From: jeffl@cruzio.com   
      
   On Sun, 30 Nov 2025 14:38:33 +0000, Cursitor Doom   
    wrote:   
      
   >Here are the photos of the suspicous resistor; let me know what you   
   >think. In addition to the blow holes, it's also slightly mis-shapen.   
   >   
   >https://disk.yandex.com/d/ommuYJD2ZKsW8A   
      
      
   I can't tell if the black area above the hole is a burn mark or a   
   shadow from the lower end of the resistor.  There are no additional   
   burn marks along the perimeter of the hole which suggests that   
   overheating was not the cause.  If it were a volcanic explosion or   
   burn mark caused by overheating, I would expect to see black carbon   
   around the inside of the hole.  Instead, it looks like clean ceramic   
   (coating) in the hole.  That could also have been caused by a bubble   
   in the coating produced during manufacture.  I believe you mentioned   
   that the resistor survived and reads the correct 1200 ohms, which   
   favor the bubble explanation.  If the carbon film resistor had been   
   overheated, it would have changed value greater than +/-5%.   
      
   Can you provide better photos of just the hole area (without shadows)   
      
   Hint, use a microscope   
      
   and fix your lighting so that you don't have any shadows.  I sometimes   
   get lazy when working with small parts and just use two flashlights.   
      
      
      
      
   --   
   Jeff Liebermann                 jeffl@cruzio.com   
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