Brother HL-1070 - B/W Laser Printer Service Manual page 82

I-20 Horizontal lines
Possible cause Step
SR electrode 1
SR connection 2
failure
Feed roller 3
I-21 Light rain
Possible cause Step
Drum unit failure 1
SR PCB failure 2
High-voltage 3
power supply
PCB failure
**Note: Make sure to use the used drum unit which has already ejected the starter
sheet. It is not possible to find the drum unit failure if you use a new drum unit
with the starter sheet.
Check
Are the SR electrodes between
the printer body and the drum
unit dirty?
Are the SR electrodes between
the printer body and the drum
unit connected correctly?
Are the feed roller shaft and
the ground contact connected
correctly?
Note: Make the printer in the light rain test mode as follows before
checking;
1. Turn on the power switch and open the top cover.
2. Hold down the panel switch until all the lamps are on, and
then release the switch.
Check
Is the problem solved after
replacing the drum unit which
contains no more starter
sheet**?
Is the problem solved after
replacing the SR PCB?
Is the problem solved after
replacing the High-voltage
power supply PCB?
IV-18
Result Remedy
Yes Clean both
electrodes.
No Check the SR
connection.
No Check the
connection between
the shaft and the
ground contact.
Result Remedy
Yes Replace the drum unit.
Yes Replace the SR PCB.
Yes Replace the High-voltage
power supply PCB.
HV.GND
contacts
(Fig.4-5,
4-6)