Chacham's Journal: Question: Xerox Docuprint 750 ink problems. Any ideas?

Just went to someone's house to fix their printer problem. It's a Xerox Docuprint 750, and the problem was that the black and yellow inks would not work. The black ink is a new cartridge (second new one, as she wondered if the other was faulty), and the yellow is low, but there is definitely ink to work with. The cable is connected tightly on both ends, and the black ink used to work before the switch.

I used the clean function, with now results. So, assuming clogged heads, alcohol was poured on the sponges. This got black to work, especially after a clean, and yellow showed a mediocre a gain, but was not working perfectly. A second printing showed a decline in both.

More alcohol can be added (followed by a clean) and have it work again, but only for one print. After that, it dies. So, i'm a bit bewildered as to what to do here.

Oddly enough, the yellow is Xerox ink, but the other two colors are not. (I'm pretty sure the black was Xerox, but i forgot.)

Does anyone have any advice?