Custom Sound 2005, Mosfet band amp, made 1988

Monitor the input to the output section with a scope and wait for it to do its thing.

Check the supply rails to see if any are drooping.

Entirely normal for mosfet designs. They don't suffer from thermal runaway.

Graham

If I recall correctly, it`s a pretty basic implementation of the classic Hitachi design.

Ron(UK)

Dummy loaded and took the heatsink up to 70 degrees C and held that power level for 40 minutes with little variation in preamp output, pa o/p or DC rails so a matter of the usual treatments for the numerous IDC interconnects, sprung IC sockets and 1/4 inputs, despite no response to twizzle stick and reported gradual fade.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Does it have a breakjack (insert, effects, etc.)between pre amp and power amp? if so try tapping flexing etc. there, or when the power has faded, try linking them out.

Ron(UK)