HP Inkjet L7780 fails to print all of the black text, just top and bottom

[RayBonnie]

The printer started just printing the top and bottom of text, (black), every 7 or so lines.

I have replaced the black cartridge and print head. Ran clean print head and alignment from the tools menu, but the fault remains.

Any thoughts would be much appreciated

[Valsimot]

Print from the printers Reports menu Print quality page, scan and post here so wee can see.

[RayBonnie]

[RayBonnie]

Just posted a scan as  requested. You will see the error in the text lines

Thank you for your help. Much appreciated

[Valsimot]

It's visible in the lower black block a huge part of the black isn't printed.

Since you run the cleaning cycles without fixing the print quality you have a defective KY printhead. 

[RayBonnie]

I replaced the BY print head with new genuine new HP brand replacement when the fault arose. It did not correct the fault in any way. When that did not work I then replaced the Black Cartridge, which also did not improve matters.

I guess the replacement new KY print head could faulty?

When I ran the Self Test Diagnostic Page the BY print head is shown as installed on the 8 July 2020. Warranty date 14 May 2021

Accumulated ink usage 1 ml. So it is being recognised as a new part.