Epson EQUITY 3865X/20 PLUS - Manual (Page 173)

2. Next, locate the hard disk drive ribbon cable that came with
your computer. If you removed a drive from the vertical
mounting position, the cable you disconnected from that
drive should be strapped to the bottom of the subassembly
by a tie wrap. Cut the tie wrap so you can access the
connectors.
The hard disk drive ribbon cable has three connectors. The
connector on one end goes to the system board. The other
two connectors (closest together) go to the hard disk drives.
Of these two connectors, you attach the middle one to the
hard disk drive in the vertical position and you attach the
end one to a hard disk drive in the lower horizontal bay.
As shown in the illustration below, there are two rows of
holes in a hard disk drive connector. One of the holes is
blocked with a plastic plug.
blocked hole
3. Notice the ribbon cable socket on the back of the drive you
just installed; you see two rows of pins. In one of the rows, a
pin is missing.
Installing and Removing Disk Drives
7-29