Tube issues, 12at7 affect KT88?

The power tubes were not moved. Only the 12AT7's. I swapped them twice, both times the Tele's ran the power tube hot, but just one. I replaced them in the same spots, so I think I have it boiled down to 2 of the 4. I was thinking about swapping them to the other channel, but don't want to press my luck. As far as I can tell, I didn't damage my speaker, and the power tube seems to be running normal with the old 12AT's back in. I will replace the power tube however, as going really hot like that probably shortened it's life compared to the others?

Thanks for the ideas, I will be getting the Tele's tested. Any other ideas? This is the first time I have encountered any issues when rolling.

Tony

I'd pick up a decent tube tester from ebay. The price you'll pay will be about the price of ONE good tube, so it will pay for itself as soon as it catches the first bad tube. Plus, it helps take the guesswork out of the equation. I'm sorry, I don't have any answers for you.
I had a bad tube or socket that lit up a power tube and split a resistor when I rolled tubes. That's when I decided I needed more test equipment to understand what was going on. In my opinion, the only downside to owning a tube tester is how big they are. But I own every other kind of test equipment, so I figured if I was going to mess with tubes, I needed to tool up. The plus side of owning your own tube tester is how many new friends you will make. It's like owning a truck or a station wagon! Good luck.

Well whatever the problem with that tube is it's causing that KT-88 to run away. Usually, if the DC voltage operating points are upset, that will upset the balance of the amp and over drive the output. Or for some reason the bias on that KT-88 is being affected and your loosing negative bias voltage on that tube. I believe in the vintage 275 the 12BH7's are the driver tubes. Is this a new 275 or a vintage 275?

Version V, newest version.

Heyraz, you are absolutly right. I am considering purchasing a tube tester.

HiFigeek, the weird thing is, only one tube runs away. I don't have the wiring schematic, but I'm guessing the first 2 AT's run the first 2 KT's, and the next 2 AT's run the next 2 KT's, with the 12AX's leading? That is what makes me think I have it narrowed down to 2 of the 4 AT's.

Tony

Tony what's the last tube in the chain before the KT-88s?