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Metrix 50 Series • Comprehensive Display with Analog Bar-Graph • 5000 Count Digital Display • Patented Live-Tren(frMMode Shows Instant Values • Storage of Up To 5 Different Readings • Surveillance Mode • Models with dBs and Frequency to 500kHz From $275 Metrix 40 Series • Exceptional All-Weather Performance • Four Year Warranty • 4000 Count Resolution • Autoranging with Manual Override • Hold & Peak Functions • True RMS AC or AC+DC • Safe to IEC348 Class 11 •4~ 'Ot- '"C from$195 ~0 v..rffIii __r..;::::~ r;·f m.~. C _ ,..cnt.\ ::.J \Of>. \,,.-"""' ~ From the home of the Mercedes Benz and BMW comes Metrix - Europe's Favourite Multimeters Metrix MX573 Metrix MX1200S & MX200 Clamp-On • True Analog and Digital • True RMS ac • 25kHz Bandwidth for Vac • Auto-Polarity Switching • Taut Band Linear Scale Analog Mo vement • 2000 Count Digital LCD Display • Power Measurements • Current Ranges to 200A/100A • Frequency to 1kHz • Resolution as lo w as 10mA • Analog Output $595 $770 Also ask about the MX545 Series anc MX579 Benchtop Multimeters and a Wide Range of Probes & Accessories ELMEASCO Instruments Ply.Ltd. Australia's Leading Test & Measuring Instrument Company NEW SOUTH WALES 18 Hilly Street, MORTLAKE P.O.Box 30, CONCORD NSW 2137 Tel : (02) 736 2888 Telex : AA25887 Fax : (02) 736 3005 VICTORIA 12 Maroondah Highway, RINGWOOD P.O.Box 623, RINGWOOD VIC 3134 Tel: (03) 879 2322 Telex ; AA30418 Fax : (03) 879 4310 QUEENSLAND 192 Evans Road, SALISBURY P.O.Box 274 SALISBURY QLD 4107 Tel; (07) 875 1444 Fax; (07) 277 3753 SOUTH AUSTRALIA 241 Churchill Road, PROSPECT P.O.Box 154 PROSPECT SA 5082 Tel; (08) 344 9000 Telex ; AA87519 Fax : (08) 269 641 1 W. AUSTRALIA 32 Teddington Road , VICTORIA PARK, W.A. 6100 Tel : (09) 470 1855 Fax: (09) 470 3173 Pricesquoteddo notinctude Safes Tax and are subject to change without notice OUR NEW 16-CHANNEL FEBRUARY 1 990 MIXER has switchable balanced and unbalanced line inputs, equalisers on each input channel, effects and foldback facilities, and LED bargraph VU meters. Details page 18. FEATURES 10 Bose Noise Cancelling Headphones by Leo Simpson Electronics cancels the noise 78 PC Program For Great Circle Bearings by P. Watson You just punch in the co-ordinates 94 The Evolution of Electric Railways by Bryan Maher Pt.28: the French TGV fast trains PROJECTS TO BUILD 18 16-Channel Mixing Desk by John Clarke New design has equalisers on each input channel 32 A High Quality Audio Oscillator, Pt.2 by Leo Simpson Construction and testing THIS NOVEL UNIT will produce the sounds of two canaries singing together in a way which will intrigue you. Seven Schmitt triggers are all it takes to set the unit twittering. .See page 50. 50 The Incredible Hot Canaraies by John Clarke Schmitt triggers give it the twitters 62 Phone Patch For Radio Amateurs, Pt.2 by Greg Swain Final assembly and troubleshooting 74 Random Wire Antenna Tuner For 6 Metres by G. Cratt Tune up a long wire for optimum VSWR SPECIAL COLUMNS 6 ·Vintage Radio by John Hill Safety with vintage radios 14 Remote Control by Bob Young Transmitter encoders & black wire syndrome 44 Serviceman's Log by the TV serviceman Another song about Sam 68 Computer Bits by Steve Payor Some ideas on computer interfacing - ~ •- . ONCE UPON A TIME, the serviceman acquired a TV analyser. It sure came in handy this month. You can read about his self-inflicted agony by turning to page 44. DEPARTMENTS 2 Publisher's Letter 3 Mailbag 26 Circuit Notebook 60 Bookshelf 84 Product Showcase 90 Back Issues 100 Ask SIiicon Chip 103 Market Centre IBC Subscription Page OBC Silicon Chip Binders LOOKING FOR A random wire antenna tuner for the 6-metre (50MHz) band? This easy to build unit will solve those antenna hassles. See page 74·. FEBRUARY1990 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 (02) 982 9553 Regular Contributors Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill Jennifer Bonnitcha, B.A. Bob Young 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. Typesettlng/makeup: Magazine Printers Pty Ltd, Rozelle, NSW 2039. Printing: Macquarie Publications Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: currently $42 per year (12 Issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP POBUSHER'S LETTER On taking risks and picking winners This month we begin presentation of a project which represents our biggest R&D effort so far - our new 16-Channel Mixer. We believe that this project would represent a large investment for any commercial organisation but for us it has been very large indeed. We're very proud of it. From start to finish, it has been more than a year in coming. Such a large project is not without a considerable element of risk. There is firstly the risk that a fair number of readers may not be interested or impressed, or may even be turned off completely, because it doesn't contain some feature or other. Second, there is always the risk that the unit may have some bugs which will cause us some pain in the future. Still, these are the risks in publishing a technical magazine. These are risks that we gladly take on as we are here to push the technology forward. In fact, we take these risks every month to some degree. In the December issue for example, we published the Digital Voice Board using the new Texas Instruments TMS3477 chip. We did so because we thought it contained some very interesting new technology and therefore merited space in SILICON CHIP. We didn't think it would be popular with many readers. Well, we were completely wrong. Both we and the stockists for Texas chips were overwhelmed with the interest from readers. All Australian stocks of the TMS3477 chips were exhausted within days of the magazine going on sale. More than that, large back orders were placed on overseas sources. The expressions of interest, and orders, came from everywhere from technical people in security firms, PA and audio manufacturers, government railways and other instrumentalities, radio stations, and even the NSW Conservatorium of Music. With the benefit of 20:20 hindsight, it would have been nice to have cornered the market in TMS3477 chips. So sometimes you can be wrong and other times you can be right. Most of the time, luckily, we are right. This month we take the risks again, in particular with the mixer. We have spent a large amount of time and money designing and presenting it. However, while we think that many readers will be interested to read about its up-to-the-minute design, we don't think it will be built in very large numbers - perhaps hundreds at the most. But then, we could be wrong again, couldn't we? Leo Simpson MAILBAG More projects wanted for model railroads I thought that I would write and let you know what I think of the magazine and what I want from it. I am by no means an electronics engineer - more a person with an interest in electronics and who wants to put together reasonable projects that work. I know how to read resistor and capacitor codes etc, and can make some sense of the circuit diagrams. Having said that, I bought my first copy of your magazine for the model train controller which I subsequently built. My area of interest is model trains and computing and control electronics to this end. I would like to see more projects dealing with railroad control, points wiring, etc and simple computer control of functions. I also enjoy the series on electric railways and bought all the back copies to obtain the full series. Thank you for a good magazine and never loose track of the person with the technical details but a strong desire to get involved in projects. Daniel Pangrazio Beverley, SA Parts substitution: traps for the unwary I would like to reply to the letter from C.H. of Cooee, Tasmania regarding transistor substitution (SILICON CHIP), Sept. 1989). You must be very careful when making assumptions, first that the device you want to substitute for is in fact a transistor, FET or whatever else. The only way to be sure of the device is to get a list of the manufacturer's symbols and start from there. Only yesterday, I was faced with the problem of replacing a device in an automatic voltage regulator. Having ascertained that the collector? /base? was shorted, I removed the device to replace it. The next step was to get the device code off the substitution charts. The device was in a TO-39 case and was coded TC6001 S 8304M. It wasn't listed in any books under TC6001S, so the next set of letters came into play. These were found in a Tandy substitution list and· the equivalent was a 2N3053. Unfortunately, the circuit of 30 components still did not work so, after many tests, I went to the manufacturers code book and found that the device was made by Thompson. It wasn't a switching transistor at all as it turned out, but an SCR device. I rest my case, so be careful. I commend you on your magazine and would appreciate it if you would expand the "Electronics for Everyone" articles. Pt.2 about capacitors should be followed up with more information on monolithics, mylar, polyester, ceramics and polystyrene. For example, what is the difference in quality between the types and in which applications can they be used or substituted? Can a monolithic be used in place of a greencap in an audio circuit? Can a polystyrene be used in place of a ceramic in an RF circuit? If this expansion is possible, I and many others would be most appreciative. Onve again, congratulations on a great publication. Errol Gear, ZL2TQJ Nelson, NZ Modifying the Studio 200 power amplifier I would like to clarify several points re my modified Studio 200 Amplifier. For your information, I originally did not wish to make a larger than necessary projectile for your circular file. (1). A premium red LED was used as a reference due to experience with voltage variations of diode references in my Tillbrook 6000 amplifier and offset errors due to this. I have found these LEDs to be very consistent in their forward voltage and they track the current source transistor VaE very well SILICON CHIP, PO Box 139, Collaroy Beach 2097. with temperature. They also give an indication that servo action is occurring due to reduced brilliance after the warm-up period. (2). Q6 and Q14 are thermally coupled by a small piece of aluminium. This noticeably improves 2nd stage tracking stability (Q4 & Q5 collector voltages). (3). Perhaps I should have speculated about CMRR (not supply rejection) as I, perhaps mistakenly, believed that closely matched differential pairs provide superior CMRR. (4). The base resistances on the input differential pair do not match and I later made a partial compromise by changing the feedback resistors to 4.7k0/100k0. There was no appreciable change in performance (DC or audible), due mainly I suspect to the replacement of the manual offset adjustment with SILICON CHIP Auto-Zero modules. (5). I don't posses either your superb test equipment or technical qualifications but perhaps the following measurements may give some indication of amplifier performance for a rough comparison with your Studio 200 Amplifier. The total noise measured on a 4½-digit DMM was 0.32mV. This measurement was made with the input terminated by a 4.7k0 resistor. An in line preamplifier using the OP27 in a similar (unswitched) circuit to your AC millivoltmeter front end (thank you for the idea) confirms this approximate result. My reference Tillbrook 6000 amplifier gave approximately 0.58mV when measured in the same way. Thank you for your fair and unbiaseo editing of my original letter and for your comments which clearly point out traps for the unwary. By the way, an article on measurement techniques for audio equipment may be of interest to readers who have a basic technical background. A. Kethel Turramurra, NSW FEBRUARY1990 3 -~ --- ..... --. .... -- -. ,,. . "" seen our catalog? Write or phone today for your FREE copy. Over 100 products shown with full details and specifications! XT 1MB 12MHz TURBO ~ MOTHERBOARD SPECIAL ~ MINI-TOWER CASE • • WITH 200W POWER SUPPLY • • MIDI-TOWER CASE WITH 200W POWER SUPPLY • Metal housing and chassis • Back plate with 8 expansion slots and power supply mounts • Switches on front panel for power, turbo mode and reset e Indicator fo r power, turbo mode and 2 x harddiskindicators e Keyboard lockwith2 keyset e Will hold3x5.25" 1x3.5" third-height drives half-heightand • All necessary hardware included e?.5"Wx16.15"Dx17''H e Weight 24.Slbs H3521 - $ 349.oo MAXI-TOWER CASE WITH 220W POWER SUPPLY e Will fit AT/386 Baby or Full (standard) size motherboards • Space saving floor· mount case • Metal housing chassis • Anti-static coated plastic face plate •Backplate with 8 expansion slots • Switches for Turbo and Reset • Indicator lights for Power, Turbo mode, Hard Disk (1 &2) operation • Keyboard lock with 2-key set • Wil l hold up to a combination of 6 half-height floppy or hard disk drives • All necessary hardware in cluded • Co lour bei!;Je • 7.35"W x 16.75"0 x 25.25" He Weight 34Ibs H352o-$499 .oo NO w $110 VQLJ SA"Ef 1 ' V, • BABY XT/AT FLIP-TOP • • • • H352S-$ 2 9 9 .oo AS $129 I AI V V >1 M5500- XT 1MB 12MHz TURBO MOTHERBOARD • • Metal housing and chassis • Back plate with 8 expansion slots and power supply mounts • Switches on front panel for power, tu rbo mode and reset • Indicator for power • Keyboard lock with 2 key set e Will hold 2x5.25" half-height and 1x3.5"third-heightdrives • All necessary hardware included • 7.5"'wx 16.15"0 x 12.75"H eWeight22 .5Ibs ~ ~ ev2oprocessor • Can be expanded to 256k, 512k, 640k or 1mb euses combinations of 414256, 41464 and 41256 • 4. 77 or 12MHz hardware or keyboard selectable operation • Front panel LED indicators supported • Eight expansion slots e Legal BIOS ROMs included • 8087 maths co-processor capability eNortonS l ratingof2.5 • Size 8.5" x 8.5" • Weight 1.1lbs e • Metal housing and chassis Anti-static coated plastic face plate Back plate with 8 expansion slots and power supply mount Switches on front for Turbo mode and Reset Indicator lights for Power, Turbo mode, Hard disk operation Keyboard lockw1th 2-key set W1fl hold up to one hard and two floppy drives All necessary hardware is included Colour beige Size 17.125"w x 17"d x 6.5"h W~19ht21/bs ~ACff With H3733 150W Power Supply- WAS $249.00 NOW $199 With H3732 200W Power Supply - WAS $299 .00 NOW $249 The cordless mouse is a "pointing device" for drawing graphics, moving objects on screen and picking up items simply by moving the mouse on the chosen item and pressing a button. Unlike mostof theothermice, the cordless mouse uses the latest Infra-Red signal transmission technology. Comes complete with driver software, test program and menu maker. H3955 INFRA-RED MOUSE- COLOUR GRAPHICS ADAPTER f OR IBM PC/XT/ AT The M5752 is a colour graphics adapter card eapable of operating with either IBM RGB or composIte monochrome monitors and features the following: • Parallel printer port • Text modes: 40 x 25 or 80 x 25 • Graphic modes; 320 x 200 or 640 x 200 • Light pen interface • Includes composite video monitor adapter • Manual included M5752 - WAS $115 00 • NOW $89 1 - - - - - - - -- - -- - - - - ------+1---,+---- 1-~1_6_9_._o_o_ _ ____~ PC/XT 150W POWER SUPPLY GAME CARD • • • Two port Runs two joysticks • • M 5850 WAS $29.50 • NOW $25.0 0 H3730 - e e Input <at>47-63Hz (110/240v switchable) Output+5V<at> 15A, -5V<at>0 .SA, +12V <at>5.5A, -12V<at>0.5A Plug compatible connectors Bufftin fan Size 5.5"w x 9.5"d x 4.625"h Weight 6Ibs WAS $ 125.00 NOW $ 89 2MB RAM CARD FOR PC/XT/AT Memory expansion for the PCIXT/AT, frees users from the aggravating drawbacks of the 640K MS-DOS limit. It fully supports both the Lotu s/lntel!MicrosoftExpanded Memory Specification (EMS) and the AST/Quadram/Ashton-Tate Enhanced Expanded Memory Specification (EEMS). It allows multi -taskin(l programs such as DESQview to acess its up to 8 MegaBytes of memory. Software for backfilling conventional memory to 640K Is also included. FEATURES Supports EMS 4.0. Enhanced Expanded Memory Specification. Up to 2 MByte of expanded memory per card using inexpensive 41256 dynamic RAM chips. Up to 4 cards are allowed to use in one AT or XT. Supports DESQview, Framework, Lotus 1-2-3 and Symphony. M5982 _ $245 .00 PrintBuffer, TurboDisk Ramdisk and backfilling software provided. COMPUTER PART# SIZE AMIGA AMIGA AMIGA D2930 D2932 D2938 3.5" 5.25" 3.5" CAPACITY 880K 360/880K 880K COMMENTS PRICE WITH ON/OFF SWITCH WITH ON/OFF SWITCH INTERNAL KIT FOR A2000 249.00 299.00 229.00 AMSTRAD D2904 3.5" 720K FOR PC1512/1640 269.00 ATARI ATARI D2916 D2918 3.5" 5.25" 720K 360/720K WITH POWER SUPPLY SWITCHABLE, WITH POWER SUPPLY 269.00 299.00 IBM IBM IBM IBM D2946 D2948 D2950 D2952 3.5" 3.5" 5.25" 5.25" 720K 1.4MB 360K 1.2MB WITH WITH WITH WITH 299.00 329.00 299.00 329.00 TOSHIBA TOSHIBA D2970 D2972 5.25" 5.25" 360K 1.2MB SUIT TOSHIBA LAPTOP SUIT TOSHIBA LAPTOP 349.00 399.00 ZENITH ZENITH D2976 D2978 5.25" 5.25" 360K 1.2MB SUIT ZENITH SUPER SPORT SUIT ZENITH SUPER SPORT 349.00 399.00 COMPAQ COMPAQ D2980 D2982 5.25" 5.25" 360K 1.2MB SUIT COMPAQ SLT 286 SUIT COMPAQ SLT 286 349.00 349.00 ADAPTER ADAPTER ADAPTER ADAPTER INTERFACE INTERFACE INTERFACE INTERFACE & & & & CABLE CABLE CABLE CABLE ALL TOSHIBA/ZENITH/COMPAQ DRIVES INCLUDE EXTERNAL POWER SUPPLIES, INTERFACE AND CABLES WE ALSO HAVE A RANGE OF DRIVES FOR OTHER BRANDS SUCH AS APPLE AND MACINTOSH AS WELL AS A RANGE OF BARE DRIVES IN 360K/720K/1.2MB/1.44MB/2.88MR FORMATS e NEW PRODUCT COMING SOON - 512K RAM CARD FOR AMIGA Pfii{ {eeson DEALER ENQUIRIES WELCOME s PERSONAL COMPUTER MARKETPLACE PHONE (02) 418 6711 FAX (02)4186713 Mail Order Address: P.O. Box 1100 Lane Cove NSW2066 FREIGHT CHARGES Include $10with order for all norma l items - heavy items, e.g. monitors add $15. 14 day money back guarantee Orde r by phone (use credit ca rd), by fax or by mail. Unless insurance is declined it will be charged at 1% of total purchase. This is for your protection. PRICES VALID AT 1 DEC 89 Ptyltd VINTAGE RADIO By JOHN HILL Safety with vintage radios Vintage radio restoration is a hobby that I pursue with great enthusiasm. However, I never let my enthusiasm take complete control for I am ever mindful of the necessary safety precautions that should be observed when working with valve equipment. This column has often mentioned the fact that lethal electrical potentials are ever present in mainsoperated valve radios. The danger takes the form of either high voltage AC or DC and to tangle with either of these nasties can end in tragedy. The electrical and electronics trades lose several workers every year due to electrocution. With this thought in mind, perhaps we should look more closely at the safety aspects of vintage radio. Electric shock can result in any number of outcomes ranging from a bit of a tickle to severe burns, or even death. It must be avoided at all cost. Workers in the electrical trades occasionally get a "belt" and some of the careless ones get belted at more regular intervals. There are odd individuals who seem to be able to withstand quite high levels of electric shock, but others cannot. The digital multimeter says it all - don't underestimate the dangers when working on valve radios, In this case, the meter is measuring the AC voltage across the anodes of a rectifier valve. 6 SILICON CHIP Anyone with a coronary problem is likely to be vulnerable to even low level shocks. The right attitude While the following may seem a little irrelevant, it does relate to safety, whether electrical or otherwise. One of my past interests was motorcycling and for the best part of 30 years I rode numerous bikes on a regular basis. Unlike many motorcyclists, I never crashed any of my machines and in 30 years I never even broke skin, let alone a bone. The reason for such a charmed existence is the fact that I always had a healthy respect for the dangers of motorcycling and rode defensively with the intention of remaining in the saddle at all times. That positive attitude paid off! My approach to working on valve radios is exactly the same. It is always in the back of my mind as to what might happen if a finger is inadvertently placed where it shouldn't be. Although I have never received an electric shock, I see little point in getting belted just to find out that it isn't nice. One really good zap is all you need, so it is my intention not to have any encounters at all. However, there is always an element of risk when working on valve equipment. In order to work on a receiver, it must be removed from its cabinet and if the set is to be tun~ ed or tested in some way, it must be worked on while it is operating. When this is the case, the enthusiast can come in contact with lethal voltages and so must work with care at all times. holding the chassis with it. Now while most sets have nothing nasty on top of the chassis, there are exceptions. For example, one set in my collection has exposed connections to the rectifier socket which is mounted on top of the chassis. It also has bare terminals on the high tension choke and these are within easy reach of probing fingers. So don't become complacent. There is always the odd set that is different and just waiting to zap the unwary. Have a good look before switching on. Booby traps There are numerous high voltage components underneath a valve chassis so don't go polcing around indfocriminately. Safe work habits need to be adopted at all times when worlcing on valve radios, otherwise you could get a nasty shock. Natural rubber perishes with age and a cord in this condition is in obvious need of replacement. Other power cords will show less obvious damage but should be replaced if there is any doubt about their condition. One of the most dangerous situations is when the chassis has been up-ended but has not been positioned safely on the workbench. If the chassis slips off the bench and ends up in your lap, the outcome could be quite electrifying to say the least. Mounting an upturned chassis on the bench so that it doesn't fall is just one single aspect of developing safe work habits. Generally speaking, the average mains operated valve radio is fairly safe to work on. In most (but not all) cases, there is nothing nasty above the chassis and all top mounted components can be touched without the danger of electric shock. The real nasties are underneath the chassis in the form of the 240V AC supply and the high 'tension DC. Dangerous potentials can be found on most components: on the power transformer, speaker transformer, intermediate frequenc} transformers, valve sockets and on many capacitors and resistors. Even if probing around with an insulated tool, it's a good idea to keep one hand in your pocket rather than In some cases, a radio set can be booby trapped by a previous repairer. I once bought a set that seemed to be a reasonably normal mantle model with a power lead and 3-pin plug hanging out the back. The odd thing about this receiver was that it was a six volt vibrator type which made the power cord and plug seem a little strange and unnecessary. Further investigation revealed that the power lead was connected to the voice coil of the loudspeaker. It would appear that someone had been using the speaker of the set with some other receiver and had used an old power cord to connect things up. Had that cord been plugged into a power point and switched on - blap! That would have been the end of the voice coil. Never assume that previous repairs or modifications have been done by skilled technicians. An old radio magazine that I read recently had an interesting question from a reader in it. He asked: "Is there any reason why the dial lamps cannot be run off the five volt filament supply for the rectifier, as the 6.3 volt supply burns them out at fairly regular intervals". It sounds like a reasonable question except that the five volt supply is tied to the high tension DC (because it supplies the filament of the rectifier). Therefore, anyone touching the dial lamps while the set is working is likely to cop the full high tension voltage and that's not a good idea! A resistor in series with the lamps would be · a safer modification. FEBRUARY1990 7 Electrolytic capacitors are capable of storing a substantial electric charge and should be discharged as a matter of course after switching a set off. Remember that switching .off at the power point doesn't always eliminate all of the nasties. Old power plugs and switches should be thoroughly checked before being put back into service. Cracked plug tops, missing screws etc do not constitute safe electrical equipment. You should also check the wiring to make sure that a previous repairman has not set up a "booby trap". However, if the person in question had connected the dial lamps to the five volt supply, it could have lead to a potentially lethal situation for some unsuspecting serviceman or vintage radio collector, as the case may be. Internal faults and short circuits in valves can also put a high potential on a component that is normally safe. While the top caps of valves are usually safe to touch, if they are shorting to a screen grid or a plate they can become quite dangerous. A short of this nature can occur if a 8 SILICON CHIP valve base becomes very loose or something detaches itself internally inside the valve. While on the subject of top caps, it should be remembered that not all top caps are connected to grids: some are plate connections. Most valves of this type will have insulated top cap connectors but this is not always the case. So once again, be careful and check if in doubt. Direct coupling Some old radios and early amplifiers employed "direct coupl- ing", an arrangement whereby the grid of a valve was directly connected to the plate of the preceding valve. The normal practice is to couple audio valves by using a capacitor and resistor network. Many claims were made in days long gone about the advantages of direct coupling. However, its use was not widespread which indicates that there were no real advantages. In my collection of vintage radios, only two have valves that are coupled in this manner. The big disadvantage of direct coupling is that the grid of the second valve has quite a high positive potential and the plate voltage of this valve will need to be correspondingly higher if the valve is to work normally. In the two direct coupled sets I have, the plate of the second valve operates at 350-400 volts DC. If there was another stage following, a much higher voltage would be needed again. These exceedingly high voltages are backed up with electrolytic capacitors and pose a considerable threat to anyone foolish enough to offer a path of least resistance. Where someone may survive a DC jolt from a conventional receiver, the direct coupled set could well be their downfall. Some valve radios operate on incredibly high voltages. No discussion on electrical safety (as it relates to valve equipment) would be complete without some discussion about electrolytic capacitors. These capacitors are used to smooth the high tension supply and they can hold a considerable charge for quite some period of time. Normally, the HT electrolytics discharge themselves when the set is switched off. However, if a receiver has an open field coil or choke, then the input capacitor will remain charged. You might not thinlc so, but there is sufficient energy in one fully charged capacitor to kill you under certain circumstances. With this thought in mind, it is always a good idea to discharge electrolytics after switching off even if they don't need it. Another fairly obvious precaution is to check out power cords, plugs and switches. IJesurrection l?adio The original vintage wireless specialists Our skilled technicians offer QUALITY repairs & restoration. We have a large stock of bakelite and timber radios fully restored and for sale. Electrical hand tools require insulated handles - particularly when working on high voltage valve equipment. Replace the tool if the insulation becomes worn or perishes. Valves, high voltage capacitors and other specialised parts available. SPECIAL - this month only: 1 O & 1 5µ.F 450 volt electrolytic caps $3.00 plus p&p WANTED - valves, radios, etc., purchased for cash. Call in to our showroom at: 51 Chapel Street, Windsor, Vic 3181 PO Box 1116 Telephone: 529 5639 VINTAGE RADIO REPAIRS i Keep that free hand in your pocket when working on an upturned chassis. Using a finger as the path of least resistance can have fatal consequences. Cords & switches If this is not done the switch will Most receivers prior to about 1950 used power cords that were insulated with natural rubber. While this material did the job quite well, it perishes with age and can become very dangerous. If using existing cords, check them out thoroughly. The same goes for old Bakelite power plugs. If they are cracked, chipped or damaged, then replace them. A good many old radios have single pole on/off switches and these should always be wired into the active side of the power supply. break the neutral line and leave the set connected to active. While I have no wish to spoil anyone's fun, the foregoing should impress upon readers the real dangers that can be encountered when dabbling with vintage radio sets. If you happen to be an old hand at the game, then nothing mentioned in this article will be new. On the other hand, if you are a new chum to the world of valves, then you could be in for quite a shock if you fail to heed good advice. ~ LAWSON RADIO has been in the business of repairing radios for 40 years. If John Hill's column has rekindled the memories, but you are not confident enough to carry out your own repairs then call us now, for an obligation free quotation. Should you want to sell or purchase a vintage radio contact Michael today. 298 GREAT WESTERN HWY LAWSON, NSW 2783 (047) 59 1254 FEBRUARY1990 9 Bose acoustic noise cancelling headphones The concept of noise cancelling has been around for a long time but now it has been incorporated into a commercial product the Bose Aviation Headset. It uses electronics inside the headset to cancel unwanted noise. Ever flown in a helicopter or military transport? If you have, you will know just how deafening is the noise inside the fuselage. The only way you can talk to anyone else on the aircraft is to use a standard communications headset. These consist of a set of headphones with a good air seal around the ears and a microphone mounted just in front of the wearer's mouth. Now communication headsets are OK as far as they go but they are uncomfortable to wear for long periods and they don't totally eliminate the noise - far from it. The big problem with any headset is that it is just not possible to stop external noise getting to the user's ears. And even if it was possible to have a hermetic seal, some noise would still pass though the headset and cause a problem. In practice, headsets (and ear muffs) produce most of their attentuation at higher frequencies and have little effect at low frequencies. The problem with noise in aircraft, of course, is twofold. Too much noise causes deafness and it also makes communication via radio difficult. Here's where this revolutionary product from Bose comes into the picture - headphones which cancel out ambient noise. The idea of noise cancelling is not new - it's been a dream almost as long as electronics has been in existence. Back in the early 60's one of the American science magazines ran an article on how it might be possible to achieve a quiet bedroom when your next door neighbour is having a noisy party. The idea was to have a microphone to pick up the unwanted noise in the bedroom, amplify the noise in an amplifier and then feed it to speakers in the bedroom to cancel it out. The idea is simple in theory but a lot more complicated in practice. Not surprisingly, not a lot has come of the idea. Noise cancelling headphones though, are a far different proposition. The airspace inside the headphones is a small closed volume which can be tightly controlled and compensated for. The principle of the Bose noise cancelling headphones is similar to that outlined above. Directly in front of each headphone driver is a small microphone which picks up both the unwanted noise and the wanted signal (from the radio or whatever). Bose's technical info represents the circuit with the composite signal being fed to one input of a summing amplifier while the other input of the summing amplifier is fed with a wanted audio signal. The result is the wanted signal with the noise cancelled out (see Fig.1). In effect though, the Bose Acoustic Noise Cancelling (ANC) Headset is a classic negative feedback system as used in all audio amplifiers. The difference here is Radio/lCS Interface Compensating Filter Bose Acoustic Noise Cancellin Limiter Headset Controller (left channel not shown) The scbematic of the Bose ANC headset: a microphone inside each earpiece picks up the noise. 10 SILICON CHIP BoomandCab!e can be attached lo either left or right earcup On/Off Switch1)10Vides failsate operation Fully Articulated Boom Adju&ment Power Input . hteradap!ersupplied) , Noise cancelling has been a dream for decades but now the Bose ANC headset has made it a reality. that the headset driver is included in the feedback loop by virtue of the pickup microphone. Any noise signals picked up by the microphone are automatically cancelled as they appear as an "error".signal in the negative feedback. Of course, there is a little more to it than that, as Fig.1 shows. The headset is equalised, presumably to give it a more intelligible response for radio communications, and the "corrected" signal is fed through a compensating filter and limiter which probably has been included to prevent any possiblity of acoustic "howl" developing. The net result is that the Bose ANC Headset can give an effective total noise reduction at the wearer's ears of around 16dB compared to the standard US Air Force headset and up to 25dB cancellation of noise in the middle and low frequency bands. The Voyager flight Just how effective the Bose headsets are was demonstrated during the 9-day non-stop around the world flight of the Voyager in 1986. Pilots Dick Rutan and Jeana Yeager wore early prototypes of the headset for the whole 9 days. They did so because the noise level in the plane was very high and without the headsets they were expected to have a major hearing loss as well as putting the whole mission in jeopardy because of noiseinduced fatigue. After the flight, the pilots were tested for possible hearing loss. The conclusion was that there was only a slight shift in the hearing threshold for both pilots, which returned to normal after a few days. As well as the noise cancelling feature, the Bose headsets feature more effective and more comfortable ear cushions. The original type, nicknamed " bonecrushers" continued on page 91 FEBRUARY1990 11 We've got the guts ,o"'1 ots sol\) t ■■■you get the glory! ~1\o BOARD SOLUTIONS KIT COMPUTER BARGAINS: ASSEMBLE IT YOURSELF & $AVE! Model Speed Mem Floppy Hard Ports XT360 XTH32 ATH32 ATH42 640K 640K 1MB 1MB 4.77110MHz 4.77110MHz 8112MHz 8112MHz 2x 360KBN/A 1x 1.2MB32MB 1x 1.2MB32MB 1x 1.2MB 42MB Mono EGA VGA 1xS,1xP $1495 1xS,1xP $1745 2xS,1xP,1xG$2395 2xS, 1xP, 1xG $2850 Please call for personalised configurations. Assembled System also available for only 99 MS-DOS & GW BASIC also available for only $ extra TOWER CASE FOR 6 DEVICES $2050 $2339 $2950 $3375 $2350 $2650 $3250 $3675 155 $ extra Need somewhere to put it all? Try Board Solution's superb Tower Case. There's room to grow in this one! Whether you're building systems or simply upgrading your existing hardware, you can bet your reputation on Board Solutions. We offer motherboards, add-on cards, cases, and so on - all built to deliver the performance and reliability today's s~phisticated computer users demand. 33MHz 386 Yes!A33meg386 board at an amazing Board Solutions price. Upgrade NOW! M'BQARD $2 7 g5 ONL V UPTO$3795 ELSEWHERE! 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Outback Electronics Headware Nambour Electronics Namoi Computers Bassham's TV & Computer Brad's Electronics Super Solex Phillip's Electronics Maartronics M&E Electronic Communic. • 2121799 412077 884 908 439 600 525 684 813 672 248 322 323 661 221 821 532 081 290 579 214 137 511 723 214 559 346133 250 400 433 475 723 895 411 604 923 274 822 788 526 603 724466 216 558 629 870 775 935 14 Day moneyback guarantee (except software) • 3 month warranty on all our products • Mail orders are our speciality! • Freight on small items is $9.00 • Insurance $1.00 per $100 of order value • All price INCLUDE sales tax • We accept Visa, Bankcard, Mastercard and Post Office COD • Call for our latest price list • Special prices apply until Feb 28, 1990-or while stocks last! JAPANESE TOP QUALITY FLOPPY DISK DRIVES Why take chances with inferior quality drives? Ours are guaranteed top quality, brand new. prime spec and fully guaranteed with full replacement warranty. 5-1/4 INCH: 360KB: ONLY $145 1_2MB: ONLV$165 3-1/2 INCH: 1.44MBONLV$175 p~s~:i BOARD SOLUTIONS Pty Ltd PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 5222 HERE'S WHY YOU SHOULD BUY FROM BOARD SOLUTIONS: • We offer only top quality, prime spec products - no seconds or rejects! • Our prices are,as good or better than any other suppliers (tell us if we're wrong!). • 99% of our products are in stock! 8MB RAM Card for PS/2, OK RAM ** MOTHERBOARDS** 10MHz XTM/Board, OK RAM Baby 286 M/Board, 20MHz/0K Baby 286 M/ Board, all-in-1 Half-size 286 M/Board, with 1MB RAM Baby 386 M/Board, 33MHz Baby 386SX M/Board, 20MHz 149.00 845.00 545.00 695.00 2795.00 1095.00 **CHIPS** 1M RAM Chip - 100nS 29.95 1M RAM Chip - B0nS 32.95 256K RAM Chip - 100nS 7.95 256K RAM Chip - B0nS 9.75 8087-2, 8MHz Co-Processor 275.00 80287, 6MHz Co-Processor 315.00 80287, 8MHz Co-Processor 450.00 80287, 10MHz Co-Processor 499.00 4 X 256K RAM Chip, 100nS 32.95 4 X 64K RAM Chip, 120nS -for VGA card 12.00 64K RAM Chip - 120nS 4.95 NEC V20 Chip 24.75 NEC V20 Chip, 10MHz 34.95 NEC V30 Chip, 10MHz 49.00 ** DISK DRIVES ** Floppy, NEC 360K Floppy, YE-Data, 720K/1.44M Floppy, YE-Data, 720K/1.44M +Frame Floppy , NEC, 1.2MB Hard, NEC 42MB, 28mS 3.5in Hard, NEC 42MB, 28mS 5.25in Frame Hard, NEC 3.5in 134MB 23mS ESDI Hard, NEC 3.5in 134MB 23mS SCSI Hard, NEC 5.25in 179MB 18mS ESDI Hard, NEC 5.25in 380MB 18mS ESDI Hard, NEC 5.25in 760MB 16mS ESDI Hard, NEC 5.25in 380MB 18mS SCSI Hard, NEC 5.25in 760MB 16mS SCSI Hard, Miniscribe 20MB, 65mS ( 140.00 175.00 199.00 159.00 745.00 775.00 1595.00 1795.00 1995.00 3995.00 5995.00 4195.00 6195.00 349.00 ** MICE & JOYSTICKS ** Joystick Logitech Mouse, 2 button serial Logitech Mouse, 2 button serial + Paint S/W Logitech Bus Mouse, 2 button + PaintS/W Mouse Mat 30.00 120.00 130.00 140.00 7.50 ** MONITORS** Monitor, Monitor, Monitor, Monitor, Monitor, Monitor, Monitor, 14in TTL, Amber 14in TTL, Green 14in TTL, Paper White 14in EGA 14in VGA 14in Multisync NEC 14in Multisync 199.00 199.00 199.00 599.00 749.00 899.00 1049.00 ** MICRO CHANNEL ** Dual Sync Adaptor, PS/2 Compatible 2MB RAM Card for PS/2, OK RAM 349.00 349.00 • We offer a 100% 14 day money-back guarantee! • We continually visit manufacturers overseas for the very latest products. • We despatch goods within 24 hours WE HAVE THE RANGE: LOOK! 599.00 ** 1/0 CARDS ** Multi 1/0 Card XT only Multi 1/0 Card, 2 Ports all 4 drive types supported Parallel Printer Card Serial RS232 Card Serial RS232 Card X 2 1/0 Plus Card - XT Only Serial/Parallel Card - XT 2 Serial, 2 Parallel, AT Games, Parallel Printer, Serial Card, 'XT'& 'AT' Multi-Serial Card , 4P-AT 99.00 145.00 27.00 55.00 79.00 85.00 55.00 75.00 99.00 199.00 ** VIDEO CARDS ** VGA Card, 800 x 600 VGA Card, 1024 x 768 Magic Combo CGA Card EGA Card, with Hercules Mode Mono Hercules Card, 16MHz operation 349.00 499 .00 129.00 249.00 115.00 ** POWER SUPPLIES ** 150W PSU, Circuit Board 150W Switching PSU - XT 180W Switch PSU - Baby AT 180W PSU, Baby AT, L Type 220W Switching PSU -AT 150W PSU Capacitor, 220nF/200V 85.00 124.00 145.00 145.00 195.00 2.60 ** KEYBOARDS ** Keyboard, 101 Keys XT/AT 101 Key Keyboard+ Mouse 115.00 199.00 ** RAM CARDS ** RAM Card, OK RAM, XT only 2MB RAM Cd, OK LIM/EEMS AT 2MB RAM Cd, OK LIM/EEMS XT 6MB RAM Card, -OK RAM 99.00 265.00 245.00 295.00 ** DISK CONTROLLER CARDS ** Floppy Disk Card, 4 Ports 1.2M/360K, 720K/1 .44M Floppy Disk Card Disk Controller, 4 port, 2In, 2Ex, or 4In ESDI Hard Disk Cont Card -AT ESDI HDD/FDD Card - AT Hard Disk Controller, 1:1 Interleave, AT HDD/FDD Controller, 1:1 Interleave, AT Hard Disk Controller, 1:1 Interleave, RLL, AT HDD/FDD Controller, 1 :1 Interleave RLL, 'AT' 275.00 SCSI Card for AT 219.00 Hard Disk Controller, 'XT' 125.00 Hard Disk Controller RLL-XT 145.00 **CASES** Case - PortaDisk 249.00 NEC APC IV Drive Mounting Bracket 35.00 Case, full size 'AT' 155.00 55.00 99 .00 130.00 349.00 399 .00 225 .00 249 .00 , Case, hinged, Baby AT Case, hinged Baby 'AT' with 200W Power Supply Case, Slimline 'XT' or 'AT' with PSU 3.5in Hard Disk External Case + Cable 5,25in Floppy Disk External Case + Cable 5.25in Full Height External Case + Cable 5.25in Case for 3.5in Drive Baby Tower Case AT Baby Tower Case+ Power Supply Case, Tower for 6 Devices, Switches at Case, Tower for 6 Devices, + PSU S/W at top Cast. Tower for 6 Devices, Switches in Middle Case, Tower for 6 Devices,+ PSU S/W in middle Case, hinged XT 125.00 249.00 249.00 99.00 115.00 125.00 25.00 160.00 299.00 Top 299.00 449.00 299.00 499.00 95.00 ** INTERFACE CARDS ** 48 Line 1/0 Card Serial RS-422 Adaptor Industrial 1/0 Card Universal Wire-wrap Card Dual Serial RS-422 Card 80286 Speed-up Card IEEE 488 Interface Card IEEE 488 Interface Card- National Compatible A-D/D-A Converter, 12 bit, 1 Channel A-DID-A Converter, 12 bit, 2 Channels Clock Card - XT EPROM Writer Card Games Card- 'XT'& 'AT' 110.00 135.00 445.00 125.00 195.00 495.00 299.00 549.00 199.00 449.00 50.00 245.00 35.00 ** NETWORK ** BK Ethernet Adaptor, 8 bit with 'T' Adaptor 16K Ethernet Adaptor, 16 bit with 'T' Adaptor Ethernet 50 Ohm Terminator Thin Ethernet Cable, 25 feet Thin Ethernet Cable, 50 feet Thin Ethernet Cable, 75 feet Auto Boot ROM for NEE1 Auto Boot ROM for NEE2 Workstation, 12MHz Diskless, with 1MB RAM 399.00 449.00 12.75 35.00 49.00 62.00 35.00 35.00 2495.00 249.00 ' P~SHdd-4- J BOARD SOLUTIO~y! PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 5222 J REMOTE CONTROL By BOB YOUNG Transmitter encoders & black • wire syndrome All remote control transmitters use some sort of encoding which then must be decoded at the receiver. This month, we start on the subject of encoders and then pass on to practical matters such as the effect of battery fumes on PC boards. If we think of an RIG set in human terms, then the transmitter encoder is the "brain" that digests the incoming information from the control sticks and knobs. This raw information, in the form of parallel varying voltages, resistances, capacitances or inductances, must then be processed and converted into serial code format or "digital speak", if you will pardon the Orwellian jargon. In the PPM (pulse position modulation) system, the Rx and servo electronics are all passive elements and derive their timing from the master clock in the encoder, thereby making it possible to run as many receivers as you wish from the one transmitter. If we carry the human analogy further, the transmitter RF section then becomes the "voice", transmitting the processed serial control data over great distances. There is an interesting aside to this analogy, for in the "Book of Zohar", an ancient Jewish book said by some to contain the secrets of Moses, there are passages in which the "The Voice" is quite carefully distinguished from "The Speech". It appears that the ancient priests converted speech into "The Voice" . "The Voice" was then described as having an action lncoder Output similar to that of water in a pond when a stone is dropped into the middle of it. The stone disturbs the water and sends out waves which reach the distant shore. This is quite an up-todate description of the effect of Hertzian waves. So ends this month's sermon. First generation digital sets used a 2-transistor monostable multivibrator as the pulse generator. These very quickly gave way under the unrelenting pressure of cost to the "half shot" circuit - see Fig 1. This was the standard pulse generator circuit found in almost every set produced between 1969 and 1985. It is still very common and is very reliable and stable. This is an 8-channel halfshot encoder board which is actually half of the encoding circuitry used in the 16-channel transmitter shown in our December issue (page 15). This transmitter was developed for John Grant of Custom Model Cars. r------ ---, r--------, Audl1ary fl Auxiliary 12 I I ._ ________ J 14 SILICON CHIP L--------' Fig.1: this early R/C transmitter circuit uses a number of "half shots" (eg, Q3, Q4, Q5) to perform encoding of the control settings. Qt and Q2 provide the clock circuit while Q7 and Q8 provide the modulator stages. The half shot pulses are fed to the modulator via the associated diodes. Eventually, this circuit gave way to the unrelenting pressure for gadgetry and sales gimmicks. The half shot is not very flexible when it comes to the addition of ancilliary control effects such as servo reversing, half rate, exponential etc. Thus we saw the advent of the discrete symmetrical encoder, usually balanced around a midpoint reference voltage. This allowed the servo control voltages to be reversed without retrimming the neutrals. This development was eventually incorporated into standard encoder chips, the Signetics NE5044 being a good example. This type of chip is very flexible and allows all kinds of gadgets to be incorporated into a model Rf<:; transmitter. There are drawbacks, of course, and two of note are RF inter£erence from the Tx RF section and shifts in neutral due to contamination on the printed circuit board. This latter problem shows up in some older "half-shot" sets quite regularly, especially those using high impedance IC encoders. The most common source of contamination is the gas vented from overcharged batteries. This produces quite pronounced shifts in neutral positions with temperature or humidity changes. If this occurs, scrub the Tx PC board with methylated spirits and blow dry with a warm hairdryer (not hot). When the neutral shift is eliminated, spray the board with Electrolube Clear Protective Lacquer (CPL200) or something similar. It really is poor design procedure to include the Nicad battery inside the main electronics chamber or housing. In all of my new industrial designs, the battery is enclosed in a separate housing and is removable for charging. The gas from venting batteries does terrible things to electronic components and leaking electrolyte will eat its way through copper circuit boards and aluminium cases in very short order. As is always the case, do not leave batteries (dry or nicad) in elecronic equipment if it is not being used. If the transmitter has a removable battery, then take it out for charging. This procedure may be somewhat tedious but is well worth the effort in the long term. The "black wire" syndrome An associated problem is the dreaded "black wire" syndrome, the bane of all modellers and probably all users of nicad batteries. Nobody seems to know just what causes this problem but on the surface it appears to be a process by which gremlins, gradually and using great stealth, exchange the copper in the negative lead from the battery for some kind of black garbage. The transformed conductor is shiny blue-black in colour, devoid of any tensile strength and with a con- ductivity approaching that of air. The transmitter thus suffers, in human terms, coronary occlusion, with its supply of much needed electrons gradually strangled off. The results can be horrific but milder effects range from from low transmitter power to lack of decoupling. The latter can give rise to RF inter£erence in the encoder and this can cause shifting or jittery neutrals. Eventually, a complete breakdown will occur. If this happens during a flight, then it's a serious matter indeed. What to do Fortunately there are very simple solutions to this problem. Standard insulated hookup wire in which the conductors are tinned (ie, normal hookup wire in which the strands are bright and shiny rather than plain copper) will slow the process remarkably. The effect shows up mainly on plain untinned copper conductors. Keeping the battery ends moist with CRC 2-26 will also help. You should examine all battery wiring every 6 months or so. Pull back the insulation and examine the copper conductor. If there is "black wire", the lead will probably fall off in your hand. Re_Q_lace all leads showing the faintest traces of this black contamination. It usually stops at the switch, but not always. A word of advice here: use an old soldering iron tip to disconnect the lead. The black stuff will contaminate the tip and render it FEBRUARY1990 15 VIRTUALLY NO UP - ALL OOWN -UP 45' --.... OFFSET ZERO REFERENCE SERVO 0/P ARM PUSH ROD TD CONTflOL SURFACE Fig.2: the servos should be set up so that they give equal travel about the neutral point. If this is not done, the control will move faster in one direction than the other. useless for soldering thereafter. If the conductor is clean and bright but plain copper, then replace the lead anyway. If it is silver (plated) then you have few worries, but you should still check it periodically. A leaking battery can chew up good leads very rapidly. Battery damage in transmitters is a problem that frequenntly confronts the R/C serviceman. Care in this area will pay dividends. · ·One final word on the "black wire" business. It has been suggested that the black dye in the PVC insulation affects the copper. I have also seen this effect on the positive (Red) lead on rare occasions and on wires of all colours when used around earth terminals. It has also been suggested that overcharging plays some part. I have seen brand new sets which have been charged once or twice and left to stand for several years exhibit the problem. As stated previously, I have yet to see a satisfactory explanation for the problem. That does not mean that an explanation has not been published but if it has I have yet to read it. 16 SILICON CHIP Perhaps all I can say for sure on this subject is that leaving sets standing unused for any length of time is very poor practice. The batteries should be cycled regularly and left in the discharged condition. Control memory With the advent of LSI, the microprocessor eventually found its way into R/C equipment for models and thus we saw the development of the PCM (pulse code modulation) system. I am not a great fan of PCM for models and prefer the . old PPM system. However, the processor has revolutionised the PPM system and we now have transmitters offering some very nice features as a result. One of these features is the ability to store the trim and throttle settings for several different models in the transmitter memory. A PPM transmitter capable of storing trim locations for three models is a very useful item. But here again I must stress that before you rush out to buy such a transmitter, remember that this all costs money and is not really essential. A well trimmed model should fly with all controls set at neutral and the control throws set in such a manner that full throw gives just enough control response to accomplish the tasks required of that model. Smooth, precise flying begins with the correct setting up of the controls. There is a very practical reason for this and it has to do with mechanical advantage and servo flutter. Using less than full servo throw is poor engineering practice indeed. For many years I flew aerobatics, pylon and helicopters on the same day using the same transmitter without memory and without undue difficulty. However, I was very careful about the trimming and setting up of the controls in each model. Every model flew with the controls set at neutral. If they did not, then I landed and retrimmed the aircraft. At first glance this may seem odd and dated, but the concept is as valid today with the processor memory encoder as it was then with the old half shot encoder. The reason is very simple. Servo output arms are a rotary device and thus will only give equal throw about neutral if the neutral reference point is goo to the control push rod. If this angle is not goo, then some amount of differential control throw will be introduced into the system and the model will respond faster in one direction than the other. Fig.2 illustrates this point. Now this can be a useful feature and is used quite often in setting up control throws, particularly on the ailerons where large amounts of differential control are desirable at times. It is not in the least bit desirable if it gives an unwanted faster roll to the left than the right or more down than up. Control geometry is a very complex subject and will form a column of its own in due course. For the moment I will just confine myself to pointing out that everything is not as simple as it looks and that hi-tech gimmickry is useful but no substitute for the careful and studied application of basic principles. All of the foregoing aside however, the new encoders do have Problems? .. .and you don't have our NEW 1990/91 This is a 7-channel symmetrical encoder developed by Proportional Systems Australia (PSA). some very nice features and the most important are listed below: Servo reversing: a slide switch is provided on the Tx to invert the pulse width on each channel, thereby reversing the direction of travel of the servo. The alternative is to rewire the servo by reversing the two outside pot wires and the two motor leads. This feature calls for a deal of caution on the part of the user in case take-off is made with the servos reversed. Let me stress right now that this is all too easy. All control throws must be checked before the first flight of the day for correct direction of travel. This applies on any Tx, even those without servo reversing. It only takes the pushrod to be accidentally replaced after adjustment on the wrong side of the servo to wreak havoc. With servo reversing, it is even easier to come undone, especially if two models are being used on the one transmitter and reversal is required for only one of the models. I have seen the odd pilot who is clever enough to fly with reversed controls but they are rare indeed. Dual rate: this is somewhat dated in my mind by the exponential system. A switch is provided for one or more channels on the front of the Tx with an associated potentiometer. The pot is adjusted to set the overall percentage of servo travel available (O - 100%) with full stick throw. On half rate, full stick throw will only deliver 50% of the available servo travel. Returning the dual rate switch to the off position restores 100% of the servo travel. This is useful for high speed flight where the controls become very sensitive around neutral. It must be remembered where this switch is before commencing any manoeuvre, particularly outside loops. I have seen models crashed by pilots starting too low to the ground in the belief that they were in "high rate" when in fact they were in "low rate" . It is very awkward to get to the rate switch in time if this error is made. Another drawback is that two distinct sets of control reflexes must be developed, one for high rate and one for low rate. Learning to fly is hard enough without added handicaps such as this. Exponential control: often switched in by an external or internal switch and gives electronic damping of the servo throw 1;1round neutral. As the name implies, the control throw follows an exponential curve, with less throw at neutral and increased pace as the stick moves to extremes. The advantage of this scheme is that the control response of the aircraft is alwavs constant whereas with dual rate, two sets of reflexive responses must be developed. Servo end point adjustment (EPA): a very useful feature and quite safe to use. It is especially useful for throttle adjustment where it is not desirable for the servo to run up against the end stops. If this happens, it increases servo drain and can burn out servo motors and amplifiers. It can also lead to Rx failure due to flat batteries in the model. A potentiometer is included in the channel for fine adjustment of one end of the servo travel. This is a very important point and sets not fitted with EPA must be set up very carefully to avoid these problems. ~ 148 page electronic parts and accessories catalogue ... Its our latest TRADE catalogue for the consumer ARISTA ... Your one-stop problem solver. ...Stylus ... ... Plugs, Jacks and Sockets ... ...Batteries .. . ... Cable .. . ...Tools and Technical Aids ... ...Plug and Power Packs ... ... Car/Auto Accessories .. . ... Boxed Hi Fi Speakers ... ... Raw Replacement Speakers ... ...Speaker Accessories ... ... Telephones and Intercom .. . ...Public Address Accessories ... .. .Security and Alarm Accessories ... ...TV/Video/Antenna Accesories .. . ... Videocam Accessories ... ... Audio Accessories ... ...Headphones ... ... Computer Accessories .. . ...Microphone Accessories .. . ...Mixers, Amplifiers. Equalizers ... Just about anything you want. .. Get your catalogue complete with "Recommended Retail Prices" free from your local ARISTA dealer or send $2.50 P & H and your return address to: AR~ ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW, 2141 FEBRUARY1990 17 A completely new design for stage or studio with equalisers on each input channel 16-CHANNEL IXING DESK In the entertainment business, nothing stays still for long. Where 8-channel mixers used to be regarded as pretty fancy stuff, they are now just not big enough. Sixteen input channels are now necessary, with the ability to mix down to two or four output channels. This new low noise design does just that. By JOHN CLARKE This design is the result of collaboration between SILICON CHIP magazine and Ja year Electronics Pty Ltd. The starting point was Jaycar's very popular and reliable 8002 mixer which, as its name suggests, has 8 input channels and two output channels (for stereo). The aim was to expand the basic design to 16 input channels and mix down to 2 or 4 output channels, making it compatible with the many 4channel recorders presently available. Quite a few extra features were added as well. Each input channel can now be switched to provide for balanced or unbalanced line inputs, as well balanced microphones. The various channels can also be switched right out of circuit when not in use, so that they make no contribution to the residual noise in the system. A LED overload indicator is fitted to each channel so that the mixer operator can keep distortion to an absolute minimum. As well, the 18 SILICON CHIP & LEO SIMPSON operator can separately monitor any of the 16 input channels via the headphone sockets so that levels can be absolutely "spot on". Signal monitoring in the four output channels is pretty fancy too. Instead of small VU meters, this new mixer has vertical LED bargraphs with average and peak indication over a range of 60dB. While the Jaycar 8002 was the starting point as far as the operating facilities are concerned, the circuit design has been completely revised and is new from the chassis up. Where the previous design was largely based on 5534 op amps, our new design uses LM833 dual low noise op amps. This has allowed us to keep the overall component count and cost under control while considerably increasing the facilities. And what about the cost? At the time of writing this first article in what will be a series of three or four, the all up cost for a kit of this 16-channel mixer as published is expected to be close to $1400. This makes it a real bargain when compared to any commercial mixing desk with a comparable range of facilities and performance. By the way, the main performance parameters are summarised in a panel accompanying this article. We think you'll agree that the specs are very good and more than comparable with the commercial mixers. We also understand that there will be a 12-channel version of the mixer which will have the same size control panel and chassis but with the unused controls blanked off. As well as this, kits of the various modules will be available separately for those readers who want to produce their own customised versions of the mixer (see the Jaycar adverts in forthcoming issues for the details). Our thanks to Jaycar for their assistance throughout the design of this complex project and for supplying all the componentry. Now, let's get down to the nitty-gritty of this instrument. Physical layout There is no way around it - a 16 channel mixing desk of this complexity is a large instrument. With timber end pieces, our prototype measures 865mm wide and 440mm deep. It weighs about 14kg. While the dimensions of the final production version are likely to be slightly different, the mixer panel itself is 828mm wide and 435mm deep. It is mounted on a chassis to place it at a comfortable angle for the operator - about 85mm high at the front and 180mm high at the back. Those latter dimensions depend to a small extent on the size of rubber feet used. All told, there are 156 knobs, 20 60mm sliders and 17 toggle switches, making a total of 193 controls on the panel. Each knob is colour coded, so that its function in each channel is clarified, making it less likely that you'll reach for the wrong knob. In addition to all the knobs and switches, there are 18 6.5mm jack The new mixer features switchable balanced or unbalanced line inputs, equalisers on each input channel, and effects and foldback control facilities. The 4 output channels are monitored using LED bargraph VU meters. FEBRUARY1990 19 ii / Four different PCB designs are used in the mixer: one for each of the input channels, one for each of the output channels, one for the effects and foldback control circuitry, and one for the power supply (not shown here) sockets for headphone monitoring and 80 LEDs in the four bargraph signal indicators. Even so, while there are a great number of knobs and switches, this is largely due to duplication of the features in each of the 16 input channels. After a short period of familiarisation, an experienced mixer operator will feel at home with this unit. Mixing features The 16 input channels are arranged in two groups of eight columns, starting from the lefthand side of control panel. At the very top of each column is a 3-position rotary switch to select microphone (mic), balanced line or unbalanced line input. The next knob down is the prefade attenuator (atten). This allows you to set the channel signal level independently of the main fader control - a very handy feature. And in between the input selector and pre-fade attenuator is the red LED (light emitting diode) overload indicator. This allows you to have signal levels under control at all times. Specifications 20 Below the pre-fade attenuator is a 3-band equaliser (EQ) giving a range of boost and cut of ± 12dB at treble, middle and bass frequencies. This will augment the tone controls that are on most electronic instrument inputs and give adequate tone adjustment for microphone signals. The sixth knob down, below the 3-band equaliser, is the 'pan' control which allows the input signal to be directed to output channels 1 or 2 or any combination between the two. The first 8 input channels can be panned to output channels 1 and 2 while the second 8 input channels can be panned to output channels 3 and 4. Below the pan control is a pair of knobs which provide for 'Effects' (sends) and 'Foldback'. The Effects control determines how much of the signal is fed to an 'effects' output which may provide reverberation, echo, phaser, flanger or possibly a digital processor which can provide any or all of these effects and a lot more besides. The 'Foldback' control determines how much of the channel signal is fed to a foldback amplifier and speakers. Foldback speakers are placed on stage so that musicians can actually hear their own playing or the lead player. Below the eight control knobs is a toggle switch. This allows each channel to be switched right out if it is not being used and so helps to minimise the total noise from the mixer. Right at the bottom of each column is a 60mm slider which is the Fader for that particular channel. And immediately above the Fader is the 6.5mm jack socket which may be used with any pair of stereo headphones. So far then, we have described the physical control features of each of the 16 input channels. Moving across the control panel we come to the columns of knobs for the output channels of which there are six: four main outputs, effects and foldback. Signal To Noise Ratio (with respect to 1 00mV input and output) 90dB from 20Hz-20kHz; 93dB with A weighting Sensitivity For 1 V Output 60mV for balanced and unbalanced inputs; 6mV for microphone Frequency Response -3dB at 15Hz & 38kHz, -1.5dB at 20Hz, -:-0.8dB at 20kHz Distortion 0.015% with respect to 1 V in and 3V out at 1kHz Equaliser ±12dB Output channels Bargraph Display Peak hold and VU meter; 60dB range with 3dB steps As with the input channels, the four output channels are arranged in columnar form, with the 20-LED SILICON CHIP All potentiometers except for the fader (slide) controls are mounted directly on the PC boards but there is still a fair amount of wiring. Much of this wiring is repetitive and involves hooking up the supply rails and making connections to the fader controls and input/output sockets. VU meters at the top. As each LED comes on, it indicates a signal increase of + 3dB and as noted above, the display gives both average (bargraph) and peak (single LED) display. Below the LED bargraph is a 5-band equaliser (EQ) giving maximum boost and cut of ± 12dB for frequency bands centred on 60Hz, 240Hz, lkHz, 3.5kHz and lOkHz. Next, below the 5-band equaliser, are the Faders, one for each of the output channels. On the far righthand side of the control panel are two columns of four knobs. These are the Effects return and sends controls, panning controls for the two effects channels between output channels 1 and 2 or between 3 and 4, and the Foldback channel level controls. In the bottom righthand corner of the mixer panel is a pair of 6.5mm sockets for stereo headphone monitoring of output channels 1 and 2 and 3 and 4. Above the headphone sockets is a toggle switch to provide for stereo or 4-channel outputs. Rear panel On the rear panel are 16 female XLR sockets for the inputs and 4 male XLR sockets for the balanced output channels. Above the latter group are six 6.5mm sockets: two for the Foldback channel outputs, two for the Effects return line and two for the Effects send line. There is also the mains fuse and the mains toggle switch, although we expect that production models of this mixer will have an il- luminated rocker switch in place of the power LED at the top righthand corner of the control panel. Block diagram Having discussed the physical layout of the controls, you can get an idea of the electronic layout of the mixer by having a look at the block diagram of Fig.1. Even though it is a large diagram, it shows only two of the input channels. However, all of the output channels are depicted, so that you don't have to leave too much to the imagination. As you can see from the block diagram, the physical layout of the controls does not really relate to the flow of signals through the circuitry. For example, the Pan and Effects sends pots come after the main Fader for each input channel which you would not necessarily expect by looking at the control panel. This is because good control layout (ergonomics) and good cirFEBRUARY 1990 21 '"Cl ..... z n ::c: 0 n t== ..... er. N N PROGRAM INPUTS 9-16 PROGRAM INPUTS 1-8 1 : MIC (BAL) 20dB .. 13 0 O PREAMPLIFIER +20d8 OdB 3u------------ 1~ 2 1 1 : MIC (BAL) 20dB 2 : LINE (BAL) OdB 3 : LINE (UNBAL) 30--------- 1~ INPUT" SELECT 20----0 3 : LINE (UNBAL) 2 : LINE (BAL) OdB PREAMPLIFIER +20dB OdB INPUT BUFFER AND ATTENUATOR 6-40d8 FOLOBACK SEND .,. !• INPUT BUFFER AND AITTNUATOR 6-40dB 3-BANII EQUALISER :!:12tl8 POST FADE BUFFER +6dB .,.. FOLDBACKf., SEND 3-BANO EQUALISER :!:12dB 1 OF 8 . 1 OF 8 CH1 BUS CH4 BUS CH3 BUS POST FADE BUFFER +6dB FOLDBACK 9-16 BUS EFFECTS 9-16 BUS .,. FOLDBACK 1-8 BUS EFFECTS 1-8 BUS CH2 BUS .,. .,. J• hh uu Win uu PAN PEAK DETECTOR EFFECTS SEND HEADPHONE MONITOR EFFECT~f • SEND HEADPHONE BUFFER OdB .... Hti fh ,. ',\ PEAK DETECTOR .,. C1 O' CH2 ' fY CHJ IN/OUT 0 IN/OUT CH1 ~ ~ N 0 cc ....cc >-<: :Jj §: ti:, :Jj EFFECTS 9-16 RETURN 0-----1 EFFECTS o----t 1-8 RETURN ':' / I [,/ I I . ( I V I I,,, I r I,,, I ~f~~~&:-7 4/2 OUTPUT BUFFER +6dB FOLDBACK 9-16 FOLDBACK 1-8 EFFECTS 9-16 EFFECTS 1-8 J;.IM CH2 CH3 CH1 CH4 SUM AMPLIFIER .,. 5-BAND LED VU METER EFFECTS 1-8 SEND LINE OUTPUT >--------------------------OF~t3:~~~pt{6 EFFECTS 9-16 SEND ILINE OUTPUT CH3/CH4 HEADPHONE MONITOR 9-16 l PROJGRAMS 4 BALANCED CH '-------0 LINE OUTPUT BALANCED LINE AMPLIFIER +6dB >------------------------0 5-BAND EQUALISER METER LED VU BALANCED CH3 '-------0 LINE OUTPUT BALANCED LINE AMPLIFIER +6dB elu~~IER ______,_________ METER LED VU 1-8 >------------------------v FOLDBACK LINE OUTPUT >-------------------------0 HEADPHONE BUFFERS 1-8 PROJGRAMS 2 BALANCED LINE OUTPUT CH l CH1 BALANCED LINE OUTPUT CH 1/CH2 HEADPHONE MONITOR ~ BALANCED LINE AMPLIFIER +6dB L----0 .BALANCED LINE AMPLIFIER +6dB E~~~ER _ _""T_ _..,._ _ _ _ _ _ _-t EQUALISER LED VU METER Fig.1: here's bow the various circuits are linlced together. Note that only 2 of the 16 input channels are shown. EFFECTS 9-16 ATTENUATOR CH3 SUM AMPLIFIER CH1 SUM AMPLIFIER The power supply is mounted in the bottom righthand corner of the chassis. It uses a toroidal transformer to keep mains hum to an absolute minimum. cuit layout aren't necessarily related. Now let's follow the signal though the block diagram for one of the input channels, as shown along the top of the 2-page diagram. The input signal goes to a 3-pin female XLR socket and then to the input switch which provides for balanced or unbalanced input operation of the preamplifier. Not shown is the other pole of the input switch which changes the gain of the preamplifier, depending on whether microphone or line input is desired. For microphone input, the preamp has a gain of + ZOdB [lOx) while for line inputs, the gain is unity. Following the preamplifier is the input buffer and pre-fade attenuator stage which, depending on the setting of the control knob, can have a gain between + 6dB (Zx) and + 40dB [lOOx). Note that the prefade attenuator is a feedback control which means that it minimises the residual noise for any gain set- ting and also can't be set down to zero, which could cause confusion for the operator. After the pre-fade attenuator stage is the 3-band equaliser, followed immediately by the main channel fader and the foldback level controls. Following the main fader is the "post fade buffer" stage with a gain of + 6dB. This feeds the headphone buffer, the effects send control and the associated pan pot. The headphone buffer also drives a peak detector stage which drives the overload LED indicator for each channel. In the lower half of the block diagram you can see all the output channels depicted. In each of the four main output channels, the signal is picked up from the associated signal bus and fed to a summing amplifier [gain OdB or unity) which then drives one of four master faders. Each master fader is followed by a buffer with a gain + 12dB (4 times) which then drives the associated 5-band equaliser. The equaliser then drives LED VU meter stages and the balanced output amplifiers which are terminated in 3-pin male XLR sockets. Immediately below the Chl and ChZ summing amplifiers are the effects 1-8 and foldback 1-8 summing amplifiers. These both drive their associated master faders and line amplifiers to provide the send and foldback outputs. The rest of the diagram is pretty much self-explanatory although it needs to be looked at in conjunction with the individual circuit diagrams which will be published in next month's issue. Mechanical design The mechanical design of the new mixer is fairly simple. Essentially it is just a large panel with a whole lot of boards attached to it via their potentiometers. The control panel is supported on a large shallow chassis which has the power supply in the righthand rear corner. A toroidal transformer is used to keep hum at a minimum even though the total power drawn is fairly high. Four different PC designs are used, including that for the power supply. All potentiometers except for the Fader controls are wired directly into the boards which helps keep the wiring at a minimum. However, there is still quite a lot of wiring in the unit, as you can see from the photographs. Next month Next month we shall present the circuit details of all the different printed circuit boards and the complete parts list. ~ The rear panel holds 16 female XLR input sockets, 4 male XLR output sockets and 6 6.5mm sockets for effects & foldback. 24 SILICON CHIP /\/ES ltltllt OUR OWN FLUID LEVEL SENSOR "r,s $19.95 ALTRONIC and OATLEY KITS ~s'"s Ktrs sc sEPr a9 Phone now, fun kits with serious applications SOLDER 60/40 fluxed S.71/K25. . . . $ 7.90] S.71/KS . $15.80 ·71 mm S.91/K25 . . . . .. $ 7.25] 91 S.91/KS. $14.50 · mm S.1.25/K25 ... $ 6.90] S.1.25/KS . . . . $13.80 1·25 mm K25 = 250gms KS = 500gms You'll need some of this ERSIN SOLDER - AUSTRALIAN MADE * Mail or Telephone Orders Welcome * Bankcard - Mastercard Delivery Rates: Orders: $1 - $9.99 $10 - $24.99 $25 - $49.99 $50 - $99.99 $100+ Visa - accepted Postage: - MOS MEMORY 1GsMosMEM1 $2.00 BI POLAR WGIC (74LS/ S) $3.00 - iGSTTLl $4.00 WGIC 1-iigh Speed $5.00 - CMOS 74HC/HCT (GS H C/ HCT) $7 .50 Delivery Disclaimer: The above postage rates cover basic postage only. Any specialised freight requirements will be charged at different rates. Sales Disclaimer: Prices subject to change without notice. * * * * * -CMOS WGIC 4000 Series (GS4000CMOS) _ LINEAR (GSLINEARl $7 85 $15 85 $17.95 $15.65 $14.95 • • This SET Normally $ _ 72 25 seo NOW ONLY Inc. Post/ Pckg PR1ce L1sT ON A D1sK ALL PRICES All Products and Components Accounting Facilities* Ordering Made Easy and FAST Even an Update Facility ORDER NOW Only $6.50* *Subtracted from your first order. • Resident on 2 of 360K 5 ¼" IBM compatible* disks. • Hard drive dependent. *To approved applicants *IBM is a Trademark of International Business Machines. Novocastrian Ph: <049> 62 -1358 . Fax: (049) 62-2005 E Iectron1c oR Supplies PTY. LTo. (008) 02-5942 24 Broadmeadow Road, Broadmeadow, 2292 Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are weh;ome and will be paid for at standard rates. Electronic speedo with LED display Fancy a digital speedo for your car? This design is based on a commercially available DPM-40 LED panel meter and is easily added to most cars. The speed of the vehicle is monitored by a· photo-sensor which picks up reflections from two white horizontal lines painted on the driveshaft. This sensor should be mounted close to the universal joint at the gearbox end, where vertical movement of the driveshaft is minimal. Each time light is reflected back to the sensor, the phototransistor turns on and feeds a signal pulse to pin 1 of ICl via a .0015µF capacitor. ICl is an LM2917 frequency- Parametric equaliser for flexible tone control There are some cases where a graphic equaliser is not appropriate, especially in low noise applications or where the multiple frequency bands of a standard equaliser will be wasted. This circuit is a parametric equaliser, or a variable frequency equaliser, that allows you to vary the frequency which is to be boosted or attenuated. The circuit can be divided into two sections. Op amps ICla and ICl b form the preamp section. The input signal is applied to VR3 which is connected to a noninverting amplifier with a gain of 3.2. You can reduce this gain to 2 by changing the 2.2k0 feedback resistor to lkO. Alternatively, you can reduce the gain of ICla to unity bv removing the lkO resistor from pin 2. ICl b has a gain of unity when 26 SILICON CHIP OUT +12V D.1l 470(! +5V 0.1! T 10 .DJ ~ 470k IC1 LM2917 11 ~ 4 • lI.,. to-voltage (F/V) converter. Its output voltage appears at pin 5 and is directly proportional to the input frequency. The output of ICl drives the IN HI input of the DPM-40 via calibration :J +5V 12 .,. DPM40 VR1 50Dfl CAL 15k .,. .,. IN HI SET FOR 2V FSR IN LO DV .,. trimpot VRl. The DPM-40 panel meter is available from Jaycar and should be set for a 2V full scale reading. Steve Calder, Parramatta, NSW. ($30) 100k 0 50krl--<l----t T 100k the boost/cut control VR2 is centred. Op amps IClc and ICld are connected as a generalised impedance converter, used here to continued on page 91 1k 100k 1'/o TO - - 0 - - - 0 VOLTMETER S1e S1b 1 PN 830k 1'/, Simple transistor beta tester There are many occasions when it is necessary to determine the beta of a transistor; eg, when matching differential pairs or for output stage matching. If you don't have one of the latest digital multimeters with a transistor test facility, this circuit will do the job. It can test any NPN or PNP transistor with a beta up to about 800, and converts the beta to a voltage reading. The conversion factor is a gain of 100 per volt; ie, if the voltmeter reads 2.75V, then the beta is 275. The circuit is based on a single TL072 op amp. As shown, S1 is 30-second bilge pump This simple circuit is ideal for use on small volume bilges (on small boats?). It's based on the National Semiconductor LM1830N fluid sensor (!Cl) and uses two probes to detect the water level. When the water reaches the top probe, the circuit activates the bilge pump for 30 seconds. Here's how the circuit works. When the water reaches the top probe, pin 12 of IC1 switches high and turns on transistor Qt. Qt in turn controls the pin 2 trigger input of IC2 which is a 555 timer wired as a monostable. When Qt turns on, pin 2 is pulled low and pin 3 goes high and switches on the relay. switched to the NPN test position. If the transistor is OK, it will be biased on via the 830k0 resistor com1ected to the + 9V rail and its base-emitter voltage will be 0.7V. This means that the voltage across the 830k0 resistor will be 8.3V and thus the base current will be 10µA. The collector current will simply be the base current (10µA) times the beta of the transistor. Let's assume a beta of 150. The collector current is then 15mA which means that the voltage across the lkO collector resistor will be 1.5V and thus the collector voltage will be 7.5V. ICla is connected as a subtractor. Its output is simply the supply voltage minus the callee- tor voltage (ie, the voltage across the lkO resistor). For the example given, the output voltage will be 1.5V which translates to a beta of 150. The PNP transistor is easier to measure since its collector voltage is across the lkO resistor on the non-inverting input of !Cl b. Thus, ICt b is simply wired as a buffer stage. All resistors should be 1 % types to obtain the required accuracy. Note that the 830k0 resistors are made up of 820k0 and 10k0 types connected in series. Sla selects either LED 1 or LED 2 to indicate either the NPN or PNP test mode. Darren Yates, French's Forest, NSW. ($20) 1H4002 + 12V FROM BATTERY C: ~ 4700 14 1M I IC2 555 .001 RELAY IC1 LM1S30 . 12 .047 TOP PROSE 9 + BOTTOM1 PROSE . 11 or 22.I: .,. When water reaches the top probe, this circuit activates a bilge pump for 30 seconds. To increase the period, just increase the lOµF capacitor. The 10µF capacitor connected to pins 6 & 7 now charges via the 2.7MO resistor and, after about 30 seconds, resets the 555 timer. This then turns the relay off until water again reaches the top probe and a further trigger pulse is received from Qt. Peter King, Airlie Beach, Qld. ($20) FEBRUARY1990 27 IT'S ON AGAIN, THE FABULOUS JAVCAR 15o/o OFF EVER HING SALE! Frequency Counter DMM + Capacitance Meter+ Transistor Tester+ 20 Amp Current+ High Impact Case! This compact DMM is housed in a bright yellow, high impact plastic case. It features a frequency counter capibilrry to 200kHz, transistor test, continurry (wrrh buzzer), capacitance meter, up to ;>() Amp current measurement and comprehensive AC/DC voltage, current and resistance ranges. Cat.QM-1555 SPECIACATIONS: DC Voltage Range 200mV, 2V, 20V, 1000V AC Voltage Range 200 mV, 2V, 20V, 200V, 750V fnputfmp_ 1 OM Ohm DC Current Range 200uA, 2mA, 20mA, 200mA, 20A Max VP Amps 10A (20A up to 60 seconds) Resistance Range 200, 2k, 20k, 200k, 2M, 20M Ohms Capecitance Range 200nF, 2uF, 20uF Frequency Range 0-20kHz, 0-200kHz Full overload protection $149.50 LESS 150¾0 $128.00 Squeaky Clean Mains Filters PROTECTION FOR: MICROPROCESSORS, TERMINALS, MfCROCOMPU• TERS, PRINTERS, DISK DRIVES AND TELEMETRY EQUIPMENT Used by Government Departments, Schools, Universities, Banks and TV Stations. For you to ensure maximum safeguard to both your hardware and software against RF noise, control tones and voltage spikes the equipment should be pre-filtered by a SQUEEKY CLEAN MAINS FILTER. $269.QQ 2 OUTLET Cat. MS-4025 $109.QQ 4 OUTLET Cat. MS-4020 15% OFF Deluxe Rack Cabinets These beautifully crafted rack cabinets will give your equipment a real 1st class appearance. All aluminium construction. Removable top and bottom panels. Natural or black finish . All dimensions conform to the international standard. Ventilated lid. Deluxe brush finished anodised front panel. Individually cartined. Supplied in flat pack form and easily assembled in a few minutes. SIDE ELEVATION: D = 254mm; C (internal chassis height); B (mounting bolt centres) Finish Cat. Cat. Cat. Cat. Cat. Cat. HB-5411 HB-5413 HB-5415 HB-5410 HB-5412 HB-5414 Natural Natural Natural Black Black Black A 44 88 132 44 88 132 B 34 57 89 34 57 89 C 38 82 126 38 82 126 Each $65.00 $75.00 $90.00 $65.00 $85.00 $95.00 +5 $62.00 $71.00 $85-00 $62.00 $80.00 $90.00 Six Natural and Black Finish Models The black or natural finish cabinets are available in 44mm, 88mm or 132mm high modules. Mounting hole centres conform exactly to International Racking Specijications both vertically and horizontally. Less 15% VIFASpeaker Kits PRICE SENSATION!!! We all know how fantastic the VIFA speaker system SA-series speaker units sound. It would not be an exaggeration to say that they generally perform as well as built equivalents that cost twice as much! SA-50 5'' Woofer/Dome Tweeter Despite this, Jaycar is constantly trying to further reduce prices for the customers' benejll. We are now proud to announce MASSIVE PRICE REDUCTIONS on the entire range of VIFA SA-Series HI-FI speaker kits. Check out the savings below, but hurry! These prices can only last while the Aussie dollar is strong - and that can change overnight. 2-Way bookshelf kit with cabinets and crossovers. 30W RMS power handling. Cabinet size: 210D x 170W x 260Hmm Cat. CS-2460/CB-2452 SA-70· 8" Woofer/Dome Tweeter Price savings are for speaker and cabinet buy only. See our catalogue for full details, or call into any Jaycar store for a demonstration. (Demo speakers are not at Concord) (Sealed cabinet) 2-Way kit complete with crossovers and cabinets. 70W RMS power handling. Cabinet size: 250D x 260W x 490Hmm Cat. CS-2471/CB-2472 SAVE SAVE $30 ONLY $369 APAIR SA-100 8" Woofer/Dome Tweeter (Bass reflex) 2-Way kit complete with crossovers and cabinets. 1 00W RMS power handling. Cabinet size: 338D x 290W x 640Hm Cat. CS-2460/CB-2482 SAVE $100 ONLY $669 A PAIR , $50 ONLY$449 APAIR 15% -130 • • • 10" Woofer 3-Way Reflex Complete with crossovers and cabinets. 130WRMS power handling. Cabinet size 368D x 300W x 940Hmm Cat. CS-2485/CB-2467 SAVE $200 • • ONLY $999 APAIR PRO SERIES POWER AMP KIT UHFNHF INDOOR TV AMPLIFIER SPLITTERS LT-3819 This unit has a 75/300ohm input and two 75/300 ohm outputs. Further splitters can then be used as this unit is designed to drive up to 8 - 10 TV points. It also has a channel 3. 4, 5A and FM switchable trap (-25d8) in case of cross modulation Of 18d8 X 2. Was $109 NOW REF: EADec'89.Jan'90 ~~~~~ "Pro Series I" L-.v' L-.v' L-.v' L-:-/ L-.v' At long last the 9 year old 5000 amp design has been totally redesigned t o accommodate latest technology! This totally new design features the best of the old ETI 5000 features including: ■ Magnificent heatsink front panel ■ Rugged chassis bar 2 rack unit construction ■ Proven Hitachi Mosfet technology , _...,....r, I , • i..~'M' BUT AU. ELSE IS NEWI Bargain of the century 100 assorted LED's including 3mm and 5mm in The new pro Series I features two especially European made 22fNA Toroidal Transformers feeding two separate paNer supplies, one for each channel. [The ETI 5000 had a common power supply for both channels). This massive bank of energy not only increases channel separation. but gives the amp an ENORMOUS LEAP in POWER HANDLING. (See specs.) Better Features. The Pro Series I not only kills the 5000 for perfomace. it has great features. For example. it has a chassis plug IEC 320 style mains inlet and a switched chassis IEC 24fN socket to power other mains equipment. It also features signal clipping LED's on the cast front panel. This keeps in mind the highly likely professional applications for this amp. Simpler to Build. You would think that this new amp would be harder to build than the straight forward 5000. Not so! The Pro Series I. intact. is far easier to build and actually has less signal distorting components than the 500'.l. What do you pay for this magic? Incredibly. we have managed to well withing sight of the old 5000 - only $100 more. That's right! You get all this for only $599! ! INCREDIBLE. As usual. the Jaycar kit comes with every conceivable pan - nothing else to buy• and Jaycar quality as a bonus! yellaN, orange, red and green. rectangular. triangular and other shapes and displays! All for less than~ each! Cat. ZD-1696 . $8.95 ~.:::. '"'""''"''! ,5 99 $89.95 NEW LED PACKS Power output (per channel, with both channels driven) Continuous: 140W RMS into 8 ohms 200N RMS into 4 ohms IHF pulse power. 190W RMS into Bohms 32W/ RMS into 4 ohms Harmonic distortion 0.005% at 100W RMS into 8 ohms 0.007% at 14(],N RMS into 8 ohms 0.008% at 200N RMS into 4 ohms 0.004% at 100W RMS into 8 ohms Intermodulation distortion (4: 1 ratio of 50Hz and 7kHz) 10Hz to 100kHz (-3dB points) Frequency response Signal to Noise More than 100dB belaN rated output (unweighted) Sensitivity 0.83V RMS for 100W into 8 ohms Approx 33k ohms Input impedance More than f1N /us Output slew rate Damping factor Greater than 50 Overload indicator Activated if output distonion exceeds 0.05% .... THE LATEST KITS KA-1717 KA-1718 KA-1719 KA· 1720 KA-1722 KC-5050 KC-5051 KC-5052 KC-5053 KC-5054 KC-5055 KC-5056 Subwoofer Adaptor Auto NiCad charger NiCad discharger RGBI to PAL encoder LaN cost mains filter 1/3 Graphic equaliser CD compressor Touch lamp dimmer Extension touch dimmer Garbage bin reminder 1/2 sterep graphic eq. FM radio/motorbike intercom $29.95 $42.50 $27.95 $39.95 $18.95 $239.00 $49.50 $32.95 $14.95 $24.95 $349.00 $69.95 QUALITY DISKS AT SILLY PRICES 5 1//4" DSDD 48TPI IICT Cat XC-4730 • , $6.50 for 10 ,,,,j. ',, · 3 1/T MF2DD 135TPI Cat XC-4736 $26.95 for 10 5 1/4" DSHD 96TPI Cat XC-4732 $18.95 for 10 Lifetime warranty Scoop Purchase! 12 KEY NUMERIC PAD (telephone style) This fantastic little keypad measures 67H x 44W x 7D. Each button is separately addressable and has a fantastic tactile feel. 0-9 plus• & I keys. Connection data provided. Japanese made. Quality. Cat. SK-0760 ► Ideal for ultralight aircraft. power boats. etc. Slim earpads stick to the inside of the helmet with velcro. Mic does the same. Safety line plugs uncouple in emergency. Amplifier unit fits into any jacket pocket. Battery powered. Cat Al-5510 $69.95 Includes two headset/mics and amplifier. TURN YOUR SURPLUS STOCK INTO CASH! Jaycar will purchase your surplus stocks of components and equipment. CALL GARY JOHNSTON OR BRUCE ROUTLEY I (02) 747 2022 IN4003 DIODES 1 Amp 300 volts Save$$$$$ 50for$3 100 for $5 STOCK UP NOW Cat. ZR-1003 HI POWER PIEZO TWEETER 400WRMS ' Brand new MOTOROLA POWERLINE horn. Includes a protection cirtuit internally which allows the new horn to handle 400W RMS. It uses a miniature light bulb and a PTC resistor. Under extreme high power surges, the PTC opens up allowing the speaker to continue to play. at a somewhat compressed power level. The resulting produc.tjs a practically blow-out proof speaker. Replaces KSN1025A. Size 177.8 x 82.55mm. Rectangular. Freq Response 1.9 - 40kHz. Volt Sensitivity (Q) 2.83V 1/2M • 100d8 Ideal for Hi-Fi and Sound Reinforcement Cat CT-1912 ONLY $37.95 RP/RB ELECTROLYTIC MADNESS HIGHER POWER DATABANKJ CALCULATOR Similar to QM-7200 but• 16 character alpha-numeric LCD display• Capacity 8000 alpha-numerics • Superior editing of old information • Soft rubber tactile keypad • 14 digit calculator with memory • Character search • Forward search Only requires 4 x AAA batteries. Measures 155 x 103 x 35. Very high performance unit! Cat OM-7026 $59.95 Another surplus buy, which saves you a fortune. High quality Japanese made Nippon Chemicon brand. Normal Sale Price Price 10+ 3,J00uF 63V RB $7.50 $3.95 $3.50 ea $4.95 $4.50 ea 3,J00uF B0V RP $8.50 4,700uF 63V RP $8.50 $4.95 $4.50 ea $4.95 $4.50 ea 6.B00uF 40V RP $8.50 10.000uF 35V RP $11.00 $5.95 $5.50 .ea Cat RU-6730 Cat RU-6731 Cat AU-6732 Cat RU-6734 Cat RU-6735 ~i EXIDE 12VOLT GEL BATTERIES 1.9AH $14.95 10+ $13.95 Cat SB-2482 $19.95 2.SAH 10+ $18.95 Cat SB-2484 15AH $59 WAS $79 10+ $55 Cat. SB-2490 C & D NICads SAVE UP TO 42% Csize a· Was $11.25 ea NOW $6.50 EA Cat SB-2459 SUNRISE BRANO A MULTIMETER KIT Ref: Silicon Chip Feb '89 woofer and dome tweeter with pre-built crossover. Acclaimed for its superb sound. The cabinets measure 480(H) X 300(W) X 290(D)mm. See our 1989 catalogue for further information. Pair of speakers and crossovers Cat. CS-2540 1.2 Ah D size Was $11.98 ea NOW $6.95 EA See Silicon Chip Nov '89 Ideal for students. who can now build something really useful. Multimeter specs: 20,000 ohms/volt. 23 ranges, continuity buzzer. Size 135 x 90 x 40 Cat. KC-5058 $149 BUY BOTH Cabinets {pair) Cat CS-2542 ONLY $34.95 FOR $250 $129 SAVE $28 OPEN STEREO CEILING ActoNUNT SPEAKER KIT PIR DOORWAY/MINI ALARM This pocket size alarm has a built in PIR sensor to detect human movement It is ideal as a personal alarm or a shop door monitor. It will either give a pleasant chime to announce customers. or an alarm sound. It's easy to install and measures only 108mm x 67mm x 35mm. It operates·on a 9 volt battery. A/~,~" ~,1;w Cat LA-5012 ONLY $49.95 l\Pi11i This is a complete system ready to install in your home. It consists of: 2 x 4" dual cone quality speakers • 2 x Speaker grills and Open an acc()l.llt with Jaycar! Find screws • 1 x 60W stereo volume controller • 2 x 20m rolls out more by calling speaker wire. Ideal for games room. bedroom. kitchen. den. etc. in to any Jaycar store or call 1021747 Simply connect to your Hi-R system auxiliary speaker outlet. Full 2022 or send us a Fax (02) 744 0767 - connection diagram supplied. Easily installed with simple hand or write! We will send you an account tools. Cat AS-3050. Manufacturers! application form by return. It's that simple! REMEMBER • JAYCAR WILL NOT BE UNDERSOLD ON GOODS OF THE SAME QUALITY • ~ ~ • :::( i I ~' ES ;m VIS4 j l~ , SYDNEY • CITY PARRAMATTA CONCORD -=---': HURSTVIUE HEAD OFFICE 115 Parramana Road Concord 2137 Telephone (02) 747 2022 Telex 72293 FACSIMILE (02) 744 0767 MAIL ORDER VIA YOUR 117 Yori( St (02) 2671614 · Mon-Fri 8.30 · 5.30 Thurs 8.30 pm· Sat 9 - 12 355 Church St {Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 9 • 5.30 Thurs R.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 MAIL ORDERS P.O. Box 185 Concord2137 HOlllNE 02 7471888 FOR ORDERS ONLY TOLLFREE (008) 022 888 ff s 3.75 S 450 $ 6:50 $8.00 ROAD FREIGHT ANYWHERE IN AUSTRAUA $13.50 GORE HILL BURANDA QLD MELBOURNE-CITY SPRINGVALE VIC POST a PACKING Sl0 -$24_99 $25-$49.99 $50-$99. 99 OVER $100 188 Pacific Hwy {Cnr. Bellevue Ave) (02) 439 47$. Mon-Fri 9 - 5.30 Sat 9 - 4pm 144 logan Rd (07)393 0777 • Mon-Fri 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- Sat9-12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 - 2 A high quality audio oscillator: Pt.2 Our new high quality oscillator has a number of interesting circuit features, some of which were described last month. This month, we describe the remaining circuitry and give the construction details. By LEO SIMPSON Last month, we concluded with the description of the oscillator circuitry. Now let us move to the square wave circuitry. This needs to provide square waves which are as square as possible (ie, with 50% duty cycle) and with minimum overshoot or droop. The rise and fall times also need to be very fast which is necessary if the oscillator is to be faster than any audio equipment under test. The output signal from the low distortion oscillator section is fed via a 2.2µF bipolar capacitor and 8.2k0 resistor to a 74C14 CMOS Schmitt trigger. Two Schmitt trigger sections, ICta and ICb, are cascaded to give a very good square wave which is precisely ad32 SILICON CHIP justable for duty cycle by tweaking the DC voltage fed to IC1a with tkO trimpot VR2. While the square wave from the second Schmitt trigger is pretty good, it is only about 12 volts peakto-peak as set by the + 12V rail from the associated 78112 3-terminal regulator. We need a square wave with an amplitude of 20 volts peak-to-peak to give the same RMS amplitude as from the oscillator and it must also have a low output impedance. The first step in achieving this is to connect the signal from IC1 b to the remaining four sections of IC1. These sections are connected in parallel to form a fast buffer circuit and drive the gate of VMOS Fet Qt 1, which is a Siliconix VNtoKM. This is an extremely fast device with rise and fall times of potentially only a few nanoseconds. Qt 1 acts as a very fast switch to boost the square wave signal to just over 20 volts peak to peak. From the drain of Qtt, the square wave signal is coupled via a 100µF capacitor to a rather unusual buffer circuit consisting of four transistors: Q12, Q13, Qt4 and Q15. It , is based on the circuit configuration used in the National Semiconductor LH0022. The four transistors effectively act as complementary compound emitter followers and they are arranged so that there is virtually no DC shift from input to output. This is accomplished in the following way. As the signal passes from the base to the emitter of Qt2, it is shifted up in potential by the baseemitter voltage. Then, as it passes from the base to the emitter of Q14, it is shifted down by almost exactly the same amount. The same process occurs in the complementary transistcirs Q13 and 015. Note that Q12 to Q15 are spec- SEE SEPARATE DIAGRAM FOR S1, S2, S3 AND S4 CDNNECl'lbNS Fig.4: here's how to install the parts on the PCBs and wire up the chassis. The idea is to build & test the power supply board first, before moving on to the oscillator board. Refer to Fig.7 for the connections to S1, S2, S3 & S4. ified as complementary types and this is important for stabilising the quiescent current through Q14 and Q15, which is set at around 1.2 milliamps. Any tendency for the current through the output transistors to increase will result in a slight increase in the voltage across the 6.80 emitter resistors and this will throttle them back. At the same time, any tendency for the Vbe of the output transistors to drift will be compensated for by an equivalent drift in the input transistors, Q12 and Q13. Since the whole buffer is effec- tively an emitter follower using small signal transistors, it has a very wide bandwidth we estimate that it is at least 30MHz. The buffer runs from a + 22V supply and so can deliver a square wave of 10 volts RMS. The 2000 trimpot VR3 in the drain circuit is provided FEBRUARY1990 33 The two lamps in the negative feedback path of the oscillator are mounted directly on the PCB. Be sure to use the types specified in the parts list (Farnell Electronics Cat. CM7374). as simple as you will ever see in an instrument of this kind but has the virtue of good linearity and excellent frequency response - more than adequate for the frequency range to 1 lOkHz. In fact, the metering circuitry is the same as used for the AC ranges of most cheap analog multimeters. D3 and D4 are simply halfwave rectifiers connected in a bridge arrangement with two 10k0 resistors. The circuit has advantages over a conventional bridge rectifier in that (a) only two diodes are used instead of four; and (b) the resulting linearity is better since only one (germanium) diode is operative at any instant. The linearity of the circuit is very good because the signal being measured is large, up to 14 volts peak or more, in relation to the germanium diode forward voltage drop of 250mV or less. Separate trimpots, VR4 and VR5, are required for metering the sine and square wave outputs since the peak to peak voltages of the waveforms are different. As mentioned above, a 10V RMS square wave has a peak-to-peak voltage of 20 volts whereas a 10V RMS sinewave has a peak-to-peak swing of 28.28 volts. Output attenuator The output attenuator is a simple resistive divider with 10 lOdB steps from 1mV to 10 volts RMS. The 4700 resistor in series and the resistance of the divider plus VR6 combine to give a nominal output impedance of 6000. Check the output voltages from the power supply before wiring it to the oscillator board. All connections to the mains switch must be run using 240V AC cable and any exposed connections sleeved with heatshrink tubing. to adjust the square wave output to exactly 20 volts peak to peak which is equivalent to 10 volts RMS. Sine/square switch S5 is the sine/square selector. It has three sections: S5a, S5b and S5c. In the sine mode, S5a switches the wiper of trimpot VR2 to the + 12V rail. This pulls the input of ICta high and effectively disables the square wave circuitry. It also turns Mosfet Qt 1 off so that no current is consumed. S5b connects either the sinewave 34 SILICON CHIP output from the oscillator or the square wave output from the aforementioned buffer stage to the tkO variable output control, VR6, and thence to the output attenuator, S6. S5c connects the signal from the wiper of VR6 to the metering circuitry. This involves germanium diodes D3 and D4, the associated 10k0 resistors, and trimpots VR4 and VR5. Metering circuitry The metering circuitry is about Power supply The power supply uses a transformer with two 12V windings connected in series. These feed two half wave rectifiers and lOOOuF filter capacitors to give unregulated supplies of about ± 33V. These are fed to LM317 and LM33 7 3-terminal regulators to give ± 22V. These regulated rails supply the oscillator and square wave buffer circuits while a 78L12 3-terminal regulator feeds the 74C14 (ICt). Construction Our prototype oscillator was built into a standard Horwood This view shows the arrangement of the hardware inside the metal case. The Horwood case will have to be disassembled into its component panels before drilling the necessary mounting holes for the PCBs, switches, meter and other hardware items. Take care with the mains wiring. metal instrument case, measuring 305 x 102 x 203mm. Two printed circuit boards are used, one for the power supply and one for the oscillator, although many of the components are mounted around the rotary switches. The oscillator board measures 207 x 93mm and is coded 04101901, while the power board measures 108 x 64mm and is coded 04101902. Before we start on the details of construction, we'll point out that this is a tricky unit to build. There is a preferred order of assembly and if you don't follow it you will find the job a lot harder. The Horwood case should be disassembled into its component panels, some of which will need drilling to mount PC boards or hardware such as switches and so on. Having disassembled the Horwood instrument case, the next task is to assemble the power supply board and get it going. This will then give you a power supply to get the oscillator board going. Check the power supply board carefully before assembling any components onto it. Look for shorts between tracks, open circuit tracks, and holes that have not been drilled. The board can then be used as a template to drill four 3mm mounting holes in the righthand side panel of the Horwood box. Now fit the board with the five PC stakes for the outputs. Next, mount and solder all the components with the exception of the power transformer. Take particular note of component polarities: diodes. electrolytic capacitors and 3-terminal regulator. Follow the component layout shown in the main wiring diagram (Fig.4). Take particular care with the 3-terminal regulators and note that the terminals for the LM337 are different from those of the LM317 (see the circuit diagram, Fig.3, in last month's issue). Before mounting the transformer, fit short lengths of sleeving over the three primary termination lugs which protrude from the side of the bobbin. These are a safety hazard and otherwise could cause an electric shock later, when you are working on the project. Now mount and solder the power transformer to the board. Temporarily terminate a 3-core mains flex (with moulded 3-pin plug) to the board and then mount the whole board assembly on the case side panel. The side panel can be temporarily earthed via the earth lead of the mains cord to make the whole assembly electrically safe. Now apply power to the supply board and measure the output supply rails. They should be close to ± 22V. It is a good idea at this stage to mark the three supply pins on the FEBRUARY1990 35 Keep all wiring leads to the front panel hardware as short as possible. The LED is mounted using a plastic bezel. board with " + ", " - " and "OV" in pencil so that you can easily identify them. It is also a good idea to temporarily wire the LED across its terminals so it can function as a power indicator. 2 x 1 POLE, 12 POSITION WAFERS ~ SHIELD PLATE \ + S1 ,S2,S3 Oscillator board The procedure with the oscillator board is to assemble it with all components except for the 74C14 (IC1) and the Mosfet (Q11). After checking the copper pattern carefully for any defects, use the oscillator board as a template to drill four 3mm holes in the base plate of the case. The only other hole which needs to be drilled in the base plate is for the earth point solder lug which is situated just behind and between the two front panel BNC sockets. With the holes in the base plate drilled, you can proceed to assemble the board. First insert the PC stakes (25 required) and then the resistors and diodes. When this has been done, install the transistors and capacitors. Note that the resistors associated with the attenuator are all 1 % types (with five colour bands) while the rest of the resistors can be 5 % types. Use a digital multimeter to check each resistor value before you insert and solder it into circuit. The two miniature incandescent lamps are 28V 40mA types (not 24V types as shown on the circuit diagram, Fig.3, in last month's 36 SILICON CHIP ALL WAFERS MAKE BEFORE BREAK Fig.5: you can either buy the wafer switches fully assembled or you can save money by assembling your own as shown here. The parts are all available from Farnell Electronic Components (see text). Don't leave out the shield plates used on switches S1-S3. issue). They have a plastic base which allows them to sit squarely on the board. For the trimpots, we suggest you use good quality Cermet types. Note that VR3 should have a rating of 0.5 watt. Oscillator checking With all components except IC1 and Ql 1 installed, you are ready to power up the board and check its operation. First, we need to check the DC conditions on the board. To do this, the circuit is set up as a DC feedback amplifier by connecting a 22k0 resistor in parallel with a .068µF capacitor between points J to G. Now connect the ± 22V rails from the power supply board and check the voltage at the junction of the 150 emitter resistors for Q9 and Q10. It should be be close to OV. Now check the quiescent current through Q9 and Q10 by measuring the voltage across the two 150 emitter resistors. For a current of 15mA, the voltage should be 0.45 volts. Provided the measurement is between 0.3V and 0.45V, no adjustment is needed. If a measurement between 0.3V and 0.45V is not obtained it will be necessary to change the 1k0 resistor between collector and base of QB. To increase the voltage, try changing the resistor to 1.2k0. To reduce it, try shunting the 1k0 resistor with a value of 10k0. To make the circuit oscillate, connect another 22k0 resistor in series with a .068µF capacitor between points H and J. Now apply power and the circuit should oscillate at close to 100Hz factually around 106Hz). With your digital multimeter set to AC voltage, use VR1 to set the output amplitude to 10 volts RMS. Also, while the board is powered up, check that + 12V appears at point N on the oscillator board. This checks that the 78112 is OK. Incidentally, if you can't obtain a 78112, you can use a 7812 instead. Square wave section With the sinewave circuit operational, you can now install IC1 and Ql 1, set VR2 to mid-travel and then power up once more. If you have an oscilloscope, you can check that a 100Hz square wave appears at pins 2 to 6 and pins 8 to 13 of ICl. It should have an amplitude of close to 12 volts peak. The square wave amplitude at the drain of Q11 should be larger, depending on the setting of VR3, and it should be almost identical at the output of the high speed buffer stage, at point 1. You can now adjust the square wave amplitude and duty cycle. Several methods are possible, depending on the test gear you have available. To set the square wave duty cycle, set your multimeter to the lowest DC range, connect it to point 1, and adjust VR2 for a zero reading. To set the amplitude to 10 volts RMS, set your multimeter to measure AC voltage and adjust VR3 to obtain a reading of 11 volts. (Yes, you read it right: 11 volts). After the oscillator is fully assembled you will want to go through and do a final tweak on VRl, VR2 and VR3. You can now put both the power and oscillator boards to one side and then work on the front panel. Front panel assembly Quite a lot of work is involved in the front panel. First, it needs to have all holes drilled and the meter cut-out made. You can use the front panel artwork as a template for this task. After that, the multiwafer switches must be assembled, according to the diagrams in Fig.5. You can purchase the switches fully assembled from C&K Electronics (Aust.) Pty Ltd, 15 Cowper Street, Parramatta, NSW 2124. Phone (02) 635 0799. By the way, all the wafer switches should be make-before-break types. This was not specified in the parts list. o-0 re re re 0--0 • .... 0 .... o--ol!"4 0--0--0 • V 0 u Ol ~ Fig.6: this is the full size artwork for the main oscillator board. Alternatively, you can buy the individual parts for the wafer switches from Farnell Electronic Components Pty Ltd, 72 Ferndell Street, Chester Hill, NSW 2162. Phone (02) 645 8888. By assembling the switches yourself you save some money and you also get more rugged switFEBRUARY 1990 37 WAFER NEAREST CLICKER PLATE S4d WAFER NEAREST CLICKER PLATE CAPACITORS ON S4a TERM IN ATE ON S4b CAPACITORS ON S4c TERMINATE ON S4d OpF 70pF WAFER REMOTE FROM CLICKER PLATE ·\ WAFER REMOTE FROM CLICKER PLATE G are 2 % types or better, as specified in the parts list in last month's article. Fit switches S4 and S2 with the three leads which run down to the oscillator board, at points G, Hand J. They should be left about 10cm long for easy termination to the board. Now, before fitting switches S1 to S4 to the front panel, you should fit the meter movement and the remaining hardware such as the two insulated BNC sockets, the sine/ square switch S5, the float/GND switch S7 and the output control VR6. WAFER NEAREST CLICKER PLATE WAFER REMOTE FROM CLICKER PLATE WAFER NEAREST CLICKER PLATE WAFER REMOTE FROM CLICKER PLATE All WAFERS VIEWED FROM REAR Fig.7: wire up the wafer switches as shown here before installing them on the front panel of the case. It is a good idea to check each resistor value with a digital multimter before mounting it in place. ches (in our opinion). However, we would have preferred to have the switches somewhat easier to rotate - their springs are just too stiff. If you do decide to assemble the switches, you will need the following Farnell Electronic Components parts: 4 mechanisms (146033) 6 wafers 1-pole 12-position (146038) 2 wafers 2-pole 6-position (146039) 3 screens (146042) 14 6mm spacers(146044). They should be assembled as shown in the two diagrams of Fig.5. Note that S6, the attenuator, is a standard 1-pole 12-position switch which is set to give 10 operating positions. It can be purchased as an over-the-counter item from most parts stockists. The shafts of all the rotary switches should be cut to a length of about 12mm before any components are wired to them. That is the easy part. You now have to wire the switch wafers as 38 SILICON CHIP shown in the diagrams of Fig.7. Note that all the resistors shown on the switch wafers are 1 % types and, as before, you should check each value with a digital multimeter before installing it. All the capacitors on switch S4 With all hardware and switches mounted on the front panel, you can complete the wiring to the oscillator board. Attach the base panel to the front panel with the two selftapping screws and then proceed to do the wiring in a way so that you won't have to push the soldering iron through existing leads to make additional connections. For example, wire the two BNC sockets first, then the float/GND switch S7, then the sine/square switch S5, then VR6 and so on. Leave the attenuator switch, S6 till last. When all the wiring between the front panel and the oscillator board is complete, you can finish the assembly of the case and do the mains wiring to the power supply. Note that there is no connection between the circuitry of the oscillator and the mains earth, although the case is earthed back to the mains. This is to avoid earthing SC04101 901 00 Fig.8: full-size artwork for the power supply board. D.DAUNER ELECTRONIC COMPONENTS WE STOCK A WIDE RANGE OF ELECTRONIC PARTS for • Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST Quartz in filter 10.9MHz 6kHz BW. $12.50 US Filter capacitor 4µF 3kV . . ... $15.00 Electromagnetic Airpump for Aquarium. . ...... $9.00 Timer Motor 240VAC 6RPH ...... $6.00 Come and see. This view shows the mounting details for the four wafer switches which are used to set the output frequency. Note that the lead length of the components mounted on the switches are kept as short as possible. problems when you are making measurements on sensitive audio equipment. Final adjustments Now power the oscillator up and repeat the adjustments to VRl, VR2 and VR3. This done, set the oscillator to the sine mode and, with the output adjusted to give 10 volts RMS, adjust VR5 to give full scale deflection. Finally, set the unit to the square wave mode and adjust VR4 for full scale deflection of the meter movement. After that, all that remains is to check the operation of the attenuator and then the frequency setting switches. You will need an oscilloscope or a frequency meter for this latter task. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Caltax Sanlca Station In Blrdwoad Road) Phone 724 6982 TRADING HOURS: Monday to Friday 9.00 a.m. to 4.00 p.m. Saturday from 9.00 a.m. to 12.00 noon. Lamp option As an interesting exercise, we have tried quite a number of different incandescent lamp combinations to see if we could get better performance. Basically, the lamp(s) required need a high resistance filament. The best lamp we found, apart from the Farnell type specified, was a 240V 15W pilot lamp with a standard bayonet fitting, as available from most hardware and lighting stores. This lamp gave lower distortion at low frequencies but longer amplitude settling times. ~ ACTIVE SHORT WAVE ANTENNA TECHNIKIT AT4SW j: (SEE SC JAN '90) COMPLETE KIT $59 BUILT and TESTED $119 (BATTERIES INC) CASE $10 LOOP ANTENNA Q TECHNIKIT PX1 COMPLETE KIT $44 BUILT and TESTED $69 (SEE SC JUNE 89) Improved signal strength & signal quality in a portable tunable antenna. .I.V....;. r.:■i;it:■i;~ PACKING & POSTAGE IN AUSTRALIA INCLUDED IN PRICES QUOTED. WRITE OR RING FOR BROCHURES ORDERS ACCEPTED ANYTIME PAYMENTS BY BANKCARD, VISA, MASTERCARD, CHEQUE or MONEYORDER TRADE ENQUIRIES WELCOME RCS Radio Pty Ltd is the only company which manufactures and sells every PCB £, front panel published in SILICON CHIP, ETI and EA. JILOA PTY LTD 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. P.O. BOX 73, GLENHUNTL Y, VIC 3163 Phone (03) 571 6303 (TECHNIKIT DIVISION) FEBRUARY1990 39 NOW OUT! products at Phone us tod L_ Audio Frequency Generator Jack O'Donnell Managing Dirtector --"\ 1-GREAT DUAL TAPE \ SAVING!~ \...--- ONE RING to AC Many combln 300 WATT INVERTER WITH AuTo S TART Opcrams from 12V Car Battery • Auto Start draws power from your battery only when appliance is plugged in and "tumod m" ic, battory can be left permanently coonoctcd if required.• Voltage Regulamd • Cun=t Rcgulamd • Current Overload unit :,elf limits Complete Kit In testing audio circuitry it is necessary to have an accurate audio signal source. It even allows you to test 455kHz IF stages! K 6750 $279.00 Fully built and tested Features: • Outgoing ~ssagc variable from 30 to 120 sec. • Annowiccmcmt-only mode • ·Incoming; message UI voice controlled • Incoming call can be monitored • Rapid erase • Has built-in microphone • great for dictation A 0512 Normally $199. This month 50 only at $149 (No back orders at this price) Frequency Range Accuracy Output Waveforms Out put Level 10Hz-1MHz +/-3% +2Hz Sine/Square Sine: 8VRMS Square: 10V P-P -20db, -40db Output Attenuator and line adjust a 1540 Normally $299 This month $249.00 SAVE $SO Beat Triggered Strobe Add more life to your 11.ext party! Aashes in time to your music, or as normal strobe. Exclusively customised by ALTRONICS~ into our H 0480 Instrument Case. Includes silk- ics1;8"w1~s $79.95 K 6755 100'5 OF USES AT HOME AND AWAY $379.00 POWERHOUSE 600W INVERTER (SccEADcc'87) This inverter has the capacity to produce 600 watts of mains power which will run a fantastic array of appliances. Ideally suimd to rurming power tools, lighting (including fluros) electric motors and much more. It can be used either as a patablc or a permanent fixture. • Manual or Auto Start facilities • Low battery cut-out. Kit version K 6770 $425.00 Fully built and tested 12V Input K 6774 ~ <t--~ 24V Input K 6775 Now $75.00 (SeeAEMJuly'85) $525.00 Tube Option K 5795 $16.50 Now $15.00 BONUS OFFER We wll/ Include a set of 4 Car Alarm WARNING stickers ($3.95 value) ABSOLUTELY FREE with every Car Alarm Kit ordered this month. The Protector Alarm Kit These are the genuine Grain Oriented Toroid Transformers as used In Electronics Australia and SI/Icon Chip Magazine Projects. Primaries 80V A (Watt) Models 87 diam. 40mm H, 1.1 kR, leads 200mm Normally $55 This Month $49 (See SC Feb '88) Toroidal Power Transformers This refined car burglar alann baa about every fcatutc you could possibly want to keep would-be thieves away. Features: Inmmal & Exmmal Sirens Duh Lamp Auber Battery back-up Delayed ond Non-delayed inputs Easy to build and install K 4370 Was $129.00 NOW a GREAT SPECIAL at $119.00 Why a Toroid? • Smaller size and weight to meet modern "Slimline" requirements • Low electricity induced noise demanded by compact equipment. • High efficiency, enabling conservative rating whilst maintaining size advantages • Lower operating temperature • Simple, quick, single bolt mounting. 500VA (Watt) Models Heat Sink Thermalloy T03 H 0503 75 cents each 10 Up for 65 cents each Normally $1.50 each Sec. V. 12+12 18+18 25 +25 30 +30 35 +35 160VA (Watt) Models 110 diam. 45mm H, 1.8kg, leads 200mm Normally $65 This Month $59 Cat No. M 3-050 M 3-055 M3060 M 3065 M 3070 M3071 M 3075 M3080 Sec. V. 12+12 18+18 25+25 30+30 35+35 35 + 35, 15 + 15 40 + 40 45+45 300VA (Watt) Models Sec.V. 1/2 Cat No. M3020 M3025 M 3030 M 3035 M 3040 30+30 35+35 40 +40 45 +45 50+50 55+55 125 diam. 45mm H, 2.5kg, leads 200mm Normally $79 This Month $69 Cat No. Sec.V. M3085 M3086 M 3088 M 3090 M 3092 M3100 M 3105 12+12 18+18 25 +25 30 +30 35 +35 40+40 45 +45 HAND-HELD MICS. Breathtaking performance without signal drop-out or noise interference. The Redford Wireless Microphone System is virtually the ultimate in an Entertainer's Microphone System (or for any roving microphone application for that maner!) All the annoying wireless microphone characteristics such as "drop-out", static and noise are completely eliminated by use of auto switching dual diversity receivers. The output of each receiver is continually monitored, with the strongest and clearest signal always selected. STANDARD MIC. C 0122 $349.00 Dynamic Range exceeding l00db is obtained by employment of a patented special Parabola level compressor and dynamic expander. FEAT URES: • No dangling Antenna or Microphone to get in your way • High Dynamic Range • Standard "AA" Batteries give long powerful operation • Advanced Technology - Automatic Switching Dual Diversity Receiving System. C 0112 Please Note: 4 different operatingfrequenciesare available ( you will need lo specifically nominate a desired frequency only if the equipment is being used in proximity with other Redford systems on the 200MHz band. Please specify if you have preference. Freq. available: 202.1MHz, 202.4MHz, 202.5MHz and 203.7MHz (use with C 0122) C 0142 $259.00 SHURE MIC.COMPLETE C0128 ROAD CASE LAVALIER MIC. C0132 $729.00 Portable PA System with inbuilt Dual Diversity Microphone Receiver The operating range ls a $349.00 minimum of SO Just released, our powerful SOW RMS, wide range amplifier speaker system with inbuilt diversity wireless mic. receiver. Fantasic for outdoor and indoor functions where high quality sound and fade free wireless microphone is required. Ideally suited for auditaiums, sporting arenas and dance halls. Will accept a tape ~rder or CD input and reproduce quality music. The unit operates on 240V AC mains. Fantastic for aerobics groups. SAVE $400 This high grade system sells elsewhere for $1290 - Altronics introductory price - only $899 C 0103 (202.4MHz) C 0105 (203.7MHz) Mkrophono, - us• a,ry ofth• R,dford UHF Wir«luJ mit;ropho11•s or Guilor Piek..,,p will,. this systt& Passive Infra-Red ~ Lite Guard Insulation breakdown can in elcc.trical wiring and appliances can be dctcrm~ with this dual Floodlight Control e ,:c:::~.:; i----------""lscc Silicon chip Oct 88) 00 altcmaton, house wiring etc. Break.down can be measured at either SOOV or IOOOV depending on the situation. Perfect for workvan, toolbox or work bench. K 2555 How often have you thought there could be a prowler outside your door? Install a Lile Guard & (once armed) any "guest" will be floodlit when detected by this highly sensitive Infra-Red Detector. Speclflcatlons: • Ralnllght, outdooc, all weatlx,r operation • Operation Time: Adjustable 1-20mins esensltlvlty: Adjustable 2fJ _50, 30 Almableto desired direction with 2 ball joints • Switching Capability: 500W max. incandescent• Operation Modes: OFF, AlITO, TEST, MANUAL, ON. beams• S5350 was $135.00 SPECIAL PCB SHORTS LOCATOR Ideal for PCB indw,try and hobbyist. A ,mall ,elf-contained unit, battery operated. U1e1 audio troc to locate shorts. • HuthrcclCllSitivityrangc,.U,cr can thus concentrate on positioo.ingoftcatprobcs without } - - - - - - - - - - - - - - - - - - - - I having to watch a meter. Simple to ONLY $99.00 SAVE $36.00 Infra Red Movement ' ·· """'" constructandopcratc. K 2650 $29.95 IRD now includes pulse count circuitry with a specific time delay between pul,c 11C111ing. Three pulac1 of IR radiation arc required to trigger the detector. Features: Lens - wide angle & narrow angle 112V DCPowercd. S 5301 $79 (3) for $180 $79 • 00 EA June 1989 for service teclmic · nly removed with on. Slmple cleanln - ..£=:r. <at> rangcmegohmmetcr. ~~p~i::ce::-=c::!r::~:: ......... U'f'IL 1IIHt IMINI MITTER FM STEREO TRANSMITTER Turn your CD player lnlo a Mini FM Transmitter Ccmvcrts CD signal to FM signal 10 you can tuJE'. in with your Wallcman or portable radio• Powered by one 1.5V pcnlitc battery • Single IC circuit makes it easy to build. K 1120 Normally $43.50 Now Only $32.00 SA VE OVER 25% AUTOMATIC N1CAD CHARGER (SEEEAJULY89) < > )~'1~.N.J+~Hl;)Jzt--l l ~1.iL;;l-5.fil.l ;I; ~1...;ffiB.~ •.~.•1~~ ~(;)a~•99t()•ar·· GENERAL PURPOSE MAINS) .. . .. RANSfORIVIERS~ ·~ -..•. -·~. . .. Gel Cell Charger N1CAD '.: ".·:., ':,;::;.. (See Silicon Chip July '89) All mains Transformers Primaries 240V • Specifications llsted refer to secondary windings. .... llili,11: : : } } M2855 ) } M 2154 \ M 2156 ·•·· ·· .....·••••· M 6672 12.6V CT 12.6V CT 12.6V CT 30V CT 0,12,15,18Vat 6,9,12,15Vat 15,17.5,20,24,27.5,30V at SENSATION I FROM $1.99 NEW NEW NEW NEW NEW Iii! 1 NEW 150mA 300mA 500mA 150mA 1Amp 2Amps 1 Amp $5.95 $7.65 $8.95 $6.95 $12.50 $17.95 $16.50 HEADPHONES month K 1685 $5.50 $6.95 $8.45 $6.50 $11 .50 $16.50 $15.00 $23.50 o Gel Coils and scaled load acid battorios • Mmitorcd battery voltage stateschargingcurront•Canaddycarstobattory lift. Microprocossorcontrolled• ldcal forradio amateurs and model racing car drivers Low 8 SECTOR BURGLAR ALARM KIT "·-'::,{ Protect your Home or Business rrom Intruders with this "State of the Art'' Burglar Alarm System and save$$$ on the cost ot commercial equivalents. Features: • Alann has 8 separate input circuits - 8 sectors can be monitored independently• Each input circuit is provided with an indicator LED and a soc;tor ON/OFF switch. e Individual so isolation allows the user to be in some lµ'Cas of the premises while others remain protccted,oglnsidc OFF, Ousidc ON.• Inputs accept both normally closed and normally open sensors. • Two inputs provided with an entry delay (botwoon 10-75 seconds). • ln1trnal trip warning buu.or • aloru ow=/occupant of ponding alarm operaticm - great for the "forgetful" amongst us. This buu.cr is presettable botwoon 5 and 55 seconds prior to alann. • Unique circuit detects automatically when either N/0 or N/C loops arc either open circuit or dead short, eg someone ls trying to bridge reed switches etc. • Switched output can be used to send a • High perfonnancc, noise attenuating earphones. • Noise cancelling microphone • Cushioned head pad • Super sturdy • Great performance • Superb, professional pilot 's headset will last a lifetime with reasonable treatment. • Includes standard aircraft jacks. silent alarm through an auto-dialler circuit or similar. (See EA Jan/Feb'85 or our 1989 Catalogue for run features) C9070 ONLY $169.00 Kit (Lesa Battery Back Up) Back Up Battery 12V K 1900 1.2AHS 5065 $149.50 $29.95 $ 4.50ea $3.95ea MICROEYE VE CTQR ==~ PRICE ON EA AVIATORS HEADSET WITH OIL -· FILLED EAR CUSHIONS 1.2V 500mAh 10 up 25ormore S 5021 AAA 1.2V 180mAH 10 up Toe intelligoDI way to SUPER Why pay $400 or more for a David Clark set? CaLNo. S 5020 AA The First Detector with GaAs Diodes Until now GaAs diodes have only boon used in sophisticated military radar equipment. The Microeye Vector is the first consumer electronics product equipped with this new tcclmology. Why Ga.As diodes make the difference • Lower thn:shold allows for a bottor signal to noise ratio • Lower signal conversion loss • Higher banicr reduces noise. Quite simply GaAs diodes increase the sensitivity of the Microcyc Vector.• Simply plugs into yom cigarette lighter socket or can be direct wired into your existing car wiring• Oips onto visor• Detects mobile radar equipment• Highway/City/Modes • Separate audio aloru for X and K bands • Visor bracket• Velcro• Cigarollt lighter plug. Microprocessor Controlled Detector Clips on to Sunvisor • Invisible from outside your vehicle • this fantastic high spec. Radar Detector detects X and K Band Radar up to an amazing 13kM. A 1530 Normally $499 Save $100 this month ..... r Ultra High Power Capacity r•sAvi. ly exciting newe ill that ell of akers are available at auch a nt price for thia month • but be /ck• stocks are limited. 15" (375mm) WOOFER Polypropylene Bass Drivers Huge 120 Watts RMS Massive 200 W Max. C3075 C3070 Normally $129 Normally $99 NOWONLY$99 YOU SAVE $30 NOWONLY$89 1O" WOOFER ,, 60Watt RMS 100W Max. C3065 100Watt RMS 150W Max. Was$69.00 NOWONLY $49.00 HUGESAWNGSONSPEAKERS · S" WOOFER -~ 60Watt RMS 100W Max. C 3060 Was $49.95 Now $39.95 SA VE $10.00 ~.r::.~. Our ALL NEW "B!ack" polyprop cone Bass Drivers exhibit quite astonishing low reg ister reproduction. Power ratings quoted are conservative. Not the cheapest but definitely the BEST VALUE we know of - ANYWHERE. 12" (300mm) WOOFER (Q 61 /2" WOOFER/Midrange 30Watt RMS 50W Max. c 3055 WAS $29.95 ' NOW ONL y "i24.00 1 61/2" Mid Range 30Watt RMS 50W Max. C 30:;/tev::'tf;,~Q NOW YOU SAVE AT $22-00 t Design Quality Weather Proof Speakers and Sound Columns by Redford • Rugged extruded aluminium construction • superb powdercoat Industrial paint finish • Engineered in Australia• Excellent reproduction• Superior to imports - yet a fraction of the price! Great for the back patio, swimming pool, games room, den, pool room etc. Wide Range Weather Proof Extension Speakers for Your Stereo System Redford is the solution-for high quality sound reproduction outdoors. the five models to choose from "fill the bill" from aplicatiom on boats to high grade paging and music entertainment installations, RUGGED EXTRUDED CONSTRUCTION These vibration free enclosures are constructed from die extruded heavy gauge aluminium and finished with incredibly durable industrial powdercoat en~l. The speaker ends arc sealed with gaskets and tough moulded "LURAN S" UV resistant end caps. The end result is "good looks" together with assured rugged durability for the Australian environment. EXCELLENT REPRODUCTION The drivers have been chosen for wide range, low distortion. mid-range "presence" (essential for high grade voc.al work) and high efficiency in general. Power Capacity: for short term the drivers will safely hancllc 150% of rated power. acoustic wadding is used to dampen bass resonance. Weather Proof Construction and use of"Doped Cones'' foam plastic and cloth is sandwiched between baffle and front grill to prevent water ingress. A first for Redford is the use of a patented cone moisture repcllant process process for all models. S ouND COLUMN TO M1c. STAND ADAPTER Ideal for portable PA systems. Adapter simply screws into column speaker and on to standard 5/8" !711'1 microphone thread. Suits all speakers/sound columns. Suitable for use on C 0505, C 0510 type microphone stands. C0990 'A' 2sox165x120mm $9.95 DESCRIPTION CLM W/P 15W/4 OHM WHT CLM W/P 15W/4 OHM BLK CLM W/P 10W/16 OHM WHT CLM W/P 10W/16 OHM BLK CLM W/P 10W/100V BLK CLM W/P 10W/100V WHT CLM W/P 20W/8 OHM BLK CLM W/P 20W/8 OHM WHT EACH PER PAIR 99.00 99.00 99.00 99.00 125.00 125.00 149.00 149.00 4LTilOnlC.) 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09). 328 1599 ALL MAIL ORDERS P.O. Box 8350 Stirling Street Exchange Perth W.A.6000 ALTRONICS RESELLERS Chances are there Is an Altronlcs Reseller right near you - check this list or phone us for details 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 cost S8lling from prices charged by Altronics Competitors. Don't forget our.ExpreH Mall and Phone Order Service-forth• coat of a local call, Bankcard, Yiu or Matercard holder• can phone order tor um• day despatch. STYLE CAT NO C SPKR C SPKR C SPKR C SPKR B SPKR B SPKR B SPKR B SPKR DESCRIPTION CLM W/P 20W/100V BLK 20W/100V WHT CLM W/P CLM W/P 40W/100V BLK CLM W/P 40W/100V WHT CLM VIFA 100W/8 OHM BLK CLM VIFA 100W/8 OHM WHT CLM VIFA 40W/100V BLK CLM VIFA 40W/100V WHT EACH PER PAIR 179.00 330.00 179.00 330.00 245.00 450.00 245.00 450.00 199.50 390.00 199.00 390.00 225.00 430.00 225.00 430.00 MORE AL TRONICS DEALERS WANTED If you have a Retail Shop, you coul~ increase your incom_e significantly by becoming an Altronics Dealer, Phone Chris Campbell (09) 328 2199 for Details. STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg $8 over 1Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 9 days from day you post order to when you receive goods OVERNIGHT JETSERVICE Up to 3 Kg is $8.00- 3Kg to 5Kg is $20.00-We process your order the day received and despatch via. Overnight Jetaervlce Courter for delivery next day Country areas please allow additional 24-48 hours. HEAVY HEAVY SERVICE -All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. $12.00 to 10Kgs, $15.00 over 10Kgs. INSURANCE -As with virtually every other Australian supplier. we send ~oods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDER - Bankcard,Visa, Mastercard Holders can phone order toil free up to 6pm Eastern Standard Time. Remember with our Overnight Jetaervlce we deliver next day. COUN TRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTCtfll K.B.Eiectronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521500 Farmer Electronics 522388 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 6241331 VI CTORIA CITY All Electronic Components 6623506 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN CAPALABAKingsway Electronics 3902399 WOODRIDGE David Hall Electronics8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724459 MACKAY Philtronics ■ 578855 ROCKHAMPTO~ Electronics (East St.) 221058Xanthos Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Soiex ■ 7724466 SA CITY Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRtSTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY '-~T.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2871385 CARINGHAH Hicom Unitronics 5247878 COUNTRY COFFS HARBOUR Coifs Habour Electronics 525684GOSFORD Tomorrows Electronics 247246 GRAFTON East Coast Electronic 431250 NELSON BAY Nelson Bay Electronics 813685 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 WA Another song about Sam Following last month's introduction to Samsung TV sets, I have another story involving this brand; a really rare fault and for several reasons, an elusive one to boot. And from the Apple Isle - well, all is not apples! As with last month's Samsung stories, this one involved a CB515F from a local motel. And this meant that I had less background to the problem than if the set had come from a private home. This is a serious problem with motel sets, as noted last month; it is seldom that one person watches the set for more than a few hours one night usually - and if they complain at all, this is often forgotten by motel staff or written off as incompetence on the part of the guest. Anyway, this story started when the manager complained that one of their sets was "hard to tune - or hard to keep in tune". Given such meagre information, I could only suggest that he bring the set in when business was a bit slack. In fact, it was several weeks before anything happened but the set turned up eventually. I set it up, switched to each channel in turn and checked the tuning. They all responded more or less normally, except that the tuning adjustment seemed to be marginally more critical than on other versions of the same model. But it was only an· impression and I couldn't be certain. The truth is, sets which use trimpots to control a voltage to a varicap tuner system are fairly critical to adjust, particularly on the UHF bands. If it were not for good AFC systems, which take over where the manual adjustments leave off, setting up would be almost impossible. Anyway, having set up the channels, I closed the door in front of the adjustments - which switches in the AFC circuit - and switched through all the channels again as a final check. All seemed well so I pushed the set to one side and left it playing. It played perfectly for the rest of the day and for most of the following day. Then, late that day, I decided to go through the channels again. And this was my first sighting of the problem; one channel was off tune, having obviously :,,, -- --- --- -- ---- --------- --------- - _, - - - - - - - - - - - - - - - - - - - - - - - - - - - """ - __ 1 : ,, ,, ., ,: PWB-MAIN-BOARD ..... M, ,.. JCllt Fig.1: channel selector and tuner circuit of the Samsung CB515F. The selector is at left while the tuner, TU001, is immediately to the right on the main board. Resistor SR105 and zener diode SD101 are near the top of the main board section. 44 SILICON CHIP l dritted outside the range of the AFC system, and had lost colour. I retuned it and it seemed to hold, at least for the moment. This behaviour was then repeated several times during the next few days and not just on the one channel. In fact there seemed to be no pattern to the problem; it came and went at random. And even those channels which held under AFC control appeared to have drifted when this was switched off. Likely suspects Well, at least I'd seen the fault and knew what I was seeking. There were two likely suspects: either the tuner (TU00l) or the selector unit with the channel selector switches, trimpots, etc which delivers the signal control voltages to the tuner. Both have given trouble in the past in a number of brands and of the two, I tended to favour the selector unit. Just why these give trouble is something of a mystery. They consists of two parts: a PC board carrying the channel selector switches plus the various other user controls (volume, contrast, brightness and colour), and a block containing the pots, etc. It is this block which usually develops a fault and since it is a sealed, non-repairable unit, it is normally discarded without the exact fault being pinpointed. My guess is that they suffer from either internal leakage or faulty (dry?) joints. Anyway, the first step was to determine which of these two sections was the likely culprit. This was done by monitoring the tuning control voltage at pin VT on the tuner. If this remained steady while the tuning drifted, then the tuner would be at fault. But if it drifted the selector would be suspect. Although this is fine in theory, such monitoring can be a time consuming procedure in the ordinary way. Fortunately, I have a Fluke 87 multimeter and this features a monitoring facility. The existing voltage is used as a reference and the meter then detects a rise or fall from this value, and gives an audible beep. It's worth its weight in gold for problems like this. Anyway, it quickly clarified the situation - the voltage to the tuner ~,," SE,S WH\Ct-\ use: 'TR \~'PO,S -f"O CON""rROL A VARl CPtP TVNE.-R 'S ¼'STE:M A.'R~ 'F~\'RLY C'R\1\CAL- TO AD:!"u'S, ""., was varying. This virtually ruled out the tuner and cast suspicion on the selector block. Since the set was still under warranty, I simply ordered a new unit from Samsung. This arrived in a couple of days and I lost no time in fitting it. The only snag was it made no difference. So was there a faulty batch and had I been saddled with a second faulty unit? Stranger things have happened but I needed help. I repacked the new unit and returned it to the service department with an explanation of the problem and a request that it be checked. The response was a telephone call a couple of days later from one of the technicians, who insisted that there was nothing wrong with the unit. And while I was trying to digest the full implications of this, he went on to suggest that the fault was probably in the IF section. I wouldn't buy that. Although not impossible, there was the varying voltage to the tuner which could not be ignored and the fact that the drift occurred on individual channels. When I raised these points, the technician tended to brush them aside. As far as he was concerned, I should look at the IF section. There seemed to be little point in arguing; that was his idea and he was stuck with it. More to the point, I was on my own. But I had to concede that, if there was nothing wrong with the replacement unit, then the chances were that the original unit was also in the clear and I had to look further afield. My problem now was that the replacement selector was back at Samsung and all I had was the original. But luck was with me. Almost immediately, another CB515F came in for one of the routine faults described last month. FEBRUARY1990 45 SERVICEMAN'S LOG -CTD That was soon fixed and I had a golden opportunity to try another selector, which I knew was OK. It was a simple job to swap the units and that settled it; the fault was just as much in evidence as before. This was gratifying technically but a bit of blow to my pride; I'd been so sure that this was another selector fault that I had hardly considered any alternatives. Now I was forced to. The most likely alternative putting aside suggestions that it was the IF strip - was the supply rail to the selector. According to the circuit, this is derived from the main HT rail (125V) via a 12k0 2W resistor (SR105) and zener diode SDl0l (UPC574) which delivers a nominal 33V to the selector. The exact voltage isn't critical - just so long as it is stable. So how stable was it? A convenient check point was at plug and socket combination SN0l which feeds the selector, at the pin marked 33V. But the reading was nothing like 33V; it was 70V plus and quite apart from the main fault, was clearly the reason I had found the pot settings unduly critical. pick this up. The set would work, all channels could be tuned, and only ari astute tester would pick the marginally more critical adjustment. So out it went into the field. Fortunately, I had a suitable zener diode on hand and this gave a rock steady 33V rail. Naturally, I had to retune all the channels but that done, the set was literally better than new. So the technician at Samsung was both wrong and right. He was wrong about the IF system but right about the selector. When I contact him again, I'll put him in the picture. Who knows, there might be a few more sets out there with the same problem. But enough of my problems here's the latest effort from J.L. in the Apple Isle. How to make work A moment's carelessness · can cause hours of unnecessary toil. This happened with a Thorn 9503 but it could equally have been any AW A or Thorn "G" chassis. The initial complaint was bad horizonatal sync and I tackled the job in the customer's home. The picture was weaving from side to side What's missing? I wasn't really familiar with this part of the board layout but I spotted the 12k0 resistor easily enough. I checked it as a matter of course and it was OK. I couldn't find the zener diode, though. I scanned the board a couple of times without success, then happened to glance at the board in the other set. And there was the zener, not far from the 12k0 resistor, in a TO92 package. Closer inspection of the faulty board revealed a couple of holes and the marking "SD101" in small print - but no zener. What was more, an examination of the copper side of the board confirmed what I already suspected; there never had been anything connected to that part of the board. In simple terms, somebody omitted to fit the zener diode during board assembly and it is unlikely that there was any test that would 46 SILICON CHIP TETIA TV TIP Kriesler 37-104 (Sharp 9C140 chassis) Symptom: Set hiccupping, just like earlier Kriesler and Philips sets with a shorted line output transistor. This one shows some leakage to ground but it is one way only and is due to an internal diode - the transistor is quite good. Cure: R644 (2.20 ½W) open circuit. This resistor feeds the 115V rail to the line stage and when it opens it takes the line load off the power supply. This supply hiccups with over-voltage, not over current as do most other Krieslers. 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. like a hula girl in full swing. Sometimes it broke up completely; at other times it was almost stable with only the slightest flicker. My first thought was that it was another manifestation of the "edge connector gunk" used on these sets. I have found an extraordinary number of different faults that can be cured just by cleaning the edge connectors of the various plug-in boards. I pulled each of the boards and cleaned their contacts and the sockets. This seemed to be enough at first, because the set came good and played perfectly for the rest of the day. But that night the customer called to say that the set was as bad as ever. This time the problem showed itself to be mechanical. It would shift between "weaving" and "breakup" each time I tapped the board, which seemed to indicate a broken joint of some sort. In this model, the sync separator is on the video/chroma output board so I pulled that board and gave the contacts an extra good scrubbing, just for luck. I didn't have any (luck) though; the fault was as bad as ever. I pulled the board again and began a detailed search. The first thing I looked at was the sync separator transistor, Q401. A multimeter test showed the transistor to be OK but while I was checking the board from the copper side, my fingers on the component side felt something that wasn't at all right. In fact, I knew what I had found without even looking. It was a old style half watt resistor that had once been very hot. It had swollen in the middle and split along its length. When I traced its tracks, I found that it was the feed resistor to the emitter of the sync separator, R405 . Its value is nominally 1000 but was in fact varying between a few thousand ohms and infinity. It took very little time to change the resistor and replace the board for a test run. Only I wasn't careful enough and my carelessness cost me dearly. A loud "psst" The set was standing against the wall in a fairly bright room. However, the back of the set was in shadow and I couldn't see all that well as I pressed the board into its socket. I have fitted these boards many times before and wasn't particularly worried. But I should have been more careful because when I switched on, there was a "psst" from inside the set and then nothing. I realised straight away that I hadn't installed the board correctly. When I turned the set around into better light, I saw that it was sitting high in its socket and more importantly, it was about half the width of a contact out of line. At least some of the contacts were touching adjacent pads as well as their own. I refitted the board, properly this time, but no joy. There was a faint raster and a quiet hiss from the speaker but nothing else. Whatever I had done, it was a workshop job from here on. Back at the shop, my first test was to see if there was any video information coming into the video/ chroma board from the IF board, PCB-HF. I didn't expect anything because of the lack of sound so I wasn't really disappointed when I found no signal. Next, I pulled plug FA, which is the input to the IF board from the tuner. I tried injecting a 1MHz square wave from a small function generator into the IF. In many sets, the harmonics from the square wave will pass through a functioning IF system and give an idea of how well it is working. In this case there was only a click as the contact was made and then nothing. Either the strip was totally dead or the harmonics weren't strong enough. It was time for some better test gear. Among my homemade test gear is a portable TV set with a modified link between the tuner and IF board. It enables me to extract IF direct from the portable' s tuner or to feed the portable with IF from a suspect tuner. It's an I :;~ It ~ ©• g~ ~ <. r,.- -- ;, .1 ---- : ~ o l~~~-;i~,~ s~ ~ g8, r=-:-...:.·1 ~L. ___J ::, ~ <t g~ ~;g > - - - - ---+-'V\1\----+-'jf----t i~ C ! ! ~ :~· ~ ~.. r- -~~~-·~ -~--J - ---'J .';.~~~~~~~~~"!.~~~~ . Fig.2: video IF and sync separator circuitry for the AWA "G" chassis. The tuner input is at top left, the video IF IC below it, and the IF and 1st video transistors to the right. The video/chroma hoard and sync separator are at extreme right. FEBRUARY1990 47 This signal then passes to Q101 (a 2SC383 HF transistor) and then to the video detector, in can T108. The first video amplifier, Q102 ideal tool for this type of inAlong with audio, H and V sync, (2SC710), is also on this board and vestigation. and an adjustable negative bias from it the signal passes through In this case, a signal from the supply, it comes close to delivering pin 3 on plug FD to the video/ portable's tuner would not activate every signal needed to test any part chroma output board. the big set, nor could the big set's of a TV set. I had to probe my way through tuner drive the portable. It looked this signal chain in an attempt to Dead IF strip as though both the IF strip and the locate the trouble. In the event, the In this case, I needed the variable tuner had suffered a major blowup. multiple outputs of the TV analyser Way back in the closing days of IF output. . I fired up the old proved quite valuable although, analyser, connected its output to monochrome TV, I had bought a looking back, I realise I could have piece of equipment called a ''B & K the IF input and switched on. found the fault with nothing more Television Analyser". It was Nothing. I adjusted the input level than a simple multimeter. from 500µV to lOmV. Still nothing. I designed for testing valve type Another thing that was working monochrome sets but is still useful swept the IF from 30MHz to against me was that bloke Murphy. 40MHz. Still no response. The IF for working on modern colour sets. He made sure that I started at the The analyser provides a monostrip was totally dead. wrong end of the chain and wasted chrome video pattern on a variable This IF strip consists of one IC an hour in fruitless poking and IF, or on any selected VHF channel. (IC101) and one transistor (Q101). prodding. It also supplies variable amplitude IC101 is an M5183P which accepts My first test was of the 20V rail positive or negative video at an adinput on pin 1 and puts out a proto the IF board and the 12V rail justable horizontal sweep rate. cessed signal between pins 7 and 8. derived from it. Both were correct and the specified voltages were present on pin 11 of the chip and the collectors of both transistors. Next, I injected IF into pin 1 of the IC. This produced no response, so I moved the probe to test point 12, the output (pin 8) of the chip. This did produce a result but not quite what I expected; an extraordinarily loud burst of sound from the speaker but no picture. (I must learn not to leave the volume control flat out when working on this kind of fault!) This was a bit confusing at first because the sound is usually taken off with the video at the video detector. This set is different in that the sound IF is generated in a separate detector attached to the collector of the video IF amplifier transistor. At first I considered that the video detector diode might be shot as this would account for the loss of picture information. I found the . diode to be undamaged, then realised that this had been a silly deduction. If this diode was the cause, then the sound would have been normal because of the two detectors. Next, I injected video at test point ~WA.'1 'jsACK lN 1'\-\~ CLOSING "DA'-(S 15, at the input to the 1st video amplifier. There was still no sign of OF IV\ONOC-H'R0IV\E:. TV, 'I HA"C> ts0UGl-\".,a picture. Finally, I fed the video to p.._ '°Pl!ZCE:" 0~ E"Q~W'('(\E..l\.lT CP-.LLED pin 3 on plug FD, the input to the A ":B&\<. TELEV\'StON AN~LYSE:."R'~ •• video/chroma board. (This is where SERVICEMAN'S LOG -CTD 48 SILICON CHIP I would have started if Murphy had not poked his nose into my affairs). Immediately, the screen lit up not with any recognisable picture but with some kind of scrambled information that looked as though it could be resolved into a picture. This was better than anything I had seen so far. Transistor checks I pulled out the IF board and tackled the video amplifier transistor. A static test with a multimeter showed no problems it had no leakage and normal junction resistances. The resistors on base, emitter and collector all read close to the circuit values, and I had already checked the collector voltage as correct. So what was going on? I refitted the board and freed some of the cables so that I could do some dynamic measurements with the board clear of the cabinet. And this time I beat Murphy. The first check was at pin 3 of plug FD, which is effectively the emitter of the video transistor. It was supposed to be 6.3V but was in fact only 0.8V. I then went right to the transistor and found that although the collector voltage was correct at 13V, both base and emitter were very wrong at 0.8V each. This was another one of those transistors that passes a static test but shorts when working voltages are applied. A minute later and I had a new transistor in place and a picture, of sorts, on the screen. I say "of sorts" because there was no sign of sync, either horizontal or vertical. And there was no colour either. I had cured the IF problem but still had the original sync troubles, or something very like them. As mentioned earlier, the sync separator transistor is on the video/chroma board and this is not easily accessible when the set is operating. What is needed is an extension lead to enable the board to be operated outside the set. I had recognised this need some years ago and used parts from a junked set to make up my own extension leads. I was showing my handywork to a colleague who surprised me by saying "I've got a full AUDIO TRANSFORMED set of those leads and I've never used 'em. Do you want 'em?" Murphy again! Why didn't I ask before I spent hours making my own? Anyway, I soon had the board out and powered up. First, I used the CRO to check the video into the noise canceller Q205 and then into the sync separator. Both were perfect, as near as I could judge. But the output of the sync separator showed nothing. Even with the CRO turned up to maximum there was only a faint ripple on the trace and nothing resembling separated sync. Again, a static check of the transistor showed nothing wrong but it was a different story when it was checked dynamically. The failure was exactly the same as in the case of the video amplifier transistor. And because this was in a pulse type circuit, it was harder to prove that the transistor was faulty. The emitter voltage was just on 19V as shown on the circuit and the base was also around 19V because the sync separator stage is normally biased off except when a sync pulse is present. The sync pulse continued on page 91 TV TEST EQUIPMENT (AUSTRALIAN MADE) SHORTED TURNS TESTER Built in meter to check EHT transformers including split diode type, yokes and drive transformers. $78.00 + $3.00 p&p HI-VOLT AGE PROBE Built in meter reads positive or negative 0-50kV. For checking TVs, microwave ovens. $84.00 + $5.00 p&p. 1 ,.i TELE-TEST TUBE TESTER & REJUVENATOR Removes cathode grid shorts & rejuvenates picture tube. Suitable for all colour tubes. 12 months warranty. $420.00 + p&p. FOR PROFESSIONAL, OEM OR AMATEUR Broadcast quality audio transformers ex-stock More th an 70 standard types available Fast prototyping service for non-standard types Comprehensive data available on request Locally manufa ctured Competitively priced HARBUCH ELECTRONICS PTY LTD 90 George St .. HOR NSBY NSW ~077 Phone (0~)476-5854 NEW PRODUCT DEGAUSSING WAND: A must for all workshops. Efficient design, strong magnetic field, low heat, double insulated with momentary on/off. $75.00 + $1 o p&p. ALSO TUNER REPAIRS FROM $17.00. Cheque, Money Order, Bankcard or MasterCard -:r.V.TuNERs) 216 Canterbury Road, Revesby, NSW 2212. Phone (02) 77 4 1154 FEBRUARY1990 49 The incredible This novel unit will produce the sounds of two birds singing together in a way which will intrigue you. They start slowly and then sing rapidly increasing trills as they compete with each other for virtuoso supremacy. By JOHN CLARKE Do you love the song of birds around your home but hate the idea of caging birds? Perhaps you can't stand the idea of cleaning out the cage - birds are messy little critters. Or perhaps you can't afford bird seed. 50 SILICON CHIP Whatever the reason, you can now have a pair of electronic birds to entertain you and your friends and, most important, you can turn them off when you don't want to listen to them. The idea of producing artificial birdsong isn't new. There have been clockwork instruments going back centuries and in the last decade or so a number of electronic birdies have come out of the emporiums of Asia. But it's been a while since we saw or heard any and so we thought, ''Why not build a new circuit?" We could have been really clever and built the unit into a fancy gilt cage complete with ornamental bird. Instead, we took an easier approach and built the circuit into a standard zippy box and then sat a couple of ornamental birds on top of it. Using two garden variety ICs and 47k +9V +9V VR1 50k 100k .,. +9V +9V + 01 1N4148 100 470k 100k 33k + 68k +9V 1000..r- +9V 470k .,. CHIRP CONTROL OSCILLATOR (a) + 471 470k .,. Bn SPEAKER CHIRP OSCILLATOR (a) .33k 330pFI 100k .,. 02 1N4148 TONE OSCILLATOR (a) 47k .001 MIXED OUTPUT +9V +9V 100k VR2 50k +9V .,. :r:<o +9V 100k POWER -'I' 9V 1 I .:;.&.. i +9V + 471" B + 47k 470+ EOc VIEWED FROM BELOW .,. CHIRP CONTROL OSCILLATOR (b) + 47.I: .,. .,. CHIRP OSCILLATOR (b) 270pFI HOT CANARIES .,. TONE OSCILLATOR (b) Fig.I: the circuit uses seven Schmitt trigger oscillators based on LM324 op amps. ICla is the on/off oscillator while the other six oscillators generate the sounds of the two canaries. a handful of resistors and capacitors, our "Hot Canaries" generate the sounds of two canaries happily chirping and trilling away. The period of trilling, chirping and pitch of each bird is different, creating a random effect as the birds come in and out of chorus. One of the problems with trying to reproduce a birdsong circuit is that so many song parameters have to be controlled - the pitch. rate of chirps and trills, and the length for which trills last. Such a circuit either tends to be very complicated or very incestuous, as certain circuit sections have to perform more than one function. Our approach was to try and come up with a good compromise produce a circuit which was not too complicated but which would also be reasonably easy to build and troubleshoot (perish the thought), if necessary. PARTS LIST 1 plastic case, 130 x 67 x 43mm 1 PCB, code SC0811 2891 , 107 x 60mm 1 front panel, 126 x 64mm 1 57mm 80 loudspeaker 1 SPDT toggle switch 1 9V on-board battery holder (DSE Cat. P-6200) 1 9V 216 battery Semiconductors 2 LM324 quad op amps (IC1,IC2) 1 BC328 PNP transistor (01) 2 1 N914, 1 N4148 signal diodes (D1 ,D2) Capacitors 1 1 000µ,F 1 6VW PC electrolytic 1 4 70µ,F 16VW PC electrolytic 1 100µ,F 16VW PC electrolytic 3 4 7 µ,F 1 6VW PC electrolytic 2 .001 µ,F metallised polyester 1 330pF ceramic or polystyrene 1 270pF ceramic or polystyrene Resistors (0.25W, 5%) 5 470k0 2 180k0 5 100k0 7 68k0 4 47k0 5 33kfl 2 15k0 2 10k0 2 3.3k0 1 330 2 50k0 miniature vertical trimpots Miscellaneous Solder, hookup wire, 4 PC stakes F EBR UARY1990 51 The completed PCB assembly clips neatly into a standard plastic zippy case. Check to ensure that none of the on-board components are fouled when the lid is screwed down. Circuitry What you need for an electronic canary circuit is oscillators - quite a few of them. And you also need to use CMOS circuitry to keep the battery drain as low as possible and so the CMOS 74C14 hex Schmitt trigger suggests itself as a device which will do the job. This is because you can make a very simple oscillator with a Schmitt trigger and just two other components: a resistor and a capacitor. A circuit using the 74C14 for an electronic canary was published quite a few years ago in another magazine but this device does have one big drawback. In any Schmitt trigger oscillator, the operating frequency is very dependent upon the high and low switching thresholds of the Schmitt trigger device. This would not be serious if the 74C14 had closely defined high and low thesholds but it doesn't. Consequently , any oscillator designed around the Schmitt triggers in the 74C14 will have an operating frequency which can vary by more than 3:1. For some circuits, the large variation can be acceptable but for a chirping canary circuit, it ain't. Clearly then, although we would 52 SILICON CHIP have liked to use the 74C14, it was not the ideal device. What we needed was a cheap device with low battery drain which could act as a Schmitt trigger device with precisely defined high and low thresholds. Well, we have accomplished that aim by using the LM324, a quad op amp package. It has low current drain and will operate from a single supply rail. Each op amp in the package can be used as a comparator and with the addition of a resistor connected between the output and the noninverting input ( + ), it can have precisely defined hysteresis which is the difference between the upper and lower thresholds. Thus, it can be used as an oscillator with a fairly precisely defined operating frequency. So let's now have a look at the complete circuit for the Hot Canaries which uses two LM324 quad op amp ICs. Essentially, the circuit consists of 7 oscillators which are connected to obtain the sounds of two canaries singing. First, there is an on/off control oscillator which switches the canary sounds off for a short while after a minute or so of continuous chirping - it's like a rest break for live musicians. The remaining six oscillators are used to generate two almost identical canaries which are then mixed together and amplified by a single transistor which drives a small speaker. IC1d, IC1c and IC2c are the three oscillators for the first canary while IC1 b, IC2a and IC2b are the three oscillators for the second canary. Note that the canary circuits are almost identical apart from changes to two capacitor values. As noted above, each of the LM324 op amps is connected as a Schmitt trigger, by virtue of the resistor between its output (pins 14, 8, 7 or 1) and its non-inverting input (pins 12, 10, 5 or 3, respectively). Also necessary to set the upper and lower threshold of each Schmitt trigger section is a voltage divider, consisting of two resistors, with the centre-point connected to the noninverting input. To make each of these Schmitt trigger sections operate as an oscillator it is necessary to connect a resistor/capacitor network from the output to the inverting ( - ) input. Each oscillator then works as follows. When power is first applied, the capacitor at the inverting input (eg, at pin 9) will have no voltage across it and the op amp output will be high. The capacitor will then start to charge up via its associated resistor, until it reaches the threshold set by the reference voltage at the non-inverting input. When that happens, the op amp output switches low and the capacitor then starts to discharge. It will continue to do so until it reaches the lower threshold voltage, again as set by the voltage at the non-inverting input. This causes the op amp output to switch high and the cycle begins again. The result is an oscillator with an approximate square wave at the output and a sawtooth waveform at the inverting input; ie, across the capacitor. So that describes the general operation of each of the 7 oscillators in the circuit. Oscillator interaction To understand how the oscillators work together to produce the sounds of canaries, let's go to one of the oscillators which is last in its TO S1 TO SPEAKER 0 ~ -- ~ '- I Fig.2: check the resistor values with a digital multimeter before installing them on the board and take care with the polarised components. You can use sockets for the two ICs if you wish. chain, IC2b. This is labelled as a "tone oscillator" and its basic frequency is set at around 2-3kHz. In fact, if the 180k0 and 470k0 resistors connecting it to other parts of the circuit were removed, it would just oscillate continuously at around 3kHz or so. Well, that would be all very nice but it wouldn't sound much like a canary. They chirp and warble. To get IC2b to chirp, we modulate it at a rate which starts at about 1Hz and then rises until ultimately IC2b is running continuously. This "chirp" frequency is generated by IC2a. To get · the chirp frequency to rise, as just mentioned, we control it with a lower frequency oscillator, !Cl b. As the voltage across its 470µ.F capacitor increases, the chirp frequency rises. So we call ICl b the "chirp control" oscillator. When the chirp oscillator rises fo its highest value, which effectively lets IC2b run continuously, the series RC network consisting_ of a 180k0 resistor and .001µ.F capacitor between pin 7 and pin 2 causes the two oscillators to modulate each other and so the tone oscillator "warbles" just like a canary. You will see that ICld, IClc and IC2c are virtually identical to ICl b, IC2a and IC2b. They produce the second canary. The outputs of IC2c and IC2b are mixed together via two 10k0 resistors to drive transistor Ql and the miniature 80 loudspeaker. This brings us, finally, to the 7th oscillator, ICla which turns the duet on and off. It initially has a low output for about 60 seconds since the 100µ.F capacitor has to charge from the full + 9V down to + 2.3V. From then on, its output goes high for about 20 seonds, low for 20 seconds and so on. When its output is low, the canaries sing. The output of ICla enables the chirp control oscillators (ICld and IClb} via diodes Dl and D2. Construction We built our Hot Canaries circuit onto a printed circuit board (PCB) measuring 107 x 60mm and coded SC 08112891. This was housed in a plastic case measuring 130 x 67 x 43mm. No particular order of assembly needs to be followed when putting the components on the board. However, we suggest you put in the PC stakes and resistors first. You can then install the two diodes, the ICs and the transistor, followed by the capacitors and trimpots. The battery holder was obtained from Dick Smith Electronics (Cat. P-6200). It is a lot dearer than the usual battery snap connector but it neatly solves the problem of mounting the battery securely. The case lid can now be drilled for the speaker holes and switch mounting hole. Secure the switch, glue the speaker to the rear of the lid and complete the wiring to the switch and speaker. Testing Now the circuit is ready for testing. Insert the battery and switch on. Test that each op amp has power and listen for the chirping sounds. Adjustment of VRl and VR2 is best done by temporarily desoldering each of the 10k0 resistors {Rl & R2} in turn. Lift Rl first and adjust VR2 so that chirping starts at a slow pace and continues up to a faster rate and then stops before starting again. If the trimmer is too far anticlockwise, the canary will hardly chirp at all and if too far clockwise, it will not stop chirping. Once this has been done, reinsert Rl, lift R2 and adjust VRl. Finally, the PCB can be clipped into position by pushing it down into the plastic case. I§;] ,0) 00 ~ ,- 0 ~ Fig.3: here is an actual size artwork for the PC pattern. FEBRUARY1990 I 53 POLYSWITCH PROTECTORS Pocket Soldering Iron Totally portable, butane powered soldering iron that fits easily in the shirt pocket. Provides up to 60 minutes continuous use at full power (equivalent of 60 watts). Temperature control from 10 to 60 watts. Ideal for service people, handymen, technicans, etc. Cat T-1370 Polyswitch Protectors are self resetting, solid state devices which exhibit a huge resistance increase when subjected to fault currents. 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Includes the Supertool and •. plugpack, 2 milling cutters, 1 wire brush, 1 grinding wheel, 4 high speed drills, 5 chuck collets (0 to 4mm), eraser sticks and instructions. $ P<>•" (l l 75 Cat T-4754 1 ACCESSORIES INK ERASERS (SET OF 5) AT LOW PRICE OF T-4760 NORMALLY $4.95 PENCIL ERASERS (SET OF 5) T-4762 NORMALLY $4.95 ill XPRESS PHONE OR MAIL ORDER SERVICE Outside Sydney (FREE Call) 008 22 6610 Sydney And Enquiries 888 2105 FAX: (02) 805 1986 or write to DS XPRESS, PO Box 321 N/Ryde NSW 2113 All Major Cre(lit Cards Accepted. O/Nite Courier Available 24 HOUR DESPATCH OF ALL ORDERS B926 1BL $295 LIMITED STOCKI Impedance calculations The powerful impedance calculation keys of the fx-61 F allow one-touch calculations of composite impedance for AC circuits (parallel/serial/mixed) that include resistors, coils, and condensers. This function also lets you calculate the absolute value and deviation angle of the calculated composite impedance. 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Dissolves deposits of dirt and tape oxide which accumulate with day to day use. Helps ensure highest quality reproduction and leaves no residue . Non conductive, safe on plastics, rubber and paints. Dries quickly. 100ml can. catN-11ss Only s'758 1mpe For The &M Band What Colour Is Your Music? /IIl!lJ Chroma-Vox Add colour to your music at parties and dances! Our new Chroma Vox uses the latest technology in Triac Driver IC's and gives you three channels which can be connected directly to speaker or headphone outlet. There's a master level control and each channel has adjustable sensitivity. With a high level of insulation between mains and signal output, insulated case and front panel, and specially selected potentiometers for the maximum safety. Will drive up to 2400W of incandescent lamps. Kit comes complete with a pre-punched, silk screened front panel and pre-punched rear panel. '4?;~~ Here's a great new project that's very simple and produces amazing results! An easy to build receiver which lets you listen to amateur radio on the 50 to 54MHz band. It uses a low noise MosFet front-end and a single IC performs most of the receiver functions (The new MC3363). It will even form the a basic 'tuneable IF' receiver module for future converters to cover other amateur bands. Full form kit comes with all components and hardware. Cat K-6005 Cat K-3162 9 Please contact your nearest Dick Smith store for the price and availability Universal UHF Remote Control Switch It's easy to build and can be used for 2 Channsl, 7 Day Sprinkler Timer Design your own garden sprinkler system for about half the cost of commerical units! The Sprinkler Timer allows you to control up to 14 sectors (2 x 7). With the aid of any standard Distributor Tap and only one or two solenoid valves you can have the healthiest garden in the street. Mains powered, the kit comes with case, pre-punched front panel, panel label and all components. Cat K-3588 Cat K-3258 sgg switching security systems, lights, doors ... almost anything you can think of! The kit consists of a 304mHz receiver, decoder IC and output relay driver on a single board. Full form kit, including pre-punched panel, panel label, PCB and all necessary components. Also comes with Department Of Communications(DOC) approved $ 5 transmitter! 7 9g VK Powermate 25 DISTRIBUTOR TAPS & SOLENOIDS NOT SUPPLIED The perfect kit for amateurs with all the grunt you need to get the most out of your shack. A high power 13.BDC supply giving a huge 25 amp continuous current rating with a peak of 35 amps. It's capable of running transmitters and amplifiers in the 100-150W class. And it's fully protected with both foldback current limiting and an over voltage crowbar circuit. Short Form Only -Includes PCB, components and necessary hardware. The DSE Variable Power Supply Kit Cat K-3210 Ideal for the service man , hobbyist, amateur, student etc. - everyone should have one. Simple to construct. - $249 ~~~---, Features: SHORT FORM KIT: • Variable 1.5 Volts to 15 Volts DC • All necessary parts supplied included plug pack • 500mA continuous • Pre-punched silk screen front panel • Overload protection • Housed in attractive compact case • No mains wiring reQuired • No drilling required Cat K-3200 CASE (Cat H-2481) & TRANSFORMERS (Cat M-2010) NOT INCLUDED $4695 Communications On & Bstwssn Bikssl Sl·m~le FM liransm·1tter For he 2M Band . The first in a great new series of easy to build projects for the FM Radio Intercom For Motor Bikes A true FM intercom which allows communication between passenger and rider as well as between bikes. It also doubles as an FM receiver for your favourite radio station. The ti:ansmitter and receiver are housed in ~ a small case which fits in the jacket pocket. · The speaker and microphone are fitted in amateur radio enthusiast. The solid state NBFM transmitter module · · • .' , · :. the helmet. As well, the microphone is produces over 1 Watt at 144MHz. The oscillator frequency, around . voice activated to save switching. Beware 24MHz, is multiplied in two stages, first a tripler ... then a doubler )hough, it is not easy to build and is best to 144MHz. The resulting signal is amplified through several stages tackled by someone with a sound knowledge before being fed to an antenna. Short form kit contains components ~"" of kit construction . Comes complete -ready and PCB. to assemble with all components, PCB, mics, 5 -----------,1r cat K-6010 speaker, case and a Pre-punched silk screened front panel. Powered by three ~ -=-ic~· !!'~,...,...j~ • ~ ~ penlight batteries (not included). ii ■•■• ,, '-:.:J , :J ":' ff . Cat K-6020 •-••• 1:· i s599 •·ri.'la ~-~ -r• I~,"! IW J"1" · "" "!-~=~====-==== · =_. ~- - DIC ?f" wa--------- "'- •' I MITH (tj.; _ _ _ __ ~· _ s7995 _ __ B918/PB MULTITAP TRANSFORMERS 1dealforA1Jdio! The M6676 is specially designed for a wide range of applications including power supplies for digital equipment and audio amplifiers. With 3 separate secondary windings for extra versatility. Cat M-6676 I""': 240 VAC 50Hz • Pewtr Rlli91: 60VA $ Isolation VoH•tt: 1OM Oh111s 0111111 WiNi911: 0-10V-17.5V/0-17.5V/0.7.5V DSE2155 S895 DSE2840 DSE2851 s5ss Primary: 240V, 50Hz Secondary Voltaqe : 6.3, 7.5 8.5, 9.5, 12 & 15V Secondary Current: 1amp Terminations: Flying leads NOW, YOU CAN MODIFY OR REPAIR PCBS WITH Primary: 240V, 50Hz Secondary Voltage: 6 3-0-6.3V Secondary Current: 150mA Terminations: Flying leads CIRCUIT FIX CF- 1 The complete kit contains the spring-loaded clamp and guide, collet knife and blade, 154 assorted copper donuts, 32 square inches of copper foil and an instruction booklet. Cat N-5900 s495 Primary: 240V, 50Hz Secondary Voltage: 4.5-0-4.5V Secondary Current: 150mA Terminations: Flying leads 5 95 V,~Ea~~~ov AC 14 T3ppef 15, 17.5, 20, 24 Secondary Current: 27.5 & 30V Terminations: Solder leads LOW PROFILE FERGUSON All one CONTACT PRINTING FRAME ER-1O Large format (225 x 300mm) spring-loaded steel printing frame will accept 210 x 275mm artwork originals, protcopy film and sensitized printed circuit boards. Comes complete with glass, backboard, yellow Pos-Neg filter and instruction manual. Cat N-5710 $1995 s WAS 39 .95 YELLOW POS-NEG FILTER ER-17 SAVE $20! Needed for all Pos-Neg exposure work. Take care - this filter can be damaged by many industrial solvents and ER-8 developer. Keep free of dust and fingerprints. Cat N-5711 $495 TARGETS AND REGISTRATIONS WAS $9.95 SAVE $5! Pack of 40 different PCB targets and crosshair registration marks for precision pattern alignment (especially suitable for multi layer or double sided PCB's). Cat N-5820 SAVE $2! WAS $5.95 WARNING LABEL PACK s3ss Perfect for those projects you build yourself! A versatile set of warning labels for just about every application. They're black, on a silver background so they stand out. Just cut out the labels as you need them, peel off the backing and lay it down. Cat N-5759 $ 50 HEATSHRINK s3s5;::~t: 1 price! - s34s5 Pl.12/20VA 2 x 6V<at>1.7A- 6V<at>3.4A-12V<at>17A M-3596 Pl.15/20VA 2 x 7.5V<at>1.3A- 7.5V<at>2.6A · 15V<at>1.3A M-3597 Pl.18/20VA 2 x 9V<at>1.1A • 9V<at>2.2A - 18V<at>1.1A M-3598 Pl.24/20VA 2 x 12V<at>.85A · 12V<at>17A • 24V<at>.85A M-3599 IU0/20VA 2 x 15V<at>.69A -15V<at>1.3A • 30V<at>.69A M-3600 Pl.40/20VA 2 x 20V<at>.51A · 20V<at>1A · 40V<at>.51A M-3601 NEED 115 VOLTS? Quality stepdown transformer from Arlec for power 115 volt equipment. Great for anything that comes from the USA. 240 volts input, SOVA capacity. Enclosed in sturdy metal case for safety it has US style 2-pin socket, fuse and 2 metre card with plug. Cat M-1156 s39s5 SJJVE $1 SPECIAL PACK PR Make professional terminations. Supplied as a pack of various lengths and sizes. On application of heat from a soldering iron or hair dryer will shrink up to 50% of original size. Retains flexibility after being shrunk. Ideal as 'strain' l'nllllllllt:Dfllll£ cord on made up leads. Cat W-4060 IIUlfllJICRllln SEMIS 1995 \t BULK BUY SPECIALS! OR AUDIO TRANSFORMERS eal for transistor radio replacements, 9000 for nsistor projects including oscillator circuits, quiring coupling transformers. Miniature size. ODELM-0222 · • Primary 3k ohm • Use - The best and most inexpensive way to buy! Stock up now before it's too late. You'll save a fortune when you buy in lots of 10 or more. Just Look .... upling • Iron Core• Size 17 (1) x 15.5 (w) x 1 )mm Cat M-0222 s195 Description BF463 Hi Voltage Trans. 2N6557 Hi Voltage Trans. 74123 Re-Trig. Monostable DEL M-0216 ·•Primary 1K ohm• Secon ohm • Use 350mW 0/P • Ferrote Core · ) x 14(w) x 11.5(h)mm. Cat M-0216 s Cat No. Z-2040 Z-2041 Z-5263 Each 0.45 0.45 0.95 10 For Just $1.50 $1.50 $5.00 MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: N.S.W.: AAMIOALE: New England Electron ics 711655 BALLINA: Ballina Electronics 867022 BOWRAL: F.R.H. Electrical 611861 BROKEN HILL: Hobbies& Electron ics 884098 COFFS HARBOUR: Catts Harbour Electronics 525684 OENILIOUIN: Deni Electronics 813672 OUBBO: Chris's Hi Fi 828711 FORSTER: Forster Village Electroni cs 545006 GLEN INNES: John Sommerlad Electronics 323661 GRAFTON: Repairs and Spares421911 GRIFFITH: Miatron1cs624534 INVERELL: lnverell Electronics221821 LEETON: Leeton Aud iotronics 532800 LISMORE: Dec ro Electronic Services 214137 MOREE: Moree Electron ics 523458 MUDGEE: Headware 723895 NAAAABAI: Namoi Computer Service 923274 NOWAA: Nowra Electronics 210722 ORANGE: Central West Electronics 626491 PARKES: Strad Music Centre 623366 PORT MACQUARIE: Comdex 834574 TAREE: Brads Electro n;cs 526603 WAGGA WAGGA: PhHllps Electron;cs 216558 YASS: Warm ;ngton Electrica l 2261116 VIC: BAIRNSDALE: LH & LM C rawford 525677 MILDURA: Pu llman Aulo Pro 232882 MORWELL: Morwe ll Electron ;cs 346133 SHEPPARTON: Andrew Guyan Electron ics 219497 WARANAMBOOL: Marrtronics 629870 OLD: AYR: Delta Electrix 831566 BUNDABEAG: Bob Elkin Electronics 721785 MACKAY: Stevens Electronics 511723 MAAYBOAOUGH: Keller Electron ics 214559 PIALBA: Keller Eleclron;cs 283749 TAS: BURNIE: Eleclron;c C;ty 314760 DEVONPORT: A .I.Eleclron;cs 248322 SA: LOXTON: G & S Elect rical 847495 MT GAMBIER: Hutchesson·s Communication Centre 250400 POAT LINCOLN: Basshams TV & Computer World 822788 WHY ALLA: Eyre Eleclron,cs454764 WA: ALBANY: Micro Electron ics 412077 BUNBURY: M;cro Electron;cs 216222 GERALDTON: Batav;a L!ghltng & E!ectn cal 211966 KAAAATHA: Daves Osc1trontc 854836 MANOUAAH: Micro Electronics 412077 VGA Graphics Adaptor More colours, higher resolution and more options with our VGA Graphics Adaptor! Perfect for AutoCAD, games, text, paint programs, graphics, charts, desktop publishing ... the lot! Fits into any IBM compatible (XT or AT) and comes with 256K RAM (expandable to 512K). Includes utilities which allow emulation of EGA, Hercules and CGA. All standard IBM VGA modes are supported plug 640 x 400 (256 colours) and 800 x 600 (16 colours). There are so many graphics modes available th ere's just no room to list them all! Comes with drivers and the exclusive Dick Smith Electronics 55 page manual. 8 Bit Version. Cat X-2018 s249 s299 New Low Prices! 16 Bit Version . Cat X-2019 LOOK ... • Expandable up to 4Mb • Selectable 8112MHz operation • Six 16-Bit and Two 8-Bit expansion slots • Selectable RAM speed - 80 or 100 nanosecond • Selectable from Owait states on read operations (with 80 nanosecond RAM) • Selectable for 80287 Co-processor • Performance - 13.7 using Norton S.I. • Battery backed real time clock on board s399 $ 119 5.25" Floppy Disk Drives High quality disk drives which are suitable for use with IBM compatible computers. 360K Fl_oppy Disk Drive. Cat X-8012 S129 RS-232 Multilink Adaptor A complete in-line tester/adaptor which makes complex and time consuming Serial connections a breeze! Comes fitted with 25 pin male connector and 25 pin female connector. With jumper pads and wires, 24 in-line switches and 8 bicolour LED's for line monitoring. • rl•)~'f~~ f1 New Low Pr,·ce Just Cat X-2024 Multifunction AT 1/0 Cards PHONES s100 Allows you to install two internal and two external disk drives. 360K, 720K, 1.2Mb & 1.44Mb drives. Includes cables for internal drives and connection for external drives. s99 The corn plete expansion for your AT computer on a single card . Complete with parallel printer port, RS 232G serial . port (second port optional) , games (joys- " tick) port, 3.5" /5.25 " floppy disk controller, cables and manual. Support up to two 360K, 720K, 1.2Mb or 1.44Mb drives. Save Controls Four Disk Drives Gives your computer superb text display and high resolution (720 x 348 pixels) monochrome graphics. Compatibility with Hercules graphics adaptor. A parallel port configured to LPTI is also fitted. Cat X-2028 Speed, power and versatility are yours with our 12MHz motherboard. You can build your own system or upgrade the old one. DRAM not included. •• OK AMIRAM Biossupplied ROM 's included Cat X-1002 Mono Graphics Adaptor Cat X-8141 IBM AT Compatible 80286 Motherboard Cat X-2654 s4995 $169 Incredible Low Price! Laser 101 Keyboards Fantastic! These won 't last, so you 'd better hurry' Fantastic 101 keyboards with 12 functio n keys, a great fee l and the lowest price ever. Cat X-3819 Only s3995 =t., ,J ~. j Net11 _ _ SECURITY AUDIO COMPUTERS H_U_N_D_R_E_D_s_o_,_ o _T _H _E_R_ co _ M_P_U_T E _R _ IT_E_M_S_ A _ Y_A_I_ LA _B _L_E_1_ • NSW• Albu ry 21 8399 • Bankstown Square 707 4888 • Blackt own 671 7722 • Brookvale 905 0441 • Campbelltown 27 2199 • Ch atswood Chase 41 1 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 4 77 6633 • Hurstv1lle 580 8622 • Kotara 56 2092 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde 878 3855 • Pa rramana 689 2188 • Penr rth 32 3400 • Ra ilway Sq uare 21 1 3H7 • Sydney City 2679111 • Tamworth 661711 • Wollongong 28 3800 •ACT • Fyshwick 80 4944 •VIC • Ballar at 31 5433 • Belmont 43 8804 • Bend igo 43 0388 • Box Hill 890 0699 • Co burg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footsc ray 689 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 326 6088 • .Richmond 428 1614 • Ringwood 879 5338 • Springvale 54 7 0522 • OLD • Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Cherms1de 3596255 • Red ban k 288 5599 • Roc khampton 27 9644 • Southport 32 9033 • Toowoomba 38 4300 • Townsv1l le 72 5722 • Underwood 34 1 0844 •SA• Adelaide City 232 1200 • Beverley 347 1900 • Elizabeth 255 6099 • Enfield 260 6088 • WA• Cannington 451 8666 • Frem antl e 335 9733 • Raine Sq 328 6944 • Mid land 250 1460 • Perth City 481 3261 • St. Marys 277 8977 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 I;(e)~ j )I )f fl ={tj ij ,J (tf71~1-o.R•D-ER_e_v_P_H.oN_e_o_u_T_s,_De_ s_v_D_N_ev_(_oo_a,_2_2e.e1_o_F_ree_c_a_n_sr_d_ne_r_Ar.ea_a_aa_2_1_os_ _ _ _ _ _ ____. The Largest Australian Electronics Retailer! 60 Stores Across Australia B91 8/PB BOOKSHELF Obtaining the best TV reception to your local branch of the Depart- ment of Transport and Communications. All state capital cities and many of the larger country towns have a branch or representative. (L.D.S). Electronic test instruments Better Television & Radio Reception; Your Self-Help Guide. Published 1989 by the Department of Transport and Communications. Soft covers, 150 x 290mm, 55 pages. ISBN 0644 104473. Who says that the Government can't produce good technical publications? This is the best book we have seen on the subject of obtaining better TV and radio reception. It is well laid out with plenty of diagrams and colour photos, and the text is easy to read and free of error. The text and photos show you how to identify various TV reception problems and the appropriate procedure to cure the problems is given. About the only criticism we can make is that the colour reproduction is not the same as you would expect to see on-screen. Still, the intended message of the photos is clear in every case. Best of all, this publication is free. Can you believe it? Just write 60 SILICON CHIP Electronic Test Instruments: A User's Sourcebook, by Robert Witte. First Edition 1987, published by Howard W. Sams & Co., Indianapolis, Indiana, USA. Soft covers, 137 x 217mm, 261 pages, ISBN 0-672-22483-6. Price $29.95 Taking measurements in electronic circuits can be prone to errors unless proper procedures are followed. These errors are generally caused by a lack of understanding of how the instrument works and the ter.hniques used to make accurate measurements. This book, designed for an audience with an understanding of basic electronics, gives a background to measurement theory and how an instrument can affect the waveform being measured. There are eight chapters altogether. Chapter 1 covers measurement theory while chapters 2-6 cover the basic test instruments (ie, voltmeters, oscilloscopes etc ). Included in these chapters are block diagrams showing the inner workings of these instruments. These allow the reader to understand how they function without needing to know the inner circuit details. Chapter 7 deals with some basic circuit theory and how it relates to measurement-taking. Chapter 8 introduces frequency-domain measurement instruments and emphasises the role spectrum analysers now play in industry. In summary, this book is a very useful reference for those involved in electronic circuit measurements. If you don't know about probe compensation, or loading effects, or how oscilloscopes or frequency meters work, it will be a worthwhile investment. Our copy came from Dick Smith Electronics and should be available from all stores (Cat.B-4999}. The price is $29.95. (D.B.Y). The guru's guide to the IBM PC Inside the IBM PC, by Peter Norton. Revised edition published 1986 by Brady Books, New York. Soft covers, 235 x 188mm, 386 pages. ISBN 0-89303-583-1. Price $44.95. As a general knowledge source on the IBM PC family of computers, this has to be one of the best books around. The author is Peter Norton, who created the famed Norton Utilities software package, so he really knows what he is talking about. Chapters 1 to 4 give an overall view of the PC family and the PC itself. Chapters 5 to 7 cover some hardware aspects, particularly the microprocessor and memory chips, discussing in some detail the configuration. Chapters 8 to 10 discuss the disc system, both the hardware and the disc operating system (DOS), as well as hard and soft discs. Our review copy came from Rod Irving Electronics. They have branches in Sydney (02) 519 3134 and Melbourne (03) 663 6151. (D.B.Y). The golden age of radio Chapters 11 to 13 cover the video section and the various graphics modes. As well, they also explore the text mode and describe some of the tricks to make its use easier. Chapter 14 covers the keyboard while chapter 15 is devoted to the peripherals such as mice and printer ports. Chapters 16 and 17 outline the built-in BIOS (Basic Input/Output System), describe how it works, and describe its operating configuration and its uses. Chapters 19 and 20 detail the DOS system and i:;how what can be done with it by the user. Chapter 21 is a brief view on the structuring of programs and how they are built. Finally, chapter 22 gives some thoughts for tinkering and exploring with the PC software. The really good aspect of this book is its friendly and easy to read style. Peter Norton makes you feel quite at home with the subject. If it is to be criticised, it is for not going far enough in details on the hardware. For example, in chapter 14 on the keyboard, there is no mention of the processor chip inside the IBM PC keyboard. And in the chapters on video standards, there is very little in the way of technical background on the monochrome and CGA video signals or what might happen if you try to use a CGA card in a machine which has its DIP switches set for a monochrome adaptor card. In fact, there is nothing at all on setting up the hardware or installing extra peripherals. So as an introductory text on the IBM PC, it is good reading but if you want more technical details, you have to look elsewhere. The Golden Age of Radio In the Home, by John W. Stokes. Published 1986 by Craig Printing Company Ltd, 67 Tay St, lnvercargill, New Zealand. Hard covers, 308 x 220mm, 162 pages. ISBN 0-47300389-9. Price $39.95. This book covers the period from 1923 to 1958, the era in which the valve wireless (radio?) rose and fell from dominance. It is based on the era of wireless in New Zealand, the manufacturing and the hardware associated with the times. Much of the book is devoted to showing many of the radio types, either by reproducing original posters or early photographs. There are also brief histories on some of the New Zealand radio manufacturers. Some of the radios shown include matching horn speakers, early "car radios" and many of the Bakelite receivers that came out. There are 10 chapters altogether. Chapters 1 to 3 cover the early history, the receivers and what they looked like. Chapters 4 to 6 deal with the manufacture of valve radios in New Zealand during the era and cover some of the major manufacturers of the time. Chapters 7 to 9 discuss some of the receivers imported from Bri- tain, America and Australia. Chapter 10 covers the increasingly popular hobby of radio collecting, and discusses some of the do 's and don'ts, where to start, what to collect and how to determine the age of a collected piece. This is not a technical book by any means but is still a good general historical guide to the early days of radio in New Zealand. Any vintage radio collector would find this worth having. To get your copy, contact Resurrection Radio, PO Box 1116, Windsor, Victoria 3121. Phone (03) 529 5639. The cost is $39.95. (D.B.Y). Designs & applications for ICs 178 IC Designs & Applications, by Robert M. Mendelson. Published 1984 by Hayden Book Company, Hasbrouck Heights, New Jersey. Soft covers, 151 x 229mm, 193 pages. ISBN 0-8104-0654-3. Price $39.95. As the title suggests, this book contains no less than 178 IC designs and applications for ICs. The text is divided into six sections. Chapter 1 is devoted to power supplies, ranging from simple series and shunt regulators to high-current switching power supplies. Chapter 2 is on operational amplifiers. These are used in a range of circuits from filters and video amplifiers to sample-and-hold circuits. Chapter 3 has 40 amplifier continued on page 89 FEBRUARY1990 61 Phone patch for radio amateurs, Pt.2 Last month, we described the circuit of our new Phone Patch unit and gave the PCB assembly details. This month, we show you how to check the unit out and give a brief troubleshooting procedure. By JOHN CLARKE & GREG SWAIN When you have completed the PCB assembly, it should be carefully checked for soldering defects and component orientation. The MC34018 should be left out of circuit at this stage. In particular, check that all wire links are in place and that the regulator, transistors, diodes and IC2 are all correctly installed. Now connect a 12V AC plugpack to the board, switch on and check that the voltage on the output of the 7808 3-terminal regulator is close to + BV. The same voltage should appear on the collectors of Q1 and Q4, and on pin 4 of IC2. 62 SILICON CHIP If this checks out, the MC34018 can be carefully inserted and soldered into place. Use a 28-pin socket for this IC if you wish (we did not bother). The PCB can now be installed in the case and the rest of the wiring completed as shown in Fig.3. You will have to mark out and drill holes in the front and rear panels to accept the necessary hardware and the cord grip grommets. If you buy a kit with an adhesive front panel label, then this can be attached to the panel and used as a drilling template. You will also have to drill a number of holes in the front panel to allow sound to escape from the loudspeaker. The output to the transceiver's microphone socket can be run using 4-way flat cable (one lead not used), while the leads to the LIU and to the transceiver's speaker output can be run using figure-8 cable. Use banana plugs to terminate the LIU leads and a 3.5mm mono line plug to terminate the leads to the speaker output. The leads to the trans~ ceiver's microphone socket are terminated in a 4-pin microphone line plug. Note that it will be necessary to instail a loop in the LIU and power leads where they emerge through the rear panel so that the cord grip grommets can get a good grip. The loudspeaker is an 80 miniature type and is affixed to the front panel using polystyrene cement (eg, Airfix). Position it so that it is directly behind the pattern of holes drilled out earlier. When all the wiring is complete, reconnect the AC power supply, switch on and check the voltages again. The voltage on pin 16 of ICl should be close to + 8V while the voltages on pins 20 and 21 should be + 5.4V and + 2.9V respectively. Testing To test the unit, you will need a double adaptor phone socket and the line isolation unit. Plug the leads from the Phone Patch into the LIU, then plug the LIU into the phone socket in parallel with the telephone. Now switch the Phone Patch and the LIU on. You should immediately hear the dial tone via the monitor loudspeaker and the VOX relay contacts should close (if not, try adjusting VR3). Check that the volume can be varied using the Monitor control. After a short period, the dial tone will be replaced by the familiar busy signal. When this happens, the VOX relay should turn on and off with the beeps (ie, on at the start of each beep, off between beeps). Adjust VR3 (VOX sensitivity) and VR4 (VOX delay) as necsssary so that the relay turns on and:off reliably. If all this checks out OK, then the receive mode is functioning properly. The transmit mode can now be tested by feeding an audio signal into the input. You can use a transistor radio or your transceiver for this job. If you now hear the audio via the monitor speaker, it means that the transmit mode is also working. The VOX should be off during this time. The wiring to the front panel switches and microphone socket can be secured inside the case using plastic P-clips. Check that all parts (especially the ICs and transistors) are correctly oriented before applying power. Now plug in your microphone and plug the Phone Patch output into the transceiver microphone socket. Set the Mic/Patch switch to the Mic position and check that you can now operate your transceiver as normal using the microphone and PTT switch. Note that if the Phone Patch is plugged into the loudspeaker socket, any incoming signals will be heard via the monitor loudspeaker. Adjust the level into the Phone The Phone Patch is connected to the telephone lines VIa a line isolation unit which is plugged into a double adaptor in parallel with your existing phone. Patch as necessary to give sufficient volume without audible overload. The final test is to use the unit in a real phone patch circuit. Brief both parties as to correct procedure before switching to Patch and switching on the LIU. Monitor the conversation and adjust VR3 so that the VOX triggers reliably when the party on the telephone speaks. VR4 should be adjusted so that the VOX remains on during the The microphone is now plugged into the Phone Patch circuit but can be switched through to the transceiver using the Mic/Patch switch. FEBRUARY1990 63 Fig.4: here is an actual size reproduction of the PC artwork brief pauses that occur between words in normal speech. Do not make the VOX delay too long though, otherwise there will be a considerable pause when it is the turn of the party at the remote transmitter. Note that when the LIU is switched on, you will be unable to use your telephone. This is quite normal and is due to loading effects. Normal phone operation is restored simply by picking up the handpiece and turning the LIU off. Troubleshooting If it doesn't work, the first job is to determine whether the problem lies in the receive or transmit sections of the circuit. If the problem lies in the receive mode (ie, you cannot hear dial tone on the monitor 64 SILICON CHIP loudspeaker when the LIU is switched on), then the problem could lie in the LIU, around Q4, or in the receive idle circuit (Q6 & Q7). If you can hear receive signals but the relay doesn't operate, suspect a fault in the VOX circuit. If the fault is in the transmit mode, suspect the circuit around Ql, Q2 and Q3. On the prototype, Ql's base voltage measured 5.9V, Q2's 3V, Q3's 2.4V and Q4's 3.9V. Their base-emitter voltages should all measure about 0.6V. The same goes for the baseemitter voltages of Q6 and Q7 when the circuit is in receive idle mode (just disconnect the LIU and the transmitter). Check the voltage on pin 24 of IC1. It should be close to 1.45V when the circuit is in receive idle mode but should be variable up A 4-pin microphone line plug is used to terminate the leads to the transceiver's microphone socket. to about 2.9V by means of VR1 when dial tone is present. If pin 24 is close to OV, Q7 may be faulty. You can easily check Q5 by temporarily shorting pin 1 of IC2 to the + BV rail. If the relay operates, the QUALITY PANASONIC SEALED LEAD-ACID BATTERIES 12V 2.2Ah normally ..$36-:95 12V 6.5Ah normally~ now$24.95 now$37.95 NI-CADS SAFT& VARTA ! AA 500mA $4:2o $2.95 C 2Ah $12.95 -$+t:95 $9.95 Great for those tricky Video sockets D 4Ah ~ $10.95 normally ..$29-:95" 9V (Subject to copyright) ~ $16.95 VIDEO LEADS ~ TRANSISTORS BC547 BC557 8D139 BC140 2N3055 MJ2955 OPTO's 4N25 4N35 MOC3021 WERE 25c 25c 95c 95c $2.50 $2.45 $1.95 $1.95 $2.75 "COLT 55" 40 CHANNEL AM/CB RADIO An amazing pocket-sized Infra red detector with a built in Siren! 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I- <C a. 0 :::c a. • 0 a: (.) :E :c (.) .... <t When all the adjustments have been completed, a metal shield should be fitted over the VOX circuit to prevent false triggering when the transmitter is activated. The shield is secured by soldering is to 5 PC stakes. w z 0 0. ~ ,_ BEND UP I 50 82 transistor is OK. Note that DB and D9 face in opposite directions on the PCB. If you install them the wrong way around, the VOX won't work. Remember that most faults in projects are due either to faulty soldering, wiring errors, or the use of incorrect parts. Check all these possibilities carefully if problems are encountered. Note that excessive noise from the receiver under no signal conditions can lock the system into the 66 SILICON CHIP <C Cl 2 :E • • • a: !:: 0 z 0 :E ,- ; 16 z 0. :c BEND UP • • • 16 ~ .... M Fig.5: this diagram shows the dimensions of the metal shield. It can be bent up from an 82 x 73mm piece of scrap tinplate. transmit mode if it is louder than the telephone signal. This will not normally be a problem on the VHF/UHF bands, where the transceiver can be effectively squelched with no signal. However, it could present problems on HF circuits where the signal strength can vary widely and make squelching difficult. Finally, a metal shield should be installed over the VOX circuit (IC2), as shown in the photographs. Its job is to prevent the VOX from being falsely triggered by the RF output of • • • • ••• • • • • • • • ••• • • • • Fig.6: this artwork can be used as a drilling template for the front panel. the transmitter. Without the shield, the VOX could have a tendency to lock up each time the transmitter is activated. Fig.5 shows the dimensions of the metal shield. 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Here we show you how the IBM parallel printer socket can be used as a general purpose interface. There comes a time in every computer enthusiast's life when he or she wishes it could do more than just sit on the desk looking pretty. If only it could actually do something, like turn on a light, measure a voltage, operate a machine tool, etc. But before you go looking for a commercial interface card, consider what you might be able to achieve with your existing hardware. The games port For example, the Apple II games port can input the analog value of four variable resistors, which don't necessarily have to be the pots in a joystick - they could be LDRs, phototransistors, thermistors etc. Also provided in the one socket are A 36-PIN SOCKET AND A HANDFUL of resistors are all you need to make a perfectly useable PC-driven function generator. The difficult part is writing good, fast software to run it. 68 SILICON CHIP three bits worth of LS TTL input, four LS TTL output bits with a - STROBE pulse, and a + 5V supply for powering external equipment. In the author's experience, this is sufficient to perform at least half of the laboratory/process control tasks that Apple Ils -are currently being used for - given some clever programming. Even a small amount of machine code can go a long way. For example, you can write an extended version of the inbuilt analog input timing routines to obtain more than the usual 8-bit resolution. The analog inputs use 555-type RC timing circuits and so the games port can be used for precision measurement of external resistors or capacitors. About 3 or 4 decimal digits appears to be the limit of accuracy, which is on par with most cheap digital multimeters. There are a wealth of low-cost commercial devices on the market, from graphics tablets to scanners, which interface solely through the Apple games socket. The IBM games port can also input the analog value of four variable resistors, although extending the precision beyond 8 bits is quite tricky. This is because any long machine code timing loops will be affected by a host of internal goings-on, the most obvious of which is the DOS real-time clock interrupt. The BIOS and other system programs in your machine may also do a number of other things which will affect timing loops - especially if they have been "enhanced" over the original IBM specification. The IBM games port can also input the digital value of four switches but no output bits are provided as such. The parallel printer port The IBM parallel printer port is a goldmine of interface bits, both input and output, and the remainder of this article is concerned with how to use this port as a general purpose interface. Since the "Centronics" parallel interface standard has been adopted by most printer manufacturers, you will find that all brands of computers will provide similar facilities to the IBM, though you may have to do some detective work to find out the actual machine addresses for the various I/O bits and bytes. Just to whet your appetite, we will conclude this article with a useful, practical example, namely an 8-bit programmable voltage source/signal generator which is so simple it will cost you less than the price of a suitable connector. Port addresses Most IBM-compatible parallel printer cards can be set to respond as either LPT1: or LPT2: . These devices appear within the microprocessor's 1/0 address space as three separate 8-bit ports, which we will subsequently refer to as PORT.A, PORT.Band PORT.C. The actual machine addresses of these ports are as follows: PORT.A PORT.B PORT.C LPTl: 378(Hex) 379(Hex) 37 A(Hex) LPT2: 278(Hex) 279(Hex) 27 A(Hex) In order to use these ports for general purpose 1/0, we need to know which bits of these three ports are connected to the outside world. Details may vary slightly from computer to computer, so obtaining a circuit diagram of your printer card is highly desirable. Another useful source of information is the manual which comes with your printer. This will contain an appendix describing the parallel interface signals. Table 1 was prepared by tracing through the circuit diagram of a PORT.A PORT.B BIT SIGNAL NAME INPUT OUTPUT D7 D6 D5 D4 D3 D2 D1 DO D7 D6 D5 D4 D3 D2 D1 DO These bits may be input but all you will get is the value currently residing in the output latch, unless the interface is genuinely bi-directional. (Check circuit diagram.) Latched TTL push-pull outputs with 2. 2nF slow-down capacitors -D7 D6 D5 D4 D3 BUSY -ACK PE SLCT -ERROR D2 D1 DO -D3 D2 not available not available D7 D6 D5 D4 PORT.C TTL inputs, no pull-up resistor -SLCT IN -INIT -D1 -AUTO FEED -DO -STROBE not available not available May be used as inputs if corresponding output bits are set to "1 " Open-collector TTL output with 4. 7kn pull-up resistor Open-collector TTL output with 1Okn pull-up resistor Open-collector TTL output with 4. 7kn pull-up resistor Open-collector TTL output with 4. 7kn pull-up resistor and 2.2nF slow-down capacitor TABLE 1: THESE ARE ALL THE 1/0 bits available from a typical IBM parallel printer port. The "signal name" column lists the signals by the names used in most printer manuals. A " - " sign in front of the name means that the signal is inverted. Refer to Fig.1 or your printer manual for the pin connections to 25-pin or 36-pin connectors. typical IBM PC ·'clone" of Asian origin. As far as we know, this would be the most typical circuit you are likely to encounter. As you can see, the eight PORT .A bits are mostly intended as outputs, while five of the PORT.B bits are available as inputs. Four of the PORT.C bits can be used as inputs or outputs. Note that some of the bits are inverted between the internal data bus and the outside world. For example, if you input bit D7 of PORT.B, it will appear as a "1" when its input signal line is grounded (logic "0"). The open-collector PORT.C bits can be used as inputs by first setting the corresponding output bits to "1". This enables the inputs to be taken low as required. A sample program will clarify the use of these open-collector bits. Assume we wanted to input the status of a simple pushbutton switch connected between the - STROBE signal line and ground. The following statements in GWBASIC will do this: PORT.C = &H37 A BIT.0 = 1 OUT PORT.C,4 X = INP[PORT.C) AND BIT.0 The OUTput statement writes to the output bits of PORT.C, which appear as "1111" externally, since D3, Dl & DO are inverted. The DO signal line can "0100" FEBRUARY1990 69 DATA BITS - - - - - - - , SLCT PE BUSY -ACK 24 - - 07 23 06 22 - 05 21 - - 04 20 -:- 03 19 18 02 DO - STROBE 01 17 16 15 - -:- -SLCT IN SIGNAL GROUNDS - INIT - ERROR -AUTO FEED i DATA BITS -STROBE DO 01 02 03 04 ..,"" 05 06 07 < I /;; ::, "' w c.. ...=l ...< c:, ::, "' SIGNAL GND I FRAME GND NC 0 2 3 4 9 10 11 12 13 14 15 impedance of the TTL outputs. Unfortunately, the pull-up and pulldown internal resistances of the TTL outputs are not equal, resulting in a non-linearity error of - ½LSB or - 5mV at mid-scale. The minimum output voltage (for a digital input of 0) is almost exactly 0.1 V, as determined by the "low" level TTL output. The maximum output voltage can be adjusted by the trimpot so that an output of 2.65 volts is obtained for a digital input of 255. Thus each step will correspond to 10mV. The output impedance is almost exactly lkO, and a token amount of filtering is provided by a .0047µ.F capacitor. A more "serious" digital audio waveform generator would use more elaborate filtering. A 3 or 4-section LC filter would reduce the distortion content from 0.5% to about 0.1 %. 16 Performance -:' - - - - - - SIGNAL GROUNDS _ _ _ __ _ _, ~ I i1~~AL I FIG.1: THESE DIAGRAMS SHOW THE pin connections for the various IBM parallel port signals as they appear from the wiring side of a 25-pin "D" connector and a 36-pin "Centronics" connector. Beware some cheap printer cables may not include all the auxiliary signals. Luckily, however, all manual T-switches switch the entire 36 wires regardless of whether they are used or not. now be taken low by pressing the pushbutton switch. After the INPut statement, X will be 1 if the switch is closed, and O if the switch is open. This is a very easy way to interface a switch, or an opto-isolator, since a 4. 7k0 pull-up resistor is already supplied internally (how convenient)! A simple waveform generator Suppose you wish to use your computer to synthesise arbitrary waveforms, from DC levels to complex audio tone bursts? No problem. Analog voltages can always be obtained using a D-A converter IC but, just for demonstration pur70 S ILICON CHIP poses, we chose to "show off" just a little by making our own from a handful of resistors. Fig.2 shows how a binaryweighted resistor network can be hung directly off the TTL data bits to produce an analog output voltage. The exact values of the resistors are fairly critical, but if you check the resistors with a digital multimeter and put the ones closest to the ideal values towards the top of the· ladder, the output voltage steps should be within ½ LSB without any further trimming. Note that the resistors do not form an exact binary sequence, as we have subtracted 400 from all of them to compensate for the internal We wrote a demonstration program in TURBO BASIC to test the performance of this simple AID converter. As you can see from the oscilloscope photograph, the output is indeed quite linear. The program is too long to be listed in its entirety here, but the basic technique is to set up an integer array of data bytes, then output them repeatedly to PORT.A as fast as possible. Note that it is necessary to disable the DOS realtime clock interrupt whilst the waveform is being output, otherwise short pauses will occur throughout the waveform at a rate of 18.2Hz. The waveform pictured has one complete cycle of a sine wave, made up of 256 samples, followed by a linear ramp from O to 255. A sample rate of 20k per second was achieved by the compiled TURBO BASIC program on a bog-standard 4.77MHz PC-XT. The simplicity of this function generator is little short of amazing but as always, there is -a hidden price. You really need to be a competent programmer to get useful performance out of it. If anything, this simple project is a classic example of the modern trend that microprocessors have brought to electronics in general - CENTRONICS PIN NO. (9) HIGH QUALITY JAPANESE 500mA Hr (2.773k) 2.7k 68!l * OUTPUT 1k!l 07 (5.585k) 5.6k * ( 8) 06 .0047 5.6k (7) 3.3k (11.21k) 0.1V TO 2.65V IN 10mV STEPS PENLIGHT NICAD BATTERIES FOR UNDER $2.00 EACH??? A 7.2V multipurpose "Six Pack" that's easily reduced in size, or dismantled. Individually insulated cells. Bulk buyer enquiries welcome . UNREPEATABLE PRICE! 5.fik $10.90 per pack 2k 05 (22.46k) ( 6) 04 (5) 03 22k 470!l 27k 18k 180k ( 4) 02 (3) 01 .,. * MAY NEED SOME ADJUSTMENT ALL RESISTORS ¼W 1% (2) UNBELIEVABLY LOW PRICE $5.90 ea DO YOU WANT A REALLY LOUD SIREN FOR YOUR ALARM? 180k 180k Comes with circuit and instructions. 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Transfer rate is 250K bits/sec Track to track access: 3mS Power consumption: +12V/390mA (startup), 210mA (idle), +5V/460mA ONLY$140 NORMALLY $175 SAVE$35 PURCHASE EITHER NEC DRIVE with a four floppy disk drive controller for our special price. - ,<at> ~ • ~, ~- This card is fully compatible with IBM's dual async adaptor for the PS/2 models 50, 60 and 80. Includes two fully programmable serial ports with two serial asynchronous communications ports (using NS16550 to ensure full compatibility and best performance). The card is autoconfiguring. It sup2orts the POS of the Micro Channel TM architecture. False-start bit detection and line break detection are built in. The adaptor provides an EIA RS-232C interface. Two 9-pin D-shell connectors (male) are provided to attach peripheral devices. megabytes of expansion memory on a PS/2 type computer system. The board uses 1MB DIP type DRAMs. Full print spooling and virtual disk facilities are provided, as well as EMS (LIM) support. Ok RAM ONLY$349 ** 2/8 Megabyte PS/2 Memory Board CATMCM8 This memory board provides up to 8 megabyte s of expansion memory on a PS/2 type computer system. Maximum capacit y is 2 megabytes using 256K x 9 SIMMs and 8 megabytes using 1M x 9 SIMM DRAMs. Ok RAM ONLY$240 Great Value FANTASTIC PRICE ONLY$349 ONLY$599 TbeTurboXT Motherboard * * NEWPRODUCT! * * CATMB!600 CAT MB286AIO Dunson XT/AT RAM CARD CATRS6 This is a 12MHz 0 wait-state PC 'AT' Computer - complete on the motherboard (minus a video card). With the "All in One", you can build up a complete AT, with power supply, case, drive, keyboard and graphics card for as little as $1298. See article in August Sihcon Chip for full details. • Up to 4MB can be fitted onto the motherboard - no need for memory expansion cards. Uses 256K or 1MB chips. • Two serial ports and one parallel port on-board. • On-board floppy drive disk controller for both 5¼" and 3½" drives. • All cables for ports and floppy drives included. ONLY$545 The MB1600 is an IBM PC/XT compatible motherboard. It measures only 8W' x 9" . The board runs at 10 MHz or 4.77MHz, providing complete compatibility with the IBM standard. Eight 62 pin edge connectors are also mounted o the board. the l/0 channel is bussed across the eight expansion slots. The heart of the MB1600 is an 80883 microprocessor. The system board supports both ROM/EPROM and R/W memory. It has space for 32K x 1 and 8K x 1 of ROM or EPROM. A full 640K of high speed RAM can be fitted on -the motherboard. SAVE$50 ONLY$99 with V20 chip $109 • High speed with 0 wait state • 6MB memory on board • LIM 4.0 compatible • Configurable for PC/XT/ AT or 386 systems. OK RAM ONLY$295 !MB Ir~~Er~~~~ ! ••••••••••••••••••••••••••••••• :I • We accept: Bankcard, Mastercard & VISA mail orders our specialty. Freight on smaller items is now $9.00 + $2.50 P&P. • All prices include sales tax • All products carry a 14 day money back guarantee (software excepted) • All products carry a full 3 month warranty • All cards come with full documentation • Ring for quantity discounts and tax free prices Due to technical advances products we supply may in some cases vary from those pictured. In all cases they are guaranteed to perform to an equal or higher standard . I I ••••••••••••••••••••••••••••••• AMATEUR RADIO By GARRY CRATT, VK2YBX Random wire ant.e nna tuner for 6-metres Looking for a random wire antenna tuner unit for the 6-metre (50MHz) band? This unit can be knocked up in a few hours and will solve those antenna hassles. Most amateurs have been in the situation, during band openings, of having the necessary equipment on hand but no suitable antenna available for immediate use. After all, most amateurs do not have the space or resources to install permanent antennas for every band. This antenna tuner solves that problem by allowing a random length of wire to be pressed into service. Thus, when the 6-metre band opens (which may well be the case by the time you read this), you will be able to get to air quickly without too much bother. Antenna problems So how does an antenna tuner im- TRANSMITTER (LOW·Z) 4- prove matters? Let's take a closer look at the basic problem. The first thing that needs to be understood is that modern HF/VHF transmitters are designed to work into a coaxial cable feeder of 50-800 impedance, with a low standing wave ratio. If these conditions are not met, the efficiency will be low and the transmitter output stage may even be damaged. One type of antenna that does fulfill the necessary requirements is a ),./2 centre-fed dipole which has been carefully trimmed to the operating frequency. If it's not convenient to use this type of antenna, the problem can be overcome by installing an antenna tuning unit Construction ANTENNA (HIGH-Z) 1 (b) ) TRANSMITTER LOW-Z °lL l fr ANTENNA (Z UNKNOWN) TRANSMITTER (LOW•Z) Cl (c) .,. -t" .,. IT ANTENNA (Z UNKNOWN) 2 (d) ~ ~ Fig.I: four networks for matching a low impedance transmitter output to a high impedance load. We settled on the ,r-matching network shown at Fig.Id because it provides good second harmonic attenuation. 74 SILICON CHIP (ATU) between the antenna and the transmitter output. Basically, an ATU can be regarded as a variable RF transformer. The ATU is simply adjusted so that the transmitter "sees" the correct 50-700 load impedance, while the output from the ATU is adjusted to accurately match the antenna (or its feeder). In effect, the ATU is used to bring the antenna system (eg, a random length of wire) into resonance. There are several impedance matching schemes that can be used to transfer power adequately from a low impedance source (in this case 50 ohms) to a high impedance load. Fig.1 shows four suitable schemes. We settled on the most complicated configuration, shown in Fig. ld, which covers all possible load variations. It was chosen because of its ability to produce good second harmonic attenuation (typically 35dB) for an output load impedance of 2-3k0. As can be seen from the accompanying photo, the unit is housed in a metal diecast box. The two variable capacitors (both 10-300pF types) are mounted directly through the front of the enclosure, along with the 6-position rotary switch. Be sure to use a diecast box that does not have PCB mounting ribs, as these can interfere with any holes that are drilled in the enclosure and prevent the correct mounting of parts. The inductor, Ll, is positioned between the two variable The antenna tuner is built into a metal diecast case which provides shielding for the circuit. It should be used with an SWR meter (situated between the transmitter and the ATU). You simply adjust the Load, Tune & Inductor controls for minimum SWR. capacitors and has 6 taps to provide optimum matching. Fig.3 shows the dimensions and drilling details. Construction is best done in the following order: (1) Drill the diecast box for both variable capacitors, the switch, output insulator, SO-239 socket (transmitter input), and ground connection. (2) Mount the variable capacitors, switch, output insulator, SO-239 socket and ground lug (to which a quarter wavelength counterpoise will be connected). (3) Wind Lt. This consists of 6 turns of 1.0mm dia. copper wire, wound to a 35mm diameter, and air spaced across 17mm. Fig.4 shows the details. (4) Attach a 20mm length of tinn- L1 : 6T, 1mm DIA COPPER WIRE 35mm ID x 17mm LONG ANTENNA TUNER ed copper wire to each lug on the 6-position single pole switch. It's best to crimp the tinned copper wire after passing it through the lugs on the switch prior to soldering, so that there is some mechanical support for these taps. (5) Fit Lt. This connects between the SO-239 input socket and the "input" terminal on the 6-position switch. The coil is best preformed prior to installation, as the inside of the enclosure is quite cramped at this stage. Make sure that the coil is mounted centrally in the case so that it clears the lid of the enclosure when the unit is assembled. (6) Connect all six taps to Lt, ensuring that they are correctly spaced one turn apart. (7) Using either desoldering braid Fig.2: the final circuit of the Antenna Tuner. It is a 1r-matching configuration with switch S1 used to select taps on the inductor. or braid stripped from coaxial cable, wire the input and output variable capacitors as shown in Fig.4. Wire another braid link between one mounting lug of the SO-239 input socket and the earth lug on the rear panel of the diecast box. (8) Connect a counterpoise made from from a 142cm length of heavy gauge insulated copper wire to the earth lug on the enclosure. This ensures correct loading. Don't leave the conterpoise out - it's vital for correct operation of the unit. Testing At this stage, the construction is complete and all that remains is to test the unit. This is best done in the PARTS LIST 1 diecast case, 120 x 53 x 75mm (Jaycar HB-5020) 1 SO-239 input socket 1 single pole 6-position switch 2 5-64pF variable capacitors (Dauner Electronics) 3 knobs to suit 1 output insulator (Dauner Electronics) 1 earth connector/binding post 1 50cm length of desoldering braid 1 800mm length of 1mm dia. copper wire 1 solder lug 2 3 x 10mm screws plus nuts . & washers (to mount SO-239 · socket) FEBRUARY 1990 75 35 ' ,l 35 32.5 32.5 - ~ "' .J ·I ~. N . J¥ ~__J---=5f ,._% I I "' N I I CASE BACK mMENSIONS IN MILLIMETRES CASE FRONT Fig.3: drilling details for the front & rear panels. receive mode and can easily be accomplished by connecting a 6-metre receiver to the input of the tuning unit and a random length of wire to the output. Check the table shown in Fig.5 for the nearest 6-metre repeater or beacon and adjust the tuner for maximum received signal. This in- volves first switching the inductor for maximum receiver noise and then peaking each of the variable capacitors for maximum signal. The use of a signal generator will assist at this point, although it is not essential. The transmit operation should be monitored using an SWR meter in the input line (ie, between the ATU and the transmitter). In this position, it can be used to ensure a good match between the transmitter output and the tuner input. All you have to do is adjust the Load, Tune and Inductor controls for minimum SWR. Be sure to select low power for all initial transmitter tests and note that the input and output variable capacitors are only rated at about 142cm COUNTERPOISE A short braid link must be run between one mounting lug of the S0-239 socket and the earth lug which runs to the counterpoise. This ensures a good RF earth. CONNECTIONS MADE WITH COPPER BRAIO STRIPPED FROM COAX Fig.4: the coil is supported inside the case by its own input lead and by the tapped connections to S1. The connections are made using desoldering braid or braid stripped from coaxial cable. 76 SILICON CHIP The rear panel holds the S0-239 input socket (at left), the insulated output socket, and the earth terminal for the counterpoise. POLYSTYRENE CAPACITORS Made here in Australia? Made Special to Type? Make sure that the coil is mounted centrally in the case so that it clears the lid when the unit is fully assembled. A 142cm-long counterpoise is connected to the earth lug on the rear panel. 80 watts. Application of higher power levels could result in RF arcing across the plates of these capacitors. This in turn could damage the transmitter. If a higher power unit is required, it is best to select input and output capacitors having larger spacing between the plates. Finally, the author would like to thank Peter, VK2XKB for his assistance in the construction of prototypes for this article. For information on the construction of antenna tuners suitable for VHF use, readers are ref erred to the the ARRL Handbook and the RSGB Handbook. ~ FIG.5: 6-METRE BAND REPEATERS FREQUENCY 50.010MHz 50.075 50.090 51 .020 51 .030 52.013 52.020 52.1 00 52.200 52.225 52.250 52.310 52.320 52.325 CALL SIGN JA21GY VS6SIX KH6EOI ZL1UHF ZL2MHB P29BPL FK8AB ZK2SIX VK8VF ZL2VH2 ZL2VHM ZL3MHF VK6RTT VK2RHV LOCATION Nagoya Hong Kong Honolulu Auckland Hawkes Bay Loloata Island Noumea Niue Darwin Tarana ki Manawatu Christchurch Wickham Newcastle 52.345 52.350 52.370 52.418 52.420 52.425 52.435 52.440 52.450 52.460 52.465 52.470 52.485 52.490 52.510 VK4ABP VK6RTU VK7RST VK0MA VK2RSY VK2RGB VK3RMV VK4RTL VK5VF VK6RPH VK6RTW VK7RNT VK8RAS ZL2SIX ZL2MHF Long reach Kalgoorlie Hobart Mawson Base Sydney Gunnedah Hamilton Townsville Mt. Lofty Perth Albany Launceston Alice Springs Blenheim Mt. Climie Polystryrene Capacitors - 1 0pF to 1 mF Voltage Range 63VDCW to 10,000 VDCW Tolerance - 0 .25% to 10% Allied Capacitors Australia manufactures capacitors to the specification of the customers using high quality, imported polystyrene and aluminium foil with a tolerance of 1 micron. Our capacitors are manufactured to the system of Total Quality Control. We can provide Just In Time delivery if required, together with a Certificate of Conformance if requested. Specific values between 1 0pF and 1 uF are no more expensive than standard value components. You can now design circuits to use a single capacitor rather than a number in parallel or series to achieve a desired value. Personalised labelling is available at no extra cost. Your component code or name can be built into the capacitor. Minimum runs of only 25 allow you to specify a particular value for a prototype run. Delivery lead time for short runs is 3 to 4 working days, and for longer runs is less than 2 weeks. We are also able to produce capacitor styles for applipations such as dual mount, end filled and mini style capacitors. INTERESTED? Call us now on: (02) 938 4690 ALLIED CAPACITORS AUSTRALIA PO Box 740 Brookvale, NSW 2100 FEBRUARY1990 77 Computer program calculates great circle bearings & distances If you want to point your beam to Recife on the eastern-most tip of Brazil, what bearing would you use? A map based on Mercator's projection would suggest a few degrees north of east but of course you know better than that. By PHILIP WATSON, VK2ZPW But what bearing would you use? If you are lucky enough to have a great circle map based on your city, that's fine. But if not, or you live somewhere between Woop Woop and Bulamakanka, finding the correct bearing is not always easy. This program will calculate the distance and bearing between any two points on earth. All you have to do is feed in the latitude and longitude of each. It was written by J. Hall and C. Hutchinson of ARRL headquarters and published in several editions of the ARRL Antenna Book. The ARRL has waived any copyright restrictions on the program. The program was originally written for a Radio Shack TRS-80 Level II computer using a form of BASIC suited to that machine. This differs slightly from GW BASIC and the version given here has been modified to suit the latter. Also, the original was written to accept degrees and decimals of a degree. Since most references quote degrees and minutes, the program has been modified to accept data in this form. Another modification has been to write the user's location permanently into the program. This is shown at line 260 which lists the location for Sydney. All you have to do is substitute your own location and the corresponding latitude and longitude figures where appropriate. The most practical way to use the program is to compile a list of major world centres, plus any special localities the you frequently contact. This can be kept at the operating position. Using the software is easy. First boot up your computer in GW BASIC, then load and run the program in the usual manner. Fig.2 shows the program listing while Fig.1 shows a sample readout. You simply enter the name of the distant location, the latitude and longitude of your own location, and the latitute and longitude of the distant location. The program then displays the required information and asks Sample Printout PROGRAM TO CALCULATE GREAT CIRCLE DISTANCES~ BEARINGS BY J. HALL~ C HUTCHINSON, ARRL HQ, JULY 1981 ARRL PROGRAM IS NOT COPYRIGHTED~ MAY BE REPRODUCED FREELY <MODIFIED BY P. WATSON, VK2ZPW> ENTER NEGATIVE VALUES FOR LATITUDES SOUTH OF THE EQUATOR ENTER NEGATIVE VALUES FOR LONGITUDES EAST OF GREENWICH <MAX 180) SYDNEY:LAT.-33DEG.55MIN. LON.-151DEG.13MIN. ENTER NAME OF DISTANT LOCATION (OPTIONAL) SAN FRANCISCO THIS LOCATION LATITUDE (DEGREES AND MINUTES)? -33.55 THIS LOCATION LONGITUDE <DEGREES AND MINUTES)? -152.13 OTHER LOCATION LATITUDE (DEGREES AND MINUTES>? 37.45 OTHER LOCATION LONGITUDE (DEGREES AND MINUTES>? 122.27 DISTANT LOCALITY: SAN FRANCISCO THE FORWARD BEARING IS 55.385 DEGREES THE GREAT CIRCLE DISTANCE IS 11861.15 KILOMETRES 6405.08 NAUTICAL MILES 7370.22 STATUTE MILES TO CALCULATE NEW BEARING PRESS ENTER? Fig.1: this sample printout shows the hearing and distance from Sydney to San Francisco, USA. You simply enter in the latitude and longitude of each location. 78 SILICON CHIP Program Listing 10 REM*** BEARING/BAS*** 20 REM A=YOUR LAT. 30 REM B=OTHER STATION LAT. 40 REM C=BEARING ANGLE 50 REM D=DEGREES OF ARC 60 REM E=INTERMEDIATE VALUE 70 REM K=CONVERSION CONSTANT,ARC TO KILOMETRES 80 REM L=DIFF IN LONGITUDES 90 REM Ll=YOUR LONG 100 REM L2=0THER STATION LONG 110 REM M=CONVERSION CONSTANT, DEGREES TO RADIANS 120 REM N=CONVERSION CONST, ARC TO NAUT MI. 130 REM S=CONVERSION CONST, ARC TO STATUTE MI. 140 CLS:KEY OFF 150 PRINT"PROGRAM TO CALCULATE GREAT CIRCLE DISTANCES~ BEARINGS" 160 PRINT 170 PRINT"BY J. HALL~ C HUTCHINSON, ARRL HQ, JULY 1981 180 PRINT"ARRL PROGRAM IS NOT COPYRIGHTED~ MAY BE REPRODUCED FREELY " 185 PRINT"(MODIFIED BY P. WATSON, VK2ZPW>" 190 DEFDBL A,A,C,D,E,L,M: 200 D=1:K=111.11:M=57.29577951308238#:N=60:S=69.041: 210 PRINT 220 PRINT"ENTER NEGATIVE VALUES FOR LATITUDES SOUTH OF THE EQUATOR" 230 PRINT"ENTER NEGATIVE VALUES FOR LONGITUDES EAST OF GREENWICH <MAX 180)" 240 IF D<>l THEN 320 250 PRINT 260 PRINT"SYDNEY:LAT.-33DEG.55MIN. LON.-151DEG.13MIN." 270 INPUT"ENTER NAME OF DISTANT LOCATION (OPTIONAL> ", N$ 280 INPUT"THIS·LOCATION LATITUD£ (DEGREES AND MINUTES>";A: 290 A1=(A-FIX<A>>:A2=A-A1:A=A2+(A1/,6):A=A/M 300 INPUT"THIS LOCATION LONGITUDE (DEGREES AND MINUTES>";Lt 310 L11=(L1-FIX(L1)):L12=L1-L11:L1=L12+(L11/.6): 320 INPUT"OTHER LOCATION LATITUDE (DEGREES AND MINUTES>";B: 330 B1=(B-FIX<B>>:B2=B-B1:B=B2+(B1/.6):B=B/M 340 INPUT"OTHER LOCATION LONGITUDE (DEGREES AND MINUTES)";L2 350 L21=(L2-FIX<L2)):L22=L2-L21:L2=L22+(L21/,6): 360 L=!L1-L2>/M 370 E=SIN<A>*SIN!B)+COS(A>*COS<B>*COS<L> 380 D=-ATNCE/SQR(l-E*E))+!.57079 390 C=(SIN(B)-SIN<A>*E)/(COS(A)*SIN(D>> 400 IF C>=l THEN C=O:GOTO 420ELSE IF C<=-1 THEN C=180/M:GOT0310 410 C=-ATN(C/SQR(l-C*C>)+!.57079 420 C=C*M 430 IF SIN(L><O THEN C=360-C 440 PRINT"DISTANT LOCALITY: "JN$ 450 PRINT "THE FORWARD BEARING IS";:PRINT TAB(36)USING"#####,###";C ; 455 PRINT" DEGREES" 460 PRINT"THE GREAT CIRCLE DISTANCE IS"; 470 PRINT TAB(35)USING"######.##";K*D*M;:PRINT" KILOMETRES" 480 PRINT TAB(35)USING"######.##";N*D*M;:PRINT" NAUTICAL MILES" 490 PRINT TAB<35)USING"######.##";S*D*M;:PRINT" STATUTE MILES":PRINT 500 INPUT"TO CALCULATE NEW BEARING PRESS ENTER ";D:GOTO 260: Fig.2: the program is written is GWBASIC but conversion to other BASICs should pose no problem. Note that you will have to customise line 260 to suit your particular location. if you want to calculate another bearing. To exit the program, you simply hit Ctrl Break. You can then exit to DOS by typing SYSTEM and pressing the Enter key And the bearing for Recife'? Oh yes - around 170 degrees, or over Antartica, close to the South Pole.~ FEBRUARY1990 79 IT'S ON AGAIN, THE FABULOUS JAVCAR 15o/o OFF EVER HING SALE! NO EXCEPTIONS That's right! No Exceptions. Every single item in your local Jaycar Store is Discounted for a strictly limited time. We have to remove hundreds of old lines for our brand new March '90 Catalogue so that we can fit many great new products in. Rather than just discount the old lines the Boss told us - Discount Everything! But you must hurry. Any regular line that is in stock at the time of purchase qualifies for the 15% discount. We will not back order goods that are out of stock during the sale at the discount price. If any out of stock item comes back into stock during the sale, you will get it at the discount price. (Pleae do not ask for the discount price after the sale.) So now is the time to make a significant saving on that big kit and other major purchases. But remember, hurry!. All savings off our current prices. THESE PRICES ALARM CLOCK MOVEMENT you can even have a dock movement 'Mti an arm. Make yM cr,vn bedside alarm clock! Supplied ith two sets of luminous hands. Alarm is swiched on/ by a switch on the back. Requires 1 • M battety. ON at. XC-0104$16.95 VARIABLE ATTENUATOR This device consist,; of a little black box v.ith a ooax TV socket on each end and a rotary oonlrof on the front. It wil atl&nualo a signal Mywhere between OMd 20dB. Ideal if you a'e in a high signal area a running one a two videos v.t,id, are generaing too much signal which you may need kl rut down. Cat. LT-3019 $8.95 PROBE TYPE DIGITAL MULTIMETER- 3.5 DIGIT rubber torch Weather proof/water resistant/shock proof. OI\ILY This tach is supplied v.ith a KryplDn globe which is 7rf'/, brighter than a sla'ldard globe. Krypton globes don't draw heavy currant like Halogen globes so your batteries last much longer. This l:>rch takes 3 x D cells and gives a briia'lt light. D cells not supplied. Replacement l<typlDn globes. $6.95 Cat. SL-2712 2 PCS $2.95 Cat. ST-3022 KRYPTON TORCH GLOBES lnaease tie btigh_,ess of Y'"' l:>rch sinply by replacing the globe. Krypllln globes a,e 70% blighter. than standard pre-focused torch globes Total length 30mm. Base Diameter 9mm. Avaiable in 4 voltages. Suit 2 cell torches Suit 3 cell torches Suit 4 cell torches and dolphin type Suit 5 cell torches asier to use than a conventional hand held. eadout is in the body of the ')robe." eludes: Logic Probe, large digts • 14mm high, ata Hold txJtton, manual or Autoranging at the ass of a txJtton, yalow high In-pact case. pecilica11ons: D Converter: 3.5 Digit C!.'OS LSI au10 polarity. is play: LCD 14 mm high +/· 1999. ver Range: "1" 000 ii reading exceeds 1990 in ach range MSD flashes. ow Battery: Indicated on display. ower Source: 2 xx 1.5V LR/SR 44 txJtton cell. imensions: 185(L) x 22(W) x 31 (D)mm. oltage Ranges: DC 200mV, 2V, 20V, 200V, 500V 11% accuracy +3 digits. Input impedance 10M SL 1/2" HIGH DENSITY DISCS Anew addition to our range ol ACT high quality discs at low, low prices. YOU CAN'T BEAT THIS. 10x31/2" MF2HD for $49.95 2V up, 1OOM SL 200mV. AC: 2V, 20V, 200V, 500V. 40HZ • 400Hz. 10M SL input imp +/·1.5% +5 digit nin aooxacy. Resistance: 0. 200 SL, 2K SL, 20K SL, 200K SL, 2,000K SL, 20 mSL 2% aco.xacy 20 MSL, others 0.8 • 1%. 250V AC/DC dra.iit p-otaction. DC/AC Current: 0 • 200mA. PTC switch p-otactad. +/· 1.5% DC, +I• 2.5% AC (AC 40Hz • 400Hz) Diode Test: Range. 2V forward voltage. 0.2 • 1.7V<at>0.8mA. Protected. Continuity: Buzzer sounds und9r 1 K SL. 0.4mA. Protected to 250V. Cat. QM-1420 $59.95 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 Cat. Cat. Cat. Cat. SL-2710 $2.95 SL-2712 $2.95 SL-2714 $2.95 SL-2716 $1.50 pair pair pair each 5 - D CELL FLASHLIGHT MACHINED AIRCRAFT GRADE ALUMINIUIVI The big btother ID our 2 • M tach. This l:>rch measures a massive 440mm long and has a KtyplDn Long Reach Beam which is 70% btighl&r tha'l normal taches. It's waterproof and shockproof and has a durable a'lodised abrasion resistant inish with a na, sip knurled grip. This tach wil last a lifetime. The American aiginals of this product sell fa about $90. Direct impat fran Asia saves you a,er 50%. Spare globe supplied In tall cap. Spare Krypton globe available- 6 volt Cat. SL-2716 $1.50 each. TORCH Cat. ST-3025 $39.95 PERFECT TIMER This LCD Timer is easily preset &an t minute to 99 minutes. Hit the startbutm and itwil countdown the time longth desired and when reached wil sound an alarm sound !or 8 seconds. Perfect fa timing a host of tlings, e.g. PC Board etching time, boiling your eggs, timing your pressure cooker ,photography, etc, elc, ek:. Measures only 60(W) x 56 (H) x 15 (O)mm, and suppHed wit, a tilting bai to sla'1d up '"1d a magnet to attach ID your ro~ige,alllf. Cat. XC-0130$12.95 '· ·=•,,.•=-•........,.,•.,.,,. .., -. ~•: , • · - , , Nw •- ~•.,,y . ~·v< -·· , · • F BUR LAR ALARM OFF SPEAKERS OFF BISHOP GRAPHICS OFF ALL KITS OFF TV ANTENNAS OFF SEMICONDUCTORS OFF TELEPHONES OFF TOOLS OFF MICROPHONES OFF PLUGS & SOCKETS OFF WIRE OFF CAPACITORS OFF SWITCHES OFF RACK BOXES OFF TEST EQUIPMENT MODEM CAPACITOR BARGAIN 2uF 440V Modem Capacitor at a silly price. We are overstocked. Cat RC 5500 Normally $12.50 Now$7.95ea Less 15% Only $6.75 SVA PCB MOUNT Know 1he time n 8trf of 24 different places in 1he world in moments. Slrrpy set 1he local time to 1he place that corresponds to yr:u home longiMe .m 1he world time artoma11Caily a~ts the time for the olher Transformer Bargain zones. The 24 zones are: • London GMT • Morrovla • Azores • Rio De Janeiro• Ca-acas • New York • Clicago • Denver • Noumea • Va-YXANer BC• YlA<on • Hawaii • Date Line • Pais • Cairo• Woscow • Welfington • Dubai • Ka-acn • Dacca • Ba,gkok • Hong Kong • Tokyo • Syooey/ Melboune The World Time also ndudes an alarm. Size 62(W) x 70(H) x 14(D)mm .m Is supplied In a wallet A 15-015V tranny for less than 1/2 normal price! The Feriuson equivalent to this now sells for around $20. This what you get for 1/4 of that: 240V AC to 30-15-0 <at> 150mA and 3V <at> 150mAS. MANUFACTURERS! We have a very large quantity of these. WAS $4.95 NOW $3.50 LESS 15% ONLY $2.97 8"""0 o'- 1SV O D1i0 I I p"""' &Voltage Connect,oro Cat.sQM-7212 $26.95 5mm l ■ LESS 15% ' lV _J 0 I O [ 'l4~1NJ LESS15% $4g g5 -----1-----------tlll diagramsetc. Included. Dimensions (excluding pins): 41W x 34D x 32H Cat MA-2622 0 - Another surplus scoop purchase! We ha11e obtained a small quantity of a front load Hi-Fi cassette deck mechanism with associated preampibias oscillator circuitry. All you need is a power supply and you have a first class HI-FI cassette deck! Ideal to be built into custom installations etc. But be quick. We only ha11e 70 sets. All circuiVconnection L1Smm Infra Red Remote Control ■ Quality Electrophone Brand ■ Two way intercom paging facility ■ Recharge socket on handset ■ Pulse/Tone dialling ■ 12 months warranty ■ SUperb sound, a qua!lty product Cat. YT-7068 ~ ONLY $279.oo ~ C Less 15% $237 .15 GUITAR SPEAKERS 15" 150W RMS Update to electronic dimming! This dimmer will replace your normal large size light switch and give you touch dimming/switching AND remote control! Uses lhe Siem"1S S5769 dimming chip as used in OU' ~ lamp dimmer kits. At a touGh of fle button on fle wal plate you can dim yourlight'and lhe light wift stay dimmed at whalever level you ift YOU/ Inger off. This function is repealed on flo remele contol. Wall unit oolour - while with fawn panel. Two year warm,ty if installed by liconced olecticim,. Specift!)Alionl! Remole con~ol dislanco - 6 mt Max light load - 350 watts Rocoiver size- t20(L) x 70fl/) x 42(D)mm Remele roq<.ires -2 x Nballeries (Pkt 2 alkaline Cat SB-2396 4.35) Remele size - 85(L) x ~ ) x 15(D)mm Cat. XR-osoo $55.oo, sup$50.oo LESS15% I 1 j ;; ~, ;LI SYDNEY - CITY ' PARRAMATIA CONCORD HURSlVILLE CatCG-2382 $129 Less 15% $109.65 12" lOOWRMS CatCG-2380 $89.50 Less 15% $76.07 10"65WRMS 1 I CatCG-2379 $59.50 Less 15% $50.57 HEAD OFFICE MAIL ORDERS ~-115 Parramatta Road Concord 2137 P.O. Box 185 Concord 2137 Telephone (02) 747 2022 HOTI.INE 02 7471888 Telex 72293 FOR ORDERS ONLY FACSIMILE (02) 744 0767 TOLLFREE (008) 022 888 MAIL ORDER VIA YOUR 117 York St (02) 267 1614 Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Church St (Cnr. Victoria Rd) (021683 3377 Mon-Fri 9 -5.30Thur~ R.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 7!XXJ Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 12 1'.f OVER $100 s 3.75 S 4.50 $ S.50 $8.00 ROAD FREIGHT ANYWHERE IN AUSTRALIA $13.58 GORE HILL BURANDA OLD MELBOURNE-CITY SPRINGVALE VIC $10 - $24.99 $25-$49.99 $50-$99. 99 188 Pacific Hwy (Cnr. Believue A11e)(02I 439 4799- Mon-Fri 9 - 5.30 Sat 9- 4pm 144 Logan Rd (0713930777 Mon-Fri 9 - 5.30 Thurs 8.30-Sat 9-12 Shop 2. 45 A'Beckett St City (031663 2030 Mon-Fri 9- 5.30 Fri 8.30- Sat9-12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr. Cnr. Dandenong Road Mon-Fri 9- 5.30 Fri 8.30 - Sat 9 - 2 IPRODUCT SHOWCASE I PC 1/0 board has 6 interfaces Mouse platform fits over keyboard This unit will be great when the usual mouse pad can't be accommodated on the desk. It simply fits over your keyboard and can be used for all types of mouse. Called 'Magic Stage', it is made out of high-quality ABS plastic and has an anti-static rubberized pad. It measures 280 x 260mm and is specially sloped for ease of use. It even features a sliding arm for storing the mouse when it's not in use. The Magic Stage costs $34.95 and is available at your nearest Rod Irving Electronics store. Phone (03) 663 6151 in Melbourne or (02) 519 3134 in Sydney. DB9 and DB25 Key-operated passive IR alarm This portable passive infrared alarm is key and battery operated and can't be turned off by would-be thieves. When triggered, it waits for 15 seconds so that it can be turned off using the key. If it isn't turned off within this delay period, it sounds an alarm for 60 seconds but will then be re-triggered if it still detects movement. The unit operates from a 9 volt battery which has an operating life of about 12 months under normal conditions. It can be mounted by using either a wall hook or the mounting screws provided. The coverage angle is about 85° while the greatest range is on an axis slightly below horizontal. 84 SILICON CHIP Electronic Solutions has come up with a multi input/output card that has six input/output facilities. These include an IBM standard parallel printer interface, an IBM compatible serial interface, a games port supporting standard joy-sticks, a real time clock with battery backup, a Microsoft bus mouse interface and an industry standard disc drive controller. For further information, contact Electronic Solutions, 5 Waltham St, Artarmon, NSW 2064. Phone (02) 906 6666. gender changers from Geoff Wood The Electronic Sentry comes complete with installation and operating instructions, two keys and the mounting screws. The . price is just $99.95 from all Jaycar Electronics stores. Anyone using RS-232 iransmission with long cables to change the gender will find these gender changers very useful indeed. The DB9 gender changer is available in male-to-male and male-to-female, and is made of a sturdy moulded plastic. The DB25 version is very versatile, having both male and female connectors fitted to both ends of a 40cm length of ribbon cable, allow- ing any combination of male/female to female/male conversion. The cost of both DB9 changers is $7.35 each and the DB25 version is $26.95. They are available from Geoff Wood Electronics, 229 Burns Bay Rd, Lane Cove, NSW. Phone (02) 428 4111. Pocket Rocket modem from NetComm Wireless infrared alarm runs off 'AA' batteries This clever unit uses a passive infrared detector to trigger an alarm when someone enters the alarm zone. It features an in-built oiezo siren and is supplied with two keyring remote controls. The unit is powered by 6 'AA' batteries, draws only 170µ,A in normal operation and has a battery life of about 10 months. The alarm time is 2 minutes, so it won't drive the neighbours up the wall. The unit also gives an audible indication when it is armed and disarmed. The unit comes complete with installation and operating instructions. It costs $199 and is available from Geoff Wood Electronics, 229 Burns Bay Road, Lane Cove, NSW. Phone (02) 427 1676. Introduced for the recent launch of the Apple Mac portable, the Pocket Rocket 1234 modem also provides portable communications for Mac SE and IBM users. The Pocket Rocket is manufactured in Australia and is a highperformance battery-operated modem capable of transmitting data at 300, 1200 or 2400 bps. It supports the Videotex standard of 1200/75 bps and fully conforms to the CCITT and Bell standards. The Pocket Rocket also supports the standard 'AT' commands for auto-dialling, auto answer and auto-disconnect; pulse and tone dialling; and built- They' re available in 4, 6, 8 and 10 positions. For further information, contact Augat Pty Ltd, 21/26 Wattle Rd, Brookvale NSW, 2100. Phone (02) 905 0533 . Bargain-priced AT keyboard New DIP switch series from Augat/ Alcoswitch Augat Pty Ltd has recently released two new series of DIP switches. The DPU series features piano style actuators while the DPU series offers a flush type actuator which prevents accidental operation. in local and remote testing pro~ cedures. An in-built miniature speaker is included so that the user can monitor the progress of the call. One of the more interesting features of the modem is its incredibly small size. It measures just 110 x 75 x 33 and is one of the smallest modems on the market. Power comes from an internal 9V nicad batte1,:y that can be recharged via a mains plugpack (supplied). The retail price of the pocket rocket is $649.00 including tax. For further information, contact NetComm Australia, Unit A, 25 Paul Street North, North Ryde, NSW 2113. Phone (02) 888 5533. Both series click when actuated to notify the operator that switching has occurred. They also feature gold plated contacts and solder-plated terminals. If you need to replace your XT's or AT's keyboard, or if you're building a computer from scratch, then you'll find this keyboard a big hit! Featuring 101 keys , it comes with a coiled cable fitted with the standard 5-pin DIN plug and will suit FEBRUARY1990 85 New Scope soldering station This new soldering station, model ETC60L-9 from Scope Laboratories, has a redesigned cartridge type heating element which gives extended service by eliminating the mica insulation. Also, a new range of hollow tips has now been released which allows the heat source to be located inside the tips. It is claimed that this gives superior PC owners who don't want to pay a king's ransom. The keys have a firm press (unlike some of the el-cheapo keyboards available) and it features LED indicators for "NUM" , "CAPS" and "SCROLL" lock. In addition, there are 12 function keys and a separate numeric keypad. The big bonus is that it costs just $69 from David Reid Electronics, 127 York St, Sydney. Phone (02) 267 1385. Get in quick before they disappear! Formatted discs from 3M What's the first thing you do when you open a new box of floppy 86 SILICON CHIP heat transfer and a faster recovery. It should be noted, however, that the new tips are not compatible with older soldering stations but the older tips will work in this model. Contact Scope Laboratories on (03) 338 1566 for further information or write to PO Box 63, Niddrie 3042. discs? Right, you have to format one of them. In fact, if you are running an office, it makes sense to format the whole lot in one go. That way, if you suddenly need another formatted disc for backing up or whatever, you don't have to worry about formatting. We hadn't thought about this but having to format every new disc is a pain, isn't it? Why don't they come ready formatted? Evidently somebody else has asked that question because now 3M Australia has introduced a line of formatted discs to suit IBM PS/2 and IBM XT/AT and compatible computers. Not only do you save between 20 and 30 minutes time in not having to format a box of 10 floppiBs, but as an introductory bonus 3M Australia is offering PC users a free Flip'n'File 10 disc box. Why didn't somebody think of it sooner? The new formatted discs will be widely available from 3M stockists. For further information, contact 3M Australia Pty Ltd, PO Box 99, Pymble 2073. Phone (02) 498 9333. Stationary mouse from Logitech For a lot of software, be it CAD, spreadsheet, wordprocessing or even some of the latest accounting packages like Attache5 , a mouse is almost a necessity as it lets you move the cursor around the screen much faster than you can move it with a keyboard. The problem with a mouse though is that they do require a reasonable amount of your valuable [uncluttered?) desk space. An alternative solution is the Trackman Stationary Mouse from Logitech. Instead of running all over your desk it stays put and operates just like the trackball on some computer keyboards. The Trackman has a small thumb-operated ball for ease of use· and three buttons for "click-on" selections. It is fully compatible with other mouses [mices?) and is packaged with Logitech Mouseware utilities. Serial and bus versions are available for the IBM PC, XT, AT WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR C Fluke 80 Series Top of the Line in Digital Multimeters ~ ~ c:c 0 lJ... Cl 0 ~ NEW Auto-Ranging Bar Graph • 3 314 digit large LCD display Digital Multimeter • • • • The Fluke 80 series offers a huge range of extra features like a 200kHz frequency counter, capacitance meter, combined analog and digital scales plus the ability to automatically record max and min and average readings and store them for up to 36 hours Check the features and check the value 1 Value at $144.00 Discount Disks ~ 51/4 Bulk Packs 5 1/4 Filesale OS 51/4 Filesale OS 3 1/2 Filesale OS 31/2 Filesale OS ~ c:c 0 lJ... Cl 0 OD HO OD HO $6.50 $18.50 $34.95 $39.95 $69.95 All Prices per Pack of Ten Disks. ~ ~ i5 c:c 0 lJ... Cl 0 ~ 80 Series Features • • • • • • • • ~ :i:(.J c:c 0 lJ... Cl 0 ~ ~ ~ c:c 0 lJ... Cl a ~ • 4 3/4 digit 4000 count resolution Digital Display updates 4 times/s 87 has analog pointer 83/85 have analog bargraph with zoom mode . Analog display updates 40 times/sec 0.5Hz to 200kHz Counter with duty cycle from 0.1 % to 99.9% 1OpF to SµF Capacitance range Input alert warns of incorrect connections 87 is a true rms 1ms Peak Min Max hold meter with backlit display Touch Hold and Relative modes Fluke83 • Analog Bargraph and Digital Display (4000 count) • Measures Volts, Current, Ohms, Frequency, Capacitance and Diode Test • Touch Hold and Relative Modes • Min/Max and Average Recording with Min/Max Alert • Input Alert and Overload Protection • 0.3% Basic DC Accuracy • Audible Continuity Fluke85 As above but offers • 0.1% Accuracy Fluke 87 As above but offers • 4 1/2 digit display • Backlighting • Analog Pointer Model 83 85 87 ~ ~ c:c 0 lJ... Cl 0 ~ Tax Paid $446.40 $525.60 Tax Free $372.00 $438.00 $630.00 $&25.00 Disk Cases DDSOL DD100L DD40L DD80L DD10 50 X 51/4 100 X 5 1/4 40 X 3 1/2 80 X 3 1/2 10x 51/4 $25.80 $29.95 $25.40 $29.95 $2.95 Disk Cleaners FDC1 FDC3 $6.95 $6.95 • • • • 4000 count resolution 41 segment analog bar graph Data Hold Max/Min stores highest and lowest readings Relative display (Offset) Continuity beeper Diode check Frequency to 40kHz UP604 IBM Breadboard Card See Review in Silicon Chip Nuvember 89. Accommodates up to 24 14-pin ICs and has all the IBM signals brought out to pin sockets on the board. Includes DB25 female socket for external connections. Suits AT/XT or compatibles. $87 .99 Basic Ranges Vdc 400mV to 1000V (i-0.3%) Vac 400mV to 750V (i-0.5%) Ade 400mA (100µA) to 20A (i-0 5%) Aac 400mA (100µA) to 20A (i-0.5%) Ohms 400n (100mn) to 40Mn (i-0.5%) DIGITAL STORAGE ADAPTER KIT Low cost accessory for your scope Converts incoming analog signals up to 20kHz into a stream of 8-bit data words for storage in 2048 word memory. Ideal for one-shot observations. Replay as many times as you like. See description in E.A. December. This is a quality locally developed AT&M kit. Complete kit (AT&M17) using top quality components and with ft• 11 instructions is just $193 .80 Matching case (ATM17-01) $27 .60 ULTRASONIC CLEANER The latest high-tech way to clean PCB's, switches, watches, drafting pens - even your dentures' Let the millions of tiny cavitation bubbles clean the surface 40000 times per second. 165x90x50mm container holds half a litre and is made of 304 stainless steel. Some people are charging $200. We had 'em for $160. Now you can have one for just $150. MADE IN AUSTIIAUA Pl12/20VA 6-0-6VC 1.67A 21.75 PL12/40VA 6-0·6V C 3.33A 31 .55 PL12/60VA 12VC5A 31.70 PL1!>'20VA 7.5-0-7.SV C 1.67A 21.75 PL1!>'40VA 7.5-0-7.SV C 2.67A 31 .55 Pl1!'/60VA 15V C 4A 31.70 9-0-9VC1.11A 21.75 PL11>'20V• PL11V4;. 9-0-9V C 2.22A 31 .55 9-0-9V-C 3.33A 0 .75 PL11V60VA 12-0·12V C 0.83A 21.75 PL2~0VA PL2-V40VA 12-0-12VC 1.67A 31 .50 12-0-12VC2.5A 4U5 PL2-VSOVA PL30-Q/40VA 9V C JA,15-0-15 C 500m41.35 PL30-Q/60VA 9V C SA,15-0-15 C 500m4t.50 PL3CY.!OVA 15-0· 15V C 0.67A 21.75 PL3c.'40VA 15-0·15V C 1.33A 31.50 PL3c.'60VA 15-0-15V C 2A 0.15 Pl4CY.!OVA 20-0·20VC05A 21.75 20-0-20V C 1.0A 31 .50 Pl4c.'40VA PL110"iOVA 110V<at> 0.55A.SQI Wrd 40.08 .,., a () ::t: ~ Kikusui COSS020 20MHz scope $979.25 (Tax Free $839.40) C0SS041 40MHz Scope $1522.40 (Tax Free $1304.85) We carry Iha full range of AT&M Kits - Refer lo our catalogue for details. Haven't got one? Call in and pick one up or request one with your next order! ~ a 0 .,., 0 :0 () ::t: ~ ~ 0 0 .,., Witte Screwdriver Sets Ch111i1 Moun1ing · Low Prolilo · 240¥ 50Ht 0 :0 TOOL BOX FERGUSON TRANSFORMERS 80 We get many enquiries for a decent set of screwdrivers. Well we've found them - Witte screwdrivers are the very highest quality. Made in Germany. Chrome Vanadium with a five year guarantee! Philips head and conventional in a range of sizes. Electronic Set $31.50 Suits Red, Yellow and Blue 1000Volt Electrician 's Set $49.50 terminals. Value at $69.95 Heavy Duty Ratchet Crimper a :0 () ::t: ~ 8a .,.,0 a :0 BUBBLE ETCHER Consists of clear acrylic lank holding etchant in a narrow vertical slot. Incorporates heater and air pump to force bubbles which remove dissolved copper. Air increases effectiveness of etchant. Uses ammonium persulphant. You can actually watch progress 1 Takes PCB's upto 300x25Smm. Operates from 240Vac $238.50 GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road , (Corner Beatrice St.) iNc 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 $5 .00 to cover postal charges. Next day delivery in Sydney add $5.00. All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MAS TE RCA RD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED () ::t: ~ ~a 0 .,., a :0 () ::t: ~ lifier IC, the AMP-02. It requires only a single external resistor to set the gain, offers internal overvoltage protection and features very high accuracy. If no external resistor is used, the AMP-02 is set for a gain of unity. Input offset is less than 100µ V and temperature drift is below 2µV/°C. Common mode rejection is 115dB and the device can withstand input overloads to 60V with power on or off. For further information contact VSI Electronics (Australia) Pty Ltd, 16 Dickson Avenue, Artarmon 2064. Phone (02) 439 8622. CAD system for the Apple Mac A new CAD and drafting system has been released by Intergraph Corporation for the Apple Macintosh. It will also run on Unix workstations and IBM XTs, ATs, PS/2s, 386s and true compatibles. The unit requires at least 2MB of RAM to run and its features include support for up to eight active views which can be displayed simultaneously on a single screen, true 3D designs, resizable windows, dialog boxes, on-screen menus, mouse support and dynamic tool palettes. For futher information, contact Intergra ph Corporation Pty Ltd, 55-61 Talavera Rd, North Ryde, NSW 2113. Phone (02) 888 9900. Jaycar store to open in Adelaide As from 1st March 1990, Jaycar will have a retail store in Adelaide. The address is 190 Wright Street, Adelaide and the store will have the full range of Jaycar kits and products. Power window winders for your car and PS/2 from dealers. Suggested retail prices are $250 for the serial version and $265 for the bus version. For further information, contact the distributor for Logitech, BJE Enterprises, 35 West Parade, Eastwood 2122 . Phone (02) 858 5611. RS422 serial card for long distance data transfer If you want to transmit serial data, the standard RS232 port is only good for 10 metres or so, which really stymies you if you want to run a really long cable, say 300 metres or more. That's where this RS422 adaptor card comes into the picture. It is claimed to be suitable for data transfer for distances up to a 900 metres and at baud rates up to 56kbps. The number of stop bits can be 1, 1 ½ or 2 and odd, even or no parity is supported. The port is selectable as COMl, COM2, COM3 or COM4 88 SILCON CHIP via DIP switches on the board. It is suitahle for use in all IBM PC/XT, AT and 386 computers and compatibles. The RS422 card is priced at $135 from Electronic Solutions, PO Box 426, Gladesville 2111. Phone (02) 906 6666 or Fax (02) 906 5222. New instrumentation amplifier from PMI Precision Monolithics Inc has released the first true high performance 8-pin instrumentation amp- Got weak arms? Course you haven't. But the idea of having power windows on your car is an attractive idea, isn't it? Why should you have to buy a new Japanese car to get them. Now you can have power windows on just about any car with these power window winders from Jaycar. They are supplied in pairs with cables and a number of adaptors to suit various winders. Also supplied is an auxiliary switch so that the driver can operate the passenger's window from the dashboard or console. The price? $219 a pair. If you want to see a demo unit, Jaycar's Gore Hill store staff have specially rigged up a door with a power winder so you can wind it up and down to your heart's content. Bookshelf - continued from page 61 designs and these range from low voltage, low current audio types to video, IF and RF amplifiers. Chapter 4 is divided into four sections: communications, voltmeters, picoammeters and detectors. The "communications" section is hardly comprehensive since it only comprises an intercom, two product detectors and a suppressed carrier modulator. Quite a wide selection of voltmeter and detector circuits are featured though, so perhaps the "communications" section was lumped into this chapter because there was nowhere else for it to go. Chapter 5 has temperature control, zero voltage switching and alarm circuits using thermocouples and other transducers. Chapter 6 comprehensively covers the topic of timers, including monostables, Schmitt triggers and some wave shaping applications. There are number of problems with a book of this type. First, the circuit explanations are very brief so it really couldn't be recommend- ed to the newcomer. Second, some of the circuits are really not practical and could be produced far more efficiently with other devices. One such example is a 30mW audio amplifier that uses an op-amp, two output transistors and an output transformer! Third, and perhaps the biggest drawback, is the fact that so many of the circuits are based on RCA ICs, many of which will be difficult if not impossible to get in Australia. Negatives aside, there are some some quite useful circuits, provided the reader can understand from the diagrams how the circuits work. Even if you can't get many of the ICs, it may be possible to use the circuits contained in the book as a source of ideas, or you may be able to modify them and substitute different ICs. With that in mind, this book will make a worthwhile addition to your library. **GREAT VALUE AND TECHNOLOGY ** CONTINUED SAVINGS ON ... AT-4000 SYSTEM 12MHz 512K 101 KBD 200W PS, etc . . $1099.00 VGA MONITOR 0.31 FOR 800x600 . $696 .00 FDD 1.2Mb 5¼ " Japan . . . $130.00 FOO 1.44Mb 3½ " Japan . $146.25 EC-F/HDD FOO/HOD CONTROLLER 1:1 . . . . . . $169.69 GAL PAL PROGRAMMER - 1 only . $350.00 COMPUTER PRODUCTS . . . AT-4000 MOTHERBOARD 12MHz 80286 AT u/g for XT . $399.00 ECI VGA-16 EGA, CGA, HGA modes Card 800x600x16 Res . . . . $399.00 AT-8000 MB 25MHz 80386 inc 0/8M 32-bit Mem Exp Board . . .... . $2266.00 AWARD POST TEST CARD . $802.00 ECI-FAX CARD FOR XT/AT . . ....... $399.00 SRAM Batt B/up Ski - Convert SRAM to NON VOL $19.95 2S+P+G $85; FDC $97.25; 101 KBD $88.43; EC-CGMA $99; CASE & 200W PS $207.98; XT/AT CLK $49.95 LEOS 3mm & 5mm (Min 100/type) . . . Red $0.04 ; Red HB $.0.07 ; Green $0.06 ; Yellow $0 .07; Orange $0.07 DIODES (Min 100/type) ... 1N4001 ; 1N400~ 1N914; 1N4148 . $0.05 QUALITY IHSKEms ... (Pkt oi 10, 100% error free, Utime Gtee) 5¼" DSDD $6.29 5¼ " DSHD .. . . . $11 .40 3½" DSDD. . . . . $14.36 3½ " DSHO . $39.00 P&P $8.50 - PRICES INCLUDE SALES TAX 26 Boron St, Sumner Park, Brisbane, Old 407 4. Ph: (07) 376 2955 WEWNGTON NZ: Ph: (04) 85 87 42 Fax: (04) 82 8850 Ken Curry Managing Director Our copy came from Dick Smith Electronics (Cat.B-1241) and has a retail price of $39.95. (D.B.Y). Fujitsu six colour plotters • Parallel and Serial Interface - GPIB also available • High Quality Resolution 0.025mm • Compact and Lightweight 420 x 260 x 95mm - 4.5kg • Wide Selection of Paper Sizes A3 down to Postcard • Wide Applicaitons Business, CAD, Hobbyists etc. FPG316 PAR/SER - $1,299.00* FPG316 GPIB - $1 ,350.00* *plus 20% Sales Tax & $10 Delivery cO FUJITSU Pacific Microelectronics Pty Ltd Unit A20/ 4 Central Avenue PO Box 189 THORNLEIGH NSW 2120 Telephone (02) 481 0065 Fax (02) 484 4460 AUSTRALIAN REPRESENTATIVE FUJITSU MICROELECTRONICS PACIFIC ASIA LTD. House Number; Converting a CB Radio To The 28MHz Band; Electronics & Brock's BMW Blaster; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding a Headset To the Speakerphone; How To Quieten the Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems; Door Minder Alarm; Low Ohms Adaptor for Multimeters; Line Isolation Unit for Phone Patch; Electronics In The Jaguar XJ40; Easy Tips on Headphone Repair. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Endless Loop Tape Player; Build Your Own Light Box; New Life for Radio-Cassette Players; Old-Time Crystal Radio. April 1988: Walkaround Throttle for Model Railroads, Pt.1 ; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players; What is Negative Feedback, Pt. 1 ; Mobile Antennas for the VHF & UHF Bands. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm; Walkaround Throttle for Model Railroads, Pt.2; Designing and Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. June 1988: Stereo Control Preamplifier (uses LM833), Pt.1; Breakerless Ignition For Cars Using Hall Effect Pickups; Mega-Fast Nicad Battery Charger; Automatic Light Controller Uses PIA Detector; RF Sniffer Probe & Preamplifier; What is Negative Feedback, Pt.2. July 1988: Stereo Control Preamplifier, Pt.2; Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show, Pt.1 ; Tone Burst Source for Amplifier Headroom Testing ; National Semiconductor LM833 Op Amp Data; What is Negative Feedback, Pt.3. August 1988: Building a Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter (uses OP-27), Pt.1; Discolight Light Show, Pt.2; Getting the Most Out of Nicad Batteries; Data on Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Switchmode Charger for 1 2V Gel Batteries; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice; Motorola MC34018 Speakerphone IC Data; National Semiconductor LM 12 1 50W Op Amp Data & Application; What is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (uses Rohm BA1404); High Performance FM Antenna; Matchbox Crystal Set; Electronic December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor for Shortwave Receivers; Electronics & Holden's New V6 Engine; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter for Computers; Ultrasonic Proximity Detector for Cars; Simple Computer Sound Repeater; 120W PA Amplifier (With Balanced Inputs) Pt. 1 ; How to Service Car Cassette Players; The Goalkeeper Gatling Gun; Massive Diesel Electrics In the USA. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher for Model Railways (uses LM3909); Build a Simple VHF FM Monitor (uses MC3362), Pt.1; Lightning & Electronic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor for CD Players; Map Reader for Trip Calculations; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Electronics for Everyone - Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics for Everyone: What You Need to Use this handy form to order your back copies ._. I I I ---------------------------------- • -- Please send me a back issue for: □ February 1 988 □ March 1988 □ April 1 988 □ May 1 988 □ July 1 988 □ August 1 988 □ September 1 988 □ □ □ June 1988 I □ 0. November 1 988 □ I I □ March 1 989 ll April 1 989 □ May 1989 □ Ju·ne 1989 □ July 1989 □ August 1989 □ September 1 989 □ October 1989 □ November 1989 □ December 1989 I t I I I I I I I I I I October 1 988 December 1 988 January 1 989 7 February 1 989 □ January 1990 Enclosed is my cheque/money order for $ ______ or please debit my D Bankcard D Visa Card D MasterCard Card No. I ._I_.___.___,___] IL..........L___,____.___,11~~~~ Price: $A5.00 each (includes postage). Overseas orders add Signature _____________ Card expiry date _ __._ _ $A 1 .00 per issue for postage . NZ & PNG orders are sent by Name__________________________ air mail. (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS Stree.._________________________ PO BOX 139 COLLAROY BEACH NSW 2097 Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ __ OR FAX: (02) 982 9553 l.._~.....__. . . . . . ~--------------------------------------90 SILICON CHIP The Serviceman Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; Led Message Board, Pt.2; Fluke's New 80-Series Multimeters. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; Led Message Board, Pt.3; Coherent CW - a New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (uses TGS812 Gas Sensor); Extension For the Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electrics; Facts On the PhaxSwitch - Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction to Stepper Motors; GaAsFet Preamplifier For the 2-Metre Band; Modern 3-Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089); Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (uses LMC669); A Guide to Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (uses BA 1404 and TDA7000) Pt.1; GaAsFet Preamplifier for Amateur TV; 1 Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc in the PC; A Look! at Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs); UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data & Applications; Install a Clock Card In Your PC; Index to Volume 2. January 1990: Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV; Speed Controller For Ceiling Fans. Note: November 1987, December 1987 & January 1 988 are now sold out. continued from page 49 drives the base more negative, turning the transistor on. In fact, the transistor was leaking internally with normal operating voltages applied, and was turned on permanently. Under these conditions, the collector voltage fell from the correct figure of 4.1 V to something like 0.1 V. I fitted a new transistor and found that the set now worked perfectly; stable sync, full colour and all. Post mortem But why had the set been dead from the tuner on? That 6.3V at the emitter of the 1st video amplifier also supplies a bias to the video IC at pin 6. So the whole IF strip was inactive when the fault was really in the video amplifier. And the tuner was inoperative because it needs an AFC voltage which is developed from a signal provided by the IF chip. Which brings me back to the point made earlier. If I had been a little more careful when replacing the board in the first place, then none of this story would have eventuated. ~ Bose noise cancelling headphones for obvious reasons, maintained a tight seal to the pilot's head. The ear surround seal in the Bose headset uses a combination of silicone gel and soft foam which follows the contours of the head to create a better seal, with only a slight amount of headband pressure. Even without the noise-cancelling electronics, the Bose headsets still boast better passive noise attenuation than many of the ordinary types on the market, especially at low frequencies. Specifications Each earpiece has its own independent noise-cancelling system, allowing for both mono and stereo use. The sound pressure servo system has been built using surface-mount technology, allowing Circuit Notebook - from page 11 it to fit inside the earcup. The impedance of the earpiece is 1500 and the system has a frequency response of 100Hz to 6kHz. The power supply required is 150mA at 11-16V or 22-32V DC. Applications A number of helicopter and aircraft manufacturers are now offering Bose ANG headsets as an optional feature but Bose see the product as having wide application in any situation where people have to work for long periods while subjected to high levels of noise. And who knows, maybe in the future your W alkman will come with noise cancelling headphones. l!t] Acknowledgement: our thanks to Bose Australia Inc, for their assistance in preparing this article. continued from page 26 represent a variable inductance. By varying dual gang pot VR1, the resonant frequency of the inductor is changed and so the circuit can vary the frequency to be boosted or cut. The filter is an LC type based on the .001µF capacitor and the variable inductance. Note that VR1 is wired so that when VR 1 a increases its resistance, VR1b reduces its resistance. As shown, the centre frequency can be tuned from around 32Hz to 17kHz and the available boost and cut is about ± 12dB. The output of the circuit is taken from pin 7 of IC1b via a 1k0 resistor and 1µF capacitor. Darren Yates, French's Forest, NSW. ($30) (Editor's note: while the circuit shown here is run from a single supply, there is no reason why it could not be modified to run with balanced positive and negative supplies). FEBRUARY1990 91 OSCILLOSCOPES TEST EQUIPMENT • 150mm rectangular ROYEL SOLDERING STATION • Useful for TTL or CMOS has high and low Indicator leds and also with pulse memory. • This is a very handy tool for the hobbyist or serious technician for tracing those hard to find faults on logic boards. The all solid-state heat sensor and control unit allows th e selection of the appropriate soldering lip idling temperature. The very high-powered element (relative to the size of the tool) will replenish heat drained from the tip during each soldering operation and will recover the tip lempreture moments after the tip is lifted . • Zero voltage switching • Zero lip potential • Aux ground connection • For soldering ironsCT6 (3mm Tip), CT7 (5mm Tip) rg m J> "m ~ 25 Q11272 .................. $34.95 "' en LOGIC PULSER (LP-540H) ~ 0 z !:! ,..... • Can be used directly to inject a signal into logic circuits without removing IC • Compatible with TTL, DTL, RTL HTL, MOS and CMOS Q11274.................. $42.95 ~ SERIES4000 SPEAKER BOXES FOR AN AMAZING ............ $250 GENERAL TOOLS BATTERIES • Type: Automatic and normal triggered In automatic mode, sweep Is obtained without Input signal • Sweep Time: 0.2µ Sec to 0.5 Sec/ Dlv on 20 ranges In 1-2-5 step with fine control and X-Y • Magnifier: X5 at all ranges • Sensitivity lnt: 1 Div or more Ext: 1Vp-p or more • Source: INT, CH-B, LINE or EXT • Triggering Level: Positive and Negative, continuously variable level; Pull for Auto • Sync: AC, HF Rej, TV (each + or·) al TV Sync. TV-H (line) and TV-V (Frame) sync. are switched automatically by SWEEP TIME/Div switch. MICRO CUTTING PLIERS AA SIZE NICAD Great for detailed cutting. These have a stainless steel head and plastic insulated handles. Length: 90mm T12050 .................... $9.95 HORIZONTAL DEFLECTION • Deflection factor: SmV to 20V/ Dlv on 12 ranges in 1-2-5 step with fine control • Frequency Response: DC to MHz (-3dB) • Max Input Voltage: 300V DC + AC Peak of 600Vp-p • X-Y Operation: X-Y mode is selected by SWEEP TIME/ Div switch • Intensity Modulation Z Axis: TTL Level (3Vp-p~50V) + bright, - dark OTHER SPECIFICATIONS • Weight: 7Kg Approx • Dimensions: 162(H) x 294(W) x 352(0) mm Q12105 ..................................................................$695 SOLDERING IRON LOGIC PROBE (LP-2800) 20MHZ DUAL TRACE OSCILLOSCOPE VERTICAL DEFLECTION • Deflection Factor: SmV to 20V/ Dlv on 12 ranges In 1-2-5 step with fine control • Bandwidth DC: DC to 20MHz (·3dB) AC: 10Hz to 20MHz (·3dB) • Operating Modes: CH-A, CH-B, DUAL and ADD (ALT/CHOP L202 only) • Chop Frequency: 200KHz Approx. • Channel Separation: Better than 60dB at 1KHz SPEAKERS BOXES Nominal Voltage: 1.2V 450mAH S15020 ......... ONLY $1.50 SURGE PROTECTOR . .... .. T12570 .....................$225 :r:1:e ROD IRVING ELECTRONICS Please quote this advertise• ment for the prices listed for this month. SYDNEY: 74 Parramatta Rd. Stanmore 2048 Phone: (02) 519 3134 Fax: (02) 519 3868 MELBOURNE : 48 A'Beckett St Phone: (03) 663 6151 NORTHCOTE : 425 High St. Phone: (03) 489 8866 BRISBANE : I I (V.C .R Computer Services) 647 Lutwyche Rd. Lutwyche. Phone: (07) 857 5617 MAIL ORDER& MICRO BENT NOSE PLIERS For delicate or high precision electronic work. Stainless steel head with plastic insulated handles. Length: 10cm T12040 .................... $9.95 •• THE BUTTON SPIKE PROTECTOR Simply plug the button Into an outlet and it will protect all equipment plugged into adjacent outlets on the same branch circuit. SPECIFICATIONS: Voltage: 240V Nominal Total Energy Rating : 150 Joules Response Time: 10ns Protection Level : 350V peak X10087 ..................$39.95 CORRESPONDENCE : P.O. Box 620, CLAYTON 3168 Order Hotline: 008 33 5757 (Toll free, strictly orders only) Inquiries: (03) 543 7877 Telex: AA 151938 Fax: (03) 543 2648 All sales tax exempt orders and wholesale Inquiries to: RITRONICS WHOLESALE • 56 Renver Road, Clayton . Phone :(03) 543 2166 (3 lines) Fax: (03) 543 2648 ORDER HOTLINE 008 33 5757 (TOU FREE) CRT DISPLAY • 150mm rectangular VERTICAL AMPLIFIER (CH1 and CH2 Identical) • Operational Modes: CH1, CH2, ADD, DUAL, ALT, CHOP • Sensitivity: SmV-5V/ Dlv 3% in 1-2-5 steps 1mV-1V/ Dlv x5% x5MAG • Bandwidth DC: DC to 40MHz (-3dB) AC: 5Hz to 40MHz (•3dB) • Rise Time: Less than 8.7nS STRICTLY ORDERS ONLY HALF ROUND NOSE PLIERS CLICK SURGE BUSTER $50 • $99.99 ······ ··· ············$5.00 Errors and omissions excepted. Prices and specifications subject to change . II has a long lip angled at 45°, for complicated or delicate work. Stainless steel head with plastic insulated handles. Length: 10cm 6 PROTECTED POWER OUTLETS Ideal for protecting personal computers, video equipment, colour TVs, amplifiers, tuners, graphic equalisers, CD players etc SPECIFICATIONS: • Electrical rating: 240V AC, 50Hz, 10A • 3 x Metal Oxide Varlstors (MOV) • Maximum clamping Voltage: each MOV: 71 Ovolts at 50 amps • Response lime: Less than 25 Nanoseconds. T12046 ....................$9.95 X10086 ....................$69.95 • Input Impedance: 1Mnt2%, 25pF±3% • Bandwidth DC: DC lo 1MHz (•3dB) AC: 5Hz lo 1MHz (-3dB) • Sweep Time (A): 0.2µs-0.5S/ Div±3% In 1-2-5 steps (X1 only) (B): 0.2µS-0.5mS/ Dlv±3o/o in 1-2-5 S1eps (X1 only) • Magnified Sweep: 10 limes±5%, Max 20ns • Linearity: ±3% or better Q12107...............................................................$1,695 POSTAGE RATES : $1 • $9.99 .......... ............... $2.00 $10 • $24.99 ..................... $3.00 $25 • $49.99 ...•.................$4.00 T12044 .................... $9.95 HORIZONTAL AMPLIFIER • Operating Modes: X-Y operation CH1•X axis, CH2-Y axis • Sensitivity: 5mV-5V/ Div± 3% In 1-2-5 steps TIMEBASE • Sweep Method: AUTO, NORM, SINGLE LOCAL ORDERS & INQUIRES (03)5437Bn Plastic insulated handles with stainless steel head. Length : 10cm BENT NOSE PLIERS $100 + .............................. $7.50 The above postage rates are for basic postage only. Road Freight, bulky and fragile items will be charged at different rates. IBM", PC" . xr·, AT". ate registered trademarks of International Business Machines. "Apple ,s a registe red trademark. Teflon· is a reg istered lrademark ol Dupont . ·oenontes registered traclemarks ol their respective owners. 4 PORT SERIAL CARD • All ports fitted • Can be used with multi-user systems. X18154 ................ $152.50 512K RAM CARD Ideal for older style P.C's. Ram ls extra. X18014 ....................... $99 1/0 ACCESSORIES G7 MONOCHROME COLOUR CARD • IBM• Colour Graphics Adapter compatible (support 600 x 200 lour colour graphics model) · IBM• Monochrome Display Adaptor compatible • Hercules Monochrome Graphics Adaptor Compatible • IBM• Printer Adapter compatible • Support Composite Monochrome monitors X18007 ..................... $139 GRAPHICS CARD TTL and Hercules compatible with printer port X18003 ....................... $99 ENHANCED GRAPHICS ADAPTOR CARD POCKET AUTO AB SWITCHES • Pocket size, auto-scanning • Allows 2 PCs to share one Printer Serial model: MS-201 • Host-powered Auto switch CGA, EGA and Hercules with 256K Video Ram X18070 ..................... $225 VGA CARD PC•/ XT•/ AT' compatible 256K Ram works with 05/2 X18071 ..................... $350 POSTCARD DIAGNOSTIC MODULE Pinpointing component problems in IBM• compatible motherboards can take hours. Usually the whole system has to be working to isolate the troubled area. But not so with the new Postcard Diagnostic Module. So no other cards are necessary to test a bare motherboard. "It now only takes seconds." Simplified debugging for: • Field service- for on-site repairs or maintenance depot work • Manufacturing test- for burn in test flaws and to do quality control • Inspection• Postcard simp• lilies incoming and outgoing test processes on stand X18048 ...................... $849 X19155 .................. $89.95 VGA 512K Pc•, XT•/ AT' compatible 512K Ram. Hardware zoom, pan, window. CL21 COMPUTER LEAD 2 M/BYTE EXTENDED MEMORY RAM CARD X18052 ..................... $225 X18072 ..................... $450 • 25 pin D Plug to 25 pin D plug • All pins wired straight through (removable terminals) • Length 1.5metres P19007 .................. $36.95 CENTRONICS CABLE • 36 Way Centronics Plug to 36 Way Centronics Plug • Shielded cable • Length: 6 metre P19013 ..................$29.95 NETWORK CARD R-NET/ S INTERFACE NETWORK CARD • Fully compatible with SMC, Novell Arenet card • Star-burst topology through RG-62 AIU coaxial cable • Zero wait at 20MHz or higher 80386 machine • 2.5 Mbps transmission rate X18162 ..................... $275 FLOPPY DISK DRIVE CONTROLLER CARD These cards will control up to 2 or 4 double sided 360K IBM• ,compatible disk drives For 2 Disk Drives X18005 ....................... $52 X18026 ....................... $39 CLOCK CARD X18024 ....................... $49 PRINTER CARD X18017 .......................$29 • Fully compatible withNovell NE-1000 Ethernet card • Built-In 15 pin D type connector • 10 Mbps transmission rate • Meets the IEEE 802.3 standard X18160 ..................... $425 This card will control 2 x double sided, double density drives, and features a serial port, a parallel port, and a joystick port or games port. It also has a clock/calendar genarator with battery backup X18040 ....................... $99 SERIAL/ PARALLEL/ GAMES CARD XT'/ AT' compatible 1 parallel port, 2 Serial ports, 2 port games adaptor. X18151 ..................... $115 Parallel interface for Centronlcs printers. E-NET INTERFACE NETWORK CARD MULTI 1/0 & DISK CONTROLLER CARD RS232 (SERIAL CARD) WITHOUT CABLE Supports 2 asynchronous communication ports. 50 baud to 9600 baud. 4 WAY DISK CONTROLLER • PC'/ XT'/ AT' compatible • 1.44 MIB, 1.2 M/8, 720K, 360K Drives X18006 ..................... $129 3.5 M/BYTE EXTENDED/ EXPANDABLE RAM AT* CARD X18056 .....................$275 1/0 PLUS CARD Provides a serial port, a parallel port and a Joystick port, and even a clock/calendar with battery backup! X18045 .....................$115 MIDI INTERFACE CARD - DS/401 The MIDI DS-401 Card is the PC standard MIDI interface that runs most popular PC music programs for sequencing, recording, composing, music printing, patch editing, music instruction and many other applications. • Run all programs designed for the Roland MPU-401 architecture • Socketed EPROM for easy user replacement • 1/3 length (short) card will lit in any computer accepting standard expansion card, including laptops • Including "Y" cable, external connector box to transport is unnecessary X18164 .....................$245 X19150 .................. $79.95 Parellel model: MP-201 Protocol transparent INCREDIBLE IBM* CARDS NEW PRODUCTS GAMES 1/0 CARD Features 2 joystick ports.(DB15) X18019 ....................... $29 386SX 16MHz MOTHERBOARD AC ADAPTOR • Output: 6V 300mA M19008 ................ $8.95 IBM* CARDS 386 CACHE 25MHz MOTHERBOARD • Processor 80386·25 • Cache controller 82385•20 • Speed: 25 MHz or 20 MHz • Memory: 32KB Cache memory (35ns) • 2 M/Byte RAM fitted (80ns) • 2/8 MB plus 32 bit memory card • Expansion slots: 1 x 32 bit, 5 x 6 bit, 2 X 8 bit • Intel• Combo Chip set: 82230, 82231 • 8105 : AMI • Landmark Test : Up to 43.5 MHz • LED display for speed indication • Ability to run 05/2, MS/DOS, XENIX • Baby AT' size board • Processor: 80386SX-16MHz (0/1 wait state) • Co-processor:80387SX-16 (optional) • CHIPS & TECH NEAT chipsets • (SMT) Surface Mount Technology for chipsets & CPU • Supports up to 2MB on board, (Sixteen 44256 and Eight 41256 sockets) • Three 8 BIT slots • Five 16 BIT slots • Memory Expansion Slot • Optional 2-8MB memory card • Supports LOTUS-INTELMICROSOFT (LIM) Expanded Memory Spee. (EMS) version 4.0 • Supports Page Interleave Mode using 100NS DRAM • 8105: AMI or PHOENIX • Turbo Light and Hardware Reset connector • Keyboard or Hardware Reset connector • Power Good Signal on board • Baby size main board • Without Ram • lntel -80386 CPU (20 MHz) • Socket for 80387 Math coprocessor • 32 bit Memory BUS system • Built-in speaker. attachment • Battery backup CMOS configuration table and real time clock • Keyboard controller and attachment • 7 Channel DMA • 16 Level interrupts • 3 Programmable timers • 8 System expansion 1/0 slots • Including 2 M/Byte RAM X18094 ..................... $900 X18107 .................. $1,600 X18105 .................. $3,000 386 MAIN BOARD for 286 NEAT MOTHERBOARD • Processor : 80286-12, -16MHz or -20MHz (0/1 wait state) • Co-processor: 80287 (optional) • CHIPS & TECH NEAT chipsets • 1·4MB dual RAM socket • 1-4MB module RAM socket on board • 640KB-384KB memory relocation • Three 8 BIT expansion slots • Five 16 BIT expansion slots • Memory expansion to 8MB • Supports EMS 4.0 • Page Interleave Technology • BIOS: AMI or PHOENIX • Hardware and keyboard switchable Clock Speed • LED speed display • Power Good Signal on board • Baby size main board • 16MHz X18090 ..................... $700 • 20MHz X18092 .....................$895 • Auto-selection and auto• transfer between mouse system PC mouse mode and Microsoft serial mouse mode • Microsoft Serial Mouse and Mouse System compatible • Super high tracking speed: 600mm/sec • Super high resolution: 200 DPI (0.12mm/dot) • Silicon rubber coated ball • Optical rotary encoder X19955 ..................$94.95 THE EVOLUTION OF ELECTRIC RAILWAYS The French railways lead the world in commercially successful very high speed passenger expresses. Their trains, called TGVs, run on dedicated tracks at 300km/h. Now coming on stream is the latest version, the TGV Atlantic. By BRYAN MAHER 94 SILICON CHIP In 1976, the French railways, Societe Nationale des Chemins de Fer Francais (SNCF), achieved world recognition with the building of a dedicated high-speed doubletrack line from Paris to Lyon. After exhaustive tests on locomotives, including a gas turbine type, the French decided on electrification at 25kV AC. By the beginning of this decade, France was busily electrifying 300km of track per year, with a goal of 4000km of new electric track by 1990. The new Paris-Lyon track bypassed all cities enroute, with stops at only two stations close to Le Creusot and Macon. The new tracks run for 388km through rural areas, avoiding any costly civil engineering works. There are no tunnels and no sharp curves. Only TGV (Train a Grande Vitesse) expresses run on these dedicated tracks while other traffic is carried by the old existing route via Dijon. For this reason and because of the high powered electric traction used, track grades of 3.5% are possible. TGVs do not need to skirt around hills - they run straight over the top. The dedicated tracks end at the outskirts of each terminal city. The TGVs then run at lower speed on existing suburban tracks into the city stations. This approach saved millions of francs compared with the cost of high speed tracks through the suburbs. The Atlantic TGV So successful was the Paris-Lyon TGV system following its opening in September 1983 that the philosophy was extended to a number of other cities. The latest system now being built is the Atlantic TGV for TGVA). Construction began on 15th February, 1985. Designed to cover the whole Atlantic seaboard, the new TGV will serve all coastal cities from Brest to Hendaye. By 1990/1991, when full operation is achieved, total passenger rail traffic in this region (population 22 million) is expected to have increased by 33%. WIDLE THE TGV LOCOMOTIVES look quite large, they are very light considering their high power. Rated at 4.4 megawatts (5900 horsepower), they weigh less than 70 tonnes and can travel at speeds in excess of 300km/hr. The Atlantic TGV, though based on the Paris-Lyon experience, has improved passenger accommodation and in-train services. There will be more powerful traction motors and braking systems and a running speed of 300km/h is to be standard throughout. First in service ori the new work was the Brittany section which opened in September 1989. The Aquitane will then come on line at the end of 1990, giving a 3-hour run time from Paris to Bordeaux. In the space of just one decade, SNCF has transformed the railway scene in the eyes of the whole FEBRUARY1990 95 '"Cl n e:; :z: 0 ('") t=: - en cc c,, - - Synrh~ COMPUTER AND SAFETY EQUIPMENT AUTOMATIC COUPLER IMPACT SHIELD BODYFRAME MADE OF HIGH YIELD POINT STEEL 13 - BRAKING CONTROLS 14 - TRACK CIRCUIT CODE SENSORS 15 - EQUIPMENT HOUSING 9 10 11 12 ; ?'.,.,. ::t ~ ZDIIJl!:O: DIRECTION DU MATERIEL 16 - TYPE Y230 POWER TRUCK 17 - TYPE Y237 B TRAILING TRUCK 18-BAGGAGECOMPARTMENT 19 - PASSENGER SEATING 20 - LIGHT ALLOY ROOF PANELS :'C;f TlllS SECTIONED VIEW SHOWS the major components in the TGV locomotives. High power freon cooled GTO thyristor banks provide variable frequency, variable voltage 3-phase drive to the synchronous traction motors. SINGLE ARM PANTOGRAPH MAIN TRANSFORMER CIRCUIT BREAKER. LINE FILTER MICROPROCESSOR-CONTROLLED TRACTION MOTOR FREON COOLING FOR SEMICONDUCTORS 6 - BRAKING RHEOSTAT 7-AU~LIARYPOWERSUPPLY 8 - MAIN COMPRESSOR 1 2 3 4 5 ,: . ··-;_; 2skv/soH C.: ' :. .,. ... , , ::,.,: TGV~ ~~~~ MAJOR COMPONENTS OF THE TGV LOCOMOTIVE commenced. The environmentally conscious approach taken by SNCF actually decreased the overall cost. The whole project was costed at 9.75 billion francs ($US1.625 billion) at June 1986 prices. Tracie For operating speeds of 300km/h, heavy rail, deep track foundations and a new type of concrete sleeper are used. The ballast extends 300mm deep under the sleepers and a strong sub-ballast layer spreads all downward forces over a wide subgrade fill and embankment foundation. In addition, the ballast extends wide and high over the line of sleepers and over 3 metres from the track centre line. This inhibits sideways track movement. L_ TO PREVENT THE TGVs and their passengers from being severely buffeted by standing waves, the tunnels must have a very large cross-section as this diagram of the Vouvray tunnel shows. world. Very high speed rail travel has become a rAalitr. Tunnel problems There are four tunnels required in the first 230km of the Bordeaux route even though, as noted above, tunnels are to be avoided for high speed trains if at all possible. A fast moving train entering a tunnel causes two large displacement sound waves to be created. The head of the train causes a high pressure wave, while the tail of the train causes a low pressure wave. Both pressure waves run ahead of the train at the speed of sound and then reflect from the far (open) end of the tunnel. These effects cause severe standing waves in the tunnel which the train then runs through. Passengers would feel great discomfort from pressure buffeting should this be allowed to occur at the high speeds of the TGV. Tunnels could not be avoided on the Atlantic TGV line. However, the first two tunnels are within 9km of the start of the new line where trains have not yet attained full speed, so they don't cause real problems. But the tunnel at Vouvray, on the high speed section, 210km south west of Paris, needed special atten- tion to minimise air buffeting. The effect can be diminished by either reducing the train speed or increasing the width of the tunnels. SNCF chose larger tunnels. To allow running at 270km/h, the tunnels are cut with a cross sectional area of 71 square metres for double track sections and 46 square metres for single track sections. The parallel single track tunnels at Villejust, 18.7km from Paris, burrow 4.8km through the difficult Fontainbleau fluid sand. To bore through such loose soil, a special full cross-section shield excavator was used. This was quicker than the old fashioned freeze methods once used. Because the shield excavator is more difficult to use on larger tunnel diameters, parallel single track tunnels were drilled rather than one double track bore. Throughout the countryside, the population greatly appreciates the lines being electrified and built around (rather than through) towns. Electric trains give no emissions to pollute the atmosphere or fields, and ugly bridges, flyovers and cuttings are avoided in urban areas. As well, SNCF provided scale models of all major civil engineering works for public discussion well before construction Special sleepers The heavy 60kg/m rails are laid on a new type of sleeper. Each consists of two large reinforced concrete blocks about 300mm deep, 450mm wide and 600mm long, with one rail bolted to each block. They are solidly held at the correct spacing by a steel girder cast into each pair. These more complex sleepers give much more solid location within the ballast, which is important for high speed track. The rails are laid in 396m lengths and then thermit-welded to form continuous track. Signalling A continuous track-to-train signalling system, developed from the Paris-Lyon model, is used on the Atlantic TGV. Lineside signals are not used; instead, the signalling information is displayed on the driver's console. 25lcV system The new Atlantic TGV lines use 25kV electrification, fed at 15km intervals by 50kV/25kV autotransformers. These balance out any unequal currents in both legs of the 50kV power feeder line. This results in a 25% reduction in harmonic interference compared with a straight 25kV transmission line. This system of electrification is FEBRUARY1990 97 AL THOUGH IT IS COMMON TO REFER to the TGV as though it was just one train, the French had over 100 TGV train sets in 1986. identical to that used by Queensland Railways, as described in part 12 of this series. Reduction of train generated harmonics is vital to the railway's own signalling and communication circuits as well as nearby radio, computer and telephone systems. the pantograph because the contact wire is pulled alternately one way and then the other. This spreads the pantograph wear evenly over its contact surface. TGV rolling stock Each TGVA train is 238 metres High speed pantographs SNCF experience shows that with well designed and constructed catenaries and contact wires, set at optimum tension, wear of the contact wire is not a serious problem, even with trains running at 300km/h. The overhead contact wire is of pure copper, with a cross section of 150 square mm. This is tensioned at 20kN (ie, at 2 tonnes) by a hanging weight/pulley system at the anchor posts which are at intervals of 63 metres. This is a phenomenal amount of tension for such a small wire section and keeps the wiring free of excess sag or stretch over the temperature range from + 60°C to -20°C. The catenary wire is of solid bronze, 62 square mm in cross section, and is tensioned at 14kN (ie, at 1.4 tonnes). The pulley tensioning system also has the benefit of reducing wear in 98 SILICON CHIP TGV LOCOMOTIVES HAVE TWO PANTOGRAPHS. This photo shows the larger low voltage (1500V DC) pantograph raised while the high voltage (25kV AC) pantograph is lowered. long with 10 articulated coaches and a locomotive at each end. The coaches ride on large highly flexible airbag secondary suspensions, with sprung free-arm primary suspension. Cylindrical shock absorbers damp out any sway, pitch or yaw, resulting in excellent passenger ride. The electric locomotives are 22.16 metres long, 4 metres high, 2.77 metres wide and weigh only 67.8 tonnes. They are of the Bo-Bo configuration and are propelled by four synchronous motors with variable frequency 3-phase drive. Each motor has 6 poles and is rated at 1.1MW (1475hp) continuous or 1.54MW on an intermittent basis. The two stage gearing to the drive axles gives a train speed of 300km/h at a motor speed of 4000rpm. This requires a motor drive frequency of 200Hz. Being synchronous, the motors rotate at a speed exactly proportional to the motor drive frequency, unlike induction motors which have inherent slip (see Pt.22: 3-phase electric locos). Inverters provide the 3-phase power supply at variable frequency, to produce the desired motor (and train) speed. To enable them to operate at a drive frequency of up to 200Hz or more, the motors are entirely constructed of sheet steel and the magnetic circuit is formed of individually insulated silicon steel laminations. Synchronous motors have a 3-phase AC supply to their stator windings, which sets up a rotating magnetic field in the air gap. The rotor windings (called field coils) are supplied with DC via graphite brushes running on insulated stainless steel sliprings. The brushes are expected to last for more than one million kilometres. The complete motor is only 740mm in diameter, 1110mm long and weighs just 1.45 tonnes. This is incredibly small and light for such a powerful motor. Compared with the 535kW DC motor used on the older TGVs, the new motor gives more than twice the power but weighs slightly less. To further minimise the unsprung weight on each axle, the traction motors are actually supported bv the locomotive body. The motors MOST OF THE BRAKING EFFORT on the high speed TGV trains is regenerative, although the locos and all coaches have large disc brakes. The regenerated power is dissipated in large resistor banks on the roof of the locomotive. hang low, well inside the bogie frame. A 2-stage gearbox in a tripod torque transmission arrangement transfers the drive to the driven train axle. This method, called flange-mounting, allows vertical and torsional movement of the bogie about the fixed motor. Power control On the high speed track sections, the rear locomotive's lightweight pantograph collects the 25kV AC at up to 430 amps from the overhead contact wire. This current is fed to the main transformer primary and then stepped down in four secondary windings for traction plus a fifth winding for auxiliaries. Each traction secondary feeds a harmonic filter and a 4-thyristor bridge rectifier. The 1500V DC from the bridge rectifiers then feeds two 8-thyristor DC to 3-phase inverters in series. The output of each inverter is variable from Oto 250Hz and up to 1246V and 588 amps in each phase to supply one traction motor. The inverters must be forcecommutated when the motors are operating at low rpm to avoid loss of torque. For this reason, the rotor position is detected by magnetic sensors to precisely control the firing of the inverter thyristors. This forced commutation of the inverters allows high torque to be used at starting with only 1.4 times the continuous rated power of the motor. As all eight motors in the train are controlled by separate 3-phase inverters, each drive axle is precisely controlled at all times. This virtually eliminates wheel slip and allows compensation for any weight transfer between drive axles. High voltage train cable While running on the 25kV high speed sections, the rear locomotive has its pantograph raised while the front loco runs with its pantograph lowered. An insulated 25kV cable runs along the length of the train, to feed the transformer primary in the front locomotive. This arrangement is reversed when running in the other direction. As noted previously, when approaching city terminal stations, the TGV trains share tracks with existing electric suburban and regional trains and these run at 1.5kV DC. Therefore the TGV trains need to switch over from 25kV AC to 1.5kV DC. To do this, they coast at 160km/h through a 1.6km section where the overhead wiring has no power. When they reach the 1.5kV DC section, they raise their heavier low voltage pantographs to continue into the city terminal. Records Many records have been set since the Atlantic TGV began running from Paris to Le Mans on 24th September, 1989. It was the world's first to carry passengers at 300km/h and the regular start to stop average of 224km/h is also a world first. In November 1989, this TGV created an unofficial world speed record of 483km/h (300mph). ~ Acknowledgements Special thanks to Dr John Nicolson of VFT Australia for photographs and data; also to SNCF engineers, to Revue Generale des Chemins de Fer, Dunod and Gauthier-Villars -of Paris. FEBRUARY1990 99 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. Adding auto-zero to a CD player Congratulations on your magazine - it's getting better all the time. I'd like to offer a suggestion which you may or may not care to air in the "Ask Silicon Chip" column, or you may like to accept or reject it as a project. I refer to the September 1989 project on nulling the DC offset of power amplifiers to zero. I think you missed a golden opportunity to explain how to apply the circuit to CD players in order to eliminate the output coupling capacitor. This capacitor is usually a poor sounding tantalum run with little or no polarising voltage across it. It is fairly widely recognised that eliminating this capacitor is the biggest single improvement it is possible to make to a CD player. In fact, most recent players Tricky FM transmitter should not work I recently built the FM stereo transmitter as described in the October 1988 issue of SILICON CHIP and it worked like a be&uty. I was really pleased. However, more recently, I have found that it does not always work in stereo with some tuners. Doing a bit of detective work on the unit, I was surprised to find that the supplied crystal is actually a 40kHz type instead of the 38kHz type specified. I feel sure that this is the reason the unit does not work with some tuners. The question is, why does it work at all? (A.L., Granville, NSW). • Now that is a tricky one. We investigated this by obtaining a 40kHz crystal ourselves and installing it in a sample FM 100 SILICON CHIP eliminate this capacitor. This means that most of the players which could use your circuit would now be out of warranty. The information needed includes: where to connect the circuit; earthing arrangements; any changes necessary to your circuit; power supply (eg, what is the current drain?); and possible re-design of the PCB for minimum size and/or one stereo board. I have attached the relevant part of the circuit of my player, a Sony CD-P 302ES, in order to get your creative juices- going. (R.A., Melbourne, Vic). • We would be reluctant to recommend to anyone that they add this circuit to a compact disc player. It would be difficult in many players to find a place to install it and the need to lift connections from the main printed circuit board could possibly lead to sound transmitter kit and presto! - it works. But not with every tuner. It seems to work quite happily with W alkman style receivers, ghetto blasters and car radios. But it won't work with better quality FM stereo tuners in hifi systems. The reason? We're guessing here but it is apparent that the cheaper tuners will work with a 20kHz pilot tone and therefore a 40kHz multiplex frequency because their decoders either use an LC or ceramic filter which is sufficiently broad to operate at 40kHz. Better quality tuners which have a 38kHz crystal in their multiplex decoder won't have a bar of that because the crystal just will not operate at 40kHz. So there is a paradox for you. The better tuners won't work. Of course, they still should receive the signal but only in mono. degradation anyway. We would also be reluctant to replace a tantalum capacitor on the grounds that it may contribute to poor sound quality. In fact, the increase in harmonic distortion that can take place with electrolytic capacitors in feedback loops only occurs when the impedance of the capacitor becomes substantial with respect to the other circuit components, ie, at very low frequencies. Our experiments in the past have shown that at midrange frequencies, tantalum or aluminium electrolytic capacitors do not lead to any measurable increase in distortion. We certainly doubt whether you could get an audible improvement in sound quality from your Sony CD player merely by changing one capacitor. Problem with ignition system I am writing to you for technical assistance with the SILICON CHIP High-Energy Ignition System. I constructed the kit as a birthday gift for my grandfather and was very disappointed when it failed to work on his vehicle. I immediately enlisted the aid of an acquaintance who is an experienced avionics technician. This is what we had at the end of the day: (1). The unit appears to be functioning correctly when on the bench. It gives a well shaped, lms wide, positive going pulse at battery voltages down to 4.5 VDC. We used both 40 and 400 resistors as output loads in this test. (2). When connected to a 12V ignition coil and a 12V battery the unit failed to produce a consistent spark. In this and the above test we simulated the points input by touching the points lead to the metal case. (3). When connected into a car ig- nition system the car cannot be started. We tried two cars: my grandfather's Kombi which uses a 12V coil and no ballast resistor and my tech-friend's Suzuki which did have a ballast resistor. With regard to kit construction, all component values and orientation have been checked by myself and my tech-friend. The only difference in construction I employed was for purely aesthetic reasons: instead of anchoring the earth lead to the case using an extra bolt, I fed the earth wire in through the grommet and attached it to a tag-washer under one of the PCB mounting bolt nuts. The wire from the PCB earth was also connected to this tag, resulting in a solid wire-earth-case connection. Can you suggest any reasons why the unit works on the bench but not in the car? Is it likely to be something like a crook solder joint? Any help you can give would be much appreciated. (K.L., Rockhampton, Qld). • In cases like these, we're almost prepared to swear (on a stack of data books) that the problem is a poor connection. This could be either in the positive or earth connections or in those to the coil primary. If you have tested the unit on the bench with a resistor load, why not continue the test with an ignition coil. You need to provide a spark gap from the high tension terminal to one of the coil primary terminals. This can done with a wire paper clip inserted in the high tension socket and opened out and bent to provide a gap of about 10mm or less to one of the primary terminals. Then if you have an audio oscillator capable of delivering about 2 volts or more, you can feed it directly into the input (ie, via diode D5) to simulate the action of the points. You should be able to run the circuit up to about 400Hz or more which corresponds to 400 sparks per second or more. The top figure will depend to some extent on your coil and the ability of your power supply to deliver a current of more than five amps. Incidentally, we'd be very wary about doing this sort of bench test New life for an American clock radio A, few years ago, we lived in the USA and we had a clock radio which we particularly like, it being a much better looking unit than the ones commonly available in Australia. The only problem is, it is designed to run off the American mains voltage of 115VAC at 60Hz. I have solved the problem of 115VAC by buying an adaptor from Tandy but although the radio section works, the digital clock is hopeless and loses time at a great rate. In the hope that maybe I could modify it, or perhaps find a changeover switch for 50Hz operation, I had a look inside the unit. Alas, I couldn't find much although I was able to identify a few of the major ICs. Among the type numbers were LM324, TDA1220 and TMS3459. I thought maybe you could get some clues from these. Can you help? (A.H., Redfern, NSW). • Well, as it happens, you have struck it lucky. The LM324 is just a common quad op amp and the TDA1220 is clearly the heart of the AM/FM radio circuitry. That leaves the TMS3459 which we using a car battery as the power source. If the car battery was close to the coil and its spark gap, there would be a big risk of an explosion - the spark could ignite hydrogen emitted from the battery. Be warned, battery explosions are spectacular and very dangerous! Amplifier couplers: do you need them? I hope to inspire a project to satisfy a question I was asked the other day. My brother has a system powered by a 35 watt per channel receiver and he wants to add a compact disc player to it. Trying to show off the dynamic range of a CD player with a 35 watt amplifier is a waste of time though. Some complex orchestral pieces require an were sure just had to be the clock chip. All we had to do was look at the pinout data and we would be able to give you the necessary modification to make it run correctly at 50Hz. All of these clock chips are designed to be universal; ie, to run at either 50 or 60Hz and with 12 or 24-hour display. They can be programmed to do this by connecting certain pins high (to the positive supply} or low, or by leaving them open circuit. The only catch was that we didn't have da t a on the TMS3459. However, we were eventually able to track the necessary data via the people at VSI Electronics and Texas Instruments. Only one pin connection has to be changed- pin 16. If you disassemble your radio again and look at pin 16 of the TMS3459, you will find that there is a track running away to the positive supply rail. This sets it to operate at 60Hz and with a 12 hour display. To set it for 50Hz and a 12 hour display, that track must be cut so that pin 16 is open circuit. (Editor's note: this information was sent to A.G., who was pleased to report that it was the cure}. amplifier of at least 300 watts; that's why NAD invented the 'power envelope' series. Your Studio 200 amplifier would have enough power to satisfy most CD needs so my brother wants to add it to his system but wants to keep his receiver and use it as a preamp because it has many features he wants to maintain (tuner, equaliser, video inputs etc}. Years ago, 1984 to be precise, I saw an advertisement in an American audio magazine for a " Soundcraftsmen PC1 Power Coupler", a black box to connect between a receiver and a power amplifier. I don't know if Soundcraftsmen make this product any more and I was wondering if you would be interested in designing one to fill a gap in the market. The other question I need ansFEBRUARY 1990 101 Counter wanted for photographic process I am a keen photographer (lots more photo gear circuits please) and process my own colour slides and Cibachrome prints. There are eight processing steps and I use an electronic timer which is quite sophisticated. It has a numerical keyboard and a few operational keys. When one program is timed out, a beeper beeps (what else could a beeper do?) and the next program number appears briefly (on a 7-segment 4-character display), followed by the actual programmed time for that step. To activate the next program I press a run/stop key and the display counts down. Now to my problem. After I have finished a few steps and am pretty busy I suddenly realise that I don't know what step is presently timing out. Panic! As I have been involved in electronics as a hobby for about 40 years I sought a simple solution and came up with the following idea. Why not put another single character 7-segment display in a jiffy box alongside the main unit and use a microswitch with a long arm mounted so that the arm is over the run/stop button? When this button is pressed the switch would close first, stepp- wered is what product is used by speaker manufacturers to dope woofer cones and where can I get it? (B.C., Grange, SA). • Using existing hifi equipment with CD players does pose a lot of problems if you want to obtain the ultimate sound quality. You are quite right in supposing that your brother's 35 watt receiver can't really do full justice to CDs. But it is more than just a question of adequate power. Strictly speaking, since CDs and CD players have a dynamic signal range of 96dB, the amplifier and loudspeakers need to have a dynamic range capability of at least 96dB if they are not going to 102 SILICON CHIP ing the new 7-segment display to the next program number. Now for the bad news. Alas, I can nowhere find a suitable circuit to build, despite looking through numerous magazines. At this point I would obviously like you to help in any way you can. There must be such circuits available somewhere. Incidentally, I note that many electronics magazines describe many fairly advanced projects but do not give much basic information. I'm sure you could publish a short article on counters in a fairly simple way. I know there are such things as incrementing and decrementing counter chips and there must be any number of contact debouncing circuits. (N.W., Peakhurst, NSW). • Yours is the sort of question that comes up quite often but is difficult to answer without actually sitting down to design the circuit you actually want. However, there is one source of information we can refer you to which should help solve your problem. Have a look at the Engineer's Notebook, available from Tandy Electronics stores. This has a number of circuits using TTL chips (ie, 7400 series) or CMOS chips (4000 series) which will help you. degrade the results. As you point out, our Studio 200 does have adequate power but that is conditional on the efficiency of the loudspeakers. Some loudspeakers are so low in efficiency that 100 watts would not be adequate. We don't intend to go right into all the ramifications here but if the amplifier is inadequate in terms of power, it is also a fair bet that its signal-to-noise ratio is nowhere near 96dB. If it is around 10 years old, it will probably be lucky if its signal-to-noise ratio is more than 80dB. So there probably is not a lot of point in just using the preamplifier part of his receiver in the signal chain. His loudspeakers probably also aren't quite up to the task. What were really saying is that if you're going to get the absolute best from compact discs, you probably have to upgrade the whole system, not just the power amplifier. Having poured cold water on your brother's receiver and speakers, we should point out that there is another point of view. Why not just hook the CD player up to the existing receiver and speakers anyhow? Sure, you won't get the ultimate results but the sound quality will still be a big improvement over the existing signal sources. Then, as finances permit, the system can be totally upgraded. For example, he might like to consider building the Studio 200 Control Unit (described June and July 1988) as well as the power amplifier. Later, the system can be topped off with a high quality set of loudspeakers. As for the Soundcraftsman PC-1 Signal Coupler, we can't see the point of it. If the receiver has preamplifier outputs, they can be coupled directly to most stereo power amplifiers. If not, it should be possible to disconnect the receiver's volume control signals to the internal amplifiers and couple them to the external power amplifier input channels instead. Your question about loudspeaker dopant is not easily answered either, as it happens. In the past, it has been common for Australian loudspeaker manufacturers to use a product called Bostik 750 but unfortunately this is no longer available. It was a non-drying PVAbased compound. With that product off the market, loudspeaker makers are relying on their own "custom" brews for doping compounds. Longer life for soldering iron tips In reply to the problem of soldering iron tip life raised by W.K. of Macquarie, ACT (SILICON CHIP, November 1989), I suggest that he tries using "Savbit" solder as manufactured by Multicore Solders. I have found that this solder really works even when using plain copper soldering iron bits. (J.E., Bullcreek, WA). ~ CENl Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7.00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your own classified ad, put one word on each of the lines below and send this form with your payment to : Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097 PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) 16 ($7.40) 17 ($7.80) 18 ($8.20) 19 ($8.60) 20 ($9.00) 21 ($9.40) 22 ($9.80) 23 ($10.20) 24 ($10.60) 25 ($11.00) 26 ($11.40) 27 ($11.80) 28 ($12.20) 29 ($12.60) 30 ($13.00) MEMORY CHIPS PRICES FEBRUARY 1990 Chip type Speed 120ns 100ns BOns PTlces (excluding tax) 38.00 42.00 50.00 SIMMS 9 x 256 or SIPPS 9 x 1Mb LP 156.00 168.00 9x1MbHPIBM 185.00 9 x 1MB LP IBM 210.00 250.00 8x1MbLP 149.00 160.00 DIP 411000 (1 Mb) 15.00 15.80 414256 (1 Mb) 16.00 17.00 3.70 4.25 4.90 41256 41464 (256) 4.60 5.00 4164 2.50 2.80 ZIP 41256 4.00 5.00 411000 (1Mb) 18.00 20.00 Sales tax 20'/4 Overnight deHvery Credit cards welcome DISCOUNTS FOR DEALERS Name ... ..... .. ... .... ...... .......... , ....... ...... ........... ..... . ... ,., ...................... ...... ................. Street ... ..................... ........... .......... ...... .., ................ , ................. ............... ....... .. Suburb/Town .................. .. ........ ........ ... .... ...... .., ....... ..... .. ... Postcode ................ . Enclosed is my cneque or money order for$ .. .... ..... ... .. .. ........ ........... or please debit my Bankcard O Visa Card O MasterCard 0 Card No --'-- - - ' - L - - - ' - ~ ~--'-- - - ' - L - - - ' - ~ ~ _ _ . . ~ - ~ '--1 Signature ....... ....... ......... ..... ......... ...... ..... .. ............ Card expiry date ....... .I.. .... . .I .... .·~ FOR SALE SATFAX: WEATHER SATELLITE picture receiving program for IBM XT/AT. Displays in 64 colours. Needs EGA colour monitor & card, AM demodulator & ADC interface. $45 plus $3 postage. RADFAX2: HF WEATHER FAX, Morse & RTTY receiving program for IBM XT/AT. Needs CGA, SSB HF, FSK/tone decoder. Also "RF2HERC" & "RF2EGA", same as RADFAX2 but suitable for Hercules & EGA cards respectively. $35 plus $3 postage. All programs are on 5.25-inch 36OK floppy disc & include full documentation. Only from M. Delahunty, 42 Villiers St, New Farm, Qld 4005. Phone (07) 358 2785. BUILD YOUR OWN LED Moving Message Board. This 16-character $1 50 short form kit was featured in FIX-A-KIT $15 PER HOUR LABOUR NO CHARGE FOR KITS THAT CAN'T BE REPAIRED 3 MONTHS WARRANTY ON REPAIRS CONSTRUCTION AVAILABLE HYCAL INSTRUMENTS DESIGN, MANUFACTURE, REPAIR OF ELECTRONIC EQUIPMENT (02) 633 5897 PELHAM Tel (02) 427 0011 Fax (02) 428 5460 FUJITSU MEMORY DRAM DIP 256K x 1 1OOns. . . $3.95 DIP 256K x 4 BOns ....... $16.00 ZIP 256K x 4 BOns . . . $16.50 DIP 1 MB x 1 BOns... . . $15.00 ZIP 1 MB x 1 BOns.. . .. $15.50 SRAM DIP BK x 8 100ns ....... $ 4.50 DIP 32K x 8 1OOns. . . . . $12.00 DRAM CONTROLLER MB1430/1 P..... $15.50 PACIFIC MICROELECTRONICS PHONE (02) 481 0065 FAX (02) 484 4460 Add Sales Tax 20% SILICON CHIP from March to June 1989. Can now be built as a three colour display using red and green LEDs. Kit consists of PC boards,. EPROM and full instructions to complete the project to a professional standard. Loaded from Centronics printer port or PC/XT keyboard. For more information, send a 41 c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. PCB ETCHING TANKS. Upright style, glass. Suit PCBs to 125 x 150mm $29.95 kit, $39.95 assembled. P&P $6.00. Other sizes on request. 5V 5OOmA plugpacks $9.95, P&P $2.50. continued next page FEBRUARY1990 103 rk---------------------, ~ BINDERS & SUBSCRIPTION COUPON To: Freepost 25, Silicon Chip Publications, PO Box 139 Collaroy Beach, NSW 2097, Australia. NO POST AGE STAMP REQUIRED IN AUSTRALIA. Start in, _ _ _ _ _ _ __ □ Renewal □ New subscription □ Please send me _ ___ SILICON CHIP binder(s) at $A 11 .95 plus $A3 p&p each (NZ p&p $A6). 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Tuners . . . . . . . . 49 Lawson Radio . . . . . . . . 9 Novocastrian Electronics . . . 25 Oatley Electronics . . . . . 71 Pacific Microelectronics 89, 103 PC Marketplace . . ...... 4,5 Pelham 103 ACS Radio . . .. 39. Resurrection Radio .... 9 Rod Irving Electronics 92,93 Silicon Chip Binders ..... OBC Signature _ _ ______ _ _ _ __ Card expiry date _ _,__ _ L-----------------------J Kit repair and build service $1 5 per hour or set rate. Phone (08) 382 8919. Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. HIGH MILEAGE SUPER-CARB. Bolt on breakthrough. The EMPR0-70 is here. Free Details. Write today: E.P.M. Power Systems, PO Box 255SC, Ivanhoe 3079. NEW SERVICE - PARTS location and supply. Want just that part of a kit or just a hard to find part? We will find and supply them tor you. No search tees. Send SSAE with requirements to Part Search, PO Box 491, Noarlunga Centre, SA 5168. Phone (08) 382 8919. TUNING IN - announcing a new concept in news bulletins. Join our dynamic team of over-unity researchers by subscribing today. News, views, feedback & linkup. All the latest on the tree energy scene. Only $25.00 for 12 issues - $3.00 for sample copy. Write today. Free Energy Connection, PO Box 255SC, Ivanhoe, 3079. ACTIVE TRANSMISSION line stereo speakers. Includes preamp. $760.00. Send SAE to 36 Palmer St, Nambucca Heads, NSW 2448. PROJECT PCBs. Talk to the outside world. ETl-1643 PC 1/0 card, PC 16ADC 1 6-channel 8 bit. Both $39 .95 each. Rear bracket & DB25 cable $16. 6502, 6809, Z-80 miniprocessor with 2 x PIA, RAM, ROM, expansion bus $49.95. Intel 8039/48/49 with wire wrap area B&T $199. Digi-125 125W power amplifier PCB $4.95. P&P $2.00. PC Computers, 36 Regent St, Kensington, SA 5068 . 104 SILICON CHIP RESISTORS, 1 % METAL film, 0.6 watt. Finest German quality, 7c each, $6 per hundred, any mixed values. SAE for tree sample & data sheet. Also BUX80 $7, 2N3055 $2.35, BC547 12c, 2N3019 $1.20, HEF4050B 80c, 1OnF greencap 20c, 1 OOnF monolithic 15c, 220nF 630 volt polycarbonate $2. P&P NSW $2 .50, interstate $3.50. Extended Pulse Burn Electronic Ignition: full kit $70, fully built and tested $99 postpaid. Chipspeed Electronics, PO Box 337, Wentworthville, NSW 2145. PC Boards Printed circuit boards tor SILICON CHIP projects are made by: • ACS Radio Pty Ltd, 651 Forest Rd , Bexley, NSW 2207 . Phone (02) 587 3491 . • Jemal Products, 5 Forge St, Welshpool, WA 6106 . Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163 . LEADER 100MHz OSCILLOSCOPE. Quad trace, delay timebase LB0-518. As new, never used. $3,500 ono. Leader dot/crosshatch generator, high voltage probe, degaussing wand, $3,800 the lot ono. Andre Berger, 116 Norfolk Rd, North Epping 2121 . Phone (02) 868 4326. WANTED SERVICE MANUAL tor UPM98 . 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