Tube amp stopped working

You might try moving the tubes from one channel to another. Just because a tube lights, does not mean that it's working.

Usually, the cathode resistors do the duty of fuses, they are designed to fry instead of the output trannies or tubes. You can usually tell visually if this has happened, but if you don't know what you are doing, don't be messing around with the bottom off, there are lethal voltages in there. Death would really ruin your Christmas, take it to a repair shop if in doubt.

I recently had the same problem with a new set of New Sensor Gold Lion Repro KT77's.Pretty bad when a new quad which was supposed to be re-checked before going to a customer..Ended up being a bad tube( no Bias at all ). Sent them back and went back to SED El34 tubes.

did you put the el34s back in and have the same problem?

Replace with your known working stock tubes, provided they were working. Always have on hand a working set of tubes to check against. My guess, one or more bad new tubes if the old ones worked. Jallen

It turned out both amps worked and the battery supply on the pre amp went on the fritz. On the upside the new tubes sound great!