Epson Equity 320SX PLUS - Manual (Page 151)

6. Locate the hard disk drive ribbon cable that you removed
from the drive in the vertical mounting position. Follow
the instructions below to attach the connector in the
middle of this cable to the horizontal hard disk drive.
As shown below, there are two rows of holes in the
connector. One of the holes is blocked with a plastic
Plug-
Notice the ribbon cable socket on the back of the drive;
you see two rows of pins. In one of the rows, a pin is
missing.
Installing and Removing Disk Drives 7-23