bad coil?
OK if you "don't have power" on the negative side it means THE DISTRIBUTOR is grounding out the negative side WHICH THE POINTS are supposed to do when they are CLOSED
So either
the points are not opening closing
the primary wire is shorted where it goes through the dist. housing
the condenser is shorted
or your wire terminal at the points is shorting out
All the distributor is (not counting the condenser) is an on/ off switch which grounds and opens the coil negative.
You should be able to put your light on the coil negative and see it flash on/ off when you do one of two things:
Either open the points manually with a tool
or crank the engine over.