Brother MFC-7240 - Page 108

2-71
Confidential
 Black horizontal stripes
Fig. 2-12
<User Check>
- Clean inside the machine and the corona wire of the drum unit.
- When the horizontal stripes appear at intervals of 94.2 mm, replace
the drum unit with a new one.
- The paper tray earth spring on the machine side may be dirty. Clean
it with a dry cloth.
- Toner attached on the developer roller (horizontal stripes at intervals of 32.5 mm)
This problem will disappear by printing approximate 10 pages. If the same
problem occurs, replace the toner cartridge.
Step Cause Remedy
1
Dirt on electrodes of the drum unit
and those of the machine
Clean the electrodes of the drum unit and
those of the machine. (Refer to Fig. 2-10
and Fig. 2-11.)
2
Bend of tray earth spring (1)
Correct bending of the tray earth spring .
(2) Replace the paper tray.
3
Scratch or dirt on the heat roller
(horizontal stripes at intervals of 53.4 mm)
Replace the fuser unit.
4
High voltage power supply PCB failure Replace the high voltage power supply PCB ASSY.
5 Main PCB failure Replace the main PCB ASSY.
CAUTION:
• Image defects which appear periodically may be caused by failure of rollers. Refer to the table below and
determine the cause based on the diameter of the rollers or the pitch at which defects appear in the image.
No. Parts name Diameter
Pitch at which defects
appear in the image
1 Developer roller ø 16 mm 32.5 mm
2 Exposure drum ø 30 mm 94.2 mm
3 Heat roller in the fuser unit ø 17 mm 53.4 mm
4 Pressure roller in the fuser unit ø 25 mm 78.5 mm
Back of paper tray
Tray earth spring