[morzh]

Art

Just calculate it.

The way to do it is this:

1. take the current of any filament that is used. All of them should be the same, so if one is say 300mA, all of them are.
2. Add the voltages of all filaments together. Like 4x6.3V+25V=50.2V.
3. Subtract this number from your Mains voltage (say 120V):
120V - 50.2V=69.8V. (use 70V)
4. Divide this number by the current:
70V/0.3A = 233 Ohm.

THIS IS YOUR RESISTANCE.

5. Using UI calculate the dissipated power:70*0.3=21W
Double that to find your power rating.

So, you need 50W 233 Ohm resistor (use the closest value you can get).

6. If the radio is not intended to work with DC, calculate a capacitor instead to not dissipate any power.