C4 Maintenance  10. Joint #6 
 
140  C Series Maintenance Manual Rev.2 
10.2  Joint #6 - Replacing the Reduction Gear Unit 
 
Removal: Joint #6 Reduction gear unit 
1.  Turn OFF the Controller power. 
2.  Remove the Arm #4 side cover. 
For details, refer to C4 Maintenance: 3. Covers. 
3.  Remove the Joint #5 motor unit and the reduction gear unit. 
For details, refer to C4 Maintenance: 9.2 Joint #5 – Replacing the Motor, Installation steps (3) through 
(11). 
4.  Remove the O-ring on the installation surface of the Arm #4 and #5. 
The O-ring of the Arm #4 is on the Arm #4 plate which was removed 
in the step (4). 
For the O-ring of the Arm #5, see the photo on the right. 
 
The O-ring will be used again.    Be careful not to lose it. 
5.  Remove the Joint #6 flange. 
Hexagon socket head cap bolts: 7-M3×6 
 
   
  Name  Quantity
Note 
Maintenance 
Joint #6 reduction gear unit  1  1539261 
Tools 
Hexagonal 
wrench 
width across flats: 1.5 mm 
1 
For M3 hexagon socket set screws 
For M2 hexagon socket head cap bolts 
For M2.5 hexagon socket head cap bolts 
width across flats: 2.5 mm 
For M3 hexagon socket head cap bolts 
For M4 hexagon socket head cap bolts 
Wrench 
For belt tension adjustment