Hi,
I am converting an old Alpha-70V to use a 3CX1200Z7 instead of
the teapot type 3CX1500V. The original filament transformer
provides 5 volts at 30 amps. The 1200Z7 wants 6.3 volts at 25
amps. I'm thinking of rewinding the secondary of a 50 va size
transformer to make a 1.3 volt, 25 amp secondary, and putting it in
series with the original Alpha filament transformer.
What I'm not certain about is feeding the bias to the new 5 + 1.3 volt
combination. I can bypass the transformer secondaries heavily, so
RF shouldn't be a problem. The cathode current will have to go in
an unbalanced manner through the transformer combination. Is this
going to be a problem, or is the 1 amp of DC cathode current going
to be trivial when compared to the 25 amps RMS already flowing?
Otherwise, I can bite the bullet and buy (gasp!) a 6.3 vac 25 amp
CT transformer... but I sure would like to use the existing 5v
winding. Of course, if it isn't used, then the (contiguous) plate xfmr
should be able to supply more current!
Any suggestions? Any 6.3 volt transformers?
73,
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