LG SPH4B-W Service Manual

3-7
Copyright © 2021 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 >
R408
R409
R5A0
R5A1
R5A2
R5A3
R5A4
R5A6R5A7
OP5
OP6
OP7
C437
C440
L301
ZD511
L308
RR503
RR505 RR506 RR507 RR508 RR509
RR510
RR511
RR512 RR513 RR514 RR515 RR516 RR517
FB305
FB306
FB310
FB314
9
FB315
FB316
FB317
R308
R505
R506
R507
R314
R508 R509
R319
RC502
0
3
R510
0
4
0
5
R512
0
6
R514
RC509
R515
R516
R518
R519
1
0
CN500
11
1
2
CN5
0
1
3
1
4
R520
1
5
R521
1
8
1
9
R525
R526
R529
2
2
2
3
R530
R531
R532
R533
C304
R534
C305
R535
C309
C502
R540
R541
R542
R543
C508
R544
C509
R547
R548
X500
C510
MCLK
R550
C515
R551
C322
R552
C517
R553
C324
C518
R554
R
555
C326
R556
C327
R557
C329
R559
R560
C331
501
R561
R562
C333
R563
C334
R564 R565
C335
R566
C337
R568
C339
R569
R574
R575
R576
OCP
R578
R579
R580
C544
R581
C545
R582
C546
R583
C354
R584
R585
R586
WR503
WR505 WR506
R396
WR507 WR508 WR509
C553
C555
C556 C557
WR510
C364
WR511
C365
WR512
R596
WR513
C367
R597
WR514
C368
R598
WR515
R599
WR516 WR517
D502
C370
C564
C371
C570
C381
IC301
C382
C383
IC303
C577
IC306
C387
C388
IC501
IC310
C391
WC502
IC312
C392
IC313
WC503 WC504
C588
WC505 WC506
C396
C398
WC509
WC510
WC511
WC512 WC513 WC514 WC515 WC518 WC519
WC520 WC522 WC523
R5F2
R5F1
C5F2
C5F1
FB510
JK501
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

LG SPH4B-W Specifications

General

Brand	LG
Model	SPH4B-W
Category	Speaker System
Language	English