Canon imageRUNNER ADVANCE 8105 Series Manual page 85

b) The area [a] of the primary charging assembly downstream duct
Toner was attached to dust which adheres to the area [a] of the duct, and the drum was rubbed against the
dust, causing the symptom.
c) The area [a] of the developing assembly sleeve cover
Toner was attached to dust which adheres to the area [a] of the sleeve cover, and the drum was rubbed
against the dust, causing the symptom.
pg. 85