OKI MC561

LCD displays nothing

Check item	Checking	Action in case of fail
Checking fuse
Fuse on SU PCB	Check whether F2 has blown.	Replace F2 or SU PCB.
Checking connections
Connection between lowvoltage power supply unit and SU PCB	Make sure the low-voltage power supply unit is connected to the POWER connector on the SU PCB properly. Check whether the cable connector is half-connected or tilted, or whether wires are broken. Check whether there is any fault in the cable assembly, e.g., missing wires.	Connect the cable properly.
Cable assembly connecting low-voltage power supply unit to SU PCB		Replace the cable with a good cable.
Connection between SU PCB and operation panel	Make sure the 16-pin FFC is connected to the OPE connector on the SU PCB properly. Make sure the 16-pin FFC is connected to the CN1 connector on the operation panel PCB properly. Check whether the cable connector is half-connected or tilted.	Connect the cable properly.
FFC connecting SU PCB to operation panel PCB	Check for broken wires using a tester. Check visually whether the sheath peels.	Replace the cable with a good cable.
Checking power supplies
AC power supplied to the printer	Check the supplied voltage from the AC power source.	Supply AC power.
5V power supplied to SU PCB	Check the 5V power at 3, 4pin of the POWER connector on the SU PCB.	Replace the low-voltage power supply.
3.3V power supplied to operation panel PCB	Check the 3.3V power at 14pin of the CN1 connector on the operation panel PCB.	Replace the SU PCB.
Checking for short circuit of power supply
5V and 24V power supplied to SU PCB	Check for a short circuit using the POWER connector on the SU PCB.7, 8pin: 24V 3, 4pin: 5V 5, 6pin: 0VL 9, 10pin: 0VP If there is a short circuit, locate it. Disconnect the cables from the SU PCB one by one to locate the short circuit.	Replace the shortcircuited component.
Checking LSI operation
I/F signal from SU PCB to operation panel PCB	Check whether signals are output to the OPE connector on the SU PCB. 9pin: Transmission data (sent from the SU PCB) 11pin: Clock 13pin: Enabling 15pin: Reset Signals should be always output under normal conditions.	Replace the SU PCB.

Display of OKI logo

Check item	Checking	Action in case of fail
Operation panel display does not change
Operation panel display	OKI logo stays on.	Replace the SU PCB.

Error message display

Check item	Checking method	Action in case of fail
Error message
Error message display	Check the detail of the error on the error message list.	Follow the instructions.