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I should have mentioned the freqs in question are under 30 Mhz... even a
junkbox fet should do it! Regards, John "John Smith" wrote in message ... 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 |
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