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.
Step 2: Remove Baffle and Carriage
Remove the two outer screws. These screws hold the carriage to the cartridge shell. They are about an inch long.
Step 3: Take Off the Baffle
You can now remove the baffle. Be careful not to bend it or scratch the roller.
Step 4: Remove the Carriage
The carriage can now be rotated upward from its seat in order to slide the roller out of the cartridge. There is a layer of foam that helps to seat the carriage onto the cartridge. Work it loose gently.
Step 5: Remove the Carriage Cont'd
With the carriage rotated vertically, you can lift the assembly off of the cartridge. Set the assembly down with the carriage on the work surface. Keep the roller from touching anything.
Step 6: Remove the Blade
Under the carriage is a pair of plastic blades which feed the toner onto the roller and collect waste toner. The roller turns toward you, so the top blade is the one which causes the toner to be streaked. Grabbing the corners of the blade assembly, you can gently work it loose from its seat on the cartridge. There will be a lot of toner, so try to keep it from flying around too much.
Step 7: Remove Excess Toner
You can use a dry cotton swab to clean the toner out of the inside of the blade assembly.
Step 8: Remove Excess Toner Cont'd
Once you've got most of the toner off of the blade assembly, you can blow off any excess with some compressed air. Don't use your mouth, you'll spit on it.
Step 9: The Culprit
In this photo you can see the plastic blade. You can see a thin line toward the bottom of the blade where it touches the roller... this is a toner deposit. You need to get rid of it.
Step 10: Cleaning the Blade
Using 91% rubbing alcohol on cotton swabs to clean off the deposits. This takes a little pressure, some vigorous back-and-forth, and a bit of patience to get the deposits to let go of the blade. You can a magnifying glass to double check that all of the toner has been cleaned from the blade. It's important not to scratch the blade so don't scrape it with a screwdriver or something. It may also help to keep the blade flat on the table, in order to prevent bending of the blade.
Step 11: Reassemble & Tips
To reassemble, reverse the procedure. First, be sure the blade is completely dry of alcohol. When replacing the blade, be sure it is fully seated against the foam. You can push down the top of the blade holder (the metal piece) to make sure it is completely seated, as shown.
Be sure that the carriage is fully pressed against the blade assembly when you replace the screws. The blade assembly must be properly seated or you will get faded areas where the toner is not evenly applied to the roller. Don't tighten the baffle screws down all the way until they are all partially replaced. Don't apply too much pressure to the inside 5 screws on the baffle when tightening. Once you've got everything back together, you can use your thumbs to cycle the roller toward you. If you missed any deposits, you'll see streaks in the toner. If the blade isn't fully seated, you may see clear areas on the roller, in which case, you'll need to remove the carriage and reseat the blade assembly.