Pertec Computer Corporation

Abraham Brand

Ashok K Desai

Eric M Dunstan

Raymond J Marinello

Evan L Barmache

Circuit means for use in a moving head type magnetic disk drive for unloading the heads under emergency conditions, such as power loss, to avoid loss of data and head or disk damage. The circuit means include a dynamic brake circuit which responds to an emergency condition to electrically short a positioner coil to thereby reduce the head support structure radial velocity to substantially zero. After a short delay, a velocity control circuit is activated, first in a low current mode to move the support structure at a controlled velocity toward the disk outer edge and then in a high current mode to enable the support structure to climb an unload ramp to move the heads axially away from the disk surface. The dynamic brake and velocity control circuits are powered by a capacitor which is charged during normal operation.

Emergency head unload system for magnetic disk drive

A transient temperature compensation system for use in a magnetic disk drive comprised of both fixed and removable disks. The system includes first and second thermistors respectively mounted immediately adjacent the fixed and removable disks. The second thermistor is preferably mounted for movement between an operative position and an inoperative position. In the operative position, the thermistor is positioned in very close proximity to the disk. In the inoperative position, the thermistor is spaced from the disk to permit sufficient clearance to enable the disk to be removed from the drive. The outputs of the two thermistors are used to develop a signal representing the temperature differential between the two discs which signal is supplied to the disk drive head positioning system. This signal is used to modify the positioning of the heads relative to the fixed disk to compensate for differences in the radial positions of corresponding tracks on the fixed and removable disks.

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Encino, CA, United States of America

Abraham Brand