I'd lean towards coupling capacitors, or the differential pair of pre-amp
type transistors at the amp input stage. A can of freeze - mist might help
narrow it down.
I'm trying to remember - there was a particular type of transistor or two
they had problems with back in those days. I think it was 2SD458, or maybe
2SC1312.

Mark Z.

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wrote in message
om...
I've recently acquired one of these amps and it has almost been
working.. It will often go for a few minutes and then the protection
relay will cut out, although sometimes it doesn't cut in to start
with. I have traced it through to the protection circuit kicking in
due to DC being present on the output of the left channel. Haven't
been able to trace it further than that yet... When it does work, it
sounds fine.
Any clues on where to start?