Brother HL-7050N - Manual (Page 167)

5 - 18 ROUTINE MAINTENANCE
HL7050_US_UG_FM5.5
4 Clean the Primary Corona Wire inside the drum unit by gently
sliding the blue tab from right to left several times.
Figure 5-24
5 Put the drum unit assembly back in the printer.
6 Close the top cover.
7 Plug the printer power cord back in, and then turn the printer
power switch back on.
Make sure to return the tab to the Home position. If you do
not, printed pages will have a black vertical stripe.
Home Position
( )