piclist 2000\06\06\222740a >
Thread: Filter Capacitors
face BY : Dan Michaels email (remove spam text)

Harold wrote:
>        I seem to recall reading of the development of the first disk drives at
>IBM inSan Jose. Rather than look at control system theory and stable
>feedback loops, someone figured that a vibrating head positioner could be
>fixed by putting a capacitor across the actuator. After the "fix", it
>shoved the head through the side of the drive.

Without seeing the ckt, this sounds like they re-discovered the
integrator. You;d think even back in 1953 or whatever, IBM would know
you need a "zero-switch" to discharge the cap on an integrator.
Easily done here. Mount the switch on the head. When the head bangs
into the side of the drive, the switch engages and resets the
integrator, which re-centers the head. Wal-la. Shoot I learned about
integrators as a sophomore. <:-)).

- Dan Michaels


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