washers on the screws and insert the screws in the aligned
holes. The locating washers are centered in the oversized
holes on the shelf directly under the screwheads, so that the
underneath surfaces of the screwheads are flush with the
outside of the shelf. Install and tighten the nuts.
(3) The left shelf is permanently attached and cannot be removed.
(4) The glides (fig. 29.3) are screwed into the housing and can
be removed by turning them counterclockwise.
b. Projection Stage.
(1) Remove the projection-stage retaining screws (fig. 2.2) at
the rear of the projection stage.
(2) Carefully lift off the projection stage and place it on it level
(3) Remove the four screws, mounting clips, lockwashers, and
hexagonal nuts that secure the plate glass cover to the top of
the projection stage. (To do this, hold the lockwashers and
nuts underneath the projection stage with one hand while
using a screwdriver with the other hand to unscrew the
(4) Carefully lift off the plate glass cover and place it on a clean,
smooth, flat surface.
(5) Turn the projection stage (fig. 32.2) over so that the convex
side of the Fresnel condenser lens is facing up.
(6) Remove the six screws and strap nuts that hold the retaining
strips (front and rear) in place.
(7) Lift off the retaining strips and lay them aside.
(8) Remove the Fresnel condenser lens and its retaining frame.
(9) Carefully remove the Fresnel condenser lens by gently sliding
it out, of the grooves of the retaining frame.
(10) To reassemble the projection stage, first, slide the Fresnel
condenser lens into the grooves of its retaining frame; be
careful not to scratch or bend the Fresnel con-denser lens,
and make sure that it is centered in the retaining frame.
(11) Place the retaining frame firmly over the opening in the
projection stage so that, the frame is centered between the
four holes used to mount the plate glass.
(12) Reinstall the retaining strips on the front and rear edges of
the Fresnel condenser lens so that the holes in the retaining
strips line up with the holes in the projection stage.
(13) Reinstall the screws and strap nuts (that secure the retain-
ing strips) while exerting gentle downward pressure on the