Thanks, that was a great idea about looking at the pulley. It looks fine, but I noticed that the motor itself moves around easily. It is anchored to the base at one point (let's call it north) with a spring. At the opposite side, south, it moves from side to side at least a half inch or more. That, of course, changes the tension on the pulley. It doesn't look like anything is missing, but what do I know? How can I get the motor anchored down so it doesn't move?