Brother DCP-7090 Service Manual page 132

 White spots on image
<User Check>
Step
Dirt on the paper dust
1 cleaning roller of the paper
tray
Dirt on the exposure drum
2
3 Clogged filter
Scratch or dirt on the fuser
4
unit
High-voltage power supply
5
PCB failure
Note:
Image defects which appear periodically may be caused by failure of rollers. Refer to the
table below and determine the cause based on the pitch at which defects appear on the
image.
<Pitches on images caused by rollers>
Part name
Develop roller
Exposure drum
Heat roller of the fuser unit
Pressure roller of the fuser unit
< Examples of image distortion >
White dots repeat in A mm distance on
the black page with printed images.
Refer to the <Pitches on images caused by rollers> table above for what represents the value A.
• Check that the fan is not clogged.
• Refer to <How to clean the drum unit>
exposure drum using a cotton applicator.
• Replace the drum unit with a new one.
• Replace the toner cartridge with a new one.
Cause
A mm
A mm
Fig. 2-19
2-92
to remove the dirt from the
Remedy
Refer to the Fig. 2-14 (P2-73)
paper dust cleaning roller.
Perform drum cleaning.
(Refer to "2.1 Drum Cleaning" in Chapter
Clean the filter.
Replace the fuser unit.
Replace the high-voltage power supply PCB
ASSY.
The pitch which
appears in the image
26.5 mm
94.5 mm
78.5 mm
78.5 mm
Black dots repeat in A mm
distance on the page.
to clean the
5.)
A mm
A mm
Confidential