HP LaserJet Pro 400 color Printer M451 series - Manual (Page 94)

3. Examine the surface of the green imaging drum on the bottom of the print cartridge.
CAUTION: Do not touch the green roller (imaging drum) on the bottom of the cartridge.
Fingerprints on the imaging drum can cause print-quality problems.
4. If you see any scratches, fingerprints, or other damage on the imaging drum, replace the print
cartridge.
5. If the imaging drum does not appear to be damaged, rock the print cartridge gently several times
and reinstall it. Print a few pages to see if the problem has resolved.
Repeating defects
If defects repeat at any of the following intervals on the page, a print cartridge might be damaged.
● 22 mm
● 27 mm
● 28 mm
● 75 mm
76 Chapter 7 Print cartridges ENWW