From: @noway.com   
      
   Last night I pulled heat sink for the last stage output transistors to   
   get a good look at the back of the power amp board. This involved   
   moderate flexing of wires coming to and from the board. All the solder   
   joints looked sound. Apart from taking a soldering iron to all of them,   
   I could see no obvious need for attention so I put everything back   
   together. After that the left channel, which was cutting out   
   consistently, either at startup or after ten minutes or so of play after   
   bringing it back by turning up the volume, was now playing without   
   cutting out. This morning both channels started up and both have been   
   playing for an hour or so.   
      
   Last night, after an hour or so of consistent play, I took more   
   measurements of the transistors of the second to last stages, playing a   
   100Hz tone, and found that the AC voltages of the emitters and bases of   
   the left channel were half or less than those of the collectors and   
   bases of the right channel. These transistors are 2SB528 and 2SD358   
      
      
   2SB528   
   L Channel -- E 4.0 -- B 3.4   
   R Channel -- E 9.2 -- B 8.6   
      
   2SD358   
   L Channel -- E 5.2 ---- B 5.8   
   R Channel -- E 10.5 -- B 11.1   
      
      
      
   This morning, playing a local jazz station in mono mode, I noticed that   
   the left channel is lower in volume and the high is missing, cymbals   
   disappear. I switched speakers to make sure they weren't the problem and   
   they weren't. I switched the preamp out and power in jacks on the back   
   to determine if this was a preamp or main amp problem. The problem   
   stayed in the left channel. My guess is that these problems are related.   
      
   NTE has replacements for 2SB528 and 2SD358, being NTE292 and NTE 291   
   respectively. Fortunately for me, I live close to Al Lasher's   
   Electronics and they have both in stock. Being that the transistors in   
   the next lower stage all measured the same when the cutting out problem   
   was not manifesting itself and the these particular transistors have   
   widely divergent readings, the problem would appear to be the   
   transistors themselves or some associated diodes, resistors or capacitors.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)