User`s guide

pinch, a diskette formatted by any drive that has no problem reading most other
diskettes should be okay.)
Basically, a track-centering test tries to step your head between two
tracks of the 'standard' diskette and read the tracks on either side. If the
number of successful reads from each track is about equal, the head is
"centered" and your drive is well-aligned with the standard diskette.
The test may indicate serious misalignment. ("Aha! That explains why my
IIgs and II+ have problems reading each other's diskettes!") Centering
adjustment is done by slightly repositioning the stepper motor (mounted on the
underside of the drive). This requires loosening the two bolts holding the
stepper-motor, rotating it clockwise or counter-clockwise, and retightening.
The adjustment/test process may require several repetitions. Each time, the
program will report "differential fractions". The smaller these numbers, the
closer you are to near perfect alignment with tracks on the diskette.
______________________________
From: Rubywand
Suppose you have just one drive and it is so far out of adjustment that it
will not boot a speed adjustment utility diskette? In this case, you can remove
the drive cover, turn over the drive, and (probably) find that the drive has a
strobe pattern on the main pulley or flywheel.
Set a fluorescent light near the drive (or do the adjustment in a room with
fluorescent lighting). Get the drive spinning via power-on booting or a PR#6
and adjust the speed for a stable pattern.
Note: If you live in a place which supplies 50Hz power and the drive is intended
for use in the U.S. or other country with 60Hz power, you may have to experiment
with + deviations in speed from a stable pattern.
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From: Rubywand
004- How do I clean my disk drive R/W head(s)?
The easiest way to clean a drive's R/W head(s) is with a Cleaner Diskette.
This is a diskette with a paper disk such as the 5.25" and 3.5" Cleaner
Diskettes available in Radio Shack's Disk Drive Head Cleaner Kits. These kits
usually include "Cleaning Fluid" (isopropyl alcohol), too.
The 5.25" Cleaner Diskette has panels you pop out to expose the cleaning
surface. Apple II 5.25" drives have a single head which contacts the disk from
the bottom and a pressure pad which presses against the top side. So, pop out
the panel on the bottom side of the Cleaner Diskette and leave the top panel in
place. When cleaning, insert the diskette with the bottom side facing down. This
lets the paper disk rub against the head and avoids wear on the pressure pad.