[R-390] BFO multi-turn knob+ Bourns near equivalent

[Bill Hawkins]

mikea said,

"Sounds good. I think I could do that in between 30 and
100 tubes. To do it all Glowbug-style, wecould use some
of those fancy Burroughs decade-counter tubes."

I still have some IBM 704 plug-in tube units, about 8"
high by 10 wide by 1.5 deep, with eight 9 pin sockets
and many terminal points. No sockets for the PIU, though.
Some even have IBM brand tubes, almost all twin triodes.

Don't have room for them in the 390, but it would be
equipment from the same period.

Bill Hawkins