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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP FOR SALE DIRECT FROM CHINA: Kinsten PCB, high-speed drill press, hookup wire. A$ prices www.kinsten.co; USD prices http://www.aliexpress.com/ store/130218 Low prices include postage. Audio + Video: Professional quality Quest AV brand equipment is made and sold in Australia exclusively by Quest Electronics. Ph 0431 920 667. sales<at>questronix.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 MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au PCBs & Micros: Silicon Chip Pub­ lications can supply PCBs and programmed micros for all recent projects. Order online or phone (02) 9939 3295. Superbright LEDs of all sizes, shapes and colours, brand names like Cree and Avago as well as low cost generic LEDs for non-critical applications. Also stocking kits, components and other assorted items. If we don’t have it, just ask, we can order almost anything in! LEDsales, www.ledsales.com.au KIT ASSEMBLY & REPAIR RF REPAIRS - Australia wide repair service of most two way radio equipment. Please contact us on (02) 4305 2301 or service<at>rfrepairs.com.au VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years experience 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 NIXIE CLOCK KITS SILICON CHIP July-Aug 2007 Full kits & spare tubes still available (For a limited time only) Phone 0403 055 374; Email glesstron<at>msn.com 122 415 or email bigalradioshack<at> gmail.com KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com WANTED WANTED: EARLY HIFIs, AMPLIFIERS, Speakers, Turntables, Valves, Books, Quad, Leak, Pye, Lowther, Ortofon, SME, Western Electric, Altec, Marantz, McIntosh, Tannoy, Goodmans, Wharfe­ dale, radio and wireless. Collector/ Hobbyist will pay cash. (07) 5471 1062. johnmurt<at>highprofile.com.au 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. amplifier. I also built a trickle-charger from the February 2005 issue and fitted the whole assembly into a small loudspeaker enclosure with an SLA battery. The intent is that the unit will be operated from the battery between charges and should last at least 12 hours on the 1.3Ah battery I have used. However, when fully charged, the SLA battery is delivering in excess of 13V and the Champion is specified to operate between 9V and 12V. Can you advise if the Champion will continue to operate under these conditions and if not, what would you recommend siliconchip.com.au doing to change it? (B. D., via email). • The AN7511 chip used in the Champion has an “absolute maximum” operating voltage of 14V with a recommended range of 3.5-13.5V. If you are trickle charging the battery at 13.8V (a typical value), there will be some voltage drop across diode D2 which should keep the AN7511’s supply more or less within the recommended range. In other words, we would expect it to receive no more than 13.5V as long as the battery does not go above 13.8V. If the battery can go above 13.8V or you just want some extra safety margin, you can change diodes D1/D2 (whichever you are using) to a 1N4004 or similar which should drop the voltage by another 0.5V or so. It would also be possible to wire two diodes in series (eg, a second diode in-line with the supply wiring) to drop the voltage further if necessary. Note that at the high end of its operating voltage range, power output quickly becomes thermally limited so if you want maximum power from the chip, it’s best to run the board at less continued next page June 2014  103 Advertising Index Altronics.........................loose insert Chemtools.................................... 75 Control Devices Pty Ltd.................. 5 Core Electronics............................. 9 Emona Instruments........................ 7 Enertel Pty Ltd............................. 11 Gless Audio................................ 103 Hammond Manufacturing............. 13 Harbuch Electronics..................... 13 Hare & Forbes.......................... OBC Ask SILICON CHIP . . . continued from page 103 than 12V; around 9V is ideal. This can be done with a zener diode. For example, if you leave D1/D2 as originally specified (1N5819) and add a 4.7V zener in series with the positive supply, with its anode to pin 2 of CON8 and its cathode to the battery positive terminal, IC2 should have a supply of around 8.7V. That will give a continuous power output of around 3W, compared to about 2W with a 12V supply. Note that you would need to use a 5W zener diode (eg, 1N5337) as it will dissipate about 1.8W when the amplifier is delivering maximum power. For a cheaper solution, you could try putting a 10-12Ω 5W resistor in series Notes & Errata Speedo Corrector Mk3, September 2013: there should be four 1µF capacitors in the parts list (not three) and the circuit should show a 1µF capacitor between pins 5 & 14 of IC1. The overlay diagram is correct. Micromite Microntroller, May 2014: a new version (Ver 4.5C) of MM­ Basic for the Micromite is available from the SILICON CHIP website. This version fixes a bug which could, in rare cases, cause the Micromite to partially erase its firmware and disable MMBasic when used with some low-cost USB-serial adapters. Other than that, no new functionality has been added. All but three chips we have supplied have the latest firmware version and those three customers have been notified. 104  Silicon Chip DOWNLOAD OUR CATALOG at High Profile Communications..... 103 www.iinet.net.au/~worcom Icom Australia................................ 8 WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au Jaycar .............................. IFC,49-56 KCS Trade Pty Ltd........................ 21 Keith Rippon .............................. 103 KitStop.......................................... 75 with the supply. This will cause the supply voltage to drop as IC2 draws more current, reducing dissipation in IC2 at higher power settings. This may also drop the supply voltage by enough at idle to keep IC2 within its ratings with a 13.8V battery but you’d have to check it. LD Electronics............................ 103 Query on channel component matching Premier Batteries......................... 12 In your various stereo preamp/power amplifier kit designs, do the various kit suppliers go to the trouble of matching components (between channels) when deemed necessary (RIAA equalisation) for example? I’ve graphically learned this lesson in many of the stereo kits that I’ve personally built. Just the other day, I checked the value of the RIAA capacitors in the old Universal Preamplifier kit (SILICON CHIP, April 1994) that I’d built some years ago. The capacitor values as measured on my trusty (but reliable) capacitance meter were all over the place so I replaced them with matched sets of the correct values and it has made quite a beneficial difference in terms of equalisation accuracy and stereo image. I don’t recall this point ever being stressed and/or even mentioned in your construction articles. Perhaps in the interests of optimised performance, it should be. My capacitance meter is my most used and valuable LEDsales.................................... 103 Master Instruments...................... 93 Microchip Technology................... 79 Mikroelektronika......................... IBC Ocean Controls............................ 10 QualiEco Circuits Pty Ltd............. 59 Quest Electronics....................... 103 RFrepairs................................... 103 RF Modules................................ 104 Rohde & Schwarz.......................... 3 Sesame Electronics................... 103 Silicon Chip Binders..................... 48 Silicon Chip Online Shop........ 38-39 Silicon Chip Subscriptions........... 96 Silvertone Electronics.................. 61 Wiltronics........................................ 6 Worldwide Elect. Components... 104 bit of test gear for such projects. (F. S., Ingham, Qld). • Ideally the components in the feedback network (which sets the RIAA equalisation) should be 5% tolerance or better. Most capacitors with a nominal 10% tolerance can be expected to be within 5% (or better) SC of their nominal value. siliconchip.com.au