Pinduoduo's face sheet is printed, and the bottom is black.

First: First, check whether the contact of the photosensitive drum is in good contact. The exposed lattice of the photoreceptor on the surface of the photosensitive drum is connected with the conductive substrate, and the charge is discharged through the conductive substrate and electrodes of the photosensitive drum.

Second: check whether the photosensitive drum scraper is lubricated (whether the shear force is too large). There is a shearing angle between the cleaning scraper and the photosensitive drum, which has great shearing force on the photosensitive drum. In order to make the photosensitive drum and scraper have good cleaning ability and good lubrication without damaging the photosensitive drum, a layer of lubricating powder is coated on the blade of the scraper. Wipe off the lubricating powder after long-term use, or when cleaning, the scraper will form a great shear resistance to the photosensitive drum, which will make the photosensitive drum run unsteadily and cause jitter (this phenomenon mostly occurs on the toner cartridge powder), which will make the photosensitive drum run unsteadily and cause failure. Therefore, when cleaning or replacing the photosensitive drum, special attention should be paid to the fact that the lubricating powder on the scraper cannot be removed. To solve this problem, just replace the scraper.

Third, there are many transmission gears in the printer. After the printer is used for a certain period of time, the problems of unsmooth and excessive wear between transmission gears often occur, which makes the meshing gap between gears too large, resulting in unstable transmission and jitter, which is also an important reason for the failure of horizontal line and black line. At this time, it is necessary to adjust the main transmission gear meshing with the photosensitive drum first, and add some lubricating paste or lubricating oil to the gear appropriately. If it is badly worn and cannot be adjusted, replace the main drive gear engaged with the photosensitive drum to eliminate the fault.

Fourth: Another reason for the horizontal black line is that the photosensitive drum is defective or improperly installed. When the photosensitive drum has defects (such as pinholes), the horizontal black lines or stains on the printed page are mostly regular. At this time, you can take out the toner cartridge and check it carefully. If there is something wrong with the photosensitive drum, it should be replaced. If there is nothing wrong with the photosensitive drum, it may be caused by incorrect installation of the photosensitive drum. Incorrect installation of photosensitive drum will lead to abnormal contact with printing paper, uneven printing and black stripes. At this time, you should open the printer box cover, take out the photosensitive drum and reinstall it correctly.