Vertical streaking is a common complaint among owners of Lexmark C500 series color laser printers. This can be caused by a buildup of toner deposits inside the toner cartridges. It is possible to service these cartridges to wring some more life out of them.
First, prepare your work area. I put the cart down on a few paper towels, as you will be spilling a little toner. I also have 91% alcohol, some cotton swabs, and a small phillips head screwdriver.
Step 1: Remove the baffle
Hold the cartridge with the roller side up. You should be able to see where the streaks in the toner on the roller. The layer of toner should be as even and solid as possible.
First take the 5 inside screws off of the baffle. Be careful not to touch or scratch the roller. These screws are short. They hold the blade assembly to the underside of the carriage. Don't apply too much pressure to these screws.