Sounds like a speaker relay to me.

I have a Denon which has had the relay contacts cleaned a few times for this
same fault. The sound can get intermittent, or even distorted due to very
little contamination of a relay contact. Of course, I do not know if your
amp has relays, but it sounds very much like the symptoms I've had.
Brian

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"Astley Le Jasper" wrote in message
...
My long serving Marantz PM 6010 OSE is ill and before I dump it, I
wondered if it was worth salvaging.

A while ago, one of the channels stopped working. However, when I
plugged a headphone socket in and then out, everything would be fine
for a few months. However, that doesn't work anymore.

Does that give anyone an idea of what's wrong with it?

It's hardly worth taking it to be checked out, because I'll have to
pay someone to look at it ... and might as well get a new amp. It
would be a shame though.

(I've checked it with different sources and also listening using
headphone, but that one channel has definitely gone.)

ALJ