Just purchased a home-build regenerative set, which had three type 12 tubes in it. Amazingly all the filaments are good.
One is a brass based cunningham 12 tipped tube with the lime getter on the press. The other two are CX-12s also cunningham,
with the interesting feature that those two have *both* a flashed getter and a lime getter on the press. Never saw that before.

Thier all basically differant versions of the WD-12: https://www.radiomuseum.org/tubes/tube_wd12.html


Most likely a product of a transitionary period for Cunningham in which they were phasing out the older lime getter in favor for the more modern flash getter.

Have you verified the heater voltage on each? 1.1V?

Russ

Yep, the two bakelite base tubes are in the radio, in use to good effect. I can't quite bring myself to fire up the brass base one yet. So
for now it's only one stage of audio. All being run off a single D cell for the filament supply. (how many Ah was a number six dry cell back
in the day?)

I would not run the BBT one either. It is probably more valuable than most radios that it would be used in.

It's an agonizing decision. In fact the tube was a dud when I got the set, until I re-flowed the pins. It was in the detector
socket of that regen set linked to in the general site. I might want to give a try, "just this once..."

=)

(how many Ah was a number six dry cell back
in the day?)25 amps... When I was a boy these were $1.25 each. But my weekly allowance was .70 cents...

I have to admit giving you "off the shelf" advice. I would try it too. Then wrap it up nicely. Just be vey careful. I don't think there is a "dim-bulb" that would work for this tube. Maybe just power the filament off of a rechargeable (lower voltage) dry cell, AA battery. Make sure that it lights prior to B+ being applied.

Russ