Brother DCP-9055CDN Basic User's Manual page 76

e
Clean the corona wire inside the drum
unit by gently sliding the green tab from
left to right and right to left several times.
1
Note
Be sure to return the tab to the home
position (a) (1). If you do not, printed
pages may have a vertical stripe.
68
f
Close the corona wire cover.
g
Repeat steps d to f to clean each of
three remaining corona wires.