And does anybody know the cold resistance or the filament?
I haven't seen any inrush current limiting circuits for the 4-1k.

73

n8zu

I just put my home made amper on the filament. Actually a 2.80 amp
amper.
I couldn't find my 7805 I use for a constant current source. So I had
the 5 ohm resistor in series with my 14 volt regulated supply. My 5
ohm resistor is 40 ft of cat3 3 pair telephone wire for a total of 240
ft of 24 AWG wire. I put that in series with the 4-1k filament and
across 14.0 volt regulated supply it draws 2.80 amps.
The voltage drop on the filament was 0.100 volts and a filament
resistance at 0.100 volts is 0.0357 ohms. Funny because at 7.5VAC
it's exactly 10 times that resistance.
I can't afford peter dahl transformers. I has to use MOT's for the
filament screen and plate supplies. I have to use 2 MOT's to get the
power I need. This works out to my advantage because with 2 filaments
in series it gives me 7.5VAC CT, but at a current that is only limited
by the 14AWG wire they use for the winding. Two MOT's 14AWG wire would
limit the inrush current to about 150 amps of instantaneous current at
the peak voltage.


73

n8zu