LG SL8YG Service Manual page 34

NO BOOTING WHEN YOU TURN THE UNIT ON, NO MESSAGE OR
"HELLO" ON FRONT PANEL
When you turn on your set, no message on the front panel, and LED doesn't work.
1-3. IC604 System PMIC_4.1 V (No 4.1 V)
1-3-1. Solution
Replace MAIN / FRINT AMP board.
1-3-2. How to troubleshoot (Countermeasure)
1) Please check 3.3 VA of IC312 pin2.
2) If PMIC_4.1 V is abnormal, replace MAIN board.
3) If PMCI_4.1 V is OK, replace FRONT board.
1-3-3. Service hint (Any picture / Remark)
[12VA to PM_4.1V]
R389
NETWORK_P_CTRL
R395
C309
10pF
R394
100K
R393
13K
(1%)
R399
1.2M NC
DGND
R 3 9 3
R 3 9 4
C 3 0 9
IC312 IC312
I C 3 1 2
R 3 6 0
C 3 0 4
R 3 3 6
C 3 4 4
C 3 9 8
C 3 4 9
B 6
C 3 7 5
C 3 7 6
F B 3 1 5
ONE POINT REPAIR GUIDE
4.7K
51K
IC312
FB
6 VIN
EN
5 SW
4 BST GND
R398 33 1uF
C308
R397 3.3K
R396 51K
(1%)
(1%)
VOUT = 0.798x(54.3K/13K+1)= 4.13V
D 3 0 4
C 3 0 5
I C 5 0 4
C 3 0 6
C 3 0 7
L311 L311
 
F B 3 2 3
C 3 4 8
L 3 1 1
C 3 1 0
C N 1 0 3
C 1 6 8
Q 1 0 2
< MAIN board top view >
1
2
 
DGND
L311
3
10UH
DGND
C307 C306
1uF
10uF
C 5 A 1
C 5 C 3 C 5 A 8 C 5 9 9 C 5 C 1
C L 5 0 1
C 3 4 7
I C 3 1 5
C 3 M 4
R 3 A 4
3-7
Copyright © 2019 LG Electronics Inc. All rights reserved.
12VA
FB317
C303 C310
100nF 100nF
PMIC_4.1V
2018.12.07
R388 del.
D304
C305
C311 C312
NC
10uF
100nF 100nF
DGND
T P 4 1 4
R 4 8 1
R 4 8 4
R 4 8 0
R 4 7 9
R 4 8 3 R 4 7 8
R 3 E 7
R 4 7 7
R 4 8 2 R 4 6 9
T P 4 1 1
F B 3 2 1
F B 4 1 4
C 3 F 3
C 1 5 1
C 2 P 3
C N 2 0 3
Only for training and service purposes.
C327
100nF
C 3 F
I C 4 0 5 T P 4 1 2
C 4 7 1
R 4 6
Q 4 0 1
R 2 5 4
C 2 6 5 C 2 6 2