I removed a Tung Sol KT120 from my Rogue Audio Stereo 90 Super Magnum tube amp a few days ago. I pulled the tube out just to take a look at it, sat it on my desk while I was working, and I put it back in maybe 30 minutes later. Fast forward to today, I set up the system in our new living room and I got a very loud hum from both speakers when I powered the system on. I had a similar problem just days ago with my Rogue tube preamp, so you could imagine the anger that ensued. Maybe it's the good Lord telling me I need to step away from the system for the next few days, I don't know, but it's frustrating.
The preamp wasn't in the mix for this setup so it's just a strange coincidence that both Rogue pieces are having tube troubles. Anyway, after hearing the loud hum I powered down the amp and popped the hood. The tube that I pulled days prior was not glowing that beautiful glow. There are four KT120's in the Rogue Stereo 90 so what I did was take the tube that was not glowing and switched it with another KT120 and the problem followed that tube thus confirming that the tube that wasn't glowing went bad somehow. I also am able to check the bias of each tube on this particular amp and I was getting a reading of ZERO in all 4 KT120 positions while the other 3 KT120's tested normal.
I just find it strange that this tube decided to call it quits after all I did was pull it out. Can anyone help me understand what happened? I mean, I handled it with care although I didn't wear gloves or anything. Thanks in advance!
