Hi!

Receiver is in a cabinet with little ventilation. Obviously likely to be a
heat related problem.

You should move it to a place where it can get better ventilation. Some of
these run quite hot.

Is this receiver losing power totally, or do some functions (like the
display and tuning buttons) continue to work? If it does, I'd bet that it's
going into protection to save your speakers from a disaster. Most--if not
all--of these units used Sanyo hybrid audio amplifier ICs (a large
many-legged black thing) and I think it's safe to say those were the weakest
point of them. They don't like heat and it seems like Technics skimped on
the heatsink in many of these units.

William