It should be remembered that FETs are a voltage controlled
current device. A tube is a voltage controlled voltage device.
A bipolar transistor is a current controlled current device.

A FET is therefore somewhere in between a tube and a transistor.
I did have some luck with a FRG7000. the IF (which does all
the work in a radio) was connected in the old triode configuration.
Signal to the 1Meg gate and the drain working into a parallel
IF can. I had a good look and the designers had used regular
transistor IF cans but ignored the tapping on the output side.

By cutting the tracks and making little jumpers i was able to
boost the rx signal by using the tap on the coil to the drain. I had to
put caps in to connect to the next stage - the IF cans were now working
as voltage transformers and improvement in reception was dramatic.
What was a 'deaf' reciever was now pretty useful.

Anyone wanting to use FETs for tube replacements should remember
they aren't voltage amplifiers - only current amplifiers.

Hope i have made myself clear? :-)

Murray vk4aok

John Smith wrote:
well, it works, there was a 1k resistor bypassed by a .01 cap on the cathode
of the 6cw4, I just hooked the source of the fet to it, adding a 500 ohm
resistor to the drain which passes though the primary of a rf xfmr feeding
the next stage, it is fed with ~16V B+. Works great, since the 6cw4 was bad
there is no way to compare how this affected preformance, but receive seems
hot... noise level good...
Even if a dozen 6cw4's dropped from the sky, I'd just look at 'em....

Regards,
John

"John Smith" wrote in message
...

Anyone ever replaced a 6CW4 Nuvistor with a fet or other transistor?
Got a schematic? Idea of one?

Regards,
John