So I picked up a used Mesa 400, I did not have a cab to test it with at the time, and I bought it on the spot. I brought it home a week or two later, to find something funky is going on with the amp. Its making very weird nasty noises, and I figure it needs new tubes, as I look at the tubes I notice the far right tube is not lit. Called the guy up, told him what was going on, he asked if it was the far right tube, as it was slow to "warm up". Anyways he sends me a little bit of cash to put towards new tubes. I bought a sextet of 6l6's swapped them out. Turned on the amp, then flipped standby. The right tube lit up a bright blue/white and the amp went dead. What could possibly be wrong with this amp?