Lexmark MX421 User Manual page 216

Troubleshooting
Action
Step 4
a
Remove, and then insert the imaging unit.
Warning—Potential Damage: Do not expose the imaging unit
to direct light for more than 10 minutes. Extended exposure
to light can cause print quality problems.
Warning—Potential Damage: Do not touch the
photoconductor drum under the imaging unit. Doing so may
affect the quality of future print jobs.
b
Print the document.
Do vertical dark lines or streaks appear on prints?
Step 5
a
Replace the imaging unit.
b
Print the document.
Do vertical dark lines or streaks appear on prints?
Vertical dark streaks with print missing
Note: Before solving the problem, print the Print Quality Test Pages. From the control panel, navigate to
Settings > Troubleshooting > Print Quality Test Pages. For non‑touch‑screen printer models, press
navigate through the settings.
Yes No
Go to step 5. The problem is
solved.
Contact customer The problem is
support. solved.
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