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09.003 How can I adjust my 5.25" drive for the best performance?


This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.

09.003 How can I adjust my 5.25" drive for the best performance?

         The typical 5.25" drive will run for months with no need for maintenance
save an occassional dusting or session with a head-cleaner disk. When
adjustment is required, it will usually be to fine-tune Speed or, less often,
to set track centering.

     If a 5.25" drive has difficuly reading diskettes, including those it
created, and head-cleaning does not help, then, the odds are it's time to
adjust speed. If your drive is a Disk ][ and does not have the external 'Speed
Knob' mod, look for a small hole on the lower right side near the back-- some
owners add this hole to allow easy access to the Speed Adjustment mini-pot
screw. If there is no hole, you will need to remove the case. (Remove bolts on
bottom and slide out the drive through the front.)

     On the 5.25" Apple 'Platinum Drive', the Speed Adjustment is accessed
through a small hole on the bottom of the drive near the front on the right
side. Non-Apple 5.25" drives may place the Speed Adjustment almost anywhere.
Look for a small hole through which you can see a screw head. If you don't fine
one, remove the case and look for a mini-pot labeled "Speed" or something

     The most popular speed adjustment software utility is, probably, dear old
Copy II Plus. From the menu, just select "Verify", then "Drive Speed". Put a
diskette into the drive you want to adjust and, turning the Speed Knob (or min-
pot shaft) use Copy II's numeric speed display to zero-in on the 'magic' 200ms.
number. (Standard Disk ][ rotation speed is 300 rpm, which comes out to be 0.2
seconds per revolution.)

     Other speed adjustment utilities show an rpm number or a hires pointer.
Whatever, all speed check routines need to read AND write; so, you will usually
need a "scratch diskette" which you do not mind having over-written.

     Track-center realignment is needed when a Disk ][ writes and reads its own
disks fine, but does not 'communicate' with many other Apple II 5.25" drives.
It generates disk errors when reading disks written by other drives and other
drives have the same problem with its diskettes.

     CALL A.P.P.L.E's APTEST, now in the public domain, tests track-center
alignment. With  this software, the user checks the alignment of the drive with
disks regarded as well aligned --- such as Apple diskware supplied with the
computer or some unprotected, original, commercial software diskette. (In a
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.


By:  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.

By:  Rubywand


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