[Boatanchors] 4-1000A Tube question

[mac]

Sounds to me like your tube is getting old and tired but it apparently  
has some good life left in it.  Are you sure about the resting current  
reading though?  The normal range of a plate current meter used with a  
rig like this would be something like 1 amp so you would be reading  
your resting current way down on the low end of the scale where the  
accuracy can be problematical.  The usual accuracy spec for meters is  
for a max full scale reading only.

Dennis D.  W7QHO
Glendale, CA

*****************
On Feb 26, 2012, at 2:57 PM, Paul Baldock wrote:

> I'm getting close to the completion of a 4-1000A grounded grid  
> amplifier.
>
> The plate voltage is 4KV. I'm running  zero bias voltage. The no
> signal standing plate current is 60mA.
>
> One unusual thing I am doing is instead of a center tapped filament
> transformer  I have two 10 Ohm resistors in series across the
> transformer "simulating" a center tap. This means there is 5 Ohms in
> series with the DC to the cathode. So at 60mA this will in fact add
> -.3V to the zero bias.
>
>  The Eimac Newsletter FCJ-59D2 says at 4KV in grounded grid the
> standing current is typically 120mA. Is my 60mA an indication of a
> low emission tube ?
>
> I do get a little over 10dB gain with 100W in and about 1200W out (75
> meters). The tube is of course an old, quite brown, commercial pull.
>
> Thanks
>
> - Paul
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html