3-5
Copyright © 2019 LG Electronics Inc. All rights reserved.
Only for training and service purposes.
ONE POINT REPAIR GUIDE
1. 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 stand-by LED doesn’t work.
1-1. IC302 System 12 VA (No 12 VA)
1-1-1. Solution
Replace MAIN board.
1-1-2. How to troubleshoot (Countermeasure)
1) Please check 25 VA of IC302 pin2 (VIN).
2) If 25 VA is abnormal, please check adapter.
3) If 25 VA is OK, but 12 VA is abnormal pin3 of IC302 (VOUT), replace MAIN board.
1-1-3. Service hint (Any picture / Remark)
< MAIN board top view >
2
R405
R407
R 4 0 8
R 4 0 9
R3A3
R3A4
R3A5
R3A6
C N 4 0 2
R5A5
X401
C 5 A 1
C 5 A 2
F 3 0 0
F 3 0 1
C431
C 4 3 2
C433
C434
C435
C436
C437
C 4 3 8 C 4 3 9
C 4 4 0
C446
Q 3 0 0
Q 3 0 1
Z D 5 0 4
L 3 0 0
L 3 0 1
L 3 0 2
F M
R R 5 0 3
RR505
RR506
RR507
RR508
RR509
RR510
RR511
RR512
RR513
RR514
RR515
RR516
RR517
FB303
F B 3 0 4
FB305
F B
R 3 0 3
R C F 5 0 0
F B 3 1 4
F B 3 1 6
JK502
FB318
R 3 0 8
R 3 1 0
R 3 1 2
R315
RC502
0
3
0
4
0
5
0
6
RC509
R 3 2 7
1
0
CN500
11
1
2
CN502
1
3
1
4
1
5
1
8
1
9
R 5 2 8
R338
R339
2
2
2
3
C 3 0 0
R4C3
C 3 0 7
C308
C309
C310
5 4 0
C311
R 5 4 1
C 3 1 2
C 3 1 3
C314
C315
C316
C317
C318
C319
R549
C4A4
C 3 2 0
C4A5
C321
C4A6
C322
R 5 5 2
C 3 2 3
R365
R 5 5 9
R366
R368
C 3 3 0
C 3 3 1
5 6 1
C 3 3 3
R370
C 3 3 4
R 3 7 1
R375
R380
R381
C
T P _ G N D
C 5 4 7
C354
C 5 4 8
C 5 4 9
C355
C356
WR505
WR506
WR507
WR508
WR509
D301
WR510
C364
WR511
WR512
WR513
C367
C370
C 3 7 9
L406
L 4 0 7
IC300
C 3 8 1
I C 3 0 1
C 3 8 2
IC302
C 3 8 3
I C 3 0 9
C390
IC310
IC311
C 3 9 1
WC502
C 3 9 2
C 3 9 3
I C 3 1 3
WC503
C 3 9 4
WC504
C 3 9 5
WC505
WC506
WC509
WC513
WC514
WC515
WC519
WC520
WC522
WC523
R4N4
FB401
R4N5
FB402
F B 4 0 3
F B 4 0 4
R4N8
R 5 F 2
R 5 F 1
C 5 F 2
C 5 F 1
F B 5 1 0
I C 4 0 2
C306
100nF
DGND
C312
10uF
/35V
R328
100K
R335
100K
R300
51K (1%)
DGND
PVDD
C307
100nF
/50V
C351
33pF
PWR_GD
C300
10uF
/35V
12VA
R305
3.3K (1%)
C323
10uF
/35V
NC
DGND
R301
47K (1%)
FB303
UBW2012-121F
R306
22
C320
10uF
/35V
C302
100nF
C313
10uF
/35V
IC302
1
PG
2
IN
3
SW
4
GND
5
BST
6
EN/SYNC
7
VCC
8
FB
L302
10UH
DGND
R307
390K
R340
56K
[25VA TO 12VA]
VOUT = 0.792x(47K/3.3K+1)= 12.072V
IC302
IC302
L302
L302