Canon iR8500 Service Manual

Also see for ImageRunner iR8500 Series: Function guide Servise manual Service manual Service manual

Contents

COPYRIGHT © 2001 CANON INC. 2000 2000 2000 2000 CANON iR8500/7200 REV.1 AUG. 2001CHAPTER 6 TROUBLESHOOTING6-542.7.11 Checking the Surface Potential Control Systema. OutlineIf an image fault occurs, it is important to find out if the cause is in the latent image for-mation block (including the photosensitive drum and the potential control system) or in thedevelopment/transfer system, requiring a check to see if the surface potential is appropriate.The service potential may be checked in service mode.b. Disabling Auto ControlAs a means of finding out if the corona current control, lamp intensity control, or devel-oping bias control mechanisms is faulty, the auto control mechanism may be disabled (here-after, “non-auto control mode”).In addition, non-auto control mode may be made use of as an emergency remedy in theevent a fault occurs in the auto control mechanism.1. Procedure1) Make the following selections in service mode, and enter ‘0’:COPIER>OPTION>BODY>P0-CNT; then, press the OK key.2) Press the reset key twice.When non-auto control mode is selected, all settings for corona current con-trol, intensity control, and developing bias control will automatically be setto standard settings stored in ROM.2. Making Use of Non-Auto Control ModeUse it to find out if the cause is on the input side or on the output side of the microproces-sor on the DC controller PCB when an image fault occurs.If any improvement is noted in non-auto control mode, a fault may be suspected in thepotential measurement unit or the DC controller PCB.c. Zero-Level CheckA “zero-level check” may be used as a means to find out whether the surface potentialcontrol circuit is good or not.REF.In a zero-level check, a check is made to find out whether the microproces-sor indicates 0 V when the drum surface potential is 0 V.Using a zero-level check, the microprocessor on the DC control PCB and the measure-ment unit may be checked.In method 1, the condition of the level shift circuit on the DC controller PCB may bechecked while in method 2 the potential control circuit may be checked.1. Method 11) Turn off the power switch.2) Short J522-1 and -2 on the DC controller PCB with a jumper wire, and disconnectconnector J3 of the potential control PCB.