3Pull the toner cartridge out and remove it from the printer..
4With a dry,
Note: To prevent damage to the toner cartridge, do not expose it to light for more than few minute. Cover it with a piece of paper, if necessary. Also, do not touch the black transfer roller inside the printer.
5Locate the long strip of glass (LSU) inside the top of the cartridge compartment, and gently swab the glass to see if dirt turns the white cotton black.