Greetings.
I wonder if anyone has some insight into this problem.

This receiver uses two STK0177 power amplifier "blocks", each with 10
in-line connectors. The LH channel is highly distorted, the RH channel
is perfect. The distortion is present on FM, AM and AUX (with sig,
gen. input) so it's not the FM demodulator - it's definitely in the
audio stages.

The DC voltages on each of the two STK0177's power amplifier pins are
as follows (with 115 VAC supply):

Pin # RH channel LH channel (volts)
1 +0.251 +0.229
2 +0.002 +0.002
3 +0.255 +0.229
4 -26.90 -26.77
5 -1.272 -1.288
6 -28.29 -28.28
7 +0.060 +0.20
8 +28.23 +28.22
9 +1.309 +1.257
0 +26.95 +26.77

(I hope the columns hold together!)

I have not yet put a 'scope on each STK0177 line to watch for clipping
or drive distortion (pin-out not known.) Nothing gets too hot and
there is no perceptible difference in temperature between the two heat
sinks (but they are thermally connected do some degree, so that's not
conclusive.).

Do people think this is a failed STK0177? Or is there another
candidate component? Unfortunately, I do not have the schematic.
Also, does anyone have a pointer or URL to the pinout and/or spec
sheet for the STK0177? I did a quick Google but with no success.

BTW, this unit is very difficult to service since all the electronics
are on one large PCB and you can't access the bottom of this PCB
without disconnecting just about everything and lifting it up (unlike
other Technics models where you can take out the metal floor plate.)

Thanks for all comments.

Cheers,

Roger