jcs@zodiac.phy.duke.edu (03/12/91)
Dear Folks,
This is my second posting about problems I'm having with my floppy drives.
Originally I thought my internal drive had failed. Now I am certain
the drive is fine (I have swapped drives both demonstrate similar
failure modes in my mac, whereas connected to any other mac, the DRIVES
work well.) In particular, my problem is,
1) A week ago the internal 800k on my mac128->512ke->plus (3rd party upgrades)
stopped working correctly. It reads disks fine, but any write activity,
corrupts the directory and makes the disk unusable ("This disk is unreadable,
shall I initialize it?") This is probabalistic, i.e., usually the drive
fails, but sometimes reads and writes work (for a few file transfers).
2) I have swapped disks and the new disk has the same problem. I have tried
the disks through the external drive port and get the same failures.
However, both disk drives work fine on machines at work.
3) I have checked the power supply voltages and both the 5v and 12v supply
are correct and stable. (I have check with a dig. voltmeter, but not
a scope, so there may be high frequency noise. Would this matter?)
4) I have checked the state control lines at the disk (CA0,1,2) with a
logic probe. They pulse low when no activity is occuring and appear
to switch rapidly when the disk is active.
5) All other functions appear normal. (I have checked the scsi, ram, and
i/o and all function well.)
6) I have run Disinfectant2.4, tried new systems, (6.0.3, 6.0.5,4.?,1.?)
and have found none write without trashing the disk.
Based on these I believe the IWM or some other aspect of the floppy
interface is failing or has failed. I need help narrowing isolating
this problem. Is there anyone else who has had similar problems or
knows of diagnostic/test software for the mac. (Any Apple designers
or techs responses would be especially welcome.)
Please respond to me by email or rn and I will summarize. Also I'd like to
thank tilley@ccu.UManitoba.CA, lll10246@uxa.cso.uiuc.edu, Richard Straka,
and Gordon Davisson for their replies to the first posting. They helped
me get this far.
Thanks in advance for any insight,
John Swartz
jcs@physics.phy.duke.edu
jcs@zodiac.phy.duke.edu
jcs@dukee.duke.edu
919-684-8279
--
John C. Swartz 1-919-684-8279
Duke University Dept. of Physics jcs@phy.duke.edu
Durham, N.C. 27706