R80/RA81 diagnostic experience?

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Tue Mar 9 11:51:19 2004

Hi
 Most all hard disk heads will damage the surface if
rotated backwards. This is because the back edge is
sharp enough to cut you as well as dig into the
surface.
Dwight

>From: "Johnny Billquist" <bqt_at_update.uu.se>
>
>On Tue, 9 Mar 2004 Gooijen H <GOOI_at_oce.nl> wrote:
>
>> I am not sure that removing the brake will help.
>
>More likely not. In fact, the break is there for a reason. To stop the
>drive when spinning down. Otherwise, it will spin for a long time. I also
>suspect that the break is engaged until you try to spin the disk up, so
>that the disk don't swing back and forth just because you move the drive
>around.
>
>> I once heard the following rumour:
>> the brake in combination with the 'heavy' motor
>> makes sure that the disk platters always rotate
>> in the same direction, never for a short instance
>> in the other direction (vibration, power flutter,
>> whatever reason). Rotation in the opposite direction,
>> for any short moment, will cause the air on which the
>> r/w head fly to disappear and result in an immediate
>> head crash ...
>
>Are you suggesting that a platter, weighting several kilograms, spinning
>at something like 3600 rpm, suddenly can change spin direction at a
>millisecond notice?
>
>> As I said, it is a rumour I once heard a few years ago.
>> Has anybody heard of this too?
>
>That's one of the more outrageous rumours I've ever heard. :-)
>The amount of energy required to do that trick would blow every fuse in
>your house, and then some. We're talking about living mass here. Physics,
>you know... ;-)
>
>However, vibration can cause a head crash...
>
> Johnny
>
>Johnny Billquist || "I'm on a bus
> || on a psychedelic trip
>email: bqt_at_update.uu.se || Reading murder books
>pdp is alive! || tryin' to stay hip" - B. Idol
>
Received on Tue Mar 09 2004 - 11:51:19 GMT