re:>>Its likely that the key weights are coming loose. It will probably need
to be serviced.<<

Mike,
Thanks for your reply. The situation is I'm using it in my teaching studio and don't want it out of commission. If it's only tightening
the weights, that doesn't seem a complicated matter. The unit's out of warranty. I'd have to pay for the repair. If I can't fix it I'll live with it.
Anyone out there done this repair. I think this was a Fatar action.
Bill