LG LAS350B User manual

SERVICE MANUAL
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.
Internal Use Only
Website http://biz.lgservice.com
FEBRUARY, 2015
MODEL: LAS350B (LAS350B, S35A1-W)
MODEL: LAS350B
(LAS350B, S35A1-W)
2.1 ch Sound Bar
P/NO : AFN77152011

1-1
CONTENTS
SECTION 1 ........ GENERAL
SECTION 2 ........ CABINET & MAIN CHASSIS
SECTION 3 ........ ELECTRICAL
SECTION 4 ........ REPLACEMENT PARTS LIST

1-2
SECTION 1
GENERAL
CONTENTS
ESD PRECAUTIONS......................................................................................................................................... 1-3
HIDDEN KEY MODE ......................................................................................................................................... 1-4
SERVICE INFORMATION FOR EEPROM........................................................................................................ 1-4
MCS / EQ HIDDEN KEY GUIDE ....................................................................................................................... 1-5
MCS / EQ PROGRAM UPDATE GUIDE........................................................................................................... 1-5
SPECIFICATIONS ............................................................................................................................................. 1-6

1-3
ESD PRECAUTIONS
Electrostatically Sensitive Devices (ESD)
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components
commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated
circuits and some field-effect transistors and semiconductor chip components. The following techniques should
be used to help reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off
any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a
commercially available discharging wrist strap device, which should be removed for potential shock reasons
prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ESD devices, place the assembly on a conductive surface
such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ESD devices.
4. Use only an anti-static solder removal device. Some solder removal devices not classified as "anti-static" can
generate electrical charges sufficient to damage ESD devices.
5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ESD
devices.
6. Do not remove a replacement ESD device from its protective package until immediately before you are
ready to install it. (Most replacement ESD devices are packaged with leads electrically shorted together by
conductive foam, aluminum foil or comparable conductive materials).
7. Immediately before removing the protective material from the leads of a replacement ESD device, touch the
protective material to the chassis or circuit assembly into which the device will by installed.
CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL OTHER
SAFETY PRECAUTIONS.
8. Minimize bodily motions when handing unpackaged replacement ESD devices. (Otherwise harmless motion
such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate
static electricity sufficient to damage an ESD device).
CAUTION. GRAPHIC SYMBOLS
THE LIGHTNING FLASH WITH APROWHEAD SYMBOL. WITHIN AN EQUILATERAL TRIANGLE, IS
INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF UNINSULATED
“DANGEROUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAGNITUDE TO CONSTITUTE A RISK OF
ELECTRIC SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE
SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE
LITERATURE.

1-4
HIDDEN KEY MODE
HIDDEN MODE KEYS
USB MODE ENTRY/UPDATE Main set ‘-’ (Volume) + Remote control ‘MUTE’
EEPROM EDIT Main set ‘-’ (Volume) + Remote control ‘OPTICAL’
EEPROM CLEAR (Initialize) Main set ‘-’ (Volume) + Remote control ‘Treble/Bass’
VERSION CHECK Main set ‘-’ (Volume) + Remote control ‘LG TV’
up Sound Effect
down NIGHT
right F.Skip (Right)
left B.Skip (Left)
enter AV Sync
OPT Status
VFD " OPT.."
POWER ON
Main set ‘-’ (Volume) + Remote control ‘OPTICAL’
Use arrow key [Sound Effect, NIGHT, F.Skip (Right), B.Skip (Left)] to move to appropriate position and make changes
Remote control ‘AV SYNC’
Display VFD “E2P CLR”
Power off automatically
Power cord unplug
SERVICE INFORMATION FOR EEPROM

1-5
1. Version & Option Check
1) Power on.
2) Press main set “-” (volume -) key and remote control "LG TV" key during 3 seconds.
3) Check MCS version.
Ex) P1412120
4) Press remote control “F.Skip (Right)” 1 time.
Check EQ version.
Ex) Q1412020
5) Press remote control “F.Skip (Right)” 1 time.
Check option.
Ex) 10010000
2. Initialize
1) Power on.
2) Press main set “-” (volume -) key and remote control “Treble/Bass” during 3 seconds.
3) Display VFD “E2P CLR”.
4) Power off automatically.
5) Power cord unplug.
MCS / EQ HIDDEN KEY GUIDE
1. Preparation
- Remote control.
- Do format USB Memory to FAT32 File system.
- USB : Update file exist only in the USB Memory stick.
Ex ) LAS350B :
MCS E:￦LAS350B_FW_201412221.bin (if USB driver is E:￦)
EQ E:￦EQ_PRG_LAS350B_141219_0_4112.bin (if USB driver is E:￦)
2. Update
1) Power on.
2) Change the USB function. [Main set ‘-’ (Volume) + Remote control ‘MUTE’]
3) Insert USB.
4) Display in VFD.
MCS : “MCS UP” “FINISH” Power off.
EQ : “EQ UP” “FINISH” Power off.
5) Loading is shown while updating.
Never remove USB or AC cord.
6) After update finish, show FINISH in VFD and power of automatically.
7) Power cord un-plug.
MCS / EQ PROGRAM UPDATE GUIDE

1-6
SPECIFICATIONS
• GENERAL (LAS350B)
Power requirements 120 V ~ 60 Hz
Power consumption 21 W
Networked standby : 0.5 W
(If all network ports are activated.)
Dimensions (W x H x D) 880 mm x 59 mm x 90 mm (34.6 inch x 2.3 inch x 3.5 inch)
Net Weight (Approx.) 1.9 kg (4.2 lb)
Operating temperature 41 °F to 95 °F (5 °C to 35 °C)
Operating humidity 5 % to 90 %
• INPUT/OUTPUT
OPT. IN 3 V (p-p), Optical jack x 1
PORT. IN 0.5 Vrms (3.5 mm stereo jack) x 1
Available Digital Input Audio
Sampling Frequency 32 kHz, 44.1 kHz, 48 kHz, 96 kHz
• AMPLIFIER
Total 120 W
Front 25 W x 2 (6 Ωat 1 kHz)
Subwoofer 70 W (4 Ωat 100 Hz)
THD 10 %
• SUBWOOFER (S35A1-W)
Type 1 Way 1 Speaker
Impedance 4 Ω
Rated Input Power 70 W
Max. Input Power 140 W
Dimensions (W x H x D) 156 mm x 300 mm x 288 mm (6.1 inch x 11.8 inch x 11.3 inch)
Net Weight (Approx.) 2.9 kg (6.4 lb)
• BLUETOOTH
Codec SBC
•Designs and specifications are subject to change without prior notice.

2-1
SECTION 2
CABINET & MAIN CHASSIS
CONTENTS
EXPLODED VIEWS ........................................................................................................................................... 2-3
1. MAIN SET SECTION ................................................................................................................................ 2-3
2. SUBWOOFER SECTION.......................................................................................................................... 2-5
3. PACKING ACCESSORY SECTION ......................................................................................................... 2-7

2-2

D
C
503
251
A42
262
B/T
KEY
CABLE5
CABLE6
CABLE7
CABLE3
CABLE8
CABLE7
CABLE6
506
257
A53
258
A54
258
504
257
506
A45
504
503
503
263
506
266
504
504
505
259
A52
264
504
K
300
USB
DISPLAY
MAIN
SMPS
B
I
G
H
A
B
E
F
H
C
DFG
E
J
J
A
K
I
CABLE2
CABLE1
CABLE4
A47
505
504
A43
A46
505
505
A48
A55
265
256
256
EXPLODED VIEWS
1. MAIN SET SECTION
NOTES) THE EXCLAMATION POINT WITHIN AN
EQUILATERAL TRIANGLE IS INTENDED
TO ALERT THE SERVICE PERSONNEL
TO THE PRESENCE OF IMPORTANT
SAFETY INFORMATION IN SERVICE
LITERATURE.

A900
2. SUBWOOFER SECTION

801 Owner’s manual 835 Wall bracket
806 Optical cable 836 Screws
808 Batteries 837 Cover foot
900 Remote control 826 Filter, Ferrite Core
803 Packing, Main
802 Box
804 Bag
3. PACKING ACCESSORY SECTION

2-8

3-1
SECTION 3
ELECTRICAL
CONTENTS
ONE POINT REPAIR GUIDE ............................................................................................................................ 3-2
1. NO POWER PROBLEM (PVDD) ............................................................................................................ 3-2
2. POWER ON ERROR .............................................................................................................................. 3-3
3. NO SOUND (PORTABLE FUNCTION) .................................................................................................. 3-4
4. NO BLUETOOTH.................................................................................................................................... 3-5
5. NO SOUND (OPTICAL).......................................................................................................................... 3-6
ELECTRICAL TROUBLESHOOTING GUIDE................................................................................................... 3-7
1. POWER SUPPLY CIRCUIT.................................................................................................................... 3-7
2. FRONT CIRCUIT .................................................................................................................................... 3-8
3. TEST & DEBUG FLOW ........................................................................................................................ 3-10
4. AMP PROTECTION.............................................................................................................................. 3-13
WAVEFORMS OF MAJOR CHECK POINT.................................................................................................... 3-14
1. CRYSTAL.............................................................................................................................................. 3-14
2. FLASH MEMORY ................................................................................................................................. 3-15
3. TACT KEY............................................................................................................................................. 3-16
4. USB....................................................................................................................................................... 3-17
5. REMOTE CONTROL ............................................................................................................................ 3-18
6. OPTICAL............................................................................................................................................... 3-19
7. PORTABLE ........................................................................................................................................... 3-20
8. AUDIO PWM ......................................................................................................................................... 3-21
9. AUDIO AMP .......................................................................................................................................... 3-23
WIRING DIAGRAM.......................................................................................................................................... 3-25
BLOCK DIAGRAM .......................................................................................................................................... 3-27
CIRCUIT DIAGRAMS ...................................................................................................................................... 3-29
1. SMPS CIRCUIT DIAGRAM .................................................................................................................. 3-29
2. MAIN - DSP CIRCUIT DIAGRAM......................................................................................................... 3-31
3. MAIN - POWER CIRCUIT DIAGRAM................................................................................................... 3-33
4. MAIN - PWM & AMP CIRCUIT DIAGRAM ........................................................................................... 3-35
5. DISPLAY/ KEY/ USB CIRCUIT DIAGRAM........................................................................................... 3-37
CIRCUIT VOLTAGE CHART........................................................................................................................... 3-39
PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-41
1. SMPS P. C. BOARD DIAGRAM ........................................................................................................... 3-41
2. MAIN P. C. BOARD DIAGRAM ............................................................................................................ 3-43
3. DISPLAY P. C. BOARD DIAGRAM ...................................................................................................... 3-45
4. KEY P. C. BOARD DIAGRAM .............................................................................................................. 3-45
5. USB P. C. BOARD DIAGRAM.............................................................................................................. 3-45

3-2
ONE POINT REPAIR GUIDE
1. NO POWER PROBLEM (PVDD)
No power problem occurs when you power on the unit
1-1. Solution
Replace SMPS board.
1-2. How to troubleshoot (Countermeasure)
1) Check the PVDD voltage 32 V at pin1, 2.
When you check the no power at this point, then replace SMPS board.
1-3. Service hint (Any picture / Remark)
< MAIN board top view >
R463
1K
CON402 pin1, 2
CON402 pin1, 2

3-3
ONE POINT REPAIR GUIDE
2. POWER ON ERROR
No display or Not working.
2-1. IC402
1) Check 3.3 VA at L405.
2) If 3.3 VA is not checked at the point, then find 32 V at pin1 of IC402.
3) 1), 2) is NG. Replace IC402.
2-2. IC404
1) Check 12 VA at L427.
2) If 12 VA is not checked at the point, then find 32 V at pin1 of IC404.
3) 1), 2) is NG. Replace IC404.
2-3. IC406
1) Check 5 VA at EC405.
2) If 5 VA is not checked at the point, then find 12 V at pin E of IC406.
3) 1), 2) is NG. Replace IC406.
< MAIN board top view >
< MAIN board top view >
< MAIN board top view >
L405
L405
L427
L427
EC405
EC405
IC402 pin1
IC402 pin1
IC404 pin1
IC404 pin1
IC406 pin E
IC406 pin E

3-4
ONE POINT REPAIR GUIDE
3. NO SOUND (PORTABLE FUNCTION)
3-1. Solution
Replace IC400 or portable jack (JK504).
3-2. How to troubleshoot (Countermeasure)
1) Please check the soldering status of JK504
2) Please check L501, L502 (PORT_L, PORT_R signal) of portable jack (JK504).
If you cannot find input signal, replace JK504.
3) If you can find input signal, check pin13, 14 of IC400.
4) If you can’t find signal at pin13, 14 of IC400, replace IC400.
3-3. Service hint (Any picture / Remark)
< USB board bottom view >
< MAIN board top view >
JK504
JK504
L501
L501
L502
L502
IC400
IC400

3-5
ONE POINT REPAIR GUIDE
4. NO BLUETOOTH
4-1. Solution
Replace IC101 on MAIN board.(No 3.3 V)
4-2. How to troubleshoot (Countermeasure)
1) Please check externally status of Bluetooth cable connection on your eyes.(at CON102 and Bluetooth module)
2) Please check 3.3 V of 3.3VA (at C174).
If 3.3 V is OK at L509, please check BT_SDA, BT_SCL, BT_RST (pin53, 51, 25) of IC101
and BT_RX, BT_TX (pin29, 27).
If you have no signal, please replace IC101.
4-3. Service hint (Any picture / Remark)
< MAIN board top view >
IC101
IC101
C174
C174
CON102
CON102

3-6
ONE POINT REPAIR GUIDE
5. NO SOUND (OPTICAL)
5-1. Solution
Replace IC401 on MAIN board.
5-2. How to troubleshoot (Countermeasure)
1) Please check 3.3 V of 3.3 VA at L505 in USB board
If you can check 3.3 V, please confirm OPT_DET signal (R428) in MAIN board when optical mode.
2) In spite of process 1), set has abnormal output, then replace IC401.
5-3. Service hint (Any picture / Remark)
< USB board bottom view >
< MAIN board top view >
P_R
P_L
P_DET
P_GND
SPDIF
GND
5V
D+
D-
GND
1OUT
2GND
3VCC
JK502
L505 600RH
C506
100NF
L504 600RH
L503 600RH
L502 600RH
L501 600RH
L506 0R
L507 0R
L508
600RH
C501
100PF
C502
100PF
C503
100PF
C505
10PF
R
L
123
4
5
6
7
8
9
JK504
1
2
3
4
5
6
7
8
9
10
CON502
R503
0R
R504
0R
R317
0R
R316 NC
1 2
3
D503
KDS226 C316
10NF
R318
100R
C317
100PF
C504
100R
L505
L505
R428
R428
IC401
IC401

3-7
ELECTRICAL TROUBLESHOOTING GUIDE
1. POWER SUPPLY CIRCUIT
INSERT POWER CORD.
Check power supply circuit.
Check circuit.
Check audio circuit.
OK
Power on.
Standby LED is normal?
Is power on?
Does it output audio?
NO
NO
NO
YES
YES
YES
YES