Universal Robots UR3 Service Manual page 25

5. Service and Replacement of Parts
6. Gently unplug the cable connectors without bending the printed circuit board.
Some connectors have a lock that must be engaged before it is pulled out of the printed
circuit board. Example below.
7. After disconnecting the wires gently remove black flexible flat ring with a small flathead
screwdriver or similar tool and pull it back over joint housing away from its original
position.
Service Manual 19 UR3