info-mac@uw-beaver (info-mac) (11/20/84)
From: ateam%ucbamber.CC@Berkeley In response to the message posted by Martin Mahoney about bad external disk drives.... Here at Berkeley we've come accross maybe 10 or so external disk drives which are bad e.g. When you insert a disk that you know is good (like a disk you just booted off of) into the external disk drive you get a message that the disk is damaged, or unreadable, or not a Macintosh disk...... We haven't figured out what causes this yet (although we're going to have to since we do all the repairs of campus Macs) but we have become relatively sure that it is the external disk drive that is causing the problem. If something like this happens I would suggest trying to copy some disks from the internal to the external drive and then try to boot up or simply use the copy (try it in both drives) if the copy doesn't work then you've got problems..... I would suggest trying to get replacement for your external drive. This may be difficult because the problem is usually not consistent, sometimes your external disk drive may work fine (usually when the tech is testing it) and then other times won't work at all (of course when you're doing something important) If you're not sure its you external drive..hook it up to another Mac and try to copy some disks (this is how we narrow it down to being the external disk)..this is also what I would do when I take it in for repair (copying disks using disk util seems to cause the problem to occur most often) Good luck, and I'd be interested to hear of other similar problems andd especially what caused them. Fred A. Huxham ateam@ucbamber
info-mac@uw-beaver (info-mac) (11/27/84)
From: <ihnp4!hplabs!bragvax!kari@uw-beaver.arpa> I recently pushed the programmer's RESET switch while the Mac was booting from the internal drive, for the first and definitely the last time. (I thought: Surely the bright people at Apple have designed the Mac to handle this gracefully... Not so.) Friends of mine claim they push the switch any time they please and nothing bad happens to THEM. I choose not to believe them from now on. The results were pretty bad: 1. Trying to boot from the same disk gave a Sad Mac Icon. Trying to boot from another disk failed. Turned the machine off, tried again, failed. After a while I managed to boot from a system disk. 2. The disk I was booting from when I hit the reset button could not be read. It could not even be erased or reformatted or zeroed. Bulking it might work, but I have no access to a bulk eraser. In the next hour I had severe problems with the Mac in that I sometimes could not read a disk in the internal drive, sometimes not in the external, sometimes not in either. I ran disk verifies and disks would fail with various rates. I believed I began to see a pattern to the failures: 3. (Theory): The internal drive head had gotten semi-permanently magnetized when I hit the reset button. It was corrupting my disks. This theory gets supported by the fact that the some of the errors were soft, failing only occasionally, (The recording had partly faded away because the disk was read with a magnetized head) and by the fact that several disks were damaged after I had pushed the button ONCE. 4. I created two new (identical) disks on another Mac I have access to (the following day at work), containing a system folder and the disk utility program. I then ran disk verifys on both drives. The internal drive would eventually start failing. I then zeroed the internal drive disk and then copied new contents from the other one. (At least with analog taperecorders, if you cannot deflux them, record on them. They contain special circuitry to deflux the heads when the recording bias oscillator is turned off. I just "massaged the head" by using it a lot.) 5. After half an hour I felt confident that the disks did not get any worse by reading them in the internal drive. I have not had any problems since then. 6. Two days later I did an inventory of all the disks I had touched while I had problems. Six disks out of about 15 I had been reading from did not verify correctly. I refused to use ANY file from any disk that did not verify correctly. I did not lose any work since I have two backups for everything (since I have one Mac at work also). 7. The above procedures were not conducted in any scientific manner. I did not keep notes. Things may have happened slightly differently. All I know is that my Mac now works, I have one disk that cannot be formatted no matter what I do, and one that fails marginally (every other verify or so). I have never had any problems with my Mac before. I have no problems now. If anyone else has had a similar experience, I would be interested in a summary. /Kari Kari Dubbelman, BRAG Systems Inc., San Mateo CA (415) 342-3963 X218 (...decvax!ucbvax!hplabs!bragvax!kari)