Well I adjusted the "bias" to get 7 mv across R72, before the adjustment it was like 9mv. Incidentally all the other .47ohm resistors in series with the power transformers have 7mv across them now as well. I played for like 2 hours at full volume and nothing bad happened. Could I have fixed it with this adjustment? I find it hard to believe. I bet next band practice it will start its crapping out thing again. *sigh* Ill keep you guys posted. Any suggestions will be appreciated.

On further inspection 2 of the transistors in the output are motorola (the TIP 147's) and two are a different brand maybe SL i think (the TIP-142's). Has someone been in this amp already?

-The Motorola transistors (Q15 and Q16) have -1volt DC on the base at all times even when playing. According to the schem they are only supposed to have -.06 volts. Every other DC measurement on the power amp side is ok +/- 5%.
-my speakers have ~40mv DC on them when nothing is being played.

Well, I guess im going to play the hell out of it on full volume right now for like 1/2 hour by myself and see what heats up. I have some cold spray to test what needs to be cooled to function.

Hey guys im a nub here and to the solid state world. I have a Crate gx-212 and i like it, it perfectly fits into the trunk of my rx8 and is perfect for practice (120w) so I desperately want to fix it. Getting another practice amp would be a waste i think. Heres whats up:

-After playing for about 1/2 an hour at any setting above 5 (50%) the gain level drops to the point where the lead channel sounds like an overdriven clean channel, and then the clean channel can barely be heard(though it remains clean sounding.)
-This happens no matter which guitar or cable I use, AND it happens even when I use an extension cab.
-Nothing inside the amp is discolored or "burnt" looking.
-http://www.ssguitar.com/index.php?action=dlattach;topic=1075.0;attach=612-schematic

I found the schematic for this amp in the schematic section. I have built tube amplifiers before and i know how to use a dmm so just let me have it straight don't dull it down for me. I don't have an oscilloscope but I can get one. What should i check?

also if I fix it and don't fail I have plenty of other broken solid state crap that I will be able to fix, so I want to learn, not just fix and forget.

Im new to the forum. I just found it searching for GX-212 schematics. I have read the sticky and I wont ask for anything in this thread, I just wanted to say thanks for making such an awesome site and thanks for the schem!