Sunday, February 1, 2015

Magic Smoke

There's two ways I learn best - studying other people's mistakes, or making my own mistakes. Today I was the subject of the mistake. My Astron power supply has two meters on the front...one for voltage and one for amperage. I noticed a few weeks ago that the ammeter was reading way too high. I rechecked the voltage, and all was fine. My loads hadn't changed, and my other ammeter wasn't showing anything amiss. I cracked open the case and found the simple pot to adjust. Since I needed to put a load on the supply to set the ammeter I left the AC plugged in. Just as I was connecting up the load, I dropped a lead. Well crud, that wasn't a nice snap or crackle. I blew the AC fuse, which was quickly replaced. I went on with the procedure, buttoned everything back up, and went to check out the radios. Unfortunately it wasn't just a fuse that gave up its magic smoke. My Elecraft KX3 refused to power on. Sitting back a few minutes and thinking through what had happened, I realized I had just exposed my beloved radio to 120V across its DC input. I opened up the KX3 but didn't see anything obvious that I was up to servicing - but I did sniff the board and caught a whiff of magic smoke. A few google searches, a visit to the yahoo group, and the KX3 is packed in a box readied for a trip back to Elecraft. Another mistake, another learning opportunity. And did you know that magic smoke comes from $100 bills? It must, because that's what it costs when I have to have other people put it back in my radios.

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