I have a Bugera 333 and recently i have been able to turn on the amp but cannot get to the tubes to warm up at all. i have checked the fuse and it seems fine. i dont want to go out and buy new tubes until i know for sure that i need to. can anyone help me figure this out?

also i was having problems with my cab getting sound out of all 4 speakers. i solved this by connecting the wires from the mono/right side to the stereo/left side. could this be harmful to my amp??