I had an EL34 go last night. I saw it glowing, and just shut down the power. I replaced the entire quad of EL34's with another known working quad. I get no power to the unit at all. There are no fuses on the back. I'm thinking there may be an internal fuse. I have not pulled the bottom cover off to take a peek, nor have I pulled out the schematic to check that. I just pulled the unit out of my rack and put my PL5 back into action. Nice to have that as a "spare"! Any ideas or experience with this amp? If I can't see anything obvious I'm going to take it to my tech on Friday. They just rebuilt some DCM TF's for me, and I told them I'd be back, but not this soon.