Repair manual

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THEORY OF OPERATION
9. COS4 Exposure Correction
The COS4 Exposure Correction circuit adjust and controls the radial luminance
of the CRT video display. This circuit, in conjunction with the Luminance
circuit, increases the brightness of the CRT video display to prevent light fall-off
in the corners. It provides a more even exposure in the finished print/slide - no
dark corners.
The COS4 vertical exposure correction (V COS4) and horizontal exposure
correction (H COS4) controls (R26 and R38), are used during initial setup of the
Digital Palette to properly adjust the vertical and horizontal radial luminance
of the CRT video display. The controls adjust the CRT video display for even
illumination - eliminating dark corners in the finished picture. Refer to the
Calibration and Adjustment Section in this Service Manual for a detailed
description on how the controls are used to adjust the CRT video display for even
illumination.