Re: Disk Drive alignement Tools

["Michael J. Mahon" <mjmahon@aol.com>]

KPR wrote:
> Anyone got any docs on how-to do an alignement job on apple II dirves..
> both the old style 5 1/4 and the duodisk units??

AFAIK, the only "alignment" adjustment on the drives is the head
stepper alignment to the center of the tracks.

This is adjusted by loosening the stepper motor mounting screws
and carefully rotating the stepper in its curved mounting slots.

I don't have a program to do this, but I have used the Copy II
Plus Hi-res disk scan in half-track mode to observe a known good
disk, and adjust the stepper to the center of the range for which
the track data is properly read on whole-track boundaries.

Of course, track 0 needs to be properly located as well, since
there are adjustments where tracks are centered on whole tracks
but all tracks are off by -1, +1, +2 tracks.

This alignment is *supposed* to be done using a specially recorded
alignment disk, by probing the head read signal on the analog board,
but I've never found a factory alignment disk.

You could, I suppose, use a *real* disk diagnostic disk with an
alignment diagnostic (copies won't work), and similarly locate
the range of adjustments over which things work, then set the
stepper to the center of that range.

In fact, you could also do this simply by reading tracks of a known
good disk.

In all cases, you are actually aligning your drive to the "good disk",
so the resulting drive alignment is only as good as the alignment of
the drive on which the disk was written.

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."