Service manual

IMl03S
Section 3
OPERATION
3.1 GENERAL
After power, video and drive signals have been applied to the monitor, the con-
trast and brightness controls may be adjusted to provide the optimum display.
3.2 BRIGHTNESS ADJUST
The
monitor is used to display alphanumeric information. The video polarity is
usually white characters on a black background. The brightness control should
then be adjusted for visual cutoff of the raster. A maximum contrast ratio can
now be obtained when video is applied.
3.3 CONTRAST ADJUST
The
video amplifier is designed to operate linearly from +.65 to +2.5 V signal
input. The contrast control should be adjusted to the point where defocusing
sets in and then backed down slightly. This occurs at a lS-20V p-p video swing
at the CRT cathode for the TV90/l20, and at a l2-lSV p-p swing for the TVSO.
In no case should contrast be adjusted to cause saturation of QlOl, as this im-
pairs the pulse response of the video amplifier.
3-1