Brother HL-1070 - B/W Laser Printer Service Manual page 78

I-15 Black spots
Possible cause Step
Drum unit 1
Fixing unit 2
SR PCB 3
Note: Clean the drum unit as follows:
(1) Place the printing samples in front of the process unit, and find the exact
(2) Turn the drum gear by finger 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?
And the problem is not solved
after printing a few pages.
Is the problem solved after the
SR PCB replaced?
portion of image defect.
Position of smudge on
the drum
Fig. 4.2
Fig. 4.3
Result
Yes
Yes
Yes
94mm interval
IV-14
Remedy
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.)
Check and clean the heat roller
with a cloth dampened with
alcohol.
Replace the fixing unit.
Replace the SR PCB.