[Arran]

Russ;
  That was the other part of the article, was how to make a WD-11 base, it has four pins, but I seem to recall that it had three pins that were the same size, and the spacing was different as well. The WD-11 sub is pretty much a given if you want to actually operate an old radio, they are fragile, and were poor design, even from new, such that they discontinued manufacturing radios with them within a few years of their introduction. I don't know when they discontinued making replacement WD-11s and 12s but it was probably within five years of them coming out, such that even RCA started offering adapters so that people could substitute them with 199s instead. There are way more sets that use WD-11s and 12s then there are replacement tubes, so it's a good thing that Westinghouse chose 1.1 Volts as a filament voltage for those sets as 1.4 volts was the standard for the very much more common octal/loctal based tubes from the 1940s, though the current draw is lower 100 ma verses 250 ma. I can't recall whether they mentioned anything about adding a resistor in parallel with the filament to bring up the current draw, although it shouldn't be needed if the rheostat has enough range.
Regards
Arran