Peavey Mark VIII Series 602

[pnut5150]

Amp was making a loud hum. Now when I power up with all connectors hooked up, I was getting arc from transistor at the end of the 73180 transistor rail. I replaced it and now it blows main fuse. With everything hooked up except the yellow wire that go to end of 73180's it will stay on and the fan work. The yellow wires run to a small board where AC mains come in. Help??

[g1]

Check the insulators between the output transistors and the heatsink.

[pnut5150]

I forgot to mention that I pulled all of the amps
Out and tested them. They all read good and all of the insulators are good and I put fresh thermal paste on them. What are the pieces on the end of transistors that the wires connect to? Can I test them?