Re: disk ][ speed adjustment

[rhsiao@ix.netcom.com (Ray Hsiao)]

dalloff@freenet.columbus.oh.us (Dave Althoff) wrote:

>
>*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.

It's also possible for the head to be misaligned.  If it is, slight horizontal
pressure on the sliding mechanism (the part on rails, not the head) during boot
up is sometimes enough to get it started.  Solution is to slightly bend the
positioning tab (the part that works like a needle and sits in the sprial
grooved "record") until you've got the right alignment.  Don't try to bend it
too much.  Had to replace mine with a hacked paperclip but it works.

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

Once had one of the IC's on the controller card catch fire and melt down.  Nasty
smell.

Ray