Oki C8800 Printer color failing

[arcadien]

Dear all

I have a Oki C8800 which isnt printing correctly

Colors are faded and black isnt being printed
Ive changed the drums of magenta yellow and black plus plus their tonners

But still not working what could it possible be ?

 

[arcadien]

Here are some example of the prints

When i change the black for the red it prints black