my wife has a small office and uses a HP officejet 8600 pro. All of a sudden the printer refused to print and the message on the display reads "problem with print head, switch off and on". Of course this was not a solution ;(
I bought a new print head, exchanged (very simple procedure) and have still the same problem. I checked every nook and cranny I could open but I don't see anything obvious.
Any idea what the real problem could be? Given that the printer was quite cheap as HP makes its margin with the ink I'm not willing to invest a lot of money (printer is about 250€, new print head was 60€).