The other thread was forking, so I thought this could be its own thread.

My good old Canon S820 inkjet photo printer developed a problem over the years where photos would print streaky and off-color.

I recently tried to fix this problem and learned some interesting things that I thought I'd share. For anyone having trouble with inkjet printers of any make/model, this might provide some interesting insights.

1. There seems to be a way that ink can wick back into and contaminate the ink tanks. In other words, black can wick back into the yellow tank, magenta can wick back into the cyan tank, etc. This will make all your colors print poorly. You can tell by popping out the tank and comparing it with a new tank. For instance, the yellow ink will look a murky gray-brown. So if this happens you have to replace all the ink tanks.

2. If you are trying to diagnose a problem with the printer, you must remember that printing on the Plain Paper setting prints only from the C, M, Y, and K tanks. The Photo Cyan and Photo Magenta tanks don't kick in until you set the paper setting to glossy photo paper. So if your pictures are printing fine on plain paper and the colors are all gross on the Photo paper setting, you know that your problem is with the Photo Cyan and Photo Magenta tanks and heads.

3. (I just discovered this tonight) The Photo Cyan tank and the Photo Magenta tank share a single print head, unlike all the other colors which get their own heads.

4. It's possible to pop out the print head assembly (just remove all the ink tanks and lift the gray thingy) and clean it out thoroughly with isopropyl alcohol. It's messy so do it in the sink. You can use a syringe or bulb to force alcohol (and later air) gently through the print heads to make sure they're all clean. Then gently press a kleenex against the print heads to wick the last of the alcohol out of the heads.

...

So I've done all of the above and I'm still left with a problem. The Photo Cyan ink is leaking out whenever Photo Magenta gets printed. I made a test page with big squares of Cyan, Magenta, Yellow, and Black, and 30% Cyan and 30% magenta. When printing the test page via the Photo paper setting, all of the rectangles print perfectly except for the Photo Magenta rectangle, which comes out a murky streaky violet/purple combination. Seeing the printout it's dead obvious what's happening: Some Photo cyan is coming out when Photo Magenta is being printed. WEIRD.

I'm sure that my printhead cleaning process did not cause this to happen. The problem existed before I tried cleaning the print head.

I've emailed Canon and I hope they have a solution. I suppose I could just buy a new print head assembly, but at this point I could almost buy a whole new (better) printer for that.