I'm on my 2nd replacement tube and now seeing bias meters out of balance, and then saw the first arc on this amp using a GZ32.

I think possibly the tubes are unreliable and going into runaway state?



Recommended Operating Conditions(reference value)
class A1, singel tube, fixed bias
Ua(b) …………………… 265 265 V
Ua……………………………250 250 V
Ug2……………………… Rg2=2k Rg2=0
Ug3……………………………0 0 V
-Ug1……………………… 14.5 13.5 V
Ia(0) ………………………70 100 mA
Ig2(0) …………………… 10 14.9 mA
Gm…………………………… 9 11 mA/V
ri……………………………18 15 kΩ
RL…………………………… 3 2 kΩ
Pout………………………… 8 11 W
Dtot…………………………10 10 %

http://www.partsconnexion.com/TUBPT2-76715.html