Chapter 1313-11F-13-1213.1.6 Checking the Surface Potential Control System0008-79141. OutlineIf an image fault occurs, it is necessary to find out whether the cause is in the static image formation block including the photosensitive drum andthe potential control system or if it is caused at time of development or transfer.An image fault may be isolated by finding out whether the surface potential is correct using service mode.2. Disabling the Auto Control MechanismsAs a means of checking the potential control system, the auto control mechanism may be disabled (hereafter, non-auto control mode).If the image fault in question is more or less corrected when the machine is in non-auto control mode, you can suspect the potential measurementunit and the DC controller PCB as the cause of the fault.You can also take advantage of non-auto control mode as a tentative remedy when the auto control mechanism has a fault.When the machine is in non-auto control mode, all settings used for corona current control, laser power control, and developing bias control will beautomatically be set to default settings.Using Non-Auto Control Mode1)Make the following selections in service mode, enter '0', and press the OK key:COPIER>OPTION>BODY>PO-CONT.2) Press the Reset key twice.3. Making a Zero-Level checkA "zero-level check" is a check made to see if the control mechanism of the DC controller PCB is identifying a 0-V level without fail when the drumsurface potential is 0 V.A zero-level check may be made in either of 2 ways, and you can use it to decided whether the DC controller PCB and the potential measurementPCB is free of error:Method 1: use it to find out if the level shift circuit on the DC controller PCB is free of a faultMethod 2: use it to find out if the potential control circuit is free of a fault(1) Method 11) Turn off the main power switch.2) Remove the upper rear over.3) Short GP33 on the DC controller PCB and GND using a cable equipped with an alligator clips or probes on both ends.Check the developing assemblyfor leakage; if normal, go to acheck on the transfer output.Make the following selections (DCvalue of the developing bias):COPIER>DISPLAY>HV-STS>BIAS.Covert the indication during printing(V) into a control voltage withreference to "Potential ControlConversion Table."Is thedeferense betweenthe actual measurement ofHVT_DEV-BIAS_DC and 'BIAS'in service mode± 10%?YESNOChecking the Developing Bias Output1) Check the transfer charging assembly forleakage.2) Make the following selections in servicemode, and try changing the setting:COPIER>OPTION>BODY>FUZZY.3) Try replacing paper.Make the following selections in service mode(level of current of transfer charging). Convertthe reading (mA) during printing into a controlvoltage based on 8.5 "Potential ControlConversion Table."Replace thephotosensitivedrum.NOYESNOYESNOIs thedifference betweenthe measurement of HVT_TRANSFER and 'TR' inservice mode+/- 10%?Checking the Transfer OutputIs the tonerimage on the photosensitivedrum before transfernormal?Replace thehigh-voltage transformer.Is the problemcorrected?YESReplace theDC controllerPCB.Replace theDC controllerPCB.ENDEnable potential control: COPIER>OPTION>BODY>PO-CNT=1BMeasure the voltage HVT_DEV_BIAS_DC during printing of J102A-8 on theDC controller PCB.Disable the potential control mechanismby setting '0' for the following:COPIER>OPTION>BODY>PO-CNT.Measure the voltage HVT_TRA duringprinting of J102A-12 on the DCcontroller PCB.
