"John Smith" ) writes:
Anyone ever replaced a 6CW4 Nuvistor with a fet or other transistor?
Got a schematic? Idea of one?

Regards,
John



I can't provide any references, but converters and preamps were some
of the first things that were transistorized. They were simple with
a single stage or at most a few, so once FETs came along they were
put to use. ON one level it was likely just to try it, but of
course the lower noise figure probably was a lure.

Given that that there might have only been one tube in the thing,
probably many were treated just as a foundation without much concern
for a direct plug in. I can picture an article in "73" from 1967
where someone talked about putting an FET in a nuvistor preamp, and
it wasn't much more than shorting out the cathode resistor (or something
like that) and a returning. The basic scheme would be the same
whether it was a triode or an FET, so it certainly is a relatively
easy thing. The same article had the author putting FETs into
other things, like a Command set transmitter, or rather the VFO
section, and that too was pretty simple.

Decades ago, I got ahold of some Collins PTOs that covered the
broadcast band, and I didn't have to do much to put an FET in
them beyond soldering in the FET and running the thing off a
12V or so supply.

It tended to get more complicated with multiple stage units, or
perhaps just that it ceased to be easy to put it back together
if it didn't work right. There'd be articles about conversions
that sometimes were about replacing function, some about modifying
the circuitry so the FET or whatever would fit in, and of course
the simplest (for the equipment, but not so much for the replacement),
a universal plug in.

Michael VE2BVW