OK, there are several things that could be wrong.
1) address of the drive
2) dead drives.
In the first case, try all the addresses unles you have a better way :-)
In the latter case, open up the unit, remove one of the drives, and tale off the cover. Check that the head(s) (9121 = 1 head) are still intact, and are not bent (problems with sticky lubricant on the drive can lead to the head being beny to completely ripped off).
If it's OK, run a head cleaning (wet type) through the drive for a while. This has resurected one drive of mine. It would get a few tracks through formatting, then give up.
Bent heads (and it's the top head on double sided drives) can be fixed bt carefully undoing parts of the drive that hold the head in place, swinging the head assembly into place, then carefully bending the head back. Then the almost impossible task of putting the drive back together starts -- it _is_ possible (just bloody difficult). You may never get the head aligned correctly again, but the drive may work. I have fixed one drive like this too.
If you've got bent heads (or the early symptoms - disks that don't eject easily) then you need to do something about the lubricant so that the problem doesn't get worse or recurr. This is just a case of carefully removing all the stivky lubricant (on only one side of the drive) and then lightly lubricating it with light oil or some similar lubricant.
Of course the eectronics could be fried too... Oh dear :-(