Laserjet 4250 print quality issue (see image)

[hfat]

Hi!

An old Laserjet 4250 has developped a printing problem which affects the top of most pages. The severity is somewhat random. I've scanned one of the worst cases and cropped the image (see lower or this link: http://postimg.org/image/jkh4v2vgb/ ).

Has anyone seen behavior like this?

The rollers haven't been changed in a while. Would it make sense to try to change them and if so, which ones? Or is it something else entierly?

Thanks!

[SHThompson]

It's not likely to be a roller unless it's part of an assembly you can replace, in other words not one of the feed rollers.

Unfortunately I'm browsing with a smartphone and can't see any pictures. If you describe the problem I may have some idea what the cause is.

[hfat]

I added a link to the image in case that helps someone actually see it.

I'll try to describe it: when it happens, what's printed is vertically distorted throughout the width of the page, kind of like if the paper skipped a tiny bit at some points perhaps.

Some parts of the top of the page are OK, as is the most of the page. It seems like the problem solves itself once part of the page is through.

[SHThompson]

That is an interesting failure.

It could even be a formatter failure although I do some other testing to try to isolate this.

The first thing I would do is an engine test, on the right side of your printer which is the same size the formatter is on there is an extra small hole in the side cover. This hole is between the formatter and the front of the printer, and if you put a small non metallic object like a toothpick through it and push straight in you will hit the engine test button on the DC controller. The engine test will print out a page of black lines, and the object is to see if the defect shows up on the engine test. You can also power off the machine and remove the formatter then power back up with the formatter still out of the machine and run the engine test again if you saw the defect. The Engine test on this machine will run just fine with the formatter removed and if you have the defect with the formatter removed and the formatter is definitely not the problem.

[SHThompson]

If the engine test works just fine with the formatter installed then I would do what is called a half self test. By the way the more correct term would probably be partial self test.

To do this test you put paper in tray 1 and print any test page that shows the defect. You pop open the top cover after the paper is in the printer and when you think the paper is under the toner cartridge in and waiting area where the defect occurs. You then remove the toner cartridge and leave the paper in the printer and look at the paper at you will normally at this point see the defect on the paper however it is not fused to the paper.

If there is no defect on the paper at this point then it is possible the fuser is causing the problem but I would repeat the test a couple of times to make sure it is not a coincidence. You are a sample page does not look like a fuser problem, but I won't rule it out as a possibility.

Now if you sold the defect on the paper then pull back the shutter on the toner cartridge so you can see the drum, the drum is the shiny roller that goes all the way across the cartridge. On the drum you should see some toner that has not been transferred to the paper yet and some toner remains where most of the toner has been transferred to the paper. Closely examine the toner on the drum if you can see the defect on the drum then the defect is either an issue with the toner cartridge which based on the picture doesn't seem likely but it's a possibility.

If the defect is happening during image formation your possibilities of a laser which is a low probability that DC controller or the formatter.

Since we can run the engine test with the formatter remove we can rule out the formatter or prove the formatter as the cause fairly simply.

If one of my posts resolves your problem please mark it as a solution. If you wish to say thank you for any post just click the thumbs up button under the post and give me some kudos, they are appreciated.