Abstract: A method of and apparatus for burnishing a surface of a magnetic disc of a disc drive are disclosed. The disc drive has a data head and an actuator supporting the head as the head flies above the surface of the disc. A controller causes the disc to be rotated at rates of rotation which will result in burnishing head fly heights which are less than a normal operational fly height of the head. An actuator controller controls the actuator to repeatedly move the head across a region of the disc during a burnishing time period. The head flies above the surface of the disc at the burnishing fly heights during the burnishing time period to thereby reduce asperities on the disc.

Abstract: A method and apparatus for testing for mechanical defects in a disc drive during manufacturing test is disclosed. Resonances in the disc drive are excited by injecting a sinusoidal test signal of known magnitude and frequency into an incoming servo position error (SPE) signal in the servo loop to provide a modified SPE. While the test signal is injected, the modified SPE is sampled and filtered to characterize the test frequency in the modified SPE which is compared to a resultant frequency characterized in the incoming SPE. The presence of resonances in the disc drive structure will result in an increase in the gain of the loop as indicated by the characterized resonant frequencies from the incoming and modified SPE. When the gain exceeds predetermined criteria, an error flag is set indicative of a failure condition for the disc drive, enabling the disc drive to be removed from test for subsequent remedial actions.