[R-390] RT301 current regulator tube

[Jacques Fortin]

Hello Tisha,

When you mention using a LM317, is it used in Voltage regulator, or in
Current regulator configuration ?
In both cases, you will need to rectify and filter the 25.2 Volts AC supply,
then use the LM317 thereafter to supply constant 12.6V DC to the filaments
or 300mA DC, whatever.
And full-wave rectification cannot be used there, unless you modify the BFO
+ PTO filament wiring...
As the maximum voltage across the filtering capacitor will reach about 35V,
it also means that a quite substantial heatsink for the LM317 will be
needed.
Worst case, 6.72W have to be dissipated from it (in either configuration).

I prefer to use the 12BY7/12BH7 trick...

73, Jacques, VE2JFE in Montreal