Re: Unidisk 3.5 replacement mechanism?

[Warren Ernst <wernst@gmail.com>]

On Jul 11, 12:10 am, A2Aviator <a2avia...@gmail.com> wrote:
> Lets put it this way, rather than in a confrontational mode, you could
> have said "I've had it work between the UniDisk and AppleDisk before",
> too.
>
> My 'decades' of experience are based on having serviced tens of
> thousands of drives, written procedures for repair and refurbishing
> them, and anywhere in between. I have never gone wrong citing what the
> Apple service documentation said, and have many times proven it to
> myself that they are generally not interchangeable. There have been
> times when it does work.
>
> But I have to say, if they have made a red and yellow ribbon cable,
> and the difference between them is a non-connected line on that yellow
> one, that they did it for good reason.  That good reason is was
> discovered long ago during one of those "what if.." moments, and ..
> gee why is that cable getting warm, and them suddenly it's red and
> smoke is everywhere.
>
> There are several revisions of drives, some are just not very common.
> Following published specifications and guidelines has never steered
> any long distance, or non-visual, or otherwise indirect communication
> wrongly and results in the desired results for the recipient.
>
> There's a better chance at large that the two are not compatible, and
> in the recent case of working with a UniDisk 3.5" - putting back the
> same type of labeled drives, and the other, both resulted in a non-
> functioning unit where the originally installed drives functioned,
> albeit poorly.
>
> The UniDisk 3.5" has never resulted in a smoked cable/drive - but
> consider this. If there's something not to it's liking, you've got an
> IWM on that UniDisk 3.5" analog card that is fairly susceptible to
> damage. ...and they're not exactly available - though they can be
> ravaged from that MacPlus .. the UniDisk analog card isn't very open
> to removing that IC, it's one of those that the vias tend to come out
> easy, and tends to like solder, not wanting to give it up due to being
> a really good heat sink. It's multi layer, has large power and ground
> planes internally.
>
> Hence my original comment, service the drive - it's easy. You know it
> works already, and you don't have to ravage something else thats
> otherwise working.
>
> Just beware of the head. Do NOT lift the head. Period. It can be
> fixed, but it's not easily explainable how. The video thats
> forthcoming will show bending and fixing the head.

Hmmm.

All I can say is that in the 20 years I've taken the drive mechanism
from relatively common AppleDisk 3.5 drives to fix a bad mechanism in
a faulty UniDisk 3.5, I have never had a problem. In fact, the 2
UniDisk 3.5 drives I have in service with my //e right now have mechs
that came from AppleDisks.

So to the original poster, my advice to you is to replace the drive
mech without fear.The UniDisk circuit board powers the mech and not
the other way around, so you don't need to worry about harming it by
replacing mechanisms.

My two cents.

Warren Ernst
former Beagle Bros tech support