[Arran]

Five pins, so it is, I don't think I have anything that uses a type 84, I do have lots of sets that use a 6X5, mostly 5 and 6 tube jobs. In any event the only real difference is in the heater current and the base, the 6X5 has a 600 ma heater. Another similar tube to an 84 is a 7Y4 loctal, I'm not sure if these were ever used in a 42-380 but they were used in some Philco sets. One thing is puzzling however, in one book I found that the maximum output current of either the 6X5 or the 84 was 75 ma, in another 70 ma, in yet another reference they say the the max on an 84 is 60 ma.
Regards
Arran