Epson EL 486UC - Manual (Page 83)

2. Locate the hard disk drive connector on the system board.
pin 1
Position the system board connector on the cable so that the
red wire aligns with pin 1 of the connector on the system
board. There is a “1” printed on the system board to
identify pin 1.
Make sure the holes in the cable connector fit over the pins
in the system board connector; then push in the cable
connector.
Caution
If you do not correctly align the holes with the pins, you
could severely damage your system board when you push
in the cable connector.
Installing and Removing Drives 5-5