It has been awhile since I started this thread so I thought I would update it and finish it off. I ran out of time working on that original i550 so I set it aside. Since then I refurbished an i860, an MP730, an i560, and today I got another i550. The more printers I do the more I learn.
This last i550 taught me a lot. This printer has really been abused and given up for dead. At first inspection all but one ink cart was empty. There was so much dust and spider webs inside that when I tried to feed paper, it would feed part way through, then back up, then proceed after a paper alignment. This misfeed occurred on every other piece of paper. After a couple of nozzle test prints, a piece of dust came out the front and feeding was fine after that. I can't imagine what I will find when I take it apart and really clean it.
I installed known good ink tanks and did several deep cleaning cycles. Some people warn about doing deep cleaning cycles and choose to print out test images of solid or mixed colors. I used to do this also, but once I learned what the real problems are and how to clean the waste ink pads, I don't ever print a test color image unit the printer is at least working at 80%. Why is this,.... because if you can't get your nozzles to print color or black, you could be damaging the printhead if you print images and there is no ink in the printhead nozzles to keep them cool. That is the primary reason for doing deep cleaning cycles. There is "NO FUNCTION" that will get ink into the printhead nozzles other than cleaning or deep cleaning cycles. This is how ink is sucked into the printhead. The first nozzle test after cleaning gave me only a 95% good Cyan Crosshatch pattern (CH) and a 50% Magenta CH, and an 80% yellow. The Magenta had the famous picket fence pattern which we now know how to explain. There are two rows of magenta nozzles and the picket fence is made when one row of nozzles is still clogged and the other prints ok. There was no black printing anywhere, not even the letters used for printhead alignment. No amount of deep cleaning cycles helped anything. Typically there are four things that can cause this. 1. Clogged nozzles. 2. Clogged ink cartridges. 3. Clogged Purge Unit. 4. Bad printhead.
I had already verified I was using good ink carts, so it had to be one of the others. I did a quick cleaning and test of the ink Caps and cycled the Purge unit to see if it was really sucking ink. A visual inspection of the ink Caps showed me that the Black Cap was so clogged with dried black ink I'm sure it could not suck anything. I flooded it with Windex and cycled it several times until I saw the Windex sucked away. I did a quick water rinse of the printhead and got all kinds of ink to come out, especially the black. I dried it off and used my 90 psi air compressor to blow all the extra water out of every location. I loaded the printhead back in the printer, installed good ink carts, ran a couple of Deep cleaning cycles to prime the ink into the printhead, then I printed a nozzle check. Bad news.... The pattern was almost the same. The magenta was now printing a broken fence which is just a little better than the picket fence,.. but again there was no black anywhere. I had thought my clean was going to work since I saw so much black come out of the bottom.
Ok, it is time to cut this story short. It was not the purge unit, as I was able to get some signs of suction out of it when I flooded it. So I started the heavy duty cleaning cycles with hot water, then over night soaking in Windex, then the next day repeat all of above,.. with no change. So back to deep cleaning with hot water, and more over night soaking with Windex and water. The next morning I found some black ink it the water so I knew I was making some progress. So more rinsing with hot water, air comp. dry, installed in printer, deep cleaning cycles, and finally, a full 95% black CH pattern in the nozzle test. Magenta is now at 90% but still has some strange nozzle patterns, but the black printhead is perfect except for one nozzle 3rd row from the top and 80% to the right. This nozzle prints but not at the correct time and it prints above where it should.
The answer to all of this is,... yes you can clean some very bad clogs, but it takes time and a lot of cleaning. There is another trick I've learned when cleaning the printhead with a stream of water. First I clean off all the ink from the top that sits on the filter screen and is dried around the cushion pads. Then I turn the printhead over and let the water hit the nozzles. This forces ink back up through the printhead and up to the filter screens. If you turn the printhead back over without letting water on the screens you can see a very important clue. If there is Cyan, Magenta, Yellow, and/or black wet ink coming out of the filters screens after you flushed the nozzles from the bottom, you know you have forced water all the way back up through the printhead and out of the filter screens. This is very good news for you as this proves that this nozzle is no longer 100% clogged. If you don't see fresh wet ink on the filter, this tells you that it is still clogged. This was the clue for my Black nozzles. I could always see wet ink on C,M,Y, but never black. I did see a lot of black ink wash away when I flooded the printhead black nozzles from the bottom. It would squirt both left and right with the force of the water jet. Why was this??? Because the black section of the printhead was still 100% clogged deep inside the printhead. The black ink that was coming out the sides of the black nozzles was the ink that was just getting dissolved by the hot water hitting the black nozzles with force.
Some people say,...where do you get the time and patience to do this. To me it is no problem. I'm retired and I get tired of planning golf 5 days a week,..so I have several hobbies, one of which is fixing and selling printers. It is also about knowledge,... the more I do the more I learn. I guess I really didn't want to be 100% retired,... I had just had enough of 33 years with IBM and Corporate "BS". What I do now is very insignificant to the positions I've held at IBM,...but you know, I get as much satisfaction today, knowing that I can help others.
I would think that this post should conclude this thread, but I'm sure others will learn from it and add their own success stories.