As an owner of a Marantz PM80SE, it has given me the usual grief of a failing STK3102, twice.
Thanks to this forum, I quickly found it to be the culprit when it first statrted acting up in 2004. And then it started all over again in 2011.
Not wanting to replace the module I again, I thought about making a discrete replacement based on the VAS of PM8000, which looked like it should work without too much headaches. But I stashed the amp in the attick instead and never made an attempt.
After some work on my brothers PM7200KI, I thought to have another go again.
Powered it up and sure enough, the output relays refused to engage.
A quick measurement on the headphone voltage divider near the red reed relay at the back of the power amp board confirmed the left output going close to a voltage rail.
Took out the STK3102 (or so I thought) and powered it up again, no more DC.
Since the replacement STK-module that I bought in 2004 was no longer functioning properly, I popped the plastic cover and found that it was a fake. Finding only SOT23 transistors and some 0805 resistors, I was a bit surprised. Okay, in a VAS it worked for about 6 years, but aren't these things supposed to be able to drive 8 Ohm loads?
No doubt many of you know about these replacements being fake, but I thought I'd share it anyway.
I do wonder, though, if I can repair this thing and stick it back in...
Hopefully these transistors aren't some Chinese knock-offs but generic transistors that I can find in a smd-codebook..
Nice posting! Your sharing is quite in-depth and solves my puzzles all the time. I will keep reading your post.