Brother HL-1260 service manual Troubleshooting of Malfunctions, No DC power supplied

4.TROUBLESHOOTING OF MALFUNCTIONS

M-1

No DC power supplied

Possible cause	Step	Check	Result	Remedy
PCBs	1	Does any PCB have the short circuit between	Yes	Replace the PCB having the
		+24V and 0V,+5V and 0V or +24V and +5V?		short circuit.
Low-voltage	2	Is the voltage of P3-8 in the low-voltage power	Yes	Replace the low-voltage power
power supply		supply PCB connector 0V?		supply PCB assy.
PCB
			No	Replace the main PCB assy,
Main PCB
LV harness				the LV harness or the DC fan
DC fan motor				motor.

M-2

Malfunction of LCD display on the control panel.

Possible cause	Step			Check		Result	Remedy
LCD module	1	Dose the voltage of the following signals				Yes	Replace the control panel
		vary to 5V or 0V when the LCD displays are					unit.
Control panel		changed through switch operations?
						No	Replace the main PCB assy,
PCB		(Check following signals using the digital
							the switch flat cable or the
		memory scope with the trigger function for
Switch flat cable							control panel unit.
		this check)
Main PCB		Signal	Main PCB Panel PCB		LCD
		PAD4	P1-9	--- P1-13 --- P2-4	--- 7
		PAD5	P1-5	--- P1-17 --- P2-3	--- 8
		PAD6	P1-11	--- P1-11 --- P2-2	--- 9
		PAD7	P1-4	--- P1-18 --- P2-1	--- 10
		LCDRS	P1-3	--- P1-19 --- P2-7	--- 4
		LCDE	P1-2	--- P1-20 --- P2-5	--- 6

M-3

Malfunction of control panel LED lamps.

Possible cause	Step		Check		Result	Remedy
LED lamps	1	Dose the voltage of the following signals stay			Yes	Replace the control panel
Control panel		0V while the "04 SELF TEST " is displayed				unit.
		after switching the power on and stay 5V for
					No	Replace the main PCB assy
PCB		about 0.5 seconds after the message goes off?
		(Do the LED lamps turn on and off in response				or the switch flat cable.
Switch flat cable
		to the signal levels of 0V and 5V?)
Main PCB		Signal	Main PCB Panel PCB
		LED1(ON LINE)	P1-13	--- P1-9
		LED2(READY)	P1-7	--- P1-15
		LED3(DATA)	P1-1	--- P1-21
		LED4(ALARM)	P1-6	--- P1-16

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