Hi!

It's looking as if the IC is shot, and it seesm to be NLA.....

It's a common problem. In a lot of these 80s Technics amplifiers, the
Sanyo power amplifier IC goes bad. I've come to believe that they are
somewhat "failure prone". Interestingly enough, it seems that other
designs using these modules were more reliable--I have some Aiwa "all
in one" stereo systems and a little Pioneer receiver that use the
Sanyo module. None of these run as hot as do the Technics
receivers...perhaps another data point?

Despite being played hard at times, these units have never caused any
trouble. Of course, most of the time I happened to come across such
older Technics gear, it had already been treated badly.

There is a more sinister problem--the Sanyo module integrates speaker
protection through electronic means. The idea is that if one of the
final transistors breaks, this electronic protection circuit will
break the path between module and speaker so that your speaker does
not become exposed to a power supply rail and burn out. Unfortunately,
the protection circuit is usually destroyed and the speaker burns out.

I thought all of the Technics amplifiers that used these hybrid
modules relied on the electronic protection. After searching for a
long time to find a nice one in working condition, I discovered an
SA-929 receiver (also based on a house numbered Sanyo integrated
amplifier module) that has an outboard DC protection relay. This
should save the speakers if anything goes wrong.

I also found that the relay itself had pitted contacts, resulting in
intermittent audio output from one speaker or another. Cleaning the
relay contacts resolved this problem, but in the process I found bad
solder joints that were aggravated by my opening the relay.

http://www.youtube.com/watch?v=K0cObJ7o8vE (SA-929)
http://www.youtube.com/watch?v=sgdTnBU0_N0 (SA-929 repairs)

I have seen at least one other report that suggested bad solder on the
protection relay's coil contacts was to blame for intermittent audio.

If you have enough room and another partially broken part, you might
try this for a fix (different amp, similar module):

http://john.ccac.rwth-aachen.de:8000/misc/rr100rep/

I've never tried it, nor is that my page.

William