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Re: Unrecognized Hard Drive



On Sun, Jan 04, 2009 at 02:14:16PM +1030, Tim wrote:
> 
> Tim:
> >> /me wonders whether warming them up, first, would have helped?
> 
> Mikkel L. Ellertson:
> > It might have - stick it in an oven or something. On the other hand,
> > it might have cause other problems. What I think was happening is
> > that the bearing lubrication had gotten into places it should not
> > have, and then prevented the drive from starting to spin up. The
> > jolt freed thing up enough to get the drive spinning. It also freed
> > the head to move as well.
> 
> I was thinking of metal contraction as it cools down seizing the moving
> parts into position (remembering my days back in school of being told
> not to leave the vices tightened up overnight).
> 
> Of course warming them up would have to be to a sensible temperature.
> Warming them up to normal operating temperatures, not roasting
> them.  ;-)
> 
> I get odd looks when I tap the back of a screwdriver with another one,
> with the first one's point in the slot, to loosen up stuck bolts.  But
> the principle's the same, you're trying to free up a moving part that's
> jammed, but with the minimal amount of force that's required.
>

Hmmm.... this discussion sounds like the now solved "stiction" problem
seen by a lot of vendors ten years+ ago when a new generation of heads
was introduced.   The issue was lubricant for the drive bearings  and
the new generation of very flat very low flying heads did not play well
together.    One vendor's explanation was that the lubricant migrated
to the landing pad area and a year later when the drive shut down the
heads would seek to the landing zone and "stick".

Folks that have ever worked with optical flats, microscope slide coverslips 
knows how solidly "flats" can stick together.

For the stiction problem the solution was to cycle the drive in software/
firmware so it would spin down for a moment a couple times a month and
do the equivalent of a "touch and go" effectivly cleaning the heads and
landing pad zone.  Later changes to the lubricant, berrings and landing
pad zone surface eliminated the need for the touch and go solution.

For a stuck drive a field solution was to give the drive a "rap" in a
corner giving additional "torque" at start up.   The power on cycle of
the drive gave the field tech. about five seconds to apply the "rap"
before the drives self protection logic shut it down.    This worked
for most but not all drives.

If the drive spins up but does not come on line then this is not the issue.

 

-- 
	T o m  M i t c h e l l 
	Found me a new hat, now what?


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