BBK LT2002S User manual

service manual
LT2002S

Catalog
1.1 Safety precautions
1.1.1 Power supply
1.1.2 Precautions for antistatic
1.1.3 Precautions for display screen
1.1.4 About placement position
1.2 Maintenance method
1.2.1 Visualized method
1.2.2 Electric resistance method
1.2.3 Voltage method
1.2.4 Current method
1.2.5 Cutting method
1.2.6 Element substitution method
1.2.7 Comparison method
1.3 Required device for maintenance
Chapter Two Operation Instructions
2.1 LOCATION AND FUNCTION OF CONTROLS
2.1.1 Remote Controller
2.3 TV SETUP
2.3.2 SOUND
2.3.3 TV SETTING
2.3.4 SYSTEM SETTING
Chapter One About Maintenance
2.1.2 Panel Control
2.2 CHANGE SOURCE OPERATION
2.3.1 PICTURE
2.3.5 NICAM/BILINGUAL RECEIVING
2.4 VIDEO SETTING MENU
2.5 20.1” TV SPECIFICATION
2.6 CHECKING ACCESSORIES
1
1
1
1
1
2
2
2
2
2
2
2
3
3
3
4
4
4
5
5
6
6
7
7
8
9
9
10
10

Chapter Three Principle and Servicing
Section One Principle of the Player
3.1.1 Introduction to the player
3.1.2 Introduction to IC used by the player
3.1.3 Block diagram of the player
Section Two Unit Circuit Principle
3.2.1 System control circuit
1. System reset circuit
2. System clock circuit
3. System control principle
4. IIC bus control circuit
5. Working state indication circuit
3.2.2 Audio circuit
1. Nicam processing circuit
2. Sound source input selection circuit
3. Audio amplifying circuit
4. Mute circuit
3.2.3 Video circuit
1. Video input and A/D conversion circuit
2. LCD image processing circuit
3. Video output circuit
3.2.4 Input circuit
1. SCART
2. Tuner circuit
3.2.5 Power circuit
1. Power supply circuit
2. Main board power supply circuit
3. Voltage stabilizing circuit
4. Power control circuit
5. Boost control circuit
6. Boost circuit
Section Three Servicing Cases
3.3.1 Servicing cases
3.3.2 Troubleshooting flow chart
Section Four Waveform diagram
11
11
11
11
12
13
13
13
14
14
15
16
16
17
18
18
19
20
20
20
21
21
21
22
23
23
25
23
26
27
27
30
30
34
46

Section Five Function Introduction to IC
3.5. 1 function introduction to STV8216
3.5. 2 function introduction to MST518
3.5. 3 function introduction to Mp1430
3.5. 4 function introduction to W79E632
3.5. 5 function introduction to TVP5146
3.5. 6 function introduction to NCP1377
3.5. 7 function introduction to TDA7266P
3.5. 8 function introduction to La7952
3.5. 9 function introduction to Mp1048
Chapter Four Disassembly and Assembly Process
Chapter Cinque PCB board & Circuit diagram
Section One PCB board
Section Two Circuit diagram
Chapter six BOM List
57
57
60
66
67
69
73
74
76
76
79
82
82
90
97

Chapter One About Maintenance
1.1 Safety precautions
1.1.1 Power supply
When maintenance personnel are repairing DVD TV, he should pay special attention to the power
with 220V 800V AC and 330V DC which will cause hurt and damage to persons!
1.1.2 Precautions for antistatic
Movement and friction will both bring static electricity which causes serious damages to integrated
IC. Though static charge is little, when a limited quantity of electric charge is added to large
scaleintegrated IC, as the capacitance is very small in the meantime, now the integrated IC is very much
easy to be struck through by static electricity or the performance will decrease. Thus static electricity
prevention is of extraordinary importance. The following are several measures to prevent static
electricity:
1. Use a piece of electric conduction metal with the length of about 2 metres to insert into the earth,
and Fetch the lead wire from the top of the surplus metal and connect to the required static electricity
device. The length and depth of the metal embedded under the earth should be determined according to
the wettability of the local soil. For humid places, it may be shorter, and longer and deeper for dry places.
If possible, it can be distributed and layed in terms of “#” shape.
2. On operating table-board, the antistatic table cushion should be covered and grounded.
3. All devices and equipments should be placed on the antistatic table cushion and grounded.
4. Maintenance personnel should wear antistatic wrist ring which should be grounded.
5. Places around the operating position should also be covered with electric conduction cushion or
Painted with antistatic paint.
1.1.3 Precautions for display screen
1. Display screen is breakable article, so please protect carefully when carrying and prevent fingers
or hard objects striking the screen to damage structure of the screen.
2. When cleaning screen, do not use organic chemicals. You should use cloth and use small
amount of special cleaning liquid in places difficult to clean.
- 1 -

- 2 -
1.1.4 About placement position
1. Never place TV in positions with high temperature and humidity.
2. Avoid placing near high magnetic fields, such as loudspeaker or magnet.
3. Positions for placement should be stable and secure.
1.2 Maintenance method
1.2.1 Visualized method
Directly view whether abnormalities of collision, lack of element, joint welding, shedding welding,
rosin joint, copper foil turning up, lead wire disconnection and elements burning up among pins of
Elements appear. Check power supply of the machine and then use hands to touch the casing of part of
elements and check whether they are hot to judge the trouble spot. You should pay more attention when
using this method to check in high voltage parts.
1.2.2 Electric resistance method
Set the multimeter in resistance position and test whether the numerical value of resistance of each
point in the circuit has difference from the normal value to judge the trouble spot. But in the circuit the
tested numerical value of resistance is not accurate, and the tested numerical value of integrated IC's
pins can only be used for reference, so the elements should be broken down for test.
1.2.3 Voltage method
Voltage method is relatively convenient, quick and accurate. Set the multimeter in voltage position
and test power supply voltage of the player and voltage of a certain point to judge the trouble spot
according to the tested voltage variation.
1.2.4 Current method
Set the multimeter in current position and test current of the player of a certain point to judge the
trouble spot. But when testing in current method, the multimeter should be series connected in the
circuit, which makes this method too trivial and troublesome, so it is less frequently used in reality.
1.2.5 Cutting method
Cutting method should be combined with electric resistance method and voltage method to use.
This method is mainly used in phenomena of short circuit and current leakage of the circuit. When
cutting the input terminal voltage of a certain level, if voltage of the player rises again, it means that the
trouble lies in this level.

1.2.6 Element substitution method
When some elements cannot be judged good or bad, substitution method may de adopted directly.
1.2.7 Comparison method
A same good PC board is usually used to test the correct voltage and waveform. Compared these
data with those tested through fault PC board, the cause of troubles may be found.
Through the above maintenance method, theoretical knowledge and maintenance experience, all
difficulties and troubles will be readily solved.
1.3 Required device for maintenance
Audio Generator
Digital oscillograph ( 100MHE)
DVD player
SMD rework station
Multimeter
Soldering iron
Pointed-month pincers
Cutting nippers
Forceps
Electric screw driver
Terminals connecting cord
Headphone
Microphone
- 3 -

- 4 -
2.1 LOCATION AND FUNCTION OF CONTROLS
2.1.1 Remote Controller
-/--
S-VIDEO SCART
PICTURE SOUND SLEEP
OSD-LANG
AVTV
MUTE STANDBY
PICTURE-SYS SOUND-SYS
DISPLAY NICAM
VOL
Toswitch the unitbetween standby modeand power on
mode.
STANDBY
1
1
2
3
4
5
6
8
9
NUMBER BUTTONS
2
Todirectly select programnumber.
TWO-DIGIT NUMBER BUTTON
3
Toswitch one ortwo-digit program number.
7
(MENU LEFT/RIGHT)
Toadjust menu settings.
SOUND SYSTEM
8
Toselect sound system.
CHANNEL
9
To increase or decrease program number.
7
10
4
SOURCE
Signal source selectrapidly:TV AV S-VIDEO SCART
SLEEP
5
Setting sleep time.
SOUND BUTTON
6
Toadjust the sound effect. There are 4 modes for your
selection in this function:User, Music, Film, News .
Toselect the soundmode if receiveNICAM orA2.
NICAM BUTTON
10
Chapter Two Operation Instructions
12
11
17
14
16
19
15
18
13
PICTURE
13
Toselect picture mode(User/Soft/Standard /Dynamic)
12
RETURN
Toreturn to previous selected program number.
MUTE
11
Toturn on sound or turn off sound .
14
OSD-LANG
Change OSD language between Russianand English.
15
(MENU UP/DOWN)
Toselect a menu item.
SETUP
16
Toenter or back tothe main menu.
DISPLAY
18
Todisplay current information of channel or source.
VOLUME
19
Toincrease or decreasevolume.
Toselect video system.
PICTURE SYSTEM
17

This TFT-LCD TV allows you to easily adjust the characteristics of the image being displayed.
All of these adjustments are made by using the control buttons on the top of the TV.
There are 7 keys for user`s control including POWER, SOURCE, SETUP , CH-,CH+, VOL- and
VOL+. The following descriptions are the introduction of these keys.
ItemName Description
POWER
Turn ON/OFF the LCD TV.
If there isno signal inputuntil 5 minutes,the machine willgo to standbymode automatically,
the indicator ofthe power willturn to red.If you wantto power onthe machine again,please press
power button.
Remote signal sensor
SOURCE
When you watchthe TV program, push thebutton to decreasechannel number.In the mainmenu,
push the buttonto select thedownward menu item.
Decreases /adjusts thevalue of theselected menu item,or decreases thelevel of audiovolume.
VOL+( )
VOL-( )
CH-( )
SETUP Enter or backto the mainmenu.
When you watchthe TV program, push thebutton to increasechannel number.In the mainmenu,
push the buttonto select theupward menu item.
CH+( )
2
8
CH
SOURCE
VOL SETUP
3
241567
Key cover board
Front cartouche
Enter or backto SOURCE menu.
1
3
4
5
6
7
8
Increases /adjusts thevalue of theselected menu item,or Increases thelevel of audiovolume.
2.1.2 Panel Control
2.2 CHANGE SOURCE OPERATION
Press [SOURCE] key on the top of the TV panel to change the input source, the menu will display
as follows:
The current source item is highlighted. Through pressing [ ] button on the remote control or [
] key on the top of the TV may change the current source item and select source item which you want
to change to. Press [ ] button or [ ] key to confirm your choice that change to highlighted source
item.
Through pressing [TV], [AV], [S-VIDEO], [SCART] button on the remote control to select
signal source directly.
TV
AV
S-VIDEO
SCART
- 5 -

Item
BRIGHTNESS
Toadjust brightness.
CONTRAST Toadjust contrast.
SATURATION
Toadjust color saturation.
2.3
This product can store up to 100-channel programs (0 99). You can select your favorite channel
through [CH+/-] or number buttons, and you can scan and store all of the channels through manual or
automatic mode.
" PICTURE " , " SOUND " ,( TV SETTING " , " SYSTEM SETTING ")
TV SETUP
In TV mode, press [SETUP] button on the remote control or [SETUP] key on the control
panel, the menu will show as follows:
# Through pressing [ ] button on the remote control, you can select main menu sections(main
menu sections consist of . Press
[ ] button to enter this menu section.
Press [ ] button on the remote control to select the item, and then press [ ] button to adjust
parameter value. Press [SETUP] button to return to main menu section.
Select " " and menu will show as follows:Press [ ] button to select items and [ ] button to
adjust.
Description
TINT To adjust picture tint, only valid in N 3.58/N 4.43/PAL60 and display mode with V-scanning frequency
equal 59.94Hz
There are four modes in picture mode: User, Standard, Dynamic and Soft. You can press [PICTURE]
button to select any one of these modes, the adjusted value is saved in User mode.
USER STANDARD
DYNAMIC
SOFT
SELECT ENTER RETURN SETUP
TINT
PICTURE
BRIGHTNESS
SATURATION
CONTRAST
50
40
50
50
PICTURE USER
SELECT ADJUST RETURN SETUP
TINT
PICTURE
50
SATURATION
CONTRAST 40
50
BRIGHTNESS 50
PICTURE USER
PICTURE
Can be changebetween: "USER", "STANDARD", "DYNAMIC" and"SOFT".
2.3.1 PICTURE
- 6 -

Item
BALANCE
TREBLE
Toadjust balance ofleft and rightchannels.
To adjust bass.
To adjust treble.
Select " "and menu will show as follows:
BASS
Description
40
50
34
BASS
BALANCE
TREBLE
SOUND
SELECT ENTER RETURN SETUP
There are four modes in sound mode: User, Music, Film, News. User may press [SOUND] button to
select any one of these modes, the adjusted value is saved in User mode.
USER
FILM
NEWS
MUSIC
Press [ ] button to select item and press [ ] button to adjust . The following is sound item
description.
SOUND USER
SOUND Can be changebetween:"USER", "NEWS", "FILM"and "MUSIC".
2.3.2 SOUND
Toenter a submenuto set channelskip and channelswap.Please refer thenext page.
Press [ ] button to select item and press [ ] button to adjust or activate.
Item
CHANNEL Tochange the currentchannel number.
CHANNEL EDIT
FINE TUNE Toadjust the channelfrequency accurately tomake the sound and picture effect better.
MANUAL SEARCH
Tosearch programs bymanual.
Description
AUTO SEARCH
Tosearch programs andstore all ofthem automatically.
Select " " and tuning menu will show as follows:
TV SETTING
CHANNEL 5
CHANNEL EDIT
FINE TUNE 122.30MHZ
MANUAL SEARCH
AUTO SEARCH
SELECT ENTER RETURN SETUP
2.3.3 TV SETTING
- 7 -

CHANNEL EDIT
SKIP
SWAP
CONFIRM
CHANNEL 5
NO
?
_ _
Item
CHANNEL
Description
SKIP
SWAP
CONFIRM
Toselect current channelhere.
Toselect "Yes " or "No ", youcan select "Yes " to make current channel unaccessible while using
[CH+/-] button tobrowse channels.
Select or enterthe channel number directly to swap with current channel.
Highlight this optionand press the [ ] buttonsto confirm theswap function.
NOTE
During the searching, you can press [SETUP] button to stop.
SYSTEM
SLEEP
LANGUAGE
TRANSPARENCY
RESET
SYSTEM SETTING
SELECT ENTER RETURN SETUP
ENGLISH
OFF
You can setup some system configuration here. Press [ ] to select " " item and press [ ]
button to enter the following section:
Description
SYSTEM
SLEEP
LANGUAGE
TRANSPARENCY
RESET
Enter color systemand sound systemchoosing.
Can change sleeptime (minute) between:"OFF","30", "60", "90","120".
Can be changedbetween: "RUSSIAN", "ENGLISH".
Tochange transparency ofOSD.
Toreset all valueto default.
NOTES
When you choose the system item, if pressing [ ] on the remote control, it will directly enter color
system choosing; if you press [SOUND-SYS] button on the remote control, it will enter sound system
choosing. Press [ ] button to select the color or sound system.
# Press [ ] button to select item and press [ ] button to adjust or activate.
Item
OFF
2.3.4 SYSTEM SETTING
- 8 -

Nicam/bilingual function is only effective in TV mode while program is coming with Nicam/bilingual.
If you can receive Nicam/bilingual signal, you can operate as follows to enjoy that.
#
# When selecting mono channel, "MONO" will show on screen; when selecting bilingual, "DUAL1"
will show on screen; when selecting bilingual II, "DUAL 2" will show on screen and when selecting stereo,
" STEREO " will show on screen.
You can select Nicam stereo, mono channel or bilingual through NICAM button on the remote
control. If stereo signal is too weak, this unit will switch into mono channel automatically.
NOTE
# SECAM system is only used by some European countries and districts, such as France.
# If the local system is SECAM L, the color system must be selected as "SECAM" and sound
system must be selected as "L".
2.3.5 NICAM/BILINGUAL RECEIVING
If no signal input in TV, AV, S-VIDEO, SCART, the screen will show like the following figure.
This unit will go into standby mode automatically with no signal input for more than 5 minutes.
If signal input in S-VIDEO, AV/SCART CVBS signal output is not recommended.
When in AV/ S-VIDEO/SCART input mode, there are 6 color system modes for selection: "Auto",
"PAL"," N 3.58", "N 4.43", "PAL60" and "SECAM". Select the right system for your video program. If you
do not know which mode your video playback devices and video media is using, you should select the
Auto mode or check and confirm this with your supplier.
The menu setup of AV/S-VIDEO/SCART modes is much the same as that of TV mode, except the
Section is invalid and a little difference in color and sound modes. In order to make this manual
pithy and concise, it is not repeated here. You can find it in preceding pages.
NOTE
# For this unit is combined by multiple functions, when inserting into SCART socket, it will not
automatically switch into SCART mode. You have to select SCART channel through [SOURCE] menu
orpressing [SCART] button on the remote control, that is a little different with that of other TV sets. If the
input channel is SCART, this unit will automatically recognise RGB or CVBS signal of SCART; when
normal RGB signal appears, this unit will automatically switch into RGB display mode.
AV
NO SIGNAL
4:50
2.4 VIDEO SETTING MENU
- 9 -

~
2.6 CHECKING ACCESSORIES
Operational Manual
Operational Manual
2.5 20.1” TV SPECIFICATION
Remote Controller Batteries(AAAX2) Power Cord
- 10 -

- 11 -
Chapter Three Principle and Servicing
Section One Principle of the Player
3.1.1 Introduction to the player
Electronic scheme of LT2002S adopts LCD components (LC201V02-SDB1 20" )+inverter
components (INV607)+MST518VA+TVP5146M1+STV8216+TDA7266P+tuner JS-6B2/121+CPU
(W79E632A40PN ), which support PAL BG/DK/I SECAM BG/DK/L/L RF signal modulating,
PAL/NTSC/SECAM/PAL60 multi-system video signals, BG/DK/I/LL/L accompanying system’s FM,
NICAM, A2 Stereo signal modulating and accompanying restore and external input SCART S-VIDEO
composite video input mode. This model is composed of power, boost components, power switch board,
main board, button board and remote control receiving board.
3.1.2 Introduction to IC used by the player
SN Materi al code Materi al
name Locati on Specs Function description Qty
1880504 IC U13 24C32N SOP Save user inf ormati on (32 K memor izer) 1
2881146 IC U4,U8 LM1117MP-1.8 SOT-223 1.8V voltage stabilizing IC 2
3882167 IC U2,U12 9435M SO8 MOS tube (power switch control) 2
4882030 IC U9 STV8216 TQFP Multi-channel sound source selection
NICAM processing 1
5882112 IC U1 LA7952 SIP Video el ectr onic s witc h (vid eo output
selec tion) 1
6882114 IC U6,U7,U10 AMS1117-3.3 SOT-223 3.3V voltagestabilizing IC 3
7883149 IC U11 TDA7266P SSO24 Audio amplifier 1
8882376 IC U3 TVP5146M1 PQFP Video A /D c onverter 1
9882638 IC U5 MST518VA PQFP LCD i mage pr ocess or 1
10 882945 IC U14 MP1430DN SOP (+)5VEXT voltage stabilizing IC 1
11 1020028 Tuner T1 JS-6B2/121 Receiver high frequency signal and switch
to AV signal 1
12 882637 IC U15 W79E632A40P N PLCC MCU ( progr ammable) 1
13 883304 IC U1 NCP1377 SOP Power I C 1
14 8824629 IC U3 AZ431AZ-A TO-92 3-end prec ision voltage s tabil izer 1

U15 MPU
W79E632X40PX
Multi-channel audio
selection
NICAM signal
processing
U9 STV8216
Tuner
SIF
MONOIN
J3
AUDIO_OUT_L
AUDIO_OUT_R
EXT_IN_R
EXT_IN_L
Mute control circuit
Q6/Q5
Audio amplifying circuit
U11 TDA7266P
8216_RST
Inverter
Board
S
video
input
Reset
circuit
Q13
Multi-channel
video switch
video A/Dconverter
U3 TVP5146
Video
channel
electronic
switch
U1 La7952
U5
MST518VA
TFT_LCDPANEL
Speaker_R
Speaker_L
AUDIO_R_AMP
AUDIO_L_AMP
MUTE
AMP_STB
control circuit
Q7
AMP_STB
AMP_STBY
AMP_MUTE
Y[0:7]
BT656DCLK
SCL_MST
SDA_MST
CS_MSA
RST_MST
SEL_I/P
Boost
components
control
circuit Q1
NO/OFF_
INVERTER
BLON
BRIGHT
H_SYNC
V_SYNC
LDE
DCLK
DR[0:7]
DG[0:7]
DB[0:7]
LOUT+
LOUT-
ROUT+
ROUT-
RESET
Sw1
Sw2
TUNER_CVBS
EXT_CVBS_IN
SCART_CVBS_IN
SB
SG
SR
S_C_IN
S_Y_IN
S_Y_IN
SCART_CVBS
_OUT
EXT_CVBS
_OUT
S
C
A
R
T
AV
terminal
TXD RXD
FBI
FB
SS SS
Q10
22.1184
MHZ
14.318MHZ
27MHZ
14.318MHZ
KEY
BOARD
KEY[1:4]
U14
Mp1430
D15/D18/D19
L15/U2
U12
Si9435
U6
AK33
U8
Ak18
U4
AK18
U7
AK33
Power
Board
+12V +5VEXT
FOR TDA7266P
+5/12V_P
FOR PANEL
10V
33DVCC
33AVCC
33VCC
D+1.8V
MST
+5V D3.3V
A3.3V
D1.8V
A1.8V
+12V_P
/RST
12V voltage
stabilizing circuit
Standby control
circuit
Q8/Q9Q11/Q12
R LED
G LED
Remote
Board
IR
Tuner
U13
24C32
73
78
24
23
2
1
SCART_OUT_R
SCART_OUT_L 19
18
SCART_IN_R
SCART_IN_L
14
15
29
28
52
53
43
SDA
SCL
40
39
11
14
12
17
8
10
5
6
20
19
11
90
91 98
34 35
15 18
23 26
58
11 14
147 150
153 154
34
143
144
146
145
84
83
82
33
Wp
5
67
HV
RTN
POWER
17
14
16
20
21
43
42
41
40
39
31
30
28
27
38
7
11/13
6
24
25
26
10
35
37
PANEL_ON
34
29
28
40
43 47
50 52
74
75
16
18
23
1
8
17
80
7
1
3
2
6
20
7
11
15
12
10
16
8
19
J
A
C
K
7
1
6
9
8
42
3
LCD image processor
3.1.3 Block diagram of the player
Block diagram of the player is shown in the figure 3.1.3.1:
figure 3.1.3.1 Block diagram of the player
- 12 -

Section Two Unit Circuit Principle
3.2.1 System control circuit
System control circuit is mainly composed of reset circuit, clock circuit and W79E632. W79E632 is
responsible for the control and coordination of the player’s system; W79E632 is a programmable MCU
processor; function of each I/O port is adjusted through software and can support the upgrading of
external upgrading device. Please refer to IC function introduction for details.
1. System reset circuit
(1) system reset circuit is shown in the figure 3.2.1.1:
U15
W79E632X440PX
Figure 3.2.1.1 System reset circuit diagram
(2) Working principle: this circuit is a typical high level effective reset circuit. After power on,
“5VMCU” changes from 0V to 5V to supply power for system control circuit, and charge CE36 through
R104. Voltage of two ends of CE36 cannot change suddenly, so 5V power supplies a high level reset
signal to pin 10 of U15 through C-E electrode of Q13 to reset W79E632. After capacitor CE36 is fully
charged, voltage on two ends is near to 5V, now Q13 cuts off, voltage of pin 10 of W79E632 restores to
low level to finish reset action. Reset time of this circuit is about 100MS, which is decided by the value of
R104 and CE36. Function of D17 is to discharge CE36 quickly to ensure the reliable reset when power
on for the second time. The trouble that appears in this circuit is that machine cannot enter standby state
after power on, and machine fault after power on.
- 13 -

2. System clock circuit
(1) System clock circuit is shown in the figure 3.2.1.2:
U15
W79E632X440PX
Figure 3.2.1.2 System clock circuit
(2) Working principle: this clock circuit is mainly composed of X4, C148 and C155, in which X4 is a
22.1184MHZ crystal oscillator; C148 and C155 are externally-connected resonance capacitors to
produce a 22.1184MHZ clock signal to provide for W79E632 to generate clock signal required by system
through internal doubling circuit to act as working clock.
3. System control principle
(1) System control schematic diagram is shown in the figure 3.2.1.3:
MST518VA
TVP5146
STV8216
PANEL_ON
control circuit
Inverter components
+5V power control
U12/Q8/Q9
Remote control board
Reset circuit
Panel
KEY1~KEY4
RESET
10
IR 14
Working indicator light
control circuit
STANDBY
POWER 17 16
ON/OFF_
INVERTER
PANEL_ON
37
8216_RST
38
\RST
7
RST_MST
39
SS FBI RXD TXD
24 613 11
W79E632X
MCU
SCART JACK
810
12
16
Figure 3.2.1.3 System control schematic diagram
- 14 -

(2) Working principle
Working process from power-on to standby: after power on, 12V power outputted by power board
outputs a group of +5V power (marked as +5VEXT in schematic diagram) through being voltage
stabilized by U14 , during which time power supply of +5VEXT and +12V is normal. +5VEXT is mainly
supplied to W79E632, MST518 and each control circuit. Reset circuit of system supplies a 120MS high
level signal to reset W79E632 through pin 10 of W79E632. Pin 40 of W79E632 is connected with a 4.7K
pull-up resistor externally, so high level reset signal is outputted when power on to pin 33 of MST518 to
reset. After system reset, left/right of 260MSand pin 40 of W79W632 output a low level signal to make the
reset of MST518 finish, now system begins to enter standby state.
Working process from standby to power-on: when W79E632 receives panel button or remote
controller wake code, pin 38, 7 o W79E632 outputs a low level signal which keeps in 170MS to give
TVP5146 and STV8216 for reset, meanwhile pin 17 of W79E632 (POWER) outputs a continuous low
level signal to make U12 on, +5V power outputs normally and other function circuit enters working state
after getting power supply. After POWER pin outputs low level, left/right of 2S and pin 37 of W79E632
(PANEL_ON) output a continuous low level signal to make Q4 cut off and make Q2, U2 (MOS tube)on.
After getting power supply, display screen enters working state. Then pin 16 of W79E632
(ON/OFF_INVERTER) outputs low level signal to make boost board enter working state and output high
voltage to lighten the background light of screen, picture displays normally and the machine enters
normal working state. During the course of power-on, the machine will generate noise. To avoid the
amplified output of noise, U15 is defaulted in low level output in standby state. After screen displays
power-on picture, a high level signal outputs to make TDA7266P enter non-mute mode to prevent
power-on noise effectively. Pin 13 of U15 (TXD) and pin 11 (RXD) are external upgrading input pin and
the upgrading will not be normal until the machine enters upgrading mode. Pin FBI is the input mode
switch pin of SCART input terminal.
4. IIC bus control circuit
(1) IIC bus control circuit block diagram is shown in the figure 3.2.1.4:
STV8216
U9
W79E632X
U13
24C32
Tuner
U15
SCL_MST
SDA_MST
SCL
SDA
MST518VA
TVP5146
U5
U3
Figure 3.2.1.4 IC bus control circuit block diagram
- 15 -

(2) Working principle: IIC bus is a kind of simple, dual-direction and synchronous serial line
developed by PHILIPS company. Only 2 lines (serial clock line and serial data line) are required to
connect between components on bus to transmit information. This bus is high-performanceserial bua
which has function of decision and synchrony of high and low speed devices required by multi-player
System with wide application range.
5. Working state indication circuit
(1) Working state indication circuit is shown in the figure 3.2.1.5:
(2) Working principle: after power on and entering standby state, pin 17 of W79E63 (POWER) is
high level, now Q9 is saturated on, STANDBY is low level and makes Q8/Q11/Q12 cut off in circuit. Now
U12 also cuts off and +5V power has no output. +5VEXT power is supplied for the dual-color light on
Remote Control board through R108 and the red light gets power supply. If the red light is on, it means
that the machine enters standby state. After power on, pin 17 of W79E632 (POWER) is low level, Q9
cuts off, STANDBY is high level, Q8/Q11/Q12 is saturated on and now U12 is also on and +5V power
outputs. +5VEXT power is supplied for the dual-color light on remote control board through R109/Q12,
the green light gets power supply and it means that machine enters working state.
Audio processing circuit is mainly responsible for the switch, amplifying and restire of audio and
composed of audio source input selection and NICAM processing circuit, audio amplifying circuit and
mute control circuit. Audio processing circuit block diagram is shown in the figure 3.2.2.1:
3.2.2 Audio circuit
Figure 3.2.1.5 Working state indication circuit diagram
- 16 -