Epson LQ-510 User Manual page 161

Installing the board
There are two basic interface board designs-one with the FG wire
not attached and one with the FG wire attached. This slight
difference changes the way the boards are installed in the printer
but does not affect the operation of the interface in any way. Check
to see which type of interface board you have.
FG wire not attached
See below
FG wire not attached
1. Use the CG screw to attach the round end of the FG (frame
ground) wire to the main board and position the other end as
shown.
FG wire attached
Skip to page 5-39
Using the Printer Options
The Interface Boards
5-37