The Magicolor 7450 carries a chip in each imaging unit. If the four colors are warning that they must be replaced, it is better for a technician to see it, since perhaps the ONC cylinders must be renewed along with the chips. It is a colour machine of a certain cost, so it is not advisable that you experiment with it. I attached the links with photos showing what an imaging unit looks like and then the position that they occupy in the machine the imaging units and those from the toner.http://www.supplydepot.com/mmSD/Images/KONICA-7450-DRUM-YELLOW.jpghttp://images.quebarato.com.mx/T440x/impresora+konica+minolta+tabloide+magicolor+7450+grafix+coyoacan+distrito+federal+mexico__7F50C_2.jpgDrums are like 25 dollars each and the chips (one for each color) are like 7 dollars each.Obviusly if you buy everything Konica original, it'll get ready to be installed and everything will get solved very easily.