JH wrote:
I have my Dad's version of this, and it has a huge mains hum on one
of the speaker channels.

Are there any well known faults with this thing? I don't want to junk
it (sentimental reasons).

(I suspect failure of the large smoothing caps in the psu board.

J.

If it has the big hum on just one channel - it's putting out DC on that
channel. What you are hearing is the sawtooth component. DO NOT hook up
speakers to that channel, there is a high likelihood of destroying it
(them). If you aren't competent to do amplifier repair get it to a shop.

Mark Z.