It turns out that I have no system with a wide, single-ended SCSI controller, which is what the tape drive needs. I'd been planning to use a Sun system, but it doesn't have one (it's an Ultra 5, one of their first IDE-based systems). All of my other SCSI-based stuff is narrow, not wide. Grumble. I did have a spare wide SCSI adapter in thebrain, but when I stuffed it in the Sun, it didn't recognize it.
I've ordered the appropriate controller board, and it should arrive sometime next week. I've also got a box of tapes for the library coming in; those were supposed to arrive today, according to the seller, but they didn't. They'll most likely arrive Monday.
Oh well; at least I'll get to do it next weekend.