Konica Minolta bizhub C650 Service Manual page 763

18. Image quality problem
18.3.15 Printer monocolor: white lines in sub scan direction, white bands in sub
scan direction, colored lines colored bands in sub scan direction
A. Typical faulty images
White lines in sub
scan direction
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B. Troubleshooting procedure
Step Section
Image check A white line or black line in sub
1
scan direction is sharp.
When printing thick paper, black
2 lines appear.
Imaging unit The surface of the PC drum is
3
scratched.
4 Dirty on the outside.
Contact terminals make good con-
5 nection between each IU and
machine.
Developing bias contact terminal
6
makes good connection.
PH unit The surface of the PH window is
7
dirty.
The problem has been eliminated
8 through the checks of steps up to 7.
708
White bands in sub Colored lines in sub
scan direction
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Check item
Field Service Ver. 8.0 Jun. 2008
Colored bands in sub
scan direction scan direction
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Result Action
YES Clean the electrostatic charger wire.
YES Select [Service Mode] → [Machine]
→ [Thick Paper Mode] and set
[Image Quality].
YES Change imaging unit.
YES Clean.
NO Clean contact terminals.
NO Clean contact terminal and check ter-
minal position.
YES Clean with cleaning jig.
NO Change imaging unit.
→ Change image transfer belt unit.
→ Change PH unit.
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