We have a problem with background light tinting. The image is otherwise perfect and fused properly.
The machine is a low mileage 4700 with only 60K copies from new.
I have replaced all cartridges to no avail. I put the machine into diagnostic mode and disabled cartridge detection & removed all toners, printed a supply sheet, blank and clean, fine. I then installed toners one at a time starting with yellow and printed a test sheet after each Y,C M fine, added the new black toner and the problem was back.
I next tried removing the magenta and installing black in that slot again fine, next I installed magenta in the black cartridge slot, this time I got a magenta background tint. I summise the problem is with slot 1, the black slot.
Hours of searching the web have suggested a number of possible problems, laser, High Voltage Board, DC Power supply, Formatter, transfer belt etc.,all without any testing guidelines.
We are in a very rural location without accesss to competent engineers so I have to look after our nine HP's best I can, unfortunately we only have one 4700 so swapping parts is not a possibility.
Any suggestions as how to pin down the problem and the best starting point would be much appreciated.
Regards
George
Northumbrian56