Troubleshooting: First, clean the inside and outside of the printer, and clean up the dust, spilled toner and paper scraps inside. Then try the machine, and the fault still exists. Ran Yan found that the paper was smooth and the transparent film met the requirements. Further inspection of the photosensitive drum found that it was damaged, and the reason was that the photosensitive drum was exposed to light for a long time. After replacing the photosensitive drum of the same model and specification, try to print and troubleshoot.