Canon LBP-1760 Service Manual page 173

I-2. Dark
<Possible causes>
1. The image density is not adjusted correctly.
Action: Adjust the image density by operating the external device.
2. Poor contact between the engine controller PCB drum grounding contact and the cartridge
contact
Action: Clean the contacts if dirty. If the problem still remains after cleaning, or parts are
deformed or damaged, replace them.
3. Poor contact between the engine controller PCB primary bias contact and the cartridge con-
tact
Action: Clean the contacts if dirty. If the problem still remains after cleaning, or parts are
deformed or damaged, replace them.
4. Defective laser/scanner unit
Action: Replace the laser/scanner unit.
5. Defective engine controller PCB
Action: Replace the engine controller PCB.
I-3. Completely blank
<Possible causes>
1. Damaged laser shutter open/close projection of the EP-52 cartridge
Action: Replace the cartridge.
2. Laser shutter arm and laser shutter are malfunctioning or damaged.
Action: If they are not moving smoothly, or parts are damaged, replace the faulty parts.
3. Poor contact between the engine controller PCB developing bias contact and the cartridge
contact
Action: Clean the contacts if dirty. If the problem still remains after cleaning, or parts are
deformed or damaged, replace them.
4. Defective engine controller PCB
Action: Replace the engine controller PCB.
I-4. All black
<Possible causes>
1. Poor contact between the engine controller PCB primary bias contact and the cartridge con-
tact
Action: Clean the contacts if dirty. If the problem still remains after cleaning, or parts are
deformed or damaged, replace them.
2. Defective primary charging roller
Action: Replace the cartridge.
3. Defective engine controller PCB
Action: Replace the engine controller PCB.
CHAPTER 4
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