Zenith Z-100 PC series Service Manual page 168

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---------------------
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VIDEO BOARD
/
ANALOG
R
• VARIABLE GAIN
R
..
R
VIDEO
R
VIDEO
G G
G
G
VIDEEO
COLOR
..
•
DRIVERS
AMPLIFIERS
CRT
B B
B B
SIGNALS
..
AMPLIFIER
•
..
i
1'\
~
HOC RESTORATION
I
~
BLANKING
LjBEAM CURRRENT
I
LIMITER
I
~--------------------------
1
1
1
H.SYNC
1
I
V.SYNC
1
1
1
1
1
1
1
1
INPUT PROCESS
AND
MODE SELECT
DEFLECTION
BOARD
,-------------­
E-W
GENERATOR
REGULATOR
N-S
GENERATOR
REGULATOR
PIN BOARD
I
HIGH VOLTAGE
I
I
REGULATOR
I
I
VERTICAL
I
I
DEFLECTION
I
I
HORIZONTAL
I
DEFLECTION
I
I
-----------------~
--------­
I
DYNAMIC FOCUS
I
DYNAMIC FOCUS BOARD
l-
- - - I
1
_ _ _ oJ
Figure 5-1. ZCM-1490 Block Diagram
The video output module contains RGB amplifiers,
brightness and contrast control, automatic brightness
limiter, and video blanking circuits. Analog signals
containing color information are supplied to the
monitor along with horizontal and vertical sync sig ­
nals. The analog red, green, and blue video inputs
are AC-coupled to a variable gain video amplifier.
The DC component of the color signals is restored
here. The resulting R,G, and B color signals are ap­
plied to video driver and video output stages. The
video output amplifiers activate the appropriate red,
green, or blue guns of the CRT, allowing information
to be displayed. Video blanking for horizontal and
vertical retrace acts to shut off the CRT during
retrace times.
Page 5-2 Circuit Descriptions