From: ohg...@gmail.com   
      
   On Tuesday, January 16, 2024 at 10:28:13 PM UTC-5, Usenetist wrote:   
   > On 1/9/24 12:24, ohg...@gmail.com wrote:    
   > >    
      
   > >    
   > > Those old Akais had lots of electrolytic caps that get weak with age. Try   
   heating the signal boards with a heat gun to see if the color returns. If it   
   does, you're going to have to recap that unit if you intend to keep it.    
   > >   
   > Can you explain the heat gun technique for bad caps... how does it work?   
      
   When I suspect a lazy/weak/ electrolytic capacitor as the cause of a failure,   
   I take my heat gun and warm up the board in question. I get the board pretty   
   hot but not hot enough to melt connectors, ribbons, or indeed the shrink wrap   
   on the capacitors.     
   If the device now performs correctly or even if the symptom changes, an   
   electrolytic becomes a strong suspect.  MOST weak capacitors improve with   
   heat, but you'll find the occasional one that actually responds better to   
   cold, but that's as about as rare    
   or more so as finding an open silicon diode (most short).  The heat may also   
   affect defective semiconductors so if heat fixes it, it could still be   
   anything on the board that's become heat sensitive, but most circuits that   
   come back to life with applied    
   heat will have a bad capacitor(s).   
      
   Once I identify weak dried out capacitors with heat, I'll either shotgun the   
   device if it's old and I want it to be long term reliable, or I'll take out my   
   ESR meter and go over the board when the board cools down if it's a board with   
   a crapload of caps    
   where shotgunning is time consuming.  One way to get all the weak ones   
   identified is to put the board in question in the refrigerator (or outside if   
   it's cold), as even capacitors that work well at room temperature and not   
   causing any immediate issues    
   may fail at very cold temps.  Capacitors that are in good condition won't be   
   bothered by the cold, so it's a good way to ferret out the ones that will fail   
   next.  Caps that work at room temp but not in cold temps are on borrowed time.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)