Troubleshooting a HP LaserJet4's greyness.
May 7, 2006 4:52 PM   Subscribe

The pages on this HP LaserJet 4 are coming out partially grey. Replace the Fuser, or something else?

It's a gift, and I don't have a need for a laser printer, per se - Therefore, I'm not interested in spending a fortune on it.

I read this, and am considering that it might just be the fuser - I got ahold of a copy of the service manual for it - I can definately do the replacement.

The text is visible on the printout with a grey background, sometimes with the ghosts of previous printouts behind it, and the printer behaves itself otherwise. It seems to have plenty of toner, and there are no errors reported. Are there any other diagnostics I can run, or websites I should be looking at?
posted by Orb2069 to Computers & Internet (8 answers total)
Look at the fuser drum after a print. If there's a buildup of toner on it, you do probably need a new fuser. Also, does the ink on the page smear? If so, that also points to a bad fuser.

BTW, if you're otherwise using an inkjet printer, the cost of fixing the LaserJet will pay for itself in no time.. those toner cartridges last freakin' forever, and are cheaper than most inkjet cartridges.
posted by Sxyzzx at 5:06 PM on May 7, 2006

Best answer: Sounds a lot like a bad drum to me. It probably has a reconditioned toner cartridge in it.

If the printout doesn't smudge when you rub your finger across it, the fuser is fine.
posted by Chuckles at 5:42 PM on May 7, 2006

I had a bad fuser roller (apparently also known as a fuser drum?) on my LJ5 last year. The ghosting of previous printouts is definitely familiar. However, as Sxyzzx suggests, physically examining the fuser roller will give you the quickest answer. In my case, there was a worn patch in the middle of the roller with text from previous printouts visible on the surface.

The replacement was actually quite enjoyable for me and my mechanical engineering roommate in college. The coolest part was seeing the giant halogen bulb inside the drum used to heat it.

Around $15 shipped from eBay makes this a worthwhile investment!
posted by corranhorn at 8:41 PM on May 7, 2006, especially the forums, is a terrific resource for this sort of question.
posted by Eater at 8:49 PM on May 7, 2006 [1 favorite]

Best answer: The fuser and the drum are separate parts.

The drum is photosensitive. It electrostatically attracts toner where it has been exposed to laser light. The toner laden drum is then rolled across a piece of paper with an even stronger charge, which moves the toner onto the paper. Finally, the paper passes through a fuser which heats and melts the toner, fixing it permanently.

It seems that there are two problems, both drum related. The drum appears to be picking up extra toner, which transfers to the paper and causes a grey background wash - a common problem with reconditioned toner cartridges. The drum also appears to be keeping charge, or toner particles, from the previous page. If the drum is not properly cleared of either a 'shadow' of the previous page could appear on the current page.

How Laser Printers Work.
posted by Chuckles at 9:19 PM on May 7, 2006

I guess the fuser roller could also pick up toner residue causing the shadow problem..
posted by Chuckles at 9:26 PM on May 7, 2006

Best answer: do a half page self test (print out a page, demo page or whatever) and stop it in the middle of printing by opening the printer up. Try stopping it when its just about to exit and also when its under the toner. You will see if the grey is coming from the toner area or the fuser. It's one or the other, unless theres some loose toner in there or something. And BTW, the laserjet 4 is a beast of a printer, make sure to sort all the hundreds of screws when you're dismantling it.
posted by psychobum at 3:01 AM on May 9, 2006

Response by poster: Turns out that it's the cartridge - the half-page print answered the question for me without having to, as you say, sort the hundreds of screws (No kidding! 'Fixing' inkjets has spoiled me.)
posted by Orb2069 at 8:04 AM on May 12, 2006

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