Canon BW Expansion Bus-C1 Service Manual page 16

Chapter 1
2) Unscrew 6 screws [1] and detach the upper rear cover [2].
3) Unscrew 4 screws [1] and detach the main controller box cover [2].
1-4
[1] [2]
F-1-3
[1]
[2]
[1]
F-1-4