Service Manuals, User Guides, Schematic Diagrams or docs for : LG Monitor 1468 CH480_6B
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R,G,B R,G,B R,G,B
SIGNAL
Video Drive Video Output
PC TUBE
Circuit Circuit
V-Sync. H-Sync.
Screen
2nd Rectifier
Circuit
Mode Control Vertical Output Anode
Transformer Circuit Circuit
-9-
V
Primary Switching
BLOCK DIAGRAM
Rectifier Control
Circuit Circuit H High Voltage
Horizontal / Vertical Generation Circuit
Drive Circuit
E
L N
AC LINE VOLTAGE
DISCRIPTIONS OF BLOCK DIAGRAM
1. PRIMARY RECTIFIER CIRCUIT
This is a circuit that transform a AC (line voltage) of wall to DC voltage as the supplied source in chassis.
It is operated by C904 (electrolytic capacitor) and D901 (bridge diode).
2. SWITCHING CONTROL CIRCUIT
This block operate to be kept the outputs of the 2nd rectified circuit in constant level in any conditions.
: no load, full load, line voltage variation, etc.
The main function is operated by IC901 (STR5717) syncronizing to H-frequency via a connector that tie
around the core of the FBT (T702).
3. 2nd RECTIFIER CIRCUIT
This block rectifying the pulse waveform of the transformer generated by switching control circuit.
It is consisted of capacitor and diode.
The output voltages are 125V, 95V, 70V, 40V, 12V and 6.3V that are necessary to the chassiss operation.
4. VIDEO DRIVE CIRCUIT
This block is pre-amplify the video signal (Red, Green and Blue) of PC to make sufficient signal of the video
output circuit.
The function is operated by IC301 (TDA4881/2).
5. VIDEO OUTPUT CIRCUIT
This block amplify the pre-amplified signal through the video drive circuit to drive the CDT (Cathode Display
Tube). The cascode amplify stages and buffer stages of each color are used to this block and the drive
transistor of cascode amplifier lies inside of the IC301. The buffer stages are consist of PNP and NPN type of
transistor.
6. MODE CONTROL CIRCUIT
This block generate the signal need to control the function of the horizontal and vertical drive circuit.
The function is operated IC201 (Gate Array) by combination of the horizontal and the vertical sync signal.
7. HORIZONTAL/VERTICAL DRIVE CIRCUIT
This block manage the function, that are H/V-position, side pincushion and H/V-hold, with the output signal of
mode control circuit. The generated vertical signal is applied to the vertical output circuit.
The generated horizontal signal is applied to the high voltage generation circuit that supply the operating
voltage of CDT (Cathode Display Tube). These are controlled by the circuit in and around IC701.
8. VERTICAL OUTPUT CIRCUIT
This block generate the signal to deflect the beam of CDT vertically.
IC601 control the waveform of deflection.
9. HIGH VOLTAGE GENERATION CIRCUIT
This block generate the voltages to operate CDT and produce the horizontal deflection energy via a Q706 and
T702 (FBT).
The high voltage is about 24kV for anode, 6kV for focus and 550V for screen of the CDT.
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