Hey guys, So yesterday i was kinda ready to rock out and after firing up my Jet City 50 head it didnt make any sound. After some troubleshooting it produced the faintest saddest amount of sound with the gain and master on 10. This makes me believe one of my powertubes wore out. Now here is the thing, the amp normally runs on 6l6's but i have none lying around. I do however have some EL34's that i could pop in and see if the powertubes were really the problem. i figured if i keep the master low i couldnt really harm the transformers or anything. is this a bad idea or is it ok as long as i keep the master low? Secondly i havent rebiased the amp yet so its still on the factory bias settings. and i happen to know Jet City biases these amps really cold in the factory to prolong tube life. i have some electrical engineering background so could i do this myself or would that be the best way to get to rock out with John Bonham in the afterlife?