asked Jul 2, 2000 at 9:56am
Hp HP OfficeJet D

HP LJ IIP+ Black Pages

I recently purchased a used HP LaserJet IIP+, which printed fine for about a week, then started giving occasional 51 errors, and now prints only solid black sheets of paper, including the internal print test routine. A friend of mine purchased an HP LJ IIIP at the same time, which he has graciously loaned to me for spare parts (since most of them are the same) in troubleshooting my printer's problems.

After reading a bunch of posts here and on a few web sites, I tried swapping out several components on my printer with those in the IIIP, including the laser assembly, the scanner motor assembly, and the density adjusting assembly. I've also inspected the optical fiber cable, which looks and feels okay (and it does transmit light), as well as testing some of the electrical connections in the wiring harnesses for resistance.

After all of this, pages still come out completely black. I managed to eliminate the 51 error (probably from the scanner motor), but I can't figure out what to do next. Am I missing something obvious? I don't have a lot of experince fixing laser printers, but I am pretty good with electronics, so I'd really appreciate some guidance here....


You're kind of barking up the wrong tree. The 51 error is a beam detect error. This in most cases is caused by the laser pca. In this case, because of the intermittent nature, it was probably the scanner motor, which normally would give you a 52 error, but I've seen a few cause a 51 error. Black pages are caused by lack of high voltage on the photoconductive drum. The toner must be getting a charge as it's transferring and the charge transfer roller likewise must be getting a charge as it's pulling down the toner
on to the page. That leaves the photoconductive drum which as we all know starts out with a charge and the laser erases the charge. Wherever there is a charge, the toner is repelled. No charge, it sticks, thus forming the image. This all proves that the high voltage unit is doing it's job and we can blame contacts to the drum as the guilty culprit. To solve the problem, you'll see a white plastic axle on the left side of the cartridge held in by 2 screws. Remove the axle and tap the shaft out so it protrudes about .050".
We use a hammer and a .050" thick washer in our shop. An alternative would be to bend out the contact in the printer so it makes firmer contact with the axle.

by moe on Jul 2, 2000 at 9:28pm Add comment


it is allready a long ago (2000) but I try to contact you. I also have a problem with my LBP-4 Lite Canon Printer. After warming up it gives an error: 50 Service.

In the documentation I find nothing about this 50.

Can you give me information please.

Kind Regards from the Netherlands,

Jan Van Dongen

[email protected]

by dongenvj on Aug 20, 2017 at 5:00am Add comment