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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP FOR SALE KIT ASSEMBLY & REPAIR LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au tronixlabs.com.au – Australia’s best value for supported hobbyist electronics from Adafruit, SparkFun, Arduino, Freetronics, Raspberry Pi – along with kits, components and much more – with same-day shipping. PCB PRODUCTION PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au NEED A NEW PCB DESIGNED? Or need to update an old board? We do PCB layouts from circuits, drawings, photocopies or sample boards. Contact Steve at sgobrien8<at>gmail.com or phone 0401 157 285. Get a new PCB and keep production going! KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com DAVE THOMPSON (the Serviceman from SILICON CHIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com MISCELLANEOUS ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects like audio, video, programming etc. The books are relatively old in most cases and vary in condition. You'll need to come in person to see what books we have and what we're willing to sell: Silicon Chip 1/234 Harbord Road (up the ramp) Brookvale NSW 2100 Where do you get those HARD-TO-GET PARTS? Where possible, the SILICON CHIP On-Line Shop stocks hard-to-get project parts, along with PCBs, programmed micros, panels and all the other bits and pieces to enable you to complete your SILICON CHIP project. SILICON CHIP On-Line SHOP www.siliconchip.com.au/shop ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. (Fig.3) on page 29 of the October 2006 issue. Q2 and Q3 are labelled on this diagram as BC337 but shown as PNP transistors. The parts list shows Q2 and Q3 as BC557, which I assume is the correct part. (P. C., Woodcroft, SA) • You can make a capacitive type pickup by winding several turns of wire around the spark plug lead. One end should be left disconnected and the other end connected to the highlevel input of the tachometer. Alternatively, a larger area pickup siliconchip.com.au could be made from sheet metal that wraps around the spark plug lead. Then connect this to the high-level input on the tachometer. You may need to experiment with the number of turns or metal area required to trigger the tachometer. The pickup may affect the voltage that is delivered to the spark plug and this method will only work if the spark voltage is positive with respect to vehicle chassis. You may also need to modify the Tachometer input circuit, The 47nF Australia’s electronics magazine capacitors at the input may need to be reduced in value, perhaps to less than 100pF. The 10kW and 100kW resistors may also need to be higher in value, eg, 470kW each. The 2.2µF capacitor will need to be a non-polarised type. If your spark polarity is negative-going, it will not trigger the tachometer. There is no need to include LEDs133 if these are not required. The circuit will work fine without them. You are right, Q2 and Q3 should be BC557 types. SC December 2018  103