Having an odd problem with a Rebel 20. Upon tube warm-up get a (very) loud uniform hum/buzz, not the usual ground issues etc. Not affected by volume (i.e. preamp tubes) *or* tube mix control (i.e. power tubes?). Not affected by bypassing the preamp and running my guitar directly into the return loop. Can still hear guitar, but becomes degraded. Haven't left it on long enough to blow a fuse etc.
My question is this: since both sets of power tubes (stock 6V6/EL84) are receiving current regardless of whether I have selected them to receive signal with the tube mix control, then does it matter which tube set I've selected where this noise is concerned (i.e. can a tube set which has not been selected with tube mix still produce an overpowering hum due to the fact that it is still receiving current)?
A secondary question I have is can I run the head with only a single set of power tubes as long as my tube mix selector is set to those tubes (i.e. do missing power tubes pose any risk if they are not selected to receive a signal)?
Thanks
My question is this: since both sets of power tubes (stock 6V6/EL84) are receiving current regardless of whether I have selected them to receive signal with the tube mix control, then does it matter which tube set I've selected where this noise is concerned (i.e. can a tube set which has not been selected with tube mix still produce an overpowering hum due to the fact that it is still receiving current)?
A secondary question I have is can I run the head with only a single set of power tubes as long as my tube mix selector is set to those tubes (i.e. do missing power tubes pose any risk if they are not selected to receive a signal)?
Thanks