Master Flow belt driven whole house exhaust fan repair

The fan blades on my whole house exhaust fan stopped spinning properly. Figured out a set screw became loose on the pulley. A few turns of a 3/8" wrench and the problem was solved. The issue wasn't the motor or the belt. I hope this helps someone. Master Flow 30BWHFS and 36BWHFS models. I forgot to add that while you are up there, spray some belt dressing on the belt. It will keep the belt healthy. Mine is near 16 years old.