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Building The Class-A Stereo Amplifier SILICON CHIP $ 50* 5 NZ $ 6 50 INCL GST AUGUST 1998 C I M A N Y D 'S A I AUSTRAL E N I Z A G A M S C ELECTRONI SERVICING - VINTAGE RADIO - COMPUTERS - SATELLITE TV - PROJECTS TO BUILD Beat-Triggered PC I/O Card With Automatic Data Logging Adding Extra Computer Memory -- Without Tears! PRINT POST APPROVED - PP255003/01272 Strobelight Build the superb OPUS 1 August 1998  1 Step-by-step instructions inside SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Contents Vol.11, No.8; August 1998 FEATURES 16  Electromagnetic Compatibility Testing; Pt.1 Symbols and standards – by Marque Crozman 40  Troubleshooting Your PC; Pt.4 Adding extra memory to your PC – by Bob Dyball 88  Special Subscriptions Offer Adding Extra Memory To Your PC – Page 40 Buy a subscription to “Silicon Chip” before end of September 1998 and get a bonus wallchart PROJECTS TO BUILD   4  The Opus One Loudspeaker System You can build this superb 2-way loudspeaker system from a kit of parts – by Leo Simpson 22  Simple I/O Card With Automatic Data Logging Easy-to-build card plugs into your PC’s parallel port and can automatically log data to an Excel spreadsheet – by Mark Roberts 54  Build A Beat Triggered Strobe Simple I/O Card With Automatic Data Logging – Page 22 It can flash in time to the music or at any speed between one and 20 times per second – by John Clarke 72  15W/Channel Class-A Stereo Amplifier Building the modules into a case plus power supply details – by Leo Simpson SPECIAL COLUMNS 27  Serviceman’s Log Neither cat proof nor kid proof – by the TV Serviceman 67  Radio Control Radio-controlled gliders; Pt.3 – by Bob Young Build A Beat Triggered Strobe – Page 54 85  Vintage Radio An Australian-made 6-transistor personal portable – by Rodney Champness DEPARTMENTS   2  Publisher’s Letter 32  Circuit Notebook 53  Order Form 90  Ask Silicon Chip 93  Notes & Errata 94  Market Centre 96  Advertising Index 15W/Channel Class-A Stereo Amplifier – Page 72 August 1998  1 PUBLISHER'S LETTER Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Ross Tester Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $59 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Pay TV points the way for Digital TV Hands up all those people who are excited about the pros­pects for digital TV broadcasting in the next five years or so. What!? Is no one excited at the prospect of all those extra channels with high definition pictures and digital sound? Well, I’m not surprised really because we’ve seen this show before, haven’t we? Remember the announcements about Pay TV and how there’d be this huge range of channels and everybody and his aunt would find something to watch at any hour of the day? It hasn’t turned out that way with Pay TV at all. Not only has it been a pretty big flop in Australia but the cost has been huge. We’ve got two (unfinished) cable TV networks strewn around the streets and the likelihood that only one of them will be viable in the long-term. And there is no prospect at all that the losing network’s cables being removed, is there? Even people who have Pay TV will tell you that they often have “30 channels of nothing” to watch. They wonder if they should be paying the monthly fees at all but the occasional good movie or sports event keeps them connected. But what will happen when the Pay TV customers realise that there are going to be a lot more “free to air” TV stations? They might just decide that they can survive without Pay TV. There is a genuine prospect that all the money invested in Pay TV will never generate a profit. Just as with Pay TV, there are likely to be many twists and turns to the Digital TV story before the ultimate farce unfolds. Did you know, for example, that as part of the plan for the introduction of digital TV, that analog broadcasts will close down in 2008? That’s just 10 years away or just eight years after digital TV is supposed to start. Consider some of the ramifica­tions. First, how many people will immediately decide not to buy a new TV set, knowing that digital TV is coming soon and that their old analog TV will probably last for at least another few years? My guess is that analog TV prices are going to drop real soon. Or will set-top converters become big sellers? How much will digital TV sets sell for? No-one knows. Second, what if you live in the country? Chances are that digital TV will not arrive for many years and will the Government really want to shut down analog services while country viewers still depend on them? It seems to be the same story as with the proposed close-down of analog mobile phones by 2000, even though country users might be left in the lurch. Third, where are the “free-to-air” TV networks going to get all the extra programs to broadcast on all these new channels? They seem to have a big enough problem now. What will happen when the existing advertising industry budget is spread over all those channels? There won’t be enough money to buy or produce decent TV programs for all time slots. What will it come down to? Talk-back TV? And who wants to watch more TV programs, anyway? As time goes on, most people are watching less, not more TV. That’s quite a lot of questions. There aren’t any good answers. It’s all likely to be a huge farce, with the Government of the day hurriedly introducing it to distract us from the real issues of the day. That happened with Pay TV, didn’t it? My feeling is that this whole concept is being rushed into by the Government without any real thought about whether consumers need or want it. One thing’s for sure. It will cause a flood of im­ported sets and that won’t be any good for the Current Account Deficit at all. Leo Simpson M croGram Computers Hard Drive Recovery Card Multi-PC Controller 8 Way 2 Control TV & Capture PCI Card Cat. No. 11637 Multi-Network Cable Tester Pro The TV tuner displays realA controller with two control keyboards, monitors, time video images on your mice and sound equipment which allow two operators computer screen. It includes simultaneous access to eight computers (not the its own television tuner to same computer). Auto scan or manual selection (key accept television signals via strokes or switch) of the PC’s is provided. This deskcable or broadcast TV. It also top model is designed for multi file server installations and the controllers can be daisy chained to provide can play audio/video from external video players like $149 two consoles with control over 64 computers. It can VCRs and camcorders. TV & Capture PCI Card $369 be located on the desktop or mounted in a 19” rack. Cat. No. 3357 FORMAT, FDISK, VIRUS......OOPS! Recover data from your hard drive after FDISK, FORMAT or DELETE commands or even after virus attacks. Supports DOS, Windows 3.x, Windows 95, OS/2 and Windows NT. Cat. No. 3374 Hard Drive Recovery Card CPU Voltage Checker Multi-PC Controller 8 way 2 Control $1999 Avoid CPU burnout! Make sure Cat. No. 11636 Multi-PC Controller 4 Way 2 Control $899 you have the motherboard jumpInternal UPS & Power Supply ers set correctly. This unit checks It’s not just a UPS but also a and displays the voltage on the 300W power supply. The UPS CPU socket before the CPU is is actually built into a standard inserted. Ideal for those who upgrade systems, install size power supply and the batmotherboards, sell processors, build systems, serteries and front panel occupy a vice and repair or for educators and schools. 5.25in drive bay. The UPS is rated at 500VA. Apart Cat. No. 3365 CPU Voltage Checker $99 from power failure, the UPS also protects against over voltage, under voltage, overload & DC short circuit. Removable Hard Drive Kits Consists of a 5.25” mounting rack & a removable tray for The unit is available in two sizes - PS/2 or ATX. Optional software provides for automatic shutdown. 3.5” hard drives. A keylock prevents inadvertent or unauthorised removal. Applications include: • securing confidential data in a safe overnight • providing off-site backups • easy interchange of OS (eg DOS to Windows NT) by simply replacing drives Cat. No. 6049 Cat. No. 6048 Cat. No. 6200 / 6224 Cat. No. 6201 / 6225 Cat. No. 6327 IDE KIt SCSI Kit IDE Tray / Frame Only SCSI Tray / Frame Only SCSI Fast Wide $111 $121 $70 $76 $169 Hi- Scan Bar Code Readers Cat. No. 8498 UPS / PS (PS/2) Int 500VA/300W Cat. No. 8588 UPS / PS (ATX) Int 500VA/300W Cat. No. 8499 UPS / PS Internal RUPS S’ware Year 2000 BIOS Card Year 2000 BIOS Card $129 High resolution CCD barcode scanners which feature multi-interface communication Bi-directional & ECP/EPP Printer Cards Bi-directional parallel ports with with RS-232C, Wand & an 83 byte FIFO buffer, configuKeyboard Emulation in one unit. rable from LPT1 to LPT6 and Simply release the RJ-45 jack to set on interrupts 3 to 15. change cables! Offering optical Achieve data transfer rates up to performance with a minium resolution of 0.125 mm & maximum reading distance of 20 mm it is possible 1Mb/sec with ECP/EPP. Both ports provide 7 selectto read high-density, laminated & acrylic-covered bar able I/O port addresses and 10 selectable IRQ’s. The single port ECP/EPP card provides 7 DMA channels codes. Cat. No. 8458 Hi Scan Bar Code Reader KB Wedge $699 while the dual port card provides two DMA channels. Also available, Long Range CCD bar code scanners Cat. No. 2314 Bi-directional 1 Port Cat. No. 2315 Bi-directional 2 Port which offer variable width and depth of field. Cat. No. 8489 CCD Bar Code Scanner Long Range KB $469 As well as our standard range. Cat. No. 2316 Bi-directional 3 Port Cat. No. 2235 ECP/EPP 1 Port Cat. No. 2236 ECP/EPP 2 Port Cat. No.8196 CCD Bar Code Scanner KB Wedge 80mm $359 Cat. No. 11515 Multi-Network Cable Tester Pro $259 External Case for CD-ROM or HD No more overheating! A cooling fan and ventilated front $429 panel allow free air flow. A $399 versatile external case for two $99 3.5” or 5.25” SCSI half height hard disk drives or CD ROM drives, tape drives etc. Featuring a built-in 80W power supply. Models for 4 & 9 drives also available. Even Pentium motherboards are not immune to the Year 2000 bug! The Year 2000 BIOS Card solves the problem of progression from 1999 to 2000 as well as 21st century leap years. It is an 8-bit card which provides year 2000 support for motherboards with a BIOS which only stores the year with two digits. i.e. 97 instead of 1997. Cat. No. 3359 This Plug and Play advanced design cable tester will test both 10Base-T (Category 3-5) and 10Base-2 (Coax) cable within seconds. It runs all tests automatically and LED’s indicate the results. It will test cable continuity, open pairs, shorted pairs, crossed pairs or reversed pairs. $45 $61 $97 $79 $94 Cat. No. 6384 Ext Case 2 x HDD or CD ROM SCSI $199 Surge Suppressors Protect your equipment & networks against power fluctuations, spikes, cross talk, induced transients & close proximity lightning strikes. Cat. No. 8386 Cat. No. 8387 RS232 RS422 DB25 DB15 $79 $59 Complete 10BaseT protection. Cat. No. 8388 10BaseT RJ45 1 Port $59 Compact Multimedia FM Radio Receiver A high quality FM stereo radio that simply plugs into a serial port while a stereo RCA cable connects to a sound card. An antenna also plugs into the unit. Fully clickable controls enable you to scan the frequencies from 87.5 to 108MHz, tune a particular station and name it as one of ten preset stations. Cat. No. 3304 E & OE Wizard Radio FM Radio Receiver All prices include sales tax $79 MICROGRAM 0898 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 FreeFax 1 800 625 777 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 Opus One 4  Silicon Chip A superb 2-way loudspeaker system to build By LEO SIMPSON Designed by well-known audio consultant Richard Priddle, Opus One is a fine 2-way loudspeaker system which really packs a punch. It has a very good 1-inch dome tweeter teamed up with two 6-inch bass drivers via a carefully designed crossover network. Virtually anyone can put these speakers together, whether they have woodworking skills or not. No special tools are re­quired either, although you will need a bottle of PVA glue and a Philips screwdriver. When you have put them together, you will have a set of speakers that you can be really proud of. These speakers have a number of features which will make them really attractive to the do-it-yourself audio enthusiast. First, they have up-to-theminute styling, with rounded edges on the top and bottom plates and a full-width snap-in grille cloth frame which sets off the side panels which are finished in black bean veneer. Second, they are very easy to put together, by virtue of the precision machining of the various panels. These have mating grooves so that the panels slide and lock into each other, pro­ducing a very rigid assembly. This new machining method is a big advance over previous knock-down cabinets whereby the sides wrapped around the front and back panels and the corners of the wraparound section depended on the flexible veneer to hold them in one piece. If you were a bit cack-handed and tore the veneer, you were in serious trouble. To make it dead easy to put these speakers together we’ve gone mad with the camera and produced a step-by-step pictorial. This was useful for us as well because it showed how easy it was to make a mistake. We made the mistakes just so you would be warned. Well, that’s our brief article. After all, you need to know what speakers have been used and how they’ve been connected. Drivers & crossover Two 175mm woofers are used in parallel in the Opus One. These are 8Ω speakers with a large ferrite magnet, a neoprene rubber roll surround and a curvilinear cone. Their Thiele/ Small parameters are: Qts 0.49; Vas 21.13 litres and Fs 46Hz (free air resonance). They have a power rating of 40 watts and an efficien­cy of 88dB/W at 1 metre. The 25mm soft dome tweeter is a beauty. It is also an 8Ω unit, with a power rating of 50 watts and an effi- ell w y r e v e r a they comp ilt systems u with fully b 0 or more 00 1 $ g n i t s o c “ story, anyway. We know you will want to rush out and buy the kit and start assembling it but before you do that why not just humour us by reading the rest of this ” Fig.1: the crossover is a Linkwitz-Riley configuration with a very low Q lowpass network for the woofers and a higher-Q high-pass network for the tweeter. This arrangement creates a time delay for the tweeter at the nominal crossover frequency of 2850Hz. August 1998  5 Fig.2: if you intend building the cabinets yourself, you will need internal cleats to hold the panels together. Use screws and PVA glue to hold everything together. 6  Silicon Chip ciency of 92dB/W at 1 metre. The tweeter and woofers are coupled together with a 2-way crossover network which is shown in Fig.1. This uses a Linkwitz-Riley configuration. This has a very low Q lowpass network for the woofers and a higher-Q high-pass network for the tweeter. This arrangement creates a time delay for the tweeter at the nominal crossover frequency of 2850Hz. The tower-style cabinet is a conventional bass reflex design with a short flared vent for low air velocity. The cabinet dimensions are shown in Fig.2. Listening tests What do they sound like? We listened to them on a wide range of music and they do give a very good account of them­selves. In particular, the tweeter is a fine unit which could be found in systems costing many times the price. The sound quality is slightly “forward” giving a very good presence on voice but they are equally good on classical music or rock. They compare very well with fully built systems costing $1000 or more. Fig.3: the finished design has a smooth frequency response from around 40Hz to above 18kHz, as shown on this diagram. The overall efficiency of the system is about 92dB/W at 1 metre. Cost & availability This loudspeaker system is available in kit form or fully built from Altronics in Perth – phone 1 800 999 007 to order. The price for a complete kit for a pair of Opus One loudspeakers is $599. If you want to build your own cabinets, you can save money and just buy the short-form kit which contains the loudspeakers, the fully assembled cross­over networks and the flared vent ports. This short-form kit costs $339. Alternatively, you can read this article and then take the lazy man’s approach and order a pair of finished loudspeakers priced at $895. Delivery charges are applicable. Before we conclude, we should note two changes to the Opus Ones which are not shown in the photos. First, the Innerbond filling material has been changed to a grey open-cell foam which is claimed to have superior damping. Second, the port is a larger diameter flared tube which is also shorter than that shown in the photos. It also looks better. When you sit down to listen to them, you will have a fine pair of speakers which look and sound great. Fig.4: the Opus One has a minimum impedance of 4Ω so it will cause no problems with your amplifier system. Now, to find out how to build the Opus Ones, just look at the pictures and read the captions on the following pages. August 1998  7 STEP 1: It’s always a good idea to do a “dummy run”. No, this doesn’t refer to the person doing the assembly – it ensures you have all the components and also helps you understand how they all fit together. STEP 7: Connect the wires from the crossover network to the appropriate spade lugs on the input terminals. The green wire goes to the red terminal and the black wire goes to the black terminal. Push completely home and check by gently tugging the wires. STEP 13: If you did the “dummy run” , about now you’d be starting to think it’s just a bit harder with glue in place. Don’t force it: use a bigger hammer (and a block of four-be-two) for a bit more gentle persuasion. The tops of all four baffles must line up, which also ensures that the whole shebang is square and true. 8  Silicon Chip STEP 2: Insert the female plastic grille retaining clips into the front baffle. The inset shows a simple wooden jig we made to prevent the clips from being damaged during insertion. This device is not patented. STEP 3: Similarly, insert the male plastic grille retainers into the grille surround. Again, the jig makes this a lot easier! Put the grille to one side – you won’t need it for some time. STEP 8: Now comes the fun part - where you get to make a real mess with the glue. Oh, did we forget to mention that you should spread an old sheet out to protect the carpet in the lounge room? Having done that, run a bead of PVA glue right the way around the channel in the bottom baffle. STEP 9: Similarly, run a bead of glue in the channels on both side baffles. Too little glue could mean air leaks conversely too much glue will not only ooze everywhere but could stop the panels completely mating. And that, no doubt, will upset the panels almost as much as you. STEP 14: Remem­b er what we said about too much glue? Here’s a perfect example but, of course, we didn’t make this mistake; we just dummied the pic to show you what not to do! Just wipe it off with a rag and remove the remnants with a damp sponge. While you’re about it, go over the whole box and remove any other gloozes. STEP 15: Once happy (truly, he was happy a minute ago. . .) you can put the top baffle on to hold everything square. BUT DON’T GLUE IT ON YET- you need access to the inside of your speaker box once all the other glue has dried. (It’s dry when the PVA glue is near clear instead of milky). STEP 4: Insert the port tube from the front of the baffle and screw it into place. To ensure an airtight seal around the tube, run a thin bead of glue right around the join between tube and the rear of the baffle. We used PVA glue but silicone sealant is also OK STEP 5: Place the speaker connection terminal plate onto the outside of the rear baffle and screw it into place. A piece of timber under the baffle will stop the terminals from being bent. STEP 6: Screw the preassembled crossover network to the inside of the rear baffle, somewhere around the centre. Orientation is not important. A dollop of glue under the crossover before screwing will ensure it won’t work its way loose later. STEP 10: Slide the side baffles into their mating channels on the bottom baffle. Their edges should line up perfectly. Beware of the trap for young players: there is a front and a back to the side baffles - the front edge has a woodgrain finish while the back edge is plain. STEP 11: Once you are happy that the side baffles are properly in position, slide the back baffle into place. Do we have to mention that the connection terminal plate goes to the bottom? No, we didn’t think so either. STEP 12: If you guessed that the front baffle was next to be placed in position, go to the top of the class. Ah, but did you have the port at the bottom? Well done! This panel may need some forcing to get it into place – grunting and puffing appears to help. STEP 16: While the method of construction will ensure the whole thing stays together while the glue dries, it’s important to force the panels together so that the glue is in turn forced right into the joints. Here we use a clamp to achieve the result - just make sure you protect the surfaces from damage. STEP 17: Curses! We only had one clamp. Here’s the alternative method of ensuring all the glue is forced into the joints: gravity! Again, you should remove any oozing glue from the outside of the cabinet before it dries. Speaking of drying, put the cabinet aside for a good 24 hours to ensure the glue dries completely. STEP 18: When completely dry remove the top baffle. Cut a small rectangle of double thickness (ie, folded over) acoustic wadding and fasten it to the inside of the top baffle, taking care to clear the glue channels. We used a staple gun but drawing pins, tacks or even a conventional desk stapler “opened out” could be used. August 1998  9 STEP 19: Similarly, cut a double thickness of acoustic wadding and fasten it to the bottom baffle. This requires some manual dexterity - it’s easiest to work through the bottom speaker cutout and around the port tube. By the way, don’t increase or decrease the amount of wadding recommended: over-damping will result and you won’t know about it until your speakers are finished! Note that the wadding supplied in the kit may have a different colour and texture than that shown. STEP 25: Both rebates for the woofers must be lined with a sealer to ensure air-tightness. Adhesive-backed foam is used - simply peel off the backing paper and stick the foam around the rebate. This stuff is not designed to go around tight radii so it’s not the prettiest job in the world. But it is all hidden by the woofers anyway, so what’s it matter? 10  Silicon Chip STEP 20: Working through the (still open) top and also the speaker cutouts, position single thickness pieces of acoustic wadding on all vertical surfaces and fasten them in place. Once again, you will need to work through the speaker cutouts in some places. STEP 21: It’s quite OK to cover the crossover network with wadding if you wish but you still need to get at the wiring. Either cut out around the crossover or simply cut a slot in the wadding and pull the wiring through. Count the loose wires - there should be six of ‘em. Pull the loose wire through the speaker cutouts. STEP 26: Connect the wires from the crossover network to both woofers. It doesn’t matter which pair of wires go to which woofer; it does matter which way around they go. Connect the red wires to the “+” terminals and the black wires to the “–” termin­als, then temporarily sit the woofers into their cut-outs. Now you’re going to check that you haven’t crossed over any connections from the crossover to the speaker drivers. STEP 27: The trick is to briefly touch a nine volt battery to the rear panel speaker terminals and check that both woofers move in the same direction. Connect the battery + to the red terminal and touch the battery – briefly to the black terminal. There should be a “thump” and you should see both woofer cones move outwards. If one moves the other way, its connections are reversed. So reverse them! STEP 22: It’s time to start putting the speaker drivers in. Connect the tweeter wires: black to the “+” (red) terminal, white to the “–” terminal. Make sure the connections are secure by gently pulling on the wires. If necessary, squeeze the connectors gently with a pair of pliers to make them a firm fit. STEP 23: Push the tweeter into its rebated cutout so that the holes in the tweeter line up with the holes in the baffle. It should be quite a firm fit, so try to get the alignment right first time! There is no “up” or “down” side but it makes sense to have the terminals on the speaker closest to the crossover network. STEP 24: Screw the tweeter into place with the screws provided: they should be nice and tight but not overtightened because it’s easy to strip the chipboard. If you do strip the hole, you could try the old “broken matchstick in the hole” routine. STEP 28: Screw the two woofers into their respective rebates, first lining up their mounting holes with the holes in the baffle. Whatever you do, do not let the screwdriver slip and punch a hole through the cone or surround! STEP 29: If all is OK, it’s time to finish off the enclosures. Run a bead of PVA glue around the channel in the top baffle, taking care not to get any on the acoustic wadding. STEP 30: Now push the top baffle all the way home onto the enclosure. It must go all the way down; you may need to give it some gentle persuasion (a fist, for example). Chances are some glue will ooze from the joints – if so, you know what to do! STEP PENULTIMATE (don’t you just love those technical terms?): While the glue dries, some weight on the top will hold everything in place. If you don’t have Sydney White and Yellow Pages, you could move interstate STEP LAST (but not least): Clip the grille onto its retaining clips on the front baffle . . . and you’ve finished. Now connect up your stereo and . . . stereo? Uh, Oh! Did you forget to build the other speaker? August 1998  11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au EMC Explained Pt.1: What do all the symbols mean? Over the last few years there has been a lot of concern over the introduction of stringent new EMC requirements that all electronic and electrical products must meet. In this short series, we will discuss the new regulations, how they came about and how they apply in Australia and New Zealand. By MARQUE CROZMAN Actually, it is a pretty dry old subject but it is crucial to Australian industry and ultimately to consumers so it deserves a thorough examination. But first, what do all the symbols mean? The most common symbol is “CE” and indicates that the equipment conforms to European standards. In fact, an electrical or electronic product cannot be sold in Europe unless it bears the CE marking. European countries have settled upon a set of uniform or “harmonised” standards. In May 1985, European Community Ministers agreed on a ‘New Approach to Technical Harmonisation and Stan­dards’ in order to remove trade barriers based on techni- cal grounds. This was to eliminate the need for separate product certification in each country. ‘New Approach’ Directives broadly set out the essential requirements which must be met before products could be sold in Europe. The standards which fill in the technical details were then provided by the IEC (International Electrotechnical Commis­sion). The IEC is made up of the standards bodies of 49 countries including all the EU and EFTA. Other bodies that have provided standards are CISPR (Comite’ International Special des Perturba­tion Radioelectriques - International Special Committee on Radio Interference) and CENELEC (Comite’ European de Table 1: Generic Standards Applicable To Electronic Equipment Emissions EN50081 Part 1 Part 2 Electromagnetic compatibility generic emission standard Residential, commercial and light industry Industrial Susceptibility EN50082 Part 1 Part 2 Electromagnetic compatibility generic immunity standard Residential, commercial and light industry Industrial 16  Silicon Chip Normatination Electro-technique) – a group set up to work out the nuts and bolts of creating common European equipment standards. What does CE mean? CE stands for “Conformit Europe­ ane” and is a set of EC Directives that are backed by standards that relate to electro­magnetic compatibility. The CE label can only be used on a pro­duct if the manufacturer can demonstrate that the product com­plies with the essential requirements of the EMC Directive (and all other applicable EC Directives). The directives most relevant to electronic products are ‘The EMC Directive’ (CE), ‘The Low Voltage Directive’ (LVD), and ‘The Machinery Directive’ (MD). The EMC Directive The European Commission’s Electromagnetic Compliance Direc­ tive 89/336/EEC relates to the electromagnetic emissions and susceptibility of electronic products. It came into full effect at the beginning of 1996. It requires that apparatus not generate excessive electromagnetic disturbance levels that would interfere with the proper functioning of other devices or radio and tele­ c ommunications equipment. Secondly, the apparatus must provide a level of immunity to electromagnetic disturbances to enable it to operate as intended. The specific levels are determined by a set of standards produced as a result of the directive. Turning that legalese into English, the standards are divided into two sections. The first covers emissions and the second, susceptibility. Emissions refer to electromagnetic radia­ tion produced by the device. relate to spe­cific tests and methods of testing. Table 2: Commonly Found Product Groups Emissions Standard EN55011 EN55013 EN55014 EN55015 EN55019 EN55022 Equipment covered Industrial, Scientific and Medical (ISM) equipment Sound and TV broadcast receivers and associated equipment Household electrical appliances, portable tools, etc Fluorescent lamps and luminaires Microwave ovens Information Technology Equipment (ITE) Immunity Standard EN55020 Equipment covered Sound and TV broadcast receivers and associated equipment For example, your hair dryer emits radiation which causes the interference to your TV set. Susceptibility refers to the amount of radiation present in the environment that the device has to withstand before its normal operation is affected. For example, some computers do odd things or crash when mobile phones are operated near them – the mobile phone produces a higher level of electromagnetic interfer­ence than the PC can withstand and it performs oddly. The standards are based on a hierarchical model, starting with generic standards that apply to all products. From there, the standards become more specific to product groups, then pro­duct families and finally, to specific products. The generic standards are the toughest to pass, with the more specific stan­dards making allowances for particular devices. The standard that best fits the product description Compliance tests If a product has either or both of these marks stamped on it, it complies with current EMC emissions standards in Australia. is the one that is used. Thus products that do not have individual standards or family stan­dards must use the generic standard – see Table 1. For products where no standard can be applied, another compliance method can be used. This is called the Technical Construction File (TCF) route to compliance. The generic and product standards specify emission and immunity levels and call up other standards that Fully Accredited Testing for Tests carried out to ensure EMC compliance include: •  conducted electromagnetic emissions. •  radiated electromagnetic emissions. •  immunity to electrostatic discharge (static electricity). •  immunity to electrically fast transients (such as switching transients). •  immunity to conducted RF (such as mains-borne interference). •  immunity to radiated RF (local RF fields). Other tests are carried out depending on the equipment might include susceptibility to mains harmonics, surges, voltage dips and interruptions. Levels and methods of testing are deter­mined by the standard being applied. Equipment that is exempt from the EMC directive: •  Equipment for export only. •  Spare parts. •  Secondhand equipment. •   Electrically benign apparatus (power consumption less than 6 nanowatts). •  Equipment for use in screened rooms. •  Amateur radio equipment. •  Military equipment. •  Active implantable medical devices. •  Educational electronic equipment designed for the study of electromagnetic phenomena. Global Markets EMC Technologies' Internationally recognised Electromagnetic Compatibility (EMC) test facilities are fully accredited for emissions, immunity and safety standards. >> NATA endorsed reports for ALL electrical products covered by the and regulations >> Accredited Competent Body for TCF approval >> Anechoic chamber for accredited immunity testing. Field uniformity ensures that your products are not "over tested". DC – 1000MHz <at> 100-200V/m, 1-18GHz & >50-100V/m >> Open Area Test Site (OATS) available for hire for DIY testing >> Low ambient OATS in Melbourne, Sydney and Auckland (NZ) >> RF testing DC – 40GHz >> CE (Europe), FCC (USE), VCCI (Japan) EMC Technologies Melbourne T: +61 3 9335 3333 F: +61 3 9338 9260 E: melb<at>emctech.com.au Sydney T: +61 2 9899 4599 F: +61 2 9899 4019 E: syd<at>emctech.com.au Auckland T: +64 9 360 0862 F: +64 9 360 0861 E: auklab<at>emctech.com.au Visit our website: www.emctech.com.au August 1998  17 MORE FROM YOUR EFI CAR! Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication EFI TECH SPECIAL Here it is: a valuable collection of the best EFI features from ZOOM magazine, with all the tricks of the trade – and tricks the trade doesn’t know! Plus loads of do-it-yourself information to save you real $$$$ as well . . . HERE ARE JUST SOME OF THE CONTENTS . . . n Making Your EFI Car Go Harder n Building A Mixture Meter n D-I-Y Head Jobs n Fault Finding EFI Systems n $70 Boost Control For 23% More Grunt n All About Engine Management n Modifying Engine Management Systems n Water/Air Intercooling n How To Use A Multimeter n Wiring An Engine Transplant n And Much More including some Awesome Engines! AVAILABLE DIRECT FROM SILICON CHIP PUBLICATIONS PO BOX 139, COLLAROY NSW 2097 - $8.95 Inc GST & P&P To order your copy, call (02) 9979 5644 9-5 Mon-Fri with your credit card details! FROM THE PUBLISHERS OF “SILICON CHIP” Table 3 EMI SHIELDING PRODUCTS Class of Equipment Type of Protection Class I Electric shock protection is achieved by (a) basic insulation and (b) protective earth All conductive parts which could assume hazardous voltages in the event of failure of basic insulation must be connected to a valid protective earth conductor. Class II Electric shock protection is achieved by double or reinforced insulation – no provision is made for a protective earth. Class III Electric shock protection is achieved by relying upon the limited current and voltage of a Safety Extra Low Voltage (SELV) supply – and it is impossible for hazardous voltages to be generated within the equipment. Table 4: Safety Classes Of Equipment Class 1 Electric shock protection is achieved by (a) basic insulation and (b) protective earthing. All conductive parts which could assume hazardous voltages in the event of failure of basic insulation must be connected to a valid protective earth conductor. Class II Electric shock protection is achieved by double or reinforced insulation – no provision is made for a protective earth. Class III Electric shock protection is achieved by relying upon the limited current and voltage of a Safety Extra Low Voltage (SELV) supply - and it is impossible for hazardous voltages to be generated within the equipment. Class III equipment does not need approval as it relies on its SELV (Safety Extra Low Voltage) power supply for protection. Plugpacks are good examples of SELV power supplies. This means that a manufacturer can export equipment without certification, by using a locally approved SELV power supply. •  Test equipment designed to gener- ate or be susceptible to EMI. •  Equipment under maintenance. •  Inputs to other devices (passive components or modules sold exclusively as OEM modules to a sole manufacturer). •  Installations unlikely to generate interference. •  Radiocommunications equipment. C-Tick marking in Australia Australia and New Zealand have adopted an EMC Framework, with harmonised standards linked to European standards. In the first stage, legislation has been passed to phase in the emis­sions part of the EMC directive. New products have needed to comply from the beginning of 1997 and existing manufactured products will be caught from the start of 1999. Products that comply with the Australian/New Zealand direc­ tive are marked with the C-Tick symbol. As our standards are traceable back to IEC standards (with amendments for local condi­tions), testing and certification is carried out in the same way as for CE approvals. Thus the cost of testing for C-Tick is incorporated into CE testing, if the product is for the European market. From the beginning of 1999, electronic products will only be able to be sold in Australia and New Zealand if they carry the C-Tick mark. If a product already has CE approval, C-Tick approval can be obtained by making a submission referencing the AS/NZS equiv­alent of the IEC standards that the product conforms to. The Australian Communications Authority has published a brochure that explains the certification procedure. The Low Voltage Directive (LVD) This safety directive encompasses FROM UK Metal wire gaskets Soft shield gaskets Oriented wire in silicones D Connector gaskets Copper beryllium fingers Board level shielding Carbon & glass tissues Nickel coated carbon tissues FROM BELGIUM Stainless steel fibres for conductor plastics FROM USA Ferrites Microwave absorbers Microwave reflectometers Nickel powders - EMI Paints Zippertubing - EMI Sheaths ITO Films Conductive silicone extrusions FROM GERMANY Suits for EMR Protection SPECIALISED CONDUCTIVES PTY LTD Tel: 61-3-9846 1490 Fax: 61-3-9846 5542 email tetazjr<at>ozemail.com.au (with minor exceptions) all equipment operating from 50V to 1000VAC and from 75V to 1500VDC. It deals with the safety aspects of equipment - protec­ tion against electric shock, flammability, mechanical, radiation and chemical hazards. There are three classes of equipment as defined in Table 4. Tests carried out to ensure compliance include: •  Protection against accessibility to live parts. •  Power input and current. •  Heating. •   Leakage current and electric strength at operating temperature. •  Moisture resistance. •  Overload protection of transformers and associated circuits. •  Endurance. •  Abnormal operation. •  Stability and mechanical hazards •  Provision for earthing. •  Creepage distances, clearances and distances through insulation. •  Resistance to heat, fire and tracking. Other tests are carried out depending on the equipment. SELV power August 1998  19 Silicon Chip Binders REAL VALUE AT $12.95 PL US P&P These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf.   Hold up to 14 issues   80mm internal width  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p. Available only in Australia. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for Table 5: Examples Of Safety Standards Safety Standard Equipment covered EN60335 Safety of household and similar electrical appliances EN61010 Safety requirements for electrical equipment for measurement, control, and laboratory use EN60536 Classification of electrical and electronic equipment with regard to protection against electric shock EN60601 Medical electrical equipment – general requirements for safety EN61293 Marking of electrical equipment with ratings related to electrical supply – safety requirements EN60730 Automatic electrical controls for household and similar use EN60065 Safety requirements for mains operated electronic and related apparatus for household and similar general use EN60950 Safety of information technology equipment EN60742 Isolating transformers and safety isolating transformers – requirements EN61558 Safety of power transformers, power supply units and similar supplies are interesting on their own, as they are usually covered in symbols. Although Australia and New Zealand have different require­ments for safety, they have harmonised their standards for elec­ trical safety and adopted the use of the Regulatory Compliance Mark (RCD) in a similar role to the LVD in Europe. It requires that certain products, determined to be “Prescribed articles” must carry the mark. Non-prescribed products are also able to carry the mark, as an indication of high standards of electrical safety. Table 6 outlines some of the common products that are deemed as Prescribed Articles. The standard that the RCD applies to is based on AS/NZS equivalents of EN60730 and EN60742m with amendments for local conditions. For example, Australian flammability standards are tighter than equivalent European standards. Products labelled with the RCD $________ or please debit my  Bankcard    Visa    Mastercard Card No: ________________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ 20  Silicon Chip Table 6 Arc welding machines Bread toasters Clothes dryers Automotive battery chargers Immersion heaters Microwave ovens Portable drills Extra low voltage power supplies Projectors Residual current devices Swimming pool equipment Vacuum cleaners symbol are also required to comply with the Australian/New Zealand EMC directive and there­fore do not have to be labelled with the C-Tick symbol as well. If a product has LVD/CE approval, gaining RCD approval requires additional testing where AS/NZS standards differ from European standards. Once tested, a submission is made referencing the AS/NZS equivalent of the IEC standards, together with a report of additional tests carried out to obtain either a cer­tificate of suitability or type approval from the regulating body. Standards Australia publishes a brochure that explains the procedure for obtaining RCD compliance, entitled “The Regulatory Compliance Mark – Your Questions Answered”. The Machinery Directive The Machinery Directive is really on the fringe of elec­tronic products but can be applied to cooling fans and or item other moving parts which pose a hazard to fingers, etc. It is mainly applicable to machines where human safety must be main­ tained. Power tools are examples that come under the Directive. Standards of the Machinery Directive include: EN61496 - Safety Of Machinery; EN62061 - Safety OF Machinery - Functional Safety Of Electrical, Electronic and Programmable Control Systems For Machinery; and EN62043 - Safety Of Hand-held Battery Powered Motor-Operated Tools and Battery Packs. 20-30 SECOND SOUND RECORDER Kit. Very good quality sound at 25 sec. kit includes PCB, all onboard components, microphone, switches & surplus speaker. TELLEFUNKEN DUAL GaAs-MES-FET Cf300, LOW NOISE (NF=1.1<at>800Mhz) Would make extremely low noise RF amp (Gps 23db). With brief info. $3 Ea or 5 for $13 NEW POCKET SAMPLER KIT FOR PC'S THAT FITS INTO A Db25 HOUSING. Data logger/sampler plugs into your Pc’s parallel /printer port & takes samples over a 0-2V or 0-20V range. Samples can be taken at intervals from one per hour down to one per 100uS. Useful, for example, to monitor battery charging. It can also be used as a basic low frequency (to about 5KHz) oscilloscope! Our kit includes all onboard components, PCB, Db25 housing & the software on a 3.5" disk:(K90) $25 PC Data Acquisition Unit Use the parallel port of your PC as a real world interface. It enables your PC to both monitor & control external events and devices. The world is a mixed analog & digital world. With the appropriate sensors the PC can monitor physical variables such as pressure, temperature, light intensity, weight, switch state, movement, relays, etc, process the information and then use the result to control physical devices such as motors, sirens, other relays, servo motors (up to 11) & two stepper motors :$200 $19 $40 **********CLEARANCE SPECIAL******** UHF AUDIO-VIDEO TRANSMITTER. Your own mini Tv broadcast station. Send video from VCR's or $15 cameras to TVs in your home. Inc. Metal case telescopic antenna & leads: 12V operation, tunable (G01) $20 or $15 with camera purchase We HAVE NEW STOCKS OF STEPPER MOTORS 30 oz./in. TORQUE, 2.5 DEG. ( 1 4 4 S T E P ) , L O W V O LTA G E , COMPACT 57 X 38MM : $14 **** TWO GREAT SPECIALS **** ***STEPPER MOTOR DRIVER KITS*** COMPUTER CONTROLLED STEPPER MOTOR KIT: can drive larger motors with optoisolation. Inc. software and notes: $50 or $65 with two used 2.5 deg. motors!! STEPPER MOTOR DRIVER KIT Kit inc. a large used 2.5 deg. (144 step / rev) motor & uses SAA1042A IC. Controls inc. ext. clock, on-board clock logic CW or CCW rotation, half or full step, enable/disable, clock speed1 motor: $25 or 2 motors:$35 FRONT SURFACED MIRRORS High quality mirrors 160x22x2.5mm. with some minor blemishes Ideal for laser & other optical projects $5 SOLID STATE 4-6A PELTIER EFFECT COOLER / HEATER 3 . 3 A <at> 1 4 V P E LT I E R : $ 2 7 , 6 A <at>15VPeltier: $35, both are approx. 40X40X4mm, can be temperature controlled by reducing supply voltage/current, will even work from a 1.5V battery!! We supply Peltier Effect device, data sheet, diagram & circuit for a small fridge / heater.. Other requirements; Insulated box, 2 large heatsinks, & a small aluminium block. This device is used in the common 15Lr car fridge. Peltier effect Device + (G02) 12V DC Fan:(G11) KIT OF THE MONTH AUTOMATIC LASER LIGHT SHOW KIT: MKIII. Similar to the kit as published in Silicon Chip May 96 issue, The display changes every 5 - 60 seconds, the time is manually adjustable. For each of the new displays there are 8 different possible speeds for each of the 3 motors, one of the motors can be reversed in rotation direction, and one of the motors can be stopped. There are countless possible interesting displays which vary from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. Now with no more mirror and motor alignment hassles with motor mounting on the PCB and mirrors now align with “Allen Key”. Kit includes PCB, all on board components, three small DC motors, mirrors, precision adjustable mirror mounts : (K83) $69 FREE ADS ON OUR WEB SITE On a trial basis we are offering Free advertising on our Web site for both COMPANIES & PRIVATE INDIVIDUALS. Recently our web pages received more than 25,000 hits per week.!!! Where else can you get so much exposure in the right place for FREE. Just E-mail us your ads. with the words “Free Ads” in the subject box and we will do the rest. www.ozemail.com.au/~oatley Oatley Electronics reserve the right to refuse to accept any advertisements we deem unsuitable for our web site DON’T FORGET TO CHECKOUT OUR Web Page and Bargain Corner *** COMING SOON *** HIGH POWER IR TRANSMITTER AND RECEIVER PAIR. APPLICATIONS INCLUDE DATA TRANSMITTER, IR INVISIBLE FENCE / GATE AND DOORWAY MONITOR. RANGE: PASSIVE MODE 10M, ACTIVE MODE 40M ALL FOR UNDER $30 HIGH RESOLUTION MONITOR Brand new 240V 30cm enclosed computer monitor + video conversion kit. Gives better resolution than TV! Limited good qty. BARGAIN PRICE. MODEL TRAIN CONTROLLER KIT: Ref: SC Jul 95. Allows two trains to run on one track, without hitting each other due to speed difference. When a train breaks an IR beam it switches off power to a portion of track, until the other train catches up & breaks another beam at another location. It uses a relay to switch sections of track. Main PCB: 96 x 66mm, IR Sensing PCB's: 59 x 14mm: (K58) $28 TRANSISTOR SPECIALS BU-205 HIGH VOLTAGE $2.50 2SD-1554 HIGH VOLTAGE $5.00 **SPECIAL**SPECIAL**SPECIAL** FOR $1 EXTRA WITH EACH ORDER WE WILL SEND A WIRING KIT !!! Great for cars, radios mobile phones, fog lights etc. 4 colours, 2 guages of wire, Spade connectors, fuse holders, fuses. 17+ mtrs. of wire. Limited offer!!! just $1 *** SPECIAL BARGAIN *** 12V/7Ah GEL BATTERY BARGAIN Fresh stock of NEW standard battery $25 NEW ! 4Ch. UHF LEARNING REMOTE Can be programmed as a spare for your current remote or to replace up to 4 other units and combine into 1:(TX1) $39 $60 *** COMING SOON *** ***** FANTASTIC NEW KIT ***** 12VDC - 240AC INVERTER FEATURES INCLUDE MODIFIED SQUARE WAVE OUTPUT, AUTO START WITH LOAD SENSING, USES POWER MOSFETS. 200 - 600VA. TO SAVE MONEY YOU CAN REWIND YOUR OWN TRANSFORMER. BASIC KIT INCLUDES PCB AND ALL ONBOARD COMPONENTS FOR $40. E-MAIL US FOR MORE DETAILS HIGH QUALITY DC MOTORS 3V - 8v DC motors with feedback winding for speed sensing ect. 40mm diameter X35mm long $3 PRO. STUDIO QUALITY REVERB Three spring units. Dim.: 425 x 110 x 33mm. Input Z=190 ohms, output Z=2.6 k ohms, recommended AC drive = 6.5 mA. A circuit diagram of a stereo preamp tested using this unit:$40(A10) *** CCD CAMERA SPECIAL *** The best "value for money" CCD camera on the market! 0.1 lux, High IR response & high res. Performs better than many cheaper models. WITH A CHOICE OF 1 OF THESE LENS Pinhole (60deg.), 78 deg.; 92 deg.; 120 deg.; $89 or 150 deg: $99 $50 *** HALF PRICE SUPER SPECIAL*** LM338 adjustable ( TO3 package ) 5A voltage regulator with internal overload protection, + application notes for a variable 1.2V- 33V 5-20A power supply. Half price at just $6 Ea or 4 for $16 UHF GARAGE REMOTE CONTROL RECEIVER: Ref:SC Dec 93. All the required electronics for UHF remote control of DC motors for garage doors, gates, and shutters. Provision for upper and lower limit switches, and has r current sensing to stop the motor if it hits an UHF DATA TRANSMISSION Stamp sized Xtal locked 433.9MHz obstruction (this feature can also be used superhetrodyne receiver module $25 to eliminate limit switches). Includes a 2 min. timer with a MOSFET for 12V light. Small matching transmitter kit: $12 PO Box 89 Oatley NSW 2223 Security code has over 1/2 million combiPh ( 02 ) 9584 3563 Fax 9584 3561 nations. RX uses the pre-aligned UHF orders by e-mail: oatley<at>world.net receiver module. Use either 1 Channel http://www.ozemail.com.au/~oatley TX (K41) or 3 Channel TX (K40). PCB & major cards with ph. & fax orders, all on-board components kit for the RX Post & Pack typically $6 only: (K23)$75...12V wiper motor for $10 OATLEY ELECTRONICS *** $2 ** YES ** $2 *** VHF VIDEO 1-2 MINI MODULATORS WITH EVERY CAMERA YOU BUY OR HAVE BOUGHT IN THE PAST. INC DATA SHEET:$ 2 (Rm2). This unit will fit neatly with our camera in our 50x 50x50mm case + swivel mount strong adjustable universal bracket : $4 Bracket only :$1.50 *** FANTASTIC BARGAIN *** COMPUTER POWER SUPPLY PCB: New assembly. 45 x 108 x 200mm. 120 / 230V AC input. DC outputs are +5V<at> 6A,+ 12V <at> 1A,-12V<at>1A,-5V<at>1A. Data Inc.RU approval. Mains input . Be Quick: (Ps6) $12 ea. or 4 for $36 SOLAREX BRAND SOLAR PANELS These are professional quality solar panels with aluminium frame and glass cover and 1 year guarantee. 30W: $290-80W:...........$650 IR RECEIVER FRONT END MODULE This device contains an IR receiver diode, an amplifier tuned to 38KHz, a bandpass filter, an AGC section & detector circuit. $2 Ea or 10 for $15 PLASMA DISPLAY BALL KIT: High Power High Frequency EHT generator that will give an exciting plasma discharge with a std light bulb or make Jacobs Ladder or Laden Jar & other EHT applications. Can be converted to a DC. Supply with a HV diode. Inc. EHT transformer + PCB + all on-board parts & 1KV. fast Diode + application notes. Req 12V <at> 0.5-2A. Special price $29. $29 16KV. Diode $1.50 HELIUM - NEON LASER TUBE & SUPPLY KIT: Helium Neon 633nM red laser heads Great for light shows or holigraphy. 2-3mW. Inc. a special high voltage supply. Tube & supply: (L03) $80 This KIT requires 12V <at> 2A. WA R N I N G ! ! ! I N V O LV E S H I G H VOLTAGE & VERY BRIGHT NOT FOR USE BY CHILDREN!! ALL LASERS MUST BE USED UNDER COMPETENT SUPERVISION. BRAND NEW STD LCD DISPLAYS 1 line x 16 char. : $16 2 line x 16 char. with LED back-light:$24 NEW HITACHI LASER DIODES 40mW / 785 nM For scientific, medical and industrial applications : $65 35 mW / 650 nM : $90 **SPECIAL**SPECIAL**SPECIAL** FOR $1 EXTRA WITH EACH ORDER WE WILL SEND A WIRING KIT !!! Great for cars, radios mobile phones, fog lights etc. 4 colours, 2 guages of wire, Spade connectors, fuse holders, fuses. 17+ mtrs. of wire. Limited offer!!! just $1 *********CLEARANCE SPECIAL********* FLUORESCENT LIGHT HIGH FREQUENCY BALLASTS European made, new, "slim line" case high frequency (HF) electronic ballasts. Flicker free starting, long tube life, high efficiency, visual flicker during operation. Reduced radio frequency interference. Similar design to one published in the Oct. 94 Silicon Chip, although these are much more complex. Dimming requires external 100K pot or a 0-10V DC source. We have a limited stock 1 x 36W tube, 28 x 4 x 3 cm: (G09F) just $18 *************SUPER SPECIAL************ 60 NEW Flat NiCad FOR $10 Space saving batteries 16X48X5.5mm With solder tags By MARK ROBERTS This easy-to-build I/O card plugs into the parallel port of your PC. It features 11 analog inputs for sampling, plus two analog outputs and eight digital outputs. It’s software con­trolled and can automatically log sampled data on the analog input channels to an Excel spreadsheet. Simple I/O card with automatic data logging T HIS SIMPLE I/O CARD can be used to sample incoming data on up to 11 channels and/or used to control other equipment via its 10 output lines. You can either switch equipment on or off via the digital output lines, or control equipment using a variable 0-5V DC signal from two separate analog outputs. An on-screen “virtual” instrument panel is used to drive the card – see Fig.1. This display is software generated and its functions are easy to follow. On the righthand side of the panel are 10 analog input channels (Channels 1-5 and Channels 6-10), with each channel showing the voltage applied to it. The 11th analog input channel is directly below Channels 1-5 and is labelled “Battery Voltage”. The latter can typically be used to monitor the voltage from a real battery or simply used as an extra input channel. 22  Silicon Chip At the top left of the panel are eight buttons labelled D0-D7. These are used to turn the digital I/O lines on or off. Only one output from D0-D3 can be on at the same time, while any combination of buttons from D4-D7 Main Features •  11 analog input channels (020V) •  2 analog output channels (0-5V nominal – see text) •  8 digital output channels (open collector) •  Analog inputs can be sampled and automatically logged to an Excel spreadsheet •  Logging interval can be set to 10 seconds, 1 minute, 10 minutes or 60 minutes can be turned on at once. When an output is turned on, the indicator light below its button “lights” up. Red indicators are used for outputs D0-D3, while yellow indicators are used for D4-D7. Fig.1 shows how the panel appears with outputs D1, D4, D5 and D7 turned on. It also shows that voltages of 6.45V, 6.36V and 7.82V have been applied to input channels 3, 7 and 9 respective­ly, while a voltage of 6.27V has been applied to the 11th (Battery Voltage) input. Immediately below the digital output buttons are two large analog voltmeters. These show the voltage on each of the two analog outputs. You can easily vary these outputs over the range 0-5V DC by dragging the two slider controls (note: the maximum output voltage depends on the supply voltage from the parallel port). parallel port. The converted digital data is then clocked out from the DOUT pin (pin 16) and applied to pin 13 of the port. The clock signal comes from pin 6 of the parallel port and is applied to pin 18 of IC4 (I/O-CK). This clock signal is also applied to the SCLK (pin 2) inputs of ICs 5 & 6 and to the SRCLK input of IC2. ICs 5 & 6 are MAX515 10-bit A/D converters and these are used to provide the two 0-5V (nominal) analog outputs. As shown in Fig.3, their data inputs (DIN) are tied together and the data clocked in via pin 5 of the parallel port. Pins 7 and 8 of the parallel port control the CS (chip select) inputs (pin 3) of ICs 5 & 6, so that only IC is active at any given time. The MAX515 is programmed by Fig.1: the I/O card is controlled using this virtual instrument panel which is writing 16 bits of serial data, clocked generated by the software. It shows the voltages present on the analog inputs in the following order: four dummy and lets you control the analog and digital output channels. bits, 10 data bits and two sub-LSB zeros. The data is clocked in on the The only other feature of real note tors and the sampled signals are then SCLK rising edge while the CS signal on the main panel is the “Logging” applied to the A0-A10 inputs of IC4 on pin 3 is low and held in a 16function (in the top lefthand corner). for A/D conversion. bit serial register. This data is then Clicking this function brings up the The signal on pin 17 (Address) of transferred to the DAC register when dialog box shown in Fig.5, so that IC4 (applied from pin 3 of the parallel CS goes high to update the output you can automatically log sampled port) selects the input voltage to be voltage. data into an Excel spreadsheet. Of converted. The EOC (end of converThe maximum output from each course, you must have Excel on your sion) output at pin 19 then goes low MAX515 is Vcc-0.4V (Vcc is the voltcomputer in order to do this. when conversion is completed and age from the parallel port). This means Once the data has been logged in, this signals the PC via pin 10 of the that if the computer supplies 5V, then you can then use Excel to produce the maximum analog output will graphs or charts in the usual manner. be 4.6V. REF1, an LM385-2.5Z You can sample the incoming data voltage reference diode, supplies (0-20V) on the 11 analog inputs at a 2.5V reference to the REFIN 10-second, 1-minute, 10-minute or (pin 6) input of both ICs, giving 60-minute intervals just by clicking a resolution of about 2.5mV for the appro­ priate button. We’ll have the two analog outputs. more to say about logging to an Excel Note that the MAX515 DACs spreadsheet a little later on. will not operate if the voltage from the parallel port is down How it works around 3V – see panel. Now take a look at the circuit – see ICs 2 & 3 provide the digital Fig.3. The circuit uses six ICs plus a outputs. IC2 is a 74HC595 8-bit 2.5V voltage reference and not much serial in/parallel out shift regiselse. ter. The data comes in on pin 14 The four main ICs in the line-up (SER) and is clocked into a D-type are a 74HC595 shift reg­ ister (IC2), storage register when RCLK (pin an MC145041 8-bit A/D converter 12) goes high. The data on the E (IC4) and two MAX515 10-bit D/A (enabled) pin deter­mines which converters (IC5 & IC6). Each of these register is being updated. main blocks is controlled via a 3-wire The eight outputs from shift serial interface that’s compatible with register IC2 directly drive IC3 SPI, QSPI and Microwire standards. which is a ULN2803 Darlington IC4 is used to sample and digitTransistor Array. This device has ise the data on the 11 analog input Fig.2: this block diagram shows the main open collec­tor outputs and these channels (Ch1-Ch10 and Batt). Each circuit sections of the I/O Card. The card can be used to drive LEDs, relays input signal is fed to a voltage divider is controlled using software, with signals or opto-couplers, to control other consisting of 330kΩ and 39kΩ resis- sent via the PC’s parallel port. circuits. The maximum voltage August 1998  23 Fig.3: the circuit uses six ICs, with each of the main blocks controlled via a 3-wire serial interface. IC4 performs A/D conversion for the analog inputs, while D/A converters ICs 5 & 6 provide the two analog outputs. ICs 2 & 3 provide the eight open-collector digital outputs which can be used to drive relays or LEDs. that can be switched by the open collector outputs is 30V. IC1 doesn’t really play any role in the circuit operation as such. This device is a Dallas Semiconductor DS­ 24  Silicon Chip 2401 Silicon Serial Number. It comes in a standard TO-92 package but only two of its pins (Data and GND) are used. Each of these devic­es comes with a unique registration number and this number is read by the software via pin 15 of the parallel port. If the number matches the number programmed into the software, the software functions normally. If they don’t match, a demon­stration version of the software is loaded instead. This means that the software supplied with each individual DS2401 Fig.4: follow this parts layout diagram to assemble the PC board. As shown here, IC3 is driving eight LEDs but you can easily modify the circuit to drive relays or opto­couplers. is tailored to match that device. The same software will not work with other hardware because the code number will be different. Power for the circuit is derived from pin 9 of the parallel port which supplies a +5V rail. This means that no external power supply is required. Construction All the parts, including the DB25M connector, are installed on a small PC board measuring 76 x 68mm. Fig.4 shows the assembly details. Begin the assembly by installing PC stakes at the external wiring positions (ie, at the analog inputs, at the outputs and at the GND positions). This done, install the 10 wire links, noting that three of these links (shown dotted) are under ICs 2, 5 & 6. The resistors and the capacitors can go in next. Take care to ensure that the two 100µF electrolytics are installed with the correct polarity. Note that our prototype shows the eight digital outputs driving eight LEDs via 2.2kΩ resistors. This is also shown on the layout diagram (Fig.4). If you want to drive relays or optocou­ plers, the output circuit should be modified accordingly. For example, a relay can be driven by connecting it directly to an output of IC3 as shown on Fig.3. The six ICs (including the DS2401) can go in next, followed by the LM385 2.5V voltage reference diode. Note that the DS2401 and the reference diode both look the same, so be careful not to get them mixed up. Finally, complete the assembly by installing the DB25M connector. Check that this part lies flat against the PC board before soldering its pins. Go over your work and check the PC board carefully for mistakes before connecting the unit to a computer, ready for testing. You can either plug the unit direct­ly into the parallel port or connect it via a DB25 male-tofemale cable. Installing the software The software comes on two floppy discs and runs under Wind­ows 3.1x, Windows 95 and Windows NT. You install it by running setup.exe on the first disc and then following a few onscreen instructions. In Windows 95, for example, you click Start, Run and then type A:\setup.exe in the space provided (assuming that the floppy No Analog Output? The MAX515 10-bit D/A converters specified will not work if the voltage from the parallel port is down around 3V. If that happens, there will be no voltage on the analog outputs, regard­less of the slider settings. There are two ways around this problem: (1) Use the optional LPT2 card from Softmark (this card supplies about 4.95V); or (2) Use an external 5V DC power supply to power the circuit. If you choose this option, remove link LK2 and connect the external +5V rail to the vacant pad next to IC2. disc is in the A: drive). The installer program creates the appropriate program group and installs a shortcut in the Start menu. In Windows 3.1x, you click File, Run and type A:\setup.exe. When you boot the software, it first opens a dialog box that lets you select between two printer ports (LPT1 and LPT2). LPT2 is the initial default but most users will need to select LPT1 since they will only have one parallel port on their comput­er. You then click OK to bring up the instrument panel shown in Fig.1. Initially, all the displays will be off, since the Power is off. You turn the display on by clicking the Power button. Parts List 1 PC board, 76 x 68mm 1 PC-mount DB25M connector 1 2-disc software package 4 PC stakes Semiconductors 1 DS2401 silicon serial number (IC1) 1 74HC595 8-bit shift register (IC2) 1 ULN2803 Darlington transistor array (IC3) 1 MC145041 8-bit A/D converter (IC4) 2 MAX515 10-bit D/A converters (IC5 & IC6) 1 LM385-2.5Z 2.5V reference (REF1) Capacitors 2 100µF 16VW PC electrolytics 2 0.1µF monolithic Resistors (0.25W, 1%) 11 330kΩ 9 2.2kΩ (see text) 11 39kΩ 1 120Ω By the way, once you’ve selected a port, it can be saved as the default by clicking the Power button to off (this rewrites the io.ini file). The software will now always boot with the new port as the default, unless you change it again. Testing It’s now just a matter of checking that everything works. To do this, first August 1998  25 Fig.5: clicking “Logging” on the virtual instrument panel brings up the Logging System I/O Interface shown at right. This lets you select the logging interval, after which you can automatically log to an Excel spreadsheet as shown above. connect a voltmeter to each analog output in turn (ie, between the output and GND) and check that the output voltage can be varied from 0-5V (nominal) as you drag the slider under the corresponding meter. The eight digital outputs can now be checked. Each output should initially be high and should go low when its corresponding button is clicked on the instrument panel to turn it on. Note that because the digital outputs are open collector outputs, you will need to connect a load to test them; eg, a relay or a LED in series with a 2.2kΩ resistor. Don’t forget the wire a diode across the relay coil as shown in the circuit, to quench the back EMF generated when the relay turns off. If you don’t do this, you Where To Buy Parts Parts for this design are available from Softmark, PO Box 1609, Hornsby, NSW 2077 (phone/fax 02 9482 1565). Prices are as follows: Hardware MAX515 10-bit D/A converter ..............................................................$8 MC145041 8-bit A/D converter ............................................................$5 ULN2803 transistor array .....................................................................$4 74HC595 8-bit shift register .................................................................$3 LM385-2.5Z reference diode ................................................................$1 DB25M connector ................................................................................$2 PC board ............................................................................................$10 Full kit (hardware only) .......................................................................$40 Optional LPT2 card ............................................................................$15 Software (two discs) plus DS2401 Version 2.0 with logging .....................................................................$32 Version 1.0 without logging ................................................................$22 Payment by cheque or money order only. Please add $5 for postage. Note: the software associated with this design is copyright to Softmark. 26  Silicon Chip can destroy the switching transistors in IC3. If the circuit is working correctly, then either the relay will turn on or a LED will light when its corresponding digital output is clicked on. Now apply a voltage from 0-20V to each of the analog inputs in turn and check that the correct voltage is displayed for each channel. If you have a variable supply, check that the reading varies as you vary the input voltage. To check the logging feature, click Logging at the top left of the main Window. The “I/O Interface - Logging System” dialog box will now open (see Fig.5) and you should be able to start the automatic logging process by selecting the “Logging Interval” and clicking the On button. Excel should now automatically be launched and the sampled data automatically logged into the spreadsheet at the selected time intervals (see Fig.5). To stop the logging process, click the Off button on the Logging System dialog box. The program will then instruct you to click the Save + Exit button, after which you can save the spreadsheet data in Excel to a file and directory of your choosing. The Logging System dialog box can now be closed by clicking the Main Form SC button. SERVICEMAN'S LOG Neither cat proof nor kid proof Many faults in TV sets are due to human factors, or sometimes “cat factors”. Flower vases, cats, boisterous children and TV sets often don’t mix well together. This month, we were blessed with not one but two recent model Sony 53cm TV sets fitted with the current BG-2S chassis and barely out of the egg. It is unusual to be servicing such new sets (particularly two of them), as they would normally be covered under warranty with a Sony Service Centre. But these two came in by accident – literally. The first one was a KV-G21F2 belonging to Mrs White, who very foolishly left a vase of freshly watered flowers on top of the set, while she went shopping. And she left Pookie, the pedi­gree Siamese cat, in charge of the house. Pookie decided, in his wisdom, to leap onto the TV set, presumably on his way to climbing the brocade curtains. Unfor­tunately, there wasn’t enough room for both the flowers and Pookie on top of the TV. The result was inevitable, with most of the water finishing up inside the TV set. The situation was compounded when the lady switched the set on that night, to be confronted by a pyrotechnic performance on the wrong side of the screen, followed by complete silence and the sickly smell of something burning. The result was not only a technical problem but a diplomatic one as well. The lady’s hus­band wasn’t all that enamoured of Pookie at the best of times and now Pookie was really in the dog house – which is a dreadful thing to happen to any cat and doubly so for a sensitive pedigree Siamese cat. There was even talk of finding a new home for Pookie! Anyway, the upshot of it all was that, by the time I ar­rived on the scene, it was pretty horrible mess, with a surpris­ ing amount of corrosion. I suspect that the vase contained more than plain water, probably having been enriched by something designed to keep the flowers fresh plus some natural chemicals from the flower stems. I cleaned it and dried it as much as possible, then made a visual inspection. I was surprised to find that the main fuse (F601) was intact but R611, a 0.1Ω 0.25W resistor supplying power to pin 2 of switch­ mode transformer T601, was open circuit. From there, I traced the circuit from pin 5 of T601 to pin 1 of IC601, an STRS6708. And this IC had broken down completely – it had obviously gone short circuit and taken R611 with it. Before replacing these parts, I made a few checks on the various rails and found a short on the main 114V rail, off pin 13 of T601. This short could be anywhere but I decided that, for August 1998  27 Serviceman’s Log – continued the moment, I would start close to the power supply and check from there. I opened the rail by disconnecting resistor R131 and inductor L802, then bridged this gap with a 100W globe, with a voltmeter across it. With the short isolated, I replaced R611 and IC601 and was rewarded with normal power supply operation and a 114V rail, up to the 100W globe. But I still had to track down the short. This wasn’t hard; the horizontal output transistor, Q802 (2SD1878), was the logical suspect and sure enough, that was it. I replaced Q802, removed the 100W globe, reconnected R131 and L802, switched on and the set came to life. Well, sort of. The first problem I observed was intermittent vertical scan. I let it run for half an hour or so to see what would happen and whether I could pinpoint any likely cause. I couldn’t and the vertical timebase problem only became worse until it failed completely. Again, I picked on what ap­peared to be the most likely suspect – the vertical output IC (IC551, LA7830). I was right once again but I must admit that it took no great mental effort – the whole thing was 28  Silicon Chip messy and badly corroded. Replacing it cured that problem. But I wasn’t out of the woods by any means. I had fixed the most obvious and immediate problems but a prolonged soak test revealed that a few more subtle ones were still lurking. In par­ticular, there was some horizontal tearing and either wrong or no colour at switch-on, although these problems usually cleared after few minutes. By now I was beginning to worry that the soaking might have created long-term damage which would continue to surface long after I had fixed all the obvious faults. The problem as far as I was concerned was how could I possibly guarantee the repair under these circumstances. All I could do was press on and hope for the best. In more practical terms, the chief suspect was the jungle IC (IC300, TDA8375A), a 56-pin monster which had scored a direct hit from the water. Quite frankly, I didn’t fancy having to replace it. It would not only be expensive but the job would be time-consuming as well. Nevertheless, that seemed to be the next logical step so out it came. This revealed several damp patches that had been under the IC, along with some wire links that were already show­ing signs of corrosion. What ever it was that had been added to the water, either deliberately or by accident, it was a pretty potent brew, attacking everything in its path. I cleaned and dried everything and fitted new links to the board. At this point, I was all set to procure a new IC but sud­denly wondered whether this might be overkill; it could be that there was no fault in the IC itself and that the faults had been due to the damp patches. Was it worth taking a punt on that? If I refitted the original IC and the fault(s) reappeared, I would have to go through the whole replacement routine again. But if it fixed the problem, I would have saved the cost of the IC plus the delay in getting it. I took the punt and I won; the old IC behaved perfectly and even after a soak test lasting several days, there were no signs of trouble. The only complaint came from Poo­kie’s master, who was frustrated at the time it took to do the job. But as I explained to him, it was essential that I (soak) test the set over several days to be sure that nothing had been overlooked. And what happened to Pookie? Nothing drastic as far as I know, apart from a few black looks and some nasty comments from his master. I did, however, suggest that the flowers should be moved elsewhere to prevent a repeat incident. The fallen Sony The demise of the second Sony KV-G21F2 was more violent than the first. It had actually fallen over onto a carpeted concrete floor. As a result, the cabinet was cracked and the set was dead. I didn’t enquire as to how this set had met this untimely fate. No explanation was offered but the Morris family has four boisterous young boys so it wasn’t too difficult to imagine what had happened. A close examination on the bench revealed that the main PC board had sustained several large cracks, the most obvious ones being around the horizontal output transformer and the front panel controls. These cracks were all repaired but it wasn’t going to be as easy as that. The large cracks were easy; it was the hairline cracks that were the real problem. There are several approaches to finding these. Visual inspection using a good light and a jeweller’s loupe is one method and it really pays to examine the board carefully adjacent to where large cracks have occurred. The other approaches are basically electrical. If a voltage or a signal cannot be found at one end of a track but is present at the other, the break is somewhere along that track. But pin­pointing it can still be difficult. The light and jeweller’s loupe may be sufficient but it often requires a very sharp point­ed probe which will penetrate the board lacquer. And in the end, it’s back to visual inspection. It took a long time to find and fix some of these hairline cracks and it was a most frustrating exercise. Finally, I was confident that I had found the last one. I switched the set on, there was a rush of sound and the picture came on. My elation didn’t last long – there was a sudden click and then silence. After some detective work, I found yet another hairline crack which had been concealed by paint and was lying between closely packed adjacent tracks. But it was of no immediate help; the set was still dead – only the standby light could be switched on and off with the remote control. So where to now? Were there more hairline cracks which I still had to find or was there a component fault as well? Either way, all I could do was go over the whole thing again to see if I could find a clue. I went back to taws and checked the power supply and rail voltages. The supply was working perfectly and the main HT rail was at 114V and was applying voltage to the collector of Q801, the horizontal drive transistor (2SC3209). And this gave me my first clue – the voltage was too high at that point because the transistor was completely cut off. The reason for this wasn’t hard to find; there was no base drive to the transistor. The set is switched on via pin 30 of microprocessor IC001 (system control), which switches on 9V regulator IC521. Among other things, this regulator supplies 8V to pins 12 and 37 of IC300, the jungle IC which had reared its head in the previous story. The regulator also switches a +15V rail to the audio output IC (IC203), via transistors Q207 and Q208. These circuits were all working but there was no horizontal drive signal (15,625Hz) from pin 40 of IC300, which accounted for the high voltage on the collector of Q801. But was this due to a fault in the IC or was it due to something connected to IC300? I went over everything I could think of that might be the cause. I soon established that the 4.43MHz crystal oscillator reference wasn’t working but couldn’t be sure whether this was a cause or an effect so I put that observation on hold. There is a “hold down” function (HD.SW) associated with pin 27 of IC001, which controls transistor Q801 and whose function it is to shut down the horizontal output stage in the event of a fault. I disconnected the circuit from pin 27 in case it was shutting things down but no joy. Finally, I took the plunge and replaced IC300. And that was it; the set burst into life and everything functioned perfectly. And it kept on working after several days soak testing. And that was about as far as I could push it. There was no way of knowing whether there were any more hairline cracks lurk­ ing in the background. There could be but until a fault develops, there’s nothing more that can be done. I mentioned earlier that the cabinet had been cracked. It was a relatively minor fault and a new cabinet would cost a couple of hundred dollars. In view of the cost, the owner was happy to live with it. So why did IC300 fail? My theory is that it was damaged by spikes, probably from the horizontal output stage, before all the cracks had been fixed. So considering everything, the owner was lucky the set was not written off. And perhaps his four bois­terous boys should be consigned to the dog house along with Pookie! The Akai stereo TV Mr Gavin is an amicable bloke who was somewhat disappointed that his 18-month old Akai CT2167A TV August 1998  29 Serviceman’s Log – continued set had broken down so soon. This Chinese-made model is a 53cm unit with remote control and Teletext. Unfortunately, the owner had found it increasingly difficult to turn the set on with the remote, until eventually it failed completely. As it came to me the set was dead except for the standby indicator LED. This at least told me that the switch­ mode power supply was working, as the 5V rail for the LED is derived from a 7V rail via Q901. In fact there are four voltage rails, the highest being at 105V. My first step was to check this voltage at the collector of Q402, the horizontal output transistor. This was present and was switchable with the remote via Q905. As for the Sony TV in the previous story, the collector voltage on the horizontal driver transistor (Q401) was high, once again suggesting a lack of drive to that stage. This should come from pin 41 of jungle IC IC301. And again, there was no 8.8MHz signal from the crystal clock oscillator at pin 2 of IC301. It fact, there was no voltage at all on that pin, or any­where else on the IC for that matter. In particular, there was little or no voltage on pin 42 which should have been 8.6V. This voltage is normally derived from the 105V rail 30  Silicon Chip via 5W resistor R306 (6.8kΩ). At least, the circuit showed it as a 5W resistor. But if the undersized unit in the chassis was rated at 5W I was a mon­key’s uncle. I pulled the resistor out and measured it, only to find that it had gone way up into the megohm range. I fitted a fair dinkum 5W unit in its place and the set burst into life and everything functioned as it should. My theory is that the increasing reluctance of the set to turn on was almost certainly due to the progressive increase in value of that 6.8kΩ resistor. Just how the wrong wattage resistor found its way into the set is anyone’s guess. Unusual video recorder My final story for this month concerns an unusual video recorder that Mrs Small brought in for service. It was one of the NEC 9000 models; one of a long-running series with many different features and cabinet styles. In this case, it was a model N9034M which is a multi-system variant of the N9034A, both of which were available in Australia, although it was originally designed to sell in the Middle East. The “M” model covers PAL, NTSC and MESECAM (a version of SECAM). That is by way of background. The actual problem involved the power supply, which is designed to automatically operate from any voltage from 90-260V AC (either 50Hz or 60Hz). It’s obviously aimed at the widest possible market and is a set that you could take almost anywhere. An interesting point here is that the power supply con­struction is completely different from the rest of the video. In fact, it’s quite possible that the power supply is not made by NEC at all but by some other manufacturer. That said, the power supply is obviously very well made. It’s built inside its own metal cage and is relatively easy to remove from the body of the recorder. But that’s the end of the easy part; working on it within the cage is a job in itself. The cage is made in two parts, each roughly “L” shaped. One half forms the top and one end, while the other half forms the other end and the bottom. The cage itself functions as a heat­sink, the heavy duty power transistors and other larger compon­ ents being mounted on one end. The remainder is the circuit is mounted on a PC board. But there’s more to it than that. From a servicing angle, this power supply has more tricks than a cartload of monkeys. Any mistakes in the diagnosis of this switchmode unit and you can blow the lot in a nanosecond. When that happens, you are right back where you started, except that you are at least $50 lighter. Unfortunately, the replacement parts are very expensive. At trade level the transistors cost $24 each and the resistors $1.62. The exception is 5W resistor R2 which was listed at $4.15 before it became “no longer available”. A quick check showed that resistor R2 (20Ω) had failed. This resistor is in the bridge rectifier secondary circuit and it blows instead of fuse F1 which is rated at 2A. More to the point, of course, was why did that resistor fail? And that is the tricky part of servicing this power supply. The circuit is such that a failure in one component can create a chain reaction that can take out several other major components, particularly the expensive power transistors. The safest procedure appears to be to make as many individual component tests as possible before applying power. In this case, the basic cause SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. Fig.1: the universal power supply in the NEC 9034-M video recorder can be tricky to service. A failure in capacitor C11 and/or C12 can also take out power transistors TR1 and TR2, along with resistors R2, R10 and R11. P.C.B. Makers ! If you need: •  P.C.B. High Speed Drill •  P.C.B. Guillotine •  P.C.B. Material – Negative or Positive acting of the fault was the failure of either electroly­ tic capacitor C11 (220µF 10V) or C12 (220µF 15V), or both. This causes transistors TR1 and TR2 (2SC6378) to go short circuit, which takes out 5.1Ω resistors R10 (5W) and R11 (1W). From this, it is easy to understand how a newcomer could be trapped by such a circuit. Simply replacing one suspect component at a time is not good enough. One needs to be sure – or as sure as possible – that all faulty components have been found and re­placed before applying power. Fortunately, none of these dire predictions eventuated. Having been forewarned by colleagues, I was extremely careful and the job was completed without incident. So I was lucky the first time. Finally, here is a little snippet from the reception coun­ter. A teenage lad came in with a video recorder and was con­cerned about the loss of the small flap, fitted on many machines, which cover the various controls. Could he buy a replacement and how much it would it cost? My assessment was that it would cost far more than it was worth; that it would be easier and cheaper to simply forget about it. But the lad was obviously not convinced. “But what about the cockroaches?” “The cockroaches? What cockroaches?” “Well, isn’t the flap put there to keep out the cockroach­es?” Well, maybe the flap was performing that function in its present environment but a I doubt whether that was what was in the designer’s mind SC when he specified it. •  Light Box – Single or Double Sided – Large or Small •  Etch Tank – Bubble or Circulating – Large or Small •  U.V. Sensitive film for Negatives •  Electronic Components and •  •  Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 •  ALL MAJOR CREDIT CARDS ACCEPTED August 1998  31 CIRCUIT NOTEBOOK 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. LOPT/shorted turns tester This circuit will determine if a line output transformer (LOPT) has shorted turns. To set it up, short the input to ground to prevent the oscillator comprising Q1 & Q2 from running, then adjust the 50kΩ trimpot VR3 until the LED turns on, then back the preset off until the LED just goes out. This done, remove the short on the input, set the 1kΩ potentiometer VR1 to its mid-way position, then adjust the 2kΩ trimpot VR2 to the crossover point. To use the tester, adjust VR1 until the LED just turns on, then connect the primary winding of the LOPT to the input. If the LED goes out, the winding has a shorted turn. A good winding will start the oscillator and light the LED, even if trimpot VR1 is set before the LED turn-on point. Stuart Williamson, Hamilton, NZ. ($35) Low voltage drop bridge rectifier The circuit below will have less than half of the voltage drop and hence power loss of a conventional bridge rectifier at DC output currents of up to 10A. At lower currents it has slight­ly more than half of the expected losses of an all-Schottky diode bridge circuit. The maximum AC input voltage is 28VAC and the minimum AC input voltage is about 10VAC. The rectifier should be used with a filter capacitor just as with conventional bridge rectifiers. The power devices should be mounted on heatsink(s) if more than 3A is needed. G. LaRooy, Christchurch, NZ. (30) Thermal protection for power FETs This circuit produces a steeply falling output current with increasing heatsink temperature. Hence a smaller heatsink can be used if it is acceptable for the output current to fall if ambi­ent temperature and therefore heatsink temperature rises. The circuit was used for fast-charging four NiCd AA cells from a 12V DC source. It could also be used for constructing protected linear power supplies or for heating ducted air whereby the heatsink raises the temperature of cool air and doesn’t affect the temperature of hot air, be32  Silicon Chip cause the transistors would be conducting much less. The key to good circuit operation is that all the transis­ tors are mounted close together on the same heatsink to ensure thermal coupling. The output current is VBE/RDSon where VBE applies to Q2 and RDSon applies to Q1. With the values shown on the circuit, around 6A can be expected at room temperature, falling to 2A with a heat- sink temperature of 100°C. G. LaRooy, Christchurch, NZ. ($30) Stepper motor driver This circuit interfaces a 4-winding vari­able reluctance stepper motor to a PC’s parallel port. It was used with a motor from an old 5.25-inch disc drive, with 150Ω wind­ings. The 40194 chip is a universal bidirectional shift register. The SL (shift left) pin is connected to output Q0 and SR (shift right) is connected to Q3. This means that when shifting has reached the last pin, it will be transferred back to the first again. Input P0 is connected to the supply rail while P1-P3 are connected to ground (0V). When the chip is reset, via the soft­ware, this will make Q0 high, for an initial output. There are four inputs from the PC port: clock, reset, and two for direction (S0 and S1). The reset pin must be held high normally and will reset the chip when taken low. The initial input will be preset at the outputs when S0 and S1 are taken high and the IC is clocked. With S0 high and S1 low, the stepper rotates in one direction, while with S1 high and S0 low, it rotates in the other direction. The four op amps (IC1) are connected as comparators to provide a full 12V swing using the 5V input from the computer port. Additional stepper motors require only two extra output lines from the computer, for S0 and S1 on their respective shift registers, as the clock and reset lines can be common to all. A sample Pascal program is included – see Table 1. David Mueller, Bayswater, Vic. ($40) Table 1: Sample Pascal Program portw[Port] := 0; portw[Port] := 8; portw[Port] := 2+4+8; portw[Port] := 1+2+4+8; portw[Port] := 2+4+8; portw[Port] := 8; for i: =1 to 50 do begin portw[Port] := 2+8; portw[Port] : = 1+2+8; portw[Port] : = 2+8; end; for i:= 1 to 50 do begin portw[Port]:= 4+8; portw[Port]:= 1+4+8; portw[Port]:= 4+8: end; {Resets the} {chip} {Set chip to present mode} {Pulse clock pin high to} {put pin Q0 on chip high} {so chip has initial state} {Clockwise} {Pulse clock : one step anti clockwise} {End of pulse} {Anticlockwise} {Pulse clock : one step anticlockwise} {End of pulse} High frequency driver protection This circuit provides protection for a tweeter which may be subjected to over-drive by the amplifier. The protection is a two-step system depending on the non-linear resistance of a lamp filament combined with a shunt transistor which conducts above a certain signal threshold. The resistance of the lamp filament increases with increas­ ing input current power and at around 5V across the lamp, the signal to the tweeter becomes very limited. At that point the transistor also conducts and effectively shorts out the tweeter. The transistor should have a small heatsink if the unit is to be run at high power for long periods. By the way, this circuit will cause distortion and is in­tended more for PA and disco applications than for hifi use. Stuart Williamson, Hamilton, NZ. ($25) August 1998  33 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au Silicon Chip Bookshop SUBSCRIBE   AND GET   10% OFF SEE PAGE 88 Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1997 (4th edition). This is a practical guide on the installation and servicing of satellite television equipment, including antenna installation and alignment. The cover­age of the subject is extensive, without excessive theory or mathematics. 383 pages, in hard cover at $55.00. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $90.00. Video Scrambling & Descrambling For Satellite & Cable TV By Rudolf F. Graf & William Sheets. First pub­lished 1987. This is an easy-to-understand book for those who want to scramble and unscramble video signals for their own use or just want to learn about the techniques involved. It begins with the basic techniques, then details the theory of video encryption and decryption. It also provides schematics and details for several encoder and decoder projects, has a chapter of relevant semiconductor data sheets, covers three relevant US patents on the subject of scrambling and concludes with a chapter of technical data. 246 pages, in soft cover at $50.00. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ ested in audio design. 336 pages, in paperback at $70.00. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $90.00. Radio Frequency Transistors Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $95.00. Guide to TV & Video Technology By Eugene Trundle. First pub­lished 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $55.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order  ❏ Bankcard  ❏ Visa Card  ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Prices valid until 31st August, 1998 been expanded to include chapters on surface mount technology, hardware & software design, semi­-custom electronics & data communications. 63 chapters, soft cover at $160.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $75.00. Understanding Telephone Electronics By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is a very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $55.00. Title o o o o o o o o o o Price Guide to Satellite TV $55.00 Servicing Personal Computers $90.00 Video Scrambling & Descrambling $50.00 The Ar t Of Linear Electronics $70.00 Digital Audio & Compact Disc Technology $90.00 Radio Frequency Transistors $95.00 Guide to TV & Video Technology $55.00 Electronic Engineer's Reference Book $160.00 Audio Electronics $75.00 Understanding Telephone Electronics $55.00 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ add $10.00 per book; elsewhere add $15 per book. TOTAL $A August 1998  37 Silicon Chip Back Issues September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. Conversion; Plotting The Course Of Thunderstorms. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System; The Care & Feeding Of Battery Packs; How To Make Dynamark Labels. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C Transmitter; Index to Vol. 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. July 1990: Digital Sine/Square Generator, Pt.1 (0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. June 1991: A Corner Reflector Antenna For UHF TV; Build A 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; A Windows-Based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _____________________________________________________________________________________________________________ _____________________________________________________________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 38  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A8 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. ✂ v August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80Based Computer; A Look At Satellites & Their Orbits. Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Audible Continuity Tester; Cathode Ray Oscilloscopes, Pt.7. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder (Uses Pressure Sensing); Adding RAM To A Computer. April 1997: Avoiding Win95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. May 1997: Windows 95 – The Hardware Required; Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags – How They Work. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­ verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. May 1996: Upgrading The CPU In Your PC; Build A High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/ Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home; How Holden’s Electronic Control Unit Works, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; The Flickering Flame Stage Prop; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Regulated Supply For Darkroom Lamps; Build A Musical Doorbell; Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: A Heart Transplant For An Aging Computer; Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Demonstration Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. March 1998: Sustain Unit For Electric Guitars; Inverter For Compact Fluorescent Lamps; Build A 5-Element FM Antenna; Multi-Purpose Fast Battery Charger, Pt.2; Command Control System For Model Railways, Pt.3; PC-Controlled LCD Demonstration Board; Feedback On The 500W Power Amplifier; Understanding Electric Lighting, Pt.5; Auto-detect & Hard Disc Drive Parameters. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­grammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light show; Understanding Electric Lighting, Pt.6; Philips DVD840 Digital Vide Disc Player (Review). October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; A Detector For Metal Objects; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. November 1996: Adding A Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. June 1998: Troubleshooting Your PC, Pt.2; Understanding Electric Lighting, Pt.7; Universal High Energy Ignition System; The Roadies' Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. December 1996: CD Recorders ­– The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­ rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Sorting Out The Problems); Build A Heat Controller; 15-Watt Class-A Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; An Automatic Semiconductor Analyser; Understanding Electric Lighting; Pt.8. May 1995: What To Do When the Battery On Your PC’s Mother­board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. June 1995: Build A Satellite TV Receiver; Train Detector For Model March 1997: Driving A Computer By Remote Control; Plastic Power November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Pre­amp­lifier;The Latest Trends In Car Sound; Pt.1. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p. August 1998  39 COMPUTERS: Adding memory To your PC Troubleshooting Your PC; Pt.4 Want to add some more memory to your computer but don’t know what type to use? This article will help you decide which type of memory is right for you. By BOB DYBALL Selecting RAM for your system used to be simple. Neglecting the video card, there were just two choices: static RAM for the cache memory and regular DRAM, or dynamic RAM, for the main memory. Unfortunately, it’s no longer quite so easy. As computer speeds have increased, so the memory choices have become more complicated. There are now several different types of DRAM and it’s important to select the correct type if you are adding extra memory to your computer, otherwise it may not work correctly. As for video RAM, well that’s a whole new ballgame again. But that’s not the end of the story. 40  Silicon Chip The system motherboard will also have an EPROM (erasable programmable read only memory), which contains all the BIOS settings so that the machine can boot up. And some of the expansion cards may include an EPROM or a ROM as well. As you might expect with computers, memory has it’s fair share of buzzwords and jargon to confuse the uninitiated. In this article, we’ll sort out what the jargon really means so that you can decide what sort of RAM is best for your PC. RAM versus ROM As most people know, the word RAM stands for “Random Access Memory”. This type of memory is known as read/write memory be­cause you can both read data from it and write data to it (although not necessarily at the same time). This contrasts with ROM, which is read only memory except when it is initially being programmed. The main differences between Static RAM, Dynamic RAM and ROM chips are summarised in Table 1. It’s worth noting that there are a number of different types of DRAM and ROM. To make matters more interesting, when someone says “ROM”, it might be a mask programmed ROM (ie, one programmed when it was made in the factory) or it could be an EPROM or Flash ROM and they are simply using “ROM” as a generic term. Most motherboards now have a Flash ROM for their BIOS. Older PCs either had a PROM or an EPROM for the system BIOS. A PROM (Programmable Read Only Memory) is designed to be programmed just once. An EPROM (erasable PROM), on the other hand, has a small window which allows you to erase the contents by exposing the chip to UV light for a short time. A special UV lamp is normally used for this but it is also possible that a chip might be erased, or partly erased, when exposed to sunlight or artificial light over a longer period of time. For this reason, the window is usually covered with an opaque sticker to prevent accidental erasure. The E2ROM is an electrically erasable PROM. This means that the memory can be erased electrically, which makes it more con­venient to reprogram. A Flash ROM is an E2ROM and most mother­boards now use this type of device to store the system BIOS since it is easy to update it with new BIOS versions. All you have to do is run a small DOS utility to load the new version code into BIOS. A word of warning here – you must be careful when repro­ gramming a Flash ROM because if you mess things up and the new code is crook, the computer might not boot. Similarly you’ll be in for trouble if you interrupt the writing to a Flash ROM. It may be possible to “hot-swap” the crook unit with the Flash ROM from an identical motherboard after boot up and then re-burn it but you cannot rely on this somewhat dodgy procedure to work all the time. If you don’t have a couple of similar PCs around to try this trick, then you will need to remove the Flash ROM and have it reprogrammed in a special EPROM programmer instead. Table 1: RAM vs. ROM Feature Retains information when power is removed? Power Consumption Dynamic RAM (DRAM) Static RAM (SRAM) ROM No No Yes Moderate H i gh Low Access Speed Fast Very Fast S l ow Main Use In PC System RAM L2 Cache RAM BIOS ROM of capacitors etched into the silicon of the IC. Like all capacitors, these “leak” and, after a couple of seconds, will “forget” what was in them. To prevent this, the memory cells are refreshed every few millisec­ onds (during the “refresh cycle”), so that the charges on the tiny capacitors in the chip are constantly topped up. The obvious drawback of this type of memory is the overhead dictates of the refresh cycle. Essentially, for a part of the overall time, the system will be busy doing nothing except re­freshing the memory. Most BIOSes, however, do have options to modify what happens in DRAM. For example, some have a “hidden refresh” that’s carried out while the PC is also busy elsewhere. Other BIOSes can allow a change in the time between refreshes. Note, however, that while it’s often possible to squeeze an extra ounce of performance out of a PC by increasing the refresh time, you should be careful here. Too long a time between re­freshes can result in errors as Alzheimer's sets in – the memory literally “forgets” the data written to it before the next re­fresh cycle comes along. Video RAM Do you remember “CGA snow?” Back before VGA, in the days of EGA, MGA and CGA video cards, you would often see some flickering on the screen. This was caused by interruptions to the video card when it was scanning the video RAM to produce its screen output. This problem was overcome in time by better video drivers, better video cards and faster memory, especially through newer “dual-ported” memory chips (more on this shortly). By the way, if the RAM on your VGA card can be expanded, check upgrade costs Static RAM or SRAM The memory cells or individual storage locations in static RAM are made up of TTL gates. Its main advantage is that it is fast but there are drawbacks. The larger the chip the more power it consumes and the more heat it must dissipate. And that adds considerably to the cost, as well as placing some restraint on the size of the memory chip. Because SRAM is considerably more expensive than DRAM, it is used in places that need moderate amounts of high-speed RAM, such as the motherboard level 2 cache (or secondary cache). Dynamic memory or DRAM The memory cells in DRAM consist The RAM used on video cards is often dual-ported which means that it can be written to and read from at the same time to speed up operation. This 3-year old Diamond Stealth card uses 2Mb of VRAM, with provision for another 2Mb to be plugged into adjacent sockets. August 1998  41 Table 2: Matching RAM To Your Motherboard CPU Memory Bus S peed Non Parity? Parity? DRAM Type 486 (1) 33MHz Yes (5) Yes (5) FP DRAM Pentium (2) 66MHz Yes (5) Yes (5) FP DRAM Pentium (3) Up to 83MHz Yes (6) N/A ED O D R A M Pentium II (4) 66-125MHz Yes (6) N/A SDRAM (7) Notes: (1). With the exception of a couple of 486 chipsets de­signed for EDO, you should use FP DRAM to avoid instability in these PCs. (2). Older Pentium PCs will usually use FP DRAM. (3). If supported, EDO RAM will be faster than FP DRAM, though EDO RAM might prove unstable at 83MHz (or higher) memory bus speeds. (4). SDRAM DIMMs are the memory of choice for faster Pentium based PCs. (5). Some older 486 PCs have no option to disable parity, so memory upgrades require parity SIMMs. More recent 486 PCs and most Pentiums that support parity will often have an option to disable it (this is saved in CMOS and changed in the BIOS setup options). (6). Many motherboard chipsets, including the popular Intel Triton, no longer support parity and default to a non-parity mode. You can easily mix parity SIMMs and non-parity SIMMs in these PCs because parity is ignored anyway. (7) Make sure you specify that these are for a Pentium II, since they will usually need to have “Serial Presence Detect” EEPROMs. If you don’t use this type of SDRAM module in a Pentium II ma­chine, the memory won’t work. before you buy. Buying the extra RAM with the card is often cheaper than buying it separately later on. As you increase the resolution and number of colours with newer VGA cards, using ordinary DRAM on the card can create all sorts of problems. Between the DRAM needing to be refreshed, your system trying to write to it and the VGA card trying to write to the screen to display the picture, things can either get slow or ugly, or both! The factor here is called memory bandwidth – there is simply not enough of it to spare with the slower types of RAM at higher resolutions. So, to overcome this problem, special types of RAM have been introduced to cater for the needs of VGA cards. These include VRAM, WRAM and SGRAM. means that it can read and write data at the same time. This makes VRAM ideal for use in video cards because the RAMDAC (ie, the digital to analog converter) can read the data it needs to display the next pixel without any interruption – even if the system is busily updating the same areas of RAM containing this data. If you are upgrading a VGA card that has VRAM, check the user manual for the VRAM chips you need for your board as there are many different configurations on the market. If you have lost the manual, check the other chips nearby as the empty RAM upgrade sockets on the VGA card will usually be in parallel with the existing chips. Apart from VGA cards, VRAM is also often used for image capture, in high speed printers and for signal processing. VRAM WRAM, SGRAM, MDRAM Ordinary RAM doesn’t allow reads and writes to be carried out simultaneously. However, VRAM or video RAM does, as it is “dual ported”, which Often, the newest types of video RAM are “vamped up” ver­sions of the latest DRAM, sometimes with some extra features thrown in. Usually, 42  Silicon Chip it’s just the latest DRAM but made dual-ported and given a fancy new acronym. For example, WRAM (or “Win-dowed RAM”) is simply dual ported RAM for use on VGA cards. It’s based on EDO type RAM, which means that it offers better performance than older types based on FP (fast page) DRAM. MDRAM is Multi-Bank Dynamic RAM. SGRAM (Synchronous Graphic RAM) is single (not dual-ported) SDRAM that is designed for use on VGA cards. Many SGRAM chips include on-chip functions to speed up line drawing operations! Parity In addition to handling data bits, some DRAM modules use an extra bit of memory to check for errors. This type of memory is known as parity RAM. Most companies now ship PCs with­out parity RAM but many older PCs can and do use parity memory. Once it was unusual to find a PC without parity RAM. Then, a few years ago and not long after SIMMs were introduced, some manufacturers found that they could shave costs by replacing the parity chip on the SIMM with another chip known as a “parity generator”. They could then sell this RAM cheaper than genuine parity RAM or for the same price but at a greater profit. With genuine parity RAM, the system detected any memory errors and warned if there was a problem. Conversely, if a parity generator was used, a parity check always returned an OK result, even if it wasn’t. This meant that the user wouldn’t be warned of any problems until much further down the track, when the problems had become much worse and affected the PC quite dramatically. These days, memory is considered very reliable and virtual­ly all systems ship with non-parity RAM. On some motherboards, there is provision in the system BIOS to enable or disable parity checking and it’s simply a matter of selecting the correct option to suit the type of RAM installed. DIMMs & SIMMs Two other terms that you will commonly hear in relation to memory are “DIMMs” and “SIMMs”. These terms simply refer to the type of module that the memory is mounted on (the packaging, if you like). SIMM stands for “single inline memory module”, while DIMM stands for “dual inline memory module”. In plain English, a SIMM has a single row of pins and a DIMM has two rows of pins. The buzzword used to be “DIP”, which is an acronym for “dual inline package”. This type of memory (now obsolete) looked just like conventional ICs and the chips were slotted en masse into rows of sockets on the motherboard, sometimes occupying up to a third of the total area. Unfortunately, the DIP sockets sometimes became dusty and corroded over time and the overall reliability suffered because of the sheer number of RAM ICs requiring sockets. SIMMs come in two basic sizes: 30pin and 72-pin. Both types are keyed with a notch at one end, so that they can only be installed the right way around on the motherboard. The 72pin SIMMs are used in more recent equipment but there are still plenty of older 286/386 PCs and 486 PCs that accept 30-pin SIMMs. Most 30-pin SIMMs used for PCs had 9 bits (8 data bits plus 1 bit for parity). 72-pin SIMMs are perhaps the most common RAM package used today but are now being superseded by DIMM SDRAM. DIMMs Featuring 64-bit data, the 168-pin DIMM package has been used for some time in the Apple Mac and is currently the standard type of RAM for most new PCs. Since the popular SDRAM (synchronous DRAM) usually comes in a DIMM package, the terms DIMM and SDRAM are often used inter­ changeably. A “DIMM” is merely the JEDEC standard package, just like 30 or 72-pin SIMMs, and can come fitted with FP (fast page), EDO (extended data out) or SDRAM chips. Common DRAM types Although SIMMs and now DIMMs have made it easier and cheap­er to upgrade RAM than ever before, you do have to choose what type of DIMM or SIMM memory you need. And that depends on your motherboard. Let’s take a look at the three basic types: (1) FP or “Fast Page” RAM: part of the delay in getting data out of RAM is simply getting the addresses loaded into the RAM to begin with. This lead to the development of FP DRAM which provides faster reads from the same “row” (or page) than conven­ tional DRAM. Many older PCs use FP DRAM but later, faster PCs will experience RAM access bottlenecks because the RAM is unable to keep up. (2) EDO or “Extended Data Out” RAM: faster than FP DRAM, 72-pin EDO SIMMs are currently the most common type of DRAM used in Pentium family motherboards. Although EDO DRAM outperforms FP DRAM, your system needs to “know” how to “talk” to it – ie, both the motherboard and the system BIOS must be designed for the job. Unfortunately, most 486 PC users must upgrade using FP DRAM since using EDO would cause timing problems. On the other hand, if you’ve upgraded a Pentium processor or if you’re doing a little overclocking to tweak it up a notch, you should consider using SDRAM since higher clock speeds could run EDO DRAM close to (or beyond) its speed limits. (3) SDRAM or “Synchronous DRAM”: SDRAM is the latest and greatest but it’s not for everyone. If you already have EDO RAM and don’t have stability problems, stick with it. On the other hand EDO RAM might not be too stable at bus speeds of 83MHz, while SDRAM with the correct speed rating can run at up to 100MHz or more. Although the most common DIMMs used in PCs are 3.3V unbuf­ fered SDRAM types, Pentium II users should check when buying DIMM RAM as they will likely need it with a “Serial Presence Detect” EEPROM. Ordinary DIMM memory might not be suitable in such ma­chines. Which type of memory? So which type of RAM should you buy if you want to add extra memory to your PC’s motherboard? The obvious answer is check the manual. The same goes if you wish to add memory Table 3: Number Of SIMMs CPU DRAM Type No. Per Bank 386S X 30-pin SIMM 2 386D X 30-pin SIMM 4 486 30-pin SIMM 4 486 72-pin SIMM 1 Pentium 72-pin SIMM 2 Pentium 168-pin DIMM 1 to a video card (it really pays to store those manuals in a safe place). If you’ve lost the motherboard manual, Table 2 will provide a useful guide as to what type of RAM should work in most situa­tions. You should also check the RAM that’s already fitted to the machine for further clues. You can usually identify the speed of the DRAM fitted to your motherboard by looking at the labelling on the individual memory chips. Usually, you will see a number such as -60 or -70 after the main type number and this gives the speed of the RAM in nanoseconds; ie, 60ns and 70ns respectively for the examples just quoted. Sometimes, however, you have to multiply the number shown by 10ns; eg, if you just see -6, the speed of the DRAM is 6 x 10 = 60ns. The above applies to both 30 and 72-pin SIMM modules and to the older DIP RAM ICs. SDRAM is also labelled with a rating related to the access speed, either in x1ns or x10ns. For example a -1 would mean 10ns. . Installing more RAM In 486 or earlier systems, you will often have to go to CMOS, select standard setup, then exit and save to have the system recognise the extra RAM you have added to the motherboard. In later 486 and Pentium machines, simply adding the memory is enough – the amount of RAM is checked each time the machine is booted up. The amount of RAM you should add to an existing system depends on the applications you wish to run. If you are running a 486 with 4Mb or 8Mb of memory and would like to run Windows 95, then you should definitely go to 16Mb or, even better, 32Mb of RAM. At this level, an upgrade in the RAM department is also usually more cost effective than a CPU upgrade. Of course, a new computer with a Pentium processor and lots of RAM is better again but if your budget won’t stretch that far, a simple RAM upgrade to your existing system can be very worthwhile. RAM is now quite cheap, so there’s no reason to run a system that’s crippled by lack of memory. Table 3 is a general guide to the type of DRAM used in various computers and shows the number of modules needed in each memory “bank”. Some August 1998  43 The system RAM is plugged into sockets on your motherboard, as shown here. Be careful when handling the memory modules, as they are easily damaged by static electricity. older motherboards will require you to fit the same size RAM modules to all banks, while others might allow you to have different size modules. You must, however, fill all the slots in a bank. It’s generally OK to mix parity and non-parity RAM in the same bank but if you do this, be sure to disable parity checking in the system BIOS. Be careful here – many older 486 and earlier machines have no option to disable parity, so you have no choice but to use parity RAM in these systems. As before, the table is a guide only – you should consult the manual for the correct memory configuration for your particu­lar motherboard. That’s because the requirements can vary from one motherboard to another. For example, in PCs running a fast CPU, extra RAM might be needed in a bank to allow “inter­leaving” to increase the effective RAM access speed. If upgrading VGA card RAM, again check the user manual for the type of RAM chips required. If you have lost the book, check the RAM chips that are already on the card. These should be quite easy to find as they will be in parallel with the empty RAM upgrade sockets. Troubleshooting If adding extra memory and other hardware, try to do things one step at a time. Don’t go adding a new VGA 44  Silicon Chip card, a faster CPU and extra RAM all at once! Also, try to use the same type of RAM in all the memory banks; eg all FP or all EDO. Many motherboard chipsets do not allow FP and EDO RAM to be mixed in the same bank, although some might allow EDO in one bank and FP in another. If you start getting errors, try going back to using the same type of SIMMs in all banks. Similarly, if you have a motherboard that takes both DIMM and SIMM memory modules, don’t be surprised if you can’t use them together. Your motherboard manual will usually advise you of any such limitations. Now let’s take a look at some of the more common problems that are encountered with memory upgrades. (1). Parity problems: most new motherboards will not even have a parity option, as many chipsets no longer have this feature. On the other hand, a parity error can occur in an older PC if you mix parity and non-parity SIMMs. On some systems, you will not be able to get into the CMOS setup after installing non-parity RAM into a system that’s set for parity checking (ie, it creates a catch-22 situation by not letting you into the CMOS setup to turn parity checking off). The trick here is to get into the CMOS setup and disable parity checking before the non-parity RAM is installed. It’s generally not too hard to distinguish parity RAM from non-parity RAM. Non-parity SIMMs will usually be fitted with 2, 4 or 8 DIP chips, while parity memory will instead have 3, 5 or 9 chips. (2). System fails to recognise extra RAM: it’s impossible to install SIMM or DIMM RAM modules back to front. Both 30 and 72-pin SIMMs are keyed with a small notch at one end, while DIMMs are keyed by having asymmetrical plug-in connectors. A common “fault” is that the extra RAM is not recognised because the modules are not fully clipped in. If you strike problems, check that the SIMM or DIMM modules are correctly seated in their connectors and that they are retained by the clips. (3). System recognises some extra RAM but not all of it: it is usually quite OK to upgrade a system with different brands of RAM and even use RAM with different speeds, as long as you remember not to mix EDO and FP RAM in this way. Your system will recognise the lowest common denominator though, so mixing a 4Mb SIMM with an 8Mb SIMM in one bank will result in only 4Mb being recognised. Mixing RAM modules with different speeds, say 60ns and 70ns, is not the evil thing some people make it out to be – just don’t try running it all at 60ns! In normal use, you can only expect the system to work reliably at the slower speed (ie, 70ns), so be sure to select this memory speed in the SC CMOS setup. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PRICE EACH (includes p&p) TOTAL Australia $A7.00; NZ $A8.00 (airmail); Elsewhere $A10 (airmail). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; Jun 89; Aug 89; May 90; Aug 91; Feb 92; July 92; Sept 92 & Nov-Dec 92 are sold out. All other issues are currently in stock. $A BINDERS Please send me _______ S ILICON CHIP binder(s) at $A12.95 + $5.00 p&p each (Australia only). Not available elsewhere. ecial See Sp r – ffe Subs O 8 Page 8 $A SUBSCRIPTIONS ❏ New subscription – month to start­­____________________________ ❏ Renewal – Sub. 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Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia August 1998  53 Everyone has seen high intensity strobe lights at par­ties, discos and nightclubs. The “stop motion” effect of each light flash makes dancers appear to move in a strange way. With this high-powered strobe the light can be made to flash in time with the music or at any speed between one and 20 times a second. By JOHN CLARKE For flashing lights – even synchronised to the music Build This Beat Triggered Strobe What is a strobe light anyway? It provides repetitive in­tense flashes of white light and is based on an Xenon gas dis­charge tube. These are the same sort of tube as used in camera flashes but instead of being flashed just once, as in a camera, they are flashed continuously. These days Xenon flash tubes are 54  Silicon Chip widely used in burglar alarms, shop displays, on police cars and so on and in these applications they usually flash at quite slow rates. In our Beat Triggered Strobe, the flash rate can be varied from slow to fast or it can be synchronised to the beat of the music. Our Beat Triggered Strobe uses two Xenon tubes and is housed in a wood- en box measuring 240 x 240 x 300mm. It is covered in black speaker carpet which looks good and prevents the box from being easily damaged. For the same reason, loudspeaker corner protectors are fitted. The strobe tubes and their spun aluminium reflector are mounted at one end of the box and are protected Fig.1: block diagram of the Beat-triggered Strobe. by a sheet of Perspex. The control panel is mounted at the other end of the box and is recessed to protect the controls from damage. On the control panel are two knobs, a jack socket for remote on/ off control, a pair of RCA sockets for the music sign­al, the power switch and the IEC mains socket which is the same as found on computers these days. The two knobs provide a sensitivity control for the music (beat) input and a flash rate control. There is also a small toggle switch to select either beat (music) or continuous flash operation (internal oscillator). above 200Hz; ie, only bass signals pass through. The low frequency signal is then fed to a peak detector which drives a Schmitt trigger and pulse generator for the beat triggered mode. Alternatively, when switch S2 selects the oscillator mode, the Schmitt trigger oscillates at a rate set by VR2. Again, the Schmitt trigger drives the pulse generator. The output of the pulse generator drives the optical isola­tor which fires a trigger circuit involving a Triac and Main Features •  High intensity flash •  Adjustable flash rate from 1 to 20 per second (internal oscilla­tor) •  Flash rate synchronised to music beat •  Remote on/off switching •  Rugged construction Xenon flash tubes We’ve already mentioned the Xenon flash tubes which are the heart of this project. A Xenon flash tube is a light source for producing a high intensity flash from the electrical energy stored in a capacitor. It comprises a U-shaped glass tube which is filled with a small amount of Xenon gas. It has metal electrodes at each end of the tube and a trigger electrode which wraps around the outside of the glass. A high voltage from a capacitor is applied to the outer electrodes and when a very high (4kV) voltage is applied to the trigger electrode, the tube fires by ionising the gas which then emits a burst of light. The duration of the light flash depends on the size of the capacitors and any stray inductance in the circuit and is normally just a few microseconds. Block diagram Fig.1 is the block diagram for the Beat Triggered Strobe. The left and right signals from a tape deck or CD player are mixed to produce a mono signal which is fed to VR1. From there the signal goes to an amplifier and a low pass filter which rolls off signals The two Xenon tubes are mounted at the focus of the spun alumin­ium reflector which is mounted behind a Perspex window to keep unwary fingers away from the high voltage. August 1998  55 WARNING! CIRCUITRY INSIDE DOTTED LINES OPERATES AT LETHAL VOLTAGE – SEE WARNING PANEL Fig.2: two Xenon tubes are used in this strobe lamp circuit. Note the remote control circuit which is grounded to the 0V line, while the 555 (IC2) is powered from the -9V line. Note also that the circuitry to the right of the MOC3021 (IC3) operates at lethal voltage. pulse transformer (T2). T2 produces a 4kV pulse to fire the two Xenon flash tubes. Diodes D4-D7 rectify the 240VAC mains supply to provide about 330V DC across the storage capacitors. The ±9V supply for the ICs is derived from mains transformer T1, diodes D8-D11 and two 470µF filter capacitors. Circuit description The circuit for the Beat Triggered 56  Silicon Chip Strobe is shown in Fig.2. It comprises one quad op amp (IC1), a 555 timer (IC2) and an optically coupled Triac driver (IC3). The two Xenon tubes each have two 6.5µF capacitors connected in parallel to give a high flash output over the full range of operation. The left and right audio inputs are mixed in inverting amplifier IC1a. The 47kΩ resistors and 0.22µF capacitors produce a low frequency rolloff for signals below 15Hz while the .015µF capacitor across the 47kΩ feedback resistor rolls off high fre­ quencies above 225Hz. The Beat Sensitivity control VR1 sets the level of signal fed to op amp IC1b which has a gain of 471 and a low frequency rolloff at 16Hz, as set by the 1kΩ resistor and the 10µF capaci­tor between the inverting input at pin 6 and ground. High fre­quency rolloff is again at 225Hz, as set by the .0015µF capacitor across the 470kΩ feedback resistor. IC1b is followed by a low pass filter comprising IC1c and associated resistors and capacitors. It is a 2-pole filter Warning 1 Flashing lights can initiate convulsions in people with epilepsy. They can also cause people to suffer nausea and head­aches. It is advisable to use the strobe for short periods only and it should be switched off if it is apparent that someone is suffering from the above effects. and rolls off the signal above 200Hz at 12dB/octave. This filter and the previous filtering on IC1a and IC1b ensure that signals above 200Hz are severely attenuated. The signal from IC1c charges a 1µF capacitor via diode D1. The result is that each bass beat in the music produces a posi­tive DC pulse across the 1µF capacitor following diode D1. Fig.3: these scope waveforms show how the Schmitt trigger (IC1d) responds to a burst of low frequency. The top trace is the audio waveform at the output of the low pass filter (pin 1, IC1c) while the lower trace is the output of the Schmitt trigger (pin 14, IC1d). Schmitt trigger modes IC1d is connected as a Schmitt trigger with positive feed­back applied via a 220kΩ resistor to the non-inverting input at pin 12. The 220kΩ resistor between pin 14 and 12 plus the 100kΩ resistor to +9V and the 47kΩ resistor to ground set the hystere­sis. If the input at pin 13 exceeds +4V then the Schmitt trigger output goes low and conversely, if the input voltage goes below +2.5V then the output goes high. If switch S2 is in position 1, each beat signal from diode D1 causes the output of IC1d to briefly go low. The scope waveforms of Fig.3 show the beat mode in action. The upper trace shows a burst of low frequency from the output of the low pass filter (pin 1 of IC1c), while the lower trace shows the resultant pulse output from the Schmitt trigger (pin 14 of IC1d). On the other hand, if switch S2 is in position 2, then the filtered signal from D1 is out of circuit and the oscillator components comprising VR2, the 10kΩ resistor and a 10µF capacitor are connected to the inverting input of IC1d. The 10µF capacitor is then charged and discharged via VR2 and the 10kΩ resistor from the Schmitt trigger output. It charges to the +3.6V upper threshold and discharges to the lower threshold of +2.3V. Fig.4: these scope waveforms show how the Schmitt trigger con­trols the monostable (IC2). The top trace is the output at pin 14 of IC1d while the lower trace is the monostable pulse (11ms) at pin 3 of IC2. Potentiometer VR2 sets the frequency of oscillation. It is wired as a variable resistor and when its resistance is low, the frequency is high and vice versa. Monostable pulse generator IC2 is a 555 timer wired as a mono­ stable pulse generator and while it may look fairly standard, there are some tricky aspects to it. First, while IC1 operates from the ±9V rails and its output can swing over almost the full supply range (actually about +7.5V to -7.5V), the 555 is only operated from the negative supply rail, ie; between 0V and -9V. So the 0V line is actually the positive supply rail for IC2. We’ve August 1998  57 used this supply arrangement for a particular reason which we’ll come to in a moment. Each time the output of IC1d goes low (to about -7.5V), it momentarily pulls pin 2 of IC2 low via diode D2 and the .01µF capacitor. The pin 3 output of IC2 then goes high and the 0.1µF capacitor on pins 6 & 7 charges up via the 100kΩ resistor. When the voltage reaches the trigger level of pin 6 (about -3V), the pin 3 output goes low. Thus an 11ms pulse is produced at pin 3 each time the output of IC1d goes low. The scope waveforms of Fig.4 show the monostable operation. The upper trace is the output of the Schmitt trigger while the lower trace shows the short duration (11ms) positive-going pulse from the monostable, pin 3 of IC2. On/off control Pin 4 is the reset input for IC2 and is normally tied high with the 10kΩ resistor to pin 8. When transistor Q1 is switched on it pulls pin 4 low to prevent pin 3 going high and so strobe flashing is stopped. Q1 is switched on by connecting its 2.2kΩ base resistor to the 0V line and this point is earthed to the metal chassis. Now this is the whole point of the unconventional supply arrangement for IC2. We wanted to use a grounded 6.5mm jack socket for the remote on/ off control and we wanted to use a cable which could be simply shorted at the end with a switch to stop strobe operation. Hence, when the 2.2kΩ resistor is connected to 0V via the jack socket, its plug and remote cable, Q1 turns on, pulls pin 4 low and IC2 is disabled. Q. E. F. or quod erat faciendum which is Latin for “which was to be done”. The 10kΩ resistor from base to emitter of Q1 prevents the transistor switching on when long lines are connected to this remote control input. Diode D2 prevents any voltage from IC1d’s output which is above ground from passing to pin 2 of IC2. Note that another reason for the unusual supply for IC2 is that it could not take a total supply of 18V (recommended maximum is 15V). Fig.5: this diagram shows the dimensions (in milli­metres) of the timber cabinet (made of MDF) and the general arrangement of the chassis bracket. 58  Silicon Chip High voltage optocoupler Pin 3 of IC2 drives IC3 via a 470Ω resistor. IC3 is an optically coupled Triac driver which incorporates an LED which triggers an internal Triac. This then triggers Triac1. Now why have we used a MOC3021 optocoupled Triac in a trigger circuit which only handles DC, not AC? We specified IC3 to get a device which provides a very high isolation between its input and output. The MOC3021 Triac driver is one of the few optocouplers which is safe to use for 240VAC mains operation and it has an isolation voltage rating of 7.5kV. Other common optocouplers such as the 4N28 only have an isolation voltage rating of 500V which is inadequate for this application. Diodes D4-D7 rectify the mains voltage and the 0.1µF ca­pacitor in series with the primary of trigger transformer T1 charges up to about 330VDC via the two series 270kΩ resistors. Also the 6.5µF capacitors connected across the Anode and Cathode connections of the Xenon tubes are charged via the two 470Ω 5W resistors. When IC3 is triggered by IC2, the internal Triac conducts and the Triac1 is triggered via the Neon and the series 680Ω resistor. The charged 0.1µF capacitor is effectively connected across the primary winding of pulse transformer T2 and a high voltage is induced into its secondary winding. This secondary winding is connected to the trigger winding on the Xenon tubes, and causes them to “fire” and conduct the charge from the 6.5µF capacitors. That Neon tube in series with Triac1 is an odd inclusion and one which you would not expect to find in a semiconductor circuit. Interestingly, it is there to stop the Triac from con­ ducting when it shouldn’t. Why? When the Triac is triggered on, it will dump a fairly large current from the 0.1µF capacitor into the pulse transformer. But the capacitor will not discharge completely because it is still being fed about 600µA from the series 270kΩ resistors. 600µA may not seem like a big current but it is well above the “holding current” of 250µA for the Triac in IC3. Hence, without the Neon tube, once the Triac was triggered into conduction, it would never turn off. But with the Neon in place, once the voltage across the 0.1µF capacitor has dropped below about 70-90V, the Neon goes open circuit and stops the current flow. Neat, huh? Power for the low voltage side of the Parts List 1 PC board, code 16305981, 173 x 85mm 1 panel label, 140 x 140mm 1 warning panel label, 57 x 27mm 1 spun aluminium reflector, 190mm diameter 1 clear Perspex reflector cover, 190 x 190 x 2.5mm 1 sheet of 1.6mm aluminium, 290 x 210mm 1 sheet of Medium Density Fibre board (MDF), 900 x 600 x 12mm 1 400mm length of 12 x 12mm DAR timber 1 1500 x 400mm sheet of 3mm thick speaker carpet 1 strap handle 8 speaker box corner protectors 1 IEC chassis mount socket with fuse holder 1 200mA 2AG fuse (F1) 1 3-pin mains plug to IEC female plug mains lead 1 DPST mains switch with Neon indicator (S1) 1 SPDT toggle switch (S2) 1 octal socket 1 octal plug 2 panel-mount insulated RCA sockets 1 PC board mount mono (or stereo) 6.35mm socket 2 100kΩ linear pots (16mm) (VR1, VR2) 2 16mm OD knobs 1 M2851 12.6V 150mA mains transformer 1 Xenon tube trigger transformer (T2; Altronics Cat M-0104 or equivalent) 2 Xenon tubes (see text) 1 Neon tube 4 15mm tapped spacers (use 9mm spacers if 25mm pots used for VR1&VR2) 1 50g tube of contact adhesive 12 M3 screws 6mm long 2 M3 x 9mm countersunk screws (to mount IEC socket) 7 M3 nuts 15 M3 star washers 3 No.6 x 6mm self tapping screws 9 5G 16mm round-head wood screws (to secure aluminium rear panel and reflector) 2 6G 20mm round-head wood screws (to secure timber rear panel) 32 4G 12mm countersunk wood screws (to secure corner protectors) 2 7G 16mm countersunk wood screws (to secure handle) 4 solder lugs (or crimp eyelets) 24 PC stakes 1 1500mm length of blue mains rated wire 1 1500mm length of brown mains rated wire 1 600mm length of green/yellow mains rated wire 1 100mm length of 0.8mm diameter tinned copper wire 1 100mm length of three way rainbow cable Semiconductors 1 LM324 quad op amp (IC1) 1 555 timer (IC2) 1 MOC3021 Triac optocoupler (IC3) 3 1N914, 1N4148 signal diodes (D1-D3) 8 1N4007 1000V 1A diodes (D4-D7,D8-D11) 1 BT136 500V Triac (TRIAC1) 1 BC338 NPN transistor (Q1) Capacitors 2 470µF 16VW PC electrolytic 1 100µF 16VW PC electrolytic 3 10µF 16VW PC electrolytic 4 6.5µF 250VAC stud-mounting capacitors 1 1µF 16VW PC electrolytic 2 0.22µF MKT polyester 1 0.1µF 250VAC MKT polyester X2 class 1 0.1µF MKT polyester 1 .022µF MKT polyester 1 .015µF MKT polyester 1 .01µF MKT polyester 1 .0056 MKT polyester 1 .0015 MKT polyester Resistors 1 470kΩ 2 270kΩ 1 220kΩ 6 100kΩ 7 47kΩ 1 22kΩ 3 10kΩ 1 2.2kΩ 1 1kΩ 1 680Ω 4 470Ω 5W 1 470Ω 2 10Ω Miscellaneous Heatshrink tubing, PVA glue, nails. August 1998  59 WARNING! ALL PARTS TO THE RIGHT OF THE DOTTED LINE OPERATE AT LETHAL VOLTAGE Fig.6: this is the component layout for the PC board. The Triac’s metal tab should be fitted with a piece of heatshrink tubing to avoid accidental contact. circuit is derived from the 12.6V centre tapped transformer T1 via diodes D8-D11 and the 470µF capacitors. These provide nominal +9V and -9V supply rails. Construction The Beat Triggered Strobe is housed in a box measuring 240mm wide, 240mm high and 300mm deep. It is made of medium density fibreboard (MDF) and is covered with black Meltrim® or similar speaker car­pet. Black corner protectors and a plastic handle add to the pro­fessional appearance of the prototype. Most of the circuit components are mounted onto a PC board which measures 173 x 85mm and is coded 16305981. This board is mounted on an L-shaped bracket measuring 150 x 140 x 210mm. This wide bracket forms the rear control panel of the Strobe. The details of the box and the L-shape bracket are shown in Fig.5. The first step in assembly is to insert and solder all components into the PC board. Its component layout diagram is shown in Fig.6. Note that the PC board is effectively divided into low voltage and high voltage sections with IC3, the opto60  Silicon Chip Warning 2 The high voltage parts of this circuit are directly pow­ e red from the 240VAC mains and are potentially lethal. THE 6.5µF 250VAC CAPACITORS & THE TERMINALS OF THE OCTAL SOCKET & XENON TUBES ARE PARTICULARLY DANGEROUS! Note that lethal voltages are present at one end of the PC board. This circuitry includes IC3, the 5W resistors, the 6.5µF storage capacitors, trigger transformer T2, diodes D4-D7, the Triac (TRIAC1), the neon and all associated parts. Do not touch any part of the circuit while it is operating and always give the 6.5µF capacitors sufficient time to discharge after switching off before working on the circuit – see text. We recommend that only experienced constructors should tackle this project. coupler, being the interface between the two sections. The first step in board assembly is to insert and solder the PC stakes at the external wiring connection points. Then insert the wire links and resistors. Table 2 shows the colour codes for all the specified resistor values. Mount the 5W wirewound resistors so that they have about a 2-3mm clearance above the PC board to aid in their cooling. When inserting the diodes, take care with their orientation. Although lower voltage types could have been used for D8-D11, we have specified 1N4007 types for all eight power diodes. This is to prevent placing incorrect types in the D4-D7 positions. Install the ICs and the transistor next, taking care to orient them as shown. Note that IC1 is oriented differently to IC2. The capacitors can be installed next. Table 1 shows the codes for all the specified capacitor values. Take care with the polarity (orientation) of the electro­lytics. Triac1 can be mounted next, with the metal tab facing to­wards potent­ iometer VR2. Potentiometers VR1 and VR2 are mounted directly onto the PC board as shown in Fig.6. If 16mm pots are used, then the 6.35mm jack socket can directly mount on the PC board, as all the bush mounting holes are in-line. Fig.7: wiring details of the chassis. With the exception of the wires to the RCA phono sockets and switch S2, all the wiring should be rated for 250VAC. Use cable ties to lace the high-voltage wiring, as shown in the photographs. WARNING! ALL PARTS TO THE RIGHT OF THE DOTTED LINE OPERATE AT LETHAL VOLTAGES August 1998  61 The chassis bracket slides out of the rear of the cabinet to reveal a neat layout. Note that a section of the PC board and a lot of wiring is powered di­rectly from the 240VAC mains supply and is potentially lethal, particularly the four 6.5µF storage capacitors which are charged to about 330V DC. However, if 25mm pots are used, the jack socket will need to be raised off the PC board with PC stakes so that its mounting bush is in line with the pot bushes. T2, the Trigger transformer, is wound as an auto-transform­ er and must be mounted as shown on the PC 62  Silicon Chip diagram. The Neon tube is soldered directly into the board and can be supported with a dab of Silastic or Blu-Tak. Secure the tapped pillars to the four corners of the PC board using the 6mm long M3 screws. Note that you will need to use tapped 15mm spacers with 16mm pots and 9mm spacers with 25mm pots. Chassis bracket If you are not assembling a kit with all parts supplied, the next step is to make the chassis bracket. This is made from a sheet of 1.6mm aluminium Fig.8: this is the full-size etching pattern for the PC board. Check the board carefully before installing any of the parts. measuring 290 x 210mm. This is bent to form a right-angle bracket, with one section measuring 140 x 210mm and this becomes the rear panel. Table 1: Capacitor Codes ❑ Value ❑ 0.22µF ❑ 0.1µF ❑ .022µF ❑ .015µF ❑ .01µF ❑ .0056µF ❑ .0015µF IEC 220n 100n 22n 15n 10n 5n6 1n5 EIA 224 104 223 153 103 562 152 Strobe and the program source. Now position the PC board in place and mark out the holes for the standoff pillars on the base of the chassis. Also mark out and drill the mounting holes for the four 6.5µF capacitors, the power transformer (T1) and the earthing screw. Affix the label to the panel and cut out the holes with a sharp utility knife. Now attach the PC board in place with four M3 x 6mm screws. Secure the IEC socket with countersunk M3 screws and attach the power transformer using two M3 screws. Use shakeproof washers for each screw. The earthing solder lugs must each be held with a screw, nut and a shake­ proof washer. The RCA sockets are attached with the insulating bushes in position. Secure the pots and 6.35mm You will need to mark out the positions for the pots VR1 and VR2, the 6.35mm jack socket and for switch S2 using the panel label as a guide. Make sure the height of these components is correct by checking the PC board on its standoff pillars up against the inside of the panel. Drill and cut out holes for the power switch (S1) and the fused IEC power socket. The earth screw is positioned just below the IEC socket. Now drill out the holes for the two RCA sockets. The holes must be large enough to allow for their insulating bushes. These isolate the metal body of the RCA sockets from the chassis bracket, to prevent ground loops between the Table 2: Resistor Colour Codes ❑ No. ❑  1 ❑  2 ❑  1 ❑  6 ❑  7 ❑  1 ❑  3 ❑  1 ❑  1 ❑  1 ❑  1 ❑  2 Value 470kΩ 270kΩ 220kΩ 100kΩ 47kΩ 22kΩ 10kΩ 2.2kΩ 1kΩ 680Ω 470Ω 10Ω 4-Band Code (1%) yellow violet yellow brown red violet yellow brown red red yellow brown brown black yellow brown yellow violet orange brown red red orange brown brown black orange brown red red red brown brown black red brown blue grey brown brown yellow violet brown brown brown black black brown 5-Band Code (1%) yellow violet black orange brown red violet black orange brown red red black orange brown brown black black orange brown yellow violet black red brown red red black red brown brown black black red brown red red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown brown black black gold brown August 1998  63 types used for power factor correction in fluorescent batten fittings and as motor-run capacitors. And as with most fluorescent battens these days they use wire-capture terminations. You poke the wires into the socket holes and they are “captured”. You will need to strip the capacitor wires back by about 10mm and then “tin” them with solder before they are inserted into the capture terminals. Once the wires are captured, you cannot pull them out again. Once the wiring is finished, you should check your work very carefully to be sure that all parts and wiring are correctly positioned. Initial voltage check The rear panel has controls for audio sensitivity and flash rate. The strobe can be used in continual flash mode or beat triggered mode. Use cable ties to keep the wiring neat and tidy, as shown here. socket with the nuts provided for each. Mount switch S2 using its nuts and locking washer. The Xenon flash tubes are mounted in the spun aluminium reflector via an octal socket. The reflector is supplied with a hole in its base and this is big enough to take the octal socket. You will have to drill holes in the base for the socket’s mount­ing screws and an earth lug. We drilled the holes to accept 6G self-tappers. Wiring details Now you can do the wiring of the chassis – see Fig.7. All the wiring, with the exception of the connections from the RCA phono sockets and to switch S2, should use 240VAC mains-rated wire. We used 260mm lengths of wire from the PC board to the octal socket and a 260mm length 64  Silicon Chip of green/yellow striped wire from the earth point to the reflector lug. Place insulating sleeving over all exposed PC pins and octal pins to prevent any possibility of accidental contact. Also place a length of insulating sleeving over the Triac’s metal tab to prevent accidental contact. The wiring to the four 6.5µF 250VAC capacitors requires special mention. These are standard stud-mounting WARNING! Lethal voltages are present on all parts at one end of the PC board & on the 6.5uF 250VAC capacitors, octal socket & Xenon tube terminals. Capacitors retain lethal voltage for some time after switch off. Fig.9: this warning label should be affixed to the metal chassis, adjacent to the power transformer. Initial testing of the Strobe can be done without having the Xenon flash tubes fitted. Firstly, be aware that the circui­try at one end of the PC board, involving IC3, the 5W resistors, the storage capacitors, diodes D4-D7, trigger transformer T2, the Triac and other associated parts, is all running at 240VAC and is potentially lethal. Set your multimeter to read DC volts and connect the common lead to the blue wire connection on transformer T1. Apply power and check for about +9V on pin 4 of IC1. There should be -9V on pin 11 of IC1 and pin 1 of IC2. Now switch S2 to the oscillator position and check that the Neon flashes at the rate set by the oscillator pot, VR2. If so, then the circuit is probably all working. Now switch off the power and wait for several minutes. Carefully measure for high voltages between the Anode and Cathode leads on the octal socket. The 6.5µF capacitors specified do have internal bleeder resistors to discharge them but you need to wait several minutes for safety reasons to be sure they are discharged. Mounting the tubes The Xenon tubes can be mounted in one of two ways. If you are using the Xenon tubes from Dick Smith Electronics or Jaycar Electronics, their extra long leads will be sufficient for them to be directly soldered into the pins of the octal socket. You should have 25mm clearance between the base of the octal socket and the base of the tubes. We covered the exposed leads with a short length of tubing 25mm in outside diameter. This was obtained from a 35mm film ca­nister. Alternatively, you could use the tubing from a “METEOR Party popper”. The tubes from Altronics have shorter leads and require extra spacing to ensure that they are correctly positioned to be at the focus of the aluminium reflector. In this case use an octal plug to solder the tubes into and then insert this plug into the socket. Note that this plug is a larger diameter than the socket and will need to be inserted from the reflector side after the socket has been mounted. Before soldering the tubes in place, make sure that the red marking is placed in the Anode position. If you place the tubes incorrectly, it is probably best to change the wiring to suit rather than try to unsolder the tube wires since the glass is easily cracked. Woodwork The box is made from 12mm MDF as shown in Fig.5. We used simple woodworking tools to make this box, however we did resort to a power jigsaw to cut out the hole for the reflector. Cut out two sheets 300 x 240mm and two sheets 300 x 216mm. These form the sides and top of the box. Cut out another piece 210 x 79mm for the rear panel. Also cut out a 216mm square piece and mark out a 180mm hole central to the square with a pair of compasses. Cut out with a jigsaw or a small fret saw. The hole can be chamfered with a half-round wood rasp. The box can now be assembled using PVA glue and some nails or screws. Note that the front panel is recessed by 10mm. This is so that the speaker carpet can be folded around the front of the box. When the glue is dry (wait six hours), file and sand the box and round off the sharp corners on each edge. The rear aluminium panel is recessed in the box by 25mm. We used 12 x 12mm cleats to provide the mounting arrangement for the chassis panel. Make sure that the chassis can slide into the box with 12mm clearance beneath it to allow for the capacitor-mounting studs. Additional 12mm cleats need to be glued in position for the 210 x 79mm MDF plate which mounts at the top of the rear panel. Note that this panel is recessed by 3mm around the top and sides to allow for the speaker carpet thickness. Isolate exposed leads of Xenon tubes using a plastic 35mm film canister (or similar) – see photo on page 62. One method of mounting the Xenon tubes (from Altronics) using an octal plug and socket. This sets the tubes at the focus of the parabolic aluminium reflector. The octal socket is fastened to the parabolic reflector using two self-tapping screws. Note the earth lead which runs from the chassis to a lug which is bolted to the parabolic reflector. The chassis panel is secured to the cleats with 5G 16mm round-head screws, while the MDF plate is secured with the 6G 20mm round-head screws. The reflector and Perspex window are secured with four equally spaced 5G 16mm round-head screws around its circumference. August 1998  65 We spray painted the front and rear sections of the box with black satin enamel. It is not necessary to paint the base, top and sides of the case. Attaching the carpet The speaker carpet is attached to the box with contact adhesive. We started by coating half of the base with contact adhesive and securing one edge of the carpet on the base. This leaves the carpet join along the middle of the base. Be sure to leave sufficient carpet overhang on each end so that it can be wrapped around the front and rear of the box. Now coat the rest of the box with contact adhesive and secure the carpet in position. Note that contact adhesive works best if you coat both surfaces and wait for it to dry before sticking down. Also, if you are using a 50g tube, apply the glue sparingly or you will run out. The bottom edge is trimmed so that it meets the first carpet edge for a neat join. The ends are com­pleted by cutting the carpet to length and folding around the edges. These are secured with contact adhesive as before. Note that the corners will need Fig.10: this is the artwork for the control panel, reproduced here half-size. to be trimmed so that the carpet will fold in without puckering. Plastic corner protectors are secured with 4G 12mm counter­sunk screws while the handle is secured to the top of the box using two 7G 16mm screws. Now you are ready to attach the Xenon tubes and octal sockets into the reflector and secure the earth. Then slide the chassis assembly into place and secure with four 6G 16mm SC round-head screws. Protect Your Valuable Issues Silicon Chip Binders REAL VALUE AT ★  Heavy board covers with 2-tone green vinyl covering $12.95 PLUS P &P ★  Each binder holds up to 14 issues ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p each (Aust. only). Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. 66  Silicon Chip RADIO CONTROL BY BOB YOUNG The art of slope soaring This month, we will look at some aspects of slope soaring or the art of staying up all day with no motor. What you need is plenty of wind, a spectacular hillside and quick reflexes. It was 23:59 on a cold night in Kiama NSW on a date long since forgotten; probably somewhere around late 1969. Any resi­ dent of Kiama NSW foolish enough to venture outside on that cold, blustery night and who bothered to glance in the direction of Saddleback Mountain would have been startled to see a brilliant searchlight burst forth from the top of the ridge. Had they held their gaze steady on the cone of light, they would have seen at precisely 12 midnight, a model aircraft leave the ridge and weave backwards and forwards along the ridge, transfixed in that beam of light. Had they been robust or foolhardy enough to watch this eerie spectacle for another 25 minutes or so, they would have seen the light blink out as the cloud base descended below the ridge. This enveloped the model, searchlight and ground-crew in a very wet blanket indeed. So ended Bill Marden’s second attempt at the Australian sailplane duration record. The model flew off inside the cloud, we knew not where. Despite an intense aerial and ground search, it did not show up that following day. We finally found it several weeks later, about a kilometre behind the ridge. Have a look at the photo on this page. It was taken at Otford, just near Stanwell Tops, a popular hang-glider location. That cliff is a very civilised baby compared to Saddleback. Any Photo 1 (left): Dennis Bailey hand launches a slope soarer out into the wild blue yonder at Stanwell Tops on the NSW south coast. A 2-channel radio is used and there is no rudder control, turns being by ailer­ons only. August 1998  67 cessful outcome. We had waited for months for a southerly buster to come through on a Wednesday or Thursday so that the three day tail-out would give us ideal conditions on a Friday or Saturday night. On the third day after a southerly, the wind settles to a strong, steady blow which is quite predictable in strength and direction for at least one to two days. World record In Germany, the winds blow up the mountains for months on end. In the 1920s and 1930s, full-size sailplane records tumbled one after the other as pilots pushed themselves to the limits of physical endurance. In the end the record stood at something like 72 hours and people were killing themselves attempting to better these times. This type of record was finally abolished because it simply became a test of a pilot’s physical endurance rather than a test of his flying skill. On the 30th of September, 1978 Brian Laging of Victoria established the current Australian R/C glider endurance record which still stands at 28 hours and 28 seconds. Such is the art of slope soaring, one of the most interesting branches of the sport of R/C flying. What is slope soaring? Photo 2: Dennis Bailey poses with his slope soarer. It has a wing span of 1.3 metres and the short stubby wings are fitted with ailerons. mistake or bad luck really tests one’s physical fitness. Climbing up and down these sorts of cliff faces is not for the cardiac-challenged (newspeak for an unfit slob), so you very rapidly learn that the best place to land your model is at the top of the hill, not the bottom. We scoured Saddleback for days looking for that model and thought nothing of it; up and down that mountain a half a dozen times. Oh to be young again! Months earlier, Bill had successfully set a new Australian R/C sailplane duration record of 11 hours, 8 minutes and 1 second at the same 68  Silicon Chip site. That was a purely daylight flight, taking off at dawn and flying until the wind ran out 11 hours later. The model was built and flown by Bill Marden. My part in the opera­tion was to provide the technical support. This was in the days when I did everything in my power to help modellers set records. The midnight takeoff was necessary because this time we were going for 24 hours or better. There was a good chance we would have got it too, if the cloud had not come down so low that night. But that is the nature of record attempts. Luck, skill and preparation all have to come together for a suc- Slope soaring makes use of the energy contained in the stream of air which is deflected upwards when winds encounter a barrier to their natural direction of flow. Fig.1 shows the concept. As the air near the slope has to travel over a longer path than the higher smoother wind-stream, it speeds up as it nears the crest and finally rolls over the crest and breaks up into turbulent, highly disturbed air on the lee side. This is often exacerbated by obstacles on the top of the rise such as trees, houses and so on. So not only do we get an upward deflection from the barrier but we also get an accelerated airstream into which we may launch our heavier-than-air machine; the stronger the wind, the greater the lift. Provided the wind keeps blowing, there is an almost unlimited amount of energy available to overcome the force of gravity. From this simple fact arise the vast differences between aircraft designed for winch-launching and slope-soar- ing and indeed the attitudes of the people who fly them. The slope brigade are the otters of the soaring community. These are fun creatures who spend their days gliding up and down the slopes, cavorting amongst the trees and fighting with each other in wild aerobatic duals, often using specially designed combat aircraft which can stand the impact of a full blown crash. Not for them the concerns that plague the flatlanders. The problems of launch stresses, wing efficiency, variable geometry and sniffing therm­als are all minor concerns. The hill dwellers have vastly different concerns. Can you land this model on a cluttered hilltop in a 20-knot breeze? Does it do three rolls in one millisecond or less? Can it loop inside the diameter of a 20-cent piece? Will it withstand the impact of flying into the slope at full speed or a midair collision? Such are the concerns of the aerial otters. This is not to say that the highlanders do not concern themselves with matters aerodynamic but with almost limitless energy available to keep the aircraft flying, the level of aero­ dynamic finesse required is shifted into other areas. For the slope brigade, manoeuvrability is more important than efficiency and this results in a markedly different approach to the design of their aircraft. Typical slope soarer Photo 1 shows a typical aerobatic slope soarer. It is small and compact with the most noticeable feature being the low aspect ratio wing which is usually fitted with ailerons. Quite often the model has no rudder control, relying entirely on the ailerons for directional control. A high rate of roll calls for a short, stubby wing fitted with ailerons. A small diameter loop calls for a short moment arm (distance between the wing and the tailplane). Inverted flight demands a symmetrical or semi-symmetrical wing section and no dihedral. All of these features are in complete opposition to the types of concerns we have discussed in the last two or three columns. Structurally, the models are vastly different. There is no need for the exotic materials used in the high aspect ratio, winch-launched models. The short, broad chord wing is very robust Fig.1: slope soaring depends on the considerable lift produced by wind being forced up and over an obstacle. On the lee side of the hill there is danger though, because of turbulence and down draughts. even when built from conventional materials and with no launch stress to worry about, they do not need to be anywhere near as strong. The handlaunch used in slope soaring places no structur­al demands on the airframe whatsoever. The model shown in photo 1 is an own design (Pylobat) and belongs to Dennis Bailey of the NSW Slope Soaring Association (NSWSSA). The NSWSSA fly at Otford near Stanwell Tops, just south of Sydney and can be contacted on (02) 9547 2277. The Pylobat has a wingspan of 1.3 metres and weighs in at 650-750g, depending on the amount of ballast carried. This type of model requires a fairly strong breeze to per­form at its best. For those days when Dennis desperately needs a flying fix and the weather is not very cooperative, he keeps a second model in the car. This is pictured in photo 3 and for those who have followed the series so far, is instantly recognis­able as one of our old friends, the 2-metre glider. In this case it is a modified Spirit built from a kit. Weighing in at 850g, here is a model that is concerned with aerodynamic efficiency. In light winds, this model will outperform its more aero­batic counterparts but with the penalty of reduced manoeuvrabil­ity. Notice that it is fitted with the conventional 2-channel, rudder/elevator control configuration. Slope soarers make great use of 2-channel systems and often the lack of rudder control is dictated by this factor. 2-channel systems are popular with the slope fliers because they are cheap and therefore more expendable than the four and 6-channel sys­tems. Due to the nature of the flying sites, there is a consider­ able risk of lost aircraft. A sudden change of wind direction, a drop in wind speed or a radio failure can result in the model being lost in dense undergrowth or worse still, the ocean. Hazards of the ocean Ten minutes in the ocean with the battery still connected will result in the copper on the circuit board being electrolyti­ c ally removed and the receiver is useless thereafter. If you do fly near salt water, carry a bottle of fresh water and a bottle of methylated spirits with you. Disconnect the battery as quickly as possible, wash the electronics immediately and thoroughly in fresh water and then with metho. The spirits will absorb the fresh water and evaporate off, leaving the electronics clean and dry. But you must be quick. Whilst the emphasis may be on simple and inexpensive mod­els, there are other streams of slope activity which call for vastly different types of approaches to the model design. One which we have already mentioned is the endurance slope soarer. This type of model does need to concern itself with aerodynamic efficiency for during a period of 24 hours or August 1998  69 Photo 3: For light wind conditions, when the lift is insufficient for slope soarers, enthusiasts often use a standard 2-metre glider, such as pictured here. Now where did that first glider get to? more, all types of wind speeds may be encountered. For example, during Bill Marden’s 11-hour flight, he took off in 20 knots of wind, suffered through a period of gusting winds of up to 50 knots that nearly drove the model back over the ridge and finally had to land because the wind dropped to almost nothing in the afternoon. Obviously a very clean, variable geometry aircraft would have a distinct advantage in this type of task. Scale models Another very popular branch of slope soaring has evolved around scale models. Here we see not only scale models of popular full-size gliders, but scale models of aircraft such as Spit­fires, Mustangs, MIG-15s and so on. In Europe where the big model has taken off in a big way, we see monster gliders that look like Boeing 747s and other airline types. Modellers are ingenious and it nev70  Silicon Chip er fails to amaze me what they will come up with next. One final note before closing: during the foregoing discus­sion it may have appeared that slope soaring is a snap and that there is little skill compared to the problems facing the flat-earthers. This is not the case. On an ideal slope it is true that it is fairly easy to stay up for long periods. However, all slopes are not equal. Some are more equal than others (if you will forgive the borrowed phrase) and the less equal can be pretty daunting. Rocky outcrops, gullies, trees and other disturbances can interfere with the airflow and create pockets of turbulence, downdrafts and heavily disturbed air. Likewise, warmer or cooler conditions will result in more or less thermal activity and so on. Thus, all of the subtle signs encountered in thermal soaring are there for the experienced slope pilot but with added spice. The slope pilot has to learn to land the model in high winds, often on rock-strewn hillsides, with the model continually trying to lift off the ground and keep flying. If the unwary or tyro pilot is foolish enough to let his model drift behind the hill, then all hell breaks loose as the model enters the turbulent lee-side, downward moving air. No, never make the mistake of thinking slope soaring is easy. It is a highly skilled art, just as all types of R/C flying are a particular form of the overall art. Each branch of the hobby has its master craftsmen and women who have taken the time and trouble to study their chosen field very carefully and who now exhibit a level of understanding that makes it all look so easy. But look at that lead photo once more and imagine yourself sitting on that hilltop on a glorious day, with a model sailing serenely above you in a clear blue sky. I can think of few better SC ways to spend your day. Bob Young is principal of Silvertone Electronics. Phone (02) 9533 3517. Their web site is at: www.silvertone.com.au Store Address: 56 Renver Road, Clayton. Victoria 3168 Postal Address: Bag 620 Clayton South. Victoria 3169 Phone: (03) 9543 7877 Fax: (03) 9543 4871 Website: http://www.rocom.com.au Email: sales<at>rocom.com.au AUDIO EXCEL 16 BIT ISA SOUND CARD * Supports Plug & Play * Full Duplex Sound * Sound Blaster Compatible * Supports Windows 3.1 and Windows 95 * Built-in Surround Sound * Supports SPDIF Digital Interface * Supports Software Wave - Table * Comes in Retail box 3.5” HARD DISK DRIVE MOUNTING KIT NOW NOW $2.00 $25.00 stock# X19971 0.2A 60V 0.4W N - CHANNEL MOSFET * V -MOS * Package: TO-92 NOW stock# X11055 $69.50 * The DC adaptor with a PC backplate is designed to allow the speakers to run off your computers internal power supply * Connected to the PC internal 5V power supply adaptor NOW $20.00 stock# P19077 * Package: TO-220 * Package: TO-220 NOW * Package: TO-220 $2.50 NOW $0.40 stock# BT137-500 12V 1A INLINE DC POWER PACK * Input: 240VAC 50Hz Output: 12VDC 1AMP. ENERGY AAP. 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App No.: N11943 * 2.5mm DC Plug $12.50 NOW $5.00 stock# P17565 105 WINDOWS 95 KEYBOARD * Designed for Windows. 105 Keyboard. 3 additional keys for Windows applications. $2.50 NOW $0.40 stock# TL074 CMOS 32K x 8 EPROM * Package: Dip 28 Pin NOW $2.80 $7.95 stock# 27C256-2 “D” SIZE NICAD RECHARGABLE BATTERY NOW NOW $3.50 $15.00 stock# X12032 WIDE BAND WIDTH QUAD JFET INPUT OP-AMP $28.50 stock# S15022 GET ON OUR EMAIL LIST! Our Email Customers receive PRIORITY notification of HOT SPECIALS and ONE-OFF BARGAINS all at rock bottom prices! We regularly broadcast new surplus stock items and other super deals via email. So, if you have an email address, we want it!!! August 1998  71 15W/Ch Class-A Stereo Am L Last month, we presented the circuit details of a 15W class-A module with extremely low total harmonic distortion. This month we show how to build two modules into a chassis to produce a stereo power amplifier. In order to obtain the extremely low distortion from a stereo pair, it was necessary to use a com­pletely separate power supply. 72  Silicon Chip AST MONTH, we stated in no uncertain terms that building a pair of these 15W class-A modules into a chassis along with a conventional (unregulated) power supply would be a sure path to disappointment. But little did we know, at the time of writing, just how difficult it would be to get the claimed performance in a stereo amplifier – even with a regulated supply. We already knew that we would have to resort to a fully regulated power supply. We had built a suitable power supply into the intended chassis and we used this setup to produce the graphs and figures featured last month. The only problem was that when we hooked up two amplifier modules and started taking meas­ urements in stereo mode, the results were less than stunning. Distortion at 1kHz and 10W was up to around .001% while the signal-to-noise ratio was only around -80dB or so. Now in any conventional amplifier these results might be regarded as satisfactory. But this was no ordinary amplifier and a signal-to-noise ratio of 80dB is a long way from 113dB. The difference is a low background hum compared to just the faintest hiss. Clearly, we still had a problem with hum induced from the transformer. This was being induced into the common earth loop formed by the signal earths back to the common program source. If we broke the loop, the distortion and noise was back down By LEO SIMPSON mplifier where it should be but that is hardly any consolation when it’s sup­posed to be a stereo amplifier. After trying lots of earthing arrangements and playing with the lead dress of the power supply cables, we came to the conclu­sion that the only practical solution was to build the power supply in its own steel box inside the amplifier chassis. So we duly built the box, rebuilt the power supply, reconnected all the leads and Above: this view of the amplifier chassis shows how the various wires and connections have been routed. This layout has been produced after much trial and error to obtain the best distor­tion, separation between channels and signal-to-noise ratio. August 1998  73 AUDIO PRECISION SCCRSTK XTALK(dBr) 0.0 & XTALK(dBr) vs FREQ(Hz) 23 JUN 98 15:15:55 -20.00 -40.00 -60.00 -80.00 -100.0 -120.0 20 100 1k 10k 20k Fig.1: this is the separation between channels across the frequency range from 20Hz to 20kHz. The curves for each channel were measured with both amplifier inputs connected to the measuring source. so on. Result: no improvement. You can imagine the sheer frustration in the SILICON CHIP workshop. Ultimately, we were forced to the conclusion that the power supply would have to be completely separate from the chassis. So that is what we did next. This works but it is an extra expense that we would have preferred to avoid. So be it. If you want this stereo amplifier to have a typical distortion of .0006% or below, it needs a completely separate fully regulated power supply. We also found it necessary to slightly change the earthing of the input circuit on the PC board. Instead of connecting directly to the “star” earth point on the PC boards, the input circuits of each power amplifier are now connected via 10Ω resis­tors. This reduces the incidence of earth currents circulating via the loop formed by the two input cables and the external program source (eg, a CD player or tuner). With the power supply presented here, the signal-to-noise ratio and harmonic distortion, when measured in stereo mode, is as published last month. The separation between channels is quite respectable, measuring around 80dB at mid-frequencies, although this is not as good as we hoped for. Fig.1 shows the separation 74  Silicon Chip across the frequency range from 20Hz to 20kHz. As far as we can tell, the only way to substantially improve upon this would be to have separate power supplies for each channel. Another crucial development was the necessity to specify good quality gold-plated binding post terminals for the speaker outputs. Initially, we used a set of readily available spring-loaded speaker terminals, on the basis that the overall power output was low and therefore heavy duty speaker connections were not really justified. However, in order to consistently obtain the very low distortion figures that we published last month, the spring-loaded terminals had to be replaced. We found that typi­ cally, they caused a doubling of the measured distortion! So while the heavy gold-plated terminals might look like an unnecessary expense, they are needed. How does it sound? The writer feels a little uncomfortable in answering this question because it requires a subjective answer. In my listening setup, I am using the SILICON CHIP Stereo Control Unit described in September & October 1993 combined with the 100W per channel amplifier described in February 1988. The loudspeakers are the highly regarded Dynaudio Image 4s while the CD player and tuner are current models by Sony (CDP-XE300 and ST-SE200 respectively). The amplifier/speaker combination has compared very well with any number of other systems over the years but when the class-A 15W/ channel amplifier was substituted for the 100W unit and the levels carefully matched, there was a distinct improvement. Put simply, the 15W class-A amplifier sounded cleaner; quite a lot cleaner in fact. And yet, going back to the 100W amplifier, it still sounded very good. Further listening seemed to indicate that the instruments spread across the “sound stage” between the two loudspeakers were more distinct, and occupying a more precise location. After considerable testing, we believe that the perceived improvement in sound quality may not be solely due to the considerably improved distortion of the new amplifier but to greatly improved separation between channels. We hope to report on this aspect further in a future issue but it appears that audio equipment which has nominally good separation under the conventional IHF-201 test method actual­ly has degraded performance when connected to “real” stereo program sources such as CD players. Amplifier case The new amplifier is mounted in a 2-unit high rack-mounting case with large finned heatsinks on both sides. On the front panel is a headphone socket, volume control and LED power indica­tor. On the rear panel is a pair of RCA sockets for the left and right channel inputs and gold-plated binding post terminals for the power amplifier output connections. The separate power supply is mounted in a standard plastic instrument case measuring 260 x 82 x 190mm. This has a bare front panel apart from the power switch. On the rear panel is a large single-sided heatsink, a fused IEC power socket and the output cable for the DC supply rails. Stereo amplifier circuit Fig.2 shows the circuit of the complete 15W per channel stereo amplifier minus the power supply. Both channels are shown, with the transistor numbering in the second channel running Q101, Q102, etc. Fig.2: this is the complete circuit of the stereo power amplifier except for the separate power supply. Note the 10Ω isolating resistors in the input earth returns for both channels. August 1998  75 Fig.3: the power supply circuit uses a toroidal power transformer with two 21V secondaries to feed a bridge rectifier and two 4700µF 50VW filter capacitors. These then feed identical positive and negative regulator circuits comprising an adjustable 3-terminal regulator and a power transistor. Fig.4: the PC board component overlay and wiring diagram for the power supply. Take care with the polarised components. 76  Silicon Chip There are a number of differences from the circuit published last month. First, there are two errors which have been corrected: (1) Q8 & Q9 are specified as BC547 and not BC546; and (2) trimpot VR1 is 200Ω, not 500Ω. The amended circuit shows the 20kΩ (log) ganged potentiome­ t er which acts as the volume control for the amplifier. We think this feature will appeal to those who want to operate the ampli­fier as a very simple no-frills system with just a CD player. Later on, if there is a demand from readers, we may develop a stereo control unit with matching performance. A stereo headphone socket is included, fed by a 330Ω 1W resistor from each channel output. The head­ phone socket incorpo­ rates speaker switching, so that if the headphones are plugged in, the speakers are switch­ed off. Interestingly, while investigating an increase in distor­tion which was eventually blamed on the spring-loaded speaker terminals, as noted above, The power transformer and bridge rectifier are mounted on a metal baseplate inside the case. The rear panel is also metal and has a large heatsink for the regulators and power transistors. we also checked whether the headphone/speaker switching caused any distortion. It didn’t. The amended circuit also includes the change to the input circuitry whereby a 10Ω resistor is connected in series with the input and feedback earthing for the differential pair, Q1 & Q2. Finally, the LED power indicator and its 2.2kΩ resistor is shown connected to the -20V supply rail. involves an LM317 and Q1, a TIP42 PNP power transistor. The LM317 is set to deliver 20V by virtue of the 120Ω and 1.8kΩ resistors connected to its ADJ (adjust) terminal. Because of the way it is connected across the 3-terminal regulator, the TIP42 transistor is forced to follow the LM317. This happens in the following way. All the current passing through the LM317 must first pass through the associated 0.22Ω resistor and diode D1. The total voltage drop across these two components becomes the Fig.5: actual size artwork for the power supply PC board. Power supply circuit Fig.3 shows the details of the power supply circuit. It uses a toroidal power transformer with two 21V secondaries to feed a bridge rectifier and two 4700µF 50VW filter capacitors. This develops unregulated supply rails of about ±29V and these are fed to identical positive and negative regulator circuits comprising an adjustable 3-terminal regulator and a power tran­sistor. To see how these work, let us consider just the positive regulator which August 1998  77 Parts List Amplifier chassis 1 2-unit high rack-mounting case 2 single-sided heatsinks, 300 (W) x 75 (H) x 49mm (D) (Altronics H-0545, DSE H-3406 or equivalent) Note: these heatsinks form the sides of the rack mounting case. 2 PC boards, SC01207981, 118 x 81mm 8 20mm fuse clips 4 M205 2.5A fuses 2 coil formers, 24mm OD x 13.7mm ID x 12.8mm long (Philips 4322 021 30362) 4 metres, 1mm dia. enamelled copper wire 1 0.5-metre length of 0.7mm dia. tinned copper wire for board links 6 2-metre lengths, medium duty hookup wire, (6 different colours) 1 2-metre length of figure-8 twin shielded audio cable 1 stereo headphone socket, insulated, DPDT switched (Altronics P-0074 or similar) 1 dual 20kΩ log, 26mm dia. potentiometer (VR2) 2 200Ω trimpots VR1,VR101; Bourns 3296W or similar 23 PC stakes 4 adhesive rubber feet 2 3-way insulated terminal blocks 4 TO-3P insulating washers 4 TO-18 heatsinks (Farnell 170-061 or equivalent) 4 100mm standoffs tapped for 3M screws 8 3M x 20mm screws 2 3M x 10mm screws 10 3M nuts 4 3mm flat washers 1 cord-grip grommet 10 BC547 NPN transistors (Philips or Motorola) (Q5, Q6, Q8, Q9, Q10, Q105, Q106, Q108, Q109, Q110) 2 BC337-25 NPN transistors (Philips) (Q11, Q111) 2 BC327-25 PNP transistors (Philips) (Q13, Q113) 2 MJL21193 PNP power transistors (Motorola) (Q12, Q112) 2 MJL21194 NPN power transistors (Motorola) (Q14, Q114) 2 BZX55C3V3 3.3V 0.5W zener diodes (ZD1, ZD101) 1 3mm green LED and LED bezel holder Capacitors 8 100µF 25VW electrolytic 2 47µF 16VW electrolytic 2 2.2µF 16VW electrolytic 2 0.15µF 100V MKT polyester or Philips MKC 2222 344 21154 10 0.1µF 100V MKT polyester 2 .0012µF MKT polyester or ceramic 2 100pF NP0 ceramic Resistors (0.25W, 1%) 4 18kΩ   4 180Ω 2 8.2kΩ   4 150Ω 2 3.3kΩ   4 120Ω 3 2.2kΩ 12 100Ω 2 1.8kΩ   2 10Ω 2 390Ω 16 1Ω 0.5W 2 330Ω 1W 2 1.8Ω 5W (for setting bias) Power Supply Semiconductors 10 BC557 PNP transistors (Philips or Motorola) (Q1, Q2, Q3, Q4, Q7, Q101, Q102, Q103, Q104, Q107) 1 plastic instrument case 260 x 82 x 190mm (W x H x D, with metal rear panel) (Jaycar HB-5910 or equivalent) 1 metal baseplate, 167 x 225mm (1.6mm aluminium in prototype) 1 power transformer, toroidal, 160VA, 2 x 21V secondaries (see text) 1 SPST mains power switch (Jaycar SK-0984 or similar) base bias voltage of the TIP42. In effect, the voltage drop across D1 is matched by the base-emitter voltage of Q1 which is then forced to repro- duce the voltage across the 0.22Ω resistor across its own 0.1Ω emitter resistor. So if the current flowing through 78  Silicon Chip 1 IEC fused power socket (Altron­ics P-8324, Jaycar PP-4004) 1 IEC mains power cord 1 M205 3A fuse 1 single-sided heatsink, 110mm x 75mm x 48mm (W x H x D) 4 adhesive rubber feet 1 PC board, 04208981, 94 x 76mm 1 3-way insulated terminal block 1 3 or 4-pole matched automotive connector set 1 4M x 20mm screw 1 4M nut 1 4mm flat washer 10 3M x 20mm screws 4 3M x 10mm screws 14 3M nuts 4 3mm flat washers 4 TO-220 mounting kits (mica insulators, insulating bushes) 1 cordgrip grommet 5 PC stakes Semiconductors 1 KBPC1004 400V 10A bridge rectifier (BR1) 1 LM317-T variable positive regulator (REG1) 1 LM337-T variable negative regulator (REG2) 1 TIP42 PNP power transistor (Q1) 1 TIP41 NPN power transistor (Q2) 2 1N5404 power diodes (D1,D3) 2 1N4004 power diodes (D2,D4) Capacitors 2 4700µF 50VW electrolytics 2 100µF 25VW electrolytics 2 10µF 35VW electrolytics 2 0.1µF 100V MKT polyester Resistors (0.25W 1%) 2 1.8kΩ 2 10Ω 2 120Ω 2 0.22Ω 5W wirewound 2 0.1Ω 5W wirewound Miscellaneous Heatshrink tubing, tinned copper wire for board links. the LM317 causes a vol­ tage drop of 0.15V across the 0.22Ω resistor, the same voltage will be produced across the 0.1Ω resistor and so Q1 will deliver 1.5A to the output. So Q1 is effectively a “current follower” and the ratio of the current delivered by the LM317 to the current from Q1 is set by the ratio of the two resistor values, 0.22Ω and 0.1Ω. This ratio is 2.2:1 and so Q1 always delivers 2.2 times the current of REG1 while always re­maining under its control. The negative regulator circuit, involving REG2 and Q2, is identical in operation. Building the power supply Since the power supply has to be up and running before you can run the amplifier, we will describe its construction first. The power transformer and bridge rectifier are mounted on an aluminium baseplate which is secured into the integral pillars in the base of the case. Our prototype’s power transformer was supplied with 18V secondary windings so we added 15 turns of 1.25mm enamelled copper wire for each secondary. These turns were wound bifilar (ie, two wires at a time) using a shuttle made from a piece of PC board copper laminate. We wound a layer of clear insulation over the extra winding to protect it. The dual regulator circuit fits onto a PC board measuring 94 x 76mm and coded 04208981. The 3-terminal regulators and two power transistors are along one edge so that they can be easily mounted on the metal rear panel. Fig.4 shows the PC board compon­ ent overlay for the power supply. Mount the resistors and diodes first, followed by the elec­trolytic capacitors, the regulators and the power transistors. Note that the electrolytics and diodes must go in the right way around otherwise the circuit is likely to be damaged at switch-on. For the same reason, do not get the regulators and transis­tors mixed up. Note that the spacing between the power transistors and regulators on the PC board matches the fin spacing on the speci­ fied single-sided heatsink. This is necessary to allow the tran­sistor mounting screws to pass right through the heatsink and the metal rear panel. Fig.6 shows the detail of the heatsink mount­ing. Also on the rear panel is the fused IEC power socket, an earth solder lug and the exit hole for the three-core DC output cable. These holes will need to The power supply case should be positioned at least 600mm away from the amplifier chassis in order to keep the induced hum to an absolute minimum. The power supply is connected to the amplifier using a 3-pole or 4-pole automotive matched connector set. The large finned heatsink is necessary to cool the power supply regulators. Fig.6: this diagram shows the detail of the heatsink mounting for the TO-220 devices in the power supply. After mounting the devices, use your multi­meter to check that there is an open circuit between the heatsink and the device collectors. August 1998  79 Fig.7: chassis wiring diagram for the power supply. 80  Silicon Chip Fig.8: this is the amended PC component overlay for the amplifier module. Take care to ensure that all transistors are correctly oriented and note that transistors Q11 and Q13 should be fitted with finned heatsinks to keep them cool. be drilled and cut as necessary. Fig.7 shows the wiring of the power supply. All the mains supply wiring must be run in 250VAC-rated hookup wire and all wiring terminals should be sleeved with heatshrink sleeving to prevent accidental contact. The three-way DC output cable was run in a short length of 250VAC three-core cable, terminated directly to the PC board at the power supply end. The other end of the cable was fitted with a 4-way plug which mates to a socket on a cable from the power amplifier. Once all your assembly work is finished, check it carefully against the diagrams of Fig.3, Fig.4 and Fig.7. Then apply power and check that the outputs are +20V and -20V DC. Then you can turn your attention to the amplifier chassis. Amplifier assembly Last month we discussed the assembly of the amplifier PC boards. In Fig.8 we show the amended PC board layout which in­cludes the 10Ω input earthing resistors referred to above. Finned heatsinks must be fitted to the TO-92 driver transistors, Q11 & Q13. Fitting these heatsinks is not easy. They are made of springy beryllium-copper to fit TO-18 metal can transistors but they will fit TO-92 transistors provided they are openedup a little as they are fitted over the plastic encapsulation. We were able to Table 2: Capacitor Codes ❑ Value IEC Code EIA Code ❑ 0.15µF   150nF   154 ❑ 0.1µF   100nF   104 ❑ .0012µF   1.2nF   122 ❑ 100pF   100p   101 do this with the aid of a pair of longnosed pliers. The devices we used are supplied by Farnell Electronic Components Pty Ltd (Cat No. 170-061). Fig.10 shows the chassis wiring diagram for the amplifier. It must be followed exactly, in order to obtain the claimed performance. You should Table 1: Resistor Colour Codes ❑ No. ❑   4 ❑   2 ❑   2 ❑   3 ❑   2 ❑   2 ❑   2 ❑   4 ❑   4 ❑   4 ❑ 12 ❑   2 ❑ 16 Value 18kΩ 8.2kΩ 3.3kΩ 2.2kΩ 1.8kΩ 390Ω 330Ω 180Ω 150Ω 120Ω 100Ω 10Ω 1Ω 4-Band Code (1%) brown grey orange brown grey red red brown orange orange red brown red red red brown brown grey red brown orange white brown brown orange orange brown brown brown grey brown brown brown green brown brown brown red brown brown brown black brown brown brown black black brown brown black gold gold 5-Band Code (1%) brown grey black red brown grey red black brown brown orange orange black brown brown red red black brown brown brown grey black brown brown orange white black black brown orange orange black black brown brown grey black black brown brown green black black brown brown red black black brown brown black black black brown brown black black gold brown brown black black silver brown August 1998  81 Repeated from last month, this photo shows one of the assembled power amplifier modules. Note that the module has been amended slightly since the photo was taken, with the addition of two extra resistors (2.2kΩ and 10Ω) and finned heatsinks to Q11 and Q13. look closely at the photograph of the amplifier chassis to see how the various wires and connections have been routed. These are not arbitrary; the layout has been produced after much trial and error to obtain the best distor­tion, separation between channels and signal-to-noise ratio, so be sure to follow the diagram exactly. There are a number of features of the wiring which require particular comment. First, the input wiring from the RCA sockets to the volume control must not be earthed to the Fig.9: this is the full-size etching pattern for the amplifier PC board. 82  Silicon Chip Fig.10: this is the chassis wiring diagram for the amplifier. Note that it must be followed exactly, in order to obtain the claimed performance. August 1998  83 The amplifier employs a volume control so that a CD player can be connected without the need for a stereo control unit. fully against the diagrams of Fig.2 and Fig.10 and the chassis photos. chassis. It must be run exactly as shown in Fig.10. Second, the DC input cable from the power supply is clamped after it enters the chassis and then terminated in a 3-way insu­lated terminal block. The 0V line is connected to chassis via an adjacent solder lug. The three supply wires to each amplifier module are tightly twisted and laid flat against the chassis. This is to minimise any harmonic radiation from the supply leads into the input circuitry of the modules. Third, the loudspeaker wires to and from the headphone socket are tightly twisted and laid flat against the chassis. Again, this is to minimise any Setting up radiation into the input circui­try. The speaker earth wires are terminated to an insulated terminal block adjacent to the headphone socket but there is no connection to the chassis at this point. Note that the headphone socket itself is insulated from the chassis. Both the active and earth speaker terminal posts are insu­lated from the chassis but short wires run from both speaker earth terminals to an adjacent solder lug on the rear panel. Again, this might seem like an arbitrary wiring arrangement but it must be followed if the best performance is to be obtained. When you have completed all the chassis wiring, check your work care- Heavy duty gold-plated loudspeaker terminals were specified in order to obtain the lowest distortion. If the loudspeaker connec­tions are poor, the distortion performance can be degraded. 84  Silicon Chip Before the amplifier can be run with signal, the quiescent (no signal) current must be adjusted on each module. To do this, remove the fuses on both modules and wire 1.8Ω 5W wirewound resistors across the adjacent PC stakes. This done, apply power and use your multimeter to check that ±20V is present on the supply rails of both amplifier modules. Next, adjust trimpot VR1 (VR101) to obtain a voltage of 1.8V DC across one the 1.8Ω 5W resistors, on both modules. This sets the quiescent current at 1A. Leave the amplifier to run for five minutes or so and then check the voltage again. It should not drift by much but if it does, readjust VR1 to obtain 1.8V again. Then leave the amplifier to run for half an hour or so and then re-check the readings. During this time the amplifier heatsinks will become quite warm and the heatsink on the power supply case will become warmer still but that is normal. Finally, check the DC voltage at the output of each ampli­fier. It should measure less than ±50mV. You can then remove the 1.8Ω 5W resistors from both amplifier modules, reinstall the fuses and place the cover on the amplifier. You can now hook up your CD play­ er and loudspeakers and sit down to enjoy some very pleasant music. SC VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG An Australian-made 6-transistor personal portable Yes, early transistor radios are now vintage and are worth restoring. One such receiver is the Kriesler 41-32, an Australian-made 6-transistor “pocket” radio that was first made in 1962. Transistor radios started to become readily available (at a price) in the mid to late 1950s. Initially, their performance left much to be desired. However, the general public was prepared to accept performance that was inferior to the good valve portables of the time in favour of a set that was relatively compact, light and portable. Another factor in favour of the transistor radio was that it operated from low voltage batteries at low current drain and so was cheap to run. In city areas, the problems of poor sensitivity and noisy operation (due to limitations in the transistors) were of little consequence as the stations were strong. In many ways, it was a blessing in disguise that the sen­sitivity was poor. The overload characteristics of these sets and the transistors they used were, to put it mildly, terrible. Imported sets Very few radios were imported into Australia until the commencement of the transistor era over 30 years ago. Australian-made valve radio were as good as any and there was no need to import sets from elsewhere. However, transistor sets started to come in from Asia in increasing numbers from that time. Initially, some early Australian transistor sets used point to point wir- ing, as was used in most valve radios. By contrast, the Japanese sets used PC boards right from the beginning in all the sets imported here. Transistorised radios lent themselves very much to the use of PC boards. Transistors could be wired in much the same way as resistors and capacitors and all the coils had become miniaturised by that time too. As a result, this type of construction became the standard within a very short time. The PC board method imposed difficulties for servicemen, however – particularly when they had to service Japanese pocket sets. Everything was crammed in, it was difficult to trace the circuit and the type numbers of transistors, etc, were unknown to Australians. As a result, it was difficult to do much with them if something went wrong. By contrast, many of the Australian manufacturers laid their boards out with more space between components and they often printed the track pattern on top of the board to aid cir­cuit Fig.1: the circuit of the Kriesler 41-32. It used six transistors, all germanium PNP types. August 1998  85 The Kriesler 41-32 was typical of transistor sets built in the early 1960s. It featured a “handspan” dial and a cabinet made from plastic and vinyl. Although described as a “pocket radio”, quite a large pocket would be required to carry it. tracing. This made it much easier when the set required repairs. One of the bugbears of servicing or restoration is disman­tling the sets to work on them. Some sets are easy to dismantle and reassemble while others are a nightmare. Regrettably, many transistor sets were horrors to work on and, as a result, were consigned to the rubbish bin before many older valve sets! The Kriesler 41-32 The Kriesler 41-32 was put into production in 1962 and is a typical Australian made 6-transistor pocket radio. A large coat pocket would be needed to carry it though. It is quite a reasonable performer, being considerably better than the first 6-transistor sets that came onto the Aus­tralian market. It used the later PNP germanium transistors in the RF and IF sections – namely the OC170 and OC169 transistors – instead of the OC44 and OC45 types used in the first Australian transistor radios. A larger than normal ferrite loopstick aerial was also used to improve the performance. The set doesn’t compare favourably 86  Silicon Chip with transistor porta­bles that have an RF stage, however. It wasn’t meant to be used in other than suburbia and, in this role, it does the job quite well. Inside the set The photograph of the back of the set shows that it used both full-size and miniature components. The tuning gang is full size, as is the trimmer capacitor and the on-off volume control. A circuit diagram was pasted onto the back of the set, which was a good idea. The circuit is relatively simple and has both voltages and currents marked on it. This helps to make servicing easier. The set uses PNP germanium transistors throughout. I don’t know about others but I find that working with PNP transistors requires some mental gymnastics for me to remember that the collector (equivalent to the plate of a valve) is negative with respect to the chassis or emitter (cathode in a valve). NPN transistors work the other way around and the voltages are like the convention we got used to with valves. Having said all that, how easy is the set to dismantle and keep operational whilst doing the service work? Not at all easy as it turns out. There are three screws and one nut to undo (as shown by the white arrows on the photo) and then the PC board can be lifted up after unclipping it at the righthand end of the cabinet. The disassembly notes in the set say “lift board from cabinet to limit of the leads”. This is fine as far as it goes but the board can’t be worked on in this condition, as the leads are not long enough to give easy access to both sides. With a little more thought it could have been made a dream to work on. If the board had been made so that it hinged at the end nearest the tuning gang, the tuned circuit leads would not have to move much at all. At the righthand end is the audio section and the leads could have been longer and dressed so that the board could swing out at right angles to the cabinet. It would then act as a prop to stop the set falling over and service would have been a breeze under these circumstances. It wouldn’t be all that difficult to modify the lead dress to accomplish most of this but it is always harder to do as a modification after manufacture. In the process of overhauling this set I ran into a real problem. The tuning gang had both sections shorting at various spots across the dial. I tried bending the moving plates with it in situ but couldn’t get it so that no shorts were occurring. It had to come out but how could that be done? It was not possible to gain easy access to the screws hold­ ing the gang onto its mounting plate, as they were behind the aluminium front The Kriesler 41-32 used a mixture of full-size and miniature components, the full-size mounting plate. In the end, parts including the tuning gang, the trimmer capacitor and the combined on-off/volume the whole set had to be discontrol. The PC board can be lifted clear from the case by removing three screws and mantled and I ended up with one nut, as indicated by the cardboard arrows. a collection of parts on the workbench, all held together troublesome easing the gang assembly glue to lock several screws into posiby a few pieces of wire. out of the set. tion into the plastic front escutcheon I decided to remove the dial scale (several had come loose and it made After that short story on how to on the front of the set as it would need it hard to tighten the nuts on them). cleaning. After prising the retaining remove a gang, I’ll get on with how clips away from the plastic dial scale, I fixed it. After a lot of mucking Several other parts on the front of the set had to be glued as well. around, the plates were bent so that it came away. The retaining clips were Cleaning the vinyl is a problem as on a circular plastic plate mounted no shorts occurred at any position of with three screws to the front of the the gang. This was confirmed using a even soap and water causes the paint multi­meter. on it to come off and the set then looks set. Removing this plate revealed two a bit weather beaten. It’s a matter of It appears that in the past, someone large holes through which I could have gained access to the gang mount- slipped with a screw­driver or some cleaning it and have some of the paint other tool when working on the set on the vinyl come off or leave it dirty. ing screws! This would have saved me native is particularly and actually damaged the gang. Hav- Neither alter­ quite some time if I had known this ing fixed that, the set was a goer and impressive. As a result, these sets beforehand. cannot be made into beautiful pieces after touching up the alignment, it Kriesler’s method of furniture like the wooden con­soles performed quite well. Batteries are a problem for many of often are. The Kriesler Technical Service Information does describe a technique these sets as specials were made for Summary quite a few brands and models. This for removing the works in such a way set used a small 9V battery called a So there it is – an old “pocket” as to have the set still operational. To do this you remove the tuning knob, 2362 which is no longer available (and 6-transistor radio of Australian manwhich would probably be expensive ufacture. It’s a reasonable performer remove the three nuts securing the if it was). So what could be used in and although it can’t be made to look aluminium gang bracket to the front a million dollars, it’s worth re­storing escutcheon and release the board from its place? because of the era it represents. It would have been nice to use six the bracket on the speaker end of the penlite cells but a pack is just too One question that remains is where receiver. The board, complete with gang, big to fit in. The only alternative is do you get transistors if they are ever a 216 which will fit in but with a needed for replacement purposes? volume control and loopstick antenna current drain varying between 10mA Germanium PNP transistors are availcan then be lifted clear to the limit of and 40mA, it won’t last long. One of able from time to time at flea markets, the speaker leads. Unfortunately, they the heavy-duty alkaline types may etc, but they are not as easily obtained missed out on telling servicemen to remove one nut in the centre of the be worth considering if the set is to as valves. In some circum­stances silibe used for entertain­ment as well as con PNP transistors can be used if the circuit board. operating conditions are changed to Yes, this will work although in my being a vintage radio exhibit. suit. The forward bias required for a opinion the method I described earlier Cabinet problems germanium transistor to conduct is is much better. Even so, if I’d had this about 0.2V but for a silicon transistor, The plastic and vinyl components infor­mation earlier, I might have got the set to pieces with less trouble. The of the cabinet were in fairly ordinary it is about 0.6V. This issue will have to be explored screw threads seemed to bind to the condition, which is now normal for SC aluminium and the nylon and it was these sets. I used some form of super- in depth at a later time. August 1998  87 3 1 2 GREAT REASO SUBSCRIBE NO Every new or renewing subscriber* between now and June 30 gets a FREE copy of the superb SILICON CHIP/JAYCAR Wall Data Chart. THAT’S WORTH $10.95 ALONE! Every new or renewing subscriber* between now and June 30 qualifies for an EXCLUSIVE 10% discount on ANY SILICON CHIP merchandise: books, software, EPROMS & microprocessors, binders, back issues, etc 88  Silicon Chip * This offer applies to Australian subscribers only ONS TO OW TO 3 The best reason of all: you’ll actually save money! Not only will you get your copy of SILICON CHIP BEFORE it’s on the news-stands – it’s cheaper getting your copy mailed direct to you – and you’ll never miss an issue! HURRY! TAKE ADVANTAGE OF THIS STRICTLY LIMITED OFFER TODAY! Yes Please! I want SILICON CHIP delivered every month to my letterbox and I want to take advantage of the exclusive subscribers’ offers. Name............................................................................................. PLEASE PRINT Address.......................................................................................... ....................................................................Postcode..................... ❑ New Subscription (month to start....................................) ❑ Renewal (Sub No from wrapper.......................................) I want ❑ One Year <at> $59 ❑ Two Years <at> $112 or ❑ 1Yr with binder <at> $72 ❑ 2 Yr with binders <at> $138 This is a YES! This offer also applies to GIFT SUBSCRIPTIONS: Call SILICON CHIP to place your order for a gift subscription. Here’s how to order: or or Fax this coupon (or a copy) to SILICON CHIP on (02) 9979 6503 – 24 hours a day Post this coupon (or a copy) to SILICON CHIP, PO Box 139, Collaroy, NSW 2097 You can even order by phone with your Bankcard, Mastercard or Visa Card: Call SILICON CHIP on (02) 9979 5644 9am-5pm, Monday to Friday FAX or POST ORDERS: Card No: Expiry Date:_______/_______ Signature:__________________________ (Yes, we do accept cheques or money orders by post!) March 1998  89 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. 100W inverter is below par Several years ago, I purchased a kit for the 12V 100W DC-DC converter as featured in the December 1990 issue of SILICON CHIP. It was intended to power a twin 50W RMS amplifier (into 4Ω) which would require ±27V supply rails. From your table of output voltages, I calculated that the transformer secondary needed to be 25.5 turns (bifilar) of 0.7mm copper wire and wound it accord­ingly. It was put into service but never seemed to be quite up to the task. I felt that the amplifier didn’t have the “kick” that it should. Recently, I started to hear some hash in the output and decided to fix that and check the output. The noise was due to two of the Mosfets breaking away from the PC board and making momentary contact with the PC pins. This was caused by the weight of the input inductor flexing the board under vibration, which eventually took its toll. I replaced the two Mosfets and fitted two more mounting screws to the board near the Mosfets. I assume from your article that the converter produces enough power for Model railway wiring and damping I am a model railway enthusiast (N scale) and am building three of your April 1988 walkaround throttles. My layout uses “common rail” wiring as described in a Kalmbach (“Model Railroad­er”) book by A. Sperandeo. Itt warns against using the same transformer to run several throttles if common rail wiring is used. Does this restriction apply to your 1988 Walk­ar­ound throttles? I am selecting a suitable 50W power amplifier module to run some bi-amped speakers and am considering the designs published in 1994 and 1995 using the Na90  Silicon Chip 100W RMS output from the amplifier it powers. With an efficient design that can swing the output close to the supply rails, this would require a power supply of close to double the amplifier output, for a sinewave. However, using a dummy load on the converter output, it only produced around 50-60W, at 60% efficiency. I have probed around the circuit with an oscilloscope and everything appears to be correct. It is running at 25kHz and the transformer phasing is correct. I have tried frequencies up to 60kHz, which produce no change in efficiency but at 60kHz the maximum output is down to around 40W. At 25kHz, with 12W output, the Mosfets are on for 4µs, a duty cycle of 20%. In a very similar design, published by another magazine some years earlier, they used 5.5 turns of two parallel 1.25mm copper wires for each primary phase of the transformer. The design was to power a twin 50W RMS amplifier. This is clearly a much higher power transformer design but is used in a similar specification converter, which leads me to my question. I saw your design, as published, intended to supply close to 200W of power for a 100W RMS amplifier? If not, why does tional Semiconductor chips. After reading the articles, however, I am confused regarding their damping factor. In March 1994, you specify the damping factor for an LM3876T design as being >150 for 8Ω loads and the same figure for an LM3886 design in February 1995. In the following month, March 1995, the stereo amplifier is specified as having a damping factor of >56 from 100Hz to 10kHz. Is there an error somewhere? (G. B., Ned­lands, WA). •  When you are using common rail wiring (the only really practical system in most cases), it is absolutely essential that each throttle has its own power supply. If you it use four Mosfets when two would be more than adequate? As your design is so similar to the earlier design, I am intending to rewind the transformer as per theirs. Their secondary is 15.5 turns of 1.25mm ECW for each phase. Can you foresee any problems with this? (C. B., Ashwood, Vic). •  As described, the converter will deliver a maximum of 100W and that is enough, provided the supply rails are correctly set to drive a 100W amplifier to full power on normal program sign­als. If you want to drive a 100W amplifier to continuous full power you would need a DC input of about 160W, depending on the particular amplifier. If your converter is delivering only around 50-60W on a dummy load, we would be inclined to suspect that perhaps the polyswitches in the outputs have become high in resistance. They can do this in some circumstances. The circuit may also perform below par if the Mosfets are not up to spec. Unless you have used BUZ71s made by Siemens or Philips, or MTP3055Es made by Motorola, you may not get the full output. Other points to check are the various large value electro­ lytic filter consider that each throttle can reverse the track polarity for its blocks, there is great potential for power supply overloads if common power sup­plies were to be used. In other words, follow the Kalmbach book to the letter. Damping factor in most good amplifiers is of academic interest only and will always be in excess of 50 for 8-ohm loads. Damping factor is a measure of the “voltage regulation” of a power amplifier – the higher the figure, the better. It is calcu­lated by dividing the load impedance (8Ω) by the output impedance of the amplifier. All of the amplifiers you list have very good damping factors. ELECTRONIC COMPONENTS & ACCESSORIES Optoelectronic ignition •  LARGE RANGE OF ICs, RESISTORS, CAPACITORS & OTHER COMPONENTS •  MAIL ORDERS WELCOME! CROYDON STORE ONLY ELECTRONIC DISPOSALS CLEARANCE! wired up. You should build the PC board using the Siemens HKZ101 Hall effect sensor overlay diagram (June 1998, page 22) but replace the 100Ω resistor with the 470Ω 0.5W unit. The 820Ω 0.5W resistor is replaced with a 2.2kΩ resistor for the photo­diode. The (+) lead from the PC board goes to the anode (A) of the LED, while the signal lead from the PC board goes to the cathode (K) of the photodiode. The GND lead from the PC board goes to the cathode (K) of the LED and the Anode (A) of the photodiode. •  OPEN FRAME 240V INDUCTION MOTORS 600 WATT AND 900 WATT. 600 WATT - $15 EACH OR 10 FOR $100 900 WATT - $18 EACH OR 10 FOR $120 •  LARGE VARIETY OF DISPOSALS TRANSFORMERS AT GIVEAWAY PRICES! Croydon Ph (03) 9723 3860 Fax (03) 9725 9443 MilduraPh (03) 5023 8138 Fax (03) 5023 8511 Truscott’s ELECTRONIC WORLD Pty Ltd ACN 069 935 397 30 Lacey St Croydon Vic 3136 capacitors in the circuit and look for any signs of overheating. The circuit will work best at around 22kHz as pub­ lished. Higher frequencies will reduce efficiency. We would not be inclined to modify the circuit to match the earlier design. Multi-purpose charger mods I have just recently read the February 1998 edition of SILICON CHIP concerning the multi-purpose battery charger. As I am a keen R/C airplane hobbyist, I am thinking about making the kit. Good batteries are important to me because of safety and also because two of my models are quite expensive (over $2000 each). Could I ask you to clarify the following couple of points for me as the kit is quite costly and I wish to be sure it can fulfil my intended function? A couple of my battery packs are only 4-cell, 4.8 volts. How would I set the charger for these batteries? How would I set the refresh for the four batteries (how does the charger know to drain down to 4V instead of 1V? These same batteries are only 1Ah (not 1.2Ah as per the specs). Is this a problem? (the specs say minimum 1.2Ah). What are SLA batteries? Can I charge my gell cells with this charger? The refresh rate of 2A seems a bit high. I would have thought this to be around 200mA instead. If it is 2A, won’t this cause the NiCd batteries to overheat due to fast discharg­ing? (L. D., Or­mond, Vic). •  The charger can be set to charge 4.8V batteries by changing the divider resistors tapping off from the 100kΩ resistor to 33kΩ. For example, the 6V divider resistors are 330kΩ in parallel with 27kΩ to give a total of 25kΩ. Replacing these with a single 33kΩ resistor will provide a facility to charge the 4.8V battery. The refresh will discharge to 1V per cell since the divi­sion ratio for 4.8V is correct. 1Ah batteries are not a problem. The timer period will, however, be a little too long. This could be reduced slightly by increasing the 820pF oscillator capacitor to .001µF. SLA stands for sealed lead acid. Gel cells are the same. Refresh at 2A is satisfactory for NiCd cells. They will run warm at M W OR A EL D IL C ER O M E I am currently building a Club­ mans Formula race car using a Toyota 4KC 1300cc engine. I have bought a High Energy Ignition kit from Jaycar in Adelaide and intend purchasing a Programmable Ignition kit (SILICON CHIP, March 1996), so that I will be able to set rev limits for the engine. I have also purchased a Crane Cams opto­electronic replacement for the points. Can you tell me how I should interface the optoelectronic device (looks like a couple of diodes, one infrared, that are interrupted by a plastic disc with slots cut in it), to the High Energy Ignition kit? Have you made any modifications or improve­ments to the high energy kit or to the programmable ignition kit that I should be aware of? (I. H., Adelaide, SA). •  This diagram shows how the optoelectronic interrupter can be 24 Langtree Ave Mildura Vic 3500 SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. August 1998  91 Electric fence lacks bite I have recently built the Electric Fence Controller de­scribed in the July 1995 issue of SILICON CHIP and I used a new 12V automotive ignition coil. I have used a 1.2Ω 0.5W resistor in series with the coil as suggested in the Notes & Errata (December 1995) but the output voltage is nowhere near the maximum of 10kV specified in the AS/ N25 3129.1-199.3 standard. I went to an Electric Fence supplier in order to measure the output voltage with a special digital this discharge but this is well within their ratings. 5-digit tachometer flashes on zero I recently built the 5-Digit Tacho­ meter as in the October 1997 issue. I find that digits one and two roll as the car revs up but digit 3 just flashes on zero and digits 4 & 5 sit on 8 & 4 respectively. I have checked the circuit time and time again for mistakes and found none, and all tests as per the book read as they should. I hope you may be able to give me some clue which may help me out. (F. M., Gulgong, NSW). •  It is evident from the symptoms that you have a number faults on the PC board which should be found merely by checking with your multimeter. With no signal being fed to the input, the unit should show “0” and the first four digits should be blanked. From your de­scription, it seems as voltmeter used for this purpose. We measured 800-900V. Can you please advise what could be done to increase the output in order to make the unit suitable to keep our animals (Kune Kune pigs) in the enclosure. The length of fence is 250m. (J. M., Tauranga, NZ) •  The high tension output voltage from the coil can be in­creased by changing the value of the 1.5kΩ resistor between pins 6 and 7 of IC1. We recommend using a 10kΩ trimpot and adjusting it until the requisite 10kV is produced. A suitable fixed value resistor can then be substituted for the trimpot. though the display is showing the first two digits all the time. That indicates that the “zero blanking” is not working and that you probably have an open circuit connec­tion in this part of the circuit (D2-D17, IC13 & IC16). To find it, it is a matter of very carefully inspecting the PC board under a bright light to find a missed solder joint. If DISP4 & 5 show 8 & 4 respectively, that indicates that some segments (a, e, d) on DIP4 are open circuit while segment g is shorted to one of the others on DISP4. Similarly, on DISP5, segment g is shorted to one of the others, probably between pins 9 & 10 on the display board. It is merely a matter of using your multimeter (on the Ohms range) to find where the short is. If you are lucky (and keen sighted) you should be able to see the shorts, probably as solder splashes. Similarly, since the display does not appear to follow the input when the engine is revved up, it appears that either the input connection is not correct or the input processing circui­try, involving IC1 & IC2 has an open circuit component. Noise in guitar sustain project I have just recently constructed the Guitar Sustain Unit as described in the March 1998 issue. The construc­ tion of the unit was easy, with only one change to John Clarke’s design being made. This was done to meet my requirements of having the unit contained in a metal case and being switched in and out with a footpad switch purchased from Altronics (Cat S-1150). The unit works fine except for a problem that I feel may be associated with the change that I had made. When the switch is pressed for both On or Off, a loud thumping noise is present throughout the amplification system and is very annoying. Was this noise present in the prototype when the PC board switch was engaged for on/off use? If not, is there anything that can be done to eliminate the noise problem that I have with the footpad switch arrangement. Another query that I have concerns the DC power supply plugpack supplied with the kit. This delivers an unregulated supply voltage of 19.7V DC. As stated, the circuit requires a 12V power supply to give 11.4V at pin 4 of IC1 and pin 8 of IC2 and 5V at pins 7, 10 & 12 of IC1. The measured voltage at pins 4 & 8 showed 16.6V, with 5.14V present at pins 7, 10 & 12. Is this 16.6V too high for the circuit even though the 5.14V is OK? Also could the higher voltage cause the noise problem associated with the footpad switch? (D. W., Capalaba, Qld). •  There should not be a large thump when switching modes, provided trimpot VR4 is adjusted to give the WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. 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. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 92  Silicon Chip same volume whether the switch is in or out, when the guitar string is first plucked. If VR4 is not adjusted properly, there will be an abrupt change in bias to the FET (Q1) each time S2 is operated. It is also possible that you are getting more thump than you should because of the high DC input voltage although this will not cause any damage to the circuit. You could fix it by using a 7812 or 78L12 3-terminal regulator to reduce the voltage to a precise 12V. Note that the 3-terminal regulator should have 0.1µF bypass capacitors at its input and output to ensure stabil­ity. Search for MV500 chip I am about to build the Infrared Remote Controlled Railpow­er project as described in the April, May & June 1992 issues and am stymied because I cannot obtain the Plessey MV500 infrared encoder/transmitter chip anywhere in New Zealand. This is particularly galling because I can buy the accompanying Plessey SL486 and MV601 ICs off the shelf. Can you help? (D. K., Dunedin, NZ). •  The three chips you refer to were discontinued some years ago now because they presumably were no longer being used in current TV and VCR manufacture. There is no substitute for the MV500 that we know of and we don’t know of any stockist for this device. Perhaps one of our readers can help in this regard. We did publish a later version of the Railpower project which used Z8 microprocessors in both the handpiece and the main circuit but it was a flop with model railway hobbyists, even though it worked extremely well. We can still supply the micro­processors for this project. Alternatively, it is possible to incorporate infrared remote control into the original Railpower project by adapting the infrared remote volume control project published in the July 1997 issue of SILICON CHIP. Kits for this project are available from Oatley Electronics and we can still supply the relevant back issues. Speed control for radio control I read with interest your article for 12/24V speed control in the June 1997 issue. Is it suitable for radio control applica­tions? Do you know of a replacement chip for a Ferranti ZN409­ CE servo amp IC? I have a number of English circuits for R/C using the above IC which is no longer available. (B. S., Koroit, Vic). •  The speed control described in June 1997 is not suitable for radio control. If you want a speed control which is controllable via a normal servo output on an R/C receiver, you would be wise to consider the design featured in the November & December 1992 issues. There is no replacement for the ZN409CE but it is currently available from both Jaycar Electronics and Oatley Electronics. These two companies have put this item into stock to cater for the Command Control for Model Railways which was described in recent issues of SILICON CHIP so the stocks will not last. Huge range of VIDEO Processors, Stabilisers, Mixers, Editors, TBC’s, Standards Converters, Switchers, Amplifiers, connectors, cables, adaptors, kits. PC editing cards & software:- FAST DV, AV Master plus, Miro DV300, DC30+, DPS Spark, Edit Bay, etc. SCSI cards & drives. PC Converters & Genlocks. Call for prices and information or ... Check our website for latest prices and MONTHLY SPECIALS http://www.questronix.com.au/~questav You can fax, post, phone or email your order. We accept AMEX, VISA, Master & Bank cards, cash and direct deposit, but not cheques. Ex-tax sales available to exempt buyers. Prompt delivery within Australia & overseas. 2/1 Leonard Street, HORNSBY, NSW, 2077 P O Box 548, WAHROONGA, NSW, 2076 Fax (02) 9477 3681 Ph. (02) 9477 3596 Email questav<at>questronix.com.au Visitors and demo's by appointment only. Resolution VCC3010 High Picture Corrector Adjust RGB/ Contrast/ Brightness/ Saturation/ Detail etc. 4 i/p Audio & Video selectors. Fade to black. Use Y/C & Comp. i/p's & o/p's in any combination. $679.00 The ultimate stabiliser E-D TBC/ Enhancer Totally eliminates 'piggy-back' signals! Full-frame 4:2:2 digital TBC. Adjust RGB, gain, black level, chroma, colour shift, etc. Freeze, enhance, bypass, four memories for settings, built-in Bars, Black Burst, etc, etc. $1,599.00 STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Notes & Errata 12V CFL Inverter, March 1998: we have been advised by Oatley Electronics that some kit-built examples of this project have been prone to over-heating. They suggest a change to the gate drive circuit for the Mosfets. This involves replacing each 22Ω resistor with a 4.7kΩ resistor in parallel with a 1N4148 diode, with its cathode connected to the associated Mosfet gate. Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 August 1998  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $145.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________  Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip and 68HC12 now combined at the new low price of $75. Debug monitors: $75 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $75. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, the 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $189, $35 tax, $10 p&p. 20-pin SOIC adaptor only $70. Credit cards accepted. GRAN­TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150 or Internet: http://www.grantronics.com.au RAIN BRAIN AND DIGI-TEMP KITS. Also 60 channel Moni-temp with alarms and PC Data logging. Mantis Micro Products, 38 Garnet Street, Niddrie, 3042. (03) 9331 4786. Fax (03) 9331 4782 http://www.home.aone.net.au/mantismp ELECTRONIC ENGINEERING SOLUTIONS: No matter what problem what industry we will find you a solution that meets your needs. Specialising in schematic & PCB design, custom Windows based software, embedded control, Windows/PC based test equipment, turnkey solutions. Fast turn around with competitive rates. DAMUE PTY LTD, 46 Whitby Road, Kings Langley NSW 2147. Phone (02) 9624 2802. Fax (02) 9624 2651 or E-mail alovell<at>ibm.net A NEW address for Acetronics http://www.acetronics.com.au On-line PCB quotes, free software, DIY PCB supplies plus many other items & services. 02 9743 9235. HOMEBUILT DYNAMO, engineering dreams into reality. “An absolutely marvellous book for the true ex­ perimentalist!” Elektor Electronics. (www.onekw.co.nz) FOR IMMEDIATE SALE due to health reasons. Large quantity of electronics consisting of: integrated circuits, assorted connec­ tors, IEC mains leads, 75# coaxial cable, 50# data cable, tele­ phones and accessories, small moulded instrument boxes, mini FM radios, power supplies, Lambda PSUs, mini 8# speakers, blower fans, SMD capacitors & resistors, large quantity of Ethernet & Lan equipment, Token ring cards, pocket Lan adaptors, mini 12V cooling fans, hubs, small quantity of tools, computer paper & lots, lots more. Too numerous to mention. A good start for anyone contemplating opening a LCR METER Inductance 0.1µH ~ 200H Capacitance 0.1pF ~ µF Resistance 1mΩ ~ 20MΩ Dissipation Factor Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. Computronics Corporation Ltd 6 Sarich Way, Technology Park, Bentley, WA, 6102 Ph. 08 9470 1177 Fax 08 9470 2844 Specifications at www.computronics.com.au Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a necessity. Phone 02 9743 5222 for current vacancies. KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. SPECIAL STEAM BOAT KITS $14 VIDEO CAMERAS - SURVEILLANCE - CCTV - ANCILLARY EQUIPMENT. SPECIALS: Ltd Qtys: DOME HOUSINGS $10! 50 LED DIY Infrared Illu­ minators $19! 380 x 0.2 SILICON Modules $69! 450 TVL DIGITAL COLOUR PCB $289! GREENCELL Battery Regenerator 4 x AA or AAA suit Alkaline, Heavy/Super Duty Zinc Chloride & Nicads with Mains Plug Pack $15! PCB MODULES: AWFUL-CMOS only $49! PREMIUM 400 x 0.05 SONY CHIPSET & MICRO-LENS CCD from $91. CAMERAS: 36 X 36 from $88. Dome from $91. DIGITAL COLOUR MODULES: 32 x 32 from $185. 330 x 2 lux from $220. DIGITAL CAMERAS: 380 x 1 from $298. 450 x 2 from $370. ACCESSORIES: 30 + Lenses, Infrared Illuminators, IR LEDs, Polarising, Colour, Infrared Cut & Pass Filters for Image Enhancement, Exposure, Focus & Glare Control. ANCILLARY EQUIP­MENT: Quads 4 pix 1 screen from $280. Switchers 4 or 8 Ch from $126. MULTIPLEXERS FULL-SCREEN FULL-RESOLUTION VCR Recording/Playback from $826. ALSO: Monitors, Outdoor Housings, Brackets, Dummy Cams, CCTV-TV/ VCR I/F Modules, Motorised Pan Units etc. Modulator/Mixer/Amplifier TV/VCR I/F Modules from $14. PACKAGED SETS! QUAD + 4 CAMERAS + Power Supplies from $689. 400 + Page CCTV Technical Reference Manual $95 or FREE! UP TO 2 Year WARRANTY available for most items! DISCOUNTS available based on ORDER VALUE, BUYING HISTORY, for CASH/CHEQUE & NEW ZEALAND BUY­ERS! BEFORE you BUY Ask for our Illustrated Catalogue/Price List with Application Notes. Allthings Sales & Services 08 9349 9413 Fax 08 9344 5905. Silicon Chip Binders   Heavy board covers with 2-tone green vinyl covering   Each binder holds up to 14 issues REAL VALUE AT $12.95 PLUS P &P  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $12.95 plus $5 p&p each (Aust. only) Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. Email: tpeters<at>pip.elm.mq.edu.au August 1998  95 14 Model Railway Projects Shop soiled but HA LF PRICE! Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) Advertising Index Altronics................................. 34-36 Australian Communications Authority......................................31 Bainbridge Technologies..............66 Computronics..............................95 Dick Smith Electronics..................... ................................ IFC,OBC,12-15 EMC Technologies.......................17 Harbuch Electronics....................93 Instant PCBs................................95 Jaycar .............................. 45-52,95 Kalex............................................31 Kits-R-Us.....................................95 This book will not be reprinted Microgram Computers...................3 Oatley Electronics........................21 Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). Enclosed is my cheque/money order for $­A__________ or please debit my Printed Electronics.......................95  Bankcard     Visa Card    MasterCard Quest Electronics........................93 Card No. Rocom Components....................71 Signature­­­­­­­­­­­­___________________________  Card expiry date______/______ Name ______________________________________________________ PLEASE PRINT Street ______________________________________________________ Suburb/town_________________________________ Postcode_________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). Procon Technology......................95 Scan Audio..................................91 Silicon Chip Back Issues....... 38-39 Silicon Chip Bookshop.................37 Silicon Chip Binders/Wallcht........18 Silicon Chip Subscriptions..... 88-89 Solis.............................................95 Specialised Conductives.............19 Truscott’s Electronic World...........91 new business. Willing to sell as one lot. Please phone for appointment to view and ask for Mike. Telephone (02) 9371 8975. Fax (02) 9388 2766. Mobile 015 406712. ELECTRONIC ENGINEERING SERVICES: digital & analog, embedded & Windows/PC based designs, complete solutions or design advice/assistance. Phone 03 9807 9886. Email caddy<at>netspace.net.au PCBS MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics (02) 9554 9760 96  Silicon Chip sesame<at>internetezy.com.au http:// www.internetezy.com.au/~sesame TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test all sorts of equipment without the cost of extra telephone lines. Melbourne 9806 0110. KIT ASSEMBLY KITS ASSEMBLED. Phone Greg for quote on 02 9829 1993. KITS ASSEMBLED at reasonable prices. Phone Neville (07) 3857 2752. Valve Electronics.........................93 Zoom EFI Special......................IBC _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: •  RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. •  Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730.