Allison, Well hats off to you, it worked! I have now fixed the faulty internals of the two faulty Micropolis hard drives by teasing out the black gooey mass that use to be the head park rebound bumper / end stops for each drive. They had turned into a black sticky mush and as you correctly identified were holding the heads from un-parking. However one of the logic board has also gone faulty so if anyone has a spare faulty drive they would be willing to part with the hopefully working bottom logic board please contact me. Drive type: Micropolis 1355 ESDI 5 1/4 full height (144 MB) Part no. 900568-11-4a Faulty PCB part number: 101942-04-3 B2 Eprom fitted: 800140-03-0 (But this is just for ref) Many thanks, Andy.