Re: Apple ][ disk speed prog/docs pointer needed

[shoppa@almach.caltech.edu (Timothy D. Shoppa x4256)]

In article <3ldiba$c0h@hal.cs.depaul.edu>, jscandor@hawk.depaul.edu (Joseph R. Scandora) writes...
>Hello Everyone.
> 
>My community college has a bunch of apple ]['s and IIgs'
>some of which have wayward disk drives.  I seem to
>remember there being a disk speed program that can
>be used to calibrate these drives, and as I have
>volunteered to attempt repairs, I find myself in
>search of such a program. Apologies if this is a FAQ.

Most of the nibble-copy programs had such an option in their
heyday.  (Locksmith, Nibbles Away, etc...)  The easy way to
align Disk ][ speed is to take the bottom cover off and use a
strobe light on the spindle, adjusting the speed until
the 60 Hz pattern becomes stationary.  Don't have a 60 Hz strobe
light?  Go to radio shack and buy a neon bulb (NE-2 or NE-2H), 
a limiting resistor (I believe NE-2 uses a 47K resistor; NE-2H
uses something smaller) and a 120 VAC power cord.  The speed control
pot is a ten-turn pot sticking off the side of the little PC board
on the rear of the Disk ][.

I've found very few "broken" Disk ]['s that needed a speed adjustment,
however.  The most common cause of death for these drives, in my
experience, is someone hooking the ribbon cable up backwards or off
by a pin.  This blows the line driver inside the drive.  (I seem
to recall it being a UNL2003, but I could be wrong.)  The second
most common cause is someone opening up the drive and fiddling with
the pots inside the drive when they didn't know what they were doing!

Tim. (shoppa@altair.krl.caltech.edu)