Canon imageRUNNER ADVANCE C5255 Series Service Manual page 1089

12) Check that the 8 LED light-receiving areas of the Drum Unit are not off from the base.
9
Installation > Installation Procedure > Installing the Drum Unit
13)
CAUTION:
Check that there is no gap between [A] the host machine and the Process Unit, and
then secure with the screw.
F-9-38
9 Installation > Installation Procedure > Installing the Drum Unit
Put the Process Unit back to the host machine, and secure with the 2 screws.
[A]
9-19
[A]
F-9-39
9-19