Xerox DC12 problem

[Vince66]

I have got a strange problem with only black color. Before 2 months i have same problem and that was with black developer when I was print a black scale from 0-100% everything is OK except 100% of black (90% black is OK?!). After replace old black developer (and print only cca. 100 prints) everyting was fine till today when I again have same problem with only black toner and only on 100% of that color (remember 90% of black color is OK).
When I print something (like text or bitmap) who have 100% black on it, I get mealy ($hit) print.

Can someone help me please !

P.S.
there are no erorr codes on printer, seems everything OK .

[xcopytech]

can you scan some print to see what is problem

[Vince66]

Try to imagine, print is like I print with developer not with toner, print (only when I print 100% black) is not "burned" to paper with oil layer. When I get by finger on it, I get smut my finger with ash (probably black developer).

Soon, I will post a scan of scale.

Thx!