Oki B721 Maintenance Manual

Also see for ES7131: User manual User manual User manual

Contents

Oki B721 Maintenance Manual Manual pdf 164 page image

Oki Data CONFIDENTIAL45487001TH Rev.1 6-31 /6. Troubleshooting procedure6.5.2 (1) LCD display errorMemo For the numbers from to after the name of the respective connectors,refer to section 6.5.2 (18) “Wiring diagram”.(1-1) LCD does not display anything.Check item Check work Actions to be takenat NG(1-1-1) Check the fuse.Fuse of the PU/CUboardCheck if F3 or F5 has blown out. Replace the PU/CU board.(1-1-2) Check the system connectionConnectionbetween the lowvoltage powersupply unit and thePU/CU boardCheck if the cable from the low voltage powersupply to the POWER connector of the PU/CU board is normally connected or not.Check if the connector is connected only inthe half-way or not, and check if the connectoris inserted in slanted angle or not.Re-connect thecable normally.Cable assemblyconnecting thelow voltage powersupply unit and thePU/CU boardCheck if the cable is half-open circuit.Check if sheath of the cable has not peeledoff or not.Check if the cable assembly is defective suchas internal wires are disconnected or not.Replace thecable with thenormal cable.Connectionbetween the PU/CU board and thecontrol panel boardCheck if the 10-conductor FFC is connectedto the OPE connector of the PU/CU boardnormally or not.Check if the 10-conductor FFC is connectedto the OPE connector of the control panelboard normally or not.Check if the connector is connected in thehalfway only or not, and check if the connectoris inserted in a slanted angle or not.Re-connect thecable normally.FFC connecting thePU/CU board andthe control panelboardCheck if the cable has open circuit or not withVOM. Check if sheath of the cable has notpeeled off or not by visual inspection.Replace theFFC with thenormal FFC.Check item Check work Actions to be takenat NG(1-1-3) Check the peripherals of the power suppliesAC power that issupplied to the printerCheck the supplied voltage of the AC powersource.Supply the ACpower.5V power that issupplied to the PU/CU boardCheck for 5V power supply at pin-1, -3 and-4 of the POWER connector of the PU/CUboard.Replace the lowvoltage powersupply unit.3.3V power that issupplied to the PU/CU boardCheck for 3.3V power supply at pin-22 of thePOWER connector of the of the PU/CUboard.Replace the lowvoltage powersupply unit.3.3V power thatis supplied to thecontrol panel boardCheck for 3.3V power supply at pin-4 of theOPE connector of the control panel board.Replace the PU/CU board.(1-1-4) Check that power supply circuit has no short-circuit.5V power and 24Vpower that aresupplied to the PU/CU board.Check that power supply circuit has no short-circuit at the POWER connector of the PU/CU board. The follow voltage must appearrespectively.pin-11, -13, -14, -15, -16: 24Vpin-1, -2, -3, -4: 5Vpin-5, -6, -7, -8, -9: 0VLpin-17, -18, -19, -20, -21: 0VPpin-10: 5VsIf any voltage does not appear and short-circuit is detected, locate the source of theshort-circuit as follows:Disconnect the cables that are connected tothe PU/CU board one cable after another untillocation of the short-circuit is found out.Replace the partcausing short-circuit.(1-1-5) LSI operation checkI/F signal suppliedfrom the PU/CUboard to the controlpanel board.Check if signals are output to the OPEconnector of the PU/CU board.Pin-5: Send data (Sending data from the PU/CU board)Replace the PU/CU board.I/F signal suppliedfrom the PU/CUboard to the controlpanel board.Check if signals are output to the OPEconnector of the PU/CU board.Pin-7: Send data (Sending data from the PU/CU board)If it is normal, signals are output always.Replace thecontrol panelboard.