Somewhat OT - can underpowered power supplies damage a system?

Gene Heskett gene.heskett at
Thu Aug 19 06:38:29 UTC 2010

On Thursday, August 19, 2010 02:27:03 am Tim did opine:

> On Wed, 2010-08-18 at 13:38 -0400, Gene Heskett wrote:
> > Subtly mixed in with this might be a longer than normal spinup time at
> > powerup, leading to higher head wear in the first turn or two of the
> > spinup,
> I wouldn't have thought that would happen.  The heads don't touch the
> drive in operation, and I thought parking the heads moved the arm
> completely off the disc.

It's been a while since they have been parked off disk.  None of the drives 
I have opened up in the last decade did anything but park them at a non-
data bearing location on the disk.  This can often be identified by a thin 
line of slightly higher polish on the surface.  They use very little 
pressure these days, and with decent brakes, usually by shorting the drive 
motor when stopping, the time the head actually touches the disk is very 
short, likewise when spinning up, the head takes off and flies at a safe 
altitude before the disk has made a full turn.  The heads fly in the 'ground 
effect', with contours such that the faster the disk turns, carrying the air 
with it, the closer to the disk the airflow pushes them, which when balanced 
against the ground effect, results in a very consistent head flying height of 
a very few microns.

Cheers, Gene
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