My HP 2840 is printing blue lines on the side of the page

SOURCE: HP LaserJet HP 2840 printing fades away on one side of page

The carousel has slipped out of alignment. Force it back with a flat blade screwdriver.

SOURCE: HP 2840 will not print on 3 inches of left side of page

Take the toner cartridge out, shake it back and forth, and turn it around in a circle a few time. Put it back in the priter, and print. Order a new toner cartridge.

If this is an inkjet printer, ignore this response.

SOURCE: 2840 only prints on right side

If you are a bit adventurous and a bit patient, you perhaps can fix this yourself, and not require any disassembling. It worked for me on a similar 'carousel' unit... hp2550L.

For extra info, check this post out. http://www . fixyourownprinter . com/forums/laser/40284 (remove spaces)

If you look closely at the spot where a toner cartridge slips into a slot of sorts, you might see left side aligned and right side just a little off of 'good alignment' for that slot. What I did is to pull on the top of the black-plastic gear. Pull it toward the center of the printer.

There is a small, white gear at the very top of the black gear (not easy to see at first). By this pulling and bending of the black-plastic gear, you can get the gear teeth free of the white gear --- for just a moment. Just enough for the gear teeth to free-up and find their proper place. It doesn't take much.

When done, take a breadth and relax. Turn power off/on, and try it out.