TM 11-2323
C4
(7) The projection stage of the PH-637/PFP, the PH-637A/
PFP, and the PH-637B/PFP is a plate glass cover, held
in place over a 10- by 10-inch opening by retaining strips.
The Fresnel condenser lens rests in grooves under the plate
glass cover. On the PH-637C/PFP, the projection stage is
a sheet metal unit which is attached the plate glass cover
and the Fresuel condenser lens. The unit is held in place
by two knurled projection-stage retaining screws located on
both sides of the housing, toward the rear, allowing the pro-
jection stage to pivot up and to the rear.
(8) In front. of the, projection stage, on top of the housing, is a
groove that holds a grease pencil used for marking cello-
phane or plastic held on the projection stage. (On the
PH-637C/PFP, the pencil groove is formed by the converg-
ing angles of the sheet metal at the front of the projection
stage and the rear of the front shelf when the front shelf
is raised.)
(9) On the right side of the housing of the PH-637/PFP, the
PH-637A/PFP, and the PH637B/PFP, next to the support
post hole, is a clamping knob used to lock the support post
in position. ( O n t h e P H - 6 3 7 / P F P , t h e c l a m p i n g k n o b i s
located on the rear of the yoke.)
(10) The housing contains an optical system composed of a re-
flector, a projection lamp glass condenser lens, a heat-
absorbing filter (PH-637B/PFP and PH-637C/PFP only),
a rear surface mirror, a Fresuel condenser lens, and the glass
cover of the projection stage. T h e h o u s i n g s o f t h e P H -
637A/PFP and the PH-637C/PFP also contain a cellophane
roll attachment, (d below).
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