in a blank slot plate. The third port on the board is via a 26-way header socket. All of these are addressable via software commands. The unit is driven by a Z80 microprocessor with the three ports provided by 6821 PIAs (peripheral interface adaptor]. For more information and a price on this card, the Smartbuf 256, contact Annabelle Bits Pty Ltd, 233 Bulwarra Road, Ultimo, NSW 2007. Phone (02) 552 1801. Filter blocks for mains interference These hefty filter blocks will suppress mains interference down to quite low frequencies . The - 3dB point is very low at 9kHz and attenuation at lO0kHz is - 30dB. This high level of attenuation is achieved with four inductors and four capacitors, rated at 250V AC. Two relatively large inductors (both wound on one toroid], at 12. 2mH are used, together with another two inductors, both 1.8mH. Combine one of these filter blocks and a couple of varistors and you have the makings of a very effective mains filter. The filters, made by Schaffner, are available at the bargain price of $16 from Oatley Elec88 SILICON CHIP tronics. They also have ample stocks of 40 joule 275V thermistors at only $2.00. Get on the blower to Oatley before they run out. Phone (02) 579 4985. Altronics has designed a rugged weatherproof loudspeaker system around high quality Vifa drivers. The bass unit is a 125mm woofermidrange unit optimised for a 5-litre bass reflex cabinet, while the tweeter is a 19mm ferrofluid cooled 19mm dome unit. The enclosure is made from a very strong aluminium extrusion while the specially moulded end caps have adjustable end brackets so that they can sit at any angle. Two finishes are available: black and white. The complete loudspeaker system is rated at 100 watts RMS and is fitted with internal overdrive protection. Recommended retail price is $199.50 each or $399 a pair. For further information, contact Altronics at 174 Roe Street, Perth, WA 6000. Phone (09) 328 1599. ,--------------AMATEUR RADIO Hobbyists communicating world wide using state-of-the-art electronics. Have you just retired? Time on your hands? Interested in starting a new hobby? Like to communicate around the world? I WHY NOT BECOME A RADIO AMATEUR? Want to know more? Join the WIA - the oldest and most experienced radio society in the world - always at the forefront of radio communiGations for hobbyists. New soldering station comes with two irons Scope has released a new temperature controlled soldering station which comes with two irons, a standard 60 watt model and a slimline 30 watt unit with its own range of miniature tips. Each iron is held in its own holder, one either side of the controller unit, and is selected by a two position switch at the front. Heat up time is about 60 seconds and the temperature settings do not have to be changed. Apart from the saving on bench space where two irons are required, this new double headed unit saves about 40% of the cost of a second soldering station. Scope also offers a factory upgrading service for owners of existing Scope stations. For further information, contact your local distributor or Scope Laboratories, PO Box 63, Niddrie, Victoria 3042. Phone (03} 338 1566. Phil Gleeson is back - with Personal Computer MarketPlace Well known computer and electronic industry identity, Phil Gleeson, founder of Avtek, is returning to the scene with a flourish, after what he says was a much needed break. His new company, Personal Computer MarketPla ce, will be marketing what is claimed to be Australia's biggest range of enhancement products for personal computers. In stock will be a complete range PC add-on cards, cases, monitors , power supplies and printers. Phil is certainly well placed to give knowledgeable service, having been in the industry for years. By the time this issue goes on sale, Personal Computer MarketPlace will have wrapped up deals with a number of major US distributors who have all the exciting add-ons featured in the US magazines. For further information and a free catalog and price list, see the advertisement in this issue or contact Personal Computer MarketPlace, PO Box 1100, Lane Cove NSW 2066. Phone (02) 418 6711. Receive AMATEUR RADIO, the monthly magazine for members of the WIA, full 9f news of DX, clubs, satellites, technical articles and lots more. Other WIA services include: • A wortd wide QSL card service • Weekly news broadcasts • Classes for all grades of amateur licences • Correspondence lessons available • Meetings, contests, field days • Representation for radio amateurs at Government level Learn more about the WIA and Amateur Radio Forward this coupon, or write to: WIA EXECUTIVE OFFICE P.O. BOX 300 CAULFIELD SOUTH VICTORIA 3162 Registered address: 3/105 Hawthorn Road Caulfield North, 3161 Please send aWIA information package to: NAME: ........................................................... . ADDRESS: ...................................................... ................................... POSTCODE ................ . 1--------------..,#, E002S1 JUNE 1989 89 8-way power board has overload cutout tronics stores (Cat. P-5619) at $25.95. Four and six-way power boards are adequate for many applications but if you have a lot of test or computer equipment which doesn't draw a lot of power, this·new 8-way board is a beauty. It is fully approved and comes with an overload cutout. The new power board is available from all Dick Smith Elec- Good quality video modulator Need a good quality video and audio modulator? This unit from Dick Smith Electronics is claimed to be suitable for use with TV games, VCRs, computers, Teletext and other graphics generators. It is PAL compatible and has a vestigial side- Polystyrene capacitors YES band filter. It also has low subcarrier intermodulation which reduces any on-screen patterning due to chroma and sound subcarrier beats. Power supply requirements are simple since the modulator has its own internal 6.2V zener regulator. It can be powered from DC supplies of more than 6 volts. Current drain is around 30 milliamps. The modulator accepts a standard composite video signal with negative sync. Full audio deviation is obtained with an input signal of 5 volts peak-to-peak. The RF output is pretuned to VHF TV channel 0 or 1. The modulator is available at all Dick Smith Electronics stores (Cat. K-6043) and has been reduced in price at $9.95. It comes with a full specifications sheet too. Digital scales for accurate weights Made here in Australia? YES Made Special to Type? YES Where From? Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors. Why design circuitry which requires additional components to achieve a specific capacitance; we can wind exactly the capacitance you need to match your design criteria within the ranges of 1 OpF to 1µF and up to 10,000VDC. Capacitors are manufactured to 0 .25%, 0.5%, 1.0%, 2.0%, 2.5% , 5%, 10% and 20% and are priced according to tolerance. All capacitors are tested to 2.5 times the rated voltage. Interested? Call us now on: (02) 938 4690 OR Cut out and post this coupon to Post Office Box 740 Brookvale, N.S.W. 2100 90 SILICON CHIP ~--------------, I I I I Yes, I am interested in your_ capacitors. Please post me details of the following values: I ... /... VDC ... / .... VDC . . . /. VDC ... / ... VDC I I Name (Please print) . I I Address ........ ... ..... I Whether you are an expert chef or have other reasons to weigh materials accurately, these digital scales from Arlec will be of interest. They can weigh items up to 2kg (41b 8oz) with a resolution of 1 gram or 0.1oz. The digital readout is a 4-digit liquid crystal display which is much easier to read than typical kitchen scales. The unit may be battery-powered from 6 AA cells or run from the mains with a 9V 100mA plugpack. Membrane switches are used to turn it on or off although it will turn itself off after five minutes of no use. The Arlec Digi-Scale is available at $59.95 from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02} 267 1385. Volume control for extension speakers Buy direct from Australia's leading manufacturer and save on quality AVTEK Modems. A range of 16 internal &external modems from low priced manual to fully automatic 2400 bps models complete with power supply, instructions and telephone connections. Designed and built in Australia, all Avtek Modems are guaranteed, with service and technical support available direct from Avtek. CALL TODAY ON 008 25 2754 or (02) 888 5333 TOLL FREE SYDNEY RESIDENTS For further information and to see how much you can save on the best modem for your needs. If you wish to pipe music into other rooms from your hifi system, you really need a stereo volume control for each pair of extension loudspeakers. This neat Redford switch volume control unit fits into a standard HPM wall box and gives five different levels as well as switching the speakers right off. Ideal for ceiling speakers in kitchens, games rooms and patios, the total power capacity is 30 watts per channel which should be more than adequate for these applications. Priced at $49.95 (Cat A-2300), the Redford volume control is available from Altronics, 174 Roe Street, Perth, WA 6000. Phone (02} 328 1599. The Way I See It: ctd from page 29 voice) when she travels under overhead power lines. Another became unconscious when exposed to transmission lines, in a highly allergic state. A third suffered convulsions and coma in similar circumstances. 'fTEK VISA DATA COMMUNICATIONS (A Member of the Ne!Comm Group of Companies) A fourth missed out on the tests. He had an acute attack of asthma while driving under overhead lines, stopped immediately but died while walking under the lines, seeking help! It makes startling reading doesn't it? But Australian highways are criss-crossed by huge transmission lines and hundreds of thousands of cars and passengers pass beneath them every day of the week - apparently without catastrophic effect. If there was to be such, those crossings would surely have emerged as accident black spots on our road maps, at least for allergy sufferers. So there you are R. M. For me, it doesn't add up but I'm open to be convinced otherwise. For the pre- sent, I'd rather leave the ChoyMonro-Smith paper in the pending basket! But the Editor-in-Chief, Leo Simpson, takes a much stronger line. He says that while human beings might be sensitive to electromagnetic radiation in ways we still don't know about, the rest of the paper, particularly the part about potentised water, is utter garbage. What do you think? ~ Subscribers Are you about to change your address? Please advise us by the middle of the month to ensure that your next issue arrives at your new address. JUNE 1989 91 ASK SWCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. A different approach to battery charging In most car maintenance manuals the instruction on flat batteries is that the live lead should always be removed before connecting an external charger and left disconnected during charging. This is understandable when it is considered that a battery charger with a 14VAC winding on the transformer would deliver peak voltages in the order of 19 to 20 volts. This would mean that the DC output pulses would be of the same order and since modern automotive electronics is apparently designed to work reliably at 16 volts DC or less, this could cause problems. What I would like to know is would there be any problem if the battery is left in circuit and charged with a constant voltage source such as a regulated power supply? The value of constant voltage would be such that when the battery reached full charge the current would be 500 milliamps or therea bouts. (D. A., Findon, SA). Beat problem with the Minimitter In reply to M. D. 's letter in the March 1989 issue of SILICON CHIP on a strange effect with the Minimitter project, some tuners do not seem to have filtering to prevent the 19kHz pilot tone appearing on the output. I discovered this some years ago when I used a mono transmitter to do the same thing. I was using a stereo tuner to receive an FM broadcast and was curious to find the stereo indicator lit. I then borrowed an oscilloscope and looked at the signals on the output. There was a nice strong 19kHz sinewave! So when I connected my little 92 SILICON CHIP • As far as we can determine, it is not necessary to disconnect the active lead from your battery when using an external charger. It is true that battery chargers have a transformer with an open circuit secondary voltage of 14VAC or more but that does not mean that the charger is able to deliver DC pulses of 19 to 20 volts to the car battery. A car battery is such a low impedance that it tends to limit the output voltage pulses of even quite large chargers. As the battery comes up to full charge, the current output of the charger automatically tapers off, so that, in a good charger design, serious overcharging does not occur. A constant voltage source would not make a good battery charger. If it really was a "constant voltage source" in the true sense (ie, able to deliver a constant voltage regardless of the load impedance), it would need an enormous current output when charging a flat battery. A better approRch would be to mono transmitter, the 19kHz was strong enough to activate the stereo decoder in the other receiver. It would appear that M. D. requires some sort of filter to remove the 19kHz coming from the tuner. (W. B., Thomastown, Vic). • Yes, you are right. On some cheaper tuners, the 19kHz pilot tone is not heavily suppressed and may be less than 20dB down with repect to the maximum audio output. Still, while that suggests that there could be interference between the 19kHz of the FM broadcast signal and the pilot tone of the Minimitter, it does not fully explain the effects observed by M. D. have a design which charged at constant current up to a certain battery voltage and then changed over to a trickle charge as the battery was fully charged. With modern regulator circuits this is a straightforward design exercise but the resulting charger would be quite a lot more expensive than the cheapie chargers you can buy from K-Mart and Target. Parking aid for pantechnicons Could you please advise if there is a dash-mounted instrument available to indicate distance from an object when backing a vehicle; ie, a small pantek. Visibility is difficult with this type of vehicle. (B. M., Dapto, NSW). • In the January 1989 issue of SILICON CHIP we published a car reversing alarm entitled "Simple Ultrasonic Proximity Detector". This gives quite a precise audible indication of distance from an object at the rear of a vehicle. It should be the ideal solution to your problem. Wants TV sound receiver Having just purchased a new colour TV set with a live chassis, I can no longer connect it up to my Studio 200 stereo amplifier to play the sound through my loudspeakers or headphones. Like many other people I have a couple of turret tuners from junked TVs. Would it be possible for the magazine to publish a quasi-split circuit to produce a mono sound signal suitable to feed to a preamp? (D. G., Julatten, Qld). • It would be possible for us to design a TV sound receiver around an old TV tuner but to be really viable it would have to work at UHF and give stereo too, otherwise not too many people would want to Problems with the UHF remote switch I am having great problems getting my UHF remote switch (March 1988) to operate. I have very carefully checked all parts and so has a technician friend of mine who h as p r onounced himself quite ba ffled by the unit. Can you plea se give me a few clues. (A. P. , Ringwood, Vic). • Yours is a familiar cry but there is no need to despair. We have now seen quite a few of these units and we can assure you that they can be made to function very well. One recent unit that we looked at had the .002 2µF capa citor for the transmitter swapped with the .0ZZµF capacitor in the receiver so that even if the circuit had been otherwise working, it had Buckley's chance of build it. We'd like to know if other readers are interested in such a project. In the meantime, do you have a VCR? If so, it is a simple matter to connect its audio output to your stereo system. operating as it should. It also had the 2.ZµF capacitor in the receiver installed the wrong way around. This quite effectively mucks up the bias on the following op amp (ICla). However, the most common problem appears to be that many people cannot get much more than one metre of range from the transmitter. We believe that most of these instances are caused by the transmitter oper ating at double the specified frequency - ie, around 608MHz. Furthermore, we have found that in the kit transmitters now being supplied, the specified 2-6pF trimmer will not tune down to 304MHz. The minimum a chievable is about 385MHz. There are two ways a round this problem. The first is to use a 4 to Z0pF trimmer, as sold by Dick Smith Electronics, (Cat. engine coolant. In our desert garage, the number of times that major engine trouble is caused by pump belt breakage or loss of water in the r adiator wa r rants the development of such a monitoring system. Installing a moving pa rt in the cooling system to indicate flow is Wants circuit for not a good idea since rust and corintermittent wipers rosion could stop the movement. Perhaps a method whereby the I would like to suggest the design water pressure at the front and of a delayed winds creen wiper kit r ea r of the engine block is for cars. I note that such a kit does monitored could be the answer. not appear to have been presented Whatever the method, this device is in any magazine for a number of long overdue. (G. H. , Meekatha rra , years. WA). I spent a lot of time making one • For those cars that don't based on a 555 timer for my car but I would prefe r the ease and already have them fitted as stanreliability of a proper kit. Some of dar d, a windscreen wiper delay the design considerations for such a unit is an excellent a ccessory, parkit should be that the original vehi- ticularly in the protracted rainy cle wiring should remain intact and periods we have had in the eastern the original wiper and washer con- states over the last 18 months or so. The only problem with desighing trols should operate as normal. It should have a loga rithmic switch such a proj ect is that it would not be viable . You can already buy pot, easily accessible to the driver, such units, ready to fit and to suit together with a LED indicator for . most cars, at large stores such as use at night. Can I also suggest that you run a Target and K-Mart and at many competition for the design of a vehi- auto accessory shops . They ar e cle engine alarm circuit which adpriced well below the likely price of vises the driver of "no flow" of a kit and they usually come with all R-2935) or Jaycar (Cat. RV-5722). This will enable the correct operating frequency of 304MHz to be achieved but the adjustment is very finicky. A better solution is to shunt the existing 2-6pF trimmer with a 10 or 12pF NPO capacitor, soldered onto the copper side of the board. The leads of this capacitor can be left about 8 or 9mm long and the capacitor should lie flat against the board. By leaving the capacitor leads long the transmitter actually radiates more efficiently and the range improves. Typically, we have been getting a range of about 20 metres. By the way, NPO ceramic capacitors (ie, those that have a zero temperature coefficient) have a black spot at the top. NPO stands for "negative positive zero". the hardware you need to fit them. We agree that these accessories may not be readily available in remote townships but the fact that they are widely available makes a magazine project not a viable proposition. The loss of engine coolant monitor is not a bad idea at all. Perhaps a sensor to monitor the level of coolant in the overflow reservoir may be a simple and practical solution for most cases. If you haven't got an overflow reservoir, that should be a first priority, particularly for cars in the "outback". As far as belt breakage is concerned, isn't the alternator warning light a good enough indicator that something is seriously amiss in the engine room? Problem with frequency counter adjustment I am having a couple of problems with the 1GHz Frequency Counter described in SILICON CHIP from November 1987 to January 1988: (1) Sensitivity adjustment: assuming that the test LED is off at switch-on, adjusting VRl will bring JUNE 1989 93 Solution to thump problem I began making audio equipment in 1977 and I was immediately confronted with the ''thump" problem that amplifiers deliver via the speakers. I decided that a simple mechanical system was the answer. It had to be safe and reliable as well as affordable. For some years I used two pushbutton switches covered with a sliding gate. One switch provided the power to the amplifier while the other switch (a double pole type] switched the speakers. The problem with that scheme was that it relied on the operator using the switches in the correct sequence. In other words, for turning on, you had to operate the power switch before the speaker switch while for turning off, you had to operate the speaker switch before the power switch. Now I use a rotating stainless the LED on but once it has turned on, adjusting VRl will not turn it off again. This is not an IC problem as I have tried three, all with the same result. Notwithstanding the above, the counter passes all the relevant tests prior to checking the 1GHz range. (2) Pressing the F4 and R4 buttons to check the 1GHz range results in a reading something like 2780 with a rapid update. Pressing R2 results in a reading of 286972.47 etc with no overflow. Your comments and assistance will be greatly appreciated. (A. P., Point Clare, NSW]. • We a re not sure why VRl in your frequency counter will not turn the LED on and off. It suggests that the hysteresis of the Schmitt trigger, IC2a, is greater than the typical figure we quoted in the November 1987 a r ticle (ie, 450mV peak-peak). Alternatively, the ga in of the preceding stages, IC2b and IC2c, may be a little lower than usual. Since you have tried three ICs, then it is possible that one of the 94 STLICON CHIP steel shaft running in teflon bearings and operating three microswitches, one for the power and one for each speaker system. This is a fairly simple system I suggest. I tried out the 100W per channel stereo amplifier described in the February 1988 issue of SILICON CHIP and the 120W module de s cr i bed in the November 1988 issue and it certainly shut down the switch on and off thump . It could be argued that the amplifier runs momentarily without a speaker loa d but I have not encountered any pr oblems to date. (G. D., Nambucca Hea ds , NSW]. • Thanks for your suggestion but we really think you are solving a problem which now doesn't exist. It is true that early solid state amplifiers, particula rly those that were AC-coupled at the output, did cause a thump at switch-on and, to a lesser extent, at switch-off. But any half-decent 1000 resistors around the circuit has the wrong value. This could easily occur with 1 % resistors which have five bands. In the 1GHz mode, pressing the F4 and R4 buttons with no input should give a reading something like 1145678kHz with rapid update while pressing the R3 button will give a reading like 1145678.~kHz with updates about once a second. The fact that your unit is not doing this suggests that you have a short between tracks in the range switching circuitry. These tracks a re Bookshelf - direct coupled amplifier these days should have negligible switch-on or switch-off thump. The SILICON CHIP Studio Series 200 amplifier you referred to is a case in point - it should have no switch-on thump and a barely detectable switchoff thump. If you have a thump problem with this or any other direct coupled amplifier then the source of it is likely to be in the preamplifier stages. In any case, the standard commercial practice these days is to fit a double pole relay in the speaker circuit. This not only mutes the amplifier at swi\ch-on but is usually arranged to give speaker protection as well. As far as solid state amplifiers are concerned, it does not matter at all whether they operate with a load or not. After all, when you operate your stereo amplifier with headphones the speakers are d isconnected and the amplifier therefore has virtually no load. very fine and you may need to examine the board very closely under a magnifying glass to find the fault. Notes & errata CD Compressor, March 1989: the two 470µF filter capacitors shown on the wiring diagram of page 29 are both reversed in polarity. This can be confirmed by looking at the photographs. Lotto Selector, May 1989: the .012µF and .018µF capacitors listed in the parts list should be 0.12µF and 0.18µF respectively. ctd from page 86 cuits . The author goes so far as to suggest that you build your pro jects from " perf" board or "whatever works best for you" whilst keeping construction neat. This seems like contradictory advice, especially for a person who fits the " no experience necessary" category. Strangely, the last chapter of the book, only two pages in length, gives the most useful information of installing an ala rm -system in your home. The point is made that no electronic surveillance system is completely foolproof but having one offers a preventa tive measure which is better than none. In summary, as a source of information on how alarms work, this text is adequate but you will need to be fairly experienced to build the circuits. The text can be found on the shelves of your local Dick Smith Electronics store. December 1987: 1 00W Power Amplifier Module; Passive lnfrared Sensor; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show . August 1988: Plasma Display; Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Switchmode Charger for 12V Gel Batteries; Vader Voice . October 1988: Stereo FM Transmitter; High Performance FM Antenna; LedLight House Number; Matchbox Crystal Set. November 1988: 120W PA Amplifier Module; Poor Man's Plasma Display; Car Safety Light; How to Quieten the Fan in Your Computer. December 1988: 120W PA Amplifier; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Receivers. January 1989: Line Filter for Computers ; Proximity Detector for Cars; How to Service Car Cassette Players. February 1989: Transistor Beta Tester; Build the Minstrel 2-30 Loudspeaker System ; LED Flasher for Mode! Rail ways. March 1989: LED Message Board; 32-Band Graphic Equaliser; CD Compressor; Amateur Band FM Receiver . April 1989: Telephone Bell Monitor/Transmitter; Auxiliary Brake Light Flasher Circuit. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For PCs; Simple Stub Fllter For SuppressinQ TV Interference. Note: Stocks of December 1987 and February 1988 are now very low. ~ r------------------------- --------- + --7 Use this handy form to order your back copies Please send me a back issue for: D December 1987 D February 1 988 D March 1988 D April 1988 D May 1988 D June 1988 D July 1988 D September 1 988 D October 1988 D February 1 989 □ March 1989 □ November 1 988 D April 1989 D August 1988 D December 1 988 D January 1 989 D May 1989 Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my □ Bankcard □ Visa Card □ MasterCard Price: $ A5.00 each (includes postage) . Overs eas orders add $A 1 .00 per issue for postage. Signature _ _ _ __ _ _ __ _ Card expiry date_ _ / __ / _ _ NZ & PNG orders are sent by air mail. Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 S t r e e ~ - - - - - - - - - - - - -- - - - - - - - -COLLAROY BEACH Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode____ NSW 2097 ~------------------------- ------------~ ]UNE 1989 95 CEN Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word ; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad , put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7 .00) 16 ($740) 17 ($7.80) 18 ($8.20) 19 ($8.60) 20 ($9.00) 21 ($940) 22 ($980) 23 ($1020) 24 ($10.60) 25 ($11.00) 26 ($1140) 27 ($11 80) 28 ($12 .20) 29 ($ 12 60) 30 ($13 00) Name ..... ...... ..... ..... Address . Suburb/Town Postcode Enclosed is my cheque or money order for $.. D Visa Card D MasterCard ..... .. ... .... .. .. ... or please debit my D Bankcard Card No [ J i Signature. ..... Card expiry date ..... ../. .. ..../. . FOR SALE BUILD YOUR OWN LED Moving Message board. $75 for a 4-character display experimenter's short form kit and $1 50 for 16 characters. Kit consists of PC boards, EPROM and full instructions to complete the project to a professional standard . Loaded from Centronics printer port or PC/XT keY.board . Equivalent commercial units start at around $1 000. For more info send a 39c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . RADFAX 2: HI-RES weather fax, Morse and RTTY receive program for IBM 96 Ii J J L~I~~ SILICON CHIP PC/XT/AT on 360K 5.25-inch floppy plus full documentation . Needs CGA, SSB HF, FSK/tone decoder. Has realign , auto-start, view , save, print. Also "RF2HERC " same as above but suitable for Hercules card and "RF2EGA" for EGA card (640 x 350 mode). Programs are $30 each plus $3 postage. Only from Michael Delahunty, 42 Villiers Street, New Farm, Old 4005. Phone (07) 358 2785 . SERVICES HI-TECH STEREO AMPLIFIERS built. Reasonable prices. For full details send SAE to 36 Palmer St, Nambucca Heads , 2448 . Advertising Index Access Communications . IFC Allied Capacitors 90 54-57 Altronics Arista Electronics 39 91 Avtek Dauner Electronics 75 David Reid Electronics . . .. 65 40-47 Dick Smith Electronics Electronic Solutions 15 Elmeasco OBC Geoff Wood Electronics .... 87 Hycal Instruments . 75 Jaycar Electronics 20-23 76-79 Oatley Electronics 55 PC Marketplace 30-31 RCS Radio. . . . .. 39 RF Devices . 28 Rod Irving Electronics IBC 19,89 WIA PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd , 651 Forest Rd , Bexley, NSW 2207. Phone (02) 587 3491. • Jemal Products, 5 Forge St, Welshpool, WA 6106 . Phone (09) 350 5555 . • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. ELECTRONICS ENGINEER: analog, digital , power design, prototypes . $35 per hour. Phone (059) 96 4353 AH. BOOKS & PLANS LOW SPEED GENERATORS for windmills, water turbines, steam engines. The definitive book: " The Homebuilt Dynamo" (1987) , 182 pages, 8 .5" x 1 2 " , hardback. Generator design and construction with ceramic magnets . Complete plans, 268 photographs, step-by-step construction details. $A85.00 postpaid airmail (brochure $A5.00 refundable). Todd-Forbes Publishing , 627 West Coast Road , Oratia, Auckland. r-s ER I - UP • FASTI>YNAM RAMS • IC-7 - I I I I I I I I I I I ''NEW KITS!'' 4164-150ns .. ........................ ..... $4 .22 4464-150ns ........ ... ......... ...... ...$17.85 41256-B0ns ..... ....... ..... ....... .... .$14.95 41256-100ns ....... .. ........... .. ..... $14 .30 1MB-1 00ns ....... ....... .. ... ..... ... ... $42.20 ..1• ■ ~to ·,, L---------"NEW" HEAT SHRINK TUBING PHS PHS PHS PHS PHS PHS PHS PHS PHS PHS 25 20 16 13 10 7 5.5 3.5 2.5 1.5 . ........ :1~:e··_ ·_-. _:r· · • 25mm .. .. .. $6.95 20mm ...... .. .. $5.00 16mm ........... $3.60 13mm ............ $3.30 10mm ............ $2.65 7mm ........ ...... $2.15 5mm .............. $1.85 3.5mm ........... $1. 70 2.5mm ........... $1.50 1.5mm ........... $1.30 • ,I' . . . • RODIRVING ELEaRONICS All sales tax exempt orders and wholesale inquiries to : RITRONICS WHOLESALE, 56 Renver Road , Clayton . Phone : (03) 543 2166 (3 lines) Fax : (03) 543 2648 SYDNEY: 74 Parramatta Rd . Stanmore. 2048. Phone (02) 519 3134 Fax (02) 519 3868 MELBOURNE: 48 A'Beckett St. Phone (03) 663 6151 NORTHCOTE: 425 High St. Phone (03) 489 8866 CLAYTON: 56 Renver Rd . Phone (03) 543 7877 MAIL ORDER& CORRESPONDENCE: P.O. Box 620, CLAYTON 3168 Order Hotline : 008 33 5757 (Toll free , strictly orders only) Inquiries: (03) 543 7877 Telex: AA 151938 Fax: (03) 543 2648 - W19026 W19046 W19066 W12790 W19006 Red 5.0" ....... $5.95 Yellow 5.0" ...... .$5.95 Black 5.0" .......$5.95 Green 5.0" ....... $5.95 Blue 5.0" ....... $5.95 W19016 W19036 W19056 W19076 W12796 Blue 10.0" ..... $10.50 Red 10.0" ..... $10.50 Yellow 10.0" ..... $10.50 Black 10.0" .....$10.50 Green 10.0" ..... $10.50 PC DRIVEN FUNCTION GENERATOR Here's a simple and low cost little unit which lets you use your personal computer to generate signals with almost any conceivable waveform. II hooks up to the computer via a standard Centronlcs• type parallel printer port. making it compatible with almost any kind of computer. Bu ilding and using it will also give you valuable insight into the growing trend towards computer•driven test instruments, too! Software included. (EA JAN 89) • Spool wire W19390 Green 50ft.. ...... $8.00 W19400 Blue 50ft ........ $8.00 W19406 Purple 50ft.. ...... $8.00 W19407 White 50ft ........ $8.00 W19408 Orange S0ft ........ $8.00 W19410 Yellow S0ft ........ $8.00 W1941 5 Black 50ft ........ $8.00 W19416 W19417 W19420 W19425 W19426 W19427 W19428 W19430 W19435 Green 100ft .....$10.75 Brown 100ft ..... $10.75 Blue 100ft ..... $10.75 Red 100ft ..... $10.75 Purple 100ft ..... $10.75 White 100ft ..... $10.75 Orange 100ft .....$10.75 Yellow 100ft ..... $10.75 Black 100ft ..... $10.75 W19460 W19461 W19465 W19475 Blue Green Red Black 500ft 500ft 500ft 500ft STRICTLY ORDERS ONLY POSTAGE RATES : $1 - $9.99 ....... $2.00 $10 - $24.99 .... $3.00 $25 - $49.99 .... . $4.00 $50 - $99.99 .... $5.00 $100 plus .. $7.50 The above postage rates are for basic postage only. Road Freight. bulky and fragile items will be charged at different rates. Errors and omissions e~cepted . Prices and specifications subject to change, xr·. IBM· . PC· . AT' . are registered trademarks of lnternatlOflill Business M achines ' Apple 1s a "Denotes registere d 1radmark s ol their respech\le ow ners [ES] V/54 This clever adaptor circuit plugs into your digital multimeter and can measure capacitance up to 2.2 microfarads. (SC NOV 87) K88119 ..... .. ........... $24.99 K88111 ....... ...... ... ..... ....................... .................. ..$49.95 WALK-AROUND THROTTLE FOR MODE HANDS FREE SPEAKERPHONE Here's a hands-free telephone that anyone can afford. With the speakerphone you can have rela xing conversations without the need to hold the phone to your ear. And if you are put on "hold" you can continue with you work while you wait. (SC SEP 88) K88130 ............................................................ ........ $89 This walk around throttle otters a host of features including pulse power, inertia (momentum). braking and full overload protection. (SC APRIL 88) K88122 ...... .. ............... $89 PRINTER BUFFER This external printer butter will allow two computers to share one printer without the bother of swapping cables. Without dynamic ram (ETI 1620 FEB 89) .....$33.75 ..... $33.75 ..... $33.75 ..... $33.75 K56012 .. ....... ....... $139.95 Dynamic Ram (extra) ........... $150 HIGH IMPEDANCE AC/DC MILLIVOLTMETER K88125 .................................. ..................... ........... $159 LOCAL ORDERS & INQUIRIES (03) 543 7877 trademark. •Precut wire W19002 Blue 3.0" ....... $4.75 W19022 Red 3.0" ....... $4.75 W19042 Yellow 3.0" ....... $4.75 W19062 Black 3.0" ....... $4. 75 W12784 Green 3.0" ....... $4.75 These days when you go to hear your favourite band or disco there is always a top light show. Now you can have many of these exciting light show effects - with the Discolight (SC AUG 88) ORDER HOnlNE 008335757 (TOLLFREEJ registorod BRAND NEW WIRE WRAP WIRE DIGITAL METER • Autoranging operation • Data•hold for easy readout • Full range protection • 0-500 volts AC-DC • 0-20Mn • Dimension & weight =133 x 29 x 17mm and 60g approx Q11270 .... ................... $69 LOW COST TESTER FOR TRANSISTORS, FETS & ZENERS This tester checks zener diodes as well as transistors and FETs , and also lets you check transistor breakdown voltages. Great tor the work bench . and also for showing how semiconductor devices operate. (EA FEB 88) K88013 ........... ..... ..$54.95 AUTOMOTIVE BRAKE LAMP MONITOR Here·s the project that won first prize in the Newcomer section of the recent Grand Aussie Hobby Electronics Contest. L-0w in cost and easy to build. it warns you if your vehicle's brake lamps aren't work ing as they should- hopefully before another motorist ra ms into your rear end! (EA MAR. 89) K89030 ....... .... ....... $24.95 DIECAST BOXES Diecast boxes are excellent for RF shielding. and strength Screws are provided with each bo x. H11451 .100 x 50 x 25mm .... $5.95 H1 1452.110 x 60 x 30mm ..... $6.50 H11453.120 x 65 x 40mm ....$6.95 H11461 .1 20 x 94 x 53mm ...$11 .50 H11462.188 x 120 x 78mm$13.50 H11464.188 x 188 x 64mm $29.50 PCB SHORTS LOCATOR HEAD PHONE AMP FOR CD PLAYERS With negligible circuit loading (EA DEC 88) K88020 .. ........... ..... $44.95 TV COLOUR BAR AND PATTERN GENERATOR Here is a design for an easy to build colour bar and test pattern generator, suitable for servicing closed-circuit or amateur TV. It provides high perlormance at a very reasonable cost. (EA OCT87) K87100 .... ........... $156.95 NOISE GATE Eliminate annoying audio noises (ETI 1429 FEB 89) K54215 .................. $49.95 HIGH ENERGY IGNITION SYSTEM Are you still cleaning points. adjusting the dwell . checking timing and all that automotive drudgery? Now you can fit this High Energy Ignition System and forget those tuneup hassles Here is a simple circuit to help you locate shorted tracks on printed circuit boards, by means of a varying audio tone. It is easily built and will cost you a lot less than equivalent commercial units.( EA FEB 89) Does your compact disc player have a headphone socket? Now you can correct that situation and listen to the music direct. without degrading the sound quality (SC APRIL 88) (SC SEP. 88) K88015 ......... ......... $22.95 K88120 .................. $24.95 K88135 .................. $49.95