3-7
Copyright © 2019 LG Electronics Inc. All rights reserved.
Only for training and service purposes.
ONE POINT REPAIR GUIDE
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 / doesn’t work.
1-3. IC301 System 3.3 V (No 3.3 VA)
1-3-1. Solution
Replace MAIN board.
1-3-2. How to troubleshoot (Countermeasure)
1) Please check 3.3 VA of IC301 pin3.
2) If 3.3 VA is abnormal, replace MAIN board.
1-3-3. Service hint (Any picture / Remark)
< MAIN board top view >
R 4 0 8
R 4 0 9
R 5 A 0
R 5 A 1
R 5 A 2
R 5 A 3
R 5 A 4
R5A6
R5A7
OP5
O P 6
OP7
C437
C 4 4 0
L 3 0 1
Z D 5 1 1
L 3 0 8
R R 5 0 3
RR505
RR506
RR507
RR508
RR509
RR510
RR511
RR512
RR513
RR514
RR515
RR516
RR517
FB305
FB306
FB310
F B 3 1 4
9
F B 3 1 5
F B 3 1 6
FB317
R 3 0 8
R 5 0 5
R 5 0 6
R 5 0 7
R 3 1 4
R508
R509
R 3 1 9
RC502
0
3
R 5 1 0
0
4
0
5
R512
0
6
R514
RC509
R 5 1 5
R516
R 5 1 8
R 5 1 9
1
0
CN500
11
1
2
CN50
1
3
1
4
R 5 2 0
1
5
R 5 2 1
1
8
1
9
R 5 2 5
R 5 2 6
R 5 2 9
2
2
2
3
R 5 3 0
R 5 3 1
R 5 3 2
R533
C 3 0 4
R534
C305
R 5 3 5
C309
C502
R 5 4 0
R 5 4 1
R 5 4 2
R 5 4 3
C 5 0 8
R 5 4 4
C 5 0 9
R 5 4 7
R 5 4 8
X 5 0 0
C510
M C L K
R550
C 5 1 5
R551
C322
R 5 5 2
C 5 1 7
R 5 5 3
C 3 2 4
C 5 1 8
R 5 5 4
R
555
C326
R556
C 3 2 7
R557
C329
R 5 5 9
R560
C 3 3 1
501
R 5 6 1
R562
C 3 3 3
R563
C 3 3 4
R564
R565
C335
R566
C337
R568
C339
R569
R 5 7 4
R 5 7 5
R 5 7 6
O C P
R 5 7 8
R 5 7 9
R 5 8 0
C 5 4 4
R 5 8 1
C 5 4 5
R 5 8 2
C 5 4 6
R 5 8 3
C354
R 5 8 4
R 5 8 5
R 5 8 6
W R 5 0 3
WR505
WR506
R 3 9 6
WR507
WR508
WR509
C 5 5 3
C 5 5 5
C556
C557
WR510
C364
WR511
C365
WR512
R596
WR513
C367
R597
WR514
C368
R 5 9 8
WR515
R 5 9 9
WR516
WR517
D 5 0 2
C370
C 5 6 4
C371
C 5 7 0
C 3 8 1
I C 3 0 1
C 3 8 2
C 3 8 3
I C 3 0 3
C 5 7 7
IC306
C 3 8 7
C 3 8 8
I C 5 0 1
IC310
C 3 9 1
WC502
I C 3 1 2
C 3 9 2
I C 3 1 3
WC503
WC504
C 5 8 8
WC505
WC506
C396
C398
WC509
WC510
WC511
WC512
WC513
WC514
WC515
WC518
WC519
WC520
WC522
WC523
R 5 F 2
R 5 F 1
C 5 F 2
C 5 F 1
F B 5 1 0
J K 5 0 1
5.1VA
3.3VA
C322
10uF
/10V
C354
10uF
/10V
DGND
FB305
UBW2012-121F
DGND
IC301
1
EN
2
GND
3
LX
4 IN
5 FB
C309
10uF
/10V
R316
240K
(1%)
R357
100K
(1%)
R309
24K
(1%)
C367
100nF
/16V
C370
100nF
/16V
R356
4.7K
C364
10uF
/10V
R308
0 OHM(1)
NC
C328
47pF
DGND
L301
470nH
VOUT = 0.6x(1+100k/((240k*24k)/(240k+24k)))= 3.35V
[5.1VA TO 3.3VA]
VOUT = 0.6x(1+(R357/(R309//R316)))
IC301
IC301
L301
L301