Working on a friend's AB165 Bassman. After recap, add bias pot to bias balance, clean and tension all sockets, clean all pots and jacks I ended up with a good sounding amp, but there was a good amount of hiss, varying with the volume. Swapped out some of the 12AX7s and the noise changed but didn't go away. Went to swap out the plate load resistors. When I heated the joint and tugged at the resistors, 2 of them just crumbled into dust. Never saw that before. Now the Bright channel is dead quiet, but still some noise in Bass channel. I'll try to swap tubes again now with the new resistors.