Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!uwvax!oddjob!hao!ames!elroy!cit-vax!ucla-cs!zen!ucbvax!BAYLOR.BITNET!BALLEWS
From: BALLEWS@BAYLOR.BITNET.UUCP
Newsgroups: comp.sys.atari.8bit
Subject: RE: Disk drive problems
Message-ID: <8711190814.AA15522@ucbvax.Berkeley.EDU>
Date: Wed, 18-Nov-87 15:35:00 EST
Article-I.D.: ucbvax.8711190814.AA15522
Posted: Wed Nov 18 15:35:00 1987
Date-Received: Sat, 21-Nov-87 16:02:29 EST
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 34

In response to Dragos Ruiu's posting about disk drive speed checking, the method
described to check for an accurately adjusted disk speed:

> If you physically remove the drive you will notice it should have
> a ring of alternating black and white spots on the flywheel. If you watch this
> wheel under a fluorescent lamp (You must be in a country with 60Hz power) the
> spots should stay still. If they don't, your drive is too slow or fast.


does not work on drives designed for the Atari 8-bit computers. This method
will accurately detect a drive running at 300 RPM but for some ungodly reason,
Atari decided their drives should run at 288 RPM! (Does anyone know WHY?!)

There are several programs available to test the disk speed but all pretty much
do it the same way:

1) read sector 1 repeatedly recording the time it takes between successive reads
2) average these times and scale them into an RPM

Obviously to be fast enough, this must be done in ML and I am not equipped
to post any of the many drive testers I have.

With regard to Stan's original problem, I might also comment about the
possibilities of alignment problems. If the drive has not been serviced at
all in many years, the alignment might have drifted. However, this should
only show up when trying to read old disks, not ones just written. It can
destroy an otherwise good disk that has been recently written to and does
appear to be a variable problem at different tracks since when a tech aligns
a drive, he tests it on track 1 and 40 and then in the middle (around track
20, I think.) For this problem, short of an oscilloscope, there is no way to
detect or repair it at home.

Scott Ballew
ballews%baylor.bitnet@wiscvm.wisc.edu