From: no@dress.invalid   
      
   Fred wrote:   
      
   >   
   > "Zack"  wrote in message   
   > news:i00qho$phq$1@news.eternal-september.org...   
   >> if you think that is old, I have an AX-630 which drops one or both   
   >> channels   
   >> intermittently.  During the dropout, the audio is low and distorted with   
   >> mostly just buzzing.  Increasing the volume sometimes breaks through the   
   >> distortion and the problem goes away for a time.  The unit has an AST   
   >> pack, so replacing just the amp (which otherwise sounds great when it is   
   >> working) would require new speakers.   
   >>   
   >> Any ideas what might be wrong with it?  Reseating the wires external and   
   >> internal does not seem to result in a fix.  Mostly happens while using   
   >> the tuner, a TX-400U - which had a bad solder joint on the output that   
   >> was fixed a few years ago.   
   >   
   >   
   > Hey Zack,   
   >   
   > You say it mostly happens while using the tuner.  I assume that's because   
   > you mostly listen to the radio.  But if it also happens when listening to   
   > other   
   > sources like CD, the problem has to be in the amp.  So here's a plan:   
   >   
   > First thing to do is attack the switches & controls with Caig De-Oxit D5.   
   > Push button switches often require removal of the front panel so you can   
   > spray de-oxit into the switch where the shaft from the button enters the   
   > switch.  Spray and then cycle the switch 8 or 10 times.   
      
   This sounds like a good idea.   
      
   > Pots only need de-oxit if they scratch or cut out when rotated from limit   
   > to   
   > limit.  If they're doing that, they need to have the de-oxit sprayed in   
      
   The controls are in remarkably good shape and don't have any noise when   
   rotated.  Kudos to Yamaha on that front.   
      
   > De-oxit is powerful stuff.  You don't have to flood the area for it to   
   > work - a   
   > quick blast will do ya if it's aimed right.  Given that both channels are   
   > cutting out individually, it's about a 98% chance the de-oxit is going to   
   > solve your problem if you do it right.   
   >   
   > But if that doesn't do it, then it's a matter of finding the bad   
   > connection by visual inspection, mechanical shock (a tap here, a tap   
   > there), thermal shock (freeze spray, heat gun), and/or good old fashioned   
   > signal tracing with a   
   > scope or signal tracer while the unit's misbehaving.  Comparing the same   
   > point in the bad channel with the working channel will tell you if what   
   > you're seeing or hearing is OK or not.   
   >   
   > Keep in mind it's possible the bad connection is inside a transistor or IC   
   > - freeze spray is good for finding that kind of problem.   
   >   
   > It really helps to have a schematic so you can see where the signal goes   
   > next if de-oxit doesn't fix it.  Given its age, you can probably find the   
   > service manual for your amp on the internet in pdf form, possibly for a   
   > few $ from   
   > one of the many service manual purveyors out there these days.  Google is   
   > your friend.   
      
   Ironically, Yamaha has since released a DSP amp with the same ID that has   
   loads of chips and gagdetry my unit does not have.  Makes Google harder to   
   use.   
      
   Thanks for the tips, they are something to try!   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)