Canon PC980 Service Manual - Page 318

CHAPTER 11 TROUBLESHOOTING C. Troubleshooting Image Faults 1 The copy is too light. (halftone area only) 2 The copy is too light. (including solid area) 3 The copy is too light. (enter image, appreciably) Cause Lens, Reflecting plate, AE sensor, Static eliminator Transfer charging roller Copy paper Transfer lower guide, Varistor Composite power supply PCB, DC controller PCB Cartridge Developing bias, Developing bias terminal Step 1 2 3 4 5 6 Checks Clean the lens, reflecting plate, AE sensor, and static eliminator. Is the problem corrected? Turn off the power in the middle of a copying run, and open the machine's top unit. Is the toner image before transfer more or less normal? (Be sure to make a check in a short time to protect the drum from light.) Is the transfer charging roller normal? Try fresh copy paper. Is the problem corrected? Measure the electrical resistance on the transfer lower guide plate and the side plate (metal) of the fixing assembly. Is it 0Ω? Replace the cartridge. Is the problem corrected? YES/NO YES NO NO YES YES NO YES NO Action End. Go to step 6. 1. Mount the transfer charging roller correctly. 2. Replace the transfer charging roller. 1. The copy paper may be moist. Instruct the user on the correct method of storage. 2. Inform the user that using non-recommended paper may not bring the best results. 1. Check to find out if the transfer lower guide happens to be in contact with a metal part (side plate). 2. Replace the varistor. 1. Check the transfer high-voltage terminal contacts for electrical continuity. 2. Check the composite power supply and the DC controller PCB. End. Replace the electric unit (composite power supply PCB, DC controller PCB). COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 11-53