Dual Rec Blown Tubes/Fuse?

[fr0tran]

I've had EL34s in my Dual Rec (with the bias switch set to EL34) for the past year and a half, roughly. I kept getting a crackling sound when after warm-up for a few min. and switching the standby off. This went on for a few months (playing ~2-3 times a week for 1-2 hrs. a sitting), and I thought it was my guitar cable b/c it would go away after a min. or so. The output volume was significatly lower also. Then the other day the crackling was not going away, and I looked at the tubes of the amp to see the right pair (2 power tubes closest to the rectifier tubes) were glowing REALLY hot orange; with the one on the left of the pair getting more orange by the second. Switching from the tube rectifiers to silicon diode made this worse. It began to smell like burning, and eventually blowing the amp's fuse. I removed all EL34 tubes, replaced with the original 6L6s that came with the amp, replaced the fuse, switched the bias back to the 6L6 setting, and turned the amp back on after a few min. warm-up , and nothing out of the ordinary happened. They were regular colored (orange insides with a glowing blue flame look outside) and did not produce a crackling sound, outputted sound normally, etc. The one EL34 tube had a brown mark on the inside (looking like it was burnt). So what the heck happened to my amp: a) the tubes old and they were going bad, b) there's something wrong with the biasing switch, c) there something wrong with the amp and I should take it in to GC (where I bought it from and have their "performance warranty") ? I can recall many months ago (a few weeks after getting the amp head new, and replacing the 6L6s with EL34s) the same thing was happening, brighter than normal color tubes, burning smell starting etc. I turned off the amp, and turned it back on, and it never happened again. Another thought I've had...some days the amp just didn't seem to sound the same as it did another day (without changing any settings). Has anyone seen this before, or know what's going on?

 

[R_ADKINS80]

Sounds like some old tubes just finally gave up the ghost. The one thing I would deffinately recomend is take it to a tech and have him check out the grid resistors for the tube sockets that had glowing tubes. Good chance is they could have got toasted to and could need some attention.