J13 To disable the power-on password, move the J13 jumper to the unused position.
A Model 30 (no 286) is a machine equipped with an 8086 CPU and low density 3.5 inch floppy drive(s). It may have a hard disk, usually 20MB. Some high density floppy drives are supported by this computer, though IBM never officially built them this way.
A Model 30 (with the 286) is a 286 with 1 1.44MB floppy drive (I've never seen on without a hard disk. They may have been offered that way. Dunno.) The hard disk may be 20, 30 or 45MB in capacity.