Hard drive for PERQ on EBAY?

The PERQ 1's hard disk is a Shugart SA4000, normally a 24 Mbyte one, although I am told some machines only had 12 Mbytes. I have the schematics for this drive, and it's possible to repair electronic faults -- all PCBs can be removed without a cleanroom [1], and you can then use normal methods to repair them. Mechanical problems are, alas, more common. Top of the list is problems with te spindle drive belt which can be replaced if you can find a suitable replamcement. I guees head/disk problems can occur, but you do then need a cleanroom. Oh, and _please_ fit the locking clip to the positioner and the screw to the spindle before moving the machine. If you don't you can do serious damage to the drive! [1] This is not always the case!. The PERQ 2T1 uses a Micropolis 1200 8" drive. You can remove the control logic board and the motor board (analogue board, basically), and of course the ICL-designed DIB (Disk Interface Board) with no problems, but don't remove the pre-amp board under the screening cover (you can remove the cover). It forms part of the HDA casing -- the head cables are connected to the back of it, it's mounted over a hole in the casting. The 3 ICs -- all custom -- on this board are socketed so you can replace those if they fail, and AFAIK there's nothing else on the board. Incidentally, there's a Schrader (?spell) valve on the HDA casing of Micropolis 1200 drive. It looks like a car tyre valve, and has a dust cap on the end. Does anyone know what it's there for? The HDA is not hermetically sealeed (there'e a breather filter) so it can't be to presurise the HDA or anything like that. -tony