Tx2-1600 stripe damper problem

[HPS]

Hello, some time ago I described in some diffrent topic, a problem that sometimes was happening on our machine. Now from couple days now we got this problem all over again, and we cannot make any way further from it, cannot do anything about it. It looks like this. When printing dark colors, like black, grey, blue - on the fastest, 2rows, 4big stripes mode, which is called "LOW" in PosterPrint quality manager that we use, that after some ammount of printed document, that color becomes softer and lighter than it should, just like it would be just 1row fireing the ink. Some1 told me that it's caused by heads being not refilled fast enough during those faster modes. Thats somewhat ture, because till now, it never happend on those 'MEDIUM' and "HiGH" modes. But now unfortuantly it does... After such action happend, I made a test draw, to locate which head has the problem, and result made me thinking it's the first one in front row (looking from control panel of Mimaki, it's the very right bottom corner one so it looks like this:

o o o o
 o o o x

I turned off machine, and looked at dampers. They were dirty, and looked someway broken. I took them out, cleaned with cleaning solution, and I was successful in that process. I put them in once again, and sucked ink to refill them half way. After that action, I was able to print for an hour or so, until the problem occured again! Now, strangly enough, the problem occures on every and each try of dark color printing, after 5-10cm printed. On every mode (i.e quality) but whats most importand, after problem occures and I'd make test draw - there are no visible sign of problems, no more clogged nozzles, everything looks completyly good (I made test on paper to be sure). What can cause such problem ? For the good sake I ordered new dumpers and capstop, but I'd like to take some advices from You guys before I start to swap parts, that can be even not to blame in this situation. Here are some pictures of everthing:
http://imageshack.us/photo/my-images/818/20120213091941.jpg
http://imageshack.us/photo/my-images/259/20120213092005.jpg
http://imageshack.us/photo/my-images/141/20120213091934.jpg

 

[HPS]

Yesterday we've got spare parts arrival, so we changed the dampers on the head we blamed at the begining, but nothing changed. After that, we started to experimenting with colors, makeing rectangles of full color of each CMYK. It shown to us, that problem comes from Cyan channel. So we changed another two dampers, on those two channels of Head 1 and 2. Unfortunatly, it still didn't recover from that error. Than we spent couple of hours on trying, and we got some result. You see, if we're using 2 rows of heads, problem is there. If only front - no problem. If only rear - no problem. Test draws are always good, no matter if 1 or 2 rows. This seems for me like a problem of hydraulic systems, maybe the pipes with ink are clogged? Is it worth to remove ink cardidge and put cardrigde with cleaning solution and than make fill-up ? For now on I started to print with only front, but it takes additional time. I also will try to change rows at 4hour shifts to not overexpose them. What do You think about those ideas ?

 

[HPS]

After a month or so of neverending tests, in conclusion we got informaiton, that it's one of two small mainboards, which controlos heads. After swaping one with another, we swaped the problem - so this is our cause. Maybe it will help someone in the future