8393 Nuvistor to 2N4416A FET conversion

Mark Vincent

I wanted to see if the nuvistors could be replaced with FETs in a 454 to be like the A version. It worked. The FET was chosen to be the same number in the A version. I added two 27V zeners from the 75V supply and a 24V and 27V zener from the 65V supply in channel 1. The other channel was original. Testing between the two proved either worked fine. The B+ to the drains was about 15V. The zeners were ones I have in stock. A 30V zener could be used with a 27V to further lower the B+. I did not see any problem with the B+ for the FETs being 15V instead if the 12V used in the 454A. The load resistors were left in, only opened to add the zeners. If I decide to make this permanent, 1,3W 2% tolerance zeners will be used. The wattage is needed. The FET pins fit the sockets easily. I found it interesting and happy to see the experiment work. If any owners of a 454 want to do this conversion, go ahead. The A version of the FET is 35V while the non-A is 30V.



It would be interesting to know what the bandwidth is with the FET's. The 2N4416 is listed as a "UHF" device.

Bob Haas