>From what I understand the 3CPX1500 5.5v filament is a PULSE SPEC. It is
the same filament as in an 8877. The guy emailing REID, as that one too...
It is ok with a directly heated cathode to turn down the filament until a
noticed drop in emission, then turn it up a click...
Not with an indirect full voltage
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Gudguyham@aol.com
Sent: Sunday, January 28, 2007 11:26 AM
To: amps@contesting.com
Subject: [Amps] 3CX1500A7 VS 3CPX1500A7
Since I had some time here Sunday morning I did some looking into the
matter
of "filament voltage" concerning these 2 tubes. This was an issue that
someone had brought up. Here is what I found, a major University built a
plasma
pulsing generator using 6 parallel 3CPX1500A7 tubes. The filament voltage
is
rated at 5.5 volts on this tube. A regular 3CX1500A7 tube is rated at 5
volts. The University project used 5 voltsof filament voltage for "longer
tube
life". This leads me to believe that if a 3CPX1500A7 is used in place of a
3CX1500A7 with filament voltage at 5 volts, that the filament may in fact
have
an expected extended life when run at 5 volts vs. 5.5 volts. Could there
then be an advantage of running the 3CPX1500A7 tube in this regard? The
University apparently thinks so. We might be splitting hairs, I do not
know, but
if a 3CX1500A7 is run at 4.5 volts Half a volt less than rated, is there
any
reduction in emission? Personally comparing the 2 tubes myself in the same
amplifier I see no reduction in power output running the 3CPX1500A7 at a
1/2
volt less filament voltage. The University report was interesting reading
and
I could give you a link to it if you want. My concern was their thoughts
on
the filament voltage aspect. Lou
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