I have konica minolta bizhub c550,it showing me P21 and P6,what is the causes?and the black is not printing well

Registration errors. Have tech come out clean IDC sensors and replace black i/u

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

clean the drum with soft cloth or run clean drum mode

Konica Minolta bizhub cooling fan not working Questions ...

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Konica Minolta bizhub printers & copiers cooling fan not working related questions and answers. Ask your Konica ... Question about Bizhub C550. 1 Answer ...

Konica Minolta Bizhub C550 Cooling fan power - Questions ...

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konica minolta bizhub c252 error c-5351 C - 5351 Is power cooling fan problem.Verify the cooling fan connectors and clean.For reset open/close the front door.

cooling fan not operating properly - HP Support Forum

The corona housing for the back drum need to be replaced. Get a new black image unit drum and developer units

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

Color registration is off check the sensor under the transfer belt and mite want to have e tech run color registration procedure. black is the reference for the color registration having developer problems with black drum does not help

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

replace the black image unit and run gradation test

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

replace the black image unit and clean sensors under the transfer belt

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

try to repl. transfer belt then clean all contact of transfer belt

write unit block the signal just try to look for the object that block the signal from write unit

look the drum unit need to be replaced