TM 9-1556
21-23
DISASSEMBLY AND ASSEMBLY
21.
ROUTINE CLEANING DURING DISASSEMBLY.
a. All parts which have been removed from the instrument should
be carefully cleaned before assembly.
(1) Optical elements should be cleaned with liquid lens-cleaning
soap. If this is not available. use ethyl alcohol as an alternative. Care
must be exercised to prevent alcohol from coming in contact with
the edges of compound lenses as the lens cement is soluble in alcohol.
If pencil marks have been placed on the unpolished surfaces of lenses
or prisms, avoid removing them to prevent difficulty when assembling.
Polish the optical element with lens tissue paper. Remove dust and
dirt with an air bulb and a clean, small camel's hair artist brush.
(2) Metal components should be cleaned in dry-cleaning solvent
applied with a stiff-bristled brush. NOTE: The solvent is highly in-
flammable. Take proper precautions when using or handling it. Also,
the solvent should be changed frequently, so it will not become satu-
rated with dirt. CAUTION: Do not clean metal components in dry-
cleaning solvent when the optical elements have not been removed.
SEALING.
a. When replacing the eyepiece and objective cells in telescopes,
apply a very light film of grease to the threaded part of the cell. The
The grease film facilitates assembly and is effective in sealing the
telescope. There should be just enough grease to make the joint air-
tight and moisturetight, but not enough to overrun onto the lenses.
b. When replacing the objective lens or the eyelens in their cells,
use black Navy sealing compound to form a seal between the lens
and the cell. If necessary, soften the black Navy sealing compound
by warming with the hands. Then roll the sealing compound into a
fine, thread-like piece and apply it around the flange in the cell upon
which the lens will rest.
c. Plug the recesses above the various adjusting screws, etc., with
plugging cement of the same color as the instrument. Smooth the
cement to hide the openings as completely as possible.
DISASSEMBLY AND ASSEMBLY
a. To preserve the parts of the instrument, it is necessary to exer-
cise care and close attention during disassembly, cleaning, and adjust-
ment. The extent of disassembly for any given repair job is determined
by the repairman when he makes his inspection.