Originally Posted by Mike D

Do you have power to both sides of the ballast resistor with key in "run" position?

Vintage Mercedes have a separate wiring set-up for when the key is in the "cranking" position. It bypasses the ballast resistor (which isn't needed and should be removed/ jumped using the Crane or Pertronix) and sends full (battery) voltage to the coil. This is done through a connection on the starter solenoid.

Normal or "run" voltage to the coil is reduced by the ballast resistor to lengthen the life of the original contact points. Since you are no longer using contact points there is no need for the resistor.

Do a continuity test on the distributor rotor and the center lead on the distributor cap. I don't see why they would have failed "out of the blue" but I've seen stranger things happen.