Yes, you can used a diode, cap, inductor, resistor or combination. I still prefer a ballast tube or power resistor. Not only is it original but certain replacement components will give a greater surge on turn on. If you use a cap and have a lamp in the radio, zener diodes will be needed to protect it from burning out when the radio is turned on.
An inductor may be the best. You won't have a turn on surge but it's larger. A small fluorescent light ballast has been suggested.
Using a diode alone won't drop enough voltage. You still need a resistor or other item in series.
A K49B drops 49 volts @ 300 ma.
Norm
: Some time ago, someone suggested a way to replace a K42B ballast resistor with someting other than a big fat wire wound resistor. I think it was a rectifier/diode and a cap. The benfit is that there isn't nearly as much heat to be disapated. Does anyone know what I'm talking about?