How to clean a Canon Canoscan 8400F

This is a how to on cleaning the glass and mirrors of a Canon Canoscan 8400F Flat bed Scanner. And how to take the scanner apart to access the inside.

The Canon Canoscan 8400F's 'glass' is actually plastic, so it can be scratched from too rough handling.

Cleaning Materials

Where I talk of plain water, I mean cool tap water. I do not recommend Isopropyl Rubbing Alcohol, as it leaves streaks. Do not use Standard glass cleaner. Standard glass cleaner may damage the plastic and leave a residue.


This problem is a color (yellow in this case, it can be any color) gradient on the right side of the scanned page. 
See the picture below of the preview screen.

Click on the thumbnails for a larger image.

Yellow stripe.jpg (80586 bytes)

You will notice a wide yellow strip on the right side of this scanned page. 
This is caused by contamination on the calibration strip and/or the mirrors in the scanning head. The contamination can show up in many forms, in this case it is a yellow strip of color down the side. Very likely it is an out gassing of the plastic case of the scanner that has settled on the surface of the calibration strip and/or on the mirrors.
Yellow stripe before.jpg (59880 bytes) This is a scan of a blank white sheet of letter size 8 1/2 inch by 11 inch paper.  This shows the Color Gradient even when a blank sheet
is scanned at 200 DPI. This image is reduced for the web.
We will start by first showing a picture of the Scanner before doing anything. PC301744.JPG (38039 bytes)
Remove the lid. The screws that hold the case together are hidden in several places. Two screws are in the recess of the hinge for the lid. Two screws are under the front cover. Later in this instruction, I will show you how to access the two screws under the front cover. 
Pardon the reflection of the overhead fluorescent light. It is not a part of the scanner.
 PC301773_edited_web.jpg (78954 bytes)

Close up of the screw in the hinge recess. There is one in each hinge recess.

PC301750.JPG (91784 bytes)
To remove the front cover to access the two hidden screws, turn the scanner upside down and with your thumbs press on the bottom of the front cover to release the clips, and tilt down. First picture shows where to place your thumbs, squeeze with a pulling motion, until the clips release as shown in the second picture. The third picture is the front cover removed from the scanner.

PC301757_edit.jpg (46730 bytes)

PC301758.JPG (41013 bytes)

PC301759.JPG (47890 bytes)


After removing the front cover, remove the four screws, two in the hinge recess and two in front. 

After removing the four screws, gently pry the rear of the case open, you may use a thin blade screwdriver in the crack to get the rear open, be gentle. There are three plastic clips that hold the front of the case from coming apart, these must be gently released with a thin screwdriver. 

PC301772.JPG (41048 bytes)  PC301764.JPG (58242 bytes)
PC301765.JPG (59855 bytes)
This image is of the two half's of the scanner case. You will notice the white strip on the inside of the top half. That is the Calibration Strip and must be clean. 

You should clean inside and outside of the glass with plain water and a paper towel. Be sure to use a dry paper towel to get the glass streak free and dry.

PC301766.JPG (51677 bytes)
Here is a close view of the scanning head assembly. There are six screws seen in this view. Remove the six screws to open the scanning head assembly to clean the mirrors. Mirrors are under this cover. PC301767.JPG (79126 bytes)
When you lift up the top of the scanning head, you will see the two connectors that connect the lamp assembly to the power supply. Carefully unplug the two wire connectors. (They are a tight fit). Then you can lay the lamp assembly aside. PC301768_Rot.jpg (63377 bytes)
This image is showing the mirrors that must be cleaned. Clean the mirrors in place, do not remove the mirrors.

Clean the mirrors very carefully and do not damage the surface, as the mirror coating is on the surface of the glass. Wet a paper towel with plain water, wring out the access water and wipe the surface of the mirrors very gently. After wiping with the wet paper towel, wipe gently with a dry paper towel.

PC301770_rot_reduced_edited.jpg (47109 bytes)

Now re-assemble the scanner in the reverse order. Tuck the wires in the scanner head so that that they do not get pinched when you put the scanner head cover back on. Replace the six screws. Do not over tighten.  Put on the top half of the scanner. Press the front of the top half of the case, so that the three tabs snap into place, 

Connect the scanner and test it.

You may want to test the scanner before replacing the four screws in the case.

Put the four screws and front cover back on after test proves good.

Try the scanner after cleaning the platen and mirrors, then if the scanner is still showing the yellow streaks, clean the lens.

I have received email from some people that still have the yellow streaks in a color scan after following all of the above procedures.
They were successful after removing and cleaning the lens. I recommend that you mark the position of the lens before removing so that you may get the lens back in the same position. 

I have also gotten an email from a user that found that if none of the above works, then you need to go further and clean the filter in front of the lens and the sensor itself. Thank you Randal for the following two pictures and instructions.

Arrow is pointing to the filter in front of the lens.

filter.jpg (79130 bytes)

The sensor is accessed by removing the 2 screws behind the taped tabs shown in  the pictures at the arrows.

sensor.jpg (72071 bytes)
Thank you Alex for the picture and comments. (January 08, 2008):

However, thanks to you and your detailed page on cleaning the scanner I was able to scan in colour the papers I had. The scanner works as new. I found out that the reason my scanner was defective was because the lens itself was very dirty.  (I don't know how the lens could get so dirty.) Upon looking at it, it looked clean but once I inserted a microfibre cloth into it, it came out black.  I also removed the sensor but everything was all right there. I should really state that I think I removed the board with the light as I could not find the actual CCD. I enclose a picture.

I would also add that to clean the lens filter you do not need to remove it from the scanner as detailed. All you need to do is to flick it down with your finger and then insert a microfiber cloth or slightly moist piece of paper towel.   Also, to remove the light sensor part one needs to push gently the carriage so as to access it.  One could also advance the scanner before beginning the repair and shut it off before the carriage returns home.

8400F light and sensor.JPG (708838 bytes)

Yellow stripe after cleaning.jpg (31551 bytes)

This is a scan of a blank white sheet of letter size 8 1/2 inch by 11 inch paper after cleaning the calibration strip and the mirrors.   It is scanned at 200 DPI. This image is reduced for the web. I wrote on the paper with a pencil to show the right and left side of the paper. Color Gradient is now gone!

Preview_after_Clean.jpg (86071 bytes)

Preview after cleaning the scanner. All better!

There is an FAQ on cleaning your scanner's glass on


I cleaned my scanner's glass another time. This time I used Pre-Moistened Eye Glass lens cloths and a Microfiber cloth.

This cleaning was done to remove some dust particles that I left the first time. The microfiber cloth was a big help in getting out the small particles of dust. It worked pretty good on fingerprints also.

ZeissLensCloths_clean.jpg (68050 bytes)

MicroFiber_cloth_resize.jpg (50613 bytes)

Bought at Walmart Eye Center.
Zeiss Lens Cloths pre-Moistened with alcohol.

Bought at Walmart in the Auto Department.
MICROFIBER Ultimate Cleaning cloth.



Copyright 2006-2015 Carl McMillan

This Page last edited: May 10, 2015