As far as I know, it hasn't had the click of death. The thing is, the same Zip disks that won't read in my SCSI Zip drive on the Centris *will* read in my USB Zip drive on my other Mac.

Both the drives and disk are old. Must be late 90s. I'm amazed they worked this long. 

Tomorrow a friend is coming over with an external SCSI drive. We'll see if we can get OS 7.6 copied to it from the Centris, and reinstall the OS on the 475.