LG 520SI, CB550BN BLOCK DIAGRAM
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BLOCK DIAGRAM
CRT
Anode
Focus
Screen
(FBT)
High Voltage
Generation
Circuit
Q301, Q302, Q303, Q304
Q311, Q312, Q313, Q314
Video Output
Circuit
R,G,B R,G,B
Video Drive
R,G,B
Q321, Q322, Q323, Q324
Circuit
MC13281 (IC301)
V
Vertical Output
Circuit
KA2142 (IC601)
)
DPMS
(IC401)
WT60P1
Mode Control
(
Microprocessor Circuit
H
Horizontal/Vertical
Drive Circuit
KB2511 (IC701)
D/D Converter
<DDC>
<H/V SYNC>
<VIDEO Signal>
PC
Transformer
(T903)
Secondary Rectifier
Circuit
Circuit
Control
Switching
Primary
Rectifier
Circuit
7N60A
( IC901)
KA3842B
(Q901)
E
LN
AC INPUT
DESCRIPTION OF BLOCK DIAGRAM
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1. Primary Rectifier Circuit
This circuit transform AC line voltage to DC voltage as
the supplied source for secondary circuit.
It is operated by C905 (electrolytic capacitor) and
D901, D902, D903, D904 (bridge diode).
2. Switching Control Circuit
This circuit operate to be kept output of the secondary
rectified circuit in constant level any conditions; no
load, full load, and line voltage variation, ... etc.
The main function is operated by the IC901 (KA3842B)
syncronizing to horizontal frequency via a connector
that tie around the core of the T502 (FBT).
3. Secondary Rectifier Circuit
This circuit rectifying the pulse waveform of the
transformer generated by switching control circuit.
It is consists of capacitors and diodes.
The output voltages are 76V, 55V, 14V, and 6.4V that
are necessary to the secondary circuit.
4. Video Pre-Amp Circuit
This circuit pre-amplify the video signal (Red, Green
and Blue) to make sufficient signal for the video output
circuit.
The function is operated by the IC301 (MC13281).
5. Video Output Circuit
This circuit amplifies the video signal which comes
from the video pre-amp circuit and amplified video
signal is applied to the CDT cathode.
6. Microprocessor Circuit
This circuit generate control signal that need to
operating of horizontal and vertical drive circuit,
DDC2B (Plug & Play), and DPM (energy saviing)
funtion. DDC2B (Plug & Play) function is operated by
combination of H/V Sync and SDA/SCL signal.
7. Horizontal and Vertical Drive Circuit
This circuit take function, that are H/V-position, H/Vsize, side-pincushion, and trapezoid, with the output of
microprocessor circuit.
The generated vertical signal is applied to the vertical
output circuit. The generated horizontal signal is
applied to the horizontal output and high voltage
generation circuit.
These are controlled by the IC701 (KB2511) circuit.
8. Vertical Output Circuit
This circuit take the vertical ramp wave from the IC701
(KB2511) and perform vertical deflection by supplying
saw-tooth current from the IC601 (KA2142) to the
vertical deflection yoke.
9. High Voltage Generation Circuit
This circuit used for generating pulse the primary coil
of T502 (FBT).
A boosted voltage–about 25kV–appears at the
secondary of T502 (FBT) and it is supplied to the
anode of the CDT (Cathode Display Tube).
10. Blanking and Brightness Control Circuit.
Blanking circuit eliminate retrace line by supplying
negative pulse to the G1 of the CDT (Cathode Display
Tube).
Brightness circuit is used to control screen brightness
by changing the DC level of the G1.
11. D/D Converter.
To obtain constant high voltage, this circuit supplies
controlled DC voltage to the FBT and the horizontal
deflection circuit according to the horizontal sync
frequency.
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