HP Deskjet 3070A Printing Problem

Hello,

Like many HP inkjet printer users (given the number of help requests in the forums), I could no longer print in black on my HP Deskjet 3070a, even though the XL cartridge (costing 25 euros) was brand new. The printer is less than 4 years old and is not used heavily.

I went through a bunch of forums including those of HP and followed all the recommended troubleshooting steps (cleaning the cartridges, semi-full reset, etc.).
Just about ready to throw the machine away, and determined not to buy another HP, I tried the last cleaning method suggested in a YouTube video by a solvent seller.

I opened the cover as if I were going to change the cartridges and unplugged the printer.
I removed the 4 cartridges.
While sliding the print head, I placed a paper towel underneath, where there is indeed a black foam.
Then I slid the print head so that the absorbent paper was under it.
With a syringe filled with acetone, I covered each nozzle (a few drops) and let it sit for a few minutes.
I repeated the operation several times (4 or 5 times), changing the absorbent paper each time and removing the excess from the nozzles with a cotton swab.

On the last injection, I let it rest overnight, before removing the next day the acetone residue from the nozzles and around them with a cotton swab. I also slid the print head several times, placing a towel soaked with acetone underneath to clean well under the nozzles.
I replaced the cartridges and printed in black successfully!!

Hoping that my experience will help some, more than HP's advice…