(3) If the meter does not indicate correctly, replace the entire meter circuit insert.

Section III. LENSES

4-23. General

The replacement of optical components, or helical focusing mounts, is not authorized. Components are matched, and if damaged beyond repair, the entire lens must be returned to the manufacturer for replacement of parts and calibration.

4-24. Cleaning

CAUTION: Do not wipe or brush inside surfaces of lens elements. They are generally soft-coated and will be damaged. Remove foreign material from inner surfaces with a syringe or light force of compressed air.

The materials and methods for cleaning lenses are listed in TM 11-6720-244-12, paragraph 4-6. Fungus, which attacks some optical glasses in tropical environments, may be removed as follows:

a. Material

Hydrogen-peroxide, 3% solution Ammonia, 28% solution Alcohol, 180 proof Distilled water

b. Removing Fungus.

(1) Just prior to use, mix 10-parts hydrogen peroxide with 3-parts ammonia solution.

(2) Moisten the lens surface with the solution and allow it to stand for several minutes.

(3) Wipe the lens surface with a clean piece of lens tissue.

(4) Thoroughly clean the lens surface with distilled water.

(5) If additional cleaning is required, wipe the surface with alcohol and dry with clean lens tissue.

NOTE: Fungus which has remained on an optical surface for a prolonged period etches the glass. In this instance, the entire lens must be returned to the manufacturer for replacement of the damaged element.

4-25. Lubrication and Gluing

The lubricants and adhesives used for repair of the KS-15(4) Camera Set lenses, and the methods of application, are listed in paragraph 4-3.

4-26 . 35mm Lens

(Fig. 42)

a. Replace damaged fluted tube (3).

b. Replace damaged serial number ring (4). NOTE: Ring must be sent to manufacturer for engraving serial number on replacement.

c. Replace damaged front ring (7).

d. Replace damaged diaphragm adjusting ring (11).

e. Replace damaged diaphragm blades.

f. Replace damaged focusing ring (20).

g. Replace damaged pressure spring (21) and sliding bar (22).

h. Replace damaged depth-of-field ring (24).

i. Replace complete helical focusing assembly (25) if any component is damaged. j. Replace missing mounting indicator (26).

4-27 . 50mm Lens Head and Focusing Scale Assembly

(Fig. 43)

a. Replace damaged index ring (5).

b. Replace damaged diaphragm adjusting ring (7).

c. Replace damaged diaphragm blades (12).

d. Replace damaged cover ring (15).

NOTE: Ring must be sent to manufacturer for engraving serial number on replacement.

e. Replace damaged sleeve (17).

f. Replace damaged spring ring (18).

g. Replace damaged focusing ring (19). 4-28. 50mm Helical Focusing Assembly

(Fig. 44)

If any components of the focusing assembly (6) (other than those below) are damaged, the entire assembly must be replaced.

a. Replace damaged or missing nipple (2).

b. Replace damaged stop spring (5).

c. Replace missing mounting indicator (7). 4-29. 50mm Viewing Unit

(Fig. 45)

a. Replace damaged finger grip (13).

b. Replace damaged stop (16).

4-30. 135mm Lens Head

(Fig. 46)

a. Replace damaged filter retaining ring (2).

b. Replace damaged retaining ring (3).

c. Replace damaged stop ring (4).

d. Replace damaged lens hood tubes and liners (5) through (8).

e. Replace damaged diaphragm adjusting ring (10).