Rows ruin the print

[SteCur]

Good evening, I purchased a day ago a printer HP OfficeJet Pro 7720 Wide Format All-in-One Printer since the first A3 print the result has been on the surface very good, but unfortunately in reality you can see parallel lines along much of the print where there should not be

[sandytechy20]

@SteCur

Welcome to the HP support community.

I understand that you are getting print quality issues, I am glad to assist you.

Clean the printhead

• On the printer control panel, swipe down to open the Dashboard, and then touch the Setup icon .
• Swipe up on the display, and then touch Printer Maintenance.
• Touch Clean Printhead, and then touch Continue.
• Examine the test page.
• If the print quality is unacceptable, touch Clean Again to continue the next level of cleaning. Repeat these steps for the third cleaning stage, if necessary.

Refer to this HP document for further assistance:- Click here

Keep me posted.

If this helps, please mark the public post as an accepted solution so that it benefits several others. 

Cheers.