Troubleshooting Of The Control Panel - Brother MFC8420 Service Manual

CHAPTER 6 TROUBLESHOOTING
6.

TROUBLESHOOTING OF THE CONTROL PANEL

L-1 Nothing is displayed on the LCD.
User Check
(1) Verify if the power switch is turned off.
Possible cause
Connection
between main
PCB, relay PCB,
and control
panel PCB
Harness
between main
PCB, relay PCB,
and control
panel PCB
Connection
between main
PCB and low-
voltage power
supply PCB
Harness
between main
PCB and low-
voltage power
supply PCB LCD
LCD
Control panel
PCB
Relay PCB
Low-voltage
power supply
PCB
Main PCB
Step Check
Main PCB and control panel
1
PCB are properly connected.
Harness wire is damaged.
2
Main PCB and low-voltage
3
power supply PCB are
properly connected.
Harness wire is damaged.
4
Replacement of LCD solves
5
the problem.
Replacement of control panel
6
PCB solves the problem.
Replacement of relay PCB
7
solves the problem.
Replacement of low-voltage
8
power supply PCB solves the
problem.
Replacement of main PCB
9
solves the problem.
Result
No
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
6-28
Remedy
Fix the connector properly.
Replace the harness with a
normal part.
Fix the connection properly.
Replace the harness with a
normal part.
Replace the LCD with a
normal part.
Replace the control panel
PCB with a normal part.
Replace the relay PCB with a
normal part.
Replace the low-voltage
power supply PCB with a
normal part.
Replace the main PCB with
a normal part.