I didn’t have to dig out the other 3.5″ enclosure after all — I switched to a USB connection, and suddenly the Mac can see the hard disk.  I can’t boot from it, though, so I’ve had to rerun all of the updates I’d made since I switched.  But my data is back.  For now, anyway.  With luck, I’ll have some time this weekend to do some better diagnosis.

I wanted to check some stuff on my Mac mini, but when I turned on the display, I was greeted by a black screen, and nothing I could do would provoke any activity.  I also couldn’t ping it, so I decided it had died.

After hunting for the power button, which I hadn’t used in a long time, I rebooted…to no avail.  So I dug out my copy of “The Missing Manual” and tried some of the exciting power-on keystrokes.  Apple-V gave me a very short bootup console log, ending with something about being unable to find something on /sbin.  So I tried again, this time with the Option keystroke to let me choose my boot device.

When I chose the built-in disk, all was well — it was even able to mount the disk in my expansion unit.  But I didn’t leave well enough alone, since I really wanted to boot my new disk; instead, I powered off, and then powered off the expansion unit.

When I tried to turn the unit back on, I didn’t see the blue power light.  But by wiggling the power cables, I got it to come up again…but not enough to boot.  So I went back to the built-in disk, and this time around, nothing I could do would mount the external disk.  I could, however, see a USB flash drive that I connected to the expansion unit, so it’s not completely dead.

At least there’s no unrecoverable data on the external disk (or, for that matter, the internal disk) — I hadn’t gotten around to moving anything critical to the Mac, just lots of media which would be tedious to recover.

I guess the next step is to dig out the 3.5-inch USB enclosure I decided not to put on craigslist and see if the disk is the culprit.  Feh.