[Arran]

Mike;
  There is no way of knowing without having more #43 tubes to sample but it may just be an idiosyncrasy of the Hickok 600 tube tester to set off the short light in that position. I have an old Precision tester that was giving me similar readings on some loctal tubes I was testing, I can't remember the type, but three of them read as shorted on the same pins.
   In any even the #43 tube is unrelated to the set not playing, usually a heater to cathode short in a power output tube will create a load 60 cycle hum in the audio but will not stop the radio from working. If it is a G.E, even a U.S model, I probably have the service info for it if you can find out what model it is, if it's a cheap TRF AC/DC set then it probably isn't a G.E.
Regards
Arran