Black lines down the page.

Printed pages have toner stains down the page.

Check the following points to resolve the issue:

• Clean the corona wire inside the drum unit by sliding the green tab.
  > Click here to see how to clean the corona wire of the drum unit.
   
• Make sure the green tab of the corona wire is in the Home position (1).
  
• The drum unit may be damaged. Replace the drum unit with a new drum unit.
  > Click here to see how to replace the drum unit.
   
• The fuser unit may be contaminated. Contact Brother Customer Service from the "Contact Us" section.