Yes, that is exactly what is occuring here, a "new" circuit is being
designed... and, a turns ratio change may have to be contemplated in the
drain circuit (existing rf transformer)--not the gate circuit, that existing
circuit, decoupled through an isolating cap should be just fine (the fet is
a high input impedance device)--this is the front end of a receiver, the
actual signal levels here are low...

But, I am interested, what roadblocks do you see to "I don't think you have
any hope of making a plug-in compatible 6CW4 replacement..." ?????

Warmest regards,
John


"Tim Wescott" wrote in message
...
John Smith wrote:

I have been toying with pen and paper...
It looks like like the grid circuit to the 6CW4 could have an isolation
capacitor inserted to remove and DC bias from the gate of the replacement
fet. And, the plate of the 6CW4 circuit could have the B+ side of the rf
xfrmr moved to a low volage supply (perhaps rectify and filter a 12v AC
heater supply to supply the new voltage.)
And, a proper bias supply constructed to supply a necessary bias to the
gate...
And, ideas?

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?

I've seen works on "transistorizing" tube radios, but the characteristics
of tubes and transistors are sufficiently different that in general you
have to approach this on a case by case basis. So while I don't think you
have any hope of making a plug-in compatible 6CW4 replacement, I _do_
think that you could often use most of a circuit designed for a 6CW4 with
some other device.

Having said all that, I would probably either buy another 6CW4, or design
& build a new circuit inspired by the old.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com