Brother HL-820 Service Manual page 79

I-11 Poor fixing
Possible cause Step
Printing paper 1
Toner sensing 2
failure
Thermistor 3
failure
Low-voltage 4
power supply
PCB failure
I-12 Image distortion
Possible cause Step
Scanner 1
Scanner LD 2
emission failure
Scanner motor
rotation failure
Scanner 3
connection
failure
Check
Is thick paper more than 42lb
weight in use?
Is the problem solved by
replacing the drum unit or the
toner cartridge?
(When printing is faint.)
Is the thermistor fitted
correctly?
Is the problem solved by
replacing the low-voltage
power supply PCB?
Check
Is the scanner unit secured to
the frame incorrectly?
Is there any play?
Is the laser diode or the laser
scanner motor defective?
Is the scanner harness
connected properly?
Is it coming loose?
IV-12
Result Remedy
Yes Instruct the user to use paper
of the recommended weight
and thickness.
Yes Toner is empty.
The toner sensing is defective,
clean the toner sensor.
If the wiper in the toner
cartridge is broken, replace the
toner cartridge with a new one.
No Fit the thermistor correctly.
Yes Replace the low-voltage power
supply PCB.
Result Remedy
Yes Secure the unit correctly and
tighten the screws.
Yes Replace the scanner unit.
Yes Connect the harness correctly.