1. Vertical black lines of more than 1 cm in width appear on both the printed document and the drum core: This is a problem with the scraper, which causes the powder on the stick core to not be scraped cleanly.
2. Vertical thin black lines appear on the printed document: Usually the scraper and the small scraper on the edge of the scraper are stuck with dirt or paper scraps.
3. Horizontal black lines appear on the printed document: Usually the magnetic stick in the toner cartridge has accumulated powder, just turn it a few times.

4. If there is obvious bottom ash on the printed document: Usually there is a problem with the drum core or toner.
5. The color of the printed document is uneven, with obvious white lines: Can you still see the toner on the magnetic stick from the outside? If you see that there is powder on some places on the magnetic stick and not on some places, it means that the toner of this toner cartridge has been used up.
6. If the printer prints a white paper: First check if there is any problem with the printer. If there is no problem, it means that there is a problem with the toner cartridge during assembly.