(2) Hold the lens firmly in one hand, and unscrew the locking
screw that tightens the split ring around the lens. It should
now be easy to twist the lens out of the projection head. I f
the lens cannot be removed easily, force the jaws of the split
ring apart with a heavy screwdriver.
Caution: Be sure that the lens is always well supported
while it is being removed. If it should drop, the projection-
stage plate glass, the Fresnel condenser lens, and possibly the
rear surface mirror would be broken, and the projection lens
might be damaged permanently.
(3) To replace the lens, reverse the disassembly instructions ( (1)
and (2) above). When the lens is inserted in the split ring,
be sure to push it up until it butts against the bottom of the
front surface mirror housing. Do not tighten the split-ring
locking screw too much ; severe constriction may damage the
Note. MWO SIG 11-2323-1 provides for the modification of the
lens installation in the split ring and prevents damage to the lens,
condenser, and glass cover plate which may be caused by the lens
failing from the projection head. The modification calls for the in-
sertion of a No. 6-32 by 1/8-inch fillister head machine screw through a
tapped hole in the metal part of the lens assembly (lens assembly
barrel). This screw secures the lens in the projection-head housing
and prevents the lens assembly from dropping out. When the lens
Is disassembled from the split ring, this screw must be removed before
the lens can be withdrawn from the retaining ring. Loosen the screw
in the retaining ring so that the lens barrel can be pushed upward
slightly. Take the window from the projection-head assembly by re-
moving the three screws holding it in place (two at the bottom and
one at the top). The No. 6-32 by /8-inch fillister head machine screw
now may be removed from the lens barrel with a screwdriver. While
removing the screw, hold the lens assembly so that it will not drop out.
When the screw is removed, pull out the lens assembly.
d. Support Arm.
(1) Remove the projection-head assembly by racking it up off the
(2) Remove the lens (c above).
(3) Remove the three screws and washers that secure the support
arm to the front surface mirror housing.
(4) To replace the support arm, reverse the disassembly instruc-
tions ((1) through (3) above).
e. Elevation Knob and Focusing Knob. To remove the elevation
knob, loosen the two setscrews in the collar of the knob, and slide the
knob off the shaft. To remove the focusing knob, loosen the two Allen
setscrews in the collar of the knob, and slide the knob off the shaft.
To replace either knob, slide it back on the shaft and tighten the