Lots of egg frying going on with nasty spikes – worse on the left than right channel – and not solved by the change of filter caps to new EBay fake Nichicon 4700uF – that aren’t even 4100uF…I’ll leave them in as the original caps are 25 years old but test fine.
Seems more like driver transistors and as most components have black leg rot, then probably noisy transistors somewhere. Not helped by the equally noisy balance pot either…
The obvious transistors to change are q420-21 I guess?
And maybe the 50V, 3.3uF electrolytics to C401-2 in the audio chain of the Voltage amp IC401.
All I can do is go with my gut feeling that this is a cap breaking down at power on and remove one at a time for a recap. I have no other logic to guide me here as I can’t even split the audio chain in half by removing one, as a collapsing DC rail could cause these noises, as well as noisy components (which I think there are too).
..and of course…these mains noises also blew my lovely Minimus 26s! Arse!