C4050i print quality issue nad p-9 error code

[Miltan]

Greetings. I've been battling with Konica Minolta C4050i for over a week now. After changing settings in service mode and swapping numerous printer parts, i still cannot find the cause of the problem. It does not print colors in a smooth way, leaving parts of the image partially colored or lacking. I also cannot get rid of error code P-9, which is related to black drum. The IU has been changed 2 times and after some time when troubleshooting the cause of bad printing, the error comes back for random reason. Even after cleaning laser window and running stabilization, the problem won't go away.

The following parts have been changed and did not solve the issue: Imagining Unit, transfer belt, HVPS, PH unit and base board. Almost everything that can be responsible.

The Scan of the halfstone pattern at 100 density and test page have been attached.

EDIT: The issue with error code P-9 was solved. I've reinstalled black drum and that seem to solve the problem.

[Synthohol]

Re: C4050i print quality issue nad p-9 error code

have you stopped the image before the fuser and checked the transfer belt? it does not look like a repeating pattern.
check the wall voltage during copy to see if there is a significant drop in supply voltage.

[Miltan]

Re: C4050i print quality issue nad p-9 error code

I have few photos from transfer belt that i will now attach. As for voltage drop, i was suspecting that it either loses or does not get enough power when printing. However even if i swapped power supply and HVPS at the same time, the problem still occured.

The transfer belt from the photos had a problem with printing blacks but that issue has been solved.

[Synthohol]

Re: C4050i print quality issue nad p-9 error code

the blocks look ok before they hit the paper. is the 2nd xfer roller and registration roller ok and does it spin freely?

[Miltan]

Re: C4050i print quality issue nad p-9 error code

I think i may found the cause on why the print quality is bad. When i was checking Paper Feed Unit and gently rolled it, i felt a bit of resistance. I disassembled it from the printer and when i was rolling the paper feed, it felt fine. Then i checked on the left side where the Paper Feed Unit is connected and noticed, when i was rolling it, there was quite a bit of resistance. I had a second printer nearby and using the same method, there was no resistance at all. Does anyone knows what's the name of the plastic with hatch on it?

[Miltan]

Re: C4050i print quality issue nad p-9 error code

Turns out Synthohol was right, it was indeed 2nd Transfer Roller Unit that was responsible for bad printing. I had suspicions about it since the left hatch wouldn't click properly. After swapping for new part, the issue was gone.