3b1 Disk Problem - Help

[Bruce Crabtree]

Dear Benevolent Network,

Yet another unix-pc has bitten the dust.  I am writing this in
the hope that someone might provide some suggestions for me.
My machine is a 3b1 with 3.5 M memory and a 67 M disk running
version 3.5. (3.5 was installed on it when I got it.)

The problem started when the floppy disk would not read
properly.  Following suggestions from postings in this
group I opened the case, removed the floppy drive, cleaned
off any dust I saw, and reinstalled it.  After I installed
the floppy disk, I closed the case and ran the 3.5 diags
to check it.  No problems were reported so I rebooted from
the hard disk.

After booting, a message appeared indicating something to the
effect that window 0 could not be opened.  The message was
followed by the '#' prompt leading me to believe that I was
in single user mode.  Unfortunately, probably due to the
late hour, instead of running fsck or trying to understand the
problem I rebooted again.

This time the machine would not boot.  Using the diagnostic
program I was able to determine that several sectors of the
hard disk could not be read.  Fortunately I had access to
a 7300 running 3.51 and was able to create a bootable disk
with fsck on it as described in the FAQ posting (thanks Lenny).  

After creating the disk with fsck on it I attempted to boot the
system using the floppy boot disk.  When prompted I inserted the
disk with fsck on it in the drive and pressed <Shift> <Del> as
described in the instructions in the FAQ. The following text
appeared on the screen during this procedure..

Version 3.5
Real Memory      = 3670016
Available Memory = 3325952
Main board is P3...P5
Floppy Unix
Please insert Floppy File System disk - disk 3 of 12
Press any key when ready

 (I insert the disk created as described in FAQ and press <Shift> <Del>.)

#HDERR ST:51 EF:1 CL:FF00 SN:FF00 SC:FF02 SDH:FF20 DMACNT:FFFF DCRREG:F0 MCRREG:8900
#HDERR ST:51 EF:1 CL:FF00 SN:FF00 SC:FF02 SDH:FF20 DMACNT:FFFF DCRREG:F0 MCRREG:8900
panic: iinit

Please record panic message.
Press hardware reset to reboot.

Since it didn't work I decided to try again and let it continue.
I then booted again using the floppy boot disk and the disk with fsck
on it but this time I pressed the space bar instead.  The following
text appeared on the screen:

Version 3.5
Real Memory      = 3670016
Available Memory = 3325952
Main board is P3...P5
Floppy Unix
Please insert Floppy File System disk - disk 3 of 12
Press any key when ready

 (I insert the disk created as described in FAQ and press the space bar.)

#HDERR ST:51 EF:1 CL:FF00 SN:FF00 SC:FF02 SDH:FF20 DMACNT:FFFF DCRREG:F0 MCRREG:8900
#HDERR ST:51 EF:1 CL:FF00 SN:FF00 SC:FF02 SDH:FF20 DMACNT:FFFF DCRREG:F0 MCRREG:8900
#HDERR ST:51 EF:1 CL:FF00 SN:FF00 SC:FF02 SDH:FF20 DMACNT:FFFF DCRREG:F0 MCRREG:8900
panic: iinit

Please record panic message.
Press hardware reset to reboot.

>From postings I see in this group I thought perhaps the power supply was
to blame.  I open the case and measured the voltage to the disk.  The
voltages were 12.1 and 5.0 volts across each pair of the disk power cable.
By this time I decided to shut the machine down and come back to it when I
had more time.  After being shut down for about 4 days I tried to boot up
and run the diagnostics.  This time I got a 'unable to Reacal' disk error
and could not continue.  I believe this was do to a stiction problem.
Thanks to the network I know about this problem and was able to get a 20 Mb
miniscribe working enough to back it up.  This time when I disassembled
the 3b1 I found that the 67 Mb disk drive is indeed a miniscribe and may
therefore have a stiction problem.  Unfortunately, unlike the 20 Mb disk,
the stepper motor appears to be sealed inside the disk unit so I can't access
it directly to nudge it.  Now I realize that I am in over my head and
humbly turn to the net for advice.

I believe that I will need to replace the hard disk, but I would like
to understand more about what has happened.  My questions are:

1. How do I get the 67 Mb disk unstuck if I can't reach the stepper motor?

2. Is there a way to recover any data from the 67 Mb disk?

3. What was preventing me from booting off the floppy?

4. What can I do to prevent this from happening again?

Thank you for you assistance,

Bruce Crabtree
ssdbruce at jarthur.claremont.edu

-- 
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Bruce Crabtree                        ssdbruce at jarthur.claremont.edu
Software Systems Design, Inc          [W] 1-714-624-2306
Claremont, CA