See below...

"Mark D. Zacharias" wrote in message
...
I'm not at all sure the voltages are far enough off to suggest a
problem
with an output IC. Have you just tried manipulating the various
controls and
switches to eliminate them first?

Yes, all OK.

If you swap the output IC's, that would be the final test.

Good point! But that is a VERY difficult job on this board (see below
in my text.) I may have to do it, though.

That's an odd STK number though, you might have trouble finding one.
I use
East Coast Transistor parts for old STK's - they can usually suggest
a good
sub number if one exists.

Thanks for that idea - will file it for future use.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and
spam
have rendered my regular e-mail address useless.


"Engineer" wrote in message
...
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