Path: utzoo!utgpu!water!watmath!clyde!bellcore!faline!thumper!ulysses!andante!princeton!udel!gatech!purdue!decwrl!decvax!mandrill!neoucom!wtm
From: wtm@neoucom.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Seagate ST225 D.O.A.
Summary: It croaks if the screws are too tight
Message-ID: <1167@neoucom.UUCP>
Date: 12 May 88 18:34:38 GMT
References: <2845@phoenix.Princeton.EDU> <637@mccc.UUCP> <5746@pyr.gatech.EDU>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 36
Posted: Thu May 12 14:34:38 1988


The only unusual failure mode for Seagate ST-225 drives that I am
aware of is that if a reall gorilla installs the drive and torques
the mounting screws (or uses screws that are too long), that this
places stress on the chassis.  The stressed chassis causes errors
in the positioner (which is apparently an open loop design, anybody
know for sure?).  Fortunately, the problem is recoverable by
backing off the mounting screws until they are not butting up
agaist the chassis and are not unduly tight.

As per the previous discussion, ST-225s should not be used with RLL
controllers -- though rumor has it that recent ST-225s are really
the same as the RLL certified ST-238 model; the ST-238 undergoing
more rigorous testing before shipping.

For experimental purposes, I have formatted an ST-225 to 32 megs as
an RLL drive and then reformatted with another controller and
haven't had any problems.  I think the drives that might have
problems are ones like miniscribes that use a dedicated servo
platter.  I also tried formatting a 45 meg Rodime 3-1/2 inch drive
that is supposed to be MFM up to 62 meg RLL (the limit of my
controller) and then switched it back to MFM without incident.  The
Rodime drive has been perking away back as MFM 24 hrs/day for
several months in this computer since I tried the RLL experiment on
it.

I've been using a Seagate ST-238 at home since Jan. 21, 1987 with
and OMTI 5527 controller.  The drive arrived with zero errors, and
has been in use several hours a day since without any incidents.

For references, check out the April '88  issue of Mini Micro
Systems magazine.  The entire issue is full of nice articles on
RLL, ESDI, SCSI, testabilty of drives, etc.  Very much recommended
reading.

--Bill