[Boatanchors] 4-1000A Tube question

[Geoff]

Be sure the filament voltage is in spec no load and full load.
The OT method of getting a little more out of a tired tube was to run the 
filament at 8V or more. While that worked it just hastened its use as a lamp 
display.
A gain of 10dB minus driving power is about average for the 4X1 at that 
voltage, it increases with more HV plus 100W is a bit on the light side even 
with an input network.

Carl
KM1H


----- Original Message ----- 
From: "mac" <w7qho at aol.com>
To: "Paul Baldock" <paul at paulbaldock.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Sunday, February 26, 2012 6:31 PM
Subject: Re: [Boatanchors] 4-1000A Tube question


> 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
>>
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