Canon LBP1760P, Service Manual

Page: 172 / 394

II. IMAGE DEFECTS
If the factor of the malfunction is identified as "image defect" by the malfunction diagnosis flow-
chart (Figure 4-1-1), find out the defective phenomenon and clear it according to the table shown
below.
Table 4-2-1
• I-1 Light: Output very light image
• I-2 Dark: Output very dark image
• I-3 Completely Blank: Output no image
• I-4 All Black: Output all black paper
• I-5 Dots in Vertical Lines : Output white dots on the paper
• I-6 Dirt on Back of Paper: Output dirt on the back of the paper
• I-7 Vertical Lines: Output vertical lines on the paper
• I-8 Black Horizontal Lines: Output horizontal lines on the paper
• I-9 Dirt: Output dirt on surface of the paper
• I-10 Blank Spots: Output image with blank spots
• I-11 White Vertical Lines: Output white vertical lines on the paper
• I-12 White Horizontal Lines: Output white horizontal lines on the paper
• I-13 Poor Fixing: Output the image with poorly fixed toner
• I-14 Image Distortion: Output distorted image
• I-15 Sharp Black Horizontal Lines: Output sharp black horizontal lines
I-1. Light
<Possible causes>
1. The image density is not adjusted correctly.
Action: Adjust the image density by operating the external device.
2. Open the top cover and remove the EP-52 cartridge while printing. Open the drum protec-
tive shield of the cartridge and check the toner image on the photosensitive drum surface.
If the toner image has not been transferred to the paper properly, go to step 3). If the toner
image on the drum is faint, go to step 6).
Do not open the drum protective shield for more than 10 seconds.
3. Deformation or deterioration of the transfer charging roller
Action: Replace the transfer charging roller.
4. Poor contact between the engine controller PCB transfer charging roller and its shaft
Action: Clean the contacts if dirty. If the problem still remains after cleaning, or parts are
deformed or damaged, replace them.
5. Defective engine controller PCB
Action: Replace the engine controller PCB.
6. Defective laser/scanner unit
Action: Replace the laser/scanner unit.
7. Defective engine controller PCB
Action: Replace the engine controller PCB.
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CHAPTER 4