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20K70
Schematic
23 pgs6.55 Mb0

LG 20K70 Schematic

- 1 -
V Safety Precautions
1. It is safe to adjust after using insulating transformer between the power supply line and chassis input to prevent the risk of electric shock and protect the instrument.
2. Never disconnect leads while the TV receiver is on.
3. Don't short any portion of circuits while power is on.
5. Unless otherwise noted, set the line voltage to 230Vac
!10%,
50Hz.
V
Test Equipment required
1. RF signal generator (with pattern generator)
2. DC Power Supply
3. Multimeter (volt meter)
4. Oscilloscope
5. Color analyzer
O
PIF (Picture Intermediate Frequency) Adjustment
1) Connect the measuring equipment to the Main Board as shown in Fig.1.
2) Set RF frequency and output level of RF SIGNAL GENERATOR as shown Table 1.
3) Turn off S1 and S3 and on S2.
4) Adjust L107 so that the DC voltage may be 2.5!0.1Vdc.
(Table 1)
O
SECAM-L' Adjustment
NOTE : This adjustment should be performed after PIF
adjustment.
1) Turn on S1 and S3 and off S2.
2) Adjust VR102 so that the DC voltage may be indicated
2.5!0.1Vdc.
O
RF AGC (Automatic Gain Control) Adjustment
The RF AGC control (VR101) was aligned at the time of manufacture for optimum performance over a wide range conditions. Readjustment of VR101 should not be necessary unless unusual local conditions exist, such as ;
1) Channel interference in a CATV system.
2) Picture bending and/or color beats, which are unusually due to excessive RF signal input when the receiver is too close to a transmitting tower or when the receiver is connected to an antenna distribution system where the RF signal has been amplified. In this case, the input signal should be attenuated (with pad or filter) to a satisfactory level.
3) Picture noise caused by "broadcast noise" or weak signal.
If the broadcast is "clean" and the RF signal is at least 1mV
(60dBu), the picture will be noise free in any area.
Adjusting the VR101(RF AGC) control to one end of rotation
will usually cause a relatively poor signal to noise ratio; Adjusting to the other end of rotation will usually cause a degradation of over load capabilities resulting in color beats or adjacent channel interference. For best results, adjust the VR101 control while performing on all over local channels, or the voltage at TP2 will be 2.3!0.1Vdc in RF level 65!1dBuV.
IC101
TDA4474
TP1
JP7 IC05
IC102
5V
JP3
S1
S3
S2
JP5
Q106
4.7kΩ
100Ω
100Ω
24
7
11
15
VR102
1
0.01pF
Signal­Generator
(B/G,D/K,I,L) (SECAM-L')
JP1
L107
16
VR102
38.9MHz
34.25MHz
5V
Power­Supply
V Multimeter or Oscilloscope
JP2
JP4
Test Point : TP1
Adjust : L107
Test Point : TP1
Adjust : VR102
Frequency
38.9MHz
34.25MHz
System
B/G,D/K/I,SECAM-L
SECAM-L'
Modulation
OFF OFF
Output level
10mVp-p 10mVp-p
Adjust
L107
VR102
Main Board(Component side view)
Fig. 1 : Connection Diagram of Equipment for PIF Adjustment
ADJUSTMENT INSTRUCTIONS
Test Point : TP2 (J8) or Observing Display
Adjust : VR101
- 2 -
O Screen Voltage Adjustment
1) Tune the TV set to receive a digital pattern.
2) Press MIX button on remote controller for Service to get into the Screen Adjust Mode.
3) Adhere the Color Analyzer on the White window of CPT face.
4) Adjust Screen Volume of FBT so that the luminance of White window is 40!1ft/L.
O
Focus Adjustment
NOTE: This adjustment should be performed after warming
up for 10 minutes.
1) Tune the TV set to receive a digital pattern.
2) Adjust the lower Focus control of FBT for the best focus of vertical line B.
3) Adjust the upper Focus control of FBT for the best focus of area A.
4) Repeat above step 2) and 3) for the best overall focus.
O
Deflection Data Adjustment (Line SVC-1)
NOTE: To enter SVC mode, press "OK" buttons on both TV
set and the Remote control at the same time.
1. Preparation for Deflection Adjustment
1) At SVC mode, press the Yellow colored button. If the Remote Controller doesn't have the Yellow button, use the button under the Channel Down(PR
U) button. And then, deflection data adjustment OSD (SVC1 mode) will be displayed.
2) Press Channel UP/DOWN button for desirous function Adjustment.
3) Press Volume UP/DOWN button to adjust the data.
VL--(Vertical Linearity)
Adjust so that the boundary line between upper and lower half is in accord with geometric horizontal center of the CPT.
VH--(Vertical Height)
Adjust so that the circle of a digital circle pattern may be located within the effective screen of the CPT.
SC--(Vertical "S" correction)
Adjust so that all distance between each horizontal lines are to be the same.
VS--(Vertical Shift)
Adjust so that the horizontal center line of a digital circle pattern is in accord with geometric horizontal center of the CPT.
HS--(Horizontal Shift)
Adjust so that the vertical center line of a digital circle pattern is in accord with geometric vertical center of the CPT.
EW--(Horizontal Width)
Adjust to that a digital circle pattern looks like exact circle.
EP--(East-west Parabola)
Adjust so that middle portion of the outermost left and right vertical line looks like parallel with vertical lines of the CPT.
EC--(East-west Corner)
Adjust so that the vertical line at every 4 corners of the screen looks like parallel with the vertical lines of the CPT.
ET--(East-west Trapezium)
Adjust to make the length of top horizontal line same with it of the bottom horizontal line.
Test Point : RK (Red Cathode of CPT Board)
Adjust : Screen Control of FBT
Test Point : Observing Display
Adjust : Focus control of FBT
Fig. 3
White window OSD
SCREEN ADJUST MODE
Fig. 2 SVC MODE for SCREEN Adjust
A
b
B
- 3 -
(Table 2)
O
White Balance Adjustment.(LINE SVC 0)
NOTE : This adjustment should be performed after screen
voltage adjustment.
1) Tune the TV set to receive an 100% white pattern.
2) Press the Yellow button on remote controller in the SVC Mode (press OK buttons on both TV set and remote controller at the same time) then you can find On Screen Display.
3) Press PSM (RED) button on remote controller. (Standard picture)
4) Press PR+ or PR- button for desirous function adjustment.
5) Adjust VOL+ or VOL- button for Gg31.
6)
Adjust VOL+ or VOL-button in each status of "Rg--"/"Bg--" for X=272
!
8, Y=295!8 with color analyzer (color temperature
11,000
o
K).
(Table 3)
O
Hold Down Check(X-ray Protection)
1) Short the both terminal of R430 on the Main2 Board and check if the TV set turns into Stand-by.
Abnormal
D407
R430
Short
FR401
To CPT(HT)
Fig. 4
Menu
VL VA
SC
VS HS EW
EP EC
ET
VZ
0~63 0~63 0~63 0~63 0~63 0~63 0~63 0~63 0~63 0~63
28 27 16 29 18 37 29 32 30 31
-1
+12
28 26 16 29 30 37 29 32 30 31
Range LG 29” Flat REMARKS(n60Hz)
Menu
RG GG
BG
Y-dly
0~63 0~63 0~63 0~15
31 31 31 12 15(D/K, I)
Range LG 29” Flat REMARKS
O OPTION Adjustment (SVC MODE:OPTION-1,
OPTION-2, OPTION-3)
NOTE: When the EEPROM has been replaced, the Option data
should be restored as the function of individual system and specification.
1) Press OK buttons on both TV set and Remote Controller at the same time to get into SVC mode.
2) Press the Yellow button several times to find OPTION-1, OPTION-2 and OPTION-3.
3) Input the correspond OPTION data referring to Table below with the numeric buttons 0~9.
Table 1. OPTION 1 Function
Table 2. Specifications for OPTION-1 data
- 4 -
Not available with SECAM-L/L’ Not available with NTSC-M
RGB input/Auto AV
Lang1
0 1 0 1
SCART
China
+AU
L-sys
M-sys
Option Code
0 1 0 1 0 1 0 1
Lang0
0 0 1 1
Function Remark
Without NTSC-M With NTSC-M Without SECAM-L/L’ With SECAM-L/L’ CCIR CH. Table China CH. Table Phono jack(AV1) Scart jack(AV1) OSD Language English Only English or Arabic/Parsi/ English or Chines English or Deutsch/Franch/Italiano.Spanish
OPTION
Data
M-sys
L-sys China
SCART
Lang0
0 1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16 17 18
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
Lang1
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1
OPTION
Data
M-sys
L-sys China
SCART
Lang0
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Lang1
1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
Table 3. OPTION 2 Function
Table 4. Specifications for OPTION-2 data
- 5 -
OPTION
Data
TOP
DCF TILT
EYE
V-curve
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Woofer
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
OPTION
Data
TOP
DCF TILT
EYE
V-curve
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Woofer
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
Set to 0 for no TXT
Set to 1 for DCF board
Set to 1 for Degaussing Coil with TILT Set to 1 for EYE module Set to 0 for Squitter AMP Set to 1 for South East Asia and China
Woofer
EYE
TILT
DCF
TOP
Option Code
0 1 0 1 0 1 0 1 0 1 0 1
Function Remark
Without TOP Teletext With TOP Teletext Without DCF(Digital Comb-Filter) With DCF Without TILT circuit With TILT circuit Without EYE With EYE Without Woofer With Woofer Normal Volume curve(Europe, CIS) Rapid Volume curve(South East Asia, China)
V-
curve
Table 5. OPTION 3 Function
Table 6. Specifications for OPTION-3 data
O Sound Pre scaler
1) Set to Scart when one of AV1 or AV2 is Scart jack. Audio out level : 500mVrms at 54% modulation ratio
2) Set to Phono when both of AV1 and AV2 is RCA Phono jack. Audio out level : 500mVrms at 100% modulation ratio. (NTSC-M : 400mVrms)
[ MSP3410(3400) Pre-scaler setting
- 6 -
OPTION
Data
ACMS
DKNica
m
H-phone
VM
Max.
vol
0, 1 2, 3 4, 5 6, 7
8, 9 10, 11 12, 13 14, 15 16, 17 18, 19 20, 21 22, 23 24, 25 26, 27 28, 29 30, 31 32, 33 34, 35 36, 37 38, 39 40, 41 42, 43 44, 45 46, 47 48, 49 50, 51 52, 53
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1
* * * * * * * * * * * * * * * * * * * * * * * * * * *
Hotel
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
OPTION
Data
ACMS
DKNica
m
H-phone
VM
Max.
vol
54, 55 56, 57 58, 59 60, 61 62, 63
1 1 1 1 1
0 0 1 1 1
1 1 0 0 0
1 1 0 0 1
* * * * *
Hotel
0 1 0 1 0
Menu
FP NP
SP S1 vol S2 vol
20 85
20 110 110
40 85
20 110 110
FM Pre-scaler Nicam Pre-scaler Scart Pre-scaler Scart1 Pre-scaler Scart2 Pre-scaler
Description
B/G,D/K,I
Scart Phono SECAM-L/L’ model
M
20 85 47 50 50
40 85 47 50 50
B/G,D/K,I M
20 85
20 110 110
20 85 25 80 80
B/G,D/K,I L/L’
Set to 0 for no TXT Set to 1 for Chinese Model Set to 1 for H/P jack
Set to 1 for VM coil magnet Buyer option
Defalt
Hotel
VM
H-
Phone
DKNic
am
ACMS
Option Code
0 1 0 1 0 1 0 1 0 1
0~
100
Function Remark
Without Auto Channel Memory System With Auto Channel Memory System D/K stereo Without DK stereo Without H/P jack With H/P jack Without VM With VM Without Hotel mode With Hotel mode Maximum volume level for Hotel mode data(Normal=36steps)
Max.
vol
BLOCK DIAGRAM
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