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|    sci.electronics.repair    |    Fixing electronic equipment    |    124,925 messages    |
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|    Message 123,827 of 124,925    |
|    Cursitor Doom to All    |
|    Resistors invisibly failing    |
|    12 Aug 23 19:36:04    |
      From: cd@notformail.com              Gentlemen,              Whilst trying to discover why there was no audio output from a 4W amp       board, I noticed there was only 0.6V on the supply pin of the audio       output IC concerned. There should have been 13.6V. This pin was fed       via a 1 ohm 1/4W resistor. DC voltage measurements showed there was       13.6V on one side of this resistor and 0.6V on the other! Clearly       something amiss here, I thought. So it must have gone open circuit.       However, there's not the slghtest sign of any phsyical damage even       under high magnification, whatsoever to it: none at all. Prior       experience has always taught me such resistors burn out in an obvious       way which is dead easy to spot. Not this one. I'm just wondering how       unusual this is and if anyone else has encountered such an issue with       a resistor. Here's a photo. The resistor in question is the one right       next to the largest electrolytic. There it is, looking all innocent       like butter wouldn't melt, yet it's caused me a massively       disproportionate amount of head-scratching, the little shit.              https://disk.yandex.com/i/dE9o0lh937qdrg              When I get that out of circuit.... just you wait....              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
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