Troubleshooting Of Malfunctions - Brother HL-1260 Service Manual

4. TROUBLESHOOTING OF MALFUNCTIONS

M-1 No DC power supplied
Possible cause Step
PCBs 1
Low-voltage 2
power supply
PCB
Main PCB
LV harness
DC fan motor
M-2 Malfunction of LCD display on the control panel.
Possible cause Step
LCD module 1
Control panel
PCB
Switch flat cable
Main PCB
M-3 Malfunction of control panel LED lamps.
Possible cause Step
LED lamps 1 Dose the voltage of the following signals stay
0V while the "04 SELF TEST " is displayed
Control panel
after switching the power on and stay 5V for
PCB
about 0.5 seconds after the message goes off?
(Do the LED lamps turn on and off in response
Switch flat cable
to the signal levels of 0V and 5V?)
Main PCB Signal
LED1(ON LINE)
LED2(READY)
LED3(DATA)
LED4(ALARM)
Check
Does any PCB have the short circuit between
+24V and 0V,+5V and 0V or +24V and +5V?
Is the voltage of P3-8 in the low-voltage power
supply PCB connector 0V?
Check
Dose the voltage of the following signals
vary to 5V or 0V when the LCD displays are
changed through switch operations?
(Check following signals using the digital
memory scope with the trigger function for
this check)
Signal Main PCB Panel PCB
PAD4 P1-9 --- P1-13
PAD5 P1-5 P1-17
---
PAD6 P1-11 P1-11
---
PAD7 P1-4 --- P1-18
LCDRS P1-3 --- P1-19
LCDE P1-2 --- P1-20
Check
Main PCB
P1-13
P1-7
P1-1
P1-6
Result
Yes
Yes
No
Result
Yes
No
LCD
7
--- P2-4 ---
--- P2-3 --- 8
--- P2-2 --- 9
--- ---
P2-1 10
--- ---
P2-7 4
--- ---
P2-5 6
Result
Yes
No
Panel PCB
--- P1-9
--- P1-15
--- P1-21
--- P1-16
VI - 11
Remedy
Replace the PCB having the
short circuit.
Replace the low-voltage power
supply PCB assy.
Replace the main PCB assy,
the LV harness or the DC fan
motor.
Remedy
Replace the control panel
unit.
Replace the main PCB assy,
the switch flat cable or the
control panel unit.
Remedy
Replace the control panel
unit.
Replace the main PCB assy
or the switch flat cable.