VTL Compact 80 Issue

Last night I went to check the bias of the amps as I had not done so in a while. I somehow over did the rotation of the bias pot for one of the tubes and it started to glow bright red. I realized what I did and proceeded to turn it down but now the tube glows red at any pot setting and the multi meter reads 1 volt no matter what I do.

Exactly what did I do, what is wrong, and what do you believe is the fix? I realize its hard to diagnose over the net based on a simple description and I will be taking my amp in for repairs after the holidays but for now i want to know as much as I can what the possible isses are with the unit. Thanks