jhune, it was the DRIVE which was broken. I have plenty of DD disks. And by the way, the hole is in the HD disks, not DD. These have different magnetic characteristics and MAY not work properly in all DD drives. It apparently needs a stronger field to write than DD disks, and not all DD drives can provide it

The Roland controller will only work with a specific model of drive which is no longer available.

I DO have an address of someone who can recondition the drives, but I have also bought a coulpe of second-hand SD35's now, so problem solved.