Please check the following points:

• Make sure that the drum unit is installed properly.
  
  
• Make sure that the belt unit is installed properly.
  
  
• Make sure that the waste toner box is installed properly.
  
  
• Perform the auto color registration or manual color registration by using the control panel.
  To see how to perform the color registration, click here.
  
  If the color mis-registration is not corrected after registering the color manually, take all the toner cartridges out of the drum unit and turn the drum unit over, then make sure that four drum unit gears are in the home position. The home position of each drum can be identified by matching the number on the drum unit gear to the same number on the side of the drum unit as shown in the illustration.
  
  
  

• Put in a new drum unit.
  To see how to replace the drum unit, click here.
  
  

• Put in a new belt unit.
  To see how to replace the belt unit, click here.