Print is washed out/completely faded on 2605dn printer

[JoeAquilina]

We have a HP Colour Laserjet 2605dn printer which has intermittent printing problems. Most of the time, the quality of printed output is fine but from time to time, the quality of printing deteriorates completely. After a time, the printing will then revert back its normal excellent quality.

The printer is networked and is used from WIndows XP/7/8/10 and Linux machines as it has throughout its life. It has only ever had genuine HP toner cartridges installed. It is not heavily used, we generally print less than 100 pages per week, often less.

The problem is that the output for all colours, and black, gets so bad as to be unreadable. The printed output is so faded that is (almost) impossible to read anything across the whole page. This can occur for all pages of a  whole document, but often it will print the first part of a multi-page print job just fine and then the quality gradually deteriorates to unreadability. Subsequent print jobs will also sometimes be unreadable but are also likely to print just fine. There appears to be trigger (that we can determine) for this behaviour or for when it will come good.

While the printer had been in use for some years, it has printed a total of just over 20,000 pages. This leads me to think that getting old should not be a problem. We have replaced all cartridges, tried recalibrating, printing cleaning pages, all to no avail. I did find a solution for a magenta colour fade issue elsewhere that involves cleaning mirrors but our problem isn't that same as that - everything fades away to nothing in our printer, it is not a case of one colour fading somewhat, this is a lot mroe drastic than that.

Any suggestions as to how we might fix this? Is there any further information that might help diagnose the cause and suggest a fix?

Thanks in advance for any suggestions.

[SHThompson]

When laser scanner mirrors get dirty the problem will be consistent, since you a problem comes and goes it is not caused by a dirty laser scanner mirror.

When the printer is failing we need to do a half self test.

Load paper in tray 1, that's the front fold down Tray, and print a test page.

Just as the trailing edge of the paper is pulled into the printer, open the cover.

At this point we want to inspect the drums in the toner cartridges and look at the toner on them. Some of the toner will not have been transferred to the cartridge and some will so you should have a dividing line across the drum where toner should seem solid on one side and dated on the other.

The point here is we are trying to see if there is enough toner being put on the drum and how much is that toner is being transferred to the paper.

I would suggest you do this test when the printer is working and then when it is failing and compare the two come on you can even take a picture of the toner on the drums, you won't have to move the shutter out of the way to see the drum when the printer is open.

When the printer is operating normally it lays down a nice image on the drum reverse from the direction you will see it on the paper. Then as the drum rotates and the paper passes it most of the toner is transferred to the paper leaving only faint residual image on the drum.

If there is plenty of toner on the drum and it is not being transferred to the paper then we can narrow down the problem and it will be a transfer problem.

If there is not enough toner being put on the drum then the issue is during image formation.

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[JoeAquilina]

Thanks for the response and the suggestion.

The printer seems to behaving itself this morning. I tried the half self test you recommended.

It seemed to me that there was plenty of toner on the drums - there was a good image being formed. The images were complete and recognisable as being what should come out on the printed page.

I will try again when it decides to misbehave and report here then; that might be a few days as this problem is intermittent.

[JoeAquilina]

The printer has just had another occurence of this problem. It affected two pages only. When I did the half self test as recommended, I could see that there was a good image being formed on all of the drums.

Subsequent pages printed after the two faulty ones are now printing as expected. So for the time being at least, it is not possible to isolate the problem to poor image(s) being formed or a transfer problem.

Will keep monitoring it and hope to catch it next time.

[SHThompson]

Your computer probably told the printer about these post on the forum that now that it knows it being watched the printer is behaving better.

[JoeAquilina]

You may be correct, and it would have been nice to think that we had frightened the printer into submission, but it seems that the printer has a short memory (or doesn't stay scared for long).

We just had another failed print. An immediate half self test this time showed that there was no image being formed on any of the drums, unlike all the other self tests when there was a good image being formed. There was no toner on any of the drums this time. There didn't seem to be any hint of any toner on the drums, not even a partial image there at all.

In that case, what is the likely next step to overcome this problem?

[SHThompson]

If it was a laser scanner problem you would normally have a beam detect error which is generated from a sensor inside the scanner.

There is a roller in each toner cartridge that puts a charge on the drum that causes it to repel toner.

The laser writes the drum, wherever the laser hits the drum becomes conductive and the charge is drained to the center core which is aluminum and it is grounded.

If the laser is working but the charge is not being drained that would say that the ground to the corr of the drums has an issue.

That ground would come from the high voltage power supply, I recently worked on a monochrome machine but the ground went through an interlock and that was the issue but I don't remember anything like that on this machine.

I would be inclined to remove the high voltage power supply and reinstall it and reseat any connectors on it. I would especially pay attention to any points that seem to be grounded.

We might be able to get a second opinion from: @davidzuts

[JoeAquilina]

I am happy to accept your advice on this since you are clearly much more knowledgeable and experienced in this area than me; having never had any experience delving into the innards of a printer, it seems like this could be a little tricky.

Is what you suggest likely to be something that I might attempt? Building & repairing PC system boxes I can do but anything more complicated (e.g. dismantling/repairing printers, laptops) is currently beyond my experience. Are there service and/or repair manuals that will help me in this and if so where do I obtain it/them?

I am certainly willing to give it a go with suitable documentation and/or instructions to follow but I don't want to go in blindly and possibly end up with a bigger mess than we currently have because of mistakes I may make due to my ignorance or inexperience.

Thanks again.

[davidzuts]

Stephen advice with the high voltage ps is very good.  In addition I would remove the back cover (lots of screws) and when looking from the rear there are two circut boards.  The one on the right is the dc controller and the one on the left is the formatter.  Both have many wires connected to them.  I would disconnect each connector one at a time and reconnect as there could be a connector which over the years is just not sitting right.  Other than that I have nothing else to offer.  You do this with the power cord removed from the printer.

[SHThompson]

You should be able to find a service manual for that machine online. You will not find it on HP's website.

Do you do any mechanical work? Generally speaking if you can change your own brakes I can teach you how to fix a printer.