1. Prepare the wiping paper and alcohol for the lens, and add alcohol to the wiping paper;
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2. Wipe the lens with the lens swab paper, from the middle outward to wipe in a spiral;
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3. Wipe to the edges and remove the stain altogether, then remove the remaining alcohol with a clean cotton swab.
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4. Replace the lens, usually if only stains can be solved by wiping, if the lens is worn and scratched because of the surface of the coating, then it needs to be solved by replacing the lens. You need to use a pry bar to open the projector, remove the light machine, remove the fixing screw with a screwdriver, and then replace the lens.