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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 function 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) when 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), D401,
D402, C401 and C416. 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 electron in the
CRT.
L404, C414, C415 modify Horizontal linearity switching individually via Q414,
RL401
3.3
EW-Pincushion and width control circuit.
The voltage across C420 can be varied in accordance with vertical parabolic wave form
and DC voltage which is generated by two stage drive Q411, Q412, Q409. The peak yoke
current is increased in proportion to the voltage across C414 as the voltage across C420 is
decreased for compensating the pincushion effect. The parabolic waveform and DC voltage
are generated from IC401 pin24.
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 are fed to the video preamplifier IC601 pin5 is Red, pin6 is Green and
pin7 is Blue, through AC coupling capacitor (C601, C602, C603).
Cut off and drive voltage are controlled by IC301via I
and 14 to control the RGB cut off voltage through IC604. Output IC604 are DC voltage for D613,
D614 ,D615 and C626, C627, C628 clamping the RGB cathode voltage.
IC603 output amplifier for R,G,B channel.
4.2
On Screen Display (OSD : IC602).
IC602 is the on screen display generator, pin5 for H-blank input, pin10 for V- blank input.
The IC602 is controlled by IC301 via SDA, SCL bus IC602 (pin7, pin8).
The on screen display signal is output from pin13, pin14 and pin15. OSD fast blanking
from pin12 for delete display in area of OSD showing. The fast blanking is active high output
= 5V while showing OSD. If no using OSD, so this pin shall be 0V.
4.3
Auto Beam Limit CCT (ABL ).
When beam current pass through R447 over 400 uA., the voltage build at base of Q418
will be low enough to turn on Q418, then the voltage of pin22 of IC601 will be pulled down
accordingly to reduce the video
Pre-amplifier gain output.
4.4
Brightness Control.
ViewSonic Corporation
2
C bus . Output of IC601 pin 16 , 15
13
Confidential – Do Not Copy
E55-2
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