[Arran]

Jayce;
  Like many things with Philco there were two things that were factored in when it came to what tubes were chosen: #1 Is cost #2 Availability. Philco was such a large manufacturer that they needed to take both into account, if they could get a deal on a rail car of one type of tube, they used them. There was one Philco tombstone, I think it was a 37/38-670 that used five 6J5G single triodes, whereas the previous 116B used one triode double diode, if you look at their roles it was obvious that they had lots of these on hand, and designed a set around using them. This was especially so in the immediate post war years (1946-48) when there were some parts shortages, Philco was continuously juggling around tube types in some models, like the 46-1201s. The only non portable I have encountered with a 117Z3 in it was a Canadian Stromberg Carlson radio-phono combo from 1950, it had six or seven tubes, other then the rectifier the rest were in series. In most series string sets, and portables after 1948, they opted for a selenium rectifier, it could deliver more current then a 'Z3 without the extra heat.
Regards
Arran