asked Apr 2, 2010 at 8:27am
Hp HP Color Copier 150

How does HP Officejet Pro L7780 test printheads?

I have an HP business inkjet printer which has printheads separate from the cartridges and are rated to last about 50 000 prints.

I got an order of 26 000 prints to do and before I started the printhead's health status was at "fair" and the print quality was degrading slightly (the printheads had probably already done over 30 000 prints).

Now that I've printed about another 20 000 prints the print quality improved and the printhead health went from "fair" to "good".

How does the printer test the printhead health? I think I remember reading that when it tests the heads it shoots a drop out of every nozzle and an optical sensor checks that a drop shoots out, is this how it does it?

Also what explains that the printhead's health improves with added use?

BTW I use a continuous ink system and the printer has done over 150 000 prints and I've never bought a single ink cartridge for it.