You wish to clean inside (under) the platen glass of your Canon 4200F Scanner; first I have to tell you that this is a pretty delicate operation. Make sure you see real dust with the help of a flashlight. Consider there could be another cause for a poor quality scan.
So why fix it if you don't have to?
Maybe you should have it serviced by a Canon technician. But if you're too far away and concerned to ship it, here is how I just did a few days ago.
You shall need the following tools
Safety gloves (optional)
2 flat screwdrivers (small)
1 Phillip screwdriver (#2)
1 Smaller Phillip screwdriver
1 sheet of paper (to be recycled) cut into small folds (8 or less)
A clean cotton rag
Window cleaner (your favorite)
I highly recommend you first put your safety glasses and gloves! Make sure you have all your time. It may take a good hour to get through. Read all of these instruction before so you have a better understanding of how this works. A good tip is to remove any part slowly enough to notice and remember how they held together. In doubt use a camera or your phone and take pictures before you start.
1. Unplug both cables.
2. Bring your scanner into a well lit area. Place it horizontally (as in a landscape pictures) the hinge cover side being on your right.
3. Pull the cover up. It should stay open. There are 2 screws (Philips) on top hinge side, between right end of glass and hinge. Unscrew both. No need to pull them out.
4. Unscrew the third screw (center) with smaller screwdriver and pull up a tiny cover. There is a fragile flat ribbon cable (1/4 in). Pull it out gently. Close the top cover.
5. Let it rest flat.
Now you are in the delicate part of this operation! :-) There is no other screw than these 3 ones you'll need to touch.
6. Since all (3) screws are completely loose, you shall feel the top is showing a slight «will» to lift. Using your two small flat screwdriver GENTLY pry OUT the BOTTOM part of this «oyster shell» starting UNDER the HINGE side, alternating with both screwdrivers, one the edge facing you. Keep it open with folded piece of paper or anything else so it does not clamp back. Do the same on the opposite side.
In other words, the top parts is now held to the bottom part with nothing else than these fragile minuscule edge claws. GENTLY slide off RIGHT the cover and the glass together, looking how the glass is inserted under on the left side.
If there is a too much resistance, one of the screws may not be loosen enough or there may be a claw still pulling.
Now you do your cleaning. But you are not over yet!
PUTTING IT BACK TOGETHER:
You should be able to reverse the operation that you just did.
Slide left together the glass and top, carefully clamping down the top to the bottom from left to right, exactly as it was. Check so you don't see any open space in between.
If not: go back.
Using your tweezers gently connect down you flat ribbon cable into its connector. Place the small cover and the only small screw.
Put back the 2 screws next. Bring back your scanner to your computer. Reconnect your 2 cables.
IF, you get an error message, first check your USB cable, then the flat cable connection!
It worked just fine for me.
on Apr 28, 2015