From: mark_zacharias@labolgcbs.net   
      
   "Jack" <@noway.com> wrote in message news:jtqirc$g96$1@dont-email.me...   
   > Mark Zacharias wrote:   
   >> "Jack" <@noway.com> wrote in message news:jtnp3c$dcf$1@dont-email.me...   
   >>> Jack wrote:   
   >>>> After a week of playing with no problems, the right channel went out.   
   >>>> It   
   >>>> was the left channel previously. I was dismayed until I remembered   
   >>>> that,   
   >>>> when I reseated the output trannies, I switch them, left for right. I   
   >>>> was further heartened when that same trick of switching off the   
   >>>> speakers   
   >>>> and turning the volume up to max brought the sound back. Since there   
   >>>> are   
   >>>> a pair of outputs in each channel, switching one of them again and   
   >>>> waiting to see which channel goes out next should tell me which tranny   
   >>>> is bad.   
   >>> After switching back one pair of the output transistors, the PNP's, NEC   
   >>> B539A's, the problem stayed in the right channel, so I replaced the   
   >>> right channel NPN, an NEC D287A with an NTE284. It's playing fine at the   
   >>> moment. I will button it up and consider it fixed until it tells me it   
   >>> isn't.   
   >>>   
   >>> Jack   
   >>   
   >>   
   >> If you have not cleaned the relay contacts yet - you are wasting your   
   >> time.   
   >>   
   >> Mark Z.   
   >   
   > I cleaned the relays a couple of years ago when I tried to tackle this   
   > the first time. Buffed the contacts with 1200 grit wet/dry sandpaper.   
   > This time I tested the relays by bridging them when the bad channel was   
   > out. didn't help. It wasn't the relay. The problem followed the NPN   
   > output transistor when a swapped them left to right and right to left.   
      
      
   OK, but 1200 grit...Wow. The coating on the contacts must not be too good   
   anymore...   
      
   I've used 6000 grit in the past and even that was too much.   
      
   I'm not sure swapping the transistor really revealed the nature of the   
   problem. As I'm sure you have seen, often we do something, it seems to fix   
   the problem, then re-occurs later.   
      
   You may very well have both channels cutting out at differnt times.   
      
   I'm getting in on this late... have you cleaned the front panel push-button   
   controls? They were NOTORIOUS for cutting out on this model.   
      
   Mark Z.   
      
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