I can't find my tube sub book at the moment.
Can anyone tell me what if any tube will sub for a 21FP4 CRT?

Thanks,

Eric

21FP4 = 21FP4A (Ground the aquadag coating), and 21FP4D (Ground the aquadag coating and omit the ion trap)...the only two subs in my book... there may be more.

:scratch2:

Thank you Max.

Eric