Hello! See what is causing the shaking. Remove the main vacuum
connection to the pump and run the pump without any load. If the
shaking goes away then you should investigate the pump bellows and
feeders for tightness. Do this by blocking the main vacuum outlet
and turning the pump by hand. It must have a reasonably constant
resistance for each of the bellows opening inside. If there is
a section that turns more easily, then you have found the problem and
you will need to overhaul the pump.
If it still shakes without any load on the pump, take off the drive
belt and then see if that stops it. If yes, it could be a problem with
the belt itself or some sort of imbalance on the pump and/or pulley.
Also, test the legs, etc., by shaking the piano by hand (be careful!)
and see if and where it is loose.
Let us know...