Epson 386/25 - Manual (Page 213)

Installing the Drive
Follow these steps to install the hard disk drive in the vertical
mounting position:
1. Locate the hard disk drive ribbon cable that came in the box
with your computer. It is a flat cable with three connectors
on it (one on each end and one in the middle).
Use the connector in the middle of the cable. As shown
below, there are two rows of holes in the end of the
connector. One of the holes is blocked with a plug.
The ribbon cable socket on the back of the drive has two
rows of pins. In one of the rows, a pin is missing.
ribbon cable connector
blocked hole
ribbon cable socket
missing pin
lnstalling and Removing Disk Drives B-13