[Crist Rigott]

Originally Posted by dieseljeep

Boost the line voltage another 10 volts or so. See what the focus and brightness looks like then. You installed E'caps, that were rated for higher B+ so no worry.
I just looked at an old Sylvania tube manual for the specs on the 21FP4 and it shows the focus voltage, rated between -200 to 1KV on pin 6. I don't remember seeing, that kind of voltage used for E'stat focusing. It was always between ground and boost.

I could boost the line voltage by 10 volts. Would that hurt the filament string?