Hello Len Warner, at 01:20 AM 7/1/98 +0100 you wrote:

>Disk spins up, heads step across smoothly, then a pause
> - and then the drive begins a slow, rhythmic clonking,
>presumably the heads hitting the end stop.

>Obviously quite a lot of the drive is working for this to happen:
>can an expert suggest a likely cause of this type of failure?

  On Seagate and Western Digital drives, this seems to happen a lot. I am
not going to get in what hard drive is better or which break down more, I
just see a lot of this type of break down in Seagate and Western Digital
Drives.

  What the problem usually is that there is platter damage on one of the
main servo's. This is why the Actuator arm is slamming back to home
position, the Click or clang noise you hear. What I mean by platter damage
is when the head hits the platter at high speed and physically scratches
the Magnetic particles off of the surface of the platter.

There are three primary areas you do not want to see a scratch:

On the inner ring "Cyl 1024," this cylinder carries what I call the Primary
Servo Track. The Primary Servo Track contains information that works in
conjunction with the printed circuit board so the computer can identify and
detect the hard drive. In most cases some data recovery companies can
recover the data off of the hard drive when this happens.

On the center area ring "Mid Cyl," this cylinder carries what I call the
Mid-Range Servo Track. The Mid-Range Servo Track contains the information
of the Tracks (Cylinders), head position, and Sector information on the
area between the Mid-Range Servo Track and the Primary Servo Track. Also
this track carries information that instructs the heads to continue on to
the Maintenance Track during post.  Usually if this cylinder is scratched a
data recovery company can recover the data.

On the outer ring "Cyl 0," this cylinder carries what I call the
Maintenance Track. The Maintenance Track contains information on how the
hard drive is setup physically, logically and the location of bad sectors.
This information is vital to the operation of the hard drive. If this
cylinder is scratched a data recovery can very seldom recover the data off
this hard drive.

  I hope this information helps you out.  IF there are other questions you
can e-mail me.

Best Regards,




Tim Lider
Advanced Data Solutions              ICQ: 7562541
Web Site: http://www.adv-data.com E-Mail: Mailto:[log in to unmask]