[R-390] RT301 current regulator tube

[Jacques Fortin]

Hello Jordan,

I already found the same.
When I plotted the V-I characteristic of this particular 3TF7, the
"regulation" plateau was in the 10 to 14V range, but the current (almost
constant across the voltage range) was 330mA !
Maybe this is a consequence of the hydrogen "escaping" the envelope.
No wonder that it can result in filament voltages higher than expected.

73, Jacques, VE2JFE in Montreal