Einstein channel 2 problem, please help!

Tonight at rehearsal channel 2 started howling/harsh vibrating noise bad when playing, even worse when not playing. What do you think? Microphonic pre-amp tube? Channel 1 seems to sound ok, so do you think the tube in V2 went bad? Please any suggestions would be greatly appreciated. I have a very important gig this Wednesday night, and I really need Einstein ready to go. Also,what is the order of the tubes? I'm assuming V1 is the closest to the input jack and then so on... Is this correct? Ive currently got ruby 12ax7's. Any opinions on groove tubes as they are the easiest availability for me? GT12AX7M's maybe?

Thanks guys.....

Please replace V1 with a E83CC Highgrade from JJ
and V2 with a 12AX7 Chinese Selected.

Thanks,

Peter

The GT12AX7M is great for V2 in my experience.

V1 and V3 are used by both channels, V2 only by channel 2.