I've been having a problem with the black cartridge in my HP 820Cxi printer getting all gummed up with ink on the bottom, making lousy print. Clean it off, and it comes right back. It also was missing a horizontal line or two - thin but noticeable. The "clean" instructions with HP troubleshooting didn't help at all. Interesting that they say there is another thing you can try, but don't do it except with NEW ink cartridges! At $30 or so each, I wasn't interested in trying that except as a last resort.
The other day, after cleaning and refilling, I got an error message telling me that my black cartridge was no longer usable, and that continued use would possibly damage the printer. I purchased a new cartridge, and replaced. The old cartridge again had the buildup of ink on the bottom. So now I got the same "unusable" message, with recommendation that the cartridge be returned for replacement. And again, the bottom was loaded with ink. Obviously this was not just leakage from a faulty cartridge.
Information found on the web indicated that HP has only one repair location, and will not sell repair parts to even their dealers. Probable repair costs, added to shipping two ways, lead me to believe that I would be money ahead by either repairing it myself, or junking the printer. It has been in service (I am a retiree using it at home) for just over three years.
There should be information on this printer accessible on-line which is not included with their on-screen maintenance information:
I also referred to this document at a Sci.Electronics.Repair FAQ site.
I removed the cartridges, and stood them upright on a multi-thickness pad of paper towel that was moistened with distilled water (from dehumidifier), figuring that this might open any ink jets with dried ink in them. A flashlight helped to see the area at the far right of the printer, where the cartridges park. Those wipers were a real mess. The Q-tip swab technique proved quite unhandy, but with a larger wad of cotton on the tip of a long and narrow needle nose pliers, I was able to clean them. There is a well to the left of the wipers that appears to have a spongy material in it - well soaked with black ink. When I tried to clean it, it just depressed down into the well and stayed that way. The pads that rest against the cartridge bottoms when in the park position were inaccessible, as they retract when the carrier moves away.
The paper toweling soaked up a little ink (I had some plastic under it). I wiped the cartridge bottoms, then replaced them in the printer. Alignment worked well - no skips or smudges. But I kept getting the error message telling me to cancel printing and align whenever I started printing, until the computer had been shut down and restarted.
The printouts are now first class, and there are no more error messages. The "unusable" cartridges both work fine. Of course it has only been one day so far though!
(From: Someone who wishes to remain anonymous.)
I can only add that the cover comes off quite nicely by unscrewing the two screws found on the top of the printer toward the back and by wedging back with wads of folded paper the four plastic clips on the printer's bottom. With the cover off you have good access to the area that needs cleaning. Also, I used rubbing alcohol rather than water. The ink well is just that. There is no spongy material there. Mine was just full of waxy ink that had accumulated there over time. Needless to say, I dug that all out. Hopefully the printer should work well for another two or three years.