[StephenB]

Hi Bob - attached is a picture of the parts inside my 37-650B... appears to be the same.  My problem was that one of small ball bearings was detached from the shaft.  I soldered it back and it works great now.  Based on your pic, it appears you are missing two ball bearings - a large and a small.  I believe there should be two small ball bearings - one on each end of the spring and there should also be three equally sized large ball bearings that hold the fine tuning shaft snugly in place.  Could it be that they went for a ride when the shaft was disassembled?  Or, you could be just missing the large ball bearing and there's still a small one stuck in the shaft.  In any event, the attached picture shows all the parts (and order) needed to make it work.