Hi all, okay, a little knowledge is dangerous…! But here goes; at high volume, after a few seconds 1 6l6 nearest the rectifier red plates and all volume is lost. Amp is immediately turned off; follows the socket, not the tube. Socket replaced Grid screen resistors replaced Bias is good still happens. the caps look good, but before i do anything soldery, is it possible the PI tube cause red plating on 1 valve? My thought is not as the coupling capacitor is ‘protecting’ the 6l6 from high voltage dc. However, it would make sense that 1 side of the push/pull is affected only. thoughts please!