9810-03X
Streaks that are parallel to the direction of feed appear in the printout
The corona assembly wires inside the main unit are dirty. Clean the wires.
← Feeding Direction
Remedy
Clean the corona assembly wires inside the main unit several times.
Press 
→ [Adjustment/Maintenance] → [Maintenance] → [Clean Wire].
→ [Adjustment/Maintenance] → [Maintenance] → [Clean Wire].
"Maintenance" > "Routine Cleaning" > "Clean Wire" in the User's Guide