1. Is there a significant amount of DC at the C yokes ? This is an
inductive load and even a volt or two will heat the ICs up.

2. Have you COMPLETELY cleaned the heatsink and applied a BEAD of HS
compound in a line directly between the mounting holes ? (even though
they dont use them)

This might help you :

http://members.aol.com/JURB6006/convergence.pdf

Also, John is absolutely correct that the WF generator could be scewing
up, like dumping DC into the STKs. That little piece of the, I'd rather
not say. Please let me know when you've DLed it. I need to take it
down. it's a copyright violation and I don't intend to keep it up.
Please get it quickly and save it. Acrobat reader 4 has no problems
with it.

Those sets also have a two (or more) sided signal board, and unlike the
old PC board problems, on a two sided board sometimes the problem will
occur hot rather than cold.

JURB