Have been asked to look at this Marantz PM6004 amplifier, report is it
"cuts out" if the volume is raised more than a third.

Had a Google and I get hits saying its "a common fault" but nothing
about resolutions.

Before tearing it apart, are there any common issues with this model?
(I found the auto shutdown "crackle" fix)
What it appears to do, on a dummy load, is the protection circuit is
kicking in, seemingly at random...

Obviously I'll get in there and measure voltages and waveforms when I
have it set up on the bench later