What would cause Ballast Resistor to keep blowing?

[mamatried01]

I got a factory 383 out of a 1968 Chrysler Newport installed in my 1969 Charger.
Ran fine when first installed till I got the alternator mounted and hooked up, now I am blowing ballast Resistors.
Why?

Thanks guys.

[Chryco Psycho]

the coil could be drawing too much power & overloading the ballast , try a new coil

[Plumcrazy]

I'd check the voltage at the batery with the engine running also.