Brother DCP-L8400CDN Basic User's Manual page 62

e
Clean the corona wire inside the drum
unit by gently sliding the blue tab from
left to right and right to left several times.
IMPORTANT
Be sure to return the tab to the home
position (1). If you do not, printed pages
may have a vertical stripe.
1
f
Repeat step e to clean each of the
three remaining corona wires.
54
g
Unpack the new toner cartridge, then
pull off the protective cover.