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VOLUME XXI
JANUARY 1946
NUMBER 1
A Postwar 16 -mm Projector: THE AMPRO PREMIER 10
By LEROY CHADBOURNE
Herewith another presentation by l.P. of data relative to outstanding equipments in the rapidly expanding 16 mm. field. Electrical and sound reproducing circuits of this popular equipment will be analyzed, by means of tracing through schematic drawings, in the next issue.
SALIENT features of the Ampro Premier 10 16 mm. projector are provisions which make it possible to lose and restore the loop while the picture is running; render it impossible for sprocket or claw teeth to scratch the film, even if the film be intentionally threaded across those teeth, and positive means for stopping the film at any time and then running it backward, or holding any frame on the screen in the manner of a still picture.
An overall view of this projector is shown in Fig. 1. It may be set up as shown on any convenient table, or on its own carrying case (see Fig. 4). The switches and controls shown on the sloping panel are, from left to right: tone control knob, projector lamp switch, volume control, motor switch, and microphone volume control knob. Just forward of the sloping panel, under a little rounded dwelling of the casing, is the projection lamp horizontal adjustment screw. The vertical adjustment screw is in the top of the casing behind the lamp housing, not visible in the picture. At the bottom of the panel is a large, knurled bakelite knob which adjusts the
tilt or projection angle. Just behind this are two switches: the upper one permits a choice of either sound or silent speed; the lower is used to make the motor run in reverse direction.
That section of the panel just above the switches can be removed, giving easy access to the governor brushes. Above this removable section is a smaller black knob, the clutch, the turning of which to maximum clockwise position makes possible the projection of single stills.
Threading the Projector
Film in the process of being threaded is shown in Fig. 2. The righthand forefinger of the projectionists rests on the gate lever which (in this most recent model) not only opens and closes the gate for threading but simultaneously and similarly controls the shoes of the upper and the lower sprockets. A twofinger loop is allowed between the upper sprocket and the gate.
The unit directly under the left-hand thumb in Fig. 2 is the pressure roller. This rides on the film during threading and maintains the lower loop until threading is completed, when the pro
jectionist moves it to its forward position. Thus the lower loop is always exactly right.
Should the loop be lost, the lower end of the gate shoe (which, as subsequently described, is under exceptionally light tension) yields to the pressure of the film and allows it to assume a forward slope as it emerges from the lower end of the gate. Moving the pressure roller to the rear position temporarily (without stopping the projector) instantly restores the loop to sound synchronization.
Thus the film path is shortened, the film does not tear. A unique arrange
FIGURE 1
JANUARY 1946