From: @noway.com   
      
   Jack wrote:   
   > Mark Zacharias wrote:   
   >> "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.   
   >>   
   >   
   > Mark,   
   >   
   > The problem returned while playing an FM station. I clicked the Phono-1   
   > button and then the FM button again and the channel came right back.   
   > Something new to delve into.   
      
   When the left channel went out again, applying slight pressure to the   
   push button circuit board brought it back. I also noticed that when the   
   channel was out, touching the metal prong in back that connects the   
   preamp to the main amp for that channel produced a 60hz hum.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)