Rock Monkey

asked Aug 17, 2012 at 9:01pm
Hp HP LaserJet 4

HP Laser Jet 4 Prints Blank Pages

My HP Laser Jet 4 prints blank pages. Well the pages are not quite blank they have smears that occur in reoccurring patterns. The more pages are run the more these smears dissipate. The pages bear no recognizable text whether I print pages from an application, the test menu, or push the recessed test print button by the multi-purpose tray. When I choose "cont self test" it seems to print keep printing indefinitely. Once or twice error 41.3 popped up then it went away. I think this occurred beccause the printer would sometimes draw up more than one page from the cassette.

I've checked the shutter on the laser and that seems to be working okay. The spring seems to be properly attached and the shutter retracts when the cartridge is inserted. The cartridge support that lies above and behind the cartridge that has also been mentioned as a possible culprit remains in place.

By way of background that may help understand the problem, the printer used to jam incessantly and eventually every time. So, I partially disassembled the paper output assembly and the fuser assembly. I found the fuser caked with hardened toner that I carefully cleaned off and some wedged bits of paper. I also would find loose toner in the bay where the cartridge sits and in the paper cassette, I guess it settled there from above.

The printer no longer jams. However, it just prints the smeared pages described above. At least when it jammed it printed the page sent to the queue. I don’t know if I might have dislodged something or reassembled it in the wrong position thus causing the smeared, blank pages.

I have also seen some reference to resistance values for the pins on fuser assembly. I get about 2.7 ohms across the power pins on the right side and continuity. On the left side there are two pairs of small pins. I get continuity across the bottom pair and a resistance reading of approx. .3 ohms. On the top pair I get mostly infinite resistance, though occasionally it flashes a number somewhere 163 to 192 k ohms on my digital meter.

When examining the toner cartridge and if I retract the door covering the green roller I see patterns similar to what appears when I attempt to print something. I don’t see anything that resembles text or graphics.

Any insight on the problem would be much appreciated
Only 3 things can cause blank pages. You have checked 2 of them, so that only leaves the HV power supply as a probable cause. The streaking you describe is most likely a bad toner cartridge. So, you have 2 problems. A defective HV power supply and a bad toner cartridge. The HV power supply sits above the paper cassette tray, so I doubt you could have done anything to it when you were poking around. BTW, the 41.3 error is caused by a sticking solenoid in the paper feed assy. It will only get worse with time and eventually cause continual feeding of blank pages until it jams.
by moe on Aug 17, 2012 at 11:12pm Add comment
It is obvious one of the issues as Moe stated is the toner cartridge. As to the other issue you need to do one more test. You need to perform a half test by putting a sheet of paper on the manual tray and send a self test from the test menu on the printer. When the paper enters the printer, quickly open the toner door to stop the printing. Now remove the toner and flip back the shutter and see what is on the drum. If you now see text, then the issue could be the transfer roller which sits below the toner cartridge. Since you mentioned cleaning up that area maybe you dislodged or caused contact issue so the transfer roller can no longer move the toner from the drum to the paper. If still no image, check the contacts inside the toner cavity that mate with the contacts on the toner cartridge. The fact that it is very hard to cause the hvps to go bad and with you messing around inside the toner cavity it would make more sense that you dislodged something causing an issue since the printer did put print on the paper before you started to "fix" your problem.
by dmzcompute on Aug 18, 2012 at 8:39am Add comment
Thanks for your prompt responses. I appreciate your insights.

DMZCOMPUTE: I put a sheet in the multi purpose tray and sent a test and when I opened the lid to stop it midway when I extracted the toner cartridge I saw the same sort of blurry pattern that had been appearing on the pages during previous tests. (I did have a hard time getting it to pick up the paper from the multi purpose tray, but that is a separate, more minor problem.)

I examined the contacts as you suggested. There being two spring loaded pegs and a wire catch on the left side and one spring loaded metal piece on the right, as well as a cog on either side. They seemed to be okay. Contacts looked pretty clean on both sides, machine and cartridge. However, it got me thinking about how all sorts of loose toner used to spill out there and I got to wondering if it might be fouling some connection or maybe have caused a short. Can toner cause a short? Does it conduct?

MOE: I pulled out the High Voltage power supply (which was easier than expected, no wires to unplug) and found a good bit of toner in there, including on the two sets of three electrical contacts, which I guess are positive and negative sides of the circuit. I cleaned it up carefully and put things back together.

When I started it up, I heard a new sound that I hadn’t heard before. You hear the start up sequence so many times; you know when something is different. It sounded like something was straining to turn; it concerned me enough that I turned it off. (I hadn’t been messing with the rollers in the most recent investigation.) When I turned it back on I heard the sound again but I let it continue. It still prints blurry pages with nothing looking vaguely like text, even when I run the engine test. After unplugging and checking the shutter again I ran it again and the strange sound had disappeared but still no text prints.

Is there a way to check with a digital multimeter if the HV power supply is putting out juice? Or looking to see if the laser is running? Am I right in assuming that there is only one moving part in the laser? Is it worth investigating more closely? Is it possible that no data is being sent to the laser? I don’t know where else the loose toner may have percolated.

The machine really hasn’t had a lot of use. I bought it new when these things first came out and really haven’t printed a lot with it, especially in the last five years because of the problems with jamming.

I don’t think I ever got 5000 pages out of a cartridge. Can a cartridge be damaged by pulling a jammed sheet out without removing the cartridge? What causes a cartridge to go bad before it runs out of toner?

What makes you conclude the cartridge has issues, the fact that the pages aren’t totally blank?

Thanks.
by Rock Monkey on Aug 18, 2012 at 8:22pm Add comment
If the laser unit had any type of failure, you would get a 51 or a 52 error code. Since you didn't mention it, maybe we should have asked, it wouldn't be a problem with the laser. The only time it would give the problem was if the beam down to the cartridge were blocked as is the case if the shutter didn't open. In that case you wouldn't get a failure code. The reason we think your cartridge is bad is that it has smudges on it that are probably the result of a failed wiper blade. There really is no way of testing the HV power supply other than replacing it. It's possible all the toner in it shorted out some components. A failure of a HV power supply will give no error codes. Hard to diagnose noises over the internet, but the fact that it went away would point at the toner cartridge as the source. Anything else would be more permanent. If you do need a replacement HV power supply, click on my name to email me for pricing and ordering details and we can get one out to you on Monday.
by moe on Aug 18, 2012 at 9:32pm Add comment