DesignJet 500/800 Series Ink Tubes Assembly C7770-60286

Ink tubes wear out.   Generally the ink in the tubes dries and air can not pressurize the tubes sucking ink from the cartridges to the print heads. Alternatively, The print heads nozzles dry up over time if they are not used.  The easiest fix is to check the print heads is to remove them, shake vigorously a few times and with a damp paper towel blot the nozzles on the bottom to remove any dry ink  Then press the print head nozzles onto a pile of paper towels to pull the Windex and disolved ink out.  Then put the print heads back into the machine and do a print head alignment to get ink through all the heads.  You might have to do this more than once to get all the nozzles working again.    HP has used a s a rule of thumb to print at least once a week to keep the printheads in good working order.   If that fails, you should replace the Ink Tube Assembly Included with the tube assembly is instructions to replace. Below is the youtube video demonstrating how to remove the covers and the i