Chapter 1414-20a. OutlineIf image faults occur, it is important to find out whether the cause is in thelatent static image formation block (including the photosensitive drum andthe potential control system) or it is in the developing/transfer system, requir-ing a check on the surface potential. (You can check the surface potential inservice mode.)b. Disabling the Auto Control MechanismsAs a way of checking the mechanisms used for corona current control, lampintensity control, or developing bias control, you may disable the auto con-trol mechanisms (hereafter, non-auto control mode).As a first-aid measure when a fault exists in the auto control mechanism, youmay use non-auto control mode; keep in mind that all outputs in non-autocontrol mode are fixed to standard values.1. Procedure1) Make the following selections in service mode, and enter '0':COPIER > OPTION > BODY > PO-CNT.2) Press the Reset key twice.In non-auto control mode, all settings used for coronal current control, inten-sity control, developing bias control will be set to standard settings stored inROM.2. Making Use of Non-Auto Control ModeIf a fault occurs in images, use the mode to find out if the cause is on the inputside or output side of the microprocessor on the DC controller PCB.In non-auto control mode, if the fault is corrected somewhat, you may sus-pect the potential measurement unit or the DC controller PCB.c. Zero-Level CheckOne way of finding out if the surface potential control circuit is good or notis to use a zero-level check.MEMO:A zero-level check is made to see if the microprocessor registers 0 V whenthe surface potential of the drum is 0 V.Using the result of the check, you can find out if the microprocessor on theDC controller PCB or the measurement unit is good or not; a zero-levelcheck may take either of the following two methods:1. Method 11) Turn off the power switch.2) Short the connectors J522-1 and -2 on the DC controller PCB with ajumper wire, and disconnect the connector J3 of the potential controlPCB.F-14-413) Fit the door switch actuator into the door switch assembly, and turn on thepower switch.4) Make the following selections in service mode, and check to see if thereading is between 0 and 30 during initial rotation: COPIER> DISPLAY>DPOT> DPOT-K.MEMO:If the reading is not as indicated, you may suspect a fault in the DC controllerPCB.5) Turn off the power switch, and detach the door switch actuator.6) Detach the jumper wire from the DC controller PCB.7) Connect the connector to J3 of the potential control PCB.8) Turn on the power switch.2. Method 21) Turn off the power switch.2) Remove the developing assembly, and slide out the process unit.3) Disconnect the connector [1] of the potential sensor.F-14-424) Remove the 2 screws [1], and detach the potential sensor support plate [2].F-14-435) Put back the developing assembly and the process unit.6) Connect the connector [1] of the potential sensor.F-14-447) Fit the potential sensor checker electrode (FY9-3041) [2] to the potentialsensor [1].When fitting the checker electrode to the potential sensor, be sure that themagnet of the checker electrode will not come into contact with the potentialsensor cover.F-14-458) Connect the cable [1] of the potential sensor checker electrode to theframe (GND) [2] of the machine.Never bring the clip into contact with the sensor cover. Be sure to keep it ful-ly away from the sensor window.Connector J3J522[1][2][1][1][1][2]
