Dave, if the mech runs at 33 and the relay pulls in it is unlikely that the plug is the problem.
-Did you replace the large 4mfd cap? Most people use another oil filled cap, I used 4, 1mfd mylar caps (200 vac or higher)similar to what I've used in the stepper plate circuits.
http://photobucket.com/gallery/user/...TIyMTU=/?ref=1
_Check the speed trimmer pot on the unit front. These are cheap wire-wound and they do develop dead spots. washing or spraying with contact cleaner will usually get them usable again.
-Since the unit did work, albeit poorly, is is possible you made a connection error.
-Check the relay contacts for pitting and make sure there is slight over-travel and "wiping" action.
Transistor can not be overlooked here, but that is rare in this circuit unless there was a short in the motor circuit while a 45 was mounted.
RobNYC