Fixing a Micropolis 1375 drive?

The problem indeed is often caused by a gummy part going to goo after some years... The head assembly can move around a fixed axis near a front edge of the disk. The extremes of this movement have a couple of bumpers of this short-lasting gummy, that after 10 years goes to a viscous black material, loosing its tickness: that is, the extremes of the movement are now some degree more than the original device. Note that the bumpers are attached to metal holders that can be moved sligtly and that are fixed to the holding structure with two bolts each. (i can provide pictures of it all). The heads when the disk is stopped down "fly" to the park position, that is on one of the extreme (the most inner position over the disks). As the disk is powered up, the electronics put the heads to the inner end of the parking area, so the mechanical lock, that holds the heads even when the disk is powered down, can be easily disengaged. On the faulty drives, because of the loss of thickness of the bumpers, this operation let the head to fall outside the park area (too much toward the inner part of the disk) causing the electronics to detect a problems, and so forcing a new park operation, and all restarts.... I fixed this problem on a couple of disks. I needed to open the disks in a very clean room (few dust around), powering the disk at open-hearth, loosing a little the two bolts of the park area extreme, and moving the bumper holder slowly with the disk in movement, so letting it retry the spin-up sequence, until it seems to regain normal operation. Then I give a little bit more of thickness (we are talking about 0.1mm more or so) and refixed the two bolts. Then I tried to power-down and power-up to be sure that all works well. This saved a couple of disks completely. If you need it, I can supply good pictures of the inside of the disk, with some more advice. Andrea