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Yamaha CR 400 right channel distortion when warmed up

pdxtim

pdxtim

Well-Known Member
Picked up a nice CR 400 for $20 at garage sale. Sounds great when first turned on but distortion occurs in right speaker when I turn up the volume and it warms up. I've used DeOxit D5 several times on the pots and switches and recently used DeOxit Gold which seems to help only temporarily. Anyone have any suggestions? Thanks in advance.
 
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pdxtim said:
Picked up a nice CR 400 for $20 at garage sale. Sounds great when first turned on but distortion occurs in right speaker when I turn up the volume and it warms up. I've used DeOxit D5 several times on the pots and switches and recently used DeOxit Gold which seems to help only temporarily. Anyone have any suggestions? Thanks in advance.
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I'll get us started. Likely thermal related failure somewhere. Get canned air and start spraying individual components until distortion goes away. Be very careful poking around a live receiver with cover off.
 
So I'm guessing that the compressed air cools things, resolving the distortion? Sounds like a good plan. Was listening to it this weekend and things definitely go downhill and it distorts when it gets warm, or when I increase the volume significantly. Will give it a try in the next day or 2 and get back to you. Thanks!
 
Hey SoCal Sam - I did the DeOxit thing on all the knobs and switches for the umpteenth time, and also sprayed the individual components with compressed air. Then I saw these 3 black and 2 green square components at back of receiver (the black one to the left has T and D234 stamped on it) and decided to zap them with DeOxit too. Whatever I did, IT FIXED IT!!!! No more garbled fuzzy sound out of right channel when it gets hot! I've been messing with this thing for nearly a year! Two questions: what are those black and green square things? And what do you think finally fixed it? Thanks very much for your help!
cr 400.jpg
 
Zapped them with DeOxit? Or canned air?

Those are output transistors.

I bet if you follow the three legs from each transistor through the board and look on the other side you'll find some bad solder joints.

988E3D0D-0069-40B0-B4C5-0050DD5B000B-1259-00000B22513E82E9.jpeg
 
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Zapped them with DeOxit. Looked at the solder joints on other side and they all looked OK. Is it logical that the DeOxit "fixed" this? Is this likely a temporary "fix"?
 
Look again with magnification. Bad connection may not be as obvious as my photo. Sometimes very hard to see. I'd just reflow all the transistor connections anyway.

Deoxit would have no effect on transistors. It does improve contact between metal surfaces though - I.e. Two sides of a broken connection. Or might have caused the board to swell just enough to close gap.
 
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