Re: disk ][ speed adjustment

[dalloff@freenet.columbus.oh.us (Dave Althoff)]

As others have said, the trimpot is half-way up on the right-hand side (as
you look at the drive from the front, upside up), and the trimpot housing
is generally blue, though I have seen grey ones.  It's a little tiny
thing, and if you are fairly precise with a drill, you can drill out a
hole in the case so you can hit it with a "greenie" without opening the case.

Use a disk speed alignment tool (available as part of most full-featured
DOS 3.3 copy programs) to get the calibration right.

*But Dave, it is my only drive, and it is so far out of whack that it
won't boot.  Can I get it close?

Try this:  Remove the four flat-head screws that attach the drive
mechanism to the bottom plate.  Unclamp the data cable from the back plane
and invert the drive, so that the bottom is facing up.  Connect the drive
to the Drie 1 connection on your controller card (if you haven't already),
open the door, and start the computer (try to boot the empty drive if you
are on a ][).  Ideally, you should be under an AC flourescent light,
because there is a strobe disc on the bottom of the main shaft on the Disk ][.
Using the appropriate set of hash marks for your house current (60Hz
US/CA/JP and some others; 50Hz most of the rest of the world), adjust the
speed until the reddish-looking hash marks appear motionless.  Reddish
looking, from a black-and-white strobe wheel?  Yeah; it is an optical
illusion.  When done, try booting the drive (you can do this with the
drive inverted).  If it works, then you can use the alignment program to
get the speed just exactly right.  If not, try cleaning the heads (Freon
is best, but unavailable); failing that, you've probably got something
major wrong with the drive or controller.

Fear not, all four of the socketed ICs are readily available.

Good luck!

--Dave Althoff, ][.
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