Epson Apex-80 - Manual (Page 132)

7. Disconnect the other end of the flat control panel cable from the
main circuit board connector. See Figure E-2.
Figure E-2.
Disconnecting the control panel cable
After you remove the case, follow the instructions below to insert the
interface board. After you have inserted the board, replace the case by
reversing steps 2 through 7.
E-4
Choosing and Setting Up Optional Interfaces