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HP Designjet 750C Plus Series Printers - System Error 070020 and 070030

In this document:

Introductionback to table of contents

This system error is displayed when drops are not sensed during the drop detection procedure. Common causes of this system error are defective ink cartridges, dirty Encoder strip, or worn Y-axis parts. Follow the steps listed below to accurately troubleshoot the issue, and replace the appropriate parts.

Parts required (part numbers are subject to change)back to table of contents

Part Description

Models C4708A, C4708B

Models C4709A, C4709B

Service Station Assembly (Required)



Ink Cartridges (Optional)

51645A, 51644C, 51644M, 51644Y

51645A, 51644C, 51644M, 51644Y

Encoder Strip (Required)



Carriage Belt (Required)



Y-Motor (Required)



Tensioner (Required)



Idler Pulley (Required)



Troubleshooting stepsback to table of contents

If parts are replaced or fixed in any of the steps listed below, attempt to verify printer functionality by turning the printer on and printing internal test prints. If functionality is verified, no additional parts should be replaced.

  1. Perform a Nozzle Print Test in Service Mode as described below:
    1. When the Error message is displayed on the front panel press ENTER.
    2. Use the ARROW key to scroll to Utilities and press ENTER.
    3. Simultaneously press the ENTER and UP arrow keys to access the Service Test submenu.
    4. Scroll to #12 Nozzle Print Test and press ENTER.
    5. Follow all front panel display prompts during the test.
  2. When test is complete, check all print cartridge patterns for excessive nozzles out.
  3. If nozzles on all cartridges appear OK, continue with step 9.
  4. If any cartridges have excessive nozzles out, clean the electrical contacts on the Carriage and Cartridge using a lint-free cloth dampened with water.
  5. Perform the Nozzle Print Test again.
  6. If the problem persists, replace the affected Cartridge(s).
  7. Following Cartridge replacement, perform the Nozzle test again and attempt to verify functionality.
  8. If the problem persists, continue with the remaining steps.
  9. Clean the Encoder strip and replaced if damaged (refer to pg. 6-27 of the 700 Series Service Manual).
  10. Turn Cartridge check on in the Device Setup menu.
  11. Attempt to verify functionality.
  12. If the problem persists, continue with the remaining steps.

Perform the Drop Detect Test and Drop Detect Calibrationback to table of contents

  1. Switch the printer on.
  2. Press ENTER.
  3. Turn Pen Checking to on.
  4. Use the ARROW button to scroll to the Utilities menu display.
  5. Press ENTER.
  6. Simultaneously press the ENTER and the UP ARROW buttons to access the Service Tests submenu.
  7. In the Service Test submenu, scroll to Test number 17.
  8. Run the diagnostic test first with the sensor blocked, then run the test with the sensor unblocked. To block the Drop Detect sensor place a small piece of paper down into the Drop Detect slot (rectangular hole closest to the Service Station).
  1. Use the ARROW button to scroll to 1C Drop Detect Cal and press ENTER.
  2. The display shows the message Calibrating indicating the calibration is in progress.
  3. If the calibration passes, the Success Calibration/Press Enter message is displayed on the front panel.
  4. Press the PREVIOUS key until Ready is displayed on the front panel.
  5. Power cycle the printer and perform an internal print to determine if the error still occurs. If the error reappears, continue with the remaining steps.

Troubleshoot the Y-axisback to table of contents

  1. Place clear tape over the Drop Detect slot (rectangular hole closest to the Service Station).
  2. Perform the Drop Detect calibration
  3. Look for ink spray on the tape.
    1. If ink is sprayed on the tape, and it is close to the center of the drop detect hole, run a Drop Detect calibration without the tape. Press the PREVIOUS key until Ready appears on the front panel. Turn the printer off then on, if problems persist continue with step 5.
    2. If ink is not spraying on the tape, continue with Step 4.
  4. Manually find the Carriage home position on the right/left hand sides, check for and remove/fix any obstructions causing carriage not to reach its home position.
  5. Check for correct cutter home position and remove any obstructions causing cutter not to reach its home position.
  6. Check that the Service Station is installed correctly.
  7. Check Carriage and Encoder interaction (the Carriage and Encoder should not touch each other).

Verify functionalityback to table of contents

Turn the printer off, then on and print several internal plots (E or D size) to verify functionality.

Copyright (C) Hewlett-Packard Co. 2000
This information is subject to change without notice and
is provided "as is" with no warranty.
Hewlett-Packard shall not be liable for any direct,
indirect, special, incidental or consequential damages
in connection with the use of this material.

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