[Amps] 3CX1500A7 VS 3CPX1500A7

[Gudguyham at aol.com]

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