I originally got a message that my printhead was defective and the printer would not print. I checked out you tube and I pulled it out and tried to clean it but I was impatient and still the printer didn't work. I thought it would be easier to buy a newer or rebuilt printhead. But when I installed the $15.00 one on Amazon, the printer got the dreaded error message that I had to unplug the computer, hide under my desk on hope this wasn't the end. (just kidding). It said to call the service people(Canon service people do not service my computer anymore because it was so old.) So I thought maybe this knockoff I bought was defective so I checked out youtube again and this time I spent more time soaking the printhead in rubbing alcohol and took the two screws out holding the plastic piece with holes. I cleaned that piece and made sure I could see daylight through the holes except one. Then I installed the printhead again and was pleasantly surprised the printer now worked again.
