Troubleshooting Image Defect - Brother MFC8440D Service Manual

7/13/2019
8.3

Troubleshooting Image Defect

Several types of the image defects can be cleared by end users. For those defects, instruct
the user to check the 'User Check' items described in each table. Even if the same image
defect appears, the following procedures should be followed in the event of specific image
defects.
See also subsection 8.4 'Location of Ground Contacts' in this Chapter
location of the grounding contacts.
!
CAUTION:
When using the machine for a special job, such as printing of name cards, print quality cannot
be guaranteed.
I-1 Light
Possible cause
Toner sensing
failure
(machine side)
Toner sensing
failure
(toner cartridge
side)
Drum
connection
failure
High-voltage
power supply
PCB failure
Engine PCB /
Main PCB
failure
Dirt on the
scanner window
Laser unit failure
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User Check
(1) Check the printer's environment. Conditions such as humidity, high
temperatures, etc. may cause this situation to occur.
(2) If the whole page is light, toner save mode may be on. Disable toner save mode
within Printer Properties tab of the driver.
(3) Try installing a new toner cartridge or drum unit.
Step Check
1 Can printing be started with the
drum unit and toner cartridge
removed?
2 Is the problem solved when 4
or 5 pages are printed after the
toner cartridge is replaced with
a full one?
3 Are all the contacts between
the drum unit and machine
connected correctly?
4 Is the harness connection
between the high-voltage
power supply PCB and the
engine PCB correct?
5 Is the harness connection
between the engine PCB and
the main PCB correct?
6 Is there any dirt on the scanner
window?
7 Is the problem solved after
replacing the laser unit?
Brother 8840D Service Manual
MFC-8440/8840D/8840DN, DCP-8040/8045D/8045DN
Result
Yes Check if the toner
sensor is dirty and
check the toner
sensor connection.
Yes The wiper of the toner
cartridge is defective.
Replace the toner
cartridge.
No Clean contact
electrodes both on the
drum unit and in the
machine.
Yes Replace the high-
voltage power supply
PCB.
Yes Replace the engine
PCB or the main PCB.
Yes Wipe it off with a soft
clean paper.
Yes Replace the laser unit.
6-35
SERVICE MANUAL
f o r information about the
Ground
Remedy
contacts
(1), (4),
(5), (6)
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