How do you know if a fax machine drum unit needs to be replaced?

You can determine if a fax machine drum unit needs to be replaced by checking for signs such as faded or inconsistent print quality, streaks or lines on the documents, or error messages indicating a drum issue. Additionally, if the drum unit is nearing or has surpassed its recommended lifespan, it may be time for a replacement. Regular maintenance checks can also help identify wear and tear on the drum unit.