Epson EQUITY 386/33 PLUS - Manual (Page 142)

The controller displays one of the following messages when an
error occurs during a diagnostics procedure:
Address mark not found
Attachment
failed to respond
Bad ECC on disk read
Bad sector flag detected
Controller has failed
Drive activity failed
ECC corrected data error
Requested sector not found
Reset failed
Seek operation failed
Write fault on selected drive
If you see one of these error messages, check the drive,
controller, cables, and power connectors. If you still get an
error, contact your dealer.
Floppy Disk Diagnostics
Floppy disk diagnostic tests may be destructive or
non-destructive. Destructive diagnostics destroy data on the
diskette, but non-destructive diagnostics do not. The following
table lists which tests are destructive and which are not.
Destructive tests Non-destructive tests
Diskette format
Random R(ead/W(rite)
Sequential R(ead/W(rite)
Drive speed
Drive change line
B-20 Performing System Diagnostics