1L6 filament voltage tolerances ( 1L6 test good fails to oscillate.)
 

Here is what I did:

Found the statement in the GE tube manual that says the 1.4 Battery Tube
Types tubes are designed to operate up to 1.5 terminal rated battery,
filament should not exceed 1.6v, ....each 1.4 volt filament section of
filament will maintained with in a range of 1.25 to 1.4 volts with nominal
center of 1/3 volts. in order to meet the recommended conditions for
operating filaments in series from dry batteries, storage batteries or
power-line......

So I adjusted (1k 10 watt || 20k 1/2 watt) the two new filament dropping
resistors (no 50A1) to the 950 ohm spec, got 1.52 volts across the filament
and the tube oscillates on all bands.

Look on Binaries for scan.

Paul P.