Brother MFC-B7720DN Service Manual

2-90
Confidential
 Horizontal stripes
 White vertical streaks on image
<User Check>
• This problem may disappear after printing multiple sheets of paper.
• Refer to <How to clean the drum unit> to remove the dirt from the
exposure drum using a cotton applicator.
• Replace the drum unit with a new one.
• Replace the toner cartridge with a new one.
Step Cause Remedy
1
Dirty charge electrodes Clean the electrodes of the drum unit and
those of the machine. (Refer to Fig. 2-13 (P2-
56) and Fig. 2-12 (P2-56).)
2
Dirt on the exposure drum Perform drum cleaning.
(Refer to “2.1 Drum Cleaning” in Chapter 5.)
3
A ground wire or ground plate
installation failure (Grounding
is not performed correctly.)
Retighten the screws of each ground wire or
ground plate. Repair the bend of the tray
ground spring of the paper tray.
(Refer to Fig. 2-18 (P2-89).)
4
Scratch or dirt on the fuser
unit
Replace the fuser unit.
5
High-voltage power supply
PCB failure
Replace the high-voltage power supply PCB
ASSY.
<User Check>
• Check that there is no dust on the toner cartridge.
• Refer to <How to clean the drum unit> to remove the dirt from the
exposure drum using a cotton applicator.
• Replace the drum unit with a new one.
• Replace the toner cartridge with a new one.
Step Cause Remedy
1
Dirt on the exposure drum Perform drum cleaning.
(Refer to “2.1 Drum Cleaning” in Chapter 5.)
2 Laser unit failure Replace the laser unit.

Brother MFC-B7720DN Specifications

General

Brand	Brother
Model	MFC-B7720DN
Category	All in One Printer
Language	English