Magnetic disc driving device for controlling the position of a magnetic head relative to the disc

摘要

A magnetic disc driving device is operated in such a manner that frequency signals recorded in an in-phase relation in servo regions of a magnetic disc of a sector servo system aligned in the radial direction of the disc are reproduced by a read pulse generating unit to produce read pulses. The read pulses are counted by a counter unit, a counting output of which is compared by a comparator to a predetermined value to detect, a dropout in servo patterns on the magnetic disc. Servo signals are produced by a controlling unit from the servo regions of sectors excluding defective sectors for which the counting outputs less than the predetermined value are produced, and a servo control operation is performed based on the resulting servo signals for achieving highly accurate control of the magnetic head position.