Improve print quality

Try cleaning the drum cylinder with alcohol and a cotton ball. Then swipe the corona wire cleaner back and forward making sure to return it to the correct place. Try a print. If it is improved - replace the drum at earliest convenience. If not improved - could be dirty laser lenses or problem with the fuser.

The drum is the part of the printer that the image of what you want to print is stored on by a laser drawing on that drum. That drum is then charged with an electrostatic shock that will draw up toner particles from your toner tray that will eventually be transferred to a piece of paper that will be heated to fuse the ink particles on the paper. That drum is photo sensitive and eventually looses its ability to be charged. You will then have to replace that drum.

How to Change a Toner Cart in a Brother HL 2040

The Brother HL 2040 laser printer has a toner cartridge that supplies toner to the drum assembly so that the printer can print properly. When the LED on the front of the printer indicates you are low on toner, you will need to replace the toner cartridge to maintain good print quality. Fortunately, the toner cartridge can be replaced without any special tools.

Instructions
Things You'll Need:

* Replacement toner cartridge (part number TN350 or TN360)
* Paper towel or scrap paper



Grasp the front cover of the printer and pull it toward you to open the toner door. Reach into the printer and grab the combined toner cartridge/drum assembly. Lift up slightly and pull it out of the front of the printer.

Place the cartridge and drum on a paper towel, spare sheet of paper, rag or other surface that can get dirty. Loose toner particles may spill from the cartridge.

Press the blue locking lever on the cartridge/drum unit to unlock the toner cartridge from the drum. Lift the toner cartridge up and away from the drum unit. Dispose of the old toner cartridge in accordance with your local regulations. Seal it in a plastic bag to keep loose toner from spilling.



Gently shake your new toner cartridge back and forth a few times to distribute the toner evenly across the width of the cartridge. Remove the plastic protective cover from the bottom of the cartridge.


Place the new toner cartridge onto the drum unit and press it down gently until it locks into place. The blue locking lever will automatically click into place. Verify that the toner cartridge is securely connected to the drum.


Locate the corona wire cleaner tab at the front of the drum unit. Slide it back and forth several times to improve the print quality of the drum. Set the tab back in the home position when finished.


Slide the combined toner cartridge/drum unit back into the printer and close the front cover.


Hope it helps...

It sounds like your print heads may need cleaning. However, here is the link from Brother support for your MFC-5890CN on how to improve print quality:

Brother MFC 5890 Print Quality

Try cleaning the black printer heads several times in a row, at least 5 times then print a black document with best quality setting.
Press the ink button, then down to select select cleaning and then press menu/set and menu/set again to select black.

your laser printer
1) print color quality is now distorted that means print skew (technician called)
2) print tint means the print color not enough density,
3) print mottle means print dirty
you may try
1) print distorted--- find out the skew adjustment from your printer manu, it is adjust the image before transfer to the drum.
2) print skew could be happened when the drum replace install not very accurate, so install it more carefully.
3) print tint---you may increase print density from the manu, not fix,
4) print tint---the toner caridge near life cycle or using the less compatible toner. so you have change the quality toner or cartridge (if near life cycle) to improve quality photo print
5）print mottle---toner quality ? or cartridge near life cycle also cause print dirty paper,

We were having a lot of print quality problems, similar to what you describe. We replaced the drum and it worked fine.

How do I clean white or black spots on printed documents? Description: First make 10 to 15 copies of a blank, white sheet of paper.
If you still see the spots on printed documents after making multiple copies, clean the drum unit as follows:

1. Remove the drum unit and toner cartridge assembly, and then remove the toner cartridge from the drum unit.
   
2. Position the print sample in front of the drum unit so you will know the exact position on the drum that is causing the poor print.
   

3. Turn the black gear on the drum as you check the surface of the OPC drum.
   The OPC drum is photosensitive so do not touch it with your fingers.
   

4. When you find the substance on the drum surface that matches the print sample, gently dab the surface of the OPC drum with a cotton swab that is lightly dampened with isopropyl alcohol.
   
Note
• Do not use a scrubbing or wiping motion because this might damage the drum.
  
• Do not try to clean the surface of the OPC drum with a sharp object, such as a ball-point pen, because this might cause permanent damage to the drum unit.
5. If the print quality still has not improved you need to install a new drum.
   

beware of generic toner!
you may need to change out your drum unit
the drum unit may have been contaminated by the staples toner.
also clean laser window under drum cartridge.

I have seen the Toner cartridge in these cause this and also thought it was drum but new toner actually fixes it, have you installed new gen toner as well as drum? Make sure you tell machine you have fitted new drum too,