akira LCT-20CH01ST, Руководство по обслуживанию

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Model No.:LCT-20CH01ST.doc
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This chapter Mainly introduces the receiving and processing of image signal and sound signal, whole
machine system control process, and whole machine power supply system (Model of LT32GJ01E is taken as
an example, other models is similar and will not be explained here for each. There are minor differences in
power supply among different models of liquid crystal screen; the details are shown in Specifications).
1. Image signal flow
RF signal is demodulated by tuner, then the obtained video signal and signals inputted from COMPONENT
terminal, AV terminal, S terminal, 2-way Scart interface and VGA interface are all sent into video-processing IC
SVP-CX32LF to be processed. Input signals with different format are changed into uniform LVDS differential
signals, and are sent to liquid crystal screen. In addition, TV video signal is processed by SVP-CX32LF to
generate 2-way CVBS signal, which is used in 2-way Scart video output.
Signal inputted from HDMI interface is decoded into digital video signal, which is sent into video decoding IC
SVP-CX32LF to be processed. After procession, the obtained uniform LVDS differential signal is sent to liquid
crystal screen through LVDS interface to screen.
2.Sound flow
RF signal is demodulated by tuner, and then the obtained SIF signal (SIF-2 signal) and audio signal inputted
from Scart1 interface are directly processed by STV-8217. The output audio signal of STV-8217 is sent into
power amplifier TDA8944J, and the amplified signal is finally sent to speaker or earphone output.
Signals from HDTV terminal, AV terminal, Scart2 interface and PC Audio are first sent into 74HCT4052D for
choosing passages, and then sent into STV-8217 for demodulation and sound effect processing. The output
audio signal of STV-8217 is sent into power amplifier TDA8944J, and finally the amplified signals are sent to
speaker or earphone output.
After the demodulation and sound effect processing of STV-8217, there is an audio output which is used for
sound output of Scart1 terminal.
3. Whole machine power supply system
There are 4 ways of voltage output in the power panel: +24V
（
6A
） 、
+12V
（
2A
） 、
+5V
（
2A
）
and +5VS
（
1A
）
.
+24V output is used by LCD screen; +12V output is used by power amplifier TDA8944J, and is also changed
into +8V output by AZ78L08ZTR-E1 to satisfy the need of STV-8217 IC; +5V output is changed into 1.8V output
and 3.3V output by DO (such as AZ1117H-1.8TRE1 and AZ1117H-3.3TRE1) to satisfy the needs ICs. +24V,
+12V and +5V outputs will be cut off in standby state. While +5VS output is the power supply of MCU, infrared
receiver and EEPROM etc, and will be cut off when the AC is turn off.
5V output will be divided into two ways: one way is changed into +3.3V and +1.8V analogue power supplies
through DC/DC converter for STV-8217 IC, ANX9011LF IC etc and peripheral circuits; other way is changed
into +3.3V and +1.8V digital power supplies through DC/DC converter for SVP-CX32 IC etc and peripheral
circuits, and this way of 5V voltage will be cut off in standby state, while the other way of 5V voltage supply
power especially for MCU, infrared receiver and EEPROM etc, and will not be cut off in standby state.
(1) Constitution and distribution of whole machine power supply
FB34
FB8
FB34
12
V
U23
AZ78L08ZTR-E1
8V
ST82X7
Pin 3
12V shutdown mute circuit
+12V（voltage of line to screen） CON1
Pin 1,2,3,4 (used by 37 inches screen)
12V power amplifier TDA8944J
Pin 3,16
+12V power
supply
CON11
Pin 1,2,3
+12V power
supply
CON403
Pin 3,4