Brother HL-4000CN Service Manual page 289

<All black>
Fig.5-22
Condition:
Print is wholly black.
Initial check:
Parts of different specifications, improper installation, damage, deformation, dirt, foreign
substance attached, etc.
Major parts to be checked:
Print head cartridge ASSY, Fuser ASSY, Transfer roll cartridge ASSY, Scanner ASSY,
MCU and HVPS PWB
Item Check
Faulty transfer
1 Is the image quality improved if the laser beam exit
window of scanner ASSY is shielded with a sheet?
Faulty scanner ASSY
2 Is the image quality improved if scanner ASSY is
replaced?
Faulty print head cartridge ASSY
3 Is the image quality improved if print head cartridge
ASSY is replaced?
V-79
Remedy
Replace the MCU and
HVPS PWB
Replace the scanner
ASSY
Replace the print head
cartridge ASSY