At this point. I can tell you what is not causing the problem.
Its not electrolytic capacitors. Its not the power supply or muting circuit transistors or diodes.Its not the MC preamplifier on the function board.
Of course its not any of the smaller circuit boards.
Its something on that function board..
The unit I have here is doing the same thing-only it might act up once a month,week ,day, hour or minute..Therefore its one major PITA to troubleshoot. I've tried heat soaking,freezemisting,boardflexing,component wiggling to try and make it act up.All efforts a big NO-GO.Right now it hasn't acted up for several weeks. I know its not fixed.. I'll probably end up swapping out all 12 of those transistors that I had you remove and check as well as the two VD-1212 diodes and the two zeners..And cross my fingers.
Usually most of the heat is generated by the two pass transistors on the power supply board( the 2 transistors on large heatsinks).Thats why there on heatsinks.
Don't we always replace those just like we always replace SC458 shithouses?
Looks like you guys are having fun, I just don't get to stop in here much lately so when I do, I have to give Dave a lot of shit.