How to repair Canon Purge Unit

[Trigger 37]

Hello to all in this forum. This topic may be beyond the capability of most people that use this forum but hopefully if we get some answers, it will help everyone. I work on all kinds of printers and especially on Canon printers. I've had the opportunity to replace many of the detailed parts on many printers and this includes the purge unit. On one i560 a spring came out of the purge unit and had fallen in the bottom of the printer. The result was the purge unit would not cycle and that led to error messages and a very clogged print head. Upon disassembly I found the spring and was very lucky to take the purge unit off of the main Carriage and disassembly the purge unit to put back the spring.

The problem is, once you take the right two screws out of the purge unit the right side falls off and the gears that drive the purge cycle dis-engage. I got luck and found a way to put it back together and it worked fine.

Now I working on the purge unit out of a MP730 All in One printer. It is basically the same unit. However, this unit has slipped the gears and is totally out of position and locked or jamed. As a result the purge unit thinks it is cycleing but doesn't really move. The Suction pads for the printhead never come up to mate with the printhead soooooo, it can never prime the printhead and therefore no ink or no colors.

Many people have seen a similar symptom,... ie. no ink on the paper. This is always a printhead that did not get primed,... which is always the fault of either the purge unit or the the ink carts ( or a clogged printhead).

What I am looking for is any kind of diagram that would show the correct way to re-assemble the purge unit gears. Everything has to be in the exact right place when the right side it put back on. The Canon Service Manual and parts Catalog do not go down to the level of disassembly of the purge unit. It is a replaceable item by part number so the service people probably never mess with it and just order a new one. There is nothing broken in this unit,... it is just slipped out of track.

If anyone has any ideas or suggestions,... please reply. If your only going to tell me to get a new purge unit,....don't bother.

Now here is some information that may help many others. The purge unit is very critical in getting the printhead primed and keeping it primed with ink. I believe that the purge unit and/or the ink carts are the number one reason that printheads end up getting clogged. For example, I have seen printers that have set for 2 months fire up and print after one power on cleaning cycle. This must have been because there was a good supply of ink from all carts, and the purge unit did it's job. When the printhead is parked for a long time on the ceramic suction pads, they keep the print nozzles slightly wet. Another way of saying the same thing is that they "Don't let the printhead nozzles dry out".

Now do the same thing after a couple of weeks if either the ink carts are getting old and do not supply ink very easy. The suction won't get ink into the nozzles, so if there is any ink left in the printhead it will probably print 1-2 pages but will then begin to be empty because no new ink is flowing. Then the printer gets parked for another week or so and the very small amount of ink in the printhead begins to dry up. The beginning of a clog. Now John Doe does a bunch of nozzle tests and each one get worse. He does a couple of more cleaning cycles which only suck the very last microdrop of ink out of the nozzles. Now they are really empty. Frustrated, John Doe goes to bed. Now the printhead really starts to dry out and the clog builds even more.

All of this usually starts with a bad or poor ink cart that is either running out of ink or has been refilled so many times that it is drying up inside or at the exit port. There could be a dozen reasons why the cart is failing, the result is always the same.

What is the purge uint is locked or stuck in some wrong way. The same result will happen. The printer I described above came from a customer that was constantly only using the black print and finally one day wanted to print color and of course it would not and no amount of cleaning cycles would fix the problem. I put a brand new printhead in the unit and got the same results because the purge unit would not even prime a new clean printhead. To get at the purge unit to even SEE it require complete disassembly of the MP730. Of all the printers I have worked on, the All in One units are the most complex. It is about a 15 step process to disassemble a MP730, to get all the way down to the carriage asm and then you can't get the purge unit off until you take out the screws that hold the paper feed asm to the carriage. In Canon's wisdom, they put one of the screws that holds the purge unit in place underneath the plastic housing of the paper feed mechanism.

So if you ever have a clogged printhead, and you clean the guts out of it using ever technique you've read on this web site,...but still it won't print,.... now you know where to start looking.

There are usually a couple of Canon Service people that watch this web site. If you know where there is a Canon Service Information Notice that is directed towards the re-alignment of the gears for ANY Purge unit, this would really help. Just about every Canon printer from the i550 to the iP6600D uses almost the same purge unit. One ore two screw may be different, and the size of the suction pads are different, but the rest is the same. I know this because I have repaired everyone of those printers down to the bottom of the waste ink pads. This also goes for all of the MP All in One printers. They are all the same.

 

[Trigger 37]

While 55 people to date have looked at this post, no one posted any comments or suggestions. Anyway, the good news is that I fixed the purge unit and put it back into the MP730, re-assembled the entire printer and it worked fine.

Since the printer had been sitting for over 3 months waiting for me to get around to it, I was very happy to see it print a tiny bit of black and a couple of nozzles of all the other colors. These were also very old ink carts and not what I would call in great condition. After 3 cleaning cycles I had a perfect nozzle check pattern. This was a printer that basically could not print anything because,....... the purge unit internal gears had slipped out of track and it would not cycle at all. The bad thing about the MP730 is that it is so large, even when you open the cover to get at the ink, you can only see one small portion of the purge unit, and it is almost impossible to reach the suction pads. This printer had been in bad condition for a long time as the ink in the purge unit was dried up.

To fix the purge unit requires complete disassembly of the printer, removal of the main carriage asm, and then you have to remove the paper feed asm to get at the very last screw that holds the Purge unit in place. Once I got the unit out it was clear the the gears were out of track. When I took the purge unit apart, everything fell out, including the cog cam that is the main item that makes everything move. This unit is virtually all mechanical. It is kind of like the Glocenspiel clock in Munchen,...Everything moves back and forth because of Cams and one drive motor. The only electrical item in the purge unit is a photo cell. As the cam rotates, a blade passes between the photo diode and this sends a signal to the main logic board that the purge unit is cycling. I'm sure it measures the times for all of this to veryify operation. Even if the unit turns but does not do it within correct time slots, the logic board knows something is wrong, and I suspect that an error condition is generated.

When many people report seeing 7 orange flashes, this can be one of three things, 1. Printhead. 2. Carriage Asm. 3. Purge Unit. The printer that I have mentioned above had "NO ERROR SIGNALS". So it was still cycling the cam but the guts were not moving anywhere. The only other wires going to the purge unit are to drive the DC motor that turns everything.

On the post above I had asked for help from anyone that might have a diagram on how to put it back together. With a lot of patients, I tried several attempts and finally got real lucky and got it back together. Then I manually cycled it to veryify that it did a complete cycle and that everything moved to where it was supposed to. I had already totally cleaned all the ink out of it and flushed the purge chambers and dried everything. I had removed the motor prior to this to make sure I did not get any water on the motor. The question was, even if it manually cycles OK, would it work in the printer.

The very bad thing about the MP730 is that to get at the inside guts, the logic card has to come out and all 12 connectors that plug into it and everything else in the printer have to come out. So to test ANYTHING, you have to completely re-assemble the entire printer. So if you put it all back together and it doesn't work, you've just wasted two evenings. I feel very fortunate that I got it all back together and it worked the first time. This is the third MP730 that I have fixed, and now I have great respect for the Canon printers. I learn more of this everyday. You CAN take Canon printer apart and put them back together,... and they work.

Hope this post helps someone else.

 

[Bird333]

Glad you got it back working! Can you describe how to put the gears back on correctly?

Thanks!

 

[primusSPA]

hi man.........ur great...u manage to repair ur printer.......new here so cant comment much abt the printer but i am sure many people would be thankful to you for sharing ur experience......tks alot for sharing ur experience

 

[jru]

Trigger 37,
Your post was beyond me, but I wanted to say thanks for sharing this.
Where have you found manuals to disassemble the printers?
Thanks again!

 

[Trigger 37]

Thanks to all those that posted,..and I hope that post helped the many others also.

Bird333,... It is going to be very difficult to explain how to align the gears and put it back together by just using words. There are many parts so I will have to take another one apart and take pictures as I go through each step. I have done this same thing on all the printers that I have repaired and I have created repair manuals for each printer. Since these are all put together in a PDF document, when anyone looks at them they can ZOOM in very close to look at each detail in the photos. I have shot each photo with my 10 Megapixel camera so the pictures are very high resolution. that is the great thing about PDF files, the images are in there at excellent resolution. I just finished repairing 2 more i550 printers and in the process of taking them apart and cleaning them, I also take out the Purge units and do a complete cleaning of them, including back washing all the ink out of the guts of the purge unit. However, I did not have to disassemble either one of them.

I can't stress how important it is to make sure the PURGE unit is clean and working good. If the purge unit can not suck ink into the printhead and PRIME it, you can never get a good print. One of the i550 printers was so bad it was showing the classic signs of "NO COLORS PRINTING AT ALL". This has happened to 100's of people and they always think it is the printhead. They clean it so much they probably damage it and then they are really up the creek. I did the normal printhead cleaning on the first unit and put it back in the printer with know good ink carts. When I printed the nozzle check, there was nothing but the black. Because I have so many printers I can swap parts around to check things out. I moved the same printhead and inks to a second i550 and did one cleaning cycle and I got a very small amount of two colors. I did a couple of deep cleaning cycles and then the nozzle check was perfect, all colors, all patterns. So This tells you how important it is to PRIME the printhead with ink. The Purge unit in the 2nd printer was working fine and Primed the printhead. I put the printhead and ink back into the first printer and it printed a good nozzle test but after a couple of prints the colors were gone again. This would suggest that the ink carts were not supplying sufficient ink and the printhead ran dry but I know this was not the case. I believe that somehow an air bubble gets sucked into the printhead and after that, it is very difficult to prime it with ink unless the purge unit is working very good.

I am still investigating the various possiblities since I have seen this problem with my printers many times and by using all my tricks it usually goes away. I have also seen 100's of posts on this forum that describe the same symptoms and most people never find the answer and usually either get a new printhead or dump the printer. Some are lucky enough to get it to work, but never know why. I need to know EXACTLY why.

In my home right now I have 14 HP printers, 5 Epson Printers, and 13 Canon Printers. This alows me many more options in testing units to verify Printhead, Ink Carts, and Printer Purge systems, to find out where the real problem is. I don't waste a lot of time testing them until after I clean each one, but testing them before and after gives me much better symptoms of what is wrong. I find if I clean them first and they end up working, I did not learn anything,... and it is all about the learning.

When I get some more anwers I'll add a new post but not to this thread.

 

[tigerwan]

Do you sell the manuals you make? or can one request them for free from you?

 

[Trigger 37]

tigerwan,.. I'm sorry,... there is no free lunch anymore. I'm just about finished with them and I will sell them on eBay for about $25. This also includes the Canon Service Manual and the Canon Parts Catalog for each printer. I figure that these manuals will save about 2 trips to the Service Center or at least keep someone from dumping the printer into the waste land and buying another printer that will be even more problems. Have you looked at the price of the ink for Canon's new "Chipped Ink Carts".

I hope to have the i550 i850 i950 and i560 on eBay in a week or so. The rest will come one at a time. After all, I'm retired and Golf and boating take up a lot of time.

 

[rpkrupczak]

Trigger 37 ... I have similar no printout on an S9000. Put in new head and still no luck. Printer sat for a year ... so put in new oem carts, too. Need the wide format prints otherwise would have just let it sit.

So figure its the purge unit. Never tried disassembling a printer but its either that or dump it. So willing to try. If you've ever done a similar printer would be interested in your input as to difficulty and whatever I should watch out for. If you have a manual that would show how to do the S-types might buy one from you as 25 bucks more would be a gamble worth taking.

Sure liked the detail in your previous posts.

rpkrupczak

 

[Trigger 37]

rpkrupczak, I have not repaired an S9000 yet but I just looked at the Service Manual for the S900 and the parts catalog for the S9000 and it appears they are the same execpt for one being the wide format. I will have to study them some more, and I believe I have an S600 that have yet to take apart. Once I see how the covers come off and look at the guts, I can give you a better answer. However, if your printer sat for a year, the odds are that the inside guts of the purge unit is totally clogged with dried up ink. Don't try and print any more, since if there is no ink getting to the printhead, especially if it is new, you could overheat it by trying to print without any ink in the printhead. If the purge unit won't suck ink, there is no way to get ink into the printhead and firing all the nozzles when they are dry will overheat them and potentially burn them out.

Try the following. Get a syringe and load it with a little Windex or hot distilled water. Open the cover and when the printhead comes to the center, squirt some windex onto the suction pads where the printhead parks. It should only take about 0.5 ml for each pad. Close the cover and let the printer do it's parking cycle and this should push some water through the purge unit. Open the covers and check the pads to see if the water is gone. You may have to do a power on/off cycle to get the purge unit to cycle. Keep doing this until you see that the water is successfully sucked down through the purge unit. Then run a deep cleaning cycle and then a nozzle test. Don't do any regular printing until you get a decent nozzle test.

If this does not work, you're going to have to get the covers off, remove the carriage asm from the printer case, remove the purge unit, and then either do a really good cleaning of it or replace it. All of this is explained in Chapter 6.0 of my Repair Manual which includes high res pictures that show each detail.

I'll be back once I find out more about the S- series.