How to confirm printhead failure

[Trigger 37]

Tin Ho,... Thanks again,... but I really thing the repair percentage should be at 99% or higher for the Canon Printers. This is because I am able to get such good parts. a while back I had a i850 printer that a customer had totally given up on. The belt drive for the carriage asm had become disengaged and the belt came off of the drive motor. The only way to fix this was total disassembly. Believe it or not the real problem was a tiny coil spring that provided tension for the drive belt. It had come off and was nowhere to be found in the printer. I got the new spring from Canon for about $.50, but had it included with many other parts I needed. So for $0.50 I was able to fix a very good printer. However, when I started I had no clue what was wrong with this printer. It could have been something very serious, like the logic card, which is way too expensive. Anyway,... when I replaced the spring, the rest of the printer has worked just terrific. It need some pretty severe cleaning, but after that was done everything printed just fine. I restored all the ink carts and refilled them. Now the printer is sold and someone is very happy with the printer they have,.... and there is one less printer in the dump.

 

[Grandad35]

One other question to Grandad35,....where can I find the details of the Dertchues??? refilling process.

Sorry for the delay on getting back to you. Here is a link to the method posted by Defcon2K:
http://www.nifty-stuff.com/forum/viewtopic.php?pid=9279#p9279

 

[Trigger 37]

Grandad35,...thanks for the link. The video is terrific. Here comes the "BUT". Since the needle goes all the way into the ink chamber, it is just passed through the sponge chamber. All the ink is injected into the fill chamber so when all is said and done,... the ink is in the fill chamber and after the neecle is remove it can "Wick" back into the sponge chamber. I don't see that this is any different than filling the ink chamber from the top. It isn't going to purge any dried up ink in the sponge chamber, or it isn't going to force iany block or trapped air to flow anyhere. It is just a different way of filling the ink Chamber.

The biggest problem I have is that after I have used a BCI-xx for several refills, the sponge no longer wants to absorb or wick the new ink and the flow rate out of the bottom of the ink cart is not as good as it should be. Also, since the flow of ink is so critical to the printhead, and all of this flow is dependant on the system being able to create a vacuum as the nozzle fires and then sucks ink from the taank, everything will flow in synchronism down through the nozzles. If there is one air gab anywhere, the vacuum is lost and no ink will flow. After all, the only suction force that is available durning printing is the micro vacuum that is created by each ink drop being ejected. The ejection of 1 ink drop is what create the short vaccum pulse that sucks in new ink. Does any one know just how small a force that is.

 

[Trigger 37]

Now back to the real topic of this thread. The continuing mystery of the Printhead,... is it a clog,.. or is it a bad printhead,... or is it bad electronic connections.

My last series of post were on the i560 printhead and the i850 printhead. This week I started working on an i950 printer and here is a picture of the first nozzle check after I turned the printer one and ran one cleaning cycle.



As you can see one half of the bottom group of nozzles on the Cyan set is not printing at all. Also you can see that in the Photo Cyan group, one half of the top group of nozzles is not printing. So this printer continues the mystery of how to identify which component is really bad.

I ran a couple more cleaning cycles and some deep cleaning clycles and tried the nozzle check again. This is what came out.



As you can see, now the Photo Cyan group is missing one half of the top and one half of the bottom,...but they are different halfs. After this centered the printhead and unlock and relocked the printhead lever a couple of times,... then retested. There was no improvement.

Then I took the ink carts out and the printhead out and cleaned the contacts on the back of the printhead and the contact in the carriage asm using Isopropyl Alcohol. The new test after this showed no improvement at all.

Next I removed the printhead and did a complete cleaning cycle using hot water and Windex. Then I soaked the prinhead for 1/2 a day. The I dried it using my air compressor whihc is set for a max of 75 psi. I also used the air compress to force air backwards through the in k jets to force any dreid or clogged ink out of the printhead. I then re-installed the printhead, deep cleaned all the ink to prime the printhead, and retested. There was no improvement or change in any of the nozzle patterns. My next test will be to take the printer apart, remove all the printhead connections at the logic card, clean them, re-install them and then run a new series of test.

Because this nozzle check appears so symetrical I do not believe it has any thing to do with a clog. I am fairly convinced that I cleaned all the ink out of the printhead. If anyone has ever seen this nozzle pattern before, please respond with some data.

One other piece of information, I printed my standard 6 color bars in the size of a 5x7 photo. All six patterns of color bars were solid with no streaks at all. you would think after seeing that print that everything was perfect.

 

[Grandad35]

Does any one know just how small a force that is.

Its been a while since I did the calculations, but based on the surface tension of the ink and the diameter of the 2 pl nozzles on my i9900, I seem to remember that the nozzles can theoretically pull about 4 psi of vacuum. That may seem like quite a high suction for such a simple device, but remember that a tree uses the same capillary action to pull water to its top branches. Actually, there are several places in the ink link between the nozzles and the cart where such high suction levels cant be supported (especially when the printer is idle for extended periods), and they are probably the limiting factor in how much suction can be pulled on a cart.

How are you cleaning your carts? There is good evidence that cold water does not clean the sponge/filter nearly as well as hot water. Rubbing alcohol is also an effective cleaner, but you have to completely purge the alcohol from the cart before refilling or the ink will have the wrong viscosity and surface tension. I have encountered two carts that didnt work properly after purging, and the problem with both was that the sponge had been moved out of position. Tapping the cart to get the sponges back into position fixed both problems.

One other piece of information, I printed my standard 6 color bars in the size of a 5x7 photo. All six patterns of color bars were solid with no streaks at all. you would think after seeing that print that everything was perfect.

While the 8 pass overprint used by Canon on photos can apparently hide such severe banding problems, the loss of of the ink coverage in some colors will severely affect the color of photo prints. The loss of a few random nozzles should not be visible, however.

 

[Trigger 37]

Grandad35,... I use the hottest water I can stand. Also, it seems much more effective to focus the hot water stream at the bottom of the printhead, direclty onto each bank of nozzles. Many times after I have clean a head, I let it soak in hot water for a couple of hours and then hit the bottom with a new stream of hot water. What I see is more ink appear at the filters when I turn the printhead over. This tells me that water is getting through the printhead from the nozzle side, and that there is still dried up ink inside the ink path but it is still being dissolved and coming out the top. I usually repeat all the process untill I don't see any more ink coming out the top of the filter screens.

This current i950 printer, which is a great 6 color printer, appears to have some kind of electrical disconnect somewhere. The other alternative would be some kind of defective logic board or faulty decoder EEprom on the back of the printhead. I'm still waiting to finish my testing on the i950, as I have a customer that despartly needs his MP730 repaired. It is a strange mystery,.. people think they can stop a paper jam after it has started by pulling backwards on the paper as hard as they can. Al this does is force the timing gears totallly out of sync. Resetting the timing gears on a Mp730 is easy,... the hard part is that you have to totally disassemble the Multifunction printer to get at the timing gears. Once you correct that problem, you can't even test it until you put the printer totally back together. If you do one thing wrong,... it's back to square one.

 

[Grandad35]

The biggest problem I have is that after I have used a BCI-xx for several refills, the sponge no longer wants to absorb or wick the new ink and the flow rate out of the bottom of the ink cart is not as good as it should be.

My comment on using hot water was in response to this statement. This is a common problem after several refills, and is why a number of us do a "hot water purge" on our carts after several refills:
http://www.nifty-stuff.com/canon-bci-6-cartridges.php

 

[Trigger 37]

Grandad35,... I had mentioned I used a VERY simplifed version of your cleaning process. Sometimes it works, sometimes it does not. I guess I'm going to have to follow yours since I know that really works. I have never used anything but the canon carts as I don't want to mess with what I know works. What I need now is about 36 hours in each day.

 

[Trigger 37]

I just wanted to let others know that I have posted a reply to a person seeking help with a faulting Canon i960 printhead. Since this is key to my ongoing post about printhhead I thought I would show the photos in this thread. This is another i960 printer I got from someone that was totally fed up and could not take it any more and went and bought a new printer. I don't know what kind, but I want to show you just how much of a waste this decision was. Here is a picture of the nozzle check on this "BAD" printer when I first powered it on and did nothing but one cleaning cycle.





Now here is the image of the first nozzle check I did after one of my standard water cleanings where I used the full force of the water faucet and the force of my sink spryer on the bottom of the printhead focused against the nozzles. I could not believe the amount of magenta ink that kept coming out. I continued the cleaning until there was no more ink. I dried the printhead and installed it and ran one PC cleaning cycle to prime the head. Then I printed the follow nozzle check.




This picture show a perfect nozzle check. This is another printer that was headed for some landfill somewhere. I didn't even change the ink carts A lot of people know the i960 is one of the best high quality printers that Canon has ever made. After this test I printed out a 8x10 high resolution photo I took of the Alps in Europe and it was beautiful. Not a flaw anywhere. There was a time many moons ago where I had really questioned if this water cleaning was really doing any good. This was because some printhead problems are not due to clogs but are many other things. This can really confuse your thinking on how to clean printheads. However, this recent experience with this i960 printhead has re-confirmed my belief in my basic water cleaning process. It is not the "Save All, do all" solution but it really does work on clogged printheads.

So that is all the news from Lake wobegone, where are the men are good looking, all the women are strong, and all the kids are above average. Take care.