The waste toner collector is now separate from the rest of the belt and its rollers.

A closer inspection is now possible to identify the cause of the quality problems. Two different faults have been observed on the three units repaired so far.

In one case, the plastic wiper blade in the toner collection unit had a very visible kink. Replacement blades are available from Aliexpress. Fitting is a matter of releasing the two retaining springs and sliding the new wiper blade into place under the plastic Archimedes screw.

In two other cases, closer inspection of the belt shows a roughness as it passes over the roller that was pressing against the wiper blade. The close up view in the second picture shows this roughness. The remainder of this guide covers the repair of that fault.