lost sound in right tube mono

While listening,the right monoblock dropped out.One slight pop and is was gone.
fuse is good
tubes all test fine
With the amps powered down I read the correct resistance at the pots(10 ohms)but powered on I read no voltage at the pots.The filaments in the tubes are working(glowing)so the tubes are powered up.
Looking inside no burnt resistors or anything obvious.
Thanks for any replies
Bad Bias pot maybe????
After I stopped whining and stomping my feet I did locate another fuse that lloks to be wired into one of the transformers (B+ rail?)
About a week ago I had a tube loose its bias,thats a sight to see,the whole plate structure glowing red.It ended up blowing the main power supply fuse,but I never bothered to check the other one(didnt know there was one til now)
I wonder if the fuse was damaged and not completly blown and just decided to let go now.
I will post after I power it up
Don't lunch too many tubes trying to diagnose it. Sounds like a bias supply problem.