From: trevor@rageaudio.com.au   
      
   On 13/08/2023 4:36 am, Cursitor Doom wrote:   
   > 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....   
   >   
      
   **Many years of experience has taught me to suspect low value (<47 Ohms)   
   resistors and high value (>100k) resistors. Both types can fail with   
   little or no visible evidence. Cracked carbon types are the ones that   
   are problematic, as metal film types seem to be far more reliable.   
      
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