[morzh]

It is actually a much better arrangement if you have a separate winding for 84 and the rest of the tubes, as in 40-180 they grounded the filaments, and so the potential between the filament and the Cathode of 84 is full rectified B+, which could be well over 250V before the load kicks in (these radios use lower voltages, the output after the field coil filter is just 185V). Still. In other radios it could be higher.

Gosh forbid that F-K short occurs, I think it could be pretty catastrophic for the power section. Even though from what I read, this is not a very common thing to happen; still better safe than sorry.