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Chapter 5---Electronics
Model 250 Service Manual 5-11
5.4 Video Processor PCB
Video Processor PCB - Main Functions
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Video signal input and multiplexing
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Sync signal stripping
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Overlay signal multiplexing
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Brightness, Contrast, DC Restore and Blanking
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Video signal gamma correction
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Sensitivity and Threshold signal input and control
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Automatic Contrast, G2, and internal image limiting
Video Processor PCB - Inputs
RGBHV VIC 1,2, & 3 - External image signals from the VICs for red, green, and
blue.
/SEL_VIC - input signal from the RGB VIC used to select the input source from
VIC #1.
RGB_OVER - from the System Controller PCB, the Menu overlays and internal
test patterns for red, green, and blue.
OVERLAY - from the System Controller PCB, switches between internal and
external sources.
CLAMP - Pulse signal from the Raster Timing Generator PCB, tells the Video
Processor PCB the timing and duration of the DC Restore.
BLANKING - Pulse signal from the Raster Timing Generator PCB, it tells the
Video Processor PCB the blanking interval during the scan.
RGB_THRESH - Threshold correction information for red, green, or blue from
the System Controller PCB. Real time data at 0-1 V.
RGB_SENS - Sensitivity correction information for red, green or blue from the
System Controller PCB. Real time data at 0-1 V.
RGB_BEAM - sense signal proportional to the cathode current averaged over
several horizontal lines in the red, green, or blue CRT. The voltage level is +
mV/mA.
/VA_OK - signal from the Video Amplifier PCB telling the Video Processor PCB
the Video Amplifier PCB is receiving red, green, and blue deflections voltages
from the Horizontal Vertical Deflection PCB.
IIC_DATA - IIC data line. Bi-directional serial line for synchronous data transfer
between the System Controller PCB and Video Processor PCB.
IIC_CLK - IIC clock line. Unidirectional clock line for control of synchronous
data transfer over IIC bus.