Re: Broken Unidisk 3.5" drive?

[Wayne Stewart <waynes@intergate.bc.ca>]

Rodney Hester wrote:

>
> The Unidisk GS/OS driver is installed and working (as you can see by the
> drive light and a faint sound that it is actively polling the drive once the
> Finder is up, and stops whenever the Finder is "busy").  Unfortunately, it
> never actually "sees" the disk in the drive, as it continues to poll even
> with a disk inserted (but the disk "slide door" does not appear to be
> unlatching).
>
> It does not work under GS/OS or ProDOS, as there does seem to be some sort
> of mechanical malfunction.
>
> The disk does not eject with the button pushed - the button appears to have
> some effect, as there is a notable change in signal on the Apple bus when
> the button is pushed (appears to act as a momentary push-switch).
>
> The cable is properly seated (and tried on two machines) and is the only
> drive connected to the IIgs at this time, to eliminate any possibility of
> connection failure.

The eject button should eject the disk except possibly while writting(never
tried).
The 3.5" UniDisk uses the same 800k mechanism as the regular IIgs drives or
the early Macs such as the Mac plus. Out of curiosity I tried a 1.4mb mechanism

once but the drive wouldn't function at all.


How to replace the mechanism in the 3.5" UniDisk

Turn the drive upside dowen and remove the 4 screws on the bottom
Lift off the bottom of the case
Remove the screw at each rear corner(two in all) and remove the top cover by
sliding it forward and up. Don't lose the 4 pieces of rubber tubing that hold
the
wires down on each side
Remove the two screws on each side(4 in all) holding the drive mechanism in
the case.
At this point you should be able to slide the drive mechanism forward and out.
The drives connector should pull out while doing this.
Slide the replacement mechanism in and plug the connector in by reaching around

the external cable with either a screwdriver or needle nosed pliers. If that
proves
difficult, you can remove the external cable hold-down screw which is easily
seen.
You could also remove the rear cover, it's held in by the only other screw that
isn't
holding down a circuitboard.
Assembly is doing everything in reverse order. The whole thing sounds much
harder
than it actually is.

    Wayne