Sound Discriminator Question

[Cory]

Hey Guys,

I'm working on an RCA 8T241 and have most of the problems ironed out but have an interesting question. It uses a 6AL5 as the sound discr, with a 5.1 ohm resistor in series with the filament. If I jump the resistor I get good sound and the plate voltages are where they should be, if not, all that passes to the output is a very quiet hum.

The resistor checks spot on, and I've swapped a couple 6AL5s thinking heater characteristics may vary. Still, what I find is that the majority of the heater voltage is dropped across that resistor and the tube doesn't warm up enough to conduct.

The easy thing to do would be eliminate that resistor but I'm pretty sure it's there for a reason Any suggestions?

Cory