Xerox 5550 用户指南

There are dark spots or marks that appear in a random pattern on the page. 

The paper path may be contaminated with toner.

Print several blank sheets of paper to remove the 
toner accumulations.

The drum cartridge may be defective.

Replace the drum cartridge.

The fuser may be defective.

Replace the fuser (in the maintenance kit).

The transfer roller may be defective.

Replace the transfer roller (in the maintenance 
kit).