Troubleshooting Image Defects - Brother HL-1070 - B/W Laser Printer Service Manual

3.2

Troubleshooting Image Defects

The following procedures should be followed in the event of specific image defects.
See subsection 3.3 for information about the location of the high-voltage contacts and
grounding contacts.
I-1 Light
Possible cause Step
Density dial 1
Toner sensing 2
failure
(printer side)
Toner sensing 3
failure
(toner cartridge
side)
Drum 4
connection
failure
High-voltage 5
power supply
PCB failure
Driver PCB or 6
main PCB
failure
Scanner unit 7
failure
Check
Is the density dial in the center
of the click position?
Can printing be started with the
drum unit removed?
Is the problem solved when 4
or 5 pages are printed after the
toner cartridge is replaced with
a full one?
Is all the contacts (HV, GND)
connected with electrode when
the drum unit is installed?
Check the harness connection
between the high-voltage
power supply PCB and the
driver PCB.
Perform the same check as
step 5 above and also between
the driver PCB and the main
PCB.
Is the problem solved by
repealing the scanner unit?
IV-5
Result Remedy
No Set it to the center
detect position.
Yes Toner sensor failure.
Check if the toner
sensor needs
cleaning and check
the toner sensor
connection.
Yes The wiper of the
toner cartridge is
defective.
Replace the toner
cartridge.
No Clean contact
electrodes both in the
printer body and on
the drum unit.
No If the connection is
normal, replace the
high-voltage power
supply PCB.
No Replace the driver
PCB or the main
PCB.
Yes Replace the scanner
unit.
HV.GND
contacts
(Fig.4-5)