I swapped the front and back tubes on that side and the next time I started it up the same thing happened. After playing for a while the sound on the right faded out and the entire interior of one tube was glowing cherry red.
I'm new to tubes. What is going on?
I realize that EL34's will have a foreshortened life in a ST 120. I only run the amp in triode.
Please advise. Thank you,