62. Electrical Requirements
of the power-cable receptacle connector and the metal frame of the
projector housing. The power switch should be turned to the ON
position, but the power cable should not be connected to the power
source. The resistance measured should not be less than 2 megohms.
63. Operational Tests
(1) Mask the plate-glass projection stage cover to provide an
8- by 8-inch aperture.
(2) Attach the power cable to the projector and to a 117-volt
(+3 volts) ac power source, and turn the power switch to
the ON position.
(3) Move the projector so that the projected screen image is at
least 40 inches wide. Focus the projector sharply, and meas-
ure the screen image to see that it is still at least 40 inches
(4) Divide the screen image into 9 equal squares. Use Photo-
electric Foot Candle Meter ME-86/U to measure the light
at the center of each square in foot candles.
(5) Calculate the arithmetical average of the illumination at the
centers of the 9 squares. Multiply the average by the image
area in square feet. The result (lumen output) must be not
less than 1,280 lumens.
b. Focusing Test. With the power switch turned to the ON posi-
tion, set the projector in such a position that, the screen image is ap-
proximately 6 feet square. Place a transparency on the projection
stage, and focus the image sharply. Then measure the image again
to be sure that it is about 6 feet square. There should be no blur
anywhere within the image area. Any blur indicates defective com-
ponents or misalinement of the optical system. There should be no
longitudinal or lateral chromatic aberration when the screen image is
viewed from a distance equal to twice the width of the screen (12 feet).