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guie.ten the fan in your computer l~s1S' I SERVICING - HIFI - t '-tc1Rott,c_____......s~~~ 120 Watt PA Amplifier Module Adding a headset to the Speakerphone The modifications are easy ~ Car salety light "'Q. Stops sideswipes at night al z 0 z ~ .5:! :0 ::, Screws and screwdrivers What you need to know Q. iii j Poor man's plasma display ■■► ~ <>, Uses an ordinary incandescent globe -g Plus - the Original & Best TV Serviceman, Vintage Radio, The Way I See It, the Evolution of Electric Railways .c G) iii 'i5, £ High Performance In Your Shirt Pocket! 3 l /2 digit LCD Display Ranes Vdc Vac Ade 200mV-1kV 2V-750V 200mA 10A Aac 200mA 10A Ohms 200O-2Mf.l 100µV 1mV 100µA 10mA 100µA 10mA o.rn 0.5% +1dig 0.75%+5dig 0.75%+ 1dig 1.5%+5dig 1%+5dig 2%+7dig 0.75%+1dig Display also has Low Battery & Over-Range Indication Built In Diode Check, Lo-Power Ohms & Continuity Test Beeper Memory Function for Relative Readings (DM6235 & DM6335) Autoranging Manual Ranging Over-Ride (DM6235 & DM6335) One Vear Warrant Hold Reading Function (DM6335) 10A Range Automatic Current Limiting Overload Protected to 1000Vdc/750Vac $88.80 $99.60 Look At The Low Pricesl DM6135 Autorang ing 3 1/2 digit 1OA ac/dc DM6235 As above with Memory function and Range Hold Prices include 9V Battery and High Quality Silicon Rubber Test Leads with Screw-On Alligator Cl ips DM6335 As above with Data Hold l0MQ Input Impedance Gotta Gatta GoldStar Dealer enquiries welcome . Call (02)736 2243 Recommended prices only including Sales Tax $118 • 80 You've Gotta Getts Goldstar from : M.,L John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355 N..S.YI', Ames Agency 699 4524 • J Blackwood & Sons• George Brown 519 5855 Newcastle 69 6399 • Auto-Catt Industries 526 2222 • D.G. E. Systems (049) 69 1625 • W. F.Dixon (049) 69 5177 • Ebson 707 21 11 • Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Pty Ltd 698 4776 • Petro-Ject 569 9655 • David Reid 267 1385 • Digitel 709 6511 • Geoff Wood 427 1676 N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 QUEENSLAND Ausl ec (07) 854 1661 • G. Brown Group (0 7) 252 3876 • Petro -Ject (075) 91 4199 • St Lucia Electronics 52 7466 • Cliff Electronics 341 4655 • L.E.Boughen 369 1277 • The Electronics Shop (075) 32 3632 • Thompson Instruments (Cairns) (070)51 2404 • Nortek (Townsvi lle)(077) 79 8600 S.AUSTR ALIA Protronics 212 3 111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688 • J Blackwood & Sons 46 039 1 • Petro-Ject 363 1353 TASMANIA George Harvey (003) 31 6533 (002) 34 2233 VICTORIA Rad io Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 430 1 • A.W.M. Electrical Wholesalers• Petro-Ject 419 9377 • J Blackwood & Sons 542 4321 • Factory Controls (052) 78 822 • Mektronics Co 690 4593 • Truscott Electronics 723 3094 W AUSTRALIA Atkins Carlyle 481 1233 • Debbie Instruments 276 8888 • Protronics 362 1044 .:.... .··.· .,,..,. ' - - .. Ef -.·,_,_. J - , NOVEMBER 1 988 FEATURES 4 Screws & Screwdrivers by Leo Simpson What you need to know 8 Quieten the Fan In Your Computer by Leo Simpson We give you the options 76 The Technology Letters by Richard Kopf Only the names have been changed 96 The Evolution of Electric Railways by Bryan Maher Pt.13: A look at diesel electric locomotives HERE'S A PLASMA DISPLAY that everyone con afford. It uses o large incandescent bulb and on easy-to-build EHT generator. Details page 40. PROJECTS TO BUILD 14 High Power PA Amplifier Module by Bob Flynn Will drive a 100V line transformer 40 Poor Man's Plasma Display by Leo Simpson Uses an ordinary incandescent light globe 64 Build a Car Safety Light by John Clarke Stops sideswipes at night 68 Add a Headset to the Speakerphone by Greg Swain The modifications are easy 87 Dynamic Balancing for Electric Fans by Steve Payor Simple yet effective technique THIS HIGH-POWER MOSFET amplifier module con drive a 100V line transformer for PA work, or con be used as a guitar amplifier. Construction starts on page 14. SPECIAL COLUMNS 28 The Way I See It by Neville Williams Look out TV servicemen: VCRs are now disposable 34 Vintage Radio by John Hill What to do about the loudspeaker 54 Serviceman's Log by the original TV serviceman My friend (the enemy) Flicker 92 Amateur Radio by Garry Cratt What's all this talk about SINAD? ARE YOU INVOLVED in electronic servicing? You 'll need to know all about the various types of screws and screwdrivers. See page 4. DEPARTMENTS Publisher's Letter Mailbag Circuit Notebook Back Issues 82 Product Showcase 2 3 32 70 90 Bookshelf 91 Subscription Page 102 Ask Silicon Chip 103 Notes & Errata 104 Market Centre ., ___ IT'S EASY TO ADD a lightweight headset to the Speokerphone described in the September issue. We show you how on page 68. NOVEMBER1988 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, VK2ZPW Norman Marks Steve Payor, B.Sc. , B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd . All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd , Waterloo, NSW 2017 . Printing: Masterprint Pty Ltd , Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rate: currently $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 PUBLISHER'S LE'l-l'ER Servicing and serviceability When you are about to buy an electrical appliance or piece of electronic equipment, do you stop to think about how you might service it? With many purchases, this may not be an important factor but with others it will be. Say, for example, you want to replace the power cord or the brushes on your fancy new electric lawn edger. Sure, you may not need to do this for years and years but when the day arrives a small repair job may- mean the difference between discarding or replacing the appliance. This is why we have included the feature on screws and screwdrivers in this issue. Over the last few years there has been a small revolution in the manufacture of a great deal of electrical and electronic equipment. The end result is that you, the purchaser, can't gain access to the interior, to do even the most minor of repairs. That this is wrong is obvious. That it is a deliberate move on the part of manufacturers to prevent their equipment being repaired by buyers is also obvious. There are a number of things you can do about this development. First, you can find out about the different types of screw fastener now being used by reading the article in this issue. Second, you can now purchase the screwdrivers you need from speciality tool suppliers. Third, and this is most important, you can decide, at purchase, that you won't buy equipment which is deliberately designed to prevent you from gaining access to its interior. Ultimately, you may be making a choice between a piece of equipment which can be repaired in the future and one which must be thrown away when it fails, no matter what the cause. Consider that we are not talking about economics here. It often costs more for the manufacturers to use tamper-proof fasteners in their products. They are making a decision to make their products unserviceable or, at least, not accessible by people without special tools and equipment. Nor are we talking about voiding of warranties. On a lot of equipment, if you break any seals or leave evidence of having made any modifications inside, the warranty will be null and void. That is OK. We can live with that. After all, if equipment is under warranty and it fails, it should be returned for service. What we are attempting to do is to make you, the consumer, a little more informed when you go to make your next purchase. It could save you a lot of money in the future. And, by having the right screwdriver on hand to do a repair job, you will have more choice about whether you fix or replace an appliance. Leo Simpson MAILBAG Easy solution to fault in GE TV I have just read the Serviceman's Log in the August edition of SILICON CHIP. Being a technician myself I feel I must comment on the story from J. L. of Tasmania. It concerns his description of a fault in a GE TV. He says the easy solution to the fault is to remove the crowbar switch transistor in the protection circuit, thus disabling the circuit completely. I cannot agree with this as the manufacturer has designed that part of the circuit to protect the rest of the set in case of certain faults occuring. It is necessary to disable protection circuits sometimes to enable a fault to be repaired but they should never be left disconnected after the fault is completed. The most likely cause of the fault is C722, a lOµF 25V electrolytic in the protection circuit. I have had quite a few of these fail. This causes the crowbar to trip and the 560 fuseable resistor to go open circuit. There is a considerable AC waveform across this capacitor in the faulty state and this is what causes the crowbar to trip. Hope the above information may be of some use. Thanks for a great magazine. R. Palmer Burnie, Tasmania Good performance from bow-tie antenna Like J. J. of Kingsley, WA (Ask SILICON CHIP; Sept. 1988), I built the UHF Bow-Tie Antenna, and tested it inside the house. I live near Singleton and the nearest UHF (SBS) and VHF (Ch.3 & Ch.5A) transmitters are at Newcastle, some 80kms away - definitely a fringe area. The old rabbit ears make Ch.3 & 5A look like Thredbo in a storm! I wasn't even sure whether · we had SBS at Newcastle. Surprise, surprise! By placing the bow-tie array against the Newcastlefacing lounge room window, I got perfect reception on SBS and near perfect reception on Ch.3 & 5A. The reception was much better than on some, "you-beaut" fringe area antennas which collapse every time a magpie lands on them. Now the bow-tie antenna is permanently installed outside under the eaves beside the picture window. When channels 3 & 5A go over to UHF in the next year or two, I'll be ready. Denis Cummings Dights Crossing, NSW PS: I had to make some small modifications. The local aluminium producers and suppliers don't have 6mm tubing. It's only available in Queensland, I'm told. I used 6mm solid rod for the bow ties and 3'mm solid rod for the reflectors. Comment: the UHF Bow-Tie Antenna is not intended for VHF reception so you must have very strong VHF signals in your area. Poor man's plasma display A much cheaper version of the plasma display can be achieved by using a normal light bulb instead of the expensive display unit. I connected a 100 watt bulb to the EHT lead and looped an earth line around the top half of the bulb. The effect is quite good, considering the cost of the bulb. Nick Labordus St Ives, NSW Comment: a number of readers have contacted us with similar information. As you can see, we've taken the idea one step further with the Poor Man's Plasma Display in this issue. Commendations for the AC Millivoltmeter I have just finished constructing two of your 1GHz Frequency Counters and am very pleased with the results. Construction was relatively straightforward, although putting in the large number of wire links was a little tedious. The stability of the crystal is very good. Drift is less than 1Hz over a period of three hours after a 10-minute warm-up. In common with most other enthusiasts, I have noticed that sometimes a project is described which really captures the interest, whether it presents a solution to some SILICON CHIP, PO Box 139, Collaroy Beach 2097. technical problem or a means to upgrade one's test equipment. Such is the case with the AC Millivoltmeter published in the August and September issues. I eagerly await the release of a kit for this project as I intend to build two of these meters; one for home and one for work. Two modifications that I recommend for the project are for a balanced input using an--XLR connector and a switchable input impedance of 20k0 and 6000. These mods would be of great use to technicians in the broadcast industry, where balanced lines running at + BdBm and a headroom of + 24dBm are standard. The thought has possibly crossed your mind, as it has mine, that this meter could be the basis for another project, a fully fledged Noise & Distortion Meter. All that needs to be added is a tunable notch filter. The "all" in that sentence is a bit tonguein-cheek, as I am aware of the difficulties of designing a notch filter which can be varied from say, 20Hz to 20kHz, and yet have a notch depth of at least 60dB. R. Tregea Pennant Hills Background music is a nuisance Back in 1982, one of the electronics magazines had a project which could cancel the vocal part of records etc so that one could sing along with the music. I would like to see a project with the reverse effect - that is, to cancel out the music. As a person with a hearing dis a bility, I find background music on TV documentaries disconcerting and obtrusive. Often, it makes the narration difficult to understand. It would be OK if the music ceased when the narration started but quite often it doesn't. S. Walker Gravely, Qld Comment: we agree that music can be a problem with many programs and not just for the hard-of-hearing. If you have a stereo TV set you can get an improvement by switching to mono but otherwise we know of no way of improving the situation. NOVEMBER 1988 3 ~~-,·~-4//fl&lf ,,, Screws & screwdrivers: what you need to know Years ago, if you were in electronic servicing, you only needed two types ·of screwdriver, flat bladed and Phillips head. If you 're still trying to get by with these two types, you stand a good chance of butchering screws and your screwdrivers. By LEO SIMPSON "Use the right tool for the job" . That's always been a good rule to work by and it still is. In this article we give you the good oil on all the different types of screw fastener in use today. If you want to service electronic equipment these days, you must have the right screwdrivers to gain access to the innards. If you don't have the right screwdrivers you 4 SILICON CHIP can be stymied before you start. And if you attempt to undo screws with the wrong screwdriver, you stand the chance of butchering the screw heads or the screwdriver, or both. If you haven't worried about this problem up till now, we'll give you a good example of screw types that can cause problems. If a screw has a cross-type head it is a Phillips type, right? Not necessarily. In fact, probably 50% or more of the cross-head screws used in today's electronic equipment are Pozidriv. The difference is very important. Superficially, Phillips and Pozidriv (pronounced "pozzy drive") screws look the same. But a Philips screwdriver won't fit properly into a Pozidriv screw. If the screw is really tight, you stand a good chance of butchering the head. On the other hand, if the screw head is case-hardened, as many are these days for use with power screwdrivers, you may break the flutes off the screwdriver tip. Compared to a Phillips head screwdriver, a Pozidriv type of the same point size [we'll explain that ◄ As a starter kit with interchangeable screwdriver bits, it would be hard to go past this set made by Vessel of Japan and sold by Colliers Tools. It has bits for slotted, Phillips and hex head screws later) looks blunter and heavier and the fluting is more complex. Where the Phillips type has just four tapered flutes to fit the screw head, the Pozidriv type has a subsidiary flute in between each pair of main flutes. Another feature of the Pozidriv head is that the flutes are not tapered whereas they are on the Phillips type. You can see the differences in one of the photos. The net effect of these differences in profile is to give a screw and driver combination which can take more torque before "cam out" occurs. In other words, you can apply more twisting force to the screw. Photographs in this article show the subtle differences between Pozidriv and Phillips screwdrivers but how do you recognise the screws themselves? Again, the differences are fairly subtle but once you know what to look for, they are easily recognisable. Look at the diagram at right. The Pozidriv screw has a more complicated crosshead design with a "star" pressed into the head, at 45 degrees to the main cross. The star runs into the cavity of the screwhead and actually accommodates the subsidiary flutes in the screwdriver head. Now that you know how to identify Phillips and Pozidriv screws, have a look at the crosshead screws on some of your appliances and electrical equipment. Look for that little star shape over the main cross - that's a Pozidriv. Now take a Phillips head screwdriver and see how it mates with the Pozidriv screw. It does so very poorly. You will see that there is a poor match between the flutes on the Phillips screwdriver and the internal driving faces of the Pozidriv screw. It is because of this poor match that screws and screwdrivers are liable to be damaged. The moral of this is that you must use the right type of screwdriver. But it goes fur- This diagram shows some but not all the screw types now being used in electronic and electrical equipment. Not shown are types such as Oval and Drive screws and tamperproof Torx, which has a pin in the centre. The Triwing type is very common in domestic electrical appliances. ther than this; you must also use the right size. large hardware stores and tool supply outlets. Point sizes Another crosshead Phillips and Pozidriv screwdrivers are sold in point sizes. Phillips come in sizes O to 4 while Pozidriv comes in point sizes 1 to 4. To be properly equipped for electronics work, you need at least point sizes O to 3 for Phillips and sizes 1 to 4 for Pozidriv. Phillips point size 4 is mainly used on cars and trucks. Just to confuse the issue, there is another type of screw which is almost exactly the same as the Pozidriv type, known as Supadriv. Thankfully, Pozidriv and Supadriv are compatible. Pozidriv screwdrivers are available from most Another crosshead style of screw and screwdriver is the Frearson type, as made by Reed and Prince (USA). This is not compatible with either Phillips or Pozidriv. Inevitably, you run the same risk of damaging the screw or driver if you use the wrong type. The Frearson screw head pattern is much more angular then the Philips pattern. The screwdrivers are not designated by point sizes but by blade diameter; eg, 3/16-inch, 1/4-inch, 5/16-inch etc. Frearson head screwdrivers are usually only available from specialist tool suppliers. NOVEMBER 1988 5 ;;;;,:,..., , At left is a T-handled Torx screwdriver from Arista which is needed if you wish to gain access to an Apple Macintosh. The other small Torx drivers are from Geoff Wood Electronics. ,::••,.,M. This diagram highlights the design of the Torx screw and screwdriver bit. Don't try to undo Torx screws with Allen keys as you will damage both screw and driver. Tri-wing screwdrivers Tri-wing screws are very commonly used in electrical appliances such as powerboards made by Kambrook and frypan controllers made by Sunbeam. They look a little like Phillips head screws except that they have three flutes (or blades) instead of four. Unlike the Phillips/Pozidriv incompatibility there is absolutely no other driver which will fit and undo a Tri-wing screw. Either you have the correct driver or you don't start on the job. They are available from specialist tool suppliers. Torx screwdrivers Torx screws and screwdrivers are yet another revolting development. They are used in quite a lot of electrical appliances and in com6 SILICON CHIP m> This handy Torx set includes sizes Tl0, T15, T20, T25, T27, T30 and T40. It is available from Bowthorpe Australia. Phone (02) 525 2133. puters, such as the Apple Macintosh. At first sight, a Torx screw looks a little like an Allen key but Allen or hex drivers do not fit properly and if you try to use them you again run the risk of damaging both screw and driver. In effect, the tip of a Torx screwdriver is a male spline which fits into the socket of the screwhead. They come in five common sizes: T15, T20, T25, T27 and T30. Incidentally, if you want to take an Apple Macintosh apart you need a Torx screwdriver with a shaft about 15cm long. Arista are now stocking a suitable unit. Apart from that, specialist tool suppliers do supply Torx screwdrivers or bits for magnetic holders in hand or power screwdrivers. A much bigger range of Torx screws are used in industry and in cars, particularly those of European origin. As well as using the sizes listed above they also use T40, T45, T50 and T55. There are also outside male versions of Torx screws and they require Torx wrenches which look similar to a ring spanner. As an even further obstacle to the home handyman or service technician, some appliance manufacturers are using a tamperproof version of Torx screws. These have a pin to stop a normal Torx screwdriver from being used. Again, specialist tool outlets can supply the bits to order. Allen and hex screws These are widely used and fortunately Allen and hex drivers are readily available. However there is another driver for Allen screws which can be useful, the ball head driver. This fits into standard Allen screws and is handy when you need to drive at an angle. Spintites and nutdrivers If you want to get inside an IBM PC or Tandy computer you need a nutdriver of the appropriate size to fit the Spintite screws. While the Spintite screw design does include a screwdriver slot, it is very shallow and difficult to use with a conventional blade screwdriver. Again, you don't want to butcher the screws so use the correct nutdriver. Alternatively, use the correct This photo highlights the differences between crosshead screws. From left: Pozidrive, Frearson and Phillips. Note the "star" pressed into the head on the Pozidriv screw. size box spanner (available in sets with 1/4-inch socket drive). Oval and drive screws These are screws with no slot or socket at all. Oval head screws are used in places such as the power supply of IBM PC computers while drive screws are used in appliances where the manufacturer is deliberately preventing an access for service. In fact, when you see appliances fitted with these screws you should be forewarned - the manufacturer has no intention of servicing the unit. It's a disposable product. However, where there is a will there is a way, to be sure. Oval head screws can generally be removed with a good pair of pliers. They should be replaced with Phillips or slot head screws which can be easily removed in the future. Drive screws can usually only be removed by butchery. The way to do it is to cut a slot in the screw head using a small abrasive disc in a Dremel Moto-tool or Arlec Supertool. Then you can use a conventional screwdriver to remove the screws which should immediately be tossed in the bin. Other special screws There is a number of other screw types which are used in specialised equipment. These include Ferry cap and the clutch head. The Ferry head screwdriver looks like a conventional box spanner. Clutch head This close-up shows the difference between Pozidriv (left) and Phillips (right) screwdrivers. Note the extra flutes on the Pozidriv type. screws have a butterfly-shaped socket. If you are lucky you can sometimes remove clutch head screws with an ordinary screwdriver but this is against the odds. Clutch head screws are normally driven in very tightly (which is why they are used) and hence you do need the correct drivers to work with them. Again, specialist tool suppliers do stock them. They normally come in seven sizes, 3/32-inch to 3/8-inch. ISO screws ISO screws are a reversal of the trend to make screws impossible to remove. They are a combination Phillips and slot head screw. They are widely used in Japanese electronic equipment and in electrical fittings such as circuit breakers. They are a good idea. Dressing of screwdrivers All screwdrivers wear with use. With flat bladed screwdrivers you can dress them to the correct profile if you have a grindstone. On the other hand, all the other screwdrivers such as Phillips or Pozidriv, cannot be redressed. Once they are visibly worn they should be tossed out. This brings us to another facet of screwdrivers. If you are using air or electrically powered screwdrivers, it is useful to know that screwdriver bits can be obtained with three degrees of hardness. For production applications, the hard- A common problem of access: this Sunbeam frypan controller uses Triwing screws. They are impossible to undo with any normal screwdriver. ness of the bit should be matched to the type of screw in use. For standard soft screws, there are standard hardness bits. For heat-treated screws and those intended for use with impact screwdrivers, use screwdriver bits with intermediate hardness. These have been specially tempered to cope with the high stress of impact use. For driving sheet metal or case hardened screws, use the degree of hardness specified by the manufacturers of the bits. Your tool supplier can help with this information. ~ NOVEMBER1988 7 Quieten the fan in your computer Are you plagued by a noisy fan in your computer? We show you a number of ways to go about making it a lot quieter. By LEO SIMPSON Let's face it, users of personal computers have been really put upon. Not only do they have to put up with inscrutable instruction manuals and impenetrable software, they also have to listen to the noisy fans in their machines. There are two main reasons why the fans in computers are so noisy. First, nearly all fans are rigidly mounted within the power supply case. That means that all the noise 8 SILICON CHIP they generate is amplified by the resonant metalwork of the computer. Second, many of the fans are very noisy in themselves and many are noisy right from the day they were installed by the manufacturers. Some have slack and noisy bearings, some produce a lot of hum and some have poor blade design and so make a lot of wind noise. But whatever the cause of the noise problem, it is not helped by mounting the fan rigidly. In fact, many fans are rivetted to the power supply case. What can you do? The first hurdle is to gain access to the fan. In many computers, this is not easy. The fan is built inside the switchmode power supply. It provides cooling for the power supply as well as the rest of the computer circuitry. To gain access to the inside of the computer you will need the correct screwdriver or nutdriver. Using the wrong screwdriver can butcher the screws on your computer. At the very least, this looks messy. At worst, it may prevent you from getting inside the metalwork. So use the correct screwdriver (see the article on screws and screwdrivers elsewhere in this issue). There is one trap to be aware of in selecting the correct screwdriver. Some computers made in Asia use screws that look like the Phillips type. However, Phillips screwdrivers don't fit too well. You may find that Pozidriv screwdrivers are a better fit even though superficially, they are not Pozidriv screws. Having extracted the power supply from the computer chassis, you now have to gain access to the interior. On IBM PCs, you may find that one of the screws holding the power supply case together has no screwdriver slot. This fiendish device is a "drive screw" and is designed to stop you from opening up the case. If you have a good pair of pliers you may be able to get a grip on the head of this screw and so remove it. Failing that, you may have to cut a slot in the head, using a hacksaw or a small abrasive cutting wheel in a Dremel Mato-tool or Arlec Supertool. When you get the screw out, throw it away. You should replace it with a self-tapper having a proper slot or Phillips head. The next job is to inspect the fan which will normally be attached to the lid of the case. It pulls air through holes in the case and blows it out though a hole or louvres in the rear of the computer metalwork. The first question to be answered is whether it is a DC or an AC fan. On most computers the fan will be a 12V DC model and it will usually'be a brushless type. It makes sense for the manufacturers to use a 12V DC fan since it means they don't have to worry about supplying a 110VAC or 240V AC fan to match the AC supply line - the switchmode supply does it all for them. Removing the power supply from your IBM-compatible is a matter of using the correct nutdriver or 1/4-inch drive socket spanner. Don't forget to disconnect the mains cord before starting work. On many computers, such as this Tandy 1000, the fan will be rivetted to the case. Turn the chassis upside down while drilling out the rivets so that metal swarf does not fall into the computer. Do not reduce the voltage to the fan below 8V. Many fan motors will Reducing the voltage not work reliably below 8V. Assuming that it is a 12V DC fan, There are two ways to reduce the you can usually gain a worthwhile voltage to the fan. One is to connect reduction in noise merely by reduc- a 2.7V or 3.3V 1W zener diode in ing the voltage fed to it. We suggest series with one of the supply leads. you try reducing the voltage to The second method is to connect a 5 around 9V. This gives quite a mark- watt resistor in series with the suped reduction in noise while not mak-· ply leads. The value of the resistor ing a big difference to the air-flow. will have to be calculated. With better quality fans, the current drain or the wattage will be stamped on the fan housing. For example, a Commodore PC5 that we modified used a Papst model 8312 DC fan rated at 1.8 watts. To find the current drain, we divided the wattage by 12V to get a current drain of 150 milliamps (ie, 1.8 7 12 = 0.15A = 150mA). To calculate the resistor value, NOVEMBER 1988 9 To mount the fan compliantly, you need to ream out the mounting boles to take small grommets. Again, turn the chassis upside down so that any metal shavings fall out. ·c,,,.. • •~:,, r This photo shows how the fan mounting screws are held in grommets to prevent transmission of fan noise to the chassis. we then divided the wanted voltage drop by the current: R = 3 -;- 0.15 = 200. Therefore, we could have used a 220 or 180 resistor, rated at 5 watts. Zener diode If you don't know the fan's current drain, it is easier to use a zener diode to drop the voltage, because no calculations are required. To fit the zener diode (or resistor) in place, cut the positive supply wire to the fan and strip about 6mm of insulation from the two wire ends. Tin the wires with solder and 10 SILICON CHIP then slip a short length of heatshrink sleeving (say 30mm) over one wire. Now clip the leads to the zener so that they are about 10mm long. Solder in the zener diode so that the positive end [cathode - the end with the stripe) is connected to the incoming supply. The negative end connects to the fan. That done, slide the sleeving over the zener, to cover both connections, and shrink it in place. Compliant mounting While reducing the voltage to a DC fan can give a worthwhile reduction in noise, you can obtain a much bigger reduction by mounting the fan compliantly. This involves the use of screws and nuts supported by small grommets. The grommets provide mechanical isolation for the fan and cut down on the transmission of noise through to the power supply case and then to the rest of the computer's metalwork. Fig.1 shows the method of mounting the fan. The four screw holes in the lid of the power supply case are drilled out to take small grommets. We used small grommets made by Advanx, type Al, and these needed a chassis hole 1/4-inch in diameter. Then the fan is secured using 3mm screws, nuts and washers. Often, as we mentioned above, the fan will be rivetted in place. This means that you will have to drill the rivets out. Use a drill which is no larger than necessary. We suggest a 3/16-inch or 7/32-inch drill. Then use a tapered reamer to open the holes in the power supply cover to 1/4-inch. Don't drill the holes to this size as there is a chance that the resulting holes will not be round. Having removed the fan, you can decide whether or not to replace it. Having proceeded this far, you may like to try the effect of oiling the bearings. You will need to strip off the cover on the motor shaft and then use a pair of fine circlip pliers to remove the circlip and then disassemble the fan. Take care with the disassembly. If the fan has roller bearings they are likely to be spring-loaded and will flick out to be lost forever. Fan replacement Frankly, we don't think it is worth trying to oil the fan motor's bearings. It is just too much trouble. If the bearings are noisy, we suggest replacement of the fan. If you do decide to replace the fan, it is better to go for a fan rated at 220VAC instead of one rated at 12V DC. All things being equal, a 220VAC fan operating at 50Hz will always be quieter than a DC fan, and this seems to apply even to brushless [electronically commutated) versions. On the other side of the coin, DC fans apparently last longer than AC fans because they have less internal heat dissipation. The latter point is significant because the noisiest fans we have come across have been AC fans with failed bearings. When you replace the fan, choose a brand of known good quality. You don't want to go through this same process in six months' time. As far as we know, fans are not specifically made for operation at 240VAC but those rated at 220VAC will work quite happily. If the fan in your computer is a nominal 3-inch type (ie, 80 x 80mm), we recommend the Papst model 8850. This is a very quiet fan with a rated capacity of 21.8 CFM (cubic feet per minute). · If you are going to purchase a fan of Taiwanese origin, we suggest you test it for noise before fitting it. We have found that some Taiwanese fans are not reliable. Cautions and provisos Before you decide to dive into COMPUTER MET Al WORK FAN I 3mm SCREW / GROMMET Fig.1: how the fan is mounted. Note the use of locknuts to secure the screws. your machine, there are some points to consider. First, don't on any account meddle with a machine which is still under guarantee. Any The Papst Model 8850: a quiet fan from Germany modification, no matter how trivial, may void the guarantee. Second, if your computer is chock-a-block with peripheral boards and a hard disc drive, it may not be wise to reduce the voltage to the fan. It is possible that reduced voltage to the fan may cause the ventilation to be inadequate. Third, if your computer has a hard disc drive, it is highly likely that most of the noise comes from the hard drive rather than from the fan. You can tell if this is the case by blocking off the fan vent with your hand. If this causes a big reduction in noise, then it will be worthwhile to proceed with the above modifications. If not, leave it alone. A final point to consider is the machine's ultimate resale value. If any modifications you make are visible and look amateurish, you will surely reduce the machine's resale value. Perhaps a reduction in noise is more important than resale value but it is still a point you should consider before proceeding with modifications. ~ FASTENER TOOLS THAT FIT BETTER,LASTLONGER VESSELL 14-PIECE RATCHET DRIVER SET Features: For a really quiet fan, we recommend the model 8850 from Papst. This uses an induction motor with an external rotor motor. It is rated for 220VAC operation but operates quite happily at 240VAC. Its noise figure is quoted at 24dB Aweighted at an output of 21.8 CFM. This figure is obtained with the fan suspended in rubber bands. 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Cat D-8310 Was $59.95 s399s • NSW • Albury 21 8399• Bankatown Squa-e 707 4888 • Blacktown 671 7722 • Bondi Junction 387 1444 • CampbetHown (046)27 2199 • Chatnrood ChaH 411 1955 • Chullon 642 8922 • Gore Hill 439 5311 • Goaford 25 0235 • HCN'Tllby 477 6633 • Uverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 1 1 ~; ~mr.':,~~~·:~s,t.8~ :«:;Ts-r~~ i l~: =:1::~!~2;.ia~.:.:,~~3~ ~;~}~~~ ~~~~~ T:= 7 9 3 ;::=~~~ THERE'S ASTORE NEAR YOUI value Plusl s2995 . . , _. , ,','! ;:~:: ::: : ~~ ~~ 4·2~~~:'1~~ ::9·5~~,l:;.:~~;7~-&~r?- :.;.;.:r:"c~°'l2~~ • Chennlide3596255• Redbank2885599• Rockhampton279644• Southport329863• Toowoomba384300• Town:nttkt 725722• Unclerwood3410844 •SA• Adelaide Chy 232 1200 • lleYerte,3471900 •St.Mays 277 8977• Elizabeth 255 6099 • Eriftekt 260 6088 • WA• Cannington 451 8666 • FNmanle 335 9733 •North~ 328 6944 • Pwth City 481 3261 • TAS • HOO.-t 31 0800 •NT• Stuart Park 81 1977 ORDER BY PHONE TOLL FREE (008) 22 6610 for DSXpress 24 HOUR DESPATCH. HIGH p The new amplifier can deliver up to 120 watts RMS into a 100V AC line. The large heatsink keeps the power Mosfets cool. This rugged 120W Mosfet amplifier module is designed specifically to drive a 100V line transformer for public address applications. It can also be used as a stand alone module for guitar amplifiers and domestic stereo amplifiers. By LEO SIMPSON & BOB FLYNN Why is there any need to design an amplifier specifically to drive a line transformer? The answer is that a transformer presents a much more difficult load for an amplifier to drive than a normal loudspeaker. For a start, the primary of a typical transformer will have a very low DC resistance which may be of the order of 100 milliohms (0. H2] or less. Second, transformers do not like direct current flowing in their windings; the resultant magnetisation causes distortion of the output waveform. 14 SILICON CHTP This means that any amplifier designed to drive a transformer must have a very low DC voltage at its output. Just consider what happens with a typical direct coupled amplifier which has a DC voltage at its output of say + 20mV. When a transformer with a primary resistance of 0.10 is connected, a current of 100 milliamps will flow through it. This will cause substantial magnetisation of the transformer core as well as increased power dissipation in the output transistors of the amplifier. To solve this problem , the amplifier circuit must include a nulling adjustment so that the DC output voltage can be set to a very low value, say less than ± 5mV. The input differential transistor pair must also be thermally bonded together to ensure that the nulled output DC voltage does not drift away from zero as the temperature changes. Another problem with a line transformer is that if the load on the secondary winding is disconnected or switched in level while substantial power is being delivered, very high spike voltages can be delivered by the transformer. These high energy spikes can easily destroy bipolar transistors unless "flyback" diodes are connected across both halves of the output stage. Even if amplifiers do include these diodes and the spike voltages are thereby limited to the supply rails, the output stage is still not safe if bipolar transistors are used. Second breakdown The particular problem with bipolar transistors is " second breakdown". This is a mechanism whereby the current passing POWER PA UFIER MODULE +51V 5A 09 0.22! 2SK134 D10 1N5404 0.47 16VW o--=t INPUT ADJUST ZERO OUTPUT + 2.2k 4.3uH 100V LINE TRANSFORMER VR1 2000 f..,. / 0.27I 3x120 1W IN PARALLEL -,LOAD D11 1N5404 04 BC556 I. 45.5V 22k L__; r-- 1.4V 3.9 5A 3.9k L____: 0.22 t-i L---+---~--+-..:.....---___.,_______________________ 51v 120W PA MODULE ~ ECB s, 0 0 G VIEWED FROM BElOW Fig.2: the first two stages of the amplifier operate in cascode mode to give greater open loop bandwidth and improved linearity. The ouput transformer is required only if you intend running a 100V line for PA work. through a power transistor is "squeezed" into narrow channels and thus causes hot spots. These can destroy the transistor. The transistor manufacturers get around this problem by specifying the "safe operating area" for each bipolar device. What this amounts to is that the transistor is derated when higher voltages are present between its collector and emitter. To give a specific example, consider the MJ15003 NPN transistor (one of the output transistors used NOVEMBER 1988 15 Cascode Operation Explained Vee A cascade stage is one where two transistors are connected in series across the supply rail. In our diagram (Fig.2) we show an idealised schematic of a cascade stage. A reference voltage of, say, 4 volts is fed to the base of 02. By emitter follower action, its emitter will be 3.4 volts and this will be the collector supply for O1 . Thus 02 maintains a constant collector voltage on 01 and so eliminates any variations in gain which would otherwise occur if the collector voltage was able to fluctuate. The varying collector current drawn by 01 is the emitter current of 02 which converts it to a voltage signal at its collector. 02 can be regarded as a "grounded-base" stage because of the constant voltage at its base. · The combined effect of operating 01 with a constant collector voltage and 02 in a groundedbase mode gives a stage with much improved linearity and band- in the Studio 200 power amplifier). This device has a power rating of 250 watts, a maximum collector current rating of 20 amps and a collector voltage of 140 volts. With a collector voltage of 50 volts you can pass 5 amps through the transistor (provided the case temperature is maintained at 25°C) and so obtain a power dissipation of 200 watts. However, at a collector voltage of 100 volts you can only pass 1 amp safely through the transistor and thus it is derated to 100 watts dissipation. Designers can cope with this situation provided they know what sort of load the amplifier is intended to drive. They can draw the load lines and select the transistor operating conditions so that the limits of the "safe operating area" are not exceeded. The problem is, when the amplifier is intended to be used with a line transformer, it is much more difficult to predict the load characteristics. This means it is 16 SILICON CHIP CASCDDE STAGE Vref. : :!:J... i .,. Fig.2: a cascode stage is formed by connecting two transistors in series across the supply rail. Note the reference voltage fed to the base of Q2. width compared with a single common-emitter stage. In the past, cascade stages have been a feature of RF circuitry. Cascade stages were originally designed around valves. The word "cascode" is derived from the phrase "cascaded via the cathode", a reference to the cathode in a valve. much more difficult to guarantee that the transistors will not be damaged by unsafe operating conditions. This is where power Mosfets come into their own. They don't have to be derated for "safe operating area" because they don't have any tendency to internal hot spots. And if they are driven hard so that their temperatures are unduly elevated, they compensate automatically by reducing their transconductance. In effect, they are just about unburstable. Their only weakness is that they can be damaged by excessive gate-to-source voltage. This can be prevented by connecting a suitable zener diode between gate and source. New circuit design With these thoughts in mind, we set out to design a new amplifier module which would be suitable for driving a 100V line transformer. It would use power Mosfets, have provision for nulling the DC output, flyback diodes across the output devices and so on. The circuit is as shown in Fig, 1. It is suitable for use with or without a 100V line transformer. When used without a transformer, it will deliver 90 watts into 80 loads and 125 watts into 40 loads. The performance is fully detailed in the specification panel elsewhere in this article. While most of the circuit is fairly standard, it does incorporate a feature which has not been seen in many published circuits to date . This involves cascade operation for the first two stages, a feature which gives improved linearity and better bandwidth. Let us now describe the circuit in detail. Ql and Q2 are PNP transistors connected as a differential input stage. The input signal is fed to the base of Ql while the negative feedback signal is fed to the base of Q2. The total current through Ql and Q2 is set by constant current source Q3. Q3 is biased by diodes Dl and DZ so that it applies close to 0.67 volts across its 6800 emitter resistor. This sets the current through Q3 at close to lmA and so the current through Ql and Q2 is 0.5 milliamps for each. In a conventional direct-coupled amplifier, the signal from the collector of Ql would be connected directly to the base of the following class-A driver stage transistor. In our circuit though, the signal from Ql connects to the emitter of cascade transistor Q4 while the output signal appears at its collector and is then fed to the base of Q5. Q5 and Q6 form a cascade class-A stage with Q7 operating as a constant current load. The base of Q7 is biased by diodes Dl and DZ (which also serve as reference voltage for Q3). With this bias voltage, the current through Q7, Q6 and Q5 is just over 10 milliamps. Five diodes, D3 to D7, provide the base reference voltage for Q6 and thus set the collector-emitter voltage for Q5 at close to 2.6 volts. (To read how a cascade stage works, see the panel at the top of this page). The output signal from the cascade stage is coupled directly to Delving Into the Mysteries of the 100V Line Why do public address amplifiers use 1 00V lines for speaker distribution? Does the speaker line operate at a constant 1 00 volts AC? How do you match a speaker to a 1 00V line? · These and other related questions cause a lot of confusion to people in and out of the public address field. The big problem with public address systems is that the very long speaker leads can have considerable voltage losses if conventional low impedance speakers are used. Imagine the voltage loss in a pair of speaker lines 200 metres long with an 80 speaker. A 200 metre length of such cable will have a DC resistance of about 5.50. This means that 40% of the power would be lost in the cable. When you consider that a PA system in a large building may have tens of kilometres of speaker wiring running back to the amplifier, the resistance losses with conventional low impedance speakers would be intolerable. The way around this problem is to feed the amplifier's output into a step-up transformer and then into the long speaker lines. Each speaker is then coupled to the line via a ~AC .,.. ~ 5W 2W 1W 100VAC LINE srnOJ 0.5W (b) Fig.3: how the amplifier output is connected to give a 100V line. Each loudspeaker is connected to the line using a separate stepdown transformer. step-down transformer which usually has tap connections to vary the loudness from the speaker. So how does the figure of 1 00 volts come into the picture? The assumption is that when the amplifier is running at full power, it will be delivering 1 00V AC to the speaker lines . This makes it easy for the PA system installer. Instead of having to calculate the total load impedance when all loudspeakers are connected, all he has to do is add up the power settings for every speaker connected and see that it is equal to or less than the power rating of the amplifier. Consider a 1 00 watt power amplifier (with 1 00V line output) . The installer can install any combination of speakers which give up to 1 00 watts . For example, he may have 50 loudspeakers all of which are connected via the " 2 watt" primary tap on their individual step-down transformers. So under the worst case conditions, when the attenuators (if fitted) on all speakers are set to maximum loudness, the maximum power delivered to each speaker will be 2 watts. Thus, provided no one modifies the installation, the loading on the amplifier will never be excessive (ie, too low in impedance). Remember that 1 00VAC will rarely, if ever, be present on the speaker lines. That only happens when the amplifier is driven to its maximum output. In the past, many PA systems used 70V lines. This is exactly the same principle as the 1 00V line except that for a given power level, resistance losses in a 70V system will be twice that in a 1 00V installation . the output stage. A 39pF capacitor from the collector of Q6 to the base of Q5 rolls off the open-loop gain of the amplifier to ensure a good margin of stability. Output stage Four Hitachi power Mosfets are used in the output stage. They are connected in source follower mode (similar to emitter follower mode with bipolar transistors). The signals to the output stage are fed via 2200 resistors to the gates of the Mosfets. These resistors also Right: the pen is pointing to the two input transistors (Ql and Q2) which must be thermally bonded together. This is done to minimise temperature drift of the output DC voltage. NOVEMBER 1988 17 During assembly, push the small signal transistors down onto the board as far as they will comfortably go before soldering the leads. The metal faces of the BF469/470 transistors (Q6 and Q7) go towards the heatsink. function as "stoppers" to prevent spurious RF oscillation. Zener diodes ZDl and ZDZ plus diodes DB and D9 prevent overdrive to the gates of the Mosfets. When the load is short circuited, these diodes limit the voltage between the gates and sources of the Mosfets to about ± 11.6 volts. The quiescent current through the output stage is determined by the setting of the 5000 trimpot, VRZ. The lOmA current (via Q7 etc) through the resistance of the trimpot provides a voltage between the gates of the Mosfets to bias them on slightly when no signal is present. This is a normal feature of all class-B amplifiers and is used to minimise crossover distortion. With Mosfets though, it is usual to set the quiescent current much higher than in an equivalent bipolar amplifier. The reason for this is twofold. First, Mosfets are even more non-linear at low currents than bi polars (contrary to what is 18 SILICON CHIP 1A M3092 BROWN +51V 240VAC 8000 63VW BLUE + GND .,. 8000 63VW -51V Fig.4: suggested power supply for the 120W PA module. Check the output rails before connecting them to the module. written in some journals). Second, at a current of 100 milliamps, the transconductance (measured in amps per volt or "mhos ") of the Hitachi Mosfets has a zero temperature coefficient. Hence, the total quiescent current for the output stage is set at ZOOmA. This relatively high current also reduces any tendency to RF instability which can be a problem with power Mosfets if their quiescent current is set too low. The high quiescent current is one disadvantage of Mosfets. It means they need a bigger heatsink and that they waste more power than an equivalent bipolar transistor amplifier. Output stage protection Apart from the zener diodes •D 010 2SJ49 J,•G 1g '---- I I '-------;11:l <at>® ~ ~ F -o.5!,Jfil~ ® ~ <at>£ ~ 1 l N <at> ~ ~ ¥ l OUTPUT (;)=+-22µF ~ ~ -GrND --mo-..DIJ,e eo3lt ~ ~ II Oll _ _ _ _ _Q_6_~_9-F-0-3-0-7----,r---.-l~ Z01 • ---;--u- e GNO ~ *a; ..-m_o..~3~ c:).001 0 0.47µF .-aru,. +.-{Ifil-e INPUT 04 ~ .-(illJ-e = -51V +5lV Fig.5: here's how to install the parts on the printed circuit board. Keep the component leads short and make sure that the Mosfet output transistors (Q8-Q11) are electrically isolated from the heatsink. The 2200 resistors shown dotted are mounted on the copper side of the board. already mentioned, the Mosfets also have have diodes D10 and Dl 1 for flyback protection. These diodes safely clamp any spike voltages, generated by the load, to the positive and negative supply rails. To protect against short circuit loads, a 5A fuse is connected in series with the supply rails to the Mosfets. An RLC network is connected between the amplifier output and the line transformer (or loudspeaker load if the transformer is not used). This network serves two purposes. First, it ensures stability of the amplifier under all loading conditions, including large shunt capacitances. Second, it effectively decouples the amplifier from the load and connecting lines at very high frequencies. This stops large RF signals picked up by the loudspeaker lines from being fed back to the input of the amplifier (via the feedback components) and being detected in Q2. Thus, it helps stop RF breakthrough. Similarly, at the input of the amplifier, there is quite a savage low pass filter which attenuates any extraneous RF signals before they get to the base of Ql. The voltage gain of the amplifier is set by the 22k0 and lkO resistors at the base of Q2. These set the voltage gain to 23. The low frequency response is set mainly by the 0.47 µF input coupling capacitor, giving a - 3dB point at about 20Hz. This could have been set for a lower frequency but this would cause problems of distortion and loading with the output transformer. DC nulling As mentioned before, it is most important that the DC voltage at the output of the amplifier be as close to zero as possible. To ensure this, the two input transistors are thermally bonded together so that any temperature drift will be minimised. As well, the 2000 trimpot VRl allows the output voltage to be set close to zero; ie, to less than ± lmV. Power supply The suggested power supply (Fig.4) for the amplifier module uses a 300VA toroidal transformer with a centre-tapped 70V secondary winding (ie, 35 volts a side). This feeds a 400V 35 amp bridge rectifier and two 8000µF 63VW electrolytic capacitors. 100V line transformer The recommended 100V line transformer was supplied by Altronics of Perth, as were the supply components. The transformer is a toroid with a rating of 160VA. It has been designed to present a 40 load to the amplifier. It has two prinmary windings and two secondary windings. The method of connection to the amplifier is shown on the circuit of Fig.1. No feedback is applied around the transformer but even so the performance is very good, both as far as frequency response and harmonic distortion are concerned. Full details are shown in the specifications panel. Construction The wiring layout of Mosfet amplifiers is very critical so the printed board is a crucial feature of the design. The printed board NOVEMBER 1988 19 PARTS LIST 1 PCB, code SC01111881, 95 x 163mm 1 cast aluminium heatsink with integral bracket, 1 95mm wide by 66mm high; Jaycar Cat. No. HH-8550 or equivalent L-shaped bracket and heatsink 4 3AG fuseclips 2 5A 3AG fuses 6 PC pins 1 plastic coil bobbin, 1 2mm diameter x 11 mm long; Siemens B65672-B-T1 or equivalent (or 4 .3µH aircored choke; see text) 4 T0-3 transistor mounting kits Semiconductors 2 2SK134 Mosfet transistors 2 2SJ49 Mosfet transistors measures 163 x 95mm and is coded SC 01111881. It is meant to be used with a large heatsink. The one shown in our illustrations is from Jaycar (Cat. HH-8550). As an alternative, the board could be used with a heavy gauge aluminium angle bracket and a large extruded heatsink. The heatsink must be reasonably large to keep the amplifier as cool as possible, for long term reliability. 4 1 1 1 9 BC556 PNP transistors BC548 NPN transistor BF470 PNP transistor BF469 NPN transistor 1 N4148, 1 N914 small signal diodes 2 11 V 400mW zener diodes 2 1 N5404 3A silicon diodes Capacitors 1 22µF 16VW PC electroyltic 1 0.47µF 16VW PC electrolytic 1 0 .27 µF metallised polyester (greencap) 4 0.22µF metallised polyester (greencap) 1 .001 µF metallised polyester 1 39pF ceramic Resistors (0.25W, 5%) 1 x 27k0, 3 x 22k0, 2 x 18k0 Assembly of the board is a straightforward matter but it should not be hurried. First, you should closely inspect the board to see if there are any shorted tracks or open circuits in the copper pattern. These should be fixed before proceeding further. The PCB component diagram is shown in Fig.5. Fit the small components first, such as the resistors and diodes. Make sure that you don't confuse -0 0 I SHAKE-PROOF •~--- e.-~- WASHERS ~--NUTS Fig.6: this diagram shows how the Mosfet output transistors are mounted on the heatsink. Use your multimeter to check for shorts between the case and heatsink as each transistor is mounted. The nuts should be soldered to the PC pattern after assembly to ensure reliable contact. 20 SILICON CHIP Transformers and Power Supply Parts 1 300VA power transformer, 70V centre-tapped, Altronics Cat. M-3092 or equivalent 1 160VA 1 OOV line transformer, Altronics Cat. M-1124 1 35-amp bridge rectifier, Altronics Cat. FB-3504 2 8000µF 63VW electrolytic capacitors 1 1 A fuse and fuseholder the small diodes (1N914s} with the 11 V zeners. The fuse clips, trimpots and small transistors can be mounted next. Ql and Q2 should be mounted so that their flat faces are touching. When you have soldered them in place, put of drop of superglue between them and squeeze them together. Note that all the transistors should be pushed close down onto the PCB before soldering (see photo). The 4.3µH choke at the output of the amplifier is wound with 19.5 turns of 0.8mm enamelled copper wire on an 11mm plastic bobbin. Two layers of wire are wound on so that the start is at one side and the finish is at the other side of the bobbin. Bend the start and finish leads at 90° and scrape off the enamel coating before soldering the choke to the board. Heatsink assembly PCB I 0.5W, 2 X 3.9k0, 2 x 2.2k0, 1 x 6800, 4 X 2200, 2 X 680, 3 X 120 1W, 1 x 5000 trimpot (Bourns Cermet horizontal mount, 0.2 x 0.4-inch), 1 x 2000 trimpot (Bourns Cermet horizontal mount) The four Mosfet power transistors are mounted on the heatsink but with their leads soldered to the printed board. The assembly is as shown in Fig.6. We used 5mm fibreglass tubing for the insulating bushes. Smear all the mounting surfaces of the Mosfets and the heatsink with heatsink compound before assembly. The transistors are mounted to the heatsink using 12mm 6BA PAPST AC and DC FANS PAPST manufactures the largest line of equipment fans in the world providing the most efficient, reliable and versatile solutions in both ac and de applications. In addition to models with sleeve bearings, proven in millions of installations, Papst offers ball bearing versions for high environmental temperatures, enhanced performance models that deliver increased airflow, quiet types with particularly favourable airflow/noise characteristics for sensitive audibility requirements , flat fans for restricted installation space and unconventional mechanical designs for special mounting requirements . Papst first for Reliability- Versatility-Availability 4 MELBOURNE: Adilam Electronics Pty Ltd Incorporated 1n V ICTORIA Suite 7 , 145 Parker Stree t, Templestowe 3106 . PO Box 13 1, Bulleen 3105 Telephone: (03) 846 251 1 (4 lines) . Telex : AA 151369 . Fax: (0 3) 846 1467 . SYDNEY: Suite 1, Ramsgate Plaza, 19 1 Ramsgate Road, Sans Souci 22 19. Telephone : (02) 529 2277. Fax : (02 ) 52 9 5893 . DISTRIBUTORS: ADEL AIDE: NS Elec tro nics (08) 46 8531. BRISBANE: St Lucia Electronics (07) 252 7 4 66. CANBERRA: Electronic Components (062) 80 4654 . PERTH: Pro-Spee Distributors (09) 362 50 11 . .•. The pen points to one of the four 22011 resistors mounted on the copper side of the board. Mount the resistors so that they are 2-3mm proud of the board while keeping their leads as short as possible. Performance of Prototype Frequency Response 125 watts into 4 ohms ; 90 watts into 8 ohms; 120 watts into 1 OOV AC line 20Hz to 50kHz (-3dB) without line transformer; 20Hz to 23kHz (-3dB) with line transformer Input Sensitivity 1 .1 V into 22k0 input impedance Harmonic Distortion ( 0.1 % from 20Hz to 20kHz -111 dB unweighted (20Hz to 20kHz); -11 9dB A-weighted )50 for 80 loads Unconditional Power Output (RMS) Signal-to-Noise Ratio Damping Factor Stability screws and nuts. Solder the nuts to the PCB pattern after assembly to ensure reliable contact. Alternatively, if the nuts are nickel plated or stainless steel, use lockwashers. As each transistor is mounted, 22 SILICON CHIP use your multimeter (set to a low "ohms" range) to check that its case is insulated from the heatsink. If the meter does indicate a short, remove the transistor and check carefully for metal swarf around the mounting holes. After the nuts have been tightened and soldered, the gate and source leads of the Mosfets can be soldered to the PCB pattern. The four gate resistors are then soldered in place, on the copper pattern side of the PC board. Install these four resistors so that they just sit proud of the PCB (see photo for details). Now closely inspect all your work for correct assembly and soldering. Make sure there are no blobs of solder bridging out tracks. As a final check on your work, connect your multimeter (set to a low "ohms" range) and test for shorts between the supply rails and the OV rail. There is a trap here - flyback diodes DlO and Dl 1 will show a low resistance for one connection of the multimeter and a high resistance for the reverse connection. Assuming that you have wired up the power supply, check the voltage on the two supply rails before mak- Fig.7: the full size PC pattern. The wiring layout is critical so the PCB pattern is a crucial feature of the design. ing connections to the amplifier board. The supply rails should be close to ± 50V DC. Switch off and wait for the 8000µF capacitors to discharge to below 5V before hooking the supply up to the amplifier. 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. Setting up Now remove the negative supply fuse from its clip and connect a multimeter set to measure up to 1A 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 (VR2) fully anticlockwise and apply power. Now rotate the 5000 trimpot for a current of 200mA. Switch off the power supply and wait for the voltage across the supply capacitor to drop. The multimeter can now be removed from circuit and the 5A fuse replaced in the negative supply line. Reapply What is Transconductance? While the gain of bipolar transistors is specified as a simple ratio of collector current to base current (and known as beta or htel, the gain of Mosfets and V-fets is referred to as transconductance. This is because a fet (field effect transistor) is a voltage controlled device; a signal of several volts into the gate gives a drain-source current of several amps. Hence, a Mosfet varies its conductance (the reciprocal of resistance) in proportion to its gate signal. power and measure the DC voltage at the output of the amplifier. Rotate trimpot VR1 to set 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 the loud- The gain of a Mosfet is specified in terms of amps per volt or in the old unit of conductance, Mho (which is "Ohm" spelt backwards and still used by American semiconductor manufacturers). The new unit for conductance is the Siemen (used by European and Japanese manufacturers) . For the 2SK134 (N-channel) and 2SJ49 (P-channel) devices, the transconductance is typically 1 Siemen (ie, 1 amp per volt) at a drain current of 3 amps and a drain-source voltage of 1 0V. speakers 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" . With that, your amplifier is ready for work. Footnote: a complete PA amplifier based on this new module will be published in a future issue of ~ SILICON CHIP. NOVEM BER 1988 23 UHF TV TUNER · San o Model T1087RA Yet an her fabulous scoop purchase. A compact high quality tuner that operates from 526814MHz (corresponclng 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. Cat. DM-1000 NORMALLY $29.95 NOW $14.95 SAVE $15.00 PRESS RELEASE DIGITAL PANEL METER CATALOGUE A brand new 18 page Lascar catalogue is available from the Australian representative, Jaycar Electronics. The catalogue features the latest Surface Mount Technology DPM's from Lascar • the world's leading DPM manufacturer. Panel meters are available In both liquid crystal and LED-type displays. All DPM's come complete with snap-on bezels. Full technical Information is provided for the 50-odd products described. Contact Jaycar branches or Head Office for a free copy of the catalogue. 3 DIGIT (0-999) PULLEY DRIVE EVENT COUNTER Quantities strictly limited I This English made counter (similar to a tape counter In VCR's ate) features 3 x 4mm high black digits on a white background. The entire assembly Is mounted Inside a rigid dlecast frame measuring 34(W) x 28(0) x 33(H)mm. A 14mm diameter pulley drives the worm gear shaft which rotates the numbered drum. Included with the unit Is a 75mm diameter rubber drive belt and an extra pulley for the other end. A large thumbwheel counter reset knob Is attached to the end of the drum assembly. When you NEED one of these you would NEVER be able to source ltl So you will have to get one now as we have less than 100 units. First to see will buy! Cat. YT-2730 41®®mnW - ', CGJENJEIBAJL Jp>UJJE,Jp>(D)§JE AUJI!DII(D) ~IF IffiJ..\Iffi.CG.lhlIN • Completely built, this module measures 63 x 35mm, has a high Input Impedance and high gain . Runs on 9V and requires a 15 ohm load. Supplied with full specs and data. Made In England! Cat. AA-0292 0NL Y $3.95 1O+ $3.50 each We have a small quantity of 15 ohm 5" x 4" speakers to suit. Otherwise just use two 8 ohm speakers In series. Cat. AS-3013 $3.95 Mixed Component Pack Bargain We've put together five of our most popular components packs for one low sensational price. PACK ·1 35 assorted pots and trlmpots Cat. RP-3902 Value $10.00 PACK 2 50 assorted RF chokes Cat. RC-5600 Value $10.00 PACK 3 150 pcs mixed capacitors Cat. RF6260 Value $10.00 PACK 4 80 pcs mixed electrolytic caps Cat. RE-6280 Value $10.00 PACK 5 50 pcs mixed tantalums Cat. RE-6695 Value $12.50 Full pack details In our Catalogue and late ads : Total $52.50 BUY ALL 5 PACKS TOGETHER FOR ONL V $29.50 Save an amazing $23 over normal pack price. Value of all components separately would exceed $40011 $7.95 AA NiCads $3.50 each or 4 for $12.50 TV INSTALLERS BARGAIN Outdoor Baluns - 300 to 75 ohm complete with small length of cable to attach antenna and F59 connector for coax connection. NORMALLV $3. 75 each NOW ONLY $10 for 10 or $1 .50 each cat. LT-3020 BELOW NORMAL WHOLESALE PRICE Don't waste money. Buy rechargeable NiCads, 450mA. Quality brand. Cat. SB-2452 CLOCK MOVEMENT WITH BUILT-IN PENDULUM DRIVER THIS IS RARE! This module measures 87mm long x 55 wide x 35mm deep and uses 1 x AA battery. Clock movement Is supplied with 3 sets of hands, and pendulum Is a suspended arm within the module which swings back and forth. A suitable pendulum can be attached to the bottom of the arm. WAS $22.95 Fit your own custom clock face. Great for novel applications. Cat. XC-0103 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 NOW $16.95 SAVE $6.00 BACK AGAIN! White Cone Midrange PASSIVE INFRA RED DETECTOR - PRICE BREAKTHROUGH 'F<at> (Q) I}{] [Ml &i □ [ffi Our most popular midrange. Large sealed back with extra clear crsip midrange. 110mm, BO watts RMS power handling, 95dB sensitivity, 10oz magnet, freq. resp. 31Hz- 7kHz. resonant freq. 310Hz. Cat. CM-2080 1986 PRICE eat your heart out Dickll 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 watt. We have extensively tested the units and have no doubt about their quallty and operation ability. Features & Specifications • Dual element pyroelectric sensor • 24 dual element detection zones in three layers • Wide angle 900 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 ~ .;;,, • 3 month guarantee Cat. LA-5017 " M]/ Yes, for a short time only, you can purchase HIGH QUALITY air spaced 75 ohm coax for the same price as our economy 75 ohm cable. Normally Its $1.20 per metre, but you can buy it for only BOit per metre. Or. Hyou buy 50 metres or more, it's only SOit metre. That's hatt pricel ONLY $22. ~ NEW'88 Polypropolene Cone Midrange We've been able to lower our price on our high power midrange. Black Poly cone. Huge 10oz magnet. 5" diameter. Specifications: Power handling 100 watts RMS system Resonant Freq. 570Hz Sensitivity 96dB Freq. Resp. 570Hz - 7kHz Cat. CM-2085 $24.95 Cat. WB-2006 . Grab a quartz crystal car clock with a set of autorrotive style hands at a price that will astonish you I Once again our suppliers huge loss Is your gain I Convert that broken/unreliable or inaccurate mechanical clock in your car to space age precision I Made in West Germany by VDO, the module measures roughly 45 x 38 x 40 deep. The compact size virtu~y ens ures that it will fit in any spacel Quantity strictly limltedl Cat. XC-0108 .....· '-,. 80t metre .... · , • ,.-··-,. . . . 50mormore 60~ metre \ ·• / LCD WATCH KIT IEC LINE PLUG These are widely used in Personal computers. Sorry albout the price, but these are genuine European plugs. They are so new the Asians haven't copied them yet. Cat. PP-4007 0.1 MONOLITHIC CAP SALE We have available a pack of 0.1 monolithic capacitors with short leads at a very special price. The only catch Is that they have cut leads ready for machine placing In PC boards. The leads are \bout 1.5mm long just long enough to go through a circuit board. The newest edition to our speaker range. 70mm cone tweeter. Norn lrrpedance 8 ohms Max power 75 watts Freq. Range 3kHz - 1BkHz Sensitivity 91.5dB Flux density 7,200 Gauss Magnet size 45(dla) x 22(dia) x 9mm Magnet Weight 47.4 grams Net Weight 170 grams Cat. CT-2000 WAS $11.95 ~ ONLY $7.95 for 100 NORMALLY $16.50 per 100 '"" - · 132 pages of electronic goodies. If you don1 have our catalogue or nyou've lost It call In to any of our showrooms for a free copy. (And a lollie Hyou have to wait). OR send a large SAE to PO Box 185 Concord 2137 and we'll post you one. Outdoor Infra Red Motion Jaycar Introd_u_c-es___.t_h_e_E_as_y_w_a_y_t_o_ ___. Detector Ideal for both residential and commercial apBuy G reencaps pllcations. Completely self contained and Don't ever run short of that greencap again. 5 easy to buy, low cost packs which represents a considerable saving over individual prices. Each pack contains 1o of each value and packs cover the complete range from 0.001 uF to 0.1 uF. Values: (10 of each) 0.001, 0.0012, 0.0015, 0.0018, 0.0022 $6 •95 TOTAL 50 pieces Cat. RG-5000 Values: (10 of each) 0.0027, 0.0033, 0.0039, 0.0047, 0.0056 TOTAL 50 pieces Cat. RG-5001 $6.95 Values: (10 of each) 0.0068, 0.0082, 0.Q1. 0.012, 0.015 TOTAL50piecesCat. RG-5002 $6.95 Values: (10 of each) 0.01s, 0.022. 0.027, o.033, o.039 TOTAL 50 pieces Cat. RG-5003 $6.95 Values : (10 of each) 0.047, 0.056, 0.068, 0.082, 0.1 TOTAL 5 0 ~ 0 0 4 ~- $9.95 A GREAT WAY TO NEVER BE OUT OF THAT ODD GREENCAP AND SAVE A PACKET AT THE SAME TIME ONLY $9.95 ·;•f:' _,., :=·:·•., .. ::-:-,._, .../ . ONLY$69.95 $30 LESS THAN ANY PIR WE KNOW OF ~ MASSIVE SCOOP PURCHASE! FOR THE PRICE OF ECONOMY COAX ri~ CONE TWEETER SAVE $2 NOW 12V CAR ANALOGUE CLOCK MOVEMENT ®[FJ&i©lg[Q) ©<at>&i~ easy to install. Designed to mount directly to a standard round junction box. The unit will automatically turn on two floodlights when someone walks within the detector range. Ideal security system to protect loved ones and property. Detection range is 40 feet long by 60 feet wide. Lights will stay on for a minimum of 10 seconds up to 15 minutes (adjustable). Works only at night. Globes not supplied. Cat. LA-5132 QNL y $139 ,.___ $14.95 Jaycar 12V/300V A SINE WAVE Inverter NOW AVAILABLE Now you can enjoy SINE WAVE power at AROUND 85% EFFICIENCY for much the same c06t as Inferior square wave - and this unit gives a genuine 300VA, not less. The Jaycar Sine Wave Inverter has tremendous surge capablllty. It will, for ex~le, start a small refrigerator. We are very proud of this Australian made and designed product. The price, however, may have to rise soon, so hurry! $399 A JAYCAR/SILICON CHIP EXCLUSIVE KIT PLASMA DISCHARGE DISPLAY Cat. M~5020 Ref: Silicon Chip August 1988 Jaycar and Silicon Chip have corrl:>lned to produce a low cost but spectacular plasma discharge display. The Jaycar kit of this project Includes the rare-earth chamber, mounting plinth, EHT transformer and inverter electronics. A 2-3 anii 12V DC power supply Is required. (A battery charger Is ideal). Call In to one of our stores forademol Cat. KC-5035 WAS$299 NEW LOW PRICE $229 SAVE$70 Savings made because of mass production of this sensational product! CLOCK MOVEMENTS WITH BUILT-IN MELODY MODULE No more messy, separate modules. All in the one easy to mount housing. lWO 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). XC0107 plays a different melody each hourthen gongs the hour. Both units are supplied with : • Clock movement • Speaker and battery holder • Hook to hang up • 3 sets of hands Cat. XC-0106 Westminster chimes/clock movement Cat. XC-0107 12 melodies/clock movement SAVE $12.95 over separate clock movement and chimes SOLAR PANELS 2Models 6 volts <at> 240mA 12 volts <at> 120mA Each panel measures 327(L) x 165(W) x 18mmthick. 6 volt panel <at> 240mA Cat. ZM-9008 $79 Solar Battery Charger I The solar panel In the lid will charge up to 4 x AA NICads In a fairly short time. It Is Ideal for yachts, campers or anywhere where 240V is not available. Cat. MB-3502 Size: 65(W) x 30(H) x 95(D)mm WAS ONLY $18.95 ea $17.95 NOW $14.95 Loudspeaker P.A. Bin Enclosure ~--- - - - - - - - - ~ SOLAR PLANT 0.45 VOLT SOLAR Designs Book TURNTABLE CELL MODULES Fane Acoustics UK, makers of speakers for the Connect In series or parallel. Two sizes. WU05.P"I.AKJ:N l~C'~'l'r D~IGN AND CX>N~TkUCTlON likes of Pink Floyd, David Bowie, Genesis, Iron Maiden etc. have produced an absolutely fanta~tic book on P.A. bin desi~ns. The book begins with construction info tn general, I.e. what materials to use, how to join timber, how to brace the cabinets, sealing, lining, wiring, crossovers, Impedance matching, etc. The second section includes 22 separate detailed designs for: reflex cabinets, horns, wedge monitors, folded horns, w bins etc. Designs accommodate 10", 12", 15" and 18" speaker components. - Wr~ OOM'.~ Cat. BF-4150 No more lopsided plants. WIii handle up to 15 kg of weight. Also ideal for store window displays. Cat. YX-2503 $17.95 ~ $3.95 10+ $3.75 0.45V 96x65x6mm Cat. ZM-9006 $6.50 10+ $6.20 $14.95 SAVE ON ADCOLA SOLDERING STATIONS :::- ~ ,,..,___ See catalogue for full specs 0.45V 75x45x6mm Cat. ZM-9005 Dear Customer There are times when due to circumstances beyond our control some advertised products may not be in stock when our ads appear. We sui;igest you phone to check availability. - BASE STATION NORMALLY$159.50 ~ SAVE$20 NOVEMBER PRICE $139.50 Cat. TS-1475 40W IRON - CT6 SOW IRON - CT7 NORMALLY $49.95 NORMALLY $55.00 SAVE $5 SAVE $7.50 NOW ONLY $44.95 NOW ONLY $47.50 Cat. TS-1478 Cat. TS-1480 FOSTER DOME TWEETER - BACK IN STOCK! The D025N25 is a brilliant tweeter. It's probably the cleanest sounding tweeter we sell. It handles enormous amounts of power and has a very smooth response. Power Handling 150 watts RMS system Freq. Response 3kHx-30kHz Resonant Freq. 1,200Hz Impedance 8 ohms SPL 91d8/1 metre Flux Density 13,500 Gauss Weight 61 O grams Cat. CT-2018 $36.50 12" GUITAR SPEAKER Finally available, our updated guitar speaker with extended frequency response. Especially suited for not only bass guitar but rythm and lead as well. Resonant Freq . 60Hz (was 80Hz) Impedance 8 ohms Freq. Response 80Hz - 5kHz Power Handling 100 watts RMS Magnet Weight 40oz Net Weight 3610 grams Sensitivity 102dB But the best news is the price - l.'.lQ INQREASE Cat. CG-2380 $89.50 Our solar education kit is designed to let you build your own solar models. This kit oomes complete with : • Solar cell module • Solar energy booklet explaining the whys and hows of solar energy • Small DC motor • Screws and nuts • Wire with motor clips • Coloured spinner discs • Paper aeroplane and bird models • Plastic turntables with 4 sizes, 5/8", Cat. KJ-6690 1", 1 1/2" and 2" • Plastic Ian-spinner ONLY $9.95 SOLAR CAR BAITERY BOOSTER Keeps your battery charged In your car when you are not using it. Cat. MB-3503 $29.95 TWEETY PIE This incredible little piezo screamer measures 87(L) x 38(H)mm emits a 116dB wail. It's ~:_afening I As used in the screamer car alarm Cat. LA-5255 NORMALLY $17 . 9_5_ _ __ SAVE$3 ONLY $14.95 IJJ---'-'"t EPROM ERASER 6 WAY POWER OUTLET WITH MAINS FILTER Not only Is It a 6 way power board, It Incorporates a voltage surge and spike protector and noise rejection filter network. Supplied with 2 metre oord and mains plug, safety shutters on each outlet. Illuminated master on/off switcvh and even a safety circuit breaker. Cat. MS-4000 $59.95 NOTE: 11 you require absolute mains suppression don't forget our Australian made Squeaky Clean Mains FIiters. 8 ,,. '1' ,,, ,,, ,,. ,,, Ill Will erase up to 9 x 24 pin devices in 40 minutes. Less for less chips. 240V Cat. XE-4950 $99.50 Replacemen Cat.X $19.95 "CRIME STORY'' SPEAKER CLOTH SALE OPTICAL TACHO Piezo Tweeter At last, an economical priced quality piezo tweeter. Another manufacturers surplus stock purchase by Jaycar. These are in other catalogues for $18.951 SPECIFICATIONS • Frequency response 3.5kHz-40kHz • SPL 94dB/1 W at 1 metre • lntermiitent peak power 100 watts • Size 78mm square • Use with or without crossovers Cat. CT-1905 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's or 60's, but it's not really suited to the loungerooms of the SO'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 trendy I UNREAL PRICE ONLY $9.95 Don't Pay $18.95 STYLE 1 Gold with black strips at about 1 1/2" intervals. Size 5' x 1 mt Cat. CF-2756 Ref: SIiicon Chip May 1988 Cat. KC-5031 Who needs a noisy car alarm, after you have Installed one of these in your vehicle. It's operated from a hidden switch. Simply turn it on when you leave your car, and ~ your car is stolen, It woni go very far without any petrol. Supplied with instructions, pre-wired switched, hardware and even two alarm stickers. Quality M&D Alarm brand. Add to this our deluxe red light flasher kit KJ-7000 $19.95, and who needs an alarm? Cat. XC-2050 $3.95 SAVE $10 $49.95 STYLE 2 Gold with gold reflective pieces through it. Size 3' x 1mt. Cat. CF-2757 "PLASTI-DIP" - - ETI 340 Deluxe Car Heavy Duty Flexible Alarm Kit Liquid Coating SELLOUT $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 1mt. Cat. CF-2758 $3.95 SAVE Plastic Dip is an air dry liquid plastic coating that produces a tough, thick pliable finish. It is ideal for making a pliable coating for the haQdles of tools, Ref: ETI Aprll 1984 See our catalogue for full details / ·· Cat. KE-4768 · ;~pplled in a470ml dipping can. Will do dozens of tools. Cat. NP-1100 $79.50 RED IN COLOUR ." , ,' . (i,' Protector Car Alarm Ref: SIiicon Chip Feb 1988 s e an p PCB, all co and hardware. Cat. KA-1703 ONLY $16.95 $79.50 VOLTAGE & CONTINUITY TESTER Ref: EA November 1987 Will test AC & DC voltages and continuity In cable on 6, 12, 24, 48, 110,240 & 415V both AC& DC. . Cat. KA-1694 NORMALLY $29.95 $229 STUDIO 200 HI FI PREAMP 300 watt unit Cat. KA- 1610 $269 kit) Full form version. Kit Includes all components except box for receiver, plezo siren and piezo transducer and battery for transmitter. These Items are available separately: Transducer Cat. AB-3440 $2.75; Piezo Cat. LA-5255 $17.95; Battery (pkt 2) Cat. SB-2420 $3.75 Cat. KC-5034 240 volt operated iron, ideal for the kit builder. Cat. TS-1450 INVERTER 40 watt unit Cat. KA-1598 $99.95 About every feature you could ever want in a car alarm. See our 1988 catalogue for full de1affs. Extras not included In kit: Back-up battery Cat. SB-2490 $22.50; Plezo siren Cat. LA-5255 $17.95; 12 volt siren Cat. LA-5700 $26.50. Cat. KC-5021 $79.50 $39.95 Remote Control (Full t-S_O _L _D _E_R_I_N ..,,,_G_.I..R _O _N___-t Ref: Silicon Chip March 1988 l-----~~::=:::::i....---1 $159.50 ;~~~~~ ~ ; t------------1 KITS $1.75 SAVE 75~ Ref: Silicon Chip July 1988 Build your own light show SAVE $20 ONL y · '(,! ~2~~9~ A specially treated piece of braid for removing solder from a PCB. Place the braid over the solder and apply soldering iron to efficiently remove solder. 3mmwide. NORMALLY $2.50 Cat. NS-3020 5 feet longl Cat. KC-5032 NORMALLY SAVE$3 ONLY $26.95 Ref: Silicon Chip June/July 1988. Excellent quality at a modest price Cat. KC-5033 ?I~1• !. ___________________________________ HEAD OFFICE 1 .,..;.,1....,...__ .__._ii1.oiii~1.iiiii1~11,;-•t .._..~w~11,; • VISA rz~--,~.~ MAIL ORDERS 0 0 13 7 POST & PACKING 7 3 _i_~_i_f_2;_ti_j...;a:;...:...;:::...$;_:_:~_:_;_:_:__ _ _ _~_l_R:_:~_:~_l_~_~_i:.;. ;1_l:..;.~-;_!_~:_:_8_ _~_v:_R_$1_oo_i_r_i_i_11_t~_:~----, ,.._ MAIL ORDER VIA YOUR "fr ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY · CITY 117 York St (02) 2671614 - GORE HILL 188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 Mon-Fri 9 • 5.30 Sat 9 • 4pm PARRAMATTA BURANDA QLD 144 Lo9an Rd (071 393 0777 • Mon-Fn 9 • 5.30 Thurs 8.30 • Sat 9 • 12 1 CONCORD ~~' HURSTVILLE Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Church St (Cnr. Victoria Road) Mon-Fri 9 . 5.30 Thurs 8.30 pm - Sat 9 • 2pm 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 121 Forest Rd (02) 570 7000 Mon-Fri 9 • 5.30 Thurs 8.30 pm - Sat 9 · 12 SPRINGVALE VIC Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 887-889 Springvale Road Mu/grave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2 _. THE WAY I SEE IT By NEVILLE WILLIAMS Look out TV servicemen: VCRs are now disposable! With SILICON CHIP now celebrating its first birthday, it's appropriate to follow up on several matters raised in earlier issues. For example, to reinforce my remarks about "throwaway" technology (June 1988), a reader from Waniassa, ACT, points out that in the USA even VCRs may now cost as much to repair as to replace! As readers may recall, the subject was raised under the heading "For all practical purposes, Mr Fixit has had his day!" In commenting on the article, the correspondent (I.J.) professes a similar pet aversion to plastic assembly pillars moulded into equipment cases. "They can be a real nuisance", he says, "especially when the head of the screw is recessed deeply into its half of the appliance body. I've had to buy extra long Phillips drivers to access the screws in some units". Adding to the list of home appliances which we nominated as being virtual throwaway items, he has: • A garbage disposal unit with a burnt-out armature; • A fan heater with worn bearings; • A fan heater with an overzealous cut-out; • A fan with a stripped gear. But you can be lucky sometimes. He continues: I did have a win recently, involving a food mixer belonging to a member of the family. It used 'triwing' screws that resemble a Phillips head but having three slots instead 28 SILICON CHIP of four. By sheer good luck, a local tool dealer had a suitable screwdriver in stock and I was able to access and fix the fault. By the same token, I would dearly like to know where I could get a screwdriver to suit our 10-year-old Sunbeam mixer. It uses screws with three slots which start at 120° intervals around the circumference, aimed at the centre. The depth varies, however, being greatest at the circumference and diminishing to zero in the middle. What a fiendish combination! Incidentally, a couple of other readers have mentioned the possibility of picking up patented drivers at specialist tool shops although more frequently as the result of good fortune rather than good management. Domestic VCRs 1.J.'s information about domestic VCRs comes from the April 1988 issue of SPECTRUM magazine, official publication of the American IEEE (The Institute of Electrical and Electronics Engineers Inc). It reports that, in response to numerous complaints about consumer video equipment failure and the high cost of repairs, SPECTRUM staff recently investigated the situation. All suppliers contacted insisted that their products were inherently reliable but they would not release statistics to support these claims. SPECTRUM says, however, that an EIA (Electronic Industries Association) survey in 1986 showed that 7 % of VCRs required service within the first year and 43 % within the initial five years of operation. On this most recent occasion, those service organisations that were willing to cooperate indicated that VCRs are inherently less reliable than TV receivers because of their reliance on mechanical functions. The majority of present day service calls, in the American scene, involve dirty heads, electrical storm damage or jammed tapes the latter aggravated by "tight designs" which will not tolerate mishandling or misalignment. Again, economy models selling for around $200 often rely on belts and pulleys for tape traverse and, in consequence, suffer more mechanical failures than dearer models using direct-drive motors. When a microprocessor fails, the cost of replacement is likely to exceed $100, or half the original purchase price of an economy model. That is bad enough but the real crunch comes with motor and head replacements which may run to around $200. That puts economy models firmly into the "disposable" category - not worth fixing. In the same article (June 1988, The Ford Car as a Wireless Transmitter Having talked about EMC (electromagnetic compatibility) in the October issue, I was fascinated recently to come across the following item item in Vol.1, No.2 of "The Australasian Wireless Review" published in February 1923: "The Ford car as a wireless transmitter: Many and varied are the stories at present being told about the Ford car. From clubman to comedian, the name of Henry Ford is considered fair game. " But the statement that the Ford car is a transmitter of wireless waves, which are detected by sensitive valve receiving apparatus, is not in jest. It is cold fact. "The magneto of the Ford is of peculiar construction, corresponding very nearly to the high frequency dynamo employed by wireless stations for the radiation of messages. page 8) under the heading "The safety aspect", I commented on the legal aspect presented by home handymen and professional oddjobbers. They have long been able to dismantle and repair most home appliances economically, in many cases using replacement flex,, plugs, sockets and other parts available over the counter in local hardware stores. Because the practice has been so widespread, and not easily addressed by industry regulations, it has been accepted on the basis that most handymen, effecting such repairs, will do so intelligently. More specifically, and I quote, that they ''will not compromise the specifications on which the device was granted type approval in the first place". I suggested, however, that if this legal "grey" area was to be progressively eroded by throwaway technology, it might be outlawed by regulations spelling out exactly "who has the legal right to repair what, in respect to anything plugged into the power mains". Anything? Yes, anything. Start framing regulations about house- "The coils might be considered the equivalent of the high tension transformers and the sparking plugs as the equivalent of the wireless spark transmitter. The sharp click of the ignition sparks are clearly audible in a wireless receiver's telephones, when a Ford car is some hundreds of yards away. "It is even possible to detect a misfiring cylinder by this means, without ever having seen the car. "It has always been understood that the Ford possessed certain advantages enjoyed by no other make but that it numbers among its accomplishments that of a wireless transmitting station, as well as a means of conveyance, seems to be the strangest story of all" . From the same source, and still on the subject of wireless history, I include a "Tip for Fans" which may interest the many readers who hold appliances and you run headlong into the question of whether your average electronic serviceman can be permitted to touch the mains circuitry in a radio or TV set, or any other piece of electronic equipment. Think it through and you'll find yourself peering into a real "can of worms". Possible legal implications I drew attention also to the rising tide of litigation "where individuals can find themselves financially accountable for any harm caused by activities which are arguably negligent or illegal". There's much more to it than mere administration. One reader, who wishes to remain anonymous, obviously did think through some of the wider implications of what had been said. He suggests that knee-jerk regulations could disadvantage people other than just the "intelligent handymen and odd-jobbers" that I'd originally had in mind. If the right to repair mains operated equipment was to be limited to licensed electricians and others with specified trade cer- seem to be dabbling in old-time wireless/radio technology. I've never come across the idea before and I'm not very optimistic about its effectiveness but, to somebody, it must have seemed like a good idea at the time 1923. Using firm cardboard or fibreboard, the idea was to make up a tube such that a pair of headphones could be wedged and. sealed firmly against the ends, held in place by their own headband or maybe a separate rubber band. This done, a small flared horn was constructed, which was then wedged and glued into a matching hole in the side of the tube. This was a tip for optimistic fans , 1923 style . How to transform a pair of headphones into a (not very) loudspeaker. It must have sounded dreadful. tificates, it might also disadvantage graduate electrical engineers. In his own case, he said, official trade level qualifications could involve extra tuition and a test covering wiring rules, plus at least twelve month ' s p ractical experience in electrician's work. Even that would not necessarily meet-the requirements in all states. Rather bitterly, he suggests (and I abbreviate): "There is a feeling I have known about, ever since I graduated, that 'engineer type ' electricians are regarded as being inferior to those who did a normal apprenticeship; that while the system allowed for those other than apprentices to get their licence, it did so only under sufference. Were engineer type electricians seen as ri v als in the professional sense, or in terms of job displacement - taking work from ordinary electricians?" One must concede that, in respect to everyday electrical contracting, electricians have to learn and employ a range of very practical non-engineering skills, if their work is to be acceptable to both supply authorities and consumers. NOVEMBER 1988 29 THEWAYISEEIT-CTD But it would be curious indeed if regulations were ever to be framed and interpreted in a way which would prevent electrical engineering graduates from repairing any form of mains powered equipment with which they might become involved. Fly/ride/drive by wire In the October issue, under the above heading, I raised the question as to whether new high-tech aircraft and road vehicles, controlled by computerised electronics, could be at risk from electromagnetic radiation. Scarcely had the article been committed to publication (in August) than ABC TV put to air a segment of QUANTUM detailing continuing research by NASA into the physics of lightning. The research had been triggered by a frightening experience on November 4, 1969 on the occasion of a manned mission to the Moon. Thirty-six seconds into the launch and at a height of 2000 metres, the huge Apollo rocket was struck by lightning and all -communication was cut. Sixteen seconds later, there was a second strike which reportedly tripped every circuit breaker and interrupted the guidance system. A major catastrophe was avoided only by on-board software checking facilities. If 1969 reads like ancient electronic history, lightning struck again on March 26, 1987 when an Atlas Centaur rocket was being launched from the Kennedy Space Center. It was carrying a communications satellite. Seconds after take-off, lightning scrambled the Atlas Centaur's electronics, forcing the controllers to destroy the . $160-million vehicle and its payload. The irony was that the launch controllers had just previously elected to ignore a warning about the charged state of the atmosphere. NASA's lightning research program is headed up by Prof. E. Philip Krider, at Mosquito Flat, about 1km from the launch pad. Krider's team use small rockets to drag a fine wire aloft when the atmosphere is known to be lightning-prone. At a height of a few hundred metres the fine wire then provides a path along which lightning tends to track. By thus initiating lightning strikes more or less to order, it becomes possible to monitor them much more frequently and accurately than would otherwise be the case. Lightning figures facts and According to Krider, the instantaneous temperature created by lightning can be five times hotter than the surface of the Sun. The speed of a lightning strike is 20 to 30 times greater than had previously been believed, while the instantaneous energy level involved approximates the total nominal power consumption of the City of New York or the whole of Australia. A major objective of the NASA research team has been to develop instrumentation that can measure atmospheric charges and gradients from ground level and thereby avoid especially hazardous launch conditions. But according to QUANTUM, they are also concerned with identifying measures which could render electronic components less vulnerable in the first place - especially in The Space Shuttle - operational again but space junk poses a growing danger. situations where the use of composite materials instead of metal drastically reduces shielding. As if to emphasise that the research was of more than academic interest, Professor Krider made a point that, on average, every substantial aircraft flying the American skies is struck by lightning once a year! It certainly reinforced the oddball scenario suggested in the October issue: • Solid-state scientists working Research into the effects of lightning is of more than academic interest. On average, every substantial aircraft f1.ying the American skies is struck by lightning once every year! 30 SILICON CHIP diligently to produce increasingly complex chips using vanishly small (and delicate?) devices and tracks. • Aviation electronics experts devising comprehensive control systems relying ever more profoundly on those same chips - and electrical wiring. • Aircraft designers resorting more and more to composite structural materials, in some cases because of their strength/weight ratio, in others because they are less visible to radar. • NASA scientists hard at work trying to minimise the apparent vulnerability of on-board circuitry, especially in the face of reduced shielding by composite materials! Surely, there's more than a suggestion here of technologists putting the cart before the horse! And if that isn't sufficient to reflect upon or to debate over morning coffee, try this one. In that same October article, I drew attention to the fact that, over the past 70-odd years, we've come to rely more and more on the electromagnetic spectrum. But over that same period, we've managed to clutter it with a huge array of deliberate but dubious signals, plus countless avoidable sources of interference. We seem to have learned little about prejudicing a future resource. Also depicted on television recently was a representation of the globe, encircled by a huge assortment of space junk. According to the accompanying commentary, there are something like 10,000 pieces of identifiable junk currently circling the Earth, each piece a potential hazard to communications satellites and other space activities. At orbital speeds, said the commentator, even a particle as small as a flake of paint could prove fatal to a human being in a space suit a new slant on Russian (or other) roulette! In their passion to be the first with the latest, I do wonder how many space researchers, over the years, have paused to think that useable space is a finite resource. "Shoot first", runs the old saying, "and ask questions later". How neatly it summarises the birth of the space age! ~ SPECTACULAR ELEASE vifa NEWSA-100 SPEAKER KIT 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. For full details please contact Sole Australian Distributor: SCAN AUDIO Pty. Ltd. P.O. Box 242, Hawthorn 3122. Fax (03)4299309 Phone: i03! 4292199 (Melbourne) 02 522 5697 (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 A ustra/ia 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 0pF 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: (02) 938 4690 ~------------ 1 Yes, I am interested in your capacitors. I Please post me details of the following I .. VDC . .. I . . . VDC . .. I . . . VDC OR Cut out and post this coupon to I Name (Please print) Post Office Box 740 I Address values: I . . . VDC __B_ro_o_k_~_1_e_, _N_.s_._w_._2_1_o_o_ _ _ L-~~~~~-~~~~J NOVEMBER 1988 31 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. Knightrider LED Scanner This is one of those "useless" novelty projects that is a lot of fun. It scans a row of light emitting diodes back and forth. It could be placed in the front of a radio controlled car, a skateboard or on the front of a child's bicycle. Most readers will have no doubt seen or at least glimpsed the American television series "Knightrider". The hero of the program is a computerised car which is even more clever than Lassie. Variously called "Knight 2000" or "Kitt", the car has a row of red lights at the front which supposedly scan the area in front of it. This circuit provides the same light scanning effect. It scans 20 light emitting diodes (LEDs) back and forth in quite an intriguing manner. It uses two cheap and readily available ICs, a 555 timer and a 4017 decade counter. The idea for this project came from a reader who suggests it both as a novelty and as a visual 12-240V 60VA Inverter This inverter can provide a 240VAC output from a 12V battery and deliver about 60VA of power. It uses three ICs, four transistors and a transformer, plus a handful of passive components. It operates at 50Hz and has a square wave output. 555 timer ICl oscillates at 50Hz and is connected to provide a duty cycle of 50%. This is achieved by connecting the 200k0 charging resistor for the 0. lµF capacitor from the output at pin 3 rather than from the 32 SILICO N CHIP D1rS1 1N4002 + 100k 16 'I' gy: VR1 100k IC1 555 3 14 g 11 ..L. f 12 89 Fig.1: the circuit uses a 555 timer IC which oscillates at about 6Hz and drives decade counter IC2. IC2 4017 76 37 deterrent to thieves. It could also be used as a back-up to real burglar alarms. ICl, a 555 timer, is wired as a conventional astable multivibrator which oscillates at about 6Hz. The square wave output from pin 3 of the 555 timer is then fed to the clock input of IC2. IC2 is a decade counter and as it counts the clock pulses at its pin 14, each of its outputs go high positive supply. However, the waveform of interest is the triangle waveform at pin 2 and this is coupled to op amp IC2a which operates as a noninverting buffer. The buffered output signal is then coupled to the inverting inputs of comparators IC3a and IC3b and to the non-inverting inputs of IC3c and IC3d. The remaining inputs of the comparators are connected to the output of op amp IC2b which sets the threshold voltage at 0.5Vcc. The comparators produce complementary square waves to drive transistors Ql to Q4. The outputs of IC3a and IC3b are paralleled to drive Q3 while IC3c and IC3d are paralleled to drive Q4. Ql and Q2 drive the transformer in push-pull mode, alternately applying 12V to one half of the primary winding and then to the other half. The output is taken from the 240V winding. VRl sets the "dead time" between Ql turning off and Q2 turning on (and vice versa). It can be used to set the output voltage from the transformer. The suggested transformer is a 60V A unit from Altronics, Cat. No. M-2165 . .,. PARTS LIST 1 printed board, SC08111881, 106 x 59mm 1 SPST toggle switch 1 555 timer 1 401 7 CMOS decade counter 1 O BC337 NPN transistors 20 rectangular red LEDs 1 1N4002 silicon diode 1 4 70µF 16VW electrolytic capacitor 1 1µF 1 6VW electrolytic capacitor 1 1 OOkO 0.25W resistor 10 1 OkO 0.25W resistors 1 2700 resistor 1 ·1 OOkO trimpot S1 A ,._....,.._...,.._.,......,.......,....._,......_.........,........,_.........,_.......,.......,_.....,_.....,.......,_._..,.._.,..._..,..._.,-.....;K LED1 LED20 Fig.2: here's how to wire up the PC board for the Knightrider. Be sure to install the ICs the right way around. Fig.3: use this actual-size pattern to etch your own PC board. in turn, for one clock period. As each output goes high, it turns on an associated transistor and two light emitting diodes. This counting process goes on continuously so that IC2 cycles its ten outputs from O to 9 repeatedly. Well that explains how the two ICs work together but it does not explain how a pair of LEDs is "scanned" back and forth. The 4017 can only count in one direction (ie, 0 to 9) so how do the LEDs go back and forth? The answer is that the outputs of IC2 are connected in such a way that the transistors are turned on in the following order: Q1, Q3, Q5, Q7, Q9, Q10, QB, Q6, Q4, Q2, and Ql. The cycle is then repeated. Each transistor drives a pair of LEDs but connected in such a way so that another undriven LED is interposed. The circuit and the wiring diagram of the printed circuit board shows how this is done. + 10 16VW - 12V 10k 1 !Cl 555 lk i- LM339 o.,l VJ\ 50Hz 100k 10k 240V OUTPUT NOVEMBER 1988 33 VINTAGE RADIO By JOHN HILL What to do about the loudspeaker The loudspeakers used in vintage radio receivers are many and varied. They range from primitive horns to permanent magnet types, with electrodynamics in between. This month, we take a look at some of these ancient speakers and the problems they pose for the vintage radio enthusiast. multiple listening stations from the one set of phones. Still another interesting technique used a gramophone sound arm to "amplify" the sound. The gramophone needle was placed on the headphone diaphragm, thus redirecting the sound through the gramophone horn for all to hear. Commercial loudspeakers Radio programs in the mid-1920s were, in the main, received on headphones - an arrangement that was hardly satisfactory for family listening. Although loudspeakers were available at the time, they were very expensive. There were many ways of overcoming this problem. One method was to place the headphones into a large bowl so that the sound was "amplified" by the shape of the bowl, thus allowing many listeners to hear the program. Apparently, there was great debate at the time as to whether a crystal or wooden bowl gave the better tone! Another early loudspeaker alternative was an acoustic adapter that connected a pair of headphones to a number of stethoscope like attachments. This gadget provided ' Speaker cones in this sad state of repair can be made to work again if one is desperate or determined enough. In this case, a replacement loudspeaker would be the best alternative. 34 SILICON CHIP At the time, commercially produced speakers operated on a similar principle to headphones and were nothing other than a large single headphone piece with a sound horn attached. While we may smirk about such things today, in the 1920s a horn speaker was the last word in loudspeaker technology. Of course, the sound reproduction of the old horn speaker left much to be desired. It had a highpitched metallic sound that totally lacked bass or any tonal quality. There was plenty of room for improvement and improvements there were. In a time span of just several years, loudspeakers went through several stages of development, including some cone types of incredible size. But none of these did much to really improve the quality of the sound until the dynamic or moving coil loudspeakers came on the scene. The moving coil speaker was the big breakthrough in speaker technology and modern speakers are the result of on-going refinement of this original idea. To my knowledge, nearly all of those very early loudspeakers prior to the dynamic speakers were permanent magnet types. However, the early dynamic speakers up until the late 1940s were mostly elec- This Rola permag loudspeaker still has the flange and bolt holes where the field coil bolted on in an earlier design. A number of manufacturers retained the field coil frame in their early permag speakers. The field coil impedance of an electrodynamic speaker is usually marked on the back of the field coil. If the marking is no longer visible, it can be checked with an ohmmeter. trodynamics, where the speaker magnet is an electro-magnet. This development went hand in hand with the ever increasing use of ACpowered sets. Early AC sets used a high tension choke to filter or reduce the 50Hz mains hum that is a characteristic of rectified DC. The choke was incorporated in the loudspeaker where it performed the dual role of choke and speaker magnet. This built in choke is known as the "field coil". When it comes to vintage loudspeakers, the one that comes to mind as far as most collectors are concerned is the electrodynamic type. This is the speaker I will concentrate on for most of this article. Horns and the very early cone speakers are relatively rare. The The Amplion "Dragon" was a popular horn-type loudspeaker from the mid-1920s era. By present day standards, it sounded absolutely dreadful. (Photo courtesy Orpheus Radio Museum, Ballarat). average collector, particularly if he is new to the game, is unlikely to have many radios in his collection that are pre-1930. On the other hand, collectors who have been scrounging for quite some time are likely to have much from the 1920s era. Although I am a relatively new collector, I have still managed to collect six horn speakers. However, I have really gone out of my way to get them. I might add that some of them cost a lot more than perhaps they are worth but if you want something badly enough you pay the going price. Keeping it original Electrodynamic loudspeakers will vary widely in their general condition. Wherever possible, a collector should endeavour to keep a radio as original as possible and the electrodynamic speaker should be either retained or replaced with a similar unit. Such ideals are not always possible, nor are they very important apart from the originality aspect. If originality is not a matter of life or death, then a more modern permaNOVEMBER 1988 35 quite OK and there is no reason why it shou,ldn't be used as a choke. If desired, both the field coil and the speaker transformer can be chassis mounted. This has the advantage of keeping all the high tension confined to the chassis which is desirable from a safety point of view. Regarding safety, it is unwise to handle an electrodynamic speaker while the set is operating. It could prove quite a "shocking experience" if the wiring is faulty. Repairing loudspeakers The "Spider" at the centre of old speaker cones acts as a damper on cone movement and holds the voice coil centred in the gap. If the voice coil is fouling the magnet, the cone can be repositioned by temporarily loosening the screw. nent magnet loudspeaker is the logical replacement. A modern loudspeaker will usually improve the sound of an old radio quite considerably. When replacing an electrodyrtamic speaker with a permag type, something must be done about the field coil circuit. As explained last month, the field coil forms a vital part part of the high tension circuitry and must be retained if the set is to function correctly. There are several ways of overcoming this problem. Perhaps the easiest way out is to replace the field coil with a 20 watt resistor of the appropriate value. Field coils generally range in impedance from 1kQ to 2.2kQ, although some go as high as 8kQ. The substitute high-wattage resistor would need to be of similar impedance to the field coil. The resistor should also be mounted where the dissipated heat will not affect the operation of other components. A heatsink-type resistor that can be bolted to the chassis is the best for this purpose. Another way is to substitute a separate choke of the same impedance as the field coil. This can be mounted on or under the chassis, wherever space is available. Unfor36 SILICON CHIP tunately, suitable chokes are not always available with the desired impedance and you may have to wire a choke and high-wattage resistor in series to match the speaker field coil. Still another option is to mount the field coil of the old loudspeaker under the chassis or in some inconspicuous part of the cabinet. While the speaker itself may be unserviceable, the field coil may be Early cone-type loudspeakers were housed in their own cabinets instead of sharing a cabinet with the radio set. (Photo courtesy Orpheus Radio Museum, Ballarat). Back in the good old days, when electrodynamic speakers were in common use, they could be rebuilt without much trouble. It was often cheaper to rewind a field coil, fit a new speaker transformer or even replace a damaged speaker cone rather than discard the whole unit and buy a new one. These old speakers were built to be serviced and all the bits and pieces, including new speaker cones, were readily available. Unfortunately, after 40 years or so, these much needed parts are no longer available. While field coils and transformer troubles aren't difficult to solve, speaker cones can be a bit of a problem. Patching the old one is about the only alternative. I have seen speaker cones in tatters yet thay still function surprisingly well. Great splits, tears and holes seem to make little difference. Often, the only adverse effect is a buzzing sound as the loose bits of cone flap about. If one cares to stick up all the tattered bits, an old speaker cone can be given a new lease of life. Almost any reasonable glue and thick drawing paper can be used to fill the large holes and missing sections of a damaged cone. It is surprising how well a damaged speaker cone can be repaired if the desire to get it working again is there. One particular part of a speaker cone that does wear out is the ridge (or ridges) around the outer rim where the cone flexes. Modern speakers often have a special super flexible synthetic reinforcement strip around the edge of the cone. Such a cone gives greatly prolonged A vintage radio restorer needs a good selection of spare loudspeakers. If possible, you should always salvage the loudspeaker when scrapping a vintage receiver for parts. Other parts such as high-tension chokes and speaker transformers should also be salvaged. life compared to the old paper type. Old speaker cones can wear very thin around the rim and holding the speaker up to a strong light will soon reveal any problems. If the light shows through, it is only a matter of time before the cone detaches itself from the rim. This particular problem is easily solved by applying a generous application of "Silastic" (silicone rubber) to the grooves at the outer edge of the speaker cone. The rubber compound needs to be rubbed in fairly firmly to ensure good adhesion to the paper. Silastic seems to be an excellent rejuvenation agent for tired speaker cones. It adheres well to the paper and provides flexibility where it is needed. Although silicone rubber was never intended for such use, it appears to be well suited to the task. Voice coil fouling Old electrodynamic speakers often have a terrible buzzing sound in them which is usually caused by the voice coil at the centre of the cone rubbing against the magnet. If the speaker has a central locating device (the "Spider"), the problem can usually be cured by repositioning the cone. To do this,-first undo the screw in the centre which releases the spider. The cone can then be repositioned and the screw tightened again. With a bit of luck, the cone will now work in a position where the voice coil no longer fouls the magnet. If you don't get it right the first time, loosen the locking screw and try again. Another way to solve this problem (sometimes) is to remount the speaker upside down. Often a speaker cone sags and distorts a little due to its own weight and the passing of time. Simply inverting the speaker can reposition the cone sufficiently to eliminate the problem. It doesn't always work but it's worth a try. Bigger is better The sound of an old radio can be improved many ways and one trick is to use a larger speaker than was originally fitted. This can be done without too much trouble with console type radios because there is usually plenty of room. Fitting a 25cm or 30cm speaker will really make the windows rattle. Smaller mantel radios can respond to the same treatment and often a larger speaker can be worked in without too much trouble. Bigger speakers give better sound. The quality of any sound system depends greatly on the quality of the loudspeaker. Even an old reaction type radio from the 1920s sounds surprisingly good when played through a modern speaker. The same set through an old horn speaker sounds absolutely dreadful. In summary, the vintage radio restorer often has to choose between sound quality and originality. Occasionally they can have both for some old speakers perform remarkably well- but not often. Many old receivers were seriously handicapped by inadequate loudspeakers. Loudspeakers, like so many other things we now take for granted, have come a long way in the past 60 years. Next month, we will take a look at restoring dials for vintage radios. ~ Vintage Radio Kits & Parts *RADIO* Suppliers of • • • • • VALVES RADIO KITS CAPACITORS RESISTORS BOOKS, ETC. Please send for our free catalogue ORPHEUS RADIO RSD 898 BALLARAT VICTORIA 3352 Ph. (053) 34 2513. Fax (053) 31 3412 NOVEMBER 1988 37 SUPER DELUXE 8 YJ"!N'l~llk • c~~JJJf110 $ 5.50 $ 6.50 N, and up to 3 x 9V batterles at the same time. • D ual colour LED in first three compartments to desigri ate 1·SV or9V . • 240V AC/50Hz. • Approval No. N 10637 Cat.M23525 . $59.95 H103843x4x4inches . H103853 x 4x5inches H10386 3 x 4 x6 inches H10387 3 x 4 x 7 inches H10388 3 x 4 x 8 inch es H103893x4x9inches H 103903 x 4x10inches 7.50 7.95 8.50 9.50 $1 0.50 $10.95 $11.95 $ $ $ $ ~a1fi~Uis Jl~a~u~ inium tops . and available in four sizes. Very popular for projects and very ecconomical! H1010 1 150x90x50mm $ 3.25 H10102195x1 13x60mm $ 4.50 H 10103 130x68x41mm $ 2.75 H10 105 83x54x28mm $ 1.95 H10110 120x65x38mm $ 2.95 H1 0 112 120x65x38mm (Metal top) $ 2.95 CD TO CAR CASSETTE STEREO ADAPTOR Enables a portable CD player or portable TV to be played through any car speaker system by using the cars cassette player. Reduces the n sk of !heft. Just plug in when _required. and remove when you are finished. Hard wiring not needed . A 10011 $29.95 'i 'IN DIN WALL P .ATr frI~fJij~ Crossovef'J g r multiway speaker systems. otherwise your bass will be degraded by intermodulation distortion and cone break up , and your treble will be distorted by bass components. These crossovers are designed to channel only the frequencies that each driver can properly handle. R ead the specifications to choose the correct one ror your need . • Fitted with 5 pin DIN socket. • Anodised aluminium plate. • Includes mounting hardware. P10940 $9.95 2WAY i0 VA .G,~£ ~5?, ,Ji;R NETWOR'< DB25SOCKET A .L PLATE • Cross over point 5,000 Hz • Impedance 8 oh ms Cat. A 16001 $4.95 2 WAY 60 WATT .C,~£§,~Q,¥tf{;~NETWORK . "tJ~~~n1cr?fa~t~~a'ilc~iY{lJ19.H . J~ E1i¥c\i'r1fi~ VERTER Input (Channel 36) : 75 ohm x 1. Output (Channel 1,3,4): 75 ohm x ~ Gain: 12d8 Power Supply : AC adapter 240V AC 50Hz/12VDC. 100mA. DC Plug . Cat. L15051 $89.95 CAR ALARM SYSTEM WITH REMOTE CONTROL • Comple~~uY0~~5i~fJ1ection system with back-up battery protected siren • Supplied with remote key switch. pager and glass breakage detector • 11 OdB siren with independent inbuilt rechargeable back-up battery • Automatically arms when ignition is switched off • Will nol s tart 30 second exit delay until last door is closed SELECT ABLE OPTIONS • Transmits signal to pager only, siren only or to both • Gives audible beep when the system is armed or disarmed • Valet mode: disarm s the system c ompletely for servi ce . etc. • Extends car power antenna when triggered for long range paging • Pressing both remote key buttons together activates panic alarm OUTPUT TER MINALS • 8 ohm siren/speaker outputs • Normally open and normally closed output terminals • 12V DC 300mA output for other alarm devices COMPONENT BREAK DOW N Mai n Unit: Controls and monitors the complete alarm system. AU input and output cables are connected to this Pager: Port able monitoring receiver "beeps" when the atarm is activated up to 2 miles away. Can also be used as a pager w hen " paging~ button is L~6)~~~~~~: ~~w~:~~t 1 ~~~Qe the alarm system is in. ie: armed/disarmed and exit/entry period. It also has a m emory LED that indicates that the system has been triggered and has auto matically reset. Remote Arm/Disarm K ey : This transmitter allows you to activate or deactivate the car from outside the vehicle. It also has a panic feature that triggers the alarm when both buttons are depressed together. Glass Breaking Sensor: This is a piezo sensor thal is activated by the frequency of breaking glass which helps to prevent false alarms. Back-up battery: Rechargeable ~~.~~~~::~~~c~f ~~~s siren . If any of the wires going to the siren are cu t it will sound . It also has a keyed manual over ri de switch for disarming or servicing . S 15056 . .. .. .. ... .. .. . ... . $399 $11.95 Cat.A 16002 DB 5 PLUG~ A PLAT $7.95 • Bla§f.~1~~t'li.?cil;,1~'il~r speaker stands. Base slope is adjustable to allow you to find the correct listening position for your speakers. • Holds speakers witha minimum dimension of 220 x 190mmm • Maximum speaker weight 30Kg • Stand height 125mm • Stand base dimension 370 x 280mm • Leg studs to stop slipping and vibrating on carpets are easily removed for smooth tile floors, etc . $17.95 .... --~ P10947 •Crossover point 2,300 Hz • Impedance 8 ohms on lights at night and off during the day. Ideal for both domestic and security use. • Turns lights off at 120 lux and on at 20 Iux • Waterproof !or outdoor use • Operates on 240V AC SOHz A15596 • Fitted with DB25S socket. (R S232) • Anod ised alu minium plate. • Includes mou ntin g hardware C10768 $99.95 Cat. T12302 .... $19.95 Cat. A 16003 $9.95 3WAY ,0WATT NET'I\/ORK •C,~£§,~\;t¥,fo~ f'/ Y ,L "SNAP TOGETHER" Cat. A 16007 $34.95 ' RCA TO RC A ISOLATION LI M10038 Cat. A15052 ................... $25.95 PRECISION INSTRUMENT $7.95 RACING BATTERY PACK SPECIFICATIONS , Input Voltage: 24V DC Output Voltage: 13·8V DC Primary Curren t : 4·2A {24V input 4A output) Output Current : 4 Amp continuous rated {S·SA max .) Size: 125(W) x SO( H ) x 90(D)mm Weight: 450 grams H1 0080 Single tray .. $3.95 H1 0081 Double tray .. $4.25 $11 .95 7·2V NICAD J;l~~~PrPn,~TI~ftU~r~n~ remote oonlrol cars, toys, and models. S15025 .. ..... 10A STEP DOWN CONVERTER DC-DC Built arou nd a heavy duty heatsink this unit features the latesl transistor t~~a"S~~ ~fnfi;~~ matt ~:~c3~?o UHFNHF/FM ANTENNA AMPLIFIER AND 2 WAY 8,~Jr!1J~u~ l'ralian frequencies. Suitable for use in houses. c aravans. boats etc . • 1 x 75 ohm input. • 2 x 75 ohm output • Gain 2 x 6dB . • Maximum outpu t 2 x 96dBuV Cat L1 5041 $39.95 • 4 piezo unils in a high impact plaslic cabinet • Input 12V DC · 200mA • Output 115dB at 1m . dual tone • Compact size 105 )( 85 x 45mm • Smart design suits interior use Cat. S15071 .. .. ............ .. $24.95 C, 0 T Cneab le: 92~ 104MHz PH ~ Freq . Res ponse: 50 • 15kHz Range: Over 300 feet in open field. Modulation: FM Power Sour ce: 9V Battery SPECIFICATIONS, Vo ttage:7·2 Chargin g Curren t: 130m A Nominal Capacity : 1300mAH Charging Time: 15 Hours $99.95 A16160 ...... ....... . $1 19.95 Cat. C12104 8 -~~&i~n ~o9lrlrr~,lm'-\~~I unils to be interlocked together • Large handle with index card slot • One piece moulding en sures trays will not jam or sieze • Size: 110(W) x 120(0) x 55(H )mm SPECIFICATIONS, In put Voltage : 24V DC Output Voltage: 13·8V DC Primary Current: 11A (24V input, 10A output) Output Current: 8 Amp continuous rated (12A max.) Size: 125(W) x SO{H) x 175(D)mm Weight: 900 gram s Requires no crossover, han dles up to 100watts. Sensitivity: 98dB Maxim um imput : 24 volts Freq. Response: 3 .2 • 30kHz Di mensions: 95mm diameter. M23528 ............ .... $39.95 ~:~t6fo f~~v~~ black. '<'7 OI TI GT EE ,- Input: 12V DC cigarette lighter, fuse protected Outpu t: standard racing pack lead and terminal to suit S15025 and Tamiya 7•2V b atteries Charge Tlme:Standard charge is 15 minutes for 7•2V batteries. 0-30 minute tim er. ~ · ✓~ A 16155 10+ $2.25 ~ti~fs FasRM[~~a';I/;,~ ~fli\?a~~ies Built around a heavy duty heatsink this unit features the latest transistor 1 J?n~~:~~ matt black wilh a unique mounting bracket makes it the best in its class. ... .......... $14.95 ................ $18.50 ............... $24.95 ...... ......... . $29.50 $15.95 ~~~~tern for cooling , top and bottom snap together (no screws required). removable Iron! and back panels . Size: 135(W) x 93(0) x 47(H )mm H10114 STEP DOWN CONVERTER DC-DC I P1701616pin P17024 24 pin P1 7028 28 pin P17040 40 pin • 1 SA J g~ t l~1W n<t?.fi~1u~t,essor isolation transformer • Designed to eliminate noise in the audio line • Does not affect the audio signal • Simply fits inline between car stereo and the separate power amplifi er FLUORESCENT WORK & - A 1ETW'.)R • Crossover point 350 and 3.000 Hz • Impedance 8 ohms fo~tJI\fo~~~p~ysnap $11 .95 $24.95 .C,'J£~fte9u¥tli,r;i together (no screws required), removable front and back panels. Size: 186(W) x 125{0) x SO(H )mm J=~l~~~s~ ~ix g~J~~In, camping etc . • Shatterproof, glare free • Cigarette lighter plug and alligator clips • 12V DC, 8 watt , transistorised P10944 a 0 Cat H101 16 ................... $7.95 • Fitted with 0825P plug . (R$232) • Anodised aluminium plate . • Includes mounting hardware . • Cross over point 800 and 5.000 Hz • Impedance oh ms Cat. A 16005 f.~Y.\'n~~~J/Mi)llbtliJ r~~LL motor. this lightweight (1 13gm) drill is ideal for many jobs . Perfect for PCB work! Has a 0.8 to 1.2mm chuck and 1mm drill bit . Requires 12V 1 AMP .(usewith M19010) 3WAY60WAT oGi\Wa ~ f.>a)(Ji:R ETWORK • Cross over point 800 and 5,000 Hz • Impedance 8 ohms • LIGHTER TO LIGHTER ~ ~ Jil~l.~ah~r~ olution to flat car batteries! Simply plug in to the cigarette lighter postions and presto! Features 5 m etre long lead , and LED indical es correct connection Cat. A15062 ................... $10.95 ,~inxd~~sxe~Smm Weight : 160 grams Cat. A10450 ... .... .. $19.95 : i~~ea~e~ :s~r~ 3kHz-30kHz • Size: 145x54rf'lm Cat. C12 103 ..... Normally $12.95 SPECIAL, ONLY $9.95 $49.95 ~ ir.:~;~~~~~I 'IPERHOR' 1cte 01spers1on tweeter, handles up to 100W. • Sensitivity: 105d8/0.5m .er tJPE HO ' . equ1res no crossover anti handles up to 1OOW! • Sensitivity: 100d8/0.5m • E : i~~dea~e~;s~n~s 3kHz-30kHz • Size 96mm diameter Cat. C12 102 ... ... Normally $12.95 SPECIAL. ONLY $9.95 s~ Male to femf i l O I 25 Detachable ptug on leads 2 mini jumpers Ideal for experimenting or temporary connections Cat. X 15665 .. ... Normally $49.95 • • • • Only $44.95 • • • • • CB SPEAKER 10cm (4") speaker 3 metre cord with 3-Smm plug Impedance 8 ohms Power 5 watts Complete with mounting bracket Cat.A12074 $24.95 FREE STANDING FOLD UP MAGNIFIER An ecconomically priced "hands free·· magnifier. lets you take care of all those tricky fine detailed jobs so often encountered in electronics. or any of many other praclical uses such as home, work. hobbies etc Cat. T10020 Normally $14.95 ,>< CKETSIZE BATTERY TESTER • Tests all 9V to 1·5V batteries including button cells. • Arms ex'lend to various battery sizes • Easy to read meter. • Requires no power source. COMPACT DISC STORAGE UNITS • Momentary or on/off models to choose from • Cord length 2·5 metres • 6·3mm plug A 17000 Momentary operation A 17005 Push On/Off operation ............. each $19.95 • $11.95 M23521 . • Holds 10/20 compact discs 1n their cases • Interl ocking modular d~sign allows vertical and hOnzontal ······· $9.95 ~:~~~~~1nto place horizontally making titles easy to rea~ . • Wall mount or free standmg . A10031 (10 discs) $12.95 A 10032 (20 discs) $19.95 SPECIAL. ONLY $12.95 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) i NEW COLOUR KNOBS! Standard metric fluted shaft with black dot marker and available in six AUTO different colours! Cat.No. H10070 H10071 H10072 Colour 1·9 Black $0.75 Blue ........ . $0.75 Green .. ... . $0.75 • Strips cable with diameter of 1 1·6 2 2·6 3•2mm • Fulty aulomatic action . Squeeze grip will simulataneously strip and eject insula1ion. • Length 180mm (7") 10+ $0.65 $0.65 $0.65 COMPUTER CABLE CIC6 6 conductor computer interface cable. Colour coded with braided shield . (to 1E422 specif ications). Copper conductor 6 x 710.16mm . 1· 9 metres 10 + metres $1.90/m $1.70/m CIC9.100 9 conductor computer interface cable. Colour coded with mylar shielding . 9 x 710.16mm. 1-9 metres 1O+ metres $2.50/m $1.95/m CIC12 12 conductor computer interface cable. Colour coded with mylar shielding. 12 x 710.16mm. 1·9 metres 10+ metres $2.70/m $2.50/m CIC16 16 conductor computer interface cable. Colour coded with mylar shield ing . 16 x 710.16mm. 1·9 metres 10+ metres $3.90/m $3.40/m CIC25 25 conductor computer interface cable. Colour coded with mylar shielding . 25 x 710 .16mm. 1-9 metres 10-t- metres $4.90/m $4.40/m STEREO WIRELESS TRANSMITTER This unit was developed to allow portable compact disc players to be used in cars by transmitting the headphone output signal directly in to your stereo FM car radio. It will also transmit any mono/stereo signal fr om any headphone output to an y FM receiver SPECIFICATIONS: • Input 3·5mm stereo phone plug Impedance 32 ohm . • Mono/stereo switch has plug mounting clip. • FM Transmission approx. 90·35MHz (Tuneable 89·9 1MHz) • Range 15 metres. (below 15mV/m at 100 metres) • Power 1·5V AAA size batteries {100 hours continuous use) •Size72x38x21mm A16100 $69.95 COMPACT DISC C, SES Threestandardreplacement compact disc cases. $6. 95 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 $17.50/m CODE KEYPAD • • • • JOINABLE PCB MOUNTING SCREW TERMINALS (GREY) 2 Way Cai P \0520 1·9 10-t $0.50 $0.45 3Way Cat. P10521 $0.75 ~ ER CONTROLLER AA801 • Enables up to 5 pairs of stereo speakers to be switched on or off in any combination. • Rated at 50 watts continuous per channel. • Stereo headphone socket available for private listening. • Constant minimum load circuit protec1s amplifier regardless of how many speakers are connected . • Dual circuit breaker protection. ROTATING LIGHT TELEPHONE BUG ALERT • Indicates if an unwanted third party is listening in to your telephone conversation • Green LED Indicates all is O.K. • Flashing red LED indicates someone else is on the line • Features Australian plug/socket for easy inline installation • Double sided lape on back of unit allows mounting onto the side o f the phone • No batteries required . Power is taken from phone line • Screwdriver supplied for adjusting and installing unit. Telephone type digital keypad. Four digit , changeable code. Over 5000 possible combinations Power consumption : SmA standby, 50mAalarm. • Two sector LED and 1 arm LEO • Wrong number lockout. • 12V DC operation • Relay output. • Panic button . • Normally open tamper switch . • Dimensions : 145 x 100 x 37m m • ACP3 compatible. Cat. A13014 ....... ... R.R.P. $79.95 SPECIAL, ONLY $69.95 Cat. A 16054 $59.95 E DIRECTOR f ·AA802) Ideal tor tt'IOse who do a lot ol dubbing and recording. Features facilities for amplifier, auxiliary, 2 tape inputs and 2 amplifier, 2 tape outputs, by simply selecting and pressing the appropiate switch you are able to: • Record from either tape unit while listening to another source thrOUf]h your system . • Dub direct from tape 1 to tape 2 whilst listening to tape 1 or 2 • Record from auxiliary to tape 1 or tape 2 while listening to auxiliary through the amplifier • Record from amplifier to tape 1 or 2 while listening to the amplifier. Motor driven rotating reflecting mirror with a fl ash rate of about 150 per minute. Large lens lit right to base. making unit weatherproof. Spare globe included SPECIFICATIONS: • Available in Blue or Orange • 150 Revolutions per minute. (approximately) • Shock absorbing rubber mounting legs • connecting wire fitted through base • 12V DC 750mA • Base diameter: 102mm Height: 140mm A 15042 A 15043 Blue $42.95 Orange ... $42.95 ,.-·--~ I 1.fe{f \ Y16019 MAIL ORDER HOTLINE 008 335757 • • (TOLL FREEJ LOCAL: 543 7877 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 i~:::t~)~fJ• ~i~LAJDE 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 MINIATURE HOBBY VICE • Lever operated suctron grip base for instant mounting and portability • Mounts on smooth non-porous surfaces. • Ideal for holding components . and other small/light objects . Cat.T12458 ... only $6.45 - MAIL ORDER HOTLINE 008335757 ITOUFREEJ (STRICTLY ORDERS ONLY) LOCAL ORDERS &INQUIRIES (03J 543 7877 TELEPHONE EXTENSION BELL • 10 metre length extension cord • Features US type plug • Use with US/Australian adaptor Y16043 SYDNEY: 74 Parramatta Ad . STANMORE . 2048 Phone: (02) 519 3 134 Fax : (02) 516 3671 NOTE: PRICES MAY VARY INTER· STATE DUE TO FREIGHT COSTS I I Rod lrvfng Electronics SOUTH AUSTRALIA: Electronic Discounters P/L, $34.95 ---~- A10030 $19.00/m $19.95 111532 H 10073 Grey ........ $0. 75 $0.65 H10074 Red .. ...... $0.75 $0.65 H10075 Yellow .. .... $0.75 $0.65 ;;;;;;;;;;; ·;~ ATIC CABLE T IPPER Dimensions : 17•2mm high. 12·8mm top diameter, 17mm bottom diameter. POSTAGE RATES, $1 - $9.99 .... $10 - $24.99 $25 - $49.99 $50 - $99.99 $100 - $199 $200 - $499 $25.95 $500ptus 4A REGULATED POWER PACK Cat. A16056 ........ $59.95 PUSH BUTTON DIALLERS Tired of old fashion dialling and re-dialling engaged numbers? These convenient push button diallers include last number redial (up to 16 digits) and instructions for an easy changeover . Cat. A12030 ... ... Normally S19.95 SPECIAL, ONLY $14.95 • 240V AC input to 13-BV DC regulated 1 A outlet • Ideal for CB, ham radio, and other high power applications • Fully over1oad and short circuit protected • Will handle up to 6A surge current • Ripple less than 1 0mV peak to peak • ~~~eatsink and vent system for • Outputs: screw terminals or 4mm banana sockets • Illuminated on/off switch • Fuse protected • Approved by the Department of Energy M19032 The above postage rates are for basic postage only. Road Freight , ~:r1~~~r~~~~~~~:t:'.1 be AU wholesale and sales tax exempt Inquiries to: RITRONICS WHOLESALE. 56 Renver Ad, Clayton. Ph. (03) 543 2166 (3 lines) Errors and omisSK>ns excepted Prices and specifications subject to change . :~~:a~S~T;n~~~aien~i~:~~~s Machines. •Apple Is a registered trademark. "Denotes registered tradmaril.s ol their respective owners. By LEO SIMPSON Man's Plasma Display The Plasma Display described in our August issue created enormous interest among enthusiasts hut many people complained about the high cost of the kit. For those people, we have come up with a much cheaper version and all the parts are readily available. There is no doubt about it. The Plasma Display described in August really did create a lot of interest. Many people were fascinated with the concept and we had lots of phone calls from readers wanting to know if there was a cheaper way. We said there wasn't. Then we had a letter from a reader asking if a large incandescent bulb could be used. Rather rashly, we said it wouldn't work. But then one of the members of our editorial advisory panel, Philip Watson, said that the Plasma Display article brought back memories of his boyhood experiments with a Ford "trembler" coil and a small incandescent bulb. "Hmm," we thought, "maybe it's worth trying". We disconnected the large Plasma Display and connected the EHT output instead to the base of a 300 watt incandescent lamp which we happened to have on hand. Presto, it worked. The display was not as spectacular as from the large plasma container presented in August, mainly because the discharge path from the lamp filament to the glass envelope was nowhere near as long. We noted that there were two main discharge paths, from the ends of the filaments to the glass envelope. There were also very small discharges from all the sharp points of the filament. These main discharges were pinkish with tinges of blue. And then, when observing the discharge in the dark, the whole bulb was lit up with a blue fluorescence. Beautiful. Then we got really adventurous and tried an ordinary 40W bulb. Yep, it lit up too with a blue discharge. In fact, every bulb we tried would work. "Why didn't we think of it before?" we thought. Well, it did require some lateral thinking and clearly, we hadn't been in lateral mode. But when you consider that an incandescent lamp is a perfectly sealed bulb containing a small quantity of inert gas, namely Argon, it should work. And it did. So OK, virtually any incandescent lamp can be made to work with the EHT generator presented in our August issue. We have to be realistic though; it isn't perfect. It does have drawbacks. First, as we have already noted, it is not as spectacular or as colourful. Nor can you order up the display you want. There is no choice. And the fact that the lamp filament has sharp points at each support means that the discharges will inevitably strike from those points. PARTS LIST 1 large incandescent lamp, preferably rated at 300W or more 1 43mm giant Edison screw socket 1 black plastic instrument case {Altronics Cat. H-0483) 1 TV horizontal output transformer (not a tripler type) 1 printed circuit board, code SC 11111881, 185 x 100mm 1 50k0 potentiometer (log or linear) 1 in-line 3AG fuseholder and 3A fuse 3 solder lugs 1 cordgrip grommet 1 1-way insulated terminal block Semiconductors 3 2N3055 silicon NPN power transistors 1 B0 140 silicon PNP power transistor 1 BC337 NPN transistor 1 1 5V 1 W zener diode 1 1N4 1 48 silicon diode 1 1N4007 silicon diode 2 1N4002 silicon diodes 1 1N5407 silicon diode 1 555 timer IC Capacitors 1 220µF 16VW PC electrolytic 1 .04 7 µF metallised polyester Resistors 2 x 10k0 0.25W, 1 x 1k0 0 .25W, 1 x 1800 0 .25W, 3 x 1500 1W, 1 x 1000 5W wirewound, 2 x 560 5W wirewound, 1 x 270 5W wirewound, 2 x 180 5W wirewound, 1 x 6 .80 1 W Miscellaneous Mica washers and insulating washers to suit T0-3 power transistors, rainbow hook-up wire, screws, nuts, lockwashers. NOVEMBER 1988 41 +0--0--0-,--------------------------------~ JA 12·15V -i 100n SW OS 1N5407 EHT TD PLASMA DISPLAY 180 SW + 220 10k 16VWI -• INTENSITY VR1 50k ~ - - - - PLASTIC---~ SIDE IC1 555 10k OE /c 0 B E • ECB 0 • C •B 0 .047! VIEWED FROM BELOW PLASMA DISPLAY EHT GENERATOR 6.Bn 1W .,. .,. .,. Fig.1: transistors Qt and Q2 drive an EHT transformer to produce high-voltage AC. This inverter circuit is rapidly turned on and off by Q3, which is driven by Q4, Q5 and IC1. VR1 varies the duty cycle to optimise the plasma display. This is in contrast with the carefully rounded filaments of the Plasma Display which generate beautifully random discharges. Second, and this is more of a problem, standard incandescent lamps are made from very thin glass. That means that when you touch the outside surface of the glass with your hand you can get quite a nasty tickle. In some cases you could even get a burn as the electric discharge can become quite concentrated. So placing your hands directly on the glass envelope is not recommended. If you do it, you'll only do it once and then you'll stay right away from it. Third, if you concentrate the electric discharge at one point on the glass envelope, say by bringing A0--0 an earthed metal electrode in contact with the glass, you can puncture the envelope. What happens is that the heat of the concentrated discharge actually melts the glass at that spot and the resulting stresses then cause a hair-line crack to develop. This quickly degrades the partial vacuum inside the bulb and the display is extinguished. So you have been warned. It is no great loss when you puncture a 100W bulb which costs less than a dollar. But if you puncture a 300W or 500W lamp it is a bigger loss. On the positive side, we have found that there are two ways to improve upon the display available from the larger incandescent lamps. You can gain quite a wor6A BRIDGE RECTIFIER (P04) 240VAC [0---;;1,-, Fig.2: if you don't have a 12V battery charger, this circuit can be used to make up a suitable DC power supply. It uses a 15V 2A transformer to drive a bridge rectifier. 42 SILICON CHIP thwhile improvement by rapidly switching on and off the EHT supply. This reduces the tendency of the discharge to jump from one or two points on the filament and instead, to spread itself more uniformly. Second, by placing an earthed wire "halo" above but not touching the glass bulb, you can obtain a more even distribution of the discharge. One of our readers suggested this idea. And to see the display to the best effect, you should view it in pitch darkness. EHT Generator As noted above, we have modified the EHT generator we produced for the Plasma Display described in August. Essentially, we are using an additional power transistor to rapidly switch the EHT generator on and off. The basic EHT generator remains much the same though, although we have improved the heatsinking. Lack of an adequate heatsink has proved to be a problem with some EHT transformers. For those who did not see the original article, let's describe the basic EHT generator and then the circuitry for modulating it. EHT stands for "extra high tension" and is the term used to describe high voltages of several thousand volts or more, whether DC or AC. The EHT generator for the Plasma Display produces about 15,000 volts (15kV) AC at a frequency somewhere between lOkHz and 20kHz. The basic EHT generator is a DC to AC converter which takes low voltage DC and steps it up to very high voltage AC at a high frequency. It uses two 2N3055 power transistors connected as a transformercoupled multivibrator. The transformer is a horizontal output transformer intended for a black and white television set. Normally a transformer of this type would be driven by the horizontal output transistor at 15,625Hz. For our circuit, the transformer is modified by adding two centretapped windings and these are driven by the two power transistors, as shown in the circuit of Fig.1. For the moment, imagine that Q3 is turned on continuously so that the power is applied to the EHT generator all the time. Each transistor's base is driven by a one-turn feedback winding while each collector drives half the main low voltage winding. When the circuit is oscillating, each transistor alternately turns hard on, which applies the full DC voltage across the associated winding, while the other transistor is biased off. So the transistors apply a square wave voltage to the low voltage winding and this is stepped up by more than a thousand times in the high voltage secondary winding. The 180 5W resistors in series with the bases of transistors Ql and Q2 are there to limit the amount of feedback current. They therefore have the effect of reducing the amount of damping on the transformer and thus improve efficiency. Initial bias to start the circuit oscillating is provided by the 1000 5W and 270 5W resistors. Modulator ICl, Q3, Q4 and Q5 comprise the modulating circuit for the EHT generator. Since the main DC supply via the 3 amp fuse can be pure DC or unfiltered DC from a battery This view shows how the 4-turn and 1-turn secondary windings are wound on the EHT transformer using two-core ribbon cable. When the windings are in place, they can be secured by running some hot candle wax over them or you can use a couple of plastic cable ties. charger, there is a need to produce a clean DC supply for ICl. This is provided by D3 and the 220µF capacitor, with voltage limiting being provided by the 15V zener diode D4. To prevent excessive current through the zener diode, a 1500 1W resistor is connected in series with D3. ICl is a 555 timer connected to oscillate continuously. The frequency of oscillation is set by the .047 µF capacitor connected to pins 2 and 6, in conjunction with the associated 50k0 potentiometer (VRl) and two lOkO resistors. ICl oscillates at a frequency of about 430Hz (actually between 415 and 450Hz, for our prototypes) and the duty cycle of the output pulse waveform varies between about 16% and 85%, depending on the setting of VRl. Normally, it is not possible to achieve a pulse waveform with a duty cycle of less than 50% from a 555. However, the addition of diode D5 allows the duty cycle to be reduced to 15 % . This makes for an interesting variation on the normal charge and discharge cycle of a 555. When the capacitor is charging to the upper threshold of the 555 (2/3Vcc), the charge path is via the upper lOkO resistor, the top portion of VRl and diode D5. When the capacitor is being discharged to the lower threshold of the 555 (1/3Vcc), the discharge path is via the lower lOkO resistor (connected to pin 2) and the lower portion of VRl, to pin 7. NOVEMBER 1988 43 I 12-1sv...: _, 'r, \1 \\ 3A IN LINE FUSE ~ ~ \ \\ \ '1$;;!/,1 \~2 / REAR PANEL (ALUMINIUM) (p)B 02 B ~ - -~ -- ~ '='C \\ 4 _1 GROMMET Fig.3: here's how to wire up the Veroboard version of the EHT generator. You can make the cuts in the tracks using an oversize drill but take care as it's very easy to make a mistake with Veroboard. A standard plastic case with a metal rear panel can be used to house the EHT generator circuitry. The EHT lead is connected to a lead from the Edison screw socket via a 1-way terminal block. Don't touch the EHT transformer while the unit is operating. 44 SILICON CHIP The variable duty cycle pulse waveform from pin 3 of the 555 is fed to the base of Q5 which turns Q4 on and off. Q4, in turn, switches Q3 on and off and thus turns on and off the negative supply rail to the EHT generator circuit. Diode D2 provides a current return path to the EHT coil of the transformer, so Q3 is protected against reverse current. D6, at the supply input, prevents damage in the event of the DC supply being reverse-connected. If that happens, the 3A fuse will blow. As with the EHT generator for the original Plasma Display, any DC power supply capable of delivering 12 to 15 volts at more than two amps is adequate. In fact, virtually any 12V battery charger will do the job, provided it can deliver 2A or more. If you don't have an adequate DC supply or battery charger, the circuit of Fig.2 will do the job. It uses a 15V 2A transformer driving a The wire loop above the light bulb is connected to a screw terminal (near pen) on the lid of the case. From there, a lead is run to the earthy end of the EHT coil as shown on the wiring diagrams. bridge rectifier. No filter capacitors are necessary. Construction We adopted quite a different method of construction for the Poor Man's Plasma Display. Instead of using a round stand based on plastic sewer pipe fittings, we have used a standard black plastic instrument case (Altronics Cat. H-0483 or equivalent). Because of the very high voltage applied to the base of the incandescent lamp, the plastic case is mandatory. We would not recommend a metal case. The specified case also has ventilation holes which are desirable because the EHT transformer does get warm after a long period of operation. Fitted to the top of case is a ceramic giant Edison screw (GES) socket which is suitable for high power incandescent lamps. The lamp we used is rated at 1000W and cost around $40. You can also use the more common 27mm Edison screw socket. Sockets and high power lamps are readily available from lighting retailers and wholesalers. To provide heatsinking for the three power transistors, the rear panel of the case must be of aluminium. We made our own panel from 16-gauge aluminium but you can purchase 2.5mm thick natural or black anodised panels to match the case (Altronics Cat. H-0488, black or H-0489, natural). The circuitry inside the case may be wired up on Veroboard or a printed board designed for the job. While the Veroboard version will certainly save you money, we only recommend it for experienced constructors as it is very easy to make a mistake in wiring it. The wiring diagram for the Veroboard version is shown in Fig.3. We'll restrict our construction instructions to the printed board The 2N3055 power transistors are mounted on the aluminium rear panel to ensure adequate heatsinking. Make sure that the transistor cases are electrically isolated from the panel as shown in Fig.5. NOVEMBER 1988 45 REAR PANEL (ALUMINIUM) +,',,- 3A IN LINE FUSE I -, ' ' ' ' 12-15V' ' , -----~~ ~ 0 I~ 2 -, GROMMET e 56{) SW 56{) SW 0 VR1 Fig.4: the PCB version of the EHT generator is much easier to assemble. Note the lead marked "to halo". This lead connects to the wire loop above the light bulb via the screw terminal on the lid. 0 HEATSINK 0 ©-INSULATING BUSH <at>;:3)-- SOLDER LUG <at>- WASHER <at>-SPRING WASHER ~ - - - - - NUT Fig.5: this diagram shows how the 2N3055 power transistors are isolated from the heatsink using mica washers and plastic insulating bushes. After each transistor is mounted, use your multimeter to confirm that its case is indeed isolated from the heatsink. 46 SILICON CHIP version. The board measures 185 x 100mm and is coded SC 11111881. Fig.4 shows the wiring details The TV horizontal output transformer comes with a mounting bracket which makes it easy to mount on the printed board with two screws, nuts and lockwashers. You will have to drill holes in the board to match those in the mounting feet of your transformer. Before you mount the EHT transformer, remove the existing low voltage winding (on the opposite leg to the large circular EHT encapsulated winding). Now wind on the two new low voltage windings. We used ribbon cable for this purpose as it makes bifilar winding easy. Wind on the two 4-turn windings together and do the same with the two one-turn windings. Secure the windings in place by running some hot wax from a candle over them. Alter- j-o ;--i A ... and you don't have our .120page catalogue • • • At last . .. a TRADE catalogue for the consumer .... .. ARISTA ... your one-stop problem solver. Video plugs and sockets . .. "7 00 00 ,.... ,.... I "j' 0 ~, Fig.6: this is the full-size PC pattern. Etched PC boards are available from the usual retailers (see back page). natively, use a couple of plastic cable ties. The diagram of Fig.5 shows how the transistors are mounted on the heatsink (rear panel) using mica washers and insulating bushes. The transistor mounting surfaces and the heatsink should be lightly Problems? smeared with heatsink compound before they are assembled together. An in-line fuseholder is used for the 3-amp fuse and the power flex is secured to a hole in the plastic base using a cordgrip grommet. When you have finished the wiring check your work carefully to see Video extension speakers . . . Video flyleads ... Video RF interference filters . .. Video splitters ... Indoor antennas .. . Video switching units . . . Down convertors . . . Video speaker controllers . . . Video camera lights ... Video tape rewinders . .. Video cine adaptors . . . Video head cleaners ... Video splicing kits . .. Video storage cases ... Video dust covers ... Video leads ... Scart plug leads . . . Video dubbing kits . .. Video headphones . . . Video shotgun and wireless microphone systems . . . Pre-amplifiers with video inputs . . . Video camera stands ... Just about anything you want. . . . Try us ... NOW! Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ARISTI\. ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 NOVEMBER 1988 47 The circuit will work with a wide variety of EHT transformers (intended for black & white TV sets). Use PC stakes to terminate wiring connections to the board and don't forget to secure the transformer secondary windings. that it agrees with the circuit and wiring diagrams. Now use an insulated terminal connector to connect a short length of stiff wire from the EHT output wire over to the earthy end of the EHT coil. Arrange the two ends so that there is a gap of about 7mm or so. Apply power from your 12V battery charger or power supply to the EHT generator and note that a continuous arc occurs across the spark gap. OK, so it works. Let it run for 15 seconds or so and then turn the power off. Feel the transistor cases to make sure that they are not running hot. After running for quite some time the transistors will become pretty warm but not so hot that you can't touch them. Now it is merely a matter of connecting a short wire from the base 48 SILICON CHIP connection in the Edison screw socket on the lid of the case to the EHT output from the transformer. Now screw the plastic case together. Carefully screw your incandescent lamp into the Edison screw socket and apply power. A colourful discharge should immediately appear in the lamp. Wire loop You may like to try the effect of an earthed wire loop above the bulb, as suggested previously. You could make it out of tinned copper wire or from a coat-hanger. We connected ours to a screw terminal on the lid of the case, with a lead then running to the earthy end of the EHT coil on the printed board. Don't let the earthed wire come in contact with the bulb, to avoid the risk of puncturing it. Remember too our warnings above about putting your hands directly on the lamp bulb. You can get quite a nasty sting from it. Keep your hands away from it. We suggest that your Plasma Display be placed in the centre of a suitable table, not near the edge. You should avoid any chance of the Display being knocked to the floor. The resulting implosion could cause flying glass and you don't want the expense of buying a replacement bulb. Other tricks Because the Plasma Display creates a high voltage high frequency field around it, it can be used to light up fluorescent tubes which are in the vicinity. That's an interesting parlour trick. You can do the same thing with neon lamps. ~ ~HITACHI 20MHz/1mV · $830 So good we give the full Spee! Display CRT ExSa!esTax $996 me tax ■· Wouldn't you pay a bit more for features like this? Graticule Accelerating Poteritial External Intensity Modulation Vertical Deflection Sensitivity Bandwidth Risa Time o Quality Hitachi engineering O Two year Warranty o Includes two quality Hitachi probes o Tough all metal case and front panel o Ideal for servicemen - small footprint and light weight (31 Ox370x130mm 6kg) o Extensive triggering facilities including TV sync and vertical mode for steady traces when input frequencies differ widely o Free 55 page operating manual with circuit diagram MAX. Input Voltage Input Coupling Input Impedance Display Mode CHI Vertical Signal Output X-Y Operation Sensitivity Bandwidth Phase Difference Horizontal Deflection Sweep Time Range Trigger Trigger Mode Trigger Source Trigger Sensitivity Order now. Call Sydney (02) 648 5455 32 Parramatta Rd, Lidcombe 2141 Fax (02)6471545 TelexAA24949 P.O.Box14Lidcombe2141 Melbourne (03) 480 0111 72-74 Chifley Drive, Preston 3072 Adelaide (08) 354 0588 Brisbane (07) 277 4422 Perth (09) 325 9333 ' BELL ] Bell Test & Measurement The measure of quality A Division of Bell-lRH Ltd (inc in N.S.W.) Prices subject to change without notice 6-inch rectangular. Internal, 8 x 10 div (1 div = 1 cm ), Horfzontal and vertica l center lines further marked in 0.2 div increments, mark ing for measurement of rise ti me Trigger Coupling Trigger Slope Calibrator Power Supply Ambient Temperature Dimensions Waight MTBF Accessories Supplied 2 kV. Voltage : 5V o r more. Effect ive bandwidth: DC t o 2 MHz. Max . inpu t voltage: 30V (DC + AC peak}. 5m V/d iv to 5V/d iv in 10 ca librat ed steps ± 3%. lmV/d iv, 2m V/d iv ± 5% when using x 5 magni f ier. Uncalibra ted co nt inuous co ntrol between steps 1 : < 2 .5. DC t o 20 MHz 1-3 dB ). DC to 7 MHz (- 3 dB) when using x5 magnifier . 17.5 ns. 50 ns when using x 5 magnifier . 300V {DC+ AC peak) or 500Vp-p AC at 1 kH z AC,GND, DC. 1M!l. approx . 25 pF. CH1, CH2 {normal o r invert), ALT, CHOP , ADD Voltage : appro x . 20mV / div in t o 50!1 Bandwidth : 50 Hz to 5 MHz (-3 dB) i nto 50!1. CH1 : X -axis. CH2 : Y -a xis. 5m V / div to 5V /di v. 1mV/div, 2mV /di v w hen usi ng x 5 magnifier. DC t o 500 kHz 1-3 dB ). 3° or less from DC to 50 kHz . 0.2 µs/ div t o 0 .2s/d iv in f9 calibrated steps ± 3%. 100 ns ± 5% w hen using x10 magnifier (20 ns and 50 ns uncafibrated ). Uncalibrated con tinuous co ntrol between steps 1 : < 2.5. Automatic {sweep runs in absence o f a triggering signa l and for signal below 30 Hz), Norma l {sweep runs when triggered ), TV' V. TV-H. CH1, CH2, V -MODE, Ex terna l , Line. 20 Hz to 2MHz 12 MHz to 20MHz I CH 1 an d CH 2 I 0 .5 div I 1.5 div I I 20m V I E.xternal I 800mV I A C. + orSquare w ave. Vo ltage: 0 .5V ± 3%. Frequency: A pprox . 1kHz Vo ltage : 100/ 120/220/ 240 V ± 10%. Frequency : 50/60 / 400 Hz. Power consumpti on : approx . 30 W. Rated range o f use : +10 to 35° C. Limits of operation : 0 to 50° C. Storage and transport : - 20 to 70°C. 310(W.) x 130IH) x 370ID) mm. 12.2 X 5. 1 X 14.6 in. Approx. 6 kg/ 13.2 lb. 20 ,000 hours for t arget value. Two AT-1 0AJ 1.5 p ro bes, Fuse , Power cable , Operation manual. I i I ,--------------------------------, 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 I ~------------------------------... Sensational Super Buy On Microprocessor Controlled Detector Clips On To Sunvlsor lnvl1lble from oul1lde your vehlcle - 1h11 f■nt■1llc high 1pec R■d■ r Detector Detecll X ■ nd K Band Radar up to ■n Amazing 13KM This super compact "Sunvisor clip on" Microeye Detector is virtually invisible from the outside of most vehicles at normal eye heioht hence its very unlikely yours would attract the attention of a thief (or the Gendarmes for that matter) However, please remember that use of Radar Detectors is not permitted in some states. Quality Sampson 1 2V Rechargeable Batteries This Quality 12V 1.2AH Lead Acid Battery Sells Elsewhere for $30! Altronlcs Price? 5os5 MICRO EYE VECTOR The First Detector With GaAs Diodes Until now, GaAs diodes have only been used in I sophisticated military radar equipment. The Microeye Vector is the first consumer electronics product equipped with this new technology. Just $15 Ultra High Power Capacity Polypropylene Bass Drivers Save 250/o Why G ■A1 Diode• Make The Difference • Lower threshold allows for a better signal to noise ratio• Lower signal conversion loss • Higher barrier reduces noise. Quite simply GaAs diodes increase the sensitivity of the Microeye Vector.•Using the latest digital processing technology the unit will filter out and ignore emissions from 80% of poorly designed Radar Detectors that emit microwaves. • Simply plugs into your cigarette lighter socket. • Clips onto sunvisor • Detects Mobile Radar Equipment.• Highway/ City Modes switch allows monitoring of City or Highway conditions. Th i■ Month (300mm) Model 100 Watts continuous input 150 Watts intermittent input Impedance 8 Ohm Sen1ltlvlty 93db Weight 3620gm s4 99 C 3070 9 9 $ Normally S139 Acce11orln Included:- Visor 15" (375mm) Model bracket • Velcro • Cigarette lighter plug. 21 Day Money Back Guarantee. Our Incredible ALC Mlc is one of the most exciting products for '88. Wireless Mics suffer from overmodulation distortion with too higher input sound level making them unsuitable for high grade vocal entertainment use of ALC (Automatic Level compressor) fixes all this. •<w~:;;;;;·;1;;:~,,s:;~;i;; ~:: s99.oo I i I\I \!: $fv~~i~tl~~nt inputl 49 !~!! Wireless • Cardiod-Uni Directional Pick-up pattern• Freq.Res.: 30Hz-15KHz • Carrier Frequency .Adjust Range : 120 Watts continuous input Super Bargain Save $50 I //W=: 1 I ::\!\1 Our~~~~-=l~~r. cone Bas~D!!!~xh!t quite astonishing :: 1 low register reproduction. The power ratings quoted are conservative. ·,, , 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 ":: ~oJ:c'::~~~~: =~d model, ■t low dl1count prlcH 1h11 month - but be : ~~/t~C:. 1 Pa slve Infra-Red LIie Guard odl ght Control How often have you thought there could be • prowler outside your door? Install a LIie Guard & (once armed) any "guest" wlll be floodlit when detected by this highly sensitive Infra-Red Detector. Please Note Floodlamps & Holders Not Supplied : :\:I; f :Hi, ii 1 1: r:: I Fantastic Negative Ion Generator There have been volumes written about the benefits of negative ions combating air pollution, cigarette smoke etc. can be very beneficial to · Asthma sufferers. Our great little Rover generates billions of ions per second! Includes tester. S5350 A0990 s185 The lite Guard detects a moving person or vehicle by comparing the background temperature with a rapid change of temperature across the detection beams. So when Lite Guard detects movement across the coverage area, it wil l turn on the floodlight(s) for 1-20 minutes as pre-adjusted . Speclflc■llon1: Detector: Dual element pyroelectric PI R sensor • Raintight outdoor all weather operation. • Photocell to deactivate sensor during daylight • Operating Voltage: 240V AC, 50Hz • Operation time: Adjustable 1-20 minutes• Se111ltlvHy: Adjustable 20'-50', 30 beams• Aimable desired direction with 2 ball joints • switching Capability: 500W m.tx. incandescent.• Operation Mode1: Off, Auto, Test, Manual Ont. 29 ~-~i~ S ========== • ~:, :1111.1111•111: ma11:::1;1e1::: a1r■•11e.s:'t:1-':'''IS11'':':,11.111c::'::::'''.'.' ..... .. ·· ·· ···· ·-•-•,•········•:-·-:-:-.:-:-/:;:::;:;:;:::;:;:;:::;:;:;:\\:/:::::::::::::;:::::::::::::::=:;:;::;:;:;:;::;:;::-.--·-:-:-:-:-:-:-:-:,:-:-:::::::::::::::::::::::;:::::::::::::::::f:::::::::::::::: :=:=:-:::::::-:.:::: ECH Company Collapse Brings Fantastic Bargains For The lectronic Enthusiast Altronics have recently purchased the following surplus quality stock from the liquidator of DTX Australia Limited. .•. Band NeW ~\\ sto~k rQuality premium Videotext PCB (Size 360mm x 150mm) This PCB is a goldmine of quality components for the Enthusiast - the value exceeds $100, yet the cost to you is from an unbelievable $3 Here is Just Some Of What You Get 1-9 5-9 $5 $4 Mains Transformer Bargain ear! 240V to 9, 15 or 24V Quality PCBMount Type Manufactured By NMB Research Limited of Japan. Primary: 240V Pins 2,4. Secondary 1: 15V<at> 300mA Pins 8,9 Secondary 2: 9V <at> 800mA Pins 6,7. Secondary 3: 24V <at> 300mA Pins 6,9 (Join Pins 7,8) Cat No. ZX0010 Normally S15 Now Simply Incredibly Priced! 1-9 $3 $2.50 10-24 10+ $3 Jat~gr~~t~~ell Great Kit Projects To Build Many Just Released Go anywhere 240V Mains Power f r.om your car or truck battery with these fantastic DC to AC Inverters Studio 200 Stereo Control Unit (SIiicon Chip June/July'88) Out-Performs Commercial Units Coating $600 Plus The Studio 200 Stereo Control Unit is companion to the studio 200 stereo power ampl ifier (or other power amps) . It features slim single unit rackmount profile, treble, bass , balance, inpu.t selector, tape monitor switch , stereo/ mono switch and volume control. Inputs include phono , tuner, CD , VCR and tape looo. K5015 s229 I I (See EA Dec'87) A must for farming, camping, mining, boating, remote settlements and wherever else 240V power isn 't available. Features: 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. Fully Bull! & Te■ted K 6770 KIT VERSION •••••••• Calling Audio Purists \ /• This Great New Amp All From Silicon Chip Is For You K 5010 K 6774 12V INPUT K 6775 24V INPUT s425 s525 s525 300 Watt Inverter With Auto Start Operates From 12V Car Battery Features: 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 0Yerload unit self limits - Single PC Board construction - easy to build as there is very little internal wiring . I:·-_P_o_1_ys_w_i_tc_h_e_s>_,o_o_(_w_it_h_P_o_1_ys_w_i_tc_h_e_s)_,oo_._s_•a_b_11_1t_y_u_n_c_o_n_d-iti_o_n_a1_.- *lj Complete Kit Dlscollte K 6750 (See SIiicon Chip July/Aug'88) Add Some Colour To Your Next Party s279.oo K 5805 . . .--.--~s159.so "f;:;;;-"6;;;~·;;-;te Flashes party lights on and off in beat with music from your amplifier. • 4 light channels controlled by 4 separate audio channels • Forward, reverse and auto-reversin!J chasor patterns• Simultaneous strobe on all four channels • Alternating light patterns • Music modulation available on chaser, strobe & alternate patterns• Inbuilt microphone for beat triggering or audio modulation of lights• Direct inputs for beat triggering or audio modulation of lights • Sensitivity control • pre- Transistor FET Zener Tester (See EA Feb/Mar'88) New updated circuit incorporates facilities for testing transistor FETs and Zeners etc. s379.oo s49.es Low-Cost Unit ,,,, ,,,,,,,,,.,.,.,. Checks Values from 1pF-100uF j JI! Upgraded Digital Capacitance Meter ) )'}( The readout consists of a bright 4-digit LED display and the full scale ··· ········ readings for each range are 9999.9nF and 99.99uF. No adjustments are necessary when taking a reading. You simply connect the capacitor to the :•:-: test terminals and select the appropriate range. The circuit can accurately ......? measure capacitance down to one picofarad (1 pF). This is made possible '(){ by the internal nulling circuit which cancels any stray capacitance ?'?}: between the test terminals or test leads. So when you measure a 5pF ::':':::\\ capacitor, the unit will display 5pF. Super Low Price on Famous EA 8 Sector Alarm System Kit sa11e SSS \ \he co• on mmerc\al ol co 111a\en\• (See EA Mag.Jan '85) et\U Feature•: • Alarm has 8 separate input circuits - 8 sectors can be monitored independently. • Each input circuit is provided with an . indicator LED and a sector On/Off switch. " Individual sector isolation allows the user to have some areas of the premises habited while others remain protected e.g. Inside Off/Outside On. • Inputs accept both normally closed and normally open sensors. • Two inputs provided with an entry delay between 10-75 seconds). Internal trip warning buuer-alerts owner/ occupant of pending alarm operationgreat for the "forgetful" amoungst us. This buzzer is pre-settable between 5 and 55 seconds prior to Alarm. • Unique circuit detects automatically when any N/0 or N/C loops are either open circuit or dead short. e.g. aomeon• trying to bridge rHCI twitch .. etc. • Switched output Can be used to send a silent alarm through an auto-dialler circuit or similar. \Ji '::::1: :Iii S 5065 KIT (without Back Up Battery) (12V 1.2AH Backup Battery) Now Only 24V To 12V DC · 3-30V to 1 amp Max.with variable current limit FEATURES: • Output 3 to 30V at 1A • Short circu it protected• Load switching• Current limiting. Dual scale meter• Housed in our Deluxe "ABS" instrument case. SPECIFICATIONS: • Output Voltage - 3 to 30V • Output Current - 0 to 1 amp (fully variable)• Load Regulation - Better than 0.2% from Oto full load • Outpu t Ripple-Less than 2mV RMS . KIT K 3210 $ 79 .OD $15.00 Converter (Silicon Chip Dec'87) Laboratory Power Supply Enables 12V appliances like stereos, 2 way radios, CB's etc. to operate from a 24V battery. • Operates from 18V-30V. Output is 13.6V at 5 amps. K Bench Top Power Supply K3300 3-5 Volts at up to 5 Amps $ 195 Designed by Electronics Australia, this supply has been one of our most popular kits. Our version incorporates refinements and is now housed in an attractive, tough "A BS" instrument case. This all new compact version has been ma.de possible by the use of a highefficiency Toroid Power Transformer. So you win f_our ways - less heat, less weight - Greatly enhanced appearance and easier to build Remember the Altronlc• Kit la fully drilled and punched. ~~~5 s59 .00 Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) Colin Fobister 437 4077 Perth 09 328 2199 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 AL TRONICS RESELLERS Chances are there is an Altronics Resellerright near you - check this list or phone us for details of the nearest dealer. PIHM Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases. however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. 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Electronics 525664 ·: . · NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 . Blue Ribbon DHlere are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you . .. ,; •.•.• ...-..... ······•: •·•:-:-:;::::::::::::::::::::::::•: ·~~ :1i1111:111iill::::::::alili1:::1111:: 111"11■.111s ::ea :1111111 ~~= :rrr \:t\:irr My friend (the enemy) Flicker Just how should a serviceman react when he encounters a fault which has never been heard of before, has the weirdest set of symptoms imaginable and which can be cured only by modifying the circuit? Is he justified in doing so, or is the customer being (technically) cheated? The story comes from my colleague in Tasmania and is one of the strangest I have heard for a long time. It must surely qualify as the mystery of the month. He asks the question: Can you explain this? A customer called me to have a look at his TV set. It seemed that he was troubled by a very pronounced flickering on SBS; but only on SBS. Chi:mnel 2 and the commercial station on VHF were perfect. When I arrived, I wondered about the SBS claim because his set was on old Philips K9 with a VHF tuner only. Then I saw the National video recorder nearby and all became clear. He was using the recorder as a tuner for SBS. So down to business. The owner turned on the TV set which promptly displayed a very good picture on both VHF channels. He then fired up the video recorder and tuned in SBS. It was showing the test pattern but strangely, was as free from flicker as any test pattern can ever be. This surprised him because for the past six months he had not been able to watch the UHF channel without the flicker. Then he said that he would show me a tape he had recorded off air. The tape he selected had material recorded four months earlier, some more recent material and some recorded only the previous night. When the tape came on screen, I could see immediately what he meant. There was a strong flicker which looked for all the world like a home movie film being projected at a dead slow speed. We tried viewing the tape one frame at a time by using the frame advance feature. In this mode, we could see that every second frame was darker than the one before. As we stepped along the tape we could see one light frame, one dark, then one light, and so on. It was just as though the brightness control was being moved from half to full on, every alternate frame. So much for the tape. When we went back to the off-air situation, SBS was still running test pattern and the picture was as steady as a rock. We recorded a few minutes of pattern but playback offered no help because it was also perfectly steady. Almost as an aside, the owner mentioned that he had once borrowed a portable TV set and with this had been able to watch SBS with no sign of the flicker. From this, he had deduced that his TV set was at fault but I was by no means so sure. Vertical collapse ?\.H L-.l PS \<9 W \'1-\ M '-( i=-R l e..tJ t> 'Fl- l Ck::~R. •.• .· 54 SILICON CHIP At this point his wife mentioned that the set has suffered from another fault - a rare, intermittent vertical collapse. It was some months since this had last happened but she asked if I would also look into this problem. I imagined that this fault would present no problems. I had a quick look at the outside antenna, a small combination unit which seemed to be quite well installed. I couldn't see any likely cause of trouble and as the customer lives in a strong signal .. . &e. r.. tt.l.... ·. 01<. .... 1.J ... . A ~INUTe;. ·· area, it was most unlikely that the antenna was at fault. The customer then admitted that he had never previously observed the SBS test pattern. He suggested that, as the fault was always present on program material, he would check it that night and advise me if the trouble was again evident. In the meantime, I took the tape with me to try it on a different VCR feeding another set. When I played the tape at the workshop, I found that there was no sign of the problem. All the recordings, both old and new, were perfectly steady. It was hard to believe that it was the same tape as the one I had seen flickering so badly that morning. In fact, there was nothing on the tape that would upset any of the sets in my workshop. Then to cap it all off, the customer rang that evening to say that the SBS pictures were flickering just as badly as ever. I went back a few days later, this time carrying my signal strength meter. First, I measured the off-air signals before they entered the video recorder. They were all very strong, more than BOdBu for the VHF channels and 69dBu for SBS. Then I measured the RF output from the recorder into the TV set. As expected, these signals were somewhat higher - VHF about 90dBu and SBS about 79dBu. These signals were all too high for comfort. In my experience anything over BOdBu can lead to cross modulation and herringbone patterning. I tried lowering the signal strength by adding an attenuator to the antenna lead and although this reduced the signal to more manageable levels, it did nothing to stop the flickering on SBS. Next, I removed the back from the set and tried adjusting the IF gain, IF AGC and RF AGC. Not surprisingly, these adjustments had no effect on the picture. In fact, with so much signal available, I could not turn the RF AGC down low enough to get into snow. Finally, I swung out the boards and in turn replaced the IF module, the IF detector module, and the chroma and luminance module. There was no effect that we could be certain about. There were some small changes to the flicker but they were so slight that we couldn't agree about their exact nature. I had to leave the job at this point but made one more suggestion to the owner. He had already tried the video recorder with another TV set. This time he should try the TV set with another recorder. As it happened, he didn't get around to this before he had reason to call me to report a new development. The symptoms had changed somewhat now and I began to think that I could see some pattern that might lead to a solution. In detail, the owner reported that the flickering was now considerably less, almost unnoticeable. Instead, the screen was showing a "line of dots" at the top of the picture and three coloured lines across the centre of the screen. The line of dots was almost certainly a vertical interval signal of some kind, either teletext or subtitle code. The coloured lines in the centre could be some kind of vertical linearity trouble, possibly associated with the intermittent vertical collapse mentioned earlier (perhaps a partial collapse). But the interesting feature was that the flickering became less noticeable when the vertical scan changed. I now felt that I might find the reason for the flicker in whatever was causing the linearity fault. Remember that, during my first visit, I had observed that the flicker coincided with the frame advance. That certain something At this point, my theory was that the set had a vertical problem and that something in the SBS vertical interval was aggravating the fault to cause the brightness modulation. What ever this "something" might be, it was present in SBS program material but not in the SBS NOVEMBER 1988 55 test pattern. It was also absent from the other channels and although it could be recorded on videotape, it was not something that would affect other TV sets. So how could this "something" cause the vertical section of the K9 to change the brightness of every second frame? A few days later I took a loan set down to the customer's home and connected it in place of the K9. It produced a perfect picture from all channels and proved that the trou56 SILICON CHIP ble was confined to the Philips set. In the workshop I duplicated the setup from the customer's home. My workshop video recorder provided an SBS signal and the lines and dots appeared just as the customer had described them. But he'd neglected to mention that the dots appeared on one channel and the lines on another. Now that I could see them clearly, I realised that they were not linearity or partial frame collapse lines as I had first thought; they were symptoms of a blanking problem. I had been caught with this fault once before and spent days sorting it out. Now came the pay-off because I could fix this fault in five minutes flat. All I had to do was replace C265, a 22µ,F electrolytic which feeds the vertical blanking pulse to pin 7 of module U260, the luminance processing module. Unfortunately, while this cured the blanking problem, it brought back the flicker. At this point, I fired up my oscilloscope to check the video signal from various stages in the hope of turning up a clue. The video input to module U260 was exactly as shown in the manual and it was quite steady on all channels. But the output from that module was quite different. While the VHF channels delivered a steady video output, that from the UHF channel was unstable, jumping up and down in exact synchronism with the flicker on the screen. Changing U260 made no difference at all. Whatever the fault was, it lay in the main circuitry, not in the module. And the odd thing about all this is that, while the amplitude of the video input from all three channels was the same, the output differed quite significantly, being much higher for SBS than for the ABC or the commercial channel. This latter observation prompted another chain of thought and led to the discovery that lowering the contrast of the SBS display completely stopped the flicker. With the contrast control about one third below full on there was no trace of flicker, although the picture had naturally lost its sparkle. In the K9, contrast is controlled by varying the voltage on pin 1 of U260. The front panel control is buffered by TS260, a BC148 transistor, and all the resistors and a capacitor around this point checked OK. The only values not as shown were the voltages on the base and emitter of the transistor, which were low. But they were only marginally low, probably due to a normal spread of component values. However, they had to be investigated. Initial checks I checked the supply voltages and the feed resistor values and could find nothing wrong. I replaced TS260 with a new BC148 but it made no difference. I eventually concluded that the lower voltage was normal for this set and that the cause of the flickering lay elsewhere Although C262, a 0.47µ,F electro on the base of TS260 seemed to be in good condition, I suspect all electros and wondered if this one was doing its job properly. I pulled it out to check its value and lo and behold, the flickering stopped. I put it back and the trouble reappeared. I changed it for another similar capacitor, and the flickering was back again. Then just _to see what would happen, I paralleled a 10µ,F capacitor across the 0.47µ,F capacitor. The flickering stopped. I began to wonder whether it was me or the set that was being stupid. It wouldn't work properly with the right capacitance but it did work properly with no capacitance or too much capacitance! I reduced the parallel capacitor to 2.2µ,F and it also stopped the flickering. Then I tried a 1µ,F capacitor with the same result. Finally, I removed the 0.47 µ,F cap, only to see the flicker back again at a much reduced intensity. I didn't try any further. I sol- dered a 2.2µ,F cap in place of the original C262 and left it at that. What was it? So what was it? The fault only appeared on SBS transmissions or recordings and then only at normal or higher contrast. It could be produced with any tape (of SBS programs) or any video recorder and it disappeared when the blanking failed. I have the feeling that the coloured line, seen when the blanking failed, has something to do with the problem. But I can't imagine by what mechanism it would cause the trouble as it was steady on every frame, while the flickering had a definite two frame cycle. And I didn't find a cause for the reported vertical collapse. I saw no trace of it and couldn't provoke the set into playing up. I had to ignore that problem in favour of trying to solve the other one. Unfortunately, I hadn't found and replaced a faulty component. All I had done was change a value to cover up the fault. I don't like sending this kind of repair back to the customer but just how much time can I afford to spend on these problem jobs? Or more to the point, how much time will the customer pay for? ELECTRONIC COMPONENTS We stock a wide range of electronic parts • For Hobby • For• service For Transmitters • For Receivers Also in stock: Valves for Transmitters - 6146, 8950, 4X150, 6JS6, 811 and many others. Valves for receivers, made by Rhode & Schwarz, Siemens & Collins. R-388, R·390(A), R392 and more. Mail order welcome D. Dauner Electronics 51 Georges Crescent, Georges Hall 2198, NSW Phone: (02) 724 6982 Telex 178 401 TV TECHNICIANS & SERVICE COMPANIES Have your Any ideas? Well, that's J.L.'s story and if anyone has any ideas both he and I PHILIPS VARICAP TUNERS (ELC2060) Repaired or Exchanged Only $17.00 ea. Ten or more $15.00 ea. Quick Service 3 Months Warranty T.V. Test Equipment Shorted Turns Tester (Silicon Chip, Sept. 88) $65.00 + Tax Hi-Voltage Probe 0 · 50kV. $70.00 + Tax (ll \r-il •. ':///1' ~ ' ,, · I , ,....... } .. -- .. I S\lS1=>e.~, ALL. E.t..EC---r'R.OS ••. I Send Faulty Tuners Cheques and money orders + P&P $2.00 or C.O.D. ;r.v.TUNERS) 216 Canterbury Road, Revesby 2212, Sydney Australia Phone: (02) 77 4 1154 NOVEMBER 1988 57 SERVICEMAN'S LOG would like to hear them. In the meantime I can only agree with his comments about the unsatisfactory conclusion. I don't like resorting to circuit modification either, but what are the economically viable options in such cases? As to a technical explanation, I can only comment in a broad sense. I am aware of cases where particular receivers baulked at particular transmissions but without any very satisfactory explanation being forthcoming. T.e letext and similar signals, in particular, caused problems in some first generation colour sets, typically Philips, National and Rank. The symptom was a row of dots across either the top, centre, or bottom of the picture. Philips receivers were particular offenders, due to the failure of C572, a 100µF capacitor between transistors TS565 and TS570 in the vertical section. A frustrating Sharp Meanwhile, from my own bench, I have a story of a frustrating fault in a Sharp CX1480 36cm colour set; so frustrating in fact that, at one stage, I was also considering a circuit modification - quite a drastic one! The history and symptoms were simple enough; the set was dead and had simply failed to operate at switch-on. Unfortunately, this was a set I had not handled before and this contributed a good deal to the subsequent frustration. Another factor was the circuit diagram which I regard as a pretty poor effort in both layout and printing quality. The layout wasn't particularly easy to follow and the image had been so greatly reduced 11-\E:' O~L-'-f 'PLUS WAS 11-\AT'" ,-o 1"M~ G.\-\~SS\S WAS EAS'-f 'RE.N\CNE ~OM 11,\E, CA~l~~looo 58 SILICON CHIP that some values were quite hard to read. The only plus was that the chassis was easy to remove from the cabinet. The first thing I found was that one of the two mains fuses (Fl 101-1102) was blown and I immediately suspected the thermistor for the degaussing coil. But the thermistor was intact. Further checking was more revealing; the power supply switching transistor, Q701 (2SD811 ), was shorted between collector, base and emitter. Well, that was no great problem. Not having a 2SD811 handy I fitted a 2SD380. In an effort to establish why Q701 had failed I checked the three other transistors in this section (Q702, 703 and 704, plus diodes D706 and 705) but found nothing wrong. So I fitted a new fuse, crossed my fingers and switched the set on. What gives? Absolutely nothing happened no blown fuses, no smoke and no sparks. There was no sound or picture either - the set was as dead as a doornail. The circuit indicates that there should be 310V on Q701's collector, this being the output of the bridge rectifier across the mains (diodes D701, 702, 703 and 704). In fact , this voltage was virtually spot on, clearing the bridge and associated filter components, but suggesting that Q701 was not receiving the necessary drive signals, and therefore not switching. But why? In circuits like this the possibilities seem endless. As is now common practice, many of the rail voltages are derived from the horizontal output transformer, including those that power the horizontal oscillator and associated drive circuits. So we have an electronic version of the internal combustion engine; it runs only because it's already running and needs a kick start to get it running in the first place. This means that there are a lot of things which could be at fault, some of them quite difficult to check. So where do you start? I decided to make another check of the stages feeding the switching transistor Q701. Rather than check NOW GET EVEN BETTER VALUE ON THESE OUTSTANDING MODEMS Avtek, the longest established Australian modem manufacturer, now gives you a chance to get even better value when you buy. Purchase any one of our modems before November 31st and you can purchase a Cybersoft Gateway V3 High Performance Communications Software Package for ½ price <at> $75.00. 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AV003 - - - - -· - - - -~- I ~ is~"•:~E 1• ,..,...........,,,............----.._...,.,.._, "-+~ ~ r.t k -"'-~cilll lb r-.i---C: l f •~~• c.~•,s c•i• 0102 2SA9~lY E> Fig.1: relevant portion of the Sharp CX1480 circuit. Many of the rail voltages are derived from the horizontal output transformer (at centre), including those that power the horizontal oscillator (IC501 at left) and associated drive circuits. Transistor Q704 apparently provides the trigger to "kick-start" the circuit. Q702 , 703 and 704 in-situ, I pulled them out and checked them on a curve tracer. This is the best check I know for doubtful transistors and they all tested 100 o/o. The same went for all the diodes, including the zener diodes in this section. I also made some attempt to check voltages but with few voltages shown on the circuit, I could only estimate what I should find. In fact, there appeared to be nothing grossly abnormal. there was no supply rail for Q601 or 602. So Q601 was pulled out and tested, and Q602 pulled out and replaced. (Note: Q602 is difficult to test because of a built-in protective diode and resistor). All this took some time but at least I had cleared that section and thrown suspicion back on the switching transistor (Q701) and its associated circuitry. Back in this section, I started going through the motions of another External supply So was the fault elsewhere, such as in the horizontal oscillator, drive, or output stages? The horizontal oscillator is part of IC501 (bottom left). Its output comes out on pin 10 and drives Q601 and the output stage, Q602. Unfortunately, the supply rail for this IC comes from the horizontal output transformer (pin 9, T602), via D601 and associated filter components. But with the set dead and no supply rail, how do you test it? Simple - disconnect the supply pin (pin 6) at R508 and feed it from an external supply. The normal voltage is about 12V but a 9V dry battery is quite adequate. The IC responded immediately and, using the CRO, I was able to establish that everything was working up to the base of Q601. There was no signal beyond this because 50 SILICON CHIP TETIA TV TIPS Sony KV1830AS (early version) Symptom: Overbright screen with strong retrace lines. Those parts of the picture that could be seen were broken up with noise and very badly smeared to the right of the images. The colour was also smeary and broken up with noise. Cure: This was really two related faults. R804 (4. 70 1/8W) was open circuit. Replacing this restored control of brightness and removed the retrace lines. Then C709 (2200µF 250V electro) was open circuit. This controls the noisy picture and the smearing. These components are on different boards, but they are close together in the circuit. They supply and control the voltage to the picture tube screen grid. voltage check, hoping that I might have missed something. The meter I use has both a conventional ohmmeter facility and a continuity checker running at about 3V and operating a built-in buzzer (very handy for tracing printed wiring, cables, &c). I started by trying to measure the voltage between base and emitter of Q702 but made the mistake of leaving the meter switched to the continuity position, from a previous check. And as I touched the test prods across the transistor, the set burst into life. And it kept running as, by reflex action, I whipped the prods away. Well, that was a start. At least I now knew that the set was capable of working, once started. But had I started it or had I temporarily cured an intermittent fault? I switched the set off and switched it on again. It was dead. I tried the test probes again. No joy. Then I realised that I had probably reversed the prods, swapped them over, and away went the set. So it was a starting problem. But where? And what had the initial fault, the blown fuse and shorted Q701, to do with this? Flying blind Unfortunately, I was flying blind. Because this was my first encounter with this type of set, I was ,, I , ~E.SE. 'SIGNF\L'S We;RE. ~LA.- "100 H\Gl-\ F~ CON\FOR1".oo OVe.'R. eocAB.\J .. ~A'PING- -ro CROSS N\O'O\JL.ATl0t'1 I & \.>eR~\tJ6t!>ONE ?~e.~~IN~.... still battling to work out the finer points of its operation. All I seemed to have established was that there was apparently something amiss with Q702 or its immediate circuitry. I pulled Q702 out and replaced it, just in case the previous test had been inadequate. No joy. I checked all the resistors, diodes, and capacitors around this stage, including a 6.Bkn resistor which had been tacked directly to the copper tracks (I've drawn it on the circuit). Again, no joy. Quite frankly, I had come to a dead end. I was half-tempted to fit a 3V battery and limiting resistor across Q702, in series with a pushbutton switch on the side of the cabinet - a kind of electronic crank handle to be used whenever the set needed to be started! But tempting as it was, I never really seriously considered this. More to the point, I decided that the time had come to ask for help. Going it alone is fine for one's ego but it can be an expensive ego trip if carried too far. So I rang the Sharp service department and spoke to a technician who had proved very helpful in the past. And as soon as I described the symptoms he obviously recognised them. He ref erred me immediately to Q704, which he explained forms part of the trigger function. Unfortunately, I'm still not sure exactly how it operates. But the real point of his comments concerned two resistors, R717 and R718, both 12okn 0.5W types, in the collector circuit of Q704. He was 99% certain that one or both would have gone high. And so, in fact, it proved to be. R718 was up to 180kf.l while R717 was no less that 250kn. There are two other similar resistors in the same part of the circuit, R719 and R720, but these were virtually spot on. So that was it. Two new resistors and the set was back to normal. And that was several months ago and there has been no trouble since. But where did this fault fit in with the original blown fuse and shorted Q701 transistor? With hindsight, I don't think that these faults had anything to do with each other; it was simply pure coincidence. And why are these two resistors an obvious weak point in the system? They don't appear to be under-rated and they showed no signs of distress. I don't know and neither, apparently, does Sharp. But the technician did clarify one point; the 6.Bkn resistor is a legitimate circuit modification, made during manufacture. What it does I don't know and it appeared to make no difference to the behaviour of this set when I removed it temporarily. So that was it; another one down. But I was tempted to fit that electronic crank handle! !f; NOVEMBER 1988 61 DAVID REID W For the electronics enthusiast ELECTRONICS PTY. LTD. VARIABLE TEMPERATURE SOLDERING IRON STATIONS ROYEL /7 HAKKO • ~ SCOPE ~ WELLER "ECT60L" "ECT-624-2" "926" • 60 Watts • 200° -470'C • LED temp readout • 50 Watts • 200° -4so·c • Made in Japan s190.oo • 40 Watts • 200 ° -4oo·c • Aux. Ground Jack 95 $189, "WTCPS" 189.95 $ "TC&O" • 21 Watt • Tip temp 360°C • Boost function 20 Watt 130 Watt Boost Pencil grip version High quality Made in Japan • • • • s51.a5 • Neon indicator • Variable temp • 250° -4so·c s27.5o s39.5o Diam S 0.71mm 250g roll . 7.95 0. 71mm 500g roll .. 15.00 0.9 mm 250g roll . 7.95 0.9 mm 500g roll . 15.00 1.25mm 250g roll . 7.95 1.25mm 500g roll 15.00 1.2 mm Hobby pack . .1.95 WORLD'S FINEST SOLDER ■ SOLPER wicK • 2mm wide • Approx 1.5 metre length O NLY $14.95 $35.95 ■ SCOPE "SKID" • Teflon tip • Self-clean nozzle 240 ■ Voll PUMP ..Heating and suction with one tool" • 30 Watt • Powertul suction • Works well with double sided boards $21 .25 ■ SCOPE "SRIO·AS" • Anti static nozzle • Self-clean $24.25 "102" ■ SIDECUTTfR • 10mm cutting edge • Foam grip handle • Hardened steel • Hardened steel construction construction S29.95 P0RTAS0L STD • Butane iron • Temp up to 400°C /l • Full~io'.~5 / ! : 1 . sll95 • Non conducting • Ceramic tip • Powerful suction ■ "101" ENDNIPPER SIDECUTTER • 8mm cutting edge • Foam grip handle S34 .95 . ,_ '. I ■ DELUXE PUMP SIDECUTTER • 14mm cutting edge • Foam grip handle "103" -- - --- ·-·- • Teflon tip • Powerful suction CUTTERS AND PLIERS S29.95 • 25 Watt • Includes stand, sponge, spare tip 12 Volt Iron ■ STANDARD PUMP HAKKO - QUALITY JAPANESE MADE HAND ONLY $53.75 .. • Equiv to 10 to 60W • Includes blow torch, hot knife, hot blow • 30 Watt • Complete with lighter plug -~ DESOLDERING PUMPS AND BRAID 5 CORE SAVBIT 60/ 40 MULTIC0RE SOLDER ONLY -~ • 30 Watt "ERSIN" - ■ LEC TK250" MICRON "T2445" '~ I ~;~~~ SCOPE POWER SUPPLY ~ -( ••,.. '~"F·-~ .. -~------,....,✓ !!~!~~~L PRO s19.5o A y s44.15 Suit "MSB" and "SSB" Model 'psu . . ,.Jis#~ • 25 Watt • Interchangeable tips 200° -soo·c • 4V supply required s47.5o s31.15 s102.oo • Same as DR30 but 30 Watt output • 20 Watt • Tip temp 370°C • Chrome plated tip II • • 10-70 Watt • 200° -soo•c • 4V supply· required • 20 Watt • Tip temp 370°C • Includes two screwdrivers, tweezers and solder s52.a5 MICRON "T2415" FOR ANY APPLICATION "MSB" SCOPE "PH20K" 60 Watt Variable temp 240°-4oo·c Earthed tip and barrel "DR50" s5l.35 s59.95 s139.95 • HAKK0 "980" • Made in Japan • LED temp indicator 124,95 $ ~ ~-:::.; ✓ ~!:;:!:PE R0YEL "DR30" -- ~ • • • • • "W/2172" • 48 Watts • 320 ° -440°c NORMALLY 5149.95 • 60 Watts • Tip temp 370 ° c • Spare tips available TRIGGER GRIP AND PENCIL GRI SOLDERING IRONS - • 20 Watt • 130 Watt Boost • Trigger grip type THE CHOICE IS YOURS ONLY ■ S29.95 "111" LONG NOSE PLIER 37mm Jaw • Foam grip handle • Hardened steel construction ONLY S29.95 O NLY SCOPE - $65.00 • ■ SCOPE WICK • 2mm wide • 2 metre length • Handy dispenser ■ SCOPE WICK - -- Made In U.S.A "170-1" ■ "0075" SIDECUTTfR • 9mm cutting edge • Scissor action blades - reduces lat,gue by 30% • Cushion gnp handle SIDECUTTER • 9mm cutting edge • Long life blades • Salety ottcut catcher s17.37 ■ "175-1" handle SIDECUTTER • 9mm cutt ing edge • Safety offcut catcher • Cushion grip handle S17.88 ONLY • 3mm wide • 2 metre length • Handy dispenser Flushcutters and Pliers ~ ~ ~ ■ $2.95 • Cushion grip S27.95 ■ "378" PLIER • 17mm serrated jaw • Cushion grip handle • Return spring s23.40 - -- - . - ·- ECONOMY HAND TOOLS ■ "HT12" DIAGONAL CUTTER • 11 mm cutting ~~~sulated handles • Spring return ONLY ■ S9.95 "HT14" DIAGONAL CUTTER • 14mm cutting edge • Insulated handles • Spring return ONLY S9.95 ■ "HT15" LONG NOSE PLIER • 20mm Jaws • Insulated handles • Spring return • Drop forged carbon steel ONLY $8.95 ■ "HTI&" 130mm CUTTER • 7mm cutt ing edge • Insulated handles • Spring return ONLY $8.25 ■ "PC2" ECONOMY CUTTER • 12mm cutting edge • Contoured handles • Spring return ONLY $5.95 ■ "PPI " DIAGONAL CUTTER • 20mm Jaw • Insulated handles • Spring return • Serrated jaw ONLY S6.95 -REIIIT&H ARLEC - Cordless DRILL'N DRIVE ■ Two speed, 325rpm (Drill), 150rpm (Screwdriver) ■ Forward & Reverse operation ■ Pilot light adds light to a dark workplace ■ Supplied with 3 drill bits & 4 screwdriver bits ■ Drills into timber, metal and hardened plastic A VERSATILE ELECTRIC TOOL DESIGNED FOR: ■ Polishing ■ Cutting ■ Engraving ■ Drilling ■ Sanding ■ Grinding ■ Milling ■ Erasing THE SUPERTDDL COMES COMPLETE WITH: 3 Engraving bits, 4 Drill bits, 1 Wire brush, 1 Grinding bit, 6 Eraser sticks, 4 Collet chucks - All housed in a handy carry case. HEATSHRINK GUN ■ ■ 1600 Watt output Dual temperature setting - 400°C & 600°C ■ 12 Month guarantee VALUE AT s65.oo ONLY $62.50 ESCORT - ~HEATSHRINK TUBING VARIOUS COLOURS AVAILABLE: BLACK, BLUE, RED, CLEAR, GREEN, WHITE AND YELLOW - 50% SHRINKAGE $ $ Dia $ 2.20 3.75 19.0mm . . . 6.25 2.50 4.20 25.0mm 9.35 . 3. 00 .. 4.70 ALL 1.2 METRES LONG • • • • • • • • • Diode check Continuity test Logic text Frequency up to 200kHz Capacitance HFE test 20 AMP AC/DC Large 20mm display High impact plastic housing • 1 year warranty AUTO RANGING DIGITAL MOLTIMETER Escort EDM 1122 3½ DIGIT MULTIMETER 3½ DIGIT "PEN" MULTIMETER • • • • AC/DC Volts Resistance Continuity buzzer Diode check As leatured in SILICON CHIP, Oct '88 MODEL - BC7790 • • • • • • • 3½ digit LCD display HFE test Diode test Continuity test Data hold 1 0 AMP AC/DC Includes case and test leads VALUE AT ONLY NEW LOW PRICE ONLY s137.oo INCL TAX LOW COST 20MHz CRO ONLY s69.oo GOODWILL LABORATORY POWER SUPPLIES GOOD WILL A basic 20MHz scope with extra features not found on similarly priced units s110.9s IGPR-SERIES I MODEL GPR-183D GPR-3020 GPR-3030 RANGE 0-18 Volt 0.3 Amp 0-30 Volt 0.2 Amp 0-30 Volt 0.3 Amp I GPR-DIGITAL MODEL GPR-1830D GPR-3020D GPR-3030D GOS-522 HIGHLIGHTS • SINGLE OUTPUT • DC SUPPLIES lncl SIT $228.66 $242.11 $252.20 Exel SIT $197.12 $208.71 $217.41 SERIES RANGE 0-18 Volt 0.3 Amp 0-30 Volt 0.2 Amp 0-30 Volt 0.3 Amp Exel SIT $304.37 $304.37 $330.46 lncl SIT $353.07 $353.07 $383.34 A maximum sensitivity of 1 mV/DIV (x5 magnification) Modes CH1, CH2, Dual , CH1 ± CH2, X-Y Choice of Sweep Displays Auto, Normal and Single shot Vertical Trigger Mode and Variable Hold-Off for ease of use 2 PROBES INCLUDED OUTPUT RIES. IGPD- SE DC POWER SUPPLIES I• DUAL ■ IGPO-DIGIT AL SERIES ■ Auto Trigger Level Lock ■ 20ns/DIV timebase ■ Variable Hold-Off DC Trigger Coupling ■ Vertical Trigger Mode GOS-522 Sensitivity 5mV/DIV to 5V/DIV, DC to 20MHz Timebase 20ns/DIV to 0.5s/DIV NEW LOW PRICE 737.75 Ex Factory - s860 Inc Tax $ MODEL GPD-3020 GPD-3030 MODEL GPD-302 0D GPD-3030D RANGE 2 x 0-30 Volt 0.2 Amp 2 x 0-30 Volt 0. 3 Amp RANGE 2 x 0-30 Voll 0.2 Amp 2 x 0-3 0 Volt 0.3 Amp ffl 127 York St, Sydney 2000 Bus1NEss HOURS MAIL ORDERS WELCOME Mon-Fri 8.30-5 .30 P 0. Box 0103 Sydney 2000 Ph (02) 267 1385 Thurs 8.30-7.00 $1 - $25: $4.00 P&P Fax: (02) 261 8905 sat 9.00-12.3 0 $26 & over: $7 .00 P&P µ . ,;;_ :2;+,' ' ~~ :. lt!I·. ' \ I!> ~-· ._,._ --·--1 Exel SIT $458.01 $515.99 lncl SIT 531 .29 $598.54 . . I~ ., Tf'.J 30.0 . .. . a• lncl SIT 692.70 $733.05 Exel SIT $597.15 $631.94 GPR-D Series (l OOV A) W LOW PRICES N,E VISA BUILD CAR SA By JOHN CLARKE Is your car in danger of being sideswiped in the street at night? This project detects on approaching car's headlights and automatically turns on the brake lights to worn the driver. Anyone who parks a car on the street at night is aware of the danger of sideswipes, particularly in wet weather or if the street is poorly lit. The problem is even worse if the parked car is dark in colour, with no reflective brightwork to warn the approaching driver. This problem has been made worse in recent years by the switch from reflective chrome bumper bars to non-reflective plastic bumpers. These days, it's all too easy for a tired or inattentive driver to be unaware of a parked car - until it's too late. This simple project is designed to This inside view shows how one of the LDRs (the headlight detector) is arranged to face through the side of the case. The other LDR faces upwards, through the lid. 64 SILICON CHIP overcome that problem. It mounts on the rear parcel shelf and watches for an approaching car's headlights. As soon as headlights are detected, it turns on the parked car's brake lights to warn the driver in the approaching vehicle. The brake lights then automatically switch off about five seconds after the car passes. During the daytime, an additional light sensor disables the circuit to prevent the car's battery from going flat. The circuit is also disabled while the ignition switch is on. This means that the car's brake lights function normally when the car is being driven. How it works Fig.1 shows the circuit of our Automotive Night Safety Light. It's very simple and is based on a 4093 quad Schmitt NAND gate IC. Let's assume initially that the ignition is off and that both LDR1 and LDR2 are in darkness. This means that both LDRs will have high resistance - up in the region of several megohms, in fact. Pins 5 and 6 of ICla will thus be pulled low by the 1ookn resistor and so pin 2 of IC1 b will be high. The other input to IClb, pin 1, is normally pulled low by the 47kQ resistor. As a result, pin 3 is high which means that D2 is reverse biased and the circuit is disabled. Now consider what happens when LDR1 detects an approaching car's headlights. When this happens, the resistance of LDR 1 immediately drops to a low value (several hundred ohms) and pin 1 THIS SIMPLE FETYUGHT goes high. Because both inputs to IC1 b are now high, pin 3 switches low and this sets off a chain reaction through the circuit. Assuming S1 is closed, DZ is now forward biased and the 10µ,F capacitor discharges into pin 3. This pulls the inputs to parallel inverter stages IClc and IC1d low. Their outputs (pins 10 and 11) thus switch high and drive Ql via 3.3k0 current limiting resistors. Ql in turn switches on the relay to activate the brake lights. The brake lights stay on while ever light shines on LDR1. As soon as the car passes, LDR1 's resistance goes high again and pin 3 of IC1 b switches high. DZ is now reverse biased and so the 10µ,F capacitor charges via the 470kn resistor towards the positive supply rail. After about five seconds, the voltage on the capacitor will be high enough to cause IC1c and IC1d to switch low again and turn Ql off. The brake lights now turn off and the circuit is ready for the next approaching vehicle. Automatic override LDRZ, Dl and IC1a automatically disable the circuit during daylight hours or if the ignition is turned on. During daylight, LDRZ's resistance is low and pins 5 and 6 of IC1a are pulled high. Thus, pin Z of IC1b is held low and the circuit is disabled. Similarly, when the ignition is turned on, pins 5 & 6 of IC1a are pulled high via Dl and a Z7k0 resistor. The circuit is then disabled as before. Note that LDRZ must be aimed in a different direction to LDR 1, so PARTS LIST 1 plastic case, 83 x 54 x 30mm 1 PCB, code SC05-1-1 088-1 , 60 x 44mm 1 piece of Veroboard, 62 x 48mm (optional - see text) 1 mini PCB relay, SPOT, 23 x 20 x 15mm 2 ORP12 LORs 1 SPST switch Semiconductors 1 4093 quad Schmitt NANO gate 1 BC337 NPN transistor 2 1 N4002 1 A diodes 2 1N4148, 1N914 diodes 1 15V 1W zener diode Capacitors 1 100µ,F 16VW electrolytic capacitor 1 1 Oµ,F 16VW electrolytic capacitor Resistors (0.25W, 5%) 1 X 470k0, 1 X 100k0, 1 X 47k0, 1 x 27k0, 2 x 3.3k0, 1 x 470 Miscellaneous Hookup wire, solder, connectors etc. D3 1N4002 470k D2 1N4148 100 + 16VWI_ .,. ENABLE B EOC .,. VIEWED FROM BELOW AUTOMOTIVE NIGHT SAFETY LIGHT Fig.1: the circuit uses a 4093 quad Schmitt NANO gate to provide the logic and to drive transistor Qt. LDRl is the headlight sensor while LDR2 disables the circuit during daylight hours. NOVEMBER 1988 65 - 0 00~00~ -1088~ Here is the full size artwork for the printed circuit board. Construction This close-up view of the PCB shows how diode D5 is installed with a loop in one end to give stress relief. Sleeve the leads of the LDRs with plastic tubing to prevent shorts when the board is installed in the case. The two LDRs are simply pushed into small holes drilled through the lid and side of the case. Note how the top LDR sits below the surface of the lid so that it cannot pick up light from an approaching car's headlights. that it cannot "see" an approaching car's headlights. If this were to occur, pin 2 of IClb would be pulled low each time a car approached and the circuit would be disabled, thus defeating the purpose of the circuit. The enable switch (S1) allows the circuit to be manually switched off 66 SILICON CHIP when not required. Power for the circuit is derived from the car battery. Diode D3 plus the 470 resistor and 100µ,F capacitor provide supply line decoupling. ZDl clamps any spikes on the supply line. D4's job is to protect Ql from spikes when the relay turns off. If you want to save money, it's quite easy to build the circuit up on a small piece of Vero board measuring 62 x 45mm. Fig.3 shows the suggested parts layout. You can use an oversize drill to make the necessary cuts in the copper tracks. Take care when working with Veroboard, though it's incredibly easy to make a mistake that's hard to find later on. If you're not too confident we suggest that you opt for the printed circuit board version shown in Fig.2. The relevant PCB is coded 05-1-1088-1 and measures 60 x 44mm. Follow the parts layout diagram carefully when building the board. In particular, make sure that the IC, transistor, diodes and electrolytic capacitors are all correctly oriented. Zener diode D5 should be installed with a loop in one lead to give stress relief (see photo). The two LDRs should be mounted at full lead length so that they can later be pushed through holes in the case. Sleeve their leads with plastic tubing to prevent shorts when the PCB is later installed in the case. Construction of the board can now be completed by connecting lengths of insulated hookup wire to the external wiring points. These leads should be made long enough to reach their respective destinations from the rear parcel shelf. Either version will fit into a small plastic case measuring 83 x 54 x a8 .mt~ 'l~[o -:-7. ~1~~\\~ LOR1 ENABLE --rn&~-1 ~-01DuF ---+12v ~ ffi - ' - G N O ( S1 ENABLE TO BRAKE LIGHT SWITCH Fig.2: install the parts on the PCB as shown here. Be sure to use the correct diode at each location. Fig.3 (right): here is the suggested parts layout for the Veroboard version. You can use an oversize drill to make the cuts in the tracks. : r.l~---~7-;_o_o_.......... -•: )•-~-~-~-~-~~ o o _ _. . o• o 3.3k oo ooo o ooo O o o o 10~F,--..+ 3.3k [ O o o o o o 00000-"-..Joooo-oo • • oo~• 100 oooooocno • oo ICl 04 RELAY 1 o f 100~F 4093 o O o?a 0 0 0 01 e I 000000 0 0 f__l&0 ~ ~ O 0 0 O 0 0 o ~ o - - o oYo o oo oo ooo o-c:::o-----.oo-£ru---ooooo ::v~::r-7-o_,::~: Be careful when working with Veroboard as it's very easy to make a mistake. Be sure to install all the wire links and take care with component orientation. Note that the LDR circuitry was modified after this photo was taken. 30mm. The board simply sits on the base with the leads emerging from a small hole drilled near by. It is then held in place by a small piece of foam rubber when the lid is screwed down. The most critical aspect of the assembly is the orientation of the LDRs. LDRl (the headlight sensor) must be oriented so that it faces out through the side of the case while LDR2 is mounted on the lid (see photo). You will have to drill and ream out holes in the appropriate locations to accept the LDRs. Make 0 0 00000-----00 the holes just big enough so that the LDRs are a push fit. If you make the holes too big, the LDRs can be glued in position from the rear using epoxy resin. Be careful not to cover the faces of the LDRs with epoxy resin, though. Each LDR should be mounted so that its face is flush with the surface of the case. Installation The best place to mount this device is on the rear parcel shelf. It GND IGNITION TO SWITCH ON BRAKE LIGHTS should be mounted so that LDRl in the side of the case looks out through the rear window. The daylight sensor should face upwards so that it will be unaffected by an approaching car's headlights. If reflected light falling onto the daylight sensor does prove a problem, try mounting the sensor in a tube further down in the case. This would also shield the sensor from street lights. Power for the unit must be derived from the unswitched + 12V rail. The most convenient place to make this connection is at the bootlight switch. Alternatively, you can run a lead through to the fusebox. The ignition lead can be connected to any point that is switched to + 12V by the ignition switch (ie, to the accessories rail). The relay contacts are simply wired in parallel with the brakelight switch. It's quite easy to find the brakelight switch. It's a pushbutton switch that is actuated by the brake pedal. Install the wiring in a professional manner and terminate all leads in automotive clip connectors (available in automotive accessory shops). Finally, the enable switch can be installed in any convenient place on the dashboard. An automotive-style push on/push off switch is the best type to use here. Don't use a switch with an integral light bezel - it will only add to the current drain from the battery. 116 NOVEMBER 1988 67 Add a headset to the Speakerphone It's easy to add a headset with inbuilt microphone to the Speokerphone described in the September issue. Now you con enjoy hands-free operation combined with total privacy. Although the Speakerphone is great for in-home use, it's sometimes not practical for use in the office. Other people can be distracted by the two-way conversation or the inbuilt electret microphone can 68 SILICON CHIP pick up too much unwanted noise. Sure, you could plug in a pair of headphones but that doesn't solve the noise problem and it isolates you from others in the office. These problems can be solved by adding a lightweight telephone headset. Only a couple of minor modifications are required to the original circuit and all switching takes place automatically when you plug the headset into the microphone socket. The on/off, mute and volume controls on the front panel of the Speakerphone all operate exactly as before. The headset pictured here is available from Jaycar (Cat. AA2018} and is especially designed for telephone use. It features a single earpiece and a boom microphone that's fully adjustable for position. 4.7k ,,.L 0.1 4.7k .068 3 TXI .068 .o ~ 10 MCO 0.1 27 RXI 7 RU X01 v+ 16 TXO +2.9V HEADPHONES ~ I 21 VB 1 16VW 47 + 16VW! - +HAGC 24 .,. VDLUME~---'-1 VLC VR1 20k I IC1 MC34018 I I (1 / / 4 2.2k .047 -------,---t1■·--t9 MCI 8 1 vcc 20 ACF CP1 11 RTX RR 25 4.7 7 100k + 16V + 1 +5.4V_......,._ _ __ 91k RRX 28 + Kl 19 CP2 12 XDC 23 LO GNO RLO 22 I I .,. I I 4.3k :vw 47 16VW RXD 26 30k 4.7 18k 16VW .01 + - 200k 4.7 + 16VW _ 2.2M 1 + 16VW _ 2.2M /SPEAKER RS { SKG CS 18 S2 MUTE 220 I .,. 1 + 16VW _ I I II I I I L _ ______________ . - - - - - - - - - - - - - - - - - - - ~ *R1+RS=250 B ("7'\ E~ VIE::ra:oM SPEAKERPHONE SC12-1·0988-1 Fig.1: this section of the circuit carries all the necessary modifications. These involve swapping the locations of the electret microphone and its 22k0 bias resistor, and rewiring the headphone socket and mute switch. It's just the shot for use with the Speakerphone but note that other headsets may not be suitable without modification. Because the microphone is now positioned closer to the user's mouth, there is less extraneous noise pickup than before. And the single earpiece means that you can still hold conversations with other workers. Of course, the big advantage is that you can now use the phone without disturbing others while keeping both hands free for note taking or operating a computer terminal. Circuit modifications In order to connect the headset to the Speakerphone we have to do two things. First, we have to switch the output signal from the loudspeaker to the headset earpiece. That's taken care of by the existing headphone socket circuit. Second, we have to switch out the existing electret microphone and switch in The lightweight headset is available from Jaycar (Cat. AA-2018) and features a single earpiece and boom mounted microphone. It plugs into the Speakerphone via a 3.5mm to 6.35mm stereo plug adaptor. NOVEMBER 1988 69 Silicon Chip Back Issues Issue Highlights November 1987: Car Stereo in Your Home ; 1GHz 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 12V DC Converter. January 1988· Bowtie UHF Antenn · I g aO ower Supply; Custo,,...~Prrr, oa--r:-iinger; Subcarrier Adapter r FM Tuners. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm ; End of File Indicator for Modems; Simple Door Minder; Low Ohms Adapter for Multimeters. March 1988: Remote Switch for Car Alarms ; Telephone Line Grabber; Low Cost Function Generator; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; Automatic Light Controller; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid ; Booster for TV & FM Signals; The Discolight Light Show. August 1988: Plasma Display; Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; Switchmode Charger for 12V Gel Batteries; Vader Voice. October 1988: Stereo FM Transmitter; High Performance FM Antenna ; Led-Light House Number; Matchbox Crystal Set. BACK ISSUES ORDER FORM Please send me a back issue for : D March 1988 D August 1 988 D April 1988 D Sept.1988 D November 1987 D December 1987 D February 1988 D May 1 988 D June 1 988 D July 1 988 □ October 1 988 Enclosed is my cheque/money order for $ _ _ _ _ __ or please debit my D Bankcard Card No I~~~~~~~~~~~~~~~~ Signature _ _ _ _ __ _ _ _ _ Card expiry date_/_/_ _ Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town, _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode____ □ Visa Card Price: $A5 .00 each (includes postage). Overseas orders add $A 1 .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 ~--- ----------------------~-----------~ 70 SILICON CHIP You will have to temporarily remove the PCB from the case to modify the wiring. We used PC stakes to terminate the leads from the 2.2k0 resistor and to make connections to the headphone socket easier. 2.2k0 resistor from circuit and disconnect the appropriate leads to the microphone and to the mute switch. The 2.2k0 resistor can then be installed in its new location and the leads from the microphone and switch connected to their new positions. The headphone socket modification is quite straightforward and involves connecting two extra leads - one to the microphone and the other to one side of the 2.2k0 resistor. The shorting link on the back of the socket must also be relocated. Fig.2: here's how to modify the wiring to accept the headset. Note the different linking arrangement on the back of the microphone socket. the headset microphone instead. To avoid complication, the circuit is arranged to switch over automatically when the headset is plugged in. But before we can do this, it is first necessary to modify the bias arrangement for the electret microphone so that one side of the microphone goes to ground. In practice, this involves swapping the locations of the microphone and the 2.2k0 resistor on the circuit. After that, it's simply a matter of rewiring the headphone socket and the mute switch (which must remain in parallel with the microphone). Fig.1 shows all the circuit details. Construction Fig.2 shows how the wiring to the headphone socket, microphone and mute switch is modified. You will first have to remove the Testing it You will need a 3.5mm to 6.35mm stereo plug adaptor to use the headset with the Speakerphone. These are available from Dick Smith Electronics (Cat. P-6500) or from Arista outlets (Cat. PA90). Once the wiring has been •completed, the Speakerphone should be tested to ensure that it still functions correctly. The unit can then be checked out with the headset plugged in. We found that it's best to keep the microphone well away from the user's mouth, to prevent overload and stop breathing noises. NOVEMBE R 1988 71 CRAFT ADE UMINIUM ASHLIGHT . . ' ~ ·. - What an excellent product! It measures 145mm long and runs off 2 - AA batteries. It is 70 times brighter than a normal tori:h 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 ftt inside a car glove box 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 these and can offer them at the amazing price of only $9.95. Spare bulbs available for only $1 .50 (Cat. ST-3002) 1 0 30 PIECE ENGINEER'S 0 ~~~ At last! A driver set incorporating those obscure shaped heads! Have you ever needed recently to service an electric tool? Chances are you would not have been able to do so because the screws holding the appliance together had strange shaped heads. Well now you can with our 30 piece driver setl This set contains all the driver bits you are EVER likely to encounter (See Below). Basic to the set is an B 1/2" Chrome-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 wtth you into the field . Th ere 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 Bits 3/32", 5/64", 7/64", 1/8", 9/64" • 4 Philips Bits No. 0, t, 2 & 3 • 4 Square Recess Bits No. 0 , 1, 2 & 3 • 6 Torx Btts T10, T15, T20, T25, T30, T40 • 2 Poz idrive Bits No. 1 & 2 • 1 x 1/4" Drive Socket Adaptor• 1 x 1/4" Drive Hex Btt Holder Bargain 1: 1.25V MES lenshead globes. Ideal for single cell torches. , .~ !!J USUALL y 50e ea 25 for $2 (only Be ea) 100 for $6 (only 6e ea) 5 volt MES torch globes . Works OK on 6V. USUALLY 50e ea 10for$1 Q ~V ~ Bargain 3: 12 volt BC car replacement globes suit tail lights, blinkers, garden lights, etc. 0f) 1/ USUALLY ABOUT $3 ea 2 for $1 Cat. SL-2662 ~ Bargain 4: 6.3V;i:?MES globes USUALLy 50e ea . 4 for $1 , · 10 for $2 . ~ 100 for $15 • j Cat. SL-2654 Limited quantities on all globes. CAR SPEAKER GRILLS ,, - -~r.i: _ :,;_~~~,· ' release handle and when the bonnet catch)your car AUTOMATICALLY you swttch alarm on . The unit will give COMPLETE under-bonnet securttyl Th,a locking device includes solenoid lock, control box, emergency Bowden cable release, screws, connector bracket and other hardware for universal fttting. lnstruc!ions supplied. Cat. LA-5400 PHOTO A BARGAIN AT ONLY $19.95 WOULD NORMALLY COST ABOUT $70 This device enables you to turn a circutt on and off optically. 1 ~~~~~Te~: .;;,~or •Tachometer, Opto lgnttion • Edge Sensor. Tape End Sensor Full specs supplied with each untt. 1 $Cast. z_ D_ 5 190 e a 9 O+ $ _ ea 1 Cat. AS -3035 SAVE$6 2. 9" X 6" quality _so_i_n_Pa_c_k_ $7_.9_5__$_12_.s_5_ INTERRUPT This device will lock the Bowden Cable (i.e. the 'wire' that goes between the bonnet 1. 7" X 5" metal grill. Black in colour. ONLY $2 ea • Metallised polyester. 60 top quality prime spec greencaps supplied from 0.001 uF to Car Bonnet Locking Device -8 .,..:-... . .!_-~ --------- $19.95 DON'T PAY Porcelain Standoff ;a0~-;~Ch ~ GREENCAP PACK o.22uF, all 100v. Cat. RG-5190 Cat. SL2660 Bargain 2: Cat. TD-2000 -- Ideal for electric fences. A round glazed porcelain insulator measuring 30 dia & 25mm high, wtth a 10mm hole thru the centre. A roofing screw would be ideal to fasten the insulator to a post. 9 DRIVER SET And its all housed in a sealable tough plastic case GLOBE BARGAINS $9.95 7 95 metal black grill. Cat. AS-3036 ONLY$3ea SAVE $7 You would expect to pay about $8 for the 7 x 5 and $10 for the 9 x 6 nornmally. -· CRYSTAL EARPIECE Micro Hi Fi Speaker 70mm long x 34mm wide oval speaker - wtth butyl rubber surround I Respectable 1W rating. Hi Fi in a matchbox. Quantities very limtted. Cat. AS-3002 $5 ea High impedance wtth 3.5mm plug. Suttable for crystal sets or for experimental use. Cat. AS-3305 NORMALLY $3.75 NOW ONLY $2.50 SAVE $1.25 ULTRASONIC PEST & INSECT REPELLERS • Frequency range 30kHz to 65kHz variable • Output level 130dB • Both unns include 240V power adaptors Single Transducer ONLY $29.95 SAVE $10 Cat. YS-5510 DUAL TRANSDUCER ONLY $39 .95 Cat. YS-5512 CAR NEGATIVE ION GENERATOR Now you can have aJI the benefrts of your home 1onIser ,n your car. This great new Jaycar direct import is durable, stylish and compact, measuring only 110mm in total length. It simply plugs directly into the cigarette lighter socket in your car. It can generate large amounts of negative ions for purifying aJr, and some ozone for eliminating odour. Jaycar's direct importing cuts out the middle man and saves you money. ON LY $34.95 ;;:;;.ar.,,:-...-: ~ SPECIAL INTRODUCTORY OFFER /, ~ AT LAST- Probe cases ~ Size 200 x 24 x 20mm Cat. HB-6400 . 11-------1 DIGITAL STEREO HEADPHONES $12.95 SASSS SAVE UP TO 39% SA700 Top of the range, excellent sound. Qualny phones. Cat. AA-2023 Features Mylar drivers, sponge earpads , metal 3.5mm stereo plug. Cat. AA-2021 240 VOLT - SAVE $50 Cat. YX-2905 WAS $29.50 NOW $1 7.95 SAVE39% SASSO Mylar drivers, freq. reponse ONLY $29.95 I Oualny English made shielded cable with a total diameter of 1mm. Ideal for screened wir ing in small spaces I Packet 5 metres • 'T-REX' WIRESTRIPPER Strip all sorts of cable without damaging the conductors. • Automatically adjusts to insulation diameter. •Cat. O"•TH-1824 OaOOo,""""· Cat. WB -2310 WAS $59.50 NOW $39.50 SAVE34% For full details see our catalogue. 20Hz-25kHz. Quality muff pads. Cat. AA-2022 '= -ULTRA THIN SHIELDED CABLE J We finally secured a reliable supply of RF probe cases. These are constantly used in kns. WAS $12.95 ,... , ... , . 1 • · • · ·· , .. / SAVE $2.00 ·.,., _ · , >··, ) GREEN RECTANGULAR LED BARGAIN WAS $39.50 NOW $24.50 SAVE 38% . , ..... . '! . -. . .' . HI QUALITY GOLD/ !!~~t!'s~~d~s 1 those expensive gold audio leads. Clearly marked in red or black. , RED Cat. PP-0236 BLACK Cat. PP-0237 NORMALLY 40e each $3.50 ea 1-10 20ctea 11 -99 16ct ea 100-999 14ct ea 1000+ 12ct ea including taxi Cat. ZD-1765 10+ $3.20 each - - - - - - - ~ - ~~• Solar Powered Exhaust Ventilation · (• ' Ideal for turntables, speakers, large amps, etc. Easy mounting wnh one 4mm diameter bolt or self tapper. Diameter 35mm at base. USUALLY 85t ea 40~ each 10+ 35e ea cat. HP-0830 This k~ contains a motor wnh press-flt brass cog, gearbox hous ing , 3mm x 110mm steel drive shaft, 2 intermediate shafts, 7 gearwheels and 6 nylon bushes. Runs off 15 - 45 volts DC. No of gears 1 5V 3V 4.5V RPM RPM RPM I Remove gas, fumes, humidity, etc by using the suns free power solar. It will remove about 35 cubic metres of air every 1/2 hour in bright If you own a Port;lsol soldering iron, sunlight. bring it into any Jaycar store for a Ideal for: • Boats •Caravans• Port-a-loos FREE gas refill. _______.. • Greenhouses• Sheds• Holiday homes• Backyard dunnies • Kitchens • Weekenders, etc. Cat. YX-2500 1/2 PRICE PLASTIC FEET Motor /Gearbox Kit SAVE $5 NOVEMBER ONLY $44.95 6 2 4 5 5 16 10 32 M 45 1~ 150 400 300 800 410 1150 4 3 2 11Cat. YG-2712 M 6 14 WIRE WRAP KYNAR WIRE ON SPOOLS We have been after this for years, and have finaJly found it. It's high quality SILVER PLATED (other companies sell wire which is not silver plated) on 50 foot spools. Available in 4 colours. RED Cat. WW-4340 BLACK Cat. WW-4341 BLUE Cat. WW-4342 GREEN Cat. WW-4343 ONLY $6.50 per reel That's only 13ct per foot I WIDERANGE MAGNAVOX 8WR $36.50 MAGNAVOX 8JX $31.50 The BWR is a high fidelity wide range twin cone a· driver. SPECIFICATIONS Power Handling 65watts RMS Resonant Freq. 43Hz Freq. Range fa- 12kHz Sensitivtty 96dB Cat. CE-2338 The 8JX is a 8" twin cone speaker suitable for medium power handling applications. SPECIFICATIONS 40watts RMS Power Handling Resonant Freq. 44Hz fo - 12kHz Freq. Range Sensitivtty 93dB Cat. CE-2333 JAYCAR FOR MAGNAVOX SPEAKERS MAGNAVOX 12W MAGNAVOX 10W WOOFERS MAGNAVOX8W The SW Mk6 is a high fideltty woofer. SPECIFICATIONS 65watts RMS Power Handling Resonant Freq. 43Hz Freq . Range fo - 5kHz Sens ilivtty 96dB Cat. CW-2109 12" woofer, medium power, low cost, high quality. 25mm voice coil wound on aluminium former. Polyurethane foam roll surround. SPECIFICATIONS The 10W Is a 10" high quality, high power, medium price woofer. SPECIFICATIONS Power Handling 75watts rms Freq. Response 30Hz - 5,000Hz Resonant Freq. 33Hz Cat. CW-2118 $56.50 $43.50 $39.50 MAGNAVOX8MV MAGNAVOX12MV 8/30 Replacement II you own a pair of 8/30 woofers, you can now easily update them. Your old 8130's handle 30 watts rms, the new BMV's handle 120 watts rms . No need to buy new cabinets, BMV's rrount in the same hole, otherwise it's a high quality, high power B" woofer for most applications. SPECIFICATIONS Power Handling 120watts rms 31Hz Resonant Freq lo - 4kHz Freq. Range Sensitivity 96dS Cat.CW-2110 The t2MV is a high woofer. SPECIFICATIONS Power Handling Resonant Freq. Freq. Range Sensltivtty Cat. CW-2125 power high fidelity 150watts rms 19Hz to- 3kHz 96dB $99.50 $99.50 POLYPROPYLENE MAGNAVOX WOOFERS JC 150 6" WOOFER JC 200 8" WOOFER SPECIFICATIONS Resonant Freq. Sensitivity Power Handling Freq. Response Cat. CW-2105 SPECIFICATIONS Resonant Freq. sensitivtty Power Handling Freq. Response Cat. cw-2112 49Hz 95dB 50 watts rms 80 - B000Hz SPECIFICATIONS Resonant Freq. Sensivity Power Handling Freq. Response Cat. cw-2120 39Hz 95dB 65 watts rms 50 - 5500Hz $ $ , 2GHz 97dB 75 watts rms 45 -4500Hz .1 Hi , I know you are not going to believe it but my name is Kit. (It's really Kitty) . Well, I work with a bunch of other girls in the Kit Department at Jaycar. You wouldn't believe it, but the other day the boss stalks in and tells me that I have to write a column to go in our ads I He says he will let me write anything, mind you, even stuff about him (not everything about him) . Well, here goes. (Hope he doesn't sack me). Well, the other week the boss called me into his office. Would you believe it-justafterknockofftime. lknewthat it was going to be interesting when he locked the door behind me ... "Let me turn the lights off' he said. I thought, well here we go! But the 11ext thing that happened was - he turned on this fantastic new lamp that we had just produced as a kit, It's the Plasma Discharge lamp/display that was described in 'Silicon Chip' in August this year. 39 "795 49 95 ______..;:;..;..;;.;;•~;...--------1' 64 95 l""::-:--=-::==-:::7::7::""' ":::-::-:--::-:-,,-----=--.;..=..;.•;;.;;;;_ ELECTRONIC ANVIL!!! ldealforthehobbyist.HammerthatlCinto that socket on our anvilll Weigt!/io~ 2040 Size 180mm long 80mm high DUMMY CAMERA S 1-4 $49.9515-9 $42.95 10-19 $39.95 20+ $37.95 Cat. LC-5310 QUALITY JEWELLERS SCREWDRIVER SET Qualtty easy to use colour coded screwdriver set 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 PLUG & SOCKET ETCH ANT CHEMICALS IN JARS • Safe for storage, childproof lids - safe from kids, no mess, no fuss. FERRIC CHLORIDE 200g Cat. NC-4251 400g Cat. NC-4252 AMMONIUM $4.95 $7.95 . PERSULPHATE 400g ~:::t"' TERMINAL STRIP $4.95 ' . ._____ __ Brand newprodue1. tt's like a standard type 12-way barrier strip or terminal strip but It has 2 st rips of 12 which can be unplugged from each 0th er. So nyou have any number 01 semi permanent "'.ir~s fro~ 1 to 12 that you have to unplug, this IS the ideal way. Cat. HM-3202 ~ - ~ ~ , • .~ . . • t-----------~.. Insulated Staples . No Staple Gun Required Grab a packet of thesel Pack of 100 plated U-shaped staples wtth soft-nylon saddle, you can hammer them In to wood, particle board etc. Nylon saddle cushionsthewiring.ldealforburglaralarms, knew they were great but this was really something. He had the blue coloured Plasma Display jar in the ~~~~/t was really spectacular in the Then he showed me his red one . .. Plasma Jar of course! You naughty boys I I told him that it was just the thing for an orgy but that seemed to go over his head. He kept looking at the display and not me! The fact that I wasn't getting paid overtime for this product orientation evening seemed to go over his head as well! AnywayBigBoys,bethefirstonyour block to have one of these new toys . You can really impress your not-soclever-as-you friends with your own lightning stomns in a jar. But don't all orderatonce .. Thegirls in the kit dept. are flat out doing our best already . a Meantime keep your iron hotl Rega rd s, =-=> ~ ~ -: ~~0t~ ·~ !::.;?!'.t·i::;:>:::... ,.. ~ •~ . .·. ' •, .. ,. ·..··. ·;· •. . -~ .- · '.~ • ~'ft._;,_ ,, i ;~1 ~_, ~I:.. !1 Y - . ---·.~ ~:~~:~ 00 ~~:E,Sutt! : · for 3C-2V or RG58 coax and heavy speaker flex. cat. HP-11ss $2.00 existing wire and new wire and squeeze. NORMALLY $1.25 for 4 or 31t ea (Two styles supplied in pack) PACK 15 for $1.95 (only13eea)Cat.HP-1207 PACK 100 for $10 (only ,oe ea) Cat. HP-"1208 ~ ~ - • n speaker flex, TV coax etc., and NO 1 CONTACT CONNECTOR BARGAIN Easy to use automatic connectors. Simply wrap around the Kit - · , . .· . ' - . 1/2 AN RCA LEAD? Well, not quite. These are a stereo lead, (figure 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 NEW KITS FOR NOVEMBER FROM JAVCAR 120WATTPA/ GUITARAMP MODULE HE LATEST KITS FM TRANSMITTER <MINI CAR SAFETY LIGHT Ref: Silicon Chip November 1988 This rugged Mosfet amp module is designed specifically to drive a 100V line transformer for PA. It can also be used for gurtar and stereo amps. Short form kit. PC board and all components supplied, including Mosfets. No power supply parts or heatsink included in krt. Heatsink extra Cat. HH-8550 $22.95 Cat. KC-5043 (kit) Refer: Silicon Chip October 1988 Listen to your compact discs playing at home on your Walkmanl This project transmitts the input signal on FM which can be picked up by the FM radio in a Walkman. Uses one IC and delivers about 200 microwatts. Full kit. Cat. KC-5041 Ref: Silicon Chip November 1988 Is your car in danger of being sideswiped at night? This project detects an approaching cars' headlights and automatically turns on the brake lights to warn the driver. The brake lights swrtch off 5 seconds after the car has passed. Circurt is disabled during the day. Qualrty Philips LDRs supplied Cat. KC-5044 ONLY $29.95 POWERMATE2 Refer: EA October 1988 Revamped version of original Powermate power supply. Delivers clean, crisp regulated 13.8V DC at up to 5 amps. Full krt. $72.50 WIRELESS DOORBELL BA-1404 Transmitter IC Cat. ZL-3995 Ref: EA November 1988 Low cost 4 digrt 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, gott ball speed, etc. Short form kit, no box or front panel supplied. Cat. KA-1708 "KNIGHTRIDER" LED SCANNER Ref: Silicon Chip November 1988 Provides the scanning effect same as on krt 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 $6.75 $8.75 STROBOSCOPIC TUNER KIT Ref : EA July 1986 This simple circuit provides crystal-locked accuracy for tuning virtually any musical instrument. It also doubles as a stable frequency reference ff you prefer to tune up by ear. Kit includes box and all parts. Cat. KA-1706 $59 ['\ :~:: ·:::_-,.~,~ i $17.95 HANDS FREE TELEPHONE HEADSET $16.95 :-.. 1 ~~:~ :~- \ \ '\\ "~J;,_ ·,·t .~;;, , ,• TRANSMITTER KIT RECEIVER KIT Cat. KC-5037 $47.50 So new, we don't even have a picture yet. As used with the Silicon Chip speakerphone project. Headset, microphone wtth lead and 3.5mm plug. Mini size ultra lightweight. Cat. AA-2018 ' SPEAKER- PHONE Ref: Silicon Chip Sept 1988 High qualrty hands free telephone adaptor that works extremely well. Full krt including box, panel, isolating transformer and all parts. Cat. KC-5040 PLAYMASTER/JA YCAR 60/60 BLUEPRINT AMPLIFIER Standard version still available Cat. KA-1652 $369 ONLY $89 ~-"" q ·;; Cat. KA-1650 See our catalogue for full details Ref: Silicon Chip November 1988 Ideal for those who want to experiment with plasma displays. This krt is basically just the power supply. You can use a 240V globe anywhere up to 300 wans. (Warning with this unit you can not touch the globe whilst it is operating). Features adjustable display. Kit includes PCB, EHT transformer, box and all components, but not globe and holder (which are readily available). Cat. KC-5045 ~$_3_2_g__________~ $75 UPGRADED 5000 BLACK MONOLITH POWER AMP RE-BORN WITH TOPOLOGY MODULES 0 ,~ t -ON Ref: Silicon Chip August 1988 What a great idea. A wireless doorbell with the option to have as many sounders as your house requires. Transmitter is mounted in a UBS Jfffy box with a pushbutton switch which mounts outside your front door. Powered by a 9V battery. Receiver mounts in plastic box and requires 12V DC plugpack, our MP-3006 will do $14,95. Use as many receivers as you require. Cat. KE-4200 I?;~~ $499 ~ • • ;LI VISA [Ii Masterearo HEAD OFFICE 115 Parramatta Road Concord 2137 Telephone (02) 747 2022 Telex 72293 FACSIMILE (02) 744 0767 ~, MAIL ORDER VIA YOUR MAIL ORDERS P.O. Box 185 Concord 2137 HOTLINE (02) 7471888 POST & PACKING $5 $9.99 S 2.00 FOR ORDERS ONL V $50 TOLLFREE (008) 022 886 'ff $10 $25 $24.99 $ 3.75 $49.99 $ 4.50 $99 .99 $ 6.50 OVER $100 $10.00 ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 117 York St. (02) 267 1614 · Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Church St (Cm. Victoria Road) Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 2pm GORE HILL 188 Pacific Hwy cnr Bellevue Ave (02) 439 4799. Mon-Fri 9 - 5.30 Sat 9 - 4pm BURANDA QLD 144 Logan Rd (07) 393 0777 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 12 CONCORD 115 Parramana 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 HURSTVILLE 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) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9. SYDNEY - CITY PARRAMATTA ' 11 May 197- The Middle East ... Dick, me old mate, After we parted company in Samoa, I returned to the Big Smoke for a few months. Saw this advert in the paper, called, they made me an offer I could not refuse, and here I am. Well, I'll tell you, I wish I had never accepted the job. This cowboy outfit is the pits. OCV A stands for Overseas Consortium for Video and Audio. A complicated way of saying television, I guess. But, know what? They've not worked in broadcasting before. Come to think of it, this mob hasn't had an overseas contract before. Sometimes I think they've never employed human beings before! The head office is in the middle United States and they're trying to run the project by remote control. In less than a year, they've sacked a project manager, two directors of engineering, and three production managers. We now have a third project accountant here. There's been 11 blokes here in the capital as chief engineer or acting chief enginner in a 16-month period. The last chief had worked at the second station for most of a year, then was requested to come here. After 15 months, they sacked him for incompetence. This happened just after he collapsed in the station. Wasn't heart trouble, thank God, but the result of stress. Anyway, he appealed to some bod in the ministry and the letter of dismissal was rescinded, so he finished his contract on medical leave. Our maintenance staff level is supposed to be six people but we've averaged four over the past 11 man- By RICHARD KOPF 76 SILICON CHIP ths. From what I see of the operations log they keep in master control, some 25 engineers have come and gone in that time. The record is held by a bloke who didn't even want to get off the plane when it arrived. He took one look at the desert and said, "I didn't think it would be like this!" They managed to pry him out of the 707 but he refused to even go to the project office. The (second) project manager came to talk to him and he insisted he would not stay. I guess OCV A just like buying plane tickets. One of the guarantees in your contract is return airfare to your point of origin. Crunchbox The blokes here before me say that every time they grizzled about anything at the project office, they were told: "If you don't like it, you can go back to the States". Which is why OCVA is having to hire engineers from other places, I guess. We have two Porns and a Lebanese at the moment. And no chief engineer. Our present director of engineering thinks he can run this station from his desk at the project office. He said one day that they never needed vertical interval swtiching back at the network in New York, since all sources were synchronous. So now we call him "Crunchbox", after the old mechanical units we still use here. \\ ' ' - - - . ~ -------,----0- - ~-~~ \ Jl . I ' The new project manager arrived a few weeks ago, after numerous promises that conditions would improve. The bloke called a staff meeting and bragged that he didn't know a thing about television. Seems he'd been a section supervisor on some company project dealing with military radio. He's a weird bloke. I fronted him one day about the condition of our company villa. All of a sudden, as the talk got heated, his head dropped forward and he just sat there. I was afraid he'd had a heart attack. When I went to get some help, the accountant said that it was all right. Apparently he goes sort of catatonic when things get too much for him. That's one hell of a way out of an argument. We have a lot of trouble with the Middle Easterners (ME's for short). In fact, the previous company got kicked out for doing business with ~ ~ / / ~ ~ ~ ~ . Introduction to these Letters Over more years than I care to remember, I have gathered stories of the real world of electronics. I look back now in dismay at those carefree, youthful days of learning the basics. What I considered to be difficult then was as nothing to the reality of work. A bright, clean lab area and a surfeit of test equipment seemed only to be expected. Little could I have conceived of a service department with poor lighting, inadequate and insufficient test equipment, and a manager who begrudged spending money even on hand tools. More fool he who brings his own, and has them pilfered by others in the section. Not long ago, I interviewed a bloke who had a really bad experience. He had accepted a job with an amusement machine company, having been promised a budget for setting up a service department. So he started with this "morn and pop" outfit. When he wanted to order an oscilloscope, the boss said: "A real technician doesn't need a crutch like that!" These days, when I read "geewhizz" stories of the leading edge of technology, my interest is tempered by memories of other times and other places. So I will share with the reader some anecdotes of real life. The stories are real; only the names have been changed to protect the guilty! NOVEMBER 1988 77 THE TECHNOLOGY LETTERS - CTD 11-\\S \S OOR ~~UT'S 11::>E:'-~OA"t>CA S , . \JN\'-••· .: I . tJ ~ , I v 1/ ~~-- VINTAG£. i\J '5 ATION. ,,,,-.._,, MO~-r OF 11'\E. GEAR C:.AN\E. F~OM A WA~I-\OO~e IN t-O~t:ot-Jo•• Israel. Which is why OCV A is here - they bid low Anyhow, the operational staff is autonomous - we have no control over them. And they have no sense of responsibility. Their attitude at the station is like it is at home. "When something is broke, we buy another one". From what I can find out, the original television scheme was planned by some US government organisation. The plan was then implemented by a company from the UK and turned back over to a US company to run. They lasted three years. I hear that when they found they'd lost the contract, they had a bonfire out behind of the station and burned hundreds of drawings and volumes of records. What's left of the station documentation is exactly one looseleaf notebook, adhering to no known engineering standard, with scrawled block diagrams of the original wiring. Few, if any, changes have been entered in the 78 SILICON CHIP last five years. The cables themselves are sometimes numbered, often with a different number at each end. Well, they are different ends after all. Most of the gear came out of a warehouse in London - it's vintage 1946 valve equipment. The VTRs were added later. They had the audacity to tell the people here it was intended to work for 15 years! The building is air-conditioned when it works - but at sign-off, everything is shut down. The system was obsolescent when installed and is really deteriorating fast. Let me tell you about our station. First up, the city is on 60Hz power. But the station was planned for CCIR standards, yes 625/50. So we have a 60-to-50Hz rotary converter in the utility building out the back. There are two stand-by generators there, also. One is 60Hz and the other is 50Hz. The latter generally wouldn't run in an emergency although the 60Hz always starts. Cutting the rotary converter across doesn't always work though, due to some problem in the control circuits. Now, one of the transmitters is capable of being fired up when we have 60Hz on the emergency distribution circuit. But what do you transmit if the studio gear, including the sync generator, is dead? The power is nominal 110-volt and varies regularly from 80 to 145V. I've logged some spikes at over 170V. Master Control is a real beaut. They have 19-inch monitors on suspended shelves, guaranteed to give you a hernia in trying to lift one down. And guaranteed to fail when we're to air. Then you have to climb over the director, stand on the video console, disconnect cables and lift the monster. The first time I did this was a real disaster. How could I have known that the TR22 VTR video fed the monitor, then the patch panel, then looped back to the TS 11 valve vision mixer? The other two outputs from the machine were unused! Vision patch panels appear in two different bays and are scattered amongst four racks. There's a rack-mounted CRO in one bay but most of the signals you need to check are in the other one. Everything in the facility is the same. Engineering stores cannot be reached save going . through the studio (frequently impossible because of production or to-air operation). When supplies are delivered, they have to be put in the chief engineer's office, to be checked off, making a really inefficient triangle for parts handling. The workshop is by the transmitters - I think it was an afterthought. There's little enough test equipment on hand, mainly because the station manager has people "putting things out of the way" in the stores area so that everything is "neat" for the numerous government inspections. This maintenance area is so small that if you pull an oscilloscope cart alongside the bench, you have to walk around three racks to get to the other end of the bench. In telecine, there's two film islands, one with a 35mm projector. Apparently, this has been used once in two years. In this room, there's buss ducts along the walls, timber covers across the floors and some cable disappears overhead. The entire building is on a concrete slab and they never thought of cable trenches. I guess you'll know the operators are rough when I tell you that we have to do a full mechanical and optical alignment of both islands every week! They have a habit of shooting sound-on-film at the wrong speeds. I can't get through to them that if you rig a projector to change the frame rate (it can be done), the sound has to change too. The VTR room is fun. It was designed for two machines but holds a TR-4, a TR-22 and a TR-70. When you try to do emergency maintenance (is there any other kind), the locals crowd around, offering advice and asking when they can use the machine for a "very important program". They also have several hundred one-hour tapes stored in this cosy area. Some of the syndicated tapes from Lebanon are multiple generation dubs. I've seen something like 240 units of recorded geometrical error. And they criticise us for "not cooperating to make the picture nice"! Bungling bureaucrats When I arrived, I found they had an intermittent problem with the TR-70. It might run fine for an hour or a day. Then, more often than not, just as it goes to air, the video drops out. I asked the night operator, how long this has been going on. "About two years", he replied. "How long has this machine been here?" "About two years." It took me about three weeks to crack it, and the problem turned out to be in the post-emphasis module; Now, an ex-factory bloke once told me that it was so critical that no field repairs should ever be done on it. So I jumped in the Land Rover, went over to the project office and asked for a spare. "You can't have it," I was told. "Look," I argued. "I know we have to keep a complete set of spare modules, by contract. If it's gone to some other station, I'll understand''. "No, we have it in the storeroom". "Why can't I have it?", I cried. "If you use the spare, we won't have a spare". No amount of pleading would separate those bureaucrats from their bungling. So I spent another fortnight with that damned module on an extender cable and finally found a choke in the differential input stage going wonky. Wound a new one on a matchstick. Machine hasn't played up since. No-one said thanks. Directors block four hours of production time, show up three hours late, demand special effects that would require half a day to rig. Then they don't get their program finished before we go to air. As usual, a complaint goes to the ministry that we are not cooperating. And if you think things are bad at "Sensational Price Offer'' I CONTACT CONTACT CONTACT ELECTRONIC PARTS PLUGS, SOCKETS & SHELLS COMPUTER SPECIALS COMPUTER SPECIALS COMPUTER BITS &. PIECES SEAGATE HARD DRIVES W /0 CONT PLUG SOLDER PLUG SOLDER PLUG SOLDER 2.79 2.20 0.70 DISK SlORAGE BOX 100 x 5 1/4" DISK HOLDER FOR· 10 ~ 5 1/4" COPYHOLDER DESKlOP ADJ/ ARM 9.00 2.75 23.00 0 DB 19 DB 23 DB 25 ... DB 19 DB 23 DB 25 SOCKET SOLDER SOCKET SOLDER SOCKET SOLDER 3.85 2.95 0.70 IBM AT /XT JOYSTICK ATARI CHALLENGER JOYSTICK 19.00 10.00 DB 19 DB 23 DB 25 BACK SHELL BACK SHELL BACKSEHLL 1.45 1.35 C-800 WITTY MOUSE MAGIC M WITTY MOUSE 60.00 65.00 XT CASE & LOCK AT CASE & LOCK 80.00 89.95 a: Ill a: 0 ; I 150 a: o.eo NICAD BATTERIES AAA 180 MAH AA 500 MAH C D D 9 3.20 2.00 5.80 5.90 11.50 12.00 CELL 1.2 AH CELL 1.2 AH CELL 4 AH VOLT 0 i I RED HOT SPECIALS D0342 MOUSE PAD S0225 NUMERIC KEYPAD C0085 ELECTRET MIC INSERT 6.00 2.95 0.45 HAND SCANNER HS 2000 MONllOR STAND 12/14" + LOCK KEYBOARD 101 KEY CLICK TYPE 375.00 19.00 99.95 ADD ON CARDS 78.00 75.00 76.00 22.95 49.95 CGA SHORT MONOCHROME + PRINTER MULTI 1/0 + FDC PRINTER CARD RS232 SERIAL 1 PORT POWER SUPPLIES 150 W 180 W 220 W lOWER 75.00 99.95 139.95 ST ST ST ST ST 225 20M 65MS 238 30M 85MS 251 40M 40MS 251-1 40M 28MS 277R SOM 40MS 350.00 430.00 790.00 1000.00 1000.00 I: J> ;= 0 :D g GOLD PLATED HIGH QUALITY LEADS BNC BNG RCA RCA PLUG PLUG PLUG PLUG 10 10 10 10 BNC PLUG RCA PLUG 3.55mm PLUG RCA PLUG 5.95 5.50 3.00 3.50 PIONEER SPEAKERS SPEAKER SPEAKER SPEAKER SPEAKER SPEAKER SPEAKER 10· 10" 10· 12• 10" 12· 60W 8 Ohm 100W 8 Ohm 120W 8 Ohm 150W 8 Ohm 200W 8 Ohm 250W 8 Ohm 29.95 54.95 59.96 69.95 79.95 149.95 m :D II GOLD PLATED HIGH QUALITY LEADS W0201 TV 10 TV GOLD 1.5M W0200 TV 10 VIDEO GOLD 1.5M W0202 VIDEO CABLE SET 3.50 3.50 9.95 ALL PRICES INCLUDE SALES TAX WHOLESALE EN_QUIRES WELCOME PRICES VALID WHILST STOCKS LAST CONTACT INTERNATIONAL Suite 2-283 Burbridge Road Brooklyn Park SOUTH AUSTRALIA 5032 PH. 08-231-2202 Fax 08-352-1449 P.O. Box 390, Cowandilla, South Australia 5 03 3 Mall Order Postage Less than $50 ............................... $3.50 $50 - $99 ...................................... $4.50 $100 · $250 .................................. $7.00 Above $250 ................................ $10.00 Heavy 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 EXPIRY DATE Card No .............................................. .. Signature: ••••••••••••••••••••••••••••••••••••••• •••••••••.••••••••••••••••••••••• (Note:. UIIJigned credit card mall ordera cannot be accepted) Name: ......................•..••••....••.•..•...•.....•...•.......••..........••• Address: .•••••••••••••••••••••••••••••••••••••••••••.•••••••••••••••••••••••••••• ........ ..••...•••••....•.. ••••...•••.. •.•.•••.••.•• Postoode: .................. . (Please allow 14 DAYS for normal mall ■ nd bank clearance delays) r0 :D g m :D the studio, you ought to try an outside broadcast. Imagine TK60s on a parade ground when it's 121 ° at 10am. I just finished an 18-hour day. Had to rebuild a portable link transmitter. One of the Americans (known as Mister Ed) set it up yesterday to check it out. Four o'clock came and he went home. Without anyone to watch them, the locals shot through. No-one on the evening shift knew the bloody thing was out there. During the night, the wind fetched it up against a concrete wall. So Crunchbox told me to fix the transmitter and Ed was supposed to supervise the camera set-up. We were covering the dedication of the new horse racing facility and the King was going to attend. Well one thing you don't mess around with in a kingdom is "de King" so I got stuck into it. Twenty-eight sheet metal screws secure one of the access panels and it was the wrong one. When I did get to the klystron, a piece of metal fell out of the waveguide coupling. 80 SILICON CHIP "Where's the spare, Shebani?", I asked my offsider. "You're holding the spare". He went on to explain that Mister Ed had changed it yesterday because the old one was weak, or something. I begged him to find the old one. "But it was old, we threw it away". Fortunately, we found it in the trash bin at the station, put it in, and the rig seemed to fire up OK. By now, however, Mister Ed was back at the station, resting. Seems he'd fallen off the roof of the OB (outside broadcast) van while taking pictures of the area with his new Minolta. Dick, I swear I'm not making this up. So we got on the blower and spent a fruitless hour trying to achieve microwave comms with the studio. In desperation, we returned there in the Land Rover. Guess what we found? The rack with the microwave receiver had not been turned on. I went for him but they held me back. About six hours later, it was all over. I swear it was the worst day of my life. Everyone else shot through to the OB, leaving me on my own in the studio with 20 or so screaming Arabs. The TR22 broke down; we had to go to the standby transmitter. I'd patched the OB link into an input of the TS11 that I didn't know was a sync-adder (I make mistakes, too) then had to hard patch it to air, until I could figure out how to match it to the mixer. The audio console blew up. Then, when it was all over, and the heroes returned, I heard Crunchbox thank someone for his help. "We couldn't have done this without your help, Ed." I can hardly wait for the end of my contract, Dick. And as if things weren't bad enough, the locals are muttering darkly: "We can run it all by ourselves." And others are saying, "It's time to go to colour." Write soon, mate, help save my sanity. I'd like to hear how you're getting on in the real world, Australia. As ever, Colin. ~ wpoD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. WOOD FOR C Now Stocking Gel Type Batteries Ideal for security systems. Five popular sizes of leakproof lead'acid batteries GEL PS-612 6V 1.2AH $17.50 GEL PS-640 6V 4.0AH $27.50 GEL PS-1212 12V 1.2AH $24.50 GEL PS-1219 12V 1.9AH $31.00 GEL PS-1265 12V 6.5AH $45.00 IJ.. Cl Stop giving your projects the 'Home Made' look! We're now stocking a range of cases that really are professional. From Iskra, they feature wrap-around top and bottom covers with a chassis having front and rear panels and two concealed side panels. The sturdy canying handle can be tilted and locked into position. Rubber feet are also provided. Finish is a pleasing dark grey/light grey enamel with a satin aluminium handle. Ideal for R.F shielding. Side panels are predrilled to take PCB's etc. We are stocking four handy sizes HTF-1 40x180x154mm $47.45 HTF-2 80x180x154mm $49.40 HTF-3 80x270x254mm $51.40 HTF-4 80x360x154mm $55.40 ~ r- s a";;-$$ ~;~pu'ia7 G Ct: a IJ.. Cl a ~ ~ G Ct: a a , MAX232 Chip! ~ :i:'-l Ct: a IJ.. Cl a ~ I Yes the genuine article from Maxim which I normally sells for $12.50. This 5V poweredl Idual RS232 Transmitter/Receiver meets all Ithe RS232 specs. Built-in converter for thel 10V supplies. Low power CMOS handles I I ±30V input and provides a 9V output swing. lldeal for battery powered systems. Wei I have bought a large quantity so you save I .J I nearty $5 at only $7.95. .. _________ _ ~ G Ct: a IJ.. Cl a ~ ~ G Ct: a IJ.. Cl a ~ - 0 I .. ii ii ii ii ii High Quality All Metal Instrument Cases ~ - NATIONAL 32000 DESIGNER'S KIT We've had to order more of these kits each time we advertise them. They are only suitable for advanced computer hobbyists and professionals. The 32032 kit comes with a 32082 Memory : ii ii ii ii ii ii Everything you need to make PCB's • O .. 0 DRILLS EZ C?SC/1 0.70mm CARBIDE DRILL EZ CBSC/1 0.80mm CARBIDE DRILL EZ C9SCl1 0.90mm CARBIDE DRILL EZ C10SC/1 1.00mm CARBIDE DRILL EZ C12SC/1 1.20mm CARBIDE DRILL EZ HSS.70 0.70mm HSS DRILL EZ HSS.80 0.80mm HSS DR Ill EZ HSS.90 0.90mm HSS DR ILL EZ HSS1 .00 1.00mm HSS DRILL EZ HSS1.20 1.20mm HSS DRILL FILM & BLADES EZ1463/2 8.5x11 FILM 10x10 GRID EZ1466/2 11x17FILM10x10GRID EZ3108 X-ACTO No.11 BLADES x 5 EZ3110 X-ACTO No.16 BLADES x 5 EZ3141 X-ACTOCUT-ALL KNIFE 10.85 10.85 10.85 10.85 10.85 5.30 4.10 4.10 2.85 2.60 4.10 7.35 3.80 3.80 4.45 PADS EZ5000 0.78mm OD DOT 1.27mm x2 EZ5001 0.78mm OD DOT 1.27mm x4 EZ5003 0.96mm OD DOT 1.27mm x2 EZ5004 0.96mm OD DOT 1.27mm x4 EZ6841ISTRIP 1.27mm OD DOT 2.54mm x1 EZD216 2.03mm OD DOT EZD101 2.54mm OD DOT EZ5014 2.54mm OD DOT 3.96mm x1 EZ5015 2.54mm OD DOT 3.96mm x2 EZD239 3.05mm OD DOT EZD102 3.18mm OD DOT EZD103 3.81 mm OD DOT EZD144 3.81 mm OD DOT EZD247 4.06mm OD DOT EZD138 4.74mm OD DOT EZD139 5.08mm OD DOT EZD109 6.35mm OD DOT EZD111 7.62mm OD DOT EZ5020 1.27mm PAD 2.54mm x 1 EZ5021 1.27mm PAD 2.54mm x 2 EZ5017 1.78mm PAD 2.54mm x 1 EZ5018 1.78mm PAD 2.54mm x 2 IC's 1.09mm 14 DIL 2.54mm x1 EZ6760 EZ6761 1.09mm 14 DIL 2.54mm x2 EZ6763 1.09mm 14 DIL 2.54mm x1 EZ6764 1.09mm 14 OIL 2.54mm x2 EZ6013 1.09mm 14 OIL 2.54mm x1 EZ6071 1.09mm 14 DIL 2.54mm x2 5.45 5.45 5.45 5.45 7.40 4.15 4,15 5.45 5.45 4.15 4,15 4.15 4.15 4,15 4.15 4.15 4.15 4.15 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 Bubble Etcher Ideal for Prototypes and small runs. Uses a minimum of etchant - ammonium persulphate - and you can watch progress. Air pump provided to give uniform action. Vertical slot is only 12.5mm wide. Two sizes $109.00 Large 300x220mm $ 84.00 Small 225x 115mm EZ6014 EZ6453 EZ6244 EZ6004 EZ6109 EZ6900 EZ6901 EZ6535 EZ6536 EZ6903 EZ6904 EZ6984 EZ6985 EZ6987 EZ6988 EZ6906 EZ6907 1.78mm 14 OIL 2.54mm x1 1.09mm16DIL2.54mmx1 1.09mm16DIL2.54mmx2 1.78mm 16 DIL 2.54mm x1 1.78mm16DIL2.54mmx2 1.78mm 18 OIL 2.54mm x1 1.78mm 18 OIL 2.54mm x2 1.78mm 24 OIL 2.54mm x1 1.78mm 24 OIL 2.54mm x2 1.78mm 28 DIL2.54mm x1 1.78mm 28 DIL 2.54mm x2 1.09mm 40 DIL 2.54mm x1 1.09mm 40 DIL 2.54mm x2 1.09mm 40 DIL 2.54mm x1 1.09mm 40 DIL 2.54mm x2 1. 78mm 40 OIL 2.54mm x1 1. 78mm 40 DIL 2.54mm x2 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 0. 79mm EDGE 1.27mm x 2 0. 79mm EDGE 1.27mm x 4 1.56mm EDGE 2.50mm x 1 1.56mm EDGE 2.50mm x 2 1.57mm EDGE 3.175mm x 1 1.57mm EDGE 3.175mm x 2 2.36mm EDGE 3.962mm x 1 64 PIN DIN 51612 x 1 64 PIN DIN 51612 x 2 64 PIN DIN 51612 x 1 64 PIN DIN 51612 x 2 64 PIN DIN 41612 x 1 64 PIN DIN 41612 x 2 64 PIN DIN 41612 x 1 64 PIN DIN 41612 x 2 96 PIN DIN 51612 x 2 96 PIN DIN 51612 x 2 96 PIN DIN 41612 x 1 96 PIN DIN 41612 x 2 5.45 5.45 5.45 5.45 5.45 5,45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 5.45 0.51mm x 0.13mm TAPE 0.66mm x0.13mm TAPE 0.79mm x 0.13mm TAPE 1.02mm x 0.13mm TAPE 1.27mm x 0.13mm TAPE 1.57mm x 0.13mm TAPE 2.03mm x0.13mm TAPE 2.36mm x 0.13mm TAPE 2.54mm x 0.13mm TAPE 3.18mm x 0.13mm TAPE 5.08mm x 0.13mm TAPE 6.35mm x 0.13mm TAPE 12.7mm x 0.13mm TAPE 3,80 3.80 CONNECTORS EZ6805 EZ6809 EZ6823 EZ6827 EZ6704 EZ6716 EZ6708 EZ6869 EZ6870 EZ6875 EZ6876 EZ6878 EZ6879 EZ6881 EZ6882 EZ6872 EZ6871 EZ6884 EZ6885 TAPES EZC3000 EZC3002 EZC3004 EZC3006 EZC3008 EZC3010 EZC3012 EZC3014 EZC3016 EZC3018 EZC3020 EZC3022 EZC3024 MISC EZ6842/STRIP EZ6843/STRIP EZ6839/STRIP EZ6851 110 EZ6029 EZ3381 IN LINE 2.54mm x 1 IN LINE 2.54mm x2 1.65mm D SUB 2.77mm x 2 D825 PATTERN 1X SCALE 2.36mm 3 DOT T05 x 1 TEMPLATE 2X SCALE 4.05 4,05 4.05 4.15 4,15 4.15 4.15 4.15 4,30 5.70 7.10 14.80 7.45 7.45 7.40 5.45 18.95 Exposure Box 30 Handy size for prototypes, Scotchcal etc. Exposure area 230x115mm. Twin SW UV lamps. Built-in timer with LCD display. Safety interlock $175.00 Management Unit, 32201 Timing Control Unit, a 32081 Floating Point Unit, a 32202 Interrupt Control Unit and 2 "Tiny Development Systems• (TDS) PROMs. Massive pack .,,0 0 of literature These are definitely not for beginners but what a great buy at only $180. (P&P $6.00 local or $15.00 airmail - it's a big pack!) See our Ad in March E.A. for full details GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road , (Corner Beatrice St.) ING IN Nsw Lane Cove West, N.S.W P.O. Box 671 , Lane Cove N .S.W 2066 Telephone: (02) 427 1676, Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $_5.00 to cover postal charges. Next day delivery in Sydney add $5.00. All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED ::0 (') l: ~ {/) I PRODUCT SHOWCASE I Hitachi's 20MHz dual trace oscilloscope Chl and Ch2 displayed), Chop (for chopped trace operation with Chl and Ch2 displayed) and Add. The last named mode adds the two vertical input signals together and displays them as a single waveform. Pulling the "Invert" knob (to the right of the Mode switch) inverts the polarity of the Ch2 signal and thus allows a differential display mode for the two input signals. Below the Mode selector is the internal trigger selector switch. This allows the timebase to be triggered from the Chl or Ch2 input. The third option is "Vert". This allows the unit to display two traces which are not locked together in frequency or phase. (You have to select the ALTernate trace mode for this to operate properly). Twenty years ago a dual trace oscilloscope that could display 20MHz signals was a pretty hotshot instrument. Nowadays it is pretty much a standard instrument but even so there are differences between competing instruments. Here we take a look at Hitachi's model V-212. The first thing you notice about the Hitachi V-212 is that it is a very compact instrument for one· that has a 15cm (diagonal) display. It measures just 310mm wide, 370mm deep and 130mm high, while the weight is 6kg. It is fitted with a tilting bail underneath so that the screen can be angled up for easier viewing. Front panel controls are simple but offer all the wanted facilities in an instrument of this price range. Right next to the screen is the power switch and below that are two small knobs for trace brightness and focus. There is also a screwdriver access hole just below the power switch. This is for trace rotation. It enables you to adjust the trace on the screen so that it is ex82 SILICON CHIP actly horizontal and parallel with the on-screen graticule. The rest of the front panel is divided into an upper and lower section. The lower section carries the controls for the two vertical amplifiers while the upper section carries the timebase and triggering controls. Vertical amplifier sensitivity is switchable in ten steps from 5 volts/div to 5mV/div (with one division equal to 1cm). Pulling out the variable knob ganged with the sensitivity switch gives an extra 5 times gain so the ultimate sensitivity is lmV/div. In the centre of this lower section of the panel is a mode selector. It selects channel 1, channel 2, Alt (for alternate trace operation with Timebase selector The timebase is switchable in 19 steps from 0.2s/div to 0.2µ.s/div. The 20th position of the switch gives X-Y operation for Lissajous displays. Pulling the 10 times switch then gives an ultimate timebase speed of 20 nanoseconds/ div. Bandwidth of the V-212 is from DC to 20MHz ( - 3dB point) for all sensitivity ranges down to 5mV/div. At lmV/div the bandwidth is stated to be at least 7MHz. As you might expect, the unit easily meets this spec. It has a useable sensitivity up to more than 40MHz and will trigger on much higher frequencies than that. In fact the V-212 has two outstanding features. The first is its reliability of triggering and the second is its fine bright trace which has a very good contrast ratio with the blue screen. In this respect, it is better than much more expensive CROs. Build quality We took a look inside the unit and can report that it is very well made. It is has two large boards which are mounted one on top of the other with shielding in between. All the electronic componentry appears to be quite standard and should be readily available so servicing should not be a problem. The unit is supplied with a 55-page instruction booklet which includes the circuit diagrams. The manual is wellwritten and comprehensive. In any case, the Hitachi V-212 comes with a two year parts and labour warranty which is an indication of how reliable the product is. It is also an indication of the local distributor 's commitment to the product. The Hitachi V-212 is priced at $830 without sales tax and $996 including sales tax. These prices include two Hitachi 10:1 (fixed) divider probes. Considering the two-year warranty and Hitachi performance and reliability, the V-212 is a good buy. For further information, contact the Australian distributors, Bell Test & Measurement, 32 Parramatta Road, Lidcombe, NSW 2141. Phone (02) 648 5455. (L.D.S.) New instrument cases from Geoff Wood Video switcher for multiple VCRs If you are one of those people with more than one video source, such as two VCRs or perhaps a video player, you may find the Arista VS300 A/V Video Selector to be of use. It takes the signals from three video sources and will select one set for viewing on a monitor. Entirely passive in operation, this video selector is effectively a 3-pole, 3-way pushbutton switch with mechanical latching. It has colour coded RCA sockets to take the video signal and stereo audio signal from three VCRs and it is supplied with a 3-way lead for connection of the output signals to a video monitor and/or stereo amplifier. For further information, contact your nearest Arista retail outlet. high and 154mm deep, not including the handle or its plastic feet. The retail price is $47.40. For further information, contact Contact Geoff Wood Electronics at 229 Burns Bay Road, Lane Cove West, NSW 2066. Phone (02) 427 1676. These days a lot of test equipment is housed in plastic instrument cases but there are some applications where these are not suitable either because of their construction or appearance. For these situations, Geoff Wood now has available attractively finished cases of sturdy aluminium construction. These are finished in two-tone baked enamel and have a swivel handle which doubles as a tilting bail for more convenient viewing of the front panel. The dimensions of the case pictured here are 180mm wide, 60mm Digital temperature • measurmg instruments Beckman Industrial Corporation now has a range of digital temperature measurmg instruments which includes benchtop models, handheld units, temperature calibrators and a range of accessories. The handheld models have ruggedised splashproof cases with LCD readout and membrane switches. Coupled with the appropriate ther- mocouple or thermistor sensor. they can cater for virtually any temperature measurement application. NOVEM BER 1988 83 NEWPRODUCTS-CTD From November 1st, Rod Irving Electronics will have a store open in Sydney. It will be open six days a week and carry the full range of Ritronics products. The address is 74 Parramatta Road, Stanmore, NSW 2048. Phone (02) 519 3134. High speed mouse has low price If you have a software package that includes a mouse you will know that you can't move the mouse too fast otherwise it momentarily disappears. This drawback has been greatly reduced with this new mousl which can be operated at speeds up to 60cm/sec. In other respects it is completely standard and interfaces with all the popular software packages. It automatically selects between Mouse Systems and Microsoft modes and is supplied with software to test, set up and operate it. Other features include high resolution (equivalent to 290 dots Pictured is the microprocessor controlled Beckman 445 which can measure up to 2000°F with 1 ° resolution (ie, 4-digit readout) and up to 200°F with 0.1 ° resolution and 0.2 % accuracy. It has a max/min measurement facility and is available with type K, J or E thermocouples. For further information on the Beckman temperature measuring instruments, contact the Australian distributor, Anitech, 1-5 Carter Street, Lidcombe, NSW 2141. Phone (02) 648 1711. Posistors for protection of semiconductors IRH Components has released a range of positive temperature coefficient thermistors which they call "posistors". They have a large increase in resistance for a small increase in temperature above their switching or "detection" point. They are mainly intended for prot.e ction of high power transistors and thyristors against over temperature. Since they are small solid state 84 SILICON CHIP Rod Irving Electronics store open in Sydney New Jaycar store for Parramatta per inch or more) and selectable baud rate between 1200, 2400, 4800 and 9600 baud. Priced at $99 including tax, it is available from Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 427 4422. devices, they have excellent thermal response and are immune to mechanical vibration. Two series of Posistors are available, PTH 487 A and PTH 59F. The PTH 487 A series are designed to be attached to power transistors via the case mounting screws. They are intended for connection in series with the base leads and will reduce the base current if the device temperature exceeds the design limit. The PTH 59F series are disc type Posistors used to protect loads and semiconductor output stages against excessive output current. For further information on the Murata Posistor range, contact IRH Components, 32 Parramatta Road, Lidcombe, NSW 2141. Phone (02) 648 5455. As from November 1st, Jaycar's Carlingford store will be transferred to 355 Church Street, Parramatta; ie, on the corner of Church Street and Victoria Road. Plenty of parking is available. Handy pack of cable ties Whether you are a keen gardener, TV antenna installer or an electronics enthusiast, nylon ea ble ties are very useful. The old art of cable-lacing seems to have been lost in favour of the ease of using cable ties. David Reid Electronics have a handy pack of black nylon cable ties in four different lengths: 270mm, 200mm, 150mm and 100mm. 20 of each length are supplied, giving a total of 80 for a price of $3.95 . Neu, l f ONOM I [ Al A/ 8 PRlnTER QUARTZ GUITAR SWITCH BOH r~~t~~ re f!~~;n9,,~o~c. I - - - , ,x no te / pi !eh , et11 9.95 1n - bu11t mik e or di r ec t , Se nul HS2n Oflltj fi/H, plug 10 t une, one octave a bove or below each ,wi tch sett ing, e mp h fier out put , 9Vdc . 2 Y 01325 ,o( lreh u,ti · butl ori A - U ,,,n tc.lt on 10D . CO!v1 P UT ER[i§s ~1 ,.-6,,.0D RESS : 6 : L ABE L S :=: 89 x 2 3 mm 1 co l umn $ 8.50 / 100 0 el, o 2 end 3 colu mn ,time price 89 x 36 mm 3 column $9,90 / 1000 105x 42mm Z eal, $1 1.50 / 10 00 127 x42mm Z eal, $12.50 11 000 l27 x6 l mm Zc ol , $15 , 50 / 1000 TELEPH □ nE .:;,_11 BUG ALERT $35 '~:.\ .. <;,. ·:·-/ f l eshing r ed LED 1nd1cate s :!f\; /!;I ~~~;o~~o~~ ~~~e:e 1 1 r"f11t\~ nt~ --- Gr een LED 1nd1cate3 cl ea r l ine Fi t ted w'l t h Au:, t pl ug / :,oc kl:!t , attache s to telephone , in,te l1 at1o n kit i ncl uded . UIDED CINE ADAPTER Tren,rer nome mov1 e, end shdes onto VCR video ta pe Pro Jects onto mi ni ,c reen , u!le video ca me re to r ecord on tap e. Fully edj u,teble w"Hh i nstr uct1ons . Save ~our va l ueble ,tl film,. $ PHOilE LlnE ____________::i TESTER ~~ fo r lete :,t USA ~~_j ~ Cet type 4 p1n phOne 24-3068 co nnector:, Duel colour EA $ I pas, neg or open c1 rcu1t Q Headphones ., Cot No0 I 06-11 s7 eo by T osh ib e/EM I New end undamege d but pla, tic he edbend need, st re ngthe ning! IOO 's.so ld.but no guar antees et th1 s pr ice ! pr Or i9inel pr ice $ 69.95 RRP $ 39 95 below co,t at $20 pr. -RUDIO~UIDEO •~ '· ·.• ···· IN-LINE ··········· · ·· ···· ····· ·• VCR / V CR EnHRnCER s69 Connect bet'w'een t'w'o VCR mechine, to i mp r ove eud10 end video s1gnal3, 'w'lt h ,epe r ete co ntro l, end multi -p urpose le6d3, 240V AC pow-er Cat 24 - 102 7 rm WIRELESS IDIKE and RECEIVER f or PA et c. 3 7. 10MHz x ta l c on t r_o l le d j f or s te b1l 1t y , ., r eng e I OO m . 1 c,;~ 3~~~ 98 $95 BRRGBin !! ! .. .IBffi PRITITER CRBLES [la i;.- s24 ·~ c. ~0~ ~01 Ideal for lerc;ie area, upto 40 3Q met re,, edju,teble ,en,itivit\j, 'w'el k- te, t plu, me mory LEDs , N.0/ N.C . outp ut, 1 ZVdc 35 I 16 now$ T HERMAL FUSES Pr otect expensive se mi co nductors and po1.,1er de vi ces 1.,11t h non - r e,e tta ble heat 3enS1 t1ve safety fuses, ope rat i ng et 58 deg cen tl 9r ode . Copec1 t y 24 0V 15 Amp . ~ INFRA-RED Just send S2-00 to above address for post/handling. VIDEO CASSETTE AD CLEANER OR BET ff Cat Were 04- I I 46 $ I 2 ,50 Nov onl ti1 04-cf149 6 S EA Regu l oted 3R POWER SUPPLY KIT c,, 11 - 15 4 0 INNOURTIUE WRLL - MOUNTING 9 01 - 5305 -1 Economy RLRRm Control Module $18 c, to 1-0 946 PANEL SPEAKERS C i nsta nt• N.C. de lay, 20 sec exit del ey end re, et 3 mins, on - off switch, 12 Vdc 2mA - You cho ose·- 250mA , 50 0mA , 750mA. I A, 1 SA. 2A, 3 A. 4 A . 5A , BA, I OA, I SA, 2 0 A each • Lucky Dip Assortments 500 0 .Sv resist o rs 20 0 . I 00 .. 30 . .. 9ree nca ps 45 .. . e lectro l 4,1hc, 2 0 .. potentiometer., 25 .. ... .. pres e t pot"' 3ll mi ca ca p:, 40 rad i o / TY k nob , EACH PAK IS . veno us f uses 25 .. .. ..... rf chokes 2 0 .. rf/if/ osc co il :, I O a ud i o tr a n,fo r m so .. .... .. . tog,1ri p, RECHARGEABLE I.E.C. Ma i n s 74 0V NO I SE F I LTE R Hf CT R IC SCREW- ;q'J ,· 1 3 A mps ,:-';~\'~~~:•,t.,' I .E. C. ;'.,~~" './,r::•;>' M 1:J iri 5 l e od . ~- 15.50 j1 L1 3 pi n pl ug , ,, ·1 1 :· •"" tdt! ~ i,4. 5 0 S"i9.so S7. 95 Save $3 ARTI- TlnKLE fflODULE Mi niature ~ Side - Cutting ' '-.. f or parall e l 2 nd ph one in st al Tir ed of those e nnoy1ng ti nkle, whe n dialli ng out? Elim1nete t hem now with An tiTelecom A.T. Module . Onl y Tin kle tw o connec tion , 1n ser ies Modul e v11l h t he bell. f ech We r e $17. 45 Hig h quolity , 11 5mm long, in:, uleted hendle,, be,t for EA elect ronics assembly etc. Ca t SCOOP PURCHASE! 20- n20 $8 M~di,r TRANSn,~1 (Based on AEM550 I Sept . 1985) · , 1gnsls to TV :,et(,) 'w'1 t h10 30m r enge on ~ ,_. ._ · ; .. UHF Ch36 . Nod1rec t • w1 r1 n9 needed :,o u,e 'w'lth vi deo came r a, toot 9V batt or 240¥ AC Cat 0 4-115 5 I 13 15 DIP ~ ~!~ e luc ky num be r 1 An in te re::i t1n9 collfic ti on of samples. manu foct ure r ·3 over- r un s a nd exce:is, 1ncl lC" s, po1s . d10des , res istors. capec1tor s , knobs , , ..... 1tchesend lots of other use fu1 Junk I PU . SHBUT DIG IT A L TON ' , , TELEPHONE ; ' • DIALLER S • : • '(,,~\h s10 num be r memo r y r e -d iel feet ur e, WA S $15 • Cat 2 4 - 30 7 0 Easi l y in sta ll ed, no t Telecom approved. Ex - Comput e r 90,000uf 20v 50,000 uf 25v ~::~6~~~ ;~: 31,OO Ouf 40 v I El e ctros 34 ,800u f 40v 20 ,OOO uf 45v 12,000uf SOv SOv 7,800u f 60v 22 .0 00u f ; :~~~~ ~ EL EC TROL YTI CS 5 9 Ne w, top quolity 34mm d i am H 8 5 mm h i gh 0 : \ ns oo...... .. ea$ 1O+ ______ ee $8. 20 f PUSH - BUT TO N T V T UN ER PCBs ~ $4 1\4;v S 4. BOOuf 200v ea $8 g 1------------8 , QQQ U f 7 5V W Cleans oi r of tobocco smoke ond bacteria; increose concentr11tion . Full instructions ore included . 150, 000uf 5v 42 ,OOOu f I Ov 60,00 □ u r 1 Sv $14.ss AUDI O/\l lO EO T Vaudio end video Send kit A deluxe version of this most popul11r kit WHh HIGH/LOW output switch, higher vo1t11ge ( - 9500v) , extro Ion emitter, professional $19 .95 Any num ber of S'w'ltctn ng co mbinet10 ns et helf hour rnte rve\s cen be performed rn e 24 hour peri od Cat 04-0105 4 $ ~ 95 Negative ION Offer _ 240V AC I OAMPS 24HR cabinet ond Ion emitter tester . Users cl11lm o greoter fee11ng of well being ond r eloxntlon . ~l{y CAR SPEAK ER T IME SW I TC H Col ~~~'tte~ nw $25 ~ lweezer, ond $49 0 40 M ITSUBI SHI PROGRA MMABLE _ .- $29.so Generator ea MU LTI - PU RPOSE Includes heet,i nk , . reamer, , craper , bru,h, Wes [;l[b□[3[3~ 2 •50 5B OC $9.95 $ 29 ,c rewdnve r , 20~2 4 56 $ · Microtemp model 4I 36A Su 1I Sig ma and others ex t r a- th in for door or Each pane l mountin g, 2 0W Elongated c hsss1s, 4 " & s·· model, eva1 l Conver I, UHf out pu1 , g Sove $ 40 VCR, co mp utt. r or TV ge me, to VHF :,i9na l , CH 1,3.o r 4 1 2V de or me1 n:, po.. . ,. er ed KIT <f •. •----Li Cot No .. 1 1-1550 ' SOLDERIDG TOOL Inbui lt siren , N.O. Was $ 39 .so UHF to VHF/ ·- ~ ; TV SIGNAL oown LconvERTER was $ 69 Thin flet -.penel st yr e ne foem'w'e ll spee ker s ( Bf? 15W 36 0x280x5 2mm) s tyl ed e, e print or u,e 1,1 our o'w'n phot o/pei nti ng Fr- eq . 9 0- I 70 00 Hz . w-e re 15 PA KS TO CH OOSE FRilf"1 •13 g 7 rt:~- t,}od::. $109 5 3AG \diell l fo r CB. ca r 3te reo, aler rn, 8. tnitt 1: r y charg er Has Lr·1723 regul ato r, all pa rt, -t i n~tr- uction:.i. ~~: : 0 ni-r,ed b1:1tteri,:,s, f(1r 'wllfd er,d ( .it reverse,4 tips • c narg~r i ncl ~·o -.2308 0 2AG 250 0 .25v, 0 . S v , 1v re,i,tor, He1r.,·1J ,j1Jt v prl) f':' 1?•io r,o l tr.11:i : , '-.__J Sefest, most re lii,ble type , LED wal k- te, I li ghl , N.0/ N.C. contacts . 12Vdc , MIN I SIZED 12M We s 11 rusesfors2 or ■ ■ - 12- 15V DC Hi gh Qual ity DRIVER '''"' r----:; DETECTORS 120 pages in full colour! VHS ~ BEST PA SS IVE a11 30t D8 9 .:,. 1Le, hu;,h den:,1ty •.--:...,--c:: 14 PI N M ol e .. .. .6. 6 5 '\ . 15 P I N M ol e .. ... 6 . 6 5 15 PI N Fem ale 7.45 082 3 r1e'w 23 pin co nnector , Mol e / Fe m o l e 3 .4 5 Covcc 2 .75 ( BSR repl ocement ) Cot 03-2057 A, mi,de for AWA, 2 3peed 3 3/ 4 5 RPM cers mic cer tdd9e, 12¥ DC oper ehon, 24 0VAC pl ug - peck $ 7.SO All ne\,1" 1 FOR CAR ALARM S ( et 19 - 52 ,,2 ARISTJ>.. . COIDPUTER ~ conn ECTDRS -~ ·. 39 UL TRRSOnIC Ag DETECTOR ONL y $,: Electronics Cntn l ogue 1.5 m e tres Ce l No 'w'cre 16 · 0770 ru119 Automati c model , $ r-i midi rect dnve . but noisy! FOR DI GITRL conPA CT DI SC The diffe re nce i n , ound dynamic:, i , emezrng! Clean and cri,p 1,,1ith excellent clar it y. l ightwei ght de, ig n end ,oft pads for comfort , fu lly adJu,teble headband. 20 - 20KHz res P. 1OOdB Ht 1Khz sens . ~ - ,,,,,, UA 339 UA 748 CA 340I LM376 14 89 e~ i f i i i i i i : ., l was$69 40 018 7406 , /4 011 7473 40 2',A 749 0 404 9 ONLY 4501 WHI L[ 45168 STO CKS 472 46 LAST I NE 55 5 LM55 6 (:i ULTRASONI C DETECTOR FOR HOME, SHOP, OFF I CE Covers door, e nd · •· · 'w' i ndo'w', etc Ideal fo r garage or 'w'Orkshop . I ncl udeo d1g1lol keypod + $ cont rol module wit h 4 Cet No reed ,w-1tchese nd ,iren . 01-0 9 20 The I O ke y d1g1t el pad r equire, t he co rr ec t 3 d1g1t code end may be ,et for iM tant or delayed e nt r y. Installation is ,imple , ell \.t i ri ng s upplied , uses STEREO HEADPHDilES •················ - ,-,.-,-,·,, .o . ·· Compl e t e RLRRffi SYSTEm Rffi/Fffi Stereo Radio 15 1 DO s9.oo LED 1 nd1cetes :,tetu:, e.g Were $ 4 .95, ...,..t,et a BARGAIN thi s is l H:! SEllO UT! til-FI STE~E O TU~NTA~LES SCOOP PURCHA SE • Cat 01- 153 2 w a, $1 9 9V botter y . r.~~~i~ $ CAR S EXTRA S I REN AVAIL . $15 Plug, i nt o e:d,ti ng module O1 - 0 92 1 ACCESSORY KIT $11 3 ex t r e r eed S'w'i tc he,. Cat O I - 0 92 2 lfae vi t h most al ar ms , detects mov eme n! in,ide the vehi cle, r elay N.0 . / N.C. 1 ZVdc 6 "'1 .95 EX-COMPUTER WIPER DELAY CONIROL FOR [A 2 ~•L. Bs with 8 .1.. DPDl ou st1 - bult on •.....-it rhe-s , simi lar to lso sl et. e nd 8 x ·oo ~ mu1 1i - turn tr impot,. e, u:ml ( et 2 4 - 000 1 i r AWA , e1,. NEWPRODUCTS-CTD multiturn potentiometer varies the discharge potential from 2kV to 25kV, with the voltage being indicated on a 4-digit liquid crystal display. With the addition of a vacuum relay attachment, current discharges with a risetime of less than one nanosecond may be applied to the equipment under test. For further information, contact Westinghouse Brake & Signal Company (Australia) Ltd, PO Box 267, Williamstown, Vic 3016. Phone (03) 397 1033. High voltage probe Low cost high density floppy discs from Microdot Rod Irving Electronics and Microdot are now marketing 5.25-inch high density floppy discs at the low retail price of $23.95 for a pack of 10. They have a lifetime warranty and come in a useful plastic box rather than the cardboard box usually supplied with low cost floppies. They are available from all Rod Irving Electronics stores and from Microdot, 46 Little Latrobe St, Melbourne and 177 Springvale Road, Nunawading, Victoria. Electrostatic discharge simulator These days, one of the problems with solid state equipment is its vulnerability to damage from electrostatic discharges. To test this characteristic, Westinghouse has released the Schaffner NSG 432 ESD Simulator which is capable of providing a known high voltage discharge. A Numeric keypad for rectangular cutout This small numeric keypad will fit into a 44 x 55.5mm cutout and has an unencoded output brought out to a row of eight pins at the top. The keys are the same as for digital phones with 10 numeric keys plus two utitlity keys. 86 SILICON CHIP The keypads are available at Jaycar stores at $3.95 each. J.V. Tuners have a neat high voltage probe with self-contained metering for measuring the EHT (extra high tension) in television sets and other sources of high voltage. The probe is priced at $70.00 plus sales tax where applicable. For further information contact J.V. Tuners, 216 Canterbury Rd, Revesby 2212. Phone (02) 774 1154. Dynamic balancing for electric fans This story came about because a repair job to a radial flow fan threw it out of balance. The problem was how to balance it dynamically when no facilities were available. This is what you can do when you are thrown back on your own resources. By STEVE PAYOR A common nightmare for the doit-yourself enthusiast is the "simple" repair job which goes wrong half-way through. Fixing it then becomes a matter of personal pride. After all, who wants to leave something in worse condition than when you started on it? Recently, I was overhauling an Email CC150 air cleaner. This is about the size of a small bookcase and contains a large radial flow fan which moves large amounts of air through a hospital grade filter. I have a couple of these at home and they maintain the air at almost clean-room standards. Anyhow, I accidentally cracked the outer rim of the moulded plastic turbines, and decided to fix it there and then instead of trying to obtain a replacement. I knew that no simple glue job would stand up to the stress and vibration, so I chose the following approach. First, I glued the joint with 'super glue" (cyanoacrylate) just to hold it together. Then I bound the joint with thin wire, looping it around the fan blades either, side of the joint, so that it couldn't be pulled apart by tension. Then I coated the whole area arou:id the joint, and the wire, with more super glue. When cured, the super glue forms a reasonable base for a covering of epoxy resin; the epoxy itself won't stick to most plastics directly, and the cyanoacrylate is too brittle by itself, but the combination of the two works well. By the way, K106 Araldite (the old "24-hour" type) is the only epoxy to use when you want a repair that will last. Anyway, I covered the entire joint with two coats of Araldite. A smidgin of black oxide pigment was mixed with the Araldite, to match the col- LARGE LOUDSPEAKER MAGNET STEEL CABINET PANEL DOUBLE-SIDED STICKY TAPE TO HIGH-IMPEDANCE AC VOLTMETER PIEZO TRANSDUCER Fig.1: the vibration sensor consisted of a piezo transducer attached to the cabinet via double-sided tape, together with a heavy mass which pressed against the centre of the transducer disc. The output from the transducer was fed straight to an AC voltmeter. our of the surrounding plastic. To maintain the balance of the fan, an identical "joint" was made diametrically opposite. Atte'r curing, it was time to see how good the balance was. With the fan at full speed, it was reasonable but could have been better. The vibration of the steel ea binet was quite noticeable to the touch. Turning the fan slowly by hand did not reveal any gross static imbalance and it became apparent that only a trial and error process would find the correct location and mass of the required balancing weight(s). After a lot of attempts though, finding the exact balance seemed an impossible task. What I needed was a quantitative measurement of the vibration, instead of trying to "feel the difference". Commercial wheel balancing machines use two vibration sensors which measure both amplitude and phase, and so it is possible to calculate directly the mass and position of the weight( s) required for perfect balance, eliminating the trial and error process. I was prepared to settle for an amplitude measurement only, so I would at least know when I was heading in the right direction. Piezo transducer A quick rummage through the workshop treasure chest (alias the junk box) revealed one of those small piezo transducers (similar to Jaycar Cat. No. AB-3440 or equivalent). When the piezo disc itself is removed from the plastic housing, it can produce surprisingly high voltages when flexed with the fingers. I attached it to the steel cabinet with some double-sided sticky tape (around the edges only) and arranged for a heavy mass to press against the centre of the disc. The mass was actually a large fercontinued on page 93 NOVEMBER 1988 87 THE EQUIPMENT YOU NEED, AT BARGAIN PRICES! '""'· --~ . ;,...;;;...,-,... ·· .-·..'...- 1 ARLEC SUPER TOOL RELAYS 10W HORN SPEAKERS White durable plastic. 8 ohms Cat. C12010 Normally $11.95 1-9 10 I $7.95 • . $6.95 1-9 10+ 100 + S.P.D.T. 3A connectors ... S14060 $1 .50 $1 .30 $1 .10 D.P.D .T. 3Aconnectors ... S14061 $1.95 $1.75 $1.30 S.P.D.T. 12VCoi! 10A240VS14114 $7 .95 ·- == $7 .50 $6.95 NICAOS! HUNG CHANG (RITRON J 20 MHz DUAL TRACE OSCILLOSCOPE •Wide bandwidth and high sensitivity •Internal graticule rectangular bright CRT •Built in component tester •Front panel trace rotater •TV video sync filter •Z axis (Intensity modulation) •High sensiti vity X-Y mode •Very low power consumption •Regulated power supply circuit COMPONENT TESTER is the special circuit with which a single component or components in circuit can be easily tested. The display shows faults of components, size of a component value, and charact eristics of components. This feature is ideal to tro ubleshoot solid state circuits and components with no circuit power. Testing signal (AC Max 2 mA) is supplied from the COMPON ENT TEST IN termin al and th e result of the test is fed back to the scope through the same test lead wire at th e same time. Save a fortune on expensive throw away batteries with these quality Nicads and Re chergers! Size Oesc. 1-9 10+ 100 + AA 450 mA.H. $2.95 $2.75 $2.50 C 1.2 AH $9.95 $9.50 $8.95 $9.95 $9.50 $8.95 D 1.2 A.H:- RECHARGEABLE 12V 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 S19.95 • Cutting • Drilling • Milling • Erasing , etc. Features : Operates on safe, low 12 volts from mains electricity via AC adaptor (supplied). Ligtit and easy to handle with touch switch and !ock for ~;t~~-ufi,tg~n~ '. ~~M~ ~:~~rr~r~mm holes in steel. 2 yea r gu arantee Contents: • 12V Super Tool • Plugpack AC adaptor • 1 spherical milling cutter • 1 wire brush • 1 grinding wheel • 4 drill bits, 0 .6, 0 .8 . 1.0. 1.2mm • Set of 5 chuck collets • 6 eraser sticks • Instruction sheets Cat. T12300 .. .. .. ...... . ..... $64.95 $12.95 ~~~~~6~~ta~~bii~~i"1ellow diode and transistor test, continuity (with buzzer) , capacitance meter, up to 20 amp cu rrent measurement and comprehensive AC/DC voltage , current and resistance ranges. 'tf~\~ 8~~/r~ easy board insertion . MODEM TR AN SFORMER PCB pins, spacing 25mm . equipment to line , 15mm between equipment pins, 25mm between line pins. CAT.No. 1-9 10+ $14.95 1-9 10+ $1.20 $1.00 100+ $0.90 $13.95 CRT (.;A f: 6M(150mm) Flat-faced h19~ brightness CAT with ln1erna1 Graticule . Effective display area: 8 x 10 d1v (1 div 10 mm) Acceleration potential : 2KV ECONOMY TRANSFORMERS VERTICAL Operating Modes : CH-A. CH-8. DUAL ADO (CH-8 can be inverted.) Dual modes: Alter: 0.2ufs - O.Sms/div. Chop. 1ins - 0.5sldiv . CHOP frequency 200KHz approximately. Deflection fa ct or : SmV1div 20Vtdiv +' 3%. 12 ranges in 1-2-5 step with fine control . Bandwidth : DC : DC - 20MHz ( 3d9} . AC: 10Hz - 20MHz 3d8) . Rise Time : Less than 17ns Overshoot : Less than 3% Input Impedan ce: 1M ohm , 5% . 20pF + 3pF Maximum Input Voltage: 600Vp-p or 300V {DC • AC Peak ). Channel Isolation: Better than 60 dB at 1 KHz TRIGGERING ~~~;(~~;~!~~~~ 0 t ~sj~~n'~ / NlxEfEi~L~{ _d;~~~i~~t~~f;r~~~ b(}. ~ore · more than 30MHz ). Source : INT. CH-A. CH-B. LINE and EXT. Slope : Positive and Negative. cont1nuosly variable with level control PULL AUTO for free-run . Coupllng :AC . HF-REJ and TV . TV SYNC Vertical and Horizontal Sync Separator Circuitry allows any portion of complex TV video waveform to be 1-9 2155 240V6- 15V 1A Cat. M12155 $9.95 10 TURN WIRE WOUND POTENTIOMETER Spectral Model 534 ¼ " shaft. $9.50 ~~7~~ i~i;i!~~na1i~;Fi:~i~ti~J~r/~lTci1t1 ~~ii~iland TV- V (Frame) are TV-V :0.5s/d1v to 0. 1m s/div. TV-H:50ufs/div to 0 .2ufs/div . l:; xpg.i;:~~~J1q~~ CH-B: X ax,s Highest Sensitivity: 5mVi div COMPONENT TESTER Component Tester : Max AC 9V at the terminal with nc load . Max current 2mA when the terminal is shorted. (Internal resistance ,s 4.7K ohm) OTHER SPECIFICATIONS Intensity Modulation : TTL LEVEL (3Vp-p) ; Positive .... .. brighter. BANDWIDTH: DC - 1MH;: MAXIMUM IN PUT VOLTAGE : SOV (DC -+ AC Peak) Calibration Voltage : 0.5Vp-p +l - 5% , 1KHz +/ - 5% Square wave. Trace Rotation :ElectricaUy adjustable on the front panel. Power Requ irements: AC: 100. 120. 220. 240V 20w Weight : 7kg approximately . Size : 162(H) x 294(W) x 352(D)mm. only $895 (tax exempt only $775) Bulk orders, schools, please phone (03) 543 2166 for special low pricing 10 + CHECK THESE FEATURES .. .. • Push-button ON/OFF switch. • Audible continuity test • Sing le function, 30 position easy to use rotary switch for FUNCTION and RANGE selection . • Transistor test • Diode test • Quality protles • 11.2" High contrast LCD • Full overload protection • 20Amp • Built in tilting bail • Capacitance meter • Instruction manual 091 550 . Normall y $165 Special , only $129 $8.95 2156 240V 6-1 5V2A Equiv (Bourns 3540S, Beckman 7256) Dials to suit 16- 1-11, 18· 1· 11 , 21-1-11. R141 00 SK R 14050 50R R14055 100R R 14 110 10K R14060 200R R1 4 120 20K R14070 500A R1 4130 SOK R 14080 1K R14140 100K A 14090 2K 1-9 10+ $9.95 ~~~~:;~~~?t\~~~~:7~ capacitance meter and transistor tester. :ii:~~~~;~ ~~i~~~(t~e2gJ~~~~es ELECTRET MIC INSERTS M1 0230 METEX M-3650 MULTIMETER 10• 1-9 $13.95 A versatile 12V electric tooi 1ur ... • Sanding • Engraving • Grinding • Polishing ULTRASONIC TR ANSDUCERS Designea 10 transmit at 40kHz (L 19990) and receive at 40kHz (L 1999 1)with up to 20V I/Pon the transmitter. These units can'I be heard and so are ideal for TV remote controls, water level detectors, burgalar alarms, motion detectors and information carriers as they can be either pulsed or used in the continuous wave mode. Full specifications below for design pu rposes. Maximum Input Voltage: 20V rms ~~~~ ~~:~~~~t~~~n~ ~MJ·: 0 110dB min . Sensitivity (dB/v/ubar) min .: - 65 min. Bandwidth (kHz): Transmit: 4.0 (at 100dB) Receiver : 5.0 (at - 73dB) Impedance: Transmit: 500 Receiver: 5000 Cal. L19990(Transmitter) . $6.95 Cat.L 19991 (R-ve,) .. .. $6.95 METEX 3530 MULTIMETER This instrument is a compact, ;uf1Jeddig~~~1tlmogt:raf~~;,,~~~~~~~d DC and AC voltage, DC and AC current, Resistance and Diode, Capacitance, T ransistor hFE and Continuity Test. The Dual-slope A-0 Converter uses C-MOS technology for auto-zeroing, polarity selection and over-range indicali(?n. Futl overload is provided. lt 1s an ideal instrument for use in the field , laboratory. workshop. hobby and home applications. Features ... • Push-button ON/OFF power switch. • Single 30 position easy to use rotary switch for FUNCTION and RANGE selection. • 112" high contrast LCD • Automatic over-range indication with the "1 '" displayed. • Automatic polarity indication on DC ranges. • AH ranges fully protected plus Automatic " Z ERO" of all ranges without short circuit except 200 ohm Range which shows "000 oroo1 - . • High Surge Voltage protection 1.5 KV-3 KV. • Capacitance measurements to 1pF • Diode testing with 1 mA fixed current. • Audible Continuity Test • Transistor hFE Test . SPECIFICATIONS Max imum Display : 1999 counts 3 112 digit type with automatic polarity indication . Indication Method: LCD display. Measuring Method: Dual -slope in A-D converter system . Over-range Indication: .. 1 •· Figure only in the display. Temperature Ranges: Operating ere to +40-C Power Supply: one 9 volt battery (006P or FC-1 type of equivalent) Cat.091540 ....... Normally $139 SPECIAL $109 Cat. M\ 2156 $14.95 $13.95 2840 240V 9V CT Cat. M12840 $5.95 $4.95 2851 240V 12-6V CT 150mA Cat. M1285 1 $5.95 $5.50 2860 240V 15V CT 250mA Cat. M12860 $5.95 $4.95 6672 240V 15-30V 1A tapped Cal . M16672 $14.95 $13.95 RCA GOLD PLATED PLUGS ANO SOCKETS For those who need the ultimate in connection. Essential for laser disc players to get that fantastic sou nd quality . Plug Cat. P10 151 $2.95 Socket Cat . P10 150 $2.25 I SPECTROL MULTIDIALS Numbe~''o(iW,1/;~,1~"1"11 Minor scale Di vision: 1/500 turn Shaft Bore: 6.35mm ( 1/4") Finish: Satin Chrome Body Size : 25.4 x 44.45mm (1 x13/4 ") Depth : 25.4mm (1.. ) Weight : 45.4g (1.6oz .) Cat.R14405 ......... $45.95 SPECIAL, $35.95 MODEL16-1-11 SOLDER ROLLS Atisolutely top quality, un like our opposition_-s! 60/40 Resin cored cat.No. Description Price T31000.7 1mm250gm ..... $8.95 T31002 .7 1mm 500gm ... $15.95 T310 10 .91 mm 250gm ..... $7.95 T31012 .91mm 500gm .. . $14.95 T31020 1.6mm 250gm .... $7.50 T3 1022 1.6"1m 500gm .. . $13.95 T3 t 030 .71 mm 1 metre .. .. $1.50 T31032 .91mm 1 metre ... . $1.25 .. $1.00 Numberof tums: 15 Minor SCale Division : 1/50 turn Shaft Bore: 6.35mm ( 1/4 .. ) Finish : Clear Anodize Body Size: 22.2mm diameter (.875"") Depth : 22.2mm (.875") Weight: 19.8g (0 .7oz.) Cat.R14400 .... .. ... $26.95 SPECIAL, $21.50 Numbe~o? 1~r'ii~ ~J·1•11 Minor Scale Divi sion: 11100 turn Sha~ Bore : 6.35mm ( 1/ 4 ") Finish : Satin Chrome Body Size: 46.04mm diameter (1.812") Depth : 25.4mm (1 " ) Weight: 85.g (3oz.) Cat.R14410 .. $46.95 SPECIAL, $37.50 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) ., a QUALITY 3mm LEDS Cat.No. Col. 1-9 210140Red $0.15 210141 Gm $0.20 210143YIN $0.20 210145Ora $0.20 10 + 100 + $0.12 $0.1 5 $0.15 $0.15 $0.10 $0.1 2 $0.12 $0.12 QUALITY 5mm LEDS Cat. No. Col. 1-9 21 0 150 Red $0.08 210151 G m $0.15 210152Ylw $0.1 5 - 10 + 100 + $0.07 $0.06 $0.12 $0.10 $0.12 $0.10 DB25 CONNECTOR SPECIALS ! TYPE 1-9 10 + 100 + gp 9S 9C 15P 15S 15C 25P 25S 25C $0.60 $0.60 $0.50 $0.65 $0.65 $0.60 $0.60 $0.65 $0.60 $0.50 $0.50 $0.40 $0.60 $0.60 $0.50 $0.50 $0.60 $0.50 $0. 70 $0. 70 $0.60 $0. 70 $0.70 $0.70 $0.70 $0.75 $0. 70 • • • • Light weight Sturdy construction Easy to remove tip Excellent value for money! $11 .95 Cat. T1 1271 ECONOMY ANTISTATIC SOLDER SUCKER • • • • Light weight Sturdy construction Easy to remove tip Excellent value for money ! $1 3.95 Cat. T1 128 1 KEY SWITCHES 1-9 10+ Cat. S12500 .. ....... Normally $7.95 1-9 10 + 25 + $4.95ea $4.25ea $3.95ea ,. cw ECONOMY SOLDER SUCKER 3 2. NEW TRANSISTORS SPECTROL 64Y MULTI TURN TRIMPOTS Cat.No. Description 1-9 R14700 10R ......... $3.50 R14710 20R ..... .. .. $3.50 R14720 50A ......... $3.50 R14730 100R .. ..... $3.50 R14740 200R ... ... . $3.50 A14750 SOOR ...... . $3.50 R14760 1K . ........ $3.50 R14770 2K .. ..... ... $3.50 R14780 SK .......... $3.50 R14790 10K $3.50 R 14800 20K .. ... .. .. $3.50 A14810 SOK ... ...... $3.50 R 14820 100K ...... $3.50 R14830 200K ... .... $3.50 R14840 SOOK ...... . $3.50 R 14850 1 M ....... ... $3.50 10+ $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3.20 $3. 20 $3.20 $3. 20 $3.20 $3.20 $3 .20 $3.20 $3.20 $3.20 HIGH INTENSITY RED LED BAR GRAPH Dimen sions: Overall : 63mm across. 5mm high. LEDs : 10 x 5mm x 1 mm Cat.No. 1-9 10 + 2 10180 $2.95 $2.75 Rod Irving Electronics-Rave two new transistors which will repface a multitude of common hard to get devices. The PN100is a NPNgeneral purpose medium power amp and switch with continuous-collector current up to S00mA The PN200 is a PNP ~eneral purpose amp at collector currents to 1 Amp Both are TO-82 plastic package PN100 REPLACES , PN222 1, PN2222. PN2222A. PN3585. PN3568, PN3569. PN3643 . PN5133. 2N2219A, 2N2222A. 2N3414, 2N34 15. 2N34 16. 2N3417. 2N3700, 2N3704, 2N3904. 2N4123. 2N4124 , 2N4401 , 2N5088. 2N52 10. PN200 REPLACES : PN2907. PN2907A, PN3638. PN3638A, PN3640, PN3644, PN4121 , PN4143 , PN4248, PN4249. PN4250, PN4355 , PN4916, PN4917. PN5910, 2N2905A, 2N3467. 2N3702. 2N3906. 2N4125 , 2N4126. 2N4291 . 2N4402, 2N4403 , 2N5086. 2N5087, 2N5447. PN1 00 Cat. T90001 PN200 Cat. T90002 1-9 10 + $0.20 $0.18 100 .- $0.15 DB 25 CRIMP SPECIALS ! Type 1·9 Female $2.95 Male .... $2. 95 10 + $2.50 $2.50 100 + $1 .95 $1.95 MULTIMETER This instrument is a compact , ru.P,ged. battery operated, hand held ~~a~~~~~:~::r6C ~da1ctng current. Resistance and Diode, for testing Audible continuity and transistor hFE. The Dual-slope A-D Converter uses C-MOS technology for auto-zeroing, polarity selection and over-range indication . Full overload is provided. It is an ideal instrument for use in the field, laboratory, workshop. hobby and home applications . Features ... • Push-button ON/OFF power switch. • Single 30 position easy to use rotary switch for FUNCTION and RANGE selection . • 1~" high contrast LCD . • Automatic over-range indicatio n with the " 1·· displayed . • Automatic polarity indication on DC ranges. -~~~FfQ~'~1~r~~es without short cirruit except 200 ohm Range which shows "000 or 001 -- . :im~W,~M~~;i;;~~~r\<o, Dimensions: 19{L) x 13(W) x 9(H )mm Cat. No. 1-9 10+ H10606 $0.40 $0.35 METEX CAR BATTERY ISOLATOR 4500H MULTIMETER 10A, 4 112 digit multimeter with digital hold, transistor tester and audible continuity tester. Desig ned for car burglar alarm back• up battery. Allows the back-up battery to be charged from the car battery and isolates the back-up battery by not allowing the back-up battery to drain back to the car battery. $3.20 A12095 $1.20 $1.45 $1.45 P10964 3 PIN LINE FEMALE CHECK THESE FEA TURES ... • Readout hold • Transistor Tester e41f2digitx ½"(H) LCD • Audible continuity tester • Push-button ON/OFF switch. • Quality set of probes •r~,~ ~~~~~ ~s~tf~iT1~ eJ~S~Is ! r~~~e~ent ,ar RF shielding, and strength . Screws are provided with each box . H1 1451100x50x25mm . $ 5.95 Ht 1452 110 x 60 x 30mm . $ 6.50 H t 1453120 x 65 x 40mm . $ 6.95 H11 46 11 20x94x53mm . $ 11 .50 H1 1462 188x 120 x78mm .. . $13.50 H114641 88 x 188x 64m m .. . $29.50 • • • • • • • and RANGE selection. Built in tilting bail Instruction manual Full overload protection hFE test Battery and Spare fuse Diode Tester Vinyl case 091560 . Normally $175 Special, only $159 • •• • .,. ■ ■• ■ SYDNEY : 74 Parramatta Ad. ST ANMOR E. 2048 Phone: {02) 5 19 3134 Fax:(02)5 163671 MELBOURN E: 48 A·Beckett St. Phone : (03) 663 6151 NORTHCOTE : 425 High St. Phone : (03) 489 8866 CLAYTON : 56 Renver Ad . Phone : (03) 543 7877 SOUTH AUSTRALIA: Electronic Discounters P/l. 305 Morphett St, ADELAIDE Phone: (08) 212 1799 NOTE : PRICES MAY VAR Y INTERSTATE DUE TO FREIGHT COSTS ~:ri?!9~~g;i~~.h automatic Indicati on Method: LCD display Measuring Method: Dual-slope in A·D converter system. Over-range Ind ication : " 1" Figure only in the display. Temperature Ranges: Operating O.C!o +40-C Power Supply: one 9 volt battery (006P or FC· 1 type of equivalent) Cat.091530 ......... Normally$109 MAIL ORDER HOTLINE 008335757 ITOUFREEI (STRIC'rl YO RDERS O NLY) SPECIAL $79 P10966 3 PIN CHASIS FEMAI E $4.95 ... ..... .............. $3.95 - LOCAL ORDERS &INQUIRIES f03J 543 7877 POSTAGE RATES , $1 - $9.99 $1 0 - $24.99 $25 - $49.99 $50 - $99.99 . $100 - $199 $200 - $499 $500 plus L!.J L!. Unen~o~~f:~~d~~di:,, gs plus two utility keys. Ltght grey in colour. O UTPUT ARRANGEMENT, Output Pin N° · Sy mbol 1 .... ............ N.A 2 ..................... Shield plate 3 .. .. .. .............. Column2 4 .... .. .. .. .... ... Row4 5 ...... ... .. .......... Column3 6 ...... ..... .. .. ... .. Row1 7 .. ..... ... .. ..... ... .Column 1 8 ........ .. .. ...... Aow2 9 ............. ....... Row3 10 .. .. .. ..... .. ...... NA Cat.C19030 1-9 10+ 100 + $2.95 $2.50 $1.95 ~~:i;~~f:es~~t~ ~~~~ ~:1e:~~t . PANEL METERS ~e~~£~~ ! at range o f panel ~~e~~w ~a~rt'o f u~~~power amps, computers, hotspot cooling etc. ~~6vh:~~?~~~e/1 ~~~~Y§11~95 115V 45,a " Cat. T12463 240V 3 1t., " Cat. T12465 115V 31t.," Cat. T12467 $14.95 $14.95 $14.95 10+ fans (mixed) only $10 each! FAN GUARDS TO SUIT 45,a" 31t.," Cat. Cat. T1 2471 T1 2475 $3.95 $3.95 ■ Rod lrvlng Electronics • Diode testing with 1 mA fixed current. • Audible Continuity T est. • Transistor hFE Test. SPECIFICATION S Ma ximum Di splay : 1999 cou nts $4.50 ...................... $3.90 (D 0<at>) ~<at>]<at>) 0 ~~ (B<at>J<at>] ~~~:~~r8~~:hf~h :reani~i:~~~tof a 4112 digit multimeter. This meter is exceptionally accurate, Uust look at the specifications), and yet, still retains an exceptionally low price! The Metex 4500H features digital hold which is normally only found on very expensive mu!timeters. This enables you take a reading and hold that read ing on display even after you have removed the probes, simply by pressing the hold button . $3.90 ...... ................ $3.50 $3.00 ...................... $2.50 0 9mm hole, available 3 colours Cat.No. Description Price 10 + P10960 3 PIN LINE MALE. P10962 3 PIN CHASfS MALE The Metex 4500H is perfect for the CHROME LED BEZELS CANNON TYPE CONNECTORS 1-9 •·:e :r··:·1 ··_·._ MAIL ORDER , local Orders: (03) 543 7877 Interstate Orders : (008) 33 5757 All Inquiries: (03) 543 7877 CORRESPONDENCE , P.O. Box 620, CLAYTON 3 168 Telex : AA 151938 Fax : (03) 543 2648 • ~~~~~;~ev~oltage protection A space. Great price too, because we import direct so you save ! .. .. ......... . . ... ... METEX 3800 •:~,~~1:~ tw S l 4030 Red .. S 14032 Green S1 4034 Yellow . PORTASOL • Four ~Rf~~fi\~~~r~h. Hot Blow. Hal Knife • No Cords or batteries • Heavy duly. tip tem~rature adjustable up to 400° C . • Equivalent to 10-60 watts • Hard working. Average continuous use 90 minuters • Refills in seconds • Powered by standard butane gas lighter fuel • Aan~e of easily replaceable screw tips rncluded • Includes metal stand for the soldering iron when working • Cap features built-in flint for igniting Portasol tip • Includes snap case for storage Cat. T12639 . . .. .... $89.95 meters al great prices! Cat.No. Description 010500 MU45 0•1mA 010502 MU45 50-0/SOuA 01 0504 MU45 0· 10OuA 010510 MU45 0-5A 0 10518 MU45 0·1A 010520 MU45 0-1A 010525 MU45 0-20V 010530 MU52 E 0-1A 010533 MU52E 0·5A 010535 MU45 VU PMetre 010538 MU65 0·S0uA 0 10540 MU65 0-1mA 010550 MUSS 0- 100uA 010560 MU65 0·20V Price 12.50 12.50 12.50 12.50 12.50 12.50 12.50 14.50 14.50 14.95 16.95 16.95 16.95 16.95 ~~~~::;~:di~~~~:'.' be AU wholesale and sates tax exempt Inquiries to : RITRONICS WHOLESALE . 56 Renver Ad, Clayton. Ph. (03) 543 2166 (3 fines) Errors and omissions excepted . Prices and specifications subject to change. l~~~·!ac~S ~T;n~~~,~~en~1~~r!~s Machines. • is a registered tradematk. Apple ·oenot~ registered tradmarl(s of their respective owners. BOOKSHELF Practical MIDI Handbook Practical MIDI Handbook by R. A. Penfold. Published 1988 by PC Publishing, London. Soft Jovers, 140 x 215mm, 150 pages. ISBN 1 870775 10 4. Price $17.95. MIDI stands for Musical Instrument Digital Interface, a subject of great interest to any musician or person wishing to get involved with electronic musical instruments. Some computers are now supplied with or have an optional MIDI port but if you want to make music, there's a lot more to it than that. This book takes you through the subject and gives a fairly good over- view. It indicates quite clearly that MIDI is really just a framework rather than being a tight specification that all manufacturers must adhere to. This means an instrument with MIDI sockets will not necessarily be compatible with another piece of MIDI gear. As an introduction to the subject of MIDI, the book is not bad although it does not go really deeply into the subject. Nor does it get down to the specifics of particular MIDI interfaces. With that in mind, it is a useful reference. Our copy came from Jaycar Electronics. 90 SILICON CHIP Substitution handbook Fane Loudspeaker Enclosure Design and Construction. Published by Fane Acoustics Ltd, West Yorkshire, England. Soft covers, 211 x 300mm, 53 pages with enclosure diagrams. Price $14.95. This book is a collection of plans for loudspeaker enclosures together with a few pages of practical information. No design theory is presented and the assumption is that anyone building these loudspeaker enclosures will be using Fane drivers. There is no infor- NTE 1988/1989 Technical Guide and Cross Reference, 4th Edition. Published January 1988 by NTE Electronics, Inc. New Jersey. Soft covers, 217 x 277mm, 604 pages. Price $17.50. This is a truly vast cross reference of electronic devices, with not just integrated circuits but all manner of active and passive devices. You can use it as a guide to substitution or as a source of data on new and obscure components. Already in the short time we have had it in our library, it has proved its worth. Our copy came from Stewart Electronic Components, 44 Stafford Street, Huntingdale, Victoria 3166. Phone (03) 543 3733. · ding to him, ''the maximum charge of a capacitor is its capacitance". In fact, capacitance is coulombs of charge per volt. So a capacitance of one Farad will store one coulomb at one volt. There are other places where we had minor quibbles about the correctness of the text but since it has been written in such a brief format this is inevitable. There are seven chapters devoted to electronic components ranging from switches, resistors and capacitors, to digital and linear integrated circuits. These are followed by one chapter on assembly tips and one of 28 pages which presents 100 circuit ideas. At the price of $4. 99 it is good value. It is available from all Tandy stores. ~ Loudspeaker design & construction Getting started in electronics Getting Started in Electronics, by Forrest M. Mims. Published 1983 by Radio Shack. Soft covers, 213 x 276mm, 128 pages. Price $4.99. This is another in a series of booklets written by Forrest M. Mims for Radio Shack. It is written and presented in note form and attempts to do the near-impossible to give a complete over-view of electronics in just 128 pages. As a down-to-earth practical introduction to the subject it is a good attempt although in one place we did not agree with the author's definition of capacitance. Accor- mation about the possible substitution of loudspeakers from other manufacturers. None of the enclosure designs are intended for hifi use. They are strictly for professional applications such as discos, stage and musical instrument work. Our sample copy came from Jaycar Electronics. Don't miss a single issue IF YOU'RE THE KIND OF READER that can't wait to get the next copy of S ILICON 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. * l" . Electro~lc i!. house ... . number , _ l ! Convert a CB radio ;i'.t · for amateur use i ... 1 5-element b Fffl antenna Hili review: Yamaha's brilliant. new CD player Constructional Projects for the Enthusiast * Amateur Radio by Garry Cratt * * * The Serviceman's Log rv Pllfs - the (?riginal &-·Besl Servicerni!n, Vintage Ra~!o, The Way I See lt1 the Evolution of Electric HiiilW,,lys f"bsc,-·b Od • e by liJJ; Qg Off Sffb IQg t6 · t itQd sc,-·1 •s 1>ti0 Q The Way I See It Collp Hifi Features & Reviews FREEPOST * SUBSCRIPTIO D New subscription D Renewal (PLEASE PRINT) Street._ _ _ _ _ _ _ _ _ _ _ _ __ _ _ __ __ _ Suburb/town _ _ __ _ _ __ _ _ _ _ Postcode_ _ __ 1 year (12 issues) 0 $A42 2 years (24 issues) D $A84 NZ & PNG (airmail) D $A65 Overseas surface mail D $A62 D $A120 0 $A130 0 $A130 0 $A240 Overseas airmail Enclosed is my cheque/money order for $ _ _ D Bankcard Card No. _ or please debit my D Visa Card I I I I I I i OQ COUPON Start in_ _ _ _ __ _ Name _ _ _ _ _ _ __ _ _ _ _ __ _ _ __ _ __ Australia ay IJJctjJ• I I I I I I I I I I Signature _ __ _ __ _ _ _ Card expiry date_!_/_ _ Subscription Hotline We can accept your subscription order by telephone. Just ring us on (02) 982 3935 and quote your Bankcard or Visa Card number and the expiry date . Detach and mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 • No postage stamp required in Australia. I I I I I I I I I I I I I I I I I W dft:J I ~-------------------------------------~91 NOVEMBER 1988 AMATEUR RADIO By GARRY CRATT, VK2YBX What's all this talk about SINAD? SINAD measurements (signal plus noise and distortion) are now the accepted method of evaluating FM receiver sensitivity, having replaced the old "20d.B quieting" method. Here's a quick rundown on what SINAD measurements are all about. Many amateurs will be familiar with valve transceivers. They were used in large numbers across Australia by amateurs keen to operate on the VHF and UHF bands. To keep costs low, some amateurs converted retired commercial equipment, some of which is still in use today. When those transceivers were originally manufactured, receiver sensitivity was measured using the "20dB quieting" method. Basically, this involved connecting an AC voltmeter across the loudspeaker output terminals, opening the receiver squelch, and measuring the noise voltage with the volume control set to some convenient level. An unmodulated carrier was then applied to the receiver and the signal level adjusted until the out- put noise was reduced by 20dB (ie, by a factor of 10). When the - 20dB level was reached, the signal generator level was noted and this became the "20dB quieting point". Receiver sensitivity was then specified as so many microvolts (µ V) for 20dB quieting. A typical figure was 5µ V. This method was popular because it was simple but it could sometimes give misleading results. Let's consider an example - a receiver that has a very narrow bandwidth due to misalignment. In this case, the 20dB quieting method will still indicate normal sensitivity. In practice, the receiver would be unable to receive intelligible signals due to severe distortion. To receive FM correctly, the receiver must have adequate band- width to include all the important FM signal components. For example, if the receiver is required to correctly demodulate a ± 5kHz signal, then it must have a bandwidth of at least 10kHz. If this bandwidth is reduced by misalignment, the receiver will not recover intelligible audio. This was the major disadvantage of the "20dB quieting" method. SINAD measurements SINAD measurements do not suffer from the above problem. Basically, SINAD is a measure of the quality of a communications signal. When a signal is introduced into a receiver, the output of the receiver will consist of the original modulating signal plus system noise and receiver distortion. Thus SINAD is defined as: Signal + Noise + Distortion Noise + Distortion Expressed in dB, the equation becomes: 20.Log Signal + Noise + Distortion Noise + Distortion Because distortion can be considered as a type of noise for this application, the equation simplifies to: 20.Log[Signal/Noise) The "Sinadder Linear 5" is part of a range of SINAD meters made by Helper Instruments Company, USA. The local distributor is RF Devices Pty Ltd, 9 Lyn Pde, Hoxton Park 2171. 92 SILTCON CHIP The big advantage of the SINAD method is that it measures both signal and noise, unlike the 20dB quieting method which only measures noise. In fact, SINAD measurements in RF equipment are similar to THD (total harmonic distortion) measurements in audio gear. To measure SINAD, we apply an FM SIGNAL GENERATIJR ANTENNA RECEIVER SPi::ER With an RF input signal of 20µ,V, the noise and distortion should be low. So when the meter is switched to the SINAD mode, the reading will be very low, say - 40dB or more. Reducing the RF signal will progressively increase the noise and distortion so the SINAD reading will rise. For today's amateur gear, the RF input will have to be reduced to around 1µ,V or less to obtain a reading of - 12dB SINAD. Fig.2 shows the test setup if no SINAD meter is available. \ SINAD METER lkHz MODULATION 3kHz PEAK DEVIATION Fig.1: basic test setup for measuring SINAD. Initially, the set level control on the meter is adjusted for a reading of OdB, then the FM signal generator output is reduced until a reading of - 12db is obtained. o-------FM SIGNAL GENERATOR ANTENNA RECEIVER 1kHz MODULATION 3kHz PEAK DEVIATION lkHz NOTCH FILTER v Receiver alignment Fig.2: this test setup can be used if no SINAD meter is available. SINAD measurements are similar to total harmonic distortion (THD) . measurements in audio gear. RF signal modulated at lkHz to the receiver and connect a SINAD meter to the receiver output. Fig.1 shows the basic setup. The peak deviation (of the lkHz test signal) should be set to 3kHz while the RF signal level should be adjusted so that the receiver hard limits. Initially, the meter should be switched to the "AC volts" range and the set level control adjusted for a reading of OdB. After that, it's simply a matter of switching to "SINAD" and reducing the generator output until a reading of - 1ZdB is obtained. The sensitivity of the receiver can now be determined simply by noting the generator output level. What actually happens inside the SINAD meter is this: when the instrument is switched to "AC volts", we get a reading of the combined signal plus noise output. When the unit is switched to "SINAD", a lkHz notch filter is switched into circuit. This filter removes the lkHz fundamental but allows all other frequencies to pass. So, in the SINAD mode, we simply get a reading of the noise and distortion components. If no noise is present, the reading is simply a measure of the distortion. Dynamic balancing for fans rite magnet from an old louspeaker. With one side sitting firmly on the centre of the piezo transducer, and the other side resting on the cabinet, it gave the transducer quite a workout when the fan was turned on. The voltage reading with a 10MO load was a steady 5V AC (straight into the input of an AC voltmeter). Next I mixed up a small amount of 5-minute epoxy and coated the underweight joint on the fan. The "vibration" reading decreased to about 1VAC. Had I gone too far, or not enough? Attaching a small piece of sticky tape dropped the reading to 0.9V, so I mixed up some more 5-minute expoxy and applied what I guessed to be ten times the mass of the piece ctd from p.87 of sticky tape. The next reading was quite a surprise - only 30mV AC. Bingo! I had hit near perfect balance after only a couple of tries - admittedly more by luck than anything else - but it was reassuring to find 0 Manufacturers often specify various test points on their circuits to assist alignment. To align the transceiver in the conventional way, a suitable signal is injected and the circuit is tuned for maximum output. However, maximum output does not necessarily indicate the optimum tuning point, particularly when considering RF amplifier stages and mixers: Tuning for maximum gain is not the same as tuning for best signal-to-noise ratio. In some cases, it's possible to improve receiver sensitivity by as much as 3dB by realigning the circuit to obtain the best SINAD reading. This is equivalent to doubling the transmitter power at the other end! ·~ that putting a small piece of tape anywhere on the fan rotor only increased the vibration, regardless of where I put it. All's well that ends well - in fact, the cabinet vibration of this particular air cleaner is now an order of magnitude better than one straight out of the factory! ~ ,, P ~ ~ -~ . ao_1 o c,ILPf ~~ ·co ~~ RCS Radio Pty Ltd is the only company which manufa.c tures and sells every PCB & front panel published in SILICON CHIP, ETI and EA. ,.'Jc 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices NOVEMBER 1988 93 OBLY7WEEKS TO GO! Ho Ho ... The big fella in the red suit is due shortly. Have you thought about Christmas presents for the hobbyists and enthusiasts in your family ( even for yourself). Your local Dick Smith Electronics store is chocka block full of great ideas - at bargain prices! Christmas morning and you forgot the batteries! Wouldn't you be popular? All those wonderful new wizz-bang goodies and not a ba~ry to make them wizz and bang! Plan ahead - if you get batteries early, you wont forget. And if you get Nicads, they can be all charged up and ready to fire . •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• ~ USE NICADS: THEY'RE CHEA,ER! Sure they cost more than ordina, y batteries. But you can charge Nicads hundreds of times so compare the plice of hundreds of ordinary oattelies! You'll save WIRE •N• Standard Nicads YES! WE STILL CABLE S-3305 s495 SELL PANEL METERS! "AAA" Size Cat180mAh SPECIALS Wee gooft! Our famous MU-45 and MU-65 panel meters missed Otrt on "AA" Size Cat500mAh S-3300 s475 Stock Up Now! Winding Wire - quality copper wire with sofder-through enamel. Range sizes available, here are just a few: 208&S (0.8mm) 100g reel, approx. 18m. Cat W-3120 Normally $4.50 this month only '1 95 22B&S (0.63mm) 25g reel, approx. 24m. Cat W-3123 Normally $3.25 this year's catalogue. But, of course, we still have them in stock -and will continue to do so. Don't let their absence from the catalogue page fool you: they',e on the shelves instead! And just to prove it, here are two of them at last year's price (that's a saving off each one!) {The old faithful) MU45 size. Cat 0-2010 s14ss '1" this month only (0.2mm) 25g reel, approx. 18m. Cat W-3132 Non11ally $3.25 this month only '1 '' 1~ -~ I 0-1.,iA DC Ml 165 size. Cat 0-2070 s19ss "Strength" Meters, too: 500uA edge-reading meter as used in a huge range of imported equipment to show battery level, audio, etc. Scaled 1-10, 32 x 10mm NOW s3 95 Introductory s79s price! HEY! THAT'S NEAR HALF PRICE! BNCtoPl259 Coax.Coble YET MORE TEST GEAR Handy! As used on many video recorders for video input. Cat W-1295 ..,,,. NOW ONLY s395 Meter Test Leads As used on a huge range of multimeters: ideal replacements. With banana meter plugs and long test probes, 900mm long. Cat W-4508 95 NOW ONIY 5 1 Test Clips Various colour IC test clips so you can make your own test and patch leads up. Mini size, suit small hook-up wire. Cat W-4588 Normally 95c ea, NOW 50C ... at bargain prices. Hobbyist CRO Most hobbyists need a CRO most don't have one. Once you've used a CRO you'll wonder how you got on without it! This one won 't break the bank, but gives a usable response to beyond 6.5MHz - ideal for most users. Try it: you'll like it! s359 SAVE $401 CatQ-1280 WAS $3.75 each Breadboard Jumper Set What a great idea! Plastic case contains 350 len~ths of jumper wire in various sizes and colours for use in making prototypes on breadboards. Saves shorts and hassles. Cat W-4012 Hand-Held RC Oscillator I '"'"' I The only thing decaying about this oscillation is the price: it's $20 off our normally low price! Perfect for the service tech, hobbyist, etc - gives you 46 frequencies in sine and square waves between 20Hz & 150Hz in the palm of your hand. cat 0-1220 -- Wass119 \ :~ .'I. $1595 ., .;, \-:!7ii-·;.\, 'r.\ h 12V Te::; sgges ~~~-~- Another beauty: this one's for auto cable testing. Actually pierces the insulation without removing cables, gives no go/ maybe/good indication with 3 leds. Also tests HT pulses from distributor Look a t t h ~ p r i c e ' Cat 0-2000 Normally $24.95 NOW Was $9.95 110mAh Cat S-3309 600mAh Cat S-3312 s595 "C" Size "D" Size "SubC" Size 2.0Ah Cat S-3311 s1495 s1595 5!j95 4.0Ah Cat S-3310 J:trnJl 1.2Ah 1.9Ah 3595 cat S-3315 5 Cat S-3316 5 37 12V 12V 95 2.6Ah 6.5Ah 3895 '5595 Cat S-3320 5 Cat S-3322 CHARGERS TO SUIT: ln-situ or loose - these chargers will see your NiCad batteries right' 0-100uA DC w~;e·ss:e; 1.2Ah Cat S-3303 s1195 s1195 "AA" Size s1595 GELL CELLS Ideal for alarms & general purpose usage. 12V 12V 0-1 ~OuA DC (Handy!) 5 metre headphone extension lead so you're not tied to the stereo! Gold plated for virtually zero corrosion , highly flexible, with a 3.5/6.5mm adaptor thrown in! Ga1 W-1165 NEW! Normally $9.95 1.2Ah Cat S-3301 'C" Size "D" Size "9V" Size High Capacity Nicads NOW s795 Plug-Pack: Standard: Super: Suitable for most general purpose in-situ (ie battelies stay inside device) charging. Handles 6 to 10 standard or high capacity "AA" cells. Cat M-9517 Handles all types and sizes of Nicads from AA through to 9V; charge up to 8 cells at once. Automatically senses size. Includes charge test meter Cat M-9505 Specifically for high capacity Nicads: also sences size and adjusts charge automati cally. (Do not use for standard Nicads except AA Size). Cat M-9506 -1~ c;C~ '~ 4~ .~ ~ ~~3995 il- 1, ~dll~. D -~-~s.::: :,V' 17 1. I. 1t1l1. MISCELLANEOUS BARGAINS: SOLDER: 200g SAVBIT solder pack, 0.91 mm. Protects your bit while you solder. Cat N-1621 Normally P. 95 NOW '6,,. 2.5MM SOCKET: lnline plastic socket for mini headphones, etc. Make up an extension lead with this one. Cat P-1232 Normally 115c NOW ONLY 45C DIN COUPLER: 5 Pin DIN to 5 Pin DIN coupler, consisting of back-to-back din sockets. Cat P-1551 Normally $5.95 NOW ONLY 1395 PLUG & SOCKET SET: 2 Pin heavy duty microphone-type plug and socket set. Cat P-1860 Normally $5.25 NOW ONLY '2,,. N CONNECTOR: Silver plated female N line.connector for quality RF applications. Cal P-2405 Normally $8.95 NOW ONLY '4" IDC PCB CONNECTOR: 11-way IDC connector for Printed circuit board edges. Cat P-2753 Normally $6.99 NOW ONLY '2" 40-WAY IDC: As above , but 40 way. Cat P-2762 Normally 1 11 90 I\IOW ONLY '5 95 50-WAY IDC: As above. but 50 way. Cat P-2764. Normally $14.25 NOW ONLY 16"" CORDLOCK EXTENSION CORD HOLDER: One of the smartest ideas we 've seen in years. Holds 2 extension corns together so they can 't come out and gives some protection against spray and moisture. Cat P-5412 Normally $4.95 NOW ONLY 13" SPOT MINI RELAY: Small in size, 2A 100V contacts with 812V (225 ohm) coi l. Designed for PCB mounting. Cat S-7120 Normally $2.95 NOW ONLY'l"' SPOT PCB RELAY: Standard size SPOT PCB mount 1 0 c;n~a~t: c~~;~~l t SA Nom1allv $8.50 2~3~· Nii IJ UNLY '6"" DPDT PCB RELAY: As above, but with double pole contacls. 200 Ohm Coil. Cat S-7130 Normally $8.50 NOW ONLY 1 6"" ROTARY SWITCHES, TOO: Save on the complete range of Dick Smith rotary switches. All same size, but choose the contacts you want . 6 Pole 2 Pos S-6302 4 Pole 3 Pos S-6303 3 Pole 4 Pos S-6304 2 Pole 5 Pos S-6305 2 Pole 6 Pos S-6306 1 Pole 12 Pos S-6312 ALL WERE S2.25 NOW: '1 95 lcoMPONENT GRABAGS Wotsa Grabag? Everything that we could grab to throw in the bag, that's wot' We've got them trom under five dollars to under fifty dollars - and in each case represent stagg ering savinys: up to 50, 60% off normal prices! What a great way to fted your junk box' ~ 1· GRABAG 1: AT LEAST :,10 WORTH Cat K-9010 ,4,,. 1 F. ..rg ' E..:~ GRABAG 2 AT LEAST S20 WORTH Cat K-9010 '9 95 P. GRABAG 3 ATLEAST S40 WORTH Cat K-9010 °19"" I GRABAG 4 AT LEAST S60 WORTH Cat K-9010 '29" / ,. 95 GRABAG 5 AT LEAST S100 WORTH Cat K-901 0 °49 / lflDA B,Af,S 1:://\J"'\LI · .: _ HURRY: LIMITED STOCKS ONLY - AND THEY'LL GO LIKE CRAZY! Now available at tiO stores: • NSW • Albury 21 8399 • Bankstown Square 70 7 4888 • Btacktown 6 71 7722 • Bondi Junction 38 7 1444 • Brookvate (Warringah Mall) 905 0441 • Campbelttown (046)27 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Liverpool 600 9888 • MaiHand 33 7866 • Miranda 525 2722 •NewcasUe611896• North Ryde88 3855 • Parramatta 639 2188 • Penrith/047)32 3400 • Railway Square 211 3777 • Sydney City 267 9111•T-661711 • Wollongong ., 8 38()() •ACT• Fyshwick 80 4944 •VIC• Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footsc:ray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Melbourne City 326 6088 • Richm0nd4281614 • Ringwood 8795338 • Springvale5470522 • QLD • Brisbane City 229 9377• Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • T-384300•Townsvitle 72 5722• Undenwood341 0844 •SA• Adelaide City 232 1200• Beveriey3471900 • SL Marys 277 8977 • Elizabeth 255 6099 • Enfield 260 6088 •WA• Cannington 451 8666 • FremanHe 335 9733 • North Perth 328 6944 • Perth C.i!J 481 3261 • TAS • Hobart 31 "~00 •NT• Stuart Part< 81 1977 NOW AVAILABLE AT ALL STORES - OR CALL TOLL FREE: (008) 22 6610 FOR HOME DELIVERY! LAST CHANCE! NEW! WELLER STATION SC)95 370 degree 2mm tip SC)9S CatT-3003 430 degree 2mm tip SC)95 Cat T-3004 370 degree 3.2mm tip 95 cat T- 3005 Tip wiping sponge Cat T-3010 s9 =rom one of the world's leading nanufacturers comes this superb new Soldering Station. It's different from most systems: it uses an advanced control system which measures the tip temperalure - to change the operating temperature, you simply change the tip. Simple yet more effective than just about any other system. Cat T-3000 ONLY $149 50 GIVE YOUR BOAT A XMAS PRESENT one that could save your life! If you own a boat without a two-way radio, you're mad. Stupid. Crazy. And possibly breaking the law. (If you go "outside" without a radio or EPIRB you are!) Yeh, we know, "It will never happen to you" Huh! Try telling that to the dozens of people lost last year (or their families). 27 Meg AM: on1,s139 As far as we can determine, the one .millionth Fun Way into Electronics kit (containing the $1000 gift certificate) is STILL OUT THERE. To date, no-one has claimed their prize, which means that the kit is probably still silting on a shelf in a Dick Smith Electronics store (or maybe at DSXpress. Or an Authorised Re-seller. Who knows!) One thing's for sure: With Christmas coming up, virtually EVERY Fun Way kit is guaranteed to be sold. So SOMEONE IS GOING TO WIN THE $1000 PRIZE IN THE NEXT FEW WEEKS. WILL IT BE YOU? Permit Nos: (NSW) TC88/2231 (ACT) TP88/7914 SE?fSATIO?fAL SAVI?fGS O?f PRODS! Why should you miss out just because this is a hobbyist magazine? These prices are too good to miss out on! Message Forwarding Phone Answer Machine Cordless Phone with the Works $100 OFF SJ9fS299 No matter what you're into, this is! Scanning? Its a suberb VHF scanner antenna. Amateur? Covers from 80 to 480MHz so you've got the 2m band sewn upl Vertical Discone type with 3dB gain, handles 500W transmitter power.Cat 0-4315 Was$169 ' NOW ONLYS129 Nows179 Low Profile Transformers WHAT AN ANTENNA! WHATA SAVING! ·i Aussie made by Ferguson, low profile and fully shrouded connections. All one low price: choose the voltage/current combination you require. PL10/20VA (2x 5V, 2A) Cat M-3596 PU15/20VA (2x 7.5V, 1.3A) Cat M-3597 PL18/20VA (2x 9V, 1.1A) Cat M-3598 PL24/20VA (2x 12V, 0.85A) Cat M-3599 PL30/20VA (2x 15V, 0.69A) Cat M-3600 ALL ONE PRICE: 95 ea S29 Big: • And More How About Now you can play by yourself and really sharpen l(OUr skills! Sensory Backgammon has 9 adjustable levels, even has game position program. Cat Y-7066 Chess? Chess? The Novag Piccolo is ideal for all levels - from beginners up. Mini sized game in fold-up wallet. Cat Y-7080 Slightly better, slightly higher price : the Kasparov Mk10 is a 238mm square set with 8 levels .. oraG/Psup.,ly .. GalM-9545 ,.-:. F: Bigger! If you need heaps of power, this one has it. Huge 4A peak gives you plenty of reserve 00mph. Great service bench supply. 13.8V DC output. Cat M-9547 -. T.'Ec al~ And Even More? 0 r~t~i~~ii~~~~r;:ie~et; v'.~~70 Yep! The Novag Allegro is suitable for everyone from novices to club tournament level with a 2K program capacity and 15MHz clock speed. 8 levels of play. Cal Y-7085 l ~~ Matte Black Quick drying, matte finish spray for general touch-up and panel finish. cat N-1010 WAS$3.95 NOW s1 Silver Spray I Anti glare silver paint in a - . handy spray can. Quick • drying, elegant finish. Cat N-1076 . 1 llll . Silastic 738RTV ~ Neutral curing Silastic " was $2.95 $ NOW 738RTV in 85g tube. No corrosion problems here. Cal N-1226 $ ~ ·, ;Was $12.95 NOW 895 And The Best ~~~:;~;i~/~'lf:~c! ~ 7 ~:=i~Irii~~; E1~:~~~s i1 ~ ----------- • 11111N: Chris's Hi-R 82 8711 • 1'«111': Forster-Village Electronics 54 5006 • Giln 1-: John Sommerlad Electronics 32 3661 •llrfflllll: Miatronics 62 4534 • IMIIII: Lyn Willing Electronics 221821 • i.Jsllcn: Oecro 21 4137 • Morie: Moree Electronics 52 3458 • Mldgll: Headware 72 3895 • Nawn: Nowra Electronics 21 4979 • W~~~ Electronics 21 6558 •VIC • Morwell: Morwell Electronics 34 6133 • s.artol: Phillips Electronics Pty. Ltd.·21 9497 • : Marrtronics 62 9870 • OID • llunallert: Bob Elkin Electronics 721785' • Kinpny: Holmes Today Electronics 62 1658 • Klwn: Splitec 94 7349 • Mlcby: Stevens Electronics 511723•Mlrltlorauall: Keller Electronics 214559•SA •MtGlllllier: Hutchessons Communications Centre 25 04!)() •WA• Albaly: Micro Electronics 4i 2071 • &lnllflol: Batavia Lighting & Electrical 23 1842 •Kamtlla: Dave's Oscitronics 85 4836 • TAS • Owonpa,t: Hey! That's probably you! Wouldn't you like to pit your wits against a smart-alee chip that's trying hard to show you it's smarter than you are? The superb Kasparov Mk12 is the ultimate in chess computers: not just 8 levels of play, but three levels of coaching, threat warnings, 8 pre-programmed study levels ... every1hing. Cal Y-7065 MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: A.I. Electronics & Hobbies 24 8322 495 Spray Nominal 12V DC output (13.8V) with 2A peak output - great as a bench supply for most small 12V audio (car radio, cassettes, etc) s75 NOW Keep Your Cool Just s279 Into Baelceammon1 Hl~ie~~ecl/:rcc;i~t~i Limited stocks only of these bargains. Once they're gone, they're gone! WAS s&.50 $ POWER! s109 95 XMASGIFTl :=- WHILE THEY LAST Including a great saving! Just plug it in to your Electrolube phone socket (can completely replace existing phone PIUS 2x if you wish!) Has call button to summon handset . from base, security coded dialling, the works! Pen-shaped lubncant for cat F-5885 general elect~oni? use. Great for getting into inaccessible areas. Cal N-1047 Yes, it actually rings a pre-programmed number to say there's a message waiting. EG - you're at work, someone rings home. Your machine tells you so you can retrieve the message remotel y! Unbelievable[ Cat F-6145 That's right: protection for you and your family for less than a hundred and forty dollars. Are you that mean? Sea Simba has all 10 marine channels fitted ; full legal power. Cat 0-1718 27 Meg AM/SSB: $1000 BONUS! Finally: Not Chess! Here's the pertect gift for the high-techer: a neg ion generator! What. you say? Fantastic for ham shacks, workshops, etc we know they work because we use them! Gal Y-9000 THE EVOLUTION OF ELECTRIC RAILWAYS Diesel electric locomotives are perhaps the most common type of loco used thoughout the world. They are used where the cost of supplying power makes electric locomotives economically unattractive. While high power electric locomotives are clearly the most efficient means of land transport, transcending every competitor in tonnes moved per dollar running cost, they do depend on the prior installation of electric power supplies and overhead contact wires above all tracks. Though the electric locomotive is cheaper than all other types, the PT.13: A LOOK AT DIESEL ELECTRIC LOCOMOTIVES 96 SILICON CHIP , '.) CONTRAST IN SCENERY - in Canada, as in Australia, diesel-electric locomotives haul heavy freight trains over long distances. The view at left shows two powerful (2.24MW) SD-40 diesel-electric locomotives at work for the Canadian National Railroad. In the photo above, a heavy NSW-SRA coal train passes through a crossing loop on the run from coal mines in north-west NSW to Newcastle. It is hauled by four 442 diesel-electric locos, each rated at 1.49MW (2000hp). overhead wiring, substations and associated feeder cables and power lines represent an investment of hundreds or even thousands of millions of dollars. The costs associated with financial arrangements and loans of such magnitude must be weighed against alternative locomotive types. In all other types of locomotive diesel, diesel hydraulic, diesel electric or gas turbine electric - the complexity and capital cost of the locomotive itself is much higher than the comparatively simple electric locomotive. It is not hard to see that the strongest case for the electric locomotive is where there is dense traffic over short to medium track length. So what should a railway company or state authority do with their main and branch lines carrying fewer trains over thousands of kilometres? Many railways worldwide have chosen diesel electric locomotives for such service. Diesel electric Why diesel electric? Why not simply diesel, like an overgrown semi-trailer? The answer lies in the power of modern diesel electric locos which can be up to 4.92MW (6600hp ). There is great difficulty in coupling such large power and torque from the engine to the driving wheels by mechanical drives. The easiest and most successful power transfer method developed to date is electric transmission. This involves one or more large diesel engines within the locomotive driving an electric generator. The electric power so generated is fed to electric traction motors which turn the loco driving wheels. Many see a diesel electric locomotive as equivalent to an electric loco which carries its own power station around with it. This is a reasonable concept, for the diesel engine/generator set carried in modern large diesel electric locomotives is larger than the power station plant in some small country towns. Naturally the price of diesel fuel vitally affects the choice between electric and diesel electric locos. It is not surprising then that low oil prices in the USA (compared to other countries) led to that country being the present front runner in diesel electric traction. NOVEMBER 1988 97 Some American railroads, such as the huge and successful Santa Fe Southern Pacific Corp Railroad, have never operated any electric locomotives. They changed over directly from steam motive power to diesel electric systems. Electrical machinery Early diesel electric locomotives used the most obvious design; ie, a diesel engine directly driving a large low speed multipole DC generator, generating up to about 500 volts DC at about 1200 amps. Usually the Co-Co wheel arrangement was used; ie two bogies, each with three driven axles. Six DC traction motors were used, three per bogie, each motor axle hung. Traction motor control Control of the motors in the early models, as illustrated in Fig.1, was by high current DC contactors with cast iron resistance banks switched in for starting. These resistance banks were progressively switched out as the train gathered speed. To reduce the starting current load on the generator, it was common practice to switch all the traction motors · in series for starting, then as speed built up, the motors might be switched into three pairs of two motors in series, or in some other cases simply all six motors directly in parallel across the generator. THE NSW-SRA 80-CLASS diesel-electric locomotive is rated at 1.492MW (2000hp), weighs 119 tonnes, and is capable of express speeds up to 130km/hr. The first unit was built by Comeng for the SRA in December 1978. Traction motors Early designs invariably used DC series motors as this type provides STARTING RESISTOR DIESEL ENGINE FIG.l(a): TO REDUCE THE STARTING CURRENT load on the generator, the traction motors are switched in series during starting. As the train gathers speed, the starting resistors are progressively switched out and the motors are switched in series-parallel combinations across the generator. 98 SILICON CHIP the greatest starting torque, hence maximum starting tractive effort. Usually 4-pole . motors were employed despite the fact that a 6-pole motor of similar type is lighter for the same power. Because so much of the weight of the locomotive comes from the heavy diesel engine, DC generator and diesel fuel tanks, the traction motors are not such a large fraction of total loco weight. As each diesel electric locomotive is (electrically speaking) a little world within itself, the designer can choose any voltage he deems optimum for the generator and traction motor system. Also the designer may choose between DC and AC systems. If AC is chosen, the frequency is also open to debate. The most convenient voltage for DC generators and motors is somewhere between 200 and 600 volts. A 1.5 megawatt loco would involve a generator current of 1500 amps if a 1000V system were DIESEL ENGINE adopted, or 3000 amps if a 500V system were chosen, or 6000 amps if a 250V system were used; the lower the voltage, the higher the current. High voltage systems bring traction motor insulation difficulties from ingress of dirt, moisture and brake block dust, particularly iron dust from standard cast iron brake shoes. Furthermore, a higher voltage motor may have more voltage between segments on the commutator, and also wastes more space in the armature winding with extra thickness of insulation. But the advantage of higher voltage lies in the lower current for the same power. This may result in less power loss in the circuit resistance and hence a slightly higher system efficiency. The advantages of lower voltage systems lie in less insulation problems, less need for filtered clean air within the electrical machinery, and easier design of control contac- STARTING CONTACTORS ALL CLOSEO oc GENERATOR I I L---------Y.Yr--------J I I L-------~--------J 300kW BRAKING RESISTORS I I L---------YM---------J FIG.t(b): AT HIGH SPEEDS, the traction motors are switched in seriesparallel across the generator and the starting and "weak-field" contactors closed. Dynamic braking is achieved by switching heavy· duty resistors (shown dotted) across the motor armatures. tors. The higher currents usually do not lead to serious voltage drop problems as the length of motor ea ble runs is short and there is room for heavy copper busbar conductors in the main generator circuits. Even when multiple locomotives are used, only low current control cables run between locos. The large traction current cables are confined within each locomotive. For example, the early diesel electric locomotive class GR17 purchased by Canadian National Railroad from General Motors in 1956 was equipped with a 466 volt DC generator rated at 2800 amps continuous. This loco was of Bo-Bo type (two bogies, each with two driven axles) with four traction motors each rated at 466 volts, 700 amps, 326kW (437hp), giving a total power of 1.3MW (1750hp). The traction motors were geared to the driving axles by a 15:62 ratio gear, giving a maximum speed of 104km/hour. The diesel engine was a 16cylinder 567-C type with 216mm bore and 254mm stroke (9.3 litres per cylinder) and was capable of running at 835RPM maximum rating. The complete locomotive with its 4200 litres of fuel oil weighed 112 tonnes. Even the much later and more powerful General Motors SD-40 type locos of 1975, which develop 2.136MW (3000hp), use a DC generator rated at 508 volts, 4200 amps. Many American designs still tend towards the lower voltage, high current philosophy. The General Motors model SD38-2, as exemplified by Canadian National's Co-Co class GF-620a of 1975, uses six traction motors each rated at 212 volts DC, 1050 amps, 223kW, giving a total· power of 1.338MW (1794hp). The six traction motors are a DC series type, with each pair of motors permanently connected in series. During starting, contactors switch all three pairs of motors in series, as shown in Fig.l(a). For higher speed, the motors are switched in series parallel as shown in Fig.l(b). For yet higher speeds, the series fields have a tapping to allow part of the field to be switched out. This NOVEMBER 1988 99 AMTRAK'S P30CH DIESEL-ELECTRIC locomotives feature a big 13,700 litre fuel tank for medium and long-haul operation. These 6-axle Co-Co locomotives are rated at 2.24MW and are geared for a maximum speed of 165km/hr. reduces the motor field strength and causes the armature to run faster. Dynamic brakes Most diesel electric locomotives use dynamic braking. This is achieved by disconnecting the armatures of the traction motors from the generator and then switching them each across a tapped heavy duty resistor. The field windings are separately excited by the diesel driven generator. During deceleration, the train momentum drives the traction motors (which now act as DC generators), and the power generated is dissipated as heat in the braking resistor. This power loss causes considerable braking force to be applied to the locomotive. In the current General Motors model SD38-2 locomotive, each of the three braking resistors is rated at 424 volts, 700 amps or almost 0.3MW of heating power per resistor. These resistors take the form of heavy cast iron grids which are cooled by large motor driven fans which draw outside air from 100 SILICON CHIP the sides of the loco and exhaust it from the top. Strangely, not all diesel electric locos use dynamic brakes. One example was the 2.24MW (3000hp) GM model SD40 of 1971 weighing 176 tonnes and rated at 104km/h. It was not equipped with any form of electric brakes but did have the standard loco and train air brakes, the Westinghouse 261 Unitized air brake system being used. Auxiliaries As well as the main DC generator (or alternator in later models), diesel electric locomotives are equipped with an auxiliary 3-phase 60Hz alternator. This supplies the headlights, cab services and battery charger. The 3-phase supply also runs the air blowers which provide forced ventilation of the traction motors and the braking and control resistors. These auxiliaries add up to a significant load - as much as 18kW in many locomotives. In some locos, the main diesel engine drives two auxiliary alternators, an air compressor and circulating water pump, as well as the main DC traction generator. The EMD model SD38-2 loco has one auxiliary alternator rated at 19kVA, rectified immediately to DC for auxiliary supply, and a second auxiliary alternator rated at 215 volts at 120Hz (at 900RPM engine speed). The low compartment front of the cab of "hood" type locos houses a large lead acid battery for powering train control circuits, auxiliary air compressor, communications systems and essential lighting. For operation in the cold mountain country of North America, the diesel fuel is preheated in a heat exchanger which is heated by the engine cooling water. Most locos in that continent are fitted with what looks like a bulldozer blade at the front. In the winter months these act as snow ploughs, a consideration Australian readers may not have had cause to ponder. Early Australian diesel electrics Since the 1950s Australian railways have made wide use of AMERICAN MUSCLE - THREE NEW GP40 diesel-electric locomotives on their way to Conrail (USA) from the General Motors Electro-Motive Division. These 2.24MW (3000hp) Bo-Bo locomotives are used for general service. diesel electric traction, starting with the imported 79 class of 1944 built by General Electric, USA. From the 50s until the present many hundreds of diesel electric locos have been built by the Australian companies Comeng of Granville, Clyde Engineering and A. E. Goodwin Ltd. Further details of Australian diesel experience will be published in a later episode. On the world scene many advanced engineering features including extra large powers up to 6MW (8000hp ), high current solid state silicon rectifiers, and high current thyristors appear in the latest diesel electric locomotives. We'll talk about those in a later episode. Acknowledgements Thanks are due to NSW-SRA, VR, Canadian National, Comeng (Granville) and Amtrak for data, drawings and photographs. ~ FOUR LOCOMOTIVES ARE used here on this NSW-SRA train to give a total power of. 5.66MW. Leading is a 1.34MW 45 class locomotive weighing 112 tonnes. Next come two 1.49MW 442 class locomotives, each weighing 115 tonnes. The fourth locomotive is another 45 class. N OV EMBE R 1988 101 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. Capacitors for vintage radios In the "Vintage Radio" article in the August 1988 issue, John Hill makes a point about how hard it is to get 25µF 450VW electrolytic capacitors (and other values). Although I suspect he knows about this, just a line in case he doesn't. Putting several capacitors in series will raise the operating voltage although changing the capacitance value. For example, putting seven 47µF 63VW capacitors in series will give a composite value of 6.7µF at 441VW. On another subject, I need a very sensitive microphone. I have built one which works but not well enough (I'm a university student not a spy). The original circuit used a TL071 but this was noisy at low voice levels. This was cured by using an NE5534AN op amp. Would using an OP27 increase the gain, or reduce noise? What about an M308AH? This device was described in a catalog as being Volume control for power amplifier I am presently constructing a power amplifier of my own design and I wish to use a CD player as the only program source. I need advice on the fitting of a line control to the amp to avoid the need for a preamp. In short, I want a power amplifier with a volume control. I imagine it could be a suitable value pot across the input but it probably isn't that simple. My current CD player doesn't have a variable output control so that's a dead end but I have seen "line divider" controls on some amps so I'm sure it can be done. The input sensitivity of my amp 102 SILICON C H IP of "super high gain". Would putting several op amps in series increase the gain? Would using split supplies change anything? (A. D., Parramatta, NSW). • Your suggestion to connect electros in series to get higher voltage ratings does have a drawback. It is just not possible to guarantee that the voltage will be equally shared across all the capacitors. If each capacitor had the same capacitance and the same DC leakage, then all would be well but they don't. The capacitance and leakage current can vary widely. It would be quite possible for one electro to have more than ten times the leakage current of another unit with the same nominal capacitance. The capacitor with the least leakage would end up with the most voltage across it and then could break down completely, leading to a chain reaction in which all capacitors fail. The way around this is to have a bleeder resistor across each capacitor. The current through the bleeder would then be arranged to be much higher than the expected leakage currents - in effect to "swamp" them. The problem is that, if you use 63VW capacitors to make up a 441VW unit, you have to use seven capacitors and seven resistors. That is not very practical when restoring an old radio in which space is sure to be limited. Now let's consider your microphone problem. You have not told us what the application is or how much gain you need. You can get more gain out of your existing preamp simply by reducing the feedback. For example, you could increase the gain to around 330, merely by changing the lOOkO feedback resistor to 330k0. But because your circuit is an inverting amplifier and has an unbypassed voltage divider to set the "half supply" point for the noninverting input of the op amp, the residual noise would be much higher than is achievable. And with that small input capacitor, the bass. response will also be very poor. In fact, the bass would be non-existent .,.,---TO RIGHT AMPLIFIER RIGHT INPUT Fig.1: how to fit a volume control to the Studio 200 power amplifier. Use shielded cable to wire the pot, as shown. modules is 500mV RMS and the output level of my CD player is 2V RMS. What is the solution? I want to go the way of the minimalist. (M. A., Hamilton Hill, WA). • Providing your power amplifier modules have a reasonably high input impedance, say 22k0 or higher, fitting a volume con- trol is easy. Just wire a 10k0 dual (log) pot to the amplifier inputs, with one channel going to each pot section. The pot wipers then connect to the amplifier inputs. To further help you, we've prepared a wiring diagram showing how it would be done with the Studio 200 power amplifier described in our February 1988 issue. r-------<------------+9V ELECTRET MICROPHONE Fig.2: this microphone preamp circuit suffers from high residual noise and poor bass response. 1k r------W,/r----<~---+9V ELECTRET MICROPHONE .,. 10 BP+ Fig.3: much better performance can be obtained by using this non-inverting op amp circuit with split supply rails. with a - 3dB point at 1.6kHz. Much better noise performance could be obtained by using the noninverting op amp circuit shown here. We have used split supplies of ± 9V but you could use up to ± 15V. The split supplies eliminate the need to bypass a voltage divider. We've used the OP27 in a conventional non-inverting op amp arrangement to give a gain of around 330 times. This is pushing the circuit to the limit (as far as guaranteeing high frequency response with low-spec devices) but we don't think you'll be worried about that. Note the heavily bypassed supply to the electret mic (100µF capacitor) and the use of lOµF and 2.2µF bipolar (non-polarised) electrolytic capacitors in the feedback and output circuit. We should point out that we have not tried this circuit but it should work without problems. The bass will be flat to below 30Hz. Questions on the Discolight so do I just connect the resistors between + 12V and pins 1, 7, 8 & 14 of IC3 to complete the project? Regarding the plasma display in the same issue, I have completed the EHT generator and am using a preserving jar filled with helium (the jar was not evacuated first). The transformer sparks but when connected to the filament of the jar it doesn't go. Is this because the jar wasn't evacuated first, before the gas was added? • Also, could you supply details of I have nearly finished assembling the PCB for the Discolight project described in the August 1988 issue and seem to have four 10k0 resistors left over. Upon checking the circuit diagram, there are 15 10k0 resistors but there are only 11 on the PC:B. The missing resistors appear to be connected to pins 1, 7, 8 & 14 of IC3 from + 12V. Do I need them? If the filament or is it copyright? I just guessed the size and shape from the photos. SILICON CHIP is a great magazine - keep it up. (B. B., Christchurch, New Zealand). • The circuit for the Discolight was originally designed around LM339 comparators. These devices have open collector outputs, necessitating the use of 10k0 pullup resistors. Later, we decided to rationalise the circuit by using LM324 op amps throughout. This meant that the 10k0 pullup resistors were no longer required. The plasma display bottle must be evacuated and the lid sealed before the gas mixture is introduced. We suggest that you talk to a refrigeration mechanic. They usually have access to a vacuum pump. However, we cannot say how satisfactory your display will be as we understand that there has been a lot of trial and error in arriving at the correct gas mixture. The filament is not copyright and, as far as we know, the shape is not all that critical - it is really just a coil opened out on one side. Long-range remote keyswitch I would like to build a remote switch based on the unit described in your August 1988 issue but with a range of 50 to 100 metres. Could you please tell me if the circuit shown could be modified by changing any components or could I use a different antenna to get this increased range? My intended use is to switch on the front light of my house from my car which is parked in the street. (R. B., Crows Nest, NSW). • Unfortunately, we cannot provide you with any information on increasing the range of this project. Legally, it is supposed to be a flea power transmitter (to prevent interference) and we doubt whether the transmitter can be greatly increased in sensitivity, apart from fitting it with a better antenna. This may be practical for a fixed in. stallation but we have not done any work along these lines. ~ NOVEMBER 1988 103 CEN'I' Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date : five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information . To run your own classified ad , put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach , NSW 2097. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7 .00) 16 ($7.40) 17 ($7.80) 18 ($8.20) 19 ($8.60) 20 ($9.00) Name ... ..... ..... .... ..... ........... ....... ..... ....... .. ..... .. . Address .... ....... ... ......... ..... .... ...... .. . Suburb/Town Postcode Enclosed is my cneque or money order for$ ...... ........ ...... ............... or please debit my D Bankcard D Visa Card Card No l._--'-I----'----'-'----......__,_._._-'----'-----'----'- '----......_--'--_.__, Signature .. . PROJECT REPAIRS PROJECT REPAIRS - Having trouble getting your EA/ETI/SC kit to work? Phone (03) 7 49 3480 for estimate or send kit to K. Hunter, 5 Yatama Crescent, Werribee 3030 . FOR SALE NEW 64K-256K PRINTER BUFFER design release. VER 4 .0 and REV G boards now available . Double-sided PCB, EPROM and instructions : $39.00. Optional additions include 2 x 7 -segment LED front panel display of percentage full, 1 to 99 copies select, 3 polled computer inputs, printer switches, computer switches, and serial converter boards. For a free catalog send a 37c stamp to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. EPROMS 2764 $4, 27256 $6 , 27512 $10, 74HC374 $1 , uP6800 104 SILICON CHIP $3, 6802 $4. All minimum quantity 100. Transistors - PNP 2N2907 A 5c , mimimum quantity 1000. Ask for Winnie on (02) 344 0173 after 6 .30pm. BOOKS & PLANS LOW SPEED GENERATORS for windmills, water turbines, steam engines . The definitive book: "The Homebuilt Dynamo" (1987), 182 pages, 8.5" x 12", hardback. Generator design and construction with ceramic magnets. Complete plans, 268 photographs, step-by-step construction details. $A85.00 postpaid airmail (brochure $A5.00 refundable). Todd-Forbes Publishing, 627 West Coast Road, Oratia, Auckland . Notes & Errata Low Ohms Tester for DMMs, Feb. 1988: the 10k0 feedback resistor between pins 6 and 2 of IC1 i s incorrectly shown on the wiring diagram (Fig.2} as lkO. Advertising Index Adilam Pty Ltd 21 Allied Capacitors 31 Altronics 50-53 Arista Electronics 47 Avtek . . . . . . . . . . 59 Ballarat Electronic Supplies 37 Bell lRH . . . . 49 Contact International 79 Dauner Electronics 57 David Reid Electronics 62,63 Dick Smith Electronics 12, 13 94 ,95 Geoff Wood Electronics . . . . 81 Goldstar . . .... IFC Jaycar Electronics . 24-27 72-75 J.V. Tuners . .... .. ..... 57 Kenwood Australia OBC Philips Components IBC Pre Pak Electronics . . . 85 ACS Radio . . . . . . . 93 Rod Irving Electronics .. 38 ,39 88 ,89 Scan Audio 31 Sulco Tools . . . . ...... 11 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • ACS 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. Switchmode Battery Charger, Sept. 1988: pin 11 of IC1 should be shown earthed on the circuit diagram on page 79. Hands-Free Speakerphone, September 1988: the text on page 19 concerning " initial circuit checks" has an error. The external 25 to 50-volt supply should be connected via a 5600 resistor to board inputs 1 and 6, not 1 and 3. Yes Yes Yes Yes Yes Yes Yes Yes 'Y( Yes !s Yes Yes In today's competitive production world, engineers need to have supply at their finger tips. The " just in time management" philosophy is proving to be a commercial reality. Philips are prepared. When you call your component supplier you need some positive answers. Philips Components promises to deliver more yes's to your questions because they are leaders in: • Quality • Product Range and Stock availability Not just platitudes but a strong commercial reality as a result of massive research investment , modern systems for efficient production and stock control and that absolutely vital element. .. top calibre , friendly people. Apart from being the largest supplier of electronic components in the world, Philips aim to be the friendliest. If you have a problem right now call the Philips "Componentline " and heanhat magic phrase ... "Yes,we can do it " . Sydney 439 3322 Melbourne 235 3677 Adelaide 243 0155 Perth 277 4 199 Brisbane 844 0191. United Notions 817 PHILIPS