[time-nuts] Nuvistors and FETs...

paul swed paulswedb at gmail.com
Tue May 4 23:57:47 UTC 2010

Good comments from everyone.
FETs are interesting. But as luck would have it and strange as this is I had
the tube.
Working quite well now

On Sun, May 2, 2010 at 11:07 PM, Burt I. Weiner <biwa at att.net> wrote:

> For what it may be worth, I've swapped Nuvistors out with FETS.  I see from
> the schematic that the Nuvistors are running on 35 Volts.  It would be
> simple to drop the 35 Volts to 12 or 8 Volts with a 3 terminal regulator in
> the receiver.  If desperation sets in, try stuffing N-Channel FETs in place
> of the Nuvistors.  The gate is the grid, the drain is the plate, and the
> source is the cathouse.  Since the FETs are usually pretty low in
> capacitance you may need to shunt the tuned circuit/s with a small piston
> type capacitor.  In one low Voltage preamp circuit I used a National U-310.
>  In another one, a Nems Clark receiver, I replaced the two RF front end
> ceramic triodes stages that ran on 150 Volts with two U-310's and rewired
> the plate supply to run off of the 12 Volts already in the receiver.  This
> made for a low noise, very sensitive front end.  All I needed to do was add
> a small quartz piston capacitor to bring the tracking in at the high end and
> the bottom end fell right end.  If you can make that work, you'll never have
> to replace those pesky wittle Nuvistors again.
> Burt, K6OQK
>  From: paul swed <paulswedb at gmail.com>
>> Subject: Re: [time-nuts] 6CW4 Nuvistors on eBay...
>> Indeed there are.
>> And even 7587s thats the TRF frontend. In one of the units V3 appears bad
>> all Rs are good voltage high on plate, 0 cathode current. But oddly when I
>> swap v1 into position same effect so somethings odd. Or my methods not
>> correct.
>> The other units working. Had to replace a shorted 6.2 V zener.
>> The 100 kc vco /lock osc is awful touchy.
>> Pretty amazing the units pretty hot sensitivity wise -80 dbm.
>> Interesting afternoon. Way in the deep corner of the basement I think I
>> may
>> have a nuvistor or two. Time to see what they are.
>> On Sun, May 2, 2010 at 4:14 PM, Burt I. Weiner <biwa at att.net> wrote:
>> >
>> > For what it's worth, I just took a look and found a bunch of 6CW4's on
>> > eBay.  See:
> Burt I. Weiner Associates
> Broadcast Technical Services
> Glendale, California  U.S.A.
> biwa at att.net
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