[Arran]

Mike;
From what I have read elsewhere those short metal tubes where called "stahl" or steel tubes, and were developed, and originally produced by Telefunken in 1938. The first time I saw some was in a war time set another collector had, they looked like oversized 6H6 tubes, and from what I can tell they carried on making them in Germany, and Poland well into the 1950s (or later), maybe some other Warsaw pact countries as well. Do they all have eight pin bases in that set? A really strange pinout, five on one side and three on the other, I would guess that the three pin side is for the tube heater plus the cathode, but since the base has a key why bother?
Regarding the line voltage, I was contemplating buying a Bush radio, and whilst the tube heaters only added up to 120 volts the B+ was as high as 180 vdc. In that case I had the idea of using a voltage doubler to raise the B+ but I never got the radio to find out if it would work
Regards
Arran