05-17-2013, 01:11 AM
As a rule the tube filament is well inside the envelope of the 5Y3 above the tube socket, so all of the heat rises. In fact the filament pins do not even get warm. If you want to see a hot running tube check out a 50Y6 rectifier or a 6BG6 horizontal output tube, I'm not counting ballasts as those are not really tubes but resistors.
Regards
Arran
Regards
Arran