Brother mfc8440 Service Manual page 246

I-5 Dirt on the back of paper
Possible cause Step
Fixing unit dirty 1
Dirt in the drum 2
unit
NOTE:
This problem may disappear after printing approximately 10 pages of completely blank sheets.
How to clean the pressure roller
Clean the pressure roller as follows
(1) Set ten or more sheets of paper in the paper tray.
(2) Check the absence of paper in the ADF and on the scanner glass.
(3) Press Copy button to copy and repeat it five times.
(4) Check whether any stain are observed on the back of paper or not.
Check
Is the pressure roller dirty?
Is any other area in the
machine dirty?
Is the transfer roller dirty?
Is the problem solved after
replacing the drum unit?
6-39
MFC-8440/8840D/8840DN, DCP-8040/8045D/8045DN
Result Remedy
Clean the pressure roller
Yes
referring to the following
procedure.
Yes Replace the drum unit
No Replace the high-voltage power
supply PCB.
SERVICE MANUAL