Hey you stole my picture!!!
When you replaced the brushes, did you take the white (bakelite?) brush holder apart? If so, there is a washer in there that isolates the circuit on one of the studs and if it's not put back together right, it won't work.
Also, if you have corrosion on your rotor slip rings (or just gunk from age) a little xylene or mineral spirits and a scrubby pad will clean them up for a better connection.
Make sure all your ground wires and stuff are connected properly. Good luck.