Haven't had a response from Chakster about the noise, but here are some more details about how I eliminated the faint rubbing sound I had that was due to the rotor rubbing on either the inner surface of the top cover (rotor too high) or on the stator itself (rotor too low). I first created a hole in the bottom of the chassis can, directly under the bearing housing in the dead center of the chassis can, using a hole punch designed for cutting thin metal. Then, while the motor was operating, I reached under the chassis with a thin blade slot-head screw driver and engaged that slotted, threaded cap situated at the bottom of the bearing well. Adjusting the position of that cap in it threaded mount moves the entire spindle assembly and everything attached to it, which includes the rotor, up or down. I gently and very slowly turned the screw driver, trying both directions because I did not know which way it needed to go, until I eliminated the periodic rubbing sound. Voila'.
