From: ajb8886@ritvax.isc.rit.edu
Subject: Re: Dead/dying Seagate drive-help!
Reply-To: ajb8886@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology
Date: Tue, 29 Sep 1992 22:43:24 GMT

In article <1992Sep28.125654.9273@europa.asd.contel.com>, markt@rocky.gte.com (Mark Tsombakos) writes:
>
>A friend of mine recently gave me a Seagate 7120 130M drive.  He told me he was
>having problems with it, and had to have it replaced.  Me, being the
>dedicated engieer and packrat, gladly took it from him.
>
>The problem with the drive seems to be that it fails to spin-up - sometimes.
>A friend told him it was a known problem with Seagate's drives of this type,
>and that the head(s) actually "stick" to the platter occasionally.  He
>confirmed his theory by demonstrating his moethod from getting the drive
>running again:  hold it in his hand and jerking it in a circular fashion.
>(as I looked on in horror)  Sure enough, we plugged it in, and it was fine.
>
>Now, I'm never going to put anything critical on the drive, figuring it may
>give out for good at any time. Has anyone else had a similar experience with
>this type of drive?  Would it be cost-effective to have it "repaired"?  Is
>it repairable??  Or should I just enjoy the extra 130M while it's around?
>
>Thanks, 
>Mark

[grin] the usual way to overcome stiction is to lift up the drive electronics
to reach the underside of the spindle motor, and give it a slight turn in
either direction.

One trick that reduced the effects of "stiction" was to run the park program
before shutting down (unfortunately this only applies to old stepper-motor
drives which do not auto-park on power down), which would move the heads to the
innermost cylinder (literally beyond the formatted space).  Since the heads
would then be touching the disk at the >innermost< part of the platter, the
spindle motor would then exert more torque on power up (due to the heads
proximity to the center spindle) to overcome the "stiction".

There is something you >might< be able to do.  I've modified a few older drives
a few years ago to allow them to overcome stiction by replacing the capacitor
used to give the spindle motor the brief "jolt" needed to get it started 
turning, with one of higher capacitance, thus resulting in slightly more power 
(and thus more torque) to the motor at the initial application of power, 
enough to "unstick" the heads.

Unfortunately, I have no such information available for the Seagate, and I
would suspect that they would frown upon such modifications.

One other possibility is to remove the drive electronics (ie. the circuit board
attached to the bottom of the drive, >not< the cover protecting the internal
platters!).  Underneath the drive electronics you'll see the lower side of the
spindle motor (the spindle of which passes through a sealed bearing into the
ultraclean drive mechanical area).  The spindle motor you're looking at will
usually be covered with heavy dust, etc.  Clean this up with compressed air (or
use zero-residue spray cleaner from radio shack).  Try to work in a >little<
WD40 near the underside of the spindle (don't worry, this won't get into the
drive itself, as the bearing is sealed). 

This tip won't solve the problem of course, but by slightly reducing the
friction exerted by the spindle at startup, it could allow the motor to apply
just that little bit of extra torque needed to unstick the heads.

One note: if at >any< time the drive shuts down AFTER spinup, then forget about
using the drive; it'll need repairs (ie. the motor controller is overloading
and/or possible burnt coil in the spindle motor).  But if it's just plain
stiction and only occurs at power up, the drive should work reliably once 
spin-up is achieved.

Hope the info is useful.

Alex

 
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