BALLEWS@BAYLOR.BITNET.UUCP (11/18/87)
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
jgroves@hawk.ulowell.edu.UUCP (11/20/87)
> >There are several programs available to test the disk speed but all pretty much >do it the same way: > Rana Systems and The Designer's Workshop were distributing SmartDOS (v. 6.1 and 8.2, respectively) which had an accurate, built in RPM tester (as well as many other useful features) This may help if you can get a copy through your local BBS or User group... -jg "Look ma, no .source!"
jwt@atari.UUCP (Jim Tittsler) (11/24/87)
In article <8711190814.AA15522@ucbvax.Berkeley.EDU>, BALLEWS@BAYLOR.BITNET (Scott Ballew) writes: > Atari decided their drives should run at 288 RPM! (Does anyone know WHY?!) At 288 RPM you have a little better than 8 mS more per revolution (compared to 300 RPM) which gives you time to squeeze that "one last (128 byte) sector" (and gap) onto a track. The bit density on the media is slightly higher than normal. At 300 RPM, you would have gotten one fewer sector per track (without shrinking the gaps, and thereby reducing margin). Jim Tittsler {ames, pyramid, imagen, sun, portal}!atari!jwt
cfchiesa@bsu-cs.UUCP (Christopher Chiesa) (04/29/88)
Hello all...
Some of you may remember my somewhat frantic postings last NOVEMBER on the sub-
ject of my "bugged" Percom AT-88 disk drive: the one that would simply suddenly
cease being able to read chosen sectors from my disks?
Well, I got a lot of responses to that original query; some suggested cleaning
the head (some saying "do it yourself," others saying "don't mess with it, take
it to a proessional"), others suggested having the head alignment checked, etc.
By all available evidence, Percom Data Corp. is long since out of business, and
the two addresses that were posted for Percom service (both in the same area in
or near Chantilly, VA) turned out to be the SAME company when I sent duplicate
letters to both addresses. They didn't bother to answer any of my questions,
just sent me a Xerox copy of their price sheet for new equipment, repairs, etc.
Didn't say how long it would take, what shipment method they recommended, or
anything else.
I was originally planning to summarize this in greater detail, a lot sooner, but
hey, I'm a college student, and a BUSY one at that... I don't think I've even
gotten around to PRINTING OUT the responses for posterity (although I DID READ
them, lest you respondents think you wasted your time).
One good aspect of this lengthy interval is that I've had time to observe the
problem more closely, and formulate another couple of questions for you experts
of the Net.
1) The drive SPEED appears to be off: 293 RPM. This is either TOO SLOW, if
the Percom AT88 is supposed to run at 300 RPM like "other standard"
drives, or TOO FAST if it's supposed to run at ATARI standard 288 RPM.
Does anyone know? Additionally, I opened the outer case to check on the
possibility of adjusting this myself (using speed-check program and the
strobe pattern printed on the flywheel), but couldn't find ANYTHING re-
sembling a "potentiometer" (variable resistor) adjustment. Any info?
2) The drive seems to work all right when first turned on, but then to
get worse as it warms up. This makes sense to me from an electrical
standpoint, but I don't know enough about it to be sure, and the problem
is STILL sporadic and hard to recreate.
3) I remember seeing something posted here by someone else, explaining a
similar degeneration in the performance of his disk drive, which he
eventually traced, as I recall, to a problem in the power supply. If
that person, or anyone who remembers (or saved) his posting, is reading
this, I'd appreciate a pointer to him, so that I could pick his brains
as to whether I'm having the same problem or similar.
Thanks in advance,
Chris Chiesa
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