Stiction

jim stephens jwstephens at msm.umr.edu
Fri Dec 8 15:52:13 CST 2006


Marvin Johnston wrote:

><snip>
>
>Has anyone seen stiction on the IDE or later drives? The only stiction I've seen
>has always been on the 5 1/4" MFM/RLL type drives, and probably ESDI/SCSI/SASI
>as well although my experience is limited on those drives.
>
>  
>
I had three cases out of it on ST-225 and relatives.

>Something else I've noticed is that if a drive has stiction, that stiction will
>return after the drive sets for a while again. Anyone know what actually causes
>stiction?
>  
>
In the case of the ST-225 they used defective magnetic lubricant on the 
axis which eventually
developed too much friction for the start up pulses in the motor to 
overcome.  A bit of a kick
as you mentioned is the only thing to try.  once the disk stack is in 
motion, the motors have to
be able to keep it going and if the friction is that great there is no 
way that taking it apart will
fix anything.

Never saw it in the smaller drives, but I did see a number of them with 
being unable to regulate their
speed, which may have been a vaiant.  They would  make different sounds 
after startup and
eventually spin down when they could not find a place to track.

This could have been a failure to spin at the right speed, or a failure 
to correctly lock
onto the reference servo and see a basic clock, or an increased friction 
keeping it from
getting up to the correct speed.

Jim



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