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 ﹒
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ViewSonic Corporation Confidential
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Do Not Copy G90f/B-3