I need a little help and advice diagnosing a problem with my Trace Elliot V-Type Combo. The amp is a 15" combo with a tube preamp (the same "V-Type" preamp you see in rackmount form from time to time) and a solid state power amp. Weirdly enough, it's not all tube but it does have a standby switch. The other day I went to noodle a bit and when I turned my amp on, there was immediately a super loud hum around the pitch of a "B" one octave below middle C. I knew something was wrong because the amp usually makes no sound (except for the sound of the fan) in standby. The hum continues no matter what, and turning up the volume increases the loudness of the hum slightly. I plugged my bass in to troubleshoot a bit and the amp still amplifies the bass, but crackles quite a bit. The gain, volume, tone controls and all switches still work. The passive and active input exhibit the same behavior. I thought it might have just been a bad tube, so I got an extra ECC 83 to troubleshoot and swapped out each tube (2 total) individually to try it out. No difference. I'm a little dismayed because I really hoped that the tubes were the problem - those are pretty easy to fix. I'm not an expert on the inner workings of the amp portion, but none of the electronic components are obviously externally damaged or loose. Everything on the inside is tidy. Also, I checked the fuse and it is not blown. I have tried different quarter inch cables, different power cables, different outlets, different speaker cabinets. I know it's not related to an external cable because the amp makes the sound as soon as it's powered up before anything is plugged into it. What do you think is wrong with my amp? I really appreciate your help because I'm not technically gifted in this area, and I don't have any amp repair places that I'm familiar with/trust. I don't want to pour a ton of money into diagnosing the problem only to find out it can't really be fixed. I love this amp and just want to get it back to working condition. Thanks!