Brother HL-820 Service Manual page 81

I-15 Black spots
Possible cause Step
Drum unit 1
Fixing unit 2
High-voltage 3
power supply
PCB
Note: Clean the drum unit as follows:
(1) Place the printing samples in front of the process unit, and find the exact
position of the image defect.
(2) Turn the drum gear by hand while looking at the surface of the OPC drum.
Check
Are the spots at 94mm
intervals?
The problem is not solved after
printing a few pages.
Are the spots at 63mm
intervals?
The problem is not solved after
printing a few pages.
Is the problem solved after the
high-voltage power supply
PCB is replaced?
Position of smudge on
the drum
94mm interval
Fig. 4-2
Fig. 4-3
IV-14
Result Remedy
Yes If toner remains stuck, wipe it
off gently with a cotton swab.
Replace the drum unit if the
OPC drum is scratched or
deteriorated (exposed).
(Refer to the following note.)
Yes Check and clean the heat roller
with a cloth dampened with
alcohol.
Replace the fixing unit.
Yes Replace the high-voltage
power supply PCB.