Typically, when an ignition control module of this type fails it would be one of the three drivers (transistors) within it that controls a specific ignition coil giving up.

The reason: The placement of the thick film ignition (TFI) module placed too close to the engine block, causing the heat-sensitive module to suddenly fail when it gets above 257 degrees.

Rod and Custom Magazine details the PerTronix Ignitor electronic ignition and how it gives modern power and safety while maintaining that vintage look to your custom.