analogJunkie

Hi Miles, If I play some big chords for a few minutes, the amp sounds like it's cutting out and then a really huge hum happens. If I put volume all the way down, it's still humming. If I switch it to standby and back the hum is still there. This hum is louder than the amp would be if it was functioning. What tubes should I look at first? Amp: Heritage Kenny Burrell Combo - 2x6L6 and 12ax7's for the pre I think. Thanks