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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP KIT ASSEMBLY & REPAIR PCB PRODUCTION FOR SALE 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 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 tronixlabs.com.au – Australia’s best value for supported hobbyist electronics from your favourite brands – along with kits, components and much more – with flat-rate $9 delivery Australia-wide. DAVE THOMPSON (the Serviceman from S ILICON C HIP) 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 KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com MISCELLANEOUS LOOKING FOR: Set of Dick Smith Electronics catalogues from 1975-1982. Must be in pristine condition. Will pay $200 for the set (inc. postage), only one set needed. Contact Melanie (on behalf of inquirer on 02 8832 3100) 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. All books can be viewed at: https://imgur.com/a/gnSWoII Some of the books may not be for sale, but the vast majority are available. Bulk discount available; post or pickup. Silicon Chip silicon<at>siliconchip.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 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. Building a hearing loop I recently got hearing aids due to a lifetime of industrial noise damage. Modern hearing aids combine audio from the microphone and telecoil, so there is no longer a requirement to choose between the transmitted audio and conversation in the room. Thus the telecoil seems ideal to allow me to rejoin my family for TV nights. I searched your archives and was delighted to see that you had published a set of articles across two issues (September/October 2010) on siliconchip.com.au “Designing and installing a hearing loop for the deaf”. Unfortunately, there is not enough information in the article for me to build my own hearing loop from scratch. I intend to construct a hearing loop amplifier to take a TOSLINK input, convert it to analog, and drive a loop using either a voltage or current amplifier. Can you advise me how to do this? (D. J., Surf Beach, NSW) • We published a project article on building a Hearing Loop Signal ConAustralia’s electronics magazine ditioner in the January 2011 issue (siliconchip.com.au/Article/876). This allows a standard audio amplifier to drive a hearing loop. Information on building the loop itself is in the articles you already mention. You can purchase a TOSLINKto-analog converter from Altronics (Cat A3195), Jaycar (Cat AC1723 or AC1715) or other suppliers. The stereo output can be mixed to mono using a pair of 4.7kW resistors, so that the mono signal can be fed to the Signal Conditioner. SC November 2019  111 Coming up in Silicon Chip Altronics Megabox V2 This new version of Altronics’ Arduino Megabox uses an Arduino Uno or Mega and now has room for two shields and provides an LCD screen, five relays, eight opto-isolated inputs and much more. It will turn your rat’s-nest Arduino prototype into a slick, professional-looking device. Advertising Index Altronics...............................77-84 Ampec Technologies................. 25 Dave Thompson...................... 111 The House of Electrical Horrors Digi-Key Electronics.................... 5 Beware! There are lots of really unsafe electrical appliances available, especially from overseas vendors on sites like eBay and AliExpress. Dr David Maddison describes many of the worst offenders, with plenty of links to YouTube videos showing just how spectacularly dangerous they can be. Emona..................................... IBC Tuneable HF Preamplifier Many low-cost SDR modules have poor HF (3-30MHz) performance. Their wideopen front ends also make them susceptible to cross-modulation from strong signal sources. This simple tuneable preamp greatly improves SDR HF performance. It has adjustable gain control and can run off a 5V supply or phantom power. Hare & Forbes..........................2-3 Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 Keysight Technologies........... OBC LD Electronics......................... 111 Universal 6-24V Battery Charge Controller LEACH PCB Assembly............. 11 This Battery Charge Controller turns a ‘dumb’ battery charger into a smart charger, suitable for use with various 6V, 12V or 24V batteries, including leadacid, gel-cell, Li-ion and LiFePO4 (lithium-ion phosphate). It has three preset charging profiles and three adjustable profiles with one to three-stage charging. LEDsales................................. 111 Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The December 2019 issue is due on sale in newsagents by Thursday, November 28th. Expect postal delivery of subscription copies in Australia between November 25th and December 12th. Notes & Errata 45V 8A Bench Supply, October 2019: in the circuit diagram (Fig.3) on pages 26 & 27, the 1nF capacitor between pins 1 & 2 of IC1a should be 100nF; D6 is an SB380 type; IC1 should have a 100nF bypass capacitor from its negative supply (pin 4) to ground; the 68W resistor below Q3 is a 1W type; the four 0.1W resistors are 1W, not 5W; the 100µF capacitor at the input of REG1 has a 63V rating; and if electrolytics are used for the two 1µF capacitors, their negative leads go to ground. Vintage Radio (Kriesler 31-2), September 2019: the vibrator circuit (Fig.2) shown on page 115 was incorrectly redrawn. The vibrator reed should be shown not touching either of the two contacts. Lintek PCBs................................ 6 Microchip Technology............. 7,89 Mouser Electronics................. 9,73 Ocean Controls......................... 13 SC Micromite BackPack............ 49 Silicon Chip Christmas Tree..... 51 Silicon Chip Shop............. 95,109 Silicon Chip Subscriptions....... 52 The Loudspeaker Kit.com......... 12 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 45 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 Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au