"Roger and Ute Brown" ) writes:

Check the tube base wiring against the 6L6 and
see if everything
goes to the correct pins for such a tube. It's possible you should have a
tube which sports a rectifier (diode section) and another tube in the same
envelope). At any rate - a part by part inspection resulting in a schematic
will tell all!

I thought of that myself. While this transmitter is so simple it has
to be pretty generic, so there doesn't have to be an article about it, I
have seen "single tube" transmitters described in old magazines that
used something intended for AC/DC use, ie a power stage with a built in
rectifier that used a high filament voltage. I'm thinking 50L6, but I'm
not sure if that is right. I don't remember if there was something in an
octal package that ran off 117volts directly.

I don't think the original poster mentioned if there was a transformer, and
somehow I suspect the lack of one would be a greater indicator of this route.

Of course, selenium recitifiers may have had a brief enough life that
someone might not recognize one by sight.

Michael VE2BVW