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T770 blue horizontal lines

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Microsoft Windows 7 (64-bit)



we have 8 years old t770 plotter and now I have a problem with blue horizontal lines.

I already change the printer head, run head cleaning, and alignment, diagnostic but still, I have the blue lines.


Any suggestion?



my firmware is updated.





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what is the printing mode you were using? if you are using Speed, you may try to change to Quality to see if issue persists. Is the diagnostic plot looks okay? You may try to do Paper Advanced Calibration as well.


You can check out this link for more information.

Although I am HP Employee
I am speaking for myself and not for HP

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Hello Angel,


This print quality Issue may be due to multiple causes. Few of the causes are listed below


1. Bad/over used print head

2. service station and left spitoon filled with ink.

3. Carriage assembly

4. Ink Leak

5. Ink sticking to bottom of carriage assembly

6. Wrong media type selected.


I suggest below troubleshooting steps,


1. Print printer information page, check and replace printheads which are out of warranty or have over 100% usage.

2. Print image quality diagnostic print, check if all color blocks are printed correctly and are solid with no banding or color overlap. If any color block is not print correctly, please replace that printhead.

3. Please ensure you are using recommended media and matching media type is selected on printer.

4. Check if service station and left spitoon are filled with ink. If yes, printer would require service.

5. Check if there is ink leak in printer. If yes, printer would require service.

6. Intiate printehad replacement, remove printheads. power off printer. using lint free cloth dampended in plain water, Clean carriage assembly (both block and electrical contacts) and clean printheads (electrical contacts and around nozlles). Do not touch or clean nozzles.

7. Perofm Printhead cleaning and alignment.

8. Print in best mode and check.


You may also try troubleshooting steps provided in below documents.


If issue persists, I sugegst you contact HP support for more help.




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