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3
.
Horizontal
3.1 Horizontal driver circuit
The output of IC401 pin26 H-Driver connect to Q402 H-driver transistor makes Q402 active ON/OFF, push
H-output Q401 to reach secondary via induction of T402
﹒
For T402 is a Transformer of reduced voltage and
converted pole
﹐
Q401 will be turn off when Q402 is on
﹐
on the contrary
﹐
went Q402 is turn off and Q401
will be on
﹒
3.2 Horizontal output circuit
Horizontal output circuit is composed by Q401
(
Horizontal Transistor
)﹐
T401(FBT), D402, D403, C401 and
C416 H-output circuit
﹐
H-Driver circuit output via T402 to switch Q401 ON/OFF to output saw tooth wave and
make DY able to control the circuit scanning of elections in the CRT
﹒
L404
﹐
C414
﹐
C415
﹐
modify Horizontal linearity switching individually Via Q414
﹒
3.3 EW-Pincushion and width control circuit
The parabolic waveform and DC voltage and generated from IC401 pin24 to Q411, Q412 and Q409
﹒
The parabolic decreased or increased for compensating the pincushion effect the DC voltage control the
H-width
﹒
4
.
Video
4.1
Video
amplifier
(
IC601
)
The video amplifier module is composed of three amplifiers for Red
﹐
Green
﹐
Blue channel
﹒
The video input signal is fed to the video preamplifier IC601
(
NT6813K
)
pin5 Blue
﹐
pin6 Green
﹐
pin7 Red
﹐
through
AC
coupling
capacitor
﹐
C601
﹐
C602
﹐
C603
﹒
The clamping pulse comes from IC301 pin33
﹒
IC603
output
amplifier
for
B
﹑
R
﹑
G channel respectively
﹒
4.2 On Screen Display
(
OSD
)
(
IC602
)﹒
IC601
(
NT6813K
)
is a on screen display generator, pin28 for H-sync input
﹐
pin10 for V- sync input
﹒
The IC601 is controlled by IC301 via SCL
﹐
SDA bus IC602
(
pin11
﹐
pin12
)﹒
4.3 Auto Beam Limit CKT
(
ABL CKT
)
﹒
When beam current pass through R447 over 500uA
﹐
the voltage build at base of Q418 will be low enough to
turn on Q418
﹐
then the voltage of pin26 of IC601 will be pulled down accordingly to reduce the video
preamplifier gain output
﹒
4.4
Brightness
Control
Brightness is controlled by varying the DC voltage of G1 with the IC301 PIN1
(
PWM
)﹒
`
4.5 Blanking
IC501
(
KA2142
)
pin4 vertical blanking pulse are fed to the base of Q501
﹐
The blanking pulse O/P is coupled to
G1 by C507
﹒
Horizontal blanking pulse are fed to IC601 pin28 and let video O/P amp cut off during the period of horizontal
retrace.
4.6 Mute.
While mode change
﹐
IC301 pin16 will pull high to turn off
﹒
The G1 voltage will down to –180V then CRT will
cut off the video output
﹒
21
ViewSonic
Corporation
Co
nfidential
-
Do
Not
Copy
G90f/B-3
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