I've had similar problems both on my Amiga 2500 and PC's. I took out the boards and cleaned all the contacts with contact cleaner, as well as all the plug-ins, blew out all the dust from the innards, put things together and the HDs worked like a charm. If you hear the drives running, this could be a fix. I have been running my 2500 daily since 1992 and haven't yet had to replace one of its drives (3 scsi drives totalling 1 gig).
