I have an HP Photosmart 6520 that had the same problem; apparently, it is a common fault with this series. The problem was a clogged print head; the solution: After placing a damp paper towel (solution of 50% water/50% Isopropyl Alcohol 99.9% pure) in the print channel, pushing the print head over it and leaving it to soak for a while, I had some, limited, success. I decided to do a thorough clean to see if that would make any difference: this required taking out the print head. To do this you need to remove the top cover trim to gain access. Lift the cartridge access cover: you will see a retaining strut on the on the rear, right side, edge; it unclips at the top. Heat the clip and lower the lid slightly, then pull on the top of the strut - this is brute force and ignorance time! There are two T10 screws on either edge, two inboard at the lid hinge plate and two under the digital display interface (which pulls forward). After removing all the screws, the trim can be lifted free: there is no need to remove...