The normal filament current is about 14 amperes at 5 volts. The grid/filament
short generally draws less than 100 ma of grid current and less than 300 ma of
plate currnet. An abnormal current of less than 0.5 ampere is not a problem
for the major floating secondary winding of a filament transformer.

In the TL-922, the filament transformer would burn after a short while because
on that same transformer there is another secondary (80 Volts) which gets nearly
shorted to ground when a filament-to-grid short occurs in a tube.

73

Tony I0JX