The early Pertronix I system have no safe guard to protect the HallCell from burning up if the ignition is in the run mode and the engine is not running, that's when they usually crap out, if you have to diagnose the engine for over 20-30 seconds without it running, but the key/ignition is in the run mode, disconnect the red Pertronix HallCell lead from the positive (+) side of the coil to prevent HallCell damage.... I assume your running the Pertronix I because you converted a Prestolite HEMI dual point?
MikeG