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HP Designjet CP Series Printers - Media Skew

	Parts required (part numbers are subject to change)
	Cleaning the drive roller
	Check/replace the media spindle
	Check/replace the rollfeed assembly
	Check/replace the overdrive gear assembly
	Performing Service Calibrations or Service Diagnostic Tests

Document number: BPP90107

Last updated: 14-Jan-2003

Minimum skill level: 2

Media skewing issues can be attributed to several causes. The most common causes of media skew are a dirty drive roller, malfunctioning right roll feed assembly, or a faulty overdrive gear assembly. Other causes may include the media spindle, or the media itself. Use the steps below to determine the actual cause of the skewing issue.

Parts required (part numbers are subject to change)

Part description	Models - C4703A, C4704A, C6085A	Models - C4723A, C4724A, C6084A
Right Rollfeed Assembly (Required)	C4704-60199	C4704-60199
Cluster Gear (Required)	C1633-40019	C1633-40019
Overdrive Clutch (Required)	C4705-60089	C4705-60089
Media Spindle (Required)	C4704-60317	C4723-60241

NOTE: If Removal and Installation instructions are needed for reference during any repairs performed, refer to the CP Series Service Manual available on the Computer Care Web site for review or download.

Accurately identifying the skewing issue will lead to a quicker resolution and repair time. First determine if the skew is happening on roll media, sheet media, or both. If the issue is affecting roll media only, the most common causes are the right roll feed assembly, or the media spindle. If the issue affects sheet media only, the most common cause would be a dirty drive roller. If skewing happens on both types of media, the solution may be a combination of roll and sheet troubleshooting.

Cleaning the drive roller

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

1. Make sure the printer is turned off from the power switch on the back of the printer.
2. Hold the Up Arrow key and the Enter key down while turning the printer on.

NOTE: Continue to press both the Up Arrow key and the Enter keys until letters begin to scroll on the lower right corner of the front-panel display.

3. Once the message "Status/Ready" is displayed on the front panel, press Enter.
4. Use the Arrow keys to scroll to Utilities and press Enter.
5. Scroll to Service Tests and press Enter.
6. Scroll to Diagnostics and press Enter.
7. Scroll to D15 Clean Roller and press Enter.
8. Remove media (if loaded).
9. Open the top cover.
10. Use the Up and Down Arrow keys to move the drive roller.
11. Using a lint-free cloth dampened with water clean the entire surface of the drive roller until free of ink and other contaminants.
12. When finished close the top cover and press the Previous key (the message "D1500 Done" will be displayed on front panel).
13. Allow the drive roller to dry.
14. Turn the printer off then on, and attempt to load media.
15. If loading is successful, try loading both roll and sheet (preferably larger than 8.5 x 11) media and attempt to recreate the skewing issue. If issue is not recreated the problem has been solved.
16. If loading is unsuccessful, or problems persist, continue with the remaining steps.

Check/replace the media spindle

1. Ensure the media is loaded correctly on the spindle (for example, roll loaded backwards).
2. Remove the media spindle from the printer.
3. Check the right side of the spindle for damage to the gear teeth, replace if needed.
4. If the spindle is replaced, load media onto the new spindle, and try re-loading media.
5. If loading is successful, try loading both roll and sheet (preferably larger than 8.5 x 11) media and attempt to recreate the skewing issue. If issue is not recreated the problem has been solved.
6. If no problem is found with the media spindle or the skewing issue persists, continue with the remaining steps.

Check/replace the rollfeed assembly

1. Remove the media spindle from the printer.
2. Check the right rollfeed assembly for tension. The gear should be stiff, but can be overpowered. Use a pencil eraser or finger to move the gear assembly.
3. If the rollfeed does not move, moves without any tension or makes any unusual noises while moving, replace the rollfeed assembly (refer to pg. 8-81 of the Service Manual).
4. Following replacement, attempt to verify functionality.
5. If no problems with the rollfeed are noticed or problems persist following replacement, continue with the next section.

Check/replace the overdrive gear assembly

1. Open the top cover.
2. Manually lift the bail assembly.
3. Try turning the overdrive rollers backwards by hand.
4. If the overdrive rollers move backwards, replace the overdrive gear and overdrive clutch assemblies (refer to pg. 8-69, 8-72 of the Service Manual).
5. If overdrive clutch locks, when attempting to move overdrive wheels backward, attempt to load media.
6. Leave the top cover open and trip the top cover sensor to view the overdrive wheels during media loading (use a small piece of paper to trip sensor).
7. Load a sheet of 8.5 x 11-inch paper.
8. Watch the media as it runs between the overdrive wheels and the bail. If the overdrive clutch is defective and the overdrive is not turning, the sheet will buckle when it hits the overdrive wheels, forming a "Media Bubble."
9. If the wheels do not turn, replace the overdrive clutch and overdrive gear (refer to pg. 8-69, 8-72 of the Service Manual).
10. Following replacement perform a C08 Accuracy calibration, a D11 Bail test, and a D05 Service Station test (instructions listed below).
11. Verify printer functionality.

Performing Service Calibrations or Service Diagnostic Tests

Following each calibration, turn the printer off to store the new calibration values in the EEROM. Turn the printer on (entering Service mode) and perform the next required calibration. Repeat this cycle until all necessary calibrations have been performed.

1. Make sure the printer is turned off from the power switch on the back of the printer.
2. Hold the Up Arrow key and the Enter key down while turning the printer on.

NOTE: Continue to press both the Up Arrow key and the Enter keys until letters begin to scroll on the lower right corner of the front-panel display.

3. Once the message "Status/Ready" is displayed on the front panel, press Enter.
4. Use the Arrow keys to scroll to Utilities and press Enter.
5. Scroll to Service Tests and press Enter.
6. Scroll to Service Calibrations or Diagnostics and press Enter.
7. Use the Arrow keys to scroll through the specific calibrations or Diagnostic tests and press Enter when the required calibration/test is displayed.

NOTE: For the best results when performing the Accuracy calibration, use a Polyester Matte film. If Polyester Matte film is not available, use HP High Gloss or Heavy Coated media.

Copyright Hewlett-Packard Co. 2001
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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