LG SL4Y Service Manual page 30

NO BOOTING WHEN YOU TURN THE UNIT ON, NO MESSAGE OR "HELLO"
ON FRONT PANEL
When you turn on your set, it will blank / no message on front panel, LCD doesn't work.
1-4. LCD System power VCC_5V
1-4-1. Solution
Replace MAIN/ LCD Module.
1-4-2. How to troubleshoot (Countermeasure)
1) Please check CN502 VCC_5V of CN502 pin1.
2) If VCC_5 V is abnormal, replace MAIN board.
3) If VCC_5 V OK, replace LCD module.
1-4-3. Service hint (Any picture / Remark)
VCC_5V
LCD_STB
LCD_RST
LCD_CD
LCD_CLK
LCD_DAT
LCD_BL
L 3 0 1
I C 3 0 1
R 3 0 8
R 5 5 2
R 5 5 9
5 6 1
C 3 9 2
5 4 0
C 3 9 1
R 5 4 1
C 3 8 1
C 3 8 2
C 3 8 3
F B 3 1 4
R R 5 0 3
R5F1 220 (M)
FB510
PZ1608U221-1R4TF
R5F2 220 (M)
C5F2
C5F1
C5F3
10uF
100nF
10nF
/10V(M)
DGND
R5F3
R5F4
R5F5
R5F6
R5F7
2 OUT
IN 3
Q502 1 COMMON
DGND
F B 5 1 0
C 5 F 1
C 5 F 2
R 5 F 1 C 3 9 5
C 3 3 0
R 5 F 2
CN502 CN502
R 3 7 1 C 3 9 3
CN502
C 3 9 4
I C 3 1 3
C 4 3 8 C 4 3 9
C 3 3 1
R 4 0 9
C 3 3 3
F B 3 1 6
R 4 0 8
C 3 3 4
C 4 4 0 I C 4 0 2
C 4 3 2
L 4 0 7
< MAIN board top view >
Front_LCD
LED+
LED-
NC
0 LCD_STB
NC
0 LCD_RST
NC
0 LCD_CD
NC
0 LCD_CLK
NC
0 LCD_DAT
3.3VA
DGND
VB0-
VB1-
C5F4 C5F6
2.2uF 2.2uF
VB1+
VB0+
C5F5
0.33uF
VLCD
R5F8
10M
L 3 0 0
F B 3 0 4
R 3 2 7 R 3 1 2
R 3 0 3
R 3 1 0
C 5 4 7
F M
T P _ G N D
F B 4 0 4
F B 4 0 3
C N 4 0 2
Copyright © 2019 LG Electronics Inc. All rights reserved.
3-8
14 LED+(A)
13 LED-(K)
12 CSB
11 RSTB
10 CD
9 SCK
8 SDA
7 VDD
6 VSS
5 VB0-
4 VB1-
3 VB1+
2 VBO+
VLCD
1
CN502
R C F 5 0 0
C 5 4 9
Z D 5 0 4
Q 3 0 0
C 5 A 1
C 5 A 2
I C 3 0 9
L 3 0 2
R 5 2 8
C 3 1 3
C 5 4 8
C 3 1 2
C 3 2 3
C 3 0 7
C 3 0 0
C 3 2 0
2
Only for training and service purposes.
Q 3 0 1
F B
C 3 7 9
F 3 0 1
F 3 0 0