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MOTION PICTURE PROJECTION 945
OPTICAL ALIGNMENT
In order to secure the maximum screen illumination possible the projecting lens, the aperture, the condensing lens and the lamp filament must be exactly on the optical axis of the optical train of the projector, because if any one of these elements has its center as little as 1-16 in. off this optical axis, the screen illumination will be greatly reduced.
Raise the automatic fire-shutter or open the gate of the projector. Pull the lamphouse (A) over until the carriage adjusting screw (B-2) hits the carriage stop (C-5) on the base (C) and push the motion picture condenser mount (F) over until its stop (F-4) is against the stop (screw A-4) on the lamphouse. (See Fig. 404.) Move the base (C) forward or backward until the front surface of the bulls-eye of the prismatic condensers is 6V2 in. from the edge of the aperture (except where state laws compel a greater distance) and fasten the base against further movement. Turn the flywheel until the revolving shutter of the projector has opened the projection lens.
The remaining adjustments must be made with the lamp lighted. (See Fig. 405 and 415.)
Move the control lever (D-l) of the Type HDS, Form E, alternating-current regulator clockwise until the pin (D-9) strikes the stop (D-10) . When the control lever (D-l) is in this position the current passes through the warming reactance or choke coil (D-ll), which prevents a sudden rush of current to the lamp filament at the start and merely brings the filament to a glow.