We do not discuss service level repairs. I will outline somethings to ensure you did cover. Very seldom 2 heads go out at the same time. You will get partial printing from any one head, when you loose both black and cyan, those are controlled by one fuse on the motherboard. You can swap the yellow and magenta cables to see if the head fires, but if it is a head problem, then you will be blowing the other fuse too.