Silicon ChipMay 1996 - Silicon Chip Online SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Why shouldn't the Internet be censored?
  4. Feature: Cathode Ray Oscilloscopes; Pt.3 by Bryan Maher
  5. Project: Duplex Intercom Using Fibre-Optic Cable by Leo Simpson
  6. Feature: Upgrade Your PC In Ten Minutes by Ross Tester
  7. Order Form
  8. Project: High Voltage Insulation Tester by John Clarke
  9. Serviceman's Log: It was a dark and stormy night by The TV Serviceman
  10. Feature: Radio Control by Bob Young
  11. Project: Motorised Laser Lightshow by Branco Justic
  12. Product Showcase
  13. Feature: Computer Bits by Geoff Cohen
  14. Project: KnightRider Bi-directional LED Chaser by Rick Walters
  15. Vintage Radio: A look at early radiograms, even back to Edison's day by John Hill
  16. Book Store
  17. Market Centre
  18. Advertising Index
  19. Outer Back Cover

This is only a preview of the May 1996 issue of Silicon Chip.

You can view 24 of the 96 pages in the full issue, including the advertisments.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

Articles in this series:
  • Cathode Ray Oscilloscopes; Pt.1 (March 1996)
  • Cathode Ray Oscilloscopes; Pt.2 (April 1996)
  • Cathode Ray Oscilloscopes; Pt.3 (May 1996)
  • Cathode Ray Oscilloscopes; Pt.4 (August 1996)
  • Cathode Ray Oscilloscopes; Pt.5 (September 1996)
  • Cathode Ray Oscilloscopes; Pt.6 (February 1997)
  • Cathode Ray Oscilloscopes; Pt.7 (March 1997)
  • Cathode Ray Oscilloscopes; Pt.8 (April 1997)
  • Cathode Ray Oscilloscopes; Pt.9 (May 1997)
  • Cathode Ray Oscilloscopes; Pt.10 (June 1997)
Items relevant to "High Voltage Insulation Tester":
  • High Voltage Insulation Tester PCB pattern (PDF download) [04303961] (Free)
Articles in this series:
  • Remote Control (June 1995)
  • Remote Control (March 1996)
  • Radio Control (April 1996)
  • Radio Control (May 1996)
  • Radio Control (June 1996)
  • Radio Control (July 1996)
  • Radio Control (August 1996)
  • Radio Control (October 1996)
Articles in this series:
  • Computer Bits (July 1989)
  • Computer Bits (August 1989)
  • Computer Bits (September 1989)
  • Computer Bits (October 1989)
  • Computer Bits (November 1989)
  • Computer Bits (January 1990)
  • Computer Bits (April 1990)
  • Computer Bits (October 1990)
  • Computer Bits (November 1990)
  • Computer Bits (December 1990)
  • Computer Bits (January 1991)
  • Computer Bits (February 1991)
  • Computer Bits (March 1991)
  • Computer Bits (April 1991)
  • Computer Bits (May 1991)
  • Computer Bits (June 1991)
  • Computer Bits (July 1991)
  • Computer Bits (August 1991)
  • Computer Bits (September 1991)
  • Computer Bits (October 1991)
  • Computer Bits (November 1991)
  • Computer Bits (December 1991)
  • Computer Bits (January 1992)
  • Computer Bits (February 1992)
  • Computer Bits (March 1992)
  • Computer Bits (May 1992)
  • Computer Bits (June 1992)
  • Computer Bits (July 1992)
  • Computer Bits (September 1992)
  • Computer Bits (October 1992)
  • Computer Bits (November 1992)
  • Computer Bits (December 1992)
  • Computer Bits (February 1993)
  • Computer Bits (April 1993)
  • Computer Bits (May 1993)
  • Computer Bits (June 1993)
  • Computer Bits (October 1993)
  • Computer Bits (March 1994)
  • Computer Bits (May 1994)
  • Computer Bits (June 1994)
  • Computer Bits (July 1994)
  • Computer Bits (October 1994)
  • Computer Bits (November 1994)
  • Computer Bits (December 1994)
  • Computer Bits (January 1995)
  • Computer Bits (February 1995)
  • Computer Bits (March 1995)
  • Computer Bits (April 1995)
  • CMOS Memory Settings - What To Do When The Battery Goes Flat (May 1995)
  • Computer Bits (July 1995)
  • Computer Bits (September 1995)
  • Computer Bits: Connecting To The Internet With WIndows 95 (October 1995)
  • Computer Bits (December 1995)
  • Computer Bits (January 1996)
  • Computer Bits (February 1996)
  • Computer Bits (March 1996)
  • Computer Bits (May 1996)
  • Computer Bits (June 1996)
  • Computer Bits (July 1996)
  • Computer Bits (August 1996)
  • Computer Bits (January 1997)
  • Computer Bits (April 1997)
  • Windows 95: The Hardware That's Required (May 1997)
  • Turning Up Your Hard Disc Drive (June 1997)
  • Computer Bits (July 1997)
  • Computer Bits: The Ins & Outs Of Sound Cards (August 1997)
  • Computer Bits (September 1997)
  • Computer Bits (October 1997)
  • Computer Bits (November 1997)
  • Computer Bits (April 1998)
  • Computer Bits (June 1998)
  • Computer Bits (July 1998)
  • Computer Bits (November 1998)
  • Computer Bits (December 1998)
  • Control Your World Using Linux (July 2011)
Items relevant to "KnightRider Bi-directional LED Chaser":
  • Silicon Chip article scan, May 1996 - KnightRider: A Bi-Directional LED Chaser (AUD $10.00)
  • KnightRider Bi-direction LED Chaser PCB pattern (PDF download) [08105961] (Free)
Create your own Internet Home Page ISSN 1030-2662 05 9 771030 266001 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.tek.com Vol.9, No.5; May 1996 Contents FEATURES 6 Cathode Ray Oscilloscopes, Pt.3 Continuing our series on these important instruments. This month, we see how oscilloscopes work at very high frequencies – by Bryan Maher 22 Upgrade Your PC In Ten Minutes We show you how you can upgrade an old 386, or even a 286, to a 486; or a 486 to full 586 performance with just one upgrade chip – by Ross Tester PC UPGRADES CAN BE QUICK AND EASY WITH THIS CHIP – PAGE 22 PROJECTS TO BUILD 14 Duplex Intercom Using Fibre-Optic Cable Most intercoms are simplex but this one is a full duplex intercom (ie, two ways at a time) and uses the very latest fibre optic cable – by Leo Simpson 30 High Voltage Insulation Tester This high voltage insulation tester can measure resistance from 1000MΩ to 2200GΩ, with a 10-step LED bargraph readout – by John Clarke DUPLEX INTERCOM USES LATEST FIBRE OPTICS – PAGE 14 57 Motorised Laser Lightshow For Spectacular Effects You’ve seen those fancy lightshows at discos and rock concerts. Now you can have your own – by Leo Simpson 80 KnightRider: A Bi-Directional LED Chaser Just Like Kit's! Everyone wanted a two-way chaser just like ‘Kit’ had across its bonnet. Now you can build the LED version or even build the real thing – by Rick Walters SPECIAL COLUMNS 40 Serviceman’s Log It was a dark and stormy night – by the TV Serviceman 53 Radio Control Multi-channel radio control transmitter; Pt.4 – by Bob Young HIGH VOLTAGE INSULATION TESTER – PAGE 30 74 Computer Bits Create your own Home Page on the World Wide Web – by Geoff Cohen 88 Vintage Radio A look at early radiograms, even back to Edison's day – by John Hill DEPARTMENTS 2 Publisher’s Letter 4 Mailbag 29 Order Form 38 Circuit Notebook 70 Product Showcase 78 Bookshelf 92 Ask Silicon Chip 95 Market Centre 96 Advertising Index LED CHASER HAS 2-WAY CHASE PATTERN – PAGE 80 May 1996  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Christopher Wilson Phone (02) 9979 5644 Mobile 0419 23 9375 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $54 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Why shouldn’t the Internet be censored? Just recently, the NSW Attorney General, Jeffrey Shaw, has announced the intention to draft legislation that will make it an offence to transmit or receive material unsuitable for minors over the Internet. Predictably there has been a howl of outrage from the civil libertarians who seem to argue that any censor­ship, on any media, is an attack on free speech. They also argue that censorship of the Internet is technically unworkable. Well, I’m not so sure about either of those arguments. On the subject of free speech, it always seems to me that the people making the loudest noises are often defending the availability of pornography. In other words, their arguments are tendentious – they either want pornography for themselves or they want to make money by selling it. While most pornography probably is harmless, do we really want it even more widely available? There is also the argument that it is up to the parents to see that their children are safeguarded from pornography and that adults should be able to make their own choice at all times. Both of these latter points look quite reasonable but they are made by people who apparently don’t have much experience with children. While it may be relatively easy for parents to prevent their children from seeing particular videos at home, it is not nearly as easy if undesirable material is available on the Inter­net. How many parents are able to watch what their children may access at any time via their computers? Remember too that more and more schools have access to the Internet both in the classroom and in the libraries. Can we have constant vigilance in this regard? It’s impossible. On the other hand, it would be entirely workable for a government authority to maintain a constant watch on what was available on the Internet. If you and I can use a “web browser” to search for particular material on the Internet, then so can a government authority. They could do it 24 hours a day. Once they detected undesirable material, they could pounce. To my mind, the real question concerning the need for censorship on the Internet is whether we need any more legisla­tion. If pornography on the Internet does not involve paedophilia or serious violence then probably little should be done about it. After all, children will be exposed to this material sooner or later as part of growing up. On the other hand, if material on the Internet does involve serious violence or paedophilia, then surely existing legislation is adequate to stop it – it merely needs to be enforced. Leo Simpson ISSN 1030-2662 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip S ONI2C3 R T C 2 ELE SW 2 7910 y, N EY OATL ox 89, OatleFax (02) 570 C a rd reflective tape with self-adhesive backing. Other motorists will see you better at night if this is stuck to chromed or unpainted car bumpers or on bicycles: 3 metres for $5. Visa PO B 579 4985 fax a rd , ) C 2 0 SOUND FOR CCD CAMERAS / UNIVERSAL ( r ne & rs: e e o t n s h o a p h AMPLIFIER P , M ith rde d o w r a d d c e Uses an LM386 audio amplifier IC and a e B a n k x accept most mix 0. Orders BC548 pre-amp. Signals picked up from e r 1 an electret microphone are amplified and & Am . P & P fo (airmail) $ drive a speaker. Intended for use for s order 4-$10; NZ world.net listening to sound in the location of a $ <at> . y t CCD camera installation, but this kit atle Aus o : L could also be used as a simple utility I A M amplifier. Very high audio gain (adjustable) makes this by E unit suitable for use with directional parabolic reflectors etc. PCB: 63 x 37mm: $10 (K64). FLUORESCENT LIGHT HIGH FREQUENCY BALLASTS European made, new, “slim line” cased high frequency (HF) electronic ballasts. They feature flicker free starting, extended tube life, improved efficiency, no visual flicker during operation (as high frequency operation), reduced chance of strobing with rotating machinery, generate no audible noise and generate much reduced radio frequency interference compared to conventional ballasts. Some models include a dimming option which requires either an external 100kΩ potentiometer or a 0-10V DC source. Some models require the use of a separate filter choke (with dimensions of 16 x 4 x 3.2cm) - this is supplied where required. We have a limited stock of these and are offering them at fraction of the cost of the parts used in them! Type B: 1 x 16W tube, dimmable, filter used, 43 x 4 x 3cm: $16. Type F: 1 x 32W or 36W tube, dimmable, no filter, 34 x 4 x 3cm: $18 (Cat G09, specify type). 27MHz RECEIVER CLEARANCE Soiled 27MHz telemetry receivers. Enclosed in waterproof die cast metal boxes, telescopic antenna supplied. 270 x 145 x 65mm. 2.8kg. Two separate PCBs. Receiver PCB has audio output. Signal filter/squelch PCB is used to detect various tones. Circuit provided: $12. 40-CHANNEL FM MICROPHONE A hand held crystal locked 40-channel FM transmitter with LCD display: 88-92MHz in 100kHz steps, 50m transmission range. Perfect for use with synthesized FM receivers: $50. SPEED CONTROLLED GEARED MOTOR Experiment with powering small vehicles, large children’s cars, garage door openers, electric wheelchairs, rotisseries, etc. etc. We supply a speed control PCB and components kit, A 25A MOSFET and a 30A diode (flyback), and a used 12V geared windscreen wiper motor for a total price of: $30. CHARACTER DISPLAYS We are offering three types of liquid crystal character displays at bargain prices. The 40 x 2 character display (SED1300F) is similar to the Hitachi 44780 type but is not directly compatible. We will also have similar displays - data available for a 16 x 4 and 32 x 4 display. Any mixture of these displays is available for a crazy price of $22 each or 4 for $70. IR TESTER USING IR CONVERTER TUBE Convert infra red into visible light with this kit. Useful for testing infra red remote controls and infra red laser diodes. We supply a badly blemished IR converter tube with either 25 or 40mm diameter fibre optically coupled input and output windows and our night vision high voltage power supply kit, which can be powered from a 9V battery. These tubes respond to IR and visible light. A very cheap IR scope could be made with the addition of a suitable casing and objective lens and eyepiece. $30. MISCELLANEOUS ITEMS 2708 EEPROMS: $1 each; 4164 MEMORY ICs: 16 for $10: AC MOTOR, 1RPM Geared 24V-5W Synchronous motor plus a 0.1 to 1RPM driver kit to vary speed, works from 12V DC: $12 K38 + M30; SPRING REVERB, 30cm long with three springs: $30 A10; MICROSONIC MICRO RECORD PLAYER, Includes amplifier: $4 A11; LARGE METER MOVEMENTS: moving iron, 150 x 150mm square face, with mounting hardware: $10. REFLECTIVE TAPE High quality Mitsubishi brand all weather 50mm wide red VHF MODULATOR KIT For channels 7 and 11 in the VHF TV band. This is designed for use in conjunction with monochrome CCD cameras to give adequate results with a cheap TV. The incoming video simply directly modulates the VHF oscillator. This allows operation with a TV without the necessity of connecting up wires, if not desired, by simply placing the modulator within about 50cm from the TV antenna. Suits PAL and NTSC systems. PCB: 63 x 37mm: $12 (K63). ‘MIRACLE’ ACTIVE AM ANTENNA KIT Available soon. To be published in EA. After the popularity of our Miracle UHF/VHF antenna kits we have produced this AM version for our ‘Miracle’ series. Large antennas are not the most attractive inside a house but sometimes this is needed to receive a weak radio signal. This kit will connect to a remote loop of wire, preferably outside where reception is good, via coax cable and allow it to be tuned from inside via varactor diodes. Radio reception is greatly improved and it can even pickup remote stations that a radio can’t receive with its ferrite rod antenna. No connections are required to the existing radio as the receiving end is coupled to the ferrite rod in the radio with a loop of wire around the radio. Excellent kit for remote country areas where radio reception isn’t very good, or where a large antenna is not possible. Great for caravanners, boats that venture far out to sea, etc. 2 x PCBs and all on-board components. BATTERY CHARGER WITH MECHANICAL TIMER Simple kit which is based on a commercial 12 hour mechanical timer switch which sets the battery charging period from 0 to 12 hrs. Employs a power transistor and five additional components. Can easily be “hard wired”. Information that shows how to select the charging current is included. We supply information, circuit and wiring diagram, a hobby box with aluminium cover that doubles up as a heatsink, a timer switch with knob, a power transistor and a few other small components to give you a wide selection of charge current. You will also need a DC supply with an output voltage which is greater by about 2V than the highest battery voltage you need to charge. As an example a cheap standard car battery charger could be used as the power source to charge any chargeable battery with a voltage range of 0-15V. Or you could use it in your car. No current is drawn at the end of the charging period: $15. AUTOMATIC LASER LIGHT SHOW KIT Kit as published in Silicon Chip May 96 issue. The display changes every 5 - 60 seconds, and the time is manually adjustable. For each of the new displays there are 8 different possible speeds for each of the 3 motors, one of the motors can be reversed in rotation direction, and one of the motors can be stopped. There are countless possible interesting displays which vary from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. etc. Kit makes an excellent addition to any lightshow and all these patterns are enhanced by the use of a fog machine. Kit includes PCB, all on board components, three small DC motors, 3 high quality/low loss dichroic mirrors: $90. Suitable 12V DC plugpack: $14. LASER LIGHTSHOW PACKAGE Our 12V Universal inverter kit plus a used 5mW+ helium-neon laser tube head plus a used Wang power supply plus an automatic laser light show kit with dichroic mirrors (as above): $200. ARGON-ION HEADS Used Argon - Ion heads with 30-100mW output in the blue - green spectrum. Head only supplied. Needs 3Vac <at> 15A for the filament and approx 100Vdc <at> 10A into the driver circuitry that is built into the head. We provide a circuit for a suitable power supply the main cost of which is for the large transformer required: $170 from the mentioned supplier. Basic information on power supply provided. Dimensions: 35 x 16 x 16cm. Weight: 5.9kg. 1 year guarantee on head. Price graded according to hours on the hour meter: We have had no serious problems with any of these heads as they were used at a very low current in their original application. Argon heads only: $300. SIREN USING SPEAKER Uses the same siren driver circuit as in the “Protect anything alarm kit”. 4-inch cone / 8-ohm speaker is included. Generates a very loud and irritating sound with penetrating high and low frequency components. Output has frequency components between 500Hz and 4kHz. Current consumption is about 0.5A at 12V. PCB: 46 x 40mm. As a bonus, we include all the extra PCBs as used in the “Protect anything alarm kit”: $12. DC MOTORS We have good stocks of the following high quality DC motors. These should suit many industrial, hobby, robotics and other applications. Types: Type M9 : 12V. I no load = 0.52A <at> 15800 RPM at 12V. Weight: 150g. Main body is 36mm diameter. 67mm long: $7 (Cat M9) Type M14 : Made for slot cars. 4 to 8V. I no load = 0.84A at 6V. At max. efficiency I = 5.7A <at> 7500 RPM. Weight: 220g. Main body diameter is 30mm. 57mm long: $7 (Cat M14). ULTRASONIC COMMUNICATOR KIT Ref: EA Sep/Oct 93. Signals picked up by an electret microphone are modulated onto an oscillator which drives a 40kHz ultrasonic transducer. This is received by a 40kHz ultrasonic receiving transducer and is amplified and detected. The detected signal is amplified by a simple three transistor amplifier to drive a speaker. This makes a communications link using ultrasound which can transmit over a few metres. The quality of the sound is limited by the narrow bandwidth of the transducers but this is an interesting experiment. Both transmitter and receiver PCBs are 63 x 33mm: $16 (K45). BOG DEPTH SOUNDER KIT Detect the presence and depth of any body filler on your car. This simple circuit uses an oscillator which is oscillating weakly. When steel is placed near the small search coil the inductance shifts and the oscillator components are arranged so the oscillator will stop running. The remainder of the circuit simply detects when the oscillator stops and gives a visual or audible indication of this. The circuit is arranged so that the change in inductance needed to stop the oscillator can be varied. This allows variable depth of filler sensing, between 0 and about 3mm. Large areas of body filler over 3mm thick are generally considered undesirable as the filler may lift or crack. Kit supplied includes pre-wound search coil (33 x 22 x 10mm). A LED is supplied in the kit as the visual indication. An audible indication can be obtained by using a low power piezo buzzer, which is recommended but not supplied with the kit: $12 (K62). $2 for optional low power piezo buzzer. HIGH VOLTAGE AC DRIVER This kit produces a high frequency high voltage AC output that is suitable for ionizing most gas filled tubes up to 1.2m long. It will partially light standard fluorescent tubes up to 1.2m long with just 2 connections being made, and produce useful white light output whilst drawing less than 200mA from a 12V battery. Great for experimenting with energy efficient lighting and high voltage gas ionization. PCB plus all on board components, including high voltage transformer: $18. PC CONTROLLED PROGRAMMABLE POWER SWITCH MODULE This module is a four-channel programmable on/off timer switch for high power relays. The timer software application is included with the module. Using this software the operator can program the on/off status of four independent devices in a period of a week within a resolution of 10 minutes. The module can be controlled through the Centronics or RS232 port. The computer is opto-isolated from the unit. Although the high power relays included are designed for 240V operation, they have not been approved by the electrical authorities for attachment to the mains. Main module: 146 x 53 x 40mm. Display panel: 146 x 15mm. We supply: two fully assembled and tested PCBs (main plus control panel), four relays (each with 3 x 10A / 240V AC relay contacts), and software on 3.5-inch disk. We do not supply a casing or front panels: $92 (Cat G20). May 1996  3 X-ON ELECTRONIC SERVICES WHOLESALE TO THE PUBLIC SEMICONDUCTORS ULN2804A 1N914 1N4004 1N4148 1N4936 1N5404 78L05 BB119 BC327 BC328 BC337 BC338 BC548 BC549 BC558 BC639 BC640 BD139 BD140 BD649 BD650 BS170 BZV85C16 BZV85C75 BZW03C75 BZV85C16 BZX79C5V6 C7805H HEF4046BP HEF4053BP HEF4066BP ICM7555CN IRF540 LF347N LM317T LM358N LM386N-1 LM393N LM833N LM1875T $2.82 $0.04 $0.10 $0.04 $0.39 $0.27 $0.95 $0.52 $0.31 $0.31 $0.31 $0.31 $0.18 $0.18 $0.18 $0.57 $0.57 $1.16 $1.16 $1.71 $1.71 $0.88 $0.37 $0.49 $1.83 $0.37 $0.18 $1.53 $1.34 $1.10 $0.82 $1.34 $8.54 $4.09 $2.14 $1.10 $1.71 $1.16 $2.14 $7.32 LM3914N LM7805CT LM7808CT LM7812CT LM7815CT LM7915CT MC68HC705C8P MTP3055E NE555N NE571N NE602AN NM93C46N PC74HC11P PC74HC42P PC74HC132P PC74HC573P PC74HC4051P PC74HC4040P PCF8573P TDA1074A TEA1100 TL071CP TL072CP TL074 W04M CRYSTALS HC-38C-32.76800-kHz HC-49/U-2.000000-MHz HC-49/U-3.579545-MHz HC-49/U-4.000000-MHz HC-49/U-10.00000-MHz CAPACITORS CERAMIC 2222-681-09688 6P 10P/5MM 22P/5MM 33P/5MM 39P/5MM 47P/5MM 68P/5MM 100P/5MM 150P/5MM CAPACITORS BOXED POLYESTER 100V MKT 2222-370-11104 100N $0.29 2222-370-11184 180N $0.37 2222-370-11684 680N $0.83 2222-370-18474 470N $0.61 2222-370-21153 15N $0.22 2222-370-21223 22N $0.22 2222-370-21473 47N $0.27 2222-370-21563 56N $0.27 2222-370-11683 68N $0.27 2222-370-18224 220N $0.33 2222-370-11334 330N $0.45 2222-370-41472 4N7 $0.22 2222-370-41562 5N6 $0.22 2222-370-42103 10N $0.22 2222-370-51102 1N $0.22 2222-370-51222 2N2 $0.22 2222-370-66332 3N3 $0.22 CAPACITORS MONOLTHIC CERAMIC 5M PITCH 0.1uF/0.2 100N $0.16 URD30E474MT 470NF $0.43 FUSES AND HOLDERS 210030SX PCB FUSE CLIP M205 $0.12 AGE10 10A 3AG 32*6MM $0.32 AGE3 3A 3AG 32*6MM $0.32 GME1 1A M205 20*5MM $0.32 GME3.15 3.15A M205 20*5MM $0.32 INLINEFUSE INLINE HOLDER $0.85 JEF-510 PCB M205 HOLDER $0.49 TO220B TO220 BUSH (56359C) $0.07 CONNECTORS 396H-3 3 WAY 3.96MM HOUSING $0.37 396H-5 5 WAY HOUSING 3.96MM SPACING $0.55 DN-8P DIN 8 WAY MALE PLUG $1.71 ETB-11-03 3 WAY PCB TERMINAL BLK $0.93 H1-40-G-07 40*1 PIN HEADER STR $0.55 ICS-8-A-T 08 PIN IC SOCKET $0.20 ICS-16-A-T 16 PIN IC SOCKET $0.31 ICS-18-A-T 18 PIN IC SOCKET $0.33 MJG MINI JUMPER SHUNTS $0.12 PLCC-44-T 44 PIN PLCC IC SOCKET $2.03 POW016 MAINS POWER CORD IEC $6.71 FERRITES 4312-020-38040 ETD49 3F3 CORE NO GAP $4.58 4312-020-41080 EFD20 3F3 CORE NO GAP $1.60 4322-021-33920 ETD49 CLIP $0.61 4322-021-35150 EFD20 CLIP $0.49 FASTENERS 030449C 4X1/2 SLOTTED PAN $5.88 PKT 100 030452B 6X1/2 SLOTTED PAN $7.25 PKT 100 030455G 8X1/2 SLOTTED PAN $6.70 PKT 100 030466A 6X3/8 SUPADRIV PAN $6.15 PKT 100 031524H M3X6 SLOTTED PAN $4.62 PKT 100 031525F M3X10 SLOTTED PAN $4.31 PKT 100 031526D M3X12 SLOTTED PAN $4.51 PKT 100 031527B M3X16 SLOTTED PAN $4.95 PKT 100 031528X M3X20 SLOTTED PAN $4.58 PKT 100 031529R M3X25 SLOTTED PAN $8.22 PKT 100 031583H M3X6 SLOTTED CSK $5.77 PKT 100 031584F M3X12 SLOTTED CSK $4.31 PKT 100 031615B M2.5 FULL NUTS $6.64 PKT 250 031616X M3 FULL NUTS $6.75 PKT 250 031630D M3 S/PROOF WASHERS $3.76 PKT 250 035941R 5mm SPACER $10.48 PKT 50 403375H 6mm SPACER $11.33 PKT 50 403377D 8mm SPACER $12.96 PKT 50 403378B 12mm SPACER $16.60 PKT 50 403380C HTLP3050-08 $12.18 PKT 50 403381A HTLP3050-12 $16.07 PKT 50 HARDWARE CV100 CABLE TIE 100*2.5MM $0.05 4  Silicon Chip $4.88 $1.53 $1.53 $1.53 $1.53 $1.53 $28.06 $2.56 $0.73 $7.20 $4.27 $3.42 $0.73 $1.34 $1.10 $1.83 $1.34 $1.34 $11.71 $15.49 $15.49 $1.83 $2.32 $3.05 $0.98 $1.27 $4.60 $2.44 $2.44 $2.44 $0.12 $0.12 $0.12 $0.12 $0.12 $0.12 $0.12 $0.12 $0.12 180P/5MM $0.12 220P/5MM $0.12 270P/5MM $0.12 470P/5MM $0.12 680P/5MM $0.12 820P/5MM $0.12 GREENCAPS GC0.001uF $0.18 GC0.0027uF $0.18 GC0.01uF $0.18 GC0.022uF $0.18 GC0.039uF $0.18 GC0.082uF $0.18 GC0.1uF-100V $0.24 ELECTROLYTIC CAPACITORS LL10/50 $0.31 RB1/63 $0.18 RB2.2/50 $0.18 RB4.7/63 $0.18 RB10/50 $0.18 RB22/25 $0.18 RB33/35 $0.24 RB47/25 $0.24 RB100/16 $0.31 RB100/25 $0.31 RB220/16 $0.31 RB220/63 $0.73 RB470/16 $0.55 RB470/25 $0.61 RB1000/16 $0.67 RB1000/25 $0.85 RB2200/25 $1.22 RB4700/16 $2.32 RB4700/50 $4.64 RB10000/25 $5.86 80x80x25mm 12V FANS B802512BL $12.00 HEATSINKS 5mm 274-2 HEATSINK TO220 LEDS AND OPTO ELECTRONICS CSL-300E1DT 3MM ORANGE ROUND CSL-300G1DT 3MM GREEN CSL-300H1GT 3MM RED CSL-300Y1BT 3MM YELLOW CSL-500E1DT 5MM ORANGE CSL-500G1DT 5MM GREEN CSL-500H1DT 5MM RED CSL-500Y1DT 5MM YELLOW CSL-620E1DT 5MM*2MM ORANGE CSL-620G1DT 5MM*2MM GREEN CSL-620H1DT 5MM*2MM RED CSL-620Y1DT 5MM*2MM YELLOW POTENTIOMETERS VG067TH1 SIDE ADJUST TRIMMERS VG067TL1 TOP ADJUST TRIMMER RELAYS R729/DC12-1C SPDT 12VDC 10AMP H100S24-1-C PCB RELAY SPDT RESISTORS MRS25 SERIES 1% 0.6 WATT MF25 SERIES 1% 1/4 WATT CR25 SERIES 5% 1/4 WATT SIP10A-102G 1K 10P 9RES RESNET SIP10A-103G 10K 10P 9R RESNET SIP10A-153G 15K 10P 9R RESNET SQP5-0R1 0R1 5W RESISTOR SQP5-82R 82R 5W RESISTOR SQP5-100R 100R 5W RESISTOR SWITCHES EDS-1-4-S DIP 4-WAY PCB 8222/RED RED PUSH BUTTON 8222/BLACK BLACK PUSH BUTTON BUZZERS TDB-12PN BUZZER 12MM PIEZO 7S3240-LA BUZZER 1.5-28VDC BATTERIES 9 VOLT BATTERY SNAP CABLES AND WIRE (PRICED PER MTR) 011251B 30 AWG 1/30 BLACK 011252X 30 AWG 1/30 BLUE 011254G 30 AWG 1/30 GREEN 011256C 30 AWG 1/30 ORANGE 011257A 30 AWG 1/30 RED 011260X 30 AWG 1/30 YELLOW CA-26 RIBBON CABLE 26-WAY $0.73 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.49 $0.49 $6.04 $2.75 $0.07 $0.06 $0.02 $0.37 $0.37 $0.37 $0.49 $0.49 $0.49 $1.71 $0.73 $0.73 $2.75 $2.93 $0.27 $0.15 $0.15 $0.15 $0.15 $0.15 $0.15 $2.26 KEEP YOUR HOBBY AFFORDABLE. THIS IS A SAMPLE OF OUR MASSIVE RANGE TAKEN FROM RECENT PROJECTS PUBLISHED. DEL CHARGE $8.00 FREE DELIVERY FOR ORDERS OVER $200. 10% DISCOUNT FOR 10+ SAME ITEM PRICES TAX INCLUDED MASTER/VISA/BANK/AMEX CARD X-ON ELECTRONIC SERVICES 1161 ALBANY HWY, BENTLEY PHONE: 09 351 9202; FAX: 09 458 5545 IF ITS NOT HERE JUST ASK. OVER 200,000 LINES AVAILABLE! MAILBAG Coolant alarm works well I appreciate the range of projects in your magazines. The coolant level alarm is fantastic. I’ve bought two and built/installed one. It works a treat (I was once caught with a warped cylinder head near Kimba in SA – due to rapid water loss). The Programmable Electronic Ignition System is great, and I’ll probably build one, especially if it comes in kit form. But I’ll certainly build one if you could come out with a project that eliminates the distributor as intimated by Anthony Nixon. I think Ford GB has such a system using two coils on a 4-cylinder engine. I hope you can do it! The Digital Tachometer is practically useless since its accuracy does not lend itself for fine tuning. Plus/minus 50 rpm is about as good as one can do by ear. J. Boehm, Surrey Hills, Vic. We agree that superficially, the Digital Tachometer has insuffi­cient resolution. However, we found that adding another digit to the display is a waste since it jitters excessively. That’s because most car engines continuously vary their revolutions. This applies even to cars with EFI, as their feedback mechanisms constantly hunt between upper and lower limits. High-power inverters can be troublesome You really grabbed my attention with your answer “Oils ain’t oils” in the Ask Silicon Chip column for March 1996. I agree with you about the superiority of Motorola power devices, particularly in hot, or wet places. However, when it comes to inverter transistors going “pop”, or “rat-tattat-smoke-stink” as they do in big inverters, I find the transistors have never been the cause unless damaged by previous torture. Your contributor is right, of course, about the unreliabil­ ity of inverters. Some are designed too close to the line, some are put together in sweatshops, and some are designed by people who don’t understand the hidden complexity of the things. The mixture of digital, analog, and magnetic components throws up problems which the power devices get blamed for. Most inverter failures are caused by saturation of the iron, from asymmetry, or failure to saturate the transistors. FETs particularly find ways to stay linear while you are trying to drive them switchmode - they talk to other devices if they get half a chance! I am so vehement about this because I had to repair over a hundred inverters from an unmentionable inverter manufacturer after they kept returning with dead transistors. These inverters went pop at turn-on for all the usual reasons like paralleled gates of power FETs, miller feedback pulses getting into CMOS chips, power supply coupling to the oscillator, loose IC sockets, and high impedance points on control board picking up noise, etc. Another common nasty was that the crystal was a bit reluctant to get going (due to poor bias on the drive gate) and the DC coupling through to the very willing output stage meant that, after the transformer saturated, it was all over. This experience (3kg of dead FETs) led me to design the Rainbowsine 300W inverter (if you will allow a plug). I think that the 12V model is indestructible and a lot more use than the 300 number indicates. I use one as a car inverter for power tools and a computer UPS. It even survives those heat guns that half-wave rectify on low power! K. McLaughlin, Nimbin, NSW. Software piracy protection: a better scheme I am writing to you in relation to H. Nacinovich’s letter about “software piracy protection” in the March issue of SILICON CHIP. The scheme he proposes, to the best of my knowledge, had already been used some five or more years ago. It was called “Prolock” and was advertised in the then computer journals with the fingerprint logo. I do not know the current distributor of it or whether it died a natural death. It is probable that it died with the other copy protection schemes that were preva­lent at the time. All of these schemes were resisted by users, most of whom chose to leave such software on the shop shelves, while others spent the whole time trying to defeat them. Hopefully, history will not repeat itself. A better way to stop software piracy is with good quality software at a reasonable price and with good backup support from the software supplier. Most good software houses like Borland and Microsoft do have very good licensing agreements to encourage the purchase of their products. This brings me to another bad experience with software. It was with trial software supplied with a computer magazine that I purchased. The problem was not with the operation of the supplied test program but with its removal after the trial. It wiped out all the links of previously installed programs, so that they had to be reinstalled. Examples of the programs it took with it were my Borland C++ 4.5 compiler (thankfully on CD) and Paradox 5.0. This was a fun time, I can tell you, especially the C++ which had to be removed fully before reinstallation. If you uninstall the trial software by file manager methods, it leaves unremovable parts in the form of subdirectories behind. This required a hard disk reformat to get rid of them but at this stage am not sure if all traces are gone as I am not prepared to waste time trying to find out. It is high time that companies that do this sort of thing should be held accountable for their software performance as depicted above. They should also be accountable if locked soft­ware fails and a loss of production occurs due to a reliable backup not being available. D. Kuenne, Ascot Vale, Vic. If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.telstra.com.au May 1996  5 While designing an oscilloscope with a 20MHz bandwidth is relatively easy, it is much harder to achieve 150MHz and even harder to get to 1GHz. In this chapter, we discuss some of the techniques which achieve this and result in the beam electronics moving at more than one quarter the speed of light. By BRYAN MAHER A good high-frequency oscilloscope is the only way to show the true shape, rise and fall times or the presence of any dis­ turbing anomalies or oscillations in your signals. A very high trace writing speed is also required, otherwise fast rising pulses will be invisible on the screen. Only a wide bandwidth oscilloscope can reveal logic circuit malfunctions or unwanted defects in input signals such as fast jitter in the sub-nanosecond range or high frequency ringing and overshoot on pulse waveforms. Typical of modern analog instruments is the Philips PM3094, a scope of 200MHz bandwidth, capable of displaying four signals simultaneously and with CRT readout of measurements on screen. Its vertical sensitivity of 2 millivolts per division is accurate to within 1.3% for large deflection in mid-screen. Main and delayed time­ bases are provided with the fastest sweep speed being 2 nanoseconds per division (when x10 horizontal magnification is used). An acceleration voltage of 16.5kV ensures sharpness and brightness of the traces. The need for wide bandwidth CROs to display the true shape of even moderate frequency signals is easily This Philips PM3094 200MHz oscilloscope can display four signals simultaneously. Vertical sensitivity is 2mV per division. Its fastest timebase speed is 2ns/div (using x10 magnification). Features are main and delayed sweep, on-screen readout and au­tomatic delta-time measurements. 6  Silicon Chip demonstrated by displaying similar waveforms on two oscilloscopes having differ­ ent bandwidths. In a particular case, the author was measuring pulse currents through a very low value resistor. Though the pulses were at the relatively slow repetition rate of 4kHz, the pulse rise time was known to be extremely fast. A simple demonstration For the demonstration, rather than use two different scopes, I used a Tektronix 7904 which has two vertical amplifi­ers, one with bandwidth of only 100kHz and one with 200MHz band­ width. When the signal was plugged into the low bandwidth chan­nel, its rise time appeared to be quite modest at about 20 micro­seconds. On the second channel though, the picture was quite different, with the pulse having a very fast rise time plus over­shoot and severe undershoot. From this demonstration it can be seen that, even with low frequency signals, it takes a scope with a really wide bandwidth to reveal the true nature of many waveforms. While there are many good scopes on the market with a bandwidth of around 20MHz or so, much lab and workshop use requires models with 10 times that figure or considerably more. Design brief What must designers do to produce an analog oscilloscope with a band- Fig.1: sectional drawing of a high performance CRO tube, capable of wide bandwidth. The total acceleration potential is 24kV, with most of that applied by the spiral post deflection acceleration (PDA) anode. width up to, say, 500MHz and with a writing speed to match? Last month, we defined “Deflection Factor” as the voltage which must be applied to the deflection plates to produce one centi­ me­tre of trace on the screen. Designers aim to keep that voltage requirement as low as possible. The deflection factor can be reduced by lengthening the vertical deflection plates and by reducing their spacing. If the vertical deflection plates are made very long and spaced close together, they must also be curved to give clearance to the deflected beam. By this means, the deflection factor can be brought down to about 6.5 or 7V/ cm which is a great improvement. It means that the vertical amplifier only needs to develop about 56V of signal for 8cm of vertical deflection. Typically, the extra capacitance of long connecting leads is avoided by bringing the deflection plate connections straight out through hermetic metal-glass seals in the neck of the CRO tube. The deflection amplifier is mount­ed adjacent to keep the leads short. However, the inevitable effect of longer deflection plates and closer separation is increased capacitance, up to as much as 16pF. That becomes a real problem at very high signal frequencies. Writing speed & brightness While the deflection amplifiers may be able to deflect the beam sufficiently at high frequencies, you still need to be able to see the trace on the screen. This is a function of the “writing speed” of the CRO tube. This is defined as the fastest speed at which the trace can travel over the screen and still be clearly visible. Consider displaying the rising edge of a high-frequency pulse signal, which has a rise time of about 300 pico­ seconds. Let’s assume that the timebase is set to 200 picoseconds/division and that the trace moves up the rising edge of the pulse 4.5 divisions vertically in 400 picoseconds. This represents a writing speed about of 100 picoseconds /division or about 1/3 the speed of light! That might seem like an extreme set of conditions but one of the photos in this article portrays this event, taken from the screen of a Tektronix 7104. This has the fastest writing speed of any scope currently available. Achieving this extreme writing speed takes some very special technology. To give a less extreme example, say we wanted to display a 500MHz sine­ wave on the screen. The period for this signal (ie, time for one cycle) is just two nanoseconds. Accordingly, with a timebase setting of 1ns/div, the trace will take 10 nanoseconds to cross the 10cm wide screen. So five cycles of the signal will be displayed, repeatedly. The persistence characteristic of a P31 phosphor screen means that the light generated by each sweep lingers for about 300 microseconds after the beam has passed so it still lingers while subsequent sweeps occur. So the display you see always consists of many thousands of sweeps superimposed. The light from those thousands of superimposed sweeps may give acceptable brightness, provided the electron beam hits the phosphor with sufficient energy. Single shot display But what happens when you want to display a very fast non-repetitive pulse? In logic circuits and many electro­physical systems, signals must have fast risetimes, yet sometimes repeat only leisurely, maybe once a minute, or less. In such cases there is no superimposition of consecutive sweeps to add trace bright­ness. Each display of the signal fades away before the next occurs. The pulse actually photographed on the Tektronix 7104 analog oscilloscope referred to above occurred only once; May 1996  7 Fig.2: electron transit time is the time taken by an electron to pass through the vertical deflection plates from A to C. With low frequency signals (a), the signal voltage barely changes during the transit time, so sufficient beam deflection occurs. With very high frequencies applied to the vertical amplifier (b), the signal voltage can change back and forth while an electron is travelling from A to C. This effect places a frequency limit on CRO tubes using solid vertical deflection plates. a one-shot, never repeated. In such a case the electron beam must be so energetic that its collision with the phosphor generates suffi­ cient light immediately, in a few picoseconds. That’s what we mean by a CRO tube capable of a fast writing speed! A high energy beam means high electron velocity. That’s one reason why wide bandwidth oscilloscopes must use very high accel­eration volt­ ages. The second reason is that to show fine detail accurately on the screen, the trace must be very thin, as well as brilliant. The light spot must be small, as little as 0.1mm in diameter. That’s difficult to achieve because the negatively charged electrons in the beam repel each other, spreading the beam. The cure for that is to accelerate the electrons to as high a velocity as possible. Typically, we need an electron beam velocity of about 90,000 kilometres per second (nearly one third the speed of light). That electron velocity requires a very high accelerating potential of about 24kV. As discussed last month, there is a conflict between accel­eration voltage and deflection factor. Increasing the accelera­tion voltage by a factor of 12, (2kV up to 24kV) will drastically spoil the deflection factor. Previously, we were concerned about the acceleration voltage measured between the tube cathode and the region near the deflection plates. The solution is to use Post Deflection Acceleration (PDA). This is shown in Fig.1. In this case, the electron beam is initially accelerated to a low velocity of about 26,000km/second, using a 2kV potential between the cathode K and the acceleration grid G3. The average potential on the vertical deflection plates Y1,Y2, rests at about the same potential as G3. Those low velocity electrons passing between the vertical deflection plates are easily deflected. So the low deflection factor obtained by long curved deflection plates and close spacing is retained. Now comes the clever part: do most of the acceleration after the beam has been deflected. Fig.1 shows that cathode K is maintained at -1850V while the acceleration grid G3 is held at about +150V. That means that the acceleration field between cathode K and G3 is 2kV. After leaving the deflection plates, the electrons come under the attraction of the +22,150V PDA potential at the screen. But before acceleration, those elec- Fig.3: distributed vertical deflection plates overcome the upper frequency limitations imposed by transit time, by segmenting the plates into many small sections. Each plate section is fed signal from a tap on a delay line. The aim is to have the signal elec­trons fly past the deflection plates at the same speed as the deflection signal propagates along the delay line. 8  Silicon Chip An oldie but a goodie: the Tektronix 7904 oscilloscope consists of a mainframe and CRO tube capable of 500MHz bandwidth, with provision for two independent plug-in vertical amplifiers and two plug-in horizontal sweep timebase units. trons must be focussed into a fine stream. This happens at G2, the “focus grid”, which is a metal cylinder. After leaving the cathode, the electrons pass through a 1mm hole in the control grid (G1), which acts as a point source. To achieve focus, we critically control the shape and strength of the electric field between the cathode, focus grid G2 and accelera­tion grid G3. Electrostatic lens The G2-G3 region is an electrostatic lens, with its focal length altered by changing the ratio of the potentials on these two electrodes. Any electrons which happen to be on the centre line when passing through G2 and G3 are equally affected by all parts of the fields here, so they pass down the centre-line of the beam. But electrons which are off centre line in passing through the region between (A) and (B), encounter the G3-G2 electric field which has a component of force repelling those electrons back towards centre. Because G2 is only a few hundred volts more positive than the cathode, the electrons near (A) are moving relatively slowly, so their path is easily affected by the fields. Thus, their track bends easily as at (B). But the path of such electrons must bend again, between (B) and (C), to prevent overshooting the centreline. This is achieved by the component of the G3-G2 field between (B) and (C), where the field is facing in the opposite direction to that between (A) and (B). Because G3 is 2kV more positive than the cathode, by the time the electrons have passed (B) and (C) they have accelerated up to 26,000km/second. So their path is bent less easily at (C) than at (B). Therefore, the bending of the path back to centre beyond (C) is gradual and progressive. The G3-G2 potential difference can be adjusted by focus control VR2 to force all electrons to come together at one small point upon reaching the phosphor at the screen. Due to the non-axial attitude of some electrons entering the electrostatic lens at (A) in Fig.1, focusing suffers from astig­matic error, causing the spot on the screen to form a tiny ellipse, rather than a circle. This is minimised by the astigma­tism control, VR3. This sets up a cylindrical electrostatic lens effect between G3 and the vertical deflection plates (Y1,Y2). Proper adjustment is obtained when the spot on screen is the best approximation of a tiny circle. Moving beyond the deflection plates, the electron beam accelerates rapidly, attracted by the Post Deflection Accel­ era­ tion (PDA) voltage of +22150V. The PDA aquadag electrode inside the screen is deposited in the form of a spi- ral which helps give a uniform electric field over the entire screen. For this and a number of other reasons, high performance CRO tubes have a very thin layer of aluminium deposited over the phosphor compounds inside the screen. The electron beam pene­ trates this aluminium to reach the phosphor. Beam electrons penetrate the aluminium layer, excite the phosphor compounds, then use the aluminium as a pathway to flow away to the aquadag layer and to the high voltage PDA supply terminal. This prevents charge building up on the screen; an important feature. By contrast, CRO tubes using acceleration voltages below 10kV often do not have an aluminium screen backing, because penetration of that metal would absorb too much of the available electron energy. Without this aluminium layer, the electrons arriving on the screen phosphor must leak across the luminescent material to reach the aqua­dag. This in turn means that, because of the poor electrical conductivity of phosphor compounds, a large number of migrating electrons will be found on the phosphor and the inner side of the front glass screen. As a result, the screen acquires a negative charge. Such a charge is undesirable, as it partially repels new electrons arriving in the beam, reducing the beam current and thereby the screen brightness. Reflecting the light The aluminium layer also acts as a reflector for the phosphor. Without it, light generated within the phosphor not only radi­ates out through the front glass but also back inside the tube, where it is wasted. In fact, some 6090% of the luminance can be wasted in this manner. An aluminium layer can reflect this light back to the screen, thereby approximately doubling the trace brightness. The aluminium backing also absorbs any unwanted negative ions which may arrive at the screen. Ions are (relatively) heavy charged atoms emitted by the cathode along with the electron beam. Any heavy ions reaching the phosphor will cause its rapid deterioration by ion-burn. Aluminising the screen prevents this problem. As well, the aluminium layer helps dissipate heat gener­ated by the impact of electrons with the phosphor May 1996  9 Oscilloscope bandwidth has a big affect on the signal displayed. Here pulses of current are being measured by the low bandwidth amplifier of a Tektronix 7904 oscilloscope. Although the pulse repetition rate is only about 4kHz, notice the severe rounding of the displayed waveform. grains. Again, this helps reduce longterm deterioration of the phosphor. Not all the effects are good though and there are some disadvantages. For a start, electrons in the beam lose 3- 5keV (energy) in penetrating the al- This view shows the same waveform as at left but displayed via the 200MHz vertical amplifier in the Tektronix 7904. Notice the pulse overshoot and severe undershoot, features which are com­pletely unseen on the lower bandwidth amplifier. uminium layer. Making the aluminium thinner would not help, as then the metal would be insufficiently reflective to light. The usual remedy is to raise the beam energy, by increasing the acceleration voltage. The aluminium backing also tends to broaden the trace seen on screen, as a side effect of the reflection of light back through the phosphor. This effect is ameliorated by making the phosphor no thicker than the electron penetration depth and using phosphor compounds having micro­ grain crystals. Another effect of the aluminium backing is to reduce the apparent contrast of the screen display. This is because ambient room light passes through the glass screen and the transpar­ent phosphor and is then reflected by the aluminium layer, to back-illuminate the whole screen. The usual remedy is to make the tube front of thick dark glass. The trace illumination then loses its bright­ ness once in passing through the glass, while any ambient room light reflected by the alumin­ium layer loses its brightFig.4: a patented “microchannel plate”, ness twice, because it makes two used in the Tektronix 2467B analog trips through the dark glass. This oscilloscope, acts as an electron multiplier technique is also used in computimme­diately before the phosphor. This er monitor and TV picture tubes. can increase the intensity of a dim The aluminium backing layer waveform a thousand times, enabling a must be thick enough to act as a very high speed trace to be clearly visible. 10  Silicon Chip light reflector, yet thin enough to allow the electron beam to penetrate to excite the phosphor. For tubes using overall accel­eration potentials between 10kV and 25kV, an aluminium backing layer 100 nanometres thick is satisfactory (100 nm = 1/4 wave­length of visible violet light). As an alternative to using very high acceleration voltages, the Tektronix 2467B 400MHz analog oscilloscope uses a patented “Bright Eye” display, a micro­channel plate behind the screen phosphor. This acts as an electron multi­ plier to increase the intensity of the trace of a dim waveform up to a thousand times. With this option, a single pulse at 500 picoseconds per division sweep speed is quite visible. High frequency limits The above techniques are very effective for increasing bandwidth and maintaining a good deflection factor and high writing speed but there are still limits. Reducing the vertical deflec­ tion factor down to 6.5V/cm, by using elongated, close-spaced deflection plates, is sufficient for analog oscilloscopes for frequencies up to 150MHz. However, the resultant increase in capacitance between the plates is prohibitive for higher frequencies, because plate charging current drawn from the deflection amplifier rises pro­ portionally to the signal frequency. At 500MHz, for example, the impedance Here, a non-recurrent pulse with a rise time of 350 picoseconds and an amplitude of 50 millivolts is portrayed on the screen of a Tektronix 7104 analog oscilloscope, at a timebase speed of 200 picoseconds/ division. This is possible only if the scope has an extremely wide bandwidth and a very fast writing speed. of a 16pF capacitor is only 20Ω and when driven by 50V or so from the deflection amplifiers, the charging current is quite consid­erable – several amps, in fact. This is a very difficult requirement at 500MHz. Worse still, above 150MHz a new effect called “electron transit time” raises its ugly head. This places an absolute upper limit on the frequencies which can be displayed on an oscillo­scope tube. Fig.2 illustrates the passage of a beam electron on its way to the screen. At low frequencies, in Fig.2(a), the potential on Y1 is positive all the time that the electron is passing through points A and B and C, so it is continually deflected upwards, as should occur. But at frequencies in the 150-1000MHz range, the signal voltage applied to the vertical deflection plates can pass through perhaps half a cycle during the time that an electron travels from A to C – see Fig.2(b). In Fig.2(b), at point A the electron is attracted upwards, at B it is heading back down, and at C it has straightened out again so the net effect is very little deflection. The result is that signals above a certain frequency cannot be displayed, no matter how the vertical amplifier is designed. This is a fundamental frequency limitation of the CRO tube itself, caused by changes in deflection signal polarity during electron transit time. The long deflection plates now defeat their original purpose which was to improve the deflection factor. Distributed deflection plates So there are two problems to be overcome with long curved deflection plates: electron transit time and high capacitance. The answer lies in the use of distributed deflection plates, as shown in Fig.3. Here the vertical deflection plates are segmented into 44 sections. The leftmost upper and lower plate segments Y1 and Y2 are supplied with signal from the vertical deflection amplifier. Subsequent deflection plate sections Y3-Y43 and Y4-Y44 all tap onto junctions of a delay line. This line consists of the series inductances L1-L41 and L2-L42, together with the distributed shunt capacitance of all the deflection plate segments. In one Tektronix design, each section (L1, L2, etc) of series inductance consists of five turns of wire. Each plate segment is 3.175mm long, with 1mm spacing between each segment. The inductive coils of the delay line and the plate segments are mounted on glass rods within the neck of the CRO tube. In Fig.3, deflection signals from Q1, Q2 travel down the line from left to right. Remember that here we are dealing with frequencies up to the UHF region, so signal reflections must be avoided. Therefore, impedance matching of source, line and load is mandatory. To achieve this, resistors R1 & R2 reduce the output impedance of Q1, Q2 to match the characteristic impedance of the delay line. Then resistors R3 & R4 terminate the delay line in its characteristic impedance to prevent end reflections. The load on the deflection amplifier Q1, Q2 is now the characteristic impedance of the delay line, about 900Ω, which is easily driven. Four leads from the deflection plate assembly at H, K, M, N are brought out through metal-glass seals in the CRO tube neck, for connection to resistors R1, R2, R3 & R4 and the deflection amplifier which is mounted adjacent. All leads are as short as possible to minimise inductive impedance at such high frequencies. Signal propagation velocity In the distributed deflection system shown in Fig.3, the aim is to have the electrons whiz through the deflection plate assembly at the same velocity as the deflection signal propagates along the line from Y1, Y2 down to Y43, Y44. Such matching of velocities results in full beam deflection at all frequencies, because each electron passing between the plates is affected by the same signal deflection voltage for the entire transit time from A to C. Unfortunately, the design of the deflection assembly and delay line results in a signal propagation velocity which is not quite constant over the entire frequency range. Velocity mismatch will eventually occur at high frequencies, resulting in reduced deflection. Early distributed deflection plates had the transmission line components outside the tube. This necessitated too many metal-glass seals for the connections through the tube neck. To overcome this problem, Hewlett Pack­ ard researchers developed a technique called “Helical Distributed Deflection Plates”. This eliminates external components since the required inductance and capacitance are built in. Each helix is equivalent to a lumped-parameter transmission line feeding the distributed plates. Each helix is a continuous strip of metal, mounted rigidly to glass rods which also support the electron gun assembly. Only four feed­ throughs in the tube neck are needed, to connect to the vertical deflection amplifier and the terminating resistors. Acknowledgements Thanks to Tektronix Australia, Philips Scientific & Industrial and Hewlett Packard for data and illustrations. Also thanks to Professor David Curtis, Ian Hartshorn, Ian Marx and Dennis Co­bley. References (1) Tektronix Aust: “XYZ’s of Oscilloscopes” and Application Notes. (2) Hewlett Packard Aust: R. A. Bell “Application Note 115”. (3) Philips/Fluke USA: “ABC’s of Oscilloscopes”. (4) Van der Ziel A. “Solid State Physical SC Electronics”, Prentice Hall, NJ. May 1996  11 ALL REFURBISHED PRODUCTS CARRY MINIMUM 90-DAY WARRANTY ● COUNTRY/INTERSTATE: FREE CALL 1800 680680 ● ALL REFURBISHED PRODUCTS CARRY A MINIMUM 90-DAY WARRANTY ● CONTACT MA HEWLETT PACKARD 334A Distortion Analyser HEWLETT PACKARD 200CD Audio Oscillator • measures distortion 5Hz600kHz • harmonics up to 3MHz • auto nulling mode • high pass filter • high impedance AM • 5Hz to 600kHz • 5 ranges • 10V out • balanced output detector HEWLETT PACKARD 8614A UHF Sig. Gen. HEWLETT PACKARD 8640B Sig. Generator HEWLETT PACKARD 654A Test Oscillator • 0.5-1024MHz freq. range • int. audio osc. 20Hz-600kHz • 800-2400MHz freq. range • select. functions: CW, lev­elled • reverse power protection • internal phase lock/synch. output, sq. wave mod., ext. • +19 to -145 dBm output AM, FM & pulse mod. power range • output attenuation 0 to -127 • low SSB phase noise dBm • sig. gen. can be phase locked • digital frequency readout • 10Hz - 10MHz freq. range • +11dBm to -90dBm output level in 1dB steps • calibrated impedance 50Ω • + 75Ω unblanced; 135Ω, 150Ω + 600Ω balanced distortion <at> 1-10MHz > 34dB below fundamental $795 $79 $525 $3995 $695 HEWLETT PACKARD 3336B Synthesizer/ Level Generator HEWLETT PACKARD 3586B Selective Level Meter HEWLETT PACKARD 1740A Oscilloscope HEWLETT PACKARD 1710A Oscilloscope HEWLETT PACKARD 141T/8552/8555A Spectrum Analyser • variable • Frequency coverage 10Hz- • Frequency coverage 50Hz20.9MHz 32.5MHz • Precise frequency & spectral • Excellent measurement purity 1 Microhertz res up accuracy ±.2dB to 100kHz • Autoranging & automatic • Absolute amplitude accuracy calibration ±.05dB at 10kHz • SSB mode provides • Unique levelled sweep demodulation capability capabilities • HPIB programmable $1650 Austron 2010B Oscillator 1MHz........................... $400 AWA A215-2 Transmission Measuring Set .......... $175 AWA E221 Level Meter ........................................ $650 AWA F240 Distortion & Noise Meter ................... $375 AWA G231 Audio 10Hz-30KHz ............................ $495 AWA G250 Test Oscillator 10Hz-610kHz .............. $525 AWA G251 Level Oscillator 50Hz-2MHz .............. $600 BECKMAN L10A Megohmeter ........................... $1400 EATON 2075 Noise Gain Analyser ...................... $6500 ESI DB62 Decade Box ......................................... $350 EUROCARD 6 Slot Frames ..................................... $40 FLUKE 408B 6kV 20mA Power Supply................. $800 GR 1381 Random Noise Generators .................... $160 HP 204C Oscillator............................................... $225 HP 332A Distortion & Noise Meter ...................... $495 HP 353 Audio Attenuator...................................... $170 HP 400EL AC Voltmeter ....................................... $195 HP 403B AC Voltmeter......................................... $150 HP410C Multimeter ............................................. $295 HP 427A Voltmeter ................................................ $95 HP 432A Power Meter C/W Head & Cable ........... $825 HP 435A Power Meter.......................................... $495 HP 652A Test Oscillator ....................................... $375 HP 1200B Oscilloscope DC-500kHz..................... $425 HP 3400A RMS Voltmeter (1mV - 300V)............. $475 HP 3406A Broadband Sampling Voltmeter .......... $575 HP 3455A 61/2 Digit DVM ................................... $650 HP 3490A 51/2 Digit Digital Multimeter ............... $295 HP 3555B Transmission & Noise Meas. Set......... $325 HP 4204A Oscillator 10Hz-1MHz ......................... $350 HP 4260 LCR Bridge............................................ $295 HP 5245L/5253/5255 Electronic Counter ............ $550 HP 5300/5302A Universal Counter to 50MHz ...... $195 HP 5326B Universal Timer/Counter/DVM ............ $295 HP 5328A Universal Counter to 500MHz.............. $695 HP 5335A 200MHz Universal Counter ............... $4500 HP 6002 50V/10A Power Supply........................ $1495 HP 8005A Pulse Gen. 20MHz 3-Channel ............. $350 HP 8690B/8698/8699 400KHz-4GHz Sweep Osc ..................................................... $2450 HP 8690B/8707A/8706A 4GHz-18GHz Sweep Osc ..................................................... $1500 MARCONI TF2006 FM Sig. Gen. 1000MHz........... $800 MARCONI TF2300A FM/AM Mod Meter 500kHz-1000MHz ............................................ $450 MARCONI TF2500 AF Power/Volt Meter .............. $180 MOTOROLA Sinad Meter ..................................... $325 NORTHEAST 4002A Transmission Meas. Set ...... $600 RACAL DANA 9500 Universal Timer/Counter ...... $350 SD 6054B Freq. Counter 20Hz-18GHz ............... $2500 SD 6054C Microwave Freq Counter 1-18GHz .... $2000 SD 6152A 512MHz Counter/Timer....................... $350 TEKTRONIX CFC 100MHz Freq. Counter.............. $270 TEKTRONIX CDC 175MHz Univ. Counter.............. $405 TEKTRONIX FG504/TM503 40MHz Fun. Gen...... $1290 TEKTRONIX 067-0502-01 Scope Calibrator......... $550 TEKTRONIX 464 Storage Scope DC-100MHz..... $1400 TEKTRONIX 465 Oscilloscope DC-100MHz ....... $1190 TEKTRONIX 475 Oscilloscope DC-200MHz ....... $1550 TEKTRONIX 485 Oscilloscope DC-350MHz........ $2400 TEKTRONIX 602 XY Display ................................ $350 TEKTRONIX 7603NIIS Scope DC-65MHz ............ $650 TEKTRONIX 7904 Oscilloscope DC-500MHz ..... $2800 W&G SPM3 Selective Level Meter C/W; W&G PS3 Signal Generator 300Hz-612kHz (pr)........ $450 WAVETEK 143 Function Generator 20MHz .......... $475 WAVETEK 907 Signal Generator 7-11GHz.......... $1600 • DC-100MHz bandwidth • 2-channel display mode • trigger - main/delay sweep • coupling AC, DC, LF & HF rej $990 • HP 1741A var. persistence expansion to full screen model available $1325 $1250 $3995 BALLANTINE 323 AC Voltmeter BALLANTINE 6310A Test Oscillator BALLANTINE 3440A Millivoltmeter $1450 BALL EFRATOM M100 Rubidium Frequency • factory cal certs • perfect for ISO accreditation • GPS applications • ruggedised military design • • • • • • • • • • • • • bandwidth DC-150MHz • trigger source channel A, B or composite • delay timebase with single sweep • main intensify timebase persistence storage mainframe internal graticule eliminates parallax error IF section 10Hz minimum bandwidth log & linear sens. control absolute amplitude accuracy to ±1.6dB direct coax input to 18GHz high res. 100Hz bandwidth true RMS response including harmonics + crest factors 300µV to 300V full scale 1% basic accuracy freq. range 2Hz - 25MHz full field portability fast response without thermal lag $2950 • true RMS • • • • • 2Hz-1MHz freq. range • digital counter with 5 digit LED display • output impedance switch selectable • output terminals fuse protected $425 response to 30mV frequency coverage 10kHz-1.2GHz measurement from 100µV to 300V accuracy ±1% full scale to 150MHz list price elsewhere over $5500 $350 $795 NEW EQUIPMENT Affordable Laboratory Instruments The name that means quality PS305 Single Output Supply • • • • • • • • SSI-2360 60MHz Scope 60MHz dual trace, dual trigger Vertical sens. 1mV/div. Maximum sweep rate 5ns/div. Component tester Delay sweep, single sweep Two high quality probes $1110 + Tax • • • • PS8203 Digital Dual Supply 0-30V & 0-5A Load & line regulation <=0.01%+3mV Ind. & tracking modes Low ripple output Constant current voltage 2 x 3.5 dual purpose digital voltmeters • PS303D Dual Output Supply • 0-30V & 0-3A • • Four separate output meters • Independent or Tracking modes • Low ripple output $420 + Tax PS305D Dual Output Supply 0-30V and 0-5A $470 + Tax 0-30V & 0-5A $300 + Tax PS303 Single Output Supply PS8112 Single • 0-30V & 0-3A Output Supply • Two output meters • Constant I/V • 0-60V & 0-5A $490 + Tax $265 + Tax Audio Generator AG2601A Pattern Generator CPG1367A $640 + Tax PS8201 Digital Single Supply digital display • 0-30V & 0-5A • Load & line regulation • Constant current analog display <=0.01%+3mV • Constant voltage $320 + Tax • 10Hz-1MHz 5 bands • Colour pattern to test PAL • High frequency system TV circuit stability • Dot, cross hatch, vertical, • Sine/Square output horizontal, raster, colour $245 + Tax $275 + Tax ● ALL REFURBISHED PRODUCTS CARRY A MINIMUM 90-DAY WARRANTY ● CONTACT TEKTRONIX 100kHz to 1800MHz Spectrum Analyser System Consisting of: 7613 7L12 7A17 TR501 TM503 WAVETEK Signal Generator/Deviation Meter Model 3000-200 incorporates a complete 1 to 520MHz FM, AM and CW Signal Generator with an FM Deviation Meter in one convenient instrument. Storage Mainframe 1.8GHz Spectrum Analyser Plug-In Amplifier 1.8GHz Tracking Generator 3 Slot Mainframe $4250 Please phone or fax today for a full specification sheet incorporating all the system’s features. SPECIAL OFFER: DM501 MULTIMETER ONLY $100 EXTRA Frequency Range: 1-520MHz selectable in 1kHz steps; 1kHz resolution; frequency programmable via rear-panel connector. RF Output Level: +13dBm to -137dBm (1V to .03µV RMS); output level continuously adjustable in 10dB steps and with an 11dB vernier; impedance = 50 ohms. RF Output Protection: resettable RF circuit breaker; RF trip voltage = 5V RMS nominal; maximum reverse power = 50W. Spectral Purity: harmonic output > 30dB below fundamental from 10-520MHz; residual AM > 55dB below carrier in a 50Hz to 15kHz post-detection bandwidth; residual FM <200Hz in a 50Hz to 15kHz post-detection bandwidth (100Hz typical). Amplitude Modulation: internal 400Hz and 1kHz ±10%; external DC to 20kHz; range 0-90%; distortion 3% to 70% AM at 1kHz. Frequency Modulation: internal 400Hz and 1kHz (±10%); 50Hz to 25kHz; accuracy ±500Hz on x1 range, ±5kHz on x10 range; distortion 4% at 1kHz. FM Deviation Meter: frequency range 30-500MHz; input level range 10mV to 5V RMS; impedance 50 ohms; deviation range 0 to ±5kHz, 0 to ±50kHz $1250 IMPORTANT: GARAGE SALE! This is our first ever Garage Sale and represents an opportunity to purchase a whole range of “as traded” and imported stock that has been accumulated over years. Some equipment is tested, others “as is” . . . You’re sure to find a bit of everything mechanical, etc. INTERSTATE/COUNTRY BUYERS: Send or phone for lists . . . All interstate lists returned to us for this sale will be opened on 1st May 1996 and drawn from a hat. First opened letter gets whatever – it could not be fairer for people out of town. All successful customers will be notified. PRICES START FROM $1.00 LOCAL BUYERS: LOCAL SALE SUNDAY 5TH MAY 1996 – 9AM to 3PM. Located at warehouse 26 Fulton St, South Oakleigh. Phone for further details. 100MHz Tektronix 465M Oscilloscope 2-Channel, Delayed Timebase VERTICAL SYSTEM Bandwidth & Rise Time: DC to 100MHz (-3dB) and 3.5ns or less for DC coupling and -15°C to +55°C. Bandwidth Limit Mode: Bandwidth limited to 20MHz. Deflection Factor: 5mV/div to 5V/div in 10 steps (1-2-5 sequence). DC accuracy: ±2% 0-40°C; ±3% -15-0°C, 40-55°C. Uncalibrated, continuously variable between settings, and to at least 12.5V/div. Common-Mode Rejection Ratio: 25:1 to 10MHz; 10:1 from 10-50MHz, 6cm sinewave. (ADD Mode with Ch 2 inverted.) Display Modes: Ch 1, Ch 2 (normal or inverted), alternate, chopped (250kHz rate), added, X-Y. Input R and C: 1MΩ ±2%; approx 20pF. Max Input Voltage: DC or AC coupled ±250VDC + peak AC at 50kHz, derated above 50KHz. HORIZONTAL DEFLECTION Timebase A: 0.5s/div to 0.05µs/div in 22 steps (1-25 sequence). X10 mag extends fastest sweep rate to 5ns/div. Timebase B: 50ms/div to 0.05µs/div in 19 steps (1-2-5 sequence). X10 mag extends maximum sweep rate to 5ns/div. Horizontal Display Modes: A, A Intensified by B, B delayed by A, and mixed. CALIBRATED SWEEP DELAY Calibrated Delay Time: Continuous from 0.1µs to at least 5s after the start of the delaying A sweep. Differential Time Measurement Accuracy: for measurements of two or more major dial divisions: +15°C to +35°C 1% + 0.1% of full scale; 0°C to +55°C additional 1% allowed. TRIGGERING A & B A Trigger Modes: Normal Sweep is triggered by an internal vertical amplifier signal, external signal, or internal power line signal. A bright baseline is provided only in presence of trigger signal. Automatic: a bright baseline is displayed in the absence of input signals. Triggering is the same as normal-mode above 40Hz. Single (main timebase only): The sweep occurs once with the same triggering as normal. The capability to re-arm the sweep and illuminate the reset lamp is provided. The sweep activates when the next trigger is applied for rearming. A Trigger Holdoff: Increases A sweep holdoff time to at least 10X the TIME/DIV settings, except at 0.2s and 0.5s. Trigger View: View external and internal trigger signals; Ext X1, 100mV/div, Ext -: 10, 1V/div. Level and Slope: Internal, permits triggering at any point on the positive or negative slopes of the displayed waveform. External, permits continuously variable triggering on any level between +1.0V and -1.0V on either slope of the trigger signal. A Sources: Ch 1, Ch 2, NORM (all display modes triggered by the combined waveforms from Ch 1 and 2), LINE, EXT, EXT :-10. B Sources: B starts after delay time; Ch 1, Ch 2, NORM, EXT, EXT :-10. X-Y OPERATION Sensitivity: 5mV/div to 5V/div in 10 steps (1-2-5 sequence) through the vertical system. Continuously variable between steps and to at least 12.5V/div. MACSERVICE PTY LTD $900 Optional cover for CRT screen – $35 X Axis Bandwidth: DC to at least 4MHz; Y Axis Bandwidth: DC to 100MHz; X-Y Phase: Less than 3° from DC to 50kHz. DISPLAY CRT: 5-inch, rectangular tube; 8 x 10cm display; P31 phosphor. Graticule: Internal, non-parallax; illuminated. 8 x 10cm markings with horizontal and vertical centerlines further marked in 0.2cm increments. 10% and 90% markings for rise time measurements. Graticule Illumination: variable. Beam Finder: Limits the display to within the graticule area and provides a visible display when pushed. Australia’s Largest Remarketer of Test & Measurement Equipment 20 Fulton Street, Oakleigh Sth, Vic, 3167. Tel: (03) 9562 9500; Fax: (03) 9562 9590 **All illustrations are representative only. Products listed are refurbished unless otherwise stated. Countr Interstate y & Call Free Ca ers 1800 680 ll 680 T MACSERVICE P/L FOR ALL YOUR FLUKE REQUIREMENTS ●   FREE CALL: 1800 680680 REFURBISHED PRODUCTS: MINIMUM 90-DAY WARRANTY ● CONTACT MACSERVICE FOR ALL YOUR FLUKE REQUIREMENTS ACSERVICE FOR ALL YOUR FLUKE REQUIREMENTS ●   FREE CALL 1800 680680 ● ALL FIBRE OPTIC TWO-WAY INTERCOM Two assembled boards, two loudspeakers and a single optical fibre cable between them produce a duplex intercom which will give hands-free communication. By LEO SIMPSON Here’s your chance to experiment with fibre optic cable and circuitry. This communications link is full duplex, meaning both parties can talk at the same time, just as on the telephone. Two boards are linked by one optical fibre to provide a voice quality hands-free link. These days, optical fibres are widely used in telecommunications and in computer local area networks (LANs). In both of these cases though, the information transmitted is digital. But optical fibres will transmit analog signals just as well, as this project demonstrates. Two identical boards are used and each one accommodates one half of the duplex link. Each has an electret 14  Silicon Chip microphone and preamplifier driving a red LED which shines down the cable. At the other end of each respective cable is a Darlington phototran-sistor which receives the modulated light and turns it into a fluctuating DC signal which is amplified and fed to a small loudspeaker. No buttons or switches need to be pushed to speak. You just speak and you will be heard at the other end. Each PC board has a call button which you press to alert the party at the other end that you wish to “trip the light fantastic”. Each board can be run from a 9V battery or AC or DC plugpack. In fact, this fibre optic kit does not use ordinary LEDs or phototransistors. The red LED specified is actually a Motorola MFOE76 fibre optic emitter, in a special purpose housing designed to mate with low-cost (100 micron core) plastic fibre using the common FLCS connector. Similarly, the specified Darlington phototransistor is a Motorola MFOD73 photodetector, again intended to mate with plastic fibre via its integral FLCS connector. The really tricky part of this project is not even shown on the circuit of Fig.1. It involves combining the optical transmit and receive signals of one board into one cable and then separating the optic receive and transmit signals at the other end, on the second board. The two optical signals are combined in the optical equivalent of a directional coupler. This takes the form of a Y-piece with two short lengths of optical fibre cut at an acute angle and then joined and held together via a length of heatshrink tubing. In the tail of the Y-piece is a socket which accepts the common cable connection. Circuit description Fig.1 shows the circuit for one of the duplex channels but remember that the sender and receiver sections are actually on separate boards. The electret microphone is biased by the 22kΩ resistor and its audio signal is amplified by op amp IC1a which has a gain of 23. Its output signal is fed to IC1b which, together with transistor Q1, provides a current drive signal to LED1, the MFOE76. When the call pushbutton is press­ ed, capacitor C4 and resistor R7 apply positive feedback around IC1a so that it oscillates audibly. This becomes the calling tone, heard in the speaker at the other end. On the receiver side, phototransistor Q2 is AC-coupled to op amp IC1c, connected as a unity gain buffer. It drives volume control VR1 and then IC2, an LM386 power amplifier which drives the loudspeaker via a 47µF capacitor. Power to the circuit can come from a 9V or 12V battery, via diode D1 or via a 9V or 12V AC or DC plugpack, via bridge rectifier BR1. Battery operation is not recommended by the way – this circuit would “eat” batteries. The transmitter LED and the power amplifier both consume more current than can be economically provided by a standard 9V battery. Following diode D1 or bridge BR1, the DC supply is regulated to 9V by a Fig.1: the intercom is an analog-only circuit, with no digital processing. The electret microphone is amplified by IC1a, while IC1b and Q1 together provide current drive to the fibre optic emitter, LED1. The optical signal is sent down the cable to fibre optic detector Q2 and its associated audio amplifier IC2. May 1996  15 16  Silicon Chip Fig.2 (facing page): this diagram shows how the boards are connected together optically to provide the full duplex intercom. 78L09 three-terminal regulator. Note that one op amp in each LM324 is unused; pin 14 is connected to pin 13 while pin 12 is not connected. Construction As noted above, two identical PC boards are required for this project. Both should be assembled completely before making any optic fibre cable connections. Fig.3 shows the component layout. We suggest installing the resistors first, followed by the capacitors, diodes, transistors, three terminal regulators and trimpots. Do not confuse the three terminal regulators with the BC547 transistors; they come in the same TO-92 package. Make sure that all the electrolytic capacitors and semiconductors are installed the right way around. IC sockets are included in the kit and should be installed with the correct orientation; upside down with respect to the board labelling. Note that our published circuit (Fig.1) and PC board layout (Fig.3) are different from that indicated in the information supplied in the kit. Specifically, we have changed C2 from 0.1µF to 2.2µF, R8 from 100Ω to 1kΩ and R7 to 390kΩ. These changes must be made on both boards. Fibre optic connections Terminating the optical fibre cable Y-piece into the FLCS connectors can be a fiddly process if they have already been soldered to the PC boards. Therefore we suggest that the two legs of the supplied Y-piece be pushed into the respective FLCS connectors and the cylindrical sleeves screwed on; do not overtighten. This done, solder the FLCS connectors to the boards. The Y-piece should be anchored to the board with a wire link which is adjacent to the bridge rectifier, BR1. The link should be inserted through the board to anchor the Y-piece and the wire ends twisted underneath, not soldered. If they are soldered, there is a risk of heat damage to the Y-piece. Now you are ready to wire the two boards together, along with the speakers and AC plugpacks, as shown in the diagram of Fig.2. You will be supplied with a length of optical fibre and each end should be cut cleanly and squarely with a utility knife. Push one end of the cable into the Y-connector on one board and the other end into the remaining Y-connector on the other board. Note that each speaker should ideally be mounted in a small box to baffle it. Operating the speakers without any baffling gives a tinny sound, easily subject to overload. The speakers should also be kept as far as possible from the electret microphones, otherwise acoustic feedback, in the form of severe squealing, will result. Adjust volume control VR1 on each board for a comfortable listening level. Check that each call button produces a tone in the speaker for the other board. Now you can sit back and have hands-free communication via optical SC fibre! PARTS LIST for duplex link (two boards required) 2 PC boards (DIY kit 39) 1 length of plastic fibre optic cable 2 fibre-optic Y connectors (see text) 2 14-pin IC sockets 2 8-pin IC sockets 4 2-way PC-mount terminal blocks 2 2.1mm DC power sockets 2 momentary contact PC-mount pushbutton switches (S1) 2 76mm 8Ω loudspeakers Semiconductors 2 LM324 quad op amps (IC1) 2 LM386 power amplifiers (IC2) 2 BC547 NPN transistors (Q1) 2 MFOE76 fibre optic emitters (LED1) 2 MFOD73 fibre optic Darlington detectors (Q2) 2 78L09 3-terminal 9V regulators (REG1) 2 1N4148 diodes (D1) 2 W02 bridge rectifiers (BR1) 2 electret microphone inserts (MIC) Capacitors 2 100µF 25VW PC electrolytic 2 47µF 25VW PC electrolytic 10 10µF 25VW PC electrolytic 2 2.2µF 25VW PC electrolytic 4 0.1µF monolithic 4 .01µF monolithic or ceramic 2 .001µF ceramic Resistors (0.25W, 5%) 2  680kΩ 4  22kΩ 2  390kΩ 2  10kΩ 2  220kΩ 6  1kΩ 6  100kΩ 2 100kΩ preset trimpots (VR1) Kit availability Fig.3 (above): the parts layout. Note that the values we show for C2, R7 and R8 are different from those appearing on the boards supplied in the kit. This duplex fibre optic intercom is designed and produced by DIY Electronics, of Hong Kong. The kit is available in Australia from Ozitronics, 24 Ballandry Crescent, Greensborough, Vic 3088. Phone/ fax (03) 9434 3806. Their price for the kit is $116.85 plus $4.00 postage and packing. They also have a simplex kit (one way communication) priced at $41 plus $4.00 postage and packing. May 1996  17 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Own a 286 or 386? Make-it a 486! Own a 486? Make-it a 586! Computer Upgrades Made Easy By ROSS TESTER So you’ve decided it’s time to replace or upgrade your computer. It’s not your choice to pension off old faithful but that impressive piece of wizz-bang electronics you purchased only a couple of years ago simply isn’t up to the rigours of today’s computing. A lot of new software, for example, is designed specifically for Windows 95 or Windows NT. Try running that on your slow old 386 and see how far you get! Even though most software has claims that it will work on a 386 system, it’s like asking a Clydesdale to line up for the Melbourne Cup. That old PC simply has to go . . . But go where? The bloke at the store tells you that as a trade-in your 286, 386 or even 486 computer is worth maybe a tenth of what you paid for it – probably less. Then there’s all your existing software and operating system. You’re comfortable with them. And despite what the bloke is telling you about the value of your system, you know that the hard disc(s), CDROMs, floppy drives, the various cards you’ve installed and even the memory chips are perfectly adequate. What a shame to get rid of them for no good reason! There must be another way. Then it dawns on you. Instead of buying 22  Silicon Chip a new computer you could go down the “new motherboard” route. This is a perfectly viable option for many people. Because the vast majority of IBM standard personal computers share just that, a common standard, it is a relatively easy task to change a mother­board. The mounting holes will almost certainly line up, the expansion slots will match with the cut-outs in the case; even the power and other cabling has fairly well standardised connections. Is it really viable? Looking through the pages of Silicon Chip, we see new Pentium motherboards advertised for between about $250 and $1300, depending on the speed and the “optional extras”. Sometimes those “optional extras” include the CPU! If you do need the CPU, it’s going to set you back another $130 to $1100, again depending on the speed required and the brand. So for about six hundred dollars or so and maybe an hour or two’s work, you could replace the motherboard in your computer with a reasonably fast 586 motherboard and processor chip and have effectively a brand new machine, right? Well, the answer is yes . . . and no. We’ve already said that most fittings will be standard. However, the problems start with all those things you didn’t want to change, the very reason you considered buying a motherboard instead of a whole new computer. Take memory, for example. When you bought your computer a couple of years ago, the chances were the memory was either individual chips (probably 41256 ICs) or, alternatively, it might have used SIMMs (single in-line memory modules). SIMMs contain either three or nine chips, which plug vertically into sockets on the motherboard. Unfortunately for you, these days no-one uses individual RAM chips and even SIMMs have changed. Instead of 30-pin SIMMs most new motherboards use 72-pin SIMMs. So your memory will have to be upgraded too. And using the industry “rule of thumb” of about $70 per megabyte, it’s clear that you’re up for much more money than you thought. Next come all those add-on cards. Some will be compatible, some not, because the expansion slots may be different. True, most motherboards still provide a limited number of the old-style 8 or 16-bit slots but there may not be enough. You may have to upgrade disc controllers, video controllers, CD ROM cards, maybe even the I/O card itself. Ah! – the I/O card. Do you have one? Perhaps not: many manufacturers placed the I/O components on the motherboard itself. But you’re replacing the motherboard and . . . As you can see, it is not as simple as might first appear. Of course, it is possible but for the average person, it can be a little daunting. So what is the alternative? Back to buying a new machine? Make-it Chips Enter a lifesaver in the form of a new chip called Make-it from, surprise surprise, the USA. Believe it or not, this chip turns your current 386 (or even a 286) into a 486 computer, with dramatic increases in speed and performance. And there’s even a Make-it 586 chip to turn your 486 computer into a full 586 specification machine! It sounds too good to be true but according to the importers of the chips, Artech Corporation, it is true. We’ve upgraded several of the “386” machines in the Silicon Chip office to prove the point. How Artech came to be the distributors of Make-it chips is an interesting sidelight: their main business is in the supply and installation of point-of- Above: the upgrade is well presented. This is the 80286 package which includes the Make-it 486 “chip”, an alternative carrier socket for those computers using PGA instead of the more normal (for ’286 machines) PLCC sockets, an IC extraction tool and step-by step instructions. The main components are shown enlarged below. Below: three different Make-it 486 packages, for 80286, 80386SX and 80386DX based machines. Not shown is the only-just-released Make-it 586 upgrade. May 1996  23 Left: this is what you should be looking for – a chip with the numbers 286, 386 or 486 somewhere on it (it is often part of a larger alphanumeric code number). In the case of this Intel 386 chip, they make it real easy to identify! In 486 machines, the chip is often camouflaged by a heatsink or even a fan. Below: the same computer about five minutes later, except that it's no longer a 25MHz ’386 – it's now a 50MHz ’486. sale terminals (POS), mainly in retail stores. The difference between the Artech POS terminals and many others is that inside each is a full-blown IBM compatible computer, exactly the same as you and I use (albeit in a different case). Many retailers use their POS terminals after hours for various “normal” computer tasks and were asking about having upgrades for increased performance. Until recently, the only method was the motherboard upgrade method but this meant intolerable downtime during a busy working day. Then Artech’s US counterparts told them about these incredible new chips that enabled a 10-minute upgrade –just long enough to get the top off the machine and plug in the chip! Artech imported some sample chips, tried them out – and they work­ ed! Word of these chips soon spread to dealers and computer suppliers, so Artech suddenly found a new business sideline. There are various models of the Make-it 486 modules, designed to suit the many variations of 386 and 486 chips in use today. These variations include the type of chip, SX or DX, and the speed at which it runs (anywhere from 12MHz up). The Make-it 486 modules use the new 486 SXLC/2 processor from Texas Instruments. With an 8K cache, clock doubling and processing speeds up to 66MHz, the SXL processor family provides up to 97% of the performance of a 486DX2. Also included is an onboard 8K cache, further enhancing the module’s performance. 24  Silicon Chip Before we go too much further, we should point out that not all 386 or even 486 computers can be upgraded. There are some really oddball designs about in which the designers have taken substantial liberties with the “standard”, to the point where they are not standard at all. The Make-it chips and modules simply do not work in these computers. Obviously, you cannot upgrade from a 386 to a 586 model. There is a Make-it module which will upgrade a 6-15MHz 286 to a 33MHz 486 but otherwise you can only go one step: 386 to 486 or 486 to 586. So what CAN you upgrade? Make-it chips and modules are made for the following: • 6, 10, 12 and 16MHz 286 machines (but not 20MHz) using a PLCC, LCC or PGA socket. 16, 20, 25, 33 and 40MHz 386SX machines where the CPU is soldered into the motherboard, as long as the computer was made after June 1991. All models except 33 and 40MHz machines are clock doubled. • 16, 20, 25, 33 and 40MHz 386DX machines where the CPU is fitted into a standard PGA (pin grid array) socket (33 and 40MHz machines are not clock doubled). • 16, 20, 25 and 33MHz 486SX and DX machines where the CPU is fitted into a socket. All of these are clock tripled. In the so-called 2-50 and 2-66 machines which are 25MHz and 33MHz machines clock doubled, the Make-it 586 chip converts them to a full 586 100MHz powerhouse! True 50MHz • Reproduced very close to life size, these are the front and back shots of the Make-it 486 module for 386DX upgrade. 386DX chips use a PGA (pin grid array) socket – 386SX chips, on the other hand, are usually soldered in place on the motherboard. 486 computers are not compatible. Is your PC a candidate? The first thing to determine is the type of CPU in your computer and its operating speed. It’s very easy to determine the type of processor: simply run the diagnostic program MSD from the DOS prompt (it should not be run from within Windows) and it will tell you exactly what you have. Determining the speed is a little more difficult. You might think that MACHINE TYPE those dinky little LED readouts on the front panel will tell you. Most of the time you’d be right but some less than scrupulous dealers have been known to set those LEDs to read just a little higher than they really should (it’s easy to change the indicated speed simply by changing jumpers). So that may be why your 50MHz machine at home doesn’t seem to run as fast as the 33MHz machine at the office! (Of course, there could be other reasons. . .) Refer to your owner’s manual: it might tell you the speed (but more than likely will only indicate a range of speeds the motherboard will handle). If you have any diagnostic software (Nortons, Checkit, etc) run that –it will not only tell you what it should be running at but what it actually runs at. (One of the machines at SILICON CHIP was supposed to be a 40MHz 386DX. Norton Utilities ‘SI’ told us that it was only running at a measly 30.5MHz!) The other possibility is that you will have to read the type of processor from its label. To do this, you will have to remove the computer cover (see your owner’s manual). Before doing this, though, it is wise to back up your hard disc and also make a copy of your CONFIG.SYS and AUTO-EXEC.BAT files and any drivers or other software which are called by CONFIG.SYS or AUTOEXEC.BAT. Of course, before opening the cover NORTON SI (V7.00) CHECK-IT (V3.0) LANDMARK (V2.0) 80286/12MHz CPU 25 OPI 19.7 CPU 2800 DS MATH 55 WS CPU 15.53 80286 with Make-it 486 CPU 30 OPI 23.64 CPU 4700 DS MATH 65 WS CPU 24.49 KEY: 80386SX/25MHz CPU 25.6 OPI 19.7 CPU 6765 DS MATH 76.5 WS CPU 37.53 80386X/25 with Make-it 486 CPU 65.5 OPI 46.2 CPU 16999 DS MATH 197.3 WS CPU 76.47 80386SX/33MHz CPU 23.1 OPI 17 CPU 6254 DS MATH 117.7 WS CPU 41.65 80386SX/33 with Make-it 486 CPU 51.9 OPI 36.1 CPU 13259 DS MATH 252.2 WS CPU 103.27 80386DX/40 CPU 43.2 OPI 30.8 CPU 11049 DS MATH 168.9 WS CPU 62.4 80386DX/40 with Make-it 486 CPU 65.5 OPI 45.6 CPU 17466 DS MATH 254.2 WS CPU 106.4 80486DX/33MHz CPU 72 OPI 50 CPU 16170 DS CPU 111.5 80486DX/33 with Make-it 586 CPU 99 OPI 68.4 CPU 39211 DS CPU 337 CPU – Central Processing Unit speed. Different programs have different ways of measuring this speed, hence the difference results. WS – Whetstones DS – Dhrystones OPI – Overall Performance Index. Takes into account the computer's operation to give one overall figure. MATH – Math performance measured in Whetstones. May 1996  25 you will have turned off the power and removed the power cord from the power point. You also need to beware of electrostatic discharges, especially if working in a carpeted room or on a synthetic (eg Laminex or similar) bench top. It’s a wise move to every so often lay your hand on the shiny metal power supply box to keep yourself at the same potential as the computer. Look for one of the largest chips on the board with the numbers “386” on it, usually as part of a larger number. For example, it might have A80386SX-25 IV printed on it. This would be a 25MHz 80386SX chip. It is usually easy to tell the difference between 386 SX and DX chips. With relatively few exceptions, SX chips are soldered to the board while DX chips are normally socketed. It is possible that either type might be covered by a clip-on heatsink or fan. If so, you will have to carefully remove it to make the identification. Sometimes, one or more expansion boards may restrict your view of the microprocessor and will need to be removed. Before doing so, make a note of which board is in which slot (that could be important). Then remove any cables from any sockets on those expansion boards (both internal and on the backplane of the computer) and remove the single Phillips head screw holding the expansion board in place. Gently rock the expansion board back and forth until it slides out of the motherboard socket. Place the expansion board where it will not be affected by electrostatic charges. Armed with the chip information, you can now determine which Makeit chip/module is the right one for you. The Make-it chips and modules are available from a number of computer stores around Australia but if you have any difficulties, call Artech Corporation on (02) 809 6095; fax (02) 808 3052. it using the adapter clip supplied. Yes, that’s right – you actually leave the existing 386SX chip in place. You then replace any expansion boards previously removed, connect all cables, put the top back on and run the cache-enabling software supplied. If you have a 386DX fitted in a PGA (pin grid array) socket, mark the position of pin one on the motherboard and remove the microprocessor with the rake tool provided. Then insert the Make-it 486 module in its place, reassemble your machine and again run the cache enabling software. If you are upgrading from a 486 to 586 using the Make-it 586 chip, it’s even simpler. Almost invariably, the 486 is socketed, so you pull it out and plug the Make-it 586 chip in its place. Because 486 machines already have the cache enabled, there is no software to run. Just turn it on and the Make-it 586 16K internal cache is operational. Beware the pitfalls! It all sounds so simple, and it is but there are a couple of (expensive) traps for young (or even old) players along the way. Perhaps the most important one is the positive identification of pin one of the chip. It should be easy but in two cases we had real trouble. And as you can install the CPU 90, 180 or 270 degrees out of the correct position, that matters! Normally, you would expect to see a dot (painted or moulded) nearest pin one, or the corner adjacent to pin one chamfered slightly. On one CPU, the 386DX25, we couldn’t see any dot but thought we had identified the chamfer using a loupe (magnifying glass). We plugged in the chip and . . . nothing. Not even the front panel Upgrading Reading the manuals supplied with the chips, it would appear the actual upgrade is the simplest part of the process – up to a point, dear Harry, up to a point! If you have a 386SX, it’s simply a matter of working out which is pin 1 of the existing 386 processor, then slipping the Make-it 486 module over 26  Silicon Chip Believe it or not, we have had Windows 95 running on an upgraded 286 machine. This is considered virtually impossible on a standard 286 machine. LEDs came on – a sure sign that the power supply was not working and a vital clue that something was wrong. On closer examination with the loupe, we found that the chip had not one but four chamfers, one on each corner. Then sure enough, we found a dot, almost impossible to see. We were lucky that time; removing and installing the Make-it module in the right position proved 100% successful. We were probably lucky because of a second problem: we found that we hadn’t inserted the chip all the way in the first time ’round. We were worried about placing too much pressure on the chip and thereby fracturing the motherboard. It was that hard to push in. So the pins had not properly mated with their holes in the socket. Had they done so, when power was applied we would have almost certainly “cooked” the Make-it chip. The second time around, we supported the motherboard from underneath and then gently tapped the PGA chip in place with the head of a screwdriver. Then we heard another story about a completely incorrect silk screen printed on a motherboard – showing pin 1 actually 90° out from where it should have been marked. When the Make-it chip was installed on this motherboard, unfortunately according to the silk screen and not to the location of the original CPU, it did shuffle off its mortal coil. The manual makes a very strong point about identification of pin one. We couldn’t agree more. But it can be difficult to do, especially when the "REAL WORLD" TESTS Machine: 80486DX/33MHz BEFORE UPGRADE (s) AFTER UPGRADE (s) 1: LOADING WINDOWS 3.11 48 33 2: LOADING COREL DRAW 5 65 46 3: LOADING PAGEMAKER 5 40 35 4: LOADING PHOTOSHOP 2.5 30 17 5: RESIZING "ZOOM" COVER 21 6: 14 CONVERSION RGB TIFF SCAN TO CMYK TIFF 110 18 7:   SEARCH AND REPLACE IN   WORDPERFECT 6 FILE 14 7.5 8:   ARCHIVE LARGE PM5 FILE USING LHA 334 288 chip is covered by a heatsink or fan. Our advice is to persevere: if you get it wrong, it could be a costly mistake! And while Artech offers a 14 day money back guarantee on the chips, they are certainly not covered against destruction by internal fire! So how does it perform? Benchmarks are one thing, the real world is another. As any politician (or computer technician) will tell you, there are lies, damned lies and statistics. Even any salesperson half worth his or her pay packet can make a computer lie through its teeth when it comes to running evaluation software. That aside, we put each of the computers modified through three “benchmark” tests which are relatively industry standard. The first of these is “Sysinfo”, part of the Norton Utilities suite (we used SI V7.0). The second is “Check-It”, a very handy program which tells you a great deal about your computer (we used V3.0). Finally, there was the old faithful, Landmark (V2.00). As you can see in the separate table, each of these programs gives wildly different figures, even when measuring much the same function. The important thing to note is the relative change before and after modification. Pretty impressive, huh? We also put some of the computers through various “real world” functions both before and after installing Makeit upgrades. These mostly involved graphics manipulation, because this is very demanding of machine “grunt”. Our yardstick was a large file containing the front cover of our new sister publication, “Zoom”. This was produced using Corel Draw 6 from two high resolution colour scans, retouched using Adobe Photoshop. What we wanted to know was how fast this page would rewrite to the screen when an amendment was made. On a standard 486DX-33 it took 21 seconds. On a Pentium 133, as expected it took much less – just 9 seconds. On the “Make-it 586” (modified 486), it took 14 seconds. That’s a very good figure for the Make-it version, bearing in mind that the task is mostly processing power (any disc activity is identical). It does tend to reinforce the manufacturer’s claims about these chips. We also noted that Windows 3.11 also took significantly less time to load. Given that much of the time in loading a program is in reading it from the disc drive, most of our operations software appeared to load noticeably faster. What if it doesn't work? Let's assume the "worst case" scenario: you've upgraded your computer and it doesn't work. Or it does work, but its performance is at best the same as before, perhaps worse. Taking the latter first, by far the most common reason is failure to run the cache software supplied with the Make-it 486 chips. The software is an integral part of the performance increase – if you don't run it, you won't get the benefit of the on-board cache. There really is no other reason for the upgrade not to work properly if it does work. If it doesn’t work at all, there are several things to look for. (1) The most obvious, and most serious, is that you have installed the chip 90° or more out of position. As we said before, this is not only quite likely to destroy the chip, but it could also damage your motherboard. Therefore, get it right the first time! In the event that you have done the unthinkable, remove the chip and replace your original microprocessor in the socket – the right way around! Hopefully, your computer should now function as it did before. If it doesn't, you have probably done some major damage. If it does work, try re-inserting the Make-it chip (the right way around). You have nothing to lose – and you might be lucky. (2) If you are upgrading a 2-50 or 2-66 machine, you may need to disable the machine's own clock doubling (ie, convert your basic machine back to a 25 or 33MHz model). Look in your owner's manual for the correct jumper to change. Almost invariably, it's just a matter of slipping a link off two pins and swapping it to another pair. (4) Check the ‘‘BIOS’’ date on the sign-on screen of your PC. If the date is pre June 1991 for the 386 upgrade, and pre June 1992 for the 486 upgrade, you could have a problem. A later BIOS (suitable for your machine) could solve your problems. (5) If none of the above apply, it looks like your machine should be on the "no go" list. It's time to ask for your money back! HOW MUCH AND WHERE FROM? Make-it 486 (all models, for 286, 386SX and 386DX computers)            $295.00 Make-it 586 (including on-chip fan)       $495.00 All chips include full instructions, removal tools as appropriate, heat­sinks, etc and have a 14-day money-back guarantee in case of non-compatibility. Make-it Chips are available from selected computer specialists, or direct from Artech Corporation Pty Ltd, 12 Rothesay Ave, Ryde NSW 2113. Tel (02) 809 6095, Fax (02) 808 3052 May 1996  27 We used the front cover of our new sister publication, “ZOOM”, for most of the “real world” comparisons. In full colour, this graphic is a real test of a computer's processing power or “grunt”. Other upgrades With all the money you've saved in not replacing your motherboard, it is now time to start thinking of other things you can do to get even better 28  Silicon Chip performance from your new, fast computer. The first upgrade to think seriously about is memory. Modern programs, especially Windows 95 and those based on it, eat memory by the boxfull. The more you give it, the more they'll like it. Before dashing out and buying memory though, read your manual to see what type it takes and in what “chunks” it can be added. It may be that you can only go up 2Mb or 4Mb at a time, for example. You may also need to buy a memory adaptor. Another worthwhile option is a go-fast video card, to minimise the bottleneck caused when the computer is trying to write information to the screen. This can be agonising when working with graphics! Or you might think about a larger (much larger) disc drive. They've come down dramatically in recent times – and you're certainly going to need more space soon! Then there are such things as CDROMS, mass storage media, modems, SCSI devices, and so on virtually ad infinitum. And that's before we even think about new software! What Are The Drawbacks? Remember that old proverb . . . if something sounds too good to be true, it possibly is! We have proved the Make-it upgrades work well, and as intended. But keep in mind they only upgrade the CPU performance. They do not give you increased disc speed, for example. You would have to upgrade the disc drive and possibly the controller for that. Video cards fall into the same category: the Make-it chip will get the information processed much faster, but a good video card is a must! Just remember that if you really do need the power and performance of a full Pentium 133 with all the bells and whistles, that's what you will have to buy! Finally, for a more detailed discussion of the merits of upgrading the various components of your computer, refer to the "Computer Bits" column in the January 1996 issue of SC Silicon Chip. ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia May 1996  29 Build this handy test instrument High-Voltage Insulation Tester This high-voltage insulation tester can measure resist­ance from 1-2200 gigaohms. It is battery powered and dis­plays the readout on a 10-step LED bargraph display. By JOHN CLARKE In all cases, when ever mains-operated equipment has been built or repaired, it is wise to test the insulation resistance between active and neutral to earth. This will verify that there is no leakage path to earth which could lead to a serious break­down later on or pose a hazard to the user if the earth connec­tion fails. Of course, a multimeter set to the high ohms range can often detect insulation problems but this is not always a valid test. That’s because a multimeter only produces a very low value test voltage (around 1.5V) and many types of insulation breakdown occur at much higher voltages. Another problem with a normal multimeter is that it will only show overrange for “good” insulation measurements rather than the actual value of the resistance. This is because insula­ tion resistance measurements usually result in readings of thou­sands of megohms (ie, gigaohms – GΩ) rather than the nominal 20MΩ maximum value for a multimeter. The Insulation Tester described here is a self-contained meter which will measure very high values of leakage Fig.1: block diagram of the Insulation Tester. The stepped-up high-voltage is applied to the test terminals via a safety resistor and the resulting voltage across the detector resistance then measured. 30  Silicon Chip resistance for a number of test voltages. It will also test capacitors for leakage. A 10-LED bargraph display is used to indicate the leak­age resistance. A test voltage switch selects between five possi­ ble values, while a 3-position range switch selects either x1, x10 or x100 scale readings. Block diagram Fig.1 shows the block diagram of the Insulation Tester. It is based on a high voltage supply, produced by stepping up from a 9V battery using a converter. This converter can produce either 100V, 250V, 500V, 600V or 1000V DC. Note that, because of the high voltages involved, a safety resistor is included in series with the output. This limits the output current to a minuscule level to (a) protect the circuit when the probes are short circuit; and (b) prevent the user from receiving a nasty electric shock. In operation, the leakage of the insulation under test causes a current to flow between the test terminals. This current is then monitored by the detector resistance between the negative test terminal to ground. The higher the leakage current, the higher the voltage across the detector resistance. This voltage is measured using a special voltmeter circuit which is calibrated to show the resistance on a LED bargraph readout. This is no ordinary meter since it cannot divert any significant current away from the detector resistance or false readings will occur. And the currents involved are extremely minute. A simple calculation will tell us exactly how small the currents flow- Feature s • LED b argraph display • Five test volt ages fr 1000V om 100 • Measu res from 1GΩ to 2200G Ω (2.2TΩ (1000MΩ) ) • Battery operated • Overr ange indicatio n the voltage across the detector resistor without drawing any more than a few picoamps (pA). Circuit details The prototype Insulation Tester was built into a standard plastic case. Be sure to use good-quality test leads, as cheaper types will show significant leakage at high test voltages. ing between the test terminals are. Assuming a 1000V test voltage and a 2000MΩ (2GΩ) resistance between the test terminals, the current flow will be just 1000/(2 x 109) = 500nA. The same resistance at a test voltage of 100V will allow only 50nA to flow. At 2200GΩ (the upper measurement limit of the Insulation Tester), the current flow is a minuscule 45pA (45 x 10-12) when 100V is applied. As a consequence, we need to measure Fig.2 shows the full circuit of the Insulation Tester. It uses six ICs, a transformer, Mosfet Q1 and a number of minor components. The step-up converter uses the two windings of transformer T1 to produce up to 1000VDC. When Mosfet transistor (Q1) is switched on, it charges the primary winding via the 9V supply. When Q1 is switched off, the charge is transferred to the second­ary and delivered to a .0033µF 3kV capacitor via series diodes D1-D3. These three diodes are rated at 500V each and so together provide more than the required 1000V breakdown. Following the .0033µF capacitor, the stepped-up voltage is filtered using a 4.7MΩ resistor and a 470pF capacitor. It is then fed to the positive test terminal via a second 4.7MΩ resis­tor. Note that these two 4.7MΩ resistors provide the current limiting function referred to earlier. Q1 is driven by an oscillator formed by 7555 timer IC2. This operates by successively charging and discharging a .0039µF timing capacitor (on pins 2 & 6) via a 6.8kΩ resistor connected to the output (pin 3). Let’s take a closer look at how this works. When power is first applied, the capacitor is discharged and the pin 3 output is high. The timing capacitor then charges to the threshold voltage at pin 6, at which point pin 3 switches low and the capacitor discharges to the lower threshold voltage at pin 2. Pin 3 then switches high again and so this process is repeated indefi­nitely while ever power is applied. The voltage at the output of the May 1996  31 32  Silicon Chip Fig.2: the circuit uses a step-up converter based on IC1a, IC1b, IC2 and Q1 to produce test voltages ranging from 100-1000V. PARTS LIST 1 PC board, code 04303961, 86 x 133mm 1 adhesive label, 90 x 151mm 1 plastic case with metal lid, 158 x 95 x 52mm 1 SPDT toggle switch (S1) 1 2-pole 6-position rotary PC board mounting switch (S2) 1 2-pole 3-position slider switch plus screws (S3) 1 red banana panel mount socket 1 black banana panel mount socket 1 test lead set (see text) 1 9V battery 1 battery holder and mounting screws 1 EFD20 transformer assembly (Philips 2 x 4312 020 4108 1 cores, 1 x 4322 021 3522 1 former, 2 x 4322 021 3515 1 clips) (T1) 1 150mm length of red hookup wire 1 150mm length of black hookup wire 1 150mm length of yellow hookup wire 1 150mm length of green hookup wire 1 400mm length of mains-rated wire 1 7-metre length of 0.25mm ENCW 1 80mm length of 0.8mm tinned copper wire 1 20mm knob 4 small stick-on rubber feet 13 PC stakes 1 100kΩ horizontal trimpot (VR1) 3 1N4936 fast recovery diodes (D1-D3) Semiconductors 1 LM358 dual op amp (IC1) 1 7555, TLC555, LMC555CN CMOS timer (IC2) 1 LM10CLN op amp and reference (IC3) 2 CA3140E Mosfet input op amps (IC4,IC5) 1 LM3915 log bargraph driver (IC6) 1 IRF820, BUZ74 or BUK455500A 500V N-channel Mosfet (Q1) 1 BC557 PNP transistor (Q2) 1 10-LED bargraph (LED1-LED10) 1 3mm red LED (LED11) Resistors (0.25W 1%) 1 10MΩ 1 36kΩ 1 8.2MΩ 1 22kΩ 1 4.7MΩ 1 20kΩ 4 4.7MΩ Philips VR37 1 1.2MΩ 1 11kΩ 1 820kΩ 3 10kΩ 1 470kΩ 1 9.1kΩ 1 390kΩ 1 8.2kΩ 1 180kΩ 1 6.8kΩ 2 120kΩ 1 1.8kΩ 3 100kΩ 1 1.2kΩ 2 82kΩ 1 1kΩ 1 56kΩ 1 100Ω 1 47kΩ 1 82Ω 1 43kΩ converter is controlled by monitoring the voltage across a resistor selected by S2b and feeding this to an error amplifier. In greater detail, S2b se­lects one of five range-setting resistors. This, in conjunction with two associated 4.7MΩ resistors, forms a voltage divider across the converter output. The voltage divider output is applied to error amplifier IC1a via a 10kΩ resistor. This stage is cascaded with IC1b for high gain. IC1b’s output, in turn, drives the threshold pin (pin 5) of IC2. If the output voltage goes too high, IC1b pulls pin 5 of IC2 slightly lower so that the pulse width duty cycle to Q1 is reduced. This in turn lowers the output voltage. Conversely, if the output voltage is too low, IC1b pulls pin 5 of IC2 higher. This then increases the duty cycle of the drive to Q1 and so the output voltage also increases. Basically, IC1a compares the voltage divider output with a fixed reference voltage applied to its pin 3. This refer- ence voltage is provided by IC3a and IC3b. IC3a is part of an LM10 dual op amp which includes a 200mV fixed reference at its non-inverting input (pin 3). It amplifies this reference by a factor of 10 to provide 2V at its pin 1 output. IC3b is connected as a unity gain buffer and provides a low impedance output for the 2V reference. Note that the reference voltage is taken from the inverting input at pin 2, while the output at pin 6 drives pin 2 via a 100Ω resistor. This resistor isolates IC3b’s output from the associated 100µF decoupling capacitor. Capacitors 4 100µF 16VW PC electrolytic 1 0.33µF MKT polyester 2 0.18µF MKT polyester 1 0.1µF MKT polyester 1 .0082µF MKT polyester 1 .0039µF MKT polyester 1 .0033µF 3kV ceramic 1 470pF 3kV ceramic IC4, a CA3140E FET-input op amp, functions as a buffer stage and is used to monitor the voltage across the detector resistor. This op amp offers a very high input impedance of 1TΩ (1000GΩ) and a nominal 2pA input current at the 9V supply. Howev­er, this input impedance and current is only valid if there is no leakage on the PC board. To prevent board leakage we have added a guard track around the input which is at the same voltage as pin 3. This effectively prevents current flow from the negative test terminal to other parts of the circuit. Specifications Test voltages ................................................100, 250, 500, 600 & 1000V Test voltage accuracy ...................................<5% Charging impedance ....................................9.4MΩ Current drain 50mA ......................................<at>1000V out May 1996  33 the test terminals are shorted, even at the 1000V setting. Switch S3 selects one of three possible resistance values for the separate ranges. Position 1 selects a 128.2kΩ resistance (120kΩ + 8.2kΩ), position 2 selects 1.282MΩ and position 3 se­ lects 12.82kΩ. These are unusual values but are necessary to correspond to a 1.28V full scale reading for the LED bargraph driver (IC6). Because of the high impedance at the negative test termi­nal, the input is prone to hum pickup and so it is filtered using a 0.18µF capacitor. Note that the earthy side of this capacitor is connected to the output of IC5 rather than to ground or to the 2V rail. This arrangement ensures that there is no DC voltage across the capacitor, thus giving the filter a fast response time. Conversely, if DC voltage had been allowed to appear across the capacitor, the circuit would have taken a considerable time to settle each time a measurement was taken. Buffer stage IC5 (another CA3140) monitors IC4’s pin 2 voltage via a 10MΩ resistor and a 0.33µF capacitor. The output from IC5 at pin 6 is thus a replica of the signal on pin 3 of IC4. It is connected to the earthy side of the 0.18µF filter capacitor, as mentioned above. Note that IC5 has been given a slow response by connecting a .0082µF compensation cap­ acitor between pins 1 and 8. IC4’s output is applied (via a 1kΩ resistor) to the pin 5 signal input of IC6. This is a log­ arithmic LED bargraph display driver which switches on LEDs 1-10 in the dot mode. Each step in the bargraph is 3dB (1.41) apart, giving a total 30dB range. Note that the lower threshold (RLO – pin 4) of IC6 sits at the +2V reference level provided by IC3b. This means that the upper threshold (RHI – pin 6) sits at 3.28V, since this pin sits 1.28V above RLO as set by an internal regulator. This 1.28V difference between RLO and RHI sets the maximum display sensitivi­ty. The 1.2kΩ resistor on pin Fig.3: install the parts on the PC board exactly as shown on this wiring diagram. Check that the LED bargraph display is correctly oriented and be sure to use Philips VR37 resistors where specified. Trimpot VR1 (between pins 1 & 5) is used to adjust the offset voltage at the output (pin 6) of IC4, while S2a sets the gain. This varies from x10 in the 1000V position up to x100 for the 100V setting. These gain adjustments 34  Silicon Chip are necessary to compen­sate for the voltage change that occurs across the detector resistance each time the test voltage is changed. The 100kΩ input resistor at pin 3 of IC4 protects the input from damage if Bend Q1 over as shown in this photograph, so that it doesn’t foul the front panel. The LED bargraph is installed so that its top surface is 19mm above the PC board. 7 sets the LED brightness. Q2 and LED11 provide the over­ range indication. If any of the LEDs is on, Q2 is biased on due to the current flowing through the 82Ω resistor. As a result, LED11 is off since Q2 effectively shorts it out. Conversely, if all the LEDs are out (which equates to a very high resistance), Q2 is biased off and so LED11 now lights to indicate an overrange. Power for the circuit is derived from a 9V battery via switch S1. There are several 100µF capacitors across the supply and these are used to decouple the 9V rail. Construction Most of the circuitry for the Insulation Tester is mounted on a PC board Fig.4: the primary of the transformer is wound first & covered with several layers of insulating tape before the secondary is installed. coded 04303961 and measuring 86 x 133mm. Fig.3 shows the parts layout on the PC board. Begin the assembly by installing PC stakes at the external wiring points (11 in all). These are located at the (+) and (-) battery wiring points, the wiring points for S3 (1-4), the three wiring terminals for switch S1, and at the (+) and (-) terminal points. Once the PC stakes are in, install the resistors, diodes and ICs. Don’t just rely on the resistor colour codes – check each resistor using a digital multi­meter, as some colours can be difficult to read. Take care to ensure that the semiconductors are correctly oriented. The capacitors can go in next, followed by the transistors and the trimpot (VR1). Note that Q1 must be mounted at full lead length so that it can be bent horizontally over the adjacent .0039µF capacitor. This is necessary to allow clearance for the lid of the case, when it is later installed. LEDs 1-10 (the bargraph) and LED11 can now be installed. Be sure to install the bargraph with its anode (A) adjacent to the 82Ω resistor. It should be mounted so that the top surface of the display is 19mm above the board, May 1996  35 The completed PC board mounts on the back of the lid and is secured using the nuts for switches S1 and S2. assembled PC board. This is fitted with a self-adhesive front-panel label measuring 90 x 151mm. Begin the final assembly by affixing the front panel label to the lid, then drill out and file the holes for the LED dis­play, LED11, switches S1, S2 & S3, and the two terminals in the end of the case. Holes will also have to be drilled in the base of the case for the 9V battery holder. This done, the front panel can be test fitted to the PC board. Check that everything lines up correctly and make any adjustments as necessary. You may need to adjust the height of the LED bargraph or LED11, for example. When everything is correct, set switch S2 fully anticlock­wise and move its locking tab (found under the star washer) to position 5. This ensures that S2 functions as a 5-position switch only. The external wiring can now be installed. Use light-duty hookup wire for the connections to S3 and the battery holder and mains-rated cable for the connections to the test terminals. Important: the leads to the test terminals must be kept well apart, as any leakage between them at the high test voltages used will affect readings. Testing so that it will later fit into a matching slot cut into the lid of the case. The top of LED11 should be 20mm above the board surface. Switch S1 is soldered directly to its PC stakes but with its pins touching the top of the PC board. You may need to cut the PC stakes to length to do this. S2 is installed directly on the PC board after first cutting the shaft to a length suitable for the knob. Transformer winding Transformer T1 is wound with 0.25mm enamelled copper wire – see Fig.4. The primary is wound first, as follows: (1) remove the insulation from one end of the wire using a hot soldering iron and terminate this end 36  Silicon Chip on pin 7; (2) wind on 20 turns sideby-side in the direction shown and terminate the end on pin 3; (4) wrap a layer of insulating tape around this winding. The secondary is wound on in similar fashion, starting at pin 4. Note that you will need to wind on the 140 turns in several layers. Use a layer of insulating tape between each layer and terminate the free end on pin 5. The transformer is now assembled by sliding the cores into each side and then securing them with the clips. This done, insert the transformer into the PC board, making sure that it is oriented correctly, and solder the pins. A standard plastic case measuring 158 x 95 x 52mm is used to house the To test the unit, apply power and check that, initially, one of the LEDs in the bargraph display lights. Assuming that the test terminals are open circuit, the bargraph reading should then slowly increase until the over­ range LED comes on. If this doesn’t happen, check that the LEDs are oriented correctly. Now check the circuit voltages with a multimeter. There should be about 9V between pins 4 & 8 of IC1; between pins 1 & 8 of IC2; between pins 7 & 4 of IC3, IC4 and IC5; and between pins 2 & 3 of IC6. There should also be a reading of 2V at TP2. If everything checks out so far, select the 1000V (or high­er) range on your multimeter and connect the positive meter lead to the cathode (striped end) of D3. Now check for the correct test voltages, as selected by S2. Note that if the output voltage is measured directly at the test terminals, the meter will show only about half the correct value because it loads the 9.4MΩ output impedance. Next, set your multimeter to read DCmV and connect it between TP1 <1 2 4 8 16 OVER RANGE + 1.4 2.8 5.6 11 22 GΩ RANGE + x1 x100 x10 ON 250V 500V 100V 600V 1000V + TEST VOLTAGE Figs.5 & 6: here are the full size artworks for the PC board and the front panel. Check your board carefully against the above pattern before mounting any of the parts, as any problems will be more difficult to locate later on. and TP2. This done, set the range switch to the x1 position and slowly adjust VR1 until you obtain a 0mV (or close to it as possible) reading. Note: nothing should be plugged into the test terminals during this procedure. Once all the adjustments have been completed, fit the front panel to the board assembly and secure it by fitting the nuts to switches S1 and S2. The unit can then be installed in the case and the knob fitted to S2 to complete the assembly. Test leads It is important to note that maximum resistance readings cannot be obtained from this instrument if the test leads touch each other or are twisted together, or if a standard test lead set is used. For measurements up to and beyond 220GΩ, we recommend high quality INSULATION TESTER test leads such as those from the Fluke range. DSE Cat. Q1913 test leads (or an equivalent type) are also capable of meaningful results above 220GΩ, provided rubber gloves are worn and the leads are not touching a common surface. Alternatively, you may be able to improve on a standard test lead set by WARNING! Take care with fully charged capacitors since they can provide a nasty electric shock. Always discharge the capaci­ tor after testing it by switching off the Insulation Tester with the probes connected. A 1µF capacitor will take about 10 seconds to discharge using this technique, while larger values will take proportionally longer. insulating the probes with heatshrink tubing. In most cases the protective shroud on the test lead banana plugs will have to be cut away to allow them to be inserted into the banana sockets. You can now check the unit by connecting the test leads across the terminals of an unwired switch. The leakage is then determined by first selecting the x1 range and then switching to the next range if necessary. If the display indicates 1GΩ on the x1 range, then the switch under test is either faulty or its contacts are closed. Note that the unit will display a reading of 1GΩ even if the actual resistance is much lower than this. Finally, when checking capacitors for leakage, be sure to select the correct test voltage. It is then necessary to wait until the capacitor fully charges before SC taking the reading. May 1996  37 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Here’s how to interface the Programmable Ignition System to the reluctor version of the SILICON CHIP Transistor Assisted Ignition. Note the break in the TAI circuit at pin 7 of IC1. Reluctor version of programmable ignition The Programmable Ignition System featured in the March 1996 issue has generated considerable reader interest and a number of enquiries as to how it may be adapted to suit the reluctor version of the Transistor Assisted Ignition (TAI) system published in May 1990. This circuit shows how it can be done. Only a few extra parts are required in addition to the TAI and the Ignition Programmer module. Since the reluctor output is processed within the MC3334P IC, the only suitable access point is at its pin 7 output. This output goes low when the coil is required to fire. The programmer board is connected to this output and drives the main coil switching Larger search coils for the metal locator These modifications allow larger search coils of 250mm in diameter to be used with the metal locator published in the May 1994 issue of SILICON CHIP. These will allow objects to be located at greater depths than previously, although the accuracy won’t be quite as good due to the larger diameter. 38  Silicon Chip The larger coils are wound with 40 turns of 0.5mm enamelled transistor (Darlington Q1) via buffer transistors Q3 and Q4. Note that the circuit between the pin 7 output of IC1 and the base of Q1 will need to be broken to allow the insertion of the programmer board. This involves cutting the track on the PC board immediately adjacent to the IC. No other alterations are required to the TAI circuit. SILICON CHIP copper wire. The null needs to be improved by connecting the anode of D1 to the wiper of a 1kΩ trimpot supplied through a 22kΩ resistor from the +7V supply – see circuit diagram. With the ground control at maximum, the trimpot can be nudged up until a low growl is achieved in the phones. A. March, North Turramurra, NSW ($20) 0-18V power supply with current limiting This is a fairly conventional power supply with a bridge rectifier and a 2200µF smoothing capacitor providing an unregu­lated rail of about +21V. REF1 provides an accurate +2.5V to VR1, a linear 5kΩ potentiometer. Its wiper voltage is applied to the non-inverting input (pin 3) of op amp IC1a. A voltage divider, consisting of 6.8kΩ and 1.1kΩ resistors, across the output feeds back about 14% of Vout to the inverting input (pin 2). IC1a com­pares both its input voltages and adjusts its output for balanced inputs; eg, if the output attempts to rise, the feedback voltage rises too, reducing the bias to transistor Q1. Current limiting is provided by transistor Q2 and switch S1. This varies the resistor between the base and emitter of Q2 and this sets the current which can flow to the output. If the voltage across the selected limiting resistor exceeds about 0.7V, Q2 conducts to shunt base voltage away from Q1. This process causes IC1a to latch up as it tries to compen­sate. IC1b monitors the voltage differential between the inputs to IC1a. Any difference will be amplified and LED1 comes on whenever pin 2 of IC1a is more than -20mV with respect to pin 3. Also, if the 21V rail drops excessively and the circuit comes out of regulation the LED comes on. This power supply is handy for testing CMOS circuitry with­ out the fear of cooking components if mistakes are made. In the 10mA mode, LEDs can be safely tested for brightness and polarity (set to 3V). Q1 can be any medium power Darlington transistor but requires a heatsink. M. Schmidt, Edgewater, WA. ($35) the board. Both the TIP2955 transistor and the 7812 regulator must be fitted with substantial heatsinks. The etching tank can be a 4-litre ice cream container. Two galvanised nails are used as electrodes, with the output wires soldered onto the top of the two nails. The salt solution is made up of water with table salt added and stirred into it until no more will dissolve. The plastic container is half filled up with the solution, with the board placed on the bottom and the nails half submerged into the solution. The unit is then switched on, in a well ventilated area and left until the board is etched. Eventually the nails will be consumed and will have to be re­placed. WARNING: this etching method must be used in a well-ventilated area, preferably outdoors, as it will produce poisonous chlorine gas in small amounts, as well as hydrogen gas. S. Isreb, Traralgon, Vic. ($30) Electrolytic PC board etcher This circuit provides a novel way to etch PC boards. It uses the principal of electrolysis to generate chlo­rine and sodium hydroxide from salty water by passing electricity through it. The chemicals produced in the reaction etch the copper of the board laminate. Whilst it may not be the fastest method, it is a good demonstration tool of how electrolysis works. The circuit is basically a current-boosted regulator. A transformer feeds 12V AC into the bridge rectifier and its output is smoothed by the 6800µF capacitor. The resulting supply of just over 16V DC is fed into the regulator circuit which, along with the 7812 regulator, uses the TIP2955 transistor to boost the current of the circuit to around 4 amps. The resulting 12V 4A supply is fed into the tank to etch May 1996  39 SERVICEMAN'S LOG It was a dark & stormy night Yes, it was; very dark and very stormy. The storm had blacked out several Sydney suburbs and, in the process, created a line surge which damaged the set featured in this month’s notes. And it was a dark and stormy exercise correcting the damage. The set was a National Panasonic model TC-68A61, fitted with an M16M chassis. It is a 68cm set, featuring remote control plus all the latest bells and whistles, and retails for around $1800. It was quite new, being only about 14 months old. I discovered later that this was not the only TV set to be damaged in this 40  Silicon Chip and subsequent storms a few days later. There were many more from all over the suburbs, one of which was described as a complete write off. The set came in with the simple description of being com­pletely dead, which it was from the customer’s point of view. A quick bench check produced a violent squeal from the switchmode power supply, suggesting a short on one of the supply rails. Unfortunately, this model set was a complete stranger to me. I had never even seen one before and had absolutely no data of any kind. Nevertheless, I decided to at least take the back off the cabinet and check for any visual clues. This operation produced its own shocks. Firstly, everything was jam-packed in – a real servicing nightmare. Secondly, the cabinet was of rela­tively flimsy plastic so that, when the back was removed, it distorted noticeably under the weight of the large tube. There were no obvious signs of damage, so I decided to pull the chassis for a closer look. This was a difficult operation, due in part to the distortion of the cabinet, although I realised later that there were some tricks which made it easier. Anyway, with the chassis out, my main aim was to try to find whatever it was that was obviously overloading the power supply, as suggested by the squealing. I went first to the hori­zontal output transistor, Q551, and checked for voltage on the collector. There was none so I pulled this transistor out, ex­pecting it to be shorted, but it was intact. So it looked as though the fault was closer to the power supply but, without a circuit, it was impossible to identify the various rails or even to know how many there were. My best effort was to find that there was a dead short to chassis from a test point labelled TPD1, which appeared to be one of the rails. At this point, I realised that it was hopeless to proceed without a manual or at least a circuit. Fortunately, I was able to find a colleague who did have a circuit and he was quite happy to lend it to me. It amounted to a total of six A3 pages! These cover a swag of boards or modules, designated alphabetically. I ran out of fingers trying to count them but I make it about 16. The accompa­nying illustration is part of the D board. Just as importantly, my colleague was able to pass on a lot of valuable information based on his own experience with this model set. Of particular value was a warning about power­ing up the set after a repair. It appears that the set is very easily damaged if other faults are overlooked. This was a kind of “good news/ bad news” situation; I was extremely grateful for the warning but not very happy about the need for it. Circuit details Anyway, now that I had a circuit I could at least begin to sort things out. The set has two switchmode supplies: (1) a main one supplying the high voltage rails; and (2) a subsidiary one supplying a 5V rail for the remote control functions, plus a 12V rail. This 12V rail is very important because, among other things, it powers standby and protection circuits. And it func­ tions continuously. The main supply centres around transformer T801 and the short I had Fig.1: portion of the D board on the National Panasonic TX-68R71. The subsidiary supply, involving T881 and its associat­ed parts, is at top left, while the main switchmode supply invol­ves T801 and transistors Q801-Q805. IC801 is at bottom centre, IC802 to the right and SCR Q821 above it. found was in fact on the main HT rail, normally operating at 139V. It involves transformer pin S2, diode D808, filter capacitor C828 and IC801. I connected the ohmmeter between TPD1 and chassis and pro­gressively removed components from this line, including IC802, C828 and some other minor components, until I came to SCR Q821. I pulled it out and the short cleared, which meant that the SCR had broken down. But what was the SCR’s function and, most importantly, why had it failed? Once again I am indebted to my colleague for saving me from having to try to work this out for myself. SCR Q821 is part of an over-voltage protection circuit, particularly guarding Q551 and the horizontal output stage in general. And it had done a good job, to the point of sacrificing itself. But the implication from such a drastic reaction could only be that it must have been a very severe voltage overload. So how could I fire up the set safely to make further tests? Normally, I would use a Variac for this job, possibly with a series lamp in the mains line as a current limiting device. Unfortunately, another colleague had passed on some hearsay advice that a Variac could not be used on these sets, although the explanation was hopelessly garbled. As it turned out, this was a furphy. It appears to have arisen from a warning in the manual, which I saw later, against depending solely on a Variac for protection before all the recom­ mended tests had been performed. But that was later and, right now, with various warnings ringing in my ears, the best I could do was settle for a 200W series lamp in the mains lead. I also took the precaution of disabling the horizontal output stage by shorting the base and emitter of Q551. Then, with a meter monitoring the main HT rail, I switched on. The reaction was quite dramatic – the meter shot up to over 200V, clearly indicating something seriously wrong with the power supply regulation system. And, as if to confirm this, in the few seconds I took to absorb the reading, there was a loud bang. The excessive voltage had proved too much for C760, a 0.47µF electrolytic rated at 160V, which had exploded. And when they explode they don’t muck about. Fortunately, this was easily fixed and there appeared to be no other damage. At this stage, I encountered another colleague who was able to loan me a copy of the service manual. This includes a section entitled “Service Hints for M16M Power Supply Repair”. And almost immediately, it begins listing “possible causes for a power supply primary shutdown”. Among other symptoms, it mentions the mains fuse, F801, being obviously O/C, and transistors Q803 and/or Q805 being physically blown apart! It also suggests checking IC801, with a low ohmmeter, in anticipation of it being “absolutely S/C between all three terminals!” The manual goes on to list all the components which should be checked in the event of a “primary shutdown”. And it includes instructions as to how components should be tested, strict warn­ings about the critical nature of many components, and the risks of using substitutes. All told, it lists no less than 16 components which should be tested before applying power. The risk appears to be that a serviceman may follow the usual practice of progressive testing; ie, find and replace a faulty component, then reapply power, check performance, and search for further faults if necessary. The manual warns that this approach could likely result in fur­ther severe damage. It’s not the most encouraging introduction to a strange set! Voltage regulation But at least I had been warned. And my attention was now directed to the voltage regulation system; to find out May 1996  41 Serviceman’s Log – continued how it worked and why it didn’t. Once worked out and explained, it is not hard to follow but it wasn’t easy coming to it cold. It all hinges around IC801 and D812, the latter an opto-coupler IC801 is a 3-terminal device. Pin 1 connects to the 139V rail, pin 3 connects to chassis, and pin 2 connects to pin 2 of the optocoupler, which is the cathode of its internal LED. Pin 1 is the anode of this LED and goes to a 12V rail from IC802. The other half of 42  Silicon Chip the optocoupler is a transistor, with the collector connected to pin 4 and the emitter to pin 3. The base is activat­ed by light from the LED. In operation, IC801 conducts between pins 2 and 3 when the voltage on its pin 1 terminal reaches 139V. This completes the circuit between the 12V rail and chassis via the LED in the associated optocoupler. The LED now glows and turns on the tran­sistor between pins 3 & 4 of this device. Pin 3, in turn, drives a transistor network consisting of Q802, Q803 and Q801. The latter is at the heart of the switchmode supply and switches the primary of transformer T801. By control­ling the oscillator activity when the main rail reaches 139V, that voltage is maintained. At this point, I decided that the best approach would be to order all the components listed as likely needing to be changed and put the set aside until these arrived. This would save time and any components not needed could go into stock. I had an idea that this would not be the last of these sets I would see. The only snag was that I was quoted up to three weeks delay on some parts. This was an irritating setback but I decided to make the most of the time by trying to pinpoint the most obvious fault – the failure of the IC801/ optocoupler combination to regulate. Testing IC801 As already mentioned, the manual suggests that IC801 is a prime suspect, most likely going short circuit. Well, I’d already cleared it of short circuits but it could still be faulty. How to test it? Well, not in situ, since power could not be applied. A preliminary resistance check revealed no continuity bet­ween any of the terminals but that didn’t really mean much. Once again my colleague came to the rescue. He had already made up a simple test jig and gave me the details. It was a simple enough arrangement to knock up and I soon had it working. And it worked very well; so well that it clearly indicated that IC801 had carked it, which was one good reason why the HT rail was not being regulated. What about the optocoupler? The manual had made the point that if the optocoupler proved to be faulty, then IC801 should be replaced automatically. Would the reverse be true? The manual suggests testing the optocoupler using an ohm­meter and I have no doubt that it is technically accurate. Howev­er, the optocouplers are very small devices and trying to test them in this manner is fiddly, at best. So I added to my collea­gue’s jig, making it a combined tester. It was all very nice in theory but I needed a known good IC801 to make it work. This was one of the components on three weeks delay, so I cheated by connecting the prods of an analog multimeter (low ohms range) across pins 1 and 2 of the optocou­pler to energise the internal LED. I could get no response from the original device but the new one, which arrived early, pro­duced an immediate response from the external green LED. Eventually, the remaining parts arrived and I replaced the SCR (Q821), IC801 and the optocoupler. I had already replaced C760 which I had blown up earlier and had spent some time checking and double checking all the other components listed – as well as some that weren’t. In theory, I should have been able to switch on safely. However, the manual suggests a proper routine for switch-on at this stage and I wasn’t prepared to take any chances. What this amounts to, in essence, is to disable the horizontal output stage, replace it with a dummy load, then wind up the supply voltage via a Variac. Talk about a belt and braces approach! In greater detail, the procedure involves lifting a 1.2Ω resistor (R561) on the X board, which is in the 139V rail to pin 9 of the horizontal output transformer (T501). At the same time, a dummy load, consisting of a 60W globe, is connected from this supply rail to chassis, most conveniently from pin 1 of the X10 plug on the D board to pin 1 of the X11 plug, which is chassis. These are not shown on the accompanying circuit. The manual also suggests lifting D560, which I did. This is to disable a protection circuit involving transistors Q553, Q554 and Q555. If this circuit had been activated by a fault, it would shut the set down and inhibit further testing. Having done all this, I connected the set to the Variac but left my 200W globe in series. I must admit that I was extremely nervous about the whole situation and felt that another belt added to the belt and braces wouldn’t do any harm. I also con­ nected the CRO to the collector of the chopper transistor (Q801). I switched on and wound the Variac up slowly. And, with only about 30V in, the CRO indicated oscillation around Q801. Beyond this level, it abruptly stopped oscillating. I gradually increased the voltage, eventually reaching 150V, which was as high as I was game to go – still no oscillation. I backed the voltage off and moved to the subsidiary power supply. I checked the 5V rail out of IC803 and, at about 100V in, it came good, as did the 12V rail at zener diode D883. Well, that was good news; very good news in fact, because according to the manual, this supply is vital for the remote control and protec­tion systems. Remote control switching But it didn’t help much with the main power supply problem. In order to follow what happened next, it is necessary to look at the remote control ON/OFF switching function. Working backwards from the switch­ mode section, involving transistors Q802, Q803, Q804 and Q805, we trace the circuit up to pin 3 of D841, the second optocoupler. And pin 4 of D841 connects to the 12V rail which we had just checked. So the role of the D841 is to switch the 12V supply to the transistors in the switch­mode supply. D841 is controlled by transistor Q841 between pin 2 and chassis. This transistor is controlled, in turn, by the remote control system on board E, involving microprocessor IC1213 and transistors Q1231, Q1207 and Q1209. I won’t bore the reader with all the details of this circuit operation – just that it finishes coming in on pin D5 on the D board and goes to the base of Q841. So the remote control system switches Q841 on or off, switching May 1996  43 So what was wrong now? All kinds of weird and complex possibilities raced through my mind, without making much sense. Then I suddenly looked up and caught sight of the 200W lamp in series with the mains; it was glowing a dull red. I had complete­ ly forgotten that the lamp was still in circuit. I disconnected it and tried again. And this time everything came good –correct HT rail voltage, no signs of distress any­where, and the set actually functioning. And functioning very well, too. Insurance D841 on or off, and turning the switchmode system on or off. It’s simple when you say it quickly. Having worked out what should be happening, I was able to trace the circuit through and establish that every stage was functioning up to the base of Q841. But Q841 wasn’t doing any­thing about it. I pulled it out and found that the base-emitter junction was open circuit. This presented something of a puzzle. As far as I can work it out, this transistor must have been working when I first turned the set on, otherwise there could have been no HT rail voltage (the excessive voltage which blew up capacitor C768). So, was Q841 damaged by a kickback from this misadventure. We’ll probably never know. Anyway, that problem was easily fixed. I didn’t have a 2SD1010 and, conscious of the dire warnings about substituting alternative components, I hesitated initially. But it didn’t appear that this was anything more than a general purpose tran­sistor so I took a punt and fitted a BC547. That started things working. As I advanced the Variac the CRO indicated that the system was oscillating and it kept on oscillating. And there was voltage on the main HT rail at test point D1 which, according to the manual, should reach its normal 139V operating voltage with an input as low as 120V. Unfortunately, it didn’t. At 120V on the Variac the best I could get was about 117V. I wound the Variac up to around 150V, which the manual warns is the limit if a normal HT value is not reached. There was no significant improvement. But there was one more job I had to do for the customer. Damage of this kind is not, of course, covered by warranty. But it was covered by the customer’s household insurance and I filled in the necessary details on his claim. As for the set itself – well, I wouldn’t nominate its designer(s) for any Oscars. I cannot escape the impression that they started off with a lot of surplus components and that they used as many of them as possible! An exaggeration? Well, maybe, but other designs have pro­duced the same end result with less components and greater reliability. More to the point, from a practical servicing point of view, I offer this advice to anyone presented with one of these sets. Do not, in any circumstances, touch it – and I mean that word “touch” almost literally – without the benefit of a manual. If a manual cannot be obtained, knock it back. To do otherwise is to do both yourself and your customer a SC gross disservice. Especially For Model Railway Enthusiasts Available only from Silicon Chip Price: $7.95 (plus $3 for postage). Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 44  Silicon Chip SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au RADIO CONTROL BY BOB YOUNG Multi-channel radio control transmitter; Pt.4 In Pt.4 this month, we look at the features of the transmitter PC board and discuss its assembly. It is a double-sided board with plated-through holes. It has conventional components on the ground plane side and surface mount components on the other. When I am writing for SILICON CHIP, I am conscious of the fact that it is an electronics magazine and not a modelling magazine. I know full well that SILICON CHIP readers devour all kinds of articles and the knowledge gained is often applied in fields other than originally intended. This was driven home to me in no uncertain manner when I presented the Speed1B motor control in November & December 1992. More of those units went into non-modelling applica­tions than into models. They found their way into electric pow­ered fishing dingys, full size autogyros, wheelchairs and a myriad of other items. The demand was so widespread that I was forced to design an add-on pulse generator to allow these units to be used without a radio receiver. This was published several months later and required a new, small circuit board which is glued to the origi­nal Speed1B PC board. When I had finally settled on the circuit for the Mk.22 RF module, I sat back and contemplated what the readers might hit me with this time. Two days after the encoder circuit was published in the March 1996 issue, I had a request from a government de­ partment for transmitters and receivers. The Mk.22 was of great interest, Fig.1: this diagram shows the component layout for the surface mount component side of the board. Crystal X1 and trimmer capacitor are also mounted on this side. they said, because the RF modules came out so easily and this would allow them to use a fibre optic link without high drama. So it was obvious that it was going to be Speed1B all over again. This time I was determined to be one jump ahead. One obvious request would be for an NBFSK (erroneously referred to as FM in the modelling trade) transmitter. Another would be for a voice modulated unit. There is a very interesting band on 30MHz which butts up against the 29MHz band (it actually starts where the modelling bands stops) and allows the use of 100mW unlicensed transmitters for voice. We already make an FM simplex radio link for this band for several non-modelling customers. A data link is an almost certain application. Another was obviously the use on frequencies not approved for modelling, but for which the potential user was already licensed. Thus, the PC board presented this Fig.2: the component layout for the groundplane side of the board. Note that the crystal socket is attached from this side – see photo. May 1996  53 The groundplane side of the transmitter board carries only a few parts. Note the upside down crystal socket. Note also that the pins for TB3, adjacent to transistor Q2, have been clipped off flush with the board surface. capacitance for the modulation wave shaping and are best lumped in with the temperature stable mylar (polyester) capacitors on the encoder PC board. C11 and C15 have been reduced to NPO .001µF capacitors. Production spreads on the FET have since dictated that R7 should be 56kΩ or less. This plays a part in the modulation pulse shaping. During the final PC board layout I was forced to add a jumper in the form of a 1206 chip resistor. This is shown on the overlay as R11 and is 1Ω. There was also a typo on the circuit. Diode D1 is a BAS16 not BA516. These circuit additions have resulted in a transmitter which is a delight to tune and service. One of the big problems with checking frequency in a modulated AM transmitter is that the modulation blanks out some of the RF and the frequency count is always low unless you have a gated frequency counter. With TB3 in place, no problem. Just switch off the modulation by shifting the AM shunt to CW. The result, a carrier only transmitter on which it is a snap to check frequency. Want to check PA current whilst tuning the PA? No problem, simply remove the shunt from TB3 and insert the meter in series with the two CW pins. Dead easy! Construction This photo shows the surface mount side of the board. The only other conventional components visible are the crystal, trimmer VC2 and the multi-pin header, TB1. Note also that links across TB2 and TB4 have been installed on this side of the board rather than on the ground plane side, as depicted in Fig.1. month is a multipurpose unit and covers all of the above. Frequency range is from 25-50MHz with suitable coil and capacitor changes. Accordingly, it has provision for components which are not required for this R/C transmitter. Most of them are of no consequence for this project, but the programming pins TB2, TB3 and TB4 need to be dealt with for circuit continuity. TB2 is there to program the oscillator for various configurations and this is hard-wired to the AM position with a link. TB3 and TB4 are used to 54  Silicon Chip program the modulator but again TB4 is of no consequence. It is also replaced with a link. TB3 howev­er is a valuable asset when testing and servicing the board as it programs the transmitter for CW or AM modulation. Circuit changes There are some minor component changes introduced since last month. R8 has been increased to 22kΩ to restrict the FET gate bias range and improve the feel of VR1 when tuning. C11 and C15 form part of the lumped The component layout diagrams for both sides of the PC board are shown in Fig.1 & Fig.2. I must point out here that due to the stringent demands placed upon this module it is best tuned on a spectrum analyser. For this reason I strongly recommend that if you do not have access to a spectrum analyser, you should buy the module fully assembled and tuned. For those not familiar with surface mount construction techniques, I would suggest reading the article “Working With Surface Mount Components”, as featured in the January 1995 issue of SILICON CHIP. You will need a pair of magnifying spectacles, a fine-tipped soldering iron and a pair of tweezers with very fine tips. Begin by tinning one pad at each of the surface mount com­ ponents positions, as set out in the above article. This is a good time to clearly establish which components are not mounted by not tinning the pads for these components. When all of the surface mount components are in place, solder the jumper links as indicated on Fig.1. These may be made from the tinned leads of resistors. The longer jumper between J1 is made from the wire-wrap wire provided in the kit. Note that L1 and L3, which appeared on the circuit last month, are not used. Their positions on the board are actually bridged by the copper tracks out so you don’t have to worry about them. Coil winding The coil winding details for L2, L4 & L5 are shown in Fig.3. The direction of winding is not important but the number of turns are. However, it is important that the secondary on L5 is wound in the same direction as the primary. The enamelled copper wire provided is easy to solder and a hot iron will soon burn the enamel away. Tin one end of the lengths of enamelled wire provided. Only tin about 1mm of the wire to minimise the risk of a shorted turn on the coil. Due to the fact that 16 turns just fit on the coil formers, snip off half of the pin protruding on the winding side of the coil base on L2 & L5, leaving just enough pin to solder the wire – see Fig.3. Solder the end of the wire to the appropriate coil former terminal and wind on the correct number of turns using tight, close spacing. This done, apply a dab of super glue to the winding to hold it into place, then place the coil former on the desk to dry. When you return, remove the desk from the coil former. Having gone through the above ritual you now have three coils with one end free. Solder this end to the appropriate terminal and mount L2 and L4. Now wind on the second­ary of L5. Care must be taken here with the beginning and end terminals (see Fig.3) and also to ensure that the secondary is wrapped over the eighth and ninth turns of the primary. The physi­ cal location of the secondary plays an important role in the drive level and thus harmonic content of the output. Secure it after it is wound with another drop of super glue. Moving the secondary closer to the base of the coil (col­lector of Q1) will increase the drive level and harmonic content of the oscillator. Mount L5, taking care to ensure that the prim­ary and secondary terminals are correctly Fig.3: coil winding details for L2, L4 and L5. Fig.4: depending on how links are made across TB3, the transmit­ter can be set to CW (no modulation) or AM (normal operation). aligned with the PC board (primary terminals closest to the crystal socket). Final­ly, solder the shield into place, making sure that the coil former is centralised in the top hole. Crystal socket At this point, it is wise to deal with the next messy job which is mounting the crystal socket. The PC board is designed to allow the crystal to be removed from the back of the case and thus the crystal must be mounted vertically. However, this dictates that the socket must be glued into the PC board flush with the top (surface mount side) of the board. Thus, viewed from the ground plane side of the PC board, the crystal socket appears to be upside down. Do not get this wrong. If you glue the socket into the wrong side of the PC board you will have ruined both items. Fit the crystal socket into the hole in the PC board and ensure that it is the right way up and flush with the surface mount. Very carefully place a drop of super glue onto the junction of the PC board and the crystal socket from the groundplane side of the PC board. Once the glue is dry, solder the two connecting wires into the pads adjacent to the crystal socket and then solder them to the socket terminals. Care must be exercised here for the plastic used in the socket is easily melted. Tin both the socket terminals and the wire ends before soldering them together with just a quick dab of the iron. The rest of the assembly is a snap, with the only special care needed with terminal blocks TB1 & TB3 and trimmer capacitor VC2. VC2 is mounted on the surface mount side of the PC board for ease of adjustment when tuning. TB1 is likewise mounted on the SM side of the board and mates with the main power connec­tor for the module. The programming pins for TB3 are mounted from the groundplane side of the board with the long side of the pins pro­jecting through the board and out onto the SM side of the board. Solder them to the pads and then remove the black plastic from the back of the board. Snip off the pins on the ground plane side of the PC board as close to the board surface as possible. This also applies to the pins on TB1, as the antenna sits in the channel between the components and quite close to the PC board. These pins could short out the antenna if left too long. Finally, mount the output FET using the hardware kit pro­vided. The mounting of this transistor is designed to heatsink the transistor firstly into the groundplane of the PC board and then from there into the transmitter case via the mounting brack­ets. As a result the transistor runs quite cool, even with the antenna retracted. That completes the assembly. Put the unit aside for a period then come back and check once more that all components are correct. Ensure that the crystal socket is adequately anchored and that the contacts are free of glue. Plug in the crystal and place the micro shunt onto the CW position on TB3 (see Fig.4). Testing & tuning This section is a little ahead of itself as the module really cannot be completely tested and tuned until mounted into the transmitter case with the correct antenna. However, I will complete the tuning sequence for those using the module in other applications. This description will assume that the module is in the case and fitted with an antenna 1.5m long (wire or telescopic). May 1996  55 I reiterate that unless you have access to a spectrum ana­ lyser, you really can’t set up this transmitter module. However, I am presenting the following details for the sake of complete­ness. First, with a continuity meter test between the power and ground pins on TB1 to ensure that there is not a direct short to ground. Remove the crystal, hook up the main power connecter or apply 9.6V to the power and ground pins of TB1. Set VR1 to mid-range and screw the tuning slugs into the coil formers so they are flush with the SM side of the PC board. Remove the micro shunt from TB3 and connect a milliammeter (200mA range) in series with the CW pins then turn on the power. The PA current will be somewhere in the order of 15mA. Set VR1 for a quiescent current of 12.5mA. This should equate to a base bias voltage of 2.2V approximately. Remove the meter and replace the micro shunt on the CW position. Now quickly go over the board and check the voltages at the supply rail (+10.3V), decoupled oscillator supply rail (+9.54V), base of Q1 (+3.7V), emitter of Q1 (+3.0V), base of Q3 (+2.2V) and collector of Q3 (+10.37V). Plug in the crystal and hook up an oscilloscope to the collector of Q1. There should be a strong 29MHz signal present at the collector. Screw the slug out (anticlockwise) watching for an increase in amplitude of the 29MHz signal until it drops abrupt­ly. Screw the slug in (clockwise) until the oscillator starts and continue on for one half turn. At this point you should have about 5V RF signal at the collector of Q1. The oscillator is now tuned. Check the frequency with a counter to ensure that you are within ±1.7kHz Kit Availability Kits for the Mk.22 transmitter are available in several different forms, as follows: Fully assembled module (less crystal) .......................................................... $125.00 Basic kit (less crystal) ...................................................................................... $89.00 PC board ......................................................................................................... $29.50 Crystal (29MHz) ................................................................................................ $8.50 Post and packing of the above kits is $3.00. Payment may be made by Bank­­card, cheque or money order payable to Silvertone Electronics. Send orders to Silvertone Electronics, PO Box 580, Riverwood, NSW 2210. Phone (02) 533 3517. of the marked crystal frequency. The final frequency will depend on the brand of crystal you have purchased. The Showa crystal supplied will be within tolerance. The frequency may be fine tuned with C2; increasing C2 will decrease the frequency. Do not exceed 33pF for this capaci­tor. Set VC2 to mid-range and, using a wave meter, field strength meter or spectrum analyser, tune L2 and L4 for maximum amplitude of the output signal. At this point I should point out that the aim here is not to tune for maximum power but to achieve a balance between output power on the fundamental frequency against harmonic content. This is the problem that arises when tuning without a spectrum analyser. To further complicate the tuning process, VR1 is best set by tuning it for minimum third order levels. It is impossible to do this without a spectrum analyser. Once the transmitter is at maximum output, take note of the harmonic levels. VC2 is fitted for suppression of 60MHz and 90MHz harmonics. Adjust VC2 for the minimum harmonic levels and then retune L2 and L4 for the maximum difference between fundamental and harmonic outputs. It should be possible to exceed -60dB on all harmonic levels. At this point, the PA current should be about 65mA. Next, set up a second transmitter at a frequency 60kHz away, with the modulation removed (CW) and of approximately equal output to the Mk.22 transmitter. Place it on a bench with the antenna fully extended and switch­ed on. Switch on the Mk.22 and position it so that a good strong third order component is clear­ly visible on the spectrum analyser display (it will be the small spike closest to the Mk.22 fundamental spike). Tune VR1 for the minimum level of third order intermodula­ tion and move out until the two fundamentals are of equal ampli­tude. At this point, the third order intermodulation component of the Mk.22 should be approximately 15dB down on that of the adja­cent transmitter. Go back now and touch up L2, L4 and VC2 and tuning is com­plete. Check the PA current once more to ensure that it is under 100mA. Next month, we will discuss the SC assembly of the encoder. Fig.5: here are the full-size etching patterns for the double-sided PC board. 56  Silicon Chip BUILD YOUR OWN LASER LIGHTSHOW You’ve seen those fancy lightshows at discos and pop concerts. Now you can build your own using an exotic blue Argon laser or you can save money and use a Helium-Neon laser instead. The lightshow is provided by a motor-driven mirror system con­trolled with simple electronic circuitry. Design by BRANCO JUSTIC May 1996  57 The interior of the helium-neon laser lightshow includes the tube itself, the high voltage power supply and the three motor mirror deflection system W HILE LASERS ARE widely used in industry and entertainment, they still have a capacity to fascinate. And they are all the more fascinating when they are deflected into myriad patterns by a motor drive system. Combine the motor drive system with a fog machine and you can have some really interesting effects, espe­cially if a blue argon laser is used. In essence, the lightshow presented here can be used with any visible laser. Well, that’s not quite true because if the laser was a high-power unit, the The exterior of the helium-neon laser lightshow is covered in grey carpet to provide a surface finish which stands up well to disco use. 58  Silicon Chip deflection mirrors would be cooked but since few readers will have the budget for a high-power laser we won’t worry too much. The photo at the start of this article shows only one of the endless number of patterns produced by this lightshow. The patterns vary from single to multiple flowers, collapsing cir­cles, rotating single and multiple ellipses, stars and so on. We are presenting two lasers in this article. The first, the 100 milliwatt (100mW) argon unit referred to above, can be purchased virtually ready to run. It needs to be hooked up to a beefy power supply and housed in a substantial carrying box, along with the motor deflection system. It also requires forced air cooling. The circuit is shown in Fig.1. The second unit is a 10mW helium-neon laser and it too is available as a ready-to-run unit needing only a suitable power supply and a box. As presented here, the motor deflection system has three motors although it could use two or four. Each motor can run at eight different speeds and one of the motors is periodically re­ versed while another is stopped for varying intervals. The specified motor is a DC type with four wires, two for the armature and two for feedback, for precise speed control. The motor drive circuit is shown in Fig.2. This shows the complete circuitry for two motors and employs an LM358 dual op amp. Circuit details Let’s describe the circuit involving op amp IC1a and tran­sistor Q1. Q1 is a BD679 Darlington transistor which drives the motor with varying DC. Q1 Fig.1: this diagram shows the power supply of an Argon gas laser. Fig.2: this dual motor control circuit employs the feedback winding of the motor to give precise speed control. It’s based on an LM358 dual op amp (IC1a & IC1b). May 1996  59 60  Silicon Chip Fig.3 (facing page): this driver circuit provides eight different voltage settings to inputs A & B on Fig.2. It also provides reversing of one motor via relay RLY1 and periodic stopping of another motor via relay RLY2. is driven by op amp IC1a which functions as an error amplifier. It compares the reference voltage at its pin 5 with the feedback voltage (derived from the motor) at pin 6. If the feedback voltage is slightly low, then the op amp increases its output to Q1 and the motor. Similarly, if the feedback voltage is slightly higher, indicating a higher than desired motor speed, the op amp will reduce its output to Q1 and the motor. The feedback signal from the motor is fed to a diode pump rectifier consist- Fig.4: this is the power supply to drive the circuitry of Figs.1 & 2. ing of diodes D1 & D2, together with capacitors C1 & C2. This produces a DC voltage (V1) which is proportional to the speed of the motor. A table is included in the diagram of Fig.2, giving typical values of V1 for a range of DC voltages to the motor. VREF, the reference voltage applied to pin 5, is preset by trimpot VR1 and is derived from 6.2V zener diode ZD1. VREF is the basic speed setting for the motor but this is varied up and down by a voltage fed to point A. Point A is driven by the circuit of Fig.3, the Automatic Lightshow Driver. The circuit of Fig.3 is designed to Fig.5: this composite board layout includes all the circuitry of Fig.3 and two dual motor drivers, as shown in Fig.2. Note that while it could control four motors, only three are used in the lightshow. May 1996  61 This photo shows a finished composite PC board and the power supply. Note that the wiring between the various sections of the com­posite board does not agree with the wiring shown in Fig.7 although it is still valid. All three motors are speed controlled, one motor is periodically reversed by relay RLY1 and one motor is periodically stopped by relay RLY2. Fig.6: component layout for the power supply of Fig.4. This close-up photo shows the mirrors attached to the drive pulleys of the motors. Note that the wiring should be laced up neatly so that it cannot foul any of the rotating mirrors. 62  Silicon Chip randomly vary the speed of up to four motors via one or two “Dual Motor Speed Con­ trollers”, as depicted in Fig.2. Note that while it can control up to four motors, only three motors are used in the laser lightshow presented in this article. The circuit is based on IC1, a 4060 14-stage binary ripple counter with a built in oscillator. Its frequency of operation is determined by C1, R2 and R1 and is about 40kHz. It is gated on and off, via diode D1, by a low frequency oscillator based on IC2c, a 2-input NAND Schmitt trigger gate. When the output of IC2c is high, the 40kHz oscillator runs and when IC2c’s output is low, the oscillator is stopped. The running time is nominal- Fig.7: here are the inter-wiring details for the composite board of Fig.5. ly one while the stop time is about five times that, with VR1 at its minimum setting. When VR1 is at its maximum setting, the stop time is about eleven times longer. So the duty cycle of the 40kHz oscillator is variable by VR1 from about 5:1 to about 55:1. In practice, the run and stop times will depend more on the hysteresis of the 4093 Schmitt NAND gate than on the time-constants of R3.C2 and R4.C2. In our prototype, the run time was less than 70 milliseconds and the minimum stop time was about 0.35 seconds. The maximum stop time was about four seconds. These variations brought about by the 4093 are not important and do not affect the circuit operation. As the 40kHz oscillator is gated on an off, the ripple counter runs or stops as well. So its 14 outputs are changed, high or low, every few seconds in an apparently random fashion. 12 of these outputs are used to switch transistors Q1-Q12 on or off. The transistors are arranged in groups of three and because of the differing collector resistors and depending on how they are switched by the 4060, they will provide eight different voltages at points A & B on the motor speed controller boards. A LED is connected in series with each transistor base, giving an indication when the respective transistor is on. Stop & reverse Pin 4 of the 4060 is also used to drive transistor Q13 and its relay. This is used to periodically reverse the direction of one of the motors. At the same time, pin 15 is buffered by the three remaining gates in IC2 and these drive a second relay to periodi­ cally stop one of the motors. Both of these measures add to the variability of the patterns produced. Fig.4 is the circuit of the 12V power supply which feeds the circuits of Fig.2 and Fig.3 and the three motors. May 1996  63 Fig.8: suggested orientation of the three motors. It is powered by a 12V 1A plugpack transformer. Fig.4 comprises four diodes and a 1000µF capacitor driving a 7812 3-terminal 12V regulator. This is bypassed at its inputs and outputs with 10µF and .068µF capacitors. Construction As far as the construction details of this project are concerned, we will assume that you already have a complete laser which is working. To make it function as a lightshow you will need to build two PC boards, mount three motors on a board and wire them all together. The circuits of Fig.2 and Fig.3 have been made available as one PC board, which has two 2-motor drive circuits on it. The layout for this composite Lasers: Dangers & Warnings The following is an brief outline of dangers and warnings for all laser devices. For more detailed guidelines we recommend contacting the “Department of Health and Radiation” in Victoria for a copy of “Safety Guidelines For Lasers In Entertainment”. ● Lasers above a certain power level (eg, over 1mW) require licensing in some states. Check with your state government department. ● Never look into a laser beam. This will cause eye damage. ● The user must be aware of all potential dangers involved in the operation of the laser. ● Gas lasers (ie, argon and helium-neon) use very high voltage at 64  Silicon Chip very dangerous or lethal energy levels. Many tubes typically require over 10kV to strike and run continuously at around 2kV. ● Do not attempt to build a laser unless you are qualified to work with high voltage equipment. ● Never touch any part of the laser supply or tube while it is operating. ● Capacitors in laser supplies retain their high voltage for long periods after being switched off. Always discharge each high voltage capacitor after switching off when making repairs to the unit. ● Warning stickers relating to both laser light and high voltage must be attached to the laser (these are included in the kit). board is shown in Fig.5. Once again, note that only three motors are required but Fig.5 shows circui­try for four motors. You can leave the unwanted bits out but they only amount to a 6.2V zener diode, a BD679 transistor, a 10kΩ trimpot and a few resistors and capacitors. Assembling the composite board is quite straightforward. PC stakes should be provided for all the external wiring connec­tions. Make sure that all polarised components are inserted correctly. It is wise to check the polarity of at least one of the supplied LEDs because it is not unusual for these to be supplied with polarity reversed; ie, the longer lead is sometimes the cathode instead of the anode. Fig.6 shows the component layout for the PC board. We sug­gest that a larger heatsink be fitted to the regulator than the one shown in our photos. The regulator heatsink in our prototype ran a little too warm for our liking. When the power supply board is completed, it should be powered up and its output voltage checked – it should be close to +12V. Do this check before connecting its output to the composite board. Fig.7 shows how the composite board is wired. The operation of this board should be checked before the motors are connected. Apply power and check for the presence of +12V and +6.2V at all points shown on the circuits of Fig.2 and Fig.3. With power applied, all the LEDs should switch on and off at regular intervals and you should hear the relays click on and off as well. Provided all LEDs operate then the board is probably functioning correctly. It is now a matter of connecting the three motors. Before that is done, they need to have mirrors fitted onto their pul­leys. This is relatively simple, although some care should be taken to keep the angle as small as possible. If the angle is too large, the laser deflection will be excessive and it will be difficult to line it up to hit the successive mirror. Excessive laser deflection will also result in patterns that are too large and have reduced brightness. Each mirror should be secured with silicone caulking com­ pound which does not set hard. This will provide a degree of cushioning for the mirrors when the motors suddenly stop or reverse direction. Inside an Argon laser, showing the brute force power supply, squirrel cage fan for cooling and the three-motor mirror deflection system. Start by placing a square (2 x 2mm) piece of electrical tape onto the rim of the pulley. This will give a sufficient angle for the mirror. This done, apply a small amount of silicone compound to the pulley and attach the mirror firmly at the de­sired angle. Fig.8 shows how the motors should be positioned with re­spect to the laser beam. We suggest that the baseboard be made of HMR (high moisture resistant) particle board for long-term stability. Any other timber will tend to warp and throw the motors out of alignment. The motors can be simply attached to the baseboard base using hot melt glue. This will allow the construc­tor to align each motor as the glue sets. You will need to run the whole system together with a laser before the glue finally sets, to make sure that the SC alignment is satisfactory. Kit Availability Kits for the laser lightshow described in this article are available from Oatley Electronics who own the design copyright. They have kits for Argon and Helium-Neon lasers as well as the lightshow controller. The pricing details are as follows: Laser light show (does not include laser or its power supply) – includes all electronic components for PC boards and three motors and mirrors: $90.00. Suitable plugpack transformer: $14.00 He-Ne laser and power supply: $80-120, depending on tube rating. Laser case kit – includes 12V power supply, precut 16mm craftwood box, plastic corners, all screws and grey carpet: approximately $90 (ring for details and availability). Argon laser: $300-500, depending on hours of usage (ie, these are second­ hand tubes). Ring for details of availability and power supply requirements. For further information on pricing and availability, contact Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985 or fax (02) 570 7910. May 1996  65 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au PRODUCT SHOWCASE Philips calibration lab takes to the road Philips’ Calibration Laboratory has created a mobile test centre, taking international standard electronic measurement equipment directly to customer premises. The mobile “Cal Lab”, housed in a temperature and humidity controlled Isuzu 2-tonne truck, needs only a 3-phase outlet at the location to perform a range of calibration tests. This will reduce the normal 10-day turnaround on instrument calibration to just a single day and in some cases to a few hours. This is expected to be a major bene­ fit to small and medium-sized businesses which usually don’t have the workload or the financial wherewithal to justify back-up test equipment. While there was no problem with the quality of Philips’ calibration service at its Moorebank (Sydney) laboratory, there was a real problem in the time taken, with obvious implications for productivity. Now businesses from Newcastle to Wollongong can have the same quality BassBox ® Design low frequency loudspeaker enclos­ures fast and accurately with BassBox® software. Uses both Thiele-Small and Electro-Mechanical parameters with equal ease. Includes X. Over 2.03 passive cross­over design program. $299.00 Plus $6.00 postage. Pay by cheque, Bankcard, Mastercard, Visacard. EARTHQUAKE AUDIO PH: (02) 9948 3771 FAX: (02) 9948 8040 PO BOX 226 BALGOWLAH NSW 2093 70  Silicon Chip on-site. The mobile lab, fitted with the latest calibration equipment, is operated by one highly experienced technician using specially developed Philips software to minimise error, time taken and therefore cost. NATA has extended its registration of the Philips Calibration Laboratory to cover the mobile lab. For further information, contact Philips Electronics Australia Ltd, phone (02) 9925 3281 or fax (02) 9929 4784 “Electronics at Work” June Expo for Sydney Semiconductor and Mitsubishi. A major feature of the expo will be EMC – electromagnetic compatibility. There will be virtually continuous EMC workshops at Homebush and, running in parallel with the expo, an international conference focusing on EMC will be conducted at the Parra­ matta Gazebo Hotel, with shuttle buses connecting the sites. In addition, there will be numerous other seminars at the Homebush site covering topics ranging from “VXI Upgrading from Rack and Stack” through to “Surface Mount Devices” and “Embedded Systems – Designs and Software.” The expo is being staged by Practical Marketing, phone (02) 9958 1811, fax (02) 9958 2759. For more information on the EMC conference, contact Steven Pulver, AEDC, phone (02) 302 1422 or fax (02) 302 1201. The “Electronics at Work” expo, being held at the Sydney Olympic Site at Homebush Bay on June 5 and 6, is planned as the Pacific Rim’s most comprehensive event for the electronics industry. It will bring together various industry bodies for a timely insight into the latest product developments. Bodies represented include the Spectrum Management Agency (SMA), the Australian Electronics Development Centre (AEDC) and the Australian Electrical and Electronics Manufacturers Association (AEEMA). The exhibition will showcase a large array of the latest products and services, with brands on show representing mainstream industry names such as Hewlett Packard, Motorola, GEC, Tektronix, Philips, Alcatel, National Virtual instrumentation seminars are free National Instruments’ upcoming seminars on Virtual Instrumentation with Windows 95 and Windows NT are different to most of the seminars these days: they’re free! Being held during May in all state capitals except Darwin and Hobart, the 3½ hour seminars are targeted at scientists, engineers and engineering managers who build or use instrumentation systems. The seminars will show how users can take advantage of the latest hardware and software technologies in computing and instrumentation, such as the high speed PCI bus, and how to build portable instrumentation systems using notebook computers and PC cards. Also included will be technical demonstrations of virtual instrumentation systems running on Windows 95 and Windows NT and National Instruments’ own virtual instrumentation software products including LabVIEW 4.0, LabWindows/CVI 4.0, ComponentsWorks, Measure for Microsoft Excel and VirtualBench. All attendees will receive copies of all seminar materials including free demo discs, along with Instrupedia, the CD-ROM encyclopaedia of instrumentation. Dates (all May) are Melbourne 7/8, Adelaide 10, Sydney 14/15, Brisbane 17 and Perth 28. Registrations to National Instruments on (03) 9879 9422, or e-mail to info.australia<at>natinst.com. YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SATELLITE ENTHUSIASTS STARTER KIT 1996 Obiat catalog A new 44-page catalog is now available from Obiat and describes their wide range of test and measuring equipment. This includes products from the world’s leading manufact­ urers such as Fluke, Metrix, Kepco, Cal­ifornia Instruments, AEMC, Black­ star, Silvertronics, Delta-Ohm, AV Power, Sadelta and Pantec. The catalog features handheld and bench digital multimeters (along with a full range of accessories), LAN testers, AC power analysers, temperature and humidity meters, desoldering stations, TV pattern and function generators, frequency counters, automotive multi­meters and a full range of electrical test equipment. To obtain a copy of the catalog, contact Obiat on (02) 698 4111, or fax (02) 699 9170. YOUR OWN INTERNATIONAL SYSTEM FROM ONLY: FREE RECEPTION FROM Asiasat II, Gorizont, Palapa, Panamsat, Intelsat HERE'S WHAT YOU GET: ● ● Hobbyist loupe range from Oatley Electronics A range of low-cost loupes, or magnifiers, has been released by Oatley Electronics. Intended for the hobbyist market, these will also find wide acceptance by technicians, QC/QA personnel and others who need a close-up view. There are four in the range, starting with a jeweller’s eyepiece (the type you see in gangster movies where the “fence” places the glass in his eye to examine the diamonds the crook has just brought in). This is priced at $3.00 and has a plastic lens. The top three in the range all incorporate two glass lenses, and are intended to be used where the loupe is placed close to the object (print, insect, coin, etc) to be magnified. The focal point is just below the base of the loupe. The smallest, priced at $8.00, is 50mm in diameter and has a magnification of 10 times. Next up is the 75mm model ($12.00), while the largest is a healthy 110mm and is priced at $15.00. All these are available by mail order direct from Oatley Electronics, 5 Lans­downe Pde, Oatley West 2223. Phone (02) 579 4985 or fax (02) 570 7910. ● ● ● ● 400 channel dual input receiver preprogrammed for all viewable satellites 1.8m solid ground mount dish 20°K LNBF 25m coaxial cable easy set up instructions regular customer newsletters BEWARE OF IMITATORS Direct Importer: AV-COMM PTY. LTD. PO BOX 225, Balgowlah NSW 2093 Tel: (02) 9949 7417 / 9948 2667 Fax: (02) 9949 7095 VISIT OUR INTERNET SITE http://www.avcomm.com.au YES GARRY, please send me more information on international band satellite systems. Name: __________________________________ Address: ________________________________ ____________________P'code: __________ Phone: (_______) ________________________ ACN 002 174 478 May 1996  71 Time-lapse VCRs from Sanyo Sanyo Australia has released two new time lapse video cassette recorders. They are designed for security applications in banks, hotels, casinos, service stations, restaurants and similar locations where cash, valuables or people require monitoring. The TLS-924P is capable of up to 24 hours of time lapse recording. With a horizontal resolution of 350 lines (B&W), the 4-head unit gives excellent VHS picture quality. Multiple recording modes also allow audio recording. Single fields can be taped one by one and also viewed separately during playback. Timer recording can be set on a daily or weekly basis, and all settings are made and confirmed via an on-screen display. If the unit is triggered (for example by an alarm sensor or duress switch), it automatically switches to an alarm recording (3 hour) mode, giving a complete recording of the event that triggered the alarm. Furthermore, an alarm scan function allows playback every five seconds of an alarm functioning. The TLS-S2500P is similar but comes in a super VHS format with more than 400 lines of resolution, even in time-lapse mode. With this model, it is also possible to record in various multiples of hours, right up to 960 hours (40 days). Sanyo video surveillance products are distributed in Australia by Javelin Electronics, phone (02) 684 4477 or fax (02) 684 2187. 100W DC-AC inverter for consumer products While many of today’s consumer electronic items offer both mains (240V) and low voltage operation, there are significant numbers that do not. Even items which use rechargeable batteries often have no provision for charging, except via a 240V outlet. Using such items away from a power point (in a vehicle, for example) has long been a problem. Powerbox Australia has solved the problem with their Motormate, a 300 watt peak or 100 watt continuous 12V DC to 240V AC inverter, which is designed to run direct from a vehicle’s cigarette lighter. KITS-R-US PO Box 314 Blackwood SA 5051 Ph 018 806794 TRANSMITTER KITS $49: a simple to build 2.5 watt free running CD level input, FM band runs from 12-24VDC. •• FMTX1 FMTX2B $49: the best transmitter on the market, FM-Band XTAL locked on 100MHz. CD level input 3 stage design, very stable up to 30mW RF output. $49: a universal digital stereo encoder for use on either of our transmitters. XTAL locked. •• FMTX2A FMTX5 $99: both FMTX2A & FMTX2B on one PCB. FMTX10 $599: a complete FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input •connector for audio and a 1/2mtr internal antenna, also available in 1U rack mount with balanced cannon input sockets, dual VU meter and BNC RF $1299. Ideal for cable FM or broadcast transmission over distances of up to 300 mtrs, i.e. drive-in theatres, sports arenas, football grounds up to 50mW RF out. FMTX10B $2599: same as rack mount version but also includes dual SCA coder with 67 & 92kHz subcarriers. • AUDIO Audio Power Amp: this has been the most popular kit of all time with some 24,000 PCBs being •soldDIGI-125 since 1987. Easy to build, small in size, high power, clever design, uses KISS principle. Manufacturing rights available with full technical support and PCB CAD artwork available to companies for a small royalty. 200 Watt Kit $29, PCB only $4.95. AEM 35 Watt Single Chip Audio Power Amp $19.95: this is an ideal amp for the beginner to construct; uses an LM1875 chip and a few parts on a 1 inch square PCB. Low Distortion Balanced Line Audio Oscillator Kit $69: designed to pump out line up tone around studio complexes at 400Hz or any other audio frequency you wish to us. Maximum output +21dBm. MONO Audio DA Amp Kit, 15 splits: $69. Universal BALUN Balanced Line Converter Kit $69: converts what you have to what you want, unbalanced to balanced or vice versa. Adjustable gain. Stereo. • • •• COMPUTERS I/O Card for PCs Kit $169: originally published in Silicon Chip, this is a real low cost way to interface •to Max the outside world from your PC, 7 relays, 8 TTL inputs, ADC & DAC, stepper motor drive/open collector 1 amp outputs. Sample software in basic supplied on disk. PC 8255 24 Line I/O Card Kit $69, PCB $39: described in ETI, this board is easy to construct with •onlyIBM3 chips and a double sided plated through hole PCB. Any of the 24 lines can be used as an input or output. Good value. 19" Rack Mount PC Case: $999. •• Professional All-In-One 486SLC-33 CPU Board $799: includes dual serial, games, printer floppy & IDE hard disk drive interface, up to 4Mb RAM 1/2 size card. PC104 486SLC CPU Board with 2Mb RAM included: 2 serial, printer, floppy & IDE hard disk $999; VGA •PC104 card $399. KIT WARRANTY – CHECK THIS OUT!!! If your kit does not work, provided good workmanship has been applied in assembly and all original parts have been correctly assembled, we will repair your kit FREE if returned within 14 days of purchase. Your only cost is postage both ways. Now, that’s a WARRANTY! KITS-R-US sell the entire range of designs by Graham Dicker. The designer has not extended his agreement with the previous distributor, PC Computers, in Adelaide. All products can be purchased with Visa/Bankcard by phone and shipped overnight via Australia EXPRESS POST for $6.80 per order. You can speak to the designer Mon-Fri direct from 6-7pm or place orders 24 hours a day on: PH 018 80 6794; FAX 08 270 3175. 72  Silicon Chip From the packaging, which shows a range of consumer products which the Motormate will power, it would appear that it is aimed at the consumer market. No information is given on the efficiency of the inverter but the Motor­mate incorporates a low battery automatic shut down to protect the vehicle battery. It also has short circuit, overheating and fuse protection. For further information, contact Powerbox Australia, 4 Beaumont Rd, Mt Kuring-gai 2080. Phone (02) 457 2244, fax (02) 457 2255. Undervoltage monitors from GEC For the correct initialisation of microprocessor circuits under con- Mobile Business Centre The HP OmniGlo 700LX Communicator Plus is claimed to be a mobile business centre, based on the HP200LX Palmtop PC platform and Nokia mobile phone’s cellular technology. It integrates voice and data communications which can be used independently or as together. For example, the user can dial a voice call from the address book in the PC or access the address book for fax numbers while in the fax application. The PC side also incorporates a range of built-in business and personal management software, which are all integrated. Because of the unit’s small, unobtrusive format, note taking, data search and even sending and receiving of faxes can be made virtually anywhere, even during meetings. Only data communications and e-mail require any configuration to operate. The OmniGlo 700LX is said to be intuitive, and user friendly to all messaging services of the GSM (global system for mobile access) network, including voice, data, fax and short messaging services. As these services are already in place in many countries around the world, the international traveller using an OmniGlo 700LX can take advantage of the international roaming agreements which exist between service providers. Further information is available toll-free from Hewlett Packard on 131 347. AUDIO TRANSFORMERS suitable for 5V circuit applications. It also has protection against noise and glitches. Contact GEC Electronics Division, Unit 1, 38 South St, Rydalmere 2116. Phone (02) 638 1888 or fax (02) 638 1798 First AMD5K86 processors shipped Manufactured in Australia Comprehensive data available Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 ditions of power start-up or power failure, GEC’s XM33064 undervoltage monitor provides a dependable means of detecting supply voltage excursions and a consistent source of reset triggering. The chip, available in SOT223, SO8 and TO-92 packages, operates at a preset threshold of 4.6V, making it AMD has started shipping the first of their new plug-in replacements for the Pentium processor, the AMD5K86. It is a fifth generation, super-scalar device that is fully compatible with the Microsoft Windows operating system and x86 software. The two chips now released are the P75 and P90 models, which give the performance of the Pentium-75 and Pentium-90 respectively. AMD claim that the chips now give PC manufacturers the freedom to choose a viable Windows-compatible alternative that will help them differentiate and market their PC products. AMD has shipped some 40 million Windows-compatible CPUs in the past four years. For further information, contact AMD Australia, Phone (02) 9959 1937. Kenwood gets gong at sound awards Kenwood’s M-29M High Power Midi System was named “Audio System of the Year (up to $1000)’’ at the 1995/96 Australian Sound and Image Awards. The 3-way, 75 watt system uses Kenwood’s Acoustic Signal Processor. This is said to recreate the ambience of an arena, jazz club or stadium and, it is claimed, can also enhance music left “flat” by compression and other dubbing techniques. The system also has an equaliser with four presets – pop, rock, jazz and classic – to tailor the audio to suit these types of music. Also included is an AM/FM synthesised tuner with 40 presets, a 5-disc programmable CD player, full logic double cassette with auto reverse and Dolby HX-Pro and Dolby B, plus a programmable timer to allow wake-up with CD, tape or radio. A turntable is optional. With a 2- year warranty, the M-29M has a recommended retail price of $999. Contact Ken­­wood Electronics Australia on (02) 746 1888. Practical Marketing Group | Electronics at Work May 1996  73 COMPUTER BITS BYhttp://www.pcug.org.au/~gcohen GEOFF COHEN HTML for beginners – creating your own World Wide Web page While there are literally millions and millions of people browsing the Internet, comparatively few have their own home page on the World Wide Web (WWW). Here’s a brief rundown on creating a home page from scratch. Although I didn’t realise it when I started using the Internet last year, Internet Service Providers (ISPs) allow you to have your own Home Page. I was pleased that my ISP (PC Users Group, ACT), allows free home pages for non-commercial use, although they do charge for commercial home pages. Another ISP I contacted (TPG) said that their charge was around $30.00 per month, depending on the usage of the page. The Hyper Text Markup Language (HTML) is the language used on the World Wide Web. When you use an Internet access program such as Netscape or Mosiac to view a web document, you are look­ing at a HTML document that someone spent some time creating. Hopefully, by the end of this article, you will be able to spend some time creating your own home page. HTML features HTML allows very attractive home pages to be created, pro­vided that you are prepared to invest some time and effort. Some of its features are: • Documents can be formatted with different font styles and sizes. • Hyperlinks can be established to other web pages and programs. • Graphical images can be included in web pages. • The newer extensions (eg, Java) offer frames, 3D features and on-screen animation. I would recommend that you download Netscape 2 (it’s available for both Windows 3.x and Windows 95) to check out these features, although they are quite complex and I won’t even attempt to cover them in this HTML primer. Web editors and HTML The preview feature of Hot Dog Pro lets you run Netscape off-line. This lets you view both the Hot Dog Pro source code (left) and also the document as displayed by Netscape (right). 74  Silicon Chip The HyperText Markup Language, as it’s name suggests, uses markup codes to create all those nifty pages you have browsed on the net. While you can use any text editor to make you own Home Page, the markup codes can make HTML editing a real chore, espe­cially if you are a HTML novice, I found that using a web page editor made life a whole lot easier. The editor I have used the most is Hot Dog Pro, an Austra­lian product. Evaluation copies are available at: http://www.sausage.com. When Hot Dog pro is loaded, you can choose to run the tuto­rial (real programmers don’t need tutorials, of course). Having done this, you can You don’t have to learn HTML codes. Just click on the appropriate buttons and Hot Dog Pro will generate the HTML source codes for you. Above: once your Web page has been created, it needs to be placed in the publishing directory of your Local System. This is done by running an ftp (file transfer protocol) program. Fig.1: Basic HTML Document <HTML> <HEAD> <TITLE> type_Document_Title_here </TITLE> </HEAD> <BODY> </BODY> </HTML> actually start the process and create a HTML document, using either the “File/New” or the Button bar. Hot Dog Pro will then produce this basic HTML document, which will usual­ly be saved in the default HTML name of Welcome.htm. This document is shown as Fig.1. As you can see, HTML codes are included inside angle brack­ ets and (nearly) all HTML codes have two parts: (1) a start such as <HEAD>, some text, pointers, etc; and (2) a matching closing command (eg, </HEAD>), with a “/” ahead of the first code. These markup codes don’t care about case but are normally written in upper case to make them more obvious in the document. Another important point is that HTML ignores blank lines, spaces and tabs, etc. A web browser will simply reformat the screen, depending on the size of it’s window. I use blank lines to separate the various codes, to make the source text easier to read. In essence, our simple HTML document is composed of four parts. The first code <HTML> and the matching last code </HTML> tell the browser that this is a HTML document. The next code pairs <HEAD and </HEAD> are for the heading of the HTML document. Between these are <TITLE> and </TITLE>, with the title’s text in the middle. The title should, fairly obvious­ly, identify the contents of the document. The <BODY> and </BODY> codes are what we are really waiting for. This is where we put all the HTML stuff a browser sees. Now the beauty of using an HTML editor such as Hot Dog Pro is that you don’t really have to learn all the codes. Instead, the Button bar and Menus do all the hard stuff for you. I just selected “H1” from the Button Bar and typed in “Large text at the top of the page” to put some large text at the top of the page. I then marked that text and clicked on the Centre button. Using Hot Dog Pro, it’s also simple to add hypertext links, images or any other HTML feature you need. I just clicked on the “External” button to add a link to a news & mail reader called “Agent”. The code Hot Dog Pro generated is not too hard to under­stand, especially if you use the Preview feature. May 1996  75 This lets you run Netscape off line, so you can generate your Web pages without wasting time on line. I have configured my Windows display to 1024 x 768 and this allows me to view both the Hot Dog Pro source code and also the document as displayed by Netscape (or whatever browser you use) – see photo. The code listed in Fig.2 only took about five minutes to generate and could be very easily expanded to a usable Home Page. When you have finished any changes, it is a good idea to check your document for any HTML syntax errors. In Hot Dog Pro, go to the menu and select “Tools/Check HTML Syntax” and it will check for errors. If it finds any, it stops and indicates exactly what the error is. I found my most common error was forgetting to close a <COMMAND> with it’s matching </ COMMAND>. Publishing your Web page Left: this is how the author’s Home Page looks with if the Web Browser has “Auto Load Images” turned off. Fig.2: A Basic Home Page <HTML> <HEAD> <TITLE>Geoff Cohen’s simple HTML test</TITLE> </HEAD> <BODY> <H1><CENTER>Large Text at he top of the Page</CENTER></H1> <BR><BR><BR> A simple List <UL> <LI>Item 1 on our list</LI> <LI>Item 2 on our list</LI> <UL> <LI>Nested Item on our list</LI> </UL> <LI>Item 2 on our list</LI> </UL> A hyperText link<BR> <A HREF=”http://webpress.net/forte/agent/”>Agent the best News & Mail reader</A> </BODY> </HTML> 76  Silicon Chip Once the page is what you want, as viewed locally on your browser, you need to press the “Publish” button. This transfers the finished HTML document to the directory you selected for the finished product. Incidentally, Hot Dog Pro can be configured to automatically translate any PC backslash (“\”) characters to the Unix “/” character. Now it’s time to run your normal Internet software and get on line. When you are connected, run your ftp (file transfer protocol) program and select the publishing directory for the Local System (mine is E:\HTML\ HTDOGPRO\WWW). The Remote System side will depend on your Internet suppli­er. They will have given you the correct address and a password when you asked for your own Home Page. This is normally different from the http address that your browser will use. As an example, my http address is http://www.pcug.org.au/~gcohen, while the ftp address is ftp.pcug.org .au/home/pcug/gcohen/WWW. Make sure you get the full details from your supplier. Once the ftp program is connected, it’s simply a matter of clicking on the Local System file (in my case Welcome. htm) and clicking on the transfer (->) key. The HTML is then transferred (it only takes a few seconds) to your web server. To test that all is well, run your browser, and type in your home page address. You should then see your home page. Note that the view will depend on whether the browser has Auto Load Images selected or not. Speed up your browsing One point I should mention is that, to speed up browsing, I don’t normally have “Auto Load Images” as the default on Nets­cape. Instead, I just click on the “Images” button if I want to see a particular image. If I am browsing through pages where I want to view all the images, I manually select “Auto Load Images” but I don’t click on “Save Options”. Thus, when I load Netscape the next time, I still have my preferred options (ie, “Auto Load Images” will be off). That’s about it really. When you change the page, just repeat the above steps: (1) edit and view locally on the browser; (2) publish; (3) get on line and ftp to the web server; and (4) test with your browser. If you have problems which you or your supplier can’t solve, you can always send me an email and I will try to help fix the problem. Short cuts One of the easiest ways of getting experience in HTML pages is to examine the HTML source for someone else’s page. With Netscape, you can either save the page (Control S) or just have a quick look at the HTML source (View/Document Source). Another thing I should mention is that if you are going to spend any appreciable time writing HTML code, there is a handy little book called the “10 Minute Guide To HTML”, by Tim Evans. It’s not one of those enormous, expensive, bloated computer manuals bit is very easy to read and understand. It gives a good grounding in HTML, with a listing of examples and HTML codes. I also found the Hot Dog Pro Help menu was great. It had a full description of HTML 2 codes, with examples. An alternative to Hot Dog Pro is a program called WebEdit, which I have also tried. I should also mention that Netscape has just released Navigator Gold 2.0 for creating Java scripts and I will check it out in the near future. Finally, for those who want to check out my home page, it is located at http://www.pcug.org.au/~gcohen SC Selecting “Auto Load Images” on the Web Browser lets you view any graphics that may be present but can significantly slow download times. Fig.3: Example HTML Codes Headlines & Text Style Headings <H1> . . . </H1>Largest heading font. <H2> . . . </H2> <H3> . . . </H3> <H4> . . . </H4> <H5> . . . </H5> <H6> . . . </H6>Smallest heading font <STRONG> . . . </STRONG> Make text bold <EM> . . . </EM> Usually shows as Italics. <P> . . . </P> paragraph begin/end markers <BR> Start a new line at the given point. Note: there is NO matching </BR> Links <A HREF=”the_Link”>Text</A> Lists <UL> . . . </UL> <OL> . . . </OL> <LI> . . . </LI> HyperText or URL link Unordered List (with bullets) Ordered List (with numbers) The list items Images <IMG SRC=”Image_filename”> May 1996  77 BOOKSHELF Satellite TV & scrambling methods World Satellite TV & Scrambling Methods, published Septem­ b er 1993 by Baylin Publications. Soft covers, 357 pages, 275 x 215mm, ISBN 0-9178-9319-0. Price $79.00. Available from Av-Comm Pty Ltd, PO Box 225, Balgowlah, 2093. Phone (02) 9949 7417. On the 14th of February 1963, Syn­ com 1, the first geosta­ tionary tele­­communications satellite, was launch­ e d from Cape Canaveral. This landmark event heralded the beginning of a new era in worldwide communications. The first commercial satellite (Tel­star 1 launched in 1962) could relay 600 telephone conversa­ tions or one TV channel. By 1974 satellite capacity had expanded to 12 TV channels and 14,400 telephone conversations. The book is divided into five sections: section 1 is an introduction to home satellite TV, section 2 covers the outdoor components, section 3 the satellite receiver, section 4 details scrambling methods, and section 5 is dedicated to troubleshooting. Satellite TV receivers have now reached the fourth genera­tion, going from a dish with an expensive coax cable carrying a 12GHz signal indoors to an amplifier and double-conversion re­ ceiver, to the second generation where the first conversion was carried out adjacent to the dish. The third generation had a fixed oscillator which down-converted a dish “block” of frequencies to an intermediate block of 950-1450MHz. This signal was carried indoors using a cheaper coaxial cable than is necessary for 4GHz. The required channel was then tuned indoors in a conventional mixer. The fourth generation has been called the “tin can special”. The receiver is essentially three metal cans: the tuner, the demodulator and the RF modulator. There is a growing trend to integrate the tuner with the demod­ulator, simplifying things even further. The down conversion to the intermediate block is still done outdoors, however. Section 2 begins with the selection of suitable antenna positioners and feeder cables. The cable from the antenna to the LNB (low noise block) needs to be of the highest quality and lowest loss, especially for the K band. The feed into the house is usually RG-59 coaxial cable for all but the longest runs. A linear actuator is the usual meth­od employed for antenna positioning. It consists of a motor, a set of reduction gears and some sort of and switchmode power supplies, NPN transistors and positive supply rails are shown. The book begins with a discussion on the physics of semicon­ductors and junction diodes. It goes on to detail the functions of Schottky, varactor, Zener, Gunn, PIN and laser diodes. Next, basic principles of transistors are detailed at length, starting with bipolar transistors, then working through the different types of field effect transistors (junction, VFET, MOSFET, etc). Finally, thyristors are covered in some detail. Amos continues with chapters on common base/gate amplifi­ e rs, common emitter/source amplifiers and common collector/drain amplifiers (emitter and source followers). Tables are given summarising the input and output resistance, current Principles of transistor circuits Principles of Transistor Circuits by S.W. Amos, published by ButterworthHeinemann UK. ISBN 0 7506 1999 6, published May 1994, 215 x 135mm, 394 pages, soft covers. Price $49.95. This is the eighth edition of this book which was first published in 1959. While this latest edition claims to be updated to include the latest equipment such as laser diodes, opto-couplers and switchmode power supplies, it unfortunately still uses PNP transistors and negative supply rails in the majority of the descriptions of transistor circuit operation. In the newer chapters, such as on digital logic 78  Silicon Chip screw thread. The dish mount must be fitted with limit switches to prevent the motor from driving the dish into the ground. The next seven chapters deal directly with all aspects of the satellite receiver itself. The power supply, which is not very elaborate, normally provides +18V, +12V, +5V and around +36V for the actuator motor. All but the last are usually fed from IC regulators. An IF of 70MHz has become the de facto standard for the US, mainly due to the telephone companies using this frequency for their early satellite communications and because most experimentation was done using their surplus equipment. Now that SAW (stand­ ing acoustic wave) filters are commonplace, there is trend towards using 130MHz for the IF. The IF bandwidth determines the ultimate quality of the picture. Although the transmitted signal has a bandwidth of 36MHz, the average domestic receiver’s bandwidth is between 22 and 28MHz, due to compromises in cost and performance. Once through the IF strip, the signal has to be demodulated. This has been done using a NE564 PLL (phase locked loop) decoder. Although this device is only specified to 50MHz, many have worked at 70MHz. The MC1496 balanced demodulator is another suitable detector and typical circuits are shown. Other detectors which have been used include the delay line discriminator, which is usually built out of discrete components, the quadrature detector and the ratio detector. Once the signal has been detected it must be amplified to 1V peak-to-peak, the high frequency pre-emphasis add­ ed during transmission must be rolled off, and the 30Hz AM signal that was imposed on it during transmission must be removed. When the video has been recovered, the next step is to demodulate the audio. This is where the greatest difference exists between satellite and standard TV reception. Up to 20 audio subcarriers can be transmitted with one video channel and these exist as FM signals in the demodulated video signal above the 5MHz video bandwidth. The video is split and run through a high pass filter for the audio and a low pass filter for the video. The high pass signal is again split in two, to allow for stereo reception. So that standard FM components can be utilised, a 10.7MHz sound IF is used. This means that the VCO mixer signal must range from 15.7-18.7MHz. From here on, the signal processing is similar to a standard FM tuner. The received signal now exists as separate video and audio, only to be combined again in an RF modulator so that it can be fed to a standard TV set. This modulator is similar to those used in video recorders to combine the video and audio and feed it out on channel 3 or 4 directly to the TV. The section concludes with an analysis of several commer­cial satellite receivers. Section four is devoted to scram- bling methods. The authors claim that the aim of this chapter is to provide an understanding of the basic techniques used in scrambling. Many of the earlier systems used fairly unsophisticated methods, such as inverting the sync or video polarity, which were trivial for the “hackers” to defeat. The continuing war between the two sides has resulted in a dramatic increase in the security of the broadcasts. Various transmission systems, with the methods used to defeat them, are detailed. The increase in security is apparent with the latest systems using DES (a data encryption standard) which requires an export licence to leave the USA. The final section covers the troubleshooting of satellite reception systems. As these are for US products, the chapters have limited relevance in Australia, although they will give a keen technician an insight into the sorts of problems which could be encountered and an idea of the type of circuitry which may have to be dealt with. To sum up, this book provides quite an interesting introduction to satellite TV, especially for those with inquiring minds, who will be wonder­ing about scrambling methods and security after seeing the title. To quote the authors: “Every true engineer and technician is, in a sense, a hacker at heart. While many will not actually try to break a system, they want to know how it works.” There are many people who fit this category. (R.J.W.) gain and voltage gain for all configurations. Bias and DC stabilisation of both transistors and FETs is the next topic covered. Calculations of DC stability for various methods of biasing are given in worked examples. The role of temperature dependent resistors and diodes is also covered. The next few chapters cover small signal, large signal, DC, pulse, RF and IF amplifiers. The circuits of most of the small signal amplifiers are directcoupled with feedback stabilisation. The large signal designs initially use coupling transformers but the later circuits are direct-coupled with AC and DC feedback, more typical of today’s designs. The Author explains the reasons why you can’t just directly couple three transistors to make a high gain DC amplifier, then goes on to describe the stabilising and biasing necessary for this setup. Differential and monolithic amplifiers (ICs) and their bias and gain adjustments follow. Several pages are devoted to pulse and video amplifiers and the compensation necessary to extend the frequency response. RF and IF amplifiers differ from those previously discussed as the passband is usually only a small percentage of the mid-band frequency. Common emitter, common base and cascode amplifi­ ers, neutralisation, stability factor, gain calculations, forward & reverse AGC (automatic gain control) and decoupling are among the topics covered. Chapter 11 covers sinusoidal oscillators such as Hartley, Colpitts, Rein­ artz, crystal and dielectric resonators (as used in satellite receivers at 11 GHz). It concludes with descriptions of phase shift, Wein bridge and negative resistance oscillators. The next chapter explains modulators, demodulators, mixers and receivers. Modulators can be either amplitude (AM) or fre­ quency (FM) types, both being in common use today. The usual demodulator for AM is the series or shunt diode but the synchronous detector is also covered. (continued on page 93) May 1996  79 KnightRider LED Scanner This circuit simulates the row of scanned lights used on the car in the KnightRider TV series. The PC board has a row of 16 LEDs which are scanned back and forth continuously at a rate which can be set by an on-board trimpot. While it is many years since the “KnightRider” series was featured on TV, it still creates interest. In particular, the row of scanning lights in the bonnet of the car has been the inspiration for a number of circuits. We published one in the November 1988 issue of Silicon Chip. That circuit had two sets of 10 LEDs interposed into two rows. This new circuit has one row of 16 LEDs and is more realistic, scanning in one direction and then the other. The circuit presented here is based on a design submitted by Andersson Nguyen, of Bankstown, NSW. At his suggestion, we’ve simply taken his circuit and produced a PC board for 80  Silicon Chip it. The 16 LEDs are mounted along one edge and only two wires go to the board: +9V (or up to +12V) and 0V. How it works The core of this circuit is a 4029 presettable up/down counter. It is made to count up, then down, then up and so on. It counts from 0-15 and back again in BCD (binary coded decimal). The four outputs (A, B, C & D) are decoded to give 16 individual outputs by a 4514 (IC4) which drives the LEDs directly. Fig.1 shows the relevant circuit details. IC1, a 555 timer, provides the clock pulses for the 4029 presettable up/ down counter, IC2. It oscillates at By RICK WALTERS several Hertz, as determined by the 2.2µF capacitor and the setting of the 100kΩ trimpot VR1. Its output at pin 3 drives the clock input of IC2 at pin 15. IC2 can be set to count to any value from 0-15 by means of four jam (preset) inputs – pins 3, 4, 12 & 13. However, in this circuit, we want the full count so the jam inputs are not used; instead, they are tied low. Therefore, it counts from 0 to 15 then back to 0 again and its four BCD (binary coded decimal) outputs are connected to IC4, a 4514 1-of-16 decoder which drives the 16 high-intensity LEDs. Thus, as the 4029 (IC4) counts from 0-15, the output pins (S0-S15) of this IC will each go high in turn, lighting Fig.1: the KnightRider circuit is simple and, just as important, simple to build. It is designed to be mounted in a vehicle, hence the regulated power supply. This can be omitted for battery or fixed supply use. the LEDs which are connected to these pins. Outputs S0 (pin 11) and S15 (pin 15) of IC4 are connected to the set and reset (pins 7 & 4) inputs of IC3, a 4027 dual JK flipflop, only one of which is used. Pins 5 & 6 of this 4027 are held high and pin 3 is held low, allowing it to act as an RS flipflop. The Q output (pin 1) of the 4027 is fed to the up/ down input, pin 10 of IC2, so that every time the first or last LEDs are lit they cause a change in the counting direction. Thus, the up/down counter will now count up from 0-15, then down to 0 again. Since only one LED is on at any time, a single 1kΩ resistor can be used for current limiting. The value of this resistor can be altered to suit the LEDs that you use but do not reduce it much below 1kΩ, as the outputs at S0 and S15 will be loaded so much that the RS flipflop will not toggle. Diode D1 is included for reverse polarity protection. The 10Ω resistor and 15V zener diode ZD1 are only needed if you intend to operate the scanner in a motor car. If not, omit ZD1 and fit a link for the 10Ω resistor. Putting it together We have designed a PC board measuring 95 x 88mm which is coded 08105961. Before inserting any components, check the board carefully against the PC pattern in Fig.3. Look for any undrilled holes, shorts between tracks or breaks in the copper pattern. There should not be any but if there are, it is better to find and fix them at this stage, than to tear your hair out later when the board does not work. Start by inserting and soldering the 19 links, then the resistors and diodes. As the easiest way to assemble a board is to insert components in order of increasing height, the next groups will be the ICs, LEDs and trimpot, followed by the capacitors. Before installing the LEDs, it is a good idea to test at least one of them for polarity, since some LEDs now available are being supplied with the May 1996  81 PARTS LIST 1 PC board, code 08105961, 95 x 88mm Semiconductors 1 555 timer (IC1) 1 4029 up/down counter (IC2) 1 4027 JK flipflop (IC3) 1 4514 1-of-16 decoder (IC4) 1 1N4004 diode (D1) 1 15V 1W zener diode (ZD1) (see text) 16 5mm high intensity LEDs (LED1-LED16) Capacitors 1 10µF 25VW electrolytic 1 2.2µF 25VW electrolytic 1 0.1µF MKT polyester Resistors (0.25W, 1%) 1 10kΩ 1 1.2kΩ 1 1kΩ 1 10Ω (see text) 1 100kΩ horizontal mounting trimpot (VR1) Fig.2 (below): use the printed circuit board overlay (below) in conjunction with the pattern (Fig.3, right) to make the construction simple. Don't forget to check the PC tracks for any damage before inserting the components. 82  Silicon Chip longer lead as the cathode instead of the anode. Using a 9-12V battery, connect one end of a 1kΩ resistor to the positive terminal and the other end to the anode of the LED. The cathode of the LED should be connected to the battery negative. You can also use a DC power supply for this test. If the LED doesn’t light, reverse its leads. If it now lights, the lead going to the resistor is the anode. If it still doesn’t light, it is a dud. Looking at each LED from the front of the PC board (LED edge), the cathode is the left lead while the anode is the right lead. When you have finished installing and soldering all the components, check your work carefully against the circuit and wiring diagrams. This done, apply power and the LEDs should immediately start scanning from one side to the other. Remember that regardless of the speed of scanning, only one LED is on at any one time. Use the trimpot to set the scanning speed. And if you want the circuit to drive 12V light globes . . . The circuit at right shows how to interface the KnightRider with high power (up to 35W) 12V bulbs. Only one circuit is shown, but you would need to build up 16 of these to have the full effect of the KnightRider. Note that the interface circuit can either replace the LEDs (LEDs 1-16 on the circuit) or, if you wish, can be connected in parallel with each LED so that the LED display operates in sympathy with the light bulbs. There is no provision made on the PC board for the interfaces. It may be possible to solder the Darlington transistors direct to the lamps or lamp sockets. The DC supply for the lamps should be taken via a suitable fuse from the battery side of D1, not from the reguSC lated supply. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd VINTAGE RADIO By JOHN HILL A look at early radiograms The first recorded words were: “Mary had a little lamb”. Of course the voice that made that historic recording was that of Thomas Edison and the year was 1877. Edison’s record was cylindrical and the surface was covered with foil. The device was crude and it had a lot of development work ahead of it before it could be of any commercial signifi­ cance. The late 19th century saw the birth of many new gadgets and inventions, the phonograph being just one of them. If one listens to an Edison cylindrical phonograph, the first impression is how terrible it sounds. Any subse- quent im­pressions simply reinforce the first. The reproduction is thin, harsh, scratchy, totally lacking in bass and distorted at particular frequencies. When I demonstrated my Edison machine to my brother, his comment was: “I had no idea they were that bad!” Looking at the recording industry at the turn of the cen­tury, it could only go one way – forwards! It’s all very fine to look back in the light of today’s knowledge and comment on how bad early records and record players were – but everything has to start somewhere. Most inventions undergo development and modification for the rest of their com­ mercial life. Whenever we look back at early sound recording, radio, motor cars or whatever, it doesn’t pay to be too critical because that was the best mankind could do at the time. New developments Most inventions start out with humble beginnings and im­prove as time progresses. The phonograph was like that and it went through many changes – from cylinder to disc, vertical “hill and dale” modulation to lateral, from huge sound horns to built in types with volume controls. But the real improvements did not come about until records were electrically recorded and could be played electrically through a radio receiver. This new era of sound recording and reproduction came in around the late 1920s. Electrically made recordings greatly improved the quality of recorded sound and electronic sound techniques opened up a whole new frontier with the advent of talking motion pictures. So, from this time on, records and radio merged closer together. Anyone with an ear for quality would prefer to listen to their records played through their radio rather than a phono­graph. Indeed, most radio receivers from the late 1920s to the end of the valve era had some provision built into them to allow a pickup to be connected. Early pickups A genuine four-minute Edison cylindrical record. These early records were “hill and dale” types; ie, the modulation of the groove was up and down, not sideways as in later years. 88  Silicon Chip Early pickups were big and heavy. They used a large magnet and were fitted with a thumbscrew for holding the “single furrow record plough” with some of the lightweight pickups of the microgroove era, the difference is amazing. So too is the difference in record life. Playing records This old magnetic pickup was made by the American Bosch Company. With its 6-ounce (170 gram) head, steel needle and lack of counterbalancing, it no doubt wrought considerable damage on many an old record. This close-up view shows the Bosch “Recreator” with its cover removed. Note the horseshoe magnet, the pole pieces and the 2kΩ coil between the pole pieces. The thumbscrew at the bottom is for securing the needle. steel needle which needed replacing after every playing. As can be seen from one of the accompanying photographs, the pick­up head contains quite a sizable horse­ shoe magnet, with a 2kΩ coil mounted between the pole pieces. The armature that vibrates inside the coil is rubber mounted and it is the agehardening of this rubber mount that causes trouble with these ancient pick­ups. If the needle carrier and armature are remounted in soft new rubber, it will restore the pickup to working order once again. Assuming that the coil is not open and the magnet has not lost its magnetism, the pickup should work. Some of these old pickups weigh in at around 6 ounces (170 grams) and many had no counterbalancing to lighten the load. Transfer all that weight onto the tiny contact area of the needle point and you have an instrument that has been scientifically designed to tear the guts out of the needle track of a record in a relatively short period of time (or record time if you will excuse the pun)! In this respect, they were no better than the acoustic sound heads they replaced –and in some cases worse. When ones compares the Bosch Now if one wishes to play 78rpm records through their old 1930 TRF receiver, it’s not just a simple matter of plugging in a pickup and away you go. If you do this it will work, no doubt, but the volume control on the set will not control the volume of the records being played. The reason for this is quite simple. In the late 1920s and early ’30s, the volume control on nearly every type of receiver was in the radio frequency (RF) end of the set, which was con­trary to later developments. In those days, the volume control took the form of a wirewound potentiometer which either varied the cathode bias or the screen voltage of one of the RF valves. In operation, the audio frequencies produced by the record pickup are fed into the audio section of the receiver. In an old TRF or early superhet receiver, the grid of the detector valve or first audio valve was the place to attach a pickup. But as alrea­dy explained, any audio grid comes after the receiver’s volume control and so the record volume is uncontrollable in such cir­cumstances. In most cases, the sound would be too loud and possi­bly distorted if the pickup output is too great for the set to handle. For this reason, the pickups of old came with an external volume control. Although these units were nothing more than a potentiometer, with perhaps a capacitor across it, they were often given names to suggest otherwise. The “ELEC-TRU-TONE” was one such example – see photo. The pickup connections to radio receivers varied depending on the manufacturer. Some used terminals while others used sock­ e ts. Some disconnected the radio section using a switch while others did not bother. With the latter arrangement, the set’s volume control needed to be turned down to prevent radio signals from coming through and interfering with the pickup signal. Early radiograms The first radiograms made an appearance during the late 1920s and May 1996  89 Early pickups required a separate volume control because the radios of the day had their volume controls in the RF section of the receiver, not in the audio stage where it was needed. The unit shown here was made by Bosch. these had a few variations too. Some had clockwork turntable motors while some were electric, or sometimes an elec­tric motor was an optional extra. These old radiograms still had the same volume control arrangements as before, with the pickup having its own external volume control. This control was usually mounted somewhere near the turntable. There was also an on/off switch and a speed con­troller. It would appear that the radiogram idea wasn’t all that popular at the time, as anyone who could afford to buy a radio would most likely already have a phonograph. A radio with a pickup was a much cheaper record playing option if you already had a turntable. However, a complete radio/record player in one would be far more convenient to operate. A few headaches Any collector who finds an early radiogram with a lift-up lid has a really collectable item. If it is in poor condition, however, he may have found himself a few headaches as well, because items such as early turntable motors, pickups and volume controls Above: this side view of the Bosch volume control clearly shows the sockets for the pickup connectors. Right: this “ELEC-TRU-TONE” volume control is similar to the Bosch unit but the case is made of bakelite (the Bosch control’s case is pressed steel). Note the four socket connections. 90  Silicon Chip can be difficult to locate and repair. So far, we have described how records were played through a radio receiver. But strange as it may seem, there was a time when the opposite was true and some radios were played through a phonograph! Back in the days when many radio receivers came only with headphones, there were problems as far as family listening was concerned. Enter the phonograph to the rescue! It was found that if a phonograph needle was placed on the earphone diaphragm, the earphone would RESURRECTION RADIO VALVE EQUIPMENT SPECIALISTS VINTAGE RADIO ✰ Circuits ✰ Valves ✰ Books ✰ Parts MAY SPECIAL! Shown here is the rear of an old AWA Duo Forte radiogram. The pickup plugs into the righthand sockets, while an extension loudspeaker can be plugged into the lefthand sockets. Post Pak Crystal Set Complete – only $25 posted includes earpiece & instructions Crystal set parts and books on construction are available. Send SSAE for Catalogue Visit Our Showroom At: 242 Chapel Street (PO Box 2029), PRAHRAN, VIC 3181. Tel (03) 9510 4486   Fax (03) 9529 5639 Silicon Chip Binders The Duo Forte’s turntable and pickup are crude by today’s stan­dards. To the right of the pickup arm is the turntable’s on/off switch and speed controller. Once again, note the extremely heavy pickup and the lack of counterbalancing at the far end of the arm. activate the diaphragm in the phonograph’s sound head. As a result, the phonograph’s sound horn would reproduce the radio program for all to hear. One can only guess at the volume level and sound fidelity of such an arrangement. Of course, this would only work on an Edison type sound head, meant for vertical (hill and dale) recordings. If the sound head was of the lateral type, a special adapter could be bought (this adapter was originally intended to convert a lateral type machine to play Edison vertical cut records). The invention of the phonograph preceded the first practi­ cal radio demonstration by 11 years. Although they both evolved separately for quite some time, the two eventually became inter­ woven. Radio technology was used to improve recording techniques and the improved recordings could only be heard at their best when played through a radio receiver. It was therefore only logical that the record playing radi­ogram would evolve to become the centre of household entertain­ment and it remained that way for many years until the advent of television, modular sound SC systems and the compact disc. These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­ tinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. May 1996  91 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. What does “HVAC” abbreviation mean? In some American electronics and do-it-yourself magazines, I have seen references to HVAC technicians. I assume this stands for “high voltage AC” but the mentions are so vague and nebulous that I cannot be sure. Can you confirm this? (D. G., Malvern, Vic). • HVAC is an abbreviation for “heating, ventilation and air conditioning”. It refers mainly to domestic and commercial installations in the US, particularly as central heating via a basement furnace is so commonplace in houses over there. However, HVAC also applies to air conditioning in trucks and cars and to industrial refrigeration equipment. Measuring clinical magnetic fields Could the Magnetic Field Strength Meter (SILICON CHIP, October 1991) be modified to measure clinical magnetic therapy devices? The frequencies of these units range from 0.5Hz to around 50Hz with pulses within these frequencies ranging around 20Hz to several hundred hertz. Choice of amplifier modules I’ve just purchased the April 1996 issue and I read with great interest the article on the new amplifier module. I started building the 200W power amplifier of February 1988 but due to other commitments, it still sits half-finished in the spare room. So far I’ve wired the two boards but haven’t purchased the power transistors. I bought one of those nifty cases with the end panel heatsinks at a sale price from Jaycar. I haven’t as yet got the power tranny but I’ve got all the other power supply bits including four 6800µF 63V electros so it seems a lot of the 92  Silicon Chip These devices can be either bipolar or unipolar and have quoted magnetic powers ranging from 50 to over 200 Gauss. (M. P., Shenton Park, WA). • As it stands, the unit is suitable for measuring AC (bipolar) magnetic fields up to 20 milliTeslas which is equivalent to 200 Gauss (one Tesla equals 10,000 Gauss). It should also be suitable for measuring fields up to 200Hz or so. However, it will not give accurate results for unipolar fields which we assume are equivalent to modulated DC fields. To obtain accurate results for the latter condition the unit would need to be redesigned using a linear Hall effect device. This would be a major redesign since the existing instrument uses AC coupling between each stage while an instrument to measure DC fields would need to be DC coupled or use a chopper amplifier at the input. checking out the circuit board, components and wiring and then following adjustment instructions, these pulses still persist and are quite loud. Can you please advise how I can eliminate these short sharp clicking pulses? (J. M., Rowville, Vic). • It appears likely that the clicking sound you experience is caused by the change in volume from normal signal amplitude to the pulsed level. VR2 should be adjusted until the clicking sound is at a low level. Loud clicks are an indication of the piezo speakers distorting and so the burst level must be reduced to prevent damage to the transducers in the long term. If you continue to have problems with the clicking sound then a 0.1µF capacitor can be connected between base and emitter of transistor Q3. This will provide a slow turn on and turn off of the burst signal. Woofer Stopper stops me, not dogs Service manuals wanted for Onkyo tape deck I have recently built the Woofer Stopper Mk.2 (SILICON CHIP, February 1996). It works but it gives off a loud clicking sound. It appears to me that it is a design problem. After carefully I have a tape deck in for repair, an “Onkyo” Model 2050. Could you advise where I can obtain the service manual (or photocopies), complete with circuit diagrams and schematic bits I already have are suitable for the new design. Do you reckon I would gain a worthwhile improvement by scrapping my current boards in favour of the new modules? I notice that most of the on- board components are the same (semiconductors, inductors, power resistors, etc), so there seems little reason not to make the latest amplifiers. Another reason is the older design is just that – 8 years old. The new modules are much easier to assemble, particularly in the output transistor mounting department. I did purchase a set of output transistors for the 200W amplifier, then I remembered I’d read something about forgeries of Motorola devices. I checked the serial numbers and sure enough, the aluminium cased transistors I bought were duds (below spec) but it was too late to get a refund by the time I found the article. (P. G., Nowra, NSW). • As mentioned in the April 1996 article, we did try a version of the February 1988 amplifier with the new transistors. Based on that, there is little reason to scrap the old circuit boards – it is still a good design. We would also be inclined to put the non-Motorola transistors into use. You have nothing to lose. While they may not be as good as the genuine parts, at least you have them and so you can complete your amplifier with no more to pay. 6-12V inverter for a car radio I need a circuit to raise 6V to 12V to use a modern radio in an old car. I came across your 6-12V converter which was a modification to the SLA battery charger of July 1992. I have assembled the kit and on open circuit I get about 13.6V DC. As soon as I give it a load, it drops to about 4.8V. I am concerned that I may not have wound the inductor correctly. Also initially, I connected 6V to the output. Would that have killed the BD679 or the IC? I am only using a basic radio of about 3W per chan- layout? Also cross reference numbers for ICs and transistors from Japanese to those used in Australia. I contacted DSE and Jaycar but they could not help with the latter. Thanking you in anticipation. (N. E. Lowe, 42 Thomas St, Busselton, WA 6280.) Pye portable TV circuit too . . . I note that some of your readers have requests for circuit diagrams for products no longer available. Such is my case and I was wondering if I might request some information, via your magazine. The model in question is a Pye Portable Model 14G1 colour television. Pye do not now have any circuit diagrams or information on this model. As an interest and challenge I am endeavouring to bring this appliance back to life! Any assistance would be greatly appreciated. (J. T. Coulter, 3 Narrunga Ave, Buff Point, NSW 2262. Phone 043 907 440.) Is Champ preamp OK for bass guitar? Can I use the PreCHAMP (SILICON CHIP, July 1994) as a preamp for an electric bass guitar? The signal from an electric bass guitar is around 5mV (I think) so could I feed the output directly from the guitar pickup to the PreCHAMP and then into the main amp? Is any modification needed? Will there be any hiss or background noise? The impedance of each pickup is about 7.2kΩ. (T. F., Sydney, NSW). nel. Light bulbs (small ones) also make the voltage drop. When winding the inductor how many turns do I aim for and do I tape the first layer and wind over that? How do you stop the first and second layer from intermingling? (R. G., Chapel Hill, Qld). • Wind about 60 turns of enamelled copper wire onto the toroid. There is no need to insulate between windings. Do not worry about the intermingling of first and second windings. No damage should have occurred to the BD679 if the output was connected to 6V since the diode will have been reverse biased. • As published, the gain of the circuit is much too high for your application. The signal from a bass guitar can be several hundred millivolts and it would overload the PreChamp severely. It is likely that you need a gain of only about 10 at most. To achieve this, change the 100Ω resistor at the emitter of Q1 to 220Ω. Background noise should not be a problem. Power supply has voltage bounce I have found the following problems with the 13.5V 25A power supply for amateur equipment published in the May & June 1991 issues of SILICON CHIP. When a heavy load is removed, as in an operation, the crowbar circuit operates and reduces the output voltage as expected. This also occurs using load resistors to simulate loads. It appears the response of the system is a little slow, causing the output voltage to rise with reduced load. The current foldback is not gradual and causes the system to oscillate. (C. M., Salisbury, SA). • Try connecting a 10µF capacitor between pin 2 of IC5 and the negative rail to prevent the crowbar operating for short term voltage rises. The response time of the power supply to load changes is set by the time-constant of the first 80,000µF capacitors and 28Ω resistors after L1. You could add in extra load resistance to improve response time. The output regulation is dependent on L2’s DC resistance. SC BOOK REVIEWS . . . Continued from P79 For FM reception the phase detector, ratio detector and phase locked loop (PLL) are detailed. In the chapter entitled “Pulse Generators”, the transistor is used as a switch, covering bistable, mono­stable and astable generators. Chapter 14, entitled “Sawtooth Generators”, shows how to use a driven multivibrator, a modified blocking oscillator, a modified Miller integrator or the constant current charging of a capacitor to generate a sawtooth waveform. It explains how a sawtooth waveform is generated for the line output drive of a TV set using the inductance of the yoke and concludes with the operation of a typical line output stage of a modern TV set. Next is an introduction to digital circuits, starting with an explanation of binary numbers and diode gate logic, then describing current IC logic gates. It continues with a return to bistables, describing JK and RS flipflops, and shows how binary counters and dividers are built up from these flipflops describing how the use of feedback can generate specific counts. The chapter concludes with information on shift registers and RAM/ROM. The final chapter contains information on devices that did not exist when the book was first published. Voltage reference diodes, series and shunt voltage stabilisers, switchmode power supplies, photodiodes and photo­ tran­sistors, thyristor inverters & drivers and UHF modulators are some of the topics in these pages. While still full of sound basic theory, the book in its present guise has really passed its “use by” date. The average student has enough difficulty coping with concepts when they are presented consistently but to switch from outmoded PNP transistor circuits with negative supply rails to NPNs and positive rails, then back again must be totally confusing. Let’s hope the next edition is a “clean sweep”. (R.J.W.) May 1996  93 electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semicustom electronics & data communications. 63 chapters, in hard cover at $120.00. Silicon Chip Bookshop Radio Frequency Transistors Newnes Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Guide to TV & Video Technology By Eugene Trundle. First pub­lish-­ ed 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $49.95. Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Digital Audio & Compact Disc Technology Electronics Engineer’s Reference Book Hard cove Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM Power Electronics Handbook Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order r Edited by F. F. Mazda. version now available First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $85.00. Surface Mount Technology By Rudolph Strauss. First pub­ lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $52.95.   Title  Newnes Guide to Satellite TV  Guide to TV & Video Technology  Servicing Personal Computers  The Art Of Linear Electronics  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Electronic Engineer's Reference Book  Radio Frequency Transistors  Surface Mount Technology  Audio Electronics Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A 94  Silicon Chip Price $55.95 $39.95 $59.95 $49.95 $55.95 $59.95 $120.00 $85.00 $99.00 $52.95 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE DonTronics HAS MICROCHIP PIC GEAR: Programmers from $20 to $225, PICBASIC: 64 $47, 57 $33, 84 $33, EEPROM: 93LC56 $5, 24LC16B $8, 24LC65 $16, CPU: 84/04/P $12, 57/04/P $12, 64/04/P $17. Serial and parallel I/F kits and lots of other stuff. VISA-MC-BC. Ask for free Promo Disk. http://www.labyrinth.net.au/home/~donmck; 29 Ellesmere Crescent, Tulla­ marine 3043. (03) 9338 6286. Fax (03) 9338 2935. KITS KITS KITS: Electronic kits for enthusiasts of all ages and abilities. Top quality. Large range. Free catalog and price list available. Call Ozitronics, 24 CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 979 6503. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Ballandry Crescent, Greensborough 3088. Tel/Fax: (03) 9434 3806 email: ozitronics<at>c031.aone.net.au. MicroZed HAVE range of PIC chips. OTP and /JW versions available. PIC 16C84 priced at $8 each plus postage. SATELLITE DISHES: international reception of Intelsat, Panamsat, Gori­ zont,Rimsat. Warehouse Sale – 4.6m dish & pole $1499; LNB $50; Feed $75. All accessories available. Videosat, 2/28 Salisbury Rd, Hornsby. Phone (02) 482 3100 8.30-5.00 M-F. A REAL BARGAIN: Riston type copper clad laminate. Develop cold, no toxic fumes, easy to use. Excellent results. Single sided 610x304 $34; 305 x 304 $17.50; 152 x 305 $9.95; 152 x 152 $6.50. Double-sided also available. 2 litre developer mix, worth $2.50, free this month. Add sales tax if applicable. Delivery $6.00. Money back guarantee. Ph (02) 743 9235. Fax (02) 644 2862. SILICON CHIP: No.1 - No.96 complete $200; Electronics Australia 1987-1995 $150, or $300 the lot. W. C. Petersen, 291 Maroondah Hwy, Narbethong, Vic 3778; or phone (059) 63 7141. SELL VERY OLD RADIOS, all kind transformers, rare valves, other gear. (07) 3856 1736. LASER LIGHT SHOW EQUIPMENT: scanners, controllers, soft­ware. Lasers, ❏ Bankcard   ❏ Visa Card   ❏ Master Card ✂ Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Card No. Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 May 1996  95 PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (067) 722 777 – may time out to Mobile 014 036 775 Fax (067) 728 987    (Credit Cards OK) Specialising in easy-to-get-going hard/software kits with on-board interpreters. Also Assembler tools. Range of support hardware too. Get your project going in hours, not months Send 2 x 45c stamps for information package Microchip Programmers, Simulators and PIC chips ➡ MicroZed Computers Altronics ................................ 66-69 68HC11 F1 boards and now 80535 (up spec 8051) Extra I/O and peripheral plug-ins too Av-Comm.....................................71 Australian made Prototype wiring kit NEW Micro NEW Scott Edwards Electronics Accessories for Stamp and second source for Stamp 1 Data Collection Proto Board now in stock Advertising Index Car Projects Book....................OBC Dick Smith Electronics........... 18-21 BASIC Stamp I and II Macintosh patch now available Earthquake Audio........................70 Harbuch Electronics....................73 MEMORY * DRIVES * MODEMS SPECIAL! (ExTax) 1Mbx9 – 70ns $25 30-pin Simms optoelectronics. Laser Dynamics. Phone (03) 532 1981. Fax (03) 9555 7449. RAIN BRAIN 8 STATION SPRINKLER KIT: Ultra reliable & versatile Hi Q kit. Rain switch & LED B/L Free!!! (SC JAN ’96). Mantis Micro Products, 38 Garnet St, Niddrie, 3042 P/F/A (03) 9337 1917 man­tismp<at>c031.aone.net.au 68HC705 DEVELOPMENT SYSTEM: Oztechnics, PO Box 38, Illawong, NSW 2234. Phone (02) 541 0310, fax (02) 541 0734. Email: info<at>oztechnics.­com.au WWW: http://www.hutch.com.­au./~ozt­ ech/index.htm. C COMPILERS: Dunfield compilers are now even better value. Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC16, 8051/2, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers for these CPUs + 6800/01/03/05 and 6502: $140 for the set. Debug monitors: $70 for 6 CPUs. All compilers, XASMs and monitors: $400. 8051/52 or 80C320 simulator (fast): $70. Demo disk: FREE. All prices + $5 p&p. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph/ Fax (02) 631 1236 or Internet: lgrant<at> mpx.com.au. MICROCRAFT PRESENTS: Dunfield (DDS) products are now available exstock at a new low price; please ask for our catalogue. Micro C, the affordable “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $139.95 each + $3 p&h • Now on special is the SDK, a package of ALL the 96  Silicon Chip SIMMS (Parity/No Parity) 4Mb 30 PIN-70 $71 $90 4Mb 72 PIN-70 $75 $53 8Mb 72 PIN-70 $133 $100 16Mb 72 PIN-70 $230 $192 32Mb 72 PIN-70 $456 $378 EDO SIMMS 8Mb (1Mbx32) – 60ns $118 16Mb (2Mbx32) – 60ns $210 MAC MEMORY 8Mb P’BOOK 190 $240 VIDEO MEMORY 256K x 16 70ns (SOJ) $17 256K x 16 70ns (ZIP) $48 LASER PRINTER MEMORY 2Mb UPGRADE $140 CO-PROCESSORS 80387SX/DX to 40MHz $100 COMPAQ 8Mb CONTURA AERO $240 All other models available $Call TOSHIBA PORTEGE/SATELLITE 8Mb / 16Mb EDO $294 / $550 All other models available $Call IDE DRIVES: SEAGATE/CONNER 1080Mb EIDE 10.5ms 3yr $283 1620Mb EIDE 14ms 3yr $360 2113Mb EIDE 10.5ms 3yr $384 MODEMS: BANKSIA / SPIRIT 28,800 BANKSIA V.34 $360* 28,800 SPIRIT V.34/V.FC $350* *Plus 14% sales tax on modems Instant PCBs................................96 Jaycar ................................... 45-52 Kits-R-US.....................................72 Macservice............................ 12-13 MicroZed Computers...................96 Oatley Electronics..........................3 Ex Tax Pricing – Delivery $8. Pricing as at 26/6/96. Phone for latest. Sales Tax On Modems 14%. Everything Else 22%. Credit Cards Welcome. We Also Buy And Trade-In Memory. PELHAM Memory Pty Ltd Suite 6, 2 Hillcrest Rd, Ph: (02) 9980 6988 Pennant Hills, 2120. Fax: (02) 9980 6991 Email: pelham1<at>ozemail.com.au DDS “C” compilers for $399 + $6 p&h • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h • DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using car alter­nators” (uses car alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Device programming EPROMs/PALs etc from $1.50 • Fixed price electronic design and PCB layout • Credit cards accepted • All goods sent certified mail • Call Bob for more de­tails. MICROCRAFT, PO Box 514, Concord NSW 2137. Phone (02) 744 5440 or fax (02) 744 9280. EDUCATIONAL ELECTRONIC KITS: Best prices. Easy to build. Full details. Latest technology. LESSON PLANS FOR TEACHERS – see our web page. Send $2 stamp for catalog and price list to: DIY Electronics, 22 McGregor St, Num­urkah, Vic. 3636. Ph/fax (058) 62 1915. Or Email laurie.c<at>cnl.com. au and let us send details. Go WWW:http://www.cnl.com.au/~laurie.c or BBS (058) 62 3303. Download details free any­time. MicroZed HAVE A Real Time Clock Kit available for use with Parallax BASIC Stamp2 – $25. Pelham........................................96 Practical Marketing......................73 Railway Projects Book.................44 RCS Radio ..................................95 Resurrection Radio......................91 Rod Irving Electronics .......... 83-87 Silicon Chip Binders....................91 Silicon Chip Bookshop.................94 Tektronix....................................IFC Telstra............................................5 X-On Electronic Services..............4 Zoom.........................................IBC _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. BUMPER PREMIERE EDITION NOW AT YOUR NEWSAGENT