[R-390] R390A help, RT301 current regulator tube

[Jacques Fortin]

Hello Sam,
To complement Renée answer, I prefer to use the "method 3":
On the RT510 socket, connect pin 2 to pin 4 and pin 5 to pin 7.
Whatever the other mods you do in the IF module area, never connect anything to pins 1, 6 and 9 (Product demodulator using nearby V505, for ex.).
You can then use either a 12BY7 or a 12BH7 in place of the 3TF7 (2HTF11B) ballast tube.
The same also applies to the R390 (non-A) RT512.
As already mentioned, those tubes do not need to test "good" as far as the filament between pins 4 and 5 exhibits continuity.

73, Jacques, VE2JFE in Montreal