How to check the Toner Cartridge?

Because old drums are in different conditions, be sure to inspect them before filling them. In order to fully understand the quality of each component. Mainly from two aspects:
1. Please use the old drum to Print a test page. If there are black dots or broken lines regularly, it means that there is a problem with the Toner Drum. After the Toner Cartridge is disassembled, find the defective part and replace it.
2. Please turn the upper gear of the magnetic roller to visually check whether the powder suction is uniform and whether it is scratched. If the powder application is uneven or there are circle lines, it means that the magnetic roller or the inner scraper is damaged.
In the above two way, we can check the condition for toner cartridge, then decide if we need to replace the new toner cartridge or not.