Repaired now, but for the archives there is a safety issue with these amps.
The earth bond wire to the amp chassis is fine but the bond to the front
panel metal is very poor, just a brass rivet to the phenolic of the pcb, of
a few ohms drop over the years. Needs redoing to the metalwork properly.

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Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/