Thanks for the replies. Yes the drive is known to be working fine. In fact its formatted. But I cant get beyond the initial install screens as it says drive not supported.

It spins up etc, and I can put it in an external SCSI drive box and see

it OK on another Mac.

I also have an Apple drive, but unfortunately I completely messed this up by - removing the speaker from the LC II to check it (sound had gone flakey) - the magnet in the speaker then attached to the drive (very briefly) after than the drive was completely dead. Hey ho.

It seems the 7.5 installer must have an Apple drive for some reason.