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dafeagin
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HP MFC drop in scan quality

I have two HP M4345 printers and one HP M5035 printer that have the same problem.  After one or two years, the scan darkness dropped to about half.  The print function, and anything else that does not go through the scanner, is fine.  I had to modify the default darkness setting to 0 or as dark as it will go just to get a decent copy.  If it is a light original, the copies are poor.  There are no error messages or flags that I can find.

This has happened to all of these devices and two other HP M4345 printers that have since been retired.  They are at different locations and environments.

Does anyone know exactly what is causing this and if there is a solution for it?
Printers and Scanners

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Last Comment
dafeagin

8/22/2022 - Mon
Michael Best

The scanners optics degrade after a certain time of usage & need service or replacement.
Michael Best

Other factors that may deteriorate the scanners optics premature are extreme climates, humidity, dusty or dirty air.
Also check the scanners glass is kept very clean.
wyliecoyoteuk

Clean the underside of the glass and any mirrors with a soft cloth.
If there is a build up of dust, the auto-exposure sensor may turn the power to the lamp up in an effort to compensate.
also check if there is a scanner calibration procedure for the devices.
(This will usually involve printing a test page and then scanning it)
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rwheeler23
Michael Best

The last comment :
"Clean the underside of the glass and any mirrors with a soft cloth.
If there is a build up of dust,"

Do not do this, unless you know exactly what you are doing... as you may cause even more dust & even scratches to the optical surfaces...

ID: 38011082
"optics degrade after a certain time of usage & need service"
(usually professional service)
wyliecoyoteuk

@ Michael-Best
That is just basic maintenance, our engineers do it all the time (I have been doing it for over 15 years!).
The underside of the platen glass often becomes coated with dust due to electrostatic attraction, similarly the mirrors.
Using a soft, lint free cloth, there should be no risk of damage. These are not the delicate optical surface of a lens.
However, you should take care not to use solvents or rough abrasive cloth, and you should avoid the surface of the CCD sensor.
Michael Best

To: wyliecoyoteuk
I agree with your comment:
ID: 38013121

As I stated:
ID: 38012336
 "unless you know exactly what you are doing"
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dafeagin

ASKER
I believe that the optics are related to the issue.  But I do not think normal wear or environment caused this.  The device I have pulled to troubleshoot only has 41,463(probably between 20,000 to 25,000 when quality dropped) scanned documents (190,039 prints).

The underside of the glass is clean.
All of the mirrors I can see without taking it apart are clean.
I have cleaned the Document feed path, the top of the glass, vacuumed the inside of the printer body and cleaned all of the metal contacts with the toner cartridge (Print is ok but I did it anyway).
I have changed the default darkness to 0 (darkest)
I have changed the toner density to 5 (Highest)

At this point I can get a a decent scan but it should be very dark.
What I need to know is why the optics droped off so suddenly.  This did not happen over time and it has not degraded further.  One day it was ok and the next it was not.  I have 4 brother MFC devices  (some much older) at the same sites that do not have this problem.  This has happened to all of our HP MFC devices.  They are in different environments.  Some are in very clean low traffic locations and some are in truck dispatch offices
It seems to me that it is more along the lines of the color toner cartridges that will stop after x cycles regardless of that colors use, but this scanner has not been through that many cycles.
Michael Best

Depending on the type & quality then the life-span of a scanner varies.

Scroll down to Table 1  Scanning cost, in this link:

http://www.greenstone.org/manuals/gsdl2/en/html/Chapter_scanners_and_scanning.htm
wyliecoyoteuk

Could be down to problems with the lamp control circuit.
There are various possibilities, depending on how the lamp is controlled.
If there is an auto exposure sensor, it may point at a white reference plate, if that is dirty or dislodged it will turn up the lamp.
Sometimes this is a separate sensor, sometimes it is the CCD itself, in which case there will be a white reference plate under the glass at one end of the scanner.
When the scanner is turned on, it will switch the lamp to full brightness for a second or so, and measure the resulting output. The result is the default "White level", and is used for calibration. If the plate is discoloured or dislodged, or the scanner is not in the correct position, the "White level" will be wrong.
I have known these reference plates to become detached on some copiers in the past. Lamp or mirror housings can be dislodged so that they are slightly out of position and this will cause a similar issue, while not noticeably affecting image quality otherwise.
Some models have a calibration procedure, which can involve using several sheets of white paper, or a printed pattern to calibrate the scanner's white and grey levels.
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Michael Best

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dafeagin

ASKER
Thank you for the multiple responses.  I was able to check and search more than I had before.  This last comment seems to best fit our pattern.  The only reason I graded as a B is that it is too costly to verify if it is just going to fail in 1 1/2 years again.  For the cost to repair, I can get a Brother MFC8890 and just replace in 2 to 4 years.  If I do get to verify, I will let you know.