Canon Printhead (i550 & MP390) cleaning tips I've experienced.
Should work w/other printers (H-P) that have channel connections (that clog) between their print ink reservoirs & their Printheads.
My Canon i550 (12 yrs old - luv it) was not printing black ink - clogged - plenty of black ink supply. (Color OK.) 3 yrs. ago bought a replacement printhead from Canon ($41) & I tried to do same & was told Canon no longer makes that replacement printhead. UGH.
Went on line & discovered Applefritter:
They share some interesting Canon printhead cleaning experiences. (Better printing thru chemistry, little elbo grease, no $, & good luck.)
I've discovered that after 3 "Deep Cleanings" on my Canon i550 printer no improvement in printing - still blank. Then for the heck of if I did a regular cleaning & print head came to life. Had to do couple more regular "Cleaning"s & prints just like new. (almost) Had similar problem w/my Canon MP390 on my ACER CPU & I did the same thing & MP390 also prints like new. (almost) Weekly maintenance "Cleaning" is recommended by Applefritter contributors.
Hope this is helpful. Use as you see fit.