merlynski
Curmudgeon Electronicist
Test the amp as described in post #28, if that shows good, the STK is the problem. If the amp shows bad then fix it it, note what you replaced to fix it. Put the old STK, or a new one, back in. If it works the amp was the problem, if it still doesn't work the amp and the STK were/are both bad. If the old STK is bad it may damage the repaired channel in the amp. These are the risks you take (and part of the challenge) owning and repairing vintage audio gear. You could try moving the good (other channel) STK over, after verifying the amp. This does risk the good STK, however. Look at the link in post #2 about custom replacements for the STK with modern replaceable discrete components. If you can solder and turn a screwdriver they are a very good upgrade as well.