scanner leaves dark spots

[yuang]

My secondhand Samsung laserprinter leaves dark spots on double sided scans through the ADF. It's always the bottom page left side. When I bought it and did the first scan it had a piece paper stuck on the exact spot. After removing the paper and cleaning the scanner glass with damp cloth no changes so have no idea why because as far I can see and feel it has no visible dirt/scratches on the scan glass.

(piece of paper)

(every other scan )

 

 

 

[Andr-1611]

Hello @yuang ,
Welcome to the HP Support Community!

you must here:

clean this glass surface intensively!

Hope this helps! Keep me posted.
Andr-1611

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Or click on the YES button to reply that the response was helpful and/or to say “Thank You”.

[yuang]

Hi @Andr-1611,

I cleaned both sides with damp cloth (water) without any visible improvements. So far I can tell its the top scanner (double sided) because its always the bottom page of the paper showing the dark spots. 

 

[Andr-1611]

Hi Yuang.

Thank you for the picture.

Some contaminations cannot be seen with the eyes. Therefore, use a magnifying glass and examine the area in question closely.

Andr-1611

[yuang]

@Andr-1611

hate bother you again, but unfortunately not even a slight improvement after almost scrub cleaning with damp towel. The glass on both side are spotless and scratch free so im very confused what could cause the darkening. 

[Andr-1611]

@yuang 

Test, A4 paper blank:
1st page with a "1" in the middle and
2nd page with a "2" in the middle
Scan the A4 sheet and upload both pages here, in original.

[yuang]

@Andr-1611