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Leo Simpson and Greg Swain present ... $3.50 DECEMBER 1987 Hi-Fi review: Tandy's bargain priced hi-fi loudspeakers Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons .) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn FEATURES 6 UHF Shenanigans with a VCR by Leo Simpson How to use your VCR to tune UHF TV stations 17 Silicon Chip Hifi Review by Leo Simpson Realistic Nova-15 two-way loudspeakers 40 Amateurs Link Coast to Coast by Ross Tester With a little help from Aussat 50 AT-Compatible Kit Computer by Greg Swain Build it yourself and save money 68 The Evolution of Electric Railways by Bryan Maher Pt.2 - Steam locomotives come of age 90 Digital Fundamentals, Pt.2 by Louis Frenzel Teach yourself digitial electronics PROJECTS TO BUILD 10 1 00W Amplifier Module to Build by Leo Simpson Rugged design has full output protection 28 24V to 12V DC Converter for Trucks by John Clarke Runs 12V CB radios from 24V 33 Passive lnfrared Movement Detector by Branco Justic Add it for your home alarm system 46 Build the Speedi-Watt by Leo Simpson Universal speed control and lamp dimmer 76 1 GHz Digital Frequency Meter, Pt.2 by Steve Payor Building the printed circuit boards SPECIAL COLUMNS 62 Serviceman's Log by the original TV serviceman All this in a brand new set 73 Amateur Radio by Garry Cratt Tuning in to the VHF bands 87 The Way I See It by Neville Williams Is the electronic servicing industry dragging its feet? DEPARTMENTS 2 Publisher's Letter 5 News & Views 18 Circuit Notebook 84 Product Showcase 96 Market Centre Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c) . No part of the contents of this publication may be reproduced without prior written consent of the publisher . Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Waterloo, NSW 2017. Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates are currently $42 per year (12 issues). Outside Australia the cost is $62 per year surface mail or $1 20 per year air mail. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such ·equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139 , Collaroy Beach, NSW 2097 . Phone (02) 982 3935 . ISSN 1 030-2662 and maximum Australian price only. * Recommended PUBUSHER'S l,EJ-J'ER Welcome to the second issue of Silicon Chip Welcome to the second issue of SILICON CHIP, Australia's newest and most entertaining electronics magazine. For those of you who have already contacted us with your reactions to the first issue, thank you very much for your wishes of support. It was nice to get moral support as we finished off our second issue. As I write this it is the 27th October, so our first issue has been on sale for less than one week. It is therefore too early to judge just how well it will be accepted in the marketplace. If the early reactions are any guide, we are mightily encouraged. That is one of the gratifying sides of publishing I have already found; the enthusiasm of readers who have contacted us. People have been very complimentary about the first issue. Some have even expressed doubt about whether we can consistently maintain such a high standard. That might sound like a back-handed compliment but it encourages us even more because we know we can do better. With your support we will certainly do better. It is a great learning exercise for us as we strive to attain a high standard, both technically and on the production side. As time goes on we are learning how to streamline the production process to minimise errors which otherwise have to be corrected during the proofreading stages. One of the drawbacks of computerised type-setting is that all the mistakes are ours alone. In times gone past publishers were inclined to blame errors on the printers but this was always a cop-out. There is no substitute for careful proofreading. Further down the track we may present an article on how SILICON CHIP is produced but that will only happen when we are well and truly familiar with all aspects of the process. We are not using a desktop publishing system by the way. Present desktop systems have too many limitations for a publication like ours. Incidentally, SILICON CHIP has had a very rapid startup. We began serious preparations for the first issue on August 10th and it was cleared to the printers early in October. Before August loth, SILICON CHIP was just a business name, a gleam in our collective eyes. We had to set up everything, buy computers and office furniture, and do all the organising that goes with a fledgling publishing operation. Now, as we approach the final deadlines for this December issue, we have generated considerable momentum. Projects have been designed and constructed and articles have been written for up to two months ahead. Indeed, some articles are written for as far ahead as June 1988. This is all part of the process of striving to produce a magazine of high standard. Naturally, it has involved a large amount of planning and long hours at the workbench, drawing board and keyboards, designing, writing, subediting, producing page layouts, proof-reading and so on. We do appreciate your comments on the magazine and any suggestions where improvements can be made. You can also help us in another way too, apart from your direct support in purchasing the magazine each month or taking out a subscription. Since we do not have a large promotions budget we are relying on word of mouth - your recommendation. Please tell your friends about SILICON CHIP. 2 SILICON CHIP THE ELECTRONICS MAGAZINE FOR THE ENTHUSIAST WE INvITE You To BECOME A SUPPORTER We believe that electronics is the most useful hobby that any person can have, particularly for a young person in school. Anyone with a good grounding in electronics is better prepared to meet the challenge of today's and tomorrow's technology. Because we strongly believe that many more people should come to know about and enjoy electronics, we decided to form a new magazine devoted to electronics enthusiasts. We have called it Silicon Chip, a name which encapsulates the driving force behind all of today's electronics technology. Silicon Chip is starting off as an independent magazine, founded by Leo Simpson and Greg Swain. We have a very small team of devoted staff including our full-time electronics engineer, John Clarke and our very experienced draughtsman, Bob Flynn. consuming approach if we were not completeWe have started as a completely indepenly independent. dent magazine, free from the influence of any existing publishing company, because we You can help us establish a high standard wanted to establish the highest possible stanfor our publication by becoming a supporter. dards for accuracy and attention to detail. We The more subscribers we get, the more also wanted complete editorial freedom. Every resources we can devote to improving the article you see in this magazine has been •quality of our magazine and to the promotion · carefully selected and prepared by us to of the understanding of electronics. establish this high standard right from the The only way that we can survive and grow is with your support. Please give us your vote outset. Similarly, our circuit and wiring diagrams by becoming a subscriber. Not only will you be have been very carefully laid out by our ensuring the survival of a completely draughtsman Bob Flynn to make them as independent publication, you will be showing logical and as easy to understand as possible. your support for a strong and healthy We could not take this careful and timeAustralian electronics industry in the future. Regular Features i I Junk mail Inside each issue of Silicon Chip you will find carefully prepared features such as: Amateur Radio, by The Evolution Garry Cratt, VK2YBX of Electric Railways The Way I See It, Hifi Review by Neville Williams Circuit Notebook Constructional Projects Digital Electronics Course For The Enthusiast The Serviceman's Log * * ** * * * * Most magazines sell their subscriber lists to mail order companies, to earn extra income. We will not do this. We will lose some money by adopting this policy but we believe that your privacy is paramount. BECOME A SUPPORTER BY FILLING OUT THE POSTAGE FREE SUBSCRIPTION COUPON OVERLEAF DECEMBER1987 3 WE NEED YOUR SUPPORT Please support our new magazine by becoming a subscriber. You can also give a year's subscription to Silicon Chip as a Christmas gift. Just fill out the postage-free coupon below, place in an envelope, and mail to the adress shown at the bottom of the page. ---------------------------7 FREEPOST SUBSCRIPTION COUPON Yes please, I would like: □ one subscription for myself □ for a gift(s) □ one for myself plus gift(s) MY NAME IS ...................................................................... ............ ..... ........ .. Mr/Mrs/Ms/other ADDRESS ......................................................... .................................. ........ .... SUBURB/TOWN ············· ······························· ················ ···posTCODE ..... .. .... GIFT 1 to: NAME ........................................................ ...... .............................................. . Mr/Mrs/Ms/other ADDRESS ......... ..................................... ................................ ........................ . SUBURB/TOWN ................ ... ............................. ....... ........POSTCODE .. ...... .. . GIFT 2 to: NAME ... ... .... ........... ..... ... ........ ........ ........ ....................... ............... ..... ............. Mr/Mrs/Ms/other ADDRESS .... ...... ................ ........... ....... ... ........... ...... ... .................. ..... ..... ....... . SUBURB/TOWN ................... ..... .......................................POSTCODE ..... ..... . Subscription cost: 1 year (12 issues) Within Australia □ $42 Overseas surface mail □ $62 Overseas air mail □ $120 2 years (24 issues) □ $84 □ 124 □ 240 Enclosed is my cheque or money order for $ ......... .or please debit my □ Bankcard □ Visa Card No ............. ....... ... ............. .... .......... ... ... .................... .. ............... ..... ........ . Signature ............. ........... .......... ..................... Card expiry date .... ../ .. ... ./ ... .. . Place your coupon in an envelope (no stamp required) and mail to: Freepost 25, Silicon Chip, PO Box 139, Collaroy Beach 2097. 4 SILICON CHIP PLEASE NOTE: Subscriptions will commence with the January 1988 issue for coupons received by Monday 21st December and with the February 1988 issue for coupons received between 22nd December and 18th i:/ I I I NEWS &VIEWS Whither ISDN ISDN is one of those confusing acronyms which give no clues as to their meaning. ISDN bears no relationship to ISD but stands for Telecom's Integrated Digital Services Network which, as far as most people are concerned, is still meaningless. What ISDN will mean is that all of Telecom's present services, whether voice, data, facsimile or whatever, will be transmitted as digital signals over the network. This will eventually simplify a lot of Telecom's operations but will probably not mean much to normal domestic users. It will, however, make a lot of difference to business because it will be possible to have up to 30 voice channels plus data channels which normally would require many separate phone lines. No doubt Telecom will charge accordingly. For the moment though, Telecom has had to delay its plans to put the system into operation because of supply difficulties. Is this what you call digital delay? Is Japanese equipment cheaper than it should be? Are you worried about the rising cost of electronic equipment from the Land of Rising Sun? Even though the exchange rate has apparently stabilised at around 90 yen to the Australian dollar, local distributors of some Japanese equipment are apparently still catching up to what their real prices should be. As an indication of this, the respected Japanese magazine, Journal of the Electronics Industry, generally lists the retail prices of new consumer electronics items in yen. If these prices were. directly converted to Australian dollars we would be paying a lot more for many Japanese electronics products than we currently are sometimes double. So if you are dilly-dallying about buying some Japanese gear get in and do it now. It won't get any cheaper. Mariner's beacon could be much more inspiring How many people in their youth have dreamed of having the romantic job of a lighthouse keeper; the splendid isolation, the peace and quiet and all that. That dream is no longer possible with the trend to convert existing lighthouses to unmanned operation while any new installations will inevitably be automated. If this example on the far south coast of NSW is all that future mariners can look forward to, we are not impressed. It virtually consists of nothing more than four precast concrete cylinders planked on top of each other with a high intensity Xenon lamp sitting incongruously on the pinnacle. Completing the impression of lack of design flair is the bank of solar cells jutting out on the sunny side. Doesn't the Department of Transport and Communications have any competent architects? Surely it would be easy enough to come up with a simple but striking concrete spire with its top truncated at an angle to mount the solar cells. Why not have a design competition? The tourists examining this blot on the landscape are Kerri, Jessica, Geraldine and Felicity Simpson. The photographer was Leo Simpson. DECEMBER1987 5 t . IUHlllfUUf .l UIU.I · llftUUfU .t HUH 1.l f l l UHF shenanigans with a VCR Many Australians want to watch UHF broadcasts from SBS and other services but their TV receiver does not have a UHF tuner. If they have a VCR this problem is readily solved. Are you one of the many people who want to have a look at SBS or other UHF TV broadcasts? Foiled because your TV does not have an inbuilt UHF tuner? Well look again because if you have a videocassette recorder you can tune to UHF and watch the broadcasts on your old TV. This fact is seldom alluded to in the instruction manual that comes with every VCR but it is a handy facility particularly if your VCR has a remote control and your TV doesn't. Consider a very common situation in Australian homes. The family TV set is a Rank model from the 6 SILICON CHIP early days of colour but it does not have a UHF tuner. In the last couple of years though, the family has purchased a VCR and uses it mainly for " time-shifting" programs or watching rented tapes. Surprisingly, the family has not twigged to the fact that their VCR can be used as the tuner for their TV and they can then use their VCR remote control to select the stations they watch. Setting up the VCR The way to set it up is as follows. Connect the antenna lead-in directly to the VCR and connect the VCR RF output lead to the antenna input of the TV. With a tape playing in By LEO SIMPSON the VCR, or using the VCR's own test pattern, tune the TV set to receive the VCR program. With older VCRs this generally means tuning the TV set to channel 3 or 4, according to a switch setting on the rear of the VCR. In more recent VCRs, the RF output is usually switchable between channel O or 1 and so the TV set should be tuned to one of these latter stations. The set-up just described is exactly as set out in the VCR instruction manual. But suppose you want to use the VCR to select the stations you watch on the TV. To do this the VCR must be in the "Standby" or "Operate" mode and the VCR/TV switch must be set to the VCR mode. This allows you to select the stations you watch with the VCR remote control while the TV set can be left permanently on the VCR setting (ie, Channel 0, 1, 3 or 4, depending on your set-up). In fact, most VCRs are supplied ready tuned to local VHF stations in the area where they are sold so it is usually not necessary to go through a tuning procedure. How does the VCR manage to deliver all station programs via its RF output? Essentially, its own inbuilt tuner picks up the stations you want and converts the program to composite video and audio signals. These are then re-modulated onto its RF output (at Ch 0 or whatever) and then delivered to your TV set's antenna socket where it goes through the whole process of detection again. Recording and watching The only time your VCR cannot be used to act as a remotecontrolled TV tuner is when you want to watch a program on one channel while recording a program on another channel. In this situation the VCR must be in the record mode and the VCR/TV switch must be set to the TV mode. This allows all the signals from the TV antenna to be fed directly to the tuner of the TV set. Now suppose you want to watch SBS broadcasts on channel 28 (or The TV/VCR switch i~ hard to find on many machines. On this older Philips machine it is one of many behind a flip-down door. On the National machine on the opposite page, the TV/VCR switch is near the REWind button. 45 as it is in many areas). Simply set the VCR in "Operate" mode, set the VCR/TV switch to VCR and refer to your owner's manual for the instruction on how to tune to UHF stations. Remember though, in most areas you will require a separate UHF antenna or a combined VHF/UHF antenna if you are to have satisfactory UHF reception. So if you wanted to watch UHF programs but have been loath to replace your old VHF only set, this is the solution. And if you don't yet have a VCR, this could be the excuse you needed to buy one. Next month, SILICON CHIP will publish construction details of a high gain UHF antenna which will cover bands 4 and 5. A stacked bowtie design, it will be less prone to aircraft "jitter" than conventional Yagi designs. ~ Horizontal jitter problem with VCR I have recently purchased a VCR and am generally pleased with it but it does present a problem when playing some rented tapes. With these tapes the TV picture has severe horizontal jitter at the top and on one severe case the picture was completely black at the top half. A number of people have suggested that this is a fault in the VCR and it should be corrected under warranty. What do you think? • This fault is commonly referred to as "flag-waving" and can be caused because the TV set's horizontal sweep circuit timeconstants are too long to suit the VCR sync pulse waveform. The solution is a fairly routine modification that would be familiar to most TV servicemen. In your case though, you imply that the picture is quite satisfactory for most of the time and it only plays up with some tapes. While that may suggest that the fault is in your VCR it is highly likely that it is not. Instead, the VCR RF output is probably overloading the tuner of your TV set. In fact , we're betting that your set is a late model Philips with a "Fringe" button. This button can be pressed to give better reception on weak signals. If you have a look at the control behind the door on the front of the set, the Fringe light should not be illuminated when the VCR station is selected. If it is automatically selected, you should reprogram your set so that the light is off in VCR mode. This instruction is buried in the instruction manual and has caused more than one unnecessary service call. As a general rule, if TV sets have a local/distant antenna setting they should be set up for "local" reception when used with a VCR. DECEMBER 1987 7 NeH'fl~anda HapPfl N'tW Yev,,, We've got your wire and cable needs all rolled upl From the finest copper wire to building mains cable (and everythln9 In between), you'll find 1t at your nearest DSE store. Buy by the metre and save, buy by the roll and really save! 3000hm Ribbon Builder's 12 Cora Indoor/outdoor black) TV ribbon or strong signal areas and/ or 300 ohm only antennas. (No balun required) Standard twin and earth, 1/113. For new building or replacement work. Buy In bulk and save morel Ideal for parallel and serial data cables, 12 d lfferent coloured multlstrand conductors plus foll and drain wire. Grey outer Insulation. l .... CatW-2070 light Cabla Data Cabla CatW-2080 3ocper 95c Builder's Power Cabla RG59U Solld 750hm Air 2Cora Mlcrollhona Space Dlalactrlc TV Coax Cablalro Quality CatW-2081 Extra heavy duty outer Insulation, cotton reinforcement for extra strength and dual multlstrand Insulated cores, wtth close-woven braid. The pro TV coax. 8.9dB/100m <at> 100MHz, only 28.SdB at 1GHzl 75 ohms, as used Air space dielectric. by Installers everywhere. 8.5dB/ When low signal loss Is Important, 100m<at> 100MHz, you want the bestl solid centre conductor with foll CatW-2082 and braid. Blac~ Insulation. aoc Cal W-2041 •2H &oc .... Mains Circuit Breakers make sense! CatW-2035 *179 per Fuses always blow at night. Where's the fuse wire? (Murphy's corollary No 328). Replace all the fuse blocks In your box with Martec Circuit Breakers. They're Just as effective as fuses (perhaps even more so) but restoring power Is as simple as pushing a buttonl Available In metric and Imperial ~~~y;;;x~=- standard (Federal type) Imperial Metric 8A Cat P-5908 16A Cat P-5920 20A Cat P-5925 10A Cat P-5910 15A Cat P-5915 30A Cat P-5929 ALL ONE PRICE: •12111 • Hard of Hearing? High Power Hand Held 2m has never been so good I Hand held powerhouse Includes push button control, 10 memories, scanning, etc. · And up to SW 'with appropriate NiCad. (Includes NICad tor 3.5W output). Cat 0 -3503 s599 Just Listening? Get your ears around a Bearcat 175XL. All the action on VHF and UHF to listen In on. • earphones •Aircraft • Business • Etc Etc Etc! • Amateurs$ Cat 0-2812 499 •C•a•t•F••5•11•9•$_1_9_•-----------· DSE's Magnificent Meter Muster! For the beginner: Audible tester too! range multimeter ludes an audible ntlnulty tester d goes all the yto 10A DCI A at all-rounder. Small enough to go anywhere, ranges Just right for the hobbyist. auto electrical, etc. Keep a couple handy - just in casei Cat a-1010 Logically Speaking ... --====, 90Thisfor.Is the one to More than a atO-1022. 3495 -:·__ J., multimeter - it also checks logic levels and displays hi, lo or pulse states. 20k/V sensitivity multimeter Is no slouch, either. ;4•0-1402695 ®- . • ~~ Pouch to suit Protects your 11111 Q-1010 meter from damage. -4000 Counf'model is twi~e as accurate Cat Q..1U11 Digital Workbench! 3.5 digit meter, capacitance checker. transistor checker just about everything the ·hobbylst or service bench could want.-1OA AC IH.>Q ranges, also has buzzer con!rnuity. Yes - It's got a 200kHz DFM built In too. Very handy - also checks transistors, diodes, capacitors. And It's a multimeter! Cat Q-1505 S169 Cat Q-1500 5 129 What did you say? Flt a telephone extension belll Just plug It In to the socket - Includes 5m cable so you can use It In another room, etc. Bewdyl Most m'meters go to 2000 counts. This one Is double. That's double the resolution. And it also features an analogue display to give you "dynamic" readings. It's great, mate. cat Q-1666 '249 Want Cannon connectors? No, not those cheap cardboard imitation "Cannon-types" every man and his dog flogs. Genuine, 100% Cannon plugs and socket. For when quality really counts. ~No R-3-11 Dacrlptlon In Line Audio Socket Panel mtg. AXR-3-32 Audio Plug In Line Audio Plug AXR-3-12 Paneimtg. AXR-3-31 Audio Socket AXR-PON-12W HI level audio line plug white AXR-PDN-118 H/lev aud line socket blue AXR-PDN-31W H/lev aud chas sock white AXR-PDN-14B H/lev aud chas plug blue (fits all plugs Orange Boot & sockets) (fits all plugs Yellow Boot & sockets) (fits all plugs Green Boot & sockets) (fits all plugs Blue Boot & sockets) AXR-LNE-12 240Vmalns line plug AXR-LNE-11 240V mains line socket 240V mains AXR- LNE-31 panel socket 240V mains AXR-LNE-32 panel plug Your local reseller is: • NIW • Ballin■: A. Cummings & Co. 86 2284 • Bowri l: F.R.H . Electrical 61 1861 • Broken Hill: Hobbies & Electronics 88 4098 • CharlNtown: Newtronlcs 43 9600 • Coffs Harbour. Coffs Harbour Electronics 52 5684 • Denillquin: Deni Electronlcs 81 3672 • fon:ter: Forster Photo Sound 54 5006 • lnverell: Lyn WIiiing Electronics 22 1821 • Leeton: Leeton Record Centre 53 2081 5 9 9 : ~::~~:le:A=r~~~~nl~ g~ .e WeUlngton's Electrical Discounts 51 4888 • Taree: Brad's Electronics 52 6603 • Tumut:Tumut Electronics47 1831 • Ultadula: Pauls Electronics 55 3989 • Wagga: Phillips Electronlcs 21 6558 • Wellington: Wellington Electrical Service 45 2325 • Windaor: M & E 1 I 1 e<r~~~~1~!· i::.~~::!~!~:r~:r~~s1c~ ~~r~n~~s. McWllllams Electronics 23 6410 • Morwell: Morwell Electronics 34 61 33 • Aoaebud: Pentronics 86 7688 • Shepparton: GV Electronics Centre 21 8866 • Sunbury: Calco Electrical 744 1564 • Warrnambool: Marrtronics 62 9870 • Werribee: Gables Photographic & Video 741 7089 •OLD• Bundaberg: Bob Elkin Electronics 72 1785 • Calms: Electronic World 51 8555 • Caloundra: Hume's Electro-Mart 91 4270 • Dya.-t: Dysart Videotronlxs 58 2107 ._ Gladstone: Supertronics 72 4321 • Mackay: Steven s Electronics 51 1723 • Mooloolaba: Mal's Electronics 44 6588 • Maryborough: Keller Electronics 21 4559 • Mt In: Outback Electrontcs 43 3331 • N1mbour: Nambour Electronics 41 1604 • Noou Heada: Sunshine Phone Systems 47 4444 • Town■ville: 0 Jrit~~T ~::c~;o~~; g~~t~o~7~~a~i;~a;6e:;::~ • Launc•ton: Wills Electronics 31 5688 •NT• Allee Springa: Farmer Electronlcs 52 2967 ~~w~=~ri: ~!1i~,.E~~~~~~s°:rf4~6: ~~~~:~~~~ ~~~~;11~:ice~lf~:;;n:.= ;~~ ~0~~ ~c~~ Jl ::;;:~::ft~~~:~~~~~! ~~~J~~s~i:~~iI~ ~t3~~:~:.~~~~:~;.: ~fJ.!.21: i~.°o:t::'J:·:r :,~~~~;o;~~~~1:I~! ~:~ DSI! Clt No Price P-1820 $5.25 P-1822 P-1824 $4.00 $4.95 P-1628 $5.75 P-1832 $10.50 P-1634 $9.95 P-1838 $7.50 P-1638 $8.50 P-1615 ~ P-1818 ~ P-1617 ~ P-1618 ~ P-1627 $9.95 P-1831 $9.50 P-1830 $7.95 P-1629 $7.50 O~~ESS DICK SMITH ELECTRONICS EXPRESS ORDER SERVICE ORDER BY PHONE TOLL FREE DSXpnlu ON (008)22 6610 For 24 hour dllpatch SYDNEY (02) AREA - 2105 ~~~~~~~~~~~~ ♦ Ifs ~~ Clvlatmu Morning. There - ♦ the klda with all their toys and 11-. And lhenl are the long • - · ' Nothing works - you forgot the batterleal ♦ Quick! Grab some guarantNd f-r-e...tl batteries from your ne-■t DSE store NOW. Before you forget Chrlltm•. PSST. Want to $ave money? Buy rechargeable NICads - even ♦ with a charger they're great value - and you'll uve heaps In the ♦ lorig runl Alk for the correct NICads at your DSE store. i fMmaltatPSE FRG-9600 Scanning Receiver ♦ ~~~~~~~~~~~~ The Complete Amateur Station! The Incredible Yaesu FT767GX all mode, all band Transcelverl With every possible feature to drag the signal in or get yours out. HF, VHF, UHF - every amateur band from 160 metres to 70 centlmetresl! With auto antenna tuner, built-in mains power supply and much morel It's the bestl! ~;~~:.:ib:~~~v~~r~~c~.;~:f~o~Oe'.oF:5:~.zCVB~~i~~ the loll With keypad or dial selection, selectable scanning functions, memory scanning and much, much morel Cat o:2a25 (• SSB to 480MHz) S1199 4995 ~!~~!b~y~~~!!~e!~~ Switched on Savings! Cat 0-2935 production line, etc! The Adcola RS-30 12 watt mains powered soldering iron. SPOT. 8mm x 13mm (240VAC 2A) DPDT. 13mm x 13mm (240VAC 2A) Ultra Mini DPDT (240V AC 1.5A) Heavy duty DPDT (125V AC 10A) Right angle PCB mount ·Duotemp- A 1m1e boost Professional quality - hobbyls_t prlcel Adcola's Duotemp solder iron with 21 watts of power PLUS a push button boost for last heating or heavy soldering. CatT-1830 95 1 49 _ STANDUD TONllS Centre OFF DPDT (125V AC 10A) Illuminated SPST {12V DC 16A) Piano ·Key DPDT Waterproof SPOT {12V DC 10A) PCB Mount Push button (120V1A) ~~lo!~!a~e~e!':~ty ,lron at such a low pricel Comes with 2 metres of cable and car cigarette lighter adaptor. Cat T-1910 ONLY 179IIO / Royal Professlonal Soldering Station t=~~;:;;:nce you expect. Transistor Audio Transformers Model M-0222 . 117• Miniature size for transistor projects etc. requiring coupling. With 3k ohm primary and secondary. Iron core. Measures 17(1) x 15.5(w) x 15(hlmm. Cat M-0216 • A 12 piece computer tool kit for those repairs, alterations, etc.Woth IC inserter/ remov~r pin straightener, _screwdrivers, reversible torque screwdriver, pilers and more. All in handy zoppered easel Cat T- 4939 WAS $1 40 NOW S1 • Model M-02156 S4S95 Similar to M-0222 but with 1k ·ohm primary and 8 ohm secondary. For 350mW 0/P . Ferrite core. 15 x 14 x 11 .5mm. Lug Cr·Imp·Ing liool Makes wire connectloris a breezel Eliminates soldering and savestimel Reliable crimping tool also.cuts and strips wire. Comes wlth ,assorted-lugs ~~a~1:~use! < S-1174 Reduced to $1.50 S-1245 Reduced to $2.75 S-1168 S-1180 $3.75 $2.50 Cat No. Price S-1217 $2.50 S-1214 S-1393 $3.95 $3.50 S-1195 Reduced $6.95 S-1253 $2.95 Transformers! s189 Computer Tool Kit' • Price Reduced to $1.25 Bargain Super Slim Mini! · cat No. S-1173 Savel Bank of 8 Interlocking switches. Great for audio work! Special price nowl Cat 5-1005 '295 Ideal for quick, on the spot repairs. 6 watt capacity on a super slim lightweight! 12 volt operation It comes with one metre of cable• Cat T.1920 $ Special Purchase The best work deserves the basil Variable temperature soldering ~ ~ s t a t i o n \with the quality, rellabl!lty and ~ 3 TralllCllven In one!! MINIATURE TINl8LES '29811 CatT-1820 Heavy Duty Power! \lil vu \lil 'V I ♦ Cat M-0216 WAS $1.40 Designed to cover PA - BGM applications. Suits all speaker impedances. Multltapped for use with 100V or 70V lines. 2, 4, 8, 16 ohm secondary. 2.5k, 5k ohm primary. Cat M-1100 ll!25 V" hardened jaws and insulated handles. About ½ the price you'd expect!' s3911 catT-3S30 Save $1 O! Z}!~. ~!!ry 50Hz Secondary - 6.3, 7.5, 8.5, 9.5, 12 & 15V Secondarycurrent-1 amp Cat M-2155 Fast drying photoreslst for one to one reproduction of circuits, diagrams, etc on metals. 200g can Ideal for PCB work. Cat N-1000 Air Duster 400g of high pressure compressed Inert gas for cleaning circuit boards.equipment, etc. Ideal for those fragile or hard to get at placesl Cat N-t050 s1595 SV DC - 1 ~· ~ _ 6 chrome plated screwdrivers with 1free running heads! Quall'>'. tools\in handy - = - = , ,) 1 E sealanl'speclally designed for high voltage applications. Neutral curing In 85g tube. Sticks and Insulates just about anything! cat N-1226 s122s <at>) 200fflA 111 • , 1210 One of the most popular supplies. Ideal for many battery powered devices. Select any of three voltages! Cat M-9525 WAS $17,50 s·Ix Vohage Selections NOW 11595 Incredibly versatllel Switch selectable 3-4.5-6-7.5-9 or 12 WAS 3s·1a·. e;astlc valuel Cat M-9520NLY 115" ~~~~:~~l!t ~!~!~Pi~~ around the home or workshop. 'Plugs Into AC power socket, DC connections via screw terminals on front of unit. cat M-9530 SAVE $10 WAS $32.95 · - ·= ··- ,, plastic case. Both Phohps,and flat head . -""""=====,:;' Cat T-4360 '595 Silastic Sealanv Adhesive RTV 38 sllastlc AC SUppIYt6V 900ml WAS $69 95 Precision Screwdriver Set ,r· - .,...,. -~ ~ s11s Cat N-1080 Ideal for anything that requ ires 9V transistor type battery. Just plugs into mains power socket! Cat M-9514 workbench isn't ,the same without one! ow 15S95 Soldering-iron with this 30g Ronson Multlfill. Even works with refillable cigarette lighters! s1595 The amazing Ariec Supertool! It drills, grinds, polishes, engraves, mills... just about anything! 10,000 RPM with a · fantastic range of :attachments. A CatT-4?S4 Butane Refill Refill your Portasol 114• Secondary Voltage - 40V <at> 10mA, 19V <at> 200mA, 11.2V <at>450mA. CatM-1200 1795 sg• Positive Photoresist Spray 3-6-9V DC<at> 200ml 00ohm/SOOohm. For modems and other telephone line applications. Complies with Telecom regulations. Isolates line from device. ~~!}J~~ s599 A healthy 16V at 900mA. Perfect for 12V DC supplies. Plugs straight into mains socket! Cat M-9567 Isolation Tr ansformer 6 ON•v 11 NOW 11295 1,1 VALUE ssso -M·u·11·1·1a·p-2·4-o·v-M·o-de-l-s-------· ?!~~a~~!r~!:s~!~l~~-r Cat 0-2945 Power Supplies! Better than batter·1es! Audio Line Transformer . Cat M- When you're working hard - you don't want to lose your cooll The FP757HD power supply Is just what the avid dx'er wants. Plugs straight Into the 757 but It's also suitable for other 12V transceivers. Rated at a superb 13.8V, 20A continuous! PTY LTD NOW 122• Hugged design has full output protection This high-power amplifier module gives very low distortion and noise. It also features foolproof protection against short-circuits and loudspeaker damage. By LEO SIMPSON & BOB FLYNN Build this 100W amplifier module Over the years there have been many power amplifier designs and most have have had one or more drawbacks in terms of expensive components, unreliability and a tendency to damage expensive speakers when they give up the ghost. We've had a close look at these past designs and have come up with the definitive solution for those who need a rugged reliable design. It gives high quality sound without breaking the bank. The four power transistors mount on a small right-angle 10 SILICON CHIP bracket which has been used in a number of the designs we have just referred to. On that basis this new module can be regarded as a high quality drop-in replacement. The right-angle bracket can be mounted on a vertical heatsink of your choice so it can be used as the basis for a high quality guitar amplifier, in public address applications or, naturally, in a high fidelity stereo amplifier. All of the transistors and other parts are readily available from just about any electronic corn- ponents supplier, with the exception of the special protection component which we'll get to in a moment. The amp module can built in two versions. The larger version, which we think most people will build as a matter of course, will deliver just over 100 watts continuous into 4-ohm loads. It uses the full complement of four output transistors. The smaller module which uses just two output transistors, will deliver 50 watts into 8-ohm loads. It can also drive 4-ohm loads but in +40V D1 1N4148 t 01+ 39V 02 1N4148 8 06 BC640 l .012 22k VR1 500r! 1k 04 c 8 t ROE245A (4P. LOAD) RDE115A (B!l LOAD) C O 1OOW AMPLIFIER MODULE ELJc BC557 8 E BC639. BC640 011-1287 0 ~ 0 8 VIEWED FROM BELOW ECB Fig.1: foolproof loudpeaker protection against component failure and over-drive is the big feature of this circuit. This is provided by the PTC thermistor in the output network of the amplifier. this case it must be used with lower supply rails if long term reliability is to be obtained. Performance of Prototype Performance A particular feature of this amplifier is its low distortion. For the 100W version, the harmonic distortion is less than 0.1 % for the entire frequency range from 20Hz to 20kHz at all power levels up to maximum. And if you can get' access to a distortion analyser, the harmonic distortion can be reduced considerably below this level by optimising the routing of the supply leads. Signal to noise ratio is better than - 100dB with respect to full power. Frequency response is flat within ± ldB from 20Hz to l00kHz. The remaining performance details are shown in the spec. panel. Protection The trouble with all high-power amplifier designs is that, if they have a transistor failure, there is a big chance that they will burn out the loudspeaker system too, despite having fuses in the power supply. Output power Frequency response (at 1 W) Input sensitivity Harmonic distortion (20Hz-20kHz) Signal to noise ratio Protection SOW version 1 OOW version 50W into 8 ohms 1 00W into 4 ohms 20Hz-1 00kHz ± 1 dB 870mV 20Hz-50kHz ± 1 dB 870mV .05% 100dB 2A fuses plus RDE115 Polyswitch 0.1% 100dB 3A fuses plus RDE245A Polyswitch Damping factor (without Polyswitches) 50 (with Polyswitches) 30 Unconditional Stability There have been documented cases in the past where such catastrophic failures have led to serious fires. What can happen is that the voice coil gets red hot because of the high fault current from the amplifier. If not detected in time, the red hot voice coil can set the 100 100 Unconditional speaker cone on fire. After that, you can have a raging fire on your hands, with enormous volumes of smoke being generated by the filling material in the cabinet. In view of this risk, many designers incorporate relay protection circuits which disconnect the DECEMBER1987 11 1000,-----r-~--"T"'""--"T"'""---,-----r----,---...,....------ 8oot---t-----+---+---+---+-----+----1---_j__ __J 10 40 70 50 80 9o VOLTAGE (VOLTS) Fig.2: this diagram shows the load lines "seen" by the driver transistors Q8 and Q9, when the output drives a 40 resistive or reactive load and the output transistors have a beta of 20. This gives a straight load line of 800 and a curved line of (56.6 + j56.6)0. Note that the curved line exceeds the dissipation ratings of BD139/140 but not the more rugged MJE340/350. loudspeaker .in the event of a large DC voltage appearing across the output. These work OK but they add up to more circuit complication and expense. Relays are not the answer when the amplifier is shorted out though. In this case most designers rely on fuse protection and hope that the output transistors will be rugged enough to withstand the heavy currents until the fuses blow. Sometimes they do, sometimes they don't. If the output transistors do blow, there is a strong chance that they will take out the driver transistors too. Nor are relays the answer if the amplifier is seriously over-driven. Turn up the volume control too far and you may drive the amplifier well into clipping. The amplifier then delivers a square wave signal to the loudspeaker which can be three or four times the maximum power it is supposed to deliver under normal conditions. This can burn out the voice coil of a tweeter or dislodge one of the turns of a voice coil on a larger speaker. Either way, this momentary event can cause expensive damage to speakers. Up to now, there has been no really effective protection against amplifier overdrive, whether deliberate or inadvertent. The protection solution Fuses and relays are not the answer. Nor are transistor protection circuits which switch off the drive in the event of an overload condition. The latter can cause quite serious audible distortion and have now gone out of vogue with amplifier designers who know what they are a bout. ;t8it++ OV 6800 + "' 50VW _ .___ _ _ _ _.,___ _ _ -40V Fig.3: this is the suggested power supply for the amplifier. Note that the ultimate power output will depend on the transformer regulation. 12 SILICON CHIP The answer is the Polyswitch, made by the US company, Raychem Corporation. This is a positive temperature coefficient thermistor with a very low resistance value, under normal operating conditions. When the current through a Polyswitch goes high it immediately switches to a high resistance state and stays in that state until the fault condition is removed. It's like a fuse which can repair itself. The resistance of the Polyswitch is so low (typically much less than 0.10) that it has a negligible effect on amplifier performance. The distortion figures we quote above are applicable whether or not the Polyswitch is used. As far as we know, this is the first time that PTC thermistors have been incorporated into an amplifier design to give comprehensive protection. It works extremely well. It allows you to drive the amplifier to full power on program signals but the moment a short circuit is applied or the amplifier is seriously over-driven the Polyswitch goes high in resistance to give protection. If a transistor fails, and causes the amplifier to deliver a large DC voltage to the speaker, again the Polyswitch goes high to give protection. After the Polyswitch has switched to its high state, it takes some time to fully revert to its low resistance condition. This depends on how much current is passing through it. If the drive level is maintained after a fault has occurred, the Polyswitch will stay high in resistance. Polyswitches are more expensive than fuses but less expensive then relay protection circuits. We think that some readers will regard the Polyswitch protection as an optional feature. That's OK; put a wire link in instead. But for complete peace of mind, put in the Polyswitches. They are very cheap insurance. The circuit Now let's have a look at the circuit of Fig.1. This is a straightforward design which is based on applications literature produced by Hitachi some years ago. Originally it was intended for use with power INPUT +40V Fig.4: four output transistors are required for the 100W version of the module. For the 50W version, leave out Rl and R2, Q12 and Q13 and change THl and the fuses, as specified in the parts list. Mosfets but these are too expensive and dissipate too much power for this application. We have adapted the circuit for use with bipolar transistors. It has proved to be very reliable. Thirteen transistors and three diodes make up the semiconductor count. The input signal is coupled via a lµF capacitor and 2.2k0 resistor to the base of Q2 which together with Q3 makes up a differential pair. Ql is a "constant current tail" which sets the current through Q2 and Q3 and renders the amplifier insensitive to variations in its supply rails (this is known as supply rejection). Signals from the collectors of Q2 and Q3 drive another differential pair, Q4 and Q5, which have a "current mirror" as their load. The current mirror, Q6 and D3, does not give this second stage a particularly high gain but it does make it very linear (ie, relatively distortion free). The output of Q5 is then used to drive the class-AB output stage consisting of drivers QB and Q9 and power transistors QlO, Ql 1, Q12 and Q13. PARTS LIST 1 OOW VERSION 1 printed circuit board, code SC11-1287, 121 x 133mm 1 heatsink bracket (Jaycar Cat. No EE-3630) 1 large single sided heatsink (Jaycar Cat. No HH-8572 or bigger) 4 3AG fuse clips 2 3A 3AG fuses 6 PC pins 1 plastic coil former, 13mm diameter x 1 0mm long; or 1, 6.8µH air-cored choke (Jaycar Cat. No EE-4030) 1 Raychem ROE 245A Polyswitch PTC thermistor 4 T0-3 transistor mounting kits 3 T0-126 transistor mounting kits Semiconductors 2 BC557 PNP silicon transistors 1 BC557, 2N2907 PNP silicon transistor 1 BC640 PNP silicon transistor 2 BC639 NPN silicon transistors 1 B01 39 NPN silicon transistor 1 MJE340 NPN silicon transistor 1 MJE350 PNP silicon transistor 2 2N3055 NPN silicon transistors 2 MJ2955 PNP silicon transistors 3 1N914, 1 N4148 silicon diodes Capacitors 1 4 7 µF 1 6VW PC electrolytic 1 1µF metallised polyester (greencap or minature) 1 0.15µF metallised polyester (greencap or miniature) 5 0 . 1µF metallised polyester (greencap or miniature) 1 .012 metallised polyester 1 330pF ceramic or miniature metallised polyester 1 68pF 1 OOVW ceramic 1 2.2pF 1 OOV ceramic Resistors (0.25W, 5%) 1 X 4 7k!l, 2 x 22k!l, 1 X 18k0, 1 x 6.8k0 0 .5W, 2 X 4 . 7k0, 1 X 2.2k0, 1 X 1 kO, 1 X 6800, 1 X 4700, 5 X 1000, 1X6.801W, 4 x 0.220 5W wirewound, 1 X 5000 trimpot (Bourns Cermet horizontal mount, 0 .2 x 0 .4-inch) SOW VERSION Delete: 1 2N3055 NPN power transistor 1 MJ2955 PNP power transistor 2 T0-3 transistor mounting kits 1 RDE245 PTC thermistor 2 0 .220 5W wirewound resistors 2 3A 3AG fuses Add: 1 RDE115 Polyswitch PTC thermistor 2 2A 3AG fuses DECEMBER 1987 13 Q7 is a Vbe multiplier, so called because it multiplies the voltage between its base and emitter by the ratio of the resistors between its base and collector and base and emitter, respectively. It effectively maintains a fixed voltage between its collector and emitter, regardless of the drive current delivered to the output stage by Q5. The voltage is adjusted by trimpot VR1. The function of Q7 is to set the DC voltage applied between the bases of QB and Q9. By doing this it sets the "quiescent current" through the output stage (ie, the current when no signal is present). This minimises crossover distortion. The complementary output transistors are connected in parallel to give high current output capability. Each output transistor has its own 0.220 emitter resistor. These are included to ensure that the output current is shared more or less -SCREWS ! _r --O-~ ---r-1--PCB -INSULATING SLEEVES 0 HEATSINK I I SHAKE-PROOF •-----~-WASHERS ~- ~---NUTS Fig.5: mounting details of the T0-3 transistors. Trim the mica washers so that they do not overlap. equally between the output transistors and to help stabilise the quiescent current. Negative feedback is applied from the output stage back to the base of Q3 via a 22k0 resistor. The level of feedback, and therefore the voltage gain, is set by the ratio of the 22k0 resistor to 1k0. The low frequency rolloff is set by the ratio of the impedance of the 1k0 resistor to the impedance of the 47 µF capacitor. This sets the - 3dB point at about 3Hz. This is not the only determinant of low frequency response though. The 1µF input capacitor and the 22k0 base bias resistor feeding Q2 have a more important effect and set a - 3dB point at about 7Hz. The two time-constants together give an overall - 3dB point at lOHz. The 330pF capacitor in conjunction with the 2.2k0 resistor feeding Q2 form a low pass filter which rolls off frequencies above 200kHz. The 68pF capacitor between base and collector of Q5 and the 2.2pF capacitor between base and collector of Q3 rolls off the openloop gain to ensure its inherent SC11-1287 The PC artwork must not be altered otherwise the high performance of the amplifier cannot be guaranteed. 14 SILICON CHIP ratings will be considerably exceeded. There is therefore a high risk of amplifier failure when driven hard into typical 4-ohm loudspeaker loads. For this reason we have specified MJE340/350 transistors as drivers. They are probably the most rugged driver transistors available. Polyswitches Two devices are specified, depending on whether you want the 100W or 50W version. For the 100W version use the RDE245A Polyswitch. For the 50W version, use the RDEl 15 Polyswitch. Both these devices will be available from Jaycar Electronics stores. Power supply The suggested circuit is shown in Fig.3 and is a centre-tapped transformer driving a bridge rectifier and two 6800µ,F capacitors. The specified transformer has a 56V centre-tapped winding rated at 2 amps. This can be obtained from Dick Smith Electronics (Cat No M-0144) or Jaycar Electronics (Cat No MF-1095). Putting it together The 50W version of the amplifier module uses only two output transistors. Note that two wirewound resistors have been omitted and the PTC thermistor is smaller than in the 100W version. stability with feedback applied. Another contributor to the amplifier's excellent stability is the output network consisting of a 6.8µ.H air-cored choke, a 6.80 resistor and 0.15µ,F capacitor. Second breakdown protection A feature of this amplifier which is not evident from the circuit diagram is the careful selection of driver transistors to prevent second-breakdown. The 2N3055s and MJ2955 transistors used as output devices are inherently rugged (and cheap) but a number of amplifier modules published in Australian electronics magazines over the last ten years or so have specified BD139/140s as driver transistors. These are plainly not suitable for an amplifier intended to deliver 100 watts into 4-ohm loads. Assuming that the output transistors have the minimum beta (current gain) of 20 and with the amplifier driving a reactive load (ie, a typical 40 loudspeaker) of (2.83 + j2.83)0 the driver transistors will "see" a complex load impedance of (56.6 + 56.60. With this load, as depicted in Fig.2, the second breakdown Assembling the board should be done as follows. First mount all the small components leaving the power transistors and heatsink till last. Note that miniature polyester capacitors can be used instead of the larger greencaps if you wish since we have made provision for both types. The 68pF compensation capacitor associated with Q5 should have rating of at least 100 volts and so should the 0.15µ,F capacitor in the output filter network. The 6.8µ,H choke is wound with 24.5 turns of 0.8mm enamelled copper wire on a 13mm diameter plastic former. Alternatively, Jaycar Electronics supply the choke ready wound (Cat No EE-4030). Mount the four 5W wirewound resistors so that they are off the board by about 1mm or so. This aids power dissipation. Now mount the heatsink bracket. It is secured to the board by the mounting screws for the four output continued on page 96 DECEMBER1987 15 -- = = == == = = = = = == == = = = = = = = = = = = =--o == = == = = -------== --------------------------- - ---- --- -- -- - = = Finally, an LCD Multimeter which accurately shows analog- type readings! All those essential dynamics that are often lost on a DMM ... often it's not so much a reading you're after as the change in readings! But there's more: the information is displayed in "bar graph" format for instant recognition and ease of reading. And if you need to expand the scale, it's a simple one-button operation to go to a 1Ox magnification! Plus a data hold function (last reading retained), a maximum hold function (highest reading retained & marked, but readings continue), diode check & continuity, etc, etc: it's one of the best general purpose multi meters available today simply because it does everything better! ~' ~ '#'II>~ no .,,. • 105 step LCD bargraph display giving 1% resolution - on any scale ( eg 10 volts on 1000V range with mag pressed). • ··•,. • Fast 10/second sampling rate for virtually 0 , 1 instantaneous display (much faster than most • •• digitals). • Automatic positive or negative indication ,;:· • DATA Hold key freezes reading immediately '· previous to pressing. This can then be magnified (by up to 10:1) for a more accurate _ \ i and precise reading. 2.?IO -~~~~•'"~--~~~~ • 6DVC V ranges (down to 100mV with '..virtual 1 mV sensitivity), 4 AC V ranges, 5 --resistance, 3 DC plus diode check and continuity ranges. • Single input terminals mean no swapping of leads when you change to different scales. Fully shrouded test leads supplied, with full instructions. 1,0 $14 Cat Q-1777 Specifications: DCV: 100mV, 2.5V, 10V, 50V, 250V, 1000V, 5Mohm impedance ACV: 10V, 50V, 250V, 750V (minimum 5k/V, 25k/V on 10V) DC: 2.5mA, 25mA, 250mA Res: 250 ohms, 2.5k, 25k, 250k, 2.5M Cont: 250 ohms max, continuity beeper approx <100 ohms Available exclusively from Dick Smith Electronics ORDER BY PHONE: TOLL FREE DSXpress ON (008) 22 6610 For 24 hour despatch Diode: Test current approx 0.5mA, reads Vf on display Measuring Method: dual integration mode Sampling: 10 times per second Power:1.5V (AA) x 2 Battery Life: Approx 800 hours or more. Size: 145 x 86 x 34mm (w x h x d) Weight: Approx 250g (inc batteries). DICKeSMITH ELECTRONICS PTY LTD HIFIREVIEW Realistic Nova-15 two-way loudspeakers While it is fairly common to see reviews of hifi equipment with prices in the stratosphere, low priced gear is rarely reviewed. We decided to turn that convention on its head by reviewing one of the lowest priced loudspeakers available, the Realistic Nova 15. Reviewed By LEO SIMPSON Let's face it, everybody would like to buy the fanciest of loudspeakers, to spare no expense and generally indulge the slightest whim. But most of us don't need or really want the most deluxe of speakers and in many cases, a less costly system will be the ideal answer. For example, you may want a smallish pair of loudspeakers to run as extensions in the rumpus room, or to use in a four speaker surround system. Whatever the reason, a pair of economy speakers has a lot of appeal which is why we decided to take a look at the Realistic Nova 15s. The Realistic Nova 15 is an efficient two-way bass reflex system which would be an ideal match for modestly powered stereo amplifiers and receivers. The Nova 15 is a compact twoway bass reflex system which is not so small that its power rating or efficiency suffers. The woofer is a nominal 20cm in diameter with a foam rubber roll surround. The roll surround allows a more linear cone excursion than the simple corrugated paper surround on cheaper speakers. The chassis is of pressed steel construction and is fitted with a ferrite magnet. The tweeter is a cone type with an effective diameter of 43mm. It is driven via a 4. 7 µF 50VW bipolar electrolytic capacitor for frequencies above about 5kHz. (Bipolar electrolytic capacitors do not require DC polarisation for their operation). The enclosure is a bass reflex system; ie, with a tuned port. This gives increased efficiency for bass frequencies compared to sealed enclosures. The enclosure is made from 12mm thick particleboard finished in genuine timber veneer (rather than simulated veneer on vinyl). As a finishing touch, there is an aluminium trim around the removeable speaker grille which adds a little style to the enclosure. Before we listened to the Nova 15s we decided to perform a few measurements to see how it behaved electrically. The first test was to measure the impedance across the entire frequency range. On some speakers the impedance can dip to very low values for some signal frequencies and thereby present a problem to the driving amplifier. Nominal impedance rating of the Nova 15s is 8 ohms. Our measurements confirm this value. We found that at no frequency did continued on page 39 DECEMBE R1987 17 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. 02 +5V 270k 03 4093 t8 E 10k .,. 21 R/W 10k Low power RAM EPROM emulator By using a low power RAM with a battery backup, you can duplicate the non-volatile storage of an EPROM without the disadvantages of the EPROM programming and erasing procedures. The diagrams show how a 6116 low power RAM can duplicate a 2716 EPROM. Note that the pinouts for the 2716 EPROM and 6116 RAM are identical except for the control pins, 18, 20 and 21. When reading both the EPROM and RAM, pins 18 Handy hints and tips Hint #1: In most circuits you can substitute low leakage aluminium electrolytics for tantalums and make a worthwhile saving in the process. Low leakage electros have very similar capacitance tolerance, power factor, leakage and size to tantalums, and the same maximum operating tempera ture of 85 degrees Celsius. The only applications where tantalums probably should not be substituted for is where they have been specified as a high frequency bypass capacitor or in an oscillator operating at above lkHz. In virtually every other application the low leakage electro will do just as well if not better. The only proviso is SILICON CHIP 23 A8 A5 3 22 A9 A4 4 21 VPP A7 1 24 iii ii 0 12 vcc 22 A9 20 if 19 A1D MCM65116,6116 6116 18 24 VCC A6 2 A3 5 CS ..I. 4.5V .,I_ A7 t 'f At 7 18 AO 8 17 007 000 9 000 9 16 006 00110 001 10 15 005 002 11 002 11 14 004 vss vss 13 003 12 and 20 are low and pin 21 is kept high. When not selected, pin 18 is taken high to put the EPROM in high impedance output mode and the EPROM in standby. When writing to the RAM, pin 21 is taken low. The circuit uses a 4093 CMOS NAND Schmitt trigger to provide automatic standby when the + 5V power is off. The pin 1 input to the Schmitt trigger goes low via diode D3 and the output goes high even if the Chip Select input at pin 2 is high. During standby, the 3V battery provides power to the 6116 RAM and 4093 Schmitt trigger via the that you should use a known reliable brand of low leakage electro such as Elna RBLLs. PIN READ STANDBY HIGH IMPEDANCE WRITE 18 12 2716 20 21 . . L L H H - vcc vcc vcc - 18 L H - L 6116 20 21 . . - L VCC L L • DON'T CARE forward biased diode Dl. When the 5V supply rail is reapplied, the lµF capacitor at pin 1 input of the Schmitt IC charges via the 2 70kfl resistor. This provides a delay before the RAM is enabled by the input line to pin 18. The circuit can be constructed on a piece of Veroboard with a 24-pin header plug used to provide the 'EPROM' terminals. Transistor oscillator Hint #2: To stop small parts from getting scattered about when you are working on a project, use half an egg carton as a set of mini storage bins. This keeps the components in one place but they are still easy to get at. Hint #3: To prevent wirewound resistors from charring your printed circuit board, space them off the board by about 3mm or so. This also aids air-flow around the resistor and helps keep it cool. Avoid having electros touching wirewound resistors too, because the heat from the resistor can dry the electro out and cause it to fail. + T et .022-.068 9V 1 I -'- This square wave oscillator can be made to run over a wide range of frequencies by selecting values for Cl and Rl. The oscillator can be turned on and off by grounding the base of Ql. Virtually any small signal NPN transistor can be used for Ql while Q2 should be a power transistor to handle the currents through the loudspeaker. +12v---------------. Courtesy light delay switch This circuit allows the interior lights of your car to stay on for ten seconds after the doors have been closed. The light(s) turns off with a gradual dimming rather than switching abruptly off. The light js also extinguished immediately if the ignition is switched on before the delay period has expired. A BUZ71 MOS field effect power transistor (Q2) is used to switch the light. This has a low onresistance and dissipates very little power when on while its high gate impedance allows direct control by a simple passive timing circuit. When a door switch closes, Ql is switched on and this pulls the gate of Q2 towards 12V by charging the lOµF capacitor . Q2 then applies 12V across the lamp. When the door is closed the door switch opens and Ql is held off due to the lkO resistor connec- Voltage regulator for 12V alternators Most vehicles utilise a solid state voltage regulator within the alternator and when these go faulty they can be expensive to replace. This simple circuit could be used to replace a faulty regulator or could form the basis of a replacement for the mechanical switching regulator found on older cars. The circuit uses transistor Q3 to switch off current to the field winding whenever the alternator voltage exceeds about 13.6V. Without field current, the alternator stops charging the battery. Normally, transistor Q3 is switched on by Q2 which is turned on by the lkn resistor between its base and the positive supply. Q2 and Q3 are turned off whenever the base of Ql is forward biased. This happens whenever zener diode Dl conducts. Voltage regulation is performed by zener diode Dl and a voltage divider consisting of Rl, R2 and R3. The divider provides 0.55 of the alternator's output voltage at the cathode of zener Dl. Dl conducts when there is 6.8V across it and transistor Ql will switch on when it has 0.7V across its base-emitter junction. Thus the voltage at the cathode of Dl must be 7.5V (6.8V + 0.7V) before Ql switches on. The charging voltage is therefore set to a nominal 13.6V. 1k GN0o-------------- ting its base to + 12V. The lOµF capacitor now begins to discharge via the lMQ resistor. As the voltage falls below 5V, Q2 gradually dims the lamp. After ten seconds the lamp is switched completely off. When the ignition is switched on, transistor Q3 is turned on and discharges the lOµF capacitor to turn off 02. 06 ~1---------------, 07 03 04 05 3x1N4004 IN0 TERMINAL R1 1k, R2 6.Bk The 1. 8k0 resistor and 0. 04 7µF capacitor connected between the collector of Q3 and base of Ql provide positive feedback to improve the switching speed of Q3. The 0.047µF capacitor between the base and collector of Ql keeps the on to off oscillation speed at an ac- ceptable rate to minimise dissipation in Q3. D6, D7 and D8 are the existing positive alternator rectifier diodes while D3, D4 and D5 provide the field excitation current. Note that Q3 should be mounted onto small heatsink. a Moola, moola, moola! Moala, brass, bread, dough - call it what will. If you have a good circuit cooking away in the ol' brain cells, jot it down on paper and send it to us. If we publish it, we'll pay you for it. Yep, up to $50 for a really good circuit and up to $10 for a handy hint. So get cracking. Send it to Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. DECEMBER 1987 19 ~YCAR JAYCAR JAYCAR JAYCARJ AYCARJAYCAR JAYCA RJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJ AYCARJAYCARJ AYCARJ AYCARJAv ~ ~YCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJ AYCARJAYCAR JAYCARJ AYC AR ,I ~YCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJ AYCARJAYCARJ AYCAR JAYCARJ AYCARJ AYCA ~YCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJ AYCARJAYCARJ AYCARJ AYCARJ AYCARJ AYCI ~YCAR ~YCAR ~YCAR ~YCAR ~YCAR \YCAR \YCAR \YCAR \YCAR \YCAR \YCAR Tuts tncredtbly ltttle ptezo screamer measures \YCAR 57(U x 33(H)mm emits a 116dB wail. It's \YCAR deafening! As used tn the screamer car alarm \YCAR kit. IYCAR Cat. LA-5255 IYCAR IYCAR At last, a good value AUSfRAUAN MADE ampltfler module that Is rugged, has the IYCAR heatstnk built tn and Is cheap! IYCAR The 'Jaybrtk ' as they are called are basically rugged Mosfet power ampltfiers IYCAR m anufactu red to high standards on fibreglass board with a s pecial DIECASr IYCAR hea tstnk. All board components are enclosed tn a special conformed coating that IYCAR IYCAR ensures that the a mp wtll operate in extreme environmental conditions. If tn the \YCAR unlikely event of a r epair being necessary the coating can be picked away and the TWO BRAND NEW MODELS, BOTH FULLY APPROVED BY \YCAR offending component replaced. The Jaybrtk will dr1ve either 4, 8 ohms or l00V THE ELECTRICITY AUTHORITY IYCAR ltne step-u p transformers and has unconditional stabtltty. They are virtually IYCAR bullet proof. IYCAR They are ideal for professionals who need slave P.A. tn a hurry or any HI FI or IYCAR The MS-4020 wtll supply up to 4 appltances. Each 240V socket ta independently soun d reinforcement appltcatlon. You simply connect filtered DC and a signal to IYCAR filtered. The filter will suppress Interference from RF sources, spikes, transien ts \YCAR them and they are gua ranteed to go! and ltghting, and supply up to 4 outlets with a total load of 10 amps. IYCAR So check out the s pecs. You will find them stunning for a PROFESSIONAL Cat. MS-4020 IYCAR IYCAR IYCAR \YCAR IYCAR IYCAR IYCAR IYCAR SPECS: IYCAR J-100 l OOW RMSmtn Into 811, wtth 45-0-45 3A transformer and 1 x BOOOµF/ IYCAR The two outlet wtll handle up to 7.5 IYCAR 75 fil ter cap each ra t! and 6A brtdge rect. 45-0-45 ts MAS permitted power su pply amps. The two sockets are not IYCAR voltage. rrhts wtll produce 30V across 80 which Is 112.5W). Max offload volts! IYCAR Independently filtered although. 125. IYCAR Cat. MS-4025 Dtstortlon: <0.1% max any frequency typ 0.06%. 0.018 0 lkHz. IYCAR Frequ en cy Response: 20 · 20kHz ±OdB (-3dB O 200kHz) IYCAR IYCAR Sen sitivity: 850mV p.p. for rated output IYCAR BEWARE! There are many Impedance: 47kn IYCAR mains filters on the market. S/Notse: Over 100 dB W.RT. 850mV IYCAR One sample we evaluated had Stabtltty: Unconditional IYCAR only one capacitor tn ltl Cat. M-0382 IYCAR IYCAR IYCAR IYCAR IYCAR J-50 50W RMS mtn Into 80, wtth 25-0-25 2A transformer, 1 x4700µF/50V IYCAR filter ca p· each stde and 3A brtdge rect. IYCAR All other s pecs the same or better than above. The RS232 surge protector is used to protect IYCAR (Filter capacitor values must be doubled for use on 411 loads) IYCAR RS232 ports from the posstbtltty of costly Ca t. M-0380 IYCAR damage from large voltage pulses caused by IYCAR ltghtntng or other power problems. IYCAR Cat. PA-0885 IYCAR IYCAR IYCAR IYCAR IYCAR IYCAR \VCAR The R523 2 1111n1 patc h box US u sed to 1T1ake IYCAR custom RS232 Interfaces . IYCAR Cat . PA-0880 I YCAR IYCAR IYCAR Microphone: 0.5mV 600 ohms ' IYCAR Pick up: 3mV 50k ohms ·· IYCAR Tape/Tuner 150mV 100k ohms ~ / IYCAR Output: 250mV IYCAR Frequency Re■pon■e: 20Hz • 20kHz ±ldB IYCAR Tone Colltrol T reble: l0kHz ±12dB IYCAR Saves modtfytng or replacing non mating Tone Control Ban: lOOHz ±12dB IYCAR RS232 cables by changing from male to Distortion: Less than 0.07% IYCAR female. All pins wtred straight through. IYCAR Slgnal/Nol■e Ratio: More than 60dB Cat. PA-0884 IYCAR Headphone Impedance: 4 · 16 ohms IYCAR Dlmen■lon■ : 12.52 x 8.26 x 3 .34 inches IYCAR VU Meter IYCAR Cal AM-4200 IYCAR IYCAR IYCAR This tester indicates the presence of all IYCAR 1YCAR Important Interface Jtnes by LED illumlnatlon 1YCAR when signal ts active. All 25 pins are 1YCAR connected straight through. ,YCAR Cat. PA-0886 Specifications: 1YCAR Sen■ltlvtty: 1YCAR 1YCAR Phono: 3 mV 1YCAR Mtc: l mV ,YCAR Line (tape or tuner): 150mV ,YCAR Sljfnal / Nol ■ e Ratio: ,YCAR Phon o: 5 5dB ,YCAR The RS232 null modem Is used to replace a ,YCAR Mtc: 6 0dB set 25 pin RS232 connectors wtth transit ,YCAR Line: 65dB DATA and receive DATA across CONNECTED. ,YCAR Frequency, Cat. PA-0883 ,YCAR Phono: 20 Hz · 20kHz (RIM ±2dB) 1YCAR Mtc: 20Hz · 20kHz ±3dB ,YCAR Line: 20Hz • 20kHz ±3dB 1YCAR Channel Balance: 0 .5dB ,YCAR 1YCAR T.H.D,: Less than 0.03% ,YCAR Cat. AM-4202 Headphone Impedance: 4 • 16 ohms 1YCAR Equall ■er: . 1YCAR Centre frequency: 60Hz, 250Hz, lkHz, 4kHz, 12kHz 1YCAR Control Gain: ±12dB ,YCAR vu meter 1YCAR 1YCAR 1YCAR 1YCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYC AR JAYCAR JAYCAR JAYC. 1YCAR JAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJ AYCAR JAYCARJAYCARJAYCARJAYC ARJAYCARJAYCAR JAYCARJAYC TWEETYPIE ONLY$17.95 SQUEAKY CLEAN MAINS FILTERS 4 OUTLET $269.00 -am,lAYBRIK 2 OUTLET $99.00 RS232 SURGE PROTECTOR $99.00 $1 9 .95 RS232 MINI PATCH BOX • $125.00 Sorry no pie yeti JA YCAR PROUDLY REINTRODUCE TWO QUALITY STEREO MIXERS ~ ;;:!i!!REO MIXER (SM2550). :· , ~ $9.95 : _. .... f FEMALE/FEMALE GENDER BENDER $18.95 RS232 MINI TESTER $169.00 BVL MULTI FUNCTION STEREO MIXER EQUALISER (MQ7200) $19.95 NULL MODEM - · ~YCAR.J A-'lc.AR L& Y~ .6 • Lt.YCAR I AYC AR IAYC AR IAYC AR IAYCAR IAYCAR IAYCAR IAYCA Q IA ~ AR i AVC AQ I AYC AA IAYCAA LAYC AR IAYC A A I AYC AO I $299 C A A IAYC AA IAYC AP I AYC JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCA R JAYCAR JAYCARJAYCAR JAYCARJ AYCARJAYCAR JAYCA R JAYCA R JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCAR JAYCARJ AYCA RJAYCAR JAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJ AYCA RJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JA JAYCA R JA JAYCA RJA JAYCAR JA . JAYCA JAYCA JAYCA JAYCA 8 CHANNEL AUDIO MIXER JAYCA JAYCA JAYCAR 8002 JAYCA A balanced Inpu t / ou tpu t 8 channel mixer with featu res found in JAYCA units costing well over $20001 JAYCA JAYCA MAIN FEATURES: JAYCA • Balanced 600 ohm mic Inputs/line inputs • Inpu t attenu ators JAYCA • Cannon connections included in the ptice • Bass, mid and JAYCA treble equ alisation on each Input• Effects (i.e. echo etc) JAYCA cap ability• Foldback on all 8 Inputs • Stereo pan on all 8 Inpu ts JAYCA • 6 0mm slide faders u sed thr ou ghou t• 19' rack m oun t JAYCA JAYCA capab ility for console mount• Profession al black fron t panel JAYCA wi th format borders and multicoloured knobs to assis t func tion JAYCA Identification • Designed fo r quick and easy service • VU meters JAYCA • Only h igh qua lity components used • 5534A OP amps used for JAYCA low n oise and very low distortion JAYCA Cat KJ-6504 JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA 30 VOLT- 1 AMP JAYCA BENCHTOP POWER SUPPLY JAYCA JAYCA Variable outpu t from 3 • 30 volts and variable JAYCA limiting over 2 ranges. JAYCA Cal KA-1574 JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA 12-:230 VOLT INVERTERS JAYCA JAYCA 40WATT JAYCA JAYCA Ref: EA August 1985 JAYCA • Run 240V appliances from you r car JAYCA • Also use as a ha ttery charger JAYCA Cal KA-1598 AM./FM STEREO TUNER SYNTHESISED REMOTE CONTROL Ref: Dec '8 5 • Feb '86 Cat KA- 1635 Ref: EA April 1986 Ca t. KA-1636 $599.00 $99.50 •••••••••• Ref: ET! July 1980 Ideal companion for power amp m odules. M ixes up to 4 Inputs (high and low level) with Individual level controls. High performance 3 band t.one controls . Ki t com es complete wtth case. Operates from 2 x 15V AC (use power amp supply or Ca t MM -2008 transformer) . For full specU\cattons check Jaycar's 1987 catalogue. Cat. KE-4014 $595.00 - $39.5 0 $89.50 EQUALIS Ref: ET! July 198 This module can b gangs a s effects u synchronous swee Cat. KE-4724 :•••/r.:r $23.50 I I ,. I . , ,..~· I",.· Ref: EA August 1981 • 4 channel mus icolor • 4 di fferent ch aser patterns • Au to & manual reverse chase • Sound triggered chase • inbuilt electret microph on e • Safe · opto Isola ted circuitry. Cat KA- 1010 I I~ : ■ ,,~I I' rl' I 111 I I I . ... . $99.95 $1 19.95 Ref: EA September 1985 • Toroidal transformer • Au tomatic regulation • Current limiting • Thermal over load protection Cat KA-1610 $249.00 Ref: EA August 1983 • Tests transistors, SCR's and Diodes without h a ving to u nsolder them. Ca t. KA-11 19 I Feb/March l -4690 $21.50 9.50 '• ., • • I I' •• -: 11I I I , I •• I ■ •• II ~ I . ·: . :". I I,', I ~I I,I I .. I I I • ., :..,-1· ...... \\ .... r.a·· 1 I , ..... 1 ,( J I I 11 ·. ·. : · ,: .. : .\ l ',, '• I I I I I! I . ·,,. ~. ....... . , 1 I I 1, I ' I I •• ! I I I y . · II ·,.1·.1} ,.1 } J} I \ . I .. A A CA YCA ~AYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCA JAYCAR JAYCAR JAYC AR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAvdt i'Jt, JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JAYCA R JAYCAR JAYCAR JA' JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYGAR .IAYr. AR .IAYr.A A .IAVN A IA' YCAR JAYCARJAYCAR J AYCAR JAYCAR JAYC ARJ AYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCf>D YCARJAYCARJAYCARJ AYCAR J AYCAR JAYC ARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAY' YCAR JAYCAR JAYCAR JAYC AR J AYC AR JAYCAR J AYCAR JAYCAR J AYCA R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR J/> '., YCAR J AYCAR JAYCAR J AYCAR J AYC AR JAYCAR J AYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR .' ,. YCAR YCAR YCAR YCAR YCAR YCAR J;, .· . YCAR YCAR YCAR YCAR YCAR Cat. LA-5162 YCAR Cat. LA-5168 YCAR r: : : : : ~ = R5P : ~ R YCAR Cat. LA-5170 + HI QUALITY 4 SECTOR $259 YCAR YCAR + DIGITAL ACCESS KEYPAD $99.50 Cat. LA-5160 YCAR Cat. LA-5017 + IR MOVEMENr DETECTOR $99 YCAR YCAR Cat. LA-5018 + ECON PIR WITH PULSE COUNf $119 YCAR + DELUXE WITH PULSE COUNf $139 Cat. LA-5019 YCAR YCAR + 1WEE1Y PIE SCREAMER $17 .95 Cat. LA-5255 YCAR For full specifications see our 116 page 1987 catalogue - it's FREE YCAR Plus all accessories for the DIY alarm installer - cable, power supplies, back•up batterie YCAR YCAR • 10,0000/volt buzzers, sirens, reeds & magnets, stickers, car alarm kits, key switches, window tape, YCAR • 19 ranges advice, etc., etc. YC AR Cat. QM-1015 YCAR cJJ~WCC~ ~<at>o liiliklilil!:lil!,U.lllilN!iil!EU ll W<at>I& CCIBII&TI~1r~~ ~, ,-:··:. !lfflllaisma:11 ! :: :: INSTALL THAT ALARM oVER THE HoJDA YS !!~: • ECONOMY POCKET $23.50 YC AR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YC AR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR YCAR (CAR (CAR (CAR (CAR (CA R (CAR (CAR (CAR (CAR (CAR (CAR (CAR (CAR fCAR (CAR /CAR / CAR / CAR /CAR (CAR (CAR fCAR /CAR f CAR (CAR fCAR (CAR ( CAR (CAR /CAR (CAR (CAR (CAR (CAR (CAR ( CAR (CAR (CAR (CAR fCAR ( CAR (CAR fCAR (CA R fCAR (CAR (CAR (CAR (CAR •WITH CONTINUITY BUZZER • 20,0000/volt • lOA DC range Cat. QM-1022 $39.95 • ELECTRONIC FETVOM • Transistor tester • Centre zero adjust • Peak to peak & rms reading Cat. QM- 1050 $79.95 These beautifully crafted rack cabinets wtll give your equipment a real 1st class appearance. All aluminium construction. Removable top and bottom panels. Natural or black finish. All dimensions conform to the International Standard. Ventilated lid. Deluxe brush finish anodised front panel. Indtvtdually cartoned. Supplied in flat pack form and easily assembled 1n a few minutes. Stde elevation: D=254mm; C (Internal chassis height); B (mounting bolt centres). Finish A B C Each +5 Cat. HB-5411 Natural 44 34 38 $65.00 $62.00 • l0AMP DIGITAL • Transistor tester • Vinyl case Cat. QM-1530 $89.95 • l0AMPWITH CAPACITANCE METER Cat. HB-5413 Natural 88 57 82 Cat. HB-5415 . Natural 132 89 126 Cat. HB-5410 Black 44 34 38 Cat. HB-5412 Black 88 57 82 $80.00 $95.00 $65.00 $85.00 $95.00 $76.00 $90.00 $60.00 $80.00 $90,00 Cat. HB-5414 Black 132 89 126 Beware of other rack cabinets that do not conform to International Rack s1zing. • Digital Mounting hole centres conform exactly to International Racking specifications • Trans is tor tester both vertically and horizontally. • Vinyl case Cat. QM-1540 ,f-3 0 $129.00 ~ • 4 1 / 2 DIGIT l0AMP • Transistor tester • Diode tester • Data hold Cat. QM-1550 $179.00 • DIGITAL WITH FREQUENCY COUNTER ~ \ (auARTZ CLOCK/COMPASS • Capacitance tester • Transis tor tester I • 20 amp current • High impact case Cat. QM-1555 $159.00 (CAR .,,:: (CAR (CAR ( CAR / CAR SAVE $6 We have a small qu:mtily ofViatel terminals left, which we are clearing out for Christmas at stlly prices. Both units are 2nd hand, but are In good looking condition. See previous ads for full specs. • Vtatel terminal With 14" colour monitor SAVE $200 (j'l('EJl'I X'Jv{5'1S P'l('ES'E'J{T :ro'l(vJtv iI .I I This great small product has many applications. It's a quartz dtgttal clock and a compass 1n one small, I I handy size. I Cat. XW-0250 I 1 oNLY I $5.95 ::·:: Cat XV-2210 :·•· · :,:,:: .·.· Viatel adaptor for your 1V (With remote) Cat XV-2212 WAS $499 NOW $299 ig~~ '( • WAS $199 NOW $129 SAVE $70 (CAR · . (CAR (CAR . (CARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR J AYC ARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR J AYCARJAYCARJAYCAR JAYCARJAYC ( C AR J AYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJ AYCARJAYCARJAYe.\~JA¥CARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYC ( CA R J AYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JAY CAR JAYCA R JAYC AR ,JAYCAR /AYCAR /AYCAR /AYCAB tAYC JAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCI JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCA RJAYCARJAYCAR JAYCI JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCI JAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCAR JAYC•- YCARJAY~AR JAYCt . .. JI ,------------, UNBELIEVABLE ELECTROLYTIC BUY Through Jaycar's surplus stock buying scheme, we have purchased a substantial quantity of an electro that would normally be out of reach of the hobbyists pocket. This electro is made in Germany by ROEDERSTEINI ~ \ 12 VOLT ILLUMINATED PUSH ON/OFF ,,,,., Sun!l!ar to the one used In the Red Llght Car Alarms and In our flasher deterrent kit cat. SP-0742 RED ~:., ~ - . 6,880uF 63V LONG LIFE ONLY $7.50!! That's rtght ROEDERSTEIN brand long ltfe, high rtpple current etched electrodes, screw terminals • all class! And at a prtce below "Taiwanese". These arc absolutely fantastic for power supplies for high power amps, etc. Electrtcal to DIN 41332 Tolerance -10 +50% Dimensions 50(D) x 80(H) Terminal MS screw QUANTITY DISCOUNTS 1 - IS $7.50 6 • 10 $7.00 ____________ ,,, \;11 - 24 $6.50 25 • 99 $6.00 l\ \ \ ~ . . QUALITY TIE CLASP MICROPHONE Low Impedance, omnt-d!recttonal electret condenser. A veiy small microphone which clips on to your tie . Supplied with 3 metres of cable and 3.5mm plug. lk ohm impedance. Frequency response 40 - 16kHz. Cat. AM-4067 $29.95 • 'v"'•·""\--f. ----------------- ' SAVE $70 WAS $269 ■ • ECONOMY 8" PA WIDERANGE - 8 OHM ,-----------------------, MASSIVE SCOOP PURCHASE ROVER NEGATIVE ION GENERATOR I I Yes, we've made anoi:per scoop purchase. The importer contacted us with his d!lemma and we purchased a quantity of these fully I imported fully guaranteed air purtflers. These units are 24 0 volt operated, draw about 1/2 watt, deltver about 250 btllton tons I with per second, and cover about 25 square metres. It's even suppiied Tester PC board and spare needles. If you've ever wondered ton generators, this MUST be the time to buy one. I abouta negative n.,, ~• ~"""'" ""'"' "'· a.,=,.,, • >m"«< S"=••:\available for: II Cat. YX-2905 ,: SAVE $50 ~,>fJ:',.. ~ • • - ·•· __ ---"" •'>:¾."''• · , · • :,~f..::.:. . ' .. . '\, ... ... , .. h ·::··· : ___ _( °' -• / ;"" .... C I II I I I I { '----------------~~-----J W~~ ©i1.1f&illA»<at>UlT~ If you don't already own a copy of the Jaycar 116 page 1987 Engin(.'Cting Catalogue drop into any one of our showrooms for a free copy. If you can't get in send a large SAE and we'll foiward you one. TV ANTENNA SELLOUT JI J1 JI J1 J1 J, JI J1 J1 J1 J; J; J1 J1 J; J1 J1 J1 J1 J1 J1 J1 J, J, J, J, J, J, J, J, J, J, J, J, ~ ~- tJ, J '. Jj :;1 J, J, / Government Instrumentalities, Schools, Public Companies. If you wish to purchase from us, simply s end us your official order and we wtll give y ou a compltmen tary 30 day accounl J, J, J, J, J, J, J1 J1 J, J1 J1 J, This is your chance to grab a 1V antenna at a bargain prtce. All these are discontinued l!nes and are greatly reduced In prtce. Some are display models hanging on our cetltng s. · Personal shoppers only. • Caravan Antenna Bu!lt tn amp. VHF/UHF and FM ~ Cat. LT-3 120 WAS $99.50 NOW $50.00 • HILLS UHF /VHF Pathfinder Cat LT-3152 WAS $139.50NOW $99.50 • VHF Metropolttan to near frtnge Cat LT-3165 WAS $57.50 • VHF Gutter Grtp Cat LT-3170 WAS $43.50 NOW $32.50 • UHF Phased Array • vertical style Cat. LT-3182 WAS $69.50 NOW $39.90 • HILLS UHF Trucolour • 18 element Cat LT-3184 WAS $89.50 NOW $59 .50 • Sportsman 1V antenna • channel 4 and 5A VHF Cat LT-3 190 WAS $59.95 NOW $35.00 J, J, J, J, J, J, J, J, J, J, J, J, J, J, J, J, J, J, J, JI WAS $13.95 SAVE 15% ~ ~_-:, NOW $11 .95 . 10+ $11.50 ea This Incredibly small m icrophone just clips on your tie or collar and transmits on FM. No more m es sy wires to bip over. • Tunable FM 88 · 108MHz • Frequency response 100 · l0kHz $ • Electret condenser type Cat. AM-4068 6. 50 Red Flasher Kit which Incorporates red switch also reduced to only This speaker has high efficiency and 1s !deal for extension speaker and low level sound reinforcement use. The heavy magnet and dual cone results tn a wide frequency res ponse. Power handling 10 watts, 200mm diameter, frequency range 60 • 18kHz. Cat. CE-2325 UNI-DIRECTIONAL WIRELESS TIE CLASP TYPE MICROPHONE 3 LOWER PRICE WAS $21 .50 SAVE 26% NOW$15.95 $19.95 · Cat. KJ-7000 SAVE $8.50 $29.95 CORDLESS PHONE The fabulous Portable Telephone that you can take anywhere around the house, garden or swimming pool. Microprocessor controlled with a range ofup to 250 metres and absolute clartty. Features: • Simple to use and easy to tnstall · just plug In • Operating range up to 250 metres (800 ft) • Securtty code system with 16,348 combinations • Call function at base unit to alert handset • Pulse dlalltng with audible tone feedback at the touch of a key Cat. Yf·7065 I JI JI JI JI JI JI JI JI JI ~ 6802 CPU Cal. ZZ-8050 NORMALLY $15.95 X'mas Special $7.95 GREAT XMAS GIFT LCD THERMQME . TRAVEL ALARM • CLOCK Features: • Easy to read R • • • • •Temperature in •c or °F 1 : :~111g ~~~z: Easy to set Small stze Carry wallet Quartz accuracy TEMPERATURE SCALE ~c;oor<F>-F';HL!~~sHe1r1 BRAND NEW DESIGN AL.SET TEMPERATURE It's about the size of a credit card, measures 85 x 55 x 8mm thick and is supplied in a handy wallet Ideal for travelling. It has an alarm which is LOUD enough to wake even a heavy sleeper AND it has snooze function. It's easy to set the time and alarm time. Display tempera• ture 1n either Celctus or fahrenhett. Uses one LR-44 battery. Cat. XW-0392 TIMESfT READING NORMAL ALARM sNooze Key-Fob style Burglar Alarm Transmitter Case We dare not say which professional alarm company sold us this one! But after months of searching we have a product for our 1988 product line-up. The [black) case measures 42(!.J (plus a little more for a keyrtng hole) 34(W) and only 11.8mm deep! The case is held together by one screw. The internals are 40.5 x 31 x 9 .7mm deep • enough room for a transmitter and battery. The lop of the case has a special hole for a i ; : ~ ~ ~ d another for a LED. ALARM ON . SLIDING INDICATOR SWITCH 10+ $3.65 ea $29.95 , J TIME READING MAX232 - NEW SEMI Dual RS232 receiver/transmitter. For new designs, the MAX232CPE makes an excellent replacement for the 1488 and 1489. Features: • Meets all EIA RS232C specs • Generates ±9V output from 5V supply• Highly useful when ±12V supply is required for RS232 drtvers, but is not available • ±30V IIlput levels • Also converts RS232 levels to TTI.., levels• 2 inputs• 2 outputs Cat ZK-8824 • $12.95 AT LAST! - - · I I ,j I I I : A unique clip together case that features moulded in mounting feet on the sides. Measures 87(1.J x 67(W) x 3 l(D)mm. Ideal for car burglar alarms, etc. Black Ill colour. Cat. HB-6075 A bargain at only$2.00 i - - - - - - -... I Ammonium Persulphate 400g in a screw top plastic MAIL ORDERS ONLY· 008 022 888 MAIL ORDERS & ENQUIRIES (02) 747 1888 - - ~------..l Mini-Mini Plastic Snap Together Case New product from Electrolube. It's pure compressed inert gas for removal of dust and air borne contamination from veiy delicate and inaccessible areas of eled:r1cal and electronic equipment. 400 ml spray pack · 550g nett Cat. NA-1018 $11 .95 • • Our Smallest General Purpose Box! At last A box for those REALLY SMALL projects · FM bugs, remote sensors, miniature radios, etc. Black tn colour measurtng (external) 45 x 35 x 19mm It Is Ideal for many applications. Case splits halfway down the sides and snaps together to save space. Cat. HB-6070 NEW ZEALAND CUSTOMERS You can purchasl' goods from us TAX FR~:E Whl'll you order by mail or call in to any of our slorl'S ask about TAX FREE priC'cs. •• • • •• ••• • JATVl-\n JI\TVAn J I-\ T V l'\n JI-\TVM. n ,J MIVl'\n J l'\ TVl"'l n ,J l"\ I V /"\n """" ' V l"\ n ,Jl"\ 1 Vl"\ n ,Jl"\ 1 Vl"'\ Jl ,Jl"I I V l"\fl VM J v n , , ,Jr-, I V MI\ ,JM.I v ru, .. ,, I ...,,.., , ....... ,....,,.." ' vn I vn, , "''"' I V l"'\ 11 .,,., , ...,,.,, , ..,,.,, V l"\1 1 vn , ...,,., , ,, JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR J . JAYCARJAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYCARJ AYCARJ AYCARJAYCARJ AYCARJAYCARJ AYCARJ AYCAR/ , JAYCAR JAYCAR JAYCAR JAYCA R JAYCA R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCt>f / /f n-:'. i , ~- TT 110. '\WrR 110. Qd.J~J..1 ~<at> 'il 'i7S) ~~ c!_l,\j c!.J, SCOOP PURCHASE!! ~f()''i75) f '9 JAYCAR . JAYCAR . .iv ' AYCA R. ...,,. JAYC ,. - A JAYC J?'.~~ilt,1 · \_ 1~~l .!.._Q0,!.0.!.._Q0~ .!._!, ~~c!_l,\j.!._!,~~~r,;;1-,jH '. wTT wfR<at>'i75)1)'~li'rR~ ~ ~~ _B_A _ R_G_A_I_N_ C_O_M _ P_O_N _ E_N_T_ P_A_C_K _S _ ' . :.(ilt ~ :;-:;JJlji~i MICROPROCESSOR CONTROLLED/ SOLENOID OPERATED HI FI CASSETTE DECK MECHANISM You guessed It, another Jaycar buy far, far below manufacturers cost where you buy at a normally s!lly pnce because other people have lost heavily. This time its a VERY HIGH QUAUIY cassette deck mechanism that cost over $35 US tn 1000 lotsl This JAPANESE MADE mechanism Is deck only · i.e. a door Is n ot fitted nor are there buttons. The deck Is not operated by mechanical buttons and all control ls by electt1c signals, therefore the deck could eas!ly be software controlled. 80 Electrolytics $10 Cat. RE-6250 150 Mixed Capacitors $10 Cal RE-6260 \\ 35 Pots, TI1mpots, Sliders $ 10 Cal RP·3902 100 mixed Semiconductors $10 Cat. ZP-8990 100 mixed BC iype transistors $11. 95 Cat. Zf-2170 100 3mm & 5mm LEDs $19.50 Cat ZD-1694 100 mixed IC sockets $24.95 Cat. Pl-6490 50 assorted Pots $7.95 Cat. RP-3900 50 assorted Resistor Networks$ 10 Cat RR-3380 Assorted Pot Cores $9. 95 Cat. LF-1280 20 Precision 1% & 2% Capacitors $12.50 Cat. RG·5198 ~ 25 RT KermetTantalums $5 Cat RZ-6692 ~ The deck also feab.lres an air damper cylinder for soft eject. massive capstan flywheel, HI FI head and excellent specs. (see below). This deck is ideal as either a fast high capacity PC memory storage or as a retrofit to an existing cassette deck to improve performance. Worth at least $80, grab one for ONLY $24.95 .:,,.........,... \ ;~~~'fu:s: Cat.AC-1590 .'; • . ·"·, .• SPECS; ) llir: \ •.. • 4 track, 2 channel Philips · .:·_, ., ' • ·\ . compact cassette deck · · ....-... __ / · • Tape speed 4. 75cm/ sec ·....._.... • Wow and flutter <0.12% RMS PHOTO INTERRUPTER This device enables you to tum a circuit on and off optically. It consists of a moulded plastic housing with an IR LED factng a phototransistor across a gap. Any object tn the gap will interrupt the IR beam and consequently switch the phototransistor on and off. The device Is very fast and !deal for counttng. timtng or • PCB or chassis mounting • Low cost • Rugged one piece construction • Very fast ;:- • Wtnding time 110 sec FF & REW C-60 • Working volts 9 - 15V • Supplied with 12 page comprehensive manual tncludtng circuit diagram, truth table, etc. APPLICATION: $8.95 • Counter sensor • Tachometer (Around 1 / 4 the • Opto ignition pt1ce of its European 'Cou sin') • Edge sensor • Tape end sensor Full specs supplied with each unit. Cat. ZD-1901 Sorry no room for a picture! AT LAST! NOW IN STOCK A high quality RF Modulator for Audio AND Video "QUALITY" RANGE OF BANANA PLUGS We have finally sourced a good quality stable VHF Modulator for both audio and video input signals. This unit wh ich measu res a ttny 35(L) x 25(WJ x 13(0) (excluding coax (RCA) output socket and tnput termtnals) is made In Japan by National (Matsushita) . It Is used on the well known NV- 180 VCR and has output switchable on VHF Ch 3 or 4Aust. The small size belies its performance! It uses state-of-the-art surface mount componentry (which also helps reduce parasitic stray capacitance) and even has a surface acoustic wave (SAW) filter! SPECS: Power +9V Input Video: ltne level (input attenuator provided) A new range of US style banana plugs. RED Piggy back style Cat. PP-0390 BLACK Piggy back style Cat PP-0391 10+ $1.75 ea AVTEK MEGAMODEM • NEW MODELS Audio: line level Output CH 3 or 4 (Aust VHF) switchable RCA iype coaxial socket Connection details and circuit diagram provided. Cal LM-3840 TV ANTENNA BARGAIN We have Just purchased a quantity of VHF 1V antennas from a wholesaler who Is no longer In the 1V antenna b ustness. The antennas are a 7 element iype suitable for metropolitan areas. They have excellent gatn and directivity for areas with moderate signal strength! For coax use use outdoor balun Cat. LT-3026 $3. 75. Australian made. These will never be this cheap agatn. Cat. LT-3166 NORMALLY $57.50 SAVE $17.55 ONLY $39.95 BREADBOARDS 100 hole - ·cat PB-8810 2420 hole - Cat PB-8818 ·.:-. $57 .50 640 hole · Cat. PB-8812 3100 hole - Cat. PB-8820 $10.75 $69.95 840 hole - Cat. PB·8814 (Note: PB-8816/18/20 are all mounted on a metal frame with banana termtnals). 1680hole - Cat. PB-8816 • Model 12 Cat. XC-4850 $375 Model 123cat. XC-4855 $449 .. .-,.,, -,,.,,., AVTEK MINIMODEM STILLAVAILABLEcatXC-4825$199 ,:.:' ' .· · '; $3. 75 $17.50 300 Baud Full Duplex - both models 1200/75 for VlATEL - model 123 1200 Baud Full Duplex - both models Data Standards V2 l, V22 - both models V23 - 123 model only Command Set Hayes with extensions) Interface ccrrr V24 (RS232) Data Format Asynchronous Power <2 watts Size 27(H) x 120(WJ x 157(D)mm Indicators 8 LEDs Internal diagnostic loop back. .. $39.95 JAYCARJAYCARJAYCAR JAYCAR JAYCARJAYCARJ AYCARJAYCARJ AY JAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJ AYCARJAYCARJAYC ..JAYCAR JAYCAR.JAYC AR JAYCAR.JAYCAR.JAYCA.B_.!AYCAB JAYCAR JAYC JAY( JAYC JAYC JAYC JAY( JAYC JAY( JAYC JAY( JAY( JAY( JAYC JAY( JAYC JAYC JAYC JAYC JAY( JAY( JAY( JAY( JAY( JAY( JAYC JAY( JAY( JAYC JAY( JAYC JAY( JAY( JAY( JAY( JAY( JAYC JAY( JAYC JAY( JAY( JAYC JAYC JAY( JAY( JAY( JAYC JAY( JAY( JAY( JAYC JAYC JAY( JAYC JAYC JAY( JAY( JAY( JAY( JAYC JAY< JAY( JAY( JAYC JAY( JAY( JAY( JAY( JAY( JAY( JAY( JAY( JAYC JAY( JAYC JAY( JAY( JAY( JAYC JAYC JAY( JAY( JAY( JAYC JAY( JAYC JAYC JAY( JAYC JAYC JAYC JAY( JAYC JAYC JAY( JAY( JAYC JAYC JAY( ( (( ,YC ~YC ,AYC JAY( JAY( JAYC JAY( JAY( JAY( JAY( JAY( JAY( JAY( JAYC ,.'(CAR JAYCAR JA .,AR JAYCAR JAYCAR JAYCAR. ,rl JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR , , CAR .JAYCAR JAYCAR .J AYCAR .J AYCAR .IAYr.AR .IAYr. AQ VAnJATVMnJATVAnJATVAn J ATVA nJATVAnJATVAMJA TVAMJA TVAMJATVA MJATVA MJATVAMJA TVAMJATVAM J A TVAMJ A TVAHJA TVAHJATVAHJATVAHJ CARJ AYCARJ AYCARJ AYCARJAYCARJ AYCARJ AYC ARJ AYCARJ AYC ARJ AYCARJ AYC ARJ AYCARJ AYC AR JAYCAR J AYCARJ AYCARJ AYC ARJ AYC ARJ AYCAR ' CARJ AYCARJ AYCARJ AYCARJ AYCAR J AYCAR J AYCAR JAYCAR J AYCARJ AYCARJ AYCARJ AYCAR J AYCAR JAYCAR JAYCARJ AYC ARJ AYCARJ AYCARJ AYC ?, CARJ AYCARJ AYCARJ AYCARJ AYCAR JAYCAR J AYCAR JAYCARJ AYCARJAYCARJ AYCARJ AYCARJAYCARJAYCAR JAYCAR J AYCAR JAYCARJ AYCARJ AYC ,, . CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR CAR '.: AR CAR CAR CAR CAR CAR CAR CAR CAR ::;AR ::;AR CAR CAR ::;AR CAR CAR ::;AR ::;AR ::;AR CAR CAR ::;AR ::;AR ::;AR ::AR ::AR ::AR ::AR ::AR CAR ::AR CAR ::AR ::AR ::AR ::AR ::AR ::AR ::AR ::AR CAR ::AR ::AR ~AR CAR CAR CAR CAR CAR CAR CAR CAR ::AR ::AR CAR CAR CAR ::AR ::AR ::AR ::AR ::AR ::AR ::AR ::AR ::AR ; AR ;AR ::AR ; AR ; AR ; AR : AR : AR : AR :AR :AR :AR :AR :AR :AR :AR ;AAR R :AR :AR :AR :AR :AR :AR :AR :AR :AR ~R 1111■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■"' JJ&WCC&~ ~<at>ll W<at>~ ~~~ ~~CCIT1I'IT~<at> IB:IT1f~ l■-111 24 TO 12V CONVERTER TELEPHONE RINGER Ref: Silicon Chip Dec '87 Well suited to nm 12 volt appliances from 24 volt Can deliver up to 5 amps. Complete kit Cat. KC-5017 Ref: Silicon Chip Dec '87 If you are tired of the sound of your phone, tty this kit Mounts inside phone - Includes buzzer. Cat. KC-5015 $19.95 HIGH IMPEDANCE AC/ · DC MILLIVOLTMETER Ref: EA Dec '87 This kit will measure AC and DC signals down to a couple of millivolts, with negligible circuit loading. Complete kit with case and meter. Cat KA-1695 $59.00 $46.50 Ref: ET! Dec '87 Thts is a cheap, no fuss way to lr1ckle charge a 12V car battery. PC board and UNIVERSAL SPEED CONTROL & LAMP DIMMER SUB CARRIER ADAPTORS FOR FM TUNERS ef: Silicon Chip Dec '87 se for control of drtlls, fans, eleclr1c blankets, soldertng rons or a dimmer. Complete kit with box, mains leads, etc. at. KC-5016 Ref: Silicon Chip Dec '87 Usten to hidden transmissions on FM broadcasts. ' i ·•.:.;. ~l'!Cli::::-:-- ; ' ' :· .. . /f\-:~ . / t : ✓ .:l ·..,~.•:·•~• OCTAVE EQUALISER MODULE ·; ( ~ -:;j/: Cat KM- 3064 $4 9 •95 Ref: AEM Dec '87 This one octave EQ module is suited for PA and professional use. Kit supplied with all components, pots, PCB. No box or hardware. Ref: Silicon Chip Nov 1987 A great project from a new monthly electronics magazine - S111con Chip. Add a two range capacitance tester for only $27.95. Ranges are O • 2200pF and O • 2.2µF. Complete kit Cat KC-5010 ~~~~ $196.00 each ONLY $299.00 I 152320,~ . ······/ METRONOME Ref: EA Nov 1987 Printed circuit board and electronics supplied. No box. Cat. KA-1693 Ref: ET! Nov 1987 Features of the ET! 1424 include a top boost and normal input, two pre-cq line inputs, bass & treble controls, effects send and return, sweep eq, 4 post eq & line inputs and master volume. PCB pots supplied when available. 6.5mm sockets, transformer and knobs are not supplied. Cat KE-4729 $19.95 CAR RADIO POWER SUPPLY Ref: Silicon Chip Nov 1987 Put that old car radio that's laying around to good use as a mantle/kltchen/garage/sunroom radio. Our kit Includes PC,O,, transfor-mer and components. You need the radio and speakers. 6 x 4-speakers 1 $10.95 each (Cat. AS-3014] • Cat. KC-5012 ~ --- ~ $13.50 each VOICE OPERATED RELAY Ref: EA Nov 1987 Eleviates the need to push the button when using a microphone. Shortform kit, no hardware. Cat KA-1692 $24.95 OFF HOOK INDICATOR FOR PHONE Ref: Silicon Chip Nov 1987 If you have two or more telephones on the one line, with this project a LED will flash on the phones not used to indicate the line 1s in use. One kit Is needed for each telephone. PC board and components supplied. (Unit mounts in telephone). Cat. KC-5011 $19.95 VOLTAGE & CONTINUITY TESTER Ref: EA Nov 1987 This handy voltage and continuity tester tests AC and DC voltages and also continuity In wires and cables. Cat KA-1694 $45.00 ,.- : ~ . After much interest in this project, we wll have available the 3mH inductors. The woofers, speaker terminals, cable and innerbond are normal stock lines. P25WO-08 10" woofer 3mH Inductor Cat CW-2136 Cat. CX-2640 Ref: Silicon Chip Nov '87 This superb 1GHz digital frequency meter will ou (perform any other instrument in its pr1ce range. It uses the h1ghest performance ICs, provides blll h frequency and period measurements, and featun ·~ .m 8 dlgtt LED readout Cat KC-5013 HIGH QUALITY GUITAR PREAMP • (PASSIVE "BANDPASS" SUBWOOFER 1GHz Digital Frequency Meter! CAPACITANCE METER FOR D.M.M . $28.95 ;;~ir~· $29.95 , - , NE\Vl KITS FOR NOVEMBER . :ARJ AYCARJ AYCARJ AYCARJ AYCAR J AYCARJ AY v"nJAYCAR J AYCARJAYCARJAYCARJ AYCARJAYCARJ AYCARJ AYCARJ AYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYC :ARJ AYCARJAYCARJ AYCARJ AYCAR J AYCARJ AYCARJAYCA RJAYCARJAYCARJAYCARJAYCARJAYCAR J AYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYC ~~~~~~~~~~ ~~~~ ~~~~~~~~~~2~~~~~~~~JAYCARJAYCARJAYCARJAYCARJAYC ARJAYCARJAYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAR JAYC KIT SALE With so many new kits, we have to clearout some of the oldies. Your chance to grab a bargain. But, be quick, some are In limited quantities. Cat. No Month/Magazine Description Was Now KA-1527 EA 8/83 Video amp buffer $12.00 $8.00 KA-1558 EA 11/84 Speed controller $28.50 $20.00 KA-1567 EA 11/84 20W amp module $24.50 $12.50 KA-1600 EA 8/85 Car stereo SOW amp $189.50 $129.50 KA-1612 EA 9/85 Dwell/Tachometer $36.95 $20.00 KA-1645 EA 4/86 CD ada ptor $32.00 $18.00 KA-1672 EA 6/86 Phone controller $59.00 $25.00 KA-1678 EA 10/86 HI power electric fence $229.00 $149.00 KM-3048AEM 8501 Current sense car alarm $89.50 $49.50 KM-3054AEM 6508 Audio clipping indicator $19.95 $14.50 KE-4000 ETI048 Buzz board $8.50 $4.50 KE-4002 ETI065 Electronic siren $8.90 $4 .90 KE-4728 ETI 6/87 Ring tone customiser $39.95 $26.95 HOUSE ALARM D.I. (DIRECT INJECT) BOX Ref: EA January 1985 This unit costs far less than often inferior commercial alarms. A unique feature Is that you can wire NO and NC alarm sensors In the one line. Cat. KA-1582 Ref: EA October 1987 $169.00 .,._,.., -_ ........... , / :<;;k1'ii;iHf :;;: \ SAVE HEAPS SOLDERING IRON TEMPERATURE CONTROL Ref: ETI October 1986 A variable control using diodes. No transformer required, soldeting iron connects through this to power outlet. Simple to install. Cat. KE-4725 :;'('~ ~====•elil TV COLOUR BAR & _:~ ;. $35.00 -~ PLA YMASTER 60/60 AMP $299 Cat. KA-1652 BLUEPRINT $349 Cat. KA-1650 STANDARD {:\):):?WrrJ+:EMER¥))} I flR§§ iA]A4i<at>ilI Jaycar will purchase your surplus stocks of components and equipment. We are continually on the lookout for sources of prime quality merchandise. MAii ORDER CALL GARY JOHNSTON OR BRUCE ROUTLEY N O W ~. N . (02) 747 2022 FUNCTION GENERATOR DUAL TRACKING POWER SUPPLY WITH DIGITAL READOUT • Incorporates curren t limiter • Floating ground .. · : ~ .'- . ~- ~ \ Ref: EA February 1987 ~-. · . , _ . ·. Ref: EA April 1982 Attractive unit matches the KA1390 (DFM). Produces sine, triangle and square waves from below 20Hz to over 160kHz. Good envelope stab!l!ty. Inbuilt 4 dtg!t frequency counter for ease and accuracy. Cat. KA-1428 • Sw!tchable from V to A • Output ± l.3V to ±22V<at> 2A - 5V <at> lA • ABS instrument case • Foldback current protect1on • Adjustable voltage to lOmV • Fully protected • LED,indicator for regulator dropout Cat. KA-1682 $129.50 $129.95 I · ~-· Cat. KA-1690 $39.95 How to run 12V CB radios from 24V 24V to 12V converter for trucks This 24V to 12V converter can deliver up to 5 amps with very little power loss. It is intended for powering CB radios and radio/cassette players in trucks which normally hove 24V battery supplies. Design by JOHN CLARKE Most larger trucks use a 24V supply for their electrical system and commonly employ two 12V or four 6V batteries connected in series to provide the voltage. This presents a problem when CB radios and radiocassette players are installed. A common method for supplying the required 12V is to tap it off from the centre point of the two (or four) batteries. This certainly works but it does have a serious long-term drawback. To describe how this occurs, let us consider the most common case where two 12V batteries are used. When a heavy current device such as a CB radio is connected, it takes all its energy requirements from the lower 12V battery in the series string. This means that the total drain on the lower battery is higher than for the upper unit. But when the batteries are being recharged this fact will not be taken into account. The two 12V batteries will still be recharged to a nominal 28.8V cutout (ie, twice the normal 14.4V setting in a 12V system) but as time goes on, the lower battery will always be undercharged while the top unit is over-charged, as the electrical system attempts to make up the required total voltage of 24V. The result will be premature failure and necessary replacement of both 12V batteries. That is a very expensive way of running 12V gear. The same problem applies if four 6V batteries are employed. The only satisfactory way to prolong battery life is to derive the required 12V from the whole 24V supply. The simplest way of doing that is to use a series regulator which can be set to deliver around 13.6 volts which is a good voltage for running 12V equipment. There is little wrong with this approach except for one problem excessive power dissipation in the regulator. Consider what happens if the 24V truck supply is running at around 28 volts (which is normal), the regulator is set to deliver 13.6V and the CB radio is drawing 5 amps when transmitting. This means that the regulator will have to dissipate over 70 watts. In the hot cabin of a truck this could be a serious problem, requiring a large and bulky heatsink. So scrub that idea, it isn't practical. Our 24-12V converter solves the dissipation problem by using a switchmode regulator. It uses a power transistor which is switched on and off at a rapid rate to provide 13.6V. -- S1 + 1ZV 20kHz OVJ1_Jl_ D1 Fig. l ':' Fig.1: this circuit cannot be used because Ql 's load is shortcircuited when the radio is connected. 28 I LOAD +0-0 D1 SILICON CHIP Fig. 2 .,.. h~ I ... i.,.. Fig.2: the circuit is based on the source-follower configuration. Vi '---4---,-+ D1 Fig. 3 Fig.3: basic operation of a switchmode supply. S1 is the transistor and turns off and on at a rapid rate. .. PARTS LIST 1 PCB code, SC111-1287, 100 x 55mm 1 folded aluminium case, 100 x 58 x 45mm 1 panel mount fuse holder 1 in-line fuse holder 2 3AG 5A fuse 2 1 0mm grommets 3 solder lugs 4 plastic PC s tandoffs 4m 1 mm enamelled copper wire 180mm 1 mm tinned copper wire 2 T0-220 mica washers and insulating bushes 1 Neosid iron cored toroid 17-146-10 Semiconductors View inside the prototype. All the parts, including the toroid coil, are mounted on a small printed circuit board to give a compact assembly. Because the power transistor is being switched on and off, it is very efficient and wastes little power. It dissipates only about 5W when delivering 5 amps. The converter has good regulation. The input voltage can range between 18V and 30V for an output voltage change of only 0.7V. The output is well filtered too. Switching ripple is 30mV peak-to-peak at the full load current of 5A, falling to 10mV p-p with no load. A small metal case houses the converter circuitry. This reduces the level of electromagnetic radiation emanating from the circuitry as well as providing a heatsink for the main switching transistor. Circuit details At first sight the circuitry looks fairly complicated but the operating principle is relatively simple. It is best understood by first referring to Fig.1. This shows a MOS (metal-oxide silicon) power transistor Ql with a square wave drive signal fed to its gate. This can be made to work perfectly well to provide a 12V output. The only drawback is that the output has the positive line at + 24V (nominal) and the negative side at + 12V with respect to the chassis of the vehicle. The problem with this is that virtually all 12V automotive gear such as CB radios and radio/cassette players need their cases earthed to the vehicle chassis. If this was done with the circuit of Fig.1, Ql 's load would be short-circuited and it would be burnt out. So back to the drawing board. Fig.2 shows another arrangement for the switching supply with the 12V output referenced to ground (vehicle chassis). It uses Ql as a source follower with the drain connected to the 24V supply. The problem with this circuit is that the gate must be driven at least 12V above the source to ensure that Ql switches on fully . In practice, this means that the gate has to be driven 12V above the 24V rail. (Life isn't simple, is it?) To solve this problem we need a drive circuit which will swing the gate between + 12V and + 36V. We can do this but it needs its own supply circuit delivering more than 36V. We solved that problem with a voltage doubler circuit. Fig.3 shows the basic operation of the switchmode supply. Switch Sl is the transistor which turns on and off at a rapid rate. When S1 is closed, current passes through the inductor to charge capacitor Cl. When Sl opens, the inductor current is diverted through the flywheel diode Dl to charge Cl and so prevent a large back-EMF being 1 1 2 1 5 1 1 1 TL07 4 quad op amp IC BUZ71 SIPMOS trans istor BC54 7 NPN transistors BY229-400 or MUR1 550 fast recovery diode 1 N4148 , 1 N9 14 s mall s ignal diodes 39V 400mW or 1 W zener diode 30V 1 W zener diode 13V 400mW or 1 W zener diode Capacitors 1 1 OOOµF 63VW PC electrolytic 2 2200µF 16VW PC electrolytic 1 1 OOµF 35VW PC electrolytic 1 2.2µF 50VW PC electrolytic 2 0.4 7 µF metallised polyeste r 1 0.01 µF metallised polyester 1 0 .0022µF metallised polyester 1 0.001 µF metallised polyester 1 4 70pF ceramic Resistors (0.25W, 5 %) 1 X 1 OOkO, 7 x 47k0, 3 x 10k0, 1 X 4 .7k0, 2 X 2.2k0 , 1 X 3900, 1 X 2700, 1 0.5W X 1000 , 1 X 470 Miscellaneous Hookup wire , solder, screws, nuts etc . developed across the switch. The complete circuit diagram (Fig.4) brings it all together. It includes a voltage doubler, a gate driver, a switchmode oscillator to provide the square wave for the DECEMBER1987 29 470 l'"'""-..-----,----.....-----.--....--wv,,-+VOR FROM ACCESSORY IGNITION SWITCH 47k SA LINE FUSE . - - - - - - - - - u ~ - - , - + 2 4 V FROM BATTERY 1000 + 0.47+ JSVW+ 47k 47k 47k 470pF-l'. 40kHz OSCILLATOR SA -.....-------0--.0---0+ VOLTAGE DOUBLER OUTPUT 13.6V, SA i- 10k 47k 2.2k B ELJc VIEWED FROM BELOW ~R GDS D5 1N4148 K A I. SHORT IF 04 VOLTAGE HIGH 20kHz SWITCH MODE OSCILLATOR 24V-12V CONVERTER · L1 : 64T, 1mm ENAMELLED COPPER WIRE ON A NEOSIO 17 -146-10 4.7k 111-1287 Fig.4: the circuit includes a voltage doubler (ICla, D1, D2, Cl and C2), a gate driver (Q2), a switchmode oscillator (IClb) and a voltage comparator (IClc) for output voltage regulation. gate driver and a voltage comparator for output voltage regulation. It uses one quad op amp integrated circuit (ie, four operational amplifiers in the one IC package), two NPN transistors, and one field effect power transistor. The voltage doubler comprises op amp ICla, diodes Dl and D2, Cl, C2 and associated components. ICla is connected as a Schmitt trigger oscillator. This works as follows: Initially, pin 6 of ICla is low and pin 7, the output, is high. This causes the 470pF capacitor at the pin 6 input to charge via the 47k0 feedback resistor. This continues until the voltage reaches the positive threshold of the Schmitt trigger, at which point the output goes low. The capacitor then discharges via the 4 7k0 resistor until the voltage reaches the negative threshold of the non-inverting input when the output goes high again. Thus ICla is an oscillator operating at about 40kHz. The square wave output is fed to a diode pump circuit consisting of Cl, D1, D2 and C2. Initially, when 30 SILICON CHIP the output of ICla is low, capacitor Cl is charged via Dl to 24V. C2 is also charged to 24V via Dl and D2. When the output of ICla goes high to about 24V, the positive side of Cl (ie, the junction of Dl and D2) is jacked up to 48V and so Cl 's charge is transferred to C2. When ICla again goes low, Cl is again charged via Dl and the cycle starts again. The voltage developed across C2 is limited to 39 volts by zener diode D3. This is fed to the gate driver stage Ql and Q2. ICl b drives the base of QZ via a 2.2kQ resistor. When the output of IClb is low, QZ is off and Ql is switched on by virtue of the resistor between its base and collector. Ql applies about 39V to the gate of Q3 and turns it on. When the output of ICl b goes high, QZ is switched on which turns off Ql and also Q3, the main switching transistor. As Q3 turns off, the inductor L1 tends to maintain its current flow and pulls the source negative. However DB clamps the source at about minus 0.7V. D6 is included to speed up the turn-off of Q3 , by ac- Close-up view of FET Q3 (left) and diode D8. See Fig.6 for mounting details. tively pulling the gate down towards OV. D7 is included to prevent the gate-source capacitance from being charged to a large negative value and thereby indirectly improves the turn-on time of Q3. Inductor Ll , a 680µ,H toroidal choke, and two 2200µ,F capacitors connected in parallel filter the square wave output of Q3 to produce smooth DC. A small load resistor of 4. 7k0 is there to discharge the capacitors if no load is connected at the time power is turned off. The 0.47 µF capacitor improves the filtering at high frequencies. A 5-amp fuse protects the output against overloads and short circuits, while a 5A in-line fuse provides protection in the case of a circuit fault. I I \ \ Voltage regulation ICl b is another Schmitt trigger oscillator (similar to ICla) with a pulse output at 20kHz. Its trigger level is modulated by the voltage comparator IClc to give voltage regulation. IClc does this by comparing the averaged output voltage from L1 with a 13.6V reference at its non-inverting input, pin 13. If the output voltage at 11 is lower than the reference voltage, the output of IClc goes low and pulls down the voltage at pin 10 of IClb. Thus the duty cycle of IClb changes so that its positive pulses are shorter. This means that Q2 is turned on for shorter periods of time and this increases the averaged output from Q3 and 11. Conversely, if the output voltage is higher than the reference voltage, the output of IClc raises the voltage at pin 10 of IClb. This makes the positive pulses from ICl b longer, turns on Q2 for longer periods of time, and thus decreases the averaged output voltage from Q3 and 11. The 0.0OlµF capacitor between pins 12 and 13 of IClc provides filtering for the error voltage (ie, the difference between the converter output and the 13.6V reference voltage). The capacitor also enables the converter to start reliably when power is first applied. ICl b oscillates at about 20kHz. This is high enough to prevent the switching of Q3 from becoming audible but not so high that switching losses become excessive. The 24V supply to the drain of Q3 is decoupled with lO00µF and 0.47µF capacitors. The supply to the remainder of the circuit is decoupled with a 470 resistor and lO0µF capacitor and protected against voltage spikes by a 30V zener diode. Note that the 24V supply is permanently connected to Q3 while the OUTPUT CONNECTED TO EARTH LU ON OUTSIDE OF CASE 5A FUSE FROM BATTE IN-LINE F FROM ACCESSORY IGNITION SWITCH 09 ! Fig.5: parts placement and wiring diagram for the converter. Use mica washers and insulating bushes to isolate Q3 and DB from the chassis. rest of the circuitry is connected to the ignition or accessory switch. This avoids the necessity for a heavy duty on/off switch. One point should be made before we complete the circuit description and that is to tell you what happened to the fourth op amp. After all, ICl is a four op amp package. The fourth op amp, associated with pins 1, 2 and 3 of the T1074, is not used and is therefore not shown on the circuit. Pins 2 and 3, the op amp inputs, are connected to the 0V line and so the op amp latches up (ie, its output goes high, to almost the + 24V supply). Construction Our prototype 24V to 12V converter was built into a folded aluminium case measuring 100 x 58 INSULATING BUSH ~ t \ ~ MICA WASHER iI SCREW HEATSINK (REAR OF CASE) NUT 10220 DEVICE Fig.6: mounting details for transistor Q3 and diode D8. x 45mm. The circuit components are mounted on a printed circuit board coded SCl 11-1287 and measuring 100 x 55mm. Start construction by installing all the low profile components on the PCB as shown in Fig.5. These include the IC, resistors and diodes (but not DB). The capacitors and transistors can then be installed. Q3 and DB should be installed with their leads about 10mm long so that they can be later bolted to the side of the metal case. The inductor, 11, is wound on a Neosid powdered iron core toroid, type 17-146-10. This requires 64 turns of 1mm enamelled copper wire, evenly wound around the toroid. Strip the enamel off the two ends of the winding before mounting the toroid on the PCB. The toroid is secured using three Ushaped tinned copper wire links as shown on the wiring diagram (Fig.5). The PCB is supported in the case using plastic standoffs. You will have to mark out and drill the necessary holes for these, along with holes for the cable entry, fuse holder, earth lug mounting screw, and the mounting screws for Q3 and DB. Deburr all holes using an oversize drill bit. Take extra care to ensure that the mounting surfaces for Q3 and DB are smooth and free DECEMBER1987 31 The circuit is housed in a compact folded aluminium case. Install grommets at external wiring points. 0 ...... 00 N """ I ........""" (.) en Oo Fig. 7: here is the full-size artwork for the PC pattern. of metal swarf. Q3 and D8 are bolted to the side of the case using TO-220 mounting kits - ie, mica washers, insulating bushes and screws and nuts. Fig.6 shows the details. Smear the mating surfaces on the devices and the case with heatsink compound prior to installation. Finally, use your multimeter to check that the metal tab of each device is indeed electrically isolated from chassis. If you do find a short, it should be corrected immediately. Once the unit has been completely assembled, it is ready for testing. Connect a 24V supply and check that the output is at about 13.6V. If the voltage is higher than this check 32 SILICON CHIP the voltage between ground and the anode of D4. This voltage should be the same as the output voltage. If necessary, the output voltage can be reduced by 0.6V by shorting out D5. Troubleshooting Double, double, toil and trouble; fire burn and cauldron bubble. Perish the thought but it is possible that your converter may not work when you turn it on. Don't panic though, it is fairly easy to get it going if it should malfunction. The hardest part about troubleshooting is poking the prods from your multimeter or oscilloscope into the case and onto the components, since it is so tightly packed. To make it easier in this respect, you may wish to remove the fuseholder temporarily, to give better access to the case. Wrap some insulation tape around the fuseholder terminals though, to prevent the possibility of shorts. The first step in troubleshooting is to check that the supply voltage is being fed to the circuit. With 24V applied to the two input cables, check that this voltage appears across D9, the 30V zener, the drain of Q3 and pin 4 of the IC. If the 47Q resistor feeding D9 cooks as soon as you connect the supply it is likely that you have connected the supply leads the wrong way around or D9 is reverse-connected into circuit. Now check that ICla is functioning. The easiest way to do this is to measure the voltage across zener diode D3. This should be close to 39V. If this voltage is not present, check the orientation of diodes Dl, D2 and D3. If they're OK, check that ICla is oscillating. This is easy to do if you have an oscilloscope. If ICla is oscillating, a 40kHz square wave with an amplitude of 24 volts peak will be present at pin 7. If you don't have an oscilloscope, you can check the DC voltage present at pin 7. It should be close to half the supply voltage . Similarly, the voltage at pins 8, 9, 10, 12, 13 and 14 should also be at close to half the supply voltage, if the other two op amps are functioning properly. If after all those checks the unit is still not delivering correct output, it is possible that Ql, Q2, D6 or D7 is at fault. Try shorting the base and emitter of Q2. This will turn off Q2 which will let Ql turn on continuously. This should apply about 37V to the gate of Q3, allowing it turn on completely and feed the full 24V to the output. If that does not happen, it is possible that Q2 is shorted. Note: disconnect the two 2200µF 16VW capacitors for this test. On the other hand, if the output of Q3 is continuously high, it ·is possible that D6 is open circuit or round the wrong way, or Q2 is open circuit. It is highly unlikely that Q3, the most rugged semiconductor in the circuit, is damaged. Infrared Movement Detector By BRANCO JUSTIC ley E·lectronics In this article, we show you how to build a passive infrared movement detector (PIR) with performance equivalent to that of expensive commercial units. The unit is very easy to build and can be used to monitor large areas such as rooms and entrances. Alternatively, when fitted with the optional narrow angle lens, it can be used for property perimeter protection or as a shop entry detector. Until fairly recently, passive infrared (PIR) movement detectors have been fairly expensive devices, due mainly to the cost of the pyroelectric sensors. That situation no longer prevails. With the development of low cost sensors and plastic lenses, the price of PIR detectors has dropped in recent years so that they are now an attractive and economical proposition for use in domestic alarm systems. In fact, a PIR detector is now virtually a must for any home burglar alarm system. This type of detector has excellent sensitivity and has a lower incidence of false alarms than ultrasonic detectors. In addition, they are easy to install and adjust. You can build this high-performance passive infrared movement detector for just $60. The PIR detector described here features a high-quality dualelement fresnel lens and filter combination that offers superior performance to single element types. The unit can either be used to trigger a central alarm system or, by increasing the triggered on time, as a self-contained alarm system. The useful range of the unit varies according to the lens fitted. The prototype wide angle unit produced a useful range of more than 10 metres, while fitting the narrow angle lens resulted in a useful range of more than 25 metres. The pyroelectric sensor At the heart of our PIR is a pyroelectric sensor which is sensitive to body heat in the range 8-10µ,m (micrometres). A pyroelectric sensor generally combines a filter, a heat-sensitive crystal, and a FET buffer stage in one package. An external filter is also often used Here is a view of the assembled printed circuit board. The wide-angle lens assembly is installed over the pyroelectric sensor at mid-left. DECEMBER 1987 33 D 2 (a) NARROW ANGLE LENS - SAME PLAN ANO SIDE VIEW ~00"•~ ~ • Wm SIDE VIEW (b) WIDE ANGLE LENS - ASSUMES 2 METRE HEIGHT ANO APPROXIMATELY 15• TILT Fig. 2 Fig.2: these diagrams show the behaviour of the narrow angle lens at (a) and the wide-angle lens at (b). With the wide angle lens, a range of up to 20-metres can be expected. to help filter out wavelengths outside the range of interest. This external filter generally consists of a white-coloured plastic sheet. Although this is almost opaque to visible light, it is transparent to wavelengths associated with BAND-PASS FILTER {WINDOW) ~ "CRYSTALS"(LiTa0 3) Fig. 1 THE INTERNALS OF A PYROELECTRIC DETECTOR 34 SILICON CHIP unit insensitive to the presence and movement of human beings in a room, which is why a lens system is needed to make the unit work. If we focus the output of a multiple lens system on the pyroelectric unit; a signal is produced when more heat falls on one of the elements than the other. A person walking across the area scanned by a multiple lens system will thus produce a voltage across one of the elements and a voltage of opposite polarity across the other. The differential voltage produced by a dual element sensor is therefore twice that produced by a single element sensor. In summary, a dual element sensor rejects heat which is common to both sensors (the common-mode signal) and produces a differential output when a person enters the capture area, due to the fresnel lens system. Fig.2 shows the behaviour of the two alternative lenses available with this project. body heat. The external filter used in our unit is actually combined with the fresnel lens. Fig.1 illustrates the internal circuitry of the pyroelectric sensor used in this project. Note that two heat sensitive lithium titanate elements (LiTaO 3) are used and these are wired so that their outputs oppose each other. This means that light which is common to both elements produces very little output (theoretically zero), a feature that makes the unit insensitive to normal heat which is distributed across large areas, such as in a room. It also makes the How it works Fig.3 shows the complete circuit diagram for the PIR Detector. Here's how it works. The infrared energy is focussed on the pyroelectric sensor (ICl) by the fresnel lens. The FET inside ICl is connected as a source follower with its output coupled via C2 to the input of non-inverting amplifier stage IC2. This stage has a voltage gain of 471 and a bandwidth of approximately 7Hz. R7 and C5 set the high frequency response while R6 and C4 roll off the response below about 0.75Hz. R3, R4 and R5 bias the pin 3 input to about 1.7V. The output of IC2 is coupled via C6 and RB to pin 2 of IC3. This is an inverting amplifier stage with a voltage gain of 100 (40dB) and a bandwidth of approximately 16Hz. From there, the signal is fed via R12 to a detector circuit consisting of Dl, R13 and Cl0. This produces a DC voltage which is directly proportional to the AC voltage produced by the pyroelectric sensor. This DC voltage is then applied to the noninverting (pin 3) input of comparator stage IC4. Trimpot VRl R1 1k r-----'tWr-------+------+------+-------+-------+-----+----A CB .01 FRESNEL ( },. LENS + 1.4V VR1 4.7k R2 47k R5 4.7M C10 R13 1M 0.1 R21 4.7k +5V C14 + 7BL05 100+ 1NOour GND R16 1M B EOc VIEWED FROM BELOW R15 220k _ __ R17 1M _ _____,..__ _ _....__ _ _ _ _ _ _ _ _ _ _ _ _____,..__ _ _ _--<1GND .,. PASSIVE INFRARED MOVEMENT DETECTOR 31-1287 Fig.3: the output from the pyroelectric sensor (IC1) is amplified by IC2 and IC3, detected by D1 and applied to comparator IC4. IC4 drives comparator IC5 which turns on Qt and the relay. (sensitivity) sets the comparator threshold voltage on IC4's inverfing input. When the detector output exceeds the comparator threshold, the output of IC4 switches high and quickly charges Cl 2 via DZ and R14. When this happens, pin 6 of comparator stage IC5 also switches high and turns on transistor Ql. Ql in turn drives the relay and a LED indicator circuit (R18 and LED 1). Diode D3 protects Ql against the back-EMF generated by the relay coil when the relay turns off. R15 and C12 sets the time constant on pin 3 of IC5 to one second. This makes the unit continually retrigger while ever there is movement within the area scanned by the sensor. If required, the time constant can be increased (by increasing the value of R15) , to make the unit function as a free-standing alarm. The relay output can either be used to trigger the central alarm console or, when the long time constant is employed, to switch on an external siren circuit. Construction A complete kit of parts for this project is available from Oatley Electronics [see parts list). All the parts, except for the LED, are mounted on a small printed circuit board measuring 61 x 114mm. The wide-angle lens assembly is made from blank PCB material and tin plate and is soldered to four large PC stakes at one end of the board. Install the parts on the PCB as shown in Fig.4, with particular attention paid to the orientation of the transistors, diodes, electrolytic capacitors and ICs . IC sockets were fitted to the prototype, but these are optional. The relay, trimpot and the pyroelectric sensor are best left till last. Mount the sensor flush against the PCB with its metal tab oriented as shown in the wiring diagram (Fig.4). Now the wide-angle lens as sembly can be made. Fig.5 shows the dimensions of the top and side pieces (note: the drawings are not DECEMBER1987 35 Altronics Will Deliver Any Of These Quality Products To Your Door Faster Than An Other Australian Su lier (Within 24 Hours To Every Capital City and Suburbs - Allow Addltonal 24 - 48 Hours For Country Areas) 1111111111 IIIIIHIIIII IIIIII IIIU 111111111 llllll lllllllllllllllllllllllllllll 11111111111111111111111111 IIU Ill II111111111111111 II IIIIIIIIIIIIII IIIIIIIIIIIIIIIIII IIIIIIIIIII111111111111111 es Operate■ From 12V Car Battery Massive 600 Watt Inverter Operatea from 12 or 24 Volt IyItemI via Internal wiring connection ■ Thermal Over Load. Current Regulated. Current Overload Big brother to our 300W Model this brilliant design can be internally connected for either 12 or 24Voperation . Full SOO watt output - and that will power a fantastic array of appliances e.g . Lighting , Electric Motors , Electric drills, Hi Fi , TV Sets, Computer. K 6752 K 6754 An ab ■olute muIt for HouH Power or for the Truck, Tractor etc. K 6770 Complete Kit Full Built & Tested . $399.oo $499.oo FHture■ : New Model /RD Has Fantastic Range With Two Mode Lens Our Price $99ea 10 or More $90ea Complete Kit Fully Built & Tested ...1 • Lens simply ' snaps' to either wide angle (range 40 feet) tor normal use or Normal angle (range 80 feet plus) for corridor applications . • Snazzy integral mounting bracket allows corner 90 deg . mounting as well as normal surface mount.(This is a fantastic feature as these work best in corners and are visually unobtrusive) • 12V DC Powered • Built•in test lamp • Alarm output SPOT 30V 1a Why Pay $150orMore tYf 1GHz Digital Frequency Meter! Counter Kit (See Silicon Chip Mag. Nov 1987 tor Details) j ~u~e~o;~~a~~~~i~~s · Silicon Chip for this Great Australian Design . $4 ,,..,;,,;,.:;:.- The Technical excellence of this counter th ~i~1~5,~t,;'~:,t's ~ees~:~~ipa~~~\d,;a':.de~ er Erase your EPROMS quick ly and safely This unit is a cost effective solution to your problems . It will erase up K 2515 Due M Id Dec' to_9 x 24 pin dev_ices in complete safety in about 40 minutes for 9 chips (less tor less chips) . . Super Bargain 1/2 Price • N • I G Fan tas tIC egat1ve on enerator $ 299 There have been volumes written about the benefits of negative ions combating air pollution, cigarette smoke etc. can be very beneficial to Asthma sutterars. Our great little Rover generates billions of ions per second! Includes tester. 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Features: • Separate audio alerts tor X and K Band . • Three operational switches: Power: On and Off: RSD (Radar Signal Discriminator) to minimize extraneous signals with a LO (local) positon and a LA (Long Range ) position : FIiter Mode designed tor instant computerized anal ysis of incoming signals with LO and LA positions. Invisible from outside your car. The Vector simply clips onto your sun visor. Thus the Gendames and would be villains are non the wiser. S 5301 - , Just think how handy it would be to have 240 Volt AC Mains Power when camping or tor your boat or Caravan . Auto Start draws power from your battery only when appliance is plugged in and " turned on". i.e. battery can be left permanently connected it desired . Heart disease strikes down many people in their early 40's (or even 30's). 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SPECIFICATIONS: Screen Front Controls Rear Controls Bottom Controls Input Impedance Bandwidth Resolution lnpuVOutput Connector Input D 1115 P 0995 •1 AC VOLTS Ranges- RMS 0-3 . 12, 1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 Holds 12 magazines, each on a spring out wire rod. Just the shot for each years set of EA's ETl's or any of your favourite magazines. Cat. B 9999 I t Going Up Next Shipment Australias Greatest Nicad Bargain $3.50 $2.95 $2.45 # $12.50 Voltage 24 V DC Current 330mA Speed 3100 RPM Air Flow 23 C.F.M. Noise Level 32dbA .__. 10-99 100up $32.50 All you do is clip the unit across the DC fuse holder (fuse removed), dial up the requir~d current (max. 10A) and if the circuit draws , more than this then the circuit "trips" or opens. Thus power is removed from the device. Features: Fast blow - slow blow setting • Manual reset button • LED fuse tripped indicator• Operates off 1 single 9V battery (not supplied) • Two current ranges0-1A & ' 0-10A • Any current setting available up to 10A • Current Settings easily adjustable via. a pot and calibrated scale.• Housed in a rugged Jiffy Box . A Must for prototyping and service work. No Electronic workshop should be without were amazed at the performance of this very compact system. n The Electroni $29.50 C 9050 Very simple to connect and operate - New Technology has enabled very compact overall dimensions (master unit only 180 x 100 x 65) hence ideal for concealing amoung book shelves etc. You Need Simply Brilliant Mylar Stereo headset and Dynamic Mic combination. Phones 30-18KHz 28 Ohms, 6.5mm stereo Jack Max. input 400mm Mlc. 84db , 600 Ohms, 6.5mm Mono Jack $229 Green Phosphor - Non glare 14 Po wer On/ Off , Contrast, Brightness Vertical size, vertical hold . Horizontal hold, horizontal position. 75 Ohm/ 10K switch selectable 18MHz 900 lines at centre screen RCA Composite Video 1V P-P This Month $199 -. , This view shows the lens supporting assembly, prior to installation of the fresnel lens. Be sure to install the lens the right way up (see Fig.2). '~if ' . --" ~ .=.__.....;__ _ 1!j + - "- Fig.4: parts layout for the PCB. The pyroelectric sensor (ICl} is mounted flush against the board. The wide-angle lens assembly covers the pyroelectric sensor and is soldered to four PC stakes. PARTS LIST 1 1 1 1 1 1 printed circuit board SPST 1 2V relay fresnel lens (see text) 4-way terminal block 4 7kQ horizontal trimpot aluminium case (70 x 40 x 130mm) 1 sheet of tin plate (1 00 x 30mm) 1 sheet of single-sided PCB (50 x 100mm) 6 PC stakes (4 large , 2 small) Resistors 5%, 0.25W) 4 x 4.7MQ, 6 x 1 MQ , 1 x 220kQ, 1 . x 47kQ, 2 x 10kQ, 1 X 4 . 7kQ, 1 x 2.2k0, 5 x 1 kQ Semiconductors Miscellaneous 1 RPY97 dual element pyroelectric detector 1 78L05 5V regulator IC 4 TL071 op amps 1 BC337 NPN transistor 2 1 N41 48 silicon diodes 1 1 N4004 silicori diode 1 5mm red LED Hookup wire , machine screws and nuts , mounting brackets Capacitors 2 1 00µF 16VW PC electrolytic 4 22µF 16VW low-leakage PC electrolytics 38 1 4. 7 µF 16VW low-leakage PC electrolytic 3 0 .1 µF monolythics 2 0.01 µF metallised polyester 1 0.0047µF metallised polyester SILICON CHIP Where to buy the parts: a complete kit of parts for this project is available from Oatley Electronics, 5 Lansdowne Pde (PO Box 89), Oatley, NSW 2223. Telephone (02) 579 4985. Prices are $57.95 for the wide-angle version, and $53.95 for the narrowangle version. Add $2.00 for pack and post. actual size). These can be cut to shape using a pair of tin snips and finished with a file. The lens unit can now be assembled by first tack-soldering the various pieces together. Make any adjustments that may be necessary, then run a fillet of solder along each of the internal corners. Finally, the plastic lens can be installed through the rear of the unit and glued in position. This is not a difficult procedure, as the lens is simply a flat sheet of plastic and will automatically assume the correct shape when correctly positioned. Note that the smooth side of the lens faces outwards. Push the lens in so that it is 1-2mm from the front of the assembly and secure it by applying super-glue along the joints. Avoid spreading the glue across the lens face, as this will alter its characteristics. The completed lens assembly can now be soldered to the PC stakes. matching cutout in the lid. Note that both the wide and narrow angle lenses have a focal length of 30mm. You don't have to worry about this if you are using the wide angle lens, since the correct focal length is automatically set by the lens assembly. If the narrow angle lens is used, you will have to carefully adjust the height of the PCB in the case so that the lens is 30mm above the surface of the sensor (ie, the board should be stood of the base by about 5mm). 30mm R 7 2 OFF SINGLE SIDED PCB ...__---+--~7T i------50mm------i l Testing This is the long-range version, fitted with the narrow-angle lens. Check that the lens is the right way up (see Fig.2) and that there is sufficient clearance around the corner mounting holes. The narrow angle lens doesn't require a supporting assembly. Instead, the lens is simply glued to a circular cutout in the lid of the case, directly over the pyroelectric sensor. A simple folded aluminium case measuring 70 x 40 x 130mm is used to house the circuit board. For the wide-angle version, the PCB should be mounted about 12mm above the base, so that the entire surface of the fresnel lens protrudes through a Nova-15 loudspeakers the impedance drop below 7 ohms and at its maximum the value was just above 17 ohms at two points in the frequency range, around 80Hz and 2kHz. This impedance characteristic means that the Nova 15s are very tractable speakers, able to be driven without problems by virtually any amplifier. Listening tests with a sine wave generator indicated that the Nova 15s were quite smooth across the whole frequency range. We noticed some prominence in the region of 4kHz and l0kHz and a slight colouration in the region of 2 to 3kHz. In the bass region, the response · is well maintained down to lO0Hz Double check the locations of all the components, then apply power to the unit. Note that several minutes of settling time are required after applying power due to some of the long time constants used in the circuit. This does not cause any real problems since, in an actual alarm installation, the unit will have power applied to it continuously. To test the unit, set trimpot VRl to about two-thirds travel (starting from the maximum anticlockwise position) and mount the unit about two metres above ground level (see Fig.2). Assumimg that the unit has an approximate 15° tilt, a range of about 10 metres should be possible. Note, however, that passive infrared detectors are much more sensitive to movements across their beams than along their beams. The voltages shown on the circuit ctd from page 17 or so, with useable output available down to about 70Hz. Below that, if the speaker is driven hard, there is a tendency to "frequency double". The latter effect means that there is more apparent bass than there really should be. On music, the Nova 15s could be described as "forward sounding" and giving some prominence to brass instruments. Overall they have a bright sound quality with good bass and clean treble. For listening on classical music though, we preferred to use a judicious amount of treble cut, so that the high end was toned down just a little. !-----2-0-FF-TI-NP-LA_TE_ _ _.J ,-~---45mm----...J~ Fig.5: the wide-angle lens assembly is made from tinplate and blank PCB material. diagram were measured in a still large room, with the sensitivity control at the two-thirds setting. The quiescent current ·was BmA from a 12V DC supply. Finally, the two-thirds sensitivity setting was found to produce reliable operation in a fairly large room. As a general rule, advance the sensitivity control only as high as it needs to be for reliable triggering. And remember, it is whole body movement we are trying to detect, not just hand movement. ~ Where the Nova 15s really score is with their efficiency which is well above the average. They can be driven to good sound levels with quite modest amplifiers which may be rated as low as 10 watts per channel. This means that they are a good match for modestly powered amplifiers and stereo receivers although Tandy state that they are suitable for amplifiers with output powers of up to 60 watts per channel. Tandy's current price on the Nova 15s is $169 each which makes them very keenly priced as they are. However, we understand that for the month of December they will be two for the price of one. At that price, they are a real bargain. ~ DECEMBER1987 39 Aussat link highlights 1987 Jamboree of the Air Amateurs make historic radio link via satellite This year's Jamboree of the Air had a special highlight. Amateur radio operators in Sydney were able to talk to those in Perth via their 2-metre repeaters. This would normally be impossible but Aussat supplied a link via satellite to enable this historic link-up. By ROSS TESTER, VK2KRT Amateur radio operators in Sydney and Perth couldn't believe their ears. VK6 stations by the score were coming up on Sydney's Manly-Warringah Repeater VK2RMB while over in Perth VK2's were thronging in on their repeater VK6RTH. For a while, most operators weren't too sure what was happening. "What an Opening!" was heard more than once. ("Openings" are changes in the ionosphere which permit long distance communication). Openings have occurred, very rarely, to permit Sydney stations to communicate with New Zealand, Southern Queensland, Victoria, even South Australia. But an opening to Perth would be considered an event to eclipse the bicentennial itself! Incidentally , the Australian QSL card from Ross Tester, VK2KRT for the first ever hand-held 2-metre contact across Australia via satellite. Ross was at Narraheen Beach on the east coast. 40 SILICON CHIP record for two metres is held between VK4ZSH (Queensland) and JA7OXL (Japan) - a distance of 6617km. Back to Australia: as more and more operators joined the "pile-up" on two metres, the truth began to emerge. And the truth was even more of an event than a crosscountry opening. The link between Sydney and Perth was actually occuring over a distance of some 72,000km - via one of the Aussat satellites! Very quietly (until amateurs found out about it, that is) amateur communications history was being made in Australia and, probably, the world. It ' s not the first time that amateur radio has gone into space. Amateurs have, on quite a few occasions, launched their own satellite repeaters as "piggy back" payloads on commercial launches. And amateurs the world over remember the Space Shuttle amateur, Dr Owen Garriot, who took along his radio a couple of years back. To the best of our knowledge though, the linking of VKZRMB and VK6RTH via a commercial communications satellite is a world first. And because of the outstanding success of the operation, it certainly won't be the last. The link was first made for a short period on Monday, October 12th. It was made again on Tuesday 13th and left active for "testing" almost continuously until the JOT A weekend of 17th and 18th October. The link was finally removed early on Monday 19th. How it happened Several of the staff at the Aussat Earth Station at Belrose (Sydney) were musing over their morning "cuppa" about JOTA: the international Scout, Guide, Brownie and Venturer's "Jamboree of the Air". JOTA is held each year, on every continent, and Scouts talk to other Scouts both within their own countries and around the world. The various scouting associations have their own amateur licences but thousands of non-Scouting amateurs lend both their stations and their time to assist the Scouts for the two days of JOT A. As you might expect, all the amateur bands are pretty active during the JOT A weekend. There are many more Scouts than stations. Given the vagaries of amateur radio, conditions cannot be guaranteed and communication is sometimes difficult. Naturally, international contacts are considered the "prize" of JOT A but equally important are the contacts between scouts in various parts of the country. Local area repeaters are also in heavy demand but their range is limited to around 100km or so. The Aussat staff had a brainwave: why not see if a Sydney repeater could be linked to the Aussat Earth Station and fed via satellite to another repeater on the other side of Australia? Scouts would get contacts previously only possible on HF and then only with great difficulty. Like many brainwaves, execution proved to be a little more difficult. But with credit to Aussat staff in Sydney and Perth, officials of the radio clubs, the Wireless Institute of Australia (WIA) and the JOT A organisers of the Scouting Association, it started happening. PERTH WESTERN AUSTRALIA ZONE 29 CONFIRM QSL S ,r - DATE GMT MHZ 2 WAY AST 73s HAAI Ql-lc s PSE L ._. Arthur J. Brean 28 Bennion St., Trigg. W.A. 602q Western Australia. From the other side of the continent - the QSL card from Arthur Brean, VK6SY, Trigg, Western Australia. Arthur was just two hundred metres from the Indian Ocean. being line-of-sight to the Belrose Earth Station at just a few hundred metres away across a gully and a couple of ridges. The Manly Warringah Radio Society agreed to have their repeater " hijacked " for the weekend of JOTA. The West Australian Repeater Group were equally as enthusiastic about having their Channel 4 repeater at Herne Hill linked to the Aussat Earth Station at Lockridge in Perth. Then came the Department of Communications. Of course, Aussat holds licences for its satellite services but could they link to the Amateur Service? Finally, approval came through from a new Department: DOC had been merged with the Department of Transport in the meantime and DOT AC finally gave the OK. In the middle of all this negotiation, of course, came the launch of Aussat 3 in August. Needless to say, this was considered a pretty significant event at Aussat, and staff time to work on the "freebie" project was simply non-existent. Then came the logistics First and foremost were the "powers that be" at Aussat. Could they justify giving free satellite time in what is, after all, an extremely expensive business? "Yes. It's great public relations!" Second came the question to the Scouting Association: did they really want such a link? Did they what! And of course, the 2-metre amateur repeaters to be used: the Manly-Warringah repeater (VK2RMB) was a natural choice, Aussats 1 and 2 were launched aboard US Space Shuttles. The Shuttle should go into space again about the middle of next year. DECEMBER1987 41 After the extremely successful launch of Aussat 3 on top of an Ariane rocket from French Guyana, organiser Laurence Adney (VK2ZLA) at Belrose Earth Station was able to devote some time to the JOT A project. Technical Details With the project given official go ahead on all counts, the "nuts and bolts" had to be organised. First was the link from the repeater to Aussat. That was the easy part signal was taken straight off air from the respective repeaters, via a normal 2-metre transceiver (a Yaesu FT230R, loaned for the event by David Folkes, VK2XDF, was used at Belrose.) In perhaps one of the best examples of a "belt and braces" approach, an 8-element Yagi antenna was aimed direct at the Terrey Hills repeater from Aussat Belrose. There was no way it wasn't going to get signal! VK2ZLA also brought in his own 2-metre transceiver to use as a system monitor (talk about carrying coals to Newcastle!) - with one of the most expensive ground planes for his magna-base antenna ever seen (he "borrowed" one of the access doors from a multi-million dollar satellite transponder controller. Yes, it worked very well, thank you). Technical development at Aussat Satellite Frequencies Sydney Downlink .. Uplink .. . . . . Perth Downlink .. Uplink . .. ... 12,575.2825MHz 14,323.2825MHz 12,575.3725MHz 14,325.3725MHz 2-metre Frequencies Sydney, VK2RMB Transmit ... .. .. ... 146.275MHz Receive .... ....... 146.875MHz Dural, VK2WI Transmit .... .. ... ... 146.40MHz Receive ............. 147.00MHz Perth, VK6RTH Transmit ........... . 146.20MHz Receive ......... .... 146.80MHz 42 SILICON CHIP . .. ' ,. , . ~ . , Aussat 1 pictured in the Shuttle cargo bay prior to deployment in space. Australia's third domestic satellite, Aussat 3, was successfully launched by Ariane rocket last August. was carried out by another Aussat staff member, Bruce Boardman (VK2XDF). Bruce designed the interface unit which triggered from the "busy" indicator on the Yaesu FT-230 transceiver to switch the Aussat transponder control from transmit to receive. Unlike the repeaters, the Aussat transponder is designed to operate in a "VOX" mode - the controller had to be hard-wired to achieve what effectively became carrier control. Equipment at the Lockridge end was supplied and fitted by Will McGhie, VK6UU, with technical support by John Sherman and the Aussat staff. One unexpected problem which needed solving was the fact that, when installed, each repeater could be triggered by the " tail" of the other, effectively locking up the system. This was simply solved by including a one second delay in the triggering of the Perth repeater. "Aha!" amateurs all over Sydney are saying. " That's why we kept losing the first word or so if Perth amateurs were too quick on the PTT!" And because of the one second delay at the Perth end, amateurs in Sydney were able to tie up the system completely by not allowing the one second to tail out. "Aha!" amateurs in Perth a re saying. "That's why we couldn't get a word in edgeways when those VK2's were coming through loud and clear! " Of course, there were a few problems with the link itself. One occurred on Friday night when a carrier locked the Perth repeater on. While full remote control was built into the Perth end, Aussat Sydney simply disconnected the link while the Perth boys D-F'd the offender (ie, they used a direction-finder to locate the source of the carrier l. Apart from these minor aberrations though, the link was incredibly successful. Not just for JOT A but for the hundreds of Sydney and Perth amateurs who contacted each other during the unofficial " testing" period on Wednesday, Thursday and Friday. A measure of the success can be gleaned from the hour-meter attached to VK2RMB. On a repeater that would be lucky to see twenty hours use in a week, a single-48 hour period (Thursday/Friday) saw a staggering 38 of hours use! Amateurs on both sides of the continent were impressed, to say the least. Thousands of contacts were made - some very brief, just to make the log for QSL purposes; others much longer. Old friends, even long-lost members of families were re-united thanks to Aussat. Even some records are being claimed: Arthur Brean VK6SY and Ross Tester VK2KRT (the author) are claiming the first 2-metre handheld contact across Australia. VK6SY was just a couple of hundred metres from the Indian Ocean and VK2KRT was at Narrabeen Beach, on the Pacific Ocean. So they cheated - just a bit! One of the best stories to come out was from Michelle, VK2FJJ, who made a chance contact with another operator in Perth, only to find that the Perth amateur lived just a couple of doors from her son. Guess who saved some phone calls! Pity the poor pasties with those thousands of QSL cards. Australia Post will be thanking Aussat all the way to the bank! Satellite details This report would not be complete without details of the "bird" - if only to correct the misinformation being broadcast at the time about the link. The spacecraft used was Aussat 1, the first of the three Aussat satellites launched on August 27, scort 1985 by the US Space Shuttle, Discovery. Aussat 1 is in geostationary orbit some 36,000km above the equator at 160 degrees E. Aussat 1, like the other two Aussats, has 15 operational transponders, 4 x 30 watts and 11 x 12 watts. It is 2.2m in diameter, 6.6m high and weighs approximately 650kg. Expected service life of Aussat 1 is seven years. (The life of the satellite is basically the amount of hydrazine fuel left on board after launch. Satellites drift out of orbit and must be moved back - when the fuel runs out, that's it). All three satellites are controlled by the Belrose Earth Station but can also be controlled from Perth. The Sydney/Perth link used Transponder 13 (maximum output 12 watts). The Aussat earth stations are capable of immense power around 2000 watts - should the situation require it. On the Kuband, from 12 to 14 Gigahertz, rain and cloud can cause considerable signal loss and the power is adjusted accordingly if these condi- AL tions occur. On the JOT A link though such power was not required. In fact, the travelling wave tube amplifiers were barely idling. And next year? Because of the huge success of the link this year, Aussat may look kindly to doing a similar link next year. Similar, but not necessarily the same. Consideration is also being given to using Aussat's South West Pacific Beam to link Sydney and/or Perth to New Zealand (or perhaps even some of the island nations of the region such as Tonga, Fiji, Tahiti and so on). Linking to a foreign country opens up a whole new set of problems, both from a logistic point of view (do they have the infrastructure necessary?) and, of course, legally. Regardless of whether the Aussat link is ever made again, the JOT A stations and the thousands of amateurs who made use of it this time were grateful for the effort made by Aussat staff in allowing them to be a part of this small piece of communications history. ~ PERFOR C Reliable Test Instruments for the Electronics Enthusiast Pocket Size Robust Handhelds LCR Meter EDM-70H • 3½ digits LCD • 6 functions • DC V • AC V DC A • Ohms • Transistor Test • Diode Check $59 I~~~ V A n -+1-c EDM-728 • 3½ digits LCD • 8 functions • DC V • AC V • DC A • AC A • Ohms • Diode Check • Buzzer ••l) $82 I~~~ lll EDM-1111A EDM-1105A • • • • • 3½ digits LCD • 7 functions 0.8% Basic Accuracy • DC V AC V • DC A • AC A Ohms • Transistor Test Diode Check • Buzzer $96 ~1~ 1 DIVISION OF EHONA ENTERPRISES PTY LTD • • • • • • 3½ digits LCD • 9 functions 0.8% Basic Accuracy • DC V AC V • DC A • AC A Ohms • Transister Test Diode Check • Buzzer CAPACITANCE $113 ELC-120 • 3 ½ digits LCD • 1% Basic Accuracy • C: 200pF to 200uF (0.1 pF) • L: 2mH to 200H (1 uH) • 20Mo (0.010) ~1~ 1 $243 SALES SHOWROOM 86 Parramatta Road Phone (02) 519 3933 Camperdown 2050 FAX (02) 550 1378 ~1~ 1 , INTERSTATE DISTRIBUTORS VIC OLD WA Radio Parts Group, Melbourne. Phone 329 7888 Baltec Systems, Brisbane. Phone 369 5900 Hinco Engineering, Perth . Phone 381 4477 ACT SA ·rAS Electronic Components, Fyshwick. Phone 47 3688 lnt'I Communications Systems, Port Adelaide. Phone 47 3688 George Harvey Electronics, Hobart. Phone 34 2233 DECEMBER1987 43 Own An lnphone And Your Neighbours Wil Be Green With Envy /4 · Here's Why /i No Installation Costs Simply Plugs Into Your Phone Socket . • lnphone Is Great Around The // Its Completely Mobile The Go Anywhere Cordless In phone Factory or Building Site is not tied to the wall with wires - you simply take it where you want. Never again need you spend half the night crouched around the kitchen bench or draughty hallway with those long winded calls. • Use It B_y The Fireside rn Your Favourite Chair • Super Handy When Sunbakmg By The Pool INPHONE is quite simply the finest cordless phone available . No other cordless phone has the quality, security and the features at any where near an affordable price of INPHONE. AT HOME you can keep in touch around the swimming pool. (Please note the equipment is not waterproof) . In the garden . Under the car. While watching T.V. In the bathroom. In Bed. Or next door when you're playing cards or having a Barbecue with your Microphone neighbours. IN BUSINESS a busy executi ve can take the INPHONE around the factory, warehouse, showroom, sales yard or construction site or into the car park, and not miss a deal ! Also INPHONE is ideal for use in restaurants. IN SPORT on the field or track , the gym, around the swimming pool, Lifesavers on the beach etc . Comprehensive 6 months . Warranty r, ,ant Performe PHOn :rilon FANTASTIC CHR MAS PRESENT Normally Great Value At $269 Exclusive Offer To Readers Of Silicon Chip Magazine This Month $199 - But You Must Mention This Advert · When Ordering We Regret This Special Offer May Not Be Available From Altronics Dealers Superb Eleco Wireless Microphone System uses Du · ersit_y R~ceivers for Lo ange, Now Available In Australia For Less Than $1,000 Altronics proudly release the Eleco System - Used Worldwide by Entertainers i.e. Rolling Stones, Dire Straites, Tina Turner and 1000's more! Superb '-"•=•ophOnP . HPprudu ho c_1n 1 pflre1 llll'I' w It" ill'yrr ·,nrl AKG ',41 ,· "0 E Ch Breathtaking performance without signal drop-out or noise interference. The Eleco Wireless Microphone System is virtually the ultimate in an Entertainers Microphone system (or for any roving microphone application for that matter!) All the annoying wireless microphone characteristics such as " drop out" , static and noise are completely eliminated by use of auto switching dual diversity receivers. The output of each receiver is continually monitored . with the strongest and clearest signal always selected. Dynamic Range exceeding 100 db is obtained by employment of a Patented special Parabola level compressor and Dynamic expander. The operating range Is a minimum of 50 metres (often this can be extended to 200 metres and more in normal circumstances). Several Frequencies are available to aleviate cross interference when two .or more systems are used in proximity. An't'n'"l,1 Brief Specifications Frequency 202.1 , 202.9, 203 .7 MHz (Please specify if you have a preference) Mlc Carrier Power 50mW (Max) Mlc Antenna built-in Dynamic Range over 100db S/N Ratio better than 90db Frequency Response 20Hz to 16KHz + or. 3db Mlc Battery 4 x AA cells Battery Life over 24 hours continuous operation . Receiver Sensitivity 12db/ micro volt for60db S/ N ratio Pre emphasis/De emphasis sous. Receiver output unbalanced 6.3mm phone jack and balanced 3 pin cannon type . Output Level (adjustable) Unbalanced 0-2.5V Balanced O t6 + or - .3V into 600 ohms. Receiver Power Supply 200 - 260VAC. (A) (B) (C) Dual Diversity Receiver $729.00 Entertainment Microphone (hand held type) Lavalier Type Microphone $349.00 $349.00 Please Note 3 different operating frequencies are available (you will need to specifically nominate desired frequency only if the equipment is being used in proxim;ty with other Eleco Systems on the 200MHz band. C 0111 C 0113 C0115 C 0121 C 0123 C 0125 C 0131 C 0133 C 0135 202.1MHz 202.9MHz 203.7MHz 202.1MHz 202.9MHz 203,7MHz 202.1MHz 202.9MHz 203.7MHz Dual Diversity Receiver Dual Diversity Receiver Dual Diversity Receiver Entertainment Microphone Entertainment Microphone Entertainment Microphone Lavalier Microphone Lavalier Microphone Lavalier Microphone $729 $729 $729 $349 $349 $349 $349 $349 $349 lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll ea nerprool Extension Weather Proof Speakers n System • Rugged extruded aluminium construction • Superb powdercoat industrial paint finish • Engineered in Australia • Excellent reproduction • Superior to imports - Yet just a fraction of the price! Altronics proudly announce the release of the superb Redford Weatherproof Speaker and Sound Column Range. Imagine a wide range speaker system which is highly directional and with efficiency approaching that of reflex horns! Redford is the solution for high quality sound reproduction outdoors. The Five Models to choose from "Fill the Bil l" from applications on boats to high grade paging and music entertainment installations. RUGGED EXTRUDED CONSTRUCTION These vibration free enclosures are constructed from die extruded heavy gauge aluminium and finished with incredibly durable industrial powdercoat enamel. The speaker ends are sealed via gaskets and tough moulded " LU RAN S" UV (esistant end caps. The end result is " Good Looks" together with assured rugged durability for the Australian environment. kcrs For Your Steri'o Great For The Back Patio,Swimming Pool, Games Room, Den, Pool Room Etc. Dimensions 260mm wide x 170mm high x 150mm D. (Mounting brackets are Included) Single dual doped cone driver 16 ohm impedance is employed to give a generally correct volume balance with main speakers - an added bonus is your amplifier load is kept to respectable limits!! Great for back patio, Den , Boat Deck etc . C 0938 C 0940 White Black $99ea $99ea $190 per Pair $190 per Pair Use 2 special dual doped cone drivers for those wanting a bit more umph! C 0943 C 0944 Black White $139ea $139ea $260 per pair $260 per pair EXCELLENT REPORDUCTION The drivers have been chosen for wide range.low distortion, mid range " presence" (essential for high grade vocal work) and high efficiency in general. Power Capacity for short term use, the drivers will safely handle 150% of rated power. Acoustic wadding is used to dampen Bass resonance. Weather Proof Construction and use of "Doped Cones" Foam plastic and cloth is sandwiched between Baffle and Front Grill to prevent water ingress. A first for Redlon/ is the use of a patented cone moisture repellant process for all models. , Using . a " Daped" . w,"d e range d. . gram · onented · nvers an di"Itte d with steel line transformer Output cable allows connection to 10W/ 5W/ 2.5W with 10 watt models 20W/ 10W/ 5W with 20 watt models and 40W/ 20W/ 10W with the 40 watt versions. ' C 0941 10W/100V line Black $119ea $220 per pair C 0942 10W/100V line White $119ea $220 per pair C 0945 20W/100V line Black $169ea $299 per pair C 0946 20W/100V line White $169ea $299 per pair C 0950 40W/100V line Black $225ea $399 per pair C 0955 40W/100V line White $225ea $399 per pair I ½ Build the Speedi-Watt This multi-purpose circuit can be used as a speed control for electric drills or fans, as a power controller for electric blankets or soldering irons, or as a table lamp dimmer. By LEO SIMPSON If you have a look around your home you will probably find a number of appliances which would benefit from a speed or power controller. We've listed a few above but we are sure that there are other equally useful applications for an economical circuit such as the one presented here. It is cheap, compact and, best of all, there is very little work in assembling it. As a bonus, it incorporates components for suppression of electromagnetic interference. We're talking about a partially assembled printed circuit module which is presently available from Jaycar Electronics stores at the low price of $9.95. You will need to add a knob , a mains cord, plug, socket and a suitable case. That's all there is to it. We'll show you how to complete the module and assemble it into a case. The whole thing should go together in about an hour. The resulting universal dimmer and speed control is suitable for lamps, fans or universal motor loads up to 500 wa tts or 2 amps at 240V AC. By universal motors, we mean AC motors with brushes such as used in electric drills, food mixers and sewing machines. The circuit module looks like this when the pot and three brass terminals are fitted. Ci~cuit details The circuit of the module is shown in Fig, 1. It is essentially a bog-standard light dimmer circuit using a phase-controlled Triac as the power control element. For those who have not come across a Triac before, it is a high power switching device developed by General Electric about 24 years ago. It is similar in function to a silicon controlled rectifier (SCR) or thyristor. In effect, an SCR is a bipolar switch which can operate on alternating currents up to 400Hz. Like a silicon controlled rectifier, it is nonconducting until it receives a trigger voltage between its gate and Al electrode. When that happens it switches into conduction and remains that way until the voltage reverses in polarity or the current dies away to zero. The difference between a Triac and an SCR is that whereas an SCR will only work with one voltage We mounted our module in this neat plastic case to make a handy speed control. The mains cords are anchored with cord-grip grommets . 46 SILICON CI-IIP 'Problems? TRIAC AC03F A2 ... and you don't have our 112 page catalogue ... R1 1k C4 .01 250VAC VR2 2M C3 .033 250VAC N--------------------------+--~ SPEEDI-WATT UNIVERSAL DIMMER 101-1287 Fig.1: the circuit is a standard light dimmer with components for RFI suppression and a snubber network included. polarity, the Triac will work with hoth. It can conduct on both halfcycles of an alternating current waveform. It can be made to control the AC power fed to a load merely by being made to conduct early or late in each successive AC halfcycle. Such a method of power control is referred to as "phase control" because the timing of the gate trigger pulses is varied with respect to the phase of the AC waveform. The device used to generate the trigger pulses is the Diac, also developed by General Electric at the same time as the Triac. A Diac is referred to as a breakover diode because it is non-conducting at all voltages up to its breakover point. When the breakover point is reached, it "breaks down" to the conducting state. It remains in this state until the voltage reverses in polari- <at> ty or the current dies away to zero. The Diac is used in conjunction with a capacitor to deliver a pulse of current to the gate of a Triac. Now look at the complete circuit of Fig. 1 which looks quite different from conventional transistor circuits. Note that it all works at 240V AC mains potential. In other words, the whole thing is potentially lethal if you touch any part of it while it is working. Don't worry, though - when it is correctly assembled it is completely safe, just like any commercial dimmer (which is exactly what it is). The Active lead connects to a single-pole switch and then to a 2.2k0 resistor which feeds two potentiometers which are both wired as variable resistors in parallel. VRl , the 500k0 pot, is the dimmer control. It feeds current to Cl, a 0.047/.lF 400V capacitor, and <at> you've got real problems! ARISTA ... your one-stop problem solver. Audio leads ... Batteries ... Chargers ... Battery holders ... Cables ... Car accessories ... CD accessories ... Converters ... "Cutec" ... Earphones .. . Fuses ... Headphones .. . Intercoms ... Knobs .. . Microphones and accessories ... Mixers ... Multimeters ... Plugs/Sockets, etc ... Plug adaptors ... Power packs and leads ... PA ... Disc and Tape care ... Security equipment ... Signal modifiers ... Solderless terminals ... Storage boxes ... Switches ... Telephone and TV accessories ... Tools and Technical aids .. . Video accessories ... Wiring accessories ... You name it and we're bound to have it ... Try us ... NOW! Get your catalogue ... it'II solve a whole lot of your problems! Just send $2 + 50c p&h and your return address to: <at> ARISTI\. ELECTRONICS PTY LTD Fig.2: wiring the Speedi-Watt is no problem at all. Just fit the mains cord and terminate the active, neutral and earth wires. PO BOX 191, LIOCOMBE, NSW 2141 DECEMBER1987 47 ,:.a'...case for a Universal Haatslnk Here's a good pro We've had these superb cases made especially for our new Economy Stereo Amp Kit (aee below). But they're SO good we thought we'd stock them as a normal line as well. Cad plated steel case with pre-puched front and rear panels (suits anythlngl), cover la grey crinkle finish, pre-slotted for heat dlaslpatlon. Magnlllcentl Size 370 X 70 X 135mm Cat H-2900 Universal hole pattern allows the mounting of virtually all 'power' type semiconductors. Ribbed walls and black anodised finish for maximum elflcleny. Cat H-3401 s349& l(k£l Bulld an amDllfler: aconomlcalfy! Here's a great first "big" project. When you've finished mucking around, build a~ ampllflerl Ifs not too difficult - our new Economy AmpHller Kit makes It a clnchl Kit Is "short form" - does not Include case (H-1900) or transformer (M-6672). Over SW per channel at <0.05% distortion, CD, tuner, disc and aux·1nput_!.~!._ s140 100W HF linear Ampllflar Designed for our HF Transceiver (K-6330) but also perfect for use with a huge range of QRP commercial gear, In the range of 3 to 15 watts output. Gives around 10 to 14dB gain so upto 100Woutput • could be obtained from a very modest Input. Cat K-6331 . .. s349 Radio Direction Finder Dick Smith's own FunWay Into Electronics Here's great value: the FunWay One Gift Box. All the components needed to build any of the projects In FunWay One ... and the book la Included tool Cat K ~ 2 8 0 5 •2&• i . .-,·. '' ·' 1/_·· ftNIWay Ona Pro)act Packs Two project packs to allow you to build any of the kits. Project Pack One allows you to build any of the first ten, Project Peck Two gives you the additional components to build any 'of the 20 kits (needs Peck One tool) l Incredibly reliable - yet very simple to build. The complete amplifier on one pcb - all you do la add a heatslnk, connect to power ... and gol Cat K-3440 · FunWay One: Project Pack One. Cat K-2800 •2295 1995 FunWay'lwo Ready for something more advanced? FunWay Two has another twenty projects to build - all on modern printed circuit boards. And we even teach you how to solder! cat K-2820 Over thirty great projects to build from all three FunWay books. And the books are lncludedl Over $120 worth of goodies crammed Into this value-packed box. CatK-2890 CALL DSXpress TOLL FREE ON (008)22 6610 For 24 hour despatch SYDNEY (02) AREA 888 2105 PTY LTD This is what it looks like when it's finished. The all-plastic construction ensures complete safety. to a second charging network consisting of a lOkO resistor and C2, a 0.047µF capacitor. When the voltage across C2 rises above about 30 volts (either polarity), the Diac breaks over and delivers a trigger pulse to the gate of the Triac. This causes the Triac to turn on and apply the full mains voltage to the load. Varying the setting of VRl alters the timing of the trigger pulses fed to the Triac and so alters the power level fed to the load. Rl and C3 form a snubber network across the Triac to protect it from back-EMF voltages generated by inductive loads each time the Triac turns off. 11, a 50µH choke, and C4, a O.OlµF 250VAC capacitor, form the interference suppression filter. These are essential components which are often not incorporated in domestic light dimmers. Wiring it up As supplied, the kit comes in a plastic bag with most of the components already installed and soldered onto the printed circuit board which measures 45 x 50mm. What you have to do is install the switchpot and the three brass terminals for the Active and Load wires. There are two Active input terminals, giving you the option of having the circuit switched or unswitched. Strictly speaking that means you only need two of the three brass terminals but we soldered all three in anyhow. Having soldered in the pot and PARTS LIST 1 universal dimmer module available from Jaycar ' Electronics 1 plastic utility box, with plastic lid, 130 x 68 x 43mm (Jaycar HB-6013 or equivalent) 1 knob 1 3-pin mains plug 1 3-pin mains line socket 1 metre of 3-core mains flex 2 cord-grip grommets 1 two-way insulated terminal block Miscellaneous Solder, superglue. terminals, you need to mount the whole assembly in a plastic case. We used a standard plastic utility case measuring 130 x 68 x 43mm (Jaycar Cat. No HB-6013). We fitted a 3-pin line socket to a short length of three-c.ore mains flex and a three-pin plug to another length of three-core flex. Both these flexes had the insulation stripped back at one end and then they were fed into opposite ends of the plastic case and anchored with cord-grip grommets. We then connected up the dimmer as shown in the wiring diagram, Fig.2. Note the two-way insulated terminal block used to terminate the earth and the neutral wires from the two mains flexes. The terminal block should not be anchored to the case but secured with a dab of Selleys Superglue. The idea is to avoid having any exposed metal work. Even the shaft and bush of the switchpot is made of nylon so that, by using a plastic case, the whole construction can be completely insulating and therefore safe. When you have completed the wiring, switch your multimeter to a low ohms range and check the continuity of the earth and neutral wires from the plug to the line socket. Check also that there is no resistance between Active, Neutral and Earth for both the line socket and plug. Now connect a table lamp and plug the dimmer into the mains. You should be able to smoothy control the lamp brightness over its whole range. With that accomplished, you can, if you wish, set the minimum brightness of the lamp by adjusting trimpot VR2. This is a trial and error process though and you should not make any adjustment to the circuit while the mains voltage is applied. ~ .1.~~.r..1;ia:.i;: RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel pu.b lished in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices 4-HOUR TURNAROUND SERVICE DECEMBER1987 49 BUILD AN AT-COlVIPXI'IHLE COlVIP R There's never been a better time to build your own IBM AT-compatible computer. Dick Smith Electronics now have a deluxe kit available with lots of options. By GREG SWAIN The DSE AT-compatible with Wordstar up and running on the screen. The monitor is Multitech's high resolution model. 50 SILICON CHIP A lot has happened to the PCcompatible market in the last few years. Take a look in just about any electronics or computer magazine these days and you'll see adverts for all sorts of computer hardware, a lot of it of Taiwanese manufacture and at prices undreamt of a few years ago. In addition to buying readyassembled hardware, you can now also buy literally dozens of PCcompatible motherboards and a host of plug-ins and peripherals ranging from floppy disc and hard disc drives to controller cards, power supplies, enhanced graphics adapter cards, and input/output (1/0) cards. The AT-compatible described in this article was assembled from boards and other hardware supplied by Dick Smith Electronics. As you'll see , the machine goes together quickly and easily at a very competitive price. Why should you assemble your own computer instead of buying a complete unit? There are several good reasons. First, you will learn a lot about computer hardware and how the computer is configured. Second, you can build the computer to match your requirements and your budget. And third, you will know how to expand and upgrade your system if the need arises later on. But perhaps the main incentive for assembling your own PC/AT { J "...,;., / t t J I. i J_ _f i l I l I I l I i ./ ! I l I J I . !' f' ! l l lI /I ! r r r r I ! l JI ! I I~ ( iillLU Everything you need to assemble an AT-compatible computer system. Clockwise from top: keyboard, case (with hinged lid), hard/floppy disc controller card, EGA card, 1/0 card, 20Mb hard disc drive, 1.2Mb floppy disc drive, power supply, motherboard (centre). compatible computer is that you can save lots of dollars. And by buying from a large organisation like Dick Smith Electronics, you can rest easy in the knowledge that if you get into trouble or need service in the future, it will be available. To get an idea of the ease of assembly of such a system, we decided to have a look at the system now being marketed by Dick Smith Electronics. We found the whole process an interesting one and on the whole quite straightforward although there were a number of hurdles to jump over before the unit would burst into song. Having read our account, any aspiring builder is sure to find the going much easier. The parts needed Before starting assembly, you have to decide how the computer is to be configured. There are quite a few options. For example, you can choose a minimum system configuration with just one 1.2Mb floppy disc drive, or you can specify two floppies or a mixture of floppy and hard disc drives. After that, you have to decide which disc controller board you require. You can also choose between two keyboards (either an 84-key unit or a 101-key unit) and four different I/O cards. Table 1 lists the various items you need to consider. Finally, there are a few basic items about which you have no choice. These include the motherboard, a 200W switchmode power supply and a case. In this article we '11 describe the assembly process for a system equipped with 512K of on-board RAM, one 1.2MB floppy disc drive. one 20Mb hard disc drive. a hard/floppy disc controller card, an EGA (Enhanced Graphics Adapter) card. and a serial/parallel 1/0 card. And, once the system is assembled, we'll show you how to configure it so that it boots up to the DOS prompt from the hard disc. Note, however, that other systems can be just as easily installed, with only minor variations in the assembly process. It's simply a matter of following the manuals supplied with the hardware. The motherboard The X1000 "Baby" AT Motherboard is literally the heart of the computer and is supplied completely preassembled. It features an 80286 microprocessor and can run at 6, 8, 10 or 12MHz (switch and software selectable). It also has eight 1/0 slots, hardware reset and keyboard lock connectors, a battery-backed CMOS memory to maintain system configuration, a real time clock and calendar. and provision for up to 1024K (1 0ECE/IIHE!l -i987 51 TABLE 1 : PARTS LIST Baby AT Motherboard .... .. ...... ........ .... .... .. ..... .$995 200W Power Supply .... ... .... ..... ..... ... ...... ..... ... $275 The 200W power supply features numerous power connectors for the motherboard and disc drives. megabyte) of on-board RAM. The necessary BIOS ROM chips are also supplied with the motherboard, plugged into the appropriate sockets. BIOS stands for Basic Input/Output System and is used to provide any special 1/0 routines for discs, terminals, printers and so on. Before mounting the motherboard in the case, you first have to install the RAM chips. These are plugged into four rows of nine sockets on the motherboard - Row 0, Row 1, Row 2 and Row 3. A minimum of 256K and a maximum of 1024K may be installed on the motherboard. Be sure to use 120ns (or faster) RAM chips, as slow speed RAM can cause the computer to intermittently lock up (lO0ns is faster, 150ns is slower). Both 64K 4164 chips and 256K 41256 chips can be used, depending on the amount of memory you wish to install. If, you are installing 512K of onboard RAM , you will need 18 41256 RAM chips. These are plugged into rows 0 and 1, with the other two rows left empty. Other system memory configurations are clearly detailed in the assembly manual supplied with the motherboard. Note that the 640K memory size requires a mixture of 256K 41256 chips and 64K 4164 chips. The 41256 devices are plugged into the first two rows (rows 0 and 1), while 52 SILICON CHIP Baby AT Case .... .... .. .. ....... .................... .... .... $175 Disc Controller: Floppy Controller .............. ...... ....... .......... ......$1 2 9 Hard/Floppy Controller .. .... .......... .. .... ... .. .. ... ... $399 Disc Drives: 1 .2Mb Floppy Drive .......... ........ ..... ..... .. ... .. .... $269 20Mb Hard Disc Drive .. ... ............ ... .. ......... ... .. $795 Display Adpater: CGA/Parallel Printer Card ..... ..... ... ..... ............. .$129 MGA/Parallel Printer Card (MGA) ... ..... .... ... ...... $149 EGA Card with Hercules Compatibility ..... ... ....... $399 Serial/Parallel/Game Card .. ......... ...... .... ... ....... $139 Keyboards : 84-Key Type .... .... .. ... ... ...... ..... ...... ... .. .. ........ $129 101 Key-Type with Numeric Keypad ... ....... .... .. $149 Note: on-board RAM for the Motherboard is an extra cost item. the 4164s are plugged into rows 2 and 3. Don't mix 41256s and 4164s on the same row. Leave the ICs in their conductive foam until you are ready to install them in the motherboard. You will find that you will have to bend the leads of the chips in slightly so that they fit the sockets. This can be done by pressing the leads against a flat surface. Try to avoid touching the leads of the ICs, since they are easily destroyed by static electricity. When installing the devices, make sure that the notched end is towards the rear of the motherboard. Next, you will have to set switches S3 and S4 on DIP switch block SWl to match the memory size. In our case, we set S3 to OFF and S4 to ON to correspond to a memory size of 512K. S1 is not used and should remain in the off position. S2 selects the the primary display adapter. Set the switch to OFF to select a Monochrome Display Adapter (MDA), and to ON to select a Colour Graphics Adapter (CGA) or a Professional Graphics Controller (PGC). S2 can be in either position if an Enhanced Graphics Adapter [EGA) is to be installed [unless a second type of display adpter is also installed). The next step is to check jumper JP4 which is adjacent to the BIOS Close up view of switch block SW1 on the motherboard. Be sure to set the switches to match your system. ROMs. This jumper is installed in the factory to suit the BIOS ROMs supplied and should be across pins 2 and 3 (ie, across the two pins nearest the front of the board. Motherboard installation Before installing any of the hardware, you first have to remove the disc cage from the case. To do this, undo the two screws at the top, then slide the cage back until the metal tongues on the bottom are disengaged. The cage can then be removed from the chassis. Next, mount the speaker on the left-hand front of the chassis - it is held in place by the metal tongues. You are now ready to install the motherboard. To do this, first screw the three metal standoffs to the base of the chassis. This done, push the plastic standoffs supplied into the ap- , KEYBOARD SOCKET 7 EXPANSION SLOTS ROM BIOS ___,_____ RAM BANKS ROW 0 Power supply installation The power supply is next. First, remove and set aside the four screws on the back of the supply (the side with the power connectors}. Next, position the supply in the case where the disc cage normally sits, and locate the two sets of wires with the 6-pin connectors. Plug the 6-pin connector with the orange lead into the rear six pins of the power connector (J18) on the motherboard. The other 6-pin connector plugs into the front six pins of the J18 connector. Don't transpose these two connectors you will almost certainly damage the motherboard if you do. With the connectors plugged into the motherboard, the power supply can now be permanently installed in the chassis. It should slide back against the rear panel, with the power switch on the right. Fasten it with the four screws previously removed. EGA and 1/0 cards ROW 1 ROW 2 ROW 3 SP£AJCBI COIIMECTllllll SW1 The XlO00 Baby-AT motherboard comes complete with BIOS ROM installed. Don't forget to remove the cardboard from the backup battery terminal. propriate mounting holes on the motherboard (don't use the holes that match the metal standoffs). Install the motherboard by sliding it from the left of the case until the standoffs engage the matching slots on the base, and secure by installing the screws in the metal standoffs. Finally, connect the leads from the various switches and LEDs on the front panel to the appropriate connectors (JP1, J15 , J21 and J22) on the motherboard. Follow the manual closely here and you cannot go wrong. A point to note here concerning the speed indicator LEDs. As supplied, the machine comes with two orange LEDs and these show the two higher speeds; ie, 10MHz and 12MHz. If you turn it on with the Turbo switch in the Off setting, the machine will boot at 8MHz and both indicator LEDs will be off. You can then change the operating speed while a program is in progress by holding down the Ctrl and Alt keys together and then pressing the "+" key. Doing this repeatedly changes the speed in the following order: 8MHz, 6MHz, 12MHz, 10MHz, 8MHz, 6MHz and so on. If you turn the machine on with the Turbo switch in the On position, it will boot up at 6MHz. Note: some programs will lock up if you attempt to change speeds while they are running and other software which is copy protected will only run at 6MHz. The X2012 1/0 card and the X2013 EGA (enhanced graphics adapter) card are plugged into the expansion slots of the motherboard. But first there are a few things to check. We'll start with the 1/0 card. This offers a variety of 1/0 functions including up to two RS-232C serial interface ports, a Centronics parallel printer port, and a games adapter port. Unless you are using other devices wiih 1/0 ports, the factory default settings on this board are the ones to use. Supplied with 1/0 card is an interface cable for the primary serial port (DB9P to DB25P) and a bracket for the secondary serial port connector and games port connector. The games adapter port is supplied as standard while the secondary serial port connector is optional. Before plugging in the 1/0 card, you should first check the settings of two DIP switches - SW1 and SWZ. The correct settings are clearly illustrated in the manual supplied with the card. It doesn't particularly matter which expansion slot you plug the 1/0 card into (we chose the slot nearest the left-hand side of the case). Use the self-tapping screws DECEMBER1987 53 - PRICED FOR HOME, BUILT FOR WORK! Bargain B & W Monitor 'D ! , \l = Makes Working E a s ~ e r ! Check it out for value! 12" B & W TTL Monitor with anti-glare screen, pan/tilt base and front mounted controls. Exceptional value and quality! Cat X-2400 s249 - Quality monitor swivel bases. Two great models to choose from. Both feature robust ~r.1-\lt\ II\ construction, 360 degree horizontal.movement and 25 degree vertical adjustment. Save $50!1 Green or Amber composite monitors at this great low price! Both feature anti-glare screen, wide video bandwidth for clearer sharper picture. 30cm screen size with front mounted controls! WAS COMPLETE WITH MONITOR! The Acer 500+ By Multltech S:o4: $ 199 II 256K RAM, single floppy disk drive, MS .DOS (version 3.2) software and monitor! Cat X-8050 System3 Amazing 640K RAM, single floppy disk drive PLUS 20Mb Hard Drive and MS.DOS (version 3.2) plus monitor! Cat X-8052 Magic Modem! The Bit Blitzer 12E, the best thing to happen to modems in years! With selectable full duplex 1200/ 1200 or 300/300 baud, auto answer/dial/ disconnect, Telecom authorised, quality construction. Hayes AT command set compatibility, fully keyboard controllable. cat X-3306 Also available Bit Blltzer 123E, same as above plus 1200/75 Viatel operation. Cat X-3307 en Blitzer Buyer's Bargain Bonus! DS/DD Cat X-3501 Box Of 10 Order by phone: 24 hour ._.11. . . . PP'E.S'S despatcll through DSX ress. n Call TOLL FREE (008)2 6610 (Sydney Area, call 888 2105) $1895 s499 s1295 s1295 Rs~32 Breakout Box. (0 1 s27so Just what you need for se'rial applications like modems, etc! Anywhere connections need constant changing! 0625 male to female with pin 1 permanently wired . The WAS others are open with wire links supplied. Cat X-3568 II I SAVE UP TO S29.95 - THIS MONTH ONLY! Pack0110 The Male/Male Gender Bender is really kinky! It does just what the female one does only differently! Save 20% now! Cat X-3565 s5995 · Almost ½ Price! $17.50 NOWs9 The Parallel Switch Box will ~ save you heaps! Lets you run i computers one printer from two or even two s499 Budget Beaters! Our new Budget DS/DD SW' Diskettes! Look at the fantastic low price! Cat X-3521 Letter Quallty or Lightning Fast! Printer Switching Buy a Bit Blitzer this month, and we'll throw in the serial cable ... FREE! That's right: your choice of either 25/25 pin "D" cable (X-3564) or 25/9 pin "D" cable (X- 8007). ~ SS/OD Cat X-3500 Box Of 10 $2495 $2695 Save S3!! System2 s1295 Hard Drive! s1995 Don't pay more! DSE quality 5¼" Diskettes are so good - we use 'em! In hard plastic storage box they make good sense. Female/Female! Adapts male Serial cables without rewiring or resoldering! Simply plug it in. Twin female 0825 sockets with all wired pin to pin! Cat X-3566 Complete! With 256K RAM, twin floppy disk drives, MS .DOS (version 3.2), serial and parallel ports and monitor! Cat X-8051 ONLY Cat X-1191 Disk Savers 20% Off· Gender Bender! sg95 System 1 Deluxe Base With anti-skid feet! Takes 22cm With front mounted locking to 35cm screens. Cat X-1190 knob. Lets you adjust the angle without removing the screen! The best of both worlds! Fast 135cps Dot Matrix printer. Choose between super speed or near letter quality. Ideal for graphics, correspondence, invoicing ... anything! 101mm to 254mm paper widths and with inbuilt tractor feed! Cat X-3225 Now there's an affordable computer system with all you need for work or playl The ACER 500+ comes with 256K or 640K RAM, single or twin floppy disk drives, optional 20Mb hard drive, keyboard selectable 4.7718MHz clock speeds, 12 months warranty, MS.DOS software and more!! Budget Base! . . 1 1 ·_ ..... -,,, / printers from one computer. No more cable changing! Just plug it in and It does the rest! ,...,.,, • 95 ~ l s3995 1 Permanent RS232 Jumper box! Just like the breakout box except that the connections are made internally and soldered for permanent connection. All 25 pins are open and wire links supplied! Cat X-3569 Save Desk Space•• With the CPU Floor Mount Stand you can mount your CPU on its side - beside the desk! Gives you back your desk for working on. Great '"" '"'""' DICK~ SMITH ELECTRONICS PTY LTD anta -ot ip? PORTASOL won't let you down. Pocket cap turns off burner - just in case! Inbuilt lighter ------ Controlled heat - equiv. 10 to 60 watts! Serviceman on the job? Hobbyist on the move? Technician on the go? When you need to solder away from power, this is what you want: Portasol. The butane-powered refillable soldering iron with more power than most mains irons! It's far better than a re-chargeable. If it's "flat", it "recharges" in seconds with standard lighter gas. And if it's not hot enough, simply wind the wick up. Try doing that with a NiCad! Perfect for all soldering applications - even those heavy jobs you'd normally want a "big gun" for. Yet it's small enough to slip into the shirt pocket (and in case you leave it on, the cap turns it off for you!) Just think of the applications apart from electronics: Boat wiring and repairs. Auto electrics. Builders/electricians. Antenna installers. And so many more. Portasol: it's a breakthrough in soldering. Throw away your old ideas about soldering. Get a Portasol and you'll get the difference. Cat T-1370 Spare tips including Catalytic Heater $1295 CatT-1371 $3 995 at ELECIRONICS DICK<at>sMRH PTY LTD Available at all DSE stores ... or phone DSXpress on (008) 22 6610 (Sydney 888 2105) The X2008 hard/floppy disc controller plugs into one of the long expansion slots on the motherboard. supplied to secure the connector brackets to the rear panel. The EGA card is next. Depending on the type of display you intend to use, you must set four switches on the switch block located at one end of the board (this is clearly spelt out in the manual}. You can then plug the EGA card into one of the expansion slots on the motherboard (we chose slot three}. 34-way cable with lines 25-29 flipped goes to the the hard drive connector (J5}. Assuming everything checks out, clip the plastic card guides into position on the metal bracket behind the speaker, then install the disc controller on the mother board. As before, you must use one of the long expansion slots. Finally, plug the connector for the Disc indicator LED into J6 (red lead to pin 1, black to pin 2). Disc controller card The manual also shows JP5 and JP6 but, in practice, these don't exist at least not on our board. The 34-way and 20-way connector cables for the disc drives can now be plugged into the controller card at locations J1, J3 and J5. Check that the blue or red stripe on each cable goes to pin 1 of its matching connector (ie, towards the rear of the board}. Fit the 34-way cable with lines 10-16 "flipped" to the floppy disc connector (J1}; the There are two disc controller cards to choose from: either the X2014 floppy disc controller card or the X2008 hard/floppy disc controller. The floppy controller is considerably cheaper than the hard/floppy controller ($129 vs. $399), but the latter should be specified if you intend installing a 20 megabyte hard disc drive. Another reason for specifying the hard/floppy controller board: if you start out with just single or dual floppy drives, you can easily add a 20Mb hard drive later on. But don't be tempted to go for the more expensive controller if you're not likely to need it. We'll describe the installation procedure for the X2008 hard/floppy controller. First, check that the default settings of the jumper connectors are correct, as set out in the manual. In particular, pins 2 and 3 of JP1 and pins 1 and 2 of JP2 should be shorted, while JP3 should be open. This partly assembled machine includes the motherboard, hard/floppy disc controller and power supply. The disc cage fits in the bottom corner. 56 SILICON CHIP The X2012 1/0 card. Check the settings of SWl and SW2 before plugging it into the motherboard. The EGA card. Its switch block (top right hand corner) must be set to suit the type of display you intend to use. These two views show the locations of the plastic guides on the two disc drives. Note that the tapered ends go towards the rear. Disc drives The hard disc and floppy disc drives are both mounted in the disc cage previously removed from the c.a se. The hard disc is first. Locate the drive select jumper (J6) at the rear of the drive and make sure it's set to D2. Be careful not to drop or jar the drive - it's fragile. Similarly, locate drive select jumper Jl on the floppy drive. If your drive is labelled DSO through to D53 , set the jumper to DSl. If the drive is la belled DS 1 through to DS4 , then set it to DS2. The next step is to screw the four plastic guide rails to the sides of the drives. This is where we struck our first snag in the assembly. Figuring out the correct locations for the guides was a little tricky but we eventually got it right after some trial and error. To save you the same hassle, the accompanying photographs clearly show the locations of the guides. The two disc drives simply slide into the disc cage. The hard disc is first and should be installed with the diecast cover uppermost. Push the drive all the way in, then install the floppy drive. You will find that the bottom lip of the floppy drive initially overlaps the hard disc drive ever so slightly. A firm push is all that's needed to overcome the problem. The disc cage can now be carefully positioned in the chassis and slid forward so that the metal tongues engage the slots in the baseplate. Check that the drives mate correctly with the front panel opening, then secure the cage with the two self-tapping screws. Finally, the various power supply and disc controller connections can be made to the two drives. Locate the four-pin power connector from the hard disc and plug it into one of the polarised 4-pin power connectors from the power supply. A second 4-pin connector plugs into the floppy drive, directly above the hard disc supply leads. The 20-way and 34-way cables from the controller board plug directly into edge connectors on the DECF.M BER1987 57 back of the two drives. Install the cables for the hard drive first, then the cable for the floppy drive. Slots cut into the edge connectors ensure correct cable polarity. Note: the 34-pin edge connectors with the "flipped" sections are installed on the drives. The other ends go to the controller card. The middle connectors are used only if two drives of the same type are installed. Powering up Now for the big moment! Plug in the monitor and keyboard, remove the protective cardboard from the floppy disc drive, and switch on. After the BIOS logo appears, the floppy drive LED should come on briefly and the system should display the message "Disc boot failure, insert system disc and press enter". When that happens, all is well and you can insert your DOS disc and re-boot the computer. The system will then ask you to enter the date and time. Press ENTER twice to bypass this procedure. You should now have the DOS prompt A on the screen. If you run into problems here, check the drive select jumper on the floppy drive and the connections between the drive and the controller card. It is normal for the system to display an equipment configuration error message at this stage. This last problem is solved by running the system SETUP program. Details of the system setup are stored in a battery-backed RAM chip on the motherboard and are accessed by pressing the CTRL, ALT and ESC keys at the same time. Select option A and update each item as it appears. The program will ask you to enter the date and time, and will request information on the disc drives fitted, the amount of memory and the display adapter. Note that the hard disc drive supplied is a type 2. When you are satisfied that all the information is correct, press E to re-boot the computer. The system should now return to the DOS prompt A, although there will be quite a lengthy pause if you have specified a hard disc in the SETUP program. 58 SILICON CHIP The two disc drives slide into the disc cage. Treat the hard disc drive carefully and install it with its diecast section uppermost. A firm push will be needed to lift the bottom lip of the floppy drive over the top of the hard drive. Both keyboards feature click-action keys. The deluxe version (top) has a separate cursor pad and the function keys are mounted along the top. Actually, we struck another snag at this point. Despite frequent reruns, the system displayed an equipment configuration error ea ch time we tried to re-boot from the SETUP program. We solved the problem eventually when we realised that we should have been specifying the special adapter option for the primary display (because we had the EGA card), and not the monochrome option. At this stage, you will be unable to access the hard disc since it has yet to be initialised. That's easily fixed though. Insert the DSPREP disc supplied with the hard drive into drive A and type DSPREP. Now type INSTALL and press the ENTER key. After that, it's simply a matter of following the instructions on the screen to initialise the disc. This procedure will take several minutes. To begin with, the system will count down as it initialises all the cylinders on the hard disc, beginning with cylinder 615 . Then, when it reaches 0, it quickly counts back in the other direction. At the end of all this, the system will display the following message: Drive One is now low-level initialised. Strike a key when ready ... Formatting the hard disc You are now ready to partition and format the hard disc. Insert your DOS disc in Drive A, type FDISK and press ENTER. Unless you have software that requires a non DOS formatted area on your hard disc, you should use the entire disc as a DOS partition. As before, it's simply a matter of following instructions on the screen. When partitioning is complete, install DOS onto the hard disc by typing FORMAT C:/S/V and then pressing ENTER. After a few minutes, the system will report on the available disc space and you will have a system that can be booted from the hard disc. All plugged in and ready to go. Stow the disc drive cables and power connectors neatly so that they don't foul the disc drives or the lid of the case. We want one So what are our conclusions? Well, we wanted one. Well, two actually. The click action keyboards are nice to use, there's scads of memory and it's blindingly fast. " Speed thrills", they say and ain't it the truth. To someone used to working with a standard IBM PC, the speed of • PRINTED CIRCUIT BOARDS See Jemal for fast production of small to medium quantities, single and double sided, plated through holes , all finishes. Immediate computer quotes. • INSTRUMENT CONTROL PANELS Innovative approaches to improve your product • MEMBRANE SWITCH PANELS this AT-compatible machine is a real eye-opener. It goes like a rocket! We teamed our machine with a Multitech high-resolution monochrome monitor and it proved to be an ideal match. It is much sharper than an ordinary monochrome monitor . Again, we wanted it. Now then, let's have another look at those prices... le ,_o - 0 0 11111111 0 ° =----~ 11111111 ° ~ -------~ .. ( t , . ~ ---- = == == =; 0 '--0 :;-:: - - - -, T - ', ......... 0 Simple concept, sophisticated technology • PRECISION METALWORK 9-inch racks , chassis and enclosures • ASSEMBLY SERVICES In-house services to complete the " one stop shop" TECHNOLOGIES GENERAL OFFICE & MANUFACTURING FACILITY 5 FORGE STREET, WELSH POOL 6106, WESTERN AUSTRALIA TELEPHONE (09) 350 5555 FAX (09) 458 6539 TELEX 95494 DECE/\!HEfl 1987 59 Save Up To 50% On Top Quality D Series Connectors! High Quality - Fantastic Value High Power Ratings Virtually all the famous "Name lo"dspeaker makers now use Bexu ene or Polypropylene Cones with their drivers. The advantages are considerable - less cone flexing or "break up", improved bottom end response and reduced enclosure sizes. One of the problems of course, has been the high cost of P-P drivers. Fortunately, with Altronlcs direct Import prices, you can now be the owner of any of these fine speakers for a lracUon of what you'd expect. Note: the conservative power ratings, the massive magnets employed and high order sensitivity specifications with these fine Drivers. Brief Specifications (All 8 ohm Voice Coil Impedance) ./1( ( ,, • C 3055 ~~~~"'o~ P 3000 P 3010 P 3020 P 3030 P 3040 P 3050 P 3090 Male 9 Pin Female 9 Pin Male PCB RVL Fmale PCB RVL Male PCB mnt. Fmale PCB mnt. Backshell cover 2.95 3.25 3.75 4.50 2.95 3.95 1.95 1.95 1.60• 3.60 3.25 2.85 3.25 1.29 P 3100 r 3110 P 3120 p 3130 p 3140 P 3150 P 3190 Male 15 Pin Fmale 15 Pin Male PCB RVL Fmale PCB RVL Male PCB mnt. Fmale PCB Backshel l cover 3.25 3.85 4.35 5.50 3.85 4.85 2.20 2.50 1.90• 2.95 2.75• 1.90• 2.40• 1.10• P 3200 P 3210 P 3220 P 3230 P 3240 P 3250 P 3290 Male 25 Pin Fmale 25 Pin Male PCB RVL Fmale PCB RVL Male PCB mnt. Fmale PCB mnt. Backshel l cover 4.95 5.50 4.95 6.90 4.95 6.25 2.20 2.45• 2.75• 3.95 3.45• 2.45• 3.10• $24.50 C 3060 Frequency Response fo-3000Hz Reaonant Frequency 36Hz Sensitivity (1 M/ 1Watt) 87db (+ 6r -2db Voice Coll 25mm Nett Weight 900gm Electromagnetic Q .48 Magnet 280 gm. C 3065 $65.00 C 3070 Frequency Response fo-:3000Hz Resonant Frequency 30Hz Sensitivity (1 M/1 Watt) 92db ( + or-2db) Voice Coll 38mm Nett Weight 2650 gm Electromagnetic Q .23 Magnet 836 gm. $49.50 Frequency Reoponse Fo-3000Hz Resonant . Frequency 33Hz Senslllvlly(M/ 1 Watt) 90db (+ or -2db) Voice Coll 38mm Nett Weight 2200 gm. Electromagnetic Q .4 Magnet 836 gm. $99.00 Frequency Response fo-2000Hz Resonant Frequency 23Hz Sensitivity (1 M/ 1 Watt) 93db (+ or -2db) Voice Coll 38mm Nett Weight 3620 gm Electromagnet Q .22 Magnet 1410 gm . IllIllII Ill IIIIIllIllIllIIllIIIIIIIllllllIIIllIllIllII IllIllIIIIIIIIIIIIIIIlllIllIllIllIIllllllllIIIIIIIIIIIIII The use of Super Heavy Duty Heatsinks as Rack Case sides now allows a myriad of Amplifiers, Power Supplies, Battery Chargers etc. to be built in an "Off the Shell" rack case. Fantaallc for Stereo Ampllflers-Each Heatslnk will accommodate an audio output stage of approximately 120W with normal efficiency and dissipation. A Great Chauls for Heavy Duty Power Supplies and Battery Chargers. We suggest the mounting of Rectifier Bridge or diodes on one Heatslnk and the R~gulator devices on the other. Order With Either Black Or Natural Anodised Front Panels 1. J• Black Anodised Front Panel Natural Anodised Front Panel r, Specifications: Heatslnks Altronics H 0590 Front Panel 3 unit Rack size 480mm x 132mm x 3mm Base 1.0mm steel, ventilation slots provided Top Cover 1.0mm steel, ventilation slots provided Internal Dimensions 125 x 370 x 250mm External Dimensions 130 x 440 x 252mm plus standard front panel Finish Black anodised aluminium plus powder coat black top/ base. PROFESSIONAL nass1s Now your preamps, Amps, Control Modules Monitor Panels etc. can look every bit as good as Technlcs Nakamlchi and other top manufacturers. at<er 8 Please Note: This product is a genuine Pan Brake Bender allowing you to make quite complex chassis boxes, lids, trays etc. It is made from solid steel and is not to be confused with inferior Non Pan Brake simple benders currently sold by our competitors. Make Your own Chassis and Cases and Save a Fortune Value Plus T 2400 ......... $99.95 Bnl FEATURES: These beautifully crafted rack cabinet boxes will give your equipment a real 1st class appearance with removable top and bottom cover panels • All dimensioning conforms to the International Standard • Natural or Black finish • Ventilated lid • Deluxe finish front panel • Individually cartoned• Supplied in Flat Pack Form - Easily assembled in minutes - Side Elevation,:- D=254mm C (Internal Chassis Height) • B (mounting Bolt Centres) . SIX NATURAL AND BLACK FINISH MODELS - The Black or Natural finish cabinets are each available in 44mm, 88mm or 132mm high models. Mounting hole centres conform exactly to International Racking Specifications both vertically and horizontally. Cat. No. H 0401 H 0402 H 0403 H 0411 H 0412 H 0413 Finish Natural Natural Natural Black Black Black A 44 88 132 B 34 57 89 44 34 88 ~32 57 89 C 38 82 126 38 82 126 Were Now $59.95 $69.95 $85.00 $59.95 $79.95 $89.95 $50 $62 $79 $52 $70 $80 18V at up to 600mA under ideal sunlight conditions, Intended for 9harging 12 volt systems such as Car, Caravan and Boat batteries etc. Cal. A 0220 Was $119 Now $99 ester For lr: lrcul Bench Too $17.50 " NO NEED TO UNSOLDER SUSPECT TRANSISTORS " FEATURES: • Output 3 to 30V at 1A * Short c i rc uit protected • Load switching • Current limiting . Dual scale meter• Housed in o ur Deluxe "ABS" instrument case . SPECIFICATIONS: * Output Voltage - 3 to 30 V * Output Current - 0 to 1 amp (full y var iable) * Load Regulation - Better than 0.2% from Ot o ful l load • Output Ripple-Less than 2mV RM S. Cat . K 3210 T r'\ The readout consists of a bright 4-digit LED display and the full scale readings for each range are 9999.SnF and 99 .99uF. No adjustments are necessary when taking a reading. You simply connect the capacitor to the test terminals and select the appropriate range . The circuit can accurately measure capacitance down to one picofarad (1pF). This is made possible by the internal nulling circuit which cancels any stray capacitance between the test terminals or test leads. So when you measure a 5pF capacitor, the unit will display 5pF. 1r1 Dead easy to bu ild and (even better ) there ara o nly 3 electrical connections required to the car wiring system . K 4010 . . .. . .... FEATURES: • Tests both NPN and PNP transistors in circuit at the touch of a switch • Tests Diodes and SCRS as well • No need to switc h between NPN and PNP-its automatic. Two LED indicators are used to show condition of device being tested . Altronlca Kit Feature • " ABS " jiffy box and test leads supplied . Cat. K 2530 539.50 This alarm drives off wouldbe thieves with an ear splitting modulated tone. Once activated it is near impossible to stay within tt;e confines of the car. Featurea: Entry Delay• Exit Delay• Alarm Timer • Lamp Flasher• Three second soft alarm reminder. Piezo siren produces modulated tone of 110dbat 1 metre. Simple to build and install. Two Sensor Input• K 2522 . . . . ... ... ..... . . . .... . .... .. ..... $79.oo This Ultras0nic Movement Detec_tor provides added protection against illegal entry via. an open window etc . Connects directly to an alarm with a normalfy open input. Detects an y movement up to 3 metres within an angle of 30 degrees. Will operate directly off 12V i.e. Car Battery etc . K 4400 $29.50 '$42.so Sharpen• up your picture when Copying Video to Video Here's a Ilmple but effective video enhancer that is super e11y to bulld at a fraction of the cost of commerc ial mode ls. Unit sharpens picture detail, and can _actually improve the quality of a copy by amplyfyrng the top end of the video signal K 5825 174 Roe St. Perth W.A. 6000 Perth Metro & After Hours (09) 328 1599 P.O. Box 8350 Perth Mail Exchange W.A.6000 your order the day received and despatch via . Australia Post. Allow approx 7 days from day you post order to when you receive goods. Weight limited 1 Kgs. - We proc ess your orde r th e day received and despatch via. Overnight JetIervlce Courier for delivery next day Country areas please allow additional 24-48 hours. Weight limit 3Kgs. - For deliveries exceeding 3Kgs and less than 10Kgs- allow 7 days f or delivery - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. - As with virtually every ottaer Australian supplier, we se nd go ods at consignees risk . Should yo u requ i re comprehensi ve insurance cover against loss or damage please add 1% to order value (minimum charge $1) . When phone ordering please request "In surance". - Bankca rd Holders can phone o rder t o ll free up to 6pm Eastern Standard Time . Remember with our Overnight Jetservlce we deli ver next da)I. Chances are there is an Altronics Reseller right near yo u - check this list o r phon e us fo r details of the nearest dealer. Pleaoe Note: Re sellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from th is Catalogue - in many c ases, however, Dealer prices will still rep resent a signific an t cost saving from prices charged by Altronics Competitors. Don't forget our Expreu Mall and Phone Order Service - for the coot of a local call, Bankcard, Visa or Maotercard holders can phone order for 1ame day deopatch. MORE AL TRON/CS DEALERS WANTED If you have a Retail Shop , you could increase your income significantly by becoming an Altronics Dealer, Phone Colin Fobister (09) 328 2199 for Details. COUNTRY ALBANY BP Electron i cs ■ 412681 ESPERANCE Es peran c e Communications 7 133 44 GERALDTON K .B .E!e c tronics & Marine 212176 KALGOORLIE Todays Electronics ■ 2127 7 7 KARRATHA Daves Oscitronics 854836 MANDURAH Lance Rock Retravision 351246 NEWMAN Watronics 751734 WYALKATCHEM D & J Pease 811132 ALICE SPRINGS Ascom Electronic s 52171 3 Farmer Electronics 522967 CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 CITY Active Wholesal e ■ 6023499 All Electronic Components 6623506 SUBURBAN ASPENDALE Giltronics 5809839 CHELTENHAM Talking Electronics 5502386 CROYDEN Truscott Electronics ■ 7 2 33860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 4114 1 1 MORWELL Mor w ell Elec troni cs 3461 33 SWAN HILL Cornish Radio Servi ces 321 427 CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE VALLEY Fred Hoe & Sons Electronics 2774311 Economic Electron ics 623762 PADDINGTON Jacques Electronics 3698594 SLACKS CREEK David Hall Electroni c s 2088808 . TOOWONG Te c hniparts 6710879 COUNTRY CAIRNS El e ctroni c World 518555 BUNDABERG Bob Elkins Electroni c s 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 NAMBOUR Nambour Electronics 411604 PALM BEACH The Electronic Centre 341248 ROCKHAMPTON Electron World 278988 Access Electronics (East St.) 21058 Purely Electronics (Shopping Fair) 280100 Xanthos Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 CITY Electronic Comp & Equip. 2125999 Force Electron ic ■ 2122672 SUBURBAN BRIGHTON Brighton Electronics ■ 2963531 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 PROSPECT Jensen Electronics ■ 2694744 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 HOBART George Harvey ■ 342233 LAUNCESTON Advanced Elect ronics 315688 George Har v ey ■ 316533 Nichols Radio TV 3161 71 CITY David Reid Electronics ■ 2671385 SUBURBAN BLACKTOWN Wa vefront Elec tronics 831 1908 CARINGHAH Hicom unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantron ic s 6097218 COUNTRY ALBURY Webb's Electronics ■ 254066 COFFS HARBOUR Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NEWCASTLE Novacastrian Elect.Suppl ies ■ 621358 NOWRA Ewing Electronics ■ 218412 ORANGE Fyfe Electronics 626491 RAYMOND TERRACE Alback Electron ics 873419 TENTERFIELD Nathan Ross Electronics 362204 WINDSOR M & E Electronics ■ Communications 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 Blue Ribbon Dealera are highlighted with a ■. These Dealers generally carry a comprehensi ve range of Altronic products and kits or will order any requ i red ~em for you . All this • ID a brand new set Most service faults fall into a particular pattern: the fault in a brand new set; the intermittent fault; the multiple fault; and even the contradictory fault where replacing a faulty component makes the situation worse instead of better. Most of us have experienced these from time to time, but how many have found them all in one set? Well, that's the gist of my main story this month and I think it sets some kind of record. See what you think. It all started with a call from a dealer colleague for whom I do service work, including warranty work on new sets. This concerned a brand new TV set - a National TC2258 - which he had just taken out of its carton, for display on the showroom floor, only to find that it appeared to be completely dead. And, since National is one of the brands I am authorised to service, it was clearly my baby. My colleague duly delivered the set and I dug out the appropriate manual. As well as the model number already quoted, some readers may recognise the set as using the National chassis type M14H. The relevant portion of the circuit is reproduced herewith to assist readers in following the story. My initial reaction to the job was somewhat blase - I assumed that it would be a relatively straightfor- t)J ALL 11-\lS IN 62 SILICON CI-IIP ~ ~N't> ward fault without any serious hassles. After all, it was completely dead. A preliminary check revealed that there was a normal HT rail at around 113V, but no sign of horizontal deflection, EHT, or any other functions derived from this part of the circuit. I stoked up the CRO and began checking through the horizontal circuit. The horizontal oscillator is part of of a 'jungle' type chip, IC601, AN5600k-R, a 42-pin monster which delivers the horizontal oscillator signal from pin 41. This part of the circuit is not shown here but the output from this pin goes to the base of transistor Q500, the horizontal driver stage. This drives the output stage, Q501 , via transformer T500 (bottom left hand corner of circuit). The CRO established that the signal was coming out of the chip OK and was being applied to the base of Q500. But that was all; there was nothing at the Q500 collector. Nor was the reason hard to find; a quick check with the meter showed that there was no voltage at this point. This voltage is normally applied via R551, an 820Q safety resistor, although the purpose of the safety resistor in this line is far from clear. Anyway, this was the problem, the resistor being open circuit. Judging by appearances, this resistor might have been nothing more than a conventional 2W metallised type but, in any case, I had nothing like this value, quite apart from any special qualities it might have. Anxious to get the set working, I made up a string of three 1W resistors: two 330Q and a 2200, making 880Q, which I reckoned was near enough for a test. Protesting squawk ~ SE"t".... I fitted the string in place and switched on. The result was a loud ,j. D30, "'"" . .,,. IO<) - . "", · 0, 47 ffiID ''" 560P500V "" TlHl5768 IC401 AN5521 l502 =-tl.1!5lA02 r ~p SOO' Fig.1: relevant portion of the National TC2258 circuit. Transistors Q500 and Q501 are at bottom left, Q503 and Q504 at bottom right, and D510 and TPE21 roughly top centre. protesting squawk from the line output transformer, then silence; the set was as dead as ever before. Further checking revealed that the horizontal output transistor, Q501, had failed. Fortunately, I had a replacement type on hand, and this was duly fitted. But, before trying again, I did what I should have done the first time and checked the value of the substitute resistor string. I need hardly add that Murphy had been at work. What I had taken for 2200 was, in fact, a 22000 resistor with a somewhat dubious colour band. My immediate reaction was to wonder whether this mistake on my part had caused the output transistor to fail, or whether it had been faulty all along, but only became apparent when I restored the voltage to the driver transistor. This was the first of many such questions I was to ask myself before I finshed with the set. I fitted a correct value resistor, crossed my fingers, and switched on. And this time all was well - no signs of protest, normal sound, and a first class picture when the tube warmed up. The only snag now was the 8200 safety resistor. I had ordered a replacement from National, along with other parts, but when the order arrived there was no resistor - it had been put on back order. Naturally, I didn't want a brand new set to go out into the field with a bodgie string of resistors in it but, on the other hand, the dealer wanted to put it on display. The upshot was that I explained the situation to him and we agreed that I return the set to him for display but on the understanding that the resistor would have to be replaced before the set was delivered to a customer. And that was more or less that or so I thought. I'm not quite sure what happened over the next few days except that it appears that my dealer friend must have left the set switched off most of the time, turning it on only when a customer showed interest in it. Anyway, it was some time before he had occasion to run it for any length of time. When he did, he was on the phone in short order. It appeared that the set had run for only three quarters of an hour, then stopped. He had switched it off for about 10 minutes, then switched it on again, whereupon it had played normally for another three quarters of an hour. He had found that this pattern could be repeated indefinitely and that a pause of as little as five minutes could restore performance, but that this seemed to shorten the playing time. And so the set landed back on my bench. My first move was to simply run it to confirm the dealer's description, and to watch for any symptoms which might provide a clue as to the nature of the fault. This approach paid off. After about 40 minutes I noticed that the picture was starting to jitter slightly from side to side, suggesting possible instability in the horizontal circuitry. A few minutes later there was another protesting squawk and the set shut down. Then, just as the dealer reported, switching the set off for a few minutes was all that was necessary to restore performance. So what now? There was little doubt in my mind that it was the horizontal system failing, the real question being why. Once again I decided that a CRO would be the best form of attack, at least initially. And this time, I selected a triple trace instrument, a BWD Model 525. I connected one probe to the base of transistor Q500, one to this transistor's collector, and one to the collector of the output transistor, Q501. With the set running cold, the waveforms were pretty much as indicated in the service manual, so it was simply a matter of waiting until the picture started to jitter. My first attempt was not very successful. I was concentrating on the output stage waveform when DECEMBER1987 63 the picture started to jitter, but this seemed to be perfectly stable. It was only a moment before the set shut down that I looked closely at the waveform at the base of Q500, and realised that it appeared to have changed shape. The change was not very marked and I put the set through a couple more cycles before I was sure that this was so. When I was, I removed the probe from the collector of Q501 and connected it to the horizontal output pin, pin 41, of IC601. Then I put the set through another cycle. This time, results were more encouraging. Initially, the waveform at pin 41 was very close to that shown in the manual, in both amplitude and shape, although it differs significantly from that at the base of Q500, due mainly to the RC network in the base circuit. But as the set approached its shut-down condition, the waveform at pin 41 changed significantly, both in amplitude (which was decreasing) and shape. However, as I noted previously, this had only a marginal effect on the waveform at the base of Q500. Nevertheless, as the signal from pin 41 continued to change, it eventually reached a point where the set shut down. Which was all very interesting up to a point, but what did it mean? My knee-jerk reaction was to blame the chip but, while I didn't entirely rule out the possibility, I quickly put that idea on hold. I am coming to the conclusion that most chips are pretty reliable these days and I am less inclined to replace them than I once was. In any case, the idea of unsoldering 42 pins doesn't particularly appeal unless all other possibilities have been exhausted. At this point I took some time off to study the circuit and form a clearer picture of how this part of it worked. This didn't seem to help much at the time, although it did prove useful later. But it did inspire me to make a voltage check of the chip, both when the set was :.unning normally, and when it was about to fail. Initially, all voltages were within normal tolerance, so I let the set run for about half an hour, then checked them again. Most of them 64 SILICON CHIP -- . A-r Tl-lAT TIME 'I l)E:Ol)e:D lT ~s TIME TO A'SAN't>OI\) -ms SC\ ENT\l=\C A??~OAC H P\ \\\'t> Re~oR"t TO il'\E ?1<\N\\1" \V~ ••. . showed only minor differences but one had dropped significantly. Pin 42 is marked 8.5V on the circuit and had actually read 8.35V when the set was cold. But now it was down to 6V and still falling. When it reached 5.4V, the set shut down. Now I felt I was getting somewhere, and my previous study of the circuit was proving useful. As nearly as I can make out the 8.5V on pin 42 is the supply for the horizontal oscillator. It is derived from the 113V rail via R511, a 6.Bkn 3W resistor (approx. top centre of the accompanying circuit). From this point, a line runs (left) to pin 42, and right to R536 (1000} and thence to the emitter of Q503 (bottom right). Protection circuit Now Q503, together with Q504, is part of an over-voltage protection circuit, designed to operate if the main HT rail should rise significantly above 113V. It works like this. Near the top centre of the circuit is a voltage divider from the 113V rail to chassis, consisting of a 18 7kQ resistor (R527), and a 20kQ resistor (R528}, both 1 %. The voltage at the junction (no load) should be approximately 10.9V. This junction in connected to a zener diode, D510, the exact value of which is not stated but is obviously somewhere around 10.9V. The other side of the zener goes to the base of Q504, which normally has no forward bias and is turned off. If the voltage rises at the zener junction, the zener will conduct, turn on Q504 and Q503, and pull down the 8.5V rail feeding the horizontal oscillator. As a result, the horizontal circuit and those circuits operating from it are shut down. At least, that was what I deduced from my study of the circuit. Some of the details were obviously still missing, but I reckoned I had enough to go on for the time being. There was either a genuine overvoltage condition on the HT rail, causing the shut-down circuit to function as intended, or there was a temperature sensitive fault in the protection circuit which was creating the false alarm. I had already checked the HT rail on several occasions and it had always been spot on, but I went through the motions again with special attention to the shut-down condition. I also checked the voltage at test-point TPEZ 1, and even the EHT. They all remained rock steady right up until the set shut down. I did note, however, that the voltage at zener D510 was somewhat lower than I calculated for a simple divider arrangement. So it looked like a false alarm. All I had to do was find out why. My first step was to apply some freezer to what I felt were likely to be temperature sensitive components in this part of the circuit: zener diode D510, zener diode D502, diode D513, and transistors Q503 and Q504. None of the diodes responded to this, but both transistors did. If either one was sprayed as the 8.5V rail was dropping towards shut-down, the voltage would rise to normal. This proved to be a rather surprising finding, in view of subsequent events. Next I monitored the various voltages applied to Q503 and Q504 as shut-down approached. I checked them first in the cold condition and found them to be virtually spot on. Then I let the set run and watched for any changes. An obvious change was at the emitter of Q503 which was virtually the same point as pin 42 of the chip, so this fell gradually as shut-down approached. The same applied to the collector of Q504, and the base of Q503, which are connected to the same line. But the real puzzle was that there was no change to the voltage on the base of Q504 (and the collector of Q503), where one would expect to find the 'alarm' voltage real or false - needed to turn on these two transistors and pull down the 8.5V rail. At this point I decided to abandon the scientific approach and resort to the primitive; ie, check each of the dozen or so components in this part of the circuit individually. The resistors were easy enough to check in situ, and all came up well within tolerance. Transistors, on the other hand, are best removed from the circuit for testing. I pulled Q504 out first and found that it was not only faulty, but faulty in a rather unusual way. It had a base to emitter short and an open circuit collector. The discovery was gratifying, of course, but was also puzzling. I couldn't relate the fault to the symptoms and, in particular, I couldn't reconcile the discovery with the fact that spraying the transistor with freezer appeared to cure the fault. But there was no point in dwelling on this. I fished out a suitable replacement transistor and fitted it , then tried the set again. Result: the set wouldn't even start. So it was back to the component by compo- nent check. I lifted zener diode D502 and it checked OK. Then I tried D513, and this proved to have a high resistance leak. So that was replaced. Still the set refused to work. I removed Q503 and checked it, but could find nothing wrong with it. I was feeling deperate now and decided to lift zener diode D510 and thus render the protection circuit inoperative. This took only a moment and the set came good immediately, with all voltages and waveforms normal. What was more, it continued to run for the next several hours, with no significant change to any of these parameters. wrong value replacement for R551? Apart from stating that I don't think this last failure happened in this way, I really can't answer these questions. In a sense, I suppose, all this is rather academic. The faults have been found and the set repaired, and that is all that really matters. At least that is the practical approach and, as I have commented on previous occasions, there is a limit to how much time one can spend mulling over the whys and wherefores of circuit behaviour under fault conditions. No more squawks Which didn't leave much to suspect except the zener, D510. As I said earlier, there was no indication as to the exact value of this, but I reasoned that it was probably a 10.BV type. So, without bothering to check the old one, I fitted a 10.BV type out of stock and tried again. And away went the set like a bought one! Fortunately, the manual describes a check for the protection circuit. It calls for the application of a progressively higher voltage, from an outside source, to test point TPE21, until the set shuts down, which it should at about 11.BV. I did this and it came out spot on. And that was more or less the end of the job. I ran the set all day for the next couple of days, then returned it to the dealer. It has given no trouble since . Naturally; I was glad to have solved the problem and to have the set off my hands, but I was less than happy about the reasons for what I found. To start with, why were there so many faults in one set, and a brand new o:i:J.e at that? A faulty safety resistor (R551), a faulty horizontal output transistor (Q501), a faulty protection transistor (Q504), a faulty diode (D513), and a faulty zener diode (D510). Did all these faults occur independently, or did one fault trigger all the rest? Or perhaps only some of them? And if one fault triggered the rest, which one was it? And did I destroy Q501 by fitting a 'RE..\I\Vll'JG ~ FA\n\FU\Ol-!) 'Pt\\\..\~S K9 .... And now for a change of scene from a very new set to a very old one: the old faithful Philips K9. The owner had been a customer since he bought the set, over 11 years ago now, and while it has developed the usual faults common to this model, it has given good service and has plenty of life yet. This particular problem is interesting because it demonstrates that there is always something new to be encountered, even in a model about which one imagines one has seen all the tricks, as I did about this one. It also emphasises that it pays to be suspicious, perhaps more so than I was on this occasion. The fault itself was fairly straightforward; the set was completely dead due, in turn, to the fact that the power supply was also DECE/IIHE/l 1987 65 VL 170 :~ C175 ....--->,;N,--_, I I I I I !~ ;~ I I I Fig.2: skeleton circuit of the Philips K9 power supply switching transistor network. Why was it tough on the transistor? completely dead. Since this is not an uncommon situation with this model, I keep a spare power supply board on hand for a quick test. By plugging in a known good board I can quickly establish whether the power supply is itself faulty, or whether it is being shut down by a fault elsewhere in the set. In this case the test clearly indicated a faulty power board and, from there, it was a short step to pinpointing the real culprit. It proved to be the switching transistor, TS170 (2N472), which had shorted collector to emitter and blown the 2A fuse , VL170, in the process. Simply replacing these two components would have been enough to put the set back into operation, but experience has taught me that there are several other faults which can initiate this failure (note: TS 170 can be a BUl 26 in some models, or even a BU326 if the original has been replaced in the field}. The main off enders are dry joints, particularly in those parts of the circuit where they can cause sparking and spikes. Joints to transformer T182 are common offenders , as are those to the main smoothing capacitors, Cl 78a and Cl 78b. All these possibilities were thoroughly checked and ruled out, the faulty components replaced, the set given a test run, and returned to the owner. All went well for about three months and I had virtually forgotten about the job until the owner turned up at the shop again with the K9 in the back of his utility. It was completely dead again and it turned out to be exactly the same fault. Naturally, I was suspicious, and I went over the board again, determined to make sure there was nothing I had missed the first time around. In fact I found nothing, and I was forced to the conclusion that it was mere coincidence, unlikely though TETIA CORNER Rank Arena C2239 (B2 Chassis) Symp'tom: No picture but sound OK. Rather dark. raster with retrace lines on channel, but raster becomes lighter off channel. Brightness and contrast controls have no effect. Y signal disappears at pin 5, IC701. Voltage at pin 2 IC701 much higher than it should be. 66 SILICON CHIP Cure: TR402 short circuit. This transistor is one of two forming a multivibrator that generates the vertical blanking signal. When it fails the blanking is turned hard on, and IC702 is permanently blocked. This information supplied by The Electronics Technicians' Institute of Australia (Tasmanian branch). this seemed. So I fitted another new transistor and fuse, gave the set a test run, and returned it to the owner. And, again, all went well for another three months. Then the set was back in the shop with the same fault. No coincidence Well, that settled it. There was no way I could accept a third failure as coincidence; there just had to be a more subtle fault that was responsible. Since I felt fairly confident that I had excluded the more common causes of this problem, such as dry joints, the alternative approach seemed to be to get the set running and make as many dynamic tests as possible. So I replaced the transistor and fuse, turned the set on, and started with some voltage checks. Unfortunately, the circuit diagram gives very little information in this regard, so the best I could do was check the voltages which were marked - which all turned out to be within tolerance - then make as many other checks as I could think of and try to relate them to what I imagined they should be. Once again I found little to make me suspicious. Having drawn a blank with the voltages, the next thing I wanted to do was check the various waveforms around this section. But, once again, the circuit is noticeably lacking in such information. Such waveforms as are shown seemed hardly appropriate to the problem. In particular, I would have liked to have known the appropriate waveform for the collector of TS 170. Fortunately, there seemed to be a way out. I plugged in my stock power board and connected the CRO to it. In so doing, I had to take into account that the negative reference point is not the chassis but a point on the circuit marked as the reference point for certain voltage measurements (marked in red}, and which is close to the negative end of the main bridge rectifier. The resultant waveform was basically a square wave, but with some ringing on the leading edge. More exactly, the basic square wave had an amplitude of about 550V, while the ringing had a peakto-peak amplitude of about 100V, or 50V above the 550V, making a total peak value of 600V. I made a note of this and was about to plug in the set's own board when I had a stroke of luck. Another K9 came in for a relatively simple fault, providing a golden opportunity for another reference. In fact, it produced a waveform almost identical with that from my own board, so I felt reasonably confident that this was how it should be. All that remained now was to check the suspect board. And this gave me my first real clue. In general terms, the waveform was the same, at least in shape, but the values were significantly different. The square wave portion was now up to 600V while the ringing amplitude had also increased, now running at a good 200V p-p, or 100V above the square portion, giving a peak amplitude of 700V. Considering the set's history over the last few months I felt sure that this was the most likely cause. But I still had to find out why it was happening and, in the process, prove that it wasn't just a normal spread of component values. And now that I had something definite to go on I began to recall some suggestions I had heard about causes of excessive ringing and possible destructive spikes. Among the suspect components is R175 (120} and R174 (560), both in the base circuit of TS 170, which, if they go high, can cause excessive ringing. Also in the base circuit is C177 (4.7µF} which apparently can cause trouble if it drops its value. These were checked and found to be spot on. Less likely suspects are R182 (0.330 or, in some cases, 100), and R176 and R177 (18kn}. These were also checked and cleared. So what now? With the base and emitter circuits seemingly cleared, what about the collector circuit? Among other things this contains three filter networks consisting of resistors, capacitors and diodes. The failure of any one of these would surely have some effect on the waveform. I started with D176, R173 and Cl 93, all of which checked out OK. So did D179 in the adjacent network, but R190 (150k0) was a different matter - it was open circuit! I replaced this and then, before returning the board to the set, checked out the third network consisting of D178, R189 and Cl 75. All were OK. I put the board back into the set, hooked up the CRO, and switched on. Up came a perfect waveform; ie, identical to the other two boards. And that, as far as I was concerned, was all the proof I needed. I have since handled several more K9s and have made a point of checking the waveform as a matter of routine. All have been essentially the same as my own stock board. So that was it. I put everything back together, ran the set for a couple of days, then returned it to the customer. Only a few weeks have elapsed since then so it is much too early yet to boast. All I can do is keep my fingers crossed and hope. -1e1gscHlADIResistor kits for Laboratory * Service * Workshop These comprehensive resistor kits are ideal for the engineer, technician and the dedicated enthusiast. No more wasting time trying to find odd value resistors. No more high procurement costs for small order quantities. Have them at your fingertips when you need them , neatly stored for quick selection in transparent rectangular tubes or compartments, clearly marked with the IEC Series resistance values. Kits are available with 50 to 586 resistance values and containing from 1,210 to 26,000 resistors, in surface mount (MELF) or leaded types. This is our Mini-MELF (LMM 0204-24) lab assortment containing 6500 resistors. For further information contact: 1 f~ ~~\ CRUSADER ELECTRONIC COMPONENTS PTY LTD ~I//J\\\"": 81 Princes Hwy, St Peters , NSW 2044 . Phone (02) 516 3855 , 519 6685, 517 2775. Telex 123993 . Fax (02) 517 1189 . APPOINTED DISTRIBUTORS Sydney: George Brown & Co Pty Ltd , 519 5855. Geoff Wood Electronics Pty Ltd , 810 6845. Wollongong: Macelec Pty Ltd, 29 1455 . Canberra: George Brown & Co Pty Ltd , 80 4355. Newcastle: Novocastrian Electronic Supplies, 62 1358. · Melbourne: Nalmos Pty Ltd , 439 5500. Jesec Components Pty Ltd , 598 2333. George Brown & Co Pty Ltd, 878 8111. Brisbane: L. E. Broughen & Co, 369 1277 . Colourview Wholesale Pty Ltd , 27 5 3188. St Lucia Electronics, 52 7 466. Adelaide: Protronics Pty Ltd, 21 2 3111. Perth: Simon Holman & Co, 381 41 55. Protronics Pty Ltd , 362 1044. DECEf\lBER 1987 67 STEAM LOCOS COME OF AGE THE EVOLUTION OF ELECTRIC RAILWAYS By the turn of the century, steam locomotives were the supreme mode of land-based transport. But there were already a number of places where electric locos were more suitable. By BRYAN MAHER The first underground city railway began operating in London in 1863, initially using steam locomotives. Yes, doubting reader, they really were steam operated. Smoke abatement measures included ventilation shafts at strategic points along the tunnels and a unique locomotive design whereby the exhaust smoke and steam was piped back into the side watertanks. But passengers still coughed and spluttered. The solution was the introduction of some electric locomotives in 68 SILICON CHIP 1890, leading ultimately to the use of electric multiple unit sets. A live third rail laid beside or between the running rails provided direct current supply to an insulated sliding brass shoe attached underneath the train. Voltages up to 750 volts were used and the return current passed back via the wheels and the running rails. The second happening destined to eventually change the face of railroading was the invention in 1897 of an internal combustion engine using compression ignition of fuel. This engine was the brain child of Germany's Herr Doktor Rudolph Diesel. Intended initially for aircraft propulsion, the failure of the diesel engine in this application lead to its use in shipping. Railway applications of the diesel engine were slow in coming though, with Sweden taking the honours for the first dieselelectric locomotive in 1913. We'll talk more about that later in this series. Electric traction develops The London Underground was not the first foray into electric propulsion for trains. The world's first electric railway carrying farepaying passengers ran in Berlin, Germany in 1879. True - it only carried twenty passengers sitting atop three flat trucks running on a narrow rail gauge (less than 500mm). This was the first use of the voltage supply on a 'live' third rail One of the world's first articulated Mallet type locos. Delivered to the Santa Fe Railroad in 1909, it weighed close to 300 tonnes in working trim and had a tractive effort of 108,300 lbs, greater than anything ever built for Australia or England. (Santa Fe photo). system. Installed at the Berlin Exhibition by Siemens-Halske, its top speed of 13km per hour was impressive, at least to the frightened passengers. In the following year, Thomas Edison opened to the public his small electric railway at Menlo Park, New Jersey USA. By 1881 a 2.5km electric tramway was operating in Berlin and Lichterfelde, Germany, while in the USA Edison commissioned the first steam driven electric power station at Perl Street, New York City the following year. Frank Sprague operated an electric railway system at St. Joseph, Missouri USA in 1887, and a larger system, The Union Passenger Railroad, at Richmond Virginia immediately followed. Tunnels again The greatly respected Baltimoreand-Ohio Railroad chose to electrify a section of their main line in 1895 because of the problems associated with steam locomotives in the 2.4 kilometre tunnel at Howard Street, Baltimore. This, the first main line electrification in America, used low voltage direct current on an overhead trolley wire (using the catenary suspension system) from 1895 until 1901 when a third rail system was substituted. In New York, Boston and Chicago, the city fathers inflicted upon their citizens the dreaded "EL", the Electric Elevated Street railroad systems, to celebrate the turn of the century. To date all systems had used direct current, of 500, 600 or 750 volts, collected from the live third rail. Difficulties with commutators, used for carrying currents into the motor armatures, placed a practical limit on the direct current voltage at around 1500 volts. Some systems, however, placed two motors in series and used 3000 volts. Massive generators were installed at four to 10 kilometre intervals along the tracks. These connected to either a live third rail beside or between the running rails, or alternatively to a catenary Wire strung high above the roof of the train. These designs are used to this day in many parts of the world. The live third rail method was adopted by the United States for elevated and underground tracks, and also by the London Underground which spread vertically and horizontally and eventually grew into the world's largest electric suburban railway system. It uses a 750 volt direct current supply. Italian pioneering Italy, always a nation to 'do it their own way', brought into use in 1900 the world's first Three Phase Alternating Current Electric Railway. As a nation without coal resources for ground-based power stations, their hydro-electric generators were inevitably situ:ited far from the rail tracks. To ease the problems of long distance electricity transmission and to allow simpler transformer substations near the tracks, alternating current was adopted. Thus track-side equipment was notably cheaper than the rotary machines used in England, the USA and Germany. A big problem arose, however, with traction motor design. Westinghouse in America was pioneering alternating current (AC) motors for workshop and stationary machine use, using the three-phase induction motor principle. But there is a big problem with induction motors in that they have a very strong tendency to run at one single speed (the so-called synchronous speed). This is an advantage in many appications but this onespeed tendency was a severe drawback in railway traction. Nevertheless, Italy persevered with the 3-phase system for their railways and in much of the country used it exclusively. By 1928, 2600km of main lines were working on 3-phase AC. Two separate overhead catenary wires hung above the train while the tracks formed the necessary third phase conductor. As you might expect, great difficulties plagued the overhead wiring at track crossovers and points. The advantages of a 3000 volt DC system were finally recognised in 1928, but so extensive was the three-phase AC system that the last of it was not converted to DC until 1971. Currently, nearly 9000km of 3000 volt DC systems provide the Italian nation with an excellent service. Full steam ahead Meantime, neither the English nor the Americans were very enthusiastic about electrified main line railways, except of course for inner city, underground and elevated track sections. Strange indeed is the history of this section of the industry. England, Australia and many other countries slowly increased their electric suburban lines and regarded them as investments in the future, but in the United States the opposite occured. Between 1890 and the World War I, the US railroad companies built close on 40,000km of these small electric commuter systems but by the time of World War II a DECEMBER1987 69 Built in 1944 for the Santa Fe Railroad by the Baldwin Locomotive Works, this 4001tonne heavy freight loco was capable of a tractive effort of 93,000lbs and high speeds. Its height was 4.87 metres and its length was nearly 30 metres. large proportion of these had gone, replaced by the spreading blight of automobile mania. English development up to the 1940s consisted mainly of raising running speeds of steam trains, track straightening, and building some beautiful top class steam locomotives capable of running for up to 600 kilometres without stopping. These locos featured a passageway through the tender to the first carriage to allow a change of crew without stopping, and a scoop below the tender to pick up water from a long trough between the rails while travelling at high speed. The English saw no need for very large tenders, and their relatively flat terrain allowed them to design steam locomotives for speeds over 170 km per hour with little need for particularly high drawbar-pull. Many of their locomotives were of . the 4-6-0 wheel arrangement, meaning four small wheels in a leading bogie followed by six larger driving wheels with no small wheels behind the drivers. With larger designs, a trailing bogie of two wheels might be added to support the extra weight of a bigger firebox. This wheel arrangement is called the 4-6-2 or "Pacific" type and was famed for its fantastic performance hauling the "Flying 70 SILICO N CHIP Scotsman''. Some 2-8-2 locomotives were in use from 1925 and in 1952 a rather strange looking 2-10-0 design took to the rails and was promptly nicknamed the "Decapod". Though the English had electric suburban trains aplenty, and were manufacturing electric locomotives for many overseas orders, they had only six electric locomotives running in their own country as late as 1948. Back in the USA Meantime across the Atlantic, the Americans were similarly concentrating all their efforts on bigger and faster steam locomotives, top class luxury trains, and straighter and stronger tracks. In the 1920s to the 1940s they reached their peak with such well remembered famous trains as the ''Twentieth Century Limited" from New York to Chicago on the New York Central system, and the "Super Chief" from Chicago to Los Angeles on the Atchi son, Topeka & Santa Fe Railroad. Few countries can boast songs eulogising their trains but such hits as "Orange Blossom Special" and "Chattanooga Choo Choo" show the high esteem in which US trains were held in their heyday. From the beginning, the American scene featured 8-wheel bogie freight waggons which were much larger than the 4-wheel goods trucks commonly seen in England. The bogie design also allowed higher running speeds. And the English weren't the only ones developing steam locomotives capable of running long distances without stopping. The Americans, with their heavier trains and mountainous country, were forced into building larger steam locomotives than any other nation. Consider the Union Pacific Railroad which crosses the Rocky Mountains at the 2.5km (8250 feet) high Sherman's Hill in Wyoming. This is via a long, long 104km continuously rising slog upwards at a 1-in-120 gradient. This mountain crossing led to the building of a number of huge steam locomotives, including the massive 4-8-8-4 "Big Boys" which developed 7.46 megawatts of power. These locos had two sets of eight driving wheels and four cylinders. They were also articulated so that they would go around bends. The Santa. Fe Railroad from Chicago to California crosses the Rockies at the 2.4km (7590 feet) high Ra ton Pass which is approached by a very long 1-in-33 gradient. This beautiful example of the steam loco designer's art enabled Santa Fe heavy freight trains to run at express speeds over thousands of kilometres. Those driving wheels are more than two metres in diameter. To conquer such obstacles the railroad as early as 1909 obtained the world's first four cylinder articulated Mallet type steam locos whose drawbar pull or tractive effort exceeded 100,000lbs. Early articulated models were not stable enough to run at high speeds, but later efforts in the late 1930s could run at passenger speeds. Known as the Mallet design, it became a symbol of the enormous size of all large US railroads. Towards the end of the steam era, the Santa Fe Railroad purchased some beautiful examples of the locomotive art, typified by the 2900 class, a 4-8-4 type with a huge tender carried on sixteen wheels, and the equivalent freight model, the 2-10-4 type 5011 class. Each tender carried 32 tonnes of fuel and 120 tonnes of water. To achieve express speeds the driving wheels of the 2900 class were just over two metres in diameter! (To give you an idea of how big that is, it's about the height of a standard domestic door!) These locomotives often ran for as much 2850km before being taken off the train for running service. Although the Santa Fe Railroad operates no electric locomotives, diesel electrics were introduced as early as 1935 and progressively in- creased in numbers until the steam era finally ended in 1959. American electric triumphs Over in the eastern side of the United States, the Allegheny and Appalachian mountains in Virginia and Pennsylvania proved to be a formidable barrier to the locomotive builders of the Chesapeake & Ohio, Baltimore & Ohio, the Virginia and the Pennsylvania Railroads. Before the first two of these amalgamated, they purchased some amazing steam motive power, including the only 2-6-6-6-0 type locomotives ever built. These claim the record for the highest power output of any steam locomotive. But the Virginia and the Pennsylvania have a more important reason to be included in our story for they both introduced electric locomotives early in the piece. The Virginia Railroad probably will hold forever its distinction of operating locomotives having by far the highest drawbar pull or tractive effort. The purpose of their line was A 1950s vintage American diesel-electric locomotive at Kingston, Rhode Island, in 1975. This loco was typical of many which replaced steam in the USA between 1940 and 1960. DECEMBER 1987 71 Pride of the Pennsylvania Railroad were the fast and powerful GG1 class electric locos. They showed the USA the capabilities of electric traction. to haul West Virginian coal up and over the Alleghenies and the Appalachians to the seaports of Chesapeake Bay. For the downhill and level coastal section of the route, their 15,000 tonne trains used one 2-10-10-2 compound steam loco having a drawbar pull of 783 kilonewtons (176,000 lbs), the highest figure for any steam locomotive ever built. For the uphill sections they cut the train into 5000 tonne sections each headed by (wait for it!) a triple-unit electric locomotive having 1234 kilonewton (27.7,500 lbs) drawbar pull, the highest figure achieved by any loco ever built. For climbing the 220km single track mountain section, mostly at a gradient of 1-in-30, traffic schedules were arranged so that loaded up-trains never had to stop at crossing loops, but slogged endlessly uphill at a steady pace, all trains of empties having to wait 72 SILICON CHIP where required. Little wonder that their plant earned the name " The Transportation Factory' ' . Contrast this with modern diesel electric locomotives rated singly at 50,000 to 80,000lbs of drawbar pull, intended to be coupled in groups of two, three, or more as needed. Eventually the Virginia Railroad was incorporated into a larger system, the Norfolk & Western Railway. The Pennsylvania RR The Pennsylvania Railroad, dating from 1831, went through a number of name changes and amalgamations before coming to its final 1874 form when , with 17,000km of track, it was the largest in the United States. It is important to our story, because it has featured high speed expresses hauled by electric locomotives over long distances for about 50 years. That's if we include the years since their acquisition in 1971 by the Government-sponsored Amtrak organization. The Pennsylvania RR purchased from the General Electric Company many wellengineered electric locos, including the legendary GGls which were top-class units lasting from the 1930s to their final replacement in 1981. These large and powerful machines, 24.23 metres (79 feet six inches) long and 4.57 metres (15 feet) high weighed in at 213 tonnes. Interestingly, their classic streamlined curves were created by the famed French-born industrial designer Raymond Loewy who also designed the Studebakers of the 50s. They are now replaced by newer electric locomotives, but more about that in a future episode. Grateful thanks to Santa Fe Railroad; Conrail; Amtrak; Swedish Railways; and the SRA of NSW for data and photos. AMATEUR RADIO By GARRY CRATT, VK2YBX Amateur radio in the VHF bands Most amateur activity in Australia occurs on the VHF bands. Here's how to listen in to these bands, plus a list of amateur repeater stations. The VHF bands provide an excellent outlet for both the social and technical needs of the radio amateur. The equipment required to operate on these bands is widely available and ranges from modified commercial FM equipment to stateof - the - art amateur radio equipment. The large concentration of repeaters in the 144-148MHz (2-metre) band confirms its popularity - Fig.1. Normally located at well elevated sites, repeaters provide enhanced mobile coverage of up to 150km, a vast improvement over the 20-30km 'line of sight' normally achievable using single frequency mobile communications. Such repeaters provide the ideal medium for regular daily 'rag chewing' for many amateurs whilst mobile to and from work, and also provide a signal source for experimentation with high gain antennas and other equipment for those interested in the technical pursuits of amateur radio. For the newcomer wishing to listen to FM communications on the VHF amateur bands, the scanning receiver offers a wide frequency l Fig.3: the discone antenna is used by many amateurs and can provide wideband coverage from 50-500MHz. A FREQUENCY DIMENSION A (cm) DIMENSION B (cm) 52MHz 146MHz 438MHz 137 49 16 144 51 17 Fig.2: this simple but effective groundplane antenna can be made for just a few dollars. It can be cut to cover either the 6-metre, 2-metre or 70cm band. range for a modest investment. Many scanning receivers cover the 6-metre (50-54MHz), 2-metre (144-148MHz) and 70cm (420-450MHz) bands, and a simple but effective groundplane antenna at the relevant frequency can be made for just a few dollars - see Fig.2. Alternatively, a wideband antenna called a 'discone' may be employed to cover all VHF bands. A typical VHF discone antenna covers 50-500MHz, and provides a gain of 3dB (Fig.3). For those enthusiasts interested in modes of communication other · than FM, the lower 2MHz of the 6-metre band and the lower 1MHz of the 2-metre band are normally DECE MB ER1987 73 Fig. 1: Operational VHFIUHF Repeaters in Australia TWO METRE REPEATERS A.C.T AREA CALL Canberra ACT VK1RAC 6900 Black Hill VK1RGI 6950 Mt. Ginini CHAN SITE NEW SOUTH WALES Coffs Harbour VK2RCH 6650 Bruxner Park W. Blue Mountains VK2RDX 6650 Mt. l3indo Moree/lnverell VK2RMI 6650 Terry Hie Hie VK2RTY 6675 Terry Hills Sydney Orange VK2RAO 6700 Mt. Canobolas Ulladulla VK2RMU 6700 Milton Pt. Macquarie VK2RPM 6700 Taree Gosford VK2RAG 6725 Somersby Bega VK2RFS 6750 Mt. Mumbulla Tamworth VK2RTM 6750 Mt. Crawney VK2RWG 6750 Mt. Flackney Wagga W'bungles VK2RCC 6800 Needle Mtn Lismore VK2RI C6800 Parrots Nest Sydney-Metro VK2RLE 6800 Heathcote Gunnedah VK2RAB 6850 Porcupine Res. Wollongong VK2RAW 6850 Mt. Murray Griffith VK2RGF 6850 Mt. Bingar Sydney-Nth VK2RMB 6875 Terry Hills Beaches VK2RAN 6900 Mt. Sugarloaf Newcastle Condobolin VK2RRT 6900 Boona Mount Syd-Lower N. Shore VK2RGR 6925 North Ryde N.England Tableland VK2RNE 6950 Mt. Rumbee Sydney-Metro VK2RWI 7000 Dural Blue Mountains VK2RMB 7050 Mt. Tomah Syd-E. Suburbs VK2ROT 7075 Paddington Newcastle VK2RTZ 7100 Mt. Sugarloaf Grenfell VK2RWM 7100 Grenfell Sydney Emergency VK2RWS 7150 Chats wood State Wide VK2RSD 7200 Mt. Emerg. Cambewarra VK2RST 7225 Lane Cove Sydney West Syd-Upper N.Shore VK2RNS 7250 Hornsby N. Wollongong VK2RIL 7275 Sublime ~oint VK2RHR 7350 Bowral Mittagong Syd-Sth West VK2RLD 7375 Razorback Shepparton Melbourne Corryong Quyen Melbourne Ballarat VICTORIA VK3RGV 6650 VK3RML 6700 VK3RNC 670 VK3RON 6700 VK3RPA 6700 VK3RBA 6750 Latrobe Valley Mildura Mt. Macedon East Gippsland Swan Hill Grampians Geelong Wodonga Omeo Robinvale Warrnambool VK3RLV VK3RMA VK3RMM VK3REG VK3RSH VK3RWZ VK3RGL VK3RNE VK3RGO VK3RVL VK3RWL 74 6800 6800 6850 6900 6900 6950 7000 7000 7050 7050 7050 SILICON CHIP Mt. Wombat Mt. Dandedong Mt. Mittamattie Quyen St. Albans Mt. Bunningyong Mt. Tassie Mildura Airport Mt. Macedon Donalds Knob Swan Hill Mt. William Mt. Anakie Mt. Big Ben Mt. Livingstone Robinvale Mt. Warrnambool Bright S. Gippsland Geelong Bendigo Melbourne W. Gippsland Melbourne Wodonga VK3RPB VK3RSG VK3RGC VK3RCV VK3REC VK3RWG VK3RTY VK3RPN 7100 7100 7125 7150 7175 7225 7350 7600 Mt. Porepunkah Bass Hill Montepellier Mt. Alexandria Mt. Dandenong Warragul Mt. Dandenong Mt. Stanley QUEENSLAND Rockhampton VK4RAR 6700 Rockhampton Townsville VK4RAT 6700 Mt. Stuart Gold Coast VK4RGC 6700 Mt. Tambourine Darling Downs VK4RDD 6750 Mt. Mowbullan Bundaberg VK4RBU 6800 Mt. Goonaneman North Coast VK4RNC 6850 N. Nambour Ipswich VK4RAI 6900 Mt. Crosby Gladstone VK4RGB 6900 Caliope Range Cairns VK4RCA 6950 Mt. Bellenden Ker Brisbane VK4RBN 7000 Mt. Glorious VK4RMK 7000 Nth Mackay Mackay Brisbane VK4RBT 7050 Mt. Cotton Brisbane VK4RAG 7150 Springhill Bundaberg VK4RBS 7250 Mt. Goonaneman SOUTH AUSTRALIA Port Pirie VK5RMN 6700 The Bluff Adelaide VK5RHO 6850 Houghton Mt. Gambier VK5RMG 6900 Mt. Gambier Adelaide VK5RAD 7000 Craters Alice Springs VK5RCA 7000 Alice Springs WESTERN AUSTRALIA Bunbury VK6RSW 6650 Bunbury Albany VK6RAL 6700 Albany Perth VK6RAP 6700 Roleystone Wyndham VK6RWH 6700 Wyndham Wickham VK6RWK 6700 Wickham Perth VK6RTH 6750 Tic Hill Albany VK6RAA 6800 Mt. Barker Perth VK6RTH 6800 Tic Hill Karratha VK6RWP 6800 Karratha Exmouth VK6REX 6850 Tower Zero Kambalda VK6RKB 6850 Kambalda VK6RBY 6900 Mt. William Bunbury Mt. Newman VK6RMN 6900 Mt. Newman Perth VK6RPD 6950 W.A.I.T. Bentley Emergency VK6REE 6975 Kalgoorlie VK6RAK 7000 Kalgoorlie Wagin VK6RAW 7000 Mt. Latham Emergency VK6REE 7000 Geraldton VK6RGN 7000 Geraldton Port Hedland VK6RNW 7000 Port Hedland Perth VK6RTY 7050 Nedlands Perth VK6RWC 7100 Doubleview Cataby VK6RCT 7200 Cataby Boddington VK6RMS 7250 Mt. Saddleback Eneabba VK6REN 7300 Ocean Hill Busselton VK6RBN 7350 Busselton North West Hobart North West Coast East Coast North East Coast TASMANIA VK7RAD 6625 Mt. Duncan VK7RHT 6700 Mt. Wellington VK7RNW 6750 Ulverstone VK7REC 6900 Snow Hill VK7RAA 7000 Mt. Barrow 70cm REPEATERS A.C.T. VK1RGI 8525 Mt. Ginini Canberra NEW SOUTH WALES Southern Highlands Gosford Sydney N. Beaches Wollongong SydneyEmergency N. Coast-Taree Blue Mountains Syd-S Suburbs Syd-W Suburbs Sydney-Metro Newcastle Newcastle Lismore N. Wollongong Melbourne Melbourne Gippsland Melbourne Wodonga Mildura Grampians Mt. Macedon Banalla Melbourne VK2RTK 8025 Bowral VK2RAG 8074 Somersby VK2RMB 8175 Terrey Hills VK2RUW 8225 Port Kembla VK2RWS VK2REE VK2RUT VK2RUH VK2RRS VK2RWI VK2RUM VK2RAN VK2RSC VK2RIL 8275 8325 8375 8425 8525 8525 8625 8625 8675 8725 VICTORIA VK3RMU 8074 VK3ROU 8225 VK3RGU 8375 VK3RAD 8525 VK3RNU 8525 VK3RRU 8525 VK3RWU 8675 VK3RCU 9275 VK3RDU 9425 VK3RPU 9725 Chatswood Taree District Kurrajong Hurstville Parramatta Dural New Lambton Mt. Sugarloaf Mt. Nardi Sublime Point Mt. St. Leonard Mt. Dandedong Carrajung Mitcham Mt. Stanley Merbein Mt. William Mt. Macedon Chassney Vale Arthurs Seat QUEENSLAND VK4RNC 8074 Mt. Nambour VK4RGC 8225 Mt. Tambourine VK4RWM 8375 Ipswich VK4RBC 8525 Mt. Cootha VK4RBU 8675 Mt. Goonaneman SOUTH AUSTRALIA VK5RWI 8525 Craters North Coast Gold Coast Brisbane Brisbane Bundaberg Adelaide WESTERN AUSTRALIA VK6RUF 8525 Roleystone Perth Hobart TASMANIA VK7R TC 8600 Mt. Nelson North East VK7RAB 8550 Mt. Arthur SIX METRE REPEATERS NEW SOUTH WALES VK2RWI 3850 Dural (Proposed) VICTORIA Melbourne VK3RTN 3675 Mt. Dandedong Melbourne VK3MH 3900 Hurstbridge Sydney WESTERN AUSTRALIA Perth VK6RSM 3200 Tic Hill Note: repeater offsets (ie, the difference between input and output frequencies) vary depending on the VHF band. 2-metre repeaters utilise a 600kHz offset; ie, the repeater transmits 600kHz higher than the received frequency. 70cm repeaters use a 5MHz offset, while 6-metre repeaters use a 1MHz offset. Fig.5: International VHF/UHF Beacons SIX METRE BAND FREQUENCY 50.010MHz 50.075 50.090 51 .020 51.030 52.013 52 .020 52.100 52 .200 52 .225 52 .250 52.310 52.320 52 .325 52.345 52.350 52.370 52.418 52.420 52.425 52.435 52.440 52.450 52.460 52.465 52.470 CALL SIGN JA2IGY VS6SIX KH6EQI ZL 1UHF ZL2MHB P29BPL FK8AB ZK2SIX VK8VF ZL2VH2 ZL2VHM ZL3MHF VK6RTT VK2RHV VK4ABP VK6RTU VK7RST VK0MA VK2RSY VK2RGB VK3RMV VK4RTL VK5VF VK6RPH VK6RTW VK7RNT LOCATION Nagoya Hong Kong Honolulu Auckland Hawkes Bay Loloata Island Noumea Niue Darwin Tarana ki Manawatu Christchurch Wickham Newcastle Long reach Kalgoorlie Hobart Mawson Base Sydney Gunnedah Hamilton Townsville Mt. Lofty Perth Albany Launceston reserved for CW and SSB modes of communication. Here, extensive use is made of multiple element directional antennas (yagis) and low noise receiver preamps to extract the maximum possible performance from equipment and so provide communications over reasonable distances. In fact communications over enormous distances can be achieved when atmospheric and ionospheric conditions are favourable (see Fig.6). To enable operators to be alerted to these favourable conditions, an international network of VHF beacons operates normally on a 24-hour basis. Thus, if an enthusiast in Australia is particularly interested in communicating with New 52.485 52.490 52.510 VK8RAS ZL2SIX ZL2MHF Alice Springs Blenheim Mt. Climie TWO METRE BAND 144.019 144.400 144.410 144.420 144.430 144.465 144.470 144.480 144.485 144.550 144.565 144.600 144.800 144.950 145.000 145.100 145.150 145.175 145.200 145.225 145.280 145.300 145.400 145.425 VK6RBS VK4RTT VK1RCC VK2RSY VK3RTG VK6RTW VK7RMC VK8VF VK8RAS VK5RSE VK6RPB VK6RTT VK5VF VK2RCW VK6RPH ZL 1VHF ZL1VHW ZL 1VHR ZL2UHF ZL2VHT ZL2VHN ZL3VHF ZL4VHF ZL4VHI Busselton Mt. Mowbullan Canberra Sydney Glen Waverley Albany Launceston Darwin Alice Springs Mt. Gambier Port Hedland Wickham Mt. Lolly Sydney Perth Auckland Hamilton Rotorua Wellington Taranaki Takaka Christchurch Dunedin lnvercargill Zealand on the 2-metre band, propagation conditions can be determined by monitoring the ZL 1VHF beacon frequency of 145.100MHz. Fig.5 shows a list of VHF beacons currently operating. When atmospheric and ionospheric conditions are favourable, FM communications on the VHF bands are often achievable over hundreds of kilometres. The VHF bands also provide access to many amateur spacecraft. The latest amateur satellite OSCAR 12 (J AS-1) uses a series of uplink frequencies in the 2-metre band and corresponding downlinks in the 70cm band. Provided low loss cable and low noise receiver preamplifiers are used it is quite normal to be able to communicate 70cm BAND 432.057 432.160 432.410 432.420 432.440 432.445 432.450 432.535 432.535 432.540 433.000 433.080 433.150 433.200 433.225 433.250 VK6RBS VK6RPR VK6RTT VK2RSY VK4RBB VK4RIK VK4RTL VK3RAI VK3RMB VK4RAR ZL2UHF ZL2VHN ZL1VHW ZL3UHF ZL2VHT ZL2VHP Busselton Nedlands Wickham Sydney Brisbane Cairns Townsville Macleod Mt. Buninyong Rockhampton Wellington Takaka Hamilton Christchurch Taranaki Manawatu 23cm BAND 1296.171 1296.420 1296.480 1297.000 1297.100 1297.150 1297.225 VK6RBS VK2RSY VK6RPR ZL2UHF ZL1UHF ZL1VHW ZL2VHT Busselton Sydney Nedlands Wellington Auckland Hamilton Taranaki via such satellites using very modest power levels (10W or less). Fig.6: Australian Distance Records BAND 50MHz 144MHz 432MHz 576MHz 1296MHz 2300MHz 3300MHz 5650MHz 10,000MHz STATIONS VK8GB to 9Y 4LL VK4ZSH to JA70XL VK3ZBJ to VK6KZ VK4ZRF to VK4ZSH VK6KZ to VK5MC VK5QR to VK6WG VK3KAJ to VK3ZBJ VK2AHC to VK2SB/VK2ZND VK3KAJ to VK3ZBJ DATE 10/4/82 24/4/83 23/1 /80 7/12/81 23/1 /80 17/2/78 25/1 /86 12/4/75 8/2/86 DISTANCE (km) 18,665 6617 2716 378 2289 1885 246 114 262 The Uniden BClOOXL scanner (Santronic Agencies, Kings grove). DECEMHER1987 75 Build this superb December 1987 1GHz Digital Frequency Meter In this second article on our state-of-theart 1GHz Digital Frequency Counter we continue describing the special circuit features which make it easy to use and give it such a high performance. By STEVE PAYOR Last month we described the circuitry on the front panel board, up to the point where the incoming signal had been squared up and prescaled to provide a 0-10MHz signal for the ICM7216A counter IC. Before it is fed into the counter though, the signal is converted from ECL to CMOS voltage levels by Q2, a 2N4258 switching transistor. When the ECL output from IC4b (pin 15} is low, Q2 is turned on and the collector voltage rises to just over + 4V. When the ECL output is high, the transistor is turned off and the 27011 collector resistor pulls the output down to 0V. The BAW62 diode is important here. Without it, Q2 would not turn off fully and if that diode has a forward voltage drop greater than 0.9V at 15mA, Q2 will not turn on fully. This means that a BAW62 diode must be used here instead of the more common 1N914 or 1N4148. In other words, don't substitute. Similarly, do not substitute an or- Comments on the Parts List (1 ). The five miniature red LEDs specified in the parts list should be the 3mm round type. If highefficiency types are used here (eg, Hewlett-Packard HLMP-1301), the 27011 current limiting resistor should be increased to 56011 so that the LED brightness matches the display brightness. (2) . Do not substitute for the specified HDSP-5501 ?-segment LED displays. The display brightness will be disappointing it you do. 76 SILICON CHIP (3) . The red LED used tor setting up and testing should be a standard type with a forward voltage of 1. 7V. (4). The 0 .047µ,F input capacitor was listed as a ceramic in the parts list. The author would prefer a highvoltage plastic type here. Either a 250V or 400V DC rating should do, depending on the intended use of the meter. Physical size must be checked as the space available for this capacitor is limited. Metallised dinary PNP transistor for the 2N4258 (or PN4258}, as this is a special type designed for highspeed saturated switching. One final note - we have chosen a fairly low value of collector load (27011} so that the input capacitance of the 7216A will not slow the fall time of the waveform too much. However, any additional capacitance at this point will kill the high frequency response. For example, connecting a CRO lead to observe the 4V p-p waveform at 10MHz will stop the counter from functioning. The 7216A counter IC Those readers not familiar with the basics of digital frequency and period measurement can refer to the accompanying panel for a brief summary. Although this summary makes the task look fairly simple, a vast amount of support circuitry is required to make a practical instrupolyester layer-type construction is the most compact. (5). The 4-40pF trimmer capacitor should be a Philips type if it is to fit into the PCB. Stability- both electrical and mechanical - is very important here. (6). The mains switch must be rated for 240V AC. Don't use a switch with a 125V, 5A rating - it might fail after a short time. An alternative to the push-on push-off type is the standard C & K miniature toggle switch, which has a more than adequate rating. The bottom corner of the display PCB is This view shows the neat and orderly layout of the parts on the display PCB. Keep all leads as short as possible and make sure that the LED bar modules line up with the front panel displays. ment. Fortunately, most of this circuitry is contained within the 7216A. Essentially, the 7216A is a fullyintegrated 10MHz universal counter IC. It contains a highfrequency oscillator, a decade timebase counter, an 8-decade data counter, and all the circuitry necessary to generate gating signals, latch data and drive an 8-digit multiplexed LED display. The 7216A is designed to drive common anode LED displays. The inbuilt segment drivers sink a condesigned to be cut away when using this type of switch. The switch itself is mounted directly on the front panel. (7). A small transparency with the "µsec" and "kHz" display annunciators should be added to the parts list. (8) . Use 24 x 0.2mm hook-up wire for all wiring. It is important to minimise the resistance between the power supply and the counter board, otherwise noise from the power supply will appear on the +5V supply at the counter board. trolled current of 25mA per segment, while the digit driver outputs can source up to 200mA each, when all the segments on a digit are lit. The display multiplex frequency is 500Hz, and so each digit has a time-slot of 250µs. In actual fact, each digit is only on for a period of 244µs. An inter-digit blanking time of 6µs is used to prevent " ghosting" between digits. We have specified high efficiency 7-segment displays (HewlettPackard HDSP-5501). These are much brighter than the normal variety, and the 7216A counter runs somewhat cooler because of their higher forward voltage drop (2.2V vs 1.7V for normal displays). The 7216A also provides an output for driving decimal points on the display but we have had to design a separate decimal point driver circuit (more about this later). The 7216A decimal point output is used instead to drive a LED which indicates that the counter has overflowed. Frequency mode Fig.8 shows a simplified frequency meter with a counter , a reference frequency and a gating circuit. The reference signal is needed to open and close the gate for precise time intervals. The 7216A provides gating times of 0.01, 0.1, 1 and 10 seconds. All timing signals within this IC are derived from a clock frequency of 10MHz which is generated by the crystal controlled on-chip oscillator (pins 25 and 26 of the 7216A). The 10MHz signal is divided internally to 100Hz and then further divided by 1, 10, 100 or 1000 to give the required gating time intervals of 0.01, 0.1, 1 and 10 seconds. Ref erring to our simplified block diagram (Fig.BJ, imagine a programmable divider (-:- 1, 10, 100 or 1000) between the reference frequency (now 100Hz) and the gate control flipflop. The division ratio of this programmable divider - and hence the gating time - is controlled by the 7216A's Range input (pin 14). Connecting the Range input (pin 14) to the Dl digit driver output (pin 23) instructs the 7216A to select the -:- 1 option for its programmable divider. Similarly, connecting it to D2 [pin 22) selects -:- 10, while D3 selects -:- 100 and D4 selects -:- 1000. DECEMBER1987 77 Frequency and Period Measurement - "!"hertz INPUT REFERENCE FREQUENCY Fig. 8 How does a digital frequency meter work? In its simplest form, it consists of three basic blocks: a gate, which can be opened and closed to let the signal through to a counter, and an accurate timing signal to control the opening and closing of the gate. We call this the reference frequency . If we open the gate for exactly one second and, say, 123 pulses get through to the counter during this time, then the counter will show a final reading of " 123". This is the frequency measurement in Hertz. If we want greater accuracy, we can increase the gating time . For example, if the gate is opened for 10 seconds, and the counter registers 1234 pulses, then the frequency is 123.4Hz. J -"p" seconds --+-/ I _J INPUT \ p pulses ,- __ JLJl_fl___ GATE I 1 .-!-- - - - - ~ 17nn17,-,nn :J ---1-~-'-----...l---l flip- 110 '---+-----' I\ ~_u, u u u u u u u _, COUNTER gate open I ~~:ed LJlJlJ7_f7 Fig. 9 REFERENCE FREQUENCY I-;!~ If the signal frequency is very low, it is more convenient to measure the period of the signal. The same building blocks are used as for frequency measurements, but are slightly rearranged . The incoming signal is now used to open and close the gate, and it is the reference signal that is gated through to the counter. For example, if three cycles of the 1 Hz reference get through to the counter during the time the gate is open , then the period of the incoming signal is three seconds and the frequency is 1 ..,.. 3 = 0.3333Hz. If greater resolution is required , we can leave the gate open for say 10 cycles of the input signal, in which case a counter reading of 34 pulses gives us a period of 3.4 seconds . The divider output is used to gate through the input signal to the counter circuit (see Fig.8) for either 0.01, 0.1, 1 or 10 seconds. In period mode, the signal flow is _rearranged. In this case, the 7216A's programmable divider is connected to input A (instead of the lOOHz internal reference) and so the gate is now opened for 1, 10, 100 or 1000 78 SILICON CHIP cycles of the incoming signal, to gate through the reference frequency to the counter circuit (see Fig.9). Frequency ratio mode When function F4 (frequency to 1GHz) is selected, a + 128 prescaler is used. In order to obtain a direct reading in kHz on this range, some DFM designs take the rather drastic step of switching to another timebase. This design overcomes the problem in a more elegant manner by making use of another operating mode which the 7216A provides - the Frequency Ratio Mode. In this mode, the 7216A takes the input for its reference counter from Input B (pin 2), instead of the internal l00Hz reference. Apart from that, the internal configuration is exactly the same as for frequency mode. Therefore, if we were to feed lO0Hz into input B, we would obtain the same result as for a normal frequency measurement. If, however, we feed a signal of 100/1.28 = 78.125Hz into Input B, the gating periods will be 1.28 times longer. Similarly, by feeding a signal of 7.8125Hz into Input B, the reading can be scaled up by a factor of 12.8, and the gating times are now 0.128, 1.28, 12.8 and 128 seconds. This is how we solved the problem of having a + 128 prescaler on the 1GHz (one gigahertz) range. We simply shifted the decimal point one place to the right (xlO) and increased the gating times by a factor of 12.8 to give the desired x128 correction factor. But just where do we get a frequency of 7.8125Hz from? We could try dividing down the 10MHz crystal oscillator frequency by 1,280,000, but there is no need to go to so much trouble. The display multiplex frequency is 500Hz, and the 7216A obtains this frequency by dividing the crystal oscillator frequency by 20,000. So all we need is an additional + 64 stage to divide the 500Hz and we have our 7.8125Hz reference. The 500Hz signal is derived from digit driver DB, filtered by a lOkn resistor and 0.0022µF capacitor, and buffered by transistors Q15 and Ql6. The signal then goes to the clock input (pin 1) of a 4024 CMOS 7-stage binary counter (IC7). The output of the sixth stage (pin 4) is the required 500Hz 64 = 7.8125Hz. Controlling the 7216A The various operating modes of the 7216A - ie, Frequency, Frequency Ratio and Period - are selected by connecting the Function Fig.10: parts layout and wiring diagram for the 1GHz DFM. Note that the lOµF capacitors on the display PCB must be installed so that they lie flat against the board. Take care with the mains wiring. input (pin 3) to digit drivers Dl, DZ or DB respectively. This job is performed by CMOS analog switches ICBa, 9a, 10a and 11a. These connect the 7216A Function input to DB, Dt, Dl or DZ when control lines Fl, FZ, F3 and F4 are high respectively. The Range selection works in similar fashion. In this case, Rt, RZ, R3 and R4 control analog switches IC8c, 9c, 10c and 1 lc. These connect the 7Z16A Range input (pin 14) to digit drivers D4, D3, DZ and Dl respectively, selecting the gating times described earlier. Note that the circuit diagram (Fig.5) published last month is in error here. Pushbutton switch Rl should be connected to pin 6 of ICBc, while R2 should be connected to pin 9 of IC9c (these connections are transposed on the circuit diagram). The PCB artwork and component layout drawings are correct. Decimal points In either Period or Frequency mode, the 7Z16A delivers a decimal point drive pulse for digits DZ, D3, D4 or D5. Unfortunately, the 7Z16A's decimal point driver cannot be used because we need to shift the decimal point one place to the right for functions F3 and F4 (100MHz and 1GHz ranges). We solved this problem by designing an external decimal point driver circuit consisting of tran- sistors Qt 7 and Q18 and a number of CMOS switches. Here's how the circuit works. Q17 and QlB are driven by the digit driver outputs of the 7Z16A via the CMOS switches. These digit driver signals are selected by ICBb, 9b, 10b or llb when Rt, RZ, R3 or R4 are high respectively. Similarly, ICBd, 9d, 10d and lld are selected by Ft, FZ, F3 and F4. Let's say, for example, that Fl and Rl have been pressed. ICBb and ICBd both close and the D5 output of the 7Z16A drives Qt7 and QlB, thus turning on the decimal point at digit 5. If RZ is now pressed ICBb opens and IC9b closes. The D4 signal now drives Q17 and Q18 to light the decimal point at digit 4. DECEMBER1987 79 Specifications Operational modes Period, Frequency to 1 0MHz, Frequency to 1 00MHz, Frequency to 1GHz Frequency range 1OHz-1 GHz ( 1. 7GHz typ.) in frequency mode; 1 0Hz-2.5MHz (5MHz typ .) in period mode Gating times 0.01, 0.1 , 1 & 10 seconds (10MHz & 100MHz ranges); 0 .128, 1.28, 12 .8 and 128 seconds (1 GHz range) Maximum Resolution 0.1 Hz (10MHz range); 1 Hz (100MHz & 1GHz ranges) ; 0.0001 µ,s (Period mode) Display High-brightness 8-digit LED display, overflow indicator, usec and kHz annunciators, leading zero blanking Sensitivity 1 MO input: better than 20mV RMS from 10Hz to 20MHz, rising to 70mV RMS at 100MHz (see Fig.6) 500 input: better than 1 0mV RMS from 70MHz to 1 GHz. Typical peak sensitivity is 50µ,V RMS at 1.2GHz (see Fig. 7) Input impedance 1 MO input: 1 M0// 10pF for signals less than 1 V p-p; 180k0//20pF for large amplitude signals 500 input: 300//1.5pF at 1GHz Overload 1 MO input: 250V RMS for frequencies up to 10MHz (short term only), dropping to 25V RMS at 100MHz 500 input: 300mV RMS Accuracy/stability Typical uncalibrated accuracy with a good quality crystal is ± 1 0 parts per million (ppm) at 25 °c with a temperature stability of ± 12 .5ppm from -20°C to +70°C. Prototypes were found to have a total warm-up drift of considerably less than 1 ppm Power requirements 240V AC, 50/60Hz Similarly, R3 and R4 select IClOb and IC11b to light the decimal points at D3 and DZ. When F3 or F4 is selected, the decimal point must be shifted one place further to the right. These digit driver lines have already been selected by the 7 216A Range selection switches (ICBc, 9c, 10c and 11c), so the output of this network is simply connected to the inputs of IClOd and 11d. These then pass the signal along to the decimal point driver circuit when either F3 or F4 is high. Pushbutton latching Control signals R1-R4 and F1-F4 are vital to the function of the entire circuit. They are obtained from a circuit which simulates the action of a bank of mechanically interlocked pushbutton switches. This greatly simplifies the physical construc80 SILICON CHIP tion and allows the use of low-cost, click-action, PCB-mounted switches. The latching circuit uses the ubiquitous 4017 CMOS decoded decimal counter as a simple "keyboard scanner". One 4017 is used for each bank of switches (IC12 and 13). Both 4017s are clocked continuously by the 500Hz clock derived from the multiplexed display. However, they are prevented from counting continuously by the 47k0 resistors which pull the CE-bar inputs (pin 13) high, inhibiting the clocking. Thus, if no buttons are depressed, the counters remain in their current state indefinitely. Suppose now that the "1" output (pin 2) of IC12 is high. If Fl is now pressed, this high is connected to CE-bar which is already high, and so nothing happens. In other words, once signal Fl has been latched, further pressing of the Fl button has no effect. Now suppose we press button F4. Initially, the "3" output (pin 7) is low, so CE-bar immediately goes low and enables the 4017 counter. Counting then proceeds from "1" to "2" to "3", but when the "3" output (ie, signal F4) goes high, CE-bar also goes high and stops the counter. F4 now remains high, even after we've stopped pressing the F4 button. All this happens very quickly, although you may sometimes just catch a glimpse of some of the function LEDs flashing briefly as the counter chases the selected push button. Power-on At power-on, we have arranged a "default" setting for the counter which selects the 10MHz Frequency mode, with the gating time set for one second. This is achieved by cannecting the F2 and R2 pushbuttons to the " O" outputs of the 4017s, and arranging for these ICs to be reset during power-up. This default setting is both desirable and necessary, since otherwise the counter could be powered on in virtually any mode. The 0.022µ,F capacitor and lMO resistor connected to pin 15 of IC12 and IC13 provide the power-on reset function. At switch-on, the 0.022µ,F capacitor pulls the Reset inputs high, thus resetting the counters. The capacitor then charges via the lMO resistor which pulls the Reset inputs low again after about 20ms. Diode DlO discharges the capacitor after switch off so that the circuit is ready for the next power-on reset cycle. Power supply The power supply is a straightforward transformer, bridge rectifier and 3-terminal regulator arrangement which provides a fixed + 5V output. The entire circuit is attached to the rear panel of the instrument case, in order to reduce heating of the 10MHz crystal and subsequent frequency drift. Ventilation holes are provided in the top and bottom of The rear panel carries the power supply components. Sleeve all mains connections to prevent accidental electric shock. Note that the mains earth wiring differs slightly from that shown here. the case to remove heat produced by the power supply. Warm air is vented from the top rear of the case, while fresh air enters the bottom of the case, just under the crystal, thereby minimising changes in crystal temperature during warm-up. If you follow our instructions for drilling and ventilating the rear panel and case, you can expect a frequency drift of less than 1 part-per-million, even with a cheap crystal. Putting it together Now let's build a frequency meter. Ease of construction has been a major design objective. The circuit is built on two self-contained modules: the power supply module, which slides into the rear panel slot; and the frequency meter module which slides into the case along with the attached front panel. The frequency meter module itself is built on two PCBs which are soldered together at right angles. These boards are the display PCB (code sc041-1187-1) and the counter PCB (code sc041-1187-2). The display PCB inserts into the third row of PCB slots in the case, behind the front panel. We '11 begin construction with the power supply assembly. If you haven't bought a kit, the first job is to prepare the rear panel. This is Close-up view of the power supply PCB showing how the 3-terminal regulator is mounted. Take care of the orientation of the four diodes. cut from 2mm thick aluminium sheet to the exact size shown in Fig.11. Round the corners very slightly so that it will slide freely into the slot at the rear of the plastic case. A row of 6mm holes across the case provides essential ventilation. You will also have to drill four 3mm holes for mounting the power transformer, power supply PCB and earth solder lug. Finally, a hole for the cord-clamp grommet is required in the lower right-hand corner of the panel. Take care in filing this hole - the grommet should compress the mains cord securely and it should not rotate. Power supply PCB The power supply PCB is coded sc041-1187-3 and measures 54 x 44mm. Solder all the parts onto the board as shown in Fig.10, but don't mount the 7805 3-terminal regulator at this stage. Make sure that the four diodes and the 2200µF electrolytic capacitor are correctly oriented. DECEMBER1987 81 CI ose-up view of the dispIay PCB . The " µ, sec"and "kHz" legends are made from film transparencies which are glued · to the LED bar modules. Once these parts have been installed, solder two short lengths (about 100mm) of hookup wire to the AC inputs, and install two PCB stakes at the + 5V and 0V outputs. Now for the 3-terminal regulator. The leads of the 7805 need to be pre-bent before it is soldered to the board. The first bend is 2.5mm from where the leads enter the plastic body. Bend the leads upwards 90 degrees, gripping the part of each lead closest to the body with a pair of needle-nosed pliers. Another 90-degree bend in the same direction can now be made about 3mm from the ends of the leads. Now solder the 7805 into the PCB. Finally, bend the leads over the edge of the PCB so that the body of the regulator sits under the board as shown in the accompanying photograph. The various items of hardware can now be installed on the rear 15 panel (see Fig.10) but first smear the underside of the 7805 regulator with thermal grease. You should also solder a 150mm-length of green hookup wire to a solder lug. Now mount the transformer on the panel, using 25mm-long screws. On the screw closest to the mains cord entry, fit a 2-way mains terminal block and secure using a washer and nut. On the other screw, fit a washer and a 5mm spacer then slip the PCB over the mounting screw and secure with a nut. The other side of the power supply PCB is secured with a screw through the rear panel, the 7805 regulator, the solder lug with the earthing wire, a 5mm spacer, the PCB and a nut in that order. Check that the PCB is reasonably level and that the regulator sits flat against the panel before tightening the screws. 33 80 194.5 1.6-2mm ALUMINIUM DIMENSIONS IN MILLIMETRES Fig.11: drilling details for the rear panel. 82 SILICON CHIP 45 Power supply wiring All mains voltage connections should be completely covered with heatshrink tubing or plastic sleeving. This is to avoid the possibility of accidental contact with any of the mains connections. The mains cord enters through the hole in the bottom right of the panel. First, strip back about 150mm of outer insulation [enough to reach the front panel switch), then secure the cord to the rear panel with the cord-clamp grommet. Terminate the active mains lead [brown) in the 2-way terminal block and the neutral lead [blue) direct to one of the transformer primary lugs. The other primary lug is connected via a short lead to the other side of the terminal block [see Fig.10). The earth lead (green/yellow) is connected to a solder lug bolted to the rear panel adjacent to the terminal block. Connect the earth lead from the 7805 regulator tab to this point also. Finally, connect the two lowvoltage AC leads from the PCB to the 0V and 7.5V lugs on the transformer secondary. The power supply can now be 'fired-up' and the + 5V rail checked. To do this, secure a 100 0.25W resistor in the terminal block in place of the front panel switch (ie, in series with the transformer primary). The resistor will act as a The counter PCB is soldered at rightangles to the display PCB. Don't forget the earth strap over the crystal and orient the trimmer so that its outer terminal goes to the + 5V rail. safety fuse should anything be amiss. Now plug-in, switch on and verify that the DC output from the PCB is close to + 5V. If you don't get the correct reading, switch off immediately and check for wiring errors. Be careful not to touch the 100 resistor during this procedure - its leads will be at 240V AC. Assuming all is well, switch off, pull the plug from the mains socket, and disconnect the 100 resistor. That completes the power supply assembly. Main counter PCB Before installing any parts on this board, carefully inspect the PC pattern for possible shorts or breaks in the copper tracks. Note also that some of the pads are quite close together, so use a fine-tipped soldering iron and take special care to avoid solder bridges. Apart from that, assembly of the main counter PCB is straightforward. The first job is to install the numerous wire links (0.6mm tinned copper wire is ideal). Once all the links are in place, the resistors can be installed, followed by the remaining components. Be sure to keep all component leads as short as possible. The transistors should be pushed down onto the PCB as far as they will comfortably go before soldering. Install two PC stakes for the power supply connections. Make sure that the transistors, electrolytics and ICs are all correctly positioned and oriented. The notch in the end of each IC, adjacent to pin 1, goes towards the rear of the PCB. The crystal is mounted flat against the PCB and is earthed using a U-shaped wire link. Note that the outer terminal of the trimmer should be connected to the + 5V side of the circuit. Display PCB The display PCB (sc041-1187-1) can now be assembled. As before, install the wire links first, followed by the resistors, diodes, trimpot VR1, and the capacitors. Note that the three 101,tF tantalum capacitors should have their leads bent so that the capacitor bodies lie flat against the PCB. The ICs can be installed next, then the transistors and pushbutton switches (R1-R4 and F1-F4). Be sure to orient the transistors correctly and check that the correct type is used at each location. The switches should be pushed into the PCB as far as they will go, with the flat side of each switch facing upwards. Now install the eight 7-segment LED displays. These must be mounted flush against the PCB. Check that the decimal point of each display is in the bottom right hand corner before soldering the pins. The two light bar modules (LED 2 and LED 3) can now be installed and adjusted so that they sit flush with the front surface of the adjacent 7-segment display. Finally, install two PC stakes on the back of the board in the LED 1 position, then install the five 3mm indicator LEDs. The latter should be stood off the PCB so that they align with the front of the 7-segment displays. Note that the cathode lead is the shorter of the two and is adjacent to the flat on the LED body. The two BNC input sockets should be left off the board for the time being. They are installed later, when the front panel is attached. That's all we have space for this month. Next month, we'll complete construction and describe the test procedure. tt DECEMBER1987 83 PRODUCT SHOWCASE Goodwill's high performance dual trace oscilloscope What is the piece of test equipment at the top of most electronic enthusiasts' wish list? Answer: a dual trace oscilloscope. Over the years such an instrument has become quite a lot dearer than it used to be so we were very interested to give this Goodwill oscilloscope a tryout. These days, most dual trace oscilloscopes have a minimum bandwdith of 20MHz so this Goodwill GOS-543 model is a bit up the scale with a bandwidth of 40MHz and a delay timebase. With such a wide bandwidth and the delay timebase there would be few tasks it would not do for the enthusiast, technician or engineer. Granted there are instruments in the region of several thousand dollars which will do a lot more but that is a different echelon altogether. In appearance, the Goodwill CRO is similar to a number of competing models from Japan, Korea and Taiwan. Its overall size is 310mm wide by 170mm high by 460mm deep. Its mass is 7.1kg, The screen size is 10cm x Bern although the marked divisions on the graticule are about 9mm. 84 SILICON CHIP Instruments with a delay timebase are often complicated to drive. On the Goodwill though, the designers have kept things fairly simple. Just below the screen are the less frequently used controls such as intensity, focus, graticule illumination and trace rotation. Adjacent to these is a test point giving a 2-volt peak-to-peak square wave calibration signal running at lkHz. On the main control panel, the lower half is devoted to the input attenuators for the two traces, marked CHl and CH2. These give an input sensitivity of 5mV/div up to 5V/div in a 1-2-5 sequence in ten ranges. The variable attenuator knob for each channel can also be pulled out to give a further x5 gain to give a maximum sensitivity ·of lmV/div. The standard timebase is from 0.5s to 0.2µs per division, again in a 1-2-5 sequence over 20 ranges. Pulling the variable timebase knob out gives a further xlO magnification to provide a maximum sweep speed of 20ns/div. With this very high speed, you can display a 100MHz trace. The usual dual trace display modes are available: CHl or CH2, both, Add or CHl - CH2 inverted. The latter mode is almost equivalent to having a differential input on the unit. Triggering controls include plus or minus slope, AC, high frequency reject, TV and DC coupling. The TV mode switches in a TV sync separator to enable the display of line, field or frame waveforms, depending on the timebase selection. A dual concentric control allows setting of the triggering level on the waveform and holdoff. This last feature controls the delay between trace sweeps to allow stable triggering on complex digital waveforms. The delay timebase is adjustable from 0.5ms to 0.2µs. A vernier control allows a fine adjustment for the portion of waveform selected. Horizontal display modes are A, A intensified, B and B triggered. The A intensified allows you to intensify a small portion of the trace, such as the risetime of a square wave. Pushing the B mode button then allows that portion of the trace to be blown up on the screen at a much higher sweep speed. For example, if you display the lkHz calibration signal on the screen using a sweep speed of lO0µs/div you get one cycle on the screen but the rise and fall portions of the trace are effectively vertical (as you would expect). By using the A intensified mode and the delay time setting at lµs, you can select a lµs portion of the trace, say the rise time, for intensification. Then, if you hit the B button, you get the risetime spread out on the screen, so that you can easily measure it. In this case, it was about 1.4µs. Flicking the trigger Caps in space Gas powered portable soldering iron How many times have you been stuck up in a ceiling installing an antenna or working on a car when a soldering job had to be done. Some soldering irons can be powered from a 12V battery but that is hardly a convenient solution. The answer is the Portasol, a gaspowered soldering iron which was introduced a few years ago but is now a much cheaper proposition. Pull off the cap, push the little slide valve to the open position to start the gas flowing, flick the flint wheel on the cap to light it and the little burner lights up to heat the tip. You can adjust the tip temperature with a regulator at the end of the case. The idea seemed novel to us at first but having tried it, we reckon it's a beauty. It can be used for very light soldering or, having turned up the gas, for heavier work. Different sized tips are available too. They screw out easily to be changed. The Portasol is very handy too in the workshop or in other places where mains power is available and where an ordinary soldering iron can be used. By the time you've waited around while the ordinary iron heats up, the Portasol has done the job, because it heats up very quickly. It would be very handy for servicemen out on the job because you don't have to bother with extension leads. The fuel is standard lighter fuel so while ever there are smokers (sad) that will not be a problem. The Portasol is widely available. Our sample came from Dick Smith Electronics. slope control to negative mode then displayed the fall time, which was measured at about 2µs. Without these timebase modes, such a measurement would be impossible. A look inside the interior reveals a well constructed unit with most components mounted on five printed circuit boards. Accessibility for service is good and most of the semiconductors would be readily available off the shelf. Two probes are provided. These have xl and xlO positions with lMO and lOMO impedances at 180pF and 22pF input capacitance respectivly. They have a frequency response which is within ldB from DC to 3MHz in the xl position and DC to 40MHz in the xlO position. A small instruction manual gives specifications and features of the unit. To sum up, we were impressed with this Goodwill oscilloscope. It offers good performance and is one of the best CROs we have come across for ease of use, especially when one considers the number of operating features. At the time of writing, the Goodwill GOS-543 40MHz oscilloscope was priced at $1462.26 including tax. This price was expected to rise with the next shipment though. Our review sample came from Geoff Wood Electronics, 229 Burns Bay Road, Lane Cove West, NSW. Phone (02)427 1676. Philips' 123 Series of solid aluminium electrolytic capacitors is now officially approved by the European Space Agency. These are rugged capacitors indeed. They have stable, low drift characteristics over long test lifetimes of 5000 hours at 125°C and 2000 hours at 150°C. The concept of electros which can operate at temperatures considerably higher than boiling water is mind-boggling. Normally electros in consumer electronic equipment are rated for temperatures no more than 85 degrees Celsius. For more info on these space approved caps , contact Philips Elcoma on (02) 439 3322. The photo shows the gantry leaning over, as is the lamp post. This is not a special consequence of Philips capacitors but is distortion in the wide-angle lens. Multi-output transformer Geoff Wood Electronics currently have stocks of a handy mains transformer which could have a variety of applications in low voltage power supplies. The transformer has two 12V secondaries each rated at one amp and one 9V winding rated at 2.5 amps. The transformer is 65mm high, with mounting centres at 93mm and the stack is 30mm. Price is $18.50. Phone (02) 476 1676. DECEMBER1987 85 Arista hobby knives Whether you are laying down tapes for a printed circuit board pattern or involved in constructing model aeroplanes, boats or trains, this set of hobby knives will be very handy. The set of three knives comes in a sturdy plastic presentation case complete with spare blades. Bargain priced Multitech 500 Blessed are those who wait; they sometimes get it cheaper. Dick Smith Electronics have now released the Multitech ACER 500 +, a PCcompatible computer complete with monitor for less than a thousand dollars. It uses an enhanced version of the NEC V20 microprocessor, enabling it to run at 8MHz as well as the standard 4.77MHz. Standard RAM complement is 256K internally expandable to 640K. With one 360K floppy disc drive, the price is $995. With two 360K floppies the price is $1295 while with one floppy and a 20MB hard disc drive the bill goes to $1995. All prices include Multitech's new "soft-white" monitor. Warranty is 12 months. AVTEK HA VE RELEASED their compact new Megamodems which are Hayes compatible and offer V21,22 or V21,22,23 modes (V21 is 300 baud duplex, V22 is 1200 duplex and V23 is 1200/75). The Megamodem is also available as a half card for the IBM PC and compatibles. Fitted with modular telephone sockets, the Megamodems are priced at $375 or $449. Phone (02) 712 3733. 86 SILICON CHIP We particularly liked the biggest knife which had a comfortable handle for those occasions when you need to use a little more force. It was much more suited to heavy cutting on model work than the familiar utility knife. The set of knives is available from all Arista outlets. Bubble etcher for PC boards Wastage of etching material can be expensive if you don't have a suitable tank. This vertical tank from Geoff Wood Electronics does not use much fluid (about 1.2 litres) but will etch large boards up to about 300 x 275mm. The fluid is agitated by a stream of air bubbles provided by a fish-tank pump. Tank and air pump are available at $119.00. Phone (02) 427 1676. THE WAY I SEE IT By NEVILLE WILLIAMS Is the electronic service industry dragging its feet? Last month I drew attention to the difficulties and delays which can be experienced these days when electronic equipment is returned for repair. It is clear, however, that the examples quoted were not isolated incidents but part of an emerging pattern affecting the whole gamut of electronic devices. As you will have noticed, I did not identify the make of the various units and this was quite deliberate. They just happened to be those that came to my notice and it would have been unfair, by implication, to single them out as brands to be a,voided. Rather, they were listed as an indication of a wider problem. At this moment, four weeks after I wrote that story, a couple of those very situations are still to be resolved. Replacement chips for my own computer printer, ordered from overseas, are still at least two weeks away so that, in the normal course of events, twelve weeks or more will have elapsed before the local distributors can be in a position to fix it. As it happens, I've just been advised that they've located a possible substitute board and may be able to effect at least a temporary repair. One must be thankful for small mercies, I guess, but that will still add up to a turnaround time of ten weeks. As I mentioned previously, I would have been in real strife had not a friend been able to lend me a standby printer of a different make, although I faced a difficulty in that the distributor was no longer able to supply a new ribbon for it or offer any meaningful assistance in obtaining one. Then there was the schoolteacher friend's near-new computer monitor, from still another supplier, who quoted six weeks to track down and repair a fault that was causing the brightness level to vary erratically. He, too, was able to get by in the meantime with a borrowed monitor, which behaved perfectly, suggesting that the problem had nothing to do with the computer itself. For him, the good news was a phone call, four weeks later, advising that he could pick up the monitor, which had been "thoroughly checked" in the meantime. The dubious news, on his arrival, was that the technicians could find nothing wrong with it. The bad news, when he got it back home, was that the brightness was as unstable as ever. When last I heard, he was still trying to work out what to do about it. (I am reminded of Murphy's first law, as applied to computers and quoted recently in the Sydney Morning Herald: '' As soon as the technician has been called, the thing that has gone wrong mysteriously fixes itself or goes into hiding until after the technician leaves".) A VCR - what's all the hurry? Then last month's story, to do with VCR problems, was mirrored by the experience of another acquaintance who happened to hear about what I had just written for the November issue. A few weeks previously, his 20-month old VCR had mangled the tape in a rented video cassette to his considerable embarrassment. He duly took the VCR to an accredited repairer, who assured him that the fault could be rectified but added that the job might take several weeks. Not prepared to wait that long, he took it elsewhere, only to be told much the same story. The second repairer undertook to do the job as quickly as possible but explained that the turnaround time really depended on how long it took to get hold of the necessary replacement parts. Annoyed with both the manufacturer and the department store that had recommended the particular brand, he had little choice but to accept the repairer's word. Four weeks later, with the VCR still in limbo, he rang the Australian distributor to protest directly to the spare parts manager. The person who actually took the call remains a mystery but was obviously unimpressed either by his complaint or his presumption in making it - virtually hanging up in his ear! DECEMBER1987 87 'Superlative' Many people have been mass-marketed into believing that digital 'music' is superior to analogue reproduction. This new ORTOFON MC30 Super Cartridge will most certainly show you where this theory goes completely wrong! Using pure silver wiring, Ortophase phase/amplitude linearity and apure platinium damping disc, the ORTOFON MC-30 Super delivers directly to both ears the superior musicality of high-class analogue reproduction. As others have already said: .. . the overall sound is one of extreme clarity which can bear comparison with CD at its best. In fact, unlike COplayers, a well designed moving-coil cartridge like this one maintains its response well beyond the 20kHz upper limit." John Barwick, Grammophone, April 1987. "The MC-30 Super is a better cartridge than most of its rivals. It's just a thoroughly musical design, and there's little that needs to be added to that bald statement. Go for this cartridge if you want a sharp, incisive sound of real refinement and with explicit stereo." Alvin Gold, HI-FI Answers, April 1987. "The MC-30 Super .. . is the child of a mating of the MC20 Super and the MC-2000 - both of which I know and adore. Once the cartridge bedded in, it was as sweet as sugar, an MC-2000 without the bite and with most of the detail ... Ortofon has plenty of reasons to believe that a market for high quality cartridges still exists, and this continued support of the LP has resulted in an outstanding transd ucer.'' Ken Kessler, HI-FI News and Record Review, March 1987. "The MC-30 Super is a superlative tracker . Highs are gorgeous - smooth, open, and sparklingly crisp . . Lowfrequency performance, too, is excellent." J. Gordon Holt, Stereophile, January 1987. For fuli details and free brochures, contact the Sole Australian Distributor, SCAN AUDIO or your nearest ORTOFON specialist. SCAN AUDIOPty. Ltd., 52 Crown Street, Richmond, Victoria 3121. Telephone: (03) 429 2199. ortofon accuracy in sound S&T .SA.4760 "One would think", he said, "that the supplier was doing me a favour in making spare parts available at all! " His reaction was to write a letter of protest to the company management, indicating his dissatisfaction as a brand customer and expressing the hope that this further complaint: (1) Would not end up in the hands of another staff member with such an objectionable, "don't care" attitude, and (2) Might motivate management to look critically at the parts situation and hopefully ease the problem in future for other customers like himself. The VCR has since been repaired but it still took all of six weeks, despite his "stirring"! "Electronic" cameras And that brings me to a freelance photographer who is a long-time friend and associate. Some time ago, he invested $150-odd in an electronic timing device which could be set to trigger a motordriven camera for multiple exposures, either in rapid sequence or spread over a much longer period, as for time-lapse photography. When he tried to use it recently, however, it went completely crazy, pulsing quite erratically. On taking it back to the local distributor, he discovered that they had no facilities in Australia for servicing the electronics in their equipment. They were well set up to deal with mechanical problems but anything electronic had to be shipped back to the factory. What was that likely to cost and how long would it take? It would take up to six weeks to reach the service department, he was told, because their policy was to collect enough items to make up a worthwhile consignment. The service department would then work out quotes for the various jobs, which would be referred back to the Australian owners. As the quotes were accepted, the repairs were set in train and enough completed jobs collected, once again, for a return consignment to Australia. That would pro88 SILICON CHIP bably add another six weeks! And the cost? He would be liable for the freight and insurance both ways - about $40 - plus the cost of repair, if authorised. Could he obtain a circuit diagram so that the unit could be serviced locally? No, they didn't think that would be possible, nor was there any provision to supply spare parts. There the matter stands, for the time being. It may well be uneconomical to provide local service for the electronics but it is rather frustrating to discover that only after the equipment has failed. In the meantime, the experience has further soured his attitude to electronic photographic equipment. From a good "mechanical" camera, he said, you could expect a life of twenty or thirty years before it had to be written off but, with equipment using electronic modules, the life expectancy seems to be anybody's guess. For one particular model camera, he said, critical spares appear to have cut out after only six years. Equipment more reliable Getting back to domestic TV and audio equipment, it is certainly true that it is far more reliable than once was the case and that service is required much less frequently. Back in the '60s, valve-type monochrome TV sets provided a good living for a whole army of servicemen, as also did the first generation of colour receivers. Nowadays, most TV sets, VCRs and hifi components survive the warranty period without incident but even so, a breakdown that takes weeks to fix can be a souring experience, whether in or out of the warranty period. Fortunately, it isn't always that way. A company mentioned last month, Hills Telefix, usually have routine faults sorted out within a day or so, and doubtless there are other such companies across Australia, large and small, of which the same could be said. Even so, Telefix Sydney Division Manager John Ridley admits that repairs can take a lot longer if they have to wait on critical spare parts from the manufacturer. There is a practical limit, he said, to the number of major bits they can carry in their own inventory, particularly as they have to cope with such a wide range of brands and models. We also talked the matter over with Jeff Beaumont, National Support & Service Manager for Tandy. He claimed that his company has always placed special emphasis on back-up service, as part of their marketing strategy. While they too have their share of problems with replacement parts, they carry a very large inventory in stock. All Tandy products, other than those retailing for less than about $50, can be returned for service via Tandy stores and are normally repaired within 3-5 days, with business computer equipment given special priority. (These days, it may cost about as much to repair an item worth $50-odd as to replace it!) At the present time, Jeff said, the average turnaround time, covering all products, was 3.2 days! How many companies could match that claim? Pointed questions As I see it, the moral that comes out of all this is a few pointed questions you should ask when buying electronic gear: • If what I'm buying breaks down, what's involved in getting it serviced? • How long does it take to get it repaired? Days, weeks or months? • Can it be fixed in the home? If not, what alternative arrangements must be made? • If repaired at a service depot, which depot, when is it open, and is there a more convenient option? • What does the warranty cover and for what period? All parts and laqbur or some parts and limited labour? • Who do I know with a unit of the same brand? What has been their experience in terms of reliability and back-up service? In short, make the kind of inquiries that an astute buyer makes when contemplating the purchase of a new car. What greater put-off is there than to learn from a neighbour that the dealer service in the area for a particular brand "stinks"! And, speaking of cars ... I was intrigued recently when a relative bought a near-new car from his local dealer a demonstrator or lease vehicle, I gather. It was covered by a 2-year extended warranty, he said, but it did not include the electronics. He would have to carry that risk himself and, while there was no special reason to expect trouble, a breakdown in that department could set him back by anything up to $500! In forewarning him, the salesman appeared to have done the right thing but, as I said, the exclusion intrigued me: a 2-year warranty on everything except the electronics. Did it mean that the electronics industry was as yet unable to make modules sufficiently rugged and reliable to match the durability of the rest of the vehicle? A representative of a large car servicing organisation, who are confronted by more stalled cars than most, was non-committal when asked the above question. "It's certainly taken a while" he said, "for vehicle and electronics manufacturers to get their act together. Under the bonnet of a car is a pretty unfriendly environment for electronic equipment of any kind. So is the passenger cab, if an electronic module is mounted where it can be dripped on by rainwater from a faulty windscreen gasket! "They seem to be getting it sorted out now but, to my mind, if electronic modules do fail, they cost far too much to replace. They'll have to get the price down, somehow!" Another friend, responsible for a fleet of company cars and trucks, referred me to the staff mechanic responsible for electrical and electronic maintenance. Obviously on familiar ground, the mechanic said that the majority of modern cars used "computers" of one type or another to control various functions in the vehicle, some relatively simple, some complex, some dedicated to particular tasks, others providing more comprehensive control. "By and large, modern electronic control units are very reliable", he said, "considering the jolting to which they are subjected, the moisture and temperature problems, and the RF radiation from everything from ignition systems to fields from broadcast transmitters sited 100 metres from the roadside. "As a general rule, if an ECU (electronic control unit) functions for six months, it will keep going for years". As for the warning about a possible $500 service charge, he expressed reservations. Depending on the make and model, he said, a major electronic breakdown could cost anything from $500 to $1200 or more - a remark that caused me to wonder whether the salesman had been as frank with my relative as I had given him credit for. So to my final question: "Why refuse warranty on the electronics in a second-hand car? Does it signify that the modules are intrinsically less reliable than the rest of the vehicle?" "Not exactly", he said and went on to suggest a couple of more pragmatic explanations: (1). An experienced mechanic can inspect and test drive a car and come up with a fairly reliable assessment of its mechanical condition. One can't be so sure about the electronics. A dormant or intermittent fault could pass undetected, if the system functioned normally on the day, rendering the warranty situation somewhat less predictable. (2). If a mechanical failure occurs under warranty, much of the cost of rectifying it is in-house labour, which can be absorbed, spread, amortised, buried - call it what you like. With an electronic failure, the labour content is normally quite small but a $1000-odd outlay for a replacement module could make a book-entry mess of an individual transaction. According to my informant, restricted warranties like that are likely to be around until the cost of replacement modules is drastically reduced or a reliable and economical exchange service is readily available. In the meantime, the buyer has to take all the risk, a situation which is hardly fair or satisfactory. That's the way I see it! ~ DECEMBER1987 89 l ?iL - - - ¥Pt,, All digital electronics equipment is made up of just a few basic building blocks known as digital logic circuits. Those basic circuits are combined in a variety of ways to process the binary data used in communications, computation, or control applications. Digital logic circuits typically accept two or more binary inputs and generate a single output. The output state is determined by the binary states of the input and the special processing characteristics of the digital logic circuit. Typically, the electronic circuit itself is not shown, because it is basically irrelevant. Only the logical functioning of the circuit is of interest. Most digital logic circuits are called gates. The basic function of a digital logic circuit is to make a decision. The logic circuit looks at the state of the input signals, then makes a decision and generates an output. Those digital logic circuits are then combined in a variety of ways to form larger, more sophisticated circuits called combinational-logic circuits. There are five basic digital logic circuits. They are the AND gate, the OR gate, the inverter, the NAND gate, Fig.1 - the generic hypothetical digital logic circuit is usually referred to as a gate. 90 SILICON CHIP BINARY { INPUTS ~ BINARY ~OUTPUT INPUT ~-__.........__ OUTP'!J A ~ B= A Fig.2 - I N P U T ~ OUTP~T A ~ B= A logic symbols for an inverter. and the NOR gate. The AND, OR and inverter circuits are really the core elements while the NAND gate and NOR gate are special combinations of the basic three, as you will see later. All digital equipment is made up of those simple elements. The Inverter The simplest digital-logic circuit is the inverter. It has a single input and a single output. Its primary function is to invert a logic signal. It converts a binary O [low) into a binary 1 [high) and a binary 1 into a binary 0. The logic symbol used to designate an inverter is shown in Fig.2. The triangle typically represents the electronic circuitry while the circle, which can be shown at the output or input [more commonly at the output), represents the inversion process. The output of an inverter is simply the opposite of its input. In digital terminology, we say that an inverter generates an output which is the complement of the input. The operation of an inverter, or any other logic circuit for that matter, is usually expressed in one of three ways: a truth table, a Boolean algebra expression, or a waveform timing diagram. Let's look at all three for the inverter. Timing Diagrams INPUT A OUTPUT B Fig.3 - input and output waveforms of an inverter. A truth table is nothing more than a chart that shows all the possible combinations of inputs and outputs of a logic circuit. A truth table (Table 1) for an inverter is shown below. The input and output binary signals in Truth Table_ 1 are identified by letters of the alpha bet as seen m Figs.2 and 3. TABLE 1 INVERTER TRUTH TABLE B (Output) A (Input) 0 1 1 0 In the truth table for the inverter (Table 1), the lefthand column represents all possible input combinations. With a single input line, only two possible states are possible. Naturally, only two output states are possible. Note that the output is the complement of the input. Another method of expressing the operation of a logic circuit is to use Boolean algebra. Boolean algebra was invented by mathematician George Boole and is a simple mathematical way to show what's going on in digital logic circuits. A Boolean expression is nothing more than a simple formula that expresses the output in terms of th(;l input. The output and the input are given a lett_er o~ letter/number designations. They are shown m Figs.2 and 3. The Boolean expression for an inverter is: B=A The way to read the above equation is: output B is equal to NOT A. The bar over the input designation A is called a NOT bar or NOT symbol. It is used to denote inversion. What that simple algebraic expression tells you is that if the input is A, then the output Bis NOT~In other words, if the input is 0 (low), then the output 1s NOTO; ie it is 1 (high). An inverter is also referred to as a NOT circuit. Instead of the NOT bar which is an unusual symbol and difficult to type and print, an asterisk or prime symbol is often used to show inversion as indicated below: B = A* or B = A' Another way of showing the operation of a logic circuit is to use timing diagrams. These diagrams show the actual input and output waveforms that occur. Those waveforms are what you would expect to see if you were monitoring the input and output signals on a multi-trace oscilloscope. Fig.3 shows the typical input and output waveforms of an inverter. The waveforms typically shown in timing diagrams are usually shown in their ideal form. That means thai. the waveforms are perfectly square, with vertical sides and flat tops. In reality, digital signals are not that perfect. Fig.4 shows what real logic signals would look like on an oscilloscope when the sweep period is very brief. The waveforms are those that you would see at the input and output of a typical inverter circuit. First, note that the sides of the waveform in Fig.4 are not perfectly vertical. The waveform rises or falls linearly. This means that the transition between the binary 0 and 1 states (or between binary 1 and 0) is not instantaneous. While digital logic circuits switch rapidly, it does take a finite period of time for the logic state to change. The times involved in changing states are referred to as the rise time and the fall time. The rise time is the amount of time it takes the logic signal to rise from 10% to 90% of its full amplitude value. The fall time is the time it takes for the logic signal to drop from 90% to 10% of its full amplitude value. Rise and fall times can be measured on an oscilloscope screen if the scope has a calibrated timebase. Another factor to be considered is propagation delay. This is the delay time between the arrival of an input signal to a logic device and the delivery of the output signal. For example, in an inverter, when the input rises from 0 to 1, the output of the inverter does not simultaneously drop from 1 to 0. There is a time delay between the input and output. This time pe~iod is the propagation delay. It is measured between the 50% amplitude points on the corresponding input and output waveforms as detailed in Fig.4. . All digital logic circuits have propagation delay. Granted they are very short, less than 10 nanoseconds in most circuits. For many applications, this is such a small time that the response is essentially considered to be instantaneous. The AND Gate The term gate is used to describe a digital logic circuit with two or more inputs and a single output. The expression gate is metaphorical and tends to describe how a typical digital circuit functions. For example, when a gate is open, a logic signal passes. If the gate is closed, a logic signal is blocked. The two basic kinds of logic gates are AND and OR. When these are combined with an inverter, they form the other two types of gates, NAND and NOR. We will consider the AND gate first. The basic logic symbol used to represent the AND DECEMBER1987 91 ~ ::::0--- z = xv A A2 O = P - - D = (AOXA2XA5) A5 Fig.5 - logic symbols for the TABLE 2 AND TRUTH TABLE FOR TWO INPUTS PROPAGATION DELAY TIME Inputs Fig.4 - inverter input and output waveforms illustrating rise and fall times and propagation delay. IPUT A PUT B PUT C 11 12 I I 13 15 I I II J 14 16 17 18 19 I I I I nI I I I I PUT D n_ n_ I Fig.6 - input and output waveforms for a 3-input I AND gate. gate is shown in Fig.5. Two, three and four-input AND gates with their inputs and outputs labelled are shown. In operation, an AND gate generates a binary 1 output if all of its inputs are binary 1's. If any one or more of its inputs is binary 0, the output is a binary 0. A truth table clearly shows the operation of an AND gate. For example, take a look at Table 2 which shows the operation of a 2-input AND gate. Here there are two inputs, X and Y. With two inputs, there will be 2 to the second power (2 2 } or four possible input conditions. There is also an output Z that occurs for each different set of inputs. Note that a binary 1 output appears only when both inputs are binary l's. Now take a look at the truth table for a 3-input AND gate (Table 3}. With three inputs, there can be a total of 23 or eight possible states. Again, the output is binary 1 only when all three inputs are binary 1. The Boolean expression for an AND gate with inputs X and Y and output Z is simply: 92 SILICON CHIP = X.Y = XY X z 0 0 1 1 0 1 0 1 0 0 0 1 Inputs TIME Z Output y TABLE 3 AND TRUTH TABLE FOR THREE INPUTS I I gate. AND X y 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 Output z 0 1 0 1 0 1 0 1 0 0 0 0 0 0 0 1 To read the above algebraic expression, you say that Z equals X ANDY. The dot between the two inputs designates the AND function. But in most cases, the dot is omitted and the input terms are simply written adjacent to one another as they would be if the terms were to be multiplied as in a standard algebraic expression. Sometimes, parenthesis are used to separate the inputs when multiple letters or letter/number designations are use, eg: F = (J2)(L7) Fig.6 shows typical timing diagrams for a 3-input AND gate. Carefully observe the states of each input and check how they correspond to the output. As you can see, a binary 1 output pulse occurs only when the three inputs are simultaneously binary 1's. That characteristic has led to the AND gate being described as a coincidence circuit, since the output occurs only during the coincidence of the binary 1 states. At times t 1 through t 5 , the three inputs are never high at the same time. However, beginning at time t 6 and ending at time t 7 , the three inputs are all high so that output D goes high. One of the most common applications for an AND As for its function, an OR gate generates a binary 1 output if any one or more of its inputs is binary 1. The output of the OR is zero only when all of its inputs are zero. Table 4 shows the basic operation of a 2input OR gate. Note that those three input combinations where binary 1 's occur on either or both inputs generate a binary 1 output. The Boolean expression for the OR function is shown below: CK CTL _ _ _ ___.I J OUTPUT-----1 Fig.7 - gating with an AND gate. gate is gating input. Fig.7 illustrates the concept. Here a clock signal from an oscillator clock (CK) is applied to one input. A control signal (CTL) is applied to the other. The purpose of the control signal is to literally open or close the gate. When the CTL signal is binary 0, the gate is closed. Any time an input to an AND gate is binary 0, the output is correspondingly a binary 0. When the CTL signal is binary 1, the gate is enabled and the clock signal applied to the other input passes through to the output. As long as the CTL signal is binary 1, the clock signal will pass through. The OR gate The other basic logic circuit is the OR gate. It can have two or more inputs and a single output. The symbol used to represent the OR gate is shown in Fig.8. ~::::D--J AX~ T: ~ D4 11 Fig.8 - logic symbols and Boolean algebraic expressions for an OR gate. = K+L 12 = AX +T9 +G 13 14 I I I 15 16 17 18 I - - - -....I . 19 110 I I INPUT K n I INPUTL --'--' I !'----------' I L = K + L To read that equation we say that J equals K or L. The plus sign indicates the OR function. The Boolean expression for the 3-input OR gate in Fig.8 is: D4 =AX+ T9 + G Fig.9 shows the operation of an OR gate using two input waveforms. The rise and fall times and propagation delays are not shown to simplify the illustration. Follow each input waveform and note the output condition for the binary 1 input condition. For example, input K goes high causing output Jto go high at time t 1 . At time t 2 input K goes low, but input L is high; thus output K remains high until time t 3 when both inputs are low. An OR gate is a useful logic function as it allows two or more individual signals to control a single output. A simple application in shown in Fig.10. Here a cooling fan motor is controlled by the output of the OR gate. The fan motor may be turned on or off by two separate inputs to the OR gate. The first input is a temperature sensor. When the temperature rises, the temperature sensor switch closes and + V (binary 1) is applied to one input of the OR gate. The other input to the OR gate is a manually operated switch which can be turned off and on to control the motor. When either input is a binary 1, the fan will turn on . The resistors at the inputs to the OR gate keep the input states at binary 0 until a switch closes. Since the logic OR chip is rated for small signals only, a driver stage is inserted into the circuit to provide the power switching required to control the motor. I TEMPERATURE SENSOR OUTPUT J ~FAN I TIME Fig.9 - input and output waveforms for an OR gate. FAN MOTOR TABLE 4 OR TRUTH TABLE FOR TWO INPUTS Inputs K L 0 0 1 1 0 1 0 1 Fig. 10 Output J Fig.to - using an OR gate to select active input to control the operation of a fan motor. NAND and NOR Gates 0 1 1 1 The use of an inverter immediately at the output of AND and OR gates makes possible NAND and NOR gates. For example, Fig.11 shows a NAND gate. It is made up with an AND circuit followed by an inverter. This cir- DECEMBER 1987 93 ~ ~ ~ z = xv NANO CIRCUIT Fig.11 - = TABLE 6 OR/NOR TRUTH TABLE FOR TWO INPUTS xv NANO SYMBOL NANO t1 :::Bo--z 12 gate circuit [left) and logic symbol. 13 14 I I I no 15 16 t7 18 19 I II I I I I Inputs 111 INPUT X INPUT Y OUTPUT Z Fig.12 - input and output waveforms for a 2-input NANO. cuit is usually represented by a single symbol which is the AND symbol with a circle at its output to indicate inversion. The operation of a NAND gate is simple to deduce. It is the output result of an AND gate inverted. This is illustrated in the NAND truth table (Table 5). TABLE 5 NAND TRUTH TABLE Outputs Inputs X y AND NAND 0 0 1 1 0 1 0 1 0 0 0 1 1 1 1 0 For a two-input NAND gate, the output is binary 1 if either or both inputs are at binary 1. The output only changes state to binary O when both inputs are at binary 1. The Boolean expression for a NAND gate is also simple to understand. It is simply the AND expression with a NOT bar over all inputs as shown below: D = EFG The operation of a NAND gate is illustrated by the waveforms in Fig.12. Note that the only time the output is a binary O is when both inputs are simultaneously binary 1. The output pulses occur during time periods t 2-t~, t 6-t 7 and t 10-t 11 .Check the inputs during those periods and you'll discover that they are high. At all other times, one or both inputs are low. A NOR circuit is shown in Fig.13 . It is an OR gate followed by an inverter. The special symbol used to represent that circuit is the OR symbol with a circle at its output to indicate signal inversion. Table 6 shows the operation of the NOR gate. The output of the NOR gate is simply the inverted or complement output of the standard OR gate with identical inputs. : ~ C = A+B NOR CIRCUIT :::::Do---NOR SYMBOL Fig.13 - NOR logic circuit and logic symbol. 94 SILICON CHIP C = A+B Outputs A 8 OR NOR 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 0 The waveforms in Fig.14 illustrate the operation of the NOR gate. Here the output is a binary O when any one or more of the inputs are binary 1. Note that the NOR output occurs only during periods t 3-t 4 and t 7-t8 • Verify that statement by using the NOR truth table (Table 6). In fact, now would be a good time to quickly review all the truth tables (Tables 1 to 6) to be sure that you fully understand the operation of the AND, OR, NAND and NOR circuits. NAND and NOR Applications All five basic logic circuits are available in integrated circuit form. A typical digital logic IC is the popular 4001 quad 2-input CMOS NOR shown in Fig.15. While any of the basic logic functions can be obtained in IC form, the most widely used are the NAND and NOR gates. They can be interconnected to perform basic AND, OR and inverting functions. For example, a NAND or a NOR gate can be used as an inverter as shown in Fig.16. To do that, all the inputs are connected together to form a single input. The resulting circuit operates just like an inverter. A NOR gate can be used for the OR function by simpt1 INPUTAJ I 12 13 14 15 16 I I I I I I I wI I INPUT 8 17 1a I ..._____.I OUTPUT C Fig.14 - input and output waveforms for a 2-input NOR. ORIENTATION NOTCH 3 7" GNO Fig.15 - pictorial diagram for the 4U01 CMOS quad 2-input NOR integrated circuit. x~x NOR NANO Fig.16 - and NOR gates connected to perform as inverters. NAND Fig.17 - NOR and NAND gates converted to OR and ~ ~ F T = FT (a) (b) (c) (d) Fig.18 - using (b) AND, ly connecting an inverter at its output. The inverter complements the output back to the standard OR output (Fig.17a). Similarly, a NAND gate can be converted to an AND function by feeding its output through an inverter as shown in in Fig.17b. Several other variations of making AND and OR gates from NANDs and NORs are shown in Fig.18. For example, a NAND gate can be used as an OR circuit by connecting inverters ahead of the inputs (Fig.18a). When used in that way, the NAND circuit is sometimes represented by the special symbol shown in Fig.18b. This is an OR symbol with circles at the inputs to and NORs for operations. NANDs OR and AND designate that special function. You can also use a NOR gate as an AND. Again all you have to do is connect inverters to the two inputs as shown in Fig.18c. When a NOR gate is used in that way, the special symbol shown in Fig.18d is sometimes used. The short quiz that follows will help you review the main facts presented in the above article. Answering those questions will help you apply what you have learned to reinforce your knowledge. Reproduced from Hands-On Electronics by arrangement. Gernsback Publications, USA. © SHORT QUIZ ON DIGITAL LOGIC CIRCUITS 1 . The output of the circuit shown below is : ---f>o----C>o--? BINARY O a. binary O b . binary 1 2. The output of an inverter is said to be the _ __ of the input. 3 . The circuit generating the output waveforms shown below is a(n): INPUT A J INPUT B OUTPUT C J n L AND function? :::0-- ::::D--t>-(b) (a) 8. The time shift between the output and input of a logic circuit is referred to as _ _ _ _ _ _ __ Lil c. 9 . A 4 -input NANO gate will have how many possible input and output states? a. 4 b. 8 c. 16 d. 32 OR 4 . A coincidence circuit is a(n): a. AND b. NOR c. inverter 5 . The Boolean expression for a a. C =A+ B + C b. C = ABC c. C = ABC 7. Which ci rcuits below perform the I I a. inverter b. AND d. NANO e. NOR 6. Which of the following is the truth table for a gate? a. 0 0 0 b. 0 0 1 c. 0 0 0 d. 0 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 0 1 0 0 1 1 1 1 1 0 1 1 1 1 1 0 NOR NOR ANSWERS TO QUIZ gate is: d. C = A = B = C 9~ = 6 x 6 x 6 x 6 = i,G ·o ·5 ABl8P uo,ie5ed0Jd ·g o pue q 'e 'L 80N ·p ·g 8 = 8 = V = 8 ·e .9 oNv ·e ·v 80 ·o '8 lLiawa1dwoo · G ~ AJBU!q ·q . ~ DECEMBER1987 95 CEN Cash in your surplus gear. Advertise it here in Silicon Chip. Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale . If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139 , Collaroy Beach , NSW 2097 . PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS Advertisers Index Our advertisers are vital to the success of SILICON CHIP. Please give them your support. Altronics ............. .. 36,37,44, 45,60 ,61 Arista Electronics .... .. .. .. .. ... 4 7 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) Name Postcode Enclosed is my cheque or money order for$ ....... ...... ..... ..... .... ..... . .. or please debit my Bankcard □ Visa □ Marantz Australia . . ..... . .. . ... IFC Microbee .. ....... ....... .. ...... IBC RCS Radio .. ........... ........ .. 49 Card No .. ... Scan Audio Pty Ltd .......... .. Signature .. Tandy Electronics ....... .. .. OBC High-power amplifier module transistors and the driver transistors. Mount the power transistors first. These must all be isolated from the heatsink by using mica washers and insulating bushes, as depicted in Fig.5. Smear all mounting surfaces with heatsink compound before assembly. Solder the mounting nuts to the PCB pattern after assembly to ensure reliable contact. Alternatively, if the nuts are nickel plated or stainless steel, use lockwashers. The two driver transistors and the Vbe multiplier (Q7) are bent over and also attached to the heatsink bracket using T0-126 mounting kits. (See Fig.6). When the whole assembly is completed, the heatsink bracket should be attached to a suitably large heatsink, preferably with vertical fins. Heatsink compound should be used between the bracket and the heatsink to improve heat transfer. Before applying power remove the two fuses from the board clips and set VR1 fully anticlockwise. 96 Dick Smith Electronics ..... Jemal Products ................. 59 Address ..... .. ... .......... ......... .... .... .. ......... .. ....... ... ........ ... ........ . . Suburb/Town ....... ....... .... ... .......... ........ .. ..... ......... ... ..... ..... 67 8,9 , 16,48,54,55 Emona . .. .. ... ........ .. .. .... .... . 43 Jaycar Electronics .. ... .. . 20-27 Crusader ..... ...... .. .. ........ .. . SILICON CHIP 89 ctd from page 15 This gives the setting for minimum quiescent current through the output transistors. Solder a 5600 5W wirewound resistor across each fuseholder. Set your multimeter to the 200VDC range (or no lower than 50V DC if an analog meter). Now apply power and measure the positive and negative supply rails. They should be within a few volts of ± 40V. Now measure the other voltages on the circuit. They should all be within ± 10% of the nominal values. The voltage at the output should be within ± 30mV of OV. No load should be connected at this stage, by the way. Now switch your multimeter back to the 200V DC range and connect it across one of the 5600 resistors. Adjust VR1 for a reading of 28 volts. This gives a total quiescent current of 50 milliamps. For the 50W version which uses only two output transistors, VR1 should be adjusted for a reading of 14 volts. This gives a total quies cent current of 25 milliamps. After five minutes or so, check {-·~" WASHER -T0126 i(F~ r~ ___ 11 O O:~::E WASHER - - HEATSINK PCB ..l_ ...- SHAKE·PR00F WASHER f;f!!J-NUT Fig.6: mounting details for the T0-126 transistors. Note that heatsink compound should be lightly smeared on the mounting surfaces. the quiescent current and readjust VR1 if necessary to get the correct voltage across the 5600 resistor. Now switch off, remove the two 5600 resistors and insert the fuses. 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