Howdy y’all. I traded my Vox night train combo for a 50 watt peavey valveking. First thing, after playing it once, was experiment with different compatable tube strengths. After all kinds of tedious testing and resting, testing and resting, I replaced all three 12ax7’s with 5751’s in V1 and V2 and a 12at7 in the PI. It sounded so damn good! Really! Like, really good for a cheap “entry level” tube amp. I figured this would be the tube set up i’d stick with. With a 5751 in the V1, the natural breakup was awesome! V2 ain’t important to me cuz I don’t bother with the gain channel. I don’t like it. Okay, long story long, i switched it on the other day after not playing it for a few days and..... no sound! I unplugged it and flipped over and saw the the 12at7 in the phase inverter burnt out. Probably just when i had switched it on. I wanna put another one in, but why bother if it’s gonna burn out! I used JJ’s. Meantime, i put a spare JJ 12ax7 in it’s place, and it still sounds good. Just beefier than with the 12at7. Any thoughts or suggestions?