Abstract: An x-ray diagnostics generator which includes a rotating anode x-ray tube includes circuitry for setting the speed of rotation of the anode dependent on exposure parameters. At particular rotational speeds, the motor bearing for the rotating anode is subject to mechanical resonances, causing vibrations which can damage the bearing. A vibration detector is provided in mechanical contact with the x-ray tube, and when vibrations due to such mechanical resonances are sensed, a signal is provided from the detector to a processor which automatically slightly alters the rotational speed.