Plastic film on the photo (thick about 6 μ m) cut the 30mm, wide 20mm shape, remove the front group of lenses, the plastic film strip in the multi thread, the outside set aside about 12mm, and with the double-sided adhesive paste in the tube wall, and then screw up groups of lenses. If too loose for plastic film slightly thicker, tight were replaced by thinner. To be re assembled and other components, adjust the focal length is successfully repairedbN3service manual download site