Hello, Hoping someone has some suggestions on things to try regarding a problem with my ENGL Invader 2. About a week ago or so, my channel 2 (crunch) of the amp stopped functioning. It produces no sound, other than a VERY light hum, that is barley audible. I never heard a pop or hiss indication of normal tube issues, but I'm still hoping this is the problem and nothing worse. However, I bought the amp new in January, and it came with 2 spare preamp tubes. I have already tried swapping the 2 preamp tubes with the 2 spots that the operator manual indicates would effect channel 2, but no success. I have not messed with power tubes, as I don't have any spares currently. However, keeping in mind all 3 other channels are absolutely perfect still, nothing at all out of the ordinary, or indication of potential malfunctions. Finally, I have checked cables, inputs, guitars, pickups and all of the easy variables. Any other thoughts would be greatly appreciated. Thanks for your time!