I have a Mitsui 618 CNC CNC surface Grinder. It had a Toshiba Tosvert VF-S3 installed for the Spindle motor. The drive failed with a bad cap that leaked on a voltage regulator circuit below it and corroded some components. It failed to go to run state so I replaced it with A toshiba VF-A3n. Very similar drive, a few years newer. The main difference is that the A3n is single phase input and the S3 was 3 phase input. Ive always had a slight noise issue which caused visible noise on the the transverse motion position sensor of the table. The sensor is a optical sensor that reads position to .4" accuracy by passing light through a perforated metal bar. The table position sensor circuit sends signals to the hydraulic valve that controls table movement. Its not a servo valve, just a straight on-off valve. After replacement with the A3n drive, the noise increased a bit to the point where the table motion is unstable. I put chokes on the input lines but to no avail. I also checked all the grounds. Any suggestions?