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BONUS DICK SMITH ELECTRONICS CATALOG SERVICING - HIFI - A;t•!)=t:ii--ii Test Your Stress Level With A Computer Uses a simple biofeedback circuit. Drum Synthesiser Simple circuit has th•wee ICs. Mains Spikes: A Hazard To Computers r,.. What you can do to avoid problems. '<t 0 a, a. Ill z 0 z C .2 iii .!:! :0 ::, a. 'lii 0 a. -~ ~ 'lii ::, < >, .c BUILD THIS LOTTO SELECTOR Choose your numbers electronically for Pools, Lotto 40 & Lotto 44. Play systems games too! High Performance In Your Shirt Pocketl "S:!:8~'.~w 3 l /2 digit LCD Display Ranges Max Res Accuracy Vdc Vac Ade 100µV 1mV 1001-tA 10mA 100µA 10mA 0.1Q 200mV-1 kV 2V-750V 200mA 10A Aac 200mA 10A Ohms 200Q-2MQ Display also has Low Battery & Over-Range Indication 0.5% + 1dig 0.75%+5dig 0. 75%+ 1dig 1.5%+5dig 1%+5dig 2%+ ?dig 0.75%+1dig Built In Diode Check, Lo-Power Ohms & Continuity Test Beeper Memory Function for Relative Readings (DM6235 & DM6335) •QOc/4c /Lori ~ .,, Autoranging -~ { Ft~ 41 Manual Ranging Over-Ride (DM6235 & DM6335) ~ W One Year Warranty Hold Reading Function (DM6335) l0A Range Automatic Current Limiting Overload Protected to l 000Vdc/750Vac $69.00* $79.00* Look At The Low Pricesl DM6135 Autoranging 3 1/2 digit 10A ac/dc DM6235 As above with Memory function and Range Hold Prices include 9V Battery and High Quality Silicon Rubber Test Leads with Screw-On Alligator Clips DM6335 As above with Data Hold l0Mn Input Impedance Got ta • G (! t ta • G 0 IdSta ,- $89 • 00* You 've Gotta Getta Goldstar from : Supported & Serviced Australia-wide by Elmeasco Instruments Pty Ltd Dealer enquiries welcome. Call (02)736 2243 Recommended prices only including Sales Tax A.C.T. John Pope Electrical 80 6576 • J Blackwood & Sons 80 5235 • George Brown 80 4355 N.S. W. George Brown 519 5855 Newcastle 69 6399 • Ames Agency 699 4524 • J Blackwood & Sons Auto-Catt Industries 545 1322 • D:G E Systems (049) 691625 • WF.Dixon (049) 69 5177 • Macelec (042) 291455 Newtek (042) 271620 • Novacastnan Electronic Supply (049) 621358 • Obiat Pty Ltd 698 4776 • David Reid 2671385 • Dig1tel 709 65 11 • Geoff Wood 427 1676 N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 QUEENSLAND Auslec 85_41661 • George Brown 252 3876 • St Lucia Electronics 52 7466 • L.E.Boughen 3691277 BAS. Aud1otrorncs 844 7566 • Colourview Wholesale 275 3188 • E.C.Q. Electronics 376 5677 The Electronics Shop (075) 32 3632 • Thompson Instruments (Cairns) (070)5 1 2404 • Solex (Townsville)(077) 72 4466 • Xanthos Electrical (079) 27 8952 $.A USTRAL IA George Brown 212 311 1 • J Blackwood & Sons 46 0391 TASMANIA George Harvey (003) 31 6533 (002) 34 2233 VICTORIA • G.B. Telespares 328 4301 • J Blackwood & Sons 542 4321 • The Electronic Components Shop 670 6471, • Factory Controls (052) 78 8222 • Mektronics _Co 587 3888 • Truscott Electronics 723 3094 • A.W.M. Electrical Wholesalers W AUSTRALIA Atkins Carlyle 481 1233 • Dobb1e Instruments 478 1366 • George Brown 3621044 PAPUA NEW GUINEA TE (PNG.) Pt Moresby 25 6322 Lae 42 6246 MAY 1989 FEATURES 4 Electronics For Everyone by Leo Simpson Pt.3: all about electrolytic capacitors DON' T TRUST LADY LUCK with this device, you can electronically choose your numbers for Pools, Lotto 40 and Lotto 44. We show you how to build it starting page 48. 16 A Look At The IPC NEAT/40E Computer by Ross Morton It comes with the new enhanced AT chipset 76 The Technology Letters by Richard Kopf The road to hell is paved with good intentions 84 The Evolution of Electric Railways by Bryan Maher Pt.19: the Burlington Northern Railroad PROJECTS TO BUILD A Synthesised Tom-Tom by Leo Simpson Low-cost design uses three ICs 20 Syntom - 38 Biofeedback Monitor For Your PC by J. Barbarello Simple circuit plugs into the printer port 48 Electronic Pools/Lotto Selector by Malcolm Young ··- Give Lady Luck a helping hand Wl} 62 Build a LED Message Board by Don McKenzie Pt.3: building the message board control unit SPECIAL COLUMNS 12 Vintage Radio by John Hill How to date old valve radios 32 Serviceman's Log by the TV serviceman Brand what? Never 'eard of it! ~ ~--- Tms MONTH, OUR TV serviceman saddled himself with a set he knew virtually nothing about. But, with the bit between his teeth, he gave full rein to his technical knowledge and eventually rode off into the sunset. Don't horse about - go straight to page 32. 44 The Way I See It by Neville Williams Are spikes on the mains a hazard to personal computers 69 Amateur Radio by Garry Cratt Simple stub filter for suppressing TV interference DEPARTMENTS 2 26 81 91 Publisher's Letter Circuit Notebook Product Showcase Subscription Page 92 Ask Silicon Chip 94 Notes & Errata 95 Back Issues 96 Market Centre THIS PERCUSSION instrument synthesiser can be used by itself or added to an existing drum kit. Find out how to build it by turning to page 20. MAY1989 1 SILICON CHIP Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advertising Manager Paul Buchtmann Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill David Whitby ,:Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Waterloo, NSW 2017. Printing: Masterprint Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rate: currently $42 per year ( 1 2 issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139 , Collaroy Beach, NSW 2097. Phone (02) 982 3935. ISSN 1030-2662 • Recommended and maximum Australian price only. 2 SILICON CHIP PUBUSHER'S LE'I-IER Does the purchaser have the right to a circuit diagram? This month I want to talk about a touchy subject but one which will be dear to many readers' hearts. It concerns the provision of servicing information for products you buy. These days, if you purchase an item of test equipment such as an oscilloscope, frequency counter or RF generator, you automatically get a full circuit diagram which is included in the instruction manual. This is a reassuring point for any purchaser, even though he or she fully expects to obtain a long and troublefree life from the new acquisition. Basically, my proposition comes down to this: if it is good enough for test equipment suppliers to freely provide service information at the time of purchase, why can't the same apply to suppliers of other electronic equipment. I'm thinking particularly of computers and computer peripherals such as video monitors and printers. Some companies do provide this information but most don't. Worse still, some refuse point blank to even sell circuit diagrams or service manuals, even for ordinary TTL monochrome monitors. Now this is bad policy. For a start, it forces the purchaser to go back to the distributor when any service is required, even for the most simple faults. Second, if the distributor goes out of business, the purchaser is left with an "orphan" product which will be virtually impossible to service, even for the most skilled technician. Never mind. that a lot of electronic gear these days uses custom components, if you have a circuit diagram, you have a better chance of having it serviced. What to do about this situation? It's obvious, isn't it. When you are purchasing any new equipment, ask your supplier to give you the relevant circuit diagram. If he refuses, or is unable to provide the circuit because of the policies of the distributor, you should strongly consider buying · another product. You may well have to balance a very competitive selling price now against the possibility that you may not be able to have it serviced in the future. Remember that even if the product runs reliably for years and years, when it does fail it will be your problem and not the retailer's. If you at least have the circuit diagram, you can often be assured of having the unit repaired and thereby keeping it in service for more years to come. And if you can purchase a service manual as well, you will be that much better off. Leo Simpson 12MHz Zero Wait-State PC 'AT' Computer, Complete on the motherboard! That's right - a complete 12MHz AT (minus video card) built right onto a "baby-sized" motherboard , only 8.5" x 13". Not only do you get superior performance (with all memory and disk running at processor speed), but you save a fortune. Plus the computer is more reliable with no plug in cards to go wrong. Other features include 12MHz zero-wait-state performance - equivalent to 16MHz on most ATs □ DISC (dynamic I/O speed control) provides superior compatibility with add-on cards □ Up to 4MB can be fitted onto the motherboard - no need for memory expansion cards. Uses 256K or 1MB chips. 0 'I\vo serial ports and one parallel port on-board □ On-board floppy drive and integrated hard disk controller :_,l"Award" BIOS with built-in setup. 7 channel DMA and 16 level interrupts URealtime clock and off-board battery backup provided And for an introductory period, the price is: Box 426 Gladesville 2111 Phone (02J 427 4422 Fax (02J 427 2542 • We accept: Bankcard. Mastercard & VISA. mail order~ our specia lly . • All prices include sa les tax only$495 • Note: Produ cts may \'ary in appearann_• from those pictured. In all cases the,' will pt•r form to the sa me or a helter sta ndard. RAM prices: • All products carry a f'ull :J month ,rnrrant_,. l00nS high speed RAM (1MB chips) ............. $395 .00 per 1MB • All cards conw with full clocunll'ntation • All products carry a 14 clay mon ey back gua rantee I .softwa re aceeph.' d i • Ring for quanti ty discounts and tax f'rl't' prin•:-,; l~ &J..y-tie--ea~auit&F-S-a~-e-thec~ acitor world, generally ha "" · han f il ,-0.11°0 . er,.a 1 _o, e_q : -1~~ - - - -.2d..... k re ..L. _ _ _ _ _ _ _ _ _ _ _..:.:,o:.:::oM::::H.:..;1P;.;,:.RE:::A::::MP...;A;;;;Mo::..·_;;_' UNITS DISPLAY 120'., Every DC power supply has one or more electrolytic capacitors. They are used wherever a large amount of capacitance is required in a small space. As already noted, they generally require a DC voltage to work properly but there are special versions which can be used with high AC voltages such as "motor start" and capacitors for 240V AC powered appliances. Well, why are these capacitors called "electrolytics"? The answer is because they contain an "electrolyte", a chemical solution through which an electric current can pass. To properly explain · the subject though, we'll have to back up a bit and repeat what we said in the first episode on capacitors. There, we stated that every capacitor has two electrodes or plates which are separated by an insulating medium known as the dielectric. And so they have. But in electrolytic capacitors, the method of construction is quite different and they involve a good deal of complex chemistry. Don't be put off though- we'll tell you just as much as you need to know, to avoid unnecessary confusion. The vast majority of electrolytic capacitors are based on aluminium foil. Inside electrolytic capacitors there are two aluminium foils 4 SILICON CHIP _LJ_ ~ 14 It over ED-8IMPSON - - - - - - , t - - - - - ----'1,-J __.. --------------+------4-.►+5V wound together but separated by an absorbent paper which is impregnated with a liquid electrolyte. Now that description might not sound all that different to the structure of a film/foil capacitor, as described in the previous episode in this series. But there is a radical difference because the impregnated paper does not perform the function of a dielectric - it is actually the negative electrode of the capacitor! Although there are two aluminium foils in an electrolytic capacitor, one is quite different from the other. The foil connected to the positive terminal of the capacitor, known as the 'anode foil', is deeply CATHODE FOIL Fig.1: inside an electrolytic capacitor. It has two aluminium foils which are wound together but separated by an absorbent paper impregnated with a liquid electrolyte. etched to greatly increase its surface area and thereby the capacitance. Secondly, the anode foil has a thin coating of oxide. Aluminium oxide is a very good insulator and it is this thin oxide coating on the anode film which actually provides the dielectric of the capacitor. This oxide dielectric is very much thinner than the film dielectric used in plastic capacitors and so th,is is another factor in the very high capacitance of electrolytic capacitors. So if the electrolyte is not the dielectric, what is its purpose? It actually provides the negative electrode of the capacitor. Since the electrolyte is a liquid (more correctly, a paste), it is in intimate contact with the deeply etched oxide surface of the anode foil and thereby allows the enormous surface area of the foil to fully contribute to the total capacitance. The other aluminium foil in the capacitor is called the "cathode film'' and it makes the electrical connection from the negative terminal to the electrolyte. The electrolyte is an organic solution, which often used to be glycol borate but nowadays is likely to be more complex, depending on the performance parameters the CATHODE LEAD ALUMINIUM CAN DISC COMPOSED OF PTFE HARO PAPER Fig.2: this cutaway drawing shows all the essential parts of an electrolytic capacitor. The anode foil is deeply etched to increase its surface area and thus the capacitance. The impregnated paper forms the negative electrode of the capacitor. ALUMINIUM FOIL ANODE WITH ALUMINIUM OXIDE DIELECTRIC ALUMINIUM i'OIL CATHODE manufacturer is striving for. Some of these more modern electrolytes are dimethyl acetamine, dimethyl formanide or butyrolactone. To summarise, an electrolytic capacitor has an anode film which is deeply etched to increase its surface area and then its surface is oxidised to provide the capacitor's dielectric. The electrolyte then provides the negative connection to the capacitor. Well, as you might expect, electrolytic capacitors are a great deal more complicated than this short description implies but this is adequate for the moment. To go deeper would take up a great deal more space. The real reason for taking so much space to describe the internal structure of an electrolytic capacitor is to make the point that it is quite different from other types of capacitors. ANODE LEAD Range of capacitance These vertical mount electrolytic capacitors range in value from 1250µF to 8000µF. Note the mounting clamps fitted to three of the capacitors. Electrolytics are commonly available over the counter in capacitances ranging from 0.47µF up to 10,000µF although they are manufactured in values as small as 0.lµF and as large as 1,000,000µF (1 Farad) for very large computer grade capacitors. In recent yea rs, another special type of pola rised capacitor known as a "super capacitor" or "double layer capacitor" has become available. These have extremely large values of capacitance, up to 1 Farad, in very small cases. But while these are electrolytics they do not use the same oxide dielectric principle as conventional aluminium electrolytic capacitors. We 'll co me to double layer capacitors later. Polarisation and voltage rating· Aside from their relatively large values of capacitance, the aspect which distinguishes electrolytics from other types of capacitor is the fact that they can only be operated with the correct polarity of DC voltage applied to them. That is a long-winded way of saying that they MAY 1989 5 :, JJ ·~•. , "Ii . i ' · ., . ·1 ' ' ' . ·,: V ; " ' ,·. - -\ These are PC-mount electrolytics, designed for direct mounting on a printed circuit board. The negative terminal is usually indicated by a minus symbol and an arrow printed on the side of the case. voltage ranges. Because electrolytic capacitors have become a great deal smaller and because their characteristics have become much more stable and reliable, it is unusual to find capacitors with a rating below 25V for the smaller values or below 16V for the larger values. It also used to be the case that for long life, electrolytic capacitors should be used in circuits at close to the rated voltage. If this did not happen, the capacitors would gradually deteriorate. Nowadays though, it is quite permissible to use a capacitor with only a fraction of its rated voltage applied to it. For example, you can use a lOOµF 16V capacitor with less than 1V applied to it. Indeed, this circuit situation is very common. However, it is still important that the DC voltage across the capacitor is of the correct polarity (ie, positive voltage to positive terminal). V and VW: what do they mean? Pigtail or axial lead electrolytics differ from PC-mount types by having a lead at each end. On these units, plus and minus symbols are marked on the case to indicate the positive and negative terminals. must have a positive DC voltage at their positive terminal. If the capacitor is operated with a reverse DC voltage, it will eventually fail and probably become a short circuit. Depending on the manufacturer, electrolytic capacitors are made with the following DC voltage ratings: 6.3V, 10V, 16V, 25V, 35V, 6 SILICON CHIP 50V, 63V, 75V, 100V, 160V, 200V, 350V and 450V. However, it is also possible to come across capacitors rated at 40V, 80V and so on. For a given value of capacitance, a capacitor rated at 75V will be much larger than one rated at 16V. Nowadays though, most parts wholesalers and retailers do not stock capacitors in all the above In SILICON CHIP and on most circuits, you will see electrolytic capacitors specified with a value and a voltage rating, such as 47µF 25VW. The value is straightforward enough but what is the meaning of "VW". VW stands for "volts working". Some capacitors are labelled "WV" which means exactly the same thing, "working volts". In some ways the VW designation is an anachronism, a holdover from the days when all electrolytic capacitors had two voltage ratings: VW and VP. VP stands for "volts peak " and is the surge voltage that the capacitor can withstand for short periods. The surge voltage is generally 20% to 30% higher than the rated voltage. It is related to the voltage used to "form" the oxide coating on the aluminium film and if it is exceeded, the capacitor is liable to fail within a very short period of time. These days most capacitors only have their rated voltage printed on them, together with their value and polarity marking. Lead types Often, you '11 see electrolytic capacitors referred to as PC-mount, vertical mount, pigtail types, axial lead or radial lead types. With the exception of the last term, all these are fairly descriptive. A pigtail type is a conventional small can capacitor with a lead at each end; these are also known as "axial lead". PC-mount types are those which have both leads coming out at one end so that they can mount vertically on a printed circuit board. These are also known as radial lead types. Of course, pigtail capacitors can be mounted on a printed circuit board too but vertical or PC-mount capacitors take up less board space. Leakage Non-polarised or bipolar electrolytics can be connected into circuit either way around. They are identified by an NP or BP label on side of the case. Polarity marking Since the voltage polarity across an electrolytic capacitor is so critical, it is important to be able to distinguish which is the positive terminal and which is the negative terminal. On most electrolytics these days, a minus symbol, and sometimes an arrow, is printed on one side of the case, nearest to the negative electrode. On the other hand, you may come across electrolytics where the positive electrode is indicated with an adjacent + symbol and there may also be an arrow to reinforce the message. On some pigtail electros, both the positive and negative electrodes may be labelled. On larger can type electrolytics, the negative terminal may be indicated with a dab of black paint. Alternatively, the positive terminal may be indicated with a dab of red paint or perhaps a + symbol moulded into the lid. Non-polarised electrolytics Having made the point above about the necessity for the DC voltage needing to be of the correct polarity, we will now muddy the water by stating that with some electrolytics, this is not a problem. These are "bipolar" or "nonpolarised" electrolytics. They are virtually two conventional electrolytics connected back-to-back inside a common can. They are made with two etched and oxidised (formed) anode foils. They can be used in circuits where the DC voltage is indeter- Compared to other types of capacitors, such as plastic or film, electrolytic capacitors have very poor insulation. In fact, it is so poor, relatively speaking, that instead of expressing the insulation resistance in terms of hundreds or thousands of megohms, it is usual to express it as "leakage current" in microamps or milliamps . Small value electrolytics, say with a value of 22µF or less, will typically have a leakage current of 10 microamps or less at the rated voltage. The larger can types, with a capacitance of lO00µF or more, will typically have a leakage current of 1 or 2 milliamps. Tantalum electrolytics Shown here larger than actual size, this NEC super capacitor has a value of .047 Farads and is rated at 5.5V. Values of up to 1 Farad are obtainable. minate (ie, might be polarised one way or the other) or where there is no DC voltage but quite substantial AC voltage. They are made in quite a wide range of DC voltage ratings although if you are buying them over the counter you will usually only be able to obtain·them with a rating of 50 volts. Non-polarised electrolytic capacitors are used where relatively large capacitors are needed, say up to lO0µF, and where the cost of alternative plastic or paper capacitors would be prohibitive. A typical application is in crossover networks for loudspeaker systems. On circuit diagrams, non-polarised capacitors are indicated with the label "BP" or " NP". They are also labelled this way on the can. Tantalum is an alternative metal to aluminium in electrolytic capacitors. Tantalum electros are in values up to lO0µF and with a restricted voltage (usually only 50V) range. Tantalum electros can be made in foil, wet sintered and solid types. Tantalum foil capacitors are similar to aluminium electrolytics in that the foil is anodised but the electrolyte is sulphuric acid. Wet sintered tantalum electrolytics have a sintered tantalum anode in an electrolyte of sulphuric acid and ionised water or a gelled electrolyte of sulphuric acid and silica. We mention tantalum foil and wet sintered tantalum foil capacitors for the sake of completeness but it is unlikely that such capacitors ever become available over the counter to enthusiasts. Most people will only come across the epoxy dipped solid tantalum electrolytics which are widely available and generally only slightly dearer than conventional aluminium electros. The solid tantalum capacitor again has a sintered tantalum anode. The porous anode pellet is impregnated with manganese nitrate and heated to 400°C. This decomposes the manganese nitrate to solid manganese dioxide which becomes the electrolyte. When they were first introduced to the market, about 20 years ago, solid tantalum capacitors had a MAY 1989 7 Table 1: Tantalum Capacitor Markings In the E12 Serles Value Alt value IEC value 0.1µF 0.12µF 0.15µF 0.18µF 0.22µF 0.27µF 0.33µF 0.39µF 0.47µF 0.56µF 0.68µF 0.82µF 1.0µF 1.2µF 1.5µF ··1.8µF 2.2µF 2.7µF 3.3µF 3 .9µF 4.7µF 5.6µF 6 .8µF 8 .2µF 10µF 12µF 15µF 18µF 22µF 27µF 33µF 39µF 47µF 56µF 68µF 82µF 100µF 100nF 120nF 150nF 180nF 220nF 270nF 330nF 390nF 470nF 560nF 680nF 820nF 100n 120n 150n 180n 220n 270n 330n 390n 470n 560n 680n 820n 1µ0 - number of advantages over aluminium electrolytics. These included better shelf life, lower leakage, wider operating temperature range (up to 125°C instead of 85°C), lower power factor and closer tolerance on value. Now, with the general improvement of aluminium electrolytics, these improvements are nowhere near as clear-cut. Low leakage (LL) aluminium electrolytics are comparable with tantalums as far as leakage is concerned and their general stability is just as good. Aluminium electrolytics are now also available (although not over 8 SILICON CHIP 1µ?. 1µ5 1µ8 2µ2 2µ7 3µ3 3µ9 4µ,7 5µ6 6µ8 8µ2 10µ 12µ 15µ 18µ 22µ 27µ 33µ 39µ 47µ 56µ 68µ 82µ 100µ EIA code (108/e tolerance) 104K 124K 154K 184K 224K 274K 334K 394K 474K 564K 684K 824K 105K 125K 155K 185K 225K 275K 335K 395K 475K 565K 685K 825K 106K 126K 156K 186K 226K 276K 336K 396K 476K 566K 686K 826K 107K the counter at retailers) with operating temperatures up to 125°C with voltage derating by a third. Substituting for tantalum capacitors In general, you can substitute low leakage aluminium electros for tantalums provided they are not being used in an oscillator or timing circuit. In the latter case, the designer has probably specified tantalum not only for their low leakage but for their closer tolerance in capacitance value. Identifying tantalum capacitors These days most tantalum capacitors are labelled with their capacitance value, voltage rating and a + sign near the positive lead. However, it is quite likely that, unless you are really keen sighted, you will need a magnifying glass to read the labelling. Some brands also use the EIA code to indicate the capacitance value. This is the same code as shown in the previous episode on film and ceramic capacitors. Table 1 shows the code for capacitors ranging from O. lµF up to lOOµF. Tantalums are normally made with a tolerance of ± 10% as indicated with a K following the 3-digit EIA code, or ± 20% as indicated with the letter M. Some tantalums indicate the polarity with a vertical line near the positive lead, together with a tiny + sign. This could be confusing to the newcomer to electronics since some older pigtail electrolytics indicated the negative end of the can with a line around one end. You may also come across tantalum capacitors that are colour coded and with the polarity shown by a dot. You hold the capacitor with leads hanging down and with the dot facing towards you. The positive lead is then the one on the right. This is shown in the diagram of Fig.3. Be warned, the colour code for tantalum capacitors does not bear much similarity to that for resistors. So to identify tantalums, you should examine Fig.3 closely. Let's explain the tantalum colour code in a little more detail. First, hold the capacitor with the leads hanging downwards. The first two colours, reading from the top down, give the first two significant figures of the capacitance value (just as for the resistor colour code). The colour of the spot then gives the multiplier, so that the value is read off in microfarads. For example, a capacitor with the first two colours yellow and violet, with spot colour black, is 47µF. The third colour on the body of the capacitor gives the voltage rating, as follows: MULTIPLIER (µF) WHITE x.01 GREY x0.1 BLACK xl BROWN x10 RED x10D VOLTAGE RATING WHITE 3VW . / YELLOW 6.3VW BLACK 1DVW GREEN 16VW BLUE 20VW GREY 25VW PINK 35VW PO~J~~E ORANGE 40VW 2ND SIGNIFICANT FIGURE - \ BLACK 0 BROWN 1 RED 2 ORANGE 3 YELLOW 4 GREEN 5 BLUE 6 VIOLET 7 GREY 8 WHITE 9 CAPACITANCE IN uF \ POSITIV LEAD CAPACITANCE IN EIA CODE VOLTAGE RATING CAPACITANCE IN uF VOLTAGE RATING POSITIVE LEAD \. 33~ -INDICATES STRIPE 35V POLARITY POSITIVE LEAD Fig.3: tantalum capacitors are usually labelled with their value, voltage rating and a plus (+)sign to indicate polarity. However, some brands use the EIA code while others may be colour coded. white ........... 3VW yellow .......... 6.3VW black ........... l0VW green ........ ... 16VW blue .. ........... 20VW grey ............. 25VW pink ............ . 35VW orange ......... 40VW As can be seen, the colour code for tantalum capacitors bears little resemblance to that for plastic film capacitors, as listed last month. In fact , the only similarity is in the code for the first two significant figures for the capacitance value. It seems that colour coding of capacitors has now fallen into disuse, partly because the code is so confusing and partly because of the improved capability for printing values on such difficult objects as dipped tantalum capacitors. Super capacitors We mentioned these capacitors earlier. These are also known as "double layer" capacitors. They are packaged to look like electrolytic capacitors but they do not use the same dielectric principle as electrolytics and they are not used in FM tuners, TVs and VCR.s for storing station settings and a host of other electronic equipment where data needs to be stored in spite of the removal of mains power. The "double layer" capacitor is the first really new capacitor to be produced in the last 25 years or so although the principle has been known for over 100 years. The main constituents are activated carbon and a sulphuric acid solution as the electrolyte. The interface between the activated carbon and the sulphuric acid forms the electric " double layer" . A basic double-layer capacitor consists of two half-cells, each consisting of an activated carbon electrode saturated with sulphuric acid and separated by an ion permeable membrane. The two half-cells make up a non-polarised capacitor cell which has a low voltage rating and so between 8 and 15 of these cells are connected in series to give a practical capacitor with a voltage rating of 5V or 10V. Really, a double-layer capacitor is more like a battery than a capacitor and that is reflected in typical applications such as low power battery backup for microprocessors. They are not a substitute for conventional capacitors because they cannot handle substantial ripple current. Nor can they deliver substantial DC current because their internal resistance is high. As a substitute for batteries in low backup power circuits though, they are ideal. Barrier layer capacitors Tantalum capacitors are available in values up to about 100~F and with voltage ratings up to 50V. In most cases, you can substitute low-leakage electros for tantalums. polarised. They can be connected into circuit either way around. Made by companies such as NEC, they can have a capacitance up to 1 Farad and usually are available in only one voltage rating: 5V. At present, their main use is as a replacement for lithium and mercury cells in microprocessor controlled appliances. Thus they are Having described double layer capacitors we should mention " barrier layer" and "boundary layer" capacitors because they may be thought to be similar. They are not. In fact , barrier layer and boundary layer capacitors are a special type of ceramic capacitor, based on barium titanate. They have relatively high capacitance values for a ceramic capacitor, up to 0.47,-iF, but at low voltage ratings, typically 12V, 16V and 25V. These days they are tending to be displaced by the even smaller " multilayer " ceramics. ~ MAY1989 9 Walkabout Wadio Car Tune-up Adaptor This inexpensive portable radio kit puts life back into 'AM' reception. Uses an RF Amp which delivers up to 120mV into 64 ohms to drive a pair of 32ohm headphones. (Headphones optional). Cat K-2720 Until Stocks Last! Turn your multimeter into a tacho/dwell meter with this simple adaptor. It's easy to build and may be calibrated for 4, 6 or 8 cylinder petrol enaines. Cat K-4400 s1495 __...-~Sa!! SS\ $2695 0 Brake Lamp Monitor A low cost and easy to build project. It warns you if your vehicles's brake lamps aren't working as they should. Cat K-4500 s2&95 RF Attenuator Box Proximity/Motion Detector 100W HF Linear Amplifier Perfect for use with a huge range of QRP commercial gear, in the range of 3 to 15 watts output. Can deliver up to 100W output with very modest input. Frequency - all amateur bands from 2-30MHz. Until stocks last!. Cat K-6331 A low cost device that can be used as part of a burglar alarm, customer indicator, etc, floods an area with low-level RF signal from a UHF oscillator and detects any movement in the area. Kit comes in short form. Cat K-8100 :59l ,,. . -.. SAVE"'$20', ""] I ') __ ,.," ~ , ~ €, ·' ,,!t t,., !l:i S ~ ~~~QF ' Cl'- l_ ..tli\ son 0 RF ATTENUATOR - ,J t'J\J De > s,.,,~ ( .,, ~-" . ~)1) Your Phone Can Bs A... s249 Telephone Bell Monitor This easy to build kit plugs in parallel with your telephone. When the phone rings, it broadcasts a sequence of tones to a portable FM radio receiver. Cat K-3102 0 lncr,dibly sasy to build! Here's value : up to 63dB attenuation (in 1dB steps from 0dB) from 50 to 500MHz - and it's$$$ less than equivalent commercial units. Rated at ¼ Watt, with a 50 ohms input impedance. Until stocks last!. IJ6!!f'1e'f7 ..,~ TELEPHONE O 0 0 tr=rr.r.1'\'Eaa... ~"\ BELL MONITOR Hands-free Speakerphone Hands free phones can be expensive. Well, here's a way to add Hand-Free Speakerphone capabilities to your existing phone ... without spending a fortune. There's even a phone jack fitted. Comes complete with case, phone cable and plug, PLUS a telephone double adaptor. Cat K-3100 s9995 Bookshelf Speakers This low cost compact Bookshelf Speaker Kit uses a Magnavox 6MV nominal 15 cm driver and a 3AC Tweeter. Buy complete kit and save. Until stocks last! K-4000 - Sleeves, baffles X-overs etc $126 K-3998 - Speaker Tweeter 3AC $6.75 K-3999 - Speaker Woofer 6MV 8 R $29.75 NEW KITS JUST RELEASED! Lotto/Pools Selector Transistor Beta Tester • Can select 6 to 12 numbers • Selects systems 36, 40 or 44 (i.e. 6 from 36 etc) •Has Auto Power shut down • Uses 9V Battery (Not supplied) Cat K-3700 This fantastic Transistor Beta Tester allows you to measure to gain of any bipolar transistor in seconds. Just connect a transistor, push the button, rotate the knob and read of the beta scale. Cat K-7200 VHF FM Monitor Receiver Passive lnfrared Detector Need a spare VHF Receiver for monitoring the local repeater or VHF Marine channels etc. Simple to construct shortform kit. All necessary components supplied. Cat K-6000 Protect your home with this compact, inexpensive Passive infrared movement detector. Comes complete with components, PCB, case PIR sensor and lens. Components for interface section are also available in kit form. (Cat K-8201) Cat K-8200 NEW KITS SUBJECT TO AVAILABILITY OF PARTS. PLEASE CONTACT YOUR NEAREST DICK SMITH STORE FOR PRICE & AVAILABILITY. Public Notice This is a small message to let you know that the really big message for 1989 is in the centre of this magazine. F rom everyone at Dick Smith Electronics. • NSW • Albury 21 8399 • Bankatown Square 707 4888 • Blacktown 671 7722 • Bondi J\ffletion 387 1444 •CampbefHown (046)27 2199 • Chatlwood Chase 4 11 1955 • Chullora 642 8922 •Gore HHI 439 5311 • Goaford 25 0235• Hornsby4776633 • Hunh'iHe5808622• Liverpoot 6009888 • Maittand 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 88 3855 • ParTam atta 689 2188 • Penrith (047)32 3400 •Railway Square 211 3777 •Sydney City 267 91 11 • Tamworth 66 1711 • Warringah Man 905 0441 • Wollongong 28 3800 •ACT• Fyshwick 80 4944 • VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Htn 890 0699 • Dandenong 794 9377 • East Brighton 592 2366 • E.uendon 379 7444 • Footlcray 689 2055 • Frank.ton 783 9144 • Geelong 43 8804 • Melbourne City 326 8088 • Richmond 428 1614 • Ringwood 879 5338 • Springvale 547 0522 • OLD • Brisbane City 229 9377 • Caim a 311 5 15 • Chermslde 359 6255 • Redbank 288 5599 • Aockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • TownavHle 72 5722 • Underwood 341 0844 • SA• Adetaide City 223 4122 • 81:Yeriey 347 1900 • St. Marys 277 8977 • Elizabeth 255 6099 • Enfietd 260 6088 •WA• Cannington 451 8666 • Fremantte 335 9733 • North Pet'th 328 6944 • Perth City 481 326 1 • TAS • Hobart 31 0800 •NT • Stuart P1111c 811977 ORDER BY PHONE TOLL FREE (008) 22 8810 FOR 24 HOUR DESPATCH VINTAGE RADIO By JOHN HILL How to date old valve radios This month, we 're going to take a general look at the subject of dating old valve radios. In particular, the following information should help newcomers to vintage radio in determining how old their sets are. If I were about 80 years of age, I would probably have a better idea of how old some of my radios are for I would remember seeing them at some time in the past. But as radio had been established in Australia some 15 years before I was born, I remember very few of the really early receivers. For this reason, dating some of my old radios initially presented some real problems. A few years further down the track, I have now reached a stage where I can date most sets to within a year or so of their manufacture. It is an important aspect of collecting to be able to accurately estimate the age of one's treasures, whether they be old radios or anything else. Come in sucker One of my early "come in sucker" purchases was a radio that was supposed to be a 1925 model. Although I was fairly green about such things at the time, I knew it was no 1925 model but it did look fairly old. Imagine my disappointment when I saw 1948 on some of the components inside. The outline of a barretta tube, which could be seen through the back cover, gave the impression that the set had very old valves in it. But I was wrong - the other valves were octal types and they certainly weren't around in 1925. Being able to date a set, even approximately, can be a distinct advantage when buying, for anyone selling an old radio usually exaggerates its age to get a better price. You'd be surprised at how many 1930s sets become 1920 models when buying from antique shops. Most antique dealers have no idea of how old a radio set is so they just make a guess - usually a very inaccurate one. There are some fairly clear-cut ways to date some receivers so let's start with the easy ones first. Dating by the label ,ei,. , Large components and a 59 output valve date this old Airzone receiver to the early 1930s - probably 1932-33. A good knowledge of the valve types used can often date a receiver quite accurately. 12 SILICON CHIP In 1934, Australian radio manufacturers fixed a label to the chassis of all locally made receivers. The label made mention of patents and reminded listeners that the set required a licence. It also carried a serial number which was preceded by a letter prefix. In 1934, the prefix was "A"; in 1935 it was "B" and so on. This letter prefix system was abandoned when production stopped during the early war years. The latest prefix I have seen is "G", although I suspect there may be a few "H's" around even though I haven't seen one. The earliest labels consisted of a plastic plate which was rivetted to the chassis. After a couple of years, this was replaced with a blue The AW A Radiolette receivers used this characteristic "cathedral" shape from 1936-38. Note also the styling of the dial which used both numbers and station call-signs. Several factors combine to suggest that this Stromberg Carlson receiver is an early post-war model. These include the cabinet style, the use of octal GT valves and an ARTS&P sticker without a letter prefix. 4 This in strument was mant,factured under a lieense granted by AUSTRALIAN RAD!O TECHNICA L. SERVICES AND PA TENTS COMP ANY LIMITED in r espect of patents controlled by it for the reception in the Commonwealth of Aus t ralfo, and such territoriell as may from time t.o tim e be ,1dministered under mandate by the said Commo n wealth of sound broad• cas t by wireless hut only fo r privat.- use and not for operation for any public or comm~. ial or revenu.- No. earning purposes. N ..8.-A Poist Office Lic: em~e is necessary. B 43482 Australian-made receivers of 1934-35 vintage carry a plastic label which is rivetted to the chassis. The B prefix on the serial number of this label indicates that the set was made in 1935. Note that listeners required a Post Office licence to operate the set legally. ARTS&P [Australian Radio Technical Services and Patents) transfer. Unfortunately, these transfers are inclined to flake off and the all important letter prefix is frequently missing or unreadable. Post war receivers used unprefixed blue or olive green labels but if there is any accurate dating system related to these transfers, I have yet to discover the details. While the previously mentioned lettering system conveniently dates those domestic receivers made between 1934 and the early war years, there are problems if the transfer is not intact. If this has happened, other information must be used to date the radio. Australian radio service manuals are of great assistance in this regard and checking out the model number [if it's known) can soon date a particular set. I have only one such manual - a 1938 edition but it has helped me quite a lot. Using the valves The valve types used in a radio can also indicate when the set might have been made although this method of dating can be a bit vague. At best, it is usually a "not earlier than" guide only. To give an example, I have a 1937 radio which was originally fitted with octal based metal valves which came into use in Australia from 1936 onwards. However, it would be wrong to assume that any radio with octal valves is a 1936 model or later. I have also seen a 1939 radio of the same make that was fitted with the old pre-octal 6 and 7-pin valve bases. Therefore, it must be realised that valve dating can have discrepancies. Then again, in some cases, valve dating is not all that bad. During the late 1920s and early 1930s, an incredible number of new valves appeared in a relatively short period of time. In fact, new valve types were so numerous during this era, few remained current before being superseded by a better valve. So in some cases, valves can date a receiver quite accurately. For example, the 2.5V era was roughly between 1928 and 1933, after which valves with 6.3V heaters were rapidly introduced. In many instances, these later valves were identical to their 2.5V counterparts, the heater voltage being the MAY 1989 13 Service manuals and advertising material from old magazines and newspapers can also be used to date valve radio receivers. In some cases, it may be necessary to consider a number of different factors to accurately determine a set's age. only difference. The 58 and 6D6 are just one such example. The old 2.5V valves can even be subdivided to get a more accurate indication of age. For example, a receiver with a 47 output valve is likely to be a year or two older than a set with a 59 output valve. I would date a radio with a 47 as around 1931 whereas a radio with a 59 is more likely to be of 1932-33 vintage. A set with a 2A5 in it may well be another year further on. I have an old Airzone that has a valve complement of 80, 5 7, 58 and 59. I believe these valves date that set to about 1933. As there is no label attached to the chassis, it must be pre-1934. It is perhaps interesting to note ..::~-:;·•· :}, \: .- ;~ ;:; r;!~~i~~:H: ,~;i1::d:;:;~~l:~~1;::~~~:: S~: -<ti:<.:1 & isicn!'!, (<r P1•1. i!r.i.i>~ r(fs.p<:: <: 1 !:If .p~h~.nh <a,iroi!1~d by it for the fP.~(}pt:cn ir, trm (~rnm(t'(!¥ we\'Slt'h d Aoit;a!i..,. <'!~d $Ut:ht,omf',ei,nft.S l!t~ <rutY frt,;ro tin);,;, •Q lor,(l ~ itdrt\imtmtod Hf\d.cr roand.ato bythse 1itJ {Q-rtil'l'<UflW<l&.hh tif s~~nd_b~oad~$1 bv Wt-rek"\l> ~t-1-1 tudy,, {9'.f ;:s,riv:♦1~ ~< .clom,$fit tir~ .. tnd ~®I' for vv~~1~!10:-. bt ,·my pul,!it or ('ommc((.ial o r ,~venue¥ .o,.;rmng ~,rpQ-~e. N!l.-A PeM Offi(.6-lic~ru:e 11 nec(l'$$i3t\'. .. '$fl(X TRANSf!R.S" G.W.GRHN&SONS»:'T"' ll'D. 1<1trnOURNi· -J..J...-_ _ _ ___,J Receivers made in Australia after 1936 carried a blue or olive-green transfer instead of a plastic label. Unfortunately, post-war receivers did not carry a letter prefix so the label cannot be used for dating. 14 SILICON CHIP that no Australian radio manufacturer was using 2.5V valves in 1936. This statement also probably holds good for most 1935 models. Octal valves Octal based valves were in common use from 1937 to the early 1950s when they were superseded by baseless miniature valves. GT octals are most likely to be found in post-war receivers although they were in service during the war years. Radios with mixed valve complements (octal and miniature) were fairly common around 1951-54. The European "P" base valves were never as popular in Australia as the American types but there were quite a few sets (mainly Philips and Mullard) which had Phased valves in them. These side contact valves were in use from 1936 onwards and were phased out with the advent of the baseless miniatures. Unless you are very well informed, dating radios by their valves is a guessing game with a fair margin for error. Even so, many types of valves give an accurate indication of a receiver's age and can, in some cases, place a set into quite a narrow time slot. Dial markings Station call signs are another way of dating old radios. There are a number of stations that either changed their frequency or their call-sign, or started transmission, at certain times. By knowing when these events took place, one can often pinpoint the age of a particular receiver. One of the more significant stations in this regard is my own local station: 3CV Central Victoria. 3CV has undergone both frequency and call-sign changes in the past with the call-sign change being the most significant of the two as far as dating is concerned. 3CV commenced transmission from Maryborough, Victoria in 1938. Prior to this, the station transmitted from Birchip under the call-sign 3MB, on a frequency of 1470kHz. This simply means that if a radio dial has 3CV marked on it, then it must be more recent than 1938. If it has 3MB on it, then the set must be pre-1938. Unfortunately, 3MB was such an insignificant station that many pre-1938 dials don't even give it a mention. 3SR Shepparton is another station that has changed call-signs. From 1933-1937, this station transmitted on 1260kHz using the call-sign 3WR. Another Victorian station, 3MA Mildura, had a frequency change in 1937 when it moved from 900kHz to somewhere around 3MB's old frequency of 1470kHz. Sill another station of interest is 4GY in Queensland which commenced transmission in 1942. Thus, any set with this station marked on the dial is likely to be a post-war receiver. Bringing it together Now let's put some of this dating information to work. One of my many Airzones is a pre-war model but has lost its blue ARTS&P transfer. It has octal valves (could be 1936 or later), it has 3MA marked on the dial at its old frequency (changed in 1937), and also lists 3WR (also changed in 193 7). In addition, the model number is just one short of my 1938 service manual, so it looks like an early 1937 model to me. Anyway, who 's going to argue? Post war receivers usually have YOU NEED THIS TV TEST EQUIPMENT SHORTED TURNS TESTER Including meter for checking EHT trans, yoke windings, drive trans. $78.00 + $3.00 P&P HI-VOLTAGE PROBE Including meter Reads positive or negative 0-50kV For TVs, microwave ovens and high voltage equipment $84.00 & $5.00 P&P TV TUNERS (PHILIPS) This receiver is from the early 1930s as indicated by the huge chassis, the numbered dial and the use of valves with 2.5V heaters. Valves with 6.3V heaters took over from about 1933. ECL 2060 Repair or exchange UV461 Repair only $17 .00 ea + $2.00 P&P CHEQUE, MONEY ORDER, BANKCARD OR MASTERCARD TO ':Y.V.TuNERs) 216 Canterbury Road Revesby 2212, Sydney, Australia Phone: (02) 77 4 1154 sole cabinet with turned legs would also be around 1928-33 vintage, while legless consoles were in vogue from the mid 1930s onwards. Sets from the 1920s This old 1927 model Astor is typical of the style used in the mid-1920s. Any receiver that is of pre-1930 vintage is truly an antique radio. a date or two stamped in ink dn some of the components. If one cares to look, Rola loudspeakers, speaker transformers and high tension chokes will have the manufacturer's date stamp on them somewhere. While this date only indicates when the component was made. one assumes that such bits and pieces went into service in a reasonably short time. Of course, it should be remembered that components such as HT chokes and speaker transformers are inclined to burn out and there is always the possibility that these components may not be the originals - so look closely. Another good method of dating is to compare a particular set with old advertising material. In recent years,- there have been a number of publications relating to the subject of vintage radio and these books have repoduced many of the old sales brochures that were used to advertise the sets. Matching a set to an advertisement gives fairly reliable dating in most cases . Only if a particular model ran for a number of years would this method be unreliable. A less accurate method of dating is by the style of the cabinet. Gothic or cathedral style cabinets were popular in the early 1930s. A con- Although I'm no real authority on sets from the 1920s, they too can be divided into certain categories. If a set has variometer tuning (ie, swinging coils), it is most likely of pre-1925 vintage. Sets with multiple dials (two or three) are usually around 1926-28 vintage. In fact, it can be said with reasonable certainty that if a radio has a separate loudspeaker, a solid timber cabinet and 4-pin battery operated triode valves, it is a valuable relic from the 1920s. Any set that is of pre-1930 vintage is truly an antique radio. Yes, there are many ways of estimating the age of an old radio, with some methods being more accurate than others. Experience is also a great help for it can give a "gut feeling" as to the age of a particular set. In short, everything helps. it MAY 1989 15 A LOOK AT THE IPC NEAT/40E COMPUTER In this article we set out to review the CMS Music Card mentioned in a previous issue, ramble all over the current computer scene and end up reviewing the IPC NEAT computer which uses the new AT standard chipset. By ROSS MORTON Regular SILICON CHIP readers may recall seeing a "CMS Music Card" mentioned in our Product Showcase section last December. At that stage, all we were able to present was a brief description and photograph. Shortly after the issue went to press, we were approached by CompuHelp Australia, the local agents for the card, to see if we'd like to have one to play with for a while. Before we could answer, they asked "Would you like it inside a computer - then you could have a look at both ... " Talk about making every post a winner! Anyway, CompuHelp Aust- ralia duly delivered an IPC NEAT/ 40E computer system to our office, with the CMS Music Card installed in one of the spare slots. The original specification of the IBM "AT" machine (which, believe it or not, is now over 4 years old) had an 80286 processor running at 6MHz with 512K of RAM (although expandable to 3MB). Since then many refinements have been made - not the least being speed (even basic ATs now run at 8MHz) and memory (up to 640K). The IPC NEAT goes beyond this: a clock speed of 16MHz means most applications run appreciably faster and it is possible to use a lot more memory, above the DOS limit of 640K. (A group of the major software suppliers have come up with a specification for extended memory known as LIMs - Lotus/Intel/ Microsoft specification). Not that the IPC NEAT is alone in using this specification; most "top end" computer manufacturers now offer this option. What's NEAT? IPC COMPUTERS COVER THE range from a large 80386 tower system down to PC XT compatible machines in quite small cases. All machines may be had with hard disc drives and 3½inch or 5¼-inch floppies. 16 SILICON CHIP Whoa! What's this "NEAT" we're talking about? What happened to "AT". Many readers would be aware that the AT machine is now very much "middle of the road" in computer performance. The newer machines based on the 80386 processor literally run rings around the older ATs or 80286 based machines. Despite the very high cost of machines based on the 80386, many customers are bypassing the AT to have "the best". This worried one 80286 manufacturer so much they decided to do continue up-grading and releasing DOS in parallel to OS/2. For these reasons, the majority of manufacturers, including IPC, have remained faithful to th8 DOS standard. Incidentally, what about that name "IPC"? It stands for Intelligent Personal Computer and is a product of Essex Electric, of Singapore. For our money, the logo is perilously close to that other three letter computer manufacturer of international standing. Golly, could that be an accident? Graphics standards The graphics capabilities of PCs have come a long way since the original days. While most computers still have the option of a mono display to retain compatibility with earlier software packages, CGA (Colour Graphics Adaptor) displays have given way to higher quality EGA (Enhanced Graphics Adaptor) and even better VGA (Video Graphics Array) displays. Emerging now are better yet "PGA" or Professional Graphics Adaptor standards, although these are found only on very few high level machines and require expensive monitors. By far the most popular is the EGA standard and this is the card and matching monitor used on the computer under review. THE NEAT/40E MACHINE under review: it uses the new enhanced AT chipset which allows performance almost to the 80386 standard to be achieved. In the turbo (zero wait state) mode it runs at 20.5MHz. something about it. The giant US "Chips & Technologies" corporation reasoned, quite logically, that if they could up the performance of the 80286 chip set to approach 80386 standard but hold the cost down, customers wouldn't be so quick to pay the extra bucks for not much more byte. Which is how the NEAT Chipset (or New Enhanced AT) came into being. The performance does approach the speed of the 386: 16MHz vs. the 386's normal 20MHz. It also allows addressing of up to 8MB of memory (RAM), along with a few other refinements such as the LIM 4.0 support already mentioned. Unless you 've been in Outer Mongolia for the last couple of years, you would be aware of IBM's much touted "micro channel" architecture and OS/2 operating system. Despite the huge amounts of money pushing this system, by and large most manufacturers have stuck with the DOS system. Even if OS/2 support increases much more rapidly than at the moment, industry analysts expect DOS to be the dominant system for many years to come - simply because of its mammoth installed base and the huge variety of software available. In fact, a recent survey of US corporations revealed over 80% had no plans to switch to OS/2 (Computerworld, February 10th issue). And the inventor/supplier of DOS, Microsoft, has promised to Appearance The IPC computer is supplied in two boxes, one holding the EGA monitor and one holding the computer, keyboard and accessories. The keyboard is individually boxed inside the main system box and comes with a clear hard plastic keyboard cover. This not only protects the keyboard in transit but can also be used as a keyboard cover when the machine is not in use. Removal of the keyboard reveals the computer itself, securely contained within a foam transportation enclosure. Also in the box are the operation manual and setup disc, DOS manual with DOS & GW BASIC discs, and a power cable. The computer supplied for this review was equipped with a 5¼-inch 1.2MB floppy disc and a MAY 1989 17 IPC NEAT/40E COMPUTER - CTD 40MB hard disc. There is also provision in the machine (and on the front panel) for an additional 5 ¼-inch drive and a 3 ½-inch drive. drive. As is typical of "AT" style machines these days, a key switch is provided to prevent system use by locking the keyboard. We're not quite sure why this feature is included: we've yet to meet anyone who actually uses the keyswitch or, more to the point, even knows where their keys are! Still, it could be a handy security device to prevent prying eyes or 0ther unauthorised access. Alongside is a system reset switch and a "turbo" switch: press the first and the machine warm boots, press the second and the little man inside pushes down on the accelerator. Two LEDs on the front panel show power on and when the internal hard disc drive is in operation. In addition, a two digit numeric display shows the speed of operation - 8 for standard 8MHz, or 12 for '"turbo". On the rear of the machine are 8 slot dust covers, of which four are taken up with standard "D" connectors for the parallel printer port and two serial (RS-232C) ports, along with the monitor (video) socket. The 5-pin DIN socket for the keyboard is on the main body of the computer. Of particular interest to us was an additional set of connectors: one 3.5mm and two RCA, along with an edge-mounted knob looking suspiciously like a volume control. This was for the CMS Music Card (the original reason for the review machine)! But more on that anon. The view inside Removing the top of the computer was simple: just a couple of screws to undo and it lifts off. Inside, the case was a joy to behold, considering some of the messes we'vP. seen THIS IS THE STANDARD IPC AT machine which runs at 8 or 12MHz. All machines are available with 84 or 101 keyboards. 18 SILICON CHIP in the past. The case is heavily plated inside to prevent corrosion (some low cost computers are either bare or have a coating of spray paint - one scratch and corrosion sets in). The layout of components within the case reflected the same care and attention - wiring all neatly dressed and tied, all major components socketed for easy service (should it ever be required), and so on. Previously mentioned is the provision for extra drives: in fact, with the top off, you can see room for a total of three 5 ¼-inch and two 3 ½-inch devices - so there's plenty of room for more hard disc drives, tape streamers, etc. Without the CMS Music Card, there are still three full length slots and one half length slot available leaving plenty of room for system expansion. Performance Sorting out the level of performance of a computer almost requires the wisdom of Job. What we're trying to say is don't believe all the figures you might read especially without qualification! And with proprietary software often looking for specific performance to be able to operate properly, there aren't all that many things that can be changed away from the "standard" before the software won't work. Fortunately, there are a couple of "yardsticks" which have evolved to help compare computers. The first of these is the "Landmark" speed test: a set of instructions is run in the computer and the resulting speed is displayed in graph form on the monitor screen. It shows the speed relative to the original IBM AT specification. On "normal" speed, the IPC NEAT/40E had a Landmark of 10.0 - very respectable. On "turbo" speed (operating with zero wait states), this increased to a whopping 20.5 . The second yardstick is the Norton "SI" - or system information. As well as showing the configuration of the machine (processor, memory, etc), it shows the speed of operation. The Norton SI on the test machine was a very respectable 18. This compares well with the normal "AT" SI of around 12/13 (depending on the machine). What this all means is that the machine is fast - very fast. Many applications could be run even fpster with the addition of the optional 80287-10 maths co-processor. But for most users not involved in, say, large spreadsheet calculations, the additional expense of the 80287 (about $500 or so) is hard to justify. We mentioned compatibility: again, this is a thorny issue. Everyone claims compatibility after all, the machines are all IBM "clones" , aren't they? Things mightn't be all they seem! Years ago, Microsoft's "Flight Simulator" became the compatibility test. If it ran Flight Simulator, it was "compatible" . Then designers made sure that, if nothing else, their machines ran Flight Simulator. Some readers may remember the bad old days when one wandered around a PC show and all the PCs were running Flight Simulator. Ask them to run anything else and they could be in trouble. Nowadays, most reviewers run whatever software they ha ve available - including, hopefully, a couple which they know are " iffy" . We tried about thirty different software packages with no problems whatsoever: everything from some very advanced games right through the spectrum of business and professional programs. Despite not being a "386" machine, it made short work of the power desktop publishing packages such as Ventura 2.0 and Pagemaker 3.0. The IPC NEAT/40E handled everything we could give it - with ease and speed. On " turbo", it flew! Documentation & software Included with the computer are DOS 3.3 (not the latest version, but nevertheless recent - and the one most favoured by PC manufacturers), GW BASIC, full manuals for both, and an IPC proprietary "setup" disc, along with its manual. A nice touch included on the IPC machine was a little batch program which comes up when you first turn the machine on. It lists the configuration of the computer (ie, the options that were fitted), and details of the 30-day money back guarantee and the 12-month warranty. It then loaded an intriguing utility program called "Directree" . It's one we hadn't heard of before but according to CompuHelp Australia (who are also the Australian agents for the US program), it allows you to manage your computer system much more efficiently and easily than just using DOS. Apparently it's similar in many respects to "XTREE" but (again according to CompuHelp Australia) does much more, and at a lower cost. DirecTree is not normally included on the machines but is available as an option for around $80. It' s well worth the extra. Conclusion Compatibles are, to use a cliche, a dime a dozen. Normally, you get what you pay for - buy low, you get low. The IPC range tends to put the lie to that statement. Th e IPC NEAT/40E is very competitively priced: the machine as reviewed sells for just under $4500 - and that includes the monitor and keyboard, sales tax and an on-site 12-month warranty service agreement. Its performance is up there with the best of them and would suit the power user, particularly in small business. Now, where's the cheque book? For further information, contact CompuHelp Australia, 35-37 Higginbotham Road, Gladesville, NSW 2111. Phone (02) 809 6966. it Footnote : This started as a review of the Creative Music System card, which was fitted to the IPC AT/40E. However, the computer itself has taken far more space than originally intended, so the CMS card will have to wait for a later issue . PCBreeze II PCB reeze is a sophisticated tool for designing Printed Circuit Boards. It allows a board to be created, viewed and modified on an IBM compatible computer. PCBreeze has been designed with ease of use in mind. Most commands are at most two keystrokes away, with additional information asked for explicitly. A pop up men u sys tem is avai lable. The menus make PCBreeze easy to learn and use but does not hinder the experienced user. The system uses a 50 mil ( 1.27 mm) grid. This resolution is more than enough for most tasks. It has two layers for the artwork as well as text and component overlay. With board area sizes of up to 400 square inches there is plenty of room to work. There is a variety of common pad and line sizes to choose from. Also standard is a DIP and SIP command to put down these pad patterns. User defined pad patterns may be saved and used as libraries later. Incl uded in PCBreeze is an Autoro uter'. Thi s will lay down a track between two points marked out by the user or accept a netlist. Hardware Supported IBM PC/XT/AT/PS2 or compatible CGA, EGA, VGA and Hercules graphics HP-GL, DM-PL, Roland Plotter Output Postscript, Epson FX/LX/LQ Pri nters Microsoft Mouse $295 Kepic Pty Ltd 4 Steinbeck PIHce Spearwood 6163 Western Australia Ph: (09) 418 5512 Dealer Enquiries Welcome MAY 1989 19 Do you have a latent urge to produce exotic drum sounds; maybe to accompany the wild gyrations of frenzied dancers? Or maybe you want to investigate a range of percussive instruments? If so, the Syntom is for you. YNTOM - a synthesised tom-tom The Syntom is a very effective percussion instrument synthesiser which can be used by itself or as an add-on to an existing drum kit. It is triggered by rapping it anywhere on the case in which case it gives out a single percussive beat or note. The pitch and decay of the note is variable over a very wide range and the pitch can also be made to fall away as well. The Syntom can also be clamped to a drum kit, in which case it will When you rap the case of the Syntom or the drum kit, the vibrations are picked up by a crystal earpiece and fed to the signal processing circuit. 20 SILICON CHIP be triggered every time the drum is struck. The unit is housed in a black plastic box with four control knobs, for Pitch, Sweep, Decay and Volume. Powered from a single 9 volt battery, it can be used to drive a power amplifier directly or the signal can be fed to a mixer. Circuit description The best way to describe the circuit is to break it up into three sections: an envelope generator, a voltage controlled oscillator (VCO) and a voltage controlled amplifier (VCA). ICl, a 741 op amp, buffers the pulse signal generated by the crystal earpiece pickup and then charges a 2.2J.lF capacitor via diode Dl. So when you rap the case of the Syntom, the earpiece and ICl generate a fast rising pulse. The decay of this pulse voltage is controlled by the lMQ decay potentiometer, VR 1. The pulse voltage is then fed to IC2a which is connected as a voltage follower so that it too acts as a buffer. The output of IC2a feeds pin 5 of IC3 (the voltage controlled amplifier) and VRZ, the 47kn sweep potentiometer. The voltage controlled oscillator comprises IC2c and IC2d, together with transistor Ql and diode DZ. The control voltage for the VCO comes from IC2b which acts as a summing amplifier. It adds the control voltage frorn the pitch control VR3 and the sweep control VRZ. IC2c acts as an integrator while IC2d is a Schmitt trigger. They operate together as follows. The control voltage from the output of IC2b charges the .001!,lF capacitor so that pin 2 of IC2c rises and pin 1 falls. When the voltage at pin 1 falls below the threshold of Schmitt trigger IC2d, the output at pin 7 goes high and turns on Ql. Ql then discharges the .001!,lF capacitor so that the voltage at pin 2 falls . This causes the voltage at pin 1 to rise until the positive threshold of IC2d is exceeded. This causes the output at pin 7 to go low and turn off Ql. Thus the cy- ~t--;,.- ~-.- - - - - , "' "' I· + By LEO SIMPSON cle continues and the result is a sawtooth waveform at pin 2 of IC2c. Provided the pitch control VR3 is not at minimum setting, the VCO runs continuously and if the sweep control VR2 is at the minimum setting, the VCO frequency is constant. The VCO output is fed to pin 3 of IC3, the voltage controlled amplifier (VGA). This can be regarded as a normal op amp but with the added facility that a variable DC voltage fed to pin 5 will control the gain over a wide range. So let's just go through the sequence of operation. When the crystal earpiece picks up a sharp vibration it generates a pulse voltage which is amplified and buffered by ICl and fed to diode Dl to charge the 2.2µF capacitor. The decay of the voltage across the capacitor is controlled by the setting of the Decay control, VRl. Thus, ICl, Dl, VRl and IC2a produce the voltage "envelope" which controls the VGA, IC3. When its pin 5 receives a positive voltage, IC3 rapidly increases its gain and the signal from the VCO is fed through to the output at pin 6. As the envelope voltage at pin 5 falls, the amplitude of the output signal from pin 6 falls away in proportion. So the envelope generator and IC3 control the way in which the VCO signal builds up and then decays away. Remember also that the envelope signal is fed to the Sweep control VR3. This causes the VCO frequency to fall so that not only does the + I ,-. .., C, C, C, C, C, M M Fig.1: the circuit of the Syntom uses three op amp packages but the key component is the voltage controlled amplifier, IC3 . The voltage al its pin 5 controls the gain over a very wide range. MAY1989 21 Fig.2: here's how to assemble the PCB and install the wiring. Warning: don't install Qt for best fit. The PCB was originally designed for a transistor with a BCE pinout while the BC549 supplied has an EBC pinout. This means that you will have to rotate the transistor until the leads match up with the holes in the board. CAPACITORS D D Value IEC EIA 1 .001µF 1 .0047µF 1n 4n7 102K 472K RESISTORS D D D □ D □ □ D D □ D □ 1 1 1 5 8 1 5 1 1 1 1 2 1MO 330k0 220k0 100k0 47k0 22k0 10k0 8.2k0 4.7k0 1.8k0 4700 2200 brown black green gold orange orange yellow gold red red yellow gold brown black yellow gold yellow violet orange gold red red orange gold brown black orange gold grey red red gold yellow violet red gold brown grey red gold yellow violet brown gold red red brown gold OUTPUT -+ ~.._ VO ____ , 9V BATTERY loudness of the signal die away but so does the pitch. By suitably manipulating the Pitch, Sweep and Decay controls, you can produce almost any musical note, from a piano key to a bass drum. The signal from the Syntom is quite sufficient to drive a power amplifier or the line inputs of a mixer. Power is provided by a 9 volt battery which is "split" by two lOkO resistors and a 47µF bypass capacitor to give supply rails of ± 4.5 volts (nominal). The centre point of the DC supply becomes the output signal earth point. Note that ICl, IC2a, IC2b and IC2c are biased from the - 4.5V supply while IC2d and IC3 are biased from the midpoint (ie, OV or earth). Construction Now let's talk about building the unit. It is housed in a standard plastic case with a plastic lid. All of the circuitry is accommodated on a small printed circuit board which 22 SILICON CHIP measures 100 x 40mm. This board looks easy to put together but there is a preferred order of assembly which makes the job a lot easier. The first step is to carefully examine the board for any open circuit tracks or bridges between tracks. The board we assembled was a good quality type with rolled solder finish but a little careful inspection at this stage can prevent heartburn later on. Step 1: insert the PC pins. 14 pins are required and as they are a very tight fit in the holes you'll need a hammer (and preferably a vise) to belt them home. Step 2: insert the resistors. 27 are required and they are all 1/4watt 5% tolerance units. To make it easier, we have listed all the needed values next to the wiring diagram, together with their colour codes. The idea is to do all the resistors of one value first, starting from the top and working down. As you install all the resistors of each value, tick the square box. Be sure to install the resistors so that their colour codes all run in the same direction across the board or down the board. This way, it makes it much easier to check that you have the correct value installed. It looks better too. When all the resistors are installed, you should have one left over. This is a 47k0 unit which is later wired across the output socket. Step 3: install the two diodes and the four capacitors. If you look closely at the diodes, you'll see a black band at one end. Install the diodes so that the black band faces towards the side of the board with all the PC pins. Check the wiring diagram on this point. Two of the capacitors are pigtail electrolytics while the other two are metallised polyester (greencaps ). Make sure that you install the electros with correct polarity. The greencap values are listed with the wiring diagram, together with their alternative markings in the IEC code and the EIA code. Step 4: install the three integrated circuits and the BC549 transistor. Fitting the ICs is simple enough but Hundreds of other items not listed - Send 40c postage stamp for list ~□~□ ©D=[]&~iJ&[m 122 PITT ROAD, NTH CURL CURL MAIL ORDERS: BOX 156. DEE WHY. NSW 2099 TELEPHONE (02) 905 1848 SUPER SPECIAL ) FM STEREO KITS 1;~m i_ .- All three modules supplied are fully assembled and aligned. Circuit diagram supplied. 1! ONLY $22 g ' -~1\~ ~~ - -~ ~ I Osc coils . . . 7Sc Transistors C AD 16 1-162 . . $3 pair I I AD 149 . S2 ea ~ Chrome push-on knobs . . 10 for $1 Slider Pot knobs . . . .. 10 for $1 ~1------------------1 = ~ ¼Meg Switch.. j ~ 1/1 Meg Single. . $1.00 2 Meg Ganged Tapped log .. $1.50 S .50 SOk Dual Concentric . . .... $1.50 25k Dual Ganged Switch $1.50 ....... 1,5 Meg Single 1OOk Dual Concenl1ic . l/1Meg Ganged Log . 25k . ~o~ego~~~ea~o~~~~~ ~~: ::~: - ] ~ :.;::: 0 c: !_ .~w ..i::: ; .gi j I I ! POTS vi ... 25k TAP 32K . .. $ .50 . $1.50 $1 .50 51 00 Double ' Pole Switch S1.50 25k 4 Gang linear . . . S2.00 20k Linear Single . . . . . S .50 t Meg Log Switch $1. 00 1 Meg OtJal Ganged Log .. $1.00 1OOk SOO Mini . . $ .50 10kSubMini .. $ .50 50k Log Switch $1 .00 250k Linear , . S .50 1OOk Log . $ .50 SOk Log .. . .. S .50 SPECIAL t OOklogSwitch. . ' $1 o. ~ ~: :~:~~ ~ 5 S .50 S1.00 $1 .50 $1 .00 $1.00 vi' ~ I . $1.50 S .50 S .50 S .50 ~ 5, .i::.. ~ ~ ,,. METERS $3 .§ 5" $1.00 · · : : :~; 50 Ohm . . .. 0.25 Meg Dual Concentric . 25k Dual Ganged Switch . . . tOk Dual Ganged Switch ... 250k OtJal Ganged Switch . . 1 Meg ½ Meg Dual Concentric Tap40kDoul>lePoleSwitch 300 Ohm Linear . 1500 Log 0.25 Meg Linear or Log . . .. vu I S. $1 .50 . $ .50 ¼ Meg Dual Concentric Linear $1.50 DUAL ri ~ be drilled in the lid of the case for the potentiometers while the case itself needs holes for the power switch, 6.5mm jack socket, four PC mounts, two for the clamp assembly and one for the battery clamp. Use the self-adhesive label as a drilling template for the case lid. Don't fix it to the lid at this stage;· just line it up on the lid and use a spike to push through it and mark the four centre points for the holes. Don't drill the holes full size; use a smaller drill (say 1/4-inch) and then use a tapered reamer or round file to bring the hole to the correct diameter to just fit the potentiometer mounting bushes. The PC board itself can be used as a template for its four mounting holes and so can the clamp Antenna $1 extra ~ S? make sure they are oriented correctly. Don't fit the transistor simply by inserting it for "best fit ". You have to rotate the transistor so that the emitter, base and collector leads match up with the holes in the same way as shown on the wirmg diagram. This is necessary because the board was originally designed for a transistor with a BCE pinout while the BC549 has an EBC pinout. That's a trap for young players, so watch it. Step 5: carefully inspect your work and compare the completed board against the wiring diagram. Step 6: drill the box . This should be done with care because it affects the overall appearance of the finished product. Four holes need to p&p .2.00 ;1-4-55 _k_H_ z -lF_c_o_ils- fo_ r_v-alv_ e_rad-io-s-. - - -.- .-. -..- .- . -$1~ . [ All the wiring inside the Syntom should be run using ribbon cable to make a neat job. Note that one of the pots has a switch on the rear which is not used. The crystal earpiece is glued in position using contact adhesive. '! ~ Dynamic microphone Desk type S4 Pfl S1 1-----1 ~ TEISCO Ceramic Microphone ~ 1 ~ 1 - -= = = : : :_:-_ _ P_P..-----''-s_2_PP_s_1_---l f 5 mixed rotary switches 12 mixed switches v• ~ $2.50 $4.50 '=~ ~ ~ Touch micro swi tches Microswitches 5A 250V ~ ~ 4 for $1 sac .. 1· Mixed resistors; handy Mixed capacitors: handy types types ~ 100 for $2 100 for $2 ;;;· ~ 1 - - - ~ - - - - + - - - _ ; __ _;__---l~ TV stick rectifiers Transistor earpiece. 0 c $1 each 4 for $1 plug & lead en U'.) 11---------'----------I! Slfder Pots . 250k dual 250k single 50k single 1Ok single 2 5k dual 1 k dual ½ Meg dual VALVES 6V6 8KB 6B06 6B05 EF86 S10 $10 S10 S7 S7 single 50c; dual $1 1 Meg dual 2 Meg dual 2 Meg single $7 S7 S6 S6 S7 S7 5AS4 EF86 68MB 6BL8 6U7 6805 6KB 6U7 6K7 6A7 $7 $10 $7 $7 $10 6V.t SS 12AX7 i? I [1-----------------l! : TUNING J [ CAPACITOR u 2 gang covers all Aust AM bands 0 ~ ~ C ~ I g ~ ~ _ ,.., $4.75 ~~~~M~ 0 I :E ~ 1 - - - - - - - - - - - - - - - - - - 1 !2. ;;;· NEW PRICE ON GRAMO MOTOR & PICKUP [ PP S3.50 NSW. "ll .~ ~ ~ ~ ~ .,. i? lnterslate S4.40 ~ 1------------------1 { VALVE SOCKETS OCTAL: 7 PIN , 9 PIN . 4 FOR $1 s .§ Hundreds of other items not listed - Send 40c postage stamp for list PARTS LIST 1 plastic utility case, 158 x 95 x 52mm 1 front panel label 1 aluminium clamp assembly 1 PC board, 1 00 x 40mm 1 crystal earpiece 1 6.5mm mono jack socket 1 miniature SPST toggle switch 4 knobs to suit potentiometers 1 9V battery 1 battery snap connector 1 battery clamp (or secure battery with double-sided tape) 4 plastic PC mounts (or pillars, screws and nuts) 14 PC pins Semiconductors 1 741 opamp(IC1) 1 LM324 quad op amp (IC2) 1 CA3080 transconductance amplifier (IC3) 1 BC549 NPN transistor (01) 2 1 N914, 1 N4148 small signal diodes (D1 , D2) Capacitors 1 4 7 µF 1 6VW pigtail electrolytic 2.2µF 16VW pigtail electrolytic .004 7µF metallised polyester (greencap) .001 µF metallised polyester (greencap) The Syntom has four controls to give a wide variety of percussive effects. The on/off switch and output socket are mounted on a side panel. assembly. The power switch and the jack socket are installed on one side of the case, as shown in the wiring diagram. Step 7: install the PC board using plastic PC mounts or with pillars, screws and nuts. PC mounts do not mate well with the plastic box so we prefer the latter method as it is more secure. Step 9: fix the label to the lid of the case. Future kits may come with the lid already silk screened so this step may not be necessary. Step 10: cut the potentiometer shafts to about 12mm long and then install them on the lid. Install the 24 SILICON CHIP power switch and 6.5mm jack socket in the case. Step 11: glue the crystal earpiece to the inside bottom of the case using a contact adhesive. Don't use an epoxy for this job as it won't stick to the smooth plastic of the case. Step 12: install all the wiring from the PC board to the pots and other hardware. We used ribbon cable as it gives a neat job. The wiring diagram shows all the details. Step 13: connect the 9V battery to the circuit and check the voltages. With the negative prod of your multimeter on the midpoint (0V} of the supply (TPl}, check that + 4.5V Resistors (0.25W, 5%) 1 1 MO 5 1 OkQ 1 330kQ 1 8 .2kQ 1 220kQ 1 4. 7kQ 5 100kQ 1 1.8kQ 8 47kQ 1 4700 1 22kQ 2 2200 1 1 MO log potentiometer 3 50kQ linear potentiometers Miscellaneous 30cm ribbon cable, solder, contact adhesive, screws, nuts, washers . Note: a full kit for this project is available from Jaycar Electronics for $42.50 . is present at pin 7 of ICl, pin 4 of IC2 and pin 7 of IC3. Check that - 4.5V is present at pin 4 of ICl and pin 11 of IC2. Because of the bias currents drawn from the 0V rail, you may find that the + 4.5V rail is closer to + 5.2V while the - 4.5V rail is closer to - 4V. These readings will be dependent on the settings of the controls. Pin 4 of IC3 is supplied via a 1.8kQ resistor from the - 4.5V rail and is likely to be around - 2.3V with respect to TPl. Rotate the Pitch and Sweep controls fully anticlockwise which stops the VCO from operating. The outputs of ICl (pin 6} and IC2 (pins 1 and 14} should now all be low; ie, around - 4V. Pin 7 of IC2 should be high (ie, around + 4V} while pin 8 should be around - 2V. Pin 6 of IC3 should be at 0V. With the pitch control above its minimum anticlockwise setting, the VCO should be operating continuously. If you have a frequency meter or oscilloscope, you can check its range by measuring the output at pin 1 or pin 7. If you want to, you can also listen to the output by connecting the crystal earpiece to pin 7 (the junction of the two 47k0 resistors would be a convenient connection point). To do this you would have to disconnect one side of the crystal earpiece from the input at pin 2 of ICl. Once you have completed all those checks, your Syntom is ready for use. ~ WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. WOOD FOR CHIPS .. WOOD FOR CHIPS .. . WOOD FOR c MORE GOODIES FROM WOODIES NEW PORTASOL □ GAS Now at last we have liquefied petroleum spe'cifically designed for use with PORTASOL gas irons . Reduce the spluttering and flaring you get with normal butane. 150g $ 5.95 knife, blow torch and hot blow. The cap contains a flint lighter. The complete kit comes in a handy case (with stand for the iron) which just about fits in your pocket. See E.A. April 88 -·an extremely Porta-Sol Professional Is attractive approach ...• It's a gas $81.00. soldering iron ... it's a blow PORTASOL STANDARD - - - - - - - - - - ~ torch ... it's a hot knife ... it's a hot SOLDERING IRON blow. And it comes in a neat carry Geoff has sold hundreds of 'em kit complete with a bit wiper. No to servicemen and technicians. cords or batteries yet it gives the Complete and ready to use like equivalent of a 10 to 60W iron . the Professional but you only You can get up to 90 minutes get the iron and bit $39.95. average continuous use from a PORTASOL TIPS single fill . And you refill it in Expand the capability of your IO AlllJ seconds using a standard butane Portasol Iron with spare tips · 111 11111 .\CI gas refill. Tip temperatures as available for standard iron in high as 400°C can be set. The kit 1mm , 2.4mm . 3.2mm , 4.8mm includes one soldering tip, a hot and hot knife tip . Professional PORTASOL PROFESSIONAL SOLDERING KIT NEW NS1 6550AN UART with FIFO 1-------------------------1 Huge Purcha WIRE WRAP of Printer a TOOLS You have been asking for this device which is used in IBM-PS/ 2 type applications and now we have the dual in line version in stock. $ 35.60 XR-2240 CMOS Programmable Timer/Cou nter Missed out on the battery operated wire wrap guns we advertised last month ? Well we have the nex1 best thing for you with this useful hand wrap tool. HAND WRAP TOOL DELUXE• 30AWG $ 19.95 We goofed and now we have a mountain of parallel printer cables. This is your chance to take advantage of us. DB25 to Centronics. During May you can get TEN for only $ 99.50 New Low P on Kikasui Oscillosc pe This very popular timer has been hard to get lately but now we have them back in stock. 1-9 $ 3.45 1o up $ 3.1 O Tax Free COS-5020 $799 .00 COS-5041TM $1220.58 KYNARWIRE STRIPPER Genuine OK wire stripper suitable for 30 AWG wire. Adjustable strip length from 20 to 30mm. $ 28.50 Model ST100-30 $ 225.00 $ 327.45 $ 449.90 $ 341.70 A 32000 R'S KIT Just a few more of 32032 version. With a 32082 MMU plus 32201 Timing Control Unit, 32081 Floating Point Unit, 32202 Interrupt Control Unit and two "Tiny Development Systems" (TDS) PROMs. Massive pack of literature Definitely not for beginners $180. (P&P $6.00 local or $15.00 airmail - it's a big pack!) Go ar Meters Have you priced DMM's lately? These Goldstar meters are outstanding value for money . DM6135 Autoranging 10Aac/dc $88.80 DM6235 as above but with Memory function and Range Hol 9 .60 DM6335 as above but with Data Hold $118.80 TRI Tax Paid $932 .50 $1424.00 New Low Pr" on GW Functio Genera o s GFG-8015F GFG-2D GFG-8016S GFG-8019 tips come in same sizes plus hot blow and blow torch . Tips are nQ1 interchangeable between irons, so specify Standard or Professional when ordering. Tips are all $12.95 each. $ 259 .66 $ 377 .85 $ 519.10 $ 394.27 .___ _ _ _ _ _ _ _ _ _~ Cable o tunities 900mm 50 way ribbon cable terminated one end with 50 way IDC socket. Would cost$$$$ more separately, only$ 8.20 1 metre 50 way ribbon cable terminated one end with IDC female socket and one end with IDC male plug. Would cost $$$$ more separately, only $12.40 0 :0 r, :c ~ ~ 0 c:, .,., 0 :0 r, :c ~ ~ 0 c:, .,., 0 :0 r, :c ~ ~0 c:, .,., 0 :0 r, :c ~ ~ c:, .,., 0 a :0 r, :c ~ ~ a c:, .,., 0 :0 r, :c 'i, "' ~ 0 c:, .,., GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road, (Corner Beatrice St.) ING IN Nsw Lane Cove West, N.S.W. P.O. Box 671 , Lane Cove N .S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add S5.00 to cover postal charges . Next day delivery in Sydney add $5.00. METER One only METRIX 512 DMM. Was $190.00 reduced to clear $150.00 ~ c:, .,., 0 0 :0 r, :c PENROSE All prices.INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MAS TE RCA RD, VISA , CHEQUES OR CASH CHEERFULLY ACCEPTED ~ 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. a 15 DIGIT C 16 C 1/ ga /b 17 d1 DIGIT B e/_l· 2 IC1 74C926 f 3 DIGIT D d g4 BO DOCOAO 11 10 1 8 r· -- - - - - - - - - - - - - - - - - - - - - - - - - 7 I I I r ___ _j I I .,. L ___ __, I I I I I I I +5V I I I I I I I I I I .,. I L _____________________ _ __ _ _______ J 02 BC338 03 BC338 Fig.1: the leading zero blanking circuitry is all contained with the dotted line. It uses three low-cost TTL ICs: a 7410 triple 3-input NAND gate, a 7408 quad 2-input AND gate, and a 7402 quad 2-input NOR gate. Leading zero blanking for digital speedos This add-on circuit was devised for a 3-digit speedometer that uses a 74C926 4-digit counter IC. It improves the appearance of the readout by automatically blanking any zeros before the first significant digit of the display. The blanking circuit uses three low-cost TTL ICs and is shown in-. side the dotted line. Here's how it works: Digit B is blanked when B (pin 8) of IC1 is high and a zero appears at the segment driver outputs. The easiest way to detect a zero is to detect when segment 'd' is on and segment 'g' is off. If these are all true (ie, pin 8 of ICl high, 'd' high and 'g' low), pin 12 of IC2a goes low and pin 13 of IC4d goes high. This high sets RS flipflop IC4a & IC4b so that pin 1 (Qbar) goes low. Thus, pin 6 of IC3a also goes low Help! Save Us From Circuit Burnout! We know we're brilliant. You've said so yourselves. But we know that there are lots of ingenious circuits lanquishing out there in readers' brain cells. So bung 'em into us and we'll publish them in their full glory . You 'll not only make some money but you'll also save us from the dreadful " circuit burnout" syndrome which happens to anyone who has to generate too many circuit ideas in too short a time. We'll pay up to $50 for a really good circuit. So transfer your circuit to paper and send it SILICON CHIP, PO Box 139, Collaroy Beach , NSW 2097. 26 SILICON CHIP and turns off Ql to blank digit B. Similarly, digit C is blanked when C (pin 10) of ICl is high, segment 'd' is on and segment 'g' is off. Pin 4 of IC4b (the Q output of the RS flipflop) must also be high (ie, digit B must also be blanked) before digit C can be blanked. When all these conditions are true, pin 6 of IC2b goes low. This in turn drives pin 8 of IC3c low, thus turning off QZ and blanking digit C. Note that transistor Ql is held off by the RS flipflop which must therefore be reset after all outputs of the 74C926 have gone through one cycle. This is achieved by connecting A (pin 7) of IC1 to the reset input (pin 6) of IC4b. Construction is not critic,al. In the prototype, the additional parts were mounted on a small piece of matrix board and connected to the speedo PCB using ribbon cable. Tim Gregory, Alberton West, Vic. ($30) Thermostat for cooling fans This thermostat circuit is designed to switch on a cooling fan when ever the temperature of a heatsink exceeds a preset limit. It's suitable for use with amplifiers and power supplies. The circuit uses an LM334 temperature sensor (IC1), an LM324 op ·-amp (IC2) and a BD139 transistor (Ql) to switch a relay. The LM334 is attached directly to the heatsink and forms a voltage divider across the supply in conjunction with a 10k0 resistor. As the temperature increases, the voltage across the 10k0 resistor rises by 10mV/°C. This voltage is applied to the inverting input of op amp IC2 which functions as a comparator. VR1, in conjunction with ZDl, sets the reference voltage on IC2's noninverting input and thus sets the temperature at which the thermostat operates. A 1MO feedback resistor is included to give the comparator a hysteresis of approximately 0.12V or 12°C. Normally, when the temperature 1.5k r-----~------~------.---W,;,-----cl+35V-40V 5W 1.2k 32V RELAY SIEMENS 1M 1 C0726 240VAC ACTIVE +1omvI·c 10k' t......._. 1 LL + ACTIVE TO FAN 0.1 L---------4.,.___.__...____ ~~-----+---_._--oov .,. v-<at>v+ VIEWED FROM BELOW Fig.2: this electronic thermostat uses an LM334 temperature sensor (IC1) and an LM324 comparator (IC2). When the temperature rises above a preset limit, pin 1 of IC2 goes low and Q1 and the relay switch off. is below the trip point, IC2's output (pin 1) is high, Ql and the relay are on, and the fan is off. When the temperature rises above the preset level, pin 1 of IC2 switches low and Ql turns off. Thus the relay switches off and the fan (which is wired across the normally closed contacts) turns on. Power for the circuit can be derived from one of the amplifier supply rails (35-40V approx). A 1.5k0 5W resistor and 12V zener diode (ZD2) provide a regulated + 1 ZV supply for the op amp and temperature sensor. The relay should be a 32V type (eg, Siemens C0726). John Whittingham, The Gap, Qld. ($25) FIX-A-KIT Bit saver for soldering irons This simple circuit helps prevent pitting of the soldering iron bit by reducing the power when it is at rest. Basically, it is a simple halfwave rectifier with two neon indicator circuits added to indicate the operating mode. D1, D2 and D3 are all 1N4004 types while LPl and LP2 are 250V neon lamps with inbuilt series resistors. When S1 is in the upper position, D1 is in series with the mains active line. D1 functions as a half-wave rectifier and feeds positive half cycles only to the soldering iron, thus giving halfpower operation. At the same time, DZ conducts on positive half cycles and so LPl lights to indicate the half-power mode. When the full power mode is selected, D1 is bypassed and the active line is switched directly to the soldering iron. D3 now conducts on the negative half-cycles of the FROM AMPLIFIER Kit Repairs - $15 per hour. Normal Rate - $30 per hour. 02 1N4004 240V TD SOL OE RING IRON No charge for kits that can't be repaired. 3 month Warranty on repairs . Construction - fixed or hourly NI0------------0 co-----1•.,.-----oc Fig.3: half power operation is achieved by switching D1 in series with the active line. LP1 and LP2 indicate the operating mode (half orfull-power). mains waveform and so LPZ lights to indicate the full power mode. D1 and D2 are effectively back to back in the full power mode. This means that no current can flow to LPl and so this lamp is off. The circuit can be built into a metal case which should be securely earthed. Aaron Mihe, Sawtell, NSW. ($15) 1 2 Month Warranty on Manufactured Kits. Custom Designing, Manufacturing, Large or Small Quantitites. HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment. Unit 4, 62 Great Western Highway, Parramatta, NSW 2150. Trading hours: Barn to 3pm Monday to Friday. MAY 1989 27 ALARMING! . Latest statistics released by a large insurance company state that 98 out of 100 houses burgled DO NOT have a burglar alarm installed. We find this to be amazing. Are you one of the 2%, or in the 98% category? Jaycar has a large range of "Do It Yourself" burglar alarms. Installing it yourself can save you $500 or more. It's not really all that hard. CONTROL PANELS from $129 Full range of alarm gear available including - power supplies, cable, reed switches, keypad, sirens, piezos, stickers, outdoor sensors, car alarm kits and accessories. ogue for fu PASSIVE INFRA RED MOVEMENT DETECTORS from $69.95 /'------ - -= .-:' -' e alls or, call into one of our showrooms. - -- JAYCAR FOR QUALITY KITS KA-1109 KA-1115 KA-1116 KA-1117 KA-1119 KA-1220 KA-1230 KA-1390 KA-1392 KA-1428 KA-1430 KA-1452 KA-1505 KA-1506 KA-1508 KA-1522 KA-1535 KA-1550 KA-1556 ·KA-1574 KA-1582 KA-1595 KA-1598 KA-1610 KA-1630 KA-1635 KA:1636 KA-1650 KA-1652 KA- 1660 KA-1675 KA-1677 KA-1681 Electric Fence 300W amp module 300W power supply 300W speaker protector Transistor tester Signal tracer Zener diode tester Freq. counter 50MHz Prescaler 500MHz . Function generator Vocal canceller Subwoofer Amp TAl Hall effect Transistor asst ignition Touch light dimmer Guitar effects BBD Ignition killer Deluxe car alarm Ultra sonic move det 30V 1A power supply House alarm Digital capacitance meter 40W inverter 12/230V 300W inverter 12/230V 12V lamp flasher AM/FM stereo tuner AM/FM remote control Playmaster 60/60 Blueprint 60/60 Electric fence Screecher car alarm Audio oscillator(metered) 3 band short wave radio $23.50 $119.95 $105.00 $2350 $21.50 $27.95 $16.95 $169.50 $46.50 $129.50 $24.95 $134.50 $44.95 $42.50 $29.95 $115.00 $23.50 $89.50 $34.95 $89.50 $169.00 $85.00 $99.95 $269.00 $12.95 $599.00 $99.50 $329.00 $369.00 $59.50 $34.95 $165.00 $79.50 KA-1682 Dual track power supply KA-1683 Battery monitor KA-1690 DI box KA-1691 TV colour bar/pattern gen KA-1692 Voice operated relay KA-1693 Metronome KA-1694 Volt/continuity test KA-1695 AC/DC Mil Ii voltmeter KA-1696 Econ. Temp probe DMM KA-1697 Utility timer KA-1698 Tran, FET, Zener test KA-1699 Bench amp- signal trace KA-1700 Power transistor tester KA-1701 RF detector probe KA-1702 50MHz Dig Freq meter KA-1704 FM Receiver KA-1705 Stroboscopic Tuner KA-1706 Cheap capacitance meter KA-1707 Powermate 2 KA-1708 Supertimer KA-1709 PC-driven Function Gen KA-1710 Beepo Continuity Tester KA-1711 TTL-analog Video Convert KA- 1712 PCB Shorts Locator KA-1714 Beat Me Metronome KM-3015 Listening post KM-3030 Ultrafidelity preamp KM-3040 Dual speed modem KM-3042 Speech synthesiser KM-3044 6000 Mosfet Module KM-3046 Super Simple Modem KM-3050 Workhorse amp $129.95 $14.95 $39.95 $159.00 $24.95 $19.95 $29.95 $46.50 $19.95 $21.95 $55.00 $39.95 $22.95 $13.50 $79.00 $55.00 $47.50 $1695 $119.00 $59.00 $49.95 $19.95 $49.95 $22.95 $29.95 $39.95 $359 00 $169.00 $43.50 $119.00 $85.00 $35.00 KM-3056 KM-3061 KM-3063 KM-3064 KM-3065 KM-3068 KE-4014 KE-4023 KE-4029 KE-4033 KE-4050 KE-4052 KE-4048 KE-4200 KE-4666 KE-4690 KE-4698 KE-4711 KE-4722 KE-4724 KE-4725 KE-4729 KE-4730 KE-4731 KE-4733 KC-5010 KC-5012 KC-5013 KC-5015 KC-5016 KC-5017 Kc:5019 100W module less MFets Microphone preamp Uo satellite decoder Octave EQ mod AS true 232 interface FM minder bug Mixer preamp Signal Spkr protector NiCad battery charger Temperature probe ETl480 50Wamp module ETl480 100W amp mod ETl480 power supply 5000 power amp RS232 Centronics inter/I ETl342 COi 4 sector house alarm Mini FM transmitter RS232 Commodore Parametric equaliser Solder iron temp control Guitar preamp Solar gen p/supply Telephone Intercom Active Crossover Capacitance meter Car radio power supply 1GHz Digi Freq meter Telephone ringer Speed control/dimmer 24 to 12V converter 100W amp module $79.50 $36.95 $55.00 $59.95 $27.95 $11.95 $39.50 $22.50 $14.95 $32.95 $27.50 $34.50 $29.50 $499.00 $32.50 $79.50 $29.95 $9.95 $16.95 $23.50 $39.50 $45.00 $12.95 $49.95 $39.95 $27.95 $28.95 $299.00 $19.95 $18.95 $59.00 $38.95 KC-5021 KC-5023 KC-5027 KC-5028 KC-5029 KC-5030 KC-5031 KC-5032 KC-5033 KC-5034 KC-5036 KC-5037 KC-5038 KC-5039 KC-5040 KC-5041 KC-5042 KC-5043 KC-5044 KC-5045 KC-5046 KC-5047 KC-5050 KJ-6502 KJ-6504 KJ-6505 KJ-6535 KJ-7000 Protector car alarm $79.50 Low ohms adapt □ MM $29.95 Ph meter $49.95 Train controller $89.00 CD H/phone amp $24.95 High Energy Ignition $4995 Optical tacho $49.95 Disco Light $159.50 Studio 200 Preamp $229.00 Remote •for Car Alarm $79.50 Wireless doorbell TX $16 95 Wireless doorbell RX $42.50 Universal power supply $12.95 Vader Voice $19.95 Speaker phone $89.00 Mini Mitter $34.95 Knightrider LEDs $17.95 120W PA/Guitar amp $7250 Car Safety Lights $29.95 Poor Mans Plasma $49.50 Mains Muzzler $55 00 Beta Tester $18.95 1/3 Graphic Equaliser $239 00 Syntom drum synth $42.50 8 channel mixer $595.00 Console Psupply above $119.00 2010 10 band stereo Eq. $169.00 Red light flasher $19.95 /fft.et"e- /et<-/tlr-ft(al(C,e, i.r 1tre-a.ft<l"u(ilf r-uaft.r SCOOP PURCHASE COMPONENTS SALE! Yet another great factory surplus buy. They lose you SAVE SAVE 15% on Photo Etch Extras See our catalogue for full details Description Film Developer & Fixer PCB Etch Resistant Developer for Etch Resistant Copying Film 125x150x6 Copying Film 200x275x2 Printing Exposur.e Frame Cat. No NC-4264 NC-4266 NC-4267 NC-4270 NC-4272 NC-4280 NORMALLY $10.95 $1 8.95 $11.95 $17.95 $17 .95 $34.95 15% OFF $9.31 $16.10 $10.16 $15.25 $15.25 $29.70 Bargain 1 12 volt lluminated pushbutton switch. Green bezel. as used in expensive car alarms. (Momentary on/ off). 12V lamp supplied. Rectangular N.0./N.C. rnntort., Normally $15.95 ONLY $7.50 10+ $6.50 ea BELOW 1/2 PRICE Cat. SP-0750 Bargain 2 Collet fixing instrument knob. Will accept 1/4' or 6mm pot shafts. 36mm diameter. 19mm height. Black polypropylene. Snap on cap cover with white marker supplied bu not pictured. Quality. $2 each 10+ $1.50 ea 5" Polypropylene Cone Midrange 8" Twincone 4 Ohm P.A. A quality midrange. Suitable for use with our Polycone woofers. Huge 10oz magnet. Black Polycone. 5" diameter. Power Handling 100W RMS system Resonant Freq. 570Hz Freq. Response 570-7kHz Sensitivity 96dB Size see 1989 catalogue Cat. CM-2085 Ideal for multispeaker sound reinforcement where 4 ohm speakers are required. Quality speaker made in New Zealand. Limited quantity. 10 watt power hand Ii ng Frequency range 60-15kHz Size: see 1989 catalogue. Cat. CE-2322 NORMALLY $24.95 SAVE $5 MAY ONLY NORMALLY $9.95 SAVE $2 ONLY 7. I Updated guitar speaker with extended frequency response. Especially suited for not only bass guitar but rythm and lead as well. Resonant Freq. 60Hz Impedance 8 ohms Freq. Response 60 - BkHz Power Handling 100 watts RMS Magnet Weight 40 oz Net Weight 3610 grams Sensitivity 102dB Cat. CG-2380 NORMALLY $89.50 SAVE $10 ONLY $79.50 $19.95 Cat. HK-7100 Bargain 3 Type 'J' thermocouple. Will measure from -200°C t +850°C! ! Supplied with 650mm varnish impregnated glass fibre sleeving. Supplied with full data. ·~"jf ~ N AMAZI NG $19.50 Cat. ZT-9400 Forget those old mercury thermometers. This new digital thermometer will read in both Cand F. Range 32-43°C and 89.6-109.4°F. Also includes buner alarm. We have seen these in other ads for as much as $29.95. Jaycars direct import cuts out the middleman and you save money. Cat. QM-5300 12V PCB SPOT Relay. 3A contacts. Quality 1·i:;, :!~;eJe brand. Size 20 x 113(6 H)mm. . .x __ Ca<. SH~ / DIGITAL THERMOMETER Bargain 4 10+ $1. 75 ea . Bargain 5 ONLY $14.95 ~- Piezo buzzer 3 - 20 volt. 24mm diameter. PCB mount. Pins 15mm apart. Height 17mm. Operating frequency 3800Hz. 85dB sound pressure. $4.95 10+ $4.50 ea Cat. AB-3458 JAYBRICK 50 WATT MOSFET AMPLIFIER "BRICK" BARGAIN The J-50 SOW RMS min into B ohms. with 25-0-25 2A transformer. 1 x 4700uF/50V filter cap each side and 3A bridge reel. Uni t measures 136 x 128 x 74(H)mm incl uding heatsink. Built and tested. See the 1989 catalogue for full deiails Cat. AA-03BO Bargain 6 Thermal cutout switches. As used in hatr dryers. etc. Very handy. Cat. ST-3800 77°C $2 Cat. ST-3810 128°C $2 NORMALLY $99 THIS MONTH $69 SAVE $30 ~ mpt· 'J' 12V l OSPST Relay . PCB mount, high quality. 10+ $3.50 •• Cal. SY-4048 Sale for storage, childproof lids - safe from kids, no mess. no fuss 12mm wide x 18 yards (approx. 16.2 metres) FERRIC CHLORIDE long. Ideal for RF screening, macro repair of PCB's. Flat heavy duty conductors or under 200g Cat. NC-4251 ~.,. floor speaker wiring. Will take 35 amps. Very $4.95 ~-.- ... 50% below cost. 400g Cat. NC-4562 --.. ~'----~ Barga in 8 A generous 3-metre long 1 5A 240V mains flex with moulded 1 0A 240V plug (All grey). NORMALLY $4-$5 VALUE THIS MONTH Cat. PS4105 3M Brand Pure Copper Foil • Adhesive Backed ETCHANT CHEMICALS IN JARS $7.95 400g Cat. NC-4254 $6.95 T ~· s$a a i:oirble 201 PORTASOL GAS After many requests. it's now available. Actual Portasol brand gas in a 150g can. Ideal for both Portasol gas soldering irons. Cat. NA-1020 ONLY $ 6 .50 ADCOLA SOLDERING STATION Station only 40W iron to suit BOW iron to suit $159.50 $49.95 $55.00 ADCOLA 240V IRONS edford Weather Proof Hi Fi Extension Speaker Sellout S30 12 watt $36.95 Cat. TS-1492 S50 16 watt $39.95 Cat. TS-1494 Purchase either of these irons and receive a FREE roll of solder - worth $6.95 Cat TS-1476 Cat. TS-1478 Cat. TS-1480 See our 1988 catalogue for full details. 10 WATT 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. Size: 275(H) x 187(W) x 135(D)mm Cat. AS-3040 PORTASOL GAS SOLDERING IRON • No cords. batteries or bottles • Heavy duty, tip temperature up to 400"C • Adjustable temperature - equivalent to 10-60 watts • Hard working, up to 60 minutes continuous use • Refills in seconds. uses standard Butane gas lighter fuel • No leakage current to sensitive circuits • Made in Ireland WELLER SOLDERIN STATION $149.50 $39.95 Cat. TS-1420 TIPS TO SUIT • 1mm tip_Cat. TS-1421 $15.95 NORMALLY $109 each ~~~= NOW ONLY $85 r-flxrHAlcrocKTiffic~focK-~ I 11 you're tired of looking at that mantle clock reading ten past one (and it's not). why not fix itl It will take about 10 minutes with one of our clock modules. We have four types. Just remove the old mechanism. Iyou throw it in the bin and replace it with an accurate quartz crystal movement! We even have ones that play Ithe old fashioned tune (Westminster Chime) and then chime the hour. Also ideal for making your own custom clock face. ISTANDARD MOV M NT · I• Very compact 56 x 56 x 15mm • Powered by 1-AA battery I• Su~;ilied with 3 different sets of hands NOW 20 WATT Uses 2 special dual doped cone driver for those wanting a bit more umph! • 8 ohms. Size: 455(H) x 167(W) x 135(D)mm Cat. AS-3042 NORMALLY $149 NOW ONLY $115 lcat. xc-0100 $12.95 14.95 IPENDULUM MOVEMENT/QUARTZ CLOCK IIdeal clock mechanism replacement for a small pendulum clock, or create your own pendulum. Yet another scoop purchase I• 3 sets of hands supplied A compact high quality tuner that operates 1• Uses 1-AA battery from 526-814MHz (corresponding to channels $l& • 28 thru 63). This tuner is designed for I Cat. XC-0103 95 Australian standard reception 1053 1973), and is offered at a very low price. IMELODY CLOCK MOVEMENT UHF TUNER Sanyo Model T1087RA (AS Knob not supplied. Cat. DM-lOOO I WAS $29.95 LAST CHANCE 1• DIGITAL STEREO HEADPHONES SAVE UP TO 39% SA 7 00 I• I Features Mylar drivers. sponge earpads. fitted with 3.5mm stereo plug. Cat. AA-2021 WAS $29.50 NOW $17.95 SAVE SASSO 39~ Mylar drivers. freq. response 20-20kHz. Quality muff pads. Cat. AA-2022 WAS $39.50 NOW $24.50 SAVE SASSS 38" Top of the range, excellent sound . Quality phones. Cat. AA-2023 WAS $59,50 NOW $39,SO AVE 34% Full details see our 1988 catalogue. ' Two d1trerem mouu,es are ava11ao1e. ~oth chime the hour after playing their tune. lxc-0106 plays Westminster chimes each hour then gongs the hour (i.e. 7pm • 7 gongs) XC-0107 plays a different melody each hour, then gongs the hour. / Both units are supplied with / Clock movement j/,,,> • Speaker and battery holder 13-AA batteries required) / / ~ 3 sets of hands • Cat. XC-0106 Westminster chimes Cat. XC-0107 12 melodies I ONLY $19.95 each I I KIT SEMICONDUCTOR SALE - BELOW COST JIWe have a few expensive specialised MASSIVE SCOOP PURCHASE. semiconductorsavailablefrompastkits.Thisis Convert the broken/unreliable or inaccurate mechanical clock th e ideal opportunity for experimenters to save 111 your car to space age precision Made 111 West heaps Please order from your local store or Germany by VDO. the module measures roughly mail order 45 x 38 x 40mm deep The compact size 1 LH0002 Current Ampl1f1ers from balanced virtually ensures that 1t will fit in any space I line driver kit d Cat EE-4714 Quantity strictly lim1te WAS $ _ NOW $ I I I I I . I\. ' I I I Cat. XC-0106 - - - - - - - Mid Size Spade Lugs - - After many requests we now have the 4.8mm spade lug, in between the standard size (6.3mm) used on cars. woofers etc .. and the baby one (2.5mm) used on~tweeters. Cat. PT-4522 Packet of 8 $1.50 SALVAGE SOME CASH Turn your surplus stock into cash. Jaycar will purchase your surplus stocks of components and equipment. CALL GARY JOHNSTON OR BRUCE ~ounEY (02) 747 2022 - - - - - 27 55 5 _, WAS Cat. EE-5900 $13.75 NOW $3 ON LY $9 ■ 95 I 2. PCD3360 Pring tone generator chip from ring ~ J tone customiser kit. ETI October 1986 - - - - CABINET HANDLE - If you are hving trouble lifting speaker cabinets, or PA bins. or any larger box. try these handles. They are easy to fit. Just drill holes and screw in. Cat. HS-8010 WAS $16.50 ea NOW ONLY $9.95 each 10+ $9.50 each 3. AMIS 3530 Modem IC Cat. EE-6075 WAS $43.50 NOW $10 4. SL490 Transmitter IC. As used in EA tuner and 8 channel remote control EA June 1987 Cat. EE-4691 WAS $21.95 NOW $4 5. SL486 Remote control preamp Cat. EE-4694 WAS $22.99 6. ML923 Receiver IC Cat. EE-4702 WAS $33.50 NOW $4 MASSIVE 225 WATT RHEOSTAT! 80% UNDER COST PRICE!! TELEPHONE INTERCOM 130mm diameter. 55 deep. This is one mea n wire wound poten tiometer! Supplied with 75mm diameter quali ty knob. Resistance 1 ohm. that's ri ght · 1 ohm. Thi s mother will pass CURRENT. Cost over $126 each to make several years ago. You may not have a use for one immediately, but it will come in ha ndy! Qua ntities limited I at. RP-4000 Ref: ETI Feb 1988 Cat. KE-473 1 $25 WAS $49.95 NOW $44.95 HOUSE ALARM DIGITAL MULTIMETER Ref: EA Ja n 1985 Cat. KA-1582 WAS $169 NOW $152.10 • FREQUENCY COUNTER • TEMPERATURE • CAPACITANCE • TRANSISTOR TESTER • DIODE CHECKER • 20 AMP • DATA HOLD CAR ALARM Ref: EA May 1984 Cat. KA-1550 WAS $89.50 NOW $80.55 SHORT WAVE RADIO Ref EA Jan 1987 WAS $79.50 NOW $71.55 pH METER Cat. OM- 1450 Ref: Sil icon Chip Apri l 1988 Cat. KC-5027 WAS $49.95 NOW $44.95 $169 PROBE & BUFFER SOLUTION Cat. OP-2230 Dear Customer, Sometimes the products we advertise are so popular they run out within a few days . At other times unforseen circumstances might hold up shipments so that advertised lines are not in the stores by the time the advert appears . And, ve,y occas ionally, an error may slip through our checks and appear in the advert. (We're human too). Please don't blame the store manager or staff, they cannot control a dock strike or a lost PCB artwork from a magazine to the PCB manufacturer for a new kit, or fix an error that's appeared in print. If you are about to drive across t own t o pick-up an advertised item, why not play safe and call the store first - j ust in case. Thanks - Jaycar and Staff WAS $79.95 NOW $71.95 AM/FM STEREO TUNER Ref: EA ApriI 1986 WAS $599 NOW $539.10 REMOTE CONTROL TO SUIT WAS $99.50 NOW $89.55 ULTRA FIDELITY HI FI PREAMP Ref: AEM Oct 1985 Cat. KM-3030 LED Bargains WAS $359 NOW $323.10 ,----- -- - -- - - - - -- - --~----,, I I BALANCED LINE DRIVER Ref: AEM 601 1 Cat. KM-3060 WAS $99.50 NOW $89.55 ~~~ Cat. KM-3063 HEAD OFFICE -~~~,· ~,~::f~~~~~~~~)a~ ~~~~i VISA Green 5mm x 5mm Cat. ZD-1762 40~ ea 10+ 35~ ea Style 2 Red 5mm with an extended centre Cat. ZD-1747 20~ ea 10+ 18~ ea I I WAS $55 NOW $49.50 •• I 40~ ea 10+ 35~ ea · --•II VoSAT SATELITE DECODER ""';.. ...... _ _ - Red 5mm x 5mm Cat. ZD-1761 4 15~ ea 10+ 12~ ea Stanley Brand Li mi ted quantities of both ~~ ' i POST & PACKING ~0~~~~¥:~~!~~~~~~r m l!fl! irn 10 1 ~FA_c_s_I_M_IL_E-'-(0_2~)_7_44_07_6_7_ _ _ _T_O_L_L_F_RE_E_(0_0_8)_0_22_ 8_8_8_ _0v_E_R$__0 _ _ _ s _0._oo_--, MAIL ORDER VIA YOUR "fi" ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.50 SYDNEY· CITY 117YorkSt (02)267 1614.- GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799 Mon-Fri 9 - 5.30 Sat 9 - 4pm PARRAMA TTA 355 Church St (Cnr. Victoria Rd)(02) 683 3377 BURANDA QLD 144 Logan Rd (07) 393 0777 Mon-fri 9 - 5. 30 Thurs 8.30- Sat 9 - 12 Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sal 9 - 12 - - .> . ' CONCORD rd. - _ i~~ ~ MAIL ORDERS 2137 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 4pm ~ § Green 5mm Cat. ZD-1748 HURSTVILLE 115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 - Sat 8.30 - 12 121 Forest Rd (02) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 12 MELBOURNE-CITY Shop 2. 45 A' Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Oandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2 Brand what? Never 'eard of it! Appliances which are not well known on the local market can pose problems for both the customer and the serviceman. For the customer they present the problem of finding someone to service them, while for any servicman who takes on the task there is the problem of spare parts supply and technical backup if needed. My main story this month involves such problems, along with the technical problem which started the whole sequence in the first place. In fact, the problem deserves a place in history in its own right. The offending device was a 50cm colour TV set made by Thomson. And if that brand doesn't ring a bell you're in good company. Thomson Grand Public (to give it its full name) is a French company and, by all accounts, one of the biggest electrical and engineering firms in Europe - some say second only to Philips in size. Be that as it may, they are certainly a very large organisation with interests extending far beyond mere TV sets. (What am I saying!) Anyway, the story started when a lady rang me and identified herself as a former customer; one I had not heard from for several years. Then she went on to explain that she had a Thomson TS5108 TV set which needed service and wanted to know if I could help. Fortunately, I have a nodding acquaintance with this set - and a manual for it - so I said, yes, I'd have a look at it. At this she heaved a sigh of relief and confessed that she had tried several other servicemen in the area and that none of them would even consider it. To be honest, I also had some reservations. The only reason I knew anything about the set was because a local dealer had sold a number of these about five years ago and I was then doing warranty service work for him. In fact, I performed a couple of minor service jobs on those sets at the time; enough to provide the nodding acquaintance, but nothing more. Spare parts Another possible reason why other servicemen may have shied clear of the set was concern about the availability of spare parts. Noone wants to spend several hours tracking down a difficult fault only to find that it involves a component for which no replacement is available. (That problem can be r ; / ; ' ' --r.c ·.ov,,r12,uv ,u1.,100,oj " IJ , N ~ ~~ j:~. I N 1 :.2 = .l -I 15n50V l - CF06 ~ 1'CF08 .,, I Df'04 J.. !'"""'' .____.__---.I a.-:,o c~ ~ - - -JFOl -- - - - - - i - - - - - - - ~ ,....- - :::F05 V2 • 2'tV _J HEATER 2 '·; ... J • :oov Fig.1: relevant portion of the Thomson TS5108 circuit. The vertical oscillator stage is on the left (TF03 & TF04), the output SCR to the right of centre (CC02), the horizontal output transformer below it, and the vertical scan coil (BF0l) to the left of this. 32 SILICON CHIP bad enough with well known brands). Fortunately I knew - or thought I knew - who handled spare parts for this set so I was not particularly worried. In the event I was wrong but only insofar as the particular firm was concerned. More about that later. In the meantime, back to the set. The lady turned up with it the next day and the first thing I did was try to ascertain the nature of the fault. The lady's description was that "most of the screen is blank". As it turned out, that was a very accurate description. But I needed to see it before I realised exactly what she meant, so I plugged the set in while she was there and fed it with an off-air test pattern. The result was like nothing I had ever seen before. All that appeared was the top quarter of the pattern but this was located at the bottom of the screen. Above it, the screen was black and, rather surprisingly, there was no evidence of the blanking period. The only other point that struck me was that what was visible of the pattern was perfect in all respects: colour, brightness and linearity in both axes. So I'd saddled myself with a set about which I knew virtually nothing and which was exhibiting a fault like nothing I had seen before. Why do I get myself into these situations? Down to business Anyway, down to business. After studying the circuit, particularly the section dealing with the vertical deflection, I realised that it contained a number of unusual features. In fact, some of these features were quite puzzling but more of that in a moment. The relevant portion of the circuit is reproduced here as Fig.1. I started with the vertical oscillator section consisting of transistors TF03 and TF04 at the extreme left of the diagram. Note that immediately above these transistors, the circuit shows the number "15" in a diamond. This is a waveform number and refers to one of the CRO patterns set out along one edge of the circuit. Unfortunately, these patterns are very small, measuring a mere 8mm wide by 6mm high, so it's hard to pick out the finer points of the trace. Nevertheless, it appeared that the oscillator waveform was as it was supposed to be, so I moved on to waveform 16, skipping transistors TF05, TF09 and TF06. Once again the waveform appeared to be OK, so I moved on to waveform 17, at the gate of the vertical output stage [SCR type CC02). The use of an SCR in this stage was just one of the circuit surprises as was the strange way in which the device is shown. But it was waveform 17 which really caught my attention, since it bore little resemblance to the published pattern, miniaturised though this was. This prompted a voltage check of the output stage and preceding driver stage, TF07. The latter seemed to be within tolerance but the anode of the SCR was well down. It's shown on the circuit as running at 24.4V but it only measured about half this figure. This not only threw suspicion on the SCR but also drew my attention to the quite strange circuitry around it. For a start, I was surprised at the low voltage indicated for the anode, considering the job it had to do. And, in fact, the waveform (21) at the anode is shown as having a peak-to-peak value of 190V. Even allowing for the inductive nature of the load, this seemed to be asking a bit much. Back tracking from the anode revealed that this supply line passes through a winding on the horizontal [yes, horizontal) output transformer [pins 3 and 6) and thence to a 21 V rail via the vertical MAY1989 33 SERVICEMAN'S LOG -CTD scan coils, BFOl. The 21 V rail (extreme right of the circuit, about half way up) is also derived from the horizontal output transformer. Anyway, back to the SCR. I suspected it was faulty and pulled it out for a test. Judging by the symbol used, I assumed that I should be able to measure continuity between cathode and anode, at least in one direction, of the internal diode. But no; there wasn't the slightest indication of this component. Then I measured between gate and cathode, expecting an open circuit indication. But again I was wrong; I found I was looking at around 400, measured at either polarity. All this suggested that the SCR was shot and that the obvious thing to do was to fit a new one. However, closer inspection revealed that the type number on the component was not the same as that on the circuit. The circuit shows CC02, whereas the component was marked ESM740. I didn't have either beast in stock, of course, so I had to contact the spare parts supplier for these sets. As I recalled, spare parts had been available, along with service, from Hills Industries so this was who I called. Unfortunately, this didn't help much because they didn't stock any spare parts for these sets. Service, yes; spare parts, no. For these I was referred to the importing agents for Thomson sets, Lemair Australia Pty Ltd. [Further details about these firms are given in the accompanying panel). And so to Lemair. Yes, they knew what I wanted, the type ESM7 40 was the current replacement, and they had ample stocks. The price of the part was around $10 and all I had to do was place an order. On an impulse I ordered two; a very wise decision, as it turned out. Fitting the SCR The two units came to hand in a couple of days and I promptly fitted one to the set. Alas for my expectations; the set behaved exactly as it had before. I hastily unhooked the SCR and measured it. It measured almost the same as the original, except that the resistance between gate and cathode was about 100 higher. My immediate reaction was to suspect that there was a fault in the set which had destroyed the original SCR and had now destroyed this one. It was a nasty thought considering what it would mean in terms of tracking the problem down. But this was where my impulse to buy two units paid off; I grabbed the second one and measured it. And it was exactly the same, except that the gate/cathode resistance was somewhat higher again, nudging 600. All of which meant, of course, that I'd been chasing a furphy; there was nothing wrong with the original SCR, only my interpretation of the symbol. [With hindsight I would have saved myself a few bad moments had I bothered to check the new SCR before I fitted it). Square one But while I heaved a sigh of relief over this little incident, I was less 34 SILICON CHIP happy about the overall picture. The simple fact was that I was back to square one. All I had learned was that it wasn't the SCR. And so I began a systematic check of voltages and waveforms from the SCR back towards the oscillator. I checked or replaced the components around TF07, TF06 and TF09, as well as the transistors themselves. In fact, I checked most of the components and all the voltages right back to the oscillator. This seemed to yield nothing worthwhile; all voltages were within a whisker of those marked on the circuit and as far as I could determine from the miniature waveforms, there was nothing suspicious here either. But there was one diversion. While I was doing this I suddenly became aware that the picture on the screen had changed. The top of the test pattern, previously about one quarter of the way up the screen, had moved to the middle of the screen, but only at the expense of linearity. Fortunately, the cause was soon tracked down. I checked the anode of the SCR and found zero volts. The reason for this was quickly traced to a 150 safety resistor [RL52, not shown here) in the 21 V supply line, which had gone open circuit. I assumed from this that, whatever the fault was, it was putting an additional load on the 21 V rail. A conventional 150 unit provided a temporary repair. But the main fault remained as elusive as ever. While pondering on the circuit I noticed a couple of preset controls: PFOl, a 2.2k0 pot in the base circuit of TF04, and PF04, also 2.2k0, in the base circuit of TF06. PFOl is a vertical frequency control while PF04 is the vertical centering control. So what would happen if I adjusted the latter? Suiting the action to the thought, I found that this would move the picture up the screen, with more of the pattern appearing at the bottom as this happened. In fact, shifting the control to its limit produced almost half the picture. Thus encouraged, I reset the pot to its original position and shorted out RF23, an 8200 resistor in series with it. L-E:N\A\R HAD AMPLe:. S,OCl(S 0~ -r-<PE:- G.SW\ 740.. • This also moved the picture up the screen, though not quite as far. But by adjusting PF04 again I was able to bring the picture right up the screen and display the whole test pattern. So to all intents and purposes, I had cured the fault. It would have been easy to leave it like that, give it back to the customer, grab the money and run. Fortunately, my conscience - and common sense - prevailed. But, interesting though this little exercise was, it didn't really tell me much. In fact, I was very little closer to solving the mystery than I had been when I started. I decided it was time to ask for help. I put in a call to the Hills Industries service department, where I eventually contacted the technician who normally handles these sets. I outlined the nature of the fault, described what I had tried so far, and raised the question as to how some of the less conventional parts of this section worked. I hoped that, with a few clues here, I might be able work something out. The technician was most attentive, asked whether I had tried this and that - which I had - and then confessed that, at that distance, there was little else that he could suggest. As for the strange circuit configuration, I gained the impression that he had puzzled over it just as I had. The upshot of the discussion was that there was only one component about which I could not be sure - a 180kn resistor (RF02) below TF05. One end of this resistor is connected to the 200V rail while the other end goes to the oscillator preset control, PFOl, via RF06 (15k0). I had probably tested it but couldn't be sure. And according to the Hills technician it sometimes goes high and "causes all sorts of problems". I thanked him for his time and went back to the bench. As soon as Thomson TV Receivers • Australian agents for TV receivers and spare parts: Lemair Australia Pty, Ltd, 23 Amax Avenue, Girraween, NSW 2145 . Their postal adress is PO Box 336, Wentworthville, 2145 . Telephone (02) 636 3033. • Service only: Hills Industries Ltd, 12 Wiggs Rd, Riverwood, NSW 2210 . Telephone (02) 533 4855. I fronted up to the set I was sure I had checked that resistor but I checked it again anyway. It was spot on value so that blew that theory. But now that my attention had been drawn to the 200V rail I realised that there was a resistor I hadn't checked: RF15, an 820k0 unit from the 200V rail to the base of TF09 and the collector of TF05. The voltage at this point is shown on the circuit as 22.8V and I had measured it at about 21 V, which seemed close enough after taking into account normal component tolerances. This is probably why I had neglected to check the resistor more thoroughly. It took virtually no time at all to lift one end of the resistor and check it with the meter. And that was it - RF15 was open circuit! I fitted a new resistor, removed the short across RF23, reset PF04 and switched on. The result was a perfect picture - a fair dinkum one this time. That was the end of the story as far as the job itself was concerned. I ran the set for a couple days, then gave it a routine touch up and passed it back to the customer. Post mortem But, of course, a post mortem was inevitable. Where had I gone wrong? Now that I knew what had happened, it was easier to analyse that part of the circuit. As shown in Fig.1, bias for the base of TF09 is derived from the 200V rail via a voltage divider consisting of RF15 (the 820k0 resistor which I replaced), RF14 (4.7k0) and RF28 (3 .3k0). The junction of the bottom two resistors in this divider chain is clamped to about 20.4V by diode DF02 which is in series with the 21 V rail. I'm not sure why this rather strange arrangement has been used but the end result is that the base of TF09 normally sits at about 22.8V (ie, about 2.4V above the voltage at the cathode of DF02). In fact, the nominal 21V rail was running a little high in this set, making the difference somewhat less. But that's not all. Further analysis revealed that the emitter of TF09 is also connected to the 21 V rail - one path being via resistors MAY1989 35 perhaps saves a set from being written off. They are a nice set, a good performer and easy to work on. And I understand they are still available on the Australian market. So if you strike one, don't write it off without a try. A novel intermittent I ... ,..._15u, NOW-n\A-r MY Aire:.NrlO~ HAD 'B(;.E..N PRAWN ,-o 11-\E: z.oov RA\ RF19 and RF20 (1.2kn and 1000) and another via RF21 and diode DF05. This means that, without the 820k0 resistor to the 200V rail, the base and emitter voltages of TF09 were virtually the same. Or, putting it another way, there was no forward bias on TF09's base. Yes, it was as simple as that; simple when you've found it, that is. So where had I gone wrong? Accepting the voltage on the base of TF09 as being close enough was a mistake. What I should have done, of course, was to measure the base-emitter voltage of this stage. Instead, I made the mistake of simply measur36 SILICON CHIP l--000 ing those voltages shown on the circuit and assuming that, if they seemed to be within tolerance, all was well. So there's a lesson to be learned there. And why didn't the fault show up in waveform 16? It probably did but too subtly to be appreciated by comparison with the miniature circuit reproduction. It was only at the next stage, waveform 17, that it became obvious. So, there it is; all (well, something) about the Thomson TS5108. Let's hope that it helps at both technical and backup level and And now, for a change of pace, here is an interesting story from a reader, A. M., of Turramurra, NSW. After some very nice remarks about these notes, and servicemen in general who conquer intermittents, he goes on to relate the story of a novel intermittent which he encountered and - eventually - cured. This is how he tells it. My interest in electronics is purely amateur but I have exprienced at least my share of intermittents over the years. When silicon power transistors first became available in the late 1960s, I was persuaded by an engineer friend to build an audio amplifier described in "Radiotronics" from May 1967 to February 1968. I can remember being very impressed by the clarity which this amplifier afforded over my old valve model. This was in the days before printed boards were readily available, so construction was on Veroboard with plug-in tags to hold components and provide connections. The cases were folded from sheet aluminium in much the same way as we had made chassis for valve equipment. The amplifier was eventually installed in a cabinet, with the preamp in a drawer. All went well for some years, apart from a few blown output and driver transistors. I eventually replaced the original transistors with 2N3055s and BD139/140s which proved to be much more reliable. Then one day I noticed tha t the left channel was down in volume but the next time I used the amplifier it was back to normal. It remained normal for some weeks and I was tempted to believe it had been imagination. But the fault now entered phase two; noise, very like that generated by a faulty coupling capacitor in a valve set, became evident before the left channel level dropped. It was obvious tha t I would have to do some servicing. Slammed drawers The first clue indicated that the fault was in the preamp, but after the volume control; slamming shut the drawer which held the preamp would stop the noise and restore the level. Unfortunately, I would not have won any Brownie points from a serviceman for my design. It required considerable effort to get at the circuit, first to extract the preamp from the cabinet and then to take it out of it's box. And, naturally, when I had it all set up to test, the fault had disappeared and nothing I could do would make it return. So I put it all back together again, once more cursing my poor design. There was no sign of the problem again for some months and I was beginning to believe that it might have gone away for good - while knowing that such things never happen in real life. Then, almost a year later, there was a drop in volume (still the left channel), a rustling noise and then, very gently at first, a motor-boat at about 2Hz. Although this increased in amplitude, it did not get out of hand or threaten to damage the speaker. Once again I found that slamming the drawer shut would cure the fault and that remained my treatment for about another year, as the problem still occurred only infrequently. But several times during that period I took the preamp out and tried to find the fault. Sometimes the whole unit would be sensitive to the slightest touch but, ultimately, my probing and tapping would cause the fault to vanish and that would be the end of that session. The only bright side was that I took advantage of these occasions to improve the accessibility, so that it was no longer such a chore to remove and replace the preamp. Eventually the motor-boating came on and did not respond to the drawer slamming treatment so, for the umpteenth time, out it came. And this time it remained on, so there was no excuse for not finding it. The supply line to the preamp was taken from the main supply rail via the usual resistor-capacitor TETIA TV TIP Philips KT2A-3 Symptom: Very dark picture . Voltages around picture tube base close to correct values. Voltage on pin 5 of colour difference modules (U178, 179 & 180) is +o. 7V instead of -0.2V. Cure: C430 (1 00µF 50V electro) open circuit. This capacitor is the main bypass on the negative rails and, in particular, on -20a which supplies the bias on the colour difference modules. When the bypass fails, the luminance path through the modules is cut off. TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015 . decoupling network. A meter across this line clearly showed the supply line gently oscillating about the 25V level. It was only varying by about 100mV, but there was no mistaking its reality. Extra bypassing of this line merely lowered the frequency and tapping, heating, or freezing the components made not a scrap of difference. This part of the preamp had an emitter follower from the volume control feeding an active tone control, using two transistors in common emitter mode. Varying the bass control had only the smallest effect on the oscillation. I had mounted the various controls on the front of the box and run short lengths of shielded wire from the Varoboard to them. I was about to give up when, for want of something better to do, I measured the resistance between the volume control and the input capacitor; ie, 10cm of inner conductor of the shielded wire. It was open circuit! After unsoldering the wire I removed the shielding and examined the inner wire. Copper went into each end of the PVC but a pull removed each piece, which was only about 1cm long inside the PVC. Carefully opening the PVC, all I found inside was a green deposit; the wire had simply corroded away. This explained the fading signal and the noise, but what about the motor-boating? Then the penny dropped. Bias for the emitter follower was provided by a divider of two 100k0 resistors from the 25V line to chassis, the base being fed from the junction. The signal was fed from a 20k0 pot through a lOµF capacitor which held the base "earthy" to AC. When this connection was broken, there was sufficient AC coupling from the final stage of the tone control, through the supply line, to the base to allow oscillation at a low frequency, these two points being in phase. But what caused the wire to corrode? I have not seen or heard of anything like this and assume that there must have been some corrosive agent in the PVC, although the outer shielding was unaffected. Perhaps I would have found the fault more quickly had I been able to use a CRO or signal tracer but I never thought of a low level signal wire disintegrating! ~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP, ETI and EA . 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices MAY 1989 37 BUILD A BIOFEEDBA MONITOR FOR YOUR PC By JIM BARBARELLO Feeling tense? Build this simple biofeedback monitor and let your computer calm you down. It can be used with any IBM PC-compatible computer. And if you don't need biofeedback, it is an interesting exercise in computer interfacing. Although most people think of the IBM PC primarily as a business computer that grinds away from 9 to 5 through spreadsheets, databases and documents, it can also be made to serve other, quite different roles. One such application is as a computer-assisted biofeedback monitor. Biofeedback is the process of monitoring a biological function that indicates your level of tenseness, and then feeding back that information to you in real time. By allowing you to see what happens when you try to relax, biofeedback lets you discover the techniques that work best for you. You can then practice those techniques to gain more control over daily tension and stress. One biological function that indicates tenseness is your galvanic skin response, usually called simply GSR, which in non-medical terms means the resistance of your skin. PROBE A 10k 3 PROBE B PLUG 1 11 IC1 7555 16 l 3V .!.. 20 As you become more tense, your rate of perpiration increases, thereby lowering the resistance of your skin. As you become less tense - as you "calm down" - the perspiration rate slows and your skin's resistance increases. A variation from your normal or average GSR is therefore an accurate biofeedback indicator of how tense or calm you are at a given instant in time. The easiest way to measure GSR would be with an analog resistancemeasuring device such as an ohmmeter (or your multimeter switched to an Ohms range). Unfortunately, analog measurements are not wellsuited to digital computers. There is, however, a surprisingly simple alternative. By using a circuit that generates a digital pulse with a duration proportional to a resistance, we can use a computer to measure the length of the pulse and then interpolate the pulselength into a resistance value. That approach forms the basis for this BIOFEEDBACK MONITOR Fig.1: the circuit uses a 7555 timer IC that's triggered by the INIT line (pin 16) of the computer's printer port. 38 SILICON CHIP Copyright 1988, Gernsback Publications. Reprinted with permission from October 1 988 " Computer Digest". ---20 0000 0000 I 1 S..!_r+t' 0 I 3V BATTERY Fig.2: the circuit can be quickly wired up on a small piece of Veroboard. The two probes are actually aluminium foil strips which are fixed to the lid of the case using double-sided tape. biofeedback monitor for IBM PCcompatible computers. The monitor's schematic is shown in Fig.1. IC1 is a CMOS 555 timer which is wired as a simple pulse generator. The width of its output pulse is the product of capacitance Cl, resistance R1, and the skin resistance present between probes A and B. Since Cl and R1 are constant, any change in the pulse width is the direct result of a change in the resistance between the probes. Now all we need to do is to trigger IC1 to force its output at pin 3 high and measure the periorl of time until the output on pin 3 goes low (ie, returns to ground). nector, the INIT line, connects to IC1 's trigger input, pin 2. Sending out a short INIT pulse from the computer triggers IC1 and causes IC1 's output, pin 3, to go high. Pin 3 goes low at the end of the pulse (ie, when Cl has charged to 2/3Vcc). Pin 11 of PL1 is the computer's BUSY line. If we have the computer check for a low on pin 11, it will know when IC1's pulse has ended. The common ground between the computer and the biofeedback monitor is through PL1 pin 20. Switch S1 applies power to the circuit from series-connected batteries B1 and B2. The batteries provide only 3 volts, so the output of IC1 will also be about 3 volts peak instead of the more usual 5 volts. Although 3 volts is much less than 5 volts, it is high enough to be sensed by the computer's printer port. The software The simplicity of the hardware is made possible by the fact that the software does most of the work in creating a screen display of your GSR. Let's look at some of the more important aspects of the program, called PCBIO (for PC Biofeerlback), as shown in Listing 1. Line 30 looks to see if a printer port is installed and determines its address. Line 50 uses that information to set the address for the trigger input (T) and output (G) to the circuit. Line 190 begins the process of initialisation. Since each person's GSR is different, the program takes five in- The printer port It may seem strange but the computer's LPT1 parallel printer port is the ideal way of interconnecting the biofeedback monitor to the computer. The PC's printer port has a number of input and output lines that are normally used to do things like initialise the printer and check for a busy status. In our circuit, a 25-pin (DB25 male) connector PL1 attaches to the PC's printer port. Pin 16 of the con- Fig.3: when you load the PCBIO program into your computer the opening screen shows a thermometer-type display that ranges from calm to tense. MAY1989 39 Fig.4: if you're tense, the indicator will move up the display and the tone from the speaker will increase in pitch. itial samples and averages them to determine a mid-range value [Y in line 220). Line 220 also calculates an increment value [INC) which is used to determine the range from full calm to full tense. Those range values are stored in array L in line 230. The actual monitoring process begins in line 250. A call to the subroutine at line 320 gets a sample from the hardware as a count stored in variable X. Lines 280 and 290 determine where the tenseness indicator should be and places it there. The monitoring session ends when either full calm is reached (L ) 22 in line 280) or when you press the ESC key during monitoring (C = 27 in line 260). The subroutine at line 320 interfaces with the hardware. Line 330 generates a short negative-going pulse to trigger IC1. Line 340 begins counting the time by incrementing variable X and checks to see if ICl 's output has returned to zero [INP(G) = 127). When it does, line 350 checks to see if another sample should be taken [Z ( XF). Variable XF is a scaling factor used to ensure that the count returned in variable X will always be above 100 [lower counts make the gauge displayed on the screen respond too quickly, and are distracting during the monitoring session). The commands LOCATE 1,60:PRINT X;: in line 350 display the actual count number just past the title -on the screen display. 40 SILICON CHIP Fig.5: the calmer you get, the lower the indicator's position and the lower the tone from the speaker. Construction The circuit can be assembled on a small piece of Vero board which is installed, along with a battery holder, in a small plastic utility case. Simply pass the component leads through the appropriate holes in the Veroboard [see Fig.2) and solder them to the copper strips. An oversize drill can be used to make the necessary cuts in the copper pattern. Glue the battery holder into the case as close as possible to one end. If you'd like to secure the circuit board, it too can be glued to the PARTS LIST 1 plastic utility box, 83 x 54 x 28mm 1 piece of Veroboard 1 SPOT miniature toggle switch 1 D825 male plug 1 double-AA battery holder 1 battery snap connector 2 AA-size 1 . 5V batteries 1 7555 or TLC55 CMOS timer IC (IC1) 1 1µ,F metallised polyester capacitor 1 10kQ 1/4 W resistor 2 solder lugs 2 3mm x 6mm-long screws plus nuts and washers 2 metres of 4-way telephone cable 1 small cable tie 2 pieces of cooking foil, 4.5 x 2cm case with a drop of silicon rubber adhesive or Blue-tak. The finger contacts are simply two aluminium foil strips fixed to the cover with double-sided tape. These are then connected to the circuit via machine screws which pass through the lid and the foil. Cut two strips of ordinary household aluminium foil to a size measuring 4.5 x 2cm. Apply doublesided tape to the dull side· of the foil strips then carefully affix them to the lid of the case. Now drill two 3mm-diameter holes in the locations shown in the photos. Place two 3mm x 6mmlong screws through the holes and secure each one using a solder lug, washer and nut. The probe leads from the PC board can then be soldered to the solder lugs. We used a length of 4-wire (2 pair) phone ea ble to connect the circuit to the DB25 male connector. A plastic cable tie was used to anchor the cable inside the case. Testing the circuit Before you hook the circuit to your computer, it is a good idea to test the circuit on the bench. The easiest way to do this is to connect a jumper wire between pins 2 and 6 and a lOOkQ resistor across the screw terminals for the finger contacts. This allows the circuit to operate as an oscillator instead of a pulse generator. If you have an oscilloscope you can then check that the circuit is oscillating. Connect the oscilloscope probe between pin 1 [OV) and pin 7 and you should see a sawtooth waveform. Alternatively, if you don't have access to an oscilloscope you can use your multimeter to check the circuit. Connect_ pins 2 and 6 as before but omit the lOOkO resistor. Then connect the multimeter, switched to a low DC voltage range, between the two finger contacts. With the circuit running, the meter should read half the supply voltage; ie, about 1.5V for a 3V supply. Having checked the circuit, remove the connection between pins 2 and 6 and then plug the DB25 connector into your computer's printer port. Using the monitor Connect PLl to your computer's parallel printer port, apply power to the biofeedback monitor by closing S1, then load BASIC and the PCBIO program into your computer. When you run the program, the computer will create the screen shown in Fig.3. In the centre is the tenseness gauge resembling a thermometer. The top of the gauge is maximum tenseness, the bottom of the gauge Fig.6: you will probably already have most of the parts for this project in your junkbox. Take care - it's easy to make a mistake with Veroboard. Fig. 7: the circuit is connected to the computer's parallel printer port via a DB25 male plug. Listing 1 1 REM** PC Biofeedback Monitor Program 2 REM** NAME: PCBIO 3 REM** c 1987, JJ Barbarello, Manalapan, NJ 07726 4 REM** V870911 10 CLEAR:DEFINT G,X:G=O:X=O:DEFSTR A,B:A=CHR$(232):B=SPACE$(2) 20 COLOR 0,6,6:CLS:KEY OFF:WIDTH 80:DIM L(22) 30 DEF SEG=64 :PA=PEEK(8)+256*(PEEK(9)) 40 IF PA=O THEN COLOR 7,0,0:CLS:GOTO 430 50 A=CHR$(232):B=SPACE$(2):G=PA+1 :L=13:T=PA+2:LOCATE 1,23,0 60 PRINT STRING$(5, 16);" P.C. BIOFEEDBACK MONITOR " ;STRING$(5, 17) 70 LOCATE 2,37:PRINT CHR$(201 );STRING$(5,205);CHR$(187) 80 FOR 1=3 TO 22:LOCATE I,37:PRINT CHR$(204);B;A;B;CHR$(185):NEXT 90 LOCATE 23,37:PRINT CHR$(200);STRING$(5,205);CHR$(188) 100 LOCATE 3,31 :PRINT "TENSE " ;CHR$(206) 110 LOCATE 13,29:PRINT "AVERAGE " ;CHR$(206) 120 LOCATE 22,32 :PRINT "CALM ";CHR$(206):PLAY "L64" 130 FOR 1=3 TO 22:LOCATE I,40:PRINT" " :P$="N"+STR$(60-I*2):PLAY P$:NEXT I 140 FOR 1=22 TO 13 STEP -1 :LOCATE I,40:PRINT A:P$="N"+STR$(60-I*2) 150 PLAY P$:LOCATE I,40:PRINT" ": NEXT l:LOCATE 13,40:PRINT A 160 LOCATE 24 ,22 ,1:PRINT "Press (ENTER) to begin, or (ESC) to end ... "; 170 AA=INPUT$(1):C=ASC(AA):IF C=27 THEN 400 ELSE IF C013 THEN 170 180 LOCATE 24,22,0:PRINT SPACE$(42); 190 LOCATE 24,34:PRINT "INITIALIZING ... "; :Y=0:PLAY"L64" :XF=1 200 GOSUB 320:IF X( 100 THEN XF=XF+ 1:PLAY "L64;N32":GOTO 200 210 FOR 1=1 TO 5:GOSUB 320:PLAY "L64 ;N34": Y=Y+X:NEXT I 220 Y=Y/5 :INC=Y/100:LOCATE 24 ,28:PRINT"Press (ESC) to End Trial."; 230 PLAY"L32" :LOW=Y-10*INC:FOR 1=3 TO 22:L(l)=LOW+(l-2)*INC:NEXT 240 REM** MONITORING 250 P$="N"+STR$(60-(L *2)):PLAY P$ :IF X=O THEN 360 260 AA=INKEY$:IF AA()<'" THEN C=ASC(AA):IF C=27 THEN 370 270 GOSUB 320 280 IF X)L(L) THEN LOCATE L,40:PRINT" " :L=L+1:IF L)22 THEN 370 ELSE LOCATE L,40:PRINT A 290 IF X(L(L) THEN L=L-1 :IF L(3 THEN L=3 ELSE LOCATE L+1,40:PRINT " ":LOCATE L,40:PRINT A 300 GOTO 250 310 REM** SAMPLING SUBROUTINE 320 X=O:Z=O 330 OUT T,O:OUT T,4 340 X=X+1:IF (INP(G) AND 128)=0 THEN 340 350 Z=Z+1 :IF Z(XF THEN 330 ELSE LOCATE 1,60:PRINT X;:RETURN 360 REM** TRIAL END 370 LOCATE 13,8,1 380 PRINT "TRIAL COMPLETED. Press (ENTER) to try again, or ( ESC) to end ... " ; 390 AA=INPUT$(1 ):C=ASC(AA):IF C=13 THEN CLS:GOTO 50 ELSE IF C027 THEN 390 400 COLOR 7,0,0 :CLS:LOCATE 10,28 ,1:PRINT"MONITORING SESSION OVER" 410 LOCATE 13,1:END 420 REM** CAN'T FIND STANDARD PRINTER PORT 430 LOCATE 10,27,1:PRINT''PRINTER PORT 1 NOT AVAILABLE" :PRINT:PRINT:END MAY 1989 41 sure that the unit is working properly, you can begin actual monitoring. You should try to concentrate on different images or thoughts and note the results on the gauge. At first it may seem that trying to calm down actually increases tension. That is normal because the untrained mind tends to race through many different thoughts. Through practice you will learn how to focus on the images and thoughts that actually decrease tension, disregarding everything else, and use them to assist you in the calming process. Tweaking Fig.8: the completed prototype. Notice how the leads to the foil strips connect to the screws that pass through the lid of the case. is maximum calm, and the centre of the gauge is average. The message on the bottom of the screen asks you to press ENTER to begin monitoring, or ESC to end the session. The room you're in should be comfortable (about 20°C). Sit in a chair that provides good support and place the biofeedback monitor next to you on a table or stand that can support your forearm. Make sure your fingers are free of oil or excess perspiration. Rest your forearm on the stand in front of the unit, place your first (index) finger on one probe and your second finger on the other probe. It is very important that you do not move your fingers or change the pressure on the probes during the monitoring session, as that will change the resistance between the probes and give a false reading. Press the Enter key with your free hand. The message on the bottom of the screen will change to "INITIALISING" and you will hear a series of beeps as the system measures your initial level of tenseness. After a short time, the message on the bottom of the screen 42 SILICON CHIP will change to ''Press C to End Trial"; you are now monitoring your changing level of tenseness. That's indicated by the moving cursor in the middle of the gauge and a beep with a changing tone. As you become more tense, the beep frequency will increase and the indicator will ascend, as shown in Fig.4. When you calm down, the beep frequency decreases and the indicator descends as shown in Fig.5. The session ends when you either press the ESC key or reach maximum calm (nirvana?). The mes~age "TRIAL COMPLETED. Press Enter to try again, or Escape to end" will appear in the middle of the screen. When you end the session, the screen will clear except for the message "MONITORING SESSION OVER". To test the unit, begin monitoring. Press down hard with your two fingers to simulate increased perspiration (tenseness). The indicator should begin to rise. Release the pressure and note that the indicator begins to fall. Press ESC to end the trial. When you are The software monitoring subroutine is sensitive to the speed of your computer. The program listing contains the fact "IF X( 100" in line 200 to adjust it for use on a standard 4.77MHz computer. Computers operating at 8MHz or AT systems will respond more quickly and produce a higher count for the same amount of time and thus seem to be racing along. To compensate for racing, simply change the "100" in line 200 to a higher number (try 300 as a starting value and adjust it until you are comfortable with the speed). Closing thoughts The biofeedback monitor is basically just a self-learning type of device that also happens to be a lot of fun. It is not meant to take the place of any necessary medical treatment or equipment. However, with practice, the device can help you learn how to reduce everyday stress and tension. Sooner or later you'll find that you do have the ability to mentally calm and relax yourself. Another interesting point is that GSR is one measure that is used by polygraphs (lie-detectors) to determine whether or not someone is telling the truth. For that reason, the device can also be used as a rudimentary "lie detector" for entertainment at parties and gatherings. And even if you don't put much store in this device as a biofeedback monitor, we are sure that it will be the basis for many interesting computer applications. ~ ELECTRON I ARLEC DIGI-SCALE '' A must for all who value 1 YEAR GUARANTEE When your phone is in use a green light will glow showing you that the system is operative. However, if the red light flashes, BEWARE a third party is probably listening to your conversation. * Easy plug-in installation. 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(02) 267 1385 Fax: (02) 261 8905 ONLY $19.95 MAIL ORDERS WE LCOME P+P RATES PO Box 010 3 Sydney 2000 $5·$25 s2s-s50 $51 over s4 s1 $9 --- , , ,. I,, . ,~I'~ -I EO!REss -- <_ _ VISA THE WAY I SEE IT By NEVILLE WILLIAMS Are surges & spikes on the mains a hazard to personal computers? Don't be surprised if the following article raises more questions than it answers. Unfortunately, that seems to be the way it is when one tries to quantify the problem of surges and spikes which occur on the supply mains and the hazards they present to personal computers. First let me emphasise that I boast no special expertise in the subject. I am aware, though, of certain commonsense precautions that can help safeguard personal computers in a home or office situation. They are set out in a separate panel for your consideration and I suggest that you read through them at this point. My day-to-day involvement with personal computers has mainly to do with word processing and allied tasks, where such precautions can be observed without undue hassle. They may be less practical in offices, in educational situations or in other computing applications. I set up my first word processor about five years ago and considering the modest cost, it worked very well. I subsequently replaced it with a more ambitious system using an Apple IIc. I'm still using that system, along with its normal monochrome monitor, Appleworks and other software, external disc drive, printer, modem, mouse and a conventional RF line filter. When first installed, a small serial/parallel converter was also included, allowing the Apple to drive the same BMC BX-80 printer that had formed part of the earlier system. 44 SILICON CHIP In the new situation, the BMC printer failed on three separate occasions, with no obvious explanation but always with the same symptoms: when self-tested, it would print out its full character set in the normal way but would not accept drive from the computer. When it failed a fourth time, so did my patience and I replaced both it and the associated converter with a new Epson LX-800 printer, retrofitted to be Apple-compatible. Since then, as per the old saying, it's been "working like a bought one" on both text and graphics! There's a point to this tale: I never did find out the real reason for the repeated breakdown of the original BMC printer. Predictably, the suppliers of the printer and the serial/parallel converter maintained that such failures were uncharacteristic of their respective products. But they did seem to agree on a couple of points: • Such things do happen on occasions (what a brilliantly perceptive remark)! • Surges and spikes on the power mains could well have had something to do with the problem. (Logical explanation or a cop-out? Take your pick!) That's about as far as their in- terest seemed to extend. I gained the distinct impression that when something faiied (in this case a printer), somebody, somewhere replaced suspect ICs or suspect boards until the fault disappeared. If it failed several times, you fixed it several times. The how, when, where or why of the breakdowns received scant consideration. A major failure I would probably have written the whole thing off as "one of those things" had it not been for a subsequent system failure of a quite different kind. During that (for some) delightfully relaxed period after the Christmas festivities, I fired up the Apple II with the intention of transcribing my hand-written notes about Peter Wright's "Spycatcher" (for the March issue). Everything was behaving normally when, pausing to rethink a particular observation in my notes, I heard an uncharacteristic "grunt" from the printer, much as happens when it is first switched on. But it was already on and the system was just sitting there waiting for me to make up my mind. When I did try to use the keyboard, I realised that the computer had locked up. Unfortunately, switching off and re-booting did not fix the problem. A couple of foreign semi-colons on what should have been blank areas of the screen indicated that something was amiss and while the word processor still worked in a fashion, any attempt to feed the text to either disc or Surges On the Phone Lines Reference: "Characteristics and Rate of Occurrence of Lightning-Caused Induced Voltage Surges in a Telephone Line" by D. Mackerras. Journal of Electrical and Electronics Engineering, Australia, Volume 5, No.3, September 1985. The line which provided the basis for Mackerras' observations over a period of about four years comprised about 3km of overhead cable and 20km of underground cable, including an exchange. A sketch map accompanying the article shows the position of nearby 50Hz high voltage power mains. It is not possible to adequately summarise the contents but the paper indicates that the pulse energy can be attributed mainly to the induced effect of ground printer simply triggered another lock-up. At that point it dawned on me that the computer could hardly have picked a worse time to break down. That became all the more evident when I discovered that just about every Apple PC repairman that I could think of was on holidays until after the new year break! Fortunately, I was able to borrow another Apple lie from a relative for a few days and that allowed me to carry on. But it also gave me time to reflect on what had happened. While I had to concede that the failure might have been purely spontaneous ["one of those things") the circumstances did seem to suggest a high voltage transient on the supply line. This was subsequently supported by the observations of an Apple dealer service manager who, after an initial examination, said that the computer appeared to have suffered more than a simple failure. With a bit of luck, they might be · able to repair it by replacing ICs, in which case I could expect a bill for around $100. Failing that, it could be a case for board replacement which would run to more like $250. Asked whether he'd seen similar (not cloud) lightning flashes and to superimposed 50Hz energy caused apparently by fault current or unbalanced voltage initiated by the same lightning occurrence. A typical recording, relative to a flash within about 1 km of the aerial section of the phone line and close to the 11 0kV cable, shows a prominent 9 cycles of mains frequency at about 200V peak-to-peak present on the phone line . Other such events involved from 4 to 48 cycles at amplitudes ranging from 1 5V to 320V. More than half of all observed lightning events involved multiple surges, the mean average number being 2. 8 with a mean average separation of 1 38 microseconds. damage before, the service manager said it was uncommon but certainly not unique. He still had a couple of other boards on the shelf from computers which appeared to have suffered a similar trauma. His intention was to work through them in detail "one of these days" and bring them back into service. In fact, he managed to salvage my original board and when I got the computer back, it seemed to be working perfectly. That is, until I attempted to feed the text down the line to one of the SILICON CHIP computers. Then, what appeared to leave my screen as perfect ASCII copy showed up on theirs as badly corrupted. So my computer had to go back for further attention, with a suggestion that there was still a fault in the modem output port that had been overlooked. Apparently, that proved to be the case, leaving me with an all-up repair bill of about $170. It seemed likely that the modem port had been damaged at the same time as the remainder of the system but there was another possibility. Thinking back, I realised that while I had been dutifully unplugging the system from the mains, I had As measured in the Queensland University Laboratory, at the end of the underground section of the cable , a maximum voltage exceeding 320V occurred at a rate of 10 events per year. Events exceeding 650V occurred once per year, with the possibility (extrapolated) of 1 400V once per 1 0 years. In · the . Brisbane area, about 84% of all lightning events can be expected in the December/ January period, with 79% of those concentrated in the late afternoon. from 2pm to 6pm . The author lists 9 other references on the same general subject but warns that allowance has to be made for measurement criteria, line configuration and the country or area in which the tests are conducted . been less diligent in disconnecting it from the phone line. So during some of the violent thunderstorms that marked December on the east coast, the system may well have been exposed to lightning induced pulses on the phone line. I might not have been aware of such damage until I actually tried to use the modem. Either that, or a voltage transient may have affected the computer in a more subtle way, rendering it liable to spontaneous failure or vulnerable to, say, a surge or spike on the power mains. Alarming picture If you have a mind to do so, it isn't difficult to put together a deeply disturbing picture of what can happen to your PC from such eventualities. Lightning was discussed in relation to NASA activities on page 30 of the November 1988 issue and again, in more detail, in the February 1989 issue [see also the accompanying panel). But what about spurious pulses on the mains attributable to other causes? With this in mind, I phoned an acquaintance who is usually a mine of information on such matters. He MAY1989 45 Surges On the Power Mains In a 1 984 brochure covering their TRANSIL transient voltage suppressors, Thomson-CSF summarise the problem as follows, presumably based on observations in France. No reference is made to reticulation mishaps. "Externally caused voltage surges are of industrial or atmospheric origin and are transmitted through the supply cables by inductive or capacitive coupling. "On 220V mains, industrially caused voltage surges can have an amplitude of 5 to 1 0kV, with durations of between 0. 1 and recalled that a university student, gaining work experience in the Philips laboratory in Artarmon (NSW), had once built up a device to record the occurrence of spikes on the 240V m::iins. Using mechanical counters (it was back in the 1960s) the circuit was set up to sense the amplitude of peaks in roughly 100V steps above the normal peak of 350 volts to 1000 volts. Apparently, the device worked well but it was amazing to see how many times the 1000 volt counter registered. Next on my list was a schoolteacher friend who has his own Apple Ilc and is involved with several more of them at the school. No, he had never experienced any similar breakdown problems but said I:ie, "I must tell you what happened the other day around this neck of the woods" - out Parramatta way. It seems that a couple of bright lads, poking around a nearby building site, had come upon some loosely rolled bare galvanised fencing wire. Sensing the opportunity for a bit of "fun", they had carriPd it upstairs in a block of units and had landed it neatly, quoit-like, across a nearby llkV power line. What followed was an almighty series of flashes and explosions, which somehow defied the protective cutouts that were supposed to operate in such an emergency. When my ever-inquisitive friend ar46 SILICON CHIP 1 00 microseconds . Their occurrence is variable. Statistics show that, in an area where there is a lot of noise on the mains, 1 kV surges occur between 1 00 and 1 000 times a year and 5kV voltage surges occur on an average of once a year. "In the case of voltage surges of atmospheric origin, lightning can produce amplitudes of 30kV for an average duration of 70 microseconds. In the case of EMP (electromagnetic pulse) voltage surges, the electrical field can reach 1 00kV/m for durations of 1 0 to 50 nanoseconds". rived on the scene a few minutes later, the charred llkV cable ends were draped across the 415/240V consumer wiring beneath. Said he: "I wouldn't like my computer to have copped that lot!" He would have relished, even less, the lot of residents out Manly way, where a truck crashed into a power pole and dropped a 33kV feeder across the 415/240V mains. I understand that the accident took out quite a few microwave ovens and TV sets in the area but it would also have been a poor lookout for any computers that happened to be powered up at the time. Distribution problems When I raised the general subject with a technical officer attached to a major electricity distribution centre, incidents like those above held no surprise for him. They were par for the course. As he said, "Our circuit breakers are normally very fast and very effective, able to isolate a high voltage line within a couple of cycles. Having isolated a line", he added, "they can test the circuit again after about 60 seconds, to see whether the problem had disappeared - as it might well have done if a momentary short has been caused by, say, a falling branch". There had been a much larger headache, he said, when they'd lost a major underground cable during the Christmas break. It failed suddenly, without warning, possibly due to unreported damage and subsequent moisture penetration. It really upset things. "Are incidents in the high voltage network reflected in the 240V mains?'' "Most definitely", he said. "Variations, surges and spikes are simply stepped down by the pole transformers''. He went on to say that a blackout involving a major shopping centre posed a particular problem, with thousands of independent fluorescent lights and other appliances sitting across the mains. No-one ever bothers to turn them off when the supply fails. An enormous peak current flows at the instant supply is restored, followed by complex current and voltage variations until everything settles down. In many cases, consumers in areas surrounding large shopping and industrial complexes share the same high-voltage feeders - as a practical and economic necessity. What happens in the shopping or industrial complex is reflected in nearby consumer mains. By the very nature of things, he said, some consumers face greater risks than others of mains supply interruptions and traumas. Too many loose ends As I said, it isn't hard to assemble a disturbing picture by lumping together lightning strikes, reticula-. tion accidents, load problems and switching transients but in the process, I became aware of certain "loose ends". Or if you prefer: questions lacking ready answers. For example, in what way are computers supposed to be especially vulnerable to spikes and surges? By simple failure of the DC power supply, by the application of excessive voltage to other components, by anomalous injection into the data circuits, or all three? A detailed documented analysis would be much more helpful - and convincing - than the usual bald statement that computers are vulnerable and that's that! Again, there 's endless talk and numerous references to spikes and surges on the power mains. But try Personal Computers - Typical Precautions • Don't expose PCs to an environment which can generate high electrostatic charges; eg, synthetic carpets, plastic furnishings, etc, especially in a naturally dry or air conditioned atmosphere. • Don't couple or uncouple units or fiddle with plugs and cables while the system is powered up. • Feed the system through a line filter. It will hopefully liinit to obtain a quantitative assessment of the potential rate, amplitude or duration of spikes and surges and one is met with mainly anecdotal answers. A detailed analysis of all such possible events would shed further light on the whole subject. (In the meantime, see the panels accompanying this article). The w ay I see it Doubts notwithstanding, it seems to me that the precautions as listed make good basic sense and are well worth observing: • Computers should not be exposed needlessly to large electrostatic potentials, or physical changes made to the set-up while it is switched on. • RF filters , preferably including a va ristor limiter, a re affordable and should attenuate most highamplitude spikes from the microsecond to the low millisecond range. If you want to build your own, ref er most of the spurious pulses on the power mains. • If possible, avoid leaving the system switched on during a thunderstorm. Better still, operate the entire system from a multi-outlet cord or filter, which can be readily removed from the power point, should the need arise. • If connected to the telephone system, unplug when not required but especially during thunderstorm activity. to the Mains Muzzler project in the January 1989 issue of SILICON CHIP. • If the system is not going to be used for some hours, switch it off until it is needed again. Reduce the number of hours it sits across the mains and you reduce in direct proportion its exposure to a reticulation mishap that the filter might not be able to cope with. • Don't just disconnect the modem when you hear thunderclaps; leave it unplugged until it is actually needed. What if the equipment needs to operate continuously throughout the whole working day? And during the evenings, or the night as well? I guess that one has to accept the added risk. Either that or you can install a more comprehensive - and expensive - line filter or conditioner, or even an uninterruptible power supply. Few personal computer applications would justify that sort of expense, however. ~ Lightning Monitor System According to a report in a recent edition of the TV series "Beyond 2000" , a system has been set up to automatically monitor the progress of thunderstorm activity across France. Groups of receptors , positioned mainly on airfields, pinpoint cloud and ground flashes , plotting them in real time as dots and crosses respectively on a video display, over which is superimposed a map of France. The intensity, track and present location of thunderstorms can be seen at a glance and precautionary measures taken. No less to the point, the system provides a means by which computers and other lightning-prone systems across France can be isolated automatically as a storm cell moves across their area. 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ELECTRONICS PTY LTD PO BOX 191 , LIDCOMBE, NSW 2141 MAY.1989 47 BUILD LOTTO Do you have trouble filling out your Lotto or Pools coupons every week? Unless you 're a New Age freak, you need a device to select the numbers in a completely random way. Our new Lotto Selector does it properly and will play the new Lotto 44 format. Design by MALCOLM YOUNG Do you try your luck every week? If you do, you'll probably want to try a completely different combination of numbers every time rather than sticking with a few tired old combinations that probably never come up. And if you are playing "Systems" games you want to pick as random a selection of numbers as you can. There's not much point in picking numbers which are not random. By using our new Lotto Selector, you don't have to think abm,1.t picking the numbers. Just push the "Select" button on the side of the Lotto Selector and lights will start to ripple across the LED display. First one LED, then two, then three and so on until a pattern of six LEDs has developed. Then the LEDs will stop and there will be your selection of six numbers. Fill out the numbers and press the button to play again. After you ' ve finished selecting the numbers for this week's game, there's no need to worry about turning the Lotto Selector off in order to save the batteries. The Lotto Selector has its own "power down" circuit which comes into operation about one minute after the last play. When it is powered down, its battery current drain is negligible, at only a small fraction of a microamp! Playing systems games Our new Lotto Selector lets you. play Systems games easily. Want to THIS ELECTRONIC t/POOLS SELECTOR play a 'System 8' game? Simple, rotate the System Select knob to 8 and then push the Select button. The unit will then go through the process of selecting 8 numbers instead of 6. Or perhaps you want to go Lotto in a big way and play a System 12 game. Simple. Rotate the System Select button to 12 and hit the Select button. After building up a random pattern of 12 rapidly moving LEDs, the Lotto Selector will stop and there will be your selection of 12 random numbers. Lotto 40 and 44 Naturally, our Lotto Selector lets you play the newly announced Lotto 44 games in New South Wales as well as the standard Lotto 40 system that will probably be current for some time in other states and in New Zealand. You can play "6 from 36" Pools too. To select which game you wish to play, Lotto 44 or 40 or Pools, just push the Game Select slide switch to the desired setting and away you go. If you don't personally try yout luck every week, the Lotto Selector would make a very nice novelty gift for one of your friends or relatives. Presentation As you can see from the photos, the Lotto Selector is housed in neat plastic case and it has two rows of numbered LEDs running right The Pools/Lotto Selector is built on two PC boards which are stacked together and attached to the lid of the case. External wiring has been kept to a minimum by mounting the two main switches on the PCBs. across the top. For Lotto 44 games, all 44 LEDs are involved in the number selection. In Lotto 40, only 40 LEDs are involved and for Pools, only 36. Even though a total of 44 LEDs is involved, the battery usage of the circuit is quite modest, helped by the fact that only a limited number of LEDs is alight at any time, plus the auto power down feature which means that the circuit only stays on for the time you are actually selecting the numbers. Circuitry In these days of whizbang micro- processor circuitry, you might expect that the Lotto Selector would be based on a one-chip micro and no doubt it would be possible to design a circuit along those lines. But no, our cunning circuit is based on cheap and readily available CMOS ICs which can be purchased over the counter virtually anywhere. However, while the parts may be as cheap as dirt and available anywhere, the circuit is cunning to the point of downright devilment. It contains such features as a pseudo random binary sequence generator (what a mouthful!), a 10 micro- PARTS LIST 1 plastic case with plastic lid, 159 x 96 x 55mm, (Altronics Cat. H-0151 or equivalentl 1 front panel to suit 1 PC board, code SC08105891, 150 x 72mm 1 PC board , code SC08105892 , 150 x 52mm 1 momentary contact pushbutton switch 1 1-pole 12-position PCmounting rotary switch (Jaycar Cat. SR-1 21 0 or equivalent) 1 4-pole 3-position slide switch (made by Taiwan Alpha) 1 12mm knob with pointer, to suit rotary switch 1 4-way AA cell holder (DSE Cat. P6114 , Jaycar Cat. PH-9204 or equivalent) 1 battery snap connector 4 alkaline 1.5V AA cells 14 PC pins 2 1 5mm tapped spacers (Altronics Cat. H-13931 4 1 0mm tapped spacers (DSE Cat. H1832 , Altronics Cat H-1390) 9 3mm x 9mm-long machine screws 1 3mm x 22mm-long machine screw 4 3mm washers Semiconductors 9 4015B dual 4-bit shift registers (IC1, IC6, IC?, IC8-IC13) 1 4093B quad 2-input NANO Schmitt gate (IC2) 1 4030B quad exclusive OR gate (IC3) 2 4001 B quad 2-input NOR gate (IC4 , IC5) 1 1 N914, 1 N4 148 silicon diode (D1) 1 1 N4002 silicon diode (D2) 44 5mm red LEDs Capacitors 1 1 00µF 16VW PC electrolytic 1 1 0µF 16VW low leakage electrolytic 1 .018µF metallised polyester 1 .012µF metallised polyester 1 4 7pF ceramic Resistors (¼W, 5 %) 1 6.8M0 1 1 MO 2 330k0 50 2 1 00k0 4 4 1k0 SILICON CHIP second monostable, an RS latch, free-running oscillators, a 12-bit counter, a 44-bit shift register and the power down circuit already mentioned. Well, all that sounds pretty complicated and so it is but as with any complex circuit, it is made up of a lot of circuit sections which are in themselves fairly simple. Now let's have a look at the circuit. You'll see that certain sections are labelled with the circuit types we have just mentioned. At the top lefthand corner is the pseudo random binary sequence generator (PRBS). This is partly responsible for the randomness of the selected numbers. Next to the PRBS is the lOµs monostable and then r.omes the RS latch. At the top is the 12-bit counter while along the bottom is the 44-bit register. Hi:wing identified some of the major sections of the circuit, let us now get down to some of the detail of how it works. Let's look at the PRBS. The PRBS The term "psuedo random binary sequence generator" needs explaining. A binary sequence generator is a circuit that produces a long sequence of binary numbers. If the sequence is reasonably long, you can regard part of it as a sequence of "random" binary numbers. However, since the sequence of numbers is not infinitely long, it inevitably repeats itself which is why we ref er to it as ''pseudo random". All pseudo random generators are based on a shift register which has feedback applied around it so that that number fed in at the input is constantly changing. Our PRBS is based on a 4015 8-bit register, ICl. Feedback around ICl is applied by exclusive-OR gates IC3a, 3b, 3c and 3d (4030), together with NAND gate IC2a. The feedback circuit takes the binary values at pins 2, 4, 5, 10 and 13 and generates new numbers to be fed into the D-input at pin 7. The new values are constantly shifted through the register with each positive-going clock transition at pins 1 and 9. The clock signal is generated by IC2b, a 2-input NAND Schmitt trigger gate which is connected as an oscillator running at about 27Hz. The binary sequence generated by ICl is 256 bits long. A bigger shift register would naturally generate a much longer sequence but 256 bits is long enough for this circuit. The pseudo random output from pin 3 of ICl is fed to a monostable pulse generator comprising IC4c and IC4d which are 2-input NOR gates. This circuit generates a 10 microsecond pulse for every negative-going transition of the signal at pin 3 of ICl. 44-bit display register Now let's go to the other end of the circuit, as it were, and have a look at the display register. This is the part of the circuit which causes the LEDs to move along and then finally stop after the requisite numbers have been selected. It involves 11 4-bit shift registers, contained in ICs 8 to 13. Actually, ICB to IC13 contain 12 4-bit registers but only 11 are required, for Lotto 44. For Lotto 40 only 10 4-bit registers are required while for Pools, only 9 registers are needed. The number of registers connected into circuit is determined by the setting of the 3-position slide switch S3. !Cs 8 to 13 are connected together in daisy-chain fashion so that the last bit of each 4-bit register connects to the D-input (D stands for data) of the next register. For example, the last bit of the 4th register, pin 2 of IC9, connects to pin 7 of IC10. And :he 4th bit of the last register, pin 10 of IC13, "wraps around" to the Data input of the first register, pin 7 of ICB, via IC5c Fig.1: the circuit of the Lotto Selector ► depends heavily on 4015 shift registers. All the LEDs are driven by a 44-bit shift register which has ls entered into it from the pseudo random binary sequence generator via the latch. The number of LEDs alight is monitored by the counter consisting of IC6 and IC7. IC2d provides the power down feature. t11 .... co Cl:) co > -< ..... ~ .,. OA =27Hz 1M CKA CKB IC1 4015 03 13 71 8 .,. IC6 4015 10 15 04 0 COUNTER DA CKA CKB 1 161 +6V RA 6 RB 14 12 1 2 06 07 08 15 08 CKB CKA 1 9 RB 14 01 15 330k l 100k RA 6 7 DA 0.18! ""60Hz 8 .,. IC7 4015 13 12 11 2 05 06 07 08 +6V IC8 4015 6 RA 14 9 RB CKA IC9 4015 RA 14 1 9 RB CKA CKB T 03 04 DB 05 06 07 08 3 10 15 13 12 11 2 16 POOLS/LOTTO SELECTOR .,. 03 04 DB 05 06 07 08 3 10 15 13 12 11 2 16 7 6 RA 14 9 RB CKA 44-BIT STATIC SHIFT REGISTER T ~ IC10 4015 DA B05060708 01 02 03 04 5 4 3 10 15 13 12 11 2 16 .,. 16 ~K IC11 4015 6 RA 12 11 2 14 9 RB CKA I I .,. Is 01 1N914 +6V AUTO POWER DOWN 100k ·-,- ~ .6.8M 16VW+ 10 100 .J: 16VWJ ON/SELECT S2 14 13 16 14 9 RB CKA 110 113 112 111 IC12 4015 6 RA 12 .,. .,. I Is 14 13 IC13 4015 .,. 110 T l1s =! -I... 6V : 16 14 6 9 1 RB RA CKA CKB 7 -- 8 ...------:lf---r----...--4.---+6V .--------------+-------------➔-------------~~------------- 0.12+ 7•oA +6V +6V PSEUDO RANDOM BINARY SEQUENCE GENERATOR ed into the 44-bit register. Ultimately, the counter will be incremented 6 times and its output at pin 5 (IC7) will go high. This will cut off IC5a and the 6-LED pattern being circulated around the display register will stop. However, this business of loading ls into the display register is not as simple as that. The circuit is arranged so that a "1" can only be loaded if no '' 1'' is already at the input, as fed back from the output. This is accomplished by NOR gate IC5c. If its pin 9 is high, as would happen if the pin 10 output or IC13 is high, then no signal from the RS flipflop gets through. Power-down The two hoards should he connected together and their operation checked before they are assembled onto the lid of the case. The display hoard can he checked separately, as described in the text. and IC5b. These two NOR gates invert the signal twice so that, in effect, the shift register's output is connected directly to the input. All the clock inputs of these register ICs, pins 1 and 9, are connected to pin 3 of IC5a. All the reset inputs, pins 6 and 14, are connected to the anode of Dl. Each register output drives a LED via a lkO resistor so that when the respective output is high, the LED is alight. Therefore there are 44 LEDs which is the number required for Lotto 44. Now what the circuit has to do is build up a random pattern of 6 or more LEDs which is then circulated around the 44-bit register. So six or more "ls" have to be loaded into the display register and the circuit has to count these 1s in order t0 know when to stop the display register circulating. The way in which it does this is quite tricky. 2nd oscillator An extra degree of randomness is provided by the second oscillator, IC2c. This is similar to IC2b but runs at about twice the speed, at 60Hz. The interaction of the 60Hz 52 SILICON CHIP signal from IC2c with the lOµs signal from the monostable (IC4c and 4d) determines how the clock signal is fed to the display register via IC5a (which normally passes signals straight through). Note that as well as providing the clock signal to the 44-bit register, IC5a also drives the RS flipflop consisting of NOR gates IC4b and 4c. The RS flipflop is toggled up and down and its output is fed via IC5c and 5b to the D input of ICB -(the start of the 44-bit display register). Still with us? Good. Note that while one input of the RS flipflop (pin 1 of IC4a) comes from IC5a, the other input, pin 6 of IC4b, comes from the lOµs monostable; ie, pin 11 of IC4d. So the RS flipflop is synchronised to the 60Hz oscillator and occasionally passes a lOµs pulse through, to ultimately become a "1" fed to the 44-bit register. When the RS flipflop lets through a lOµs pulse, the 12-bit counter comprised of IC6 and IC7 is incremented by one. Supposing that the game being played is standard Lotto 44 (ie, 6 from 44 ), the counter will be incremented every time a "1" is load- As noted previously, the circuit has no on-off switch but incorporates an automatic "power down" feature. This makes use of the feature that CMOS ICs use negligible power if their outputs are unloaded and they are not changing state. Therefore the Lotto Selector has the battery permanently connected to all ICs. The power-down feature is provided by IC2d and associated diodes, Dl and D2. When the Select switch S2 is pressed, the lOµF capacitor at pin 12 of IC2d is charged to almost + 6V via diode D2. A line from this capacitor also goes to pin 6 of IC2b and pin 9 of IC2c so these two oscillators can now start running. As well, switch S2 is connected to the reset pins of IC6 and IC7 so that the counter is reset to zero. At the same time, all the reset pins of the 44-bit display register (pins 6 and 14 of ICs 8 to 13) are all taken high via diode Dl. So the act of pushing S2 sets the whole circuit into operation. The voltage on the lOµF capacitor stays high for long enough for the number selection process to go though the whole cycle (even if 12 numbers have to be selected) and then let the LEDs stay illuminated for about one minute. After this time, the voltage across the lOµF capacitor falls to the lower threshold of IC2d and its output at pin 11 then goes high. This output is connected to the reset line for the 44-bit register via a lOOkO resistor. This resets the display + ~ BATTERY S~ ,._,~ Fig.2: the Lotto Selector is built onto two boards, the larger one being the display board carrying the 44-bit register. The other board carries the remaining circuitry. After assembly and checking the two hoards are stacked together on the case lid. 0 CAPACITORS □ □ □ Value 0 .18µF 0.12µF 47pF IEC 180n 120n 47p f.lA 184K 124K 47K RESISTORS □ □ □ □ □ 1 1 2 2 44 Value 6.8Mf2 1 MO 330kf2 1 OOkfl 1 kO 4-Band Code blue grey green gold brown black green gold orange orange yellow gold brown black yellow gold brown black red gold register so that all its outputs go low and all LEDs are extinguished. At the same time the enable line to the two oscillators (pin 6 of IC2b and pin 9 of IC2c) will have gone low and so these two oscillators will stop operating. This means that none of the CMOS stages will be changing state and the quiescent current of the circuit will be extremely low . In fact, the leakage current through the lOOµF bypass capacitor across the battery is likely to be higher than the current drawn by the CMOS ICs. Note that connecting the reset line from pin 11 of IC2d to the 5-Band Code blue grey black yellow brown brown black black yellow brown orange orange black orange brown brown black black orange brown brown black black brown brown display register via a lOOkO resistor is a little odd. The more conventional way of doing it would have been to connect the line direct from pin 11 to the reset pins and then have a lOOkn pull-down resistor to ensure that the reset line was definitely low when it was supposed to be. However, usmg that arrangement would have meant that the lOOkO resistor would have the full supply voltage across it when the reset line was high fas it is in the power down condition). This is undesirable as it results in a fixed current of 60 microamps. So we have connected the resistor as shown to give zero current in the reset condition. Battery options Our circuit is shown powered at 6V from four 1.5V AA cells. When the display is stationary, the current drain varies from about 27 to 55 milliamps, depending on the number of LEDs alight. If you use high brightness LEDs instead of the conventional types we specified, you can change the LED resistors to 2.2kn. This will more than double the battery life. Either way, you should use alkaline cells for best battery life. MAY1989 53 The counter board is attached to the back of the display board and retained by the nut of the rotary switch at the lefthand end and by a long machine screw through the tapped spacer at the righthand end, as shown here. Construction Here the Lotto Selector has been set for a System 10 game in which 10 LEDs are alight. The selected game is Lotto 44 - note the setting of the slide switch. Current drain is proportional to the number of LEDs alight but the circuit powers down after about one minute to conserve the batteries. 54 SILICON CHIP The Lotto Selector circuitry is accommodated on two printed circuit boards. The larger of the two, measuring 150 x 72mm and coded SC08105892, is for the display board. It accommodates the 44 LEDs, their series resistors, and the six 4015 ICs. The other board, which we 'll refer to as the counter board, measures 150 x 52mm (code SC08105891) and takes the rest of the circuitry, including the rotary switch. The first step in construction is to carefully examine both boards for any faults in etching, shorts between tracks or pads and open circuits (breaks) in tracks. This done, identify the + 6V and 0V tracks and check with your multimeter (switched to an ohms range) that these tracks are not shorted. Step 1: insert and solder the PC pins in both boards. A total of 14 pins is required and as they are a tight fit you'll need a small hammer . to put them in. You can also install the tinned copper wire links at this stage. One of the links on the counter board follows a circuitous route so it needs to be made of insulated hookup wire. Step 2: insert and solder the resistors on both boards. We have listed all the resistor values and their colour codes below the board wiring diagrams. The idea is to do all the resistors of one value first , starting from the top and working down. As you install all the resistors of each value, tick the square box. Be sure to install the resistors so that their colour codes all run in the same direction across the boards or down the boards. This makes it much easier to check that all resistors are of the correct value. Step 3: insert and solder the two diodes and the five capacitors. Dl is a small signal diode, type 1N914 or 1N4148. Make sure the band at one end matches that on the diagram. D2 is a larger diode (because it has to pass the brief but heavy charging current for the 10µ,F capacitor) and it should be installed so that its cathode band is closest to IC1. The 100µ,F capacitor is mounted on the display board. Make sure its polarity is correct. The same goes for the 101-tF electrolytic on the other board. The three other capacitors are listed next to the wiring diagram, together with their alternative markings in the IEC and EIA codes. Step 4: install and solder the integrated circuits. Make sure that pin 1 of each IC (near the dimple or notch in the IC package) corresponds to the same orientation as shown on the wiring diagram (Fig.2). We soldered all ICs directly into circuit but there is nothing to stop you from fitting IC sockets they do make it delightfully easy to change an IC if you have to do so. Step 5: fit and solder the LEDs. They should all be soldered so that they stand up above the display board by the same amount. One way to do this is to insert all the LEDs into the board and bend the leads slightly so that they don't fall out again. This done, place two ~ = 0 ~ (.) UJ ....I UJ (I) 0 ~ ~ 0 ....I + N+ ~ + ~ + ~ + ~+;+ ~+~+ ~+~+ ~+~+ + ~+ ~ + ~+~+ Lt)+ ,.... r,... (t) N+o:::t+ ,.... (t) ;::+ ~+ ~+~+ o,+c::;+ ~ + + (1) r,... + re + 0 0 CD+~+ Lt)+~+ o:::t + ~ + M+ CL. L 7 ~ + 00 ---....I (l)W..JW(.)1- Nt .....+ :::Et- W(.) 1-W Cl) ..J >W (/)"' .• + (\I ,... ,... 0,.... ,... a>e a:,• •• r-- <0 _J Fig.3: here is an actual size artwork for the front panel. pieces of 15mm-thick timber on your workbench to act as board supports. Place the board on these timber supports so that the LEDs fall through and are supported on the bench surface. Solder the LEDs and then check to see that they are all in line and at the same level. Step 6: insert and solder the switches. Slider switch S3 , on the display board, is easy enough to fit , as it will only go in one way. The same applies to the rotary switch S1, on the counter board. However, before fitting the rotary switch you should set it so that it only provides 6 .positions. You can do this by removing the fixing nut and washer and lifting out the indexing ring and then repositioning so that the tab goes in hole 6. The switch should now provide 6 positions. The shaft of the switch should be cut to about 17mm long. Do this before you solder the switch onto the board. When inserting the rotary switch into the counter board do not force it. If the PC holes are not quite big enough, they should be drilled out to the right size (1/16in or 1.5mm). If you try to force these switches in and then solder them, they can be unreliable. Step 7: carefully inspect your MAY1989 55 The final step in the assembly is to stack the two printed hoards together on the lid of the case. Fig.4: above are the actual size artworks for the two printed hoards. 56 SILICON CHIP work and compare the completed boards against the wiring diagram [Fig.2). Do not interconnect the boards at this stage. Preparing the case Use the self-adhesive label as a drilling template for the case lid. Don't fix it to the lid at this stage; just line it up on the lid and use a spike to push through it and mark the centre points for the holes. Take care that all the LED holes line up because this will have a big effect on the overall appearance. Don't drill the holes oversize. If you are using 5mm LEDs, the hole size for a snug fit is about 4.5mm. We suggest you use a 4mm or 11/64-inch drill and then use a tapered reamer or rat-tail file to enlarge the holes to the correct size. You can check the fit of the LEDs in the lid by using the counter board assembly. Do the LEDs all line up nicely? Good. If not, now is the time to make adjustments. Use the counter board as a template for its four mounting holes on the lid. You will also need to drill a hole in the case for the Select pushbutton, SZ. Step 8: fix the label to the lid of the case. Future kits may come with the lid already silk screened so this step may not be necessary. Step 9: check the operation of the counter board. To do this you need to connect the plus ( + ) and minus ( - ) lines to the battery or to a power supply of between 3 and 9V DC. Then there are the Data in and Data out, Reset and Clock lines to manipulate. Connect the Reset line [the arrow marked '3' near ICl 1 on the display board diagram) low for normal operation. Connect it high to extinguish all LEDs. Connect the Data line (the arrow marked '5' near ICB on the display board diagram) high (ie, the + 6V line) to feed 1 's in. You can then clock them along manually by taking the clock line [the arrow marked '4' on the display board) alternately high and low. Check that the Game Select slid·e switch works correctly. In the Lotto 40 mode, LEDs 41 to 44 should never light. In the Pools mode, LEDs 37 to 44 should never light. The Pools/Lotto Selector is powered by four AA cells housed in a snap-in holder. The holder can he retained using double-sided tape. To start the Lotto Selector running, you just push the Select button on the end of the case. A random pattern of LEDs then starts to build up one by one as they move across the display. The unit turns off automatically. Check that taking the Reset line high extinguishes the LEDs. Tha t done and the display board can be pronounced a goer. Step 10: interconnect the two boards and check that the whole circuit operates as it should. If you find problems, remember that the most common problem with a circuit of this sort is solder shorts between tracks or IC pads. Carefully examine the boards for these faults and for missed or poor solder joints. Step '11: mount the two boards on the lid of the case. The counter board first has to be attached to the display board. Attach two 15mm tapped spacers to the counter board. The spacer nearest the rotary switch is retained with a 9mm machine screw while the other is retained with a 22mm screw. The counter board is then attached to the display board. At one end it is retained by the nut on the rotary switch. At the other end it is retained by a 10mm tapped spacer over the 22mm machine screw. That done, you need to fit three more tapped 10mm spacers to the display board. The whole assembly can then be fitted to the lid of the case and retained with four 9mmlong screws. Step 12: fit pushbutton SZ and the battery holder to the case. Connect the battery snap and you are in business. Now you can go Lotto as often you want. ~ MAY l9RQ 57 ~ It F % SOLDERING SPECIALS IN '89 ' De-Solder Iron SPECIAL $49.95 Ideal/or the service teclinician and hobbyist alike. Allows components to be quickly and cleanly removed with one hand. Comes with a cleaning wand. 240V AC 5(M I, 30WISl!C Approval W/2228llluy 1ingle handed actionlSimple cleaning action. " : NEW FOR '89 T 1250 Normally $59.95 Temperature Adiustable 250°c to 450°·c Excellent new iron, acrowdriver temperature adjilltable between 250oC and 450oC enabling very delicate 10ldcring on low 1euing1 with surprising heat energy reserve oo maximum ,ctting. Relative temperature ii indicated by LED lamp lrigbtnosa. 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Energy Saving; Built-in photo cell deactivates unit in daylight. s5350 was $135.00 SPECIAL ONLY $99.00 Please note: Aoodlamps & holders not 1uppllod 1 Flat Kay Cam Lock ~•1/,/\ /. , · ,.,. ~ ·~ , ' · . ._ ~ ' Zinc alloy dic-c• bwirlg with lt&lnl,u neelc:ap. Koy mnovable ra eltbc,rpcaitJoo. ~ •:s~i';E~ ;r.:scd. NowoNLY$4.00e■ S 2552 Span, Key Blmlu SI 20 eL Telephone or Security Keyboard Switch Matrix Typs Speclnotlom: Omtacl Conductive rub~r. Rating DC 24V·SmA. Contacl kc1Ji111.ance 200 Ohrm. Max. Wllh•l•nd Voll•Ko 1.'IOV AC, Bounce Sm IIOc. max. S 5380 WERE $9.90ca 10 up $8.90ca NOW ONLY $7.S0ea ******** Portable Multimeter With Bench Stand I Speclllc ■tl ona: Include ■ Continuity Buuer 20,000 Ohms/Vo lt DC • 8,000 Ohms/ Vo lts AC, Mirror backed scale • Overload protected, 10 amp DC current ·ange Unique carry hand le doubles as Frequency Range 100Hz - 150MHz, in 6 ra nges RF Output Level 100mV RMS Accuracy +/-3% Modulallon:-• Interna l (30% depth) 1KHz • External SOHz - 20KHz • Crystal Locked Oscillator. ..$a9':'(fO a bench stand $29.95 Q 1550 $225.00 Digital Multimeter wi7iiaum-1ncapaci1arice..,+-----=~= A=u=d=i=-o= = F-=requency 7 I 1I in IGene rato_r ~ck the features of top digital multir,1etcr from~ Labtcch range.: • Continuity Test• Qu.uer Sound: l..cH than 200 ohm I DC Voltage .2, 2, 20, 200, 1000V I DC Current :ioouA, 2tnA, 20mA, 200mA, 2A, JOA AC Voltage .2, 2, 20, 200; 750V I AC Current 200uA,2mA, 20mA, 200mA, 2A, JOA R~slstance 200, 2K, 20K, 200K, 2M, 20M I General: polarity and LO-BAT indication• Ovcrrangc Indication I Maximum Common Mode Voltage: SOOY peak All the normal ranges of current, resistance and voltage plus a convcnienl and simple to use -:apacitanoe meter this quality five ranges, plus tl'11nsistor tester. • Capacitance: 5 Ranges 2000pF - 204F • Transistor Tester Display: 3 1/2 digit LCD, 0.5" height, with IIn testing audio circuitry it is necessary o Power: 9V alkaline or carbon-zinc battc1y. Dimensions, Weight: 170mm x 87mm > 42mm, 350 grams vc an accurate audio signal sourc:e. It even allows you Specifications: Input lmped.moe: ! OM on all ranges Normal Mode Noise Rejection: 4tidh at 601-lz (!K wibalanoed) Common Mode Noise Rejection: l0Odb at (501-{z Overload Protection: 1000V de Of ~e:O=:u: :~~~ ~~:.~~nd. (--f \~ :j .% • _ I +/- 3% +21-iz I~;~,~;;~".';'" Sn,e: SY RMS Accuracy SPECIAL PRICE $99.00 • Beat Triggered Strobe (SeeAEMJury•s5) . Fantastic pulsating high voltage Plasma discharge continually changes shape and direction. Mode selectable to either ''.•~<"'.; ,. D~.;.lf;t We havo lots of specials we couldn't fit. Come In and look around and make sure you have our NEW 1989 Catalogue (See EA Dec'86) \.\ ! strobe. Exclu.,ivcly customii1ed by Altronics Price Breakthrough for '89 A 0120 $199.00 NOW PRICE SLASHEDTO $15Q into our II 0480 h111trumct1t Cuc. Includes l'lillc. screened panol. K 5790 $79.95 NOW $75.00 For lnoreaaed Power Two Smooth power for stereo, TV & computers. AJtronic.11 cuJ1Lomi:11Cd ver!iion lK1u.~d in Nlrong JiITy Box. Nidwl NJ>raycd for EMI ithiolding. Tube Option K 5795 $16.50 NOW $15.00 K 6040 was $39.50 m . (Soc EA Nuv'87) Simply clips acrOH11 tl:c DC Fu."IC holder, OfferM protection adjustable from 0-IOA in 2 ranges. Fe:itwes: • rut bl.:,w • slow blow set1'..i •1,. ~ Al/30% OFF! • Manua! ,cset button. • LED fuse tripped indicator. • Operates off 1 single 9V battery (not supplied) 8 Pin 14 Pin 16 Pin 18 -Pin 20 Pin 24 Pin 28 Pin • Two current Setting., euily adjustable via a pot and calibrated scwle. • 1-louxd in a rugged Ji!Ty Rox. A mu1t for prototyping and ,ervice work. No Elecll'onic workahop ahauld be withoul one. K 2535 GREAT VALUE AT $39.50 Save $200 and More by Building This Fine Kit ProJect NOW ONLY $35.00 DC Electronic Fuse !Active Directlnjection Box 7 Gold Plated Sockets For applications demanding 100% long life contact reliability. 0530 0532 0534 ,i 0536 · P 0538 0540 42 • Frequency range 10Hz-100KHz in 4 ranges • Output level 3V RMS max. adjustable • Attenuator Odb - 10db, -20db, -30db, -40db, -50db plus fine adjustment. • Output impedan_c e 600 Ohms unbalanced • Output waveforms - sine and square • Slnewave harmonic distortion (typical) - 1 KHz less than .01% 100Kz less than .02% • Square wave rise and fall times .sons. Add More Life To Your Next Party f1uhes in time to your mu.,ic, or as normal endless fascination as it 1uzz.les and arcs. Supplied complete with AC Mains Adaptor, This Ultra low distortion osci llator is comparab le w ith the very best laboratory standard sine wave oscillators. As well as having very low distortion it has excellent envelope stability, square wave output and output meterin Line Filter and Conditioner (SceEAJuly'88) -r-r4 ~,~~~-+1.u"-'t~wi-; ..,...... ,..,..,: fingertip control or sour..d activated e.g. from voice er sound sy,-,tcrn. Provides 1 Output Attenu ator: -20db, -40db and fmc adjust_j. '•' Plasma Lamp Display I • ~1540 was $249.00 NOW $199 _ _ .:-!~ Featurea: Delayed and instant inpu • Entry and exit delay• Panic alarm input • Battery backup• Line monitoring• Soft alarm start • Lamp telltale ouput Au x iliary relay for external siren etc. • Key switch operation • Operates on virtua lly any type of sensor. I K 1910 '$89.OO $ 0 l----------------l-,'/. 5 I Audio Oscillator & I Function Generator SpecIf1cat1ons: 1FrcquencyRange !OHzlMHz peak on all ranges Up To Now Similar Lamps Sold Por $1,000 And More NEW FOR '89 SAVE I totcst4?~Kllz_IFstagcs! System Fantastic New Alarm Project - Easy to Build as it all assembles on a single PCB. Include ■ 12V 1.2 amp hour Inbuilt lead calcium backup battery. (See EA Aprtl '89) ~-'i• I I I I ... - · I(See EA Oct '87) Coovcrts high impedance unbalanced input, to Ilow impcdanc:e balanced outputs. Oo:,.ens of IstudicvPA uses. lfu~~ • Sturdy dleaut box powder coat I•• Professionallylndu.,L ,creen printed. Black toueh flnlsh 1• Earth l,ola le switch. • +Sdb pod. 1• Phantom powerlne phi, Internal 9V bat. K 55so $45.00 NOW $39.00 $155.00 &½ Discolite ___ 1//1/, K 2540 -~~ I I I I II I I I I I (See SIiicon Chip July/Aug'BB) ~ ~ ~ Add Some Colour To Your Next Party - Great For Parties, Shop Displays & Special Lighting Effects The Discolite flashes party lights on &off in beat with music from your amplifier. • 4 light channels controlled by 4 separate audio channels • Forward reverse & auto-re'.1ersi ng chaser patterns • Simultaneous strobe on all four channels • Alternating light patterns • Music modulation avadable on chaser strobe & alternate pat1ern.s. ~ ~ ~ ·~/VHA/~,,, , , , . e (SeeE.A. March'88) Time your STD calls and Save Money. Timing is adjustable from 10 secoo.ds to 15 Utility Timer (: . ,.• ~ • . ~" ~ ' ~ ' tl ' t, "' ~ 7 :, , ~ 7 ·~ 1... ...'" \, - ,•. ,. : r•'I(• . and silk screened front panel. K1425 waa 2 $ S.50 NOW S0MHZ Digital Frequency Meter (See EA May '88) Fantastic for Work Bench & Tool Box For Les, Than $100 Easy to build. Over 50MHz in 5 ranges. I Features high input impedance overflow LED indicator. KHz & MHz LED Indicators. All componcnts mount onto a single PCB. Complete with pre· punched & silk sa-cencd front panel. Ideal for u.<C in testing CD radios, High power rugged reliable design featuring l ow diatortioc and inbuilt spemr protectioc. All components, including output tranistors mount on a single PCB. Suitable for high quality guitar amp. public address ex in a high fidelity stereo amplifier. Kit includes angled heatsink bracket, main heatsink and unlike other kit suppliers. the In-Built Polyswitch for loudspc.aker protection. Output Power: IOOW into 4 Ohms 150W into 4 Ohms NOW$65.00 K 5150 $99.00 150W Veralon 1V 11 & AM Radios etc. K 2510 K 5140 $69.00 100W Veralon 1 $25.00 SAVE (See SC Dec'87 or our ' 89 Cat for full spes.) $99.00 VALUE NOW$95.00 ,----------------, Capacitance Meter 12/240V Inverter for Small Appliances (See SC Nov'87) Adaptor I Great for band selecting (See EA Aug '85) exact values e.g. exact values for timer circuits adaptor increases the range of your digital multim:ter. It allows measurements up to 2.2uF. Plugs directly into your nx:ter via inbuilt banana plugs. Kit includes prepunched silk screened front panel. Suits Labtech Q HT75 K 2520 was $24.99 NOW $20.00 SAVE!!! I I I I I I I Il '- Doubles as Battery charger under normal mains conditions K 6705 $89.00 This inverter is ideally suited to powering low wattage mains appliances from the ea_, battery whi le camping. Simi larly, it has uses in boatin g. Typically, it ca n be used to power an electric shaver, electric blanket, electric can opener or a _40W _ ,ght-bulb_. l o,,-~ ____________ Car Parking Proximity Detector (See Silicon Chip Jan'89) Ever reversed into a parking spot and hit the car behind you7 Well this proximity detector is the answer. A bU1.1.or 1Lar1.J hocpit1g and just before you hit the object the buzzing becomes continuous. Connects to your reversing !ight circuit, so it comes on automatically every time you reverse. Effective range of about 1 metre. Complete with all parts, boxes and cable. K4310 MOST USEFUL KIT $34.50 NEW FOR '89 4lTiROIIIO Desk Mounted Magnifier Lamp • I _) egger Merer See EA April/May 89 Gh::cks electrical wiring and appliances for insulation breakdown. Insulation breakdown can be determined by the use of this dual range mcgomn. meter. Ideally suited for checking breakdown in electrical wiring, appliances transformers, automtivc generators and altcmaton etc. Breakdown can be K2s55 mc&.SU.rCd at either 500V or I OO0V depending on the o:quired 1tltuation. Would HiJ clcctriciaru or tccluticia,u wmk win, tool box ur work bench. REAL VALUE $79.00 Find Circuit Faults In A Jiffy This unit magnifies any object under a clear, cool f luorescent light. ·.. A 0980 $229 Normally $270 Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) Colin Fobister (02) 437 4077 Melbcurne (Vic/Tas Only) Brian Sorensen (03) 811 9967 Perth (W.A., S.A., OLD., N.T.) ' (09) 328 2199 174 Roe St. Perth W.A. 6000 PHONE TOLL FR.EE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 AL TRONICS RESELLERS Chances are there is an A ltronics Rese ller right near you -check this list or phone us for detai ls of the nearest dealer . PI•••• Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases. however, Dealer prices will still represent a significant cos t saving from prices charged by Altronics Competitors. ~~='.;'~.~~~~I iP.,~~~~J~~l,.':'~,E~~~~!:c~r~lh•o']~.~:~ ~~~~e s::J!~~~r'::: call, Blue Ribbon DHlero are high lighted with a ■ These Dealers generally carry a comprehe nsive range of Altronic prod ucts & kits or w ill order any req uired item for you. STANDARD DELIVERY & PACKING CHARGE $4.00 to 1Kg $7 over 1K AUSTRAL,A WIDE - We process your order the day received and despatch via. ustralia .Post . ·Al low approx 7 da'fs from day you post order to when you receive goods $7 .00 OVERNIGH" JE ERVICE - We process your order the day received and despatch via. Overnight JetMrvlce Courier lo r delivery next day Country areas please allow additional 24-48 hours. Weight limit 3Kgs (3Kgs cove rs 95% of Orders) . $10.00 HEAVY HEA\LY SERVICE - A ll orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. INSURANCE _ As with virtually every other Australian supplier, we send goods at consignees risk . Shou ld you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1) . When phone ordering please request ,·1nsurance·· . TOLL FREE PHONE ORDER -,- Bankcard.Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Ovemlght JetMrvlce we deliver next day . A COUNTRY ALBANY BP E l ectronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K.B.E lectron i cs & Marine 212176 KALG0ORLIE Todays E l ectronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom El ectronics 521713 Farmer El ectronics 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOURNE Winscott Tradi n g 6995740 SUBURBAN CHELTENHAM Ta l king Electronics 5842386 CROYDEN Truscott El ectron i cs ■ 7233860 PRESTON Preston Electron ics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Delsound P/ L 8396 155 SUBURBAN CAPALABA David Ha ll Electronics 3902399 FORTITUDE VALLEY Economic Electron ics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 5 18555 BUNDABERG Bob Elk i ns E l ectronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron World 278988 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE So lex ■ 722015 SA CITY Electronic Comp & Equip . 2125999 Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIES BEACH Force Electron i cs ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force E l ectronics ■ 3471188 LONSDALE Force E l ectronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Ey,e Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON . George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878 CHARMHAVEN Charmhaven Electronics 043926266 SMITHFIELD Cha ntronics 60972 18 COUNTRY COFFSHARBOUR Coifs 525684 NELSON BAY Ne lson Bay Electron ics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA E w i n J . mMo,o ,emc, A,Mo< e,oc,rn"'" "''" •••oso, • , e '""'°"'" m= wo«ONGONG "•"' '""'°"'" ■ m~e d Part.3 Build your own LED Message Board In this third episode on the LED Message Board, we give the full construction details for the message board controller. We also give the setting up procedure and troubleshooting. Designed by DON McKENZIE Building the LED Message Board is firstly an exercise in logistics. At present you cannot buy a complete kit, with everything .down to the last nut and bolt. You will have to go out and buy many of the bits separately. 62 SILICON CHIP As noted last month, a short form kit is available from the designer, Don McKenzie. Included in this kit is a number of bare, double-sided boards with plated through holes. One is the main CPU board, one is the interface board and four others are identical, being the LED display panel itself. Also included are assembly instructions and a programmed EPROM which is absolutely necessary if the unit is to work. To build the project you will need a fair degree of experience and a good tool kit which will include a digital multimeter. A logic probe is also desirable although not mandatory. We'll describe the construction of the message board controller this month and the LED display panel next month. The processor board, . BC1 C4 • BC5 IJ Qecs interface board and power transformer are all housed in a standard plastic instrument case available from Dick Smith Electronics (Cat. H-2507). The processor board is based on the designer's well debugged Z80-controlled printer buffer circuit. Hence the board is labelled "PBUFF". Since this board was intended as a printer buffer, it has provision for a number of RAM ICs which are not needed in this . Message Board application. Hence eight 16-pin IC positions at one end of the board will be vacant. IC sockets may be used for the remaining ICs, including the Z80, 8255 and EPROM. They are recommended by the designer. One point to watch is that you should make sure that all sockets fit into the board before you start soldering them into place. Because the ICs are closely packed together some chunky sockets will not fit. Two changes to the board pattern are necessary for the Message Board application. They are as follows: • Solder neat wire links from E12 pin 17 (8255) to E13 pin 13 and from ElO pin 17 (Z80) to E13 pin 12. This enables the 8255 port A to interrupt the CPU. • There is a sharp 45° angle track which juts out from the component side of J6 near pins 6 and 7. Cut this track and then solder a neat wire link between pin 6 of E9 (address C000H enable) and pin 11 of J2. This provides the clock signal for the 74LS373 on the interface board. Having made those changes, use your multimeter to check that the ground and + 5V lines are not shorted together. As you progress BC7 Fig.I: parts layout for the PBUFF processor board. IC sockets should be used for all the ICs so that the ICs can be installed in turn and tested as detailed in the text. Note the orientation of E12. Close-up view of the completed processor board. Do not remove the protective cover from the EPROM window - you could accidentally erase the contents if you do. A heatsink must be fitted to the 7805 regulator. along, do the same test for + 5V and ground shorts at regular intervals. Since these two lines go to every chip, and at least one of these lines goes to almost every other component, they are the most likely to short. They are also the hardest faults to find and isolate when all the sockets are installed. Examine the board on both sides for defects before assembly. Any fault on the solder side can be easily fixed but once you have your sockets in, the component side of the board is impossible to fix without removing these sockets. So pay particular attention to the component side artwork before assembly. Check any suspicious sections with a meter. MAY1989 63 Building the LED Message Board~:.-·c ~ ~~ • CD D1 "'· 7~~5 G• (le C30 BC1c::» •C eB eC 05 04 eB •E eE eB eC •C eB eC 03 02 01 •E eB •E •E e(]I]e• •+ RUN J5 D825 MALE OUTPUT J3 CENTRDNICS 36 PIN FEMALE INPUT Fig.2: parts layout for the interface board. Make sure that the Q1-Q7 driver transistors are correctly installed and that the pins of the Centronics and DB25 connectors are correctly aligned with the pads on the PC board. Now install the IC sockets on the board. Take note of the orientation of the ICs as they are not all oriented in the same direction. This has been done to minimise the size of the board. Once you have the sockets installed in position, they can be soldered in. Install the resistor network into the board as shown on the overlay, with pin one away from the 555 timer circuitry, and solder it in place. Install all the resistors as shown on the overlay into their mounting holes. They can now be soldered in and the legs cut off flush with the solder joint. Install the BC (bypass) capacitors. Install the Cl, C5, C6, C7 and CB capacitors. Capacitors C2, C3 and C4 are polarised and must be soldered in the correct way around. Install diodes Dl-D4, then mount the 7805 with the tab facing away from the diodes. The heatsink can be fitted at this stage. Install transistor Ql and the crystal. Don't push the crystal -fully down onto the board, but leave enough length on the legs so that they don't short out the tracks underneath. J2 and J6 header sockets A 26-pin male header can be soldered into the J2 position. By using a 26-pin me type crimp header and flat ribbon cable, the connection can ultimately be made to the interface (MMBCNT) board. A 16-pin male header can be soldered into the J6 position. By us- Where to buy the parts A complete set of printed circuit boards plus the programmed 2764 EPROM and full instructions are available from the designer, Don McKenzie, for $150 . The specially made grey Perspex channel, suitable for all LED colours, is also available from Don McKenzie for $50 plus $15 for packing and postage . Write to Don McKenzie, 29 Ellesmere Crescent, Tullamarine, Victoria 3043. All the semiconductors and other parts are readily available from parts suppliers such as Jaycar Electronics, Dick Smith Electronics, Altronics, Geoff Wood Electronics and David Reid Electronics. 64 SILICON CHIP ing a 16-pin female me type crimp header and 22cm of flat ribbon cable, the connections can be made to the front panel controls. Don't cut off the spare wires . The pads marked GND and + 5V are used for test connections. PC pins can be soldered into these pads. Now you can make ready for checking out the PBUFF board. Connect two insulated wires about 22cm long from the Reset button to pins 9 and 1 of J6 (see Fig.3) The Data LED can be wired directly onto the board. Don't install the chips yet. Connect up your power pack or transformer. As the circuit has a diode bridge at the input, it doesn't matter which way around you connect the positive and negative terminals. With your multimeter check that ground and + 5V are not shorted together. Power up the unit and check that the + 5V is there before proceeding. All OK? Power down and install chips E12 (8255) and E13 (74LS04}. Power up again and check the + 5V. If the LED is not already on, press the reset button. The LED should light up brightly. No LED? Then you have one of th~ following faulty: E12, E13, Reset button, reset circuit, LED circuit, or more likely you have the LED wired in back to front. Power down and install E9 (74LS00}, ElO (ZB0A}, Ell (EPROM) and power up. The LED should be flashing at about 4 times per second. If the LED is flashing, it indicates that the Z80A is running and the software is doing its job but a RAM fault exists. With no RAM installed this is to be expected. If the LED doesn't flash as expected at any time during the construction of this kit then refer to the "It Doesn't Work Department". Power down and install E14 (6264) and power up. The LED should be on most of the time and blink off for a short period. This indicates a pass for the 6264 and a fail for the 555 timer. Well, once again this is to be expected if the 555 isn't installed. Power down, install the 555 and power up. The 555 timer is used to interrupt the ZB0A so that controll- , ed updates of the message board This view shows the completed interface board installed in the case but with the connector to Jl from the adjacent PBUFF (processor) board removed for clarity. Note the heatsink fitted to the 7805 regulator (bottom, left). can be achieved. For the technically minded, the output of the 555 timer (pin 3) has a duty cycle of 3µs low and 0.95ms high. During power up or reset, the LED lights up for 1 to 2 seconds and then goes off. It doesn't work department Yes, with all of the components installed, the 7805 will get warm enough to burn your finger, but no other component should. However, the ZBO does get quite warm, which may be a worry for those unaccustomed to micros. Let's outline the four major faults found in these kits: (1). Bad socket solder joints (open circuit). (2). Faulty socket connections (open circuit). (3). Solder shorts between tracks (short circuit). (4). Point not soldered (open circuit). The rear panel of the Message Board controller. The DIN socket is for connection of a standard IBM PC keyboard. Below the DIN socket is the 36-pin Centronics port and next to it the 25-pin DB25 socket for connection of the LED display panel. Faults 1 and 2 can usually be found with a logic probe. Any pin on any chip should be in one of three states: high, low or bobbing. Well almost every pin. If no LEDs light up, this is known as a high imMAY 1989 65 (n), 5-PIN DIN SOCKET TO KEYBOARD CORD CLAMP -- GROMMET 3 ~1 '(_:} J5 DB25 MALE OUTPUT TO DISPLAY BOARD J3 CENTRONICS 36 PIN - - FEMALE INPUT FROM COMPUTER •• AB J4 TO DIN SOCKET Hl J1 .__MAINS CORD 1 \ J6 i1 MMBCNT C PBUFF POWER TRANSFORMER J6 ~ LED2 '~ LE01 Fig.3: how it all goes together. J2 on the PBUFF hoard is connected to Jl on the MMBCNT board via short 26-way flat ribbon cable. Be careful to note the orientation of pin 1 on the two connectors when installing the cable. pedance state. Check over all chips for ground, + 5V and other signals. Make sure that there are no high impedance states anywhere. Exceptions to the rules The input and output ports of the 8255 could show anything random as this may not get programmed correctly on power up. The data bus may also show high impedance states under certain conditions. Pressing the Reset button will bring some life into the data bus. If a high impedance state is found where it shouldn't belong, then check with your meter for zero ohms between the solder pad under the board and the pin of the chip. If you find no connection then pull out the chip and check between 66 SILICON CHIP the solder pad and the socket connector itself. Still no connection? Try soldering this point again. If this doesn't work then you could be up for a complete socket replacement (a nasty job for a newcomer). Sometimes, bending the legs of the chips at a slightly different angle, or just pulling and reinserting a chip, can remove socket problems. Faults 3 and 4 are ones that you have created. A close visual inspection and perhaps a check around with an ohmmeter will usually overcome these faults. A magnifying glass may help you. Clock checks With a logic probe check E10/6. This should be bobbing up and down, as this is the clock signal. No clock? Remove E10 and check E13 /4 for activity. Still no clock? Check E13/3. If no dock is found here, try removing E13 and test the socket contact of E13/3. No clock? It has to be one of the following: the crystal, Cl, C6, R1, R2 or Q1. Is Q1 connected the right way around? If you are getting the clock to pin 6 of the CPU socket without the Z80A in and no clock with the ZBOA in, then it may be the ZBOA itself. Clock working but still no results? Remove E14 and check that the LED flashes at about 4Hz. The software checks the RAM and if none is present the LED is flashed at this rate. If this checks out OK, then it should mean that the system is working up to the point short of a RAM check. OK, where do we go from here? Press the reset and check the MREQ line, Z80A pin 19. If it is bobbing then the CPU is attempting to read the ROM. Press the reset and check the IORQ line, Z80A pin 20. If this is active then the CPU is attempting to access the 8255 ports. Check all ROM and RAM signals. All pins except ground and + 5V should be active. The Z80 should show activity on most pins. Reset can be checked using the Reset button. Pin 26 should be low when the Reset button is pressed and high when the Reset button is released. E13/8 should show the inverse levels to the CPU/26G (see the reset circuit diagram). The 8255/35 should have the same levels as E13/8. As mentioned before, the Data LED should light up when the Reset button is pressed and then go out when the button is released. This is an indication that the reset circuitry is working correctly. WAIT (24) should be high; BUSREQ (25) high; and INT (16) high. A13 (3) bobbing after reset means that the CPU is trying to send information to the message board controller. NMI (17) should be bobbing as this is connected to the output of the 555 timer. Quinella test What would happen if you had a short between Address 7 and Data bit 3, or A13 and ground, or etc. We don't know, but I dare say the beast won't work at all. How do you find these shorts? Do what I call a " quinella test". Using your meter, check for zero ohms between pin 1 and pin 2 of the ZB0A. Then check pins 1 and 3, 1 and 4, right up to pins 1 and 40. Step on to pins 2 and 3, 2 and 4 etc, up to pins 2 and 40. Get the idea? You end up checking pins 39 and 40. Zero ohms will be found at some points, as these points are tied together. Check the circuit to verify these shorts. If a short is found where it shouldn't be, you have found your problem; well at least you know which tracks to look at. This quinella test can be done on all PARTS LIST Other hardware 1 plastic instrument case, 250 x 190 x 80mm (Dick Smith Cat. H-2507 or equivalent) 1 Altronics 21 56 multitap 2-amp transformer 1 3-core mains cord and 3-pin plug 1 cordgrip grommet 2 LED bezels 1 5-pin DIN socket CPU Board 1 double-sided, plated through board, code PBUFF (available from Don McKenzie) 2 40-pin IC sockets 2 28-pin IC sockets 2 14-pin IC sockets 1 8-pin IC sockets 1 26-way dual row male header strip 1 16-way dual row male header strip 1 heatsink to suit 7 805 regulator 1 SPST miniature toggle switch 1 momentary contact pushbutton switch Semiconductors 1 Z80A microprocessor (E10) 1 8255 programmable peripheral interface (E1 2) 1 6264 static RAM (E14) 1 EPROM (E11) - available from Don McKenzie 1 7 4LS04 hex inverter (E13) 1 7 4LSOO quad 2-input NANO gate (E9) 1 555 timer (E15) 1 BC548 NPN transistor (Q1) 1 7805 3-terminal +5V regulator 4 1N4002 diodes (D1-04) 1 red LED (LED 1 ) 1 4.9152 MHz crystal (X1) in a small case Capacitors 1 2500µ,F 16VW PC electrolytic (C4) 1 22µF 16VW tantalum electrolytic (C2) 1 1 OµF 16VW tantalum electrolytic (C3) 13 .01 µF ceramic (BC1-BC11, C7, C8) 1 680pF ceramic (C6) 1 220pF ceramic (C1) 1 150pF ceramic (C5) Resistors (0.25W, 5%) 1 100k0 1 1k0 1 3300 1 10k0 1 2700 1 4.7k0 1 SIP resistor network package with 7 x 4. 7k0 resistors with one common pin 1 50kn trimpot and 270k0 resistor (to replace R7) Interface board 1 double-sided plated through PC board, code MMBCNT (available from Don McKenzie) 1 20-pin IC socket 1 1 6-pin IC socket 2 1 4-pin IC sockets 1 8-pin IC socket 1 2 amp 2AG fuse 2 PC fuse clips 1 26-way dual row male header strip 2 26-way IDC (crimp type) female headers fitted to a 22cm ribbon cable for interconnection with the PBUFF board 1 36-pin female Centronics connector 1 25-pin male D825 connector 1 heatsink to suit regulator Semiconductors 1 7 4LS373 octal latch (E1) 1 7 445 decoder (E2) 1 7 4LS 151 8-input multiplexer (E3) 1 7 4LS02 quad 2-input NOR gate (E4) 7 8D646, 8D648, 8D650 or SE9400 PNP transistors (01 to 07) 1 6A bridge rectifier (D1 ) 1 7805 3-terminal +5V regulator 1 red LED (LED 2) Capacitors 1 2500µ,F 16VW PC electrolytic (C4) 1 1OµF 1 6VW tantalum electrolytic (C3) 1 3.3µF 16VW tantalum electrolytic (C1) 6 .01 µF ceramic (BC1-BC5, C2) Resistors (0.25W, 5%) 2 100k0 1 1500 10 1k0 1 2 .20 10W 7 4700 wirewound MAY1989 67 The two PC boards and the power transformer are mounted on 6mm pillars in a standard plastic instrument case and secured using machine screws and nuts. The interface board is also secured to the rear panel using the Centronics and DB25 connectors. chips if no fault is found at the Z80A. Try the 8255 next. Assembling the interface board The initial procedure is the same here as for the PBUFF board. Check the board very thoroughly for faults before any assembly work is done. Then install the IC sockets, the resistors (except for RB), the bypass capacitors BC1-BC5, and capacitor C2. Capacitors Cl, C3 and C4 are polarised and must be soldered in the correct way around. Install the diode bridge Dl, the 2AG PCB mount fuseholder and 2-amp fuse, and the 7805 regulator. The 7805 must face away from C4. The heatsink can be fitted to the 7805. Output sockets Before fitting the DB-25 male con68 SILICON CHIP nector and Centronics female connector it is necessary to bevel the edge of the circuit board with a file or a sharp knife so that the connector solder lugs will slip over the solder pads more easily. Carefully position each connector, making sure that the numbers on the lugs correspond with the numbers printed on the pads of the circuit board. Resistor RB is a 2.20 10 watt wirewound type which has to dissipate a fair amount of power. It should be stood up about 5mm from the surface to provide more effective cooling. When the board is fully assembled, you can remove the power pack from the PBUFF circuit board and connect it to the MMBCNT board as shown on the overlay. Check that you have + 5V on the sockets and that it is the correct polarity. If all is OK then power down and connect power to the PBUFF circuit by taking it from the pads as shown on the overlay. Reapply the power and once again check that there is + 5V on both the PBUFF board and the MMBCNT board. If all is OK, then power down again. Now install the ICs, making sure that they all have the correct orientation. Power up again for one last check of the power supply on the MMBCNT circuit board and if all is OK then power down again and link the two circuit boards together via a short header cable by using PBUFF connector J2 and the MMBCNT connector Jl. Be careful to note the orientation of pin 1 on the two connectors. When power is re-applied the RUN led should be on, indicating that data is being sent to the message board display. ~ AMATEUR RADIO By GARRY CRATT, VK2YBX Build this simple stub filter to eliminate TV inter£erence One of the hazards to radio amateurs operating on the VHF and UHF bands is the possibility of causing television interference (TVI) to neighbours. Fortunately, many TVI problems can be easily cured by building and fitting a simple stub filter to the TV antenna feedline. A recent government proposal to charge a $60 investigation fee to persons who complain of TVI makes this article on the construction of a simple yet effective filter particularly timely. The most suitable type of filter for a particular situation is determined by several factors but the most important in cases of amateur radio interference is ease of fitting. This is because anyone experienc- ing TVI is unlikely to possess much patience - it is important that the filter can be rapidly installed. Secondly, the filter must look acceptable (ie, not look like a can of worms) and thirdly, it must be cheap to make. While there can be cases of TVI caused by IF or audio stage detection (and these situations require specific cures), the primary reason that TVI is experienced in a I I I I A14 OPEN STUB )112 OPEN STUB , 12 SHORTED STUB 290 435 580 870 1015 FREQUENCY (MHz} Fig.1: this diagram shows the effects of both terminated (short circuit) and unterminated (open circuit) quarter wavelength and half wavelength stubs for the 2-metre band. populated area is simply due to overload of the front end of the tuner. After all, a television receiver is expected to deliver a reasonable picture from a signal of only a few hundred microvolts, yet that same receiver needs to remain unaffected by a nearby amateur VHF or UHF transmitter which could have a legal power output of over lkW EIRP. In fact, the transmitting antenna could well be aimed directly at the antenna for the affected TV set. Thus, it is hardly surprising that television receivers do suffer from front end overload in such situations. Theory of operation By far the simplest yet most effective type of filter that can be installed at the antenna terminals of a television set is the coaxial stub. The operation of a stub filter is based on the fact that a cable cut to a quarter wavelength of the offending signal frequency and with one end open circuit (ie, unterminated) presents a very low impedance at the other end (the feed point). This fact can be used to greatly reduce the unwanted signal while letting other signals pass unaffected. A stub also presents this low impedance at odd multiples of a quarter wavelength. When the stub is made to a half wavelength in length, any impedance at the terminated end is reflected at the feed point. Fig.1 shows how the use of either MAY 1989 69 the desired frequency. Two or three such stubs may be cascaded to achieve a notch depth of - 70dB or so, which should be more than adequate for even the most serious overload situation. 0 = '2- 20 z ~ 40 et :::, z ~ ...< 60 TWO STUBS - - SPACED BY "/J4 AT I Construction 80 FREQUENCY 31 Fig.2: a single unterminated quarter wavelength stub is capable of producing 30dB of attenuation at the desired frequency and at odd harmonics of this frequency. Cascading two such stubs will give a notch depth of about - 70dB. This cascaded stub filter was cut to provide around 70dB of attenuation at 146MHz. The input and output leads go to Belling Lee connectors so that the filter can be easily installed in the antenna line. quarter wavelength or half wavelength stubs in either the unterminated (open circuit) or terminated (short circuit) condition can be made to produce filters for the 2-metre band (144 to 148MHz). Such stubs can be used to reduce interference across all TV bands. A quarter wavelength unterminated stub connected across a 75-ohm TV feeder cable is capable of producing 30dB of attenuation at The coaxial stub has the advantage of simple construction and broad bandwidth (single stub only). It can be built using standard TV style coaxial cable and Belling Lee type connectors, so that the entire filter can be made to plug into the antenna socket at the back of the television set. Fig.3 shows the layout of a single stub filter while Fig.4 shows a cascaded stub filter. The length of the stub is quite predictable and will lie between 65 % and 85 % of a quarter wavelength in free space, depending on the "velocity factor" of the ea ble used. That term needs explaining. The "velocity factor" is the ratio of the speed of electromagnetic radiation (ie, radio signals) along a cable to the speed in a vacuum. Since radio signals always propagate more slowly along a ea ble than in a vacuum, the physical wavelength of a radio signal in the cable will always be shorter than for a vacuum. This decrease is given by multiplying the wavelength 'in vacuo' by the velocity factor. Table 2 shows velocity factors of several commonly used coax cables. Fig.5 shows a cascaded stub filter for the 2-metre band. The dimensions shown assume a frequency of 146MHz and the use of cable with a velocity factor of 0.66. Thus, the length of the stubs is: 114A x Vf = 34cm. 4 FEEOLINE ~ _ COAXIAL _ I_ ----~ - - - -7, - -- - -7 r----- - STUB Fig.3: basic scheme for a single stub filter. the velocity factor of the cable must be considered when calculating the stub length. 70 SILICON CHIP _____ - - - - - II II 11 11 11 II II II II II II II 11 II 1 II I II II I, I, _ _ _ _ _ _ _ _ I, II _ _ _ _..... Fig.4: a cascaded stub filter is made by installing two stubs one quarter of a wavelength apart. TABLE 1: TV CHANNEL NUMBERS & FREQUENCY LIMITS Channel 9 195-202MHz Channel 10 208-215MHz Channel 11 215-222MHz BAND I Channel o 45 -52MHz Channel 1 56 -63MHz Channel 2 63-70MHz BAND IV BAND II Channel 3 85-92MHz Channel 4 94-101 MHz Channel 5 101 -108MHz BAND Ill Channel Channel Channel Channel 5A 6 7 8 137-144MHz 174-181 MHz 181-188MHz 188-195MHz Channel ·28 Channel 29 Channel 30 Channel 31 Channel 32 Channel 33 Channel 34 Channel 35 526-533MHz 533-540MHz 540-547MHz 547-5 54MHz 554-561MHz 561 -568MHz 568-575MHz 575-582MHz BAND V Channel 39 603-610MHz TO TV SET Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 610-617MHz 617-624MHz 624-631 MHz 631-638MHz 638-645MHz 645-652MHz 652-659MHz 659-666M_ Hz 666-673MHz 673-680MHz 680-687MHz 687-694MHz 694-701 MHz 701-708MHz 708-715MHz TO ANTENNA BELLING LEE PLU G BELLING LEE SOCKET I. 1-14 X VF FOR 146MHz = 514mm x 0.66 = 339mm Fig.5: a practical cascaded stub filter for the 2-metre band. The stubs should initially be made about 50mm longer than shown to allow for trimming. The stubs should initially be made about 5cm longer than the calculated value to allow precise trimming late r on. They are soldered directly to the feedline (1/4 wavelength apar t) by carefully cutting away part of the outer jacket and braid of the feedline to expose the centre conductor . Connect both the braid and centre conductor of each ~tub to the feedline, then wrap the connection in insulation tape to prevent shorts. The free end of each stub should be left open circuit. Setting up Once the stubs have been soldered to the feedline, the entire assembly should be connected between a 144MHz antenna and a 2-metre receiver . By monitoring the local repeater or beacon frequency (even if this isn 't the precise fr equency to be attenuated), the stubs can be trimmed in small amounts (say 6mm at a time) to provide maximum attenuation a s indicated by the receiver's 'S' meter . Alterna tively, tho se amateurs equipped with a signal genera tor will be able to ti:im the stub to a precise frequency. However, the results will be quite satisfactory using the repeater method, as the filter will have an effective bandwidth of several MHz. Once cut to the length providing ma ximum attenuation, the stubs can be taped to the main coax f eedline and secured with plastic cable ties to make a nea t assembly. When using coaxial stubs one must be careful that the harmonic resonances also attenua ted by the stub do not fall on television chan- Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel Channel 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 715-722MHz 722 -729MHz 729-736MHz 736-743MHz 743-750MHz 750-757MHz 757 -764MHz 76 4-771MHz 771-778MHz 778-785MHz 785 -7 92MHz 792 -799MHz 799-806MHz 806-813MHz 813-820MHz nels in use. For example, an unterminated quar ter wavelength stub cut to attenuate 146MHz will also attenuate 438MHz and 730MHz. If any of these fre quencies corresponds with a wanted TV channel we would be defeating the purpose of the filter. However, it is possible to shift the ha rmonic resonances. If we cut the stub short er than a quarter wavelength, it can be tuned to resonance by placing a trimmer capacitor across the open end, and the harmonic resonances will move higher in fre quency. It is also possible to cut the stub longer and insert a trimmer in series with the feeder connection. In summary, stub filters for the 2-metre and 6-metre bands are easy to make. They can go a long way towa rds pacifying the neighbours and preserving the image of responsible use of the spectrum by radio amateurs. it: TABLE 2: VELOCITY FACTORS OF COAXIAL CABLES Type RG-6 RG-8 RG- 11 RG-58 RG-59 RG-59(F) RG-17 4 RG-213 Impedance 75 50 75 50 75 75 50 50 Velocity Factor 0. 659 0.659 0.659 0.659 0.659 0.79 0.66 0.66 MAY 1989 71 AT LAST! A Cheap Stepping Motor /COMPUTERLEAD BARGAINS\ Once again we have purchased a bulk shipment of HIGH DUALITY Philips brand 4-phase Unipolar Stepping Motors I The manufactuier was forced to sell this stock FAR BELOW his cost and we can pass these massive savings on to you! The motor, Philips #9904 112 06001 is a high performance bidirectional unit featuring a 7°30' step (48 steps per rev) with 40mNm max working torque. Full data is provided . INCLUDED IN THE COST is a Sprague UCN4202 4-phase stepper motor driver chip. This will drive the motor directly from logic and a nominal 12V supply. Once again full data on the chip is included. The current WHOLESALE cost of the motor ONLY from Philips is over $75 +20% sales tax ie. around $90. You can purchase the motor and driver IC in 1-off from us for this month only $591 That makes the stepper under $501 Limited Quantity. Cat. YM-2700 $59 Stepper Motor and UCN 4202 chip UCN chip available sepa rately $10 (Cat ZK-8842) Philips SAA 1027 4-phase driver IC (designed especially for the motor) Cat. ZK-8843 $15. Data included with SAA 1027. L I CONNECTORS- cf,1{/E $2.00 each Hurstvi lie York Street Springvale Melbourne City Buranda Old Compare our prices with your normal supplier. Description 1-9 Boxes 3.5" 1S/20 Cat. XC-4720 $39.95 35" 2S/2D $46.95 Cat XC-4721 3.5" 2S/HD Cat XC-4722 $99.00 x, 5.25' 1S/20 Cat XC-4725 $22.00 5.25' 2S/20 Cat XC-4726 $26.00 5.25' 2S/HO Cat XC-4727 $41.00 SYNTOl\1 - Drum Synthesiser Ref: Silicon Chip May 1989 Fantastic drum synthesiser kit that will add real depth to any performance. See the 1989 Jaycar cat for full details. Cat KJ-6502 $42.50 H 4 BOOKS FOR ONLY $79.95 Battery Powered Cordless Soldering Iron "TOILET DUCK" The alternative to the gas'type portable irons. Uses 2 x C Ni Cads and they can be recharged in the 'Duck'. Tip retracts back into the body of the iron when not in use. Named after the famous toilet cleaner as it looks the same. Supplied with one tip and one spare plus small quantity of solder. Dimensions Length (0/A) 210mm x 30(W)mm. Charger not supplied. FOR MORE INFO SEE 1989 CATALOGUE. Cat. TS-1430 Extra tips Cat. TS-1432 $4.95 ONLY $19.95 ..,.-:::'' 1/ __ Cat. WW-4314 Cat. WW-4316 Cat WW-4336 VERBATIM DISKS AT UNREAL PRICES Sat till 4pm, Thurs till B30pm Sat till 4pm Thurs till 8.30pm Thurs till B.30pm Sat till 2pm, Fri till 8.30pm Fri till B.30pm Thurs till 8.30pm $2.50 each You get National Linear Data books Vol 1. 2 & 3 and the ALMOST-IMPOSSIBLE-TO-GET latest printing of National Semiconductors Linear Applications. (Please note that Linear Applications can't be sold seprately). Cat BN-4000 .. ... ·:··.... , .. , . I , I • I _) ONLy $4.95 • IOC Plug Cat PP-0902 (250 available) National Linear Data & Applications Set ·.: ·•:·:,-.(• " ONLY $3.9 5 • Solder Socket with Metal Backshell Cat. PS-0901 (100 available) Cat. PS-0903 (300 available) ~ . ,.:•·....··•-.:. . . . . ·. . . . .: .. • . .·.. 35" length Black C,at. WW-4310 Green Blue Cat. WW-4312 Red Packsof100NORMALLY$5.95 5.5' length Blue Cat. WW-4332 Red NORMALLY $6.95 Packs of 100 $2.00 each $2.00 each .. - - ., '" '~ WIRE WRAP WIRE BARGAIN Save $2 per pack Another surplus stock buy. AIJ'lphenol series 57 (same as Centronics 36 pin but with only 24 pins) Save a fortune over normal prices. • Solder plug with metal backshell Cat. PP-0900 (100 available) 10+ Boxes $37.95 $43.95 $89.00 $21.00 $24.00 $39.95 - " . At last! A driver set incorporating those obscu,e shaped heads I Have you ever needed to service an electric tool? Chances are you would not have been able to do so because the screws holding the appliance together had strange shaped heads. Well now you can with our 30 piece driver sell This set contains all the driver bits you are EVER likely to encounter (See Below) Basic to the set is an 8 1/2' Chrome-Vanadium driver which wi ll accept any of the 28 hardened steel bits supplied. All held in the socket by a small magnet· so yoc can use it in any position . The screw-together hollow handle will hold several tips so you don't have to take the whole set with you into the field . There is a tip here to suit almost any screw/ nut you may come across. INCLUDES ALL OF THESE PIECES: 5 biu for Slo tted 9CI..... . Here'swhatyouget • 5 Slotted Bits 0-1, 3-4, 5-6, 8-10, 12 • 5 Hex Bits 3/3'!', 5/64", 7/64", 1/8", 9/64" • 4 Philips Bits No. 0, 1, 2 & 3 • 4 Square Recess Bits No. 0, 1, 2 & 3 • 6 Torx Bits T10, T15, T20, T25, TJO, T40 ·· 2 Pozidrive Bits No. 1 & 2 • 1 X 1/411 Drive Socket Adaptor • 1 x 1/4" Drive Hex Bit Holder And its all housed in a sealable tough plastic case. Cat.TD-2000 $19.95 CD t I? 5bi t 1 lorH•• • c•ew t I 0-1 ).:0 - - - - - " " - -..... 8-10 ~ ~ ~ ~ I!!!/ ,,.,. 'r.:p'"'' '{""'"','.:::z. ,,,,. ~ "" ,,, 0 \.,!_) ~ . ~ , SbltllorTor• • se ,ew s ~ '29 ~ ( 3 - •• · ·· A 0 ~ ° ' ~ " • ••~ ~ ~ - - ; , - , ..,_....-■; [ \:=a ~ "' ;£'°'~• I I I I I I I I , ~ •I ____ 24 PIN CENTRONICS TYPE • me Socket I SAVE 50% on normal price • 250 Male to 250 Male 1.8mt Cat. PL-0856 I Normally $19.95 I ONLY $9.95 SAVE $10.00 • 250 Male to 250 Fema le 1.8ml Cat. PL-0855 I Normally $1995 $9.95 SAVE $10.00 I • CentronicsONLY Plug to 250 Ma le · 1.8mt Cat PL-0854 I Normally $18.95 I ONLY $9.95 SAVE $9.00 I ~ ~ ~, --■■--' c::, I C::::::12 ,, ... Automatic Telephone Diverter NEW MooEL FoR 19s9 This device will divert an incoming call to, say, an unattended office, surgery or home, to another location. (Two exchange lines are required). The unit will divert EITHER of the incoming lines. Supplied with 240V plug adaptor, instructions and telephone leads. Double adaptor Cat. YT-6020 $4.95 may be req uired. Measures 190(W) x 110(0) x 35(H)mm Cat. YT-651 0 $249 Quality Disks at Stf~ PfC'ieu Another Jaycar direct import. Would you believe - computer disks with a LIFETIME GUARANTEE for less money than you have ever had to pay before! 51/4" DSDD 48TPI DOUBLE SIDED/DOUBLE DENSITY Cat. XC -4730 $6.50 for 10 3 1/2" MF2DD 135TPI DOUBLE SIDED/DOUBLE DENSITY Cat. XC-4736 $26.95 for 10 ;,: 51/4" DSHD 96TPI DOUBLE SIDED/HIGH DENSITY "/ , 1, Cat. XC-4732 / /# ·1 $18.95 for 10 Al l disks are supplied with envelope, index labels and write-protect tabs. Remember, these disksight be cheap ut they are good quality. We are so impressed by the .quality we are happy to offer a lifetime guarantee. NEW KIT - Versatile Sub-Woofer Adaptor Rer EA April 1989 This unit enables you to get from a stereo signal subwoofer signal information. You can then feed the subwoofer signal thru a separate power amp/subwoofer speaker enclosure. It's a great way of having the space benefit of high performance book-shelf speakers with thundering bass down to 30Hzl The Jaycar kit includes all specified components, metal case Cat. KA-1717 $29.95 100 watt Mosfet Subwoofer Amp to suit. /Rer EA August 1982) Cat. KA-1452 $134.50 /power supply extra) 100 watt 250mm Subwoofer speaker /as discussed in text) Cat. CW-2119 $129.50 2010 MkllA Stereo Equaliser (1 octave) This is the famous Jaycar 2010 one control per octave equaliser. This kit would look good with any Hi Fi system and performs beautifully. For full details see the Jaycar 1989 catalogue Cat. KJ-6365 ONLY $125 SAVE UP TO AN AMAZING 200 HUNG CHANG 20MHz CRO 8" (200mm) PLASMA LAMP The most beautiful thing we have ever seen. Just imag ine. a beautfful plasma display in your own home for under $200! Watch as the red glowing element in the centre of the 200mm glass sphere projects beautiful blue lightning outwards to the inner surface of the ball where n magically changes back to crimson. This event occurs simultaneously at least 50-100 times all over the inside of the sphere and is constantly in motion. ., It is truly beautiful to watch. The intensny of the display can be controlled by a slider pot mounted on the attractive base. In addnion you can trigger the performance by means of a sensitive sound activated circun. The entire unit comes with ns own dedicated power supply and is packaged in an attractive gift carton. This beautfful instrument will give countless hours of pleasure and relaxation and is truly unique. Cat. XP-1000 CRO • NORMALLY $899 Cat. OC-1900 NOW ONLY $719 SAVE $180 PROBES (TWO) NORMALLY $9 NOW ONLY $79 for 2 SA VE $20 $169 SAVE. $30 Cat. OC-1902 Jaycar is now accepting account applications from all established companies who can exhibit good trade referen ces For application details see our store managers or phone (02) 747 2022 SALVAGE SOME CASH Turn your surplus stock into cash. Jaycar will purchase your surplus stocks of components and equipment. CALL GARY JOHNSTON OR BRUCE ROUTLEY (02) 747 2022 Ref Silicon Chip Feb. '89 This is a co-operative speaker project between Silicon Chip and Jayca r. Using an 8' woofer and a dome tweeter with pre-built crossover unit the system has been acclaimed for its superb sound reproduction. The cabinets measure 490:H) x 303(W) x 290(D)mm FOR FURTHER INFORMATION SEE OUR 1989 CATALOGUE AVAILABLE NOWI Pair of speakers and Crossovers Cat. CS-2540 Cabinets (pair) Cat. CS-2542 PURCHASE BOTH SPEAKERS AND CABINETS TOGETHER AND PAY ONLY $269 JAYCAR - LEADING THE WAY IN NEW PRODUC~S 1 g~:i~fs ~rhRlg!dles ,/1/ .~. QUALITY AND DESIGN FUNCTIDNABILITY AT A DOWN TO EARTH PRICE - A JAYCAR DIRECT IMPORT PRODUCT -rr-L- c ,.9 · .·.·.".·.··· Jaycar proudly announce a range of 5 beautiful black. direct t---o-----l import rack cabinets. Give your equipment a real 1st class appearance. All aluminium construction. removable top and bottom panels. black finish with ♦ high quality brushed anodised front panel. Handles and rubber feet supplied, along with all screws. nuts. etc .. to assemble. Individually cartoned, supplied in flat pack. These cabinets really look the part and check out the \w; prices compared to other ones. Each A B C D E ~ HB-5380 255 73 177 305 75 $39.50 $36.50 HB-5381 353 98 203 401 100 $49.50 $46.00 HB-5382 429 62 203 481 69 $49.50 $46.00 HB-5383 429 95 292 481 100 $65.00 $61.00 HB-5384 429 122 292 481 126 $75.00 $70.00 l't-fASSI VE SCOOP PL'UCIIASE Powerful 12V DC Motor! This motor, as used in automotive thermatic type fans. has incredible torque. It is a ·pancake· style unit with a 8mm diameter output shaft (with flat). We have scooped up a smallish quantity of these at a great price! Grab one now for an incredible $25. Worth over $6011 ·.•.' ··. ·.. [ · ··· J ·. . 3 mounting holes -- . : : ~ Let Ja year tempt you into making that decision NOW and SA VE UP TO $200 PER PAIR. 1. . '. .······ · •·····........... ··.. _.--- All our s tores have the new upgraded Vifa kits on demonstra tion so drop in and have a listen. Remember, you will pay about twice as much for II similar pre-built, imported speakers when, in fac~ they will pr obably have Vifa speakers in them anyway. See our1989 catalogue for full details. (Demonstration speakers are n ot at Concord). 1 JAYCARDlruT AL-MULTIMETER"\I SA-130. . (With almost everything - SAVE $50 over others) 3-way klt LOOK AT THESE FEATURES . . LCD d I • 34 ranges - 3•5 digit isp ay • High impact yellow case • Small size - only 133 x 70 x 30mm • 10 amp AC and DC. DCV > 1% worst • Diode tester - continui ty buzzer • Frequency counter 10Hz - 200kHz • Built-in 20MHz logic probe • Capacitance tester lpF - 20µF • Tilting Bail - Safety test leads • One hand operation with unique feature where probes can mount into either side of the case $25 Cat YM-2706 Dimensions 130 {approx\ dia 40{approxl daep 20mm shah length 8mm output shaft - -- . Thinking about investing in a VIFA speaker kit? SPECS Speed 1800 RPM<at> 12V Torque 1.Skg/cm<at> 1800 RPM Power Consumption 70W<at> 12V Weight 600 grams triangularly spaced <at> 105mm ·-• with cabinets I complete and crossovers . 130W RMS power handling. I cat. CS-2485/CB-2467 I I SAVE I $200 I ONLY $999 I A PAIR • SA -100 2-wayklt complete with cabinets Jaycar Soldering Iron and cros sovers . 1OOW RMS power handling. Cat. CS-2460/CB-2482 Ideal for the hobbyist and handyman. Our lowest price 240 volt quality iron has a stainless steel barrel. 30 watt. Cat. TS-1450 $16.95 SAVE Ultrasonic Air Humidifier $100 CREATE YOUR OWN CLIMATE IN YOUR ONLY $699 OFFICE OR HOME ECONOMY DIGITAL MULTIMETER Digital multimeter at an analog price I • 3.5 digit LCD display • 20 ranges • Diode checker • DC 10 amp. 1000V. 0-20M ohm. etc • 1500 hour battery fife • One hand operation with unique feature where probes can mount into either side of the case • Tilting b,j_il • Safety test leads • 3 month warranty Cat. OM-1410 $59.9. Features • Cu tout switch when water runs out • Generous 6.75 litre water tank • Ultra quiet operation • Adjustable intensity control • Adjustable humidity control • Air filter included • Humidifies up to 4.000 cubic feet Specifications • 40 watts • 240V AC power source • Humidity control 30 - 90% • Dimensions 375(L) x 1SO(W) x 290(H)mm Cat YH-5500 ONLY $449 WAS SELLING FOR $149 in 1986 APAIR NOW ONLY $99.50 2-waykit complete with cabinets and crossovers. 70W RMS power handli ng. Cat. CS-24711C82472 SAVE $50 kit with cabinets and crossovers. 30W RMS power handling. Cat. CS -2450/CS-2452 SAVE $30 ONLY $369 A PAIR NEW KITS FROM JAYCAR Telephone Bell Monitor / Transmitter Ref: Silicon Chip April 1989 This kit simply plugs in parallel with your telephone. When the phone rings, it broadcasts a sequence of tone signals to a portable FM radio. You can buy a cheap portable radio for around $20 to act as a receiver, that's far cheaper than a kit would cost. Kit includes PCB, box, telephone plug and all specified components. Cat. KC-5048 $16.95 Auxiliary Brake Light Flasher Auto Tune Up Adaptor Ref: Silicon Chip April 1989 Reduce your chance of a rear end collision by building this simple lamp flasher kit. It drives an auxiliary brake lamp mounted on the rear parcel shelf. Kit includes PCB, box and all specified components. Cat. KC-5049 $17.95 Ref: EA April 1989 Turn your multimeter into a tac ho/dwell meter with this simple adaptor. It's easy to build and may be calibrated for 4, 6 or 8 cylinder petrol engines. Any multimeter above 20kN will do, analog or digital. Kit includes PCB, die cast box and all specified components. Cat KA-17H, $29.95 Her: ~1l1con Chip March 1989 TOTALLY NEW DESIGN - STUNNING AUDIO PERFORMANCE ... I I , Jaycar. along with Silicon Chip have taken the best features of the 28 band graphics and ····•..... I . . .. . incorporated them into this TOTALLY NEW ELECTRONIC DESIGN which features VASTLY ·-...._ ... / SUPERIOR audio performance to our old graphics. Apart from the 4 extra bands (which now .._.. extend from 16Hz ,to 20kHz) the new 'Studio Series' graphic features radically new slide pots. especially m~de for the project. Mounted in a standard 19' 2 unit configuration, and power directly from mains. $24.95 . $239 SEE THE JAYCAR 1989 CATALOGUE FOR FULL TECHNICAL SPECS Cat. KA-1711 CONTINU ITYTESTER PCB SHORT Cat. KC-5047 Cat. KC-5046 $55.00 r•seat Me" Metronome This unusual project is actually a metronome that has its rhythm set by simply tapping the unit at the desired rateu can tap it with a drum stick, pencil - even your fingernail 4 times, and the "Beat Me" mimicsate at which it was tapped indefinitely - so simple! The Jaycar kit includes case, speaker and all electronic components. It runs on a 9V battery (not supplied). $22.95 Size: 130x 68x41mm JT\at: Vf . _........~. . ~._.l . ._. .n .. ._.1,.,~......_. , SYDNEY • CITY PARRAMATTA . - ' CONCORD HURSTVILLE . _...... . ,,. Refer Silicon Chip Jan 89 A line filter kit for your computer which incorporates an effoctive filter for mains borne interference and a varistor to clip dangerous spike voltages. Kit includes PCB. box (HB-5446) 4 mains sockets and all specified components. $19.95 VISA _.,., ,., $18.95 Refer EA Feb 89 This simple kit will helpyo1J locate shorted tracks on printed circuit boards by means of a varying audio tone. It's easily built and much cheaper than commercial units. Cat. KA-1712 . ,.,. ..... . ...... . . . __ .,. __ ,., BETA TESTER Refer EA Feb 89 This all-singing, all-dancing continuity tester kit features three audio tones, operation over six decades of resistance, auto-polarity reversal. and an ambient current so low, it needs no ON/OFF switch. Kit includes PCB, box and all specified components. Batteries extra (Cat. SB-2369 $4.35 for 2 Alkaline) Cat. KA-1710 ~ Refer Silicon Chip Feb 89 Great NEW kit. Will measure the gain of a transistor, test NPN. PNP and power transistors. PLUS. by trial-and-error, you can identify BCE on an unmarked device. Kit includes PCB, box and ------◄ all specified components. $49 • 95 BEEPO ----------- . :: -- ~:==~~:=~-~~:~i;~t~;=;~~~~;;;~I;~-; . . ... .. . JTL -ANALOG VIDEO CONVERTER Refer EA Feb 89 This kit will allow you to use an analog RGB colour video monitor as a CGA colour monitor for your IBM PC or compatible. Kit includes PCB, box, panel. D sockets and plug and all specified components. Ref: EA Apri I 1989 This device will warn you if your vehicles brake lamps aren't working as they should - hopefully before another motorist rams into your rear end. Kit includes PCB, box and all specified components including 12V bezel. Cat. KA-1715 ~ 1/3 Octave Graphic Equaliser Cat. KC-5050 Car Brake Lamp Monitor HEAD OFFICE Cat. KA-1714 MAIL ORDERS 1 137 $29.95 POST & PACKING 0 8 ,..L_::_i_i_i_~~_l_;_<:.;..:_:a'-;_;:_4_ic_:7_~:_:__ _ _ _ _~_l_R:_:~_i_~-~-~-~C_11_!_;_:0_~_:~_:_:B___t_~E-R$_1_oo_i_:i_l_~_1_1_1____, _M_A_1_L_O_R_DE_R_v1_A_Y_o_u_R_~=-R_o_A_D_F_R_EI_G_H_T_A_N_Y_W_H_E_R_E_I_N_A_u_s_T_R_A_LI_ A_S_1_3._so_ __, L.I 117 York St. (02) 2671614 - Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Ctuch St (Cm. Victoria Rd) (02) 683 33n Mon-Fri 9 - 5.30 Thurs 8.30 pm -Sat 9 - 4pm 115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30 - 5.30 -Sat 8.30 - 12 121 Forest Rd (02) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 12 GORE HILL BURANDAQLD MELBOURNE-CITY SPRINGVALE VIC 188 Pacific Hwy cnr Bellevue Ave (02) 439 4799 Mon-Fri 9 -5.30 Sat 9 -4pm 144 Logan Rd (07) 393 0777 Mon-Fn 9 - 5.30 Thurs 8.30 -Sat 9 -12 Shop 2, 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 -12 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2 27th June 197Zenith, USA. Dear Richard, Here I am, in the area made famous by Sinclair Lewis. But of course, you worked in this vicinity, didn't you? Jobs are funny things. You and I have both had some pretty horrible experiences. But let me tell you about something that happened to one of my mates from that contract job in the Middle East. Kevin left the e about the same fune I did, returning to Melbourne. After a few weeks taking it easy, he started applying for jobs. He went for one interview and was told it was down to a short list between him and another bloke. A few days later he got the usual letter: " ... you have not been successful on this occasion". Thinking no more a bout it, Kevin proceded to check out other posi- 76 SILICON CHIP "Well, it was an honest mistake. We don't really want him, you see". "So he resigned his previous job in good faith and you're prepared to turn him out on the street. Don't you read the letters you sign?" Kevin didn't accept their job offer. As he said in a letter to me, "If that's what they're like in the begintions. The following week, he got a ning, matters can only get worse frantic phone call from that firm. later on!" I've noticed that "in the begin"Are you still available for the ning" attitude. A bloke takes a new R&D job?" "Yes," Kevin replied. "What job and is listened to initially. But happened to the other bloke, might I the longer he's there, the less his ask?" opinions are accepted. Manage"We made a mistake. The ment seems to take incumbent persecretary sent the letters out but r,:onnel for granted- and think that got them crossed up. We really a new person magically has the better answers. wanted you". "So what happened to the other bloke?" Field service "He fronted up this morning Which is why I became a field that's when we found out what had service engineer. The job allows me happened". "So what happened to the other to travel around the country and to be an instant expert! Even more so, bloke?" "We asked him to wait in the in my case. The foreign touch enhances an already significant foyer for a short time". "And if I accept the position, aura of respect from station managers. what happens to the other bloke?" Maybe it's because they're paying large fees to the field service company - they subconsciously want to feel they're getting their money's worth. Often, I have confirmed problems on site with the staff engineers who frequently know more about the By gear than I do! Their recommendaRICHARD KOPF tions, though, were ignored by their 0 ~ 0 > v~ ' TMe:. DIFFE.RE.NCE: (FOR IV\ANA 8E:Tu>6£N \~CU~E-N"r &. ~ ~~ONN£,L-••• bosses. So in I come, often having only studied the manual on the plane trip, with no prior experience on a given piece of equipment. My opinions are accepted, even if I insist that some piece of test equipment must be bought or rented. In any case, I'm happy to take advantage of the "outside expert" syndrome. I learned straight away to seek the advice of the men on the spot from the old bloke who broke me in. Big Ralph taught me that one learns more from listening than talking and that some pretty cluey people exist. If you solicit their help, it makes them happy and makes your job easier. There are a few dills around, too, but you can spot them pretty quickly and steer clear. Big Ralph hated chief engineers. I've seen him insult them, drop rude comments and generally be obno_xious. But they put up with it 'cause he was brilliant. Ralph could identify faults almost instinctively. I've seen him diagnose a VTR servo pro- blem with nothing more than a picture monitor. We came to this flagship station when I started. Ralph was lining up a VTR when he saw the reflection in the monitor of the chief engineer walking up. Ralph started to mutter: "If there's anything dumber in the world than a chief engineer I don't know what it is. A chief couldn't find his backside with both hands and a radar guidance system". I didn't know where to look! But the bloke turned and left without a word. Hail to the chief The chief here is certainly a case for the books though. He'd worked for this group at another station and was sacked for drunkenness on the job. He came to Zenith and made an appointment with the station manager, having learned that the prior chief was retiring. Most of his references were false but they didn't check them out and hired him on the spot. Some weeks later, a vice president came to Zenith and saw the bloke. He queried the station manager, only to be told that the man "sounded" all right. At any rate, the chief was kept on - and kept on with his elbowbending. He hired a summer relief engineer who was on the staff for nearly six months. The chief telephoned him at home one day to tell him not to come in any more. But another engineer had tendered his resignation that very morning. That fact had slipped the chief's fogged mind. When he realised, he couldn't admit that he'd made a mistake. So the channel went understaffed for two months. The station manager finally paid a healthy fee to a personnel agency to find a suitable engineer - who came from interstate and was paid a large sum for moving expenses. The station manager is a gem, too. He recently lured a weather girl from an opposition station. She was only here a few weeks when the manager's wife chanced to see MAY1989 77 THE TECHNOLOGY LETTERS - CTD the news one night. Exit one weather girl. The wife had been one of a long line of weather girls at the channel - but she was the one who married his exalted highness. Based on past performances, the wife was taking no chances. Learning the local gossip is another reason to get on-side with the local engineers. Actually, I came here to commission a semi-automated switching system - a custom job, engineered to specifications. It looks to be a way of doing more work with less people. Of course, the system is not very good but it was planned by the station manager. The chief engineer didn't want to get involved. We got it on-line a couple of days ago, then started to find the bugs. As it was built to a price, many compromises were made by the design engineer, who is on-site also. Now, our hero has never worked in broadcasting. After the first few foul-ups, the master control operator started to grizzle at him. "We have a lot of audio exception commercials here, for some reason", the operator said. "But the two sources we need most booth announcer and audio cart are not on the breakaway row". "That's not my problem", said our designer. "I only build what I'm told". The system is essentially single vision and single audio. On the vision side, there is a program bus and a preview bus. There is a breakaway row for exception audio which can be taken at any time but does not include the two most used sources, as the local bloke said. A preset facility exists for "irregular" audio and is initiated by the next video take. If you're sitting in network control and the link starts to break up, you naturally hit Black to keep from blowing the transmitter off the air. If you've preset something for the un-coming break, however, it goes rt, --AALPH HA, e:D Q\JG I NE;.£.RS ... 78 SILICON CHIP along with the black. Murphy will likely decree that the local break comes at that point - and your audio cart is not re-cued. Several times, a break started without any audio. It was discovered that the video crosspoint control was sensitive to the slightest impulse but the 14-relay sequence in the audio section did not latch until the 14th had operated. Our designer solved this problem by putting a sign on the console: "Warning! Hold down switches at least 5 milliseconds". No-one laughed, however. There was a changeover switch that swapped the program and preview buses. The audio preset and breakaway rows were, however, only associated with the normal program bus. With only a single vision path, an instruction in the copy book to "super slide 707" was meaningless. Confusion & chaos I watched one break degenerate into complete chaos. After a twominute debacle, the master control operator screamed, "How do you expect anyone to switch this?". "Not my worry, old man", our designer replied. "Electronically, the system works. Whether it fits into a real-time situation is nothing to do with me". The best foul-up of all, though, was the cutover to the 11pm live news program. Seems there was a mystery switch at the audio console which determined whether its line output went to the downstream master control switcher or not. So the network movie was ending, the master control operator did the final break, punched control B and raced to load the videotape features for the news. The audio operator in control A saw his line VU meter looking right but was monitoring console output rather than off-air. This was at the director's instruction since he objected to the poor quality off-air signal in the station. At this point in time, the talking head in the news studio was leading into the feature VTR story, network was running a commercial, and net- work audio was on-line, somehow. The master control operator was loading slides and planning his next VTR loads when he noticed that the VTR and master control console VU meters weren't tracking. He ran over to the console, cranked up the audio monitor, then screamed over the intercom, "Wrong audio to air!" The director replied, "Get off the intercom". The master control operator tried again with the same response. Suddenly, the "hotline" rang in Control B. The director snarled, picked it up, and heard an irate station manager asking him why the wrong audio was to air. "Wrong audio to air", the director screamed over the intercom to master control. Two minutes of ID slide went to air from master control while the studio supervisor and the technical director patched around the master control console completely. The night's programming then continued from Control B until the final bars of the national anthem. A witch hunt occurred the next day. The audio operator maintained it wasn't his problem and blamed the master control operator. The assistant chief engineer admitted he hadn't instructed anyone about the mystery switch but said that it had never been active prior to the commissioning of the new gear. The matter was dropped. Three nights later, the same thing happened again, except that the previous audio operator was now on master control. But he still insisted that it wasn't his fault. I telephoned my boss about the embarrassing situation. "We pay you to commission what the client ordered. Just do that and don't get involved", he told me. The road to hell One final humorous note about this installation, which did have nothing to do with us. The audio cartridge machines the master control operator has to load were in Control A, about 15 metres down a corridor from the console. This studio facility is almost brand new. They spent $4.5 million on a new building - and moved most of the existing equipment from the old plant. The foyer ' s beaut, though: designer chairs in black leather that cost $500 each; original oil paintings on the walls; carpeting you sink into. Control A looked like a set from "2001" with walnut panelled walls, recessed monitors, an imposing custom console and God - sorry, the Director - at the centre, his faithful audio companion to his left and the vision mixer ready on the right. Never mind that the associated studio camera CCUs are across in Control B, accessible by intercom - on a clear day. I picked up a promotional brochure for clients which read: "Our intentions are to provide the capability to tape a show in one studio, cut commercials in another, and maintain programming from Master Control - simultaneously". As G. B. Shaw put it: "The road to Hell is paved with good intentions". They tried the noble experiment once. Four videotape machines, two telecines with one colour camera apiece, and one multi-station intercom are a recipe for disaster. The "full utilisation" attempt started at 1pm. A syndicated tape talk show is playing back via master control. There are three commercial breaks with at least one videotape play in each in the first half hour. Also, the network closed news feed must be recorded. Both the directors have VTR inserts. The master control operator admits he has a logistics problem. ''Why can't these engineers cooperate?" moans one director. As things get busy, the telecine operator starts to quiver. Director A wants slide 247 on film 7. Director B wants film number 472 on film 9 (7 and 9 are the telecine colour cameras. 6 and 8 are the b&w cameras that no-one uses, geddit?). The master control operator yells that he needs slide 247 on Film 7 in 12 seconds. Telecine pulls the hot slide out of 7. Director A screams over the intercom that he needs that slide back "right away". Director B requests his film on 9 be mov- Polystyrene capacitors YES Made here in Australia? YES Made Special to Type? YES Where From? Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors. Why design circuitry which requires additional components to achieve a specific capacitance; we can wind exactly the capacitance you need to match your design criteria within the ranges of 10pF to 1µF and up to 10,000VDC. Capacitors are manufactured to 0.25%, 0.5%, 1.0%, 2.0%, 2.5%, 5%, 10% and 20% and are priced according to tolerance . All capacitors are tested to 2.5 times the rated voltage. Interested? Call us now on: (02) 938 4690 OR Cut out and post this coupon to Post Office Box 740 Brookvale, N.S.W. 2100 ----------.---------, I I Yes, I am interested in your capacitors. I Please post me details of the following values: I ... /... VDC . . . / .. VDC . / VDC ... / ... VDC I Name (Please print) I Address I I I I --------------L~~~~ ~-~ ~~~ ~~J MAY 1989 79 Buy direct from Australia's leading manufacturer and save on quality AVTEK Modems. A range of 16 internal & external modems from low priced manual to fully automatic 2400 bps models complete with power supply, instructions and telephone connections. Designed and built in Australia, all Avtek Modems are guaranteed, with service and technical support available direct from Avtek. CALL TODAY ON 008 25 2754 or (02) 888 5333 TOLL FREE SYDNEY RESIDENTS ,For further information and to see how much you can save on the best modem for your needs. ■El 'fTEK [II V/S4 ATA COMMUNICATIONS (A Member of the NetComm Group of Companies) ed to 7 "because the colour is nicer" . Director A hits the intercom to Control B. "Tweak those cameras, T.D." Of course, the technical director is setting up an effect on the vision mixer, some distance away. Master control wants the technical director to adjust Film 7. Naturally, there are no interlocks on the intercom so half of the output is feedback. And this was only the first half-hour. This place reminds me somewhat of that New England channel I left. They planned a new building, also. One of my fellow workers said I was foolish to leave a place that was expanding and had lots of opportunities for advancement. Cynically, I replied that they 80 SILICON CHIP would probably build a showcase with no thought for the employees. Then I learned that the cost of the new facility meant moving the old equipment. I saw the architect's drawings before I left: imposing foyer, a triangular-shaped building, big columns out the front. As the facility dwindled down to the apex, one got to the operational areas. They planned to continue with minimum staff - only the new building probably necessitated roller skates so the operators could move quickly from telecine to videotape. Not only were they separate rooms but situated about 20 metres from one another down a corridor with a dog-leg. When I said there was no point staying on there, this was confirm- ed the week I left. Their film editor had been one of the blokes who did not go out on the wildcat strike. Seems the station had a profit sharing plan but you had to be there over five years to draw any benefit from it. This is why he risked the angry picket lines. But about 4 years and 11 months into his employment, they wrote off his job. Bye bye, bozo. From what I gather, only the four top people ever benefitted from the profit-sharing plan. Maybe the s.tudio supervisor will .get a piece of the action. My nemesis, he seems their kind of person. A couple of incidents concerning him just before I left need mentioning. He was whinging one day about having to frequently replace the special and expensive globes in the news director's desk lamp. I suggested putting a diode in the line. "That won't work". "Bloody hell", I said. "I'll do it after sign-off". "No, I'll do it now. I want to prove to you and the other fellows that you're not as smart as you think". So he proceeds to unplug the lamp, snip one lead, drop a 1-amp rectifier diode in series, plug it in and switch it on. "My God, it works!" That saved them some bucks and I tried to suggest another way of saving money but he wouldn't be in it. Every week he used to go buy parts and pick up a box of 10 327 indicator globes. You know how many of these little devils get used in VTRs and telecine. I showed him in the ea ta log that the price break at 100 was significant. Also, I pointed out that if they used 387 types, the long life variety - although costing more - would be more cost effective. But he reckoned the budget wouldn't stand it, so I guess he's still buying 10 every week at a premium price. My next stop is a certain UHF station I believe you're familiar with, Dick. I'll let you know what they've done to it. Write soon, with more lowdown on high security. And how did your first TV job finish? Regards, Colin. ~ I PRODUCT SHOWCASE I ~~•-.,--1 --=-:-=====--=-5:.==:=~:~~ ~~ =-==~ :,../ '\11o;~ 20MHz dual trace CRO from Goldstar These days, 20MHz dual trace oscilloscopes are regarded pretty much as standard "no frills" instruments with very similar features and all at much the same price. Still, it does pay to look closely at the features and then at the price before you buy. Goldstar's Model OS-7020 dual trace oscilloscope is a case in point. Like most other models, it has a rectangular CRT with an 8 x 10cm screen, 20MHz bandwidth and a maximum sensitivity of lmV/cm. But it does have features that aren't standard on competing models. For example, it has a LED to indicate triggering. This might seem like a small point but it is very handy when you are trying to trigger on a difficult or high frequency waveform. In fact, the Goldstar excels in its triggering ability, being able to trigger on signal frequencies to above 40MHz. When you are pushing to these limits, the trigger LED is very handy. So too are the LEDs to indicate that the variable timebase and vertical attenuator controls are not in their calibrated settings. Without these visible reminders it is quite easy to take erroneous measurements off the screen. The Goldstar also has comprehensive triggering facilities, including video sync separator giving TV-V and TV-H triggering (for viewing video signal waveforms) and a holdoff control for better syncing on complex digital waveforms. When you've digested all the performance features, its overall good presentation, proper tilt handle, good instruction manual and the fact that it comes with two switchable probes, it looks very competitive. But at the moment the Goldstar OS-7020 is available at a very special price of only $699 including sales tax. That makes it absolutely unbeatable. Get in for yours now, while stocks last. See the Goldstar dealer listing on the inside front cover. Doodad panel from Lance Chapman This front pa nel assembly from a Kreisler TV set is definitely one for your parts box. While you might throw away the escutcheon itself, it does have a wealth of parts on it, as this partial list shows: 5 miniature pots with matching push-on knobs, 6 multi-turn trimpots (for varicap tuning), 7 ganged pushbutton switches on a separate PC board, 1 3.5mm mono socket, 1 push-on push-off DPDT mains switch, several multiway p!.ugs and sockets and a 270 loudspeaker. The speaker would actually be ideal for the Hands-Free Speakerphone project described in the October 1988 issue. The price of this cornucopia of parts? - $25. It is available from Lance Chapman, 122 Pitt Road, North Curl, NSW 2099. MAY 1989 81 Heavy duty antenna rotator from Arista Are you a keen listener to long distance FM or shortwave reception? Are you an active amateur radio operator or do you have difficult TV reception, from different points of the compass? If you answer yes to any of these questions then you are in the market for this nicely made antenna rotator from Arista, the AAR2. It is built like a battleship and will handle vertical mast loads of tip to 50kg. Speed of rotation is 75 seconds for one complete 360° turn and the unit has a mechanical stop which prevents any tendency to rotate while the unit is unpowered. Maximum wind loading area for any antenna array is 0.25 square metres. The unit is also fully approved for electrical safety (Energy Authority Approval No. N1499). Our photo shows it sitting on a Dip meter from Danner Electronics flat surface, as it would when mounted on a tower plate or horizontal base. However, it is also supplied with a heavy duty bracket to allow vertical pole mounting. It is supplied with a companion double-insulated well written instruction manual. At the moment, the DM-4061 is available at the special price of $99 although quantities are limited. Contact Dauner Electronics, 51 Georges Crescent, Georges Hall, NSW 2198. Phone (02) 724 6982 . High power variable resistors If you are into RF design work, a dip meter is an essential tool for checking the resonance of LC circuits. This model DM-4061 by Parameters covers the range from 1.5MHz to 250MHz in six switched ranges. It can also be used as an adsorption wavemeter, for checking the operating frequency of a circuit without making any connections. It comes with 6 plug-in coils and a 82 SILICON CHIP 240V AC-powered controller. Recommended retail price of the AAR2 is $169.95. For further information, phone Arista Electronics Pty Ltd on (02) 648 3488 for the name and location of your nearest Arista stockist. When you need to dissipate a lot of power in a dummy load it is nice to be able to dial up the precise value you need and then pump in hundreds of watts without worrying whether it will all go up in smoke. These high power resistors from Geoff Wood Electronics can really take it. They are continuously rated at 320 watts, 640 watts for 15 minutes and 1280 watts for 4 minutes. Naturally, if used as variable resistors, they must be derated in proportion to the amount of the resistance in circuit. This is easy enough to db because the unit also has a particular current rating, depending on the resistance value . The PRN-553 series unit pictured has a resistance of 330 but other va lues from 10 to 3000 are available to order. They are priced at $151.60 including sales tax. For lots of resistance contact Geoff Wood Electronics at 229 Burns Bay Roa d, Lane Cove West, NSW 2066. Phone (02) 427 1676. Solid state relays rated for 30A surge These Chipswitch solid state relays from International Rectifier are based on IR's power Mosfets. They essentially consist of two identical power ICs connected back to back for AC control and with an internal light emitting diode for actuation. High resolution frequency counter In most low cost frequency counters, you don't get any better than 2-digit resolution when measuring frequencies of 99Hz and below. Usually, the only way to improve matters is to take a measurement of period and then calculate the reciprocal. However, on the Sigmotek ITC-4 high resolution counter you have the option of turning up the gating time to get as much resolution as you want. In fact, there is a tradeoff between resolution and gating time. The latter can be varied between 10 milliseconds and 1.5 seconds. The ·difference between the Sigmotek ITC-4 and other low cost counters is that the ITC-4 is a microprocessor-based unit. When measuring low frequencies is takes a period measurement and automatically calculates and displays the frequency. m this way, you can have as much resolution as you want for Each Chipswitch is a normally open SPST switch with a 1 amp rating at up to 280V AC. They have precise zero voltage turn on and zero current turn-off. Typical current to actuate the switch is 5mA DC. They are ideally suited to interfacing microprocessors to AC loads such as small motors, lamps, solenoids and solenoid valves, and high power motor starters. For further information, contact NSD Australia, 3/12 Victoria Street, Lidcombe, NSW 2141. Phone (02) 646 5255. Portable digital thermometer This portable 3 ½-digit thermometer has an operating range really precise measurements or, if you are measuring signals that are not so stable, you can turn down the gating time for less resolution. Measurement range is from l0Hz to 120MHz and sensitivity is typically 5mV at lOHz, ranging to 20mV at 120MHz. We found the ITC-4 works very well and it is much less confusing to use than many counters which have lots of buttons on the front panel. It is available from David Reid Electronics at $343 including sales tax. That's a top buy. David Reid is at 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385. D.DAUNER between - 40°C and + 50°C and is switchable to give a readout in the Fahrenheit scale. A presettable alarm can be programmed to sound whenever a certain temperature is exceeded and similarly a low alarm can be set off when things get too cold. The digital thermometer is priced at $57.60 from David Reid Electronics. Phone (02) 267 1385. ELECTRONIC co WE STOCK A WIDE RANGE OF ELECTRONIC PARTS for • Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST CFE 455 RESONATOR $2.80 ea • 7552 COAXIAL CABLE (4 SHIELDS) CG7 $0.90/ MTR • 50 ONLY METAL PROJECT INSTRUMENT CASES 370mm(L) x 90mm(H) x 180mm (D) $4.50 ea • Come and see. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Caltex Service Station In Blrdwood Road) TRADING HOURS: Monday to Friday 9.00 a.m. to 4.00 p.m. Saturday from 9.00 a.m. to 12.00 noon. MAY1989 83 THIS IS HIGH TECHNOLOGY, 1928 style. At the time these were the longest, heaviest and most powerful electric locomotives in the world. They were powered from an llkVAC 25Hz overhead wire but used a large motor generator on board to develop around 500 volts DC for the traction motors. THE EVOLUTION OF ELECTRIC RAILWAYS In this episode we tell the story of the Burlington Northern Railroad which is now the biggest railroad company in the USA and possibly the w~>rld. It started as the Great Northern which was very much a pioneering railroad company. By BRYAN MAHER Like a blast of thunder, two powerful electric locomotives burst forth from a tunnel in the rugged Cascade mountains in Washington State, USA. They were pulling a heavy 16-car express train carrying over 400 passengers, tended by a small army of porters, dining-car staff, guards and brakemen. The time was 1929, in midwinter, the scene the eastern portal of the new Cascade Tunnel, the longest tunnel in North America, straight as a gun barrel, almost 13 kilometres long and almost 900 metres above sea level. Twice as long as any Australian tunnel, this new tunnel replaced the old 4.Zkmlong Cascade tunnel of 1900 vintage and many kilometres of twisting climbing mountain track. The old Cascade tunnel, in opera- PT.19: THE BURLINGTON NORTHERN RAILROAD 84 SILICON CHIP BUILT BY GENERAL ELECTRIC IN THE 1940s, this was the longest and heaviest electric locomotive ever built. Weighing 362 tonnes and measuring over 30 metres (101 feet) long, it developed 5000 horsepower. Such a long locomotive was practical on the Great Northern tracks which employed long straight runs and very gen.t ie curves. tion for a few years under steam locomotives, gave passengers an awful journey. They had to endure loco smoke and exhaust fumes as the powerful steamers battled up the steep 1 in 45 grade for the whole length of the tunnel. 3-phase electrification With passengers fainting and grown men succumbing to the lack of air, the then-owner, the Great Northern Railroad, electrified the old Cascade tunnel in 1909. They used a 3-phase high voltage supply with two overhead conductors. This meant that the traction motors were 3-phase induction types which were difficult to control, giving jerky acceleration and an uncomfortable ride for passengers. This was because the speed of induction motors was then only controllable by crude pole-switching methods. To solve the problem of the old tunnel and its difficult route, the Great Northern Railroad embarked on the greatest mountain hard-rock bore ever attempted in North America. It was started in 1927 and by 1929 the new Cascade Tunnel was open for traffic and electrified, along with a section of mountain mainline at 11,000 volts 25Hz AC single phase. At the same time, the Great Northern introduced the longest, heaviest and most powerful singlecab (ie, not articulated) electric locomotives in the world at that time - a record that would stand for many years. (In the l 940s they introduced an even larger electric loco as shown in the photograph above). DC or AC While the Europeans had been using series motors with commutators on AC supplies, over in the USA the Great Northern engineers had observed that the series motor with commutator and brushes is naturally a DC machine. Furthermore, when running on DC, such a motor gives a greater starting torque and pulling power than any other type of motor. The loco's tractive effort is proportional to the square of the motor current in amps. This presented a problem because the engineers wanted to use a high-voltage (1 lkV AC) 25Hz supply for the new 214km-long Cascade section. Accordingly, the engineers came up with the 5000 class electrics, a design unique in big locomotives, even to this day. Instead of the usual large stepdown transformer, the 5001 to 5012 electric locos carried an 1 lkV AC single phase 3.4MW induction motor. This was shaft-coupled to a separately excited DC generator. This was why the locos were so heavy. They weighed close to 200 tonnes. Ward Leonard control The DC generator supplied low voltage in the 500V range to the six series DC motors. Motor control was provided simply by varying the 100 ampere generator field current, a very much simpler task than breaking the 5000 to 7000 amps MAY1989 85 AN ARRAY OF GREAT NORTHERN Railroad power: a 5000hp electric, a 5400hp four unit diesel electric and a 2-8-8-2 oil burning steam locomotive. Note how much larger the electric loco is in comparison to the diesel electrics. total traction motor current. And all the while the big AC-DC motorgenerator ran at full speed within the loco body. This control method is called "Ward Leonard" control. The total locomotive tractive power was 2.46MW (3300hp) at a traction motor speed of 430 RPM. This very long 1-C-C-1 design used large diameter driving wheels in each of the two huge driving bogies and a massive single axle leading truck at each end to help guide the long locomotive around mountain curves at up to 75km/h. Expresses and large freights were all hauled at creditable speed through the electrified mountain section. During high traffic periods it was common to see a steam locomotive running through the electrified section, express passenger train in tow, with a 5000 class electric loco leading the lot. In these cases, the steam locomotive would idle through the tunnel to avoid the smoke menace, with the electric loco doing all the work. Such an 86 SILICON CHIP electric-steam combination had previously been used by another railroad, the B & 0, in the Baltimore city tunnel. The beginning But we have started our story of the mighty Burlington Northern Railroad in the middle. Let's go back to the beginning. The story began way back in 1849 at Aurora, 52km west of Chicago, Illinois, when a group of local businessmen met one night and formed the Aurora Branch Railroad. The new corporation's first president was Stephen F. Gale, who guided the fledgling railroad for the first three years, so beginning a line of 17 dynamic leaders, all far-sighted, innovative, progressive businessmen. Their first line was built of scrap rail purchased from the Buffalo and Niagara Falls Railroad of New York State. This 9.6km stretch was laid from Batavia, Illinois to Turner Junction (now West Chicago), there to join up with the tracks of the Galena & Chicago Union Railroad which carried the tiny Aurora train on into Chicago. Because their order of secondhand locomotives and wagons did not arrive in time, the inaugural trip was made using borrowed rolling stock and motive power. This inauspicious beginning left the railroad world of the day totally underwhelmed. How could the other railroads guess at the time that they had witnessed the birth of the greatest railroad of the future United States? Expansion The baby corporation prospered, expanded, bought out opposing lines, changed its name and its aims, grew and never looked back. The line was purchased by a consortium of Boston men in 1852 and expansion accelerated. Its name was changed to the Chicago, Burlington & Quincy Railroad Company and by 1864 just over 640km of track had been laid throughout the state of Illinois. During the next 106 years, the C.B.& Q.R.R. (or the "Burlington" as it became affectionately known) spread its tracks beyond its native Illinois and also built its own highclass track from the original Aurora terminal right into Chicago. Spreading far and wide, 204 affiliate lines were added to the fold , tripling the Burlington's size. Two major acquisitions were the Burlington and Missouri RR and the Hannibal & St. Joseph RR Co. Hannibal RR The Hannibal Railroad began in 1852. One of its original purposes was to cross Missouri to connect with the Pony Express and exchange mail. This railroad was the first in the world to have a TPO or "travelling post office" for mail sorting on the move. As a result, this railroad was sometimes visited by Jesse James and other infamous train robbers. The Hannibal line also made Kansas City the great rail centre and south-west gateway it is today, and built the first bridge across the Missouri river at Kansas City. Opened on 4th of July 1869, this 425 metre long structure connected the railroad to St. Louis and the southern states. B & MR The other major early acqms1tion, the Burlington & Missouri RR Co, had begun in 1852 in the state of Iowa. Their first train ran in 1856, with c0nstruction reaching the Missouri river not far from Omaha in November, 1869. Once acquired by the Burlington, both these railroads continued building westward, reaching milehigh Denver in the Rocky Mountains in 1882. The Burlington was the progressive railroad, aggressively braving new lands, attacking new construction problems, and building new tracks ahead of the farmers and lumber workers. They actively promoted new settlers, even operating large offices in the eastern states of the US and in England, Scotland, Sweden and Germany to attract farming migrants. The railroad settled 20,000 farmers on their new lands THE NORTHERN PORTAL OF THE Cascades Tunnel in Washington state: this was the longest tunnel in North America and was originally electrified at llkV AC. Now it is fitted with ventilation shafts and diesel electrics power the trains through it. in a 10-year period from 1870 to 1880. The Burlington was always a leader in improvements and new technology. It re-ra iled many lines with heavier rail, relaying and straightening the original path in the process, and progressively introduced larger locomotives, longer cars and wagons. George Westinghouse conducted tests on his new air braking system on a Burlington train in 1886/87, so revolutionising train braking methods worldwide. Great Northern Naturally other progressive rail- road builders existed in the USA. One such empire builder of incredible foresight was James Jerome Hill. Without any government land grants, he built the Great Northern across the very north of the USA, from east to west. Using heavy rail and sound building design from the outset, the line today follows almost the original path from St.PaulMinnesota, Twin Cities, and Duluth on Lake Superior to the Pacific Ocean at Seattle and Vancouver, Canada . Along the way the line had to cross the Rocky Mountains at Summit, Montana, and then pierce the Cascade Ranges between Berne MAY 1989 87 ed the railroad completion, allowing them all to become states by 1890. Large locomotives HANDSOME IS AS HANDSOME DOES goes the saying and this Northern class loco was certainly handsome. The loco weighed over 230 tonnes while the tender was 180 tonnes. It regularly pulled express trains at over 160km/h. and Scenic, in Washington State. And that's where our story for this month began. Outside the electrified area, for service in the mountain country, the Great Northern Railroad built some notable very large steam locomotives. The Northern Pacific The Great Northern was not the only east-west line in the northern reaches of the USA. Before the Great Northern was completed another railroad, the Northern Pacific RR, became the first northern transcontinental line. It had its birth in an Act of Congress signed by President Abraham Lincoln on 2nd July, 1864. Commissioned to build a railroad to open up western development, the Northern Pacific was to run from Duluth, Lake Superior to Puget Sound in Washington State. Land grants were provided in this virgin territory which was sold by the company to finance progressive building. Construction began simultaneously in Minnesota, at Portland, Oregon and Tacoma Washington, the latter using materials fetched by ship via Cape Horn. Throughout Montana Territory the railroad employed General Custer to protect construction crews from Indian attack. The company was bankrupt in the crash of 1873 but after a 5-year delay, construction was recommenced and completed in an eastwest track joining ceremony at Gold Creek, Montana Territory on 8th September, 1883. Rapid growth of the North West Territories follow- A switchback line was initially built to cross the difficult Cascade Range until completion of the 2.9km Stampede Tunnel section in 1888. While businessmen bought and sold the company, introducing a number of re-organisations and a technical name change , the Northern Pacific's engineers forged ahead in the development of heavier, longer and more powerful steam locomotives. One, the 2-8-8-4 Mallet 5000 class at 568 tonnes, was claimed to be the heaviest locomotive ever built [or likely to be). Built in 1928 by the American Locomotive Company [ALCO) this loco was 38.1 metres (125 feet) long and 4.98 metres (16 feet 4 inches) high. As an aside, readers may not realise that a loco of such height could not run anywhere in Australia where overhead electric wiring exists, as the loco would be higher than our minimum overhead contact wire height of 4.572 metres. This was a big loco. Another classic steamer was the No. 2760 4-8-4 express locomotive, regarded by many buffs as a beautiful example of heavy engineering. Made by Baldwin and called the "Northern" class, it was copied under that name by most other US railroads. At 231.8 tonnes, with two cylinders 710mm in diameter and 810mm stroke and fed with steam at 300psi, the "Northern" developed a tra ctive effort of 36.3 tonnes (80,000 lbs). On the flat prairie lands it regularly achieved 160km/h , at which speed it fHIS NORTHERN PACIFIC STEAM LOCO was the world's heaviest. Built in 1928, it weighed over 560 tonnes and was over 38 metres long (125 feet). Note the height of the man standing beside it. 88 SILICON CHIP AMERICAN LOCOMOTIVE POWER IN THE late 1960s: five Great Northern diesel electrics, developing 11,750hp, haul a long freight train across the 546-metre long Gassman Conlee trestle in North Dakota. developed a maximum 3.952MW (5300ihp). Three competitors These three railroads, the Burlington, the Northern Pacific and the Great Northern, simultaneously competed and co-operated with each other, as each fed the other business over their territories. And just as no public company is inviolate, these "big three" railroads bought and sold each others shares. In 1901, the Northern Pacific and Great Northern cojointly purchased on the stockmarket over 90% of Burlington's shares, giving them control, though all three continued competing while trading separately under their own names. During this period great technical advances were pushed forward by all three companies. The Burlington operated the first printing telegraph (which gave birth to the modern teletype) in 1910. In 1915 they were the first railway to use train-to-ground radio communication from a radio transmitter at Riverside. Of course this was still in the days of morse code operation. Centralised traffic control, using one central signal box to control long sections, was in use in 1927, one of the first in the world. By 195 7 over 2500km of track was controlled by this advanced signalling method. Pioneer Zephyr The Burlington was the first railroad outside Germany to use streamlined diesel electric express trains. The "Pioneer Zephyr" was placed in service on the Burlington Railroad in 1933 and subsequently, in January 1934 commenced a regular service from St.Paul to Min- neapolis and on to Chicago. As our photo of the original train shows it was a radical departure for trains of the time. The train's high speed diesel engine was directcoupled to a DC generator driving the head-end traction wheels. After only five months' operation, the Pioneer Zephyr train demonstrated its high speed endurance capabilities by running non-stop over the 1600km from Denver to Chicago, setting many world records. The top speed attained on that run was 180km/h and the cost of the diesel fuel used for the whole 1600km trip was only $14.64 (in 1934 US dollars). The Burlington introduced road freight diesel electric locomotives in 1944 and within nine years they had replaced 95 % of its steam locos. Cheap diesel oil in the early 1950s accelerated the demise of steam. The biggest ever electrics The Great Northern, pleased with its previous success with the M AY 1989 89 long Cascade tunnel. Ventilation shafts now allow modern diesel electrics to run through the tunnel and the whole mountain line. Northern Pacific developments THIS WAS THE BURLINGTON ZEPHYR which was the first high speed streamlined diesel electric in service in the USA. While it looks ugly today, it was regarded as the utlimate in streamlined styling in 1934. It ran at speeds up to 180km/h. In 1930 the Northern Pacific introduced petrol-electric passenger locomotives. Perhaps better called a "rail car", these unusual 86-tonne units had a petrol engine direct-coupled to a DC generator, with DC traction motors in the bogies. They were built at a cost of $80,000. Full diesel electric locomotives like the 2802 Co-Co class, generating 2.24MW (3000hp), and the larger 3611 class Co-Co units modernised the NP. These were a far cry from the very early days of lightweight steamers when on one occasion, in 1881 before the Missouri river bridge was built at Bismarck, Dakota, railtracks were laid directly across the frozen river ice. Burlington Northern ,.;:;;.~ . "'•' THIS UGLY-LOOKING BEAST was a petrol electric railcar cum loco put into service on the Northern Pacific railroad in 1930. 5012 class electric locomotives in the Cascade tunnel region, introduced the 5018 class in the 1940s. In the process, they set a still unbroken record for the longest and heaviest electric locomotive ever built. Built by General electric, these 31-metre long 362-tonne giants developed 3.73MW (5000hp) at their 16 driving wheels. Their 2-DD-2 wheel arrangement, though not unique, is unusual. They drew up to 540 amps from the 1 lkVAC 90 SILICON CHIP overhead conductor when starting a freight train. GN dieselisation The changeover to diesel locos came in the late 1940s and 1950s. This process eventually saw not only the demise of the beautiful examples of the steam builder's art but also ultimately killed off the electric locomotives. Sadly (perhaps unwisely?), all overhead wiring was torn down from the electrified section, including even the Our story comes to a climax in 1970 when all three railroads, the Burlington, the Northern Pacific and the Great Northern, merged into one, forming the greatest single railroad in present-day America. The name chosen for this megalith was Burlington Northern. They run the longest lines in the USA, stretching from Seattle in Washington State to St. Louis to Chicago to Galveston, Texas on the Gulf of Mexico. Burlington Northern today caters for every kind of user, including shipping in the Atlantic and the Pacific. The shipping interests were originated by the Great Northern from its very beginning and continue today. They even have freight depots in every Australian capital city. ~ Acknowledgement: thanks to the Burlington Northern, to former staff of the Great Northern, Northern Pacific and the Burlington Railroads and especially to Pat Stafford of River Falls, USA for information and photos. Don't miss a single issue IF YOU'RE THE KIND OF READER that can't wait to get the next copy of SILICON CHIP, then why not have the magazine delivered direct to your door? Each month, we'll bring you the best and brightest electronics magazine in the business, put together by Australia's most experienced team. * * * * * * Convert l CB radio for amateur use Constructional Projects for the Enthusiast Hili review: Yamaha's brilliant new CD player the Original & 8:est IV Servlee rt1,:1n, Vintage Radio, The Way I See !t, the Evolution of Electric Plus - Railways Amateur Radio The Serviceman's Log Vintage Radio The Way I See It Hifi Features & Reviews FREEPOST * SUBSCRIPTION COUPON □ □ New subscription Renewal Start in _ _ _ _ _ __ Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Street_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ __ 1 year (12 issues) □ $A42 Australia 2 years (24 issues) □ $A84 NZ & PNG (airmail) □ $A65 □ $A130 Overseas surface mail □ $A62 □ Overseas airmail □ $A 120 $A130 □ $A240 Enclosed is my cheque/money order for $. _ _ _ or please debit my □ Bankcard Card No. □ Visa Card □ MasterCard Subscription Hotline We can accept your subscription order by telephone. Just ring us on (02) 982 3935 and quote your Bankcard or Visa Card number and the expiry date. Detach and mail to : FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 I I I I I I I I I I I I I I I I I Signature _ _ _ __ _ _ _ _ Card expiry date_ _ / __ /_ _ • No postage stamp required in Australia. W dft.J I ~------------------------ -------------~ MAY 1989 91 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Wants upgrade for 24/12V converter With regard to the 24V to 12V DC Converter (SILICON CHIP, December 1987), what modifications may be made to improve the power output? I would like to modify the unit to deliver up to 20 amps or possibly build a new unit with upgraded ratings. I make the request on behalf of many campervan and motor-home owners and owners of vehicles equipped with 24V systems. I am currently converting a Nissan Civilian bus to a motor-home and wish to dispense with gas equipment on board where possible. It is of course equipped with a 24V supply, hence my query. The units on-board which are of concern are: 150-litre 12/240V refrigerator; 12V evaporative cooler; l00W radio transceiver; 12/240V TV set; and 12V car radiocassette player. All this equipment should ideally be operational, both stationary and on the move, from the vehicle power supply. I am also carrying a portable lkW power unit capable of supply- Sound effects for model railroads I have been dabbling with model railway sound effects since transistors and miniature loudspeakers made it possible to house such systems in a model locomotive. The best I've done with an on-board sound system is a diesel engine sound similar to that described by you recently, housed in an 0-gauge locomotive. As you pointed out, a small speaker cannot reproduce the sounds realistically. I do not find the system of placing speakers around the layout very convincing and have adopted another approach which you 92 SILICON CHIP ing 240V AC but it is not considered to be a proposition for mobile operation. I would appreciate any assistance you may be able to provide. [H. B., Karrinyup, WA). • We don't believe a 20A device would be a very practical device for us to describe as it would require very expensive output devices and filtering components. Instead, it would be more practical to build a number of 24V to 12V converters (our present design can deliver up to 5 amps) to run the appliances you have. Alternatively, if you need to run all these appliance together, we suggest installing an additional alternator and a separate largecapacity 12V battery. Loop system for PA work I am writing to you for advice on a loop system to be connected to the speaker line of a PA system so that people wearing suitable hearing aids can pick up the amplified signal from the loop. Am I on the right track with the following theory?: run 6 or 8 turns may care to take up. The technique is to provide each driving position with heaphones through which the sounds are reproduced. Of course, this is of no use for spectators but the effect for the driver is magnificent - with very little imagination he is inside the locomotive. You could easily test this for yourself by connecting headphones to the system you have described in the December 1988 issue. [N. C., Pascoe Vale, Vic). • Thanks for your letter about your headphone system of producing loco sound effects. It sounds like a really good system and we'll give it a try at the first opportunity. of hook-up wire around the perimeter of the auditorium or under the (wooden) floor to form a "loop", then measure the DC resistance of the loop and approximate this reading to the reactance of the loop, then use a suitable line transformer to match the loop to the speaker line. I have not seen any information about this subject and would appreciate an article in SILICON CHIP. (R. T., Jindalee, SA). • We understand that some churches and auditoriums do have audio loop systems installed as aids for the partially deaf but we've not had any firsthand experience. However, such a loop would undoubtedly present a low impedance load to the driving amplifier and so normal line [eg, lO0V) transformers would not be necessary or desirable. It should be possible for the amplifier to drive the loop directly. If other readers have had more experience with such systems we would appreciate more info. Parts for diesel sound simulator I read the article on the Diesel Sound Simulator in the December 1988 of SILICON CHIP but have been unable to locate any supplier who has it in kit form. Could you please advise me if anyone sells this unit as a kit? [I. M. , Inverell, NSW). • We don't know of any supplier who sells this project as a complete kit but you shouldn't have any trouble buying the parts. For example, all the semiconductors, including the MC3340P DC attenuator and the photo-interruptor, are available from Geoff Wood Electronics (phone 02 427 1676). The PC boards can be purchased from any one of the suppliers listed at the back of this magazine. The rest of the parts can be purchased separately from any one of the major retailers. Query on the FM stereo transmitter I would like to use the FM stereo transmitter (SILICON CHIP, October 1988) in a public speak. ing application, in conjunction with a portable recording Walkman. I have a Sony ECM-144 electret condenser microphone and a Sony WM-F36 Walkman. I plan to use this setup to record presentations I give in Toastmasters' clubs. Sometimes I will also need to feed a signal to a public address system which is the reason for the enquiry. Could you recommend a circuit that I could use to either tap the microphone output before it goes into the W alkman or from the output. I would prefer to tap into the microphone as it is a mono unit and I am going to have to make an adapter for the recorder which has stereo inputs. The microphone output impedance is 2.7k0 unbalanced and the WM-F36 Walkman has a quoted input sensitivity of 2.5mV ( - 50dB) for a low impedance mic. One other point is that I have been told that wireless microphones which do not have a crystal controlled transmitter frequency are unstable. Has it been your experience that this Loudspeakers in cavity walls I do enjoy your magazine which seems to be the only one left that caters for electronics enthusiasts who derive their pleasure from actually building things. I am writing to suggest some topics which I would find interesting. The first concerns loudspeakers. We all like good quality music but most wives dislike loudspeakers on the grounds that they are ugly, take up too much space and have wires. Why can't they be built into cavity walls? Most expensive car sound systems which claim all sorts of things about high design exhibits this problem? I am very pleased to see that you have maintained the very high standard for the magazine that you started out with in 1987. It is the best electronics magazine in Australia. (D. H., Annandale, NSW). • Your proposal to use the FM stereo transmitter in a public address application presents a few problems. First, you would need a preamp stage to boost the signal from your microphone to line levels, to suit the FM transmitter. The preamp would probably need a gain of 100 or so and there preferably should be some sort of automatic level control so that the transmitter operates at a good average level of modulation. Second, while it is possible to record from an FM transmission with the Sony WM-F36, it is not easy to connect the signal available at the headphone socket to a PA amplifier. The problem is that the headphone wires act as the antenna and if you disconnect the headphones you can't pick up the signal. This means that you need an interface circuit to provide a separate antenna for the W alkman. The FM stereo transmitter will not be as stable as a crystal controlled transmitter. However, any drift that it does have should not cause .any problems over the quality do that with speakers mounted in doors. The second is about in-circuit testers which can be used with oscilloscopes and give different patterns according to what they find. 1 built cme but found that while the results were interesting it is not all that useful. The cost of my tester was about $5 but I have seen an advertisement for a CRO which has an inbuilt tester for about $500 extra. This suggests that there are in-circuit testers with different levels of sophistication and I would like to learn more. The third topic is probably an old chestnut and concerns recharging short times that you would be using it, even if it was for an hour or more. There is a bigger problem with wireless controlled microphones in general and that has to do with lack of stability of the transmitted signal as the speaker moves about the room. This is partly because of varying signal propagation as the user moves around the room and partly because user movements cause the transmitter's tank circuit loading to vary. This inevitably causes the transmitter to vary in frequency. Crystal controlled wireless transmitters do not have this problem. Having said all ~hat, is there any reason why you can't plug your microphone directly into the Walkman and carry it about with you as you speak? You could then plug the headphone output of the W alkman into the FM stereo transmitter and solve the PA problem that way; ie, feed the recovered audio signal from an FM tuner into the line input of a PA system. You might object to carrying both the FM transmitter and a W alkman but it could be the most practical solution. In the meantime, we will give some thought to the concept of a crystal controlled wirele ss microphone. dry cells. I am enclosing a circuit which you might like to develop. I'm going to make one just to find out if it really does work. (M. F., Frenchs Forest. NSW). • Your point about loudspeakers in cavity walls is interesting. It used to be quite the fashion in American publications in the 1960s although generally the systems to be built in were of very much larger capacity than today's models. Many current model speakers could easily be built into wall cavities but we're not sure whether they would sound as good as conventional floor mounting systems on stands. If you were starting from scratch we have no doubt that a tweeter MAY 1989 93 Advice on the Minstrel speakers I am in the market for my first hifi system and intend to build the Minstrel 2-30 loudspeakers (SILICON CHIP, February 1989). More specifically, my aim is to construct the crossover networks and speaker cabinets. Before I can commence the crossover however, I need to iron out a few details. I refer in particular to the electrolytic capacitors in the crossover networks. From the text and diagr.ams, I was unable to determine the voltage ratings of Cl, C2 and the 16.8µF capacitor. In addition, I could not determine the impedance of either the woofer or the tweeter. and woofer combination installed in a. large sealed cavity would perform very well. The problem with such an arrangement is that it is not too practical if you want to move house. Why not take another approach to making loudspeakers less obtrusive - a bass subwoofer with very small satellite speakers? Thanks for the copies of the articles on an in-circuit component tester and dry battery recharging. Did you see the dry battery recharger on page 38 of the January 1989 issue? We haven't had experience with in-circuit component testers so we can't state whether they are worthwhile or not. Tri-wing screwdriver bits for appliances I found the article on "Screws & Screwdrivers" in the November issue most interesting and I agree with many of your comments about tamperproof screws. However, my specific question involves Tri-wing screws. I have a number of appliances which use these screws and when I attempted to order a Tri-wing bit from a specialist supplier they said that Tri-wings came in five point sizes. The question is, which point size 94 SILICON CHIP Could you please supply the relevant voltage ratings and impedance values? • . The voltage ratings are not critical. We used metallised polyester capacitors for Cl and C2 and these were rated at lOOV DC. There is no such beast as a 16.8µF capacitor. As shown on the circuit and wiring diagrams, this value is obtained by connecting a lOµF bipolar electrolytic and a 6.8µF bipolar electrolytic in parallel. Both of these capacitors were rated at 50V DC. The woof er and the tweeter each have a nominal impedance of 8 ohms. However, you should note that the crossover network was specially designed to suit the drivers specified. If you use do I go for? I have a number of appliances made by Black & Decker and Hotpoint but I can't get the screws out so I can't even send the suppliers a sample screw to help select the right bit. Please help. (I. F., Kempsey, NSW). • In our experience, one size of Tri-wing screw is widely used in electrical appliances. You should use point size 3 to fit them. Problem with Vader Voice I would like to ask about the PCB pattern for the Vader Voice described in the September 1988 issue of SILICON CHIP. I have made this project up but cannot get it to work, although the oscillator is operating. On checking for faults I found that on the PCB pattern pins 14 & 15 of IC2 are joined together whereas the circuit diagram shows pins 15 and 16 joined together, with pin 14 being the signal input. I have corrected this situation trackwise and there does appear to be some distortion but behind the sound there is a high-pitched whistle which I would estimate to be above 3.5kHz. Do you have any suggestions please? (G. W., Granville, Qld). other drivers, the sound quality could be compromised. Ready-built crossovers are available from Jaycar Pty Ltd. These are supplied along with the four drivers and all other necessary bits and pieces (but not the cabinets) for $149.00. The cabinets are available separately for $129.00 for a pair in kit form. Alternatively, you can buy ready-built crossover networks from Nelson Components Pty Ltd, 18/59 Moxon Rd, Punchbowl, NSW 2196 (phone 02 709 5296). If you do elect to make your own crossovers, Nelson Components can supply pre-wound coils and all other individual components. The drivers are available separately from Jaycar. • Yes, there is a discrepancy between the parts layout and circuit diagrams but this has no effect on the circuit operation. The 4051 is used here simply as a single-pole double throw (SPDT) switch which is toggled between the AC output of microphone preamp ICla and OV. The fact that pin 15 is tied to pin 14 rather than pin 16 therefore has no bearing on the operation of the circuit. When it is operating in the Vader mode but with no speech present only a faint reedy whistle should be audible from the loudspeaker . If the whistle is loud, you probably have a fault which could be nothing more serious than a short between tracks, say between pins 11 and 13. The main problem with this circuit is making sure there is sufficient acoustic isolation between the electret microphone and the speaker. Provided acoustic feedback is minimised, the sound quality in the non-Vader mode is quite good. Notes & Errata Stereo Compressor for CD Players, March 1989: the two 470µF electrolytic capacitors used in the power supply are shown reversed on the wiring diagram (Fig.4). The circuit diagram (Fig.3) is correct. Silicon Chip Back Issues November 1987: Car Stereo in Your Home; 1 GHz Frequency Meter; Capacitance Adapter for DMMs. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars ; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier ; Breakerless Ignition For Cars ; Mega-Fast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid ; Booster for TV & FM Signals ; The Discolight Light Show. August 1988: Plasma Display ; Remote Chime/Doorbell; High Performance AC Millivoltmeter ; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Switchmode Charger for 12V Gel Batteries; Vader Voice . October 1988: Stereo FM Transmitter ; High Performance FM Antenna; LedLight House Number ; Matchbox Crystal Set. November 1988: 120W PA Amplifier Module; Poor Man 's Plasma Display; Car December 1987: 1 00W Power Amplifier Module; Passive lnfrared Sensor; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter. January 1988: __.----;..._,.. - owtie UHF Antenna; r ki wer Supply; Custom nger ; Subcarrier Adapter for M Tuners. February 1988: 200 Watt Stereo Power Amplifier ; Deluxe Car Burglar Alarm ; End of File Indicator for Modems. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber ; Endless Loop Tape Player . April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools ; Slave Flash Trigger; Headphone Amplifier for CD Players. Safety Light; How to Quieten the Fan in Your Computer. December 1988: 120W PA Amplifi er ; Diesel Sound Generator; Car Antenna/Demister Adaptor ; SSB Adaptor for Shortwave Receivers. January 1989: Line Filter for Computers : Proximity Detector for Cars; How to Service Car Cassette Players. February 1989: Transistor Beta Tester; Build the Minstrel 2-30 Loudspeaker System; LED Flasher for Model Railways. March 1989: LED Message Board; 32-Band Graphic Equaliser ; CD Compressor ; Amateur Band FM Receive r: Map Reader for Trip Calculations. April 1989: Telephon e Bell Monitor, Transmitter; Au xiliary Brake Light Flasher Circuit; Building th e 3 2-Band Graphic Equaliser. - - - - - - - - - - -------- - - ---HACK ISSUES ORDER FORM - - - - ·- · ·--·- ··- ··-·-· - · Please send me a back issue for: 17 March 1 988 □ April 1988 n n August 1 988 n September 1 988 January 1989 17 February 1 989 n n n May 1988 n n October 1 988 I I November 1 988 November 1 98 7 I I March 1989 December 1 98 7 June 1988 n n February 1 988 July 1988 I I December 1 988 I I April 1989 n Enclosed is my cheque/money order for $ _ _ _ _ _ _ or please debit my [l Bankcard Visa Card I I MasterCard Card No I Price: $A5.00 each (includes postage) . Overseas orders add $A 1 .00 per issue for postage. Signature _ _ _ _ _ _ _ _ _ __ Card expiry date_ _ / __ / _ _ NZ & PNG orders are sent by air mail. Name _________________ _ _ ____ _ _ _ _ (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS Street._ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ __ _ __ PO BOX 139 COLLAROY BEACH Suburb/town, _ _ _ __ __ _ _ _ _ _ _ Postcode___ _ NSW 2097 '- - ·- ·- -· -· - · -·- - - - - l I -------------------------~ I\ I.\ Y l!lll!J 95 CEN'l Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word ; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing d;i.te: 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 , l,)Ut one word on each of the lines below and send this form with your payment to : Silicon Chip Classifieds , PO Box 139, Collaroy Beach, NSW 2097 . PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) 16 ($740) 17 ($7 80) 18 ($8.20) 19 ($8 60) 20 ($9 .00) 21 ($940) 22 ($9.80) 23 ($10.20) 24 ($10.60) 25 ($11 00) 26 ($1140) 27 ($11.80) 28 ($12 20) 29 ($12 60) 30 ($1300) Name .. ..... .. . .. .... .. .. .. . ... ... ... ... . .. . .. ...... ......... · · · ··· · •• · •• · ·· · · ·· · Address Postcode Suburb/Town Enclosed is my cneque or money order for$.. Bankcard D Visa Card D MasterCard or please debit my D Card No I I Signature ..... ... Card expiry date .... .. ./ ... .. . ./ .. FOR SALE 1 MEG PRINTER BUFFER KIT - REV H boards now available . Supports SK to 1 MEG. $39 kit consists of doublesided PCB, EPROM and instructions. Optional additions include 2 x 7 -segment LED front panel display of percentage full, 1 to 99 copies select, 3 polled computer inputs, printer switches , computer switches_, and serial converter boards. For a free catalog send a 39c stamp to Don McKenzie ; 29 Ellesmere Crescent, Tullamarine 3043. RADFAX 2: HI-RES RADIO facsimile, Morse and RTTY program for IBM 96 SILICON CHIP PC/XT/AT on 360K 5.25-inch floppy plus full documentation. Need CGA, SSB HF, FSK/tone decoder. Has re align, auto-start, view , save, print . Also " RF2HERC" same as above but suitable for Hercules card and "RF2EGA" for EGA card (640 x 350 mode) . Programs are $30 each plus $3 postage . Only from Michael Delahunty, 42 Villiers Street, New Farm, Qld 4005 . Phone (07) 358 2785 . SERVICES HI-TECH STEREO AMPLIFIERS built. Reasonable prices. For full details send SAE to 36 Palmer St, Nambucca Heads, 2448 . Advertising Index Allied Capacitors 79 Altronics 58-61 Arista Electronics 47 Avtek 80 Chapman, L.E. 23 Dauner Electronics 83 David Reid Electronics . . . . . 43 Dick Smith Electronics 10, 11 Electronic Solutions 3 Elmeasco . . . . . . . OBC Geoff Wood Electronics . 25 Goldstar . . . . ·.... IFC Hycal Instruments . 27 Jaycar Electronics 28-31 72-75 J.V . Tuners . . . . . .. . 15 Kepic . . ...... . . . .. . . 19 RCS Radio . 37 Rod Irving Electronics IBC PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd , 651 Forest Rd , Bexley, NSW 2207. Phone (02) 587 3491. • Jemal Products, 5 Forge St, Welshpool , WA 61 06. Phone (09) 350 5555 . • Marday Services, PO Box 19-189 , Avondale, Auckland , NZ. Phone 88 5730 . ELECTRONICS ENGINEER: analog , digital , power design , prototypes. $35 per hour. Phone (059) 96 4353 AH. BOOKS & PLANS LOW SPEED GENERATORS for windmills, water turbines, steam engines. The definitive book: " The Homebuilt Dynamo" (1987) , 182 pages, 8 .5" x 1 2", hardback. Generator design and construction with ceramic magnets. Complete plans, 268 photographs, step-by-step construction details. $A85 .00 postpaid airmail (brochure $A5.00 refundable). Todd-Forbes Publishing , 6 27 West Coast Road , Oratia, Auckland . DIGITAL METER • Autoranging operation • Data•hold for eas y readout • Full range protection • Serv ice temperature and hu m idity =0 - 40 C and bel o w 80°·0 RH • Dimension & weight =133 x 29 x 17mm and 60g approx "NEW KITS!" Q11270 .... ........ .. .... ..... $69 DIECAST BOXES Di ecast bo xes are excellent tor RF shielding. and strength . Screws are pro vided with eac h bo x. H1 1451 100 H1 1452 110 H1 1453 120 H11461 120 H11462 188 H11464188 SURGE BUSTER 6 PROTECTED POWER OUTLETS Idea l for protectin g personal co mpute rs, video equipment. colour TVs . amplifiers, tu ners. graphic equalisers. CD pla yers etc SPECIFICATIONS: • Electr ical rat ing : 240V AC, 50Hz. 10A • Complies wi th Au strali an Standards. App rova l No.10084 • 3 x Metal Oxide Vari stors (MOV) • Su rge Spike Rating (ea ch MOV): 4.500 amps (8 x20us) • Energy Absorb. Factor each MOV: 75 joules (10 x 1000us) • Maximum clamping Voltage : each MOV: 710 volts at 50 amp s • Response time : Less than 25 Nanoseconds . RCA GOLD PLATED CHASSIS SOCKET PC DRIVEN FUNCTION GENERATOR Here's a simpl e and low cost little unit w hi ch lets yo u use your pe rsonal computer to genera te sig na ls wit h almost any conceiva ble w aveform . It hook s up t o th e c ompu ter v ia a standa rd Centronicstype pa rallel printer port. making it compat ible with almo st an y kin d of c omputer. Building and using it will also gi ve you va lu abl e insight into th e growing trend towa rds co m p uter-driven te s t instrument s. too! Softwa re inclu ded. (EA JAN 89) CAPACITANCE ADAPTOR FOR YOUR DMM This clever adaptor c irc uit plugs into yo u r dig ital m ultimeter and can mea sure capacita nce up t o 2.2 mi c rofarad s. (SC NOV 87) K88119 ....... ... .... .. .. $24.99 K88111 .. ...... .. .... ... ... .... ..... .. .. .... ..... ..... .......... ...... .$49.95 .:_~~=-- / Thi s wa lk around th r ottle offers a hos t of featu res inc luding Price Z1 0141 3mm Z10143 3mm Z10 145 3mm Orange .. $0.20 2 101 50 5mm Red 2 101 51 Z10152 5mm Orange. HANDS FREE SPEAKERPHONE Here's a hand s-free te leph o ne that an yon e ca n afford. With the s peakerpho ne yo u can have relaxing co n ve rsation s w ith o ut th e ,I' • • $0.85 • • SYDNEY: 74 Parramatta Rd . pulse power, inertia (momentum ), brakin g and full Stan more. 2048. Phone (02) 51 9 3134 Fax (02) 519 3868 ove rl oa d prot ect io n. MELBOURNE: 48 A' Beckett St. Phone (03) 663 6151 K88122 .... ..... ... .. .. .... ... $89 NORTHCOTE : 425 High St. .... ...$0.10 need to hold the ph one to your ea r. And if y ou are put o n "hold" you ca n continu e w it.h you work wh ile you wait. (SC SEP 88) 5mm Gree n .. .. $0.15 K88130 .. ... .. ............ .... ..... .... .. ........ .. .... .. ......... ... .... .. $89 PRINTER BUFFER CLAYTON : 56 Renver Rd. $0.15 _., CANNON TYPE CONNECTORS AT SPECIAL PRICES !! Cat. no . Descripti_o n Ill -·~ -·- P1 0962 3 p,n chass,s male$2.40 P10964 3 pin chassis lemale$3.25 OU-..< _,, • H•snm, (~ • w ipe for reliability. Description 1-9 8 pin .... .... .. .$0.20 14 pin ... .. .. .. .$0.25 16 pin .. ...... . $0.35 18 pin .... .... $0.40 20 pin ......... $0.40 22 pin .. .. ..... $0.40 24 pin ........ . $0.40 28 pin .... .. .. . $0.50 40 pin .. ... $0.50 1O+ $0.15 $0.20 $0.20 $0.30 $0.30 $0.30 $0.30 $0.40 $0.40 (:' S,11 ' """"'-"D G " ~ ••--0 c_...1••- .. _~ .,..,_.tR ..........__ - H_.,. ,::cs,u.• ATTHII Thi s exte rnal printer b uffer wi ll allow two c ompute rs t o share on e printer w ithou t th e bothe r of swapping cable s. With o ut exc iting lig ht show effects • with th e Discolighl tran sis tor break d own vo ltag es . Great for the wo rk bench , and also for sh owi ng how semic onductor dev ices ope ra te. (EA FEB 88) K88013 .... ... .. .. .. ..... $54.95 PCB SHORTS LOCATOR Here is a simple circuit to help you locate sh o rted tracks on printed circuit boards , by mea ns of a varying aud io tone. It is easily built and will cost you a lot less than equivalent commercial units.( EA FEB 89) K88015 ....... ... ....... .$,22.95 Phone (03) 543 7877 MAIL ORDER& CORRESPONDENCE: PO Box 620 . CLAYTON 3168 Order Hotline : 008 33 5757 (To ll free . stri ctly orders only) Inquiries (03) 543 7877 Telex AA 151938 Fax (03) 543 2648 HIGH IMPEDANCE AC/DC MILLIVOLTMETER (SC AUG 88) K88 125 ..... .... ..... .. ... .. ........ ........ .... .... ... .. .. ...... .. ...... $159 as well as tran sistors and FETs, and also lets you c heck K56012 ... ....... .. .. .. $139.95 Dynami c Ram (extra) .... .. .... $1 50 ""'1~ is alway s a top li ght show. Now you can have many of th ese This tes te r c hecks ze ner diodes Save a small fo rt une on these " Direc t Import" low profile le sockets! PCB mounting solder tail. All tin plated phosphor bronze or berryllium and dual (:, -=ED .us,c Th ese days w hen you go to hea r your favourite band or disco there LOW COST TESTER FOR TRANSISTORS, FETS & ZENERS LOW PROFILE IC SOCKETS Phone (03) 489 8866 dynamic ram (Ell 1620 FEB 89) - • ,. ........L O ~ L l " " " ' " " E L I DISCOLIGHT SC Price P10960 3 pin line male ...... $2.90 • RI TRONICS WHOLESALE . 56 Ren ver Road . Clayton . Phone: (03) 543 2166 (3 lines) Fax (03) 543 2648 (SC APR IL 88) ~ Cat. No. P10550 P10560 P10565 P10567 P10568 P10569 P10570 P10572 P10575 '' , ,,,, ,,, ,, ' " 'f f// ..,_ WALK-AROUND THROTTLE FOR MODEL QUALITY LEDS .....$0.15 Green ... $0.20 Yellow ...$0.20 • $0.90 All sales ta x exempt orders and wholesale inquiries to : ,...- -•·-·""" 3mm Red. ·•·e··_··. :r··:1: $1.00 RODIRVING ELECTRONICS ------==--:: ::::=• Des c ripti o n Fo r the ultimate c onnection ! Cat. no.P10229 Normally $1 .75 1-9 10+ 100+ ••• X10086 .......... ... ... .. ... $69.95 Cat. no . 210140 x 50 x 25mm .. .. $5.95 x 60 x 30mm .... $6.50 x 65 x 40mm .... $6.95 x 94 x 53mm .. $11 .50 x 120 x 78mm$1 3.50 x 188 x 64mm$29.50 AUTOMOTIVE BRAKE LAMP MONITOR Here·s the project that won first prize in the Newcomer sec tion of the recent Grand Aussi e Hobby Electronics Contest. Low in cos t and easy to build , it warn s you if your vehicl e's brake lamps aren't wo rking as they should• hopefully before anothe r motorist ram s into your rear end! (EA MAR. 89) K89030 .... ... ....... .... $24.95 HEAD PHONE AMP FOR CD PLAYERS Does you r compact disc player have a headphone so cket? Now you ca n c orrect that s ituation and listen to the mu sic dire ct, With negligible circ uit loading (EA DEC 88) K88020 ... .. ... .... ..... .$44.95 TV COLOUR BAR AND PATTERN GENERATOR ORDER HOTLINE Here is a design fo r an easy to 008 335757 build col our bar and test pattern generator, su itable for servicing closed-c ircuit or amateur TV. It pro v ides high perfo rm ance at a very reasonable co s t. (EA OCT 87) K87100 ... .... .. .. .... $156.95 NOISE GATE Elim inate annoying audio noises (ETI 1429 FEB 89) K54215 ............ ...... $49.95 HIGH ENERGY IGNITION SYSTEM Are you still cleaning points, adju sting the dwell , c hecking timin g and all that automotive drudgery? Now y ou c an fit this without degrading th e sound quality (SC APRIL 88) High Energy Ignition System and forget those tun eup hassles (SC SEP. 88) K88120 ...... ... .........$24.95 K88135 ..... ............. $49.95 (TOLLFREEJ STRICTLY ORDERS ONLY LOCAL ORDERS & INQUIRIES (03) 543 7877 POSTAGE RATES: $1 - $9.99 ............ ....... .. $2.00 $10 - $24.99 .............. $3.00 $25 - $49.99 ... ..... .. .... .. ... $4.00 $50 - $99.99 ... .... .... .... $5.00 $100 plus ... .. ......... .. S7.50 The above postage rates are for basic postage only. Road Freight. bulky and fragile items will be charged at different rates . Errors and omi ssions excepted . Prices and specifications subject to change. 1sM ·. PC . xr . AT ". are registered 1rademarksol lnternallonal Bus111ess Machines •Apple ,s a trademark ·Denotes regis1ered tradmarks of then respective owners registered [E S] V/£4