Brother HL-820 Service Manual page 84

I-19 Downward fogging of solid black
Possible cause Step
Drum unit 1
High-voltage 2
power supply
PCB
I-20 Horizontal lines
Possible cause Step
SR electrode 1
SR connection 2
failure
Feed roller 3
Check
Is the problem solved after
replacing the drum unit?
Is the problem solved after
replacing the high-voltage
power supply PCB?
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?
IV-17
Result
Yes Replace the drum unit.
Yes Replace the high-voltage
power supply PCB.
Result Remedy
Yes Clean both electrodes.
No Check the SR
connection.
No Check the connection
between the shaft and
the ground contact.
Remedy
HV.GND
contacts
(Fig.4-
5,4-7)