[Boatanchors] Revisiting: the R390A & 3TF7 substitutes

[Drew P. via Boatanchors]

Doug Hensley done wrote:

 "Poking around for information on a solid state replacement
 schematic, I found some interesting comments on a fix. 
 People are reporting that Rick Mish puts a 40 ohm 10 watt
 Dale resistor where pins 2 & 7 had been and removes the
 socket.  A seller or two on the e-Place are marketing
 G-10 9 pin plugs with a current regulator and pair of
 resistors mounted on a small vertical board.  It, I
 guess, is a more professional solution but I have not found
 a circuit for it yet or parts list.
 I really don't want to go chasing after 3TF7 tubes so
 polling the list here for what seems to work best for them."
 
Replacement schemes for the ballast tube are myriad and controversy-generating. For a wealth of information on the topic, go to r-390a.net Click on references, Pearls of Wisdom. There you will find a vast wealth of collective wisdom on the topic which was distilled from the R-390 List over the years.

Drew