[Misc] Problem Black C500

[Cosminake]

Hi everyone,

I have a Bizhub Pro C500.
Problem with black, but only in polychromy and color overlays. If I print black text, the print is perfect.

I've attached a scan.

What should I do?

Thank you!MINOLTA67.pdf

[JustManuals]

Re: Problem Black C500

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[Mick01]

Re: Problem Black C500

Hi,
your sample is a bit unclear however. Try and stop the print prior to entering the fusing unit. Check the image before fusing. Could also be a second transfer problem. Again stop the paper before fusing and check the image on the transfer belt.
hope this helps to isolate your issue

[Cosminake]

Re: Problem Black C500

On the transfer belt, the image seems to look ok.
I recently rebuilt the fuser assembly. New pressure, new fuser. Is there any setting for the fuser assembly after rebuilding it?

[Mick01]

Re: Problem Black C500

There is a fusing speed adjustment you can perform. In my experience it should not cause your issue though. Did you check the image on the paper prior to it entering the fuser? I've seen a faulty upper fusing roller give a similar problem.

[Cosminake]

Re: Problem Black C500

There is a fusing speed adjustment you can perform. In my experience it should not cause your issue though. Did you check the image on the paper prior to it entering the fuser? I've seen a faulty upper fusing roller give a similar problem.

The image before entering the fuser it looks ok.
When I touch the printed paper, all areas covered with black are in relief. I think it can be a problem with black toner density.

[Mick01]

Re: Problem Black C500

It could be a density issue, or a pressure issue. Calibrate the controller and look at the black Dmax values to see if the machine has a black density issue.

[Cosminake]

Re: Problem Black C500

I made an automatic gamma adjustment. I've attached the result.
There seems to be a problem with DCBias on black.
What should I do?

Mick01, thank you very much for help!

[Mick01]

Re: Problem Black C500

Happy to help. It doesn't show dc bias level on the pic you sent from what I can see. Usually bad bias readings are due to worn developer or faulty tank. It appears though it completed auto gamma successfully. This indicates the levels within tolerances. Where is the machine at in regards to the pm cycle. It may need a pm (drums, devs, charge units). A good starting point is to replace the dev.
good luck

[Cosminake]

Re: Problem Black C500

15k copies ago I've changed:
- developers
- drums
- drum cleaning blades
- charging coronas
- fuser
- pressure

Before changing the developers, I've cleaned very well all dev units.

[Mick01]

Re: Problem Black C500

Have you calibrated the RIP? Looking at the actual vs target should give a good indication of black density. It will also make adjustments to the black Dmax when printing. Try outputting test patter 81 or 82 and see what the density is for all colors. What is the thickness of the paper? You mentioned that the print is raised in high density areas. It could be pressure related. Carefully check all sleeves in the fusing unit. Check the one way clutch underneath the fusing unit.
Hope this gives you some ideas.