I have an HP3500 which I've had from new since 2004. On the whole it's been remarkably reliable but recently I have problems with a multicoloured stripe which appears down the lefthand side. It doesn't matter what type of document I'm printing - result is the same. I replaced the fuser about 12 months ago which seemed to solve the problem but gradually it came back after a few months. If I print several copies the stripe disappears and basically the more printing I do the better it gets. I'm using mostly remanufactured cartidges now but the problems started before I switched. I don't notice any difference in quality with non HP cartridges. Currently I have a mix of HP and non HP cartridges installed.

Hi Richard,
Dots, Lines and smudges on the printouts are usually due to deteriorating cartridges and cleaning the green drum of the cartridge may help temporarily. Take out the cartridge and inspect them. You may observe the lines on the green drum. Gently clean the roller/ green drum with a dry, soft, lint-free cloth wiping off the toner dots marks/ lines. (corresponding to the location where you are having a green line on the paper)
Also, make sure that the visible inside of the printer are clean and there is no spilled toner inside, which sometimes results in dots.
Moreover, streaks (thicker lines) and dots etc indicate faulty PCR Roller which is located behind the green drum inside the cartridge. Observing the PCR with the help of a sharp torch light would let you assess the condition of the PCRs at the corresponding location where lines are appearing. Replace the Cartridges one by one and inspect the prints for the changes. I think you would be able to identify the faulty cartridge/ rollers. Also, if the waste toner area is filled and/or the plastic wiper/ cleaning blade removes the leftover toner/ waste from the drum and holds the waste is worn out, it results in spilled toner usually at edges and at early stages lines only.
Moreover, the function of the fuser is to fuse the toner onto the paper and it is usually done at the end of the printing process just before the paper is ejected (and the image/ toner on the paper is just fused - not changed). The fault at the fuser area usually results in smudges, ghosted image or unbind toner (which easily gets erased when touched). The time during the printing cycle when the toner is spread on the paper, additional toner (resulting in lines) is shifted to the paper due to cartridge related issues, which results in lines. Note that after cleaning the rollers, the print quality improves and the lines disappear or lighten. Try and check if the above suggestions work.

Hope it helps! Good Luck! Thanks for using Fixya!
CreativeTECH