Brother HL-820 Service Manual page 83

I-17 Gray background
Possible cause Step
Print paper 1
Drum unit 2
Note: The following cases increase the possibility of this problem.
1) The drum unit is at the end of its life.
2) There is dust or paper powder.
3) A large amount of paper whose width is narrower than A4 is printed.
4) Acid paper is being used.
I-18 Hollow print
Possible cause Step
Print paper 1
Note:
This problem may appear on the first 10 to 20 pages immediately
after replacing the toner cartridge.
Check
Does the paper being used
meet the paper specification
(weight, etc.).
Is the problem solved after
replacing the drum unit?
Check
Is thick paper of more than
42lb being used or extremely
rough surface paper?
IV-16
Result Remedy
No Recommend to change the
paper to a specified type of the
paper.
Yes Recommend to change the
paper to a fresh pack paper.
Yes Replace the drum unit.
No Replace the high-voltage
power supply PCB.
Result Remedy
Yes Recommend to use the
specified type of paper.
No Refer and compare with I-14.