03-23-2015, 02:21 PM
Ron,
I don't mean this to be a step by step tutorial but a few suggestions having been through similar problems. In older receivers like this one your fingers or a IR thermometer can be your friend. When a channel is biased wrong is will run hotter, especially the later stages output transistors.
Another area to check out is some type of thermal-component issue. While transistor testers are good they sometimes don't pick up on thermal stresses. If care is used a hair dryer and a can of cool spray can be your friend. By thermally heating and cooling some areas you can narrow down the search. I had a speaker protection transistor in a JVC that gave me fits. The only way I found the problem was alternating heat/cool until I hit this transistor. Bingo!
Your description of fine and then distortion returning sounds thermally related. Assuming that voltages are staying stable.
Good luck,
Mike
I don't mean this to be a step by step tutorial but a few suggestions having been through similar problems. In older receivers like this one your fingers or a IR thermometer can be your friend. When a channel is biased wrong is will run hotter, especially the later stages output transistors.
Another area to check out is some type of thermal-component issue. While transistor testers are good they sometimes don't pick up on thermal stresses. If care is used a hair dryer and a can of cool spray can be your friend. By thermally heating and cooling some areas you can narrow down the search. I had a speaker protection transistor in a JVC that gave me fits. The only way I found the problem was alternating heat/cool until I hit this transistor. Bingo!
Your description of fine and then distortion returning sounds thermally related. Assuming that voltages are staying stable.
Good luck,
Mike
Cossor 3468
GE 417A
Philco 118H
Radiola 17/100
Scott 800B6
Silvertone 6130
Stromberg 535M
Truetone D1952
