Konica minolta bizup c550 printing black copy what will i do?

try this

Self Help Product Support Konica Minolta Business Solutions Inc

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

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

"Dirty" could be one of 3 things... Transfer belt, Imaging unit and fuser unit. Make 5 copies in jam the machine by opening a cover. remove pages and see where the "dirt" originates from.

P6 : cyan image unit problem. P21 come after P6, and it's also too a cyan unit image problem. replace the cyan image unit.

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

replace the yellow imaging unit.

If the message Change Imaging Unit Magenta displayed refer to imaging unit with contents a developer.The Imaging unit life is 80.000 copies.
The imaging units located after front door when is located the waste toner box.
If the message M toner end/change the M toner displayed refer to toner cartridge
The toner cartridge life 15.000 copies 5% saturation.In full color mode the color saturation is 80% and the color toner life is 6.000-8.000 copies.
I think your problems is a toner not the developer.

remove the filter and housing from the i/u and vac out the spilt developer, do the same on the underside, if background/halo is still there increase the seconary transfer value by 2 for plain paper