Right, I scavenged an internal IDE Zip100 drive from Freecycle 
I've popped the front of it, however can't see any way to get the top of so that I can get the little spring out - is there any way to get further inside it. I'm sure this is never going to work, there's probably something much more fundamentally wrong with the SCSI one as well, but it's worth a try I guess It would be so much easier if I could just find a SCSI one that worked in the first place (and preferably a 250 MB one as I have a parallel one of those and 6 Zip250 discs from a previous Freecycle pickup a while back), but life's never easy is it? 
I've popped the front of it, however can't see any way to get the top of so that I can get the little spring out - is there any way to get further inside it. I'm sure this is never going to work, there's probably something much more fundamentally wrong with the SCSI one as well, but it's worth a try I guess It would be so much easier if I could just find a SCSI one that worked in the first place (and preferably a 250 MB one as I have a parallel one of those and 6 Zip250 discs from a previous Freecycle pickup a while back), but life's never easy is it?