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AcuLaser C1100, CX11N & CX21N: Black or coloured dots appear in the print (traffic lighting)

RELATES TO:

  • Black dots appear on the page in a Black & White print.
  • Coloured dots appear on the page in a Colour print.
  • AcuLaser C1100, C1100N, CX11N, CX21N and all variants.

     

EXPLANATION:

This article explains what to do if you see sets of dots appear on your printouts.  This print quality issue is known as traffic lighting, and can be identified as follows:

  • In a colour print, sets of all four colours appear: black (K), cyan (C), magenta (M) and yellow (Y), also known as CMYK dots.
  • In a black & white print, there will be single dots of black only.

Traffic lighting can be caused by installing a toner cartridge incorrectly, where the locking mechanism scratches the drum of the photoconductor unit (PCU). It can also indicate a problem with the PCU itself, or with a hardware compnent.

SOLUTION:

  1. Examples of print quality issues indicating a traffic lighting problem (click on an image to view an enlarged version).



      Figure 1 Figure 2 Figure 3
      Coloured dots 51mm in from the right side, circled in red Close-up of CMYK dots in Figure 1 Close-up of CMYK dots in Figure 1
      Figure 4
      Numerous sets of CMYK dots, also outside the printed area


      Figure 1: Sets of CMYK dots appear in a single column.

      Figure 2: Enlargement of Figure 1, with the CMYK dots circled in red.

      Figure 3: Enlargement of CMYK dots.  Note the four colours in each set of dots, in the order Black, Cyan, Magenta and Yellow.


      Note:

      In a Black & White print, only a black dot would appear.


      Figure 4: Example of severe traffic lighting where the CMYK dots appear in a random pattern rather than in a single column. Note that your print sample may not show as many dots as this.


    • Browse the full samples library for this issue.
    • Refer to the AcuLaser C1100, CX11N and CX21N: Print Quality Troubleshooting Guide to create a standardised colour print sample similar to the above examples, or if you have a print quality issue that does not match any of these examples.

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  2. Identify the affected parts.




    If the dots appear in a single column, as shown in Figures 1, 2 and 3:

    1. Measure the distance from the right-hand edge to the line of CMYK dots.
    2. If the distance is approximately 51mm, this indicates that a toner cartridge is not installed correctly, and the toner lock has damaged the PCU drum as a result.
    3. If the distance is not around 51mm, the issue may be caused by another part. Proceed to Step 3 below to remove and check the PCU, and if the PCU is scratched or otherwise damaged then contact Epson for further advice.

    If the dots do not appear in a single column, as shown in Figure 4:

    1. Count approximately how many sets of dots appear on the page.
    2. If there are six or more sets of dots, or if the problem is getting worse over time, there may be a problem with both the PCU and the developer rollers, or another hardware component.

      If so, contact Epson as your printer may require a service.

      Note:

      You will need to replace the PCU as well to resolve the print quality issue, but any hardware issues must be resolved first. Do not replace the PCU until the printer has been serviced.

      The PCU is a user-replaceable, consumable product.


    3. Otherwise, proceed to Step 3 below.

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  3. Remove, check, and clean the photoconductor unit.



    1. Remove the PCU.

      Note:

      For handling and care instructions, see your user guide (available from the Epson website) or the following related article: AcuLaser C1100, CX11N & CX21N: How to remove and reinstall the photoconductor unit.


    2. Clean the PCU with a dry, lint-free cloth, and check the drum for signs of damage.

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  4. Reinstall the PCU, then test the print quality again by printing.



    1. Reinstall the PCU. For handling and care instructions, see your user guide (available from the Epson website) or the following related article: AcuLaser C1100, CX11N & CX21N: How to remove and reinstall the photoconductor unit.
    2. Print a document to test the print quality. Use the colour test sheet (PDF) to create a document matching the examples in Step 1.

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  5. If the problem remains, replace the PCU.



    The photoconductor unit is a user-replaceable, consumable product.  For instructions on how to replace it see your user guide (available from the Epson website) or refer to the following related article: AcuLaser C1100, CX11N & CX21N: How to replace the Photoconductor Unit.

    However, if you have identified any other problems from Step 2, then contact Epson first for advice before you replace the PCU.

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