In article , Dave Plowman (News)
wrote:
Got an 'interesting' fault on an ancient Linsey Hood amp. Switch on a
light etc, and sometimes *one* channel bursts into loud mains hum - but
carries on working. And the output transistors get very hot. It's not
normally susceptible to mains born interference - so any guesses before
I rip it apart?

Both channels seem to match ok before this happens.

My immediate suspiscion is as others have commented. That the channel may
be oscillating at HF. That can explain the 'sometimes', etc.

Check the bias (when not showing the problem), dressing of the wiring loom,
output zobel, etc.

Slainte,

Jim

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