A friend dropped by an old (early 80s?) solid state amp that was blowing fuses. I confirmed that and then he told me that the volume was not as loud before the fuse popping. So I thought it would be an easy fix. I started with the output transistors and found 2 out of 6 bad. I ordered a new full set and put them in with new isolators. Still blowing fuses. I hooked it up to the variac and only got about 5V AC applied before the speaker started humming loudly. I'm guessing that something is shorted but I have no idea what or where to start. Any help would be appreciated. I have tools and am willing to learn. I have attached a couple of pics. Thanks in advance.