No spark in a 1972 250C

I changed the dist cap, rotor, points and condenser on my 1972 6 cyl 250C. Now I have no voltage to the ballast resister or the input to the coil. The engine turns over fine and everything else on the car works. The ign switch seems ok. I traced the wires from the ballast resistor to a large electronic module (?) located below and to the front of the battery box. What is this unit? Could this be my problem? How do I trouble shoot this unit? Thanks!!!!! Dave.