That guy is me - nobody anyway. Not quite new though as I registered in 2014 and have some amount of feedback if you even bothering clicking on...
It's not unusual that due to sample variation the actual filament impedance can be all over the places. Depends on the regulation of the filament...
Did you ground the chassis?
Don't own the amp but I think it is better to disconnect the B+ (HV supply) first before trimming. After a satisfying voltage level is reached,...
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