Brother HLL3290CDW Service Manual page 167

(2) Turn the drum unit gear by hand so that the glued exposure drum surface comes to the
front.
(3) If the position of the dirt on the drum and the dots on the print sample matches, wipe the
exposure drum surface with a cotton bud until the dirt and paper dust comes off.
Note:
Do not clean the exposure drum surface with anything sharp like a ball pointed pen.
Fig. 2-21
Fig. 2-22
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Confidential