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How to service your car's cassette deck l~S1S' 1 SERVICING - HIFI - l:,\JC,C1RO"'C!,.,.i3 1);1;M•lt• al;!•!IHH A 1.,ine Filter For Your Computer· Projects to build: Computer sound repeate .... f Proximity detector z ~ for cars -:; Stops those embarrassing dings and scrapes ,2 _!;! :a:::, Q. assive diesel-electrics I the ited States 1ii 0 Q. -~ ~ ~ <( Plus: ~ The Original & Best TV Serviceman, Vintage Radio, The Way I See 11, Amateur Radio, Kit Clinic, The Technology Letters i j £ Hili review: Marantz LD50 OMS bass reflex loudspeakers PORTABLE LCD DIGITAL THERMOMETER LOGIC PROBE Without removing an IC or cutting off the cIrcuIt, the logic pulser can 1nJect a signal into logic cI rcuIts to c heck if the IC is good Two pulse rates (0 5 & 500Hz) are switch selectable, to enable the use of either an oscilloscope or logic probe as the 1nd1cat1ng device • 0 5Hz/500Hz pulse rate • Auto output polarity • Trigger input & ou tput • Overload protection • 1 000mA output with low duty cycle pulse ONLY s46.ao • The logic probe Is a convenient and reliable troubleshooting tool for 1nd1cat1on of logic state In TTL and CMOS d1g1tal electronics It Is an essential tool for anyone engaged In repair of digital log ic • • • • 50MHz frequency 1 Ons pulse detectable LED displays logic HI , Lo, pulse, high impedance , V+ & V Pulse latch and TTL/CMOS switch selection VALUE AT ONLY VOLTAGE DETECTION PROBE s38.4o ONLY s57.so DYNAMIC MICROPHONE with ON/OFF SWITCH HEADPHONE/ MICROPHONE HEADSET • • • • This portable detector gives both an audible & visual signal when AC or DC voltage Is present • Voltage range 50-500VAC, 3-220VDC ONLY Temperature range - 40C to +50C • Selectable 1 sec or 1 5 sec sensing tim e • Presettable H1- Lo alarm • Stainless steel probe with 1 m cable • Bu1lt-1n table stand and pocket clip This unit has a wide range of appl1cat1ons such as food processing, heating & vent1lat1ng , agricul ture , laborato ri es, industrials , refrigeration, etc Uni-d1rect1onal 600 ohm impedance 1 00 Hz - 15,000Hz Vanous colours available, Red , Blue, Yellow , Black, Gold and White ONLY$ "WAS $149.95" s549.95 This high quality microphone system co mprises of a 240 volt rece iver, complete with earner and output signal leve l meters and volume control It connects directly into th e MIG input on your amp Designed for stage and theatre work th is system Is ideal for any situation where wired m1c 's cannot be used 127 York St, Sydney 2000 Ph (02) 26 7 1385 Fax: (02) 261 8905 14.95 The " WIRE FREE" 1nfrared transceiver system allows yo u to listen to TV/VC R, H1-F1 , or other audio source at your desired volume level without d1sturb1ng others In the room and without being tied to the audio source by a cord • Operating distance 50ft ONLY $ .00 gg MAIL ORDERS WELCOME P 0 Box 0103 Sydney 2000 $1 - $25 $4 00 P&P $26 & over : $7 .00 P&P Vls.4 JANUARY 1 989 FEATURES HAVING TROUBLES WITH your car's radio-cassette player? We show you how to service it yourself and save money. See page 6. 4 The Goalkeeper Gatling Gun by Leo Simpson 6 18 40 78 80 Last ditch anti-missile defence How to Service Car Cassette Players by H. Davidson Do the job yourself and save money Marantz LDSO Loudspeakers by Leo Simpson Compact 2-way system has bi-ground wiring terminals The Technology Letters, Pt.2 by Richard Kopf An American settles in Australia Kit Clinic & the UHF Remote Switch by John Clarke It will work only if you follow the instructions The Evolution of Electric Railways by Bryan Maher Pt.15: Massive diesel electrics in the USA PROJECTS TO BUILD 26 Ultrasonic Proximity Detector for Cars by Greg Swain Stops those embarrasing dings & scrapes 32 A Line Filter For Your Computer by Leo Simpson Filters interference & dangerous spike voltages 44 120 Watt Public Address Amplifier, Pt.2 by Bob Flynn Wiring details and final assembly 68 Simple Computer Sound Repeater by John Clarke Don't put up with a weak beeper THIS SIMPLE ULTRASONIC distance indicator will stop those embarrassing parking dings and scrapes. We show you how to build it starting page 26. SPECIAL COLUMNS 14 Vintage Radio by John Hill Troubleshooting the transformers 54 Serviceman's Log by the original TV serviceman Copping it right in the neck 62 The Way I See It by Neville Williams Feeling really crook? You may need an electron transfer! 71 Amateur Radio by Garry Cratt Relative signal strength indicator for scanners AN IMPLODING TV picture tube can do a lot of damage but our serviceman wasn't sucked in. His story starts on page 54. DEPARTMENTS 2 Publisher's Letter 86 Product Showcase 3 Mailbag 92 Ask Silicon Chip 94 Notes & Errata 11 Subscription Page 20 Bookshelf 38 Circuit Notebook 95 Back Issues 96 Market Centre IF YOUR COMPUTER often crashes, the Mains Muzzler line filter may be the solution. It filters mains-borne interference and clips dangerous spike voltages. Details page 32. JANUARY 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 Advertising 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 Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers ·may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Waterloo, NSW 2017. Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rate: currently $42 per year (12 issues) inside Australia. For overseas rates, . refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. ISSN 1030-2662 • Recommended and maximum Australian price only. 2 SILICON CHIP PUBUSHER'S LE'l·l'ER The great dry battery recharging conspiracy One of the circuits featured this month in our " Circuit Notebook" pages is for a dry cell recharger. For those who have never come across the idea of recharging dry cells it is an interesting circuit although we have made no big deal about it. Some people, though, may think we are being brave even to publish it in the form that we have. Why? Because of the great dry battery recharging conspiracy. You've never heard of it? Supposedly, it goes like this. "The battery manufacturers of the world know that you really can recharge dry cells but they would lose lots of sales if people recharged them so they deliberately suppress the information. They even print warnings on the battery cases so that users do not attempt to charge them. " We have had a number of readers recently who suggested we should publish a story on recharging dry batteries and so it was a happy coincidence when another reader actually sent in a circuit to do the job. So we decided to publish it (and to hell with the consequences?). But you only have to read the charging procedure that you have to go through to effectively recharge dry cells to realise that the battery manufacturers are not suppressing anything. While we have not tried it, we are quite sure that if you build up the circuit as described in Circuit Notebook and follow the procedure carefully for recharging, you will get a number of cycles out of a dry cell. But for most users it is hardly a practical proposition. First of all, you can't recharge a dry battery that has been allowed to go flat. That much is true. So the battery manufacturers are right on that score. Second, you have to individually recharge the cells as soon as possible after every use. You can't recharge a 9V battery. So the battery manufacturers are right on that score too. Third, you need a special "dirty DC" charger. An ordinary charger won't work. So much for the great dry battery recharging conspiracy. It is like a lot of other conspiracies that get a run every now and then. There are all the really good designs for electric vehicles that have been purchased and suppressed by the established car manufacturers. And there are the designs for special carburettors that give phenomenal petrol mileage but have been suppressed by the oil companies. They and any number of other conspiracy theories do not stand up to any serious examination. So go ahead. If you want to try recharging dry cells, give the circuit in Circuit Notebook a go. For our part, when we want batteries that actually can be recharged, we'll go for nickel cadmiums. Leo Simpson MAILBAG Tutorial on the 120W PA amplifier After reading your article describing a 120W power amplifier designed to have a low DC output, I came to the conclusion that perhaps a 10 minute tutorial on balance may be in order. Certainly you can adjust the trimpot to obtain balance but this is the easy part. Maintaining it is the tricky part. First, even if both transistors in the long tail pair were exactly equal an input offset will occur (and drift) if the current is not equally divided between the two collectors. So it is desirable to have the current equally divided. Don't forget that input offset currents in your circuit are significant and these change dramatically with temperature if the input pair is of unknown matching. Consider a beta of 100 for the BC556s and your current ratio of more than 2:3. This gives an input offset current of 2µ,A (200µ,A difference in collector current divided by the beta) which gives an input offset of 44mV (2µ,A x 22kn). Yes, you adjust this out but only at one temperature and one supply voltage. So where is your imbalance coming from? You have two dominant sources. The most horrific of these is the 40 odd volts difference in collector potentials. The Early Effect is significant. The early voltage of a BC556 may be high but suppose even Muddle over line transformer connections I look forward to each issue of your magazine and haven't been disappointed yet with the content. I haven't built any project of yours as yet but, after building many projects over a period of 30-plus years, I do have most of the things I need. Whatever I do build will have to be much better than the device it will replace. However, after giving you a wrap up I wish to point out an error in the November issue on page 17 regarding various output levels to speakers on a 100V line. I refer to Fig.3(b). The wiring of the taps should be reversed to what you have shown. The tap shown as 0.5 watts is the 5 watt tap and the SILICON CHIP, PO Box 139, Collaroy Beach 2097. if it was 250V. This gives a current imbalance of about 1/6 (250/40}. Your two equal load resistors are not valid for Early Effect elimination because of your cascade amplifier in one side. The solution is to put the cascade amplifier on both sides. You can use the same base bias circuit and you need not put in a load resistor (ie, collector to negative rail). The two cascade amplifiers here help significantly over one (one is more harm than good) and help significantly over no cascade amplifiers by reducing the effect of the difference in early voltage between the two transistors in the long tail pair. The second source of imbalance is the fact that the load resistor of the long tail pair is not twice that of the current source resistor (6800}. A value of 3.9k0 is three times what it should be. Of course, for the suggested 1.36k0 value to work you must put a diode connected transistor in series with it. There are some further small points but I feel they are worth mentioning. First, you have a dissipation imbalance in the long tail pair of 25mW or more because of the different collector potentials. This is not to be dismissed instantly as insignificant even if your transistors are stuck together. Second, I prefer to see the null adjust on the collector load sides. The reason is better temperature stability of the input offset adjustment and it will have the additional effect of tripling transconductance of this stage by by removing additional emitter resistance. Donald Kay Lockleys, SA 5 watt tap is in fact the 0.5 watt tap. With the smaliest amount of primary winding in circuit the stepdown ratio is much smaller than when the full primary winding is used. With a small step-down ratio we will have a greater voltage on the secondary than would be obtained with a larger step-down ratio. The primary winding will be tapped at about 31 % of the total winding to give the 10:1 5W:0.5W output range on the particular transformer. I originally got caught on this one when I was doing some PA work too. Your article on the "The Technology Letters" , if true or near enough to be able to protect the guilty, seems very much like what goes on in so many organisations. I was told I didn't need TV circuits when I was doing field service on TV sets. It sure made life difficult. Often, they wouldn't give you the tools to do your job but would supply more costly items that you didn't need anyway and which just sat around in the corner gathering dust. You just shakes yer head. R. D. Champness Benalla, Vic. Comment: thanks for the tutorial but we don't agree. First, most texts on the subject of drift state that it is more important to balance base-emitter voltages than collector currents. Nor do we see that Early Effect (base width modulation due to varying collector voltage) has anything to do with DC drift, especially as the relevant collector voltages are virtually constant. Nor do we see that the load resistor of the long-tail pair should be twice the 6800 current source resistor. In any case, the circuit was intended to hold the DC output voltage to within ± 5mV. It achieves that easily. Insulation for the Plasma Display I am writing about the Plasma Display project featured in the August issue. The text states that one should be extremely careful when using (read: touching) the display that one doesn't come too close to the jar lid otherwise a nasty shock could be received. Anyone who has been introduced to the action end of an EHT tripler will understand the truth in that continued on page 91 Comment: Erk; we try to clear up confusion on 100V lines and end up adding to it. You are so right. The taps give higher power than the full primary winding. Of course the installer rarely has to worry about this he just connects to the taps he wants. JANUARY 1989 3 ARTIST'S IMPRESSION OF the M-Class Frigate which is currently under consideration for the Australian and New Zealand navies. Twelve new frigates will be built eight for Australia and four for New Zealand. := i~,1#,< - f T -~/ ':!?:!~--- ~-----·-----------.. ,,,. .,_, _, GOALKEEPER last ditch antimissile defence Naval ships are extremely vulnerable to missile attack, as the Falklands and the Iran/Iraq wars have shown. The Phalanx gatling gun system was devised to combat missiles hut it has been surpassed by the Dutch-designed Goalkeeper system. Goalkeeper is being considered for the new Anzac frigates to he built in Australia. By LEO SIMPSON A ship under missile attack is in deep trouble. It has only a few seconds to identify the threat and then take drastic defensive action. If more than one missile is launched within a short time, it is in even deeper trouble. What to do? The days have long since passed when naval seamen had the ability to identify a threat and then take action to repel the attack. These days computers are used to monitor the air, identify friends and foes and to fire the weapons. The Goalkeeper is a last ditch defensive system against missiles. If the ship's medium and short range missiles have not been able to repel attacks, the Goalkeeper is intended to shoot missiles to pieces 4 SILICON CHIP before they hit the ship. The gun itself is a 7-barrel gatling gun which fires 30mm tungsten-capped shells at the rate of 4200 per minute or 70 shells a second. Muzzle velocity is 1150 metres per second. A brief burst of fire lasting only two or three seconds is enough to destroy any incoming missile after which the Goalkeeper system switches to track the next identified "threat" in readiness to destroy it too. Goalkeeper was developed by the Signaal Division of Philips and is completely autonomous. It allows incoming missiles to come quite close before it destroys them; a process which would be quite unnerving for any observer. And it has a sound unlike any other gunfire; a shattering roar at 70Hz. What was wrong with Phalanx? Phalanx is an anti-missile system fitted to some of Australia's naval ships but, as demonstrated in recent conflicts, it is not infallible. It too is a gatling gun (ie, a multiple barrel machine gun) firing 20mm "penetrators" made from depleted uranium (to make them very heavy). The problem for any anti-missile system is that it must search out and identify threatening airborne objects and then, having identified a particular threat, it must lock onto it until it is either destroyed or moves away. It then must lock onto the next threat and repeat the process. A particular weakness of the Phalanx system is that its radar system cannot do two jobs at one time. When it is tracking a particular object it cannot search the sky for other threats. Goalkeeper copes with that problem by having two radar systems. One is a search radar. It is a linear array "tube" which rotates rapidly at 60 revolutions per minute to quickly identify moving targets. It is powered by a travelling wave tube (TWT). The TWT gives a high power output for penetration thrciugh the most difficult weather conditions and it also allows great flexibility in operating frequency and pulse repetition frequency to counteract jamming. In conjunction with its weapons control computers, Goalkeeper's search radar can keep track of up to 30 objects in the sky. Having identified all the flying objects in the sky out to a distance of 30km or more, the Goalkeeper's computer gives them all a priority in terms of the threat they represent. Each object's distance, speed and direction is taken into consideration. Having assessed which object is the most threatening, the Goalkeeper's tracking radar then locks onto it. The tracking radar uses a 1-metre parabolic dish with dual feedhorns so that it operates in two frequency bands. One feedhorn gives a very narrow "pencil" beam for very accurate tracking at low altitudes. The latter is important when tracking sea-skimming antiship missiles because conventional radar can become confused between the target and its reflection off the surface of the sea. By continuously comparing the return signals from the two frequency bands (I and K-bands ), the tracking radar can track fast moving objects with very small radar cross-sections; eg, small missiles and shells. The galling gun The gun itself is a GAU-8/7 gatling gun made by General Electric and originally used on the US Air Force A-10 attack aircraft. For use in the Goalkeeper system it has been adapted to a naval gun mount and integrated with the two radar systems just described. The tracking radar and the gatling gun are mounted so that they track together. The total rotating assembly, comprising the gun, radar systems, turret, ammunition drum and other paraphernalia, weighs more than 6 tonnes. It is rotated and elevated electrically with DC motors. Maximum rate of rotation of the gun mount is one revolution per second. Accelerating such a heavy mass with the motors causes a peak electrical load of 90kVA which is supplied by nickel cadmium batteries. Naturally the slewing of the gun is restricted so that it does not shoot off parts of the ship and the barrel elevation can be varied between - 20° and + 80° with respect to the ship's deck. The computer system automatically compensates for pitch, roll, yaw and heave and flexing of the ship's deck due to heavy sea movement. While the gun has a very high firing rate of 4200 rounds/minute, its ammunition feed-and-storage drum (a belt system) only takes a total of 1190 rounds. This might not seem like much but it only takes a 2 or 3-second burst to destroy a missile. This means that about 6 or more missiles can be engaged and destroyed. After that, it takes about 25 minutes to reload the ammunition drum. How will it perform under real battle conditions? That has yet to be determined although the system has been extensively tested in the North Sea by the Netherlands Navy. Presently, the US navy is using an old hulk with a Goalkeeper system mounted on it. Missiles and shells are being fired at it to prove the system. No doubt it works well in such tests but what features will be produced by the missile manufacturers to beat it? ~ GOALKEEPER IN ACTION during recent trials. The 7-harrel gatling gun fires 30mm shells at the rate of 4200 per minute. JANUARY 1989 5 Don't spend big dollars getting your radiocassette player fixed. You can do the job yourself. The most common cassette player problems are found in this article. By HOMER L. DAVIDSON The cassette music comes to a sudden halt with no rewind or fast-forward movement. So you push the FM button only to hear distorted music as you move into another lane on your way to work. In disgust, you flip the radio to AM to get the local traffic report but the radio still sounds dreadful. You try to adjust the volume control but that only produces loud scratching noises and the sound cuts in and out. Nothing is going right this morning so you eject the cassette and some of the tape is left in the machine. What a mess! Incidents like that happen every day to someone but "Why me?" you exclaim. You want to kick it or hit it with a hammer except both are out of reach. Enough is enough - this weekend, you are going to whip the tape player out and work it over. Yes, just about anyone with nimble fingers and a little patience can keep an auto cassette player in tip-top shape (with a little help from this article). Where to start Like the electronic technician, you must consider the symptoms, isolate the probable section and then locate the component(s) on the schematic diagram and in the player itself. You should have a schematic diagram to locate the suspected components. Check the service instructions as a small diagram may come 6 SILICON CHIP in the package. Of course, you may need a magnifying glass to see all the wiring close up. If you have a few tools and an analog or digital multimeter, you are in business. Cleaning up the tape head may solve distorted or RF FM FM FET RF RF AM AM CONV TO IF TO AM DETECTOR AM +8.9V Fig.I: check the AM-FM slide or pushbutton switch with erratic AM or FM. It may simply need cleaning. Often, the AM-FM switch provides DC voltage to the front-end components. DEFECTIVE MOTOR TAPE REEL DIRTY ANO SLUGISH INTERMITTENT BOARD CONNECTIONS PRESSURE KEEPER BENT DIRTY CAPSTAN LEADS PRESSURE ROLLER DIRTY BROKEN TAPEHEAD LEADS This photo shows the parts that can cause problems in a typical auto cassette player. You should check out each of the parts in turn as described in the article. weak cassette music. Wiping off the motor belt and pinch roller may cure some speed problems. No rotation may result from a broken belt or defective cassette motor. Intermittent cassette music may be caused by broken tape head connections. Distorted and weak music may be solved by making accurate voltage measurements around the suspected output transistors or IC components. But hang on a bit - let's take things one step at a time before we fall flat on our faces. We'll look at each of the common problems and see how they are solved. A good clean up of the tape head and surrounding parts may save a few tapes and cure many tape speed problems. Be sure to remove all the oxide from the small gap areas of the tape head. down movement of the tape. To cure this problem, remove the dry capstan/flywheel, clean up the bearing area, and apply a dash of light phono grease or vaseline. Often, the motor belt and capstan are found under the cassette assembly. You will have to remove the bottom cover to clean up the moving components. In other cases, the whole cassette assembly must be removed to get at the motor belt. Always mark down any wire leads or components you must remove to get the assembly free for clean up. Erratic FM If the AM or FM reception appears intermittent or erratic after switching from one to the other, suspect a dirty AM-FM switch. In some radio-cassette players the selection is made with a pushbutton or slide type switch, while in the later digital models the bands may Clean up time Sometimes a good clean up with a cotton bud stick and alcohol can solve a lot of problems. First, clean off the front of the tape head to prevent weak, dead or distorted music. Get all the oxide off the small gap areas of the tape head. Those areas are very small and can easily be plugged with stubborn oxide dust. Next, wipe off the motor drive belt with a clean cloth moistened with alcohol. Inspect the rubber belt for loose or cracked areas. Clean off the motor pulley and capstan flywheel with a cotton bud. If everything looks OK, whirl the flywheel with your fingers and check if it rotates freely. Incidentally, when we mention alcohol in this article, we're talking about isopropyl alcohol which can be obtained from your local pharmacist. As a second preference, you could use methylated spirits (preferably obtained from your pharmacist) although it does tend to leave a residue. Sometimes a gummed up flywheel bearing slows Clean up that noisy volume control with cleaning fluid and an extension tube poked down inside the control body. Rotate the control shaft after spraying to clean up the dirty contacts. JANUARY 1989 7 S2 h.__TO RADIO _}. LEOl .,. ~ LE + 220l .,. Fig.2: check the cassette switch and isolation resistor when no voltage is found at the motor terminals. Replace the motor if tape movement is erratic or intermittent. Dead A broken or dislodged belt, or a defective cassette motor, can halt tape rotation. Check the price of a new motor before ordering one to make sure it's worth it. If a replacement motor is very expensive, you may be better off buying a new player. be changed by pushing in the tuning knob. Often, the AM-FM switch applies voltage to the respective circuits (see Fig.1). Whatever switching system is used, the switch contacts must be cleaned. Often, you can quickly tell if the switch is dirty by moving the switch button after switching to the correct program. If the switch contacts are dirty, the sound will cut in and out. To clean the switch contacts, spray cleaning fluid (eg, WD40) down inside the AM-FM switch assembly. In most cases, you will have to remove the top cover to get at the switch assembly. After spraying, work the switch back and forth to help clean up the contacts. While you're at it, clean up all the other pushbuttons and switches located within the player. Keep the spray nozzle away from the motor belt and capstan/flywheel assembly; the chemicals in the spray can damage them. Rough volume control While you have the cleaning spray can out, give the volume control a squirt or two. After the radio has been used for several years the volume control seems to wear and get dirty at the comfortable volume setting. Sometimes the sound may jump up and down with a noisy control. The life of the control may be extended for many months or years with a good clean up. Remove the top cover and place the plastic nozzle from the spray can into the opening of the control where the contacts come out. Note that the volume control cannot be cleaned from the outside of the radio, by squirting cleaning fluid into the shaft area. Give each section of the volume control a couple of squirts, then rotate the volume-control shaft. Do that at least twice for each control section. Remember, there are two volume-control sections for the stereo output channels. Likewise, clean up the balance and tone controls while you are at it. If that doesn't do the job, replace the component with an equivalent part. 8 SILICON CHIP no tape action Improper or no tape rotation may be caused by a stretched motor belt, a broken belt or a dead motor. If the belt is loose, it can come off when the tape player is started up. Or, after several years use, the belt can crack and break. Usually, the broken belt is found loose inside the player mechanism. Slow tape speed may also be caused by the presence of oil on the belt. Remove the motor drive belt and clean both sides with alcohol and cloth. One method the electronic technician applies in checking out a loose belt is to hold the capstan and belt while the motor is rotating. If the motor pulley turns inside the belt, the belt is too loose. If the motor ceases rotation, you may assume the belt is not slipping. A sure sign that the belt is slipping is a shiny surface on the motor pulley. If the motor appears to be dead, it may be defective or there may be no voltage at the motor terminals. Measure the voltage across the motor terminals (12-14 volts). If the voltage on the motor terminals is incorrect, check the tape motor switch, the isolation resistor and the power supply components (see Fig.2). If the correct voltage is found and the motor refuses to rotate, check for continuity between the motor terminals using your multimeter set to the low-ohm scale. All resistance measurements should be made without voltage applied to the player. The reading should be a Critical voltage and resistance measurements on transistor and IC components may indicate a leaky or open circuit component. Cl - 51+ LEFT TAPE HEAD I ..._CHECK FDR BROKEN TAPE HEAD lOOpFI CONNECTIONS ./ .,. 21 ICl PREAMP .,__ _ __. .,. Fig.3: intermittent music may result from broken tapehead leads. You may find individual small wires or two shielded cables connected to the tape head. They fray from head movement. fraction of an ohm and should vary only slightly as you rotate the motor's shaft. In some cases, the motor may operate intermittently. When power is applied, the player may start up but at other times it's dead. To investigate this problem, remove the motor belt, apply power to the player and spin the motor pulley. The motor will either take off or pull slightly as it is rotated. Replace the motor if it plays normally after rotating the motor pulley or is intermittent. It probably has open-circuit commutator sections. Intermittent tape head Suspect broken wire connections to the tape head if the sound is intermittent. The sound may cut in and out on either or both channels. Often, one channel may only have a hissing sound while the other channel is normal. A loud rushing noise indicates that the tape head is open in that channel. Check the tape head for broken wire connections (Fig.3). You may find separate wires or two shielded cable wires to the tape head. Double check each soldered connection. The outside shield may be used as the common return wire. Solder all wires to the head using a low wattage soldering iron. Make sure no flexible wire ends touch the adjoining connection. Improper rewind Improper rewind or fast forward may result from oil or residue on the motor drive belt. Poor pressure of the idler wheel can also cause improper rewind and fast forward. Check the idler wheel for sluggish operation or an uneven rubber drive area. Clean off the motor pulley, belt and flywheel for slow or uneven fast forward. A good clean up and lubrication of the idler pulley and motor drive areas solves most erratic or slow rewind and fast forward operations. Clean off each spindle or turntable drive pulley with alcohol and a cotton bud. A drop of light oil on each pulley bearing may help. Do not over lubricate or let oil drip on the rubber pulleys or drive belt. minutes with tape spilling out, the tape may wind around the pinch roller and capstan drive shaft. If enough tape spills out, it's difficult to remove the ejected cassette. Sometimes the take-up reel will stop for a moment and then start up again, spilling out tape. If this happens, check the take-up reel drive pulley and belt. Clean up the drive pulley and belt with alcohol or replace the belt if it's loose. You should also remove the take-up spindle and inspect the bearing for gummed up grease or dry areas. A drop of light oil on the spindle bearing is enough. Clean off any excess oxide on the capstan drive and all tape guides. Do not overlook a defective cassette as the cause of tape spillage. Try another one. Critical voltage tests Accurate voltage and resistance measurements around the motor, transistors and IC components will often quickly track down any faults. Suspect the power supply or a leaky (or shorted) component if low or no voltage is found on the supply pins of a device. For example, low voltage on the collector terminal of a transistor may indicate a leaky component which should be replaced. A transistor may also be defective if there is no bias voltage between its base and emitter terminals. An open transistor is indicated if there is no voltage across its emitter resistor. Likewise, low voltage on the supply pin of an IC may indicate a faulty IC or an incorrectly functioning power supply. Often, comparing voltage and resistance measurements between the two audio channels will help to locate a defective component. Accurate resistance measurements from the terminal connections of transistors and ICs to ground can also help isolate a defective stage. Distortion in one channel Since most distorted sound problems are found in the audio output stages, try to locate the suspected +12.1v------------~ 2700 470 _ _ _ _ __.-.:.11+ F---ro SPEAKER 1 Spits out tape Spilling out of tape may be caused by an erratic or stopped take-up reel assembly, or by an uneven pinch roller. Check the pinch roller for sticky or packed oxide. It's usually a good idea to clean off the rubber pinch roller when cleaning up the tape head. Inspect the pinch roller for excessive tape down around the bearing support. If the player operates for a few Fig.4: after locating a leaky transistor, check each bias resistor for correct value. Make sure both transistors test OK and check the replacement before installation. JANUARY 1989 9 TAPE DECK TUNER ASSEMBLY MOTOR RADIO BOARD VOLUME CONTROL AND PREAMP BOARD OUTPUT SECTION This photograph shows the general layout inside a typical radio-cassette player. The output transistors or audio power ICs will be mounted on a heatsink or bolted to the chassis. output transistors or audio power IC on the chassis. These components will either be bolted to the metal chassis or to separate heatsinks. Note that an audio power IC stage may be part of a single package containing a stereo pair or may be a separate component. First, take voltage measurements on each transistor terminal. Be sure to write them down on the schematic with a pencil. Determine from the voltage measurements if either of the output transistors is open circuit or leaky. Remove any suspect transistors and test them in a transistor checker. Most DMMs these days have an in-built transistor test function. Double check all the bias resistors while the transistors are out of the circuit. Often, with a leaky output transistor, you will find a burned bias resistor. You should also take accurate resistance measurements of each bias diode. A leaky bias diode may produce slight distortion in one of the audio channels. Do not overlook an open-circuit speaker coupling capacitor as the cause of dead or really weak audio. Dead channel A fault in a dead audio channel is usually easy to locate. If both channels are dead, first check the power supply output. If this is OK, check the voltages on the supply pins of the audio power ICs (or on the collectors of the output transistors). A low voltage on the supply terminal may indicate a leaky IC or power transistor. If only one channel is faulty, compare its voltage readings with the good channel. In some circuits, you will find a preamp driver IC ahead of the output IC so be sure to check this as well. Sometimes, you will find very little difference in 10 SILICON CHIP , CAPSTA N FLYWHEELS Rapid changes in the direction of the cassette player may be caused by dirty contacts on the prongs and commutator. Clean off both with alcohol and a cleaning stick. voltage measurements between the two channels, even though one IC is defective. Before replacing a suspect IC, measure the resistance from each terminal to ground. Compare those measurements with the functioning audio output IC. Sometimes the meter readout will keep changing, which could indicate charging or discharging of a capacitor in the circuit. Leave the probe set on the same terminal until the reading steadies. If the resistance measurement is way off from the good channel, then the IC or an associated component is open or leaky. Changes direction Suspect a loose belt or dirty commutator when the cassette player rapidly keeps changing directions. If the belt is OK, look for a two or three-prong component placed on a rotating commutator, on top or underneath the chassis. The long prongs are silverplated and eventually become corroded. You can often restore correct operation by cleaning the prongs (or contacts) and the rotating commutator with alcohol. Conclusion Keeping your auto cassette player in tip-top shape may not be as difficult as you imagine. Of course, you may not be able to repair all the faults that can occur in a cassette player. But if you can only do the clean up procedure, you will have saved quite a few dollars. So next time that auto cassette player gives up, give it your best shot. You might just be able to nurse it back to health and save a few dollars. ~ This article first appeared in Hands-On Electronics, USA (September 1988); reprinted with permission. Don't miss a single issue IF YOU'RE THE KIND OF READER that can't wait to get the next copy of SILICON CHIP, then why not have the magazine delivered direct to your door? Each month, we'll bring you the best and brightest electronics magazine in the business, put together by Australia's most experienced team. * * * * * Electro111c · •*··· ho11se t> number t Convert a CB radio j for .amateur use r r_: \~ Hili raview: Yamaha's brilliant new en player Constructional Projects for the Enthusiast ...,,· Pl_tf$:.~ the · Orlginat & Best'rV.Servicern""sii.:·y 1ntag•,(·:~ ~, .- f;adl(?, 1he: W-ay ·us~& It, t h.e,.Evnlution ot Electrlc .. y•.;., -:,~ ' ·• Ri!i!'Wii'f$ ' · ·· ,\~- · ' "'-. ·q t Amateur Radio by Garry Cratt The Serviceman's Log The Way I See It Hifi Features & Reviews FREEPOST * SUBSCRIPTION COUPON □ □ Renewal New subscription Start i ~ - - - - - - Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree~-------------------Suburb/tow ~ - - - - - - - - - - - Postcode_ _ __ Australia 1 year (12 issues) □ $A42 2 years (24 issues) □ $A84 NZ & PNG (airmail) □ $A65 □ $A130 Overseas surface mail □ □ Overseas airmail □ $A 1 20 $A62 $A130 □ $A240 Enclosed is my cheque/money order for $ _ _ _ or please debit my □ Bankcard Card No. I □ Visa Card □ MasterCard I I I I I I I I I I I I I I I Subscription Hotline We can accept your subscription order by telephone. Just ring us on (02) 982 3935 and quote your Bankcard or Visa Card number and the expiry date. Detach and mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 I Signature _ _ _ _ _ _ _ _ _ Card expiry date__/_/__ • No postage stamp required in Australia. W cflt:J I ~--- - - --------------------------------~ JA NUARY 1989 11 of the great, money saving reasons most amateurs shop at Dick Smith Electronics. YAESU When it comes to selection, price V or sales and service back-up - there's nowhere else to gol Big Performance From A Tiny Hand-Held! w, j ... WWW WWilW WWW 'J The ideal 2m for the novice . .. or anyone wanting the best in hand-held performance. 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You're missing out on the latest news, stock exchange and financial information, sport results and TAB information, weather reports and forecasts, even recipes, jokes and much, much more. It comes to you absolutely FREE - courtesy of the Australian Television Network. On a normal TV, it's the little colour flashes you see in the black bars between picture frames when your TV "rolls". Unless you have a Teletext TV or decoder, you don't even know they're there! And don't forget, most stations transmit popular programmes with subtitles for the hearing impaired. This Teletext decoder will let you see subtitles too! Until now, you've had to buy a specially equipped TV to receive Teletext. Now you can buy just the Teletext decoder - and keep your TV set! It's not a kit - it's ready to go. And because it plugs into your video cassette recorder, costly duplication of the tuner section is eliminated. So you save! Isn't it time you had the benefit of Teletext in your home? Cat L-4468 ONLY AVAILABLE FROM VINTAGE RADIO By JOHN HILL Troubleshooting the transformers Transformers are a fairly common component in electrical and electronic circuits and a number of different types are to be found in old valve radios. Here's a run down on the various types that you'll encounter. A valve radio has several different transformers, all of which perform critical circuit functions. A typical 240-volt mains operated receiver will have a power transformer, a number of intermediate frequency (IF) transformers and a loudspeaker transformer. Very early radios of 1920s vintage will most likely have a few audio transformers, while battery operated vibrator radios will be fitted with a special vibrator transformer. Vibrator transformers differ from power transformers in that they step up low tension voltages to high tension voltages. Many of these old transformers have modern counterparts. A transistor radio can still have a power transformer and will still have IF transformers, but they are such a radical departure from the valve radio versions that one would not recognise them as being related. Parts availability Many components in valve radios can be replaced with modern This photo clearly shows the diminishing size of radio power transformers. From left: an old 2.5 volt transformer from the early 1930s; a 6.3V transformer from about 1950; and a transformer from a modern transistorised radio. 14 SILICON CHIP equivalents (eg, resistors and capacitors), but not so transformers. About the only components that cen still be bought across the counter are speaker transformers (also known as audio line transformers). If you want other types of transformers for valve radios, the only alternative is to scrounge and use serviceable secondhand units. In recent months I have read a number of suggestions implying that old power transformers can be dangerous and that they should be earthed as a safety precaution. In the past, valve radio power transformers were always wired with 2-core flex, not 3-core. However, it has been suggested that they should be earthed because the insulation breaks down with age. In my (admittedly limited) experience, I have never had much trouble with power transformers. I have replaced just one only to find out later that there was no need to replace it. The problem turned out to be a crook connection, not a crook tranny. Power transformers give very little trouble and I have yet to encounter any type that has a real problem. I know that they can and do break down - but not often and rarely without cause. A power transformer from a transistor radio differs greatly from its valve counterpart. It usually has a single secondary winding of 6, 9 or 12 volts. The low tension secondary current is then rectified to DC and the whole set works off that one voltage. These power transformers are quite small because a transistor radio rarely consumes more than 50 milliamps Vintage Radio Kits & Parts ORPHEUS These ancient-looking components are audio frequency transformers from the 1920s. These transformers were used to couple the audio output stages. From left: Emmco, Viking and Ferranti. at 6 volts - perhaps 150 milliamps if it's a cassette radio. On the other hand, a valve radio power transformer is much larger and has a number of secondary windings for various purposes. Secondary voltages of 5, 6.3 and 285 volts are common. The 5V winding is for the rectifier filaments, while the 6.3V winding goes to the heaters of the other valves and to the dial lamps. The 285V secondary is rectified and filtered to give a high tension DC supply of 250 volts or thereabouts. Electrical efficiency An interesting comparison can be made at this stage between the efficiency of transistorised equipment and the inefficiency of valve equipment. The filaments of a 5Y3 rectifier valve draw 2 amps at 5 volts. The other receiving valves will consume anything from 0.3 amps to 0.7 amps at 6.3 volts, while the dial lamps typically consume 0.3 amps each. When plugged into 240-volt mains, the cost of running a valve radio is still .pretty minimal (50-60 watts) but a transistor radio virtually costs nothing to run (about one watt). Just a single dial lamp on a valve radio consumes roughly 10 times more current than an average transistor radio. So if you read somewhere that valve equipment is Loudspeaker transformers can be unreliable so it's always a good idea to have a good stock of spares. In particular, you should always save the speaker transformer if you junk a set, along with any other parts that might prove useful. *RADIO* Suppliers of • • • • • VALVES RADIO KITS CAPACITORS RESISTORS BOOKS, ETC. Please send for our free catalogue ORPHEUS RADIO RSD B98 BALLARAT VICTORIA 3352 Ph. (053) 34 2513. Fax (053) 31 3412 inefficient, believe it! The high filament and heater consumption is the reason for the somewhat larger power transformers fitted to valve radios. Those old power transformers used lots of copper wire and iron and neither size nor weight was ever a serious consideration. It was common practice to attach the speaker transformer to the frame of the loudspeaker but this won't always be the case. In some sets, you'll find the speaker transformer mounted on the chassis. JANUARY 1989 15 Intermediate frequency (IF) transformers became smaller as time progressed. You can easily check these units out by testing each of their two windings for continuity. Corrosion is often a problem with IF transformers, so they can give trouble. IF transformers are very simple units consisting of tuned primary and secondary windings. These windings are designed to resonate at a specific frequency (455kHz is a common intermediate frequency). The primary and secondary windings can be tuned with either a trimmer capacitor or an adjustable iron core. One of the reasons a superhet receiver is so selective is because the IF transformers are tunable. However, it is advisable to use a radio frequency generator when tuning them so that they can be tuned to the correct frequency - but that's a story for some other time. Early IF transformers of the capacitor-tune type can have their own particular problems when tuning. If a metal screwdriver is used for tuning (not the best instrument but often used), it's possible to short circuit the high tension between the trimmer screw and the shielding can which is earthed. The resulting high voltage discharge can not only give the operator a helluva fright but there is also the possibility of burning out one of the fine windings in the IF transformer. The amount of HT voltage and the size and condition of the electrolytics would have some bearing on this matter. The bigger the zap, the greater the likelihood of damaging the transformer. Speaker transformers IF transformers can be either slug tuned [left) or capacitor tuned (right). Always use an RF generator [usually set to 455kHz) when making adjustments. This will ensure that the IF transformers are tuned to the correct resonant frequency. Some of the older valve radios even have two power transformers. A particular set in my collection has one transformer for the rectifier only, plus a second transformer for the heaters of the remaining valves. The old 2.5V valves of the late 1920s and early 1930s required rather large power transformers to supply the high current needed. When those 2.5V valves were superseded by 6.3V types of lower 16 SILICON CHIP amperage, there was a reduction in the size of power transformers. IF transformers Intermediate frequency transformers, as used in superhet valve radios, serve as tuned coupling stages between valves prior to the detector stage. There are usually two or occasionally three IF transformers in a superhet receiver, depending on the number of stages of IF amplification. Speaker transformers may seem to be a strange device to those accustomed to working with modern radios as most transistorised circuits connect directly to the loudspeaker. With valve equipment, it's necessary to connect the output valve or valves to the speaker via a speaker transformer. These transformers are usually mounted on the speaker frame itself and more often than not carry markings such as: 5500/8, 7000/8, 5000/3.5, plus quite a number of other variations. The first figure of these numbers indicates the output load of the valve (as stated in the valve manual), while the second figure represents the speaker voice coil impedance in ohms. Using the three Problems? ... and you don't have our .120page catalogue . .. .w· ) This is what an IF transformer looks like when it's removed from its metal can. The two windings are sealed in wax to prevent corrosion. Take care when handling the transformer as the winding leads are easily broken. examples given, a 50000 speaker transformer primary matches with a 6V6 and a 6AQ5; 55000 matches a 6F6, 42 or 2A5; and 70000 works with an EL33 or a 6M5 . For best results, the loudspeaker should be correctly matched to the output valve(s)with the appropriate speaker transformer. In practice, mismatching is fairly common in old sets but this doesn't seem to cause any problems. Audio transformers Some mention should be given at this stage to the old audio transformers of the 1920s. It was common practice in the early days of radio to have up to three stages of transformercoupled audio amplification. For example, a mid-1920s model receiver could consist of one or two stages of radio frequency (RF) amplification (all with separate tuning capacitors and dials), a detector and two or three audio stages. Transformers were used to couple the low gain triode valves. Common problems Of all the transformers mentioned so far in this article, the speaker transformer is usually the most troublesome and the one most likely to burn out. A totally mute receiver is often the result of a burnt out primary winding in the speaker transformer. This problem is easy to troubleshoot. You simply unsolder the primary connections and check for an open circuit with an ohmmeter. Such a problem will cause the screen grid of the output valve to glow red hot - a sure indication of a crook speaker transformer. Continuity checks are also applicable when checking out IF transformers. An IF transformer has only two windings and four connections so it shouldn't be difficult to check for an open circuit in either winding. Corrosion is often a problem in IF transformers. Power transformers can be checked in a similar manner and a conmtinuity check on the primary winding will soon indicate a problem. The HT secondary winding should produce the same voltage (or have the same resistance) either side of the centre tap. But generally speaking, it is the finer primary winding of a transformer that gives trouble. This can be due to burn out or to an internal disconnection to one of the leads. While most power transformers give no trouble, there are occasions when they do break down and need replacing. Of course, the ultimate repair is to rewind the defective winding. The easiest course is to simply substitute another transformer of similar size and specification. [§;;I At last . .. a TRADE catalogue for the consumer ARISTA ... your one-stop problem solver. 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Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ARIST~ ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 JANUARY 1989 17 HIFIREVIEW Marantz LD50 DMS bass reflex loudspeakers Over the years Marantz loudspeakers have come in a large variety of shapes and sizes, from the small to the super-big. Now, with Ken Ichiwata at the design helm, they have taken an almost classic European approach and produced the LD50 DMS Mini Monitor, a compact 2-way system. By LEO SIMPSON As with most compact hifi loudspeaker systems today, the Marantz 1D50 is a bass reflex system with a small port. This gives the most extended bass reproduction and efficiency from a small enclosure. Dimensions of the LD50s are 420mm high x 270mm wide x 282mm deep, with the rear ter- minals projecting a further 20mm. Weight is 9.5kg. Enclosure volume is about 22 litres which is fairly small for the size of bass driver specified. The enclosure is finished in a simulated black timber veneer and the grille cloth is also black. The bass driver is a nominal 20cm unit with a clear polypropylene cone and neoprene rubber The Marantz LD50 is a compact (22 litre) bass reflex system with a tuned port. This technique is now common with compact loudspeaker systems and provides good efficiency and extended bass reproduction. 18 SILICON CHIP roll surround. The curvilinear cone (ie, not a straight-sided cone) has an effective diameter of 150mm and is driven by a 25mm diameter voice coil. Handling the treble end of the spectrum is a nicely finished ferrofluid-cooled soft dome tweeter with a diameter of only 19mm. It is recessed into its front mounting plate which also functions partly as a horn. Crossover network Coupling the two speakers to the amplifier is a fairly complex crossover network consisting of three inductors, three capacitors and two wirewound resistors. The crossover frequency is 2. 4kHz although this is not specified in the Marantz literature. Evidently quite a lot of work has gone into the design of the crossover network. The feed to the woofer is reasonably conventional, with a series inductor and shunt capacitor giving a treble rolloff of 12dB/octave. The tweeter feed is more complex though and employs two series LC networks, one being in shunt with the tweeter. We assume the series LC networks are there to smooth out any irregularities in the tweeter's response. We noted with interest that the three inductors in the crossover network are oriented at right angles to each other to minimise any mutual coupling. This is desirable to minimise any degradation in the crossover network's performance. Bass tuning The bass reflex port takes the form of a 53mm diameter tube Bi-grounding and bi-wiring One of the unusual features of the Marantz LD50s is the presence of three wiring terminals on the rear panel, for connection to the power amplifier. One terminal is red, for connection to the active ( +) speaker terminal on the power amplifier while the other two terminals are black. These black terminals both connect to the negative (- ) or earth speaker terminal on the amplifier. The idea of using two earth return leads for each loudspeaker is to keep the return currents from the woofer and tweeter separate. Marantz argue that not only is it necessary to carefully design the crossover network so that the various elements do not interact with each other, but that the earth returns for the treble and bass should be kept separate. This improves the clarity of the signal. This concept of separate earth which is 245mm long, not a great deal less than the internal depth of the enclosure. The baffle of the LD50 is notably dead (ie, non-resonant) and is a sandwich of particleboard and Medite, a material which is similar to Customwood. In effect, there are two baffles sandwiched together with the one made of Medite being that at the front. The grille cloth frame fits around and over the Medite baffle which is an unusual method of construction although Marantz make no mention of it in their literature. Bi-ground wiring The most unusual feature though is that the LD50s have three connecting terminals - one red and two black. One of the black terminals is for the negative return currents from the woof er while the other is for the treble return current. As explained in the accompanying panel, the idea of having separate return wires is to keep the treble and bass signals as separate as possible. This may seem a returns was originally developed when stereo sound reproduction first came into being. Tests showed that stereo reproduction was better when the earth returns from the two loudspeakers were kept entirely separate instead of using a common return inside the stereo amplifier. So these days, in good amplifiers, there are separate wires from the two negative terminals for the speakers back to a single earth point at the power supply. This idea makes sense because the impedance of a common earth return means that a voltage will be developed across it, due to the current through the two speakers. This "common impedance" voltage will be subtracted (vectorially) from the signal voltages applied to the two loudspeaker systems and thus degrade the stereo separation. strange idea since the bass and treble signals are sourced as a common signal from the amplifier but it could have a number of benefits. For example, if non-linearities in the woofer cause a distorted current waveform, the resulting signal voltage across the negative return wire is completely isolated from the tweeter network. To connect the speakers with double returns, Marantz suggest the use of 3-core mains ea ble which is not a bad idea. However, for those who do not wish to bother, Marantz supply the LD50s with a wire link to bridge the two black terminals together so that conventional figure-8 speaker ea ble can be used. Marantz do not make a big point about heavy gauge connecting cables although the three terminal posts will certainly take heavy cables without problems. Recommended amplifier power to drive the LD50s is 30 to 100 watts and we would agree with that, albeit with an emphasis on the upper end of that range. Efficiency is probably on the low side of In some audiophile literature this idea has been taken further with the concept of "bi-wiring" of loudspeakers. This involves a crossover network inside the loudspeaker but separate active and negative feed wires for the treble and bass signals; ie, four separate wires from the amplifier to each loudspeaker system. Marantz has taken a middle-ofthe-road approach by having a biground system, possibly reasoning that three wires are potentially less confusing than four ." Either way, the concept is likely to cause some argument in hifi and engineering circles. Certainly, measures to avoid common impedances are desirable but engineers are likely to cite the Principle of Superposition and how it makes extra wires unecessary. Care to buy an argument? We'd like to hear from you. average these days, with a quoted sensitivity of 88dB (lkHz/1 W/1metre ). In other words, to make the LD50s really come to life, you need an amplifier capable of 100 watts per channel. Impedance curve As the accompanying impedance diagram shows, the LD50s have a minimum impedance of just under 70 at 200Hz so they will not present any loading problems, even to amplifiers that are notably fussy in this regard. Marantz are vague in specifying the frequency response of the LD50s, just quoting it as 35Hz to 30kHz, with no decibel limits. Our tests indicate that it has a very smooth response over the audible frequency range and that it has a usable bass response down to below 40Hz, which is quite good for a system of this size. Depending on your musical tastes, you may prefer to use a slight degree of bass boost with the LD50s. For best results on classical music though, we would leave the continued on page 21 JANUARY 1989 19 BOOKSHELF Practical Digital Electronics Handbook Practical Digital Electronics Handbook, by Mike Tooley. Published 1988 by PG Publishing, London UK. Soft covers, 138 x 217mm, 197 pages. ISBN 1 870775 00 7. Price $19.95. This text gives quite a good overview of the digital electronics scene for the technician or enthusiast. There are a total of 9 chapters and 5 appendices. Chapter 1 is an introduction to integrated circuits and covers such topics as the type of packages used, logic families (eg; TTL, CMOS), power supplies and 3-terminal regulators. It also includes a suggested circuit for a 5V supply. Chapter 2 is probably the most crucial in the book and is devoted to logic gates. Probably the treatment of this chapter is just a little too light-on for good understanding by the reader although the presentation is about on a par with other chapters. Chapter 3 covers monostables, flipflops and shift registers. Chapter 4 is titled 'Timers" but covers only one, the 555. Chapter 5 is a brief introduction to microprocessors while chapter 6 20 SILICON CHIP deals with memory devices. Chapter 7 covers input/output devices for microprocessors while chapter 8 covers interfaces such as the RS-232 and the IEEE-488 general purpose instrument bus. Chapter 9 is on microprocessor buses but it covers only the IEEE-1000 bus (also known as the STE bus). Other well known buses such as the VME-bus are not mentioned. Appendix 1 is devoted to data and has quite a few pinout diagrams for TTL devices but only a few for the much more widely used CMOS devices. It also has binary, hex and ASCII conversion tables. Appendix 2 is the largest chapter in the book at 57 pages and features digital test equipment projects. Included are a regulated power supply, a logic probe, pulser, pulse generator, RS-232 breakout box and so on. We can sum it up by saying it is well written but could do with more depth in the treatment of the subject. Still, that would make it a much larger book. Our copy came from Jaycar Electronics. Antennas For Radio Amateurs The ARRL Antenna Book. 15th edition, published July 1988 by the American Radio Relay League, Newington, Connecticut, USA. Soft covers, 278 x 210mm, 719 pages. ISBN O 87259 206 5. Price $39.95 (from DSE stores). Books on antennas, any kind of antenna, are hard to come by so the latest edition of the "ARRL Antenna Book" is of great interest. The last edition was produced in 1982 and had 327 pages. The 15th edition is more than double this size, at over 700 pages, and has been considerably revised over the old edition. Many of the antenna designs presented are the same as in previous editions but there is so much new material that those with the old editions will still find it a worthwhile purchase. In all, there are 28 chapters in the book plus an extensive bibliography and a glossary of antenna terms. The first chapter is entitled "Safety First" and starts out with a discussion on tower safety and the installation of high antennas. Even though this will be of interest to many amateurs, the pages on electrical safety and lightning protection are far more important. An often overlooked hazard among amateurs is exposure to , electromagnetic radiation and there are a couple of very useful pages on estimating the amount of exposure likely from typical installations. The next two chapters are entitled "Antenna Fundamentals" and "The Effects of the Earth", and are devoted to antenna theory and the effect of soil conductivity on signal propagation. Chapter 4, on selecting antennas, is a broad survey on the types of antenna for amateur radio operation. Chapters 5-20 are then devoted to the theory and construction of a whole range of antennas but always with a view to amateur radio activities. Some of the anten- nas covered include: loops, broadband antennas, log periodic arrays, yagis, quads, long wire and travelling wire (rhombics), direction finding, mobile and maritime. Chapter 21, on antenna materials, is devoted mostly to wire gauges and aluminium tubing. There is also a comprehensive list of manufacturers but that won't have much relevance outside the USA. Chapter 22 is on antenna supports, ranging from trees to mast and rooftop installations, while chapter 23 is on radio wave propagation - a very useful chapter. Chapter 24 is on transmission lines and this is followed by two chapters on transmitter matching to the line and matching the line to the antenna. Chapter 27 is on antenna and transmission line measurements, including SWR, directional couplers and noise bridges. Chapter 28 is on the use of Smith Charts and gives numerous examples. So whether you are an amateur radio operator or not, if you have an interest in antennas, this book is not to be missed. It is a very useful source of information on a wide range of antennas. We can thoroughly recommend it. It is available from all Dick Smith Electronics stores. Digital Audio Fundamentals Introducing Digital Audio. CD, DAT and Sampling by R. A. Penfold. Published 1988 by PC Publishing, London UK. Soft covers, 139 x 215mm, 103 pages. ISBN 1 870775 05 8. Price $16.95. This little book offers easy-toread non-mathematical explanations of digital audio technology as used in compact discs and digital audio tape recorders. Some knowledge of audio principles and logic circuits is assumed although there is a chapter on digital devices which covers gates, flipflops, registers and so on. Marantz LD50 DMS Loudspeakers tone controls flat. We found the overall sound quality to be excellent. The bass is very well defined but the treble is even more so. We really did like that tweeter. During our fairly brief tests we were not able to verify the validity of the double return wires although we did try what we considered to be a fairly tough test. This involved connecting one of the LD50s to ,t he amplifier via three long wires of The last chapter of the book also covers sound synthesis techniques and the MIDI (musical instrument digital interface) system. For those who want to improve their knowledge of digital audio without getting too heavily into it, this book is worth having. Our copy came from Jaycar Electronics. ~ ctd from page 19 light gauge. One member of staff was then deputised to bridge out the black terminals at the rear of the speaker while a monophonic program was played through it. Either way though, the sound quality of the LD50s is very satisfying. Recommended retail price of the 1D50 DMS Mini Monitors is $699 a pair. For further information and an audition, contact your local hifi dealer. For the name and location of your nearest Marantz dealer, phone Marantz toll-free on (008) 22 6861 (in Sydney dial 742 8322) or write to PO Box 125, Concord West, NSW 2138. ~ · Conclusion On this rough and ready test we concluded that any improvements brought about by the bi-wiring must be pretty subtle and probably not demonstrable with a simple test. 25 (\ 20 I \ \ I " - I'-.... / 0 15 " ~I'-..... \ I ,I - V I j I ~ .......... 1,./ / I I 1k 100 FREQUENCY (Hz) I 10k 20k Fig.1: this is the impedance curve for the Marantz LD50 system. Note the peaks at 70Hz and 1.3kHz. The minimum impedance is 70 at 200Hz which means they will not present any loading problems to the amplifier. JANUARY 1989 21 JAYCAR'S SENSATIONAL PRICE BREAKTHROUGH. . . ECONOMY DIGITAL MULTIMETER Lowest Price Jaycar Digital Multimeter EVER. Another Jaycar exclusive direct Import. Digital Multimeter at an Analog price!! • 3.5 digit LCD display • 20 ranges • Diode checker • DC 10 amp, 1000V, AC 10 amp, 1000V, 0-20M ohm, etc. • 1500 hour battery life • One hand operation with unique feature where probes can mount into either side of the case • Tilting bail • Safety test leads • 3 month warranty Cat. QM-1410 ONLY $59.95 DIGITAL MULTIMETER (With almost everything) A Jaycar exclusive direct Import. Save a massive $50 over similar equipped units. LOOK AT THE FEATURES • 34 ranges • 3.5 digit LCD display • High impact yellow case • Small size - only 133 x 70 x 30mm • 1O amp AC and DC. DCV under 1% worst case • Diode tester • Continuity buzzer • Frequency counter 1OHz - 200kHz • Built-in 20MHz logic probe • Capacitance tester 1pF - 20uF • Tilting bail • Safety test leads • One hand operation with unique feature where probes can mount into either side of the case. • 3 month warranty Cat. QM-1400 ONLY $109 SAVE $50 PLASMA DISPLAY KIT SELLOUT If you've been thinking of experimenting with a plasma discharge display kit now is the time to buy. We have to make room for our new built-up unit, so the kits must go. Buy now and save yourself E,l,T'~E Q U I C K . Plasma Display Kit \,.. , . "·'\ Ref: Silicon Chip August 198B ... ,. -- .' •.... •. .,:_ Originally sold for $299. Due to mass production It has ·. · · ·:·.-..-,:." recenUy been selling for $229. Now you can own one for only $129.50 saving you a massive $169.50 off original selling price. Cat. KC-5035 Poor Mans' Plasma Display Ref: Silicon Chip November 1988 All the electronics of the big kit are Included but no vacuum jar. You can use a large wattage normal 240V light globe BUT BE CAREFUL. Cat. KC-5045 Normal Price $75 NOW ONLY $49.50 30 PIECE ENGINEER'S DRIVER SET At last! A driver set incorporating those obscure shaped heads! Have you 1Ner needed recently to service an el9ctrlc tool? Chances are you would not have been able to do so because the screws holding the appliance together had strange shaped heads. Well now you can with our 30 piece driver sell This set contains all the driver bits you are EVER likely to encounter (See Below). Basic to the set is an 8 1/2" Chrom&-Vanadium driver which will accept any of the 28 hardened steel bits supplied. They are held into the socket of the driver by a small magnet - so you can use the driver In any position. The screw-together hollow handle will hold several tips so you don1 have to take the whole set with you Into the field. There is a tip here to suit almost any screw/nut you may come across. Here's what you get: • 5 Slotted Bits 0-1, 3-4, 5-6, 8-10, 12 • 5 Hex B~s 3132", 5/64", 7/64", 1/8", 9/64" • 4 Philips Bits No. 0, 1, 2 & 3 • 4 Square Recess Bits No. 0, 1, 2 & 3 • 6 Torx Bits T10, T15, T20, T25, T30, T40 • 2 Pozldrlve Bits No. 1 & 2 • 1 x 1/4" Drive Socket Adaptor • 1 x 1/4" Drive Hex Bit Holder And Its all housed in a sealable tough plastic case $19.95 PERSONALDATABANK/CALCULATOR UNDER $40 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 phone numbers can1 be retriiNed by anyone but you. m Other features included: • Auto power off ,r .. • Edit fe_ature ;~• 10 digit calculator ' ·• • Includes battery We have seen these for as much as $79.95. But with our direct lrrporting we can offer them at about 1/2 that price. Cat. QM-7200 ONLY $39.95 TltOl'HCA " ,, co ,, ,,,. GH t J 0/' ,: 7 I{ 4 0 R $ $ 2 L MN 6 T IJ V ' r" wx {J :, C~J!J~ ~;,t SMOKELESS ASHTRAY ~f• ' At.P 10-801( MC f'A,t:tt "" z• MMAI:« y " A "' • (l!JOOfc a OIRF:C:T IMPORT In this day and age, cigarette smoking is becoming socially unacceptable. This product will help the poor old smoker by removing all smoke from a cigarette sitting In the ashtray. It works like thls:Swltch the unit on, and It will just sit there In the off mode. When you "light up" si"1)1y tap the ashtray and It turns on and rusn for 1O minutes before going back to the standby mode. The unit has a silent motor which draws . the smoke Inside and through activated charcoal • layers to purWy the air. Operates on 2-C size batteries or a 3V DC power source. The ashtray section (where the cigarette sits) Is made from Melamine and just lifts out to empty and clean. Size: 125mm x 125mm x 75mm. Cat. YX-2930 ... .... #. f114f):• .t,<11;f,J,H / ONLY $14.95 Machined Aircraft Grade Aluminium Flash light What an excellent product I It measures 145mm long and runs off 2 - AA batteries. It Is 70 times brighter than a normal torch and the beam Is adjustable from spot to beam, and it's waterproof and shockproof. Durable anodised abrasion resistant finish, with a non slip knurled grip. This torch will last a lifetime. Small enough to flt 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. Spare bulbs available for only $1 .50 (Cat. ST-3002) -~Cat. ST-3000 ~ • I" I • ~ UNBELIEVABLE SOLDERLESS LUG PACK The most beautiful thing we have ever seen. Just imagine, a beau!Wul plasma display In your own home for under $2001 Watch as the red glowing element in the centre of the 200mm glass sphere projects beautWul blue lightning outwards to the Inner surface of the ball where It magically changes back to crimson. This iNent occurs simultaneously at least 50-100 times all over the Inside of the sphere and is constantly In motion. It is truly beaurnul to watch. The intensity of the display can be controlled by a slider pot mounted on the attractive base. In addition you can trigger the performance by means of a sensitive sound activated circuit. The entire unit comes with Its own dedicated power supply 1 ', and Is packaged In an attractive gift carton. This beautttul Instrument will give countless hours of pleasure and relaxation and Is truly unique. Cat. XP-1000 e 1 $199 Another surplus buy. A bag of approximately 200 assorted insulated solderless terminals. Included are ring terminals in many different sizes, lug terminals, cable joiners, and solderless lugs to connect Into terminal block. These normally cost between 15 and 30e each. We estimate the notmal price for these parts would be around $50. LIMITED QUANTITY 'Cat. HP-1210 ONLY $10 MagnWy the savings you make by buying at Jaycarl Also good for checking small corrponents as wel~ Every toobox should have one. Lens 35mm dla., handle 40mm long. Cat.OM-3500 ONLY 99~ each (Does not magntty our prices eitherl) TAG TANTALUM BARGAIN We have about 20,000 pcs of a 4.7uF 16V tag tantalum made In West Germany. Normally worth 75e each. Grab yourself a bargain. Cat. RZ-6636 10 for $2 100 for $15 1000 for $110 · 120WATIPA/ GUITARAMP MODULE KIT tage V: lve Sale We are holding small stocks of BRAND NEW valves going back to the 40's and beyond! Over 170 different types are available but most are in vary small quantities. Stock will not be kept at local stores it will have to be ordered in for you against pre-payment. This does not guarantee that the stock may have already been sold. All the valves are one price $5 ea. If sold out money refunded in full. Stock is new but NO WARRANTY is offered. Normal mail O.K. See list of part numbers: CAR SAFETY LIGHT KIT Ref: Silicon Chip November 1988 This rugged Mosfet amp module Is designed specifically to drive a 1OOV line transformer for PA. It can also be used for guitar and stereo """s. Short form kit. PC board and all components supplied, including Mosfets. No power supply parts or heatslnk included in kit. Heatslnk extra Cat. HH-8550 $22.95 Cat. KC-5043 (kit) Ref: Silicon Chip November 1988 Is your car In danger of being sideswlped at night? This project detects an approaching cars' headlights and automatically turns on the brake lights to warn the driver. The brake lights switch off 5 seconds after the car has passed. Circuit is disabled during the day. $72.50 6FC7•6BY7•6CG7•6CK6•6CH&6AU5Gl•6BJ6 •6AN8A•6BA8A•3V4•1 R5•1S5•6AL3•6AK8 •6BMS-6EM7•6SA7GT•6BH8•6S2•6CM7•5AS4 •6BX7GT •6BW7•6BS8•6BN6•6B R5•6BK7B •6BJS-6BJ7•6BF&6BE7•6ABS-6AC7•6AH4GT •6AB5•6A6•6AB4•6AG5•6BD6•6BD5Gl•6BC8 •6AU7•6BC90•6AS8•6AQ6•6AN&6AS5•6AQ7 •25Z4G•2SZ5•12AT&UF41•9AOS-12A&117Z3 •9AKS•6Y6G•7AN7•12AU&12AX4GTB•12BD6 •12BV7•12BA7•1207GT•12K7GT•12SA7•12SG7 •12SQ7GT• 12SN7•12SK7GT-15A6•21 A&16A5 •15DO8•6SC7•6AU4GT•6SR7•6SH7GT •6CD6GA•6CD&6BQ6GT•6DB5•6DA5•6DE6 •6DS8•6ES6•6EV8•6ET6•6C6•6B27•6CF6 •EC86•6CM4•6CO6•6DA4·6N3•6JN8•6G6 •6F8G•6W6GT•6R7•6N7•UCH21•UCL83-UY1 N •UCH42-UCH41•1AB&1A&1A5GT•1AB&PCL83 •UBL21 ·EM87• PGL83• DL93•3A5•3A4•3O4 •3O5GT•5GK3•ER4GYB•5U8•1D7G•1D8GT • 1F6•35C5•50ENS-32L7GT •C8•C1 •6AN8A •6BH8•6BV8•12AQ5•12A ~7•6AW8A•6ADB •6EH7•6BQ6GTB•6BQ7 A•6BZ6•6AB8•6BF5 •6AM5•6CM7•6BH8•6BU8•6AT6•6AD8 •6EM5•6EB8•6V9·6X2•6W6GT•6N8•12AA6 •12BA& 12BE6•6U8•6CW7•6CD6"6005•CB 1C •CF1•CY31•6CD6GA Ref: Silicon Chip November 1988 Provides the scanning effect same as on kit car in Knightrider TV program. Use for burglar alarm applications, novelty applications on kids toys, etc. PC board and all components supplied. Cat. KC-5042 Ref: EA November 1988 Low cost 4 digit timer which can measure intervals from a few microseconds to hundreds of seconds. You can measure the speed of a slug from an air rifle, go~ ball speed, etc. Short form kit, no box or front panel supplied. Cat. KA-1708 $59 $17 95 HANDS FREE TELEPHONE HEADSET $16 .95 So new, we don't even have a picture yet. As used with the Silicon Chip speakerphone project. Headset, microphone with lead and 3.5mm plug. Mini size ultra lightweight. Cat. M-2018 Econom ron 25 watt general purpose Iron. Ideal for beginners. Generous mains power cord. Supplied on attractive card with soldering Instructions on the back. Cat. TS-1450 SPEAKERPHONE Ref: Silicon Chip Sept 1988 High quality hands free telephone adaptor that works extremely well. Full kit Including box, panel, isolating transformer and all parts. Cat. KC-5040 J Conical spare tip Cat. TS-1453 $4.95 ONLY $89 ~ ~ t l l M ~~ 0oi: ·;; Metal Stand to suit Jaycar Soldering lorn Sturdy metal base with sprung stand and heat resistant ferrule holder. Cat. TS-1500 ·, >1-W~ 0 >l!lh?«- AA NiCads $3.50 each or 4 for $12.50 Spare sponge to suit Cat. TS-1501 95e Don't waste money. Buy rechargeable NiCads, 450mA. Ouallty brand. Cat. SB-2452 $2.20 Size: 3.5mm x 6mm dia. OUR MOST POPULAR KIT IN 1988! FM Stereo Transmitter ''MINI MITIER" Ref: Silicon Chip October 1988 This fantastic project enables you to transmit a signal IN STEREO over the FM band. The range Is limited to about 20 metres or so, so lrs not a nuisance to anyone else. It uses a single 1.5V AA (penlight) cell which lasts for ages. Just Imagine! You can listen to your CD player on your FM headphone receiver while washing your earl You can play your Walkman CD player over your car stereo - no wiresl The possibilities are · endless! Set up your own micro FM Radio Station I The Jaycar kit of this project Includes the hard to get Rohm BA 1404 chip and the CORRECT 38kHz .------==-------- ■ crystal - even harder to getl All other spec~ied SPECIAL IC AND CRYSTAL FOR parts are included as well. MINIMlnER KIT AVAILABLE Cat. KC-5041 SEPARATELY BA-1404 Trans IC 38MHz Mini Crystal Cat. ZL-3995 Cat. RQ-5298 $6.75 $8.75 ONLY $29.95 Ideal marine use. Has car cigarette lighter plug for convenience. Extra long cord. Cat. TS-1470 ....----;;""',·- • Refer: EA October 1988 Revamped version of original Powermate power supply. Delivers clean, crisp regulated 13.8V DC at up to 5 amps. Full kit. SAVE Cat. KA-1707 . WAS $119 $109 UHF/VHF~FM INDOOR ANTENNA \ 1---------------■1 ron THIS IS RARE! Tonearm cable. Yes, we've finally been able to locate a small quantity of 4 core tonearm cable. This cable is twisted together and total diameter is approx. 2mm. 1 metre length. Cat. WH-3035 $ 2 Brand new omnidirectional mini mic insert. Ideal for all those miniaturised circuits. Operating Voltage 1.5 to 15V DC Current Consump. 0.5mA or less (6V supply) Frequency Range 40-10,000Hz Output Impedance Same as load resistance (150 ohm - 5k ohm) Sensitivity 66dB ±3dB SIN Ratio More than 40dB Cat. AM-4008 10+ $1.90 POWERMATE 2 KIT 9 When your car alarm goes off you want EVERYONE to know about itl Many car alarms these days make the same 'electronic' noise that Is increasingly being Ignored. This motorised siren makes a racket like the old police cars of the 60's & 70's. You would have heard the noise when the air-raid sirens came on in old WWII movies. EVERYBODY takes notlcel Grab one now at the never-to-be-repeated price of only $25. Cat. LA-5280 NORMALLY ABOUT $70 ONLY $25 "KNIGHTRIDER" LED SCr1.NNER KIT ALL ONE PRICE each JAYCAR BRAND Motorised Siren still the ultimate noise maker A~ofher surplus bu~ Save $1 o_over normal price ., r • Rotating inner loop · ✓VHF/UHF/FM receptk..n • Built in UHFNHF mixe. • Slim line design • Can be wall mounted • Single 75 ohm cable & , · ... plug connection \' .. Cat. LT-3132 • ! !/ '°k j., !_ . , ONLY $24.95 SAVE $10 ..· ·. .. $1 UHF TUNER Sanyo Model T1087RA Yet anotner scoop purchase A compact high quality tuner that operates from 526-814MHz (corresponding to channels 28 thru 63). This tuner is designed for Australian standard reception (AS1053 1973), and is offered at a very low price. Knob not supplied. it Cat. DM-1000 /' NORMALL}l $29.95 NOW SAVE.~15.00 $1 4.95 ~ NEW MINI TOGGLE SWITCHES Plug-In TIME SWITCHES Quallty mini switches with black plattened actuator. Rated at SA 125V. available in a single and double pole styles. SPOT Cat. ST-0546 24 HOUR: Switch an appliance "ON" and "OFF" up to 24 times in any 24 hours I Uses simple analogue dial with program pins (8 pins supplied which means that extra pins are required for more than 8 operations/ day) . It is VERY easy 10 set and operate - as opposed to programmable digital types I It also has a manual override 1hat does not affect original program setting. 12 month warranty. Cat.XW-0400 $3.25 ea DPDT 10+ $3.00 ea Cat. ST-0547 $3.75 ea 10+ $3.50 ea ULTRA MINI TOGGLE SWITCHES $23.95 Ultra small size. Body only 8mm x 9mm (DP version) and 8mm x 5mm (SP version) Rated at 3A 125V. SPOT Cat. ST-0540 $2.20 ea DPDT 1 0+ $2.00 ea Cat. ST-0542 $2.60 ea 1 0+ $2.40 ea 7 DAY: Can switch "ON" and "OFF" up to 42 times a week at two hour intervals (16 program pins supplied however) . Works and looks the as the 24 hour XW-0400 otherwise. Cat. XW-0405 $24.95 White Cone Midrange 12V ILLUMINATED PUSH BUTTON Economy push on/push off with large RED (20x20mm) actuator with a chrome surround. Perfect for fake car burglar alarms. Rated 12V 10 amp 3 pole. Cat. SP-0745 Our most popular midrange. Large sealed back with extra clear crsip midrange. 110mm, 80 watts RMS power handling, 95dB sensitivity, 10oz magnet, freq. rasp. 31 Hz - 7kHz, resonant freq. 31 OHz. Cat. CM-2080 $22.50 ONLY $6.95 VERBATIM DISCS AT UNREAL PRICES Compare our prices with your normal supplier Description 1-9 Boxes 10+ Boxes 3.5" 1S/2D $39.95 $37.95 $46.95 $43.95 -·------, Cat. XC-4720 3.5" 2S/2D Cat. XC-4721 3.5" 2S/HD $99.00 $89.00 $22.00 $21.00 $26.00 $24.00 $41.00 $39.95 Cat. XC-4722 5.25" 1S/2D Cat. XC-4725 5.25" 2S/2D Ca!. ~C-4726 5.25" 2S/HD Cat. XC-4727 8,#erufo,. 9 JAYCAR No.1 FOR DISCS JAYCAR No1 FOR EX-STOCK KITS ~ KA-1109 KA-1tt5 KA-1tt6 KA-1117 KA-1119 KA-1220 KA-1230 KA-1390 KA-1392 KA-1428 KA-1430 KA-1505 KA-1506 KA-1508 KA-1522 KA-1535 KA-1550 KA-1556 KA-1500 KA-1574 KA-1582 KA-1595 KA-1598 KA-1610 KA-1630 KA-1635 KA-1636 KA-1650 KA-1652 KA-1660 KA-1670 KA-1675 KA-1 6n KA-1681 KA-1682 KA-1683 KA-1688 KA-1689 KA-1690 KA-1691 KA-1692 KA-1693 KA-1694 KA-1695 KA-1696 KA-1697 KA-1698 KA-1699 KA-1700 KA-1701 KA-1702 KA-1703 KA-1704 KA-1705 KA-1706 KA-1707 KA-1708 KM-3015 KM-3030 KM-3040 KM-3042 KM-3050 KM-3056 KM-3061 KM-3063 KM-3064 KM-3065 KM-3067 KM-3068 KE-4014 KE-4023 KE-4029 KE-4033 KE-4050 KE-4052 KE-4048 KE-4200 KE-4204 KE-4220 KE-4405 KE-4666 KE-4690 KE-4698 HEAD OFFICE Electric Fence 30rJN amp module 30rJN powe,- supply 30rJN speake,- prntectOI' TransistOI' teste,Signal tace,Zener diode tester Freq. counte,- 50MHz Prescaler 500MHz Funclon gene,-atOI' Vocal canceHe,TAl Hal effect TransistOI' asst ignition Touch i tt dim me,Guitar e ects BSD ~nitionkiNe,eluxe car alarm Ultra sonic move det. Railmaste,- contotte,30V 1Apowe,- supply Housealaim Di~al capacitance mete,40 inve,-te,- t 21230V 30rJN inverter t 21230V t2V lamp Hasha,AMll'M stereo tune,AM/FM remote contrcl Playmastar 60/60 Bluep,-int 60/60 Electric fence Light save,Screecher car alarm Audio oscHatOI' (mete,-ed) 3 band shOl't wave radio Dual track powe,- supply Battery monitOI' Electronic stroboscope Ex~ power supply DI ox TV colour ba,,tpatte,-n gen Voice ope,-ated relay Metronome VclVcontinuity test AC/DC MiHvcltrnete,Econ. Temppiobe DMM U!litylme,Tran, FET, Zena,- test Bench amp- signal trace Powe,- •ansistOI' taste,RF detect°" rr,coe 50MHz Dig req mete,UnaFilte,FM Receive,Stroboscopic Tune,Cheap capacitance meter Powe,-mate2 Superime,UsteninJ post Ultrafid ity p,-eamp Dual ::ed modem ~ synthesise,10%-i"":~~fess MFets ~oa~t:c Octave Ea mod RS true 232 inte,-face NiCadchar~ FMminde,Mixe,-p,-eamp ~nal Spkr piotectOI' ad Qatte,-y cha,,ger TemperallJle p,-obe ET1480 SOW amp module ETl48010rJN amp mod ETl480 power supply 5000 powe,- amp 5000 1rJ octave ~aiise,ETl499 1SrJN Mos tamp ETl581±/·15V power suf RS232 Centronics inte,ETl342CDI 4 sectOI' house alann 23.50 $tt9.95 $105.00 $23.50 $21.50 $27.95 $1 6.95 $169.50 $46.50 $129.50 $24.95 $44.95 $42.50 $29.95 $115.00 $23.50 $89.50 $34.95 $109.95 $89.50 $169.00 $85.00 $99.95 $249.00 $12.95 $599.00 $99.50 $329.00 $369.00 $59.50 $15.99 $34.95 $165.00 $79.50 $129.95 $14.95 $13.95 $26.95 $39.95 $159.00 $24.95 $19.95 $29.95 $46.50 $19.95 $21.95 $55.00 $39.95 $22.95 $13.50 $99.00 $39.95 $55.00 $47.50 $16.95 $109.00 $59.00 $39.95 $359.00 $169.00 $43.50 $35.00 $79.50 $36.95 $55.00 $59.95 $27.95 $24.95 St t.95 $39.50 $22.50 $14.95 $32.95 $27.50 $34.50 $29.50 $499.00 $219.00 $109.50 $27.50 $32.50 $79.50 $29.95 MAIL ORDERS KE-47tt KE-4722 KE-4724 KE-4725 KE-4728 KE-4729 KE-4730 KE-4733 KC-5010 KC-5012 KC-5013 KC-5015 KC-5016 KC-5017 KC-5019 KC-5021 KC-5023 KC-5027 KC-5028 KC-5029 KC-5031 KC-5032 KC-5033 KC-5034 KC-5035 KC-5036 KC-5037 KC-5038 KC-5039 KC-5040 KC-5041 KC-5042 KC-5043 KC-5044 KC-5045 KJ-6502 KJ-6504 KJ-6505 KJ-6531 KJ-6535 KJ-6655 KJ-7000 • I Mini FM tansmilte! RS232 Commodore Parametric equalise,Seide,- iron temp contra Ring tone customiser Guitar p,-eamp Sclar gen plsupply Active Crossove,Capacitance mete,Car radio fl!!W8'" supply 1GHz Dig, Freq meter Telephone nn3,e,Speed contro dimmer 24 to t 2V conve,-te,t OrJN amp module Protect°" car alarm Low ohms adapt DMM Phmete,Train contrcller CD H/phone amp Qptical tacho D,sco~t Srudio PreamJ. Remote IOI' Cat aim Plasma dischat~e Wireless dOOl'b ITX Wireless dOOl'bell RX Unive,-sai powe,- supply Vader Voice ~kerphone Mille! K~tride,-LEDs t PM3uita,, amp ~~~~~W!~a Syntom drum synth 8 channel mixer Conscle Psupply above 2801 t fJ octave Eq. 2010 to band ste,-eo Eq. Hail EffectTrigge,- kit Red light lashe,- $9.95 $16.95 $23.50 $39.50 $29.95 $45.00 $12.95 $39.95 $27.95 $28.95 $299.00 $19.95 $18.95 $59.00 $38.95 $79.50 $29.95 $49.95 $89.00 $24.95 $49.95 $159.50 $229.00 $79.50 $129.50 $16.95 $42.50 $12.95 $19.95 $89.00 $29.95 $1 7.95 $72.50 $29.95 $49.50 $42.50 $595.00 $119.00 $239.00 $169.00 $99.95 $19.95 GEL ATTERY URPLUS (, We have purchased a quantity of National brand 6 volt Gel rechargeable batteries. Th9S8 are Ideal for burglar alarms, or where any back-up power supply is needed . Conned two in series to give 12 volt. Two sizes available: 2.4 AM P 6 VOLT Cat. SB-2490 9. 5 5+ $8.95 ea 8 AMP 6 VOLT Cat. SB-2492 2 95 5+ $22.50 ea LIMITED STOCK UHF/VHF A SEPAR 0 If your TV has both a UHF and VHF inpU1 socket on the back and you have a UHFNHF combined antenna, you will need one of these. The LT-3016 will separate the UHF and VHF signals and direct them into the correct socket on your TV. Cat. LT-3016 POST & PACKING ~o~{~:~:~~1~~o;~l~r ,~~ i!fl! IHI - ~ ~ ~ , : ~,i::f~~~~;jo~)a~4~~~~i2137 ""';___.. _ _ ~F_A_c_s_1M_I_LE_(_o_2)_7_4_4_0_7_6_7_ _ _ _T_O_L_L_F_R_E_E_(O_0B_)_02_2_B_BB___0v_E_Rs_10_0_ _ _$_10_.oo_ _~ : I ■ VISA s "fr ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 188 Pacific Hwy (Cnr . Believue Ave) (02) 439 4799 Mon-Fri 9 • 5.30 Sat 9 - 4pm 111vorkSt. (02)2671614· Mon-Fri 8.30 . 5.30 Thurs 8 30 pm · Sat 9 - 12 PARRAMATTA 355Church St (Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 9 - 5.30 Thurs 8.30 pm• Sat 9 - 2pm BURANDAQLD 144 Logan Rd (07) 393 0777 Mon-Fri 9 - 5.30 Thurs 8.30 • Sat 9 - 12 115 Parramatta Rd (02) 745 3077 · Mon-Fri 8.30 - 5.30 • Sat 8.30 - 12 MELBOURNE-CITY Shop 2. 45 A"Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 121 Forest Rd (02) 570 7000 Mon-Fri 9. 5.30 Thurs 8.30 pm • Sat 9 - 12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2 n1 ICONCORD :,,.,.;=....,.;.;c:......!) MAIL ORDER VIA YOUR '---------------------------------------' GORE HILL SYDNEY - CITY ~-=" ~ I HURSTVILLE Simple ultrasonic proximity detector Do you hove trouble parking close to a wall or getting out of tight parking spots? This ultrasonic distance indicator will save you from those embarrassing dings and scrapes. By JOHN CLARKE & GREG SWAIN Sometimes it can be really difficult to judge parking distances, particularly if you're trying to back up close to a wall or loading dock. It only takes one mistake and ... kerunch! To solve this problem, we set about designing a circuit that would warn the driver before the crunch 26 SILICON CHIP point. The result is the ultrasonic distance indicator featured here. It can be easily fitted to just about any sort of vehicle and has a range of about 1 metre. The idea behind the device is simple. A couple of ultrasonic transducers are mounted on the rear bumper bar and monitor the distance between the vehicle and any large obstruction which could be a wall or another vehicle. As the vehicle reverses and gets closer, the beep rate from a small piezo transducer gradually increases until, at a preset distance, the transducer gives a continuous tone which says "this far and no further". To make it easy to operate, the ultrasonic ranger is automatically switched on whenever reverse gear is selected. That's done simply by deriving the power supply from the switched line to the reversing lights. You can set the minimum distance trip point to whatever figure you like by means of a trimpot. As an option, you can also set 100 +BV ~+.;::.::;:......----------+--------------....---+BY +12V VIA REVERSING SWITCH 10 100 16VW! 16VW! .,. 100 + 1k 470k 470k + 16VW+ 2.2k 40kHz ADJUST VR1 22k 14 470k nm 22!l IC3 555 10k ULTRASONIC TRANSMITTER SCS•401T 1M 01 1N414B . 40kHz OSCILLATOR BURST OSCILLATOR - - - - - - - - - - - - - - - - - - - - - -- -~-----t1------t-----t1----+BV 1.2k ULTRASONIC RECEIVER SCM-401 4 470k .,. R D 14 15k - 2 IC5 Qlt,:--~IM,--+----, >----1-----13 CK 4013 s 6 1.2k 4.7k 7 RETURN DELAY DETECTOR AVERAGE SIGNAL 4.7k SCHMITT 1.8k 1M .---------+-~--------------..--+Bv 10k 2 'HIT' OUTPUT 10k EXTRA 0ts1:~c E_____. VR3 47k .,. 10k 10 + 16VW! .,. PIEZ0 TRANSDUCER AUDIO TONE RATE AUDIO OSCILLATOR CAR REVERSING ALARM Fig.1: IC2b is the burst oscillator and controls IC3 which drives the transmitter. When the reflected signal is received, it clocks Q-bar of IC5 low. IC5's output, in turn, controls the beep indicator circuit (IC2c, IC4 and IC2d). and select a second minimum distance trip point. This feature would be useful on station wagons and vans which require sufficient clearance for the rear door to be opened. A switch mounted on the dashboard will enable you to select between the two distances. How it worlcs Two ultrasonic transducers and five ICs are used in the circuit. In operation, the ultrasonic transmitter sends out a burst of signal and the receiver then detects the reflected signal from the object. The time taken for the signal to return is used to determine the distance. Fig.1 shows all the circuit details. Let's look at the transmitter circuit first, since this is by far the easiest to understand. IC3 is a 555 timer and is wired as an astable oscillator which runs at 40kHz. The output signal appears at pin 3 and drives the ultrasonic transducer via a 220 resistor. Trimpot VR 1 allows the frequency to be precisely set to 40kHz. Pin 4 of IC3 is the reset input and this is controlled by the output of burst oscillator stage IC2b. When pin 4 is high, the 555 timer oscillates; when pin 4 is low, the 555 stops. JANUARY 1989 27 r300us--------30ms _JlJlJLJUl___ I I ~~y _J I 3 ~3 T_Rs~_:~_fl_T_ _ _ _ _ _ _ _ _ PIN 1 IC2a _ I flJUl JUl ---------1 PIIC!52 _J _ PIN 1 IC2a I SHORT RANGE RETURN SIGNAL _ fUlJ I I..._______________, (LOW AVERAGE VOLTAGE) I LONG RANGE-fUUl RETURN SIGNAL (HIGH AVERAGE VOLTAGE) Q ___.flfill_JUl_ I 1-----.L .. L nnI.._______ _Ju I PIN 2 IC5 Fig.2: the top waveform shows the bursts of 40lcHz signal at the output of IC3. D-type flipflop IC5 is reset at the start of each burst which means that its Q-bar output is set high. When the reflected signal arrives at the ultrasonic receiver, IC5 is clocked and its Q-bar output goes low. It remains low until reset at the start of the next burst. ULTRASONIC RECEIVER I +12V VIA REVERSING SWITCH 100uf ~ GNU r ULTRASONIC TRANSMITTER +PIEZO- TRANSDUCER Fig.3: here's how to mount the parts on the PCB. Make sure that you don't swap the 555 and TLC555 timers because that would upset circuit operation. Leave out VR3 and switch S1 if you only require one . set distance (see text). IC2b is wired as a Schmitt trigger oscillator. A voltage divider consisting of two 470k0 resistors sets the bias on the non-inverting input while a third 470k0 resistor sets the hysteresis levels to 1/3 and 2/3 of the supply voltage. In operation, the .039µ,F timing capacitor charges mainly via D1 and its series lOkO resistor and discharges via the lMO resistor. This is because D1 is reverse biased during each discharge cycle. This gives a train of pulses at pin 14 which are each high for about 28 SILICON CHIP 300µ,s and low for about 30ms. What this means is that IC3 provides a 300µ,s burst of 40kHz oscillation every 30ms. This 30ms gap is to allow sufficient time for each burst to be reflected back to the receiver before the next burst is transmitted (see Fig.2). As well as controlling IC3, the output of IC2b is also wired to the reset input (pin 4) of D-type flipflop IC5. When pin 14 of IC2b switches high, it resets IC5 so that its Q-bar output goes high. As we shall see, it is IC5 that allows the circuit to determine the delay time between the transmitted and reflected signals. Receiver circuit The reflected 300µ,s burst signal .is picked up by the ultrasonic receiver and fed to pin 3 of ICla. ICla is an AC-coupled non-inverting amplifier with a gain of 11 as set by the 47k0 and 4.7k0 feedback resistors. The .01µ,F capacitor in series with the 4.7k0 resistor rolls off the frequency response below 3.4kHz. Following ICla is an identical op amp stage, ICl b, which is also wired with a gain of 11 (ie, the two stages together provide a gain of 121). The amplified 40kHz signal appears at pin 7 of IClb and is applied to pin 6 of Schmitt trigger stage IC2a. DC bias for the noninverting input is derived by filtering the output of IClb via a 1.2k0 resistor and 10µ,F capacitor. IC2a's job is to monitor the output of ICl b for amplified 40kHz burst signal. As soon as the signal input on pin 6 exceeds about 400mV, the output at pin 1 swings high and low (ie, it squares up the signal). This output signal then clocks flipflop IC5. What happens now is that Q-bar (pin 2) of IC5 immediately switches low on the first positive going clock input from IC2a. If you're not too familiar with D flipflops, just remember that the data (D) input at pin 5 is transferred to the Q output by the clock input. Because the D input is connected to the positive supply, this means that Q goes high and thus Q-bar must go low. Fig.2 shows the waveform details. Note that additional clock pulses from IC2a have no further effect on the Q-bar output after it switches low. It remains low until reset high again by the output of IC2b at the start of the next transmitted burst signal. What this all means is that Q-bar is set high at the start of the transmitted signal and remains high until that signal is reflected back to the receiver. The further away the object is, the longer it takes for the signal to come back and the longer the Q-bar output stays high. The output signal from IC5 is PARTS LIST 1 PCB, code SC05102891, 105 x 60mm 1 plastic case, 130 x 67 x 43mm (or larger) 1 plastic case, 83 x 54 x 30mm 1 40kHz ultrasonic transmitter 1 40kHz ultrasonic receiver 1 piezo transducer 1 SPOT toggle switch Semiconductors The PCB clips neatly into the specified case but you can use a larger case if you wish. Use shielded cable to make the connections to the ultrasonic transducers and note how the 3-terminal regulator is oriented. D 7808 3-terminal regulator 1 6V 1W zener diode 1 N4148, 1 N914 diodes LM339 quad comparator LF353, TL072 dual FET input op amp 1 555 timer 1 TLC555CP CMOS timer 1 4013 dual D-type flipflop Capacitors 2 1 OOµF 1 6VW PC electrolytic 4 1 OµF 16VW PC electrolytic 1 .04 7µF metallised polyester (greencap) 2 .039µ,F metallised polyester 2 .01 µF metallised polyester 1 .0068µ,F metallised polyester 2 .001 µF metallised polyester t~ ~ ~ 1 1 2 1 1 ~~~!!:::::~~~~~-~ Fig.4: the printed circuit board is coded SC05102891 and measures 105 x 60mm. filtered using a 15k0 resistor and 10µ,F capacitor and fed to pin 5 of comparator stage IC2c. This stage compares the filtered 'average signal' with the voltage on pin 4, as set by either VR2 or VR3. Switch Sl selects between these two trimpots, which provide the distance set adjustments (ie, the distances at which the transducer emits a continuous tone). Actually, the way in which the circuit works from here is really quite devious. What goes on? Well, comparator IC2c controls oscillator stage IC4, which in turn controls Schmitt trigger oscillator IC2d. Let's look at this in greater detail. The 'average signal' from IC5 is also connected to the frequency control input of IC4. This IC is a We mounted the ultrasonic transducers CMOS version of the .more familiar in a small plastic case. Mount the case 555 timer and oscillates at a frequency of about lHz when its pin 5 so that it can be easily removed when the car is to be washed. is at + 8V. Resistors (0.25W, 5%) 2 x 1 MO, 7 x 4 70k0, 1 x 1 OOkO, 2 X 47k0, 1 X 27k0, 1 X 22k0, 1 x 15k0, 7 x 1 OkO, 3 x 4. 7k0, 1 x 2.2k0, 2 x 1.8k0, 2 x 1.2k0, 1 x 1 kO, 1 x 220, 1 x 100, .2 x 47k0 miniature vertical trimpots, 1 x 22k0 miniature vertical trimpot Miscellaneous Hookup wire, shielded cable, solder etc. But IC4's operation is a bit trickier than that. As the voltage on its frequency control input (pin 5) decreases, its output frequency increases. And this is precisely what happens as the car gets nearer to the obstruction (ie, a wall or another car) behind it. The closer the car gets, the lower the 'average signal' voltage and the higher the output frequency from IC4. This, in turn, increases the audio beep rate. This situation continues until the 'average signal' voltage drops below the voltage on pin 4 of comparator IC2c. When that happens, pin 2 of IC2c switches low and JANUARY 1989 29 For the prototype, the audio transducer was mounted on one end of the case but this will not be pratical for all installations. Mount the unit towards the back of the vehicle to keep the leads to the transducers short. 7 CAR REVERSING ALARM _J L Fig.5: here is a full size reproduction of the front panel artwork. shuts down the IC4 beep oscillator. The pin 3 output of IC4 controls Schmitt trigger oscillator IC2d. When pin 3 is low, D2 is reverse biased and IC2d oscillates at about lkHz and drives the piezo transducer via a 4.7kO resistor. When pin 3 of IC4 subsequently goes high, the .0068µ.F capacitor at the inverting input of IC2d charges via D2 and the IC2d oscillator stops. In practice, this means that we get a series of lkHz beeps which increase in rate as the car gets closer to the object. This beep rate continues to increase until IC2c shuts down IC4. When that happens, pin 3 of IC4 goes low and IC2d drives 30 SILICON CHIP the piezo transducer continuously. Power for the circuit is derived from the + 12V supply rail to the reversing lights. This is fed to a 3-terminal regulator to give a + 8V supply, thus making the circuit independent of changes in battery voltage. Zener diode D3 ensures that high voltage spikes on the supply line are kept out of the regulator. Construction The circuit for the reversing alarm is built on a small PCB coded SC05102891 (105 x 60mm). Fig.3 shows the wiring details. Start construction by installing The completed unit can be easily tucked away in a corner of the boot. Power for the circuit comes from the + 12V rail to the reversing lights. all the low profile components first. These parts include the resistors, diodes, wire links and ICs. Note that the ICs, diodes and electrolytic capacitors are all polarised parts and must be correctly oriented as shown in Fig.3. The 3-terminal regulator must also be installed the right way around. It should be mounted with its metal tab facing towards the adjacent edge of the PCB (see photo). Push the regulator down onto the board as far as it will comfortably go before soldering the leads. Attention can now be turned to the wiring. Shielded audio cable is used for the connections to the 40kHz transducers while all other connections can be run using medium-duty hookup wire. Be sure to make the leads long enough to reach their required destinations when the unit is mounted in position. Switch Sl and its associated wiring can be deleted if you only require one minimum set distance. If you do decide to leave Sl out, delete VR3 also and connect a wire link between the wiper of VR2 and pin 4 of IC2. Just wire the link between two of the vacant pads that would normally be used to terminate the switch wiring. The reversing alarm can be bench tested by connecting it up to a 12V power supply. Switch on and check that there is + 8V at the regulator output and on the IC supply pins. Now lie the two transducers side by side away from any obstructions and check that the piezo transducer beeps at about a one second rate. If this checks out, move your hand close to the sensors. The frequency of the audio beeps should increase. If the beeps don't increase in frequency, try adjusting trimpot VRl. This trimpot sets the transmit frequency and should be adjusted for maximum sensitivity. VR2 and VR3 should be adjusted to give the desired minimum set distance (ie, a continuous audio tone] for each setting of S1. Installation We housed the prototype PCB in a plastic case measuring 130 x 67 x 43mm but you can use a larger case if you wish. The ultrasonic sensors were housed in a separate small plastic case measuring 83 x 54 x 30mm. The PCB is secured to the inside of the plastic case using the integral side pillar supports. You will have to drill holes in the case for the screened transducer leads, the power supply wiring and leads for the piezo transducer. Just how you mount the unit will depend on the type of vehicle you have. In any case, the unit should be mounted towards the rear of the vehicle (eg, in the boot] to keep the leads to the ultrasonic transducers short. This will also make it easy to tap into the reversing light circuit for the power supply rail. The two ultrasonic transducers can be mounted below the rear bumper bar and secured using a suitable bracket. We suggest that you come up with some sort of plug and socket arrangement so that the transducers can be easily removed when the car is to be washed. If the transducers do get wet, they will operate normally again after they have dried out. But be warned - if the transducers are saturated with water (eg, when it rains] you will not be able to rely on the circuit when parking. !§;l .,..__,SPECit~1tR ~ <:;;:i vKa ::.-:.:::=:::;: NEW SPEAK 1lw-:::::: ]1~l I-lti I,,,: %t ::.¾1~ Since the introduction of VIFA speaker kits in Australia in 1985, thousands of speakers have been built with superb results . VIFA is now proud to release four new speaker kits ranging from a mere $399 to $1199 per pair including cabinets. Never before have speaker kits been so popular in Australia than after the heavy devaluation of the dollar. Similar fully imported quality loudspeakers are today typically 2-2½ times more expensive. And these speakers may very well be using Danish VIFA drivers anyway, as VIFA supply more than 50 of the world's most respected loudspeaker manufacturers with drivers. But why the big savings? Because fully imported speakers suffer from 25% import duty, 20-30% freight, 30% sales tax and 28% handling charges (typically). So if you would rather put your money into better quality than in other people's pockets, VIFA speaker kits are the only way to go. Are they difficult to build? No, the kits are supplied with all parts needed including fully built crossovers and pre-cut flatpack cabinets ready to assemble. No soldering or carpentry skills are needed; just a Phillips head screwdriver, some simple hand tools and a few hours of your leisure time. Are they as good as people say? Read the reviews, listen and compare with any other speakers twice the price or more. Need we say anymore? VIFA for the quality conscious audiophile. I·•-❖❖ ! For full details please contact Sole Australian Distributor: SCAN AUDIO Pty. Ltd. P.O. Box 242, Hawthorn 3122. Fax (03)4299309 Phone: (03! 4292199 (Melbourne) (02 5225697 (Sydney) (07 3577433 (Brisbane) (09) 3224409 (Perth) Stocked by leading stores throughout Australia Polystyrene capacitors YES Made here in Australia? YES Made Special to Type? YES Where From? Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors. Why design circuitry which requires additional components to achieve a specific capacitance; we can wind exactly the capacitance you need to match your design criteria within the ranges of 1 OpF to 1µF and up to 1 0,000VDC. 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: 1 Yes, I am interested in your capacitors. (02) 938 4690 I ./ ... VDC ... / ... VDC. OR Cut out and post this coupon to Post Office Box 740 ~ B _r_oo_k_v_a1_e,_ N._s_.w_._ 2_1_o_o___ I Please post me Name details of the fol lowing values: VDC ... / .. VDC (Please print) I Address L~~~~~- ~~~~~~J JANUARY 1989 31 Mains Muzzler: a line filter for your computer If you suffer from a noisy mains supply and your computer often crashes, the Mains Muzzler could be the solution. It incorporates an effective filter for mains borne interference and a Varistor to clip dangerous spike voltages. By LEO SIMPSON Some computers are much more prone to interference than others. This can extend to machines which are ostensibly identical. In our own editorial office we have two Commodore PC-5 (IBM-compatible) machines, each fitted with 20 megabyte hard disc drives. If both machines are in use and a mains glitch occurs, one machine is much 32 SILICON CHIP more likely to reboot than the other. So it is not possible to predict with any certainty whether a particular machine will be prone to mains borne interference. If you do have a problem in this regard, a mains filter such as the Mains Muzzler can help. It is designed to attenuate high frequency signals, commonly refer- red to as "hash". It is most effective for signal frequencies of 500kHz and above. For low frequency signals it is not very effective but then neither is any other mains filter on the market. What won't it do? No mains filter can cope with short term reductions in the mains voltage which may last for a millisecond or so. If your lights dim or flicker momentarily when your fridge or washing machine turns on, or when someone turns on a vacuum cleaner, then that indicates that your mains voltage supply has dropped momentarily. This is because most appliance motors draw a heavy surge current at the moment of switch-on. Inevitably, the heavy surge current causes a drop in the mains supply from your switchboard and that drop in mains voltage may be enough to cause your computer to re-boot. There are three things you can do to prevent these short-term reductions in your mains supply. First and most expensive is to use an uninterruptible power supply. This will maintain the mains supply to your computer regardless of fluctuations or short term reductions in the line voltage supply from your electricity supply authority. An uninterruptible power supply (UPS) will even maintain the supply for a few minutes after a blackout occurs. This gives you enough time to save any material you have been working on and then close down your computer properly, parking the hard disc and so on. For businesses which cannot afford loss of computer data, an uninterruptible supply is a great idea. A less costly way of coping with short term reductions in the mains supply is to use a constant voltage transformer (also known as a "line conditioner"). This is a specially designed transformer which will regulate its output voltage within a small percentage range, for quite large variations in the input voltage. Such transformers are fairly expensive but they are effective. Another good way to insure against mains drop-outs is to have a separate "clean line" run from your switchboard to your computer. For a modest cost an electrician can run a separate circuit and this will be much less prone to interference from your domestic appliances. What about fluorescent lights? Then there is the problem of fluorescent lights. Does your computer often reboot when someone switches on a fluorescent light? It does, eh. And how old is the fluorescent light fitting? About 30 years old. Uh-huh. Well, you may be suffering from the dreaded "power factor correction capacitor" syndrome which we could abbreviate to the PFCC syndrome. "What's that?" you say, -~- A .01 250VAC 240VAC .01 250VAC SIOV S20K275 E .01 250VAC 1M 1W CASE N L2 L1, L2 : 13.5T,1 .25mm DOUBLE TOUGH ENAMELLED COPPER WIRE WOUNO IN ANTI-PHASE DN A NEOSID F9 FERRITE TOROID TYPE No.28-756-36 MAINS MUZZLER Fig.1: the circuit of the Mains Muzzler is a low pass filter. It passes the 50Hz mains supply while attenuating high frequency signals. The SIOV-S20K275 varistor attenuates large spike voltages. "Run that past me once more." Well older fluorescent light fittings, as fitted in older homes, were often intended for use in factories or office blocks. Because of this, they were fitted with power factor correction capacitors. These are usually about 3µF in capacitance and are wired directly across the mains supply, between Active and Neutral. The capacitors compensate for the lagging current through the iron-cored ballast inductor and thus "restore" the power factor to close to unity. The problem with power factor correction is that, when the mains voltage is first applied to the fluorescent light circuit , the capacitor is virtually a short circuit. Inevitably, this causes the mains voltage to drop drastically for a millisecond or so which is enough to cause some personal computers to reboot. Again, this problem cannot be cured by the Mains Muzzler or any other mains filter circuit, although the measures outlined above will work. Alternatively, you could decide to remove the power factor correction capacitor. This will not have any effect on the operation of your fluorescent light. It is just a matter or disconnecting the capacitor. They are generally housed in a large aluminium container and retained within the fluoro fitting by one or two screws. Removing it now might save you from a messy clean-up at some time in the future if the capacitor decides to spill its insides out. The capacitor should be disposed of without puncturing the can. The oil inside is one of the polychorinated biphenyls (PCBs) which are now regarded as environmentally hazardous. Incidentally, if you suspect that you have power factor correction capacitors in your fluorescent light fitting but you are not confident about mains wiring, have your local licensed electrician do the job of removal. Note also that some fluorescent lamps which do not have a starter employ a series capacitor for the starting function. In this case the capacitor must be not be removed otherwise the light will not work. ]ANUARY1989 33 CORD CLAMP GROMMET Neutral to discharge the capacitors when the power is disconnected. It will also discharge any mains capacitors in the computer's power supply. Why did we put the resistor in? It can prevent a shock from the pins of the IEC mains socket on computers. These pins are inevitably exposed when the detachable cord is removed. N MAINS CORD EARTH GREEN/YELLOW ~ FRON {E Construction A © ,e <at>~ 12mm x 48A NYLON SCREWS AND NUTS \ A I © ©~ I 1• .o, GROMMETS (E;f \ ~ ~I © Fig.2: wiring details for the Mains Muzzler. All wiring to the PCB and to the mains sockets must be run using 250V AC-rated cable. Note that Nylon screws and nuts are used to secure the mains socket that sits above the inductor. This is to prevent the possibility of shorts. Muzzler circuit The circuit of the Mains Muzzler is a low pass filter. It passes the 50Hz mains supply while attenuating high frequency signals. It has a .01µF 250V AC capacitor connected directly across the Active and Neutral lines. These then pass through inductors 11 and 12 which are both wound on a ferrite toroid. After the inductors, both Active and Neutral lines are bypassed to 34 SILICON CHIP the earth line via .01µF 250V AC capacitors. To protect the computer against large spike voltages, a Siemens Varistor, type SIOV-S20K275, is connected between Active and Neutral. Normally open-circuit, this device becomes a very low impedance (ie, a short circuit) to any large voltage spikes. Finally, a 1MO 1W resistor is connected between Active and We built our prototype Mains Muzzler into an attractive extruded aluminium case with . folded aluminium cover. This is finished in blue and grey powdercoat enamel which stands up well to knocks and scuffs. The case is just long enough to comfortably accommodate four surface mounting mains sockets (as made by Ring-Grip or HPM). While not presently stocked by parts retailers, the Betacom case can be obtained directly from the Australian distributors Temple Smith Australia Pty Ltd, 2-12 Harp Street, Campsie (PO Box 196), NSW 2194. Phone (02) 78 3436. In other states, phone Melbourne (03) 781 1013; Adelaide (08) 365 1000; Perth (09) 272 7122; and Brisbane (07) 252 7466. The case is available by mail order for $24.95 plus $4.00 for packing and postage. Payments may be made by cheque or credit card. Alternatively, you could use a large diecast aluminium box although the mains sockets will have to be staggered (ie, not mounted in a straight line) to fit on the lid. A suitable diecast case is available from most parts retailers (eg, Jaycar Cat HB-5016). All the filter components are mounted on a printed circuit board measuring 70 x 120mm (code SC10101891). This fits easily into either of the specified cases. Assembling the board is quite a straightforward process although there is a little work to be done in winding the ferrite toroid. This has two windings, each 13.5 turns of 1.25mm double-tough enamelled copper wire. These are wound on as shown in the accompanying diagram and photo. Before installing the toroid on the PARTS LIST The PCB is mounted inside the case on 6mm standoffs. Note that all mains wiring to the sockets passes through 8mm rubber grommets. The pen points to one of the two Nylon screws used to secure one of the mains sockets. 1 extruded aluminium case with cover, 230 x 11 0 x 30mm (Betacom Cat IC4-3); or one aluminium diecast case, 190 x 110 x 60mm (Jaycar Cat HB-5446 or equivalent) 1 printed circuit board, 120 x 70mm, code SC10101891 1 moulded 3-pin plug and 3-core mains cord 4 surface mount 3-pin mains sockets 1 cordgrip grommet 1 Neosid F9 ferrite toroid, 31.5mm OD, 19mm ID, 12 .5mm high, type 28-756-36 1 SI0V-S20K275 varistor (Siemens) 3 .01µF 250VAC capacitors (Philips 2222-330-41103 or Wima MP3) 1 1 MO 1W resistor 2 metres 1.25mm-dia doubletough enamelled copper wire 1 2 8mm rubber grommets 3 solder lugs 4 6mm standoffs 6 4mm x 1 2mm roundhead screws & nuts (to secure mains sockets) 2' 4mm x 1 2mm Nylon roundhead screws & nuts 4 3mm x 1 2mm countersunk screws & nuts (to secure PCB) 4 3mm shakeproof washers M'iscellaneous SC10101891 Fig.3: you can use this full-size pattern to etch your own PCB. printed board, the ends of the coils must be carefully scraped clean of enamel and then tinned with solder. After pushing the four tinned leads through the board holes, crimp them over to mechanically hold the toroid down on to the board. Then the leads can be soldered. By the way, the holes for the toroid leads can be drilled with a No 55 drill or a 1/16-inch drill. The holes for the various input and output mains leads to the board should also be drilled with a 1/16-inch drill; Before mounting the four surface mount mains sockets on the lid of the case you will need to do a certain amount of drilling. Each socket requires two 1/8-inch diameter holes for the mounting screws and three 8mm holes for the mains leads. These latter holes are fitted with 8mm grommets to prevent chafing of the lead insulation. One of the mains sockets mounts just above the toroid and the screws are likely to interfere with the inductor windings. To prevent any possibility of damage to the 250VAC-rated hookup wire, four rubber feet (if Betacom case not used). windings, the screws in question should be of Nylon. All the wiring inside the Mains Muzzler should be run using wire with 250VAC-rated insulation. Three solder lugs are used to terminate the earth wires for the mains cord, from the printed board and from the earth line to the mains socket. The printed board is mounted inside the case using 6mm metal standoffs, screws and nuts plus shakeproof washers. Use your multimeter (switched to a low Ohms range) to check all the wiring before using the completed Mains Muzzler. ~ JANUARY 1989 35 ONE FOR THE BUSINESS PEOPLE ■ ■ Fully installed in your vehicle for under $2500. That's normallX agreat price but you II also gel a special bonus worth $2691 Cat F-7951 ■ There are a lot of EA & Silicon Chip readers who have businesses: technicians. electricians, engineers, ate etc. How do you keep in touch? A lost phone call is often alost customer! Get yourseH a Cellular Phone -ii goes where you gol But get yourself a good'un - like this superb Audiovox. Full hands free operation - so it's legal in those states with strange laws. $2495 1 Cordless Phones are becoming so popular - they're undoubtedly the ultimate in convenience. This one features long range, security code dialling, paging function, builtm charger and more! CatF-5885 Everything you'd ever want in a TAM! Full beeperless remote control. two standard (cheap!) tapes for convenience ... it's a beauty! Cat F-8300 - WAS$59.95 NOW s49a5 s339 ALARMING LED stallS lndlcato11 1911 lnllulH tltllper prollctlon \ J Not just for cameras - it's great for getting into intricate parts in videos, computers, models, etc. Has blower brush, silicon cloth, lens tissue. cleaning fluid and swab. Cat C-7530 s295 Video/ Audio Storage Keep dust (your video's N 1 enemy!) at bay by keeping your tapes stored safely away. Holds up to 24 video tapes or 36 audio tapes safely and securely. Cat C-3058 s1995 SAVE $5/ You've seen the reports in the newspapers: burglary is on the increase. Don't let your place be next on the ■ list! NEWs I Our new Alarm Control Unit is perfect for the home, office, factory ... anywhere. Fully professional quality (it's actually based on a commercial module) but so simple for the home handyman to install. Do it yourself and save afortune AND you'll be the only one who knows the details of your own system & wiring! 4 llldivid11lly contro11a•1e ---, ~ ~ \ l •- ~~ f t ! l i ~ Already got a good car stereo? Why buy a new one just to receive AM Stereo? And why put up with mono any longer? This superb converter gives you great AM stereo with your existing set-up • so you won't have to spend a fortune! And this month, we've slashed the price by another $10 so you too can hear the superb sound of AM Stereo. cat A-6030 It Does It All! rdless phone rfection! Famous GE and, has 10 memories d security code and so doubles as internal tercom ! Cat F-7200 Camera Cleaning Kit ~~~TI~ ~ op Quality G Heavy duly st■I case wltll OWN A VIDEO ~. Try these! :.~ ,.,.+~ you what's happening ~"""""'~===~=~ for ■lxi■I■ nrsatillly seclol1 And to complete your system ... M=Reed ~ ~~ ~!'most reliable, yet simple form of window/door "" protection. Surface type (suit aluminiumwindowsetc)Setof ~ magnet and switch. L-5210 ~ 911 Concealed type (suit wooden -,., Sit doors, frames etc). Magnet & Switch. L-5212 Heat Sensor ~ Why not make sure you don't burn down? Your alarm can l<Y# after that, too with this heat ir..nsor! ~ ::s~:::~r S13'5 Economy Horn Speaker gives earpiercing wail to almost wake the dead! Cat C-2705 •4• set *2'° switch set for roller/tilt Individual Magnet: Special doors. Cat L-5227 911 ,5111 Cat L-5214 *1 With inbuilt tamper protection, stops them disabling your alarm speaker. cat L-5300 Window Foll Part of 111e alarm system Strobe Lamp • and also a YISlble deterrent. Individual Swltcll: HomCover Cat L-5215 S ~ ~ ~4- • 32m roll adhesive foil: Cat L-5200 ~ ~ Connecting Cable: ~ . 'I..'\ ~ - '14• roll 1 ~ ~ Blueflashlnglampwarnsifyouralarmhas ~t~ered. even after the horn st0 P5• Foll terminal blocks: Cat L-5205 00 ' ea rt\s\\1{_ - ~a.. 17• · s399S various types to suit every application. 4Core: Suits detection devices needing power or horn speakers with tamper protection, etc. catw-2100 ~ 95clm Of /100m roll 4 Core Phone Cable: ~!~r':r!~:it's walked on, tt goes off. Put In doorway or hall for optimum protection. cat L-s210 Mv111C1d ciraHry ■i■ltllim false ar1111s. flltv complies witll aolse pelfltlon llfllltlons S1111 asclHator INlllt in • '24• Censtalll 12V oatput for PIR'g and otlter accasories PLUS ea, L-5140 s199 Emergency Button Just in case! Prowlers, peepers. snowdroppers:. Similar to above, but small diameter. Suits. Permanent installation (not flexible). Cat W-2~120 75e/m or $/100m roll Other tvoes of cable (fig 8, multi core, etc always in stock). Gell-Cell Batteries Rechargeable batteries for back-up use. Various sizes available ~•pending on caracii required) but general .=-.its_,_~_nda_._~_._ .._:_"_·_·__:_1:,..•c_~_,a_rl_f_.... _,_=_1'11_._11a_l' _________ ll ~_~_;~-ig_~~_:_~_~:_~_~e-thb.~m_tt.!o~.t-al~-~2_~:_sc-ar.es·t·h·e_ _ _;_u3r.pos_a•.1-~ " · sl11na 19 lluyl) dlalle11, etc. -,., ~ ~~ 111 N.S.W.: BALLINA: Ballina Electronics 86 7022 BOWRAL: F,R.H. Electrical 61 1861 BROKEN HILL: Hobbles & Electronics884098 CHARLESTOWN: Newtronlcs 43 9600 COFFS HARBOUR: Coifs Harbour Electronics52 5684 DUBBO: Chrls's HI FI 82 8711 FORSTl!R: Forster Village Electronics 54 5006 GLEN INNES: John Bommerlad Electronics 32 3661 GRAFTON: Repairs and Spares 42 1911 GRIFFITH: Miatronics 62 4534 INVERELL: Lyn WIiiing Electronics 22 1821 LISMORE: Decro Electronic Services 21 4137 MOREE: Moree Electronics 52 3458 MUDGEE: Headwan, 723895 NOWRA: Nowra Etectronlcs210722 WAGGA WAGGA: Phillips Electronics 216558 VIC:MORWELL: Morwell Electronics 34 6133 BHl!PPARTON: Phffllpa Electronlcs Ply Lid 21 9497 WARRNAMBOOL: Marrtronlcs 62 9870 OLD: BUNDABERG: Bob Elkin Electronics 72 1785 KINGAROY: Holmes Today Electronics 62 1658 MACKAY: Stevens Electronics 511723 MARYBOROUGH: Keller Electronics 214559 TAS: DEVONPORT: A.I.Electronics 24 8322 SA: LOXTON: G & S Electricat 84 7495 MT GAMBIER: Hutchesson'• Communication Centre 250400 WA:ALBANY: Micro Electronics 41 2077 BUNBURY: Micro Electronics 21 6222 GERALDTON: Batavia Lighting & Electrical 21 1966 KARRATHA: Daves Oscltronlc 85 4836 NOW AVAILABLE AT ALL STORES - OR CALL TOLL FREE: (008) 22 6610 FOR HOME DELIVERY! Component Grabags Our bargain component grabags have been incredibly popular .. they've 1·ust about all gone except for these two (which we had ots more of!) And now to clear them out we've slashed the price.But hurry! Grabag 4: At least $50 worth of bits and pieces Cat K9040 Was stupendous value at $29.95 NOW ANOTHER TEN BUCKS OFF AT JUST 5 19"5 Grabag 5: At least $70 worth or so ... Cat K-9050 Was fantasmagorical value at $49.95 WHILE THEY LAST. SAVE $15 .. 95 Now 5 Moving Iron, too! Both same price: 1995 88 MORE METERS! Capacitance, Transistor Check Too! s129 s119 56995 : Don, Choke on These! ALL ONE PRICE/ Quality RF chokes in all values from 1uH to 4.7mH. Grab some or the junk box: you never know! 470uHCatL-1811 560uH Cat L-1813 820uH Cat L-1817 1.0mH Cat L-1820 1.5mH Cat l-1822 s 1ea25 u::mg::t:m1 ASK FOR $1 OFF ti FERRIC! . s3495 Will the bargains never end? A dollar off a 500ml bottle of concentrated ferric chloride etchant is great value in anyone's language! Cat N-5652 .- · : Stepdown· Tranny 240 to 115 volt for US & Japanese items. In case with fitted mains lead and parallel socket. Cat "1-1156 Isolation :?! 600 ohm to 600 ohm telephone circuit isolation transformer. Fully approved by Telecom Engineering branch. Cat M-1~10 ~""::: $ 1695 OUR BULK PRICE. Why risk your valuable IC's by soldering them in? And what happens at service time? Use these quality sockets - and save as well!' Type Cat No Was Now 8 Pin OIL P-4080 20c 10c 14 Pin OIL P-4140 25c 20c 16 Pin OIL P-4160 30c 15c 18 Pin OIL P-4180 35c 20c 20 Pin OIL P-4200 45c 35c 22 Pin OIL P-4220 50c 25c 24 Pin OIL P-4240 55c 30c 40 Pin OIL P-4250 65c 35c TV COAX Air Space Cat W-2082 1.00/m Solid (RG59U) Cat W-2081 75c/m 3 2 ;:,i~r;:~:1~~381:/:5;:!nc.r::3~~ :2;5s!~:.Y::~k~i~ gg~~: ~~a:::.:~~~ ~,4 ~ ::~;::;;;~~; 4300 • 5722 • 341 0844 232 1200 • Underwood \ Time to replace that old co-ax? We have air solid dielectric, low loss 75 ohm cable. • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 677 7722 • Bondi Junction 387 1444 • Campbelltown (046)27 2199 • Chatswood Chaae 4111955 • Chullora 642 8922 • Gore Hiil 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • N-ca•He 61 1896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Warrlngah Mall 905 0441 • Wollongo111128 3800 •ACT• Fyshwlck 80 4944 • VIC • Ballarat 37 5433 • Bendigo 43 0388 • Box HIii 890 0699 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frank1ton 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 Townsvllle 72 30C 95 SOCKET TO ME! While stocks last! • Toowoomba Normally &Oc ea This month: 1A secondary with taps every couple of volts from 6.3 to 15V. Perfect for projects! Cat M-2155 ss9e5 22uH Cat L-1779 33uH Cat L-1783 47uH Cal L-1787 68uH Cal L-1791 82uH Cal L-1793 100uH Cat L-1795 150uH Cat L-1799 220uH Cat L-1803 330uH Cat L-1807 Amplifier Tranny ;,j General Purpose Tranny Handy "hold" button freezes reading so you don't have to take your eyes off the circuit. 14 ranges including diode check. Cat 0-1521 1.0uH Cat L-1759 1.5uHCatL-t761 2.2uH Cat L-1763 3.3uH Catl-1765 4. 7uH Cat L-1767 6.BuH Cat L-1769 8.2uH Cat L-1TT1 10uH Cal L-1773 15uH Call-1775 6- Big rating - 94V <at> 3A or 47V <at> 6A. Also ideal for big amps, linears, etc etc. cat M-0150 Handy for the technician or hobbyist: digital temperature readout from -20 to +1370 degrees C. Also has standard multimeter ranges and diode checker too. Cat 0-1511 Low Cost -With Data Hold Need A Tranny? Power Supply Tranny Need to know Temperature? 5O°/o OF Yes! 50% off one of the handiest IC's they ever invented. Grab a handful while they're cheap (careful of the sharp pins, though!) Cat Z-6145 The great unwashed think a tranny is a transistor radio. You know battar don't youl · 28 volts a side at 2A. Perfect for medium power audio amps. Cat M-0144 All the usual multimeter ranges (including 10A DC/AC) plus transistor Hie and capacitance to 20uF. And it has bu~~r continuity!. Cat 0-1500 A RANGE OF SELECTED KITS THIS MONTH. 555's 34 Moving iron means t~ey're suitable for AC as well as DC. Ideal for power supplies, etc - in two carefully chosen ranaes (you can always change them with shunts and multipliersT) 0-20V Cat 0-2080 0-10A Cat 0-2090 $ 25°/o OFF •SA• Adelaide City Beverley 3471900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • Fremantle 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Par1< 811977 315 degree 2mm tip SCJ95 Cat T-3002 370 degree 2mm tip SCJ95 Cat T-3003 430 degree 2mm tip SCJ95 Cat T-3004 370 degree 3.2mm tip CatT- 3005 ~ 5 Tip wiping sponge Cat T-3010 $500FF! WELLER STATION From one of the worlds's leading manufacturers comes this superb new Soldering Station. It's different from most systems: it uses an advanced control system which measures the tip temperature - to change the operating temperature, you simply change the tip. Simple - yet more effective than ·ust about any other system. t T-3000 Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Pulse charger for dry cells Contrary to popular belief, it is possible to recharge dry cells using the pulse-charge method. There are a few provisos, however: • the cell should be recharged as soon as possible after use, to limit irreversible chemical breakdown; • the cell must not be allowed to discharge to less than 1V before recharging; • you must recharge cells individually (ie, AA, C and D cells only - you can not satisfactorily recharge a 9V battery); • you must ensure that the cells are not overcharged. The circuit shown here will safely recharge a dry cell in 12 hours from a 12V source (eg, a car battery). IC2a and IC2b form a square wave oscillator which runs at about 20Hz. Its output (at pin 4) is gated by IC2c which is controlled by the output of comparator ICl. When pin 6 of ICl is high (ie, during recharging), the square wave output from IC2c is buffered by IC2d and applied to the base of Ql. This pulses Ql on and off to supply r---+---+---------4----------+-----+---+9V 1k 10k :Jl .,. IN SILICON CHIP +9V 100 + 25VW+ 10 + 16VW:r: .,. current to the battery. At the same time, Q3 is pulsed on and off to drive charging indicator LED 2. Because the output of comparator ICl is high, Q2 is also turned on during the charging cycle. This gives a small amount of bleed current which increases charge retention. When the battery voltage rises above 1.6V, the output of ICl switches low and shuts off the square wave pulses to Ql and Q3. This stops the current pulses to the battery and lights LED 1 to indicate the charged condition. Darren Yates, Frenchs Forest, NSW. ($30) , - - - - - - - - - - - - - - - - + 1 2-14V 02 1N4002 electronic fuse 38 OUT +12V 200-250mA DC Are you sick of blowing fuses in your digital multitmeter when using the low DC current ranges? This 200-250mA DC electronic fuse will save you the hassle of fuse replacement. It is simply inserted in series with the meter and the load. The circuit uses an LM393 comparator and a C106Y1 SCR (silicon controlled rectifier) to latch a relay (RLl). Diode Dl sets the reference voltage on ICl 's non inverting input at + V - 0.6V. The inverting input monitors the load current through the relay contacts and the 2.70 resistor. .,. AA + .,. IN + V O - - . - - - 6800 RL 1 SCR1 C106 .___ ___._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ DY With no load current, the voltage on pin 2 is higher than on pin 3. Thus, pin 1 will be high and the SCR and relay will be off. When the load current exceeds about 220mA, the voltage on pin 3 will drop below the reference voltage on pin 3 and so pin 1 will switch high. This then turns on the SCR and opens the relay contacts to . - - - - - - - - - - - -....----+sv +12V 1489 IC1a 4.7k IC4b LINK 4 10 IC1b 11 LINK 2a,b .,. LINK 2 IC1c LINK 3 -5V 11 LINK 1 Fig.2: the RS422 signal from IC3a (Fig.1) is fed to pins 14 and 15 of IC4 which is a quad RS422 line receiver. This feeds IC2 which in turn drives the RS232 input of the computer. Fig.1: the RS232 signal is fed to quad line receiver IC1 which in turn drives IC3. This gives an RS422 signal at pins 13 and 14. RS232 to RS422 adaptor This circuit was developed to transfer data between two computers that were too far apart for the RS-232 serial method to be reliable. One way would have been to use a pair of modems but that would have been too expensive. The method chosen was to convert RS232 to RS422 and back. The RS422 is a differential +12vo-----1 7805 ceiver. This drives IC2, a 1488 quad RS232 line driver which then drives the RS232 input to the local computer. serial data system so that noise induced onto the lines is ignored. Because noise has no effect, RS422 can be used for long distances at high data rates. Four ICs are used for the converter and two for the power supply. ICl is a 1489 quad line receiver that accepts RS232 signals from the local computer and sends to it to IC3, a 26LS31 quad differential line driver. The received RS422 signal from the remote computer is fed to IC4, a 26LS32 quad RS422 line re- The power supply was designed to allow the circuit to be used with a Microbee (pin 9) or with a 9 to 12V plugpack supply. This is regulated down to + 5V with a 7805 3-terminal regulator. The 7660 converter circuit provides the - 5V line required by IC2. C. Boardman, Mosman Park, WA. ($35) n n 1-------------n+sv _J LJ LJ L-ov 7 n n ,-+SY TX SIGNAL 47 7660 -------n-sv 10 n-+SV LJ LJ + ovo--_.___.....,._ _ _ __..,__ _ _....,_o ,.. u_ OV -+sv Fig.3: this circuit can be used to give the + 5V and - 5V supply rails. WIRE A RX SIGNAL -ov WITH NOISE SPIKE TX SIGNAL RX SIGNAL I NOIS~ 1~1KE _flJUE +12V - - - OV J1J7JfE . prevent overload of the meter. LED 1 and its associated 5600 current limiting resistor are wired in parallel with the relay. Thus, the LED lights when ever the overload protection circuit trips. The circuit -+sv WIRE B --12V 1 + 2V - - - OV --12V Fig.4 at left shows how a noise spike can corrupt data on an RS232 line. This problem can be solved by converting to RS422 (Fig.5, above) because noise induced onto the lines is ignored. is reset by pressing normally closed pushbutton switch S1. Finally, note that the LM393 is a dual device so the inputs (pins 5 & 6) of the unused comparator should be connected to the OV line. The cir- cuit could also be built around an LM339 quad comparator but again, the unused inputs should be connected to 0V. Peter King, Yacht "Miracle", East Coast, Australia. ($20) JANUARY 1989 39 G'day, as they say 'ere, Colin. Sure was glad to hear from you, buddy, and to know that I'm not alone in travail. Although I felt a bit island-happy after leaving the South Pacific, I'm not sure that I've arrived in the real world yet. I was really looking forward to coming here, you know, since I'd tried before to come to Australia. Now that I am here, I have my own tale of w _ Back in the States, I had applied for a job installing microwave repeater gear after seeing an item on Australia in a magazine. Well, I got knocked back quick smart, as I did not have an engineering degree. I was amazed, thinking of university qualified engineers slaving in the outback. Since arriving in Australia, however, I have learned that things are not always as they seem. There is great emphasis on paper qualifications but exceptions to the rule outnumber them. I have learned that public service jobs must be advertised. The lurk is to make the qualifications beyond the typical applicant and the pay below what he would probably earn otherwise. Thus, a worker from within the system can then be accepted for promotion. Having worked for Ma Bell as a callow youth, I had a lot to say against that mob. But when I found here that getting the telephone service reconnected where we first lived would take at least six weeks, I was aghast! Back before we left the States, one Monday afternoon, I called the local operating company to advise them that we were moving across town and needed the phone on quickly there. By RICHARD KOPF ers 40 SILICON CHIP It was an old house and had only one instrument downstairs. Before the removalists had left on the Wednesday afternoon, two blokes turned up and reconnected the existing telephone. They also ran a lead upstairs to the master bedroom - don't ask me how; the only evidence afterwards was that the extension worked. And they lef.t no mess or visible cable. They were gone inside of ninety minutes and the total bill for this service was $26.00 - that pittance and less than two days of lead time. How about that, then? The telephone was one of the first contentions between myself and the chief engineer at my new job. It seemed to be my fault that the telephone wasn't on quickly enough. As a senior technician, I was expected to be on call whether I was rostered on or not. One wild night One night, I got a call from master control. The transmitter had carked out but came back up. They wanted someone to go look at it, just in case. Having had a few, I suggested that it might not be the best idea for me to go out. But they insisted, as the supervising tech who was rostered for on-call did not respond. Now this was the first instance that Mohammed had had to go to the mountain on his own. And in a Land Rover I'd never driven before. ----------------------------------------- had criticised the Land Rover's conSince standing orders were that the dition. And the supertech believed I -vehicle be topped up and in working had pointed the bone at him. order at all times, I never thought to Granted, he had gone AWL and check the gas (petrol) before I granted he had not replenished the started off. supplies up top. But I was too new a Well, the station owner had had boy to name names and had not the thing out shooting that afterdone so. I merely described the noon and got back late. By the time I facts. was at the foot of the mountain, I If I had wanted to do a hatchet noticed the gauge. Fortunately, I job on him, he would have known it had three or four dollars in my unmistakeably. Actually, he was a pocket which would hopefully buy me enough petrol to make the round trip. It wasn't too bad for the first 20 minutes or so. Then, just before I reached the summit, she started to slide. I got it stopped, though it was sideways on, and worked out how to get it into 4-wheel drive. That made the difference and I made it the rest of the way. Once inside, the relative warmth of the transmitter building was welcome. I looked at the gauges and the rig seemed to be healthy. I -spoke to master control, suggesting we put the standby rig to air. I 4/~-llr:,:.-----~ \ could then do a physical inspection ,_....,,..~,,,,r~~ of the main transmitter. They didn't want to be bothered. "Why did you bother to send me up here?" I reckoned it was fierce enough ~II I: 'RSAC~\S:D '04S.. out that I might stay the night - unii~ SuN\M\ij SHS:.. til I walked into the kitchen and found that the emergency provi,, S~'R:-r~D TO SL-lDE."•· f •• sions had all been used up. There wasn't even a grain of instant ' ~\\Ii'' coffee. though it was during the installaAgain on the horn, I told the m.c. tion of colour gear and I was the on(master control) operator I was ly person in hundreds of kilometres coming down, even if it was over that had colour experience. the side. (See, I spell "colour" the right "Don't joke about it, mate," he way, Colin, just like in a proper said. "A couple of years ago, dictionary). another bloke did just that". Hail-to-the-Chief, though, never I felt too ornery to let a little snow tired of trotting out all his muck me about and got back to the pretty good bloke, cluey and friend- theoretical knowledge. And the two station without problems. I left an ly. But I always felt he would go to or three unqualified kids on the entry in the log. The next morning, I any lengths to avoid station strife, staff were quick to follow his came in at eight, the usual time. even if it meant giving his men little example. And was promptly roasted for going or no support. I quickly tired of hearing about up to the transmitter in dangerous Never Twice the Same Colour The chief engineer conditions alone. (NTSC). After a couple of weeks of The chief engineer, however, this, I conceded one day that PAL Furthermore, the big boss had learned of the log entry and was ir- was the bane of my life. I sometimes was probably better but pointed out ritated (to put it mildly) because I wondered why I was hired that I had been watching colour , Ii I . -~~-~·,.\¼~ -.,.~e:.N, :rus-r :BE.ro'Re:. (J JANUARY 1989 41 THE TECHNOLOGY LETTERS - CTD telecasts since 1953, when Australians had hardly heard of television at all - much less colour. Then they took the tack that the whole process was much better here, as the government had spent much time and money before deciding on the best system. My reply to that was that the best system depended on the kind of receivers the Japanese were prepared to build. My statement that a government study to research a foregone conclusion (influenced by the Japs and the UK) was a boondoggle and a complete waste of money did not win me any friends. About this time of course, some funny fella was making zillions of dollars selling CB radios. Now, you know, they were not legal to use here. No problem with someone selling them, or buying them. You just weren't supposed to do anything with the purchase. Naturally enough, another foregone conclusion was reached about the proper system to licence again, what the Orientals were building. Of course, they had to legalise existing equipment, so they could grant an amnesty and get the licence fees. Or so they thought, anyhow. Ocker knocker My, I am rambling on, like a true Ocker knocker. If I was really down on Down Under I would have left, wouldn't I? Not long after we arrived, I met an American couple who had just returned again. They couldn't cope with the culture shock the first time around - until they got "home" and discovered that all the things they hated in the US had got worse, and the things they liked were diminishing. Fact is, I liked Australia well enough to buy a house, sine~ the station manager led me to believe the position was going to be permanent. And of course, I enjoyed all the "new toys" to install and interface. !'F I"'1' WA"-1\e:D -ro VO A ~~"fCME-r ~ ON \.-\\M, He. lM:?U\--'D H~\J ~ t<.tJOWN 1-r" UNtv\\STA\<~A&-'1'", .. 42 SILICON CHIP One of the plans was to go automated. The chief engineer had convinced the board that a substantial investment (in a VCR cartridge machine) would allow two people to run the entire station after the evening news. This with the help of a PDP-11 computer, of course. It had not actually arrived but I was given the job of designing a machine interface to accommodate it, as well as making a control system for all operating points: the production and news studio, master control, and the individual telecine islands and VTR bays. Since I had several different voltages to deal with, I elected to design around discrete component logic modules. It took me about an hour with the various equipment manuals to work up one interface circuit which used only a couple of trannies and three diodes. Just about then, Chiefie saunters by my desk, sees the circuit diagram and whinges, "Surely you can do that with just one transistor. If I were designing it ... " And he goes into his office for two hours and comes out triumphant with a circuit that will work. One which I had considered and discarded. "Do it this way!" he orders. "Yes," I replied, "that will work. But if two stations inadvertently call for the same projector, this diode will blow. Mine, on the other hand, is fail safe." He was always starting the oneupmanship and sulking when the game plan fell apart. That is why he hired untrained and unqualified people, I think. He seemed to have a need to be smarter than his men. The next part of the saga was his insistence that the control module project be built by his newest protege. I had some misgivings but briefed Newey on the circuit diagram and general component layout before advising him to "Build one and test it first." Two mornings later he crowed, "They're all done!" "All tested and functional?" "Well, I did not know how to test them ... " So I went to see for myself. It took me nearly three days to debug the I ••• G:-om~s ou-r T('(\ UtOPHAN"n,..."< Wl'f'H A c,Rcu,-r ~Prf' w,u_ WORK"-'Of\JE W\\\c..t\ ! HAl> c.&JS,t>t-'RED, AN1) tnSCARt:>£. Ou, lot. We had been told that there was no money or time for fancy PCBs so Veroboard had been opted for. Newey had made different mistakes on each module - uncut tracks, jumpers going to different places, missing components. When I mentioned the automatic VCR before, I should have said that the board took a dim view of the expense of lots of cartridges to feed the beast. Thus, it became a practice to dub film and reel-to-reel VTR commercials to cartridge. Then, if they were not logged for a couple of days, they were reused. It was not uncommon to see the same commercial dubbed three times in a single week. People really know how to waste money in saving it! X marks the spot When I first arrived, I was amazed to learn that no system drawings existed of the old facility. And even more surprised by the X's on the equipment. When I asked what they were for, I was told, "That's where you kick 'em when they play up, mate!" Having worked on valve VTRs in the old days, I can appreciate that attitude. Unfortunately, it is a practice which does not necessarily enhance state-of-the-art equipment. Several weeks after the installation of the first telecine chain, a problem of intermittent chroma was noted. One of the lads also discovered that when you reseated a certain module, it cured the problem for a time. This discovery was relayed to all the operating staff. One Saturday morning, a bloke who would have been better playing footy kneed said module and broke the backplane connector. I was called in to identify the problem and growled at the tech. He said, "This bloody Yank equipment is too weak - it's not made for Australian conditions ..." A couple hours' work with the special extraction tool and reseating the leads into a new connector shell had things fixed up OK but left me with shaking hands, I can tell you! Another thing I discovered in the beginning which drove me up the wall was the chief's habit of never following up on a temporary fix. I found one coax cable in one of the racks that had been made of two spliced together. All of my design work and installation was coupled with hours on the drafting board. Naturally, the junior techs complained about this waste of time: "We never had any need of junk like this before." But this approach paid dividends. Some months after I left, I was introduced to the new chief engineer. He'd come from interstate and remarked that at first he had despaired of finding any professionalism "in this place"; but complimented me on my work practices. "Those drawings saved me hours of work," he said. He also recognised that the stock control method I set up for spare parts was effective. Indeed, I had one occasion to call to borrow an obscure IC and was told by one tech that they had no such part. Although it had been a long time since I had been in the place, it took me less than one minute to crossreference said component and pull it out of the bin. Nest building You will have gathered that I have moved on. It was not by choice. Of several things I did wrong, the worst was to overhear Chiefie trying to feather his own nest. He was supposed to be negotiating the purchase of certain equipment from another station and I heard him on the telephone arranging to buy it through his own company name to resell to our employer. Also, after a staff meeting, the big boss had decided a suggestion of making company shares available to workers was a good continued on page 91 JANUARY 1989 43 120W public address amplifier - 2 Last month we presented the circuit for our new 120W PA amplifier and showed you how to assemble the PC boards. This month, we show how to assemble everything into a rack-mounting case. By LEO SIMPSON All the parts for the 120W PA Amplifier mount neatly into the high energy rack mounting case as sold by Altronics (Cat. H041B). We will assume that you have a completely finished chassis with all holes drilled. The order of assembly is to wire up the power supply, then the input sockets, install the mixer board and potentiometers and then the power amplifier module. To make the wiring job easier, we suggest you remove the front panel by undoing the four retaining screws. Not only will this make access to the chassis easier but it will lessen the chance of scratches to the front panel while assembly is in progress. In fact, it is a good idea to put 44 SILICON CHIP masking tape over the edges of the front panel, to avoid damaging the anodised finish. Power supply wiring The first step in wiring the power supply is to install the power cord, mains fuseholder and insulated terminal block. The power cord should be installed using a cord-grip grommet, to firmly anchor it. Then fit the mains fuseholder and wire it and the power cord to the 4-way insulated barrier strip. We used a neon-lit miniature double-pole rocker switch for the power switch although a larger type probably would be better for ruggedness and reliability. We suggest that both the mains switch and fuseholder be fitted with heatshrirtk sleeving to cover up the live terminals. Since we have recommended that the front panel be removed from the chassis for the initial wiring, leave out the mains switch at this stage and substitute two short loops of insulated hookup wire across the insulated terminal block. Later, when the front panel is installed, the loops can be removed and the mains switch wired into circuit. The toroidal power transformer is bolted to the rear panel of the chassis. It is sandwiched between two large neoprene washers and retained by a 90mm diameter steel plate. Then install the bridge rectifier and two chassis mounting BOOOµF 63VW electrolytic capacitors. The main earth point is via two solder lugs adjacent to the insulated terminal block. Install the earth wiring exactly as shown in the photos and in the wiring diagram. Now before proceeding further, MIC 1 ~~- 'D R ~AUX1 ~ A R C MIC 2 ~AUX2 1OOV LINE TRANSFORMER POWER TRANSFORMER E PREAMPLIFIER BASS Fig.1: this diagram shows how everything is wired together in the chassis. Be sure to use shielded cable where shown, to keep noise to a minimum. The supply wiring to the power amplifier is run using heavy gauge tinned copper which is sleeved with plastic tubing. Arrange the wiring as shown in the photos to minimise distortion. JA NUARY 1989 45 This view into the right rear corner shows how the lOOV line transformer and power transformer are mounted. Install the mains wiring in a professional manner and insulate the exposed mains connections at the switch with plastic sleeving. check the power supply operation. Carefully check your wiring and then apply power. The supply rails should be close to ± 50V DC. Switch off and wait for the B000µF capacitors to discharge to below 5V before proceeding with further work on the chassis. Disconnect the power plug from the mains. Caution: remember that the power supply puts out a total of 100 volts DC. This is a potentially dangerous voltage. Make sure you don't come in contact with it. Now proceed to install the rest of rear panel hardware. This includes the toroidal line output transformer which mounts the same way as the power transformer. PCB installation The mixer board can now be installed. It can be mounted on plastic PCB mounts or using screws, nuts and spacers, as in our prototype. You can then install the shielded 46 SILICON CHIP cables from the input sockets to the mixer board. The line inputs are wired in using figure-8 shielded cable while the balanced microphone inputs use twin-shield cable (ie, two insulated wires in a common shield). At this stage we suggest the power amplifier module be installed. Smear heatsink compound over the mounting surface of the heatsink bracket and secure it to the lefthand heatsink with four screws and nuts. You can now wire up the power supply to the amplifier module. Now while these connections look straightforward they must be done exactly as shown in our photos. The three supply wires are run in stiff heavy gauge (say 16 gauge) enamelled or tinned copper wire which is then sleeved. The reason for arranging the wiring as shown is that small variations in the layout can lead to very large increases in harmonic distortion, particularly at the high frequencies. Using the layout shown, we were able to keep the harmonic distortion to below 0.3 % across the whole audio frequency range at up to full power. This is a good result for a powerful amplifier with a line transformer. Setting up the power amp module Now remove the negative supply fuse from its clip and connect a multimeter set to measure up to lA across it. Do not connect a load or the output transformer to the amplifier at this stage. The output stage quiescent current can now be set. Rotate the 5000 trimpot fully anticlockwise and apply power. Now rotate the 5000 trimpot for a current of 200mA. Switch off the power supply and There is plenty of room inside the chassis which means that the amplifier is easy to work on. We suggest that you bind the shielded input leads with plastic cable ties to prevent them from fraying and coming adrift. it to zero; ie, to less than ± lmV. Leave the amplifier with power connected for an hour or so and then check the settings for DC output and quiescent current. Reset if necessary. It is normal for both settings to drift slightly. Now you can connect the 100V line transformer or a loudspeaker and check for the presence of hum or any other signal. With no signal applied the amplifier should be absolutely quiet. Touching your finger to the input should cause the speaker to emit a small "blurt". Completing the wiring Follow this photograph closely when installing the supply wiring to the power amplifier. The leads are run about 2.5cm above the edge of the board and drop straight down to their respective PC stakes as shown. wait for the voltage across the supply capacitor to drop. The multimeter can now be removed from circuit and the 5A fuse replac- ed in the negative supply line. Reapply power and measure the DC voltage at the output of the amplifier. Rotate trimpot VRl to set You can now fit the front panel and power switch. Install the potentiometers and wire them to the mixer printed board. This wiring is run in shielded cable for the Mic 1, Mic 2, Aux 1, Aux 2 and Master Volume pots and in ordinary hookup wire for the Bass and Treble controls. Do not connect the shielded output lead from the mixer board to the power module at this stage. Connect the positive and negative JANUARY1989 47 ,/' Here's a close-up view of the wiring to the auxiliary sockets and the balanced and single-ended input microphone sockets. If you want to save money, it may be possible to leave out two of the microphone sockets (see text). power leads from the BOOOµF filter capacitors to the respective terminals on the mixer board. The OV lead from the power amp module then connects to the OV input on the mixer board. Now you can check voltages on the mixer board. Apply power and check the voltage across each of the 33V zeners. It should be 33 volts or less. Then check the 3-terminal regulator outputs. They should be + 15V for the 7815 and - 15V for the 7915. If you don't obtain these voltages, switch off and check your work carefully before proceeding further. Now check for the presence of + 15V at pin 8 of ICl, IC4 and IC6 and at pin 7 of IC2, IC3 and IC6. Then check for - 15V at pin 4 of all six ICs and the emitter of Q12. Finally, switch your multimeter to the lowest available DC voltage range. Check that the output voltage at each of the op amps is close to zero; ie, less than ± 20mV at pins 1 and 7 of ICl, IC4 and IC6 and at pin 6 of IC2, IC3 and IC5. Finally, connect the short shielded lead between the mixer output and the power amplifier input. Note The rear panel of the 120W PA Amplifier is clean and uncluttered. Two plastic binding terminals (above the mains fuse) are used for the 100V line output, while all the input sockets are grouped together at right. 48 SILICON CHIP SC01112881 ~,,____0. J ,. .,. I I 0 I °1' ~ ..... ~· 0 Fig.2: above is the full-size PC pattern for the mixer board (code SC01112881). Fig.3: this is the full-size pattern for the power amplifier board. The pattern is critical and must not be altered. that the shield is not connected at the power amp input. Your new public address amplifier is now ready for work. Options If you want to save some money, there are some features of the PA Amplifier that could be left out. For example, if you only intend driving 80 or 40 loads, the 100V line transformer can be omitted. The load is simply connected to the output side of the 40 resistor and its parallel 4.3µH inductor. For further information about lOOV lines in PA work, see page 17 of the November issue. Similarly, if you only intend using unbalanced microphones, you can save a few dollars by leaving out the XLR sockets. But note that you must still use shielded cable and include all the connections shown on Fig, 1. If you intend using balanced microphones, then leave out the single ended input sockets. lf; JANUARY 1989 49 ,--------------------------------, I I Why Waste Your time With Other Suppliers Altronics Can Deliver Any Of The Quality Products 1 To You Tomorrow - Just Phone Your Order Toll Free I Jack O'Donnell On 008 999 007 I M/Director Country Clients Please Allow Additional 48-72 Hours I I 1 I 1 ~-------------------------------~ Go Anywhere 240V Maine Power From Your Car or Truck Battery With These Fantastic DC to AC Inverters Power Capacity opylene Ba•• Driver• Save 25% Thie Month 12" (300mm) odel 100 Watts continuous input 150 Watts intermittent input Impedance 8 Ohm Sen1ltlvlty 93db Weight 3620gm 9 9 $ C 3070 Normally S139 15" (375mm) Model 120 Watts continuous input 200 Watts intermittent input Impedance 8 Ohm Sen1ltlvlty 92db C 3075 Weight 4120 gm Normally $179 149 $ }\/ Our all new "Black" polyprop cone Bass Drivers exhibit quite astonishing ?/ low register reproduction. The power ratings quoted are conservative. ii? While they may not be the cheapest around they definitely represent the best value we know of· Anywhere. The real exciting new, 11 we have the top Hlllng 12 and 15 Inch model, at low dl1count prlcea thl1 month-but be quick stocks are limited. Our Top Selling Professional' Stereo Console Mixer 300 Watt lnverte W A \ Feature,: Auto start draws power from your battery only when appliance is plugged in and "turned on" i.e. battery can be left permanently connected if required. Voltage Regulated Current Regulated • Current Overload unit self limits single PC Board construction easy to build as there is very little internal wiring. ; ·~150 s279 It d K 6755 Power House 600W In~ rter (See EA Dec'87) A must for farming, camping, mining, boating, remote settlements and wherever else 240V power isn't available . Fe■turea: Strong custom steel chassis • Industrial grade power coat finish • Can be configured to operate off either 12V and 24V DC• Very little internal wiring• Manual or Auto start facilities • Low battery cut out • Compact Toroid transformer. V 70 KIT VE.HSIO I s425 Fully Bull! & Teated 12V INPUT A 2570 Normally $499 This Month s449 Save $50 This Month Our sophisticated ' NEW' Audio Mixing Console is ideal for 'live· recording • PA mixing • Fantastic Tape recordings • Even Stereo/ Mono VCR recording . A truly professional deck that features separate R/ L 5 band graphic equalisers• Echo and Peak LED level indicators• Talkover facility • Separate H/ Phone level contro l • Patch switch bank • Individual microphone, Phone 1 Phone 2, Aux/Line 1, Aux/Line 2, and Master slide level controls . Blend up to two magnetic or crystal turntables, two tape decks or tuners and two microphones all at once!' SPECIFICATIONS: • Input Mic 1-0.5mV 600 Ohms Mic 2-0.5mV 600 Ohms Mic 2-0.5mV 600 Ohms (low imp.) 2.5mV .10K Ohms (low imp.) Phone 1 & 2 (Mag) 3mV 50K Ohms Phone 1 & 2 (Cry) 150mV 100K Ohms Tape/ Tuner 1 & 2 150mV 100K Ohms • Equalleer 5 frequency bands-60Hz , 250Hz, 1KHz, 4KHz, 12KHz-Boost Cut range-plus or minus 12db <at> Centre frequency. • Output 1.5V/0.775V (Selectable) • Frequency ReaponM 20Hz to 20KHz plus or minus 1db • Dl1tortlon Lessthan0.05% • S/N Ratio More than 50db • Headphone Impedance 4-16 Ohms• Echo 8 .B.D.System • Delay Time 30-200mS • Echo Repeat Control • Delay Time Control• Dlmen1lon1480 Ill x 240 /Wl x 110 /Hl Toroi Tran formers Why a Toroid? • Smaller size and weight to meet modern " Sl imline" requirements. • Low electrically induced noise demanded by compact equipment. • High efficiency enabling conservative rating whilst maintaining size advantages. • Lower operating temperature. • Simple, quick single bolt mounting Dlmen1lon1 and Weight 180 VA Modelt 110 Diam . 45mm H. 1.8Kgs Leads 200mm a 180 S65 10 up Cat.No. M 3050 M M M M 300 VA Model• 125 Diam . 45mm H. 25Kgs Leads 200mm 3055 3060 3065 3070 M 3075 S62 ea SEC.V 12 18 25 30 35 40 + 12 + 18 + 25 + 30 + 35 + 40 S79 Cat.No. M 3085 M 3086 M 3088 M 3090 M 3092 M 3100 10 up S75 ea SEC.V 12 + 12 18 + 18 25 + 25 30 + 30 35 + 35 40 + 40 !~~:?§~~ !!\ : ! :! !!!!!!!!!!!I! lll--~:: :111111:~1111:1: :~ 1:: :111:: :111:: :::!:~:!; ** * ** HIGH TECH Company Collapse Brings Fantastic Bar~ains For LI:!~~:E~~i1i~!~~:: iU::0:// / W:):) 1.6 Amps Pins 7,8- Seconder:; 2: 12V <at> .35 Amps Pins 11 , 12 - Secondary 3: 20V<at> .35 Amps Pins 7, 12 (join 8, 11) !!F \ t! i : : Cat. ZX 0090 3 2 1 ®®ii M;I:: Stereo F;:'::::Value $ $ +12Vsupply (case neg .) Single terminal wire video input. With Dynamic Mic \ Great For 2-Ways, Intercoms ( P.A.'• & 100 Other ,\ Communication usH. :) Super Comfortable. ) Headphone Spees. 20Hz :::' 20,000Hz, 32 Ohm, 102 db/ uW, c::( 4: Ij il! sl'4£ s,o.oo ; Il Now s29.es ., Were Sellin Plasma Fantastic pulsating high voltage Plasma discharge continual -ly changes shape & direction. Mode selectable to either fingertip control or sound activated e.g. from voice or sound system. Provides endless fascination as it sizzles & arcs. Supplied complete with AC Mains Adaptor. Price Breakthrough For '89 A 0120 10 or More $15.00 ea !;~:Tt~;1;~~~;rfii::. ii Ii'~-?J i~~~~rt~i1~ir~~2;~i~fif~:fu. 1-10 M 2165 \'l.6-~0 ' 11. \l :L :~ ?•:•/• Output Two Simple Secondaries, each with just one tap, permit an amazing range of outputs. 240Vto 9, 12, 15, 18, 21, 24voltsat60VA (60W) . Use of high grade Silicon steel has enabled surprisingly compact dimensions (70mm x 70mm x 58mm High) . ~0(1•• I1 (~!~~i~) =W:c: Multipurpose SOVA Transformer -&''~ s19.oo 0020 Amazing Price zx Huge Savings On Top Selling Multlpurpose Mains Transformers Get One For The Work Bench 2 Amp Regulated Power Supply Multipurpose 120VA Transformer Another Quality Transformer from Altronics. The M 2175 is wound on expensive grain oriented steel. Look at the size! Just 110mm wide by 65mm High by 65mm Wide. Weight 1.25Kgs. Primary: 240V Secondary: 1 0-12V <at> SA, 15V<at> 4A Secondary: 2 0-12V<at> SA, 15V<at>4A. , · ...,.&\\1 -.1.ot,.. " g~ 1•[i· -,"·'[~~,~ · -,.:;:"":.,,.. 1, .. .... Save Up To 50% On Top Quality D Series Connectors! Fanta,t/c Value D Series Computer Connectors. Gold Plated Professional Serles Items Marked • are 1/2 Price or LHs :;;cl ~.·1!·_ . ~ .•.,. , ... •· $39· This Month s30 10 or More $26.00 ea M 2175 RF Signal Generator SPECIFICATIONS: Frequency Range: 100KHz - 150MHz in 6 Ranges. RF Output Level: 100mV RMS Accuracy: +/ -3% Modulation:• Internal (30% depth 1KHz• External 50Hz • 20KHz • Crystal Locked Oscillator. $30 D89 P 3000 P 3010 "3020 P 3030 P 3040 P 3050 P 3090 Male 9 Pin Female 9 Pin Male PCB Rt/L Fmale PCB Rt/L Male PCB mnt. Fmale PCB mnt. Backshell cover D815 2.95 3.25 3.75 4.50 2.95 3.95 1.47• 1·_95 .95 1.80• 3.00 3.50 2.50 2.25 Superb Redford Wireless Microphone System Uses Dual Diversity Receivers for long Range, Noise Free Pure Fldellty Reproduction. Now Available In Australia For Less Than $1,000 Altronics proudly release the Redford Dual Diversity System - Used Worldwide by Entertainers i.e. Rolling Stones, Dire Straites, Tina Turner and 1000's more' Superb Microphone Reproduction Compares with Shure,Beyer and AKG Unique Microphone design completely Ellmlnates "Dangling" Antenna Breathtaking performance without signal drop-out or noise interference. T he Eleco Wireless Microphone System is virtually the ultimate in an Entertainers Microphone system (or for any roving microphone application for that matter!) All the annoying wire less microphone characteristics such as " drop out", static and no ise are comp letely eliminated by use of auto switching dual diversity receivers. The output of each receiver is conti nuall y monitored. with the strongest and clearest signal always selected . Dynamic Range exceeding 100 db is obtained by employment of a Patented special Parabola level compressor and Dynamic expander. The operating range Is a minimum of 50 metres (often this can be extended to 200 metres and more in norma l ci rcumstances) . Several Frequencies are available to aleviate cross interference when two or more systems are used in proximity. / /"; ' Brief Specification• Frequency 202.1, 202.5, 203.7MHz (Please specify if you have a preference) Mlc Carrier Power 50mW (Max) Mlc Antenna built-in Dynamic Range over 100db S/N Ratio better than 90db Frequency Reaponse 20Hz to 16KHz +or. 3db Mlc Battery 4 x AA cel ls Battery Life over 24 hours continuous operat ion. Receiver Sensitivity 12db/ mic ro volt for60db S/N rat io Preemphasll/De emphasis sous. Receiver output unbalanced 6.3mm phone jack and balanced 3 pin cannon type . Output Level (adjustable) Unbalanced 0-2.SV Balanced Oto+ or •.3V into 600 ohms. Receiver Power Supply 200 • 260VAC . Prices (A) Dual Diversity Receiver $729.00 (B) Entertainment Microphone (hand held type) (C) Lavalier Type Microphone $349.00 Frequencies C 0111 $349.00 iver and Bonus Offer SAV E $78 Choose Rece 1 ~~~~:!~1}r~ i ~ i ;ni; ~ ~ ~ ; i ~ i i iir ~; n~~ ; ;~; j ; : ~~:nnge~~;g in c 0113 C 0115 C 0121 C 0123 gi~i Dual Diversity Dual Diversity Dual Diversity Entertainment Entertainment Receiver Receiver Receiver Microphone Microphone 202.1MHz 202.5MHz 203.7MHz 202.1MHz 202.5MHz t:~: !:~ ~!~~~~~~~: !gH~~; l\!\lll\1!11:J:rm er ... 1II IIll IIIIIIll 1111111111111111'1111111111111111111111 III IIIIII I111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 IIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII :..·_·_, Wide Range Weatherproof Extension Speakers For Your Stereo System AT LAST Design Quality Weather Proof Speakers I\ ::i:.1:.;~r.::~~~cklf~ i~~Jfl~r~~r~ f}~1~~]1~~is;~ii:rt. • !·~~Jj}!~!~!~:i ~;~f~~Et~ 1.~1r~:~~~;; ,;1~~~~.~:r: 1 0 ~ Pool, Games Room,: :'·:·-···· · :.J Den, Pool Room Etc.·. · · ) ::: Dimensions 260mm wldei,.:,.,.Jj,;,,,,,,,j)' x 170mm high x 150mm D. ·,· Mt··:••::--(Mounting brackets are .- H. . . . sound reproduction outdoors. The Five Models to choose from "Fill the Bill" from app lications on boats to high grade paging and music entertainment installations. RUGGED EXTRUDED CONSTRUCTION These vibration free enclosures are constructed from die extruded heavy gauge aluminium and finished with . incredibly durable industrial powdercoat :: enamel. The speaker ends are sealed via :: gaskets and tough mou lded "LU RAN S" UV ,: resistant end caps. The end result is .. Good ::, Looks" together with assured rugged :;: durability for the Australian environment. i EXCELLENT REPRODU CTION \:: The drivers have been chosen for wide range, low distortion, mid range" presence" (essential for high grade vocal work) and high efficiency in general. Power Capacity for short term use, the drivers will safely handle 150% of rated power. Acoustic wadding is used to dampen Bass resonance. Weather Proof Construction := and use of "Doped Conea" Foam plastic ,: and cloth is sandwiched between Baffle ,: and Front Grill to prevent water ingress. A :;: first for Redford is the use of a patented :=:-:-:-:-:-:-:.- cone moisture repellant process for all :':':':::':':::: models. :i :, { :; ,; :: ,: 1, . gg~1~ ::~~ ::::: :~: ::~ ;::~ 'tt:)';!=tttt 20 Watt 8 Ohm (Max 30 Watt) Use 2 special dual doped cone drivers for those wanting a bit more umph! C 0943 C 0944 Black White $139ea $139ea $260 per pair $260 per pair I!!!\!i!!!!:ll!:::::::1:11:::11!!! l!!\\!iii\li\l\lll\!:!!~i!l!i\\l\ . ~:: !l llll-&B 111111111 1111111:IIIS :111 l :l l &1::~~ 1 1 120W Public Ad Am llfle Hi Fidelity Specification 30Hz • 30KHz Freq.Response Less than .3% Total Harmonic Distortion :•: FM.Stereo1Transmltter This professional quality public address amplifier offers performance equal to or better than commercial units at about half the price. Ideally su ited for halls, churches, clubs and even temporary setups. Inputs 2 balanced mic with 3 Pin XLR connectors.: 2 auxiliary suitable for direct connection to C.D. tuner etc. Outputs 4 Ohm, 8 Ohm or 100V line output configuration. (See SIiicon Chip Nov'88) K5020 s499 ~l~l~t·I ;:,?:i~f amplifier is suitable for testing virtually any audio d ev ice. Feature1:lnput capability from 10mV to 10V • Inbuilt spea k er, ove r lo ad indicator and external speaker s o cket. • Requires Extern a l !H 5V AC supply. K 2100 s65.oo Save $200 Or More On Commercial PA Amps RF Detector Probe (See EA May'88) This simple RF probe is ideally suited fault finding and trouble-shooting in AM radios. Feeds directly in the input of an audio amp. Requires external supply. Ideally suited for use with the K 2100 Bench Amp. K 2565 s12.oo Power Transistor Tester (See EA May'88) Hand select translator for power output stages. This tester has been designed specifically fo .r bipolar transistor with a continuous collector rating of at least one amp. Super simple operation allows for testing of current gain and Vbe of all popular power transistors. Suitable for both N.P.N and P.N .P. types. . K 2532 s24.es LED Light The House Number Identify Your House • Build The LED Light. (See Slllcon Chip Oct'88) The LED light m akes y ou r hou se easily recognis a bl e at night by illuminating your house number. Great for pe ople vi s it ing , eas y for tax is and em e r gency services to locate you at n ig ht. A n y n umber can be configured incl u di n g A lp hanumeric combination s. A u t omat ic operation w orks only at n ight. Au t omatic s w itch off app rox. 4. 5 hrs. 64 LEDS su pp lied. K 1960 s59.es Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept . Sydney (NSW Only) Colin Fobister 437 4077 Perth 09 328 2199 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 ALTRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. PI- ■-■ Not■: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catal,>gue - in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don't forg■ t our Expr■H Mall and Phone Order Service • for the coil of ■ local c■ II , Bankcard, Yiu or Mnterc■ rd hold■r ■ c■ n phone order for um■ day d■■ p■ tch. STANDARD DELIVERY I PACKING CHARGE $4.00 lo 1Kg $7 ow■r 1Kg AUSTRALIA WIDE - We process yo ur order Iha 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 you r order the day rece ived and despatch via. Ow■rnlghl J■ t■■ rvlc■ Courter for delivery next day Country areas please allow additional 24-48 hours. Weight limit 3Kgs (3Kgs covers 95% of Orders) . $10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDER - Bankcard ,Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our o..rnlghl J ■t ■■ rvlc■ we deliver next day. WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esper an c e Commun ica ti ons 7 13344 GER AL DT O N K.B .Electronics & Marine 212176 KALGOORLIE Toda y s Electroni c s ■ 2 1 2 777 KARRATHA Da v es Os c itr on i c 854836 MAN DU RAH Lance R ock Retravision 351246 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Asco m Elect ro n ics 52 1713 Far mer Electronics 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Com ponents 6623506 SOUTH MELBOURNE Winscott Trading 6995740 SUBURBAN CHELTENHAM Talking Electronics 58 42386 CRO YDE N Tr usc o tt El ec tr o ni cs ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 M OR WELL Morwell Electronics 346 133 QUEENSLAND CITY Delsound P/ L 8396155 SUBURBAN CAPALABA David Hall Electroni cs 3902399 FORTI T UDE VALLEY Eco no mic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUN DABERG Bo b Elk ins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 ROCK H A MPTO N Access El ect r o ni cs (E a st St.) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Sole x ■ 72201 5 SA CITY Electronic Co mp & Equip . 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 37705 12 CHRISTIES BEACH Force Elect ro ni c s ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electron i c s ■ 347 11 88 LO N SDALE F orce Elec tr on i cs ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBAR T George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 267 1385 CARINGHAH Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantron ics 609721 8 COUNTRY CO FFS HARBOUR Coifs Habour Electronics 525684 NELSON BAY Nelson Ba y Electronics 81 3685 NEWCASTLE No voc ast r i an l; lect.Su pp lie s ■ 62 1358 NOWRA Ewing El e ctronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electroni cs 775935 WOLLONGONG Newtek El ectronics ■ 271620 Blue Ribbon Dealers are highlighted with a ■. These Dealers generally carry a comprehensive range of Altroni c products and ki ts or w il l o rder an y req uired item for yo u. Copping it right in the neck As a disgruntled colleague once commented, the worst thing a TV serviceman has to deal with is the customer. While unfair to the majority, I have to agree that a few can be very frustrating. They either don't trust you, insist that they know what's wrong, provide vast quantities of irrelevant data or, worse still, cover up the truth. Those thoughts were prompted by one of the most unusual and puzzling experiences that I have encountered for a very long time. In fact, it was like nothing I have ever encountered before. More to the point, it has left me wondering whether my trust in an old and valued customer has been misplaced. The set involved was a General GC181. It was sold to the customer by one of my dealer colleagues in January 1979, making it close to 10 years old when this incident occurred. I covered the warr~ilty service for the set and have serviced it ever since. The truth is it has not needed much attention, having developed only two serious faults in that time. The first one involved a total failure and turned out to be a fairly common fault in this set. There is a 0.1µ,F 1000V capacitor across the mains at the switch and this is prone to breakdown, taking out the main fuse. But this can be a trap for young players. The type of capacitor used is often one of the self-healing variety and when the serviceman examines the set, there may not be any obvious fault which caused the fuse to fail. In desperation, he may be tempted to simply fit a new fuse and put the set back into operation. The catch is that once these capacitors fail, the chances are that they will fail again in a very short time. So the customer is saddled with a nuisance call within a few months, or even weeks, and the serviceman's reputation suffers accordingly. The correct procedure is to replace the capacitor, preferably with a more reliable variety. The other fault occurred quite recently. The customer complained of poor picture quality and this turned out to be loss of focus· another common problem with thi~ set. This is due to failure of the focus pot, caused by internal arcover and resultant destruction of the element. I fitted a new focus pot and all was well. But these are asides, even though mention of them may possibly help some readers. The real story is yet to come. The owner Front view of the General GC181 set, showing how the phosphor was stripped from the screen. Note the damage to the shadow mask which is visible behind it. There was a lot of damage to the chassis as well. 54 SILICON CHIP But first a few words about the owner because this is important to the story. He is a bachelor, now retired, who lives alone. I first met him when he bought the set and we have met socially on many occasions over the years. In short, we have become quite friendly. For his part he turned out to be one of those intensely loyal customers who boasted that he would never let anyone other than myself ever lay a finger on his set. Such loyalty can be both touching and embarrassing; the more so because it may be difficult to justify. (I'm really a very 'umble person). This rear view shows the broken tube neck and the gun facing in the wrong direction. The gun has been re-positioned slightly to give a clearer picture but is essentially as I found it. happened at that stage but one thing was obvious: the tube had So that is some of the background been "let down to air" with a rush; against which this story is set. It a rush so great that the air had began when the customer phoned stripped the phosphor from the me to say that the set had screen and propelled some object developed what he described as "a against the shadow mask with conblack flower in the middle of the siderable force. screen". I did a bit of a double take My guess was that this was the on that, trying to visualise what gun and that it wa s now lying inside kind of faulty picture tube voltage the tube at the bottom of the screen. would cause what I took to be a As it turned out, I was only half dark patch on the screen. Not havright. ing much success, I simply said I'd My first step was to remove the be around to look at it as soon as plastic back from the cabinet and possible. · try to work out what had happened. What I found, of course, was This ba ck is held on with seven something quite different, and I screws: five machine screws which have no doubt that the reader is · mate with metal inserts in the way ahead of me. One glance was cabinet woodwork and two self tapsufficient; the phosphor had been ping screws which mate with the stripped from the centre of the antenna terminal panel. I mention screen in a roughly circular patch this because it is significant in about 12cm in diameter, with jagg- regard to what comes later. ed edges which had reminded the A proper mess customer of the petals of a flower . I found myself looking at a right Through this opening could be proper mess. The neck of the picseen the shadow mask and it was ture tube had broken off behind the also in a bad way. It had been hit yoke, about where the purity from behind, with a prominent dent magnets sit, and was lying in the in the centre and a vertical split almost as long as the diameter of bottom of the ea binet. But the real surprise concerned the "flower". the gun. I had no reason to doubt it I didn't know exactly what had Black flower had hit the shadow mask but I was wrong about it sitting in the bottom of the tube. It was sitting in what was left of the neck but - and this is the weird part - the front of the gun, which normally .faces the screen and carries the getter assembly, was pointing out of the back of the neck. The accompanying photograph illustrates this better than words. So what had happened? On the face of it, it appeared that the gun, either before or after it hit the shadow mask, made a 180° turn and came out the tube front-end first. And significantly, subsequent examination of the gun revealed that the pin end had been very severely mutilated. So had this hit the shadow mask? That was not all. The neck board had of course been separated from the gun as the latter shot inwards and had been broken in two as well as suffering some other minor fractures. I made a mental note that if necessary, it might be possible to repair it, assuming no replacement was available. But what really caught my eye was a metal bracket at the right hand end of the chassis. This is made from 1.2mm (18 gauge) mild steel and is about 19cm high and 15cm wide. It supports the tripler, an aluminium heatsink for the power supply chopper transistor, and sundry minor components. And it had obviously been dealt a pretty solid wallop, which had given it a severe twist. Once again, the accompanying photograph tells the story better than words. There didn't appear to be any damage to any of the components on this panel but what intrigued me was how it had been bent. The panel is quite substantial, so much so that an attempt to straighten it by hand was abandoned. I'm not saying I couldn't have done it but it would have been a painful exercise. Rather than speculate, I turned to the customer for clarification. When had this happened and how? He shrugged his shoulders. All he could tell me was that he had used the set one evening, not bothered with it the following morning, gone to his golf club for lunch and a round of golf in the afternoon and JA NUARY 1989 55 : ' \ \ " =-'- lt?f!l//i \.\~'t) Spontaneous implosion Which didn't help much. It could have happened at any time over a period of some 18 hours and there was no indication as to how it had happened. On this basis I had to assume it was a case of spontaneous implosion, even though I had never known a tube to implode in this manner. From the faceplate, yes; but not from the neck. And if it was such an implosion, how could this account for the damage to the metal panel? As far as I could see the only "missile" that could have caused this was the neck board, thrashing around on the end of its cables after it become detached from the gun. But as can be seen from the photograph, the SILICON CHIP ' . ~1~;;~~~-:.~~;~:-:--.. . .-" NE.VS:.R \<.NOWN A -rue£ 1~ T'-IIS MANNE~ discovered the damage only when he went to turn the set on for a 6 o'clock news session. 56 "-=...._"''""" . ~~ ... ~ J't I. ,, panel is bent towards the picture tube neck, so that it would have had to have been a whipping action to bend it that way. One problem with this theory was whether there would have been enough room for all this action, with the cover in place. There certainly would not have been while the tube was intact but it might have been possible after the neck broke off. Another problem concerned the simple ballistics of such an action. Could something as light as the neck board acquire enough kinetic energy to bend such a substantial piece of metal? Sure, there was a neat puncture in the plastic cover on the neck board which could be made to mate up with the top corner of the panel, supporting the idea of an impact between the two. But there for the moment was -- -~-- --· .J. ...·c.,, __ .. ' ' \ \ \ <at>.\~(. ,...0 where I had to stop speculating. The customer brought me back to earth with the obvious question, "Is it worth fixing?" I did a few mental calculations. There was the cost of a new tube, with no allowance for the old one, the cost of fitting it, and repairs to or a replacement for the neck board. Allowing for any other minor damage but assuming there was nothing serious, I came up with a ballpark figure of $400. I added that if he decided to go ahead, I would need to make some more tests and checks before risking the cost of a tube. But he cut me short. "It's not worth it. The set is 10 years old. I'd rather put that money towards a new one. You can have the old one for bits if you like." So we left it at that. I loaded the set into the van, took it back to the shop and arranged to get photographs taken. Then I decided to take a closer look at it, for a couple of reasons. First, I thought that it might be possible to salvage the set, at least on personal basis. If I could score a tube, perhaps from a set written off for other reasons, I might have a set good enough to use as a monitor, or even to donate to the local retirement village charity. Second, I was still puzzling over how the damage had occurred. Perhaps a closer inspection might provide a clue. So a few days later, during a slack period, I made an effort to fire up the set. At least I hoped to get sound out of it and confirm that most of the circuits were working. Also I wanted to measure the EHT to see whether it had gone high and possibly punctured the tube. This is not unusual, though I have never known a tube to disintegrate for this reason. Dead as a doornail But the set did not respond; it was quite dead. I checked the mains fuse and found it intact, so I decided to slip the chassis out for a closer look. This is quite easy, it being held with a couple of simple plastic clips. In fact, the chassis is little more than a rectangular metal frame which holds the main (mother) board horizontally in the bottom of the ea binet, the whole assembly measuring about 33 x 20cm. And this provided the next surprise. It was just as well the customer had decided to cut his losses because there was no way that the set could have been salvaged. In order to understand what had happened it is necesary to describe this part of the set in some detail. To the left of the picture tube, sitting above the mother board but with their lower edges almost in contact with it, is a nest of four vertical boards held in a plastic frame attached to the rear of the chassis. From the left these are the chroma board, video board, vertical board and the horizontal board. They are all 80mm high and range from 120mm to 75mm long. ' [ c,w;;,,,,&,,., , , :Iii This picture shows the top edge of the bracket, to the right of the tube, and the manner in which it was bent. Note that it has been bent towards the tube which only adds to the mystery. And at least one of them had received a mighty wallop on its upper edge, forcing it down against the mother board. The vertical boards appeared not to have been damaged, but they had made a horrible mess of the mother board. It was cracked from front to back, with another crack extending from approximately the centre of the main crack to the left hand edge. There is no way that the board could have been salvaged; it was a write-off. All of which served only to deepen the mystery. What had struck the blow? As with the bent bracket, the most likely culprit seemed to be the neck board, TETIA TV TIPS Hitachi CEP288 Symptom: Very bright picture, no colour and retrace lines. Subbrightness control will reduce brightness somewhat, but not enough and still with no colour. Cure: Check voltage at Test Point 11, near the chroma delay line. This should be about 1 .5V. If it reads OV, suspect a short circuit to ground inside one or other of the transformers T552 or T553. thrashing around as a result of the implosion. But as before, it was hard to accept that it could acquire enough energy to do so much damage. It was all very puzzling. I had to admit that the theories I had evolved were not very convincing but were the best I could come up with if I accepted the customer's version of events. A cynical colleague Later, I had an opportunity to discuss the matter with a colleague and to show him the physical evidence. Being a cynical type and not knowing my customer, he had no doubts about what had happened. His theory was that someone had removed the back for what they regarded as a legitimate reason, such as looking for a fuse if the set had failed. Then while the set was in this vulnerable condition, an accident had occurred; something heavy had fallen across the back of the set, from right to left, first bending the metal bracket, then breaking the neck off the tube and finally forcing the vertical boards down onto the mother board and wrecking it. As he summed it up: "I don't believe that that kind of damage could have JANUARY 1989 57 SERVICEMAN'S LOG HOW 11-1£, e:A~S ])()tJT 6'!:.L.\EVE A WO'RO YOU T£.L.I.. HIM,•• NO,~ occurred unless the back had been removed". And I have to agree that on the physical evidence, such a scenario makes sense. But it just doesn't fit the personality of the customer I know. He would be the last person in the world to delve into the back of a TV set and he is adamant that there was no one else in the house at a time when this could have happened. Break and enter? Vandalism? The house was well secured while he was out and there was no sign of forced entry. In any case, what vandal is going to take the trouble to remove the back in order to the wreck the set and then carefully replace the back afterwards? And when I say carefully, I have 58 SILICON CHIP in mind those seven screws I mentioned earlier. Several do -ityourself types, as well as a few of my colleagues, have been caught out by these. Superficially they all look the same; same heads, same diameter, same length, same colour. So it is almost inevitable that the first time someone handles them they will mix up the metal threads and self tapping threads, with resultant thread butchery. But there was no such butchery. If the back was removed and replaced whoever did it was very careful or very lucky. It's not conclusive evidence but just one more puzzling factor. So which theory is right? Was it all the result of a spontaneous implosion, or was the set mucked about with? And if the latter, by whom? And why the secrecy? I'm afraid your guess is as good as mine. Murphy takes a holiday Well, after all that inconclusive theorising and speculating, here is something much more down to earth. It concerns two Sharp CX-1461 34cm sets, both with the same fault - well almost. An alternative to the above title could be: "The same only different" . In the first case the customer turned up at the shop with the set and complained that it was completely dead. Judicious questioning elicited the fact that it had been cranky for some time, in that it would not function when first switched on but could be made to run by operating the on-off switch several times. Once running it would give no further trouble during that run. As a result of this observation the customer inevitably concluded that the on-off switch was faulty. Naturally I doubted that it would be that simple and said as much to the customer. Whether I convinced him or not I don't know but he agreed to leave the set with me. And would you believe it, within hours of that encounter in walked another customer with the same model set and almost the same story: the set would function sometimes when switched on but not always. It also could sometimes be made to function by repeated operation of the on-off switch. And it had become more cranky of late and now had failed completely. Not surprisingly, this customer came up with the same diagnosis as the previous one; the switch must be faulty. I expressed the same doubts as before. Privately, I was daring to hope that both sets had the same fault. That would really put the day's work in the black - and give Murphy a good solid kick in the pants, to boot. In any case, it seemed like too good a chance to miss so I pushed the other jobs to one side and selected the second of the two sets for a preliminary check. At first switch-on it was quite dead, at least superficially. On im- lcONrusTI 0 41 8 3CE [ t~ PF"2 R'!l2~ 1 . 71( ! l/2WI PWB - 0 DUNTKl77 Fl'!l2'!1 2,21< !l/2WJ Relevant portion of the CX-1461 circuit. Note the IC (IC701) which replaces the regulator transistor and associated discrete components. pulse I activated the on-off switch a couple of times and, hey presto, the set burst into life. Of course, it could have been a faulty switch but I was basing my doubts on the fact that I had never had to replace a switch in this model and that the switches used in most modern sets are particularly reliable. It is several years since I had a switch failure and that was in an old Decca model 33. Supply problem So, putting aside the switch theory for the moment, all the indications were that we had a power supply starting problem. And significantly, once the set was running it produced a first class picture, right up to standard in every respect. The idea that it was a starting problem reminded me of my story in the November 1988 issue of SILICON CHIP, involving another Sharp set, the slightly later CX-1480 model. It too had a starting problem. My recollection was that the two circuits were similar and I wondered whether this was another case of 120kn resistors going high. Unfortunately the manual showed that the power supplies were quite different and that the 120k!J resistors did not even exist. The manual did devote a couple of pages to a description of how the power supply worked and this looked promising at first. But that promise was not fulfilled. The explanatory circuit used differed from the main circuit in that a number of components were omitted. And the text, as well as mixing up some terminal connections, was written in, at times, incomprehensible Japlish. The main thing I learned was that an IC (IC701, IX0205CE) was used in place of the usual regulator transistor and associated components. This combined three transistors (error detection, driver and switching transistor) plus the reference zener diode and four resistors in a single TO3 package but with four terminals. So much for the theory. It was time to pull the chassis out and make a few measurements. When I switched it on this time it refused to start, which was actually a help. The first check was the voltage out of the main bridge rectifier, across the 22µF electrolytic, C708. This proved to be normal, thus ruling out any lingering doubts about the switch or other components up to that point. From here I traced the voltage up to pin 2 of transformer T701, then to pin 4 and finally to pin 1 of IC701. continued on page 66 JANUARY 1989 59 In January? OK, so we couldn't wait! Grab a kit bargain now and save 25% AND six months. YOU REAP THE BENEFIT! Low Cost MOSFET Amplifier Module IR Remote Control Stereo Preamp Try this one for size: AEM's 60 watt mosfet amplifier module. 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Cat K-3429 $74S WAS $9.95 The 50 ohm attenuator kit gives you up to 63dB attenuation in 1dB steps from 50 to 500MHz. cat K-6323 WAS $69.95 $ NOW 5245 ~ 60 Stores Across Australia Head Office & DSXpress Order Centre: Phone f021 888 3200 • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • Campbelltown (046)27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Goslord 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • MalHand 33 7866 • Miranda 525 2722 • NewcasHe 67 1896 • North Ryde 88 3855 • Parramatta 689 2188 • Penrith (047)32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Warrlngah Mall 905 0441 • Wollongong 28 3800 •ACT• Fyshwlck 80 4944 •VIC• Ballarat 315433 • Bendigo 43 0388 • Box Hiil 890 0699 • Oandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richmond 428 1614 • Ringwood 879 5338 • Sprlngvale 547 0522 •OLD• Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • Townsvllle 72 5722 • Underwood 341 0844 • SA • Adelaide City 232 1200 • Beverley 347 1900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enlleld 260 6088 • WA • Cannington 451 8666 • FremanHe 335 9733 • North Perth 328 6944 • Perth City 481 3261 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 . THE WAY I SEE IT By NEVILLE WILLIAMS Feeling really crook? You may need an electron transfer! If you're curious about the above heading, move over. After reading a brochure referred to me by a NSW reader, so am I! "Biological electron transfer" might herald a whole new concept in medical treatment - or it may simply be a further debatable example of a century-long pursuit of the supposedly therapeutic properties of electricity. It seems likely that the reader who forwarded the brochure was reacting to discussion of another health matter in the September issue under the heading"Could We End Up Drinking Nickel-Cadmium Cocktails?" It had to do with an interview, brought to my notice by T. A. of Par- .· ramatta, NSW. Visiting Canadian environmentalist, Dr David Suzuki, had claimed that used nickelcadmium batteries should be recycled, to prevent their contents from becoming an environmental health hazard via council garbage tips. While not necessarily rejecting Dr Suzuki's warning, I said that I could find no support for his concern in technical literature, or by academics : or the battery companies themselves. Nor have any readers, since then, taken up my invitation to shed further light on the subject. I wonder whether they/you will be more forthcoming on the supposed therapeutic benefits of electricity? This time around, I am indebted to I. H. of Port Macquarie, on the north coast of NSW. To a letter, 62 SILICON CHIP directed principally to Leo Simpson, he adds the following footnote: Enclosed is a pamphlet from a supplier of vitamins, etc, detailing their latest wonder material germanium. I think you or Neville Williams could write a very good article on the claims made for this substance. On receipt of the above, my first reaction was to look out another "medical" pamphlet which had come my way recently, via the letterbox. Reading and comparing the two, I began to wonder how old the apparent interest might be in the supposed benefits of electrical. therapy. Seeking a possible clue, I searched through a century-old article by Andrew Wilson PhD, FRPS, &c (Edinburgh and Glasgow Universities) entitled "Nerves or No Nerves, or the Art of Feeling". Andrews admits to being at a complete loss in trying to explain nerve action, attributing it only to some as yet unknown mechanism which he thereafter refers to as ''nerve force". I quote: " ... a mechanism so subtle and incomprehensible, that the greatest authorities of our day own their in- ability to solve its depths, and admit their helplessness with the best possible grace." Overlooked or ignored? There is no hint in the article that "nerve force" could have anything to do with electrical phenomena or that nerves and/or muscles could respond in any way to electrical stimulation. I found this intriguing, to say the least, because in 1791 Luigi Galavini, Professor of Anatomy in Bologna, Italy, had published his paper "Animal Electricity or Galvanism", detailing his memorable experiments with frogs legs. Five years later (1796), Allessandro Volta had suggested an apparent link between Galvanic electricity and that produced by chemical means. How or when academics like Andrew Wilson and/or neo-medical entrepreneurs caught up with these century-old observations I'm not sure. But I do know that, in the early 1920s, my grandfather showed me a do-it-yourself medical gadget that he'd bought some years previously to treat rheumatism, gout, lumbago, sciatica, arthritis or whatever else, of that nature, people suffered from in those days. I can recall it only as a clinical looking black box, complete with knobs, switches, fabric-covered leads, nickel plated pads and hand grips. When connected to a battery, it buzzed audibly and produced high voltage electricity which could be applied to the body or between the hands, as per the instructions. ponded with a writ for one million dollars in damages, returnable in the state of Texas. When he had not proceeded with the action twelve months later, RADIO NEWS repeated the allegations and backed them up with a detailed technical report on a Kiro-Vox, which they had managed to acquire in the meantime, complete with the maker's official instructions. A "squegging" oscillator The circuit of the "Kiro-Vox", as published by "Radio News" in December 1925. While it contains two variable capacitors and two variable inductors (variometers) it is basically very similar to a 1-valve regenerative receiver. One could feel it doing its job (it produced a tingling sensation, anyway) but whether it was more beneficial than other contemporary treatments seemed to be open to argument. I refer to patent medicines, patent liniments and that incredible procedure of exposing one's bared rump/hip/thigh to "injections" by a jar full of angry bees. Yes, my grandfather resorted to this on a number of occasions, but · whether apis mellifera (bee) therapy cured the original pain or merely masked it was equally open to question! A "pure swindle" While there have been doubts about the therapeutic merit of beestings, potions and old-time electric shocking coils, there was certainly no indecision on the part of the (American) RADIO NEWS staff, in December 1924, when they reported on two "wonderful" new diagnostic instruments: the "Neurophonometer" and its electrically identical twin called. the ''KiroVox" - apparently derived from "Chiro". According to RADIO NEWS, both were being "foisted on the public" by a so-called Doctor Rogers and both, they said, were "pure swindles". Their opinion was based mainly on pretentious claims and explana- tions, presumably intended to attract the public and self-styled practitioners, but which made no technical sense either to RADIO NEWS laboratory staff or to qualified physicians and surgeons, from whom they had sought medical opinion. The purported role of the new instruments was to help physicians locate "impingements and sublaxations" - the latter (according to Webster's dictionary) signifying a partial or incomplete dislocation. They were said to achieve this by measuring the resistance of the nerves and so locating the point at which there was a constriction of the "life flow" - whatever that meant. Apart from anything else, the idea of being able to isolate and measure nerve resistance by way of external pads and contact probes defied common sense. Any indication so obtained would depend primarily on contact/skin resistance and on the total body resistance between the contact areas. RADIO NEWS rounded off the first article with an offer of $1000 (a substantial sum in those days) plus all expenses if the builder of the device(s) could demonstrate to a panel of qualified scientific and medical authorities that his equipment had a genuine therapeutic value. To this, "Doctor" Rogers res- As indicated by the accompanying circuit, it appeared to have been contrived from a contemporary 1-valve (UV-201A) regenerative receiver, with enough bits and pieces added to account for four 0-100 panel dials, plus a meter showing battery voltage, a filament rheostat, binding posts, &c. Assembled on a panel, mounted in a black carrying case with removeable lid, and plugging into a separate power supply (battery) box, it looked sufficiently convincing to boost the standing of a practicioner lacking more formal qualifications. A larger than normal grid capacitor (.005µF instead of .00025µF) ensured that it would be prone to grid blocking or squegging, and the multiplicity of controls provided the opportunity for any amount of pretentious fiddling to set the audible squegging tone to the desired frequency. Setting up involved clamping a pad to the patient's forehead, placing the search electrode on the skin under the occipital protuberance and adjusting the oscillation tone to a "singing" sound, like a "high pitched tone from a horn", not "coarse like a foghorn". This procedure was described in the instructions as "tuning the patient in". This done, the diagnostic procedure involved searching down the spine until the oscillation stopped and drawing conclusions about the impingements and sublaxations by noting this position and also doing some calculations based on the 0-100 dial readings. Pure buncombe RADIO NEWS described all this as "the purest buncombe, just simply JANUARY 1989 63 THE WAY I SEE IT - CTD bait for the gullible .. . if the ludicrousness of it all does not strike you, we give up!" Whether the Kiro-Vox and Neurophonometer survived the acrid criticism by the late Hugo Gernsback and his team we have no way of knowing but we have not heard of any more such devices since then. On the other hand, high voltage shocking coils or pulsers are still with us in a variety of forms, mostly transistorised, and recommended in sales brochures for the treatment of lumbago, sciatica and arthritis; head, neck and back pains; tendonitis, muscle and joint pains; sporting injuries and post operative and amputation "phantom" pains. Some are supposed to be used in conjunction with acupuncture points - and at that point I give up. If the medical fraternity itself is at odds about acupuncture generally, how is a mere layman to decide whether it makes sense or otherwise to stimulate acupuncture points with a needle, a digital wavetrain, or the field from some gismo containing a powerful magnet? It so happened that, while writing this, I met up with a friend who was wearing an electronic pulsing device on his belt. After explaining what is was, he confided: "The physio suggested I try it but whether it's doing me any good, I wouldn't have a clue" . Shades of the 1920s! Technical jargon If the story of the Kiro-Vox emphasises nothing else, it certainly does draw attention to the use of pretentious technical jargon, capable of impressing a layman but making little sense to a technically informed reader. That brings me back to the pamphlet forwarded to me by I. H. and the notion of biological electron transfer whatever that signifies. The bold heading reads: "Germanium - one of the most exciting health-giving substances ever discovered". The pamphlet goes on the say that it was used in the USA in 1922 to treat anaemia, and subsequently by the Russians for its "unique" rejuvenative properties. This, despite the fact that germanium is normally regarded as being highly toxic. Nothing daunted, and allegedly funded by the Japanese Government, an "inquisitive engineer" , Dr Kusuhiko Asai, was intrigued to find traces of germanium in coal, in living plants, and in many natural food products. But the richest sources of all, says the pamphlet, were healing substances such as Ginseng, Shitake mushrooms, aloevera, comfrey, garlic, and shelf fungus - the last-named said to have been valued for centuries by the Russians as a treatment for cancer. Where have I heard those words before? Oh yes, I almost forgot, and I quote: "not surprisingly, analysis of the healing waters at Lourdes, France, also revealed a high germanium content". (What, no miracles?) Admittedly, all this is outside my area of expertise but I find the inferences and the logic distinctly tenuous. I wonder how many other elements might prove to be common to those same sources, if one really went looking for them. As it is, Dr Asai is said to have climaxed ten years of research with the development of a safe, nontoxic compound which he called Ge-132 (biscarboxyethyl germanium sesquioxide). With a name as long as that, it ought to be able to kill or cure just about anything! Nor was the good doctor troubled either by doubts or modesty. According to the pamphlet: "Dr Asai hailed Ge-132 as a miracle cure for everything from headaches to life threatening conditions". Lest the reader still entertain any lingering reservations, the pamphlet seeks to reinforce the therapeutic claims by associating them with germanium the "powerful semiconductor", which provide ed the basis of the first transistor in 1948. This on the basis of "germanium's electron transfer properties as an agent of human health" . The way I see it Here I'm on more familiar ground and I fail completely to see any logical connection between the two disciplines. As mentioned in recent articles, nickel, cadmium and mercury are all very useful in electronics for promoting and supporting the movement (transfer?) of electrons but that doesn't imply potential curative properties; on the contrary, they've all been nominated as potential health hazards. Even as a semiconductor, germanium is only one of many such materials and none of them is particularly adept at "transferring" electrons. Copper does it ever so much better, with its inherently low resistance to current. (Oops - I nearly said current flow)! In Australia alone, there must be countless millions of kilometres of copper wire, "transferring" electrons endlessly hither and yon. Then again, if a semiconductor is necessary for whatever it is supposed to do as an "agent in human health", why not an organic compound of silicon, which has proved to be far more useful electronically than germanium? But no, the pamphlet is adamant: " Teamed with oxygen, germanium hones our natural defences, So if you're feeling really crook, don't sit around hopefully nibbling OC44 transistors. Take the advice of the TV pill adverts & "see your doctor" 64 SILICON CHIP helping the body protect itself. Through its specialised electron transfer ability, germanium works with oxygen to maximise cell energy. And when the work is done, the unique structure of organic germanium enables it to help oxygen clear out the debris: spent electrons". Debris? Spent electrons? What on earth are spent electrons? The mind boggles. I've been involved in electronics for sixty odd years and never as much as heard of them. What's more, when I mentioned the term to some technical friends, they just guffawed. If I'm not careful, one of them will end up trying to convince me that spent electrons are the ones left behind in low-emission TV picture tubes: worn-out, tired, listless electrons that can't quite make the distance to the phosphor screen! I. H. 's pamphlet, I'm afraid, presents much the same sort of credulity barrier that faced Hugo Gernsback back in 1924/25. So if you're feeling really crook, don't sit around hopefully nibbling OC44s (a once popular Germanium transistor). Take the advice of the TV pill adverts and "see your doctor"! Mains supply radiation To change the subject, the same letter in the September issue (T. A., Parramatta, p.22} made passing reference to "alleged radiation" from 50Hz power wiring and from such things as domestic electric blankets. I tended not to take his remarks too seriously, on the grounds that no ill effects have been positively identified in the home, while arguably hazardous industrial and medical situations are subject, these days, to fairly close supervision. It was with interest, therefore, that I came across a paper on the general subject in the latest issue of the IREE/IE Aust. Proceedings. I quote the full title for those who may be able to gain access to it and, as well, to the many references listed by the author: Journal of Electrical and Electronics Engineering Australia; Volume 8, Number 3, September 1988: "Power Lines and the Environment - The Electrical Impact" by K. J. Callaghan. The author is a senior engineer with the Queensland Electricity Commission, responsible for power line projects in the southern sector of that state. By way of preamble, he makes some interesting points, at least one of which may have puzzled readers of the September article. (1). Discussion of this general subject involves both magnetic and electric fields but because they exist simultaneously, they are normally grouped for convenience under the one heading; hence electromagnetic interference (EMI), . electromagnetic compatibility (EMC), &c. (2). Because overhead power lines and street wiring are so visible and unavoidable, they tend to attract the more attention from environmentalists. In fact, higher magnetic fields are common in homes, and in industrial and medical situations. Train at home NOW for money making CAREERS IN ELECTRONICS · · · OMd .r~cure ~ /u(:u,re. -,,_ NOW, AT HOME IN SPARE TIME, you can acquire the necessary skills in Electronics to help you secure a guaranteed future. You need no previous qualifications and there is no need to change your daily routine . Study when and where you choose. The course is compiled by experts and skilled tutors are ready to guide and assist you. THE FUTURE IS ELECTRONICS. Take a look around you. Electronics control and guide our everyday lives. From Home Computers to Space Travel, from Microwaves to Robots we are part of an electronic revolution. This revolution will continue and many job opportunities will be created ... opportunities that are available to you. MORE THAN JUST ELECTRONICS MANUALS. ICS courses are more than just 'Do it Yourself' manuals ... they are complete, comprehensive programs designed to give you the skills and knowledge necessary to succeed in your ambitions. And you receive at no additional cost ... yours to keep, all the equipment necessary to ensure that you have a complete and thorough understanding of Electronics through actual hands-on experience. ICS Australia 398 Pacific Highway, Lane Cove, NSW 2066 ~ Sydney: 427 2700 or Austwide (STD FREE) (008) 22 6903 Reviewed by the National Magazine, Electronics Australia as being extremely accurate, practical and very reasonably priced as well as giving an excellent background to anyone wishing to take up a career as an electronic~ technician . Don't delay ... complete and mail the coupon TODAY! SEND FOR FREE FACTS! - - - - - • Courses not generally suitable if age under 15. - norn DlJo[l) AUSTRALIA - - SC119 - , ....,, - /-'\ --~.- Mr/Mrs/Miss--,-,- - - - - - - - - - - - Age _ _ _ Address _ __ _ _ (Please pnnt clearly) _ _ _ _ _ _ _ __ __ _ __ _ _ _ _ _ _ _ P/code _ _ _ _ _ Phone _ _ _ _ __ TICK ONE □ Basic Electronics D Digital Electronics I I I ~, ,~! Department of Electronics 398 Pacific Highway, Lane Cove, N.SW 2066 □ Industrial Electronics I I I I I II ~---------------------~-----------------------~--~ D Complete Electronics Technician JANUARY 1989 65 · THE WAY I SEE IT- CTD (3). Applied to power lines and equipment, the term "radiation" has connotations of an implicit hazard by association with nuclear and high-power RF energy. In fact, 50Hz energy has a wavelength of around 6000km, and any "radiation" detectable within several hundred metres of the source is a near-field phenomenon and should be regarded as such. The author quantifies the magnetic and electric fields at ground level under typical high voltage transmission lines, pointing out that they tend to cancel down with proper design and phase balance. They are normally small compared with the Earth's static field and the electric fields present in thunderstorm conditions. In private homes, the 50Hz magnetic field can be greater than under power lines, especially near certain appliances and neutral/ earth links. A high, though not necessarily hazardous, electric field exists close to some electric blankets, according with our advice in the September issue to avoid leaving them switched on for long periods while you sleep. Nature, man-made and us On the subject of "Field Effects on Natural Ecosystems", Callaghan acknowledges some critical reports but suggests that they are mostly flawed. Serviceman's Log - SILICON CHIP It has been claimed, for example, that the growth rate of certain species of trees adjacent to high voltage lines is accelerated but this could be the result of opening up the easement area. Equally, a conflicting observation that the growth rate is sometimes retarded could be due simply to residual corona damage to the tips of the foliage. Bird migratory patterns do not appear to be affected by the field. Small animals are partially shielded from the electric field by the ground cover; for large animals, the changed forage conditions appear to be more significant than field effects. The performance of honeybees appears to be diminished somewhat by high electric fields but this can be mitigated by shielding the actual hive. And so on. His conclusion: "There is currently no scientific evidence of any environmental effect of 50Hz electric and magnetic fields on nature, above the negligible level". In the area of interference with man-made systems, the power line engineer has an admitted responsibility to minimise arcing and corona effects, which could affect communications systems. As well, due attention must be paid to possible magnetic and electric induction, earth current loops, &c. The latter section of the paper deals extensively with "Field Ef- ctd from page 59 So far, so good. At this point it appeared that with only a few components likely to be involved, a check of each component in turn might be the best approach. Remembering the faulty resistors in the CX-1480, I began by checking the resistors. R710 (along with diode 709) was disconnected first, then R709, R705 and 706. All checked OK. The next suspects were the electrolytic capacitors. I lifted C713 (100µ.F) and it checked OK. Then I lifted and measured C711 which connects to pin 4 of IC701. Supposedly 3.3µ.F, it measured only 66 . about 0.1µ.F. Eureka! Yes, that was it. A new 3.3µ.F capacitor was fitted and at first switch-on, the set came good immediately. And it continued to do so for a large number of switch-on cycles. I considered the point proved. In fact, I can now reveal that that particular capacitor is not even shown on the explanatory circuit mentioned earlier. Dare to hope So, one down, one to go. Dare I hope? Naturally I went straight to that capacitor. I unsoldered one pigtail from the board and as I fects on Biological Systems" and it is clear from the references that the author has taken due account of available literature. While a great deal of research has been undertaken since the 1960s, the findings again tend to be inconclusive. This despite the fact that, after 3-4 generations of exposure to power line fields, possible acute effects should have become selfevident. No long-term effects have ever been confirmed and no mechanism has been suggested whereby such long-term exposure could induce problems . Callaghan's overall summary: "Currently, the overwhelming opinion of the world's scientific/ medical fraternity is that long-term exposure to power line fields has not been shown to constitute a biological hazard to man". All this may be reassuring but is it the final word on the subject? Can we rest assured that she really will be right mate? I don't think so. If I'm conservative about miracle cures - Kira Voxes, shocking coils, organic germanium, &c - I feel much the same way about the environment. Even with the best of intentions our understanding of the environment is never quite unbiased or complete. The way I see it, in the pursuit of scientific achievement and technological progress, it's not a bad philosophy to always err on the side of caution. ~ lifted that end, the capacitor came clean away; the other pigtail was corroded where it entered the body and had obviously been making intermittent contact for some time. A new capacitor restored the set to normal operation, all in a matter of minutes. You don't get many breaks like that; Murphy will have a heart attack if he finds out. But as I commented earlier, the two faults were the same only different; the same capacitor but faulty for different reasons. The first capacitor had simply died of old age - a common fault with low value types - while the second one might well have retained its capacitance but suffered a broken lead. ~ WOO D FOR CHIPS ... WOOD FOR CHIPS ... WOOD F OR CHIPS ... WO OD F OR CHIPS .. . WO OD FO R CHIPS ... WOOD F OR CHIPS ... WOOD FO R C NEW - A,r onditlon NEW - Shop Layout omfort Half Price Opportunity To make room fo r all our new product we have refitted ou r shop. D rop in and see us som etime. From our buk store we have selected a range of products to otter to you at around hall our normal price - ,n some cases less than haN price. Here is your chance to stock up. Dual Wipe Solder Robinson Nugent Sockets 6 pin were $0.20 each 8 pin were $0.20 each 18 pin were $0 .35 each 20 pin were $0.45 each 24 pin were $0.45 each 24 pin Skinny DIP were $0.45 each now only St 00 for 10 no"I only $1.00 for 10 now on:y $1 .75 for 10 now only $2.25 lor 10 now only $2 .25 for 10 now only $2.25 fo r 10 Dual Wipe W.W. 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P.O . Box 67 1, Lane Cove N .S.W. 2066 Telephone: (02) 4271676, Fax: (02) 428 5198. 8.30am to 5.00 pm Monday to Friday , 8.30am to 12 noon Saturday. Mail O rders add $5 .00 to cover postal charges. Next day delivery in Sydney add $5.00. ~ ..,, a a a now only S0.50 each Were S1 .40 IJ... Cl 0 ~ now only S2.20 each now only $2.10 each now only $2 25 each now only S2.70 each \>PO a )) r, :i: ~ ~ i ffi TO GLAOESVII..LE DR~ Tax exemption cert ificates accepted if line value exceed s $10.00. BANKCARD, MA STERCA RD, VISA, CHEQUES OR CASH CHEERFULL Y ACCEP TED Weak beeper? Build the repeater! Does your computer have a weak beeper? Do you have trouble hearing it? You can solve that problem with this Computer Sound Repeater which turns a weak beep into a much more audible low frequency tone. By LEO SIMPSON & JOHN CLARKE Some computer models do not use a speaker but use a tiny piezoelectric transducer which puts out a high frequency 'beep'. For people who have severe hearing loss, this is just about inaudible. We're thinking specifically of Amstrad computers in this instance but the problem does occur with other brands. Our solution is the Computer Sound Repeater. It is a little box which sits on top of your computer. Whenever the computer beeps, to indicate a wrong keystroke, during a game or whatever, the Sound Repeater emits a low frequency "blurt" which is much ·more audible to those with poor hearing. The Sound Repeater is low in cost and simple to build. It uses an electret microphone, one LM324 quad op amp IC, one transistor, one small loudspeaker and a handful of other bits. How it works The circuitry in the Sound Repeater has been adapted from that in the Discolight, as published in the July and August 1988 issues of SILICON CHIP. The electret microphone is used to pick up the Left: each time your computer beeps, this gadget emits a low frequency "blurt". The circuit is housed in a low-cost plastic case. sound of the computer's internal beeper. The electret microphone has an internal FET source-follower to buffer it and this is powered via the 4.7k0 resistor. The audio signals from the electret microphone are then fed via a .01µ,F capacitor to pin 10 of ICla, which is connected as a noninverting amplifier with a gain of 30 times. ICla feeds a lOOkO trimpot (VRl) which sets the sensitivity of the circuit. The signal then passes to ICl b, which is identical to the previous stage, thus giving a total gain of about 900 at the maximum setting of VR1. Following IClb is a twin-T filter stage which is more or less tuned to the frequency of the computer's beep. Our circuit has values selected to centre it close to ZkHz. The .01µ,F capacitor and the 220k0 resistor at the input of ICla and ICl b also function as a high pass filter , so that the circuit does not respond to low frequency sounds. Any tone signal picked up and amplified by ICla, 1b and le is then rectified by diode Dl. The rectified signal is filtered with a 1µ,F PARTS LIST 1 plastic utility box, 1 30 x 68 x 43mm (Altronics Cat H-0153 or equivalent) 1 PCB, code SC07104891, 66 x 62mm, 1 electret microphone insert 1 50mm 80 loudspeaker 1 1 2V AC plug pack Semiconductors 1 LM324 quad op amp IC 1 BC338 NPN transistor 4 1 N4002 silicon diodes 2 1 N4148 small s ignal diodes 2 1 OV 1 watt zener diodes 68 SILICON CHIP Capacitors 2 470µ,F 25VW PC electrolytics 1 1 00µ,F 16VW PC. electrolytic 1 1µF 1 6VW PC electrolytic 6 .01 µ,F metallised polyester (greencap) Resistors (0.25W, 5%) 4 X 220k0, 1 X 180k0, 2 X 100k0, 1 x 47k0, 1 x 27k0, 4 X 8.2k0, 1 x 4.7k0, 2 X 3.3k0, 2 X 1 kO, 1 x 6800, 2 x 3300 0.5W, 1 x 1 20 1 W, 1 x 1 OOkO miniature trimpot 05 1N4002 04 1N4002 12VAC 1211 1W .,. 06 1N4002 330!l 1k ,----..---'YWr------------...------------------.....---+10V 811 SPEAKER 220 k 220k Li~~l~-11---""I 100k 14 180k 1 ~: c· .,. 3.3k .,. C 8.2k COMPUTER SOUND REPEATER 8.2k 1&vw·T -,. + 27k T .,. B EOc VIEWED FROM BELOW .OlJ .01! C C Fig.1: tone signals picked up by the microphone are amplified by ICla & IClb, filtered by twin-T filter stage ICld, and rectified by D1. When the voltage across the lJ.lF capacitor exceeds lV, pin 7 of IClc switches high and turns on Qt. capacitor to produce a DC voltage at pin 5, the non-inverting input of IClc. This stage operates as a comparator, comparing the DC voltage at pin 5 with a reference voltage at pin 6, which will be about 1 volt DC, as set by the 220k!2 and 27k!2 resistors. If the voltage at pin 5 exceeds 1V, the output of IClc will go high and turn on transistor Ql, via diode D2. Q2 then drives the loudspeaker with half-wave rectified 50Hz AC via diode D4. By using rectified AC we dispense with the need for a low frequency oscillator and an amplifier to drive the loudspeaker. Current through the loudspeaker is limited to a safe value (for the transistor) by the series 120 resistor. Dtode D3 is connected across the transistor to protect it against inductive kickback when it turns off. Power for the circuit comes from a 12VAC plugpack. This not only provides DC for the op amp circuitry but also the power to drive the loudspeaker, as noted above. The plugpack feeds two half-wave rectifiers (D5 and D6) and two The PCB has been designed to clip into the notched ribs on opposite sides of the case. We used super glue to secure the loudspeaker and electret microphone to the lid. Power comes from a 12V AC plugpack. JANUARY 1989 69 12VAC 100 ELECTRET MICROPHONE._.---;m.l + Fig.2: here's how to mount the parts on the PCB. Take care with component orientation and be careful not to confuse the various diodes. At right is a full size reproduction of the PCB. ~0~~~01~2~10~~~0 ,n~ l~ _./iiOl~~~! I '' 00000000000000000 oo~ 00000000000000000 000 00000000000000000 an ~oooo o oo o ~-=~~ SPEAKER {l ' - 0 --00 ooo ooo 0000 0000 il!:02 ~ 0000 000 .. ()~Q + ~~ 1pf :i 0 if 000 ELECTRET ·MICROPHONE If you want to save money, you can build the circuit on a small piece of Veroboard. But be warned - if you use Veroboard, it's very easy to make a mistake. 470µ,F 25VW filter capacitors, to provide positive and negative supply rails. These are regulated with 10V zener diodes D7 and D8 to provide regulated supply rails of ± l0V. Note that you can't use a DC plugpack to power this circuit. It needs 50Hz AC to drive the speaker. Construction Our prototype Computer Sound Repeater was housed in a standard plastic utility box measuring 130 x 68 x 43mm. (Altronics Cat H-0153 or equivalent). We designed a small printed board to accommodate the 70 SILICON CHIP + 11 ! 1 o o o O 00 O 0 ~0000 00 o O 01 o O '0 Fig.3: wiring diagram for the Veroboard version of the Sound Repeater. You can make the cuts in the tracks using an oversize drill. circuitry. It measures 66 x 62mm and is coded SC07104891. Fig.2 shows the parts layout on the PCB. Take care when installing the polarised parts and be careful not to mix up the various diodes. As an alternative, you can build the circuitry on a piece of Veroboard. To help you do this we have shown a Veroboard component layout. This can be checked against our photograph of a Veroboard version of the circuit. After drilling a pattern of holes in the lid of the case (to let the sound out) the loudspeaker can be mounted. We used a quick and dirty method: super glue. The electret can be mounted in a hole in the lid too and held in place with a dob of super glue. When construction is complete check all your work carefully before applying power. Check the supply rails ( ± lOV) with your multimeter. Pin 4 of the LM324 should be at + 10V while pin 11 should be - l0V. Pins 1, 8 and 14 should be close to 0V. Pin 6 should be be close to + 1V and pin 7 should be close to - lOV. You can test the unit, without turning on your computer, by whistling softly, at high pitch, into the microphone. Each time you do so, the speaker should "blurt". ~ AMATEUR RADIO By GARRY CHATT, VK2YBX Relative signal strength indicator for amateur gear A relative signal strength indicator can be a very useful gadget but is seldom encountered on modern scanning receivers and 2-metre hand-helds. Here's a simple circuit that you can build yourself for just a few dollars. Being able to monitor the level of received signals can be quite an advantage, particularly if you are evaluating a new antenna or monitoring propagation paths. In addition, a signal strength meter can also be useful as a tuning indicator, particularly in difficult reception conditions. Retrofitting a signal strength meter to an existing piece of equipment is not usually an easy task. On small hand-held transceivers, there's usually not enough room on the front panel and even on larger scanning receivers the job can be a mechanical nightmare. The answer is to build a selfcontained external signal strength meter which can be mounted piggyback fashion on the existing gear, or simply plugged in as required. That's the approach taken here. We opted for a bargraph display and designed the circuit so that only two connections to the receiver were required. How it works Fig.1 shows the circuit of our signal strength indicator. As can be seen, it uses an LM3915 dot/bar display driver from National Semiconductor. This device was +12V C1 INPUT .001 Construction 2x1N914 02 0-11a.--1,,4--+-4---t GND + LM3915 D1 .,. chosen because of its logarithmic response which is similar to a conventional "S" meter. Don't use devices which have a linear response (eg, the LM3914). Cl couples a 455kHz IF (intermediate frequency) output from the receiver to diodes Dl and D2. These rectify the IF signal and apply it to pin 5 which is the input pin for IC1. Capacitor C2 decouples any remaining RF on pin 5 while Rl and VR1 on pin 7 set the LED brightness. VR1 is also used to set the meter sensitivity. Its wiper connects to pin 6 which is the Rm (reference high) input. By varying the setting of VR 1, we can vary the reference voltage on pin 6 and thus the signal level at which the last LED in the series lights. A functional block diagram of the LM3915 IC is shown in Fig.2. Pin 9 of IC1 is the mode select input and controls either bar or dot mode operation. In this application, we want the display to function in bargraph mode and so we have connected pin 9 to pin 3. If you want to operate in dot display mode, just leave pin 9 open circuit. R1 1k .,. VR1 10k Fig.1: the circuit uses an LM3915 IC which drives 10 LEDs in bargraph mode. VR1 sets the sensistivity of the indicator. The circuit is so simple that it should only take about 15 minutes to build it up on a small piece of Veroboard. But be careful - it's very easy to make a mistake with Veroboard. Use an oversize drill to make the cuts in the copper tracks and be sure to install the LEDs, IC and diodes the right way around. If you like, you can use different coloured LEDs at the top end of the JANUARY 1989 71 The LM3915 Dot/Bar Display Driver LED Fig.2 shows a simplified block diagram of the LM3915 . Basically, it consists of a high impedance input buffer which drives a series of 1 0 comparators. Each of these comparators has its non-inverting input biased to a different level by means of a 1 0-step voltage divider which is connected to a reference voltage. As shown here, the top of the resistor string (pin 6, RH1) is connected to an internal 1.25V reference voltage (ie, the chip maintains 1.25V between pins 7 and 8). This means that the output from the buffer amplifier must exceed 1 .25V for the last comparator in the series to switch low and light its LED . The previous LEDs in the series are turned on in 3d8 steps in response to a rising input signal to pin 5 . This pin connects via a 20k0 resistor to the buffer amplifier. In practice, the reference voltage can be easily adjusted by connecting a voltage divider to pins 7 and 8 as shown in the NS Linear Databook. For the signal strength meter, pin 8 (REF ADJ) has been connected to ground to give a 1.25V output from pin 7. This voltage is then sampled by VR1 and applied to pin 6 (RH1). By simply adjusting VR1 , we can set the maximum voltage at which the last LED in the series lights and thus the sensitivity of the meter. A feature not completely shown by the block diagram (Fig.2) is the LED brightness control. This is set by the load resistance connected between pin 7 and ground . The output of each comparator consists of an NPN transistor and an scale. For example, you could use green LEDs in the first seven positions and red LEDs in the last three positions to indicate high signal strengths. It's really up to you. Check your work carefully before applying power. You can either derive a suitable 9-lZV supply from the receiver or you can use a separate 9V battery. The completed 72 SILICON CHIP v' Ult. 4.l!k 121 l.l1k 13 I I I'✓ . I'✓ LED MOGRAM CURRENT ml DUT 7 THIS lOAD DETERMINES LED BRIGHTNESS - REF ADJ I I Ulll -=1 I I v•--, I.SI> J 0.4111: I I •t• I , v• FROM l'IN It I 2• SIG § IN !-'--W,.,.+-t+ 4-1 l-= L_____________ J internal feedback loop regulates the transistor drive which in turn controls the current through the LED. Finally, the chip also contains a mode select amplifier at pin 9 (again not shown completely). This permits multiple LM391 5s to be circuit board could be housed in a small plastic case. Receiver connection Most scanning receivers on the market today either use the industry standard MC3357 (or LM3357) IF chip or an improved version of this - the 3359 or 3361. This circuit can be used with any of cascaded, and controls bar or dot mode operation . For a bargraph display, pin 9 is connected directly to pin 3; for a dot display, pin 9 is left open circuit. For further information on the LM3915 , refer to the National Semiconductor Linear Databook. those integrated circuits. The MC3357 is a dual conversion low power narrow band IF strip. It contains (among other things) a local oscillator for conversion to a second IF of 455kHz, a mixer and limiting amplifiers. There are sufficient gain stages to provide a suitable signal level at pin 3 (the mixer output), which can then be The MC3357 Narrow Band IF Chip If you have a scanner, it will most likely include the MC3357 IF chip or a near equivalent. As shown in Fig .3 , this chip includes an oscillator, mixer, limiting amplifier, quadrature discriminator, active filter , squelch, scan control and muting circuitry - all in a 16-pin package. It is specially designed for use in FM dual conversion communications gear. The mixer-oscillator combination converts the input IF (eg, 10. 7MHz) to 455kHz and makes this signal available on pin 3 for external filtering. After filtering, the 455kHz IF signal is applied to an internal limiter and then demodulated using a conventional FM quadrature detector. To measure the received signal strength, it's simply a matter of connecting the input to the signal strength meter directly to pin 3 (before the signal is filtered and passed to the limiting amplifier) . If you want further information on the MC335 7, refer to the Motorola databook on Linear and Interface Integrated Circuits. used to drive the indicator. The connection to the receiver IF chip should be run using miniature RG178 coaxial cable or similar, Vee making sure that the braid is connected to the ground of the IF strip. A simple detachable connection could be made using a 3.5mm phono plug and socket arrangement, although care should be taken to ensure that the internal shorting contacts in the socket are disabled. li: '~ensational Price Offer" I IC Ill 0 IC 0 _, c :I CONTACT 00027 00372 00390 00387 00245 00260 00100 00282 00392 00350 00012 00297 00342 00040 00359 00528 I Iii0 IC 0 00419 00420 :I 00427 00450 i CONTACT CONTACT COMPUTER PERIPHERALS RETAIL 80.00 MULTI 1/0 CARO + FOC .. 26.95 PRINTER CARD .. TOWER COMPUTER CASE + OISPLA Y 325.00 80.00 XT CASE + LOCK . COPYHOLDER 0/TOP, AOJ/ARM . 22 .95 DISK STORAGE BOX, 100 x 5¼" . 11 .00 DISK STORAGE BOX, 80 x 3.5 " . 10.50 JOYSTICK FOR XT/AT .. 19.00 KEYBOARD, 101 KEYS . 89 .95 MONITOR LEAD IEC PLUG TO SKT .. 3.99 XT M/BOARD 8 MHZ, 0 RAM . 119.95 GENIUS MOUSE GM6 + . 9!1.00 4.50 MOUSE PAD . AT MOTHERBOARD, 12 MHZ, 0 RAM . 499.00 AT/XT CASE, RESET + KEY. F/TOP . 59.95 XT CASE, TURBO LED SPEED DISPLAY 79.95 PRINTER RIBBONS BROTHER 1509 RIBBON 14.95 BROTHER 1724 RIBBON . 14.95 COMMODORE CP80 RIBBON . 10.50 12.95 EPSON EX800/1 000 RIBBON . OTHERS AVAILABLE. CALL NOW. COMPUTERS GOLD PLATED LEADS 00005 XT TURBO, 1OMHZ, 640K , 2 x 36K FOO, 101 KEYBOARD, FLIP LID CASE, LED SPEED DISPLAY . . . . ... 1125.00 00001 SHERRY AT 640K, 1 x 1.2M FOO, 101 KEY/BOARD, EXPANDABLE TO 1MB, 6/1 OMHZ, CGA CARD, SERIAUPARALLEL PORTS . . .... 1895.00 SHERRY EGA COLOUR MONITER 695.00 640 X 350 W0057 LEAD GOLD W0064 LEAD GOLD W0029 LEAD GOLD MALE . W0042 LEAD GOLD MALE . W0207 LEAD GOLD MALES . SCANNERS BNC MALE TO MALE . . BNC MALE TO RCA MALE RCA MALE TO 3.5mm 5.95 5.50 ~ r- 3.00 RCA MALE TO RCA 0 :D 0 3.50 RCA MALE TO 2 RCA !II 3.95 I COMPUTER POWER SUPPLIES 379.95 00237 HS3000 SCANNER . MUSIC CARD 00145 MUSIC CARD - See Product showcase section . ·00057 00061 D0060 00058 00358 150 150 200 200 220 WATT FOR XT. 89 .95 WATT FOR XT SQUARE . 89 .95 WATT COMPACT FOR AT .. 145.00 WATT ST ANDA RD FOR AT .. 119.95 WATT FOR TOWER COMPUTER . 169.95 I _______________ 350.00__,__________________ i 0 :D I CONTACT US FOR HARO TO GET ITEMS. MANY OTHER PRODUCTS AVAILABLE. SEND FOR FREE PRICE UST. BROCHURES ANO FULL SPECIFICATIONS FOR "AT" COMPUTER AVAILABLE UPON REQUEST. :D ALL PRICES INCLUDE SALES TAX WHOLESALE ENQUIRES WELCOME PRICES VALID WHILST STOCKS LAST - - - - - - CONTACT INTERNATIONAL Suite 2 -283 Burbridge Road Brooklyn Park SOUTH AUSTRALIA 5032 PH. 08-231-2202 Fax OB-352-1449 P.O. Box 390, Cowandilla, Soqth Australia 5033 Mall Order Postage Less than $50 ............................... $3.50 $50 · $99 ...................................... $4:50 $100 · $250 .................................. $7.00 >-bove $250 ................................ $10.00 Heally Items adds extra • IBM is reg. trade mark of International Business Machines • XT, AT and Atari are registered trade names 0 BANKCARD O MASTERCARD O VISA Card No .............................................. .. EXPIRY DATE Signature: ....................................................................... . (Note: unsigned credh card mail orders cannot be accepted) Name: ........................................................................... . Address: ........................................................................ . ...................... .. .. .... ... .. ... .. .. .. ........ Postcode: .................. . (Please ~llow 14 DAYS for normal mall and bank clearance delays) JANUARY 1989 73 YOU'LL ALWAYS FIND A BARGAIN AT JAYCAR 7 6 WAY RCA SOCKET ~ARGAIN I BARGAIN BAGS 1/2 PRICE booboo. I BACK AGAIN! I3kg Bigger than ever. Contains between 2.5 and of an amazing range of brand new Igoodies. No two bags are Identical and every bag greal value. P P extra $5 due to Irepresents heavy weight. No 7 day return. & MOLEX PINS These have been selling for $4.50 for 100. We now have available a new style and can offer them at 1/2 the previous price. Cat. Pl-6541 ONLY $2.25 for pack 100 ISTILL ONLY $12.95 E.XB-9000 - - - - - METEX 4.5 DIGIT MULTIMTER BARGAIN - - - - - - - - Our impon manager made a big Instead of ordering our standard style he ordered one I with an extra hole In the centre for more rigid mounting. So, they don, fit any of our panel cutouts for kits. So, you haven't cut your panel for a 6 way RCA socket yet - these are ideal. I Total size 120mm x 22mm. I•O Q • O Q Q Q ~ I I Cat.PS-0268 NORMALLY $2.25 each I JANUARY PRICE 80~ ea I 10+ 850 •• W _ _j:=S=TYL = U =S= = PRESSURE , GUAGE • Digital hold • 10Amp • Transistor tester • Audible continuity tester See catalogue for fu ll specs Cat.QM-1550 Remember these! Sit your tone arm on this and check the tracking weight. Too heavy tracking force will daniage expensive stylii. Made In Japan. Nagaoko brand. LIMITED QUANTITY Cat.M0250 NORMALLY $179 JANUARY ONLY $139 SAVE IEC LINE PLUG 1bc,c arc widely u,cd in personal computers. These were ,clling for $ 14.95, but we have n:1oun:ed them and can offer them at a reasonable price. Cat. PP-4007 NOW ONLy $7 .95 Ph: 683 3377 ONLY 50~ each $40 Bruce's Bargain PCB TERMINAL STRIP BARGAIN AnOlher surplus stock buy. These are a high quality black thermoplastic PCB terminal strip. As used by the alarm industry. Available in 4 way and 10way. Units are supplied unassembled - i.e. you have to screw the screws in. Normal Price 10+ 100+ Cat. HM-3204 4way $2.50 $1 .50 $1.30 Cat. HM-3205 12way $4.95 $2.00 $1.80 $1.50 BELOW WHOLESALE PRICE ,. ✓.::ii DIGITAL STEREO HEADPHONE BARGAIN Save 39% off catalogue prices. See our catalogue (p97) for full detalls. AA-2021 Features Mylar drivers, sponge earpads, metal 3.5mm stereo plug. Cat.M-2021 WAS $14.95 CARLINGFORD MOVED TO PARRAMATTA 355 CHURCH STREET Cnr VICTORIA Rd. AA-2022 Mylar drivers, frequency response 20-25kHz. Quality muff pads. Cat.M-2022 WAS $39.50 NOW $24.50 SAVE $15.00 WAS $29.50 NOW $17.95 SAVE $11.55 AA-2023 Top of the range, excellent sound. Quality phones. Cat.M-2023 WAS $59.50 NOW $39.50 ULTRA THIN SHIELDED CABLE TURNYOURSURPLUSSTOCK INTOCASHII Quality English made shielded cable with a total Jaycar willcomponents purchase your SA VE $20 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ , stocks of andsurplus equipment L-C=--c..c..:...c::......,..=..::.._ diameter of 1mm. Ideal for screened wiring in mall spaces. Packet 5 melres CALL GARY JOHNSTON OR WATCH OUT FOR OUR NEW BRUCE ROUTLEY (02) 747 2022 Cat. WB-2310 SPEAKER KIT NEXT MONTH STOP PRESS ONLy $2.50 CONTACT CONNECTOR BARGAIN Easy to use automatic connectors. Simply wrap around the existing wire and new wire and squeeze. 12" GUITAR SPEAKER NORMALLY $1.25 for 4 or 31~ ea (Two styles supplied in pack) PACK 15 for $1.95 (only13tea)Cat.HP-1207 PACK 100 for $10 (only 10eea) Cat. HP- 1208 0 GOVERNMENT INSTRUMENTALITIES, SCHOOLS, PlJlll,IC COMPANIES CAR SPEAKER GRILL IF YOU WISl 1TO P\JRCIIASh FROM US, SIMPLY SEND US YOUR O1-l'ICIAL ORDER AND WE WILL GIVE YOU A • COMPLIMENTARY 30 DAY ACCOUNT QUALITY JEWELLERS SCREWDRIVER SET Quality easy to use colour coded screwdriver sel with swivel plastic heads. Screwdrivers include slotted 1.0, 1.6, 2.4, 3mm Philips No. 0, 1 Supplied in transparent plastic case. Cat. TD-2005 $5.95 =>==<=: 1/2 AN RCA LEAD? Well, not quite. These are a stereo lead, (ligure 8 shielded) with two 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 each FIX THAT CLOCK!!! If you're tired of looking at that mantle clock reading ten past one (and It's not), why not fix ltl It will take you about 1O minutes with one of our clock modules. We have four types. Just remove the old mechanism, throw It in the bin and replace it with an accurate quartz crystal movement! We even have ones that play the old fashioned tune (Westminster Chime) and then chime the hour. Also :;~~~r::: :~;~,;::; clock face. • Very compact 56 x 56 x 15mm , Powered by 1-AA battery • Supplied with 3 different sets of hands Cat. XC-0100 [;:;::::t; Q. <at>I . ., , - 11 ~ : --.,. 'i•' • • $12.95 ~ . j .\ 1/. "-' i« L 0 i , : . . . . . ~o/ . PENDULUM MOVEMENT/QUARTZ CLOCK Ideal clock mechanism replacement for a small pendulum clock, or create your own pendulum. • 3 sets of hands supplied • Uses 1-M battery Cat. XC-0103 $16.95 Two different modules are available. Both chime the hour after playing their tune. XC-0106 plays Westminster chimes each hour then gongs the hour (I.e. 7pm • 7 gongs) XC-0107 plays a dttferent melody each hour, then gongs the hour. Both units are supplied with: • Clock movement • Speaker and battery holder (3-M batteries required) • 3 sets of hands Cat. XC-0106 Westminster chimes Cat. XC-010712 melodies ONLY $19.95 each 12V CAR ANALOGUE CLOCK MOVEMENT MASSIVE SCOOP PURCHASE! Convert the broken/unreliable or Inaccurate mechanical clock In your car to space age precision. Made In West Germany by VOO, the module measures roughly 45 x 38 x 40mm deep. The compact size virtually ensures that It will fit In any spacel Quantity strictly limited. Cat. XC-0106 PASSIVE INFRA RED DETECTOR · PRICE BREAKTHROUGH ALARM CONTROL PANEL It had to happen II Jaycar was the first to offer pulse count PIR's and lately we were the first to offer pulse count for less than $100. We are proud to announce another first In PIR's. A QUALITY PIR FOR ONLY $69.95 FULL PRICE Sure, you are probably thinking "but what about the quality and reliability". There's nothing worse than an alarm system that false triggers, you know the old story about the boy who cried wow. We have extensively tested the units and have no douqt about -their quallty and operation ability. Features & Specifications • Dual element pyroelectrlc sensor • 24 dual element detection zones In three layers • Wide angle 90" multi layer coverage • 12 metre range • Operation voltage 7.5 • 16V DC • Tamper protected • LED Indication • Size 65(H) x 84(W) x 46(D)mm • Colour beige • Relay output Dl'ru•~ • 3 month guarantee Cat. LA-5017 II;/ fi•'rP. ONLY $69.95 This low cos~ but professlonaly made steel encased alarm has most of the main features of professional control boxes including : • Lockable baked enamel steel box including tamper switch • 3 sectors NO Cl( NC • Trigger Instantaneously ff any sensor wiring cut • Space In box for back-up battery • 24 hour Instant circuit that Is not governed b keyswitch, for smoke detector, ect. • Facility to connect re mote keyswltch (alarm will latch if remote wiring Is cut, whether alar is "off" or ·on· • Built-in siren driver • Relay output control provides 12V DC for bells, sirens. ate • Diagnostic audible and visual alarm status indicators • Simple one key operation. Ideal for nontechnical people to operate once Installed • Dimensions 230(H) x 170(W) x 70(D)mm • Net weight 1.8kg Cat. LA-5162 NORMALLY $149 SAVE $20 ONLY $129 Gel battery to suit Cat. SB-2480 $22.50 Power supply to suit 1SVAC Cat. MP-3021 $29.50 $30 LESS THAN ANY PIR WE KNOW OF ONLY $9.95 Piezo Tweeter At last, an economical priced quallty plezo tweeter. Another manufacturers surplus stock purchase by Jaycar. These are In other catalogues for $18.951 SPECIFICATIONS • Frequency response 3.5kHz-40kHz • SPL 94dB/1W at 1 metre • lntermiltent peak power 100 watts • Size 78mm square • Use with or without cross011ers Cat. CT-1905 UNREAL PRICE ONLY $9.95 Don't Pay $18.95 "CRIME STORY'' SPEAKER CLOTH SALE Another surplus stock purchase. The quality Is first class; the only problem Is the colour. It would have been totally In vogue In the 1950'& or 60's, but It's not really suited to the loungerooms of the eo·s. If you have speakers In the rumpus room, garage, boys room etc .• that require cloth then this cloth Is Ideal". Oh, we haven't told you about the colour yeti • It Is also Ideal If you REALLY want to be MEGA trendyl STYLE 1 Gold with black strips at about 1 1/2' Intervals. Size 5' x 1 rnt Cat. CF-2756 $3.95 SAVE $10 STYLE 2 Gold with gold reflective pieces through It. Size 3' x 1mt. Cat. CF-2757 JANUARY INSTALLERS SPECIAL DEAL ALARM PANEL AND 3 PIRs PURCHASED TOGETHER ONLY $320 SAVE $38.85 on normal prices $2.95 SAVE $7 STYLE 3 It's a bit more down to earth. It's brown with red, black and green fleck. Size 3' X 1rnt. Cat. CF-2758 $3.95 SAVE $6 NORMALLY $49.95 SAVE$5 NOW ONLY $44.95 See catalogue for full specs C t TS-1475 BASE STATION Cat. TS-1478 a. SOW IRON • CT7 NORMALLY $159.50 SAVE ON ADCOLA SOLDERING IRONS S30 12 watt $29.95 SAVE $7 Cat. TS-1492 SS0 16 watt $32.95 SAVE $7 Cat. TS-1494 5 watt power handling, widerange speaker. Cat. AS-3020 Bohm ONLY $3.95 10+ $3.65 •• 100+ $3.20 •• SAVE $20 NORMALLY $55.00 DECEMBER PRICE SAVE$7.50 NOW ONLY $47.50 Cat. TS-1480 $139.50 _Quality Stacking Banana Plugs • NEW RANGE OF COLOURS I • NEW LOWER PRICES! RED BLACK GREEN BLUE YELLOW $1.25 ea Cat. Cat. Cat. Cat. Cat. PP-0390 were $1.95 PP-0391 were $1.95 PP-0381 PP-0382 PP-0383 10+ s1.10 •• GASSOL PORTABLE SOLDERING TOOL WITH OPTIONAL BLOWTORCH At last. A reasonably priced portable gas soldering iron that can double as a small welder or heater with an optional tip. Save $10 over other gas soldering irons. • Use anywhere 1' • Uses standard butane gas fuel • Temperature adjustable• equivalent to 10-60 • Soldering up to 400-C • Welding up to 1300°C (Optional tip) • Use for heat shrinking (Optional tip) • Refills In seconds • Up to 60 minutes continuous use • Reasonably priced replacement tips • Includes one 1mm soldering tip Cat. TS-1410 I I ONLY $29.95 Welder Tip Cat. TS-1411 Spare soldering tip 1mm Cat. TS-1413 KIT'S COLUMN ONLY $9.95 ONLY $9.95 PEST & INSECT REPELLER SELLOUT • Frequency range 30kHz to 65kHz, variable • Output level 130dB • Both units Include 240V to 9V DC 200mA plug packs, worth $15 alone. Piezos worth about $9 each, also. HI Guys, Kit here again. Even though it's January and as hot as blazes (I nearly said something else) the slave-driver boss has still got me writing this column AND making kits (with the other girls). SINGLE TRANSDUCER Cat. YS-5510 Were $29.95 ONLY $19.50 Originally sold for $55.00 Strips all sorts of cable without damaging the conductors. • Automatically adjusts to insulation diameter • One hand operation Cat. TH-1824 DUAL TRANSDUCER MODEL Cat. YS-5512 Were $39.95 ONLY $27.50 KIT SEMICONDUCTOR SALE We have a few expensive specialised semiconductors available from past kits. This is an ideal opportunity for experimenters to save heaps. Please order from your local store or mail order. 1. LH0002 CH Current AmplWiers from Balanced Line Driver Kit • AEM6011 Cat. EE-4714 WAS $27 .55 NOW ONLY $9 2. PCD 3360 P Ring tone generator chip from Ring Tone Customiser Kit. ETI October 1986. Cat. EE-5900 WAS $13.75 NOW ONLY $5 3. AM IS 3530 Modem IC. Cat. EE-6075 WAS $43.50 NOW ONLY $18 VR Remote Control Chips As used In EA Tuner Remote and 8 Channel Remote Control. EA June 1987. 4. SL490 Transmitter IC Cat. EE-4691 WAS $21.95 NOW ONLY $6 5. SL486 Remote Control Preamp Cat. EE-4694 WAS $22.99 NOW ONLY $7 6. ML923 Receiver IC Cat. EE-4702 12 VOLT ILLUMINATED BEZELS Another surplus scoop purchase. These bezels look Identical to the expensive rectangular illurrinated switches for car alarms, except that there Is no switch. Quality European brand Arrow Hart. Normally worth $15 each. Complete with globe. Yellow Orang) Blue Green Cat. Cat. Cat. Cat. SL-2670 SL-2671 SL-2672 SL-2673 ONLY $3.95 ea 10+ $3.50 •• There is only a small quantity of blue and green. Plenty of yellow and orange. We also have a small quantity of Yellow Square and round style. Yellow Square Cat. SL-2675 Yellow Round Cat. SL-2678 .. $3.95 ea / .:. ·:· .... , ... .{{' ,• . \. \_. .._:;:. ___ .'•:"··• ' ' 10+ $3.so •• .,_·,· WAS $33.50 NOW ONLY $9,50 SIREN BARGAIN Unbelievable ear splitting 120dB. 12 volt 300mA. Normally $29.95 Limited quantity available for $19.95 SAVE $10 Cat. LA-5720 CERAMIC CAPACITOR PACKS NORMALLY $12.95 ·- l■-G _R _O_M _M _E _T---~----■■1 ~ BARGAINS 3.5mm hole grorm18t. Panel cutout 6.5mm. Cat. HP-0700 ~ Packet of 20 $ 1.00 t 0mm hole grommet. Panel cutout 17mm. Cat. HP-0705 Packet of 10 $1.20 OPEN AN ACCOUNT WITH JAYCAR Jaycar is now accepting account applications from all established companies who can exhibit good trade references. For application details see our store managers or phone (02) 747 2022 Jaycar has already Introduced you to the easy and economical way to buy resistors and greencaps. Now you can purchase ceramics In packs, so, you'll never run out of one again. Eight, easy to buy, low cost packs which represent a considerable saving over buying Individual parts. At tee each ceramic, you figure out the savings. Each pack contains 10 of each value and packs cover the complete range from 1pF to 0.1uF. Values (10 of each) tpF, 1.2, 1.5, 1.8, 2.2, 2.7 Values (10 of each) tOOpF, 120, 150, 180,220,270 Total 60 pcs Cat. RC-5390 $6.95 Total 60 pcs Cat. RC-5394 $6.95 Values (10 of each) 3.~F. 3.9, 4.7, 5.6, 6.8, 8.2 Values (10 of each) 33~F. 390,470,560,680,820 Total 60 pcs Cat. RC-5391 $6.95 Total 60 pcs Cat. RC-5395 $6.95 aues o eac Values (10 of each) .OOUF, .0022, .0033, .0047, .0056, .0068 Total 60 pcs Total 60 s Cat. RC-5396 $6.95 Values (10 of each) 33pF, 39, 47, 56, 68, 82 Values (10 of each) .0082uF, .01, .022, .033, .047, .1 Total 60 pcs Cat. RC-5393 $6,95 Total 60 pcs Cat. RC-5397 $7 .50 • But, seriously though our stores were very busy at Christmas time selling many kits to you • as well as other goodies of course. JANUAR~Y · SPECIAL • -~~, $ 9 ■9 5 • .• SAVE $3.00 As you can Imagine, we were VERY flat out over the Christmas season - making kits I meanl Talking about Christmas - you should have been at our Chrissy party! In past years its been a bit boring sometimes (until the boss gets thrown, clothes and all, Into the pool) but this year I had a balll I can't remember the WHOLE night except to say that I THINK It was NOT boring . •. (Funny the way the young ~h':g~~nager guys now look at me Well, the boss is happy now that he has his German toy back from the panel beaters. You should see him - all smiles. He has one of THOSE Car Safety Light kits (Ref: Silicon Chip November 1988) Installed, our best car alarm kit and all the other gadgets he can stuff In. He is really a good stuffer. Just give him a job & he'll stuff It upl (Sorry Bossi) BACK TO WORK DEPT. We have some great new kits coming up. The first that comes to mind Is a fantastic new 33 BAND, 1/3 Octave graphic equaliser. (See SIiicon Chip Feb. 1989). We will also be Introducing a range of low cost but high performance Hi Fi Speaker kits with Taiwanese drivers made to Euro specs. but not with Euro prices. Keep your eyes open for them. We are also doing a great special price on the Plasma Lamp displays this month. See our ad on the opposite page In column one. I can not Imagine the kit ever being cheaper, so get one while they last. So that's about It for this month. We girls hope we can survive the heat In the Kit Dept. The boss only allows us to turn the airconditioner on for 2 hours in the middle of the day. He has to take a tablet every time the electricity bill comes In. In the meantime keep your Iron cooll ~\:l_}~N~~iv I SAVE UP TO AN AMAZING $200 • Wide bandwidth and high sensitivity • Internal graticule st _r~~~~i~~~l~r:~~!7o~~;r~u~l~:~~:~:t~~ er • Z axis (intensity modulation)• High sensitivity X-Y mode • Regulated power supply circuit ~ Hu NG CHANG 20 MHz C RO ~ SPECIFICATIONS Effective Display Area 8 x 10 div (1 div- 10mm) VERTICAL Operating Modes CH-A, CH-B, DUAL, ADD (CH-B can be Inverted) Alter; 0.2ufs • 0.5ms/div. Chop; 1ms Dual Modes 0.5Sidlv CHOP frequency 200kHz approximately 5mV/div 20V/div ±3%, 12 ranges in Deflection Factor 1-2-5 step with fine control DC; DC - 20MHz (-3dB), AC; Bandwidth 10Hz • 20MHz (·3d8) Less than 17ns Rise Time Less than 3% Overshoot 1M ohm ±5%, 20pF ±3pF Input Impedance ,,___~ - - - · - - - - · ..__ ........ ~ ·-- ----·· ..·---- · - HORIZONTAL NORMAL and AUTO 0.2ufs - 0.5s/div ±3%, 20 ranges in 1-2-5 step with fine control 5·times (5x MAG) 3% Sweep Modes Time Base Sweep Magn~ier Linearity TRIGGERING Sensitivity INTERNAL; 1 div or better for 20Hz 20MHz (Triggerable to more than 30MHz). EXTERNAL; 1Vp-p or better for DC-20MHz (T riggerable to more than 30M Hz) INT, CH-A. CH·B, LINE and EXT Positive and negative, contlnously variable with level control PULL AUTO for free-run Source Slope TOTAL PRICE FOR CRO &TWO PROBES COMPONENT TESTER Component Tester Max AC 91/ at the terminal with no load. Max current 2mA when the teminal Is shorted. (Internal resistance is 4.7k ohm) CRO - NORMALLY $899 NOW ONLY $719 SAVE $180 Cat. OC-1900 PROBES (TWO) NORMALLY $99 cat. ac-1902 SAVE NOW ONLY $79 for 2 SAVE~---$20 - - - - - - -"- -----~ ~ ONLY $798 Simple PC-driven function generator Kit Ref : EA January 1980 Here's a simple and low cost little unit which lets you use your personal computer to generate signals with almost any conceivable waveform. It hooks up to the computer via a standard Centronics-type parallel printer port, making It compatible with almost any kind of computer. Cat. KA-1709 $49.95 GREENCAP PACK • Metallised polyester. 60 top quality prime spec greencaps supplied from 0.001 uF to 0.22uF, all 1OOV. Cat. RG-5190 $200 EPROM Eraser 'SCREECHER' CAR ALARM KIT Scare the pants of would-be thieves! This car alarm is fitted under the dash of the car. When a thief breaks in (alter entry delay) an unbelievably loud shrill sound goes off • INSIDE THE CAR making It too unbearable to proceed with stealing the car. The alarm has a dash lamp flasher, exit and entry delays, a 3 second soft alarm to remind you to turn it off, and automatic resetting. The Jaycar kit includes the direct Import 116dB screecher, dash lamp, PCB and all components. ~ - - - - - - Cat. KA-1615 Will erase up to 9 x 24 pin devices In 40 minutes. Less for less chips. 240V operation. Cat. XE-4950 $99.50 Replacement tube Cat. XE-4951 $34.95 60 In pack $7.95 DON'T PAY $12.95 HEAD OFFICE MAIL ORDERS POST & PACKING 21 37 J'A~fifrl_i_i_i_i_f_i_~_r_!_:~;_:_:_:_:_:_:1__ _ _ _ _~-~-~-{-~-~-i-~-~~r-~_;~~-:-~_:_:,___ _M~~,tl_ ■ jf_~l_!__ i_t_R_$1_oo_i_!i_]_1_ _ MAIL ORDER VIA YOUR ff ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY· CITY 117YorkSt. (02) 2671614- GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799 • Mon-Fri 9 • 5.30 Sat 9 - 4pm PARRAMATTA 355Church St (Cnr. Victoria Rd) (02) 6833377 BURANDA OLD r . 144 Logan Rd (07) 393 0777 Mon-Fri 9 · 5.30 Thurs 8.30 - Sat 9 - 12 CONCORD MELBOURNE-CITY Shop 2. 45 A'Beckell St City (03) 663 2030 ' HURSTVILLE VISA S MasferCard. "==a=~;a;;;....,:; Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 • 12 Mon-Fri 9 . 5.30 Thurs 8.30 pm • Sat 9 • 2pm 115ParramattaRd(02) 7453077 Mon-Fri 8.30-5 .30- Sat 8.30 - 12 121Forest Rd (02) 570 7000Mon-Fri 9. 5.30 Thurs 8.30 pm • Sat 9 • 12 Mon-Fri 9 - 5.30 Fri 8.30 • Sat 9 • 12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. 0andenong Road Mon-Fri 9 . 5.30 Fri 8.30 . Sat 9 . 2 ~ • • • 1n1c This episode of Kit Clinic looks at the UHF remote switch as featured in our March 1988 issue. A lot of readers have had trouble with this project which will work only if you follow the instructions. Dear SILICON CHIP, I have built the UHF remote switch to team with my car burglar alarm. I urgently need to get it going because my neighbours are starting to gfve me a hard time. This is understandable because I've been fumbling for my car alarm switch at 6.00am in the morning and setting off the alarm. I've checked the unit out closely and so has a technician mate of mine and we can see nothing wrong with it. Can you suggest where the fault would lie? • One of the big problems about a circuit operating at 302MHz is that components are critical. Not only have you got to have the right components but you must mount them in the right way. Component lead lengths must be short. For capacitors, transistors and resistors and any other components for that matter, lead lengths should be no more than a few millimetres long. To demonstrate just how important it is to keep lead lengths short, consider the inductance of a lead only 10mm long and 0.5mm in diameter. This is given by the formula: L = .0021(2.303 log 1041/d - l)µH where 1 = length in cm d = diameter in cm For the above figures, this gives a result of 7 nanohenries. That can be very significant at 300MHz. It represents an impedance of 13.20. If you have a capacitor with leads 10mm long, the inductance of the leads can easily stop it functioning as a capacitor at 300MHz. IT WASN'T HARD TO SEE why the reader's transmitter (at left) wouldn't work. For starters, the .0022µF capacitor was much too large. But the real p~ohl_em was the BFR9~A transistor which was not properly connected into circmt. The photo at right shows how the transmitter should look. 78 SILICON CHIP Resistors are just as badly affected. If they have leads 10mm long their inductance and stray capacitance effects can play havoc with the circuit. All that is really just a preamble, setting the scene so to speak. The reader's problems When we had a look at this reader's transmitter and receiver units we had cause to wonder whether he had read the article or even looked at the accompanying photos. The transmitter had the most obvious problems. First, there was this humongous .0022µF capacitor which was much larger than in our prototype unit. The MC145026 integrated circuit was installed in a socket. This, combined with the fact that the capacitor was physically larger than it should have been, prevented the capacitor from laying over the top of the IC, as it did in our prototype. This meant that the reader had to resort to having quite long leads on the .0022µF capacitor and he had to sleeve the leads with cambric to stop them from shorting together. Well, IC sockets are more trouble than they're worth in a lot of circuits. We seldom use them in our projects because they are often unreliable. True, they do allow you to change ICs quickly but unless you do something silly like reverse the supply voltages, ICs are very reliable. In truth, neither the use of the socket or the large .0022µF cpacitor probably stopped the transmitter from working. We mention them solely because they were noticeable deviations from the original circuit and, as such, we would have expected a "technician" to fix them before giving up on the circuit. The real reason why the trans- A MUCH BETTER JOB had been made of the receiver although 5mm clearance holes had not been drilled to take the transistor bodies. It wouldn't work because lpF ceramic capacitors had been used where ever .0011,LF (1000pF) types had been specified. In addition, there were problems with L2. Once these problems had been cleared, the receiver worked as intended. mitter did not work was that the BFR91A transistor was not connected into circuit. Instead of being mounted on the underside of the board with its body sitting in a 5mm hole in the board, it was mounted on top of the board and with its collector and base leads soldered between the 2-6pF trimmer and 470pF capacitor, respectively. The emitter lead was soldered through to the centre hole which does not connect anywhere but was meant to be drilled out to 5mm in diameter. We corrected these deviations easily enough and after that the transmitter worked as it should. Another small point, which did not affect the transmitter operation, was that the LED leads were not long enough to allow the LED to protrude from the case. Receiver PCB On the receiver side, the problems were not so obvious. In this case, the two BFR91A transistors were at least properly connected into circuit although 5mm holes had not been drilled in the board to take the transistor bodies. A more serious problem was that 12 was not correctly wound and the coil had been glued to the coil former. Some of this glue had penetrated the threads of the slug and so it was glued solid and therefore not adjustable. That was enough to stop the receiver working properly but the real killer was the use of lpF capacitors where .OOlµF (l000pF) capacitors were specified. The three capacitors concerned are associated with the receiver input stage - there was no way it could work. And while we can well understand how easy is to be confused by capacitor labelling, the capacitors in question were simply labelled "1 ". Being very tiny ceramics, they could only be lpF and not .OOlµF. Having fixed 12 and replaced the lpF capacitors with .OOlµF units, the transmitter and receiver worked as they were supposed to. Lessons learnt It is our opinion that projects involving RF circuitry can be tricky for readers to build but if this project had been assembled correctly, so that it was identical to our prototype as shown in our photos, it would have worked. Note that no components had failed or been damaged. Nor had the circuit failed to work because some of the components had much longer leads than they should have had. We often see RF projects that have failed to work because of long component leads but in this case the problems were much more obvious. A careful visual inspection revealed all the faults. For our part, we are conscious that our assembly instructions need to be quite specific but if our instructions are ignored there are bound to be problems. ~ JANUARY 1989 79 By BRYAN MAHER THE EVOLUTION OF ELECTRIC RAILWAYS During dieselisation, US railroading swung away from the greatest steam locomotives ever built to large numbers of small diesel locos which were used in multiples. But they also built some monster diesel electrics and even experimented with gas turbine electrics. The world's first oil engine locomotive ran in England in 1894. Made by Priestman Bros. of Hull, this 9kW (12hp} four wheel powered truck could pull a few wagons but did not cause many ripples in the railway world at the time. Its mechanical .transmission was too difficult to control. · 80 From 1896 onwards Richard Hornsby of Lincoln, England (later Ruston-Hornsby) produced more than 20,000 "oil" engines, a few of which were used to drive railway vehicles in the early period. It remained for the Mallesta and Sodermanlands Railway of Sweden to show the world in 1913 how it should be done. Theirs was the first true diesel electric locomotive to be regularly used for passenger transport. It employed a diesel engine and DC generator combination mounted in a four wheel coach. One driven axle was powered by an axle-hung DC series motor in the modern manner. The diesel engine was of Atlas design, built with all the electrics by two Swedish companies which formed Allmanna Svenska Aktiebogola t, today known as ASEA. Some critics regard their larger 1917 model as the first diesel electric which could truly be called a "locomotive". To the USA Despite this successful start by Sweden, when it came to the race to build the biggest and most powerful PT.15 MASSIVE DIESEL ELECTRICS IN THE USA . SILICON CHIP ABOVE: HERE TWO GENERAL ELECTRIC U-50 class diesel electrics are coupled back to back to haul a heavy freight train over the Rocky Mountains. The U-50s had two V16 diesel motors giving a total power of 3.73 megawatts (5000hp). Note that each loco has four 2-axle bogies. The photo on the facing page shows one the huge 3.4MW (4500hp) gas turbine locos built by General Electric for the Union Pacific Railroad. The Union Pacific operated 40 of these giants during the 1960s while no other railroad ever got beyond one or two trial machines. diesel electric locomotives the scene shifted to the United States. And the Americans have since led most of the world, by building on the original Swedish design. Not that the US railroads wanted big for big's sake - rather their drive was (and still is) the sheer necessity for a private company to prosper and slay in business. Unlike those of our country, US railroads live in a world of fierce competition. Only the best, most efficient, most economical (in dollars per tonne-kilometre moved) can survive. Today in the USA, with essentially all passenger traffic gone to Amtrak (the US Government-owned passenger line), airlines, buses or private cars, the fight between private railroads is for the freight business. To satisfy the customers, the railroad must regularly run fast freight trains at up to 145km/h. To keep running costs down, large diesel electric locomotives must haul freight trains three or four kilometres long, weighing 5000 to 20,000 tonnes or more, even in Rocky Mountain country. So American railroads made a very rapid transition from steam locos to diesel, as noted in our last episode. And the rest of the world followed suit, largely because they had to. The big three American steam locomotive manufacturers Baldwin, The American Locomotive Company (Alco) and Lima - all had trouble seeing the diesel .electric trend coming. Then all found that tradition means little in competitive business. Three newcomers to the loco building business had appeared upon the American scene. Steam's last day Though spring was officially blending into summer, the drizzling rain had made the day more like autumn. Apart from that, April 4th, 1960 was much the same as any other day and four young American boys could not be expected to realize that transportation history was being made right there and then. Perched on the back fence in their customary train-watching posture, like crows on a clothes line, they could hear the roaring bark of yet another beloved giant steam locomotive. Huge 550-tonne Mallet 2-8-8-2s and faster 2-6-6-2s had been hauling unit coal trains and fast freighters past their suburb since forever, or so it seemed. Their families lived not far from Roanoke, Virginia, right beside the right-ofway of the mighty Norfolk and Western Railway. Lately some diesel electric locomotives had been added to the fleet but these had to be coupled in multiple. In many places the boys had seen locos like the early EMD Co-Co diesel electric model E8A. These were quite heavy at 152 tonnes, yet not very strong with a mere 11 tonnes (25,000lbs) drawbar pull, despite using a big 1.64MW (2200hp) diesel engine. It required six of these diesel electrics to pull the heavy N&W coal trains up the mountains, a task previously performed by a single large steamer like the early 2-10-10-2 Virginian 800 class or the older 2-8-8-8-4 700 class. The 700 class drawbar pull was a fantastic 76 tonnes (168,000lbs). This, the most powerful steamer ever built, could singlehandedly pull a 7100 tonne coal train up a 1 in 62 mountain grade. Wow! Those young boys could not have known that the Norfolk & Western company had retained the services of these giant steam locos a decade or more longer than other US railroads. The reason was simple - the steamers were the best and most economical solution. Sure, some of those youngsters had, while holidaying in other areas, observed with astonishment strings of diesel electric locomotives multiple-heading long freights. One lad had once been amazed to see a long freight hauled by no less than 10 diesel electric locos, all controlled by one engineer at the front. The nation's young citizens couldn't yet appreciate the running battle waged by salesmen from General Motors' Electro Motive Division against Norfolk and Western's steam locos. In the 1940s and '50s, EMD's philosophy was to offer to all US railroads standard general purpose diesel electric locomotives of power rating around 1.1 to 1.6MW (1500 to 2200hp). JANUARY 1989 81 TIIE UNION PACIFIC RAILROAD'S "BIG BOY" was reputedly the most powerful steam locomotive ever built. This giant was the equivalent of two steam locomotives under one huge boiler and produced 4.5MW. EMD's concept was that it was cheaper to purchase standard diesel electric locomotives and couple as many as needed together to perform each haulage task. Other manufacturers would provide sets of two, three or four units more-orless permanently coupled together, all controlled from the head end, ·classed as a single loco of great power rating. The etymological inferences in classing four machines as "one locomotive" was above the kids' collective heads. Absorbed in their daily train watching, how thrilled the bcys were when the mighty Y6b class 2-8-8-2 rounded a bend and appeared in view. As it blasted its way up the heavy grade, part of the Appalachian mountain climb, the very ground shook with the reverberation of that monster steam locomotive. History was indeed being enacted before their eyes. Little did they know it but they were witness82 SILICON CHIP ing the final run of the last steam locomotive under full commercial load in the United States. Their customary enthusiastic waving to the engineer produced a rather sad response - the loco whistle seemed more like a banshee's wail. The giant Y6b class steamer, all 550 tonnes of her, finished that day's run with a 5000 tonne coal train in tow, then quietly drifted into the maintenance shop. Her fire was dropped into the ash pit and the locomotive allowed to go cold, to be demolished the following day and sold for scrap. And the Y6b class locos were no more than 8 years old! In practice, the Y6b class locos were just as efficient and less complex than the competing diesel electrics. They were scrapped only because it became impossible for the N & W to remain the only steam powered railroad in the USA. Though the Norfolk and Western had always built its own steam locomotives, all suppliers of vital components had ceased trading in such items. Enter the new loco makers Now the N & W railroad would have to purchase all diesel electric locomotives from amongst the three or four remaining loco manufacturers. The EMD plant at La Grange in suburban Chicago, Illinois could turn out enough diesel electric locos to supply all the USA and much of the world but they had competitors: Alco, Fairbanks-Morse and General Electric. The American Locomotive Company (Alco) at Schenectady, a steam locomotive manufacturer from way back, took on diesel electric production and even licensed manufacturers in other countries, to build to their designs. Despite (or because of?) their record total of 78,000 steam locomotives constructed over the years, Alco found the change to diesel electric production difficult. But the company persevered and produced many successful designs. In 1965 Alco dispatched to Australia five of the largest diesel electric locomotives ever exported from the US. These model C628 CoCo 2.05MW (2750hp) 176-tonne locomotives went into service at Hamersley Iron's iron ore railway in Western Australia. Three years later the A. E. Goodwin company of Australia built under licence even larger Alco locomotives. These were model C636 2.69MW (3600hp) machines for the three Western Australian iron ore mines: Mt. Newman, Robe River and Hamersley. Back in the US of A, some of those kids, when on holiday to other states, had once found themselves travelling in a train hauled by a Baldwin diesel electric locomotive of unusual design. Baldwin diesel electrics The Baldwin locomotive works, founded by Mathias Baldwin at Philadelphia in 1831, had prospered under steam locomotive production for over one hundred and twenty years. That company could be proud of many locomotive building records, including the first Mallet articulated locomotive. Baldwin's huge company plant, capable in 1940 of producing three THIS WAS THE DADDY OF ALL diesel electrics, the Union Pacific DD50 "Centennial". They were effectively two standard diesel electric locos on the one chassis. Rated at 4.92 megawatts (6600hp) these huge beasts weigh 247 tonnes and are almost 30 metres long. Note the huge fuel tank hanging underneath and the massive 8-wheel bogies. large steam locomotives per day, did not succeed in the race to the top in the diesel electric world. Traditionally they had custom built steam locos to the designs and requirements of each railroad. When the American Baldwin company did enter the diesel electric market, they continued to think big. In 1940 Baldwin engineers designed their prototype "Centipede" locomotive number 600, meant to contain eight 560kW (750hp) eight-cylinder diesel engines, each mounted across the loco body. Each diesel engine was to drive a DC generator, the whole loco thus to produce a total power of 4.5MW (6000hp). Engineering difficulties prevented all eight diesel engines being installed, so they ran with four, giving 2.25MW (3000hp). Mildly successful, 53 such locomotives were produced and sold to three US railroads. Sadly, today the Baldwin Locomotive Company is no longer in business. The General Electric Company, widely experienced in electric locomotive production since the 1920s, had less trouble in turning to diesel electric manufacture than did factories like Baldwin which had enormous investments in plant tailored to steamer production. Possibly that fact alone was enough to severely dent the fortunes of the Baldwin works but a worse mistake was their failure to see that railroads no longer needed single huge locomotives. Union Pacific "Big Boys" Union Pacific was and is one of America's most successful railroads, based in Wyoming. Wyoming is a mountain state, wherein the UP Railroad has for more than a century powered their trains over the Sherman Hill summit of the Rocky Mountains on the way to the west coast cities. From the marshalling yards of Cheyenne, long trains weighing up to 7000 tonnes would constantly stream up on the 104km (65 mile) climb to the peak of Sherman's Hill. They had always used giant steam locomotives. Their 2100 class engines had a 4-12-2 wheel arrangement which was almost unique in the world. Later came the articulated "Challenger" 4-6-6-4s and by 1941 JANUARY 1989 83 came the regular passing of the "Big Boys", reputedly the greatest and most powerful steam locomotives ever built. These 4-8-8-4s were a thing of beauty, power and grace, despite their enormous size. Made by Alco, these 4.5MW (6100hp) steam giants single-handedly hauled 5000 tonne trains over the Rockies. The loc0$Ilotive alone weighed 351 tonnes Imd the huge twelve wheel tender carried 30 tonnes of coal and 110 tonnes of water. The whole engine with tender fully loaded weighed close to 600 tonnes. They would eat up a full load of coal in 90 minutes flat on Sherman's Hill! That 135,400lbs (61.4 tonnes) tractive effort had to come from somewhere. No fireman could shovel coal that fast. Mostly his efforts would be expended inside that ship-like tender, trimming the coal as it slid towards the mechanical feed screw which force-fed the huge firebox. The fireman would have enjoyed the ride down the western slope. The double track Union Pacific line has been repeatedly straightened and graded, till now it carries a 145km/h speed rating for fast freights, all the 561km distance from Laramie down the long slope to Evanston (most of the width of Wyoming)! Gas turbine locos In 1949 the Union Pacific Railroad purchased from the General Electric Company something radically new - a 260-tonne gas turbine electric locomotive. Only a demo model, the men said, but the older steamer "engineers" looked at the new machine with suspicion and awe. "Can that crate full of airplane engine-cum-electric power house pull a train like our steamers?" No coal shovel was needed! But that "gas turbine crate" could exert a powerful pull on the drawbar, its 3.4MW (4500hp) driving through every one of its 16 wheels. The BoBo-Bo-Bo wheel arrangement was something quite new. Union Pacific bought fifteen of those gas turbine electrics in 1954, and often coupled two of them together, controlled by the one engineer at the head end. Such a combination proved about equal to a "Big Boy" in speed and pulling power. AS IF ONE CENTENNIAL was not enough, here are two DD50s coupled together to give a total of 9.84 megawatts or 13,200 horsepower. These were EMDs first locos to use alternators instead of generators and they used silicon rectifiers to produce the DC for the eight traction motors. 84 SILICON CHIP By 1959 a further order of gas turbine locomotives was delivered but this time GE made them as twounit locomotives by literally joining two machines together, giving a total of 6.34MW (8500hp). A twelve wheel fuel tank hauled behind catered for the heavy fuel consumption of the gas turbines. While the all up weight of the twin unit loco plus tender was comparable to that of the steam Big Boy, these GE gas turbine electric locomotives could certainly pull. They ·gave a total of 109 tonnes (240,000lbs) of tractive effort! The devlopment of gas turbine locos The General Electric Company had been into electric locomotive building from 1920, even before EMD began. GE had never been in the steam business so were not lulled into any false sense of future trends as the traditional steam loco niakers were. That fact, together with GE's worldwide financial power and diversity, accounts for GE being the only major competitor against EMD in today's world of diesel electric locomotive manufacture. But GE were not as committed to "off the shelf" locomotive selling as EMD. Consequently, when the Union Pacific Railroad wanted some exceptional locomotives designed and built, they went to GE to develop gas turbine locomotives from existing airplane engine technology. So successful were these GE gas turbine electric locomotives that the Union Pacific Railroad operated 40 of these giants during the 1960s, while no other railroad in the world ever got beyond one or two trial machines. The advantages of gas turbines lie in their high power to weight ratio but they guzzle fuel at an alarming rate. Gas turbines give their most efficient service when run at constant speed on full load for long periods. This suited the Union Pacific Railroad's long haul up the 1 in 122 grades approaching the 2515 metre peak of Sherman Summit on the Rocky mountains, running from the Cheyenne marshalling yards in Wyoming to Utah. Gas turbines are very inefficient in starting/stopping service, when idling or running on light load. Therefore GE included within the loco a 276kW (370hp) standard diesel engine and generator which supplied sufficient power for the downhill run. This had enough power to overcome rail friction, run the air compressors for the brakes, and supply the train control and headlights. It also provided traction motor field power for dynamic braking. The small diesel engine was also used to move the locomotive around marshalling yards. This meant that the big gas turbine did not have to be started for short runs. Due to the high noise level and high pitch sound of gas turbine engines, objections would have been raised if these locomotives had been used in heavily populated areas. However Union Pacific crosses the Rocky Mountains in sparsely populated areas, so few environmental objections arose. Due to the high turbine speed and the dry, high temperature ignition environment within a running gas turbine, these machines are more ANOTHER BIG POWER LOCO used by the Union Pacific was the C855 made by Alco. These are much bigger than any diesel loco even seen in Australia or anywhere else for that matter. They were rated at 4.1 megawatts (5500hp). susceptible to damage caused by dust in the air intake than are diesel engines. Therefore, great care was taken with intake air filtering in those locomotives. GE monster diesel electrics In 1964, General Electric continued its success by building a batch of 3.73MW (5000hp) diesel electric locomotives. These had an unusual Bo-Bo-Bo-Bo wheel arrangement (ie, four 2-wheel bogies) with all 16 wheels driven by eight DC series traction motors. Designated the U50 class, they employed two 16-cylinder diesel engines. Alco answered the challenge by producing three C855 class 4.1MW (5500hp) Bo-Bo-Bo-Bo diesel electrics for the same railroad. And this was not the last of Union Pacific's forays into big big power locos. EMD's novel design Breaking away, temporarily, from their general-purpose off-theshelf philosophy, the Electro Motive Division of General Motors designed a line of monster diesel electric locomotives for Union Pacific. These are unique in many respects. As the year was 1969, the hundredth anniversary of the completion of the UP line, this locomotive class was called " Centennial" . Each loco had two 16-cylinder V16 diesel engines, with a total rating of 4.92MW (6600hp). They employed huge 4-axle bogies with all wheels driven. Also a first for EMD was the use of alternators and silicon rectifiers to provide very large DC currents for the DC series traction motors. The complete locomotive weighed 247 tonnes. Today the Union Pacific operates a very successful railroad using 1400 diesel electric locomotives altogether, one of the largest fleets in the USA. But today's trend is away from the 5000 and 6000 horsepower monsters towards more modern and more economical designs. That's a story for a future episode. ~ JAN UA RY 1989 85 I PRODUCT SHOWCASE I Goldstar DM-6335 auto-ranging DMM Computer aided loudspeaker design Digital multimeters are becoming smaller all the time and this new model from Goldstar continues the trend. Easily fitting into the palm of your hand, the DM-6335 measures up to 1000 volts DC or 750 volts AC and has a 3 ½-digit liquid crystal display. There are five DC voltage ranges - 200mV, 2V, 20V, 200V and 1000V - and four AC voltage ranges, with 750VAC being the top range. There are also five resistance ranges: 200n, 2kn, 2okn, 2ookn and 2oookn (ie, 2Mn maximum resistance measurement). There is also a continuity (low resistance) range which has an audible beeper to allow you to use it without looking at the readout. Both the voltage and resistance measurement functions include auto-ranging and auto-polarity (the latter being standard on all DMMs) so there is no need to switch ranges. The unit can measure AC and DC current in two ranges: 200mA and 10A. The DM-6335 also includes a "data hold" button which enables A new software package for computer-aided loudspeaker optimisation and design is now available. Called Calsod, it runs on IBM PC/XTs or PC-compatibles with a minimum of 512K of RAM and a colour graphics card. Included with the software is a 140 page user manual which features a number of design examples explained in detail. When running this software the designer uses graphical curve fitting techniques to develop models of the sound pressure and impedance curves of individual loudspeaker drivers. A passive crossover network can be defined with up to 60 components and then Calsod optimises the summed acoustic output of the drivers in a multi-way system to achieve the desired response. Standard filter target functions include Butterworth, Linkwitz-Riley and constant voltage designs. List price of the package is $349 including postage and handling. For further information contact Audiosoft, 128 Oriel Road, West Heidelberg, Victoria 3081. you to hold a reading so you can write it down or compare it with an earlier reading which can be stored with the "Mem" button. These are both handy features. Recommended retail price is $118.80 and this includes a 1-year warranty. The Goldstar range of digital multimeters is widely available from electrical wholesalers and retailers. EPROM burner for IBM PCs & compatibles Electronic Solutions has just released a comprehensive EPROM burner with "drop down" menu software. It is suitable for programming most EPROMs and comes with a high quality ZIF (zero insertion force) socket and the capability to add three more sockets if required. Some of the EPROMs catered for include 2716, 2732, 2764, 27128, 27256, 27512, 2804, 2816, 2864 and 58064. The EPROM burner comes complete with software and user 86 SILICON CHIP Miniature blow-torch from Dick Smith manual for $245 (tax included), and with a 14-day warranty. For further information contact Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 427 4422. Dick Smith Electronics has introduced a new butane-powered pencil size blow torch which is very convenient to handle. It can be used for silver soldering, brazing small articles, bending or shrinking plastics, glass crafts, jewellery making and repair or assembly of models. The torch holds enough gas for 30 minutes operation and can be quickly refilled. Price of the torch is just $14.95 while the butane gas refill is $2.80. It is available from all Dick Smith Electronics stores. Impressive 200mm plasma display Music synthesiser card for IBM PCs & PC-compatibles It had to happen. The Taiwanese are in on the act. Following the considerable interest shown in our Plasma Display articles published in the August and November 1988 issues, a commercially produced Plasma Display is now being imported by Jaycar The glass display bulb is 200mm in diameter with a black plastic pedestal which accommodates the electronics. It is powered by a 12V 800mA DC plugpack. Instead of having a single main discharge path which wanders all over the inside surface of the bulb, this plasma display has numerous discharges which move about continuously like the tentacles of a Medusa. It is quite eery to look. The internal electrode is also quite strange to look at. Made of glass with a conductor poked up inside it, it appears to almost be on fire. The internal electrode glows red wherever a discharge strikes from it. The discharge itself is blue If you have ever wanted to play music on your IBM PC or compatible you now have the chance with this music synthesizer card from Contact International. The half-size IBM card has three outputs and a thumboperated volume control. There are two RCA sockets providing stereo line outputs to an external amplifier and a stereo headphone socket for 3.5mm jack plugs. It will work with 320 or higher impedance phones. The card is supplied with software on several IBM format floppy discs, together with two instruction manuals. Hardware required is an IBM PC/XT (or AT} or compatible with a minimum RAM of 256K. The software works under DOS 3.0 or higher. We assume that a colour graphics card is also required. Interested buyers should check this point. Price of the music synthesizer card is $350 including sales tax. For further information write to or phone Contact International Pty Ltd, Suite 2, 283 Burbridge Road, Brooklyn Park, SA 5032 (PO Box 390, Cowandilla, SA 5033}. Phone (08} 231 2202. and then glows red as it strikes the glass envelope. The intensity of the display can be varied with a level control and it can also be sound modulated via an internal electret microphone. Priced at $199 , the plasma display is available from all Jaycar stores. Economy 25 watt soldering iron If your budget does not run to one of those fancy temperature con- trolled soldering irons you should consider this economy 240VAC 25 watt iron from Jaycar. It comes with a stainless steel barrel and a pre-tinned copper tip which is easily changed over if need be. JANUARY 1989 87 The sample submitted to SILICON CHIP came with a pointed tip but for most work a wedge or chisel tip is more effective. A minute or so's work with a file will easily fix that problem and you have an iron which works well and doesn't cost the earth. It is available from all Jaycar stores. Nicad charger comes with 4 AA cells Is DAT dead? Yes, says Akai While the arguments go on about the introduction of DAT recorders, Akai has come to the conclusion that DAT (digital audio tape) recorders are dead, at least for the time being. Therefore they have put a lot of money into developing their new top end stereo cassette deck, the GX-95. It features Dolby HX-Pro, $5000 insurance is included in the purchase price of each Surgebuster. This will pay for the repair of any appliances which are damaged due to voltage surges while a Surgebuster is in use. Available from all Dick Smith Electronics stores, the Click Surgebuster is $49.95. Eveready has released a new compact charger for use with AA and AAA size nickel cadmium cells. Known as the Eveready ACC86 Recharger, the unit is a plugpack design with compartments for four cells. One to four cells may be charged at a time and there is a LED indicator to show that the unit is on. The ACC86 comes blister packed with four AA size nickel cadmium cells and is now widely available from department stores and sales outlets across Australia. Surge protected power outlet When you need this product you might not even know it but you'd regret not having it if you didn't. Could you follow all that? The product in question is a surge protected power outlet, the Surgebuster. It plugs into your normal mains power point and protects any equipment plugged into it against high voltage spikes. These could be 88 SILICON CHIP B and C noise reduction and a new record/playback head design which effectively gives separate record and playback heads on a single head core. The GX-95 has just about every feature you could possibly think of on a cassette deck and infrared remote control. Recommended retail price is $1295 and the unit comes with a 2-year warranty. It is available only at selected Akai hifi dealers. Computer oscilloscope from Heath/Zenith caused by lightning or surges on the line. Made by Click Industries Pty Ltd, the unit contains three metal oxide Varistors (MOVs) to protect against voltage spikes between active and neutral, neutral and earth, and active and earth. It can be used to protect any appliance and is a wise precaution for those appliances which are permanently powered such as refrigerators and VCRs. In the future your computer might be your oscilloscope. But why wait for the future? The Heath/ Zenith SC-4802 computer oscilloscope is now available in Australia. It converts the computer into a dual trace 50 MHz digital storage oscilloscope. Using the accompanying software, all the scope functions are provided via the computer's keyboard and all waveforms, measurements and menus are displayed on the screen. By taking advantage of the computer's computational (ie, ability to do sums) and storage capabilities, the software allows complicated test procedures to be carried out. Regardless of where you live in Australia, you can take advantage of Rod Irving Electronics' discount prices either through our Sydney and Melbourne stores or our Mail Order Service. Simply phone your orders through on (008) 33 5757 for the cost of only a local call. (Inquiries and local orders phone (03) 543 7877) -= ~ ,--=-= NICADSI Save a fortune on expensive throw away batteries with these quality Nicads and Rechargers! Size Desc. 1-9 10+ 100+ $2.95 $2.75 $2.50 $9.95 $9.50 $8.95 $9.95 $9.50 $8.95 = NEW TRANSISTORS Rod Irving Electronics have two new transistors which will replace a m1,lltitude of common hard to get devices. - DB25 CONNECTOR SPECIALS! WIRE WRAP IC SOCKETS These quality 3 level wire wrap sockets are tin-plated phosphor bronze. Cat.No. Description 1-9 10+ P10579 8 pin $1.50 $1.40 P10580 14 pin $1.85 $1.70 P10585 16 pin $1.95 $1.80 P10587 18 pin $1.95 $1.80 P10590 20 pin $2.95 $2.70 P10592 22 pin $2.95 $2.70 P10594 24 pin $3.95 $3.50 P10596 28 pin $3.95 $3.50 P10598 40 pin $4.95 $4.50 Type 1-9 Female $2.95 Male ... $2.95 The PN1 OOis aNPN general purpose PN3638A, PN3640, PN3644, PN4121, PN4143, PN4248, PN4249, PN4250, PN4355, PN4916, PN491 7, PN5910, 2N2905A, 2N3467, 2N3702, 2N3906, 2N4125, 2N4126, 2N4291 , 2N4402, 2N4403, 2N5086, 2N5087, 2N5447. 10 + $0.15 joins. (Note: This mode cannot be used continuously.) A _range of 6 long-life tips are available. ROYEL DR-30 (21 WATT) •3mmtip • 240V operation, no transformer required • Safety Standards Approved • 6 months warranty Cat T12640 . . .. ........ ' 1i=t' • 6.Smmtip • 240V operation, no transformer required • Safety Standards Approved • 6 months warranty Cat T12650 . $5.50 $0.10 $0.12 $0.12 $0.12 QUALITY 5mm LEDS Cat. No. Col. 1-9 2 10150 Red $0.08 21 0151 Gm $0.15 2 10t52Ylw $0.15 10+ 100 ➔ $0.07 $0.06 $0.12 $0.10 $0.12 $0.10 ~ fifL a_i!I; b MAIL ORDER HOnlNE 008 335757 fTOLLFREEJ • GOLD INSERT LOW PROFILE IC SOCKETS • • • • Gold machined pins Extremely high quality Anti-wicking . Ideal for professional use or where field service ol components is required. Cat.No. Description 1-9 10+ P10620 8 pin $1 .20 $1.10 P10624 14 pin $1.60 $1 .50 P10626 16 pin $1 .90 $1.B0 P10628 18 pin $2.00 $1.80 P10630 20 pin $2.20 $2.00 P 10632 22 pin $2.40 $2.20 P10634 24 pin $2.60 $2.40 P10640 28 pin $2.90 $2.60 P10644 40 · pin $3.00 $2.70 7404 7406 7416 7445 74123 . 74LS162 74LS393 LM339 LM3086 5256 $0.50ea $0.50ea $0.50ea $0.60ea $0.50ea $0.50ea $0.90ea $0.50ea $0.50ea $4.00ea 1 MEG DRAM MCM 511000P-10 $59.95 10 + $3.90 ...................... $3.50 P10962 3 PIN CHASJS MALE 3 .t SPECTROL 64Y MULTI TURN TRIM POTS RECHARGEABLE12V 1·2AH GELL BATTERY Leakproof, long service life batteries ideal for security systems, emergency lighting or as a computer backup power supply, etc. Cat. S15029 ...... Normally $19.95 CODE KEYPAD P10966 3 PIN CHAS IS FEMALE • • • • $4.95 ...................... $3.95 Telephone type digital keypad. Fou r digit, chan'?.eable code Over 5000 possible combinations. P.owerconsumption : SmA standby. 50mA alarm. • Two sector LED and 1 arm LED. • Wrong number lockout. • 12V DC operation • Relay output. • Panic button . • Normally open tamper switch. • Dimensions: 145 x 100 x37mm • ACP3 compatible. Cat. A13014 .......... R.A.P. $79.95 Cat.No. R14700 R14710 R14720 R14730 R14740 R14750 R14760 R14770 R14780 R14790 R14800 R14810 R 14820 R14830 R 14840 R14850 Description 1-9 10R .. .. $3.50 20R ......... $3.50 SOR ....... $3.50 100A ....... $3.50 . 200R ...... . $3.50 SOOR ....... $3.50 1K ...... ... $3.50 2K ........ $3.50 SK .... . $3.50 10K ......... $3.50 20K . ...... $3.50 SOK .. ...... $3.50 1OOK .... ... $3.50 200K ....... $3.50 500K ..... .. $3.50 1M ...... .... $3.50 10 + $3.20 $3.20 PANEL METERS GALORE! We have too many of th~ following panel meters, so we're sellmg them to you at bargain prices. Don't miss out! Cat.No. Description Price Q10500 MU45 0-1mA ....... 10.50 010502 MU45 0-SOuA ..... . 12.50 010535 MU45 VU ............. 10.95 010533 MU52E 0-5A ........ 14.50 1~9 10+ 2155 240V 6·15V 1A Cat. M12155 $9.95 $8.95 2156 240V 6-15V 2A Cat.M12156 $14.95 .S13.95 2840 240V 9V GT Cat. M12840 $5.95 $4.95 2851 240V 12-6V CT 150mA Cat. M 12851 $5.95 $5.50 2860 240V 15V CT 250mA Cat. M12860 $5.95 $4.95 6672 240V 15-30V 1A tapped Cat. M16672 $14.95 S13.95 $17 .50/m .'Vttti.. :r..··:1....:e··_._·.. ., . RODIRVING ELECTRONICS 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 SOUTH AUSTRALIA: Electronic Discounters P/L1 305 Morphett St, ADELAIDE ~2~r:e~~~BJs2Jf 1 9 Y JA ~y INTERST ATE DUE TO FREIGHT COSTS Diecast boxes are excellent for RF shielding, and strength. Screws are provided with each box . H11451 100 x 50 x 25mm . $ 5.95 H11452110x60x30mm . $ 6.50 H11453120x6Sx40mm. $ 6.95 H11461120x94x53mm $11.50 H11462188x 120x78mm ... $13.50 H11464188x 188x64mm ... $29.50 MAIL ORDER: Local Orders: (03) 543 7877 Interstate Orders: (008) 33 5757 All Inquiries: (03) 543 7877 CORRESPONDENCE: P.O. Box 620, CLAYTON 3168 Telex: AA 151938 Fax: (03) 543 2648 - I MAIL ORDER HOTLINE OOIJJS757 ~ [TOLL FREE, STAICl\.YORDERSONI. Y) · • LOCAL ORDERS & INQUIRIES fOJJ 543 7877 HOOKUP WIRE Plastic boxes with aluminium tops, and available in four sizes. Very popular for projects and very ecconomical! H10101 150x90x50mm $ 3.25 H10102 195x113x60mm $ 4.50 H10103 130x68x41mm $ 2.75 H10105 83x54x28mm $ 1.95 H10110 t20x65x38mm $ 2.95 H10112 t20x65x38mm $ 2.95 (Metal top) Cat. No. Oescrlp11on W11251 13/. 12 TNDBLK W11252 13/. 12 TLD BROWN W1 1253 13/. 12 TLD ORANGE W11254 13/.12 TLD YELLOW W11255 13/. 12 TLD GREEN W11256 13/. 12 TLO BLUE Wl 1257 13/. 12 TLD WHITE PRICES PEA 100 METRE ROLL 1-9 10 + $5.95 $5.00 W1126014/. 20RED W1126114/. 208LACK W11265 14/.20 BLUE Wl 1268 14/.20 WHITE PRICES PER 100 METRE ROLL 1-9 10+ $12.00 $3.20 $3.20 $10.00 W11270 24/.20 RED W11272 24/.20 BLACK W11274 241.20 GREEN PRICES PEA 100 METRE ROLL 1~ 10+ $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $19.00/m D $3.20 $3.20 $3.20 $3.20 BE~ Red and white twisted Conductors : 2 x 1 strand 0.17mm Sheath: 0 .0 . 2 x 1.35mm Cat.W 1-9 rolls 10 + rolls DIECAST BOXES UTILITY BOXES cw ECONOMY TRANSFORMERS CANNON TYPE CONNECTORS 1-9 P10960 3 PIN LINE MALE. SPECIAL, ONLY $69.95 WHILE STOCKS LAST IN QUANTITIES OF 10 ONLY ROYEL DR-50 (30 WATT) ROYEL DR-60 (40 WATT) $5.95 IC SPECIALS! $39.50 •Smmlip • 240V operation, no transformer required • Safety Standards Approved • 6 months warranty Cat T12645 . . ........... .. $44.50 P.A. SPEAKERS Low dual cone, wide range. 200mm (Sin .). Ideal for public address, background music, etc. Tremendous Value at these prices! . ..... ....... Cat.C12000 1-9 10+ I ••• LO~L;-77 bunon depressed, the power is $0.12 $0.15 $0.15 $0.15 100 + $1.95 $1.95 ,.-•-.~ • temperature recovery from larger 10 + $2.50 $2.50 LOW PROFILE IC SOCKETS - doubled, allowing much heavier work to be completed , or a rapid 100 + $4.50 ...................... $3,90 Save a small fortune on these ·• Direct Import" low profile IC sockets! PCB mounting solder tail. Dual wipe. All tin p!ated phosphor bronze or berryllium and dual wipe for reliability Cat.No. Description 1-9 10+ P10550 Spin ......... $0.20 $0.15 P10560 14 pin ....... .. . $0.25 $0.20 P10565 16 pin .......... $0.35 $0.20 P.10567 1B pin ......... $0.40 $0.30 P10568 20 pin ........ .. $0.40 $0.30 P10569 22 pin .......... $0.40 $0.30 P10570 24 pin ..... $0.40 $0.30 P10572 28 pin .......... $0.50 $0.40 P10575 40 pin .... ...... SO.SO S0.40 I The DUOTEMP range are designed to idle with a normal tip temperature of 360°G, without its button depressed. In this mode they are ideal for delicate work such as printed circuit boards. With the 100+ $0.50 $0.50 $0.40 $0.60 $0.60 $0.50 $0.50 $0.60 $0.50 10+ P10964 3 PIN LINE FEMALE 100 + $0.18 10 + $0.60 $0.60 $0.50 $0.65 $0.65 $0.60 $0.60 $0.65 $0.60 Cat. No. Col. 1-9 2 10140 Red $0.15 2 10141 Gm $0.20 210143Ylw $0.20 2 10145O,a $0.20 RCA GOLD PLATED PLUGS AND SOCKETS For those who need the ultimate in connection. Essential for laser disc players to get that fantastic sound quality. Plug Cat. P10151 $2.95 Socket Cat . P10150 $2.25 $3.00 ..... ................. $2.50 The PN200 is a PNP general purpose amp at collector currents to 1 Amp. Both are TO-82 plastic package PN2907, PN2907 A , PN3638, $0.70 $0.70 $0.60 $0. 70 $0.70 $0.70 $0.70 $0.75 $0.70 QUALITY3mmLEDS . DB 25 CRIMP SPECIALS! medium power amp and switch with continuous collector current up to 500mA. PN100 REPLACES: PN2221, PN2222, PN2222A, PN3585, PN3568, PN3569, PN3643. PN5133, 2N2219A, 2N2222A, 2N3414, 2N3415, 2N3416, 2N3417, 2N3700, 2N3704, 2N3904, 2N4123 , 2N4124, 2N4401 , 2N5088, 2N52 10. PN200 REPLACES: TYPE 1-9 gp 9S 9C 15P 15S 15C 25P 25S 25C - --·-=====at KEY SWITCHES 1-9 Cat. S12500 .. $14.00 $12.00 W11280 32/.2 BROWN W11282 321.2 BLUE PRICES PER 100 METRE ROLL 1-9 10+ $20.00 $18.00 POSTAGE RATES: $1 - $9.99 ... $10 - $24.99 $25 - $49.99 $50 - $99.99 $100 - $199 $200 - $499 $SOO plus The above postage rates are for basic postage only. Road Freight, ~~~kr~~~lr~~~;~~~:t~'.I be All wholesale and sales tax exempt inquiries to: RITRONICS WHOLESALE, 56 Renver Rd, Clayton. Ph. (03) 543 2166 (3 lines) Errors and omissions excepted. Prices and specifications subject to change. :~~;•:.i~s~j;;,~~~afk>¼~~~~~s Machines • Apple is a registered trademant. 'Denotes registered tradmarks ol their respective owners Now TDK have improved the situation with the release of their VHS-C three pack in their E-HG (extra high grade) formulation. The three pack is a convenient size where one C-cassette is not long enough. The three pack will be available at TDK dealers and selected department stores for $56.85. Image sensor for closed circuit TV '." ··/, ~ , , ·.,· . ..1/ One possibility is the averaging of successive samples of a repetitive waveform to eliminate random noise superimposed on the signal. Included in the software is a Basic-compiled executable program as well as a source listing for those who want to customise the program. Computer generated cursors can be placed anywhere on the displayed waveforms to simultaneously provide direct readouts of voltage differential, time differential and frequency. Waveforms can be saved on disc and compared. later with a "live" waveform. Up to two stored and two "live" waveforms may be displayed simultaneously. Anything displayed on the screen may also be printed out. For further information on the Heath/Zenith SC-4802 computer oscilloscope contact the Australian 0 distributor, Anitech, 1-5 Carter Street, Lidcombe, NSW 2141. Phone (02) 648 1711. Special VHS-C 3-pack from TDK There is no doubt that the popularity of video camcorders is growing by leaps and bounds with the market being a battleground for Video-8 and VHS-C formats . Up to now though, VHS-C cassettes have not been all that readily available and certainly not cheap. ft~ '-'o/. ..~ ru +tic '-' '-'$ '-' c.:=; .~~ ......,.._,..._ 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 90 SILICON CHIP Ever wanted to put a TV camera into your model train? Now it can be done. A complete video camera subassembly incorporating a solid state image sensor is now available from Philips Elcoma. It needs only a chassis and lens system to form a complete black and white camera for machine vision and surveillance applications. The unit consists of a CCD (charge coupled device) imager and all the necessary drive and video processing circuits, plus power supply. Included in the user-selectable options are interlaced or noninterlaced signal, automatic or manual iris lens, and internal or external sync. When used as the basis of a machine vision system, the unit provides a non-interlaced signal with 604 (horizontal) by 294 (vertical) picture elements, corresponding to a horizontal resolution of up to 450 lines. Light sensitivity is good - the unit is claimed to give a useable picture down to ambient light levels of Mailbag - continued from page 3 Heavy duty automotive solenoid This is a handy item if you want to install accessories in your car or wish to modify the existing wiring to make the accessories more reliable. The solenoid is fitted with quickconnect terminals for easy wiring and is turned on and off by a 0.5 lux. The specified signal to noise ratio is 46dB and bandwidth is 5.8MHz. Surface mount components have been used extensively to make the assembly as small as possible. The printed circuit boards fold up to make a unit just 89 x 40 x 45mm, with a mass of 125 grams. Power required is 12 volts DC at about 165 milliamps membrane switch which mounts on the dashboard. A selection of labels is also provided and these include legends for windscreen washers, hazard lamps and spot lights. The solenoid is rated at 30 amps DC. The solenoid and membrane switch is available at $30 from Prepak Electronics, 27 Cowper Street, Granville, NSW 2142. Phone (02) 637 1221. For further information, contact Philips Elcoma, 11 Waltham Street, Artarmon NSW 2064. Phone (02) 439 3322. Footnote: about that video camera in a model train - it's already available. Lionel Trains, Inc in the USA, are offering a number of their O-scale locos with inbuilt camera. The video signal is conducted along the rails. The technology letters - ctd from p.43 idea. He told Chiefie to spread the word to the men. Instead, he bought the entire block himself. The man was a prime example of the saying, "He wouldn't shout if a shark bit him!" At the Christmas party, I had a bit of a giggle when he expressed dismay that he had forgotten his wallet. Then I was told this is a standard ploy. He never seemed to have money or a cheque book. He figured to have the last laugh by reorganising the department. One day I was told, "Your job no longer exists." The next day, however, another senior technician started. He was clever enough to negotiate taking the job contingent on receiving a number of courses given by the suppliers. After a year in which he spent 28 weeks away from the station, he resigned to take a better position with another company. During this interval, I have been involved in the security industry. That's an even funnier scene but I'll save those stories for the next letter. Hoping to hear from you soon, Colin. Regards, Dick. ~ statement. However, if the device does pose such a threat, is there any reason why one could not insulate the lid rim with a silicone sealant? The silicone (eg, Silastic) would prevent direct contact with the lid and would help hold the jar in place. Also, it can be obtained in various colours if required. Is this a viable solution or would it cause interference with the operation of the unit? The discharge spheres at Expo '88 are approximately 50cm in diameter and are nothing short of fascinatingly awesome, albeit with an absurd price tag. This project may be the closest one will ever get to the real thing. It's good to see the editorial staff haven't been bitten by the computer bug. Keep up the excellent work. S. McBride Townsville, Qld Comment: there is nothing wrong with the idea of using silicone sealant but when it cures it would make the jar very hard to remove from the base. which houses the EHT circuitry. ~ DESIGN MANUFACTURE REPAIR of Electronic Equipment No Job too Small or too Large Industrial and commercial control and testing systems, designed and manufactured to your requirements. Audio Amplifier Modules: from 60 Watt rms 0.01 % THD to 500 Watt rms 0.0001 % THD (Only 5 connections to be made). Temperature Meters: from -200 deg. C. to 1300 deg . C. Remote Sensing up to 1 km HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment (02) 633 5897 (02) 92 6309 Fax (02) 925 0840 JANUARY 1989 91 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question . Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Solution to tape player problem With reference to the letter from R. P., of Latrobe, Tasmania, in the ••Ask Silicon Chip'' pages of the October issue, I think I may be able to help. A couple of years ago, I repaired a friend's auto-reverse car cassette player that had the same fault (ie, it continually shuttled between forward and reverse). Not having seen the unit before, all I could do was to take it out of its case and have a look at how it worked. I found that there were two nylon pulleys of about half an inch in diameter, and about half an inch apart, that spun together via a square cross-sectioned rubber belt. This assembly was mounted near the play head and spun around whenever a cassette was playing. I can't remember the exact operation but the fault turned out to be a loose belt between these two pulleys, causing slippage. Any "lost motion" here results in Problem with the FM stereo transmitter I have come across a problem with the Mini-mitter. I have built one and it oscillated in and out of stereo at about one second intervals. I was. able to stop this oscillation by fitting a 0.1µF capacitor from pin 13 to GND. This does not affect the received sound. Your comments would be of interest. Now a comment on the House Number that Glows, as published in the October issue. The 4020 gets too hot to touch. I used a 3300 resistor to pin 16 and it now runs well. (G. W., Bombala, NSW). 92 SILICON C HIP the mechanism not knowing which direction of play it is supposed to be monitoring and hence it continually hunts. The best advice I can give regarding a repair of this kind is to have a real good look at the works. It is amazing how much you can learn about these machines just by looking closely at what still does work in them. I would even go as far as spinning the flywheel with my fingers , without power on, just so I could get a better look. (N. G., Ryde, NSW). • That is good advice, N. G. With mechanical faults , careful observation is the best method going. Another slant on auto-reverse decks With regard to R. P. 's letter on auto-reverse cassette players, I have serviced a number of these decks with this type of fault. These cassette decks provide the auto-reverse in quite an ingenious manner. Under the clutch platen of • As indicated in the Notes &: Errata on page 96 of the December issue, there was an error in the circuit and wiring diagram of the FM stereo transmitter project. The capacitor should have been .001µF instead of .01µF as marked. It should work without problems with the correct value. As far as the House Number project is concerned, the 4020 should not even be warm let alone hot. The fact that yours does get hot indicates that the 4020 is faulty or has one of its unused outputs shorted to the positive or negative supply line, probably with a small blob of solder . You can confirm this by careful inspection of the copper side of the board. both drive and take-up spindles is a small magnet which induces pulses in a nearby Hall effect sensor when the spindle rotates. These pulses are fed to an amplifier and delay circuit which controls a solenoid. The solenoid operates about 0.7 seconds after pulses cease and changes the drive from one spindle to the other and also operates a changeover switch to monitor pulses from the other sensor. A continual attempt at reversing about once a second indicates a drive failure, either by a belt or the motor. A belt failure is easily seen on disassembling the unit. There is also a common motor fault which can be fixed, if you are careful. The motors used in many auto-reversing decks are prone to develop a burnt low spot on the commutator and will tend to stop at that point, even though they are drawing some current. Careful dismantling of the motor, a light cut of the commutator in a lathe and a very slight increase in brush pressure is the solution. Warning: the speed governor is an integral part of the motor. Treat it very carefully and do not touch the adjustments. (D. B., Glen Iris, Vic). • Thanks for that answer, D. B. It seems from the letters published here and last month, that these auto-reverse cassette decks are troublesome beasts. We hope that this info will be of help to readers. More background on cassette players I read, with wry amusement, the letter from R. P., of Latrobe, Tasmania, in the October issue asking for help on auto reverse tape players. I may be able to shed a little light on the subject. For the uninitiated, auto reverse units can be very frustrating and I wouldn't be surprised at the number of units External timebase for 1GHz DFM I recently completed the 1GHz Digital Frequency Meter (published November, December 1987 and January 1988) and it is a little beauty. Thank you for the article. I ran into trouble with a poor crystal at first but I fixed the problem with another from an old counter kit from the US. My meter is now stable to 1 ppm (part per million) or so. But I want to use a spare mini oven unit as an external oscillator. This unit puts out 10MHz at about 4 volts peak to peak. Your circuit on page 40 of the November 1987 issue shows an external oscillator connection at pin 24. Can I disable the oscillator circuit at pins 25 and that have ended up in the drum at the end of the bench. In order for the unit to know when one side of the tape is finished, there will be a sensor under one or both take-up spools. These sensors can range from simple wiper contacts, to a reed switch and magnet through to Hall Effect devices. Regardless of the type, they all generate pulses while the tape is moving. In R. P. 's case, the spools are not producing these pulses, hence the unit thinks that the tape has finished and selects the other side. As the spools stop turning, the unit again selects the first side and so on. Possible causes are main drive belt slipping, idler wheels off each flywheel are dirty or dirty contacts on the wiper under the spools. The simple rule with tape players is to clean all idler wheels and the surfaces that they run on, clean the drive belt, pulleys and flywheels and finish up with the tape path (pinch rollers, head etc). Use "clear" metho and a cloth to clean parts (including the rubber ones) and don't be afraid to really scrub them either. Never apply too much oil to shafts as it will only attract dust. Use a point to apply the oil (ie, just a 26 and feed my external oscillator into pin 24 after isolating it from the + 5Vline? If that is OK, what should be done with pins 25 and 26 to prevent any spurious problems? There is plenty of room in the case to place the oven between the power supply and main counter boards. So my only problem is lack of info on the 7216A circuitry. I have enjoyed SILICON CHIP so far and will be renewing my subscription. Keep up the good work. (R.S., Gibson, WA). • There are two ways in which you can connect an external oscillator to the 1GHz frequency meter. First, if you want to retain the existing oscillator crystal between pins 25 and 26, you need to use the external oscillator input at pin 24. But you tiny drop) and never apply it where it can get onto any rubber parts. Finally, if a drive belt in a malfunctioning machine is more than two years old, replace it. It shouldn't cost more than a few dollars. (P. H., Alice Springs, NT). • All manner of cassette and VCR belts are available from Belnew Pty Ltd, PO Box 1110, Parramatta, NSW 2150. Phone (02) 689 3327). Can't get special parts Your magazine provides interesting projects but there are drawbacks to some of them. You give pictures, layouts, etching patterns, parts lists and construction details but what is the point of publishing all this info if you cannot buy the necessary components? I know I can get them in kit form but I would like to make my own PC board, my own housing for the finished project and so on. If you can design the project, why can't you tell us the suppliers that will have the critical components. (P.H., Browns Plains, Qld). • Yours is a familiar cry if ever there was one. We can understand exactly how you feel. The problem can't just feed a signal into this input - you have to "enable" it. To do this you need to disconnect the control input, pin 1, from 0V and connect it to pin 23. Note that the on-chip oscillator (pins 25 & 26) will continue to function when the external oscillator is selected. The external oscillator frequency must be greater than 100kHz or the chip will enable the on-chip oscillator. However, since you intend to build the oven oscillator into the case, there would seem to be no need to use the external oscillator function. Instead, all you need do is to disconnect the 10MHz crystal and associated capacitors from pins 25 and 26 and connect the output from your oven oscillator to pin 25 (the onchip oscillator input). Do not make any connection to pin 26. is that there are only a few suppliers who are willing to grab the opportunities presented by the projects published in SILICON CHIP. Even then, some of the kit suppliers take months before they manage to bring a particular kit onto the market and then they don't do much to advertise that it is available. There is a wonderful opportunity here for small electronics components suppliers to get in on the act. As yet though, the only component retailers who can supply most of the special semiconductors are Geoff Wood Electronics and David Reid Electronics. In the meantime, it is usually cheaper to buy a kit even if you have some of the parts in your collection. Bits for the high energy ignition I am interested in the High Energy Ignition but where in South Australia can I get the parts? Repco Auto parts had not heard of the Siemens HKZ101 when I enquired at their main headquarters here in SA. (L. B., Netley, SA). • To our knowledge, the Siemens HKZ101 is only stocked by Jaycar JANUARY 1989 93 Reluctor input for high energy ignition I have a query regarding the High Energy Ignition system featured in the June 1988 issue of SILICON CHIP. Do you intend to present a circuit for use with a reluctor type pickup? I have a 1987-model Sigma with a faulty ignition module. The replacement cost is in excess of $400 which to me is prohibitive. Any help you could give in adapting your circuit to my car would be greatly apstores. Repco stores will know nothing of the Siemens device but should be able to supply the right Bosch rotor for your car. You can buy the MJ10012 and MC3334P separately from Jaycar but buying their complete kit is a better proposition. Queries on the FM antenna Thanks for a good down-to-earth magazine. The October issue was really enlightening. I am definitely going to build the FM transmitter. I would appreciate a simple method to use the headphone jack of my hifi system, as the line inputs for the FM transmitter cannot be connected in any other convenient way. Would a simple lead with impedance matching resistors in the 6mm plug be appropriate? Could you suggest what resistor values to use? The FM antenna is a must for me as I experience unbelievable multipath distortion (as observed on my TV} and would love to send a clean signal to my FM tuner. Your antenna is the answer as I do not feel like spending $600 or so to get a tuner with complex front-end circuitry to overcome poor signal quality. Your design looks right and the installation instructions are great. However, could you clarify a few questions? The diagram on page 29 of the October issue shows the active dipole with two values, 1440 and 94 SILICON CHIP preciated. The pickup coil resistance is 6000 ± 500 but the inductance is unknown. (E. B., Hughesdale, Vic}. • In the May issue we published abridged data on the Motorola MC3334P and this included Motorola's suggested circuit with a reluctor pickup. One of our readers recently phoned to say that he had made the circuit work with a Ford distributor containing a reluctor pickup which he had obtained from a wrecker's yard. On that basis, give the circuit a try. You've got little to lose and it should work. 1400mm. 1400mm appears to be the correct value from the values shown for the lower elements of the folded dipole. The acrylic insulator is shown as 50mm wide in the drawing and 40mm in the parts list. The 38mm spacing between holes makes 50mm look like the correct figure. I would appreciate a polar plot of the antenna characteristics and what its effective impedance really is. The text implies it is 3000. The paragraph on narrow acceptance angle is OK but a graph says it all. The "ARRL Handbook" says that folding the active dipole helps increase its bandwidth and a friend mentioned that it improved the matching impedance. I am sure it does more. The antenna size and weight is large. Is a 1.2mm thick boom strong enough? Would this change the impedance? Can I use Duralumin (an aluminium alloy containing small amounts of copper, magnesium, manganese and silicon. Ed.} or does this also affect the impedance? I'm a scrounger and have a few old broken TV antennas in the garage. I use a 3-element FM antenna and would modify it if it matched your design. The "What Is a Yagi Antenna" explanation is just too brief. Your last paragraph is not incorrect but seems too simplistic. Could you elaborate on these issues as they must have been considered in your design? (J. T., Ringwood North, Vic} • Wattalotta questions! As far as the FM transmitter is concerned you can feed signals from your amplifier's headphone jack directly into the line inputs. No matching resistors are required since the headphone output has a low impedance. In the diagram showing the antenna, both dipole . dimensions are correct. The plan view of the complete antenna shows the dipole with the correct "electrical" length of 1440mm which takes into account the effect of the small vertical end elements. We would like to be able to publish polar plots of antennas but unfortunately we don't have those measurement facilities. Folding a dipole increases the nominal impedance at its resonant frequency from 750 to 3000. Adding a reflector and directors then lowers that impedance. Folding the dipole also increases the bandwidth. We could go on but to explain it all would take a lot of space and quite a lot of maths. In presenting this article we were not attempting to give an exhaustive explanation of design principles. A 1.2mm boom thickness is fine. Have a look at commercial antennas. Their booms are thinner. You can use any metal you like and it won't affect the electrical performance as a receiving antenna. As far as adding more directors are concerned, what we said is correct. Designing a Yagi antenna is a very much a tradeoff between size, complexity, gain and bandwidth. Increasing the number of directors to increase the gain will tend to have a deleterious effect on bandwidth. Sure, you could add more directors but to get a real benefit in gain, without losing bandwidth, the antenna would have to be a great deal larger and therefore not practical. Notes & Errata Poor Man's Plasma Display, November 1988: the Veroboard wiring diagram on page 44 contains an error in the wiring to the 555. Pin 3 is shown connected to the positive supply line. The copper strip between to the 1k0 resistor and short supply link should be cut. Silicon Chip Back Issues Issue Highlights November 1987: Car Stereo in Your Home ; 1 GHz Frequency Meter; Capacitance Adapter for DMMs. December 1987: 1 00W Power Amplifier Module; Passive lnfrared Sensor for Burglar Alarms ; Universal Speed Control and Lamp Dimmer; 24V to 1 2V DC Converter. January 1988: 4~ wtie UHF Antenna; ~ iti1Bow er Supply; Custom P~ \ RJ!ige< Subcarrier Adapter for~ ers. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm ; End of File Indicator for Modems; Simple Door Minder. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Low Cost Function Generator; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools ; Slave Flash Trigger; Headphone Amplifier for CD Players. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars ; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars ; Automatic Light Controller; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid ; Booster for TV & FM Signals; The Discolight Light Show . August 1988: Plasma Display ; Remote Chime/Doorbell ; High Per- formance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Electronic Fish . Bite Detector; Switchmode Charger for 12V Gel Batteries; Vader Voice . October 1988: Stereo FM Transmitter; High Performance FM Antenna; Led-Light 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. BACK ISSUES ORDER FORM Please send me a back issue for : D December 1987 D February 1 988 D June 1988 D July 1988 November 1 988 D D December 1988 Enclosed is my cheque/money order for $ ______ or please debit my D Bankcard D Visa Card D MasterCard D March 1988 D August 1988 Card No D April 1988 D Sept.1988 D November 1987 D May 1988 D October 1988 ~I~~~~~~~~~~---~~ Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_/__J_ _ Name.________________________ (PLEASE PRINT) Stree..__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/tow ,__ _ _ _ _ _ _ _ _ _ _ _ Postcode____ ~----------------- Price: $A5.00 each (includes postage)'. Overseas orders add $A1 .00 per issue for postage . NZ & PNG orders are sent by air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 ___________________ J JANUARY1989 95 T CEN'l'R£ 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 1 5 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 ($7 00) Name .. .. ·· · ·· · · · · •·· · · · · · ...... ... ..... ··· ·· ·· ·· ·····" Address Suburb/Town Enclosed is my cneque or money order for$ .......... .. D Bankcard Card D Visa Card Postcode ... or please debit my D MasterCard No l~~~--~~~~~--~~~~~-~ Advertising Index Allied Capacitors . . . . . . . . 31 Altronics . . . . . . . . . . . .50-53 Arista Electronics . . 17 Avtek . . . . .. . . IBC Ballarat Electronic Supplies 15 Contact International . . . .. 73 David Reid Electronics . . . . IFC Dick Smith Electronics . . 1 2, 1 3 36,37,60,61 Geoff Wood Electronics . . . . 67 Hycal Instruments . 91 ICS . . . . 65 Jaycar Electronics 22-25 74-77 Kenwood Australia ... OBC RCS Radio . . . 90 Rod Irving Electronics . . . 89 Scan Audio . . . . . . . . . . . 31 Signature ......... ............. .. ... .. ....... .......... ....... ........ Card expiry date ..... ../... .. .../ ........ PC Boa rds FOR SALE BUILD YOUR OWN LED Moving Message board. $75 for a 4-character display experimenter's short form kit and $1 50 for 1 6 characters. Includes PC boards, EPROM and full instructions to complete the project to a professional standard. Loaded from Centronics printer port or PC/XT keyboard. Equivalent commercial units start at around $1000. For more info send a 39c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. RADFAX 2: HI-RES RADIO facsimilie, Morse and RTTY program for IBM PC/XT on 360K 5 .25-inch floppy plus full documentation. Need CGA. SSB HF BATTERY PACKS Replacement for G.E., Motorola, Kenwood, lcom, etc portables. Low cost. Guaranteed. Mobile Communication Systems, PO Box 261, Woodville, SA 5011. 96 SILICON CHIP FSK/tone decoder. Has re -align, autostart, view, magnify, save, print. Also "RF2HERC" same as above but suitable for Hercules card and "RF2EGA" for EGA card (640 x 350 mode). Programs are $30 each plus $3 postage. Only from Michael Delahunty, 42 Villiers Street, New Farm , Qld 4005. Phone (07) 358 2785. PLASMA BALLS, JARS from $80. "Poor Man's Plasma Display" power supply drives our 12-inch ball. Phone (02) 319 2427 . AMSTRAD CPC664 colour computer. 64DKtronics extra plus RS232 games and communications disks. $650 plus freight & insurance. Mobile Communication Systems, 54 Russell Terrace (PO Box 261 ), Woodville, SA 5011 . RADIO/TV RESTORERS - We have a large stock of new valves . Send SAE for list or phone Shellharbour TV Service, 26B Mary St, Shellharbour, 2529 . (042) 95 1175. 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, 2139 Great North Rd, Avondale, Auckland, NZ. Phone 88 5730 . 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 . NOW SAVE EVEN MORE ON THESE OUTSTANDING MODEMS Avtek, the longest established Australian modem manufacturer, now gives you a chance to get even better value when you buy. Just check the features and the prices of Avtek and you'll see why it's the modem chosen by more and more PC users. More compact and reliable than most and suitable for data transfer between PCs, on-line services, E-mail and all videotex facilities like VIATEL (Model 123 only). Available as a standalone RS232 model or as a plug-in true ½ card for IBM PCs and compatibles. Specifications: Data Standards CCITTV.21 (300/300 baud full duplex). Data rates - CCITTV.23 (1200/75 baud). AN/DEAL FIRST MODEM! A fuly automatic operation, HAYES-compatible smart modem. Choose from 3 model 21/23 12 123 models (internal or external) 300/300, 1200/75 300/300, 1200/1200 300/300, 1200/1200, 1200/75 $ 325 325 399 A highly reliable data communicator at a budget price. The compactly designed Minimodem II is supplied complete with Telecom-approved, pushbutton phone. PHONE NOW FOR FAST DELIVERY PH: (02) 888 5333 All Avtek modems are sold complete with power supply, instructions and telephone connections. Designed and built in Australia, service and technical support for modems is available direct from Avtek Data communcations. MAIL ORDERS WELCOME. AVTEK, P.O. BOX 651, LANE COVE 2066. 30-DAV. NO-QUESTIONS-ASKED, MONEY-BACK GUARANTEE. 89] YTEK ATA COMMUNICATIONS (A Member of the NetComm Group of Companies) SEND COUPON TODAY! 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