screen grid resistor blown on triple rec

[Metaghius]

3 channel triple rec power tube 4 had a screen resistor burn up..its the 1.5K that is connected to pin 4 of the tube socket..this happened to tube 6 a few months back..I have spare resistors that I purchased from MESA, power amp tubes all replace also..is this a sign that I may have a failing transformer?

another note to mention which may be crazy...at our rehearsal space my amp sits extremely close to the front of an 18" sub..could the vibration be causing the tube to vibrate and then decide to fail???? just trying to figure whats causing this...

 

[mikey383]

I wouldn't say it's a sign of a failing transformer, but a sign of failing power tubes. The screen grid resistor is one of the components that can go when a tube fails.

How old are your tubes? It may be time for a complete retube.

For what it's worth, I had a SG resistor burn up in my Dual, and it was because the previous owner had blown a tube, and just kept sticking bigger fuses in until it held and finally burnt the SGR. I always wondered why it sounded better with 2 tubes than all 4....then when I was doing a bias mod, I found that the tubes wouldn't bias right and found the burnt SGR.