Unscrew 1 screw on FPC, unsolder 4 joints of relays.

Unscrew 3 screws.

Unscrew 1 screw on FPC, unsolder 4 joints of optocoupler. Be aware the ring and ring position points by arrows. It's easy to fall off, so I keep it as the last step, after completely remove FPC, install the new one immediately.

There are some plastic pads stick on old FPC, remove and install them on the new FPC.