No spark

No spark coming from coil, replaced coil and rewired to factory wiring. Coil positive to ballast resistor along with ignition and distributor positive, other side of ballast resistor is 12 volt supply. Ballast resistor test good, ground on coil going to ground on distributor. Turn key to on 8.4 volts at coil, turn motor over 12 volts at coil, but still no spark. I have run out of ideas. I have not hooked a timing light up yet, but I hooked a power probe up to the - side of coil looks like signal is being sent properly. I am lost any help would be great.