Epson LQ-850 User Manual page 149

Interface Boards
3. Fit the interface board under the built-in tractor as shown in the
illustration. Next, carefully insert the pins on the optional
interface board into the mating connector on the main board.
Secure the board with the screws provided.
4. Attach the plug end of the FG wire onto the FG pin located on
top of the interface board.
5. Reassemble the printer, taking care not to pinch the FG wire
between the upper and lower sections of the case.
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