Thanks, Don. I have one 838. Was going to look it up and see what it was
for. That circuit just looks like a winner. Of course, with my newly
acquired supply of 4-125's, I will go that route. Still looking for mod
transformer.Again, thanks to all who responded!!
Joe W4AAB
Donald Chester writes:
You might be able to use a pair of 838's or 805's in place of the 203A's.
The 838's have the same pin connections, while the 805's bring the plate
lead out of a plate cap on top of the tube; otherwise they are essentially
the same tube, with the same filament current as the 203A. The 838 and
805 run zero bias up to about 1000 volts on the plate. Above that, they
require a few volts of bias to keep the resting plate current at a
reasonable value.
Also, a 211 is a near-identical tube, but it is lower mu, and would
require larger grid voltage swing and more bias, so your present audio
driver might not work satisfactorily with this tube.
I have seen 203A's advertised from time to time, not any more overpriced
than other triode transmitting tubes in this era of audiophools with an
excessive supply of oxygen-free money but lacking in fully oxygenated
brains.
Don K4KYV
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