Samsung LA20S51B User manual

TFT-LCD TV
Chassis Model
SP20SO LA20S51B
Manual
SERVICE
TFT-LCD TV CONTENTS
1. Precautions
2. Product Specifications
3. Disassembly & Reassembly
4. Alignment & Adjustments
5. Troubleshooting
6. Exploded View & Parts List
7. Electrical Parts List
8. Block Diagram
9. Wiring Diagram
10. PCB Layout
11. Schematic Diagrams
12. Panel Description

2 Product Specifications
2-2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
2-2 Pin Assignments
RCA Green
RCA Blue
RCA Red
RCA White
RCA Red
Y
GND
Pb (Cb)
GND
Pr (Cr)
GND
Audio L
GND
Audio R
GND
2-2-1 DVD
RCA White
RCA Red
CVBS
Audio L
GND
Audio R
GND
2-2-3 A/V
RCA Yellow
Pin Separate
1
2
3
4
5
GND
Y
C
GND
GND
2-2-2 S-Video
Pin Separate
Red
Green
Blue
GND
GND (DDC Return)
GND-Red
GND-Green
GND-Blue
No Connection
GND-Sync / Self Test
GND
DDC Data
H - Sync
V - Sync
DDC Clock
2-2-4 D-SUB

2 Product Specifications
2-3
Separate Sync
2-3 Timing Chart
This section of the service manual describes the timing that the computer industry recognizes as standard for
computer-generated video signals.
C D
AO
E
BP
Video
Sync Sync
Video
QR S
A : Line time total B : Horizontal sync width O : Frame time total P : Vertical sync width
C : Back porch D : Active time Q : Back porch R : Active time
E : Front porch S : Front porch
H/V Composite Sync
Sync-on-Green
79.976
12.504
1.067
1.837
9.481
0.119
75.025
13.329
0.038
0.475
12.804
1280/75Hz,50Hz
1280x1024
1024/75Hz
1024 x 768
60.023
16.660
1.219
2.235
13.003
0.203
75.029
13.328
0.050
0.466
12.795
0.017
78.750
Positive
Positive
Separate
31.469
31.777
3.813
1.589
26.058
0.318
70.087
14.268
0.064
0.858
13.155
0.191
28.322
Negative
Positive
Separate
µ
µ
µ
µ
µ
IBM
640/75 Hz,
60Hz, 72Hz
640 x 480
800/75 Hz, 56Hz,
60Hz, 72Hz
800 x 600
1024/60Hz
1024 x 768
VGA2/70 Hz
720 x 400 VGA3/60 Hz 640 x 480
Table 2-1 Timing Chart
31.469
31.778
3.813
1.589
26.058
0.318
59.940
16.683
0.064
0.794
15.761
0.064
25.175
Negative
Negative
Separate
37.500
26.667
2.032
3.810
20.317
0.508
75.000
13.333
0.080
0.427
12.800
0.027
31.500
Negative
Negative
Separate
46.875
21.333
1.616
3.232
16.162
0.323
75.000
13.333
0.064
0.448
12.800
0.021
49.500
Positive
Positive
Separate
48.363
20.677
2.092
2.462
15.754
0.369
60.004
16.666
0.124
0.600
15.880
0.062
75.000
Negative
Negative
Separate
Mode
VESA
Timing

3 Disassembly and Reassembly
3-1
3 Disassembly and Reassembly
This section of the service manual describes the disassembly and reassembly procedures for the LA20S51B TFT-LCD TV.
WARNING: This monitor contains electrostatically sensitive devices. Use caution when handling these
components.
3-1 Disassembly
Cautions:1. Disconnect the monitor from the power source before disassembly.
2. Follow these directions carefully; never use any metal instrument except provided jig to
separate the cabinet.
1. Place monitor face down on cushioned table and r emove 6 screws and remove stand.
2. Lift up the rear cover and remove 7 screws from the power board.

3 Disassembly and Reassembly
3-2
3. Remove 8 screws from the main board and disconnect cables.
4. Lift up the power board and main board.
5. Remove 6 screws from the BRKT and lift up the BRKT.

3 Disassembly and Reassembly
3-3
1. After confirm there is nothing on the desk, turn the
LCD module over and put it on a flat desk set to
the ground.
2. Remove 2 screws for the lamp unit.
3-2 Replacement Order of Lamp Assemblies
5. Lift up the panel.

3 Disassembly and Reassembly
3-4
3 Disassembly and Reassembly
3-4
3-3 Reassembly
Reassembly procedures are in the reverse order of disassembly procedures.
4. Please fix the new lamp units on the LCD module :
opposite process 2 and 3.
3. Slide the lamp unit out. Please take out the lamp
unit from the LCD module.
Slide the lamp unit out.
Slide the lamp unit out.

4 Alignments and Adjustments
4-1
4 Alignments and Adjustments
4-1 General Alignment Instuction
1. Usually, a color LCD TV needs only slight touch-up adjustment upon installation.
Check the basic characteristics such as height, horizontal and vertical sync.
2. Use the specified test equipment or its equivalent.
3. Correct impedance matching is essential.
4. Avoid overload. Excessive signal from a sweep generator might overload the front-end of the TV.
When inserting signal markers, do not allow the marker generator to distort test result.
5. Connect the TV only to an DC power source with voltage and frequency as specified on
the backcover nameplate.
6. Do not attempt to connect or disconnect any wire while the TV is turned on.
Make sure that the power cord is disconnected before replacing any parts.
7. To protect aganist shock hazard, use an isolation transform.

4-2 Factory Mode Adjustments
4-2-1 Entering Factory Mode
1. To enter “Service Mode” Press the remote -control keys in this sequence :
- If you do not have Factory remote - control
- If you have Factory remote - control
4-2-2 Factory Mode Tree
4 Alignments and Adjustments
4-2

4 Alignments and Adjustments
4-3

4 Alignments and Adjustments
4-4

4 Alignments and Adjustments
4-5
7. Test Pattern ( Test Pattern of VCTi)
1) VCTi
2) Toshiba
3) Gray Bar
4) Gray
5) Green
6) Color Bar
7) Cross
8. Bus Stop
- Bus stop is used data communication.
9. Chcek Sum
- Display the current check sum size of the MICOM.
10. Reset
- Initializes the data in the MICOM.
11. T-VNC25PEA-0004 2004/06/22
- Display the MICOM program version.
4-2-3 White Balance
High Low
263 5, 267 5 267 5, 263 5
x, y x, y

4-2-4 Calibration
4 Alignments and Adjustments
4-6

5 Troubleshooting
5-1
5 Troubleshooting
5-1 No Power
Does proper DC 14V/5V
appear at Pin 3. Pin 9 of
CN100? Check CN803 Pin3, Pin9 in I/P
Board.
Yes
No
No
No
No
No
Does proper DC A5V
appear at FT144? Check IC101 and IC105.
Yes
Does proper B3.3V
appear at Pin 2 of IC111? Check IC111.
Yes
Does proper DC B1.8V
appear at Pin 4 of IC112? Check IC112.
Yes
Does proper DC B8V
appear at FT130? Check IC109.
1
2
3
4
5

5 Troubleshooting
5-2
No
No
No
Check IC704 and IC802.
Yes
Does proper DC 5V_P
appear
at Pin 2 of IC104? Check IC104.
Yes
Does proper DC 9V_S
appear at FT127? Check IC110.
Yes
Yes
Does proper DC B5V
appear at FT131? Check IC108.
6
7
8

5 Troubleshooting
5-3
WAVEFORMS
1 2
5
3
6
44
7 8

5 Troubleshooting
5-4
5-2 No Picture (TV, Video, S-Video, DVD)
Check C800(TV)
Check C822(Video)
Check C824(S-Video)
Check C821(DVD)?
Check the input signal.
Yes
Check the IC802.
WAVEFORMS
9
9No

5 Troubleshooting
5-5
Does the signal appear at
Pin 110 (Tuner sound signal)
and Pin 113, 114 (VCR sound)
and Pin 115, 116 (DVD) Pin 117,
118 (PC) of IC802 (VCTj)?
(RF) Check Tu01 (TV Tuner).
(Video) Check the CN913.
(DVD) Check the CN901.
Yes
Does the signal appear at Pin
123, 124 of IC802 (VCTj)? Check IC802.
Yes
Does the signal appear
at Pin 2, 5 of Pin 16, 19 IC600? Check the IC600 (Audio amp)
and related circuit of IC600.
Yes
Replace the speaker.
5-3 No Sound
No
No
No

8 Block Diagrams
8-1
8 Block Diagram
- This Document can not be used without Samsung’s authorization.
8-1 Signal Path Block Diagram

8 Block Diagrams
8-2
8-2 Input Power Block Diagram