The print head is made to be a replaceable part because sometimes they need to be replaced! The funny part with a Pro-100 is that it is far cheaper to buy a new Pro-100 with included $250 rebate, 50 sheets of big paper and a full set of ink. When I needed a print head, the estimate was $200. Allowing for the value of the ink and paper, a new printer was free (after the Canon rebate).

A very pleasant surprise was that the "new" printer accepted the partially used cartridges from the "old" broken printer. Not a drop of ink was wasted!

When I was a workin' man, I serviced large format inkjets. A lot of customers used Canons instead of HPs because they were less expensive. Several of the Canons (not all, I worked on probably several hundred of them) would have issues caused by ink, non- Canon variety. With those Canons it was possible to drain the ink out of the printheads and the inkfeed tubes. I would refill the printer with Canon inks and it would usually work fine. (tried to not replace the printheads if possible as they were $500-$700 ea). Not every printer using non-eom inks would have this problem, but enough of them to convince me to use Canon inks in my Pro-100. Your description of the inks fading running the nozzle check indicates an issue with the printhead, not software. It could be caused by the ink or just a bad printhead. Possible bad connection to printhead, reseating it might help. Good luck.

Agreed, blaming the ink is the myth of purists and is bunk. Inks are not made in heaven with witches around a cauldron using Fillet of a fenny snake and other ingredients** that are impossible to analyze by modern chemistry instrumentation. The ingredients and formulations have been around for decades, nothing amazing and new.

UV stabilizers are common and low cost so are standard in aftermarket inks. OEM inks contain components that are analyzable by modern chemistry instrumentation and thus aftermarket can duplicate or improve on OEM inks.

** http://www.shakespeare-online.com/plays/witcheschants.html