From: chuck@deja.net   
      
   On Mon, 16 Jul 2012 12:23:23 -0700, Jack <@noway.com> wrote:   
      
   >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.   
      
      
   As Mark said, the switches on the front are a major problem and need   
   to be cleaned.  I would buy a can of Deoxit  5 and spray it into all   
   the switches and work the push buttons in and out.  Chuck   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)