I have the very same problem that is described on this page: http://www.fixya.com/support/t181776-pixma_mp780_printer_not_printing Before I changed the black ink cartridge, it showed to be half full. I changed the black ink cartridge because your solution (link above) said to. The problem is still there. Nothing is different. The screen still shows the cartridge to be half full. I am using Canon ink cartridges. FYI, if I am printing grey letters, they print. But if I change them to black, it produces a clean unprinted page. Thanks for your help.
Open your list of printers. r/click on the 780 and open properties. fo to the last tab "maintenance" and run cleaning 2 or 3 times then run deep cleaning 2 or 3 times. and see how this helps. If you've never done it before you might want to take out the print head and clean it with alcohol. Take out all the ink like you were changing them then reach in and gently pull out the container that holds the ink. This is the print head. Clean it and replace it, then run clean and deep clean again. run Nozzle check to see how clean it's become and you'll definetly see a difference in your printing. good luck
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