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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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