Disconnect the following connectors from the logic board:

Camera/IR board cable.

Optical drive fan.

When removing the optical drive fan connector, it is helpful to use a spudger or your fingernails to push the ears on either side of the connector toward the top edge of the iMac.

To aid in removing the camera/IR board connector, it is helpful to use one hand to pinch the cables against a spudger and pull up toward the top edge of the iMac while pulling up gently on the cables with your other hand.