Commonly caused by High voltage discharge or arcing from a dirty primary charger corona and grid.|
You need to clean your drum unit.
Open the front door and pull out the Drum unit.
Look on top of it for a small (usually) blue slider, sitting in a 10mm slot that runs the length of the Drum unit. This is the corona cleaner.
Slide this back and forth about 6 times, ensuring you return it to the original starting position.
Reinstall the Drum unit and try printing.....