MPC305 Colour Registration out at 1200x1200 DPI Only

[Smee]

As the title says, Im working on an MPC305 with bad colour registration ONLY at 1200x1200 DPI. When printing at 600 DPI its fine, when printing the calibration sheets they are all fine except on the last one - the colours dont line up, and also when I do the internal test sheet SP1103-1 the colours are out, again its at 1200DPI.

Sounds like a board fault to me. So far ive replaced the controller, BICU, both NVRAMS's, both lasers, ITB belt assy, all PCU's. The parts were from a new donor machine that is known to be good.

All firmware was over written / updated, not just the ones that were out. It has done 5000 colours and 50,000 black prints. Its like a new machine again with all those new parts, and theres really nothing left to replace!

Only thing I can think of left is there must be some sort of ITB speed sensor thats not part of the ITB assy itself...Ive had this fault on a ProC7501 and it was the ITB speed sensor. Different machines but worth a go if I knew where to look, the manuals for the new machines dont go into specifics enough!

Anyone else had this fault or got any ideas?
Cheers.

[Iowatech]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

Any chance you could share a picture or two of the bad prints? That would be really helpful.

[Zeldaman]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

Hi there!
Yep, some photos be cool. By the way maybe the itb-motor-unit D1176241 is faulty.
Greetings...

[JonJames]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

Had a similar issue on a 305 where only 1200x1200 was affected. Our symptoms were a yellow background on the test page and customer prints.

Turned out it was the HV board in the end !

[Smee]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

Heres some samples...im going with ITB motor seeing as the machine slows down for 1200DPI...If it dosnt it would look erratic like these samples.

[slimslob]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

It looks to me that either the ITB motor speed or the polygon mirror motor speed is off at 1200, depending on whether the registration is off in the main scan direction or the sub scan direction. I would say replace the ITB motor as Zeldaman mentioned or the polygon mirror motor. If you could attach another copy of either the 1200x1200 Calibration or the Color Test Pattern with the direction of paper travel indicated we can tell you which motor.

[Smee]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

I agree with the ITB motor, it cant be the laser as these machines have 2 - 1 for the K and C drums, and the other for the Y and M drums. I dont think they would both fail at the same time, and I have replaced them anyway.

I will replace the ITB motor and let you know of the results.

The paper is fed short edge feed.

Thanks heaps!

[Iowatech]

Re: MPC305 Colour Registration out at 1200x1200 DPI Only

Crap, too late!
Oh well, I'll just put this here anyway in case it might help sooner or later.
Based on the orientation of the text, I am going to guess those pictures were printed SEF. (If this is not correct please ignore the rest of this.)
As such, I would think that if the ITB or it's drive system had anything to do with this problem the defects would only be in the main scan direction, and not in the sub-scan direction as the pictures appear to show.
I've had a problem similar to this on an older machine when I foolishly did a memory clear. I had to re-enter all the values from the birth certificate and then go through all the forced line adjustments to get rid of that. (My diploma from the School of Hard Knocks class on Why Not To Use The Memory Clear shows several hours wasted and a very kind customer getting somewhat annoyed. Not something I'll forget soon.)
If that machine has a birth certificate, you might want to at least compare the values it lists dealing with color to the ones in service mode. Also, if you haven't tried already, the forced line adjustments might be something to do. Maybe double check that the ID sensors are clean enough for the higher resolution prints. At least that's what I'd start with, especially if there have been energetic storms or construction nearby the machine lately.