bizhub c351 low quality grey (black)

[Guest]

Hi,

everything that is not 100% black so it's grey has a lot of lines that cross only the darker grey - please see the scanned paper. This is printed on plain paper - on thick paper the problem is more obvious.The machine has 230000 copies made but i just changed the belt and the black drum (not the entire black UI only the drum) and the problem persist. I cleaned the black LED but no improvement after that. I'm running out of ideas so please help me. Thanks.

Updates. I decrease the density on halftone pattern in service mode and it seems that lines appear on colors too. Also i attached another scan on 250 g thick 3 paper where you can see how bad the black is.

[mo0651]

Looks like a charge wire streak. Have you cleaned the main charge?

[tasta]

Hi, thank you for your post. To be honest i do not know where the charge wire is but i will study this and i will clean this. I will be back with results. Also in the upper right part (portret position) is a much darker zone. Can this be from fusing unit?

[stryker3k]

If you have only changed the drum, then i would change the entire IU. The dev in the IU is prolly stuffed. I have never changed anything but the entire IU, but that is KM's policy.

[tasta]

Hi, i already test the machine with another black IU and the problem persist so is not from dev.

[stryker3k]

Hi, i already test the machine with another black IU and the problem persist so is not from dev.

Considering you have done Belt, IU, and cleaned the LED, it could be the LED itself or even the HV. When you cleaned the LED, did you use a moist cloth/cleaner strip? Dry doesnt always clean it properly.

I just noticed that you say that those lines show up on colours too? If that is so, I would say belt (or possibly HV but that is unlikely). Did you test it with a new belt? or just a used one? Coz i cant see the fuser causing banding like that.

[tasta]

Considering you have done Belt, IU, and cleaned the LED, it could be the LED itself or even the HV. When you cleaned the LED, did you use a moist cloth/cleaner strip? Dry doesnt always clean it properly.

I just noticed that you say that those lines show up on colours too? If that is so, I would say belt (or possibly HV but that is unlikely). Did you test it with a new belt? or just a used one? Coz i cant see the fuser causing banding like that.

Hi, the belt has only 500 on counter and it looks perfect. The old one had some banding on it but the current one is perfect so i think that is not the transfer belt. In the colour tests the banding are almost invisible and the color of lines is fade white - opossite to the black tests where the lines are black ( see attachements on first post ). I really do not know what else i can do.... The led was cleaned with a dry pad but because i spotted the banding on colors too is not the led. Maybe the electronic part of the led's?

[stryker3k]

Hi, the belt has only 500 on counter and it looks perfect. The old one had some banding on it but the current one is perfect so i think that is not the transfer belt. In the colour tests the banding are almost invisible and the color of lines is fade white - opossite to the black tests where the lines are black ( see attachements on first post ). I really do not know what else i can do.... The led was cleaned with a dry pad but because i spotted the banding on colors too is not the led. Maybe the electronic part of the led's?

Hard to say, you have replaced everything except for the LED.the white lines on the colours might be a seperate problem altogether. I am thinking the K LED is faulty going by what has been replaced. I have never had to replace an LED on that model, but there is always a first time i guess. I would still try cleaning the LED with a moist cleaning pad because it does make a dramatic difference over a dry one (even thought it is usually shadowing on the black that you clean the LED for.)

[tasta]

Hard to say, you have replaced everything except for the LED.the white lines on the colours might be a seperate problem altogether. I am thinking the K LED is faulty going by what has been replaced. I have never had to replace an LED on that model, but there is always a first time i guess. I would still try cleaning the LED with a moist cleaning pad because it does make a dramatic difference over a dry one (even thought it is usually shadowing on the black that you clean the LED for.)

Hi, i've cleaned the LED with moist pad and nothing has changed. I'm waiting for another IU (maybe it was a sad coincidence with the one i already test the machine) and i will see the results. Thank you for your advices.