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HP DesignJet T790

Diagnostic Part 3: Printheads & Paper Advance

This test is designed to check whether the Printheads and the Paper Advance Mechanism are working correctly. This part of the Image Quality Test should NOT be used to check for color consistency or accuracy.

Banding

If the Printer is experiencing a banding problem, you will see repetitive horizontal bands within the printed image.

  • Darker horizontal bands or lines repeated along the vertical band (from top to bottom at the same distance).
  • Whiter horizontal bands or lines along the vertical band (from top to bottom at the same distance).

The plot is printed in Best or Normal mode (according to the menu option selected) with Error Hiding ON. The top band has 100% ink density patches while the bottom band has 50% ink density patches.

If banding does NOT occur in ALL the colors, then it is more than likely a Printhead problem. In this case, try the following:

  1. Check that the appropriate print quality settings are being used (refer to the User’s Guide for more information).
  2. Recover the printheads using the option through the Front Panel. Press "arrow down", then "wrench" and then select Image Quality Maintenance/ Clean Printheads. Reprint the Diagnostic Print or the print file and if the problem persists, replace the faulty Printhead.

If banding does occur in ALL the colors, then it is more than likely a Paper Advance problem:

  • If the bands are light, it means that the paper has advanced too much.
  • If the bands are dark, it means that the paper hasn’t advanced enough.
  • In high quality modes, graininess in ALL colors can indicate problems either with alignment or Paper Advance.

Corrective Action

In order to solve problems that result in banding, try the following:

  1. Check that the appropriate print quality settings are being used (refer to the User’s Guide for more information
  2. Check that the loaded media is the same type as selected in the printer. You can verify the media type selected through the Front Panel. Press "arrow down", then press paper icon.
  3. If the customer is using low quality paper, try recommending better quality paper (preferably HP paper). Printer performance can only be guaranteed by using recommended papers.
  4. Perform the Paper Advance Calibration using the same type of paper that will be used for the final print . Press "arrow down", then "wrench" and then select Image Quality Maintenance/ Paper Advance Calibration/ Calibrate

Paper Advance.

If there is white point banding in only one color band and the problem cannot be fixed using the Printhead recoveries, in some cases using the force a drop detection option can fix this issue.

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