1941 GE J620 Ye old ballast tube

[Knifeswitch]

This unit is the first series string radio I have entered and though I get the concept, it is new territory for me. The filaments are fed AC right off the line through what was a BL42D ballast tube. Someone apparently long ago tried to repair this as the tube was gutted and some ancient power resistors were in place under the chassis. The socket just became a terminal. It was botched pretty badly. I deciphered the RMA code for the pinout and such. After reading an article on ballast tubes I realized it wasn't just as simple as figuring the correct resistor values. They're not given and in the correct circuit shown in the diagrams, I lose the math upstairs in the brain department. Plus if I understand this correctly, we want the resistance value to change as the set comes up to temperature. This is a six tube set with 1800mA of filament and (2) 250mA pilots. R18 is the ballast. Any kind shove in the right direction would be much appreciated. Came here as a AK guy. Very glad this is here!