Misaligned vertical lines on T790 24" have replaced all scan axis parts

[pbrooks259]

Hi, on a T790, am getting Misaligned vertical lines (pic attached) on a T790 24" have replaced all scan axis parts--idler pully with bracket, encoder strip, belt, carriage, scan axis motor, rear carriage bushing.  Replaced ink tubes assy. w/ trailing cable with refurbed one from LPS a few weeks ago--leaking at carriage.  I have adequately lubed the scan axis.  I checked continuity of each wire in the trailing cable; all appear continuous, but at certain bends I suppose one could be a bit discontinuous, don't know.

I first suspected the motor as during the scan axis test 86:01 would be thrown up right when the rear bushing is about to enter the channel that it rides in and when the carriage would bump up onto the cutter bar (if I started the scan axis test on the left end).   So I assumed those 2 spots created extra draw on the motor, so I assumed a bad motor.   With the carriage in the center position most times it would make it thru the scan axis test OK.

I checked voltage of the scan axis motor during an internal GIS print and was reading anywhere from 2.6V to 11.0V.   Maybe I have deficient power to the scan axis motor.  Don't know right now.   Seems like I would get more voltage in the 12V to 24V range.   But right now I don't know whether it is a 12V or 24V motor--I need to look on the motor, but probably does not state voltage, maybe does.

I have performed the printhead alignment several times.

What board upstream from the carriage would most likely result in a continuation of the misaligned vertical lines.  The misalignment is equivalent to the length of the printhead nozzles and are misaligned with each swath of the carriage (again pic attached).

Right now, I am getting 59.3 because apparently I did not switch over my old line sensor.   I am wanting to know if this is caused by a bad board what would it likely be:   Main pca, PSU, or what?   I am getting ready for the next step in case it is needed.  Something tells me this is something more that what I have done so far.

I was able to do the scan axis test again after all of the above replacements.  The only thing was that I got 42:10 when I started the test with the carriage on the left end--I think when it ramped up on the cutter bar.   Maybe a bad replacement motor????   After all of the above replacements I was still getting misaligned vertical lines.

Thanks for any input.

[pbrooks259]

Can a bad line sensor cause misaligned vertical lines as pictured?   But it does successfully get through the printhead alignment.

Would running the line sensor calibration detect whether the line sensor is bad?  I assume so.

At any rate STILL getting misaligned vertical lines.   Replaced all parts in the scan axis EXCEPT the line sensor--had to use my old one to use a used replacement carriage from LPS in order to avoid 59.3:00.

On Monday, a printhead alignment would help although I could still see a bit of vertical line misalignment but not as bad.

But now a printhead alignment does nothing.  It is like the printhead alignment is no longer maintained, no longer saved.  Or it aligns printheads OK (successfully)  but something is still wrong with the alignment.

Could this be in the firmware although I have updated it to the latest?

Just for fun I threw a few parts at it:   I tried a different interconnect PCA--no change.   I tried a different formatter board but I think it was of the wrong type and got 59.3 (original hard drive was used; formatter CN727-60115 Rev. A? was used).

I plan to try a replacement ECM (main pca and PSU).     ....but MAYBE it is the line sensor.   Don't know really.

[pbrooks259 · Accepted solution]

I feel pretty stupid!  All it needed was a:

line sensor calibration

I had the printer perform that calibration and horizontal misalignment (or possibly left to right offset?) was resolved [vertical lines (perpendicular to the printer axis) look fine].    I have never experienced having to do the line sensor calibration in order to get rid of horizontal misalignment (again, or left to right offset?).   I was pretty much accustomed to "printhead alignment" addressing any horizontal misalignment, but it did not work in this case.  But it did work significantly at first but then later "printhead alignment" did nothing to correct the problem.

For the line sensor calibration, if you do not have some type of glossy photo paper loaded or to load, change the active paper type temporarily to an acceptable glossy photo paper in order to perform the calibration; ideally I suppose you should have some type of glossy photo paper loaded.  I changed my "bright bond" to "HP High Gloss Photo" paper or something of the sort.  After the calibration, I changed it back to "bright bond".

Thanks to Kiran's (copytechnet.com forum) thought that it could be a bad "line sensor" which prompted me to have the printer run the line sensor calibration.

[D Hook]

Glad you were able to solve the problem.  Your posting will help others.  Thanks!