Sony 650MB Magneto-Optical drive

From: Mark <>
Date: Sun Mar 21 14:29:17 1999


Yesterday I bought an old Sony SMO-S501-11 external SCSI 650MB magneto-optical
drive. This takes 5.25" double-sided 600MB or 650MB disks; it came with 15
600MB disks.

There are some things which hopefully someone on classiccmp will know about, or
at least know where to point me.

The drive works, at least partly. I think the lens may need cleaning, since
sometimes it does not recognise disks; this is using freshly-cleaned disks.
Does anyone have a spare 5.25" MO head cleaning disk? Or a cleaning kit for
5.25" MO disks themselves? (But see below, the real fault may be

I got the drive working on my Amiga, and also an (emulated) Macintosh. Does
anyone have the driver software for MS-DOS PCs that would have come with this
drive? This is necessary to allow 650MB disks to be used under MS-DOS (650MB
disks use 1024-byte sectors).

When the drive refuses to work, inserting a disk results in:
 - Drive spins up
 - A click sound about every two seconds for about ten times
 - Drive spins down.

This repeats twice, after which the drive reports:
Sense Key : Not Ready (0x02)
Add. SenseCode : Logical Unit Not Ready, Cause not Reportable (0x04)

I'll describe a little about the drive itself. It was made in March 1990. It is
SCSI-1, and old MO drives were much slower than current ones; according to the
manual, the drive has a read speed of 680K/sec with an average seek time of
95ms. Spindle speed is 2400rpm.

Interestingly, the actual mechanism does not seem to be SCSI. It is attached to
a SCSI controller inside the case. The drive mechanism part number is
SMO-D501-99. It uses two card-edge connectors, one 34 way the other 20 way. Is
this EDSI or something???

On the SCSI controller PCB is one firmware EPROM, whose label reads:
     ? SONY '88 '89

On (one of) the mechanism's PCBs are three EPROMs, whose labels read:
        D501 D501 D501-00
       MMP-32 MDP-21 DCP-83
   ? SONY '88 '89 ? SONY '88 '89 ? SONY '88 '89

I tried to dump the data from all four EPROMs. Three seem okay, but the DCP-83
one gave errors. If this EPROM is marginal/bad, that may explain the problems
I have been having getting disks to be recognised -- it seems that immediately
after powering up the drive from cold, disks can be recognised, but after it
has warmed up the drive is much more picky. Do bad EPROMs usually behave like
this, or is it more likely to be some other component?

If anyone has one of these drives, and has dumped the DCP-83 EPROM, or knows
where I might get hold of an image of this EPROM, please let me know. I would
also like to get hold of the OEM manual(s) for this drive.

On a related subject, I want to get hold of disk geometry information for
various types of MO disk for a FAQ that I'm writing. For example, 600MB 5.25"
disks have 576999 sectors of 512 bytes. 640MB 3.5" disks have 310352 sectors
of 2048 bytes. I need this info for all other types of 5.25" MO disks.

-- Mark
Received on Sun Mar 21 1999 - 14:29:17 GMT

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