From: cd@notformail.com   
      
   On Sat, 16 Mar 2024 20:44:58 +0000, liz@poppyrecords.invalid.invalid   
   (Liz Tuddenham) wrote:   
      
   >Chuck  wrote:   
   >   
   >> On Thu, 14 Mar 2024 20:56:32 +0000, liz@poppyrecords.invalid.invalid   
   >> (Liz Tuddenham) wrote:   
   >>   
   >> >I was asked to repair a Pioneer QX-949 quadraphonic tuner/amplifier.  It   
   >> >is a complex beast and one channel had gone down to almost nothing.   
   >> >Luckily the service sheet was available and I traced the fault to the   
   >> >board which houses the tone controls and filters.   
   >> >   
   >> >The gain is in two stages with the tone controls around the second   
   >> >stage.  On one of the channels, the voltages on the single transistor   
   >> >for that stage were all wrong.  After lifting the transistor off the   
   >> >board, it became apparent that the base bias was far too high and the   
   >> >finger of suspicion pointed to the inter-stage coupling capacitor   
   >> >feeding in leakage current from the preceding stage.   
   >> >   
   >> >I tested the capacitor, which was marked "4.7".  It read exactly 4.7k in   
   >> >both directions on an ohm-meter !!!   
   >>   
   >> Was it a light blue Sanyo?   
   >   
   >It was indeed!   
      
   Sounds like a known issue, then. Unless Chuck is psychic, of course.   
      
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