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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP Where do you get those HARD-TO-GET PARTS? FOR SALE tronixlabs.com - Australia’s best value for hobbyist and enthusiast electronics from adafruit, DFRobot, Freetronics, Raspberry Pi, Genuino and more, with same-day shipping. 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 PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www. ledsales.com.au 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 PCBs & Micros: SILICON CHIP Publications can supply PCBs, programmed microcontrollers and other specialised parts for all recent projects and some not so recent projects. Visit the Online Shop at www.siliconchip.com.au for On-Line SHOP www.siliconchip.com.au/shop details and to place your order, or phone (02) 9939 3295. KIT ASSEMBLY & REPAIR 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. Phone NZ (+64 3) 366 6588 or 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. $10 inspection fee plus charges for parts and labour as required. Labour fees $35 p/h. Pensioner discounts available on application. Contact Alan on 0425 122 415 or email bigal radioshack<at>gmail.com ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words plus 95 cents 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. Ask SILICON CHIP . . . continued from page 110 since the Spacewriter was designed. You could still program it if you obtain a parallel printer port to USB converter. Jaycar sell these (www.jaycar. com.au/usb-to-parallel-bi-directionalcable/p/XC4847) and there are plenty of other suppliers if you do a search for parallel printer port to USB converter. siliconchip.com.au Why Jacob’s Ladder must be battery-powered I’m currently building Jaycar’s Jacob’s ladder kit of your February 2013 design and I’m very curious as to why I shouldn’t run this off the 230VAC mains. I’m thinking of using a 12V DC plugpack with a 56,000µF capacitor bank. Is it an issue of spikes getting back onto the mains? Or rather of high voltage (230VAC) being in the kit? (R. R., NZ.) • Running from the mains could reduce safety should the circuit 0V be connected to Earth, or due to a breakdown in the mains transformer or isolation failure in a switchmode supply. The high-tension voltage generated could spark back through the mains through such a fault or via a low impedance path (eg, water), . . . continued on page 112 September 2016  111