The other day I put a pair of KT88s into my 2204. I used a Biasrite to bias them. One side read fine but the other gave a weird negative reading. The tubes are matched fairly well so I went with the one side reading. Played the amp for a couple hours without incident. When I went to play the amp the next day, I popped an HT fuse. Sure enough, one of the 88s must have died. So I pulled them and put in a pair of 34s. Now my Biasrite is acting weird. I tried to bias the 34s and I get this really bad squeal through the speakers if I turn the bias pot past a certain point. With the Biasrite removed, there is no squeal no matter where the pot is set. Amp plays fine. I just don't know where the bias is on the tubes now. It should be OK as the squeal starts at about 30ma (if I can trust the Biasrite) and 70% is 46ma for 34s with my amp's plate voltage which is on the low side. I'm thinking one of the probes may be bad. I don't know. I'm wondering if anyone else has had a similar problem with a Biasrite.