Date: Mon, 3 Dec 2018 09:41:49 -0500
From: Bob Maser <bob.maser@gmail.com>
To: amps@contesting.com
Subject: [Amps] 3CX1500D3 Triodes
<I acquired a couple of 3CX1500D3 tubes and wonder if I can just plug them
<in. They are medium mu tubes. The tube I have been
<running in my homebrew amp uses 3CX1200D7 which are Hi mu triodes. The
<filament specs are the same and the plate HV specs are
<similiar. My power supply has an output of 4200V which is within the specs
<for both tubes. Physically, the two tubes are identical and
<the price was right.
<Bob W6TR
## Nope, wont work. The MU is too low, being only a mu of 24. With zero
bias, the tube will
idle at 1.8 A at 4.8 kv ! Would require 100 vdc of bias to get the
idle current down to 100 ma.
You would then require one heluva lot more drive to overcome the 100 vdc of
bias.
This is why low mu triodes are not used in GG.
http://www.g8wrb.org/data/Eimac/3CX1500D3.pdf Look at the constant current
chart at the bottom.
Then u can see where the zero bias line intersects with plate current. Then
look again, this time with bias
then u will see how much bias required to get the idle down to a reasonable
level. The tube was designed
for grid driven, Class C, industrial heating.
Jim VE7RF
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