no magenta printing out

Following the suggestions above I have just resolved this problem. My exact problem was that the Magenta colour was printing out at different densities across the page - from faint at either side to solid in the middle. 
The procedure I followed was to dismantle the printer until I could get at the laser/scanner unit, take that out, and take the top off. I discovered that the mirror for the magenta toner was very dusty so I cleaned it with a cotton bud (dry, no water or solvent for fear of damaging the surface coating of the mirror), taking the opportunity to clean all the others at the same time. 
After reassembling, the printer is now perfect again. I did not perform any resets or recalibrations following this operation.
Some comments:
1. Disassembling is a fairly complex job, involving disconnecting most of the loom from the back PCBs. You need to do this to be able to remove the rear internal panel so that you can get at the laser/scanner assembly. Don't worry too much. though, because all the plugs are different sizes so it should be fairly straightforward reassembling it all. It worked out fine for me!
2. The bottom screw for the laser/scanner assembly (in my case, although there are actually holes for two screws) is located behind two thin metal panels which spring out from the bottom of the printer body, just above the paper tray.
3. I think there is a bit of a design flaw in these printers (if it's fair to describe it as such). Two of the mirrors (magenta and yellow) are angled upwards so that dust can collect on them, while the other two are angled down. Of the two that are angled up, the Magenta one is at the bottom and is most likely to collect dust. The laser/scanner assembly is not sealed so it is easy for dust to get into it. Furthermore there is a fan alongside the bottom mirror so there will be more dust in the air in this area. It would not surprise me if this is a fairly common problem for these printers after a certain amount of use.

Thanks! It fixed it for me, too. My photos now print beautifully, just like the day I bought the LaserJet printer.

I have gone to the trouble to lay out each step of the process, along with photos, to help others: see my website for this.

I took my printer apart and cleaned the mirrors. However, after putting it back together my pages are printing out with magenta toner all over the background. Does anyone know what I did wrong.

My Color Laserjet 2600n was having this problem. I phoned HP (UK) and they're replacing the printer even though it's two years out of warranty.

The solution here looks like a good one but it's worth seeing if HP can help you first I think.

I just got off the phone with HP customer no-service and they said that since my printer is out of warranty (1.5 years old) that I could either pay for an express exchange of $279+tax for a refurb or buy a new one for $374. Thanks to this list now I may have a chance to get my printer fixed after just buying all new printer cartridges that set me back almost $400. Can anyone provide detailed instructions and/or pictures on how to disassemble the printer? Thank you in advance!

Thanks nick11 - I now have my printer back working again like new.
tom/

Fixed it for me! Thanks a million. Use an air duster to clean the optics and reset the printer to default settings once all reassembled, which will force a recalibration. Make sure the optical unit is properly seated before replacing all the boards and wires at the back though. (I didn't, and had to take the whole lot out again to pop it into place properly!)
Mousematt

Magenta cartraiage is emty or replace it

Dust on the lenses and mirrors will cause this problem.

You will need to remove both sides and the back plate to get at the optics box.

Try cleaning all of the laser optical path.

there is some error with printer board

Dear Fix Ya

my HP 2600N Is printing white pictures red as it gets lower down the page. can yoou please advise on why this is.

Kind Regads
Kam

we followed all the steps and the printer began printing worse...the colors are even more faded than before....we tried it a second time and used an alcohol swab, and lease cleaning sheets, and now the printer wont print at all...not even one dot. All the connections are right, the lenses are as clean s they can be, and the was no dust left behind....help please.....

although there are a lot of screws, you will have to open it again, take all the parts out and put them back, but make sure you will do it turning all the screws tight, also, and most important, do not do this with the cartridges in the printer.
also, when you finish, set the printer to clean itself, it will ask you to insert cartridges, open hatch, clean the printing film, insert cartridges and it is all done, also, please calibrate it!!!!

You made my day, i had the same as everyone else, cleaned the mirror and it works fine.
Thank you so much

Lynne