First, make sure that the SCSI ID selector cable (a bundle of about 7 colored wires) are connected between the inner tray and the hard drive itself).
Second, check jumper settings. Here's what we've found works. If you pull the drive tray out, you can slide the bottom cover off and see the circuit board on the Quantum drive. Toward the front of the drivem, you'll see a row of about 14 pairs of gold colored pins, two pairs have black jumpers on them. Simply remove the jumpers, and slide the cover back on. Reinsert the tray & the MX should automatically boot & mount the drive. At this point you should be able to initialize that SCSI ID as HFS+.