Brother International HL-1660E Service Manual - Page 87

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 power supply PCB Main PCB LV harness DC fan motor 2 Is the voltage of P4-8 in the low-voltage power Yes Replace the low-voltage power supply PCB connector 0V? supply PCB assy. No Replace the main PCB assy, the LV harness or the DC fan motor. M-2 Malfunction of LCD display on the control panel. Possible cause Step Check Result Remedy LCD module 1 Control panel PCB Switch flat cable 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) Yes Replace the control panel unit. No Replace the main PCB assy, the switch flat cable or the control panel unit. Main PCB Signal PAD4 PAD5 PAD6 PAD7 LCDRS LCDE Main PCB Panel PCB LCD P1-9 --- P1-13 --- P2-4 --- 7 P1-5 --- P1-17 --- P2-3 --- 8 P1-11 --- P1-11 --- P2-2 --- 9 P1-4 --- P1-18 --- P2-1 --- 10 P1-3 --- P1-19 --- P2-7 --- 4 P1-2 --- P1-20 --- P2-5 --- 6 M-3 Malfunction of control panel LED lamps. Possible cause Step Check Result Remedy LED lamps 1 Control panel PCB Switch flat cable Dose the voltage of the following signals stay Yes 0V while the "04 SELF TEST " is displayed after switching the power on and stay 5V for about 0.5 seconds after the message goes off? No (Do the LED lamps turn on and off in response to the signal levels of 0V and 5V?) Replace the control panel unit. Replace the main PCB assy or the switch flat cable. Main PCB Signal LED1(ON LINE) LED2(READY) LED3(DATA) LED4(ALARM) Main PCB Panel PCB P1-13 --- P1-9 P1-7 --- P1-15 P1-1 --- P1-21 P1-6 --- P1-16 VI - 11