[ARC5] BC-348 Solid State Replacements

[Jim Haynes]

Yeah, I have one of those R-392 receivers and converting it to FETs
is a project a long time on the back burner.

I remember FETRONS - believe the original application was in AT&T O and
N carrier systems which used an awful lot of 407A and 408A tubes.  Which
were equivalents to 6AK5 and 2C51 except for 20V and 40V heaters as
the equipment ran off the 48V central office battery.  Now I believe those
FETRONS were intended as direct replacements and did not require lowering
the B+.  I also recall that there were two different FETRONS for replacing
one of the tube types, depending on whether it was used as an oscillator
or as an amplifier.

Seems like someone also was making FET plug-in replacements for Collins
S/Line gear at one time.