Unsticking a Seagate ST-419 head

Al Kossow aek at bitsavers.org
Thu Oct 20 09:07:14 CDT 2016

On 10/20/16 2:05 AM, jim stephens wrote:
> I actually years ago unstuck drives by removing them, hooking them to cables long enough to allow me to have access to
> them external to the system with power, and just holding them in the air and giving them a sharp twist around the axis
> of the drive.  That was enough to unstick most.

I will probably just set this one aside for the day I have access to a spin stand
and a pair of heads moved with D/As.

The simple tricks work if the spindle bearing is gummy, or the head is slightly stuck.
This one is bad enough you can see the flexure twist.
It is going to have to be disassembled.

It is out of a pair of Gould 68000 development systems that I got from Erik Klein. Very
unusual boxes built out of Valid Logic 68K multibus boards, with their own SASI and serial
interface cards and 3com ethernet, running Valid's 4.1BSD. So far, I've been able to recover
most of the root file system disk. The usr disk is the one with the stuck head. I have one
more pair of drives from the other unit, I'm hoping either they come up, or there are enough
sectors that aren't bad that I can piece together the file system. I can see the header files,
so at least I have some information on how you talk to their boards.

David Gesswein has been a huge help through this whole effort. The Adaptec 4000 was set up for
18 sectors/trk, and he modified mfm_read to get that working with these drives.

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