Brother HL-1070 Service Manual page 72

I-4
Possible cause
Corona failure
Harness
connection
H.V. power
supply PCB
Ditto
Main PCB
Driver PCB
Download Free Service Manual and Resetter Printer at http://printer1.blogspot.com
All black
Step
1 Is the corona wire of the drum
unit broken?
2 Are the electric terminal
springs in the printer body and
the electrode on the bottom
face of the drum unit dirty?
3 Is the scanner unit connected
with the driver PCB correctly?
4 Is the problem solved after
H.V. power supply PCB
replaced?
5 Perform the same check as in
step 3.
6 Is the problem solved after
main PCB replaced?
7 Is the problem solved after
driver PCB replaced?
Check Result
Yes
Yes
Yes
Yes
No
Yes
Yes
IV-8
Remedy
Replace the drum
unit.
Clean the terminals
in the printer and on
the drum.
Check the harness
connection between
the scanner unit and
the driver PCB.
Replace the H.V.
power supply PCB.
Replace the panel
sensor PCB.
Replace the main
PCB.
Replace the driver
PCB.
HV.GND
contacts
(Fig.4-5)