cp3505n very light print in middle of page

[Bink]

Model cp3505n color laser: I replaced a broken lever lock on the right side. after reassemble black prints very faded in middle section of page. I have reassembled and made sure gears are aligned at least three time. I have eliminated the actual cartridge, the fuser and the transfer belt as being the problem by using these in an identical machine. I have run full calibration about 6 times.

If I change the print color to red in the middle of the page it prints just fine. Really seems to be something with the black cartridge slot.

I try to do a cold restart but does not work - just ignores the depressed button.

only other hint may be when printer is in ready mode I hear a repetitive buzzing (right side is off)

Any help would be appreciated.

[cs_steve]

Could be a problem with a dirty laser scanner (try cleaning it directly in the center of the black laser scanner mirror). The buzzing noise makes you think more of an electronics board hum, although they do emit small noises, could possibly be a problem with the high voltage power supply board...