I finally went and bought myself a PEB, listed as untested, and complete with RS-232, Disk Controller, and 32K cards. And as seems to be usual with untested systems, it doesn't work. (at least not entirely)
I typed in the following program listed in the Disk Memory System manual, in order to test the drive:
100 OPEN #1:"DSK1.X" 110 CLOSE #1
The LED on the controller lit up for a fraction of a second, but the drive itself was lifeless, with me getting an I/O ERROR 00. The manual, however, says that I should normally get an I/O ERROR 06, and that 00 means that the drive could not be found.
For what it's worth, the drive spins up when the PEB is first powered on, and the LED on the drive lights up when shutting it off.
Where should I start with troubleshooting this?
(BTW, I thought that members here were exaggerating about how loud the PEB's fan is; turns out it really is that loud )