1. Print an internal test page
Start with a configuration or internal test page. This removes the computer, application and print driver from the test.
- If the internal page is defective, inspect the copier’s imaging system.
- If it is clean, test the driver, application and network printing path.
- If printing is clean but copies are defective, inspect the scanner glass and document feeder.
2. Identify the defect
- Vertical line: Check the slit glass, drum, charge system and developer path.
- Horizontal band: Measure the distance between repeated marks.
- Light image: Check toner delivery, transfer, drum life and density settings.
- Gray background: Check media settings, charge components and developer condition.
- Smearing: Check paper type, moisture, fuser temperature and pressure.
- One-color defect: Inspect that color’s imaging and toner system.
3. Separate scanning from printing
- Print an internal page.
- Make a copy from the platen glass.
- Make a copy through the document feeder.
- Compare the defect’s location on all three pages.
A line appearing only through the feeder commonly points to contamination on the narrow slit glass.
4. Measure repeating defects
Measure from one mark to the next in millimeters. A consistent distance often indicates a rotating drum, roller or fuser component. Compare the measurement with the manufacturer’s repetition chart before ordering parts.
5. Test color separation
Print individual cyan, magenta, yellow and black test pages when available. A defect in only one color usually narrows the problem to that color’s drum, developer, toner delivery or laser path.
6. Change one item at a time
Record the original condition, perform one cleaning or substitution and print the same test again. Changing several items together makes it difficult to identify the actual cause.
Technician documentation
- Equipment model and page count
- Supply-life readings
- Media type and paper tray
- Defect location and repetition distance
- Colors affected
- Tests and cleaning performed
- Parts replaced and final results