LG 42LB4D Operating instructions

LCD TV - 2007
Troubleshooting
42LB4D
LCD Flat Panel

LCD TV - 2007
General Guidance
An isolation Transformer should always be used during the servicing of a receiver whose chassis is not
isolated from the AC power line. Use a transformer of adequate power rating as this protects the technician
from accidents resulting in personal injury from electrical shocks. It will also protect the receiver and it's
components from being damaged by accidental shorts of the circuitry that may be inadvertently introduced
during the service operation. If any fuse (or Fusible Resistor) in this TV receiver is blown, replace it with the
specified. When replacing a high wattage resistor (Oxide Metal Film Resistor, over 1W), keep the resistor 10
mm away from PCB. Keep wires away from high voltage or high temperature parts.
Before returning the receiver to the customer, always perform an AC leakage current check on the
exposed metallic parts of the cabinet, such as antennas, terminals, etc., to be sure the set is safe to
operate without danger of electrical shock.
Leakage Current Cold Check (Antenna Cold Check) With the instruments AC plu
g
removed from power
source, connect an electrical jumper across the two AC plug prongs. Place the AC switch in the on position,
connect one lead of ohm-meter to the AC plug prongs tied together and touch other ohm-meter lead in turn
to each exposed metallic parts such as antenna terminals, phone jacks, etc. If the exposed metallic part has
a return path to the chassis, the measured resistance should be between 1MΩand 5.2MΩ. When the expose
d metal has no return path to the chassis the reading must be infinite. An other abnormality exists that
must be corrected before the receiver is returned to the customer.

LCD TV - 2007
SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service manual and its supplements and addenda,
read and follow the SAFETY PRECAUTIONS on page in this publication. NOTE: If unforeseen circumstances
create conflict between the following servicing precautions and any of the safety precautions in this
publication, always follow the safety precautions.
Remember: Safety First.
General Servicing Precautions
1. Always unplug the receiver AC power cord from the AC power source before;
a. Removing or reinstalling any component, circuit board module or any other receiver assembly.
b. Disconnecting or reconnecting any receiver electrical plug or other electrical connection.
c. Connecting a test substitute in parallel with an electrolytic capacitor in the receiver.
CAUTION: A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result
in an explosion hazard.
2. Test high voltage only by measuring it with an appropriate high voltage meter or other voltage
measuring device (DVM, FETVOM, etc) equipped with a suitable high voltage probe. Do not test high
voltage by "drawing an arc".
3. Do not spray chemicals on or near this receiver or any of its assemblies.
4. Unless specified otherwise in this service manual, clean electrical contacts only by applying the followin
g mixture to the contacts with a pipe cleaner, cotton-tipped stick or comparable non-abrasive applicator;
10% (by volume) Acetone and 90% (by volume) isopropyl alcohol (90%-99% strength)
CAUTION: This is a flammable mixture.

LCD TV - 2007
Unless specified otherwise in this service manual, lubrication of contacts in not required.
5. Do not defeat any plug/socket B+ voltage interlocks with which receivers covered by this service
manual, might be equipped.
6. Do not apply AC power to this instrument and/or any of its electrical assemblies unless all solid-state
device heat sinks are correctly installed.
7. Always connect the test receiver ground lead to the receiver chassis ground before connecting the test
receiver positive lead.
Always remove the test receiver ground lead last.
8. Use this receiver only with the test fixtures specified in this Training manual.
CAUTION: Do not connect the test fixture ground strap to any heat sink in this receiver.
SERVICING PRECAUTIONS
continued

LCD TV - 2007
Power Supply
Troubleshooting

LCD TV - 2007
2.5V0V3.4V on13
0V0VGND12
6.110V6V11
3.2V0VDIM10
0V0VGND9
5V5V5Vs8
2.7530.22VBRI7
3.2V0VERR6
3.2V0VI-C5
0V0VGND4
5V5V5Vs3
3.0V0VVon2
5V5VACD1
P201 RunStandby
Connector
0V0VGND10
11.990V129
0V0VGND8
3.460V3.47
0V0VGND6
6.110V65
0V0VGND4
0V0VGND3
18.860V192
18.860V191
P202 Run
Stan
dby
Connector
Power Supply Connectors
With Test unit measurements
Power Supply trouble shooting 42LB4DS Power Supply

LCD TV - 2007
3.23V0VVon/Off - 3.2Vdc12
3.27V0VADIM - 3.2Vdc11
0V0VGND10
0V0VGND9
0V0VGND8
0V0VGND7
0V0VGND6
23.93V0VVBL - +24.12VDC5
23.93V0VVBL - +24.12VDC4
23.93V0VVBL - +24.12VDC3
23.93V0VVBL - +24.12VDC2
23.93V0VVBL - +24.12VDC1
RUN modeStandbyLabelP205
BALLAST / INVERTER
2.75V0VVBR- +2.7Vdc13
3.23V0VVon/Off - 3.2Vdc12
3.27V0VADIM - 3.2Vdc11
0V0VGND10
0V0VGND9
0V0VGND8
0V0VGND7
0V0VGND6
23.93V0VVBL - +24.12VDC5
23.93V0VVBL - +24.12VDC4
23.93V0VVBL - +24.12VDC3
23.93V0VVBL - +24.12VDC2
23.93V0VVBL - +24.12VDC1
Run ModeStandbyLabelP204
BALLAST / INVERTER
Power Supply Ballast Connectors
With Test unit measurements
Power Supply trouble shooting

LCD TV - 2007
1 KOhm*24V1.2 KOhm*24V
1 KOhm*24V1.2 KOhm*24V
1 KOhm*24V1.2 KOhm*24V
1 KOhm*24V1.2 KOhm*24V
1 KOhm*24V1.2 KOhm*24V
0GND0GND
0GND0GND
0GND0GND
0GND0GND
0GND0GND
∞
BRT CTRL
1 KOhmBRT CNTRL
∞
INV. CTRL
93.4 KOhmINV. CNTRL
10.9 KOhm3.4V_ON10.9 KOhm3.4V_ON
0GND
0GND0GND0GND
0GND
1.3 KOhm*6V0GND1.3 KOhm*6V
1 KOhm*12V
0GND
∞
PWR_DN
1 KOhm*12V0GND5.5 KOhmPWR_DN
1 KOhm*12V
.7 KOhm*12V0GND1 KOhm*12V.7 KOhm*12V0GND
0GND
0GND5.5 MOhm*5V_STB0GND0GND4 MOhm*5V_STB
0GND
1 KOhm*3.4V
∞
BT_CNTRL
0GND1 KOhm*3.4V99.7 KOhmBT_CNTRL
1 KOhm*6V
0GND
∞
ERR_OUT
1 KOhm*6V0GND
∞
ERR_OUT
1 KOhm*6V1.3 KOhm*8V
∞
INV_CTRL
1 KOhm*6V1 KOhm*8V93.4 KOhmINV_CTRL
0GND
0GND0GND0GND0GND0GND
0GND
0GND8 MOhm*STB0GND0GND7 MOhm*STB
1 KOhm*3.4V
2 KOhm*19V
∞
PWR_NF
1 KOhm*3.4V1.7 KOhm*19V
∞
PWR_NF
1 KOhm*3.4V2 KOhm*19V
∞
AC_DET
1 KOhm*3.4V1.7 KOhm*19V100.7 KOhmAC_DET
P200
P201P202P200P201P202
Resistances with Board Disconnected
Resistances with Board Connected
47LB1DA POWER SUPPLY

LCD TV - 2007
+12.0V
+12.0V
+6.0V
+6.0V
CS4344
CS4344 CS5340 CS5340
PQ05DZ1U
PQ05DZ1U
KIA78R09
KIA78R09 KIA78R09
KIA78R09
MC33078
MC33078
X260
X260
HYB18T512(4EA)
HYB18T512(4EA)
AZ1117H-1.8
AZ1117H-1.8 LM75 LM75
ICL3232CBNZ
ICL3232CBNZ
+5.0VST
+5.0VST
+3.3V_L
+3.3V_L
AT/NT Tuner
AT/NT Tuner
+5V_L
+5.0V
SI3865
SI3865
PQ05DZ1U
PQ05DZ1U
Standby Power
Run Power
Live-on
AZ1117H-3.3
AZ1117H-3.3 LGDT3703(MAIN) LGDT3703(MAIN)
SC1565-1.8
SC1565-1.8 ISL6549CB
ISL6549CB
1.2V
1.8V
ISL6549CB
ISL6549CB 1.8V MK3727D
MK3727D 74LVT16373(2EA)
74LVT16373(2EA) S29GL256
S29GL256
THC63LVD1023
THC63LVD1023
+3.3V_L
HYB18T512(4EA)
HYB18T512(4EA) MK3727D MK3727D
+19.0V
+19.0V NTP3000
NTP3000
NTP3000
NTP3000
1.8V
BA033FP-3.3
BA033FP-3.3 MTV416 MTV416
AZ1086-1.8
AZ1086-1.8
AZ1117H-3.3
AZ1117H-3.3
SC1565-2.5
SC1565-2.5 MST3369
MST3369
9.0V
TEA6420
TEA6420
9.0V
CS8416
CS8416
KIA78R09
KIA78R09
MK3727D
MK3727D
MIC2505
MIC2505
3.3VST_MICOM
24C08
24C08
FRC94XYH
FRC94XYH
Live-on
24C512
24C512
STMAV335
STMAV335
ISP1504
ISP1504
MIC2505
MIC2505
KIA7805
KIA7805
AZ1085S-3.3
AZ1085S-3.3
AZ1085S-1.8
AZ1085S-1.8 24C16 24C16
FRC
FRC
SC1565-2.6
SC1565-2.6 MIC3910-2.5 MIC3910-2.5
SC1592-1.0
SC1592-1.0
12.0V
HY5DU281622
HY5DU281622
SC2595-1.0
SC2595-1.0
Power Supply Voltage Distribution Diagram

LCD TV - 2007
ATI
(X260)
I2C Master
AT/NT Tuner
0xC2
HDMI
ADC
(MST3361)
0X9C
Temp.
Sensor
(LM75)
0X94
U-Com
(MTV416)
0x50
I2C_CH1 (+3.3V_L & +5V_L)
I2C_CH2 (+3.3V_L & +5V_L)
I2C_CH3 (+3.3V_L)
Port
Expander
(M62320)
0X74
Audio
Switch
(MSP4450K)
0X80
DASP
(NTP3000)
0X54
PDP Module
0x1C
VSB/QAM
(LGDT3703)
Main
0X1C
Live Dead
CS8416A
0X20(W)
0X21(R)
EEPROM
(24LC512)
0xA6
CH1
CH2
CH3
FRC94XYH
0xD4
EEPROM
(24LC16)
5V
5V 5V
2.5V
I²C Bus Controller Block Diagram
Stand-By Power Operation
Power Supply trouble shooting

LCD TV - 2007
Check X500 (18.43MHz)
Normal?
Re-download
MTV416GMF (IC309 )
Normal?
YES
NO
Replace MTV416GMF (IC309 )
and Re-download
Check SI3865( MAIN PCB)
(Q702) pin 2,3
5V Normal?
Replace Power board
Check P702 (MAIN PCB)
are all input
voltages Normal ?
YES
Check SI3865
(Q702) Pin #5 2.5V
Normal?
NO
NO Check P702 wafers
& Connectors
Normal ?
YES
Check P701(MAIN PCB)
Pin#3,8
5V Normal ?
YES
Replace power board
NO
Replace SI3865(Q702)
YES
NO
NO
YES
Power Supply trouble shooting

LCD TV - 2007
47LB4DS
Video Trouble Shooting Guide
47LB4DS
47LB4DS
Video Trouble Shooting Guide
Video Trouble Shooting Guide

LCD TV - 2007
ATI
X260
M_SIF
NTP3000
I2S
SPDIF
I2S
CVBS(NT Main)
DDR2
64MBx2
Flex Bus
RGB 30bit
TP
A
Analog
Front
End USB 1.1
I2C Port0 I2C CH1
I2C CH2
I2C CH3
USB (upgrade ready!!)
Inactive IC when in
Standby Mode
Video
Scaler
0
Video
Scaler
1 or 2
Active IC when in
Standby mode Audio
Video
TP
AV2 / L/R
MNT Out L/R
COMP1 L/R
COMP2 L/R
RGB L/R
TP_IN1
AV1
AV2
AV1, Y/C1
AV2, Y/C2
Flash
(NOR 32MB)
Latchx2
24C512
Cable
VSB
LGDT3303
63LVD1023
1080P
LVDS
Con.
Dual
AV1 / L/R GPIO
I2S
ATI
X260
MPEG decoder
COMP2
RGB
CS8416
HDMI SPDIF
I2S
I2S
MST3361
1HDMI +
1ADC
RGB
HDMI1/2/3
SPDIF SPDIF
Opt.
FRC94xyH
DDR1
16MB
RGB odd
RGB even
120Hz
TPB
USB 1.1 USB(EMF)
PCI
3:1
Demux
Air
MTV415
Micom 24C16
3:1
Demux
MSP4450K
I2S
AT/NT
SIF
Stand-By Mode IC Operation Block Diagram
Video Trouble Shooting
Video Trouble Shooting

LCD TV - 2007
Check L729(2.5V) Check
Power connector Replace Power board
Check THC63LVD1023
(IC601)#9(DE),
#15(Clk),
#7(Hsync),#8(Vsync)
Check X260 (IC101)
Check P600
#47(DISP_EN),
#33(TXAC-) ,
#32(TXAC+) ,
#17(TXBC-) ,
#16(TXBC+)
Check THC63LVD1023
(IC601)
Check LVDS Cable
Check PDP/LCD
Module
Control board
1
2
3
4
5
Y
NY
Y
Y
Y
N
N
LVDS Transmitter
#47(DISP_E
N):
3.3V
GND
#33 (TXAC-) :
#32 (TXAC+) :
#17 (TXBC-) :
#16 (TXBC+) :
74.25MHz
74.25MHz
74.25MHz
74.25MHz
#(Clk) : 74.25MHz
NO VIDEO / OSD
Video Trouble Shooting
Video Trouble Shooting

LCD TV - 2007
Video Data to LCD Panel.
Test points From LCD
control board
Video Data to LCD Panel.
Test points From LCD
control board
Video Trouble Shooting
Video Trouble Shooting LCD Control Board
LCD Control Board

LCD TV - 2007
Check: Video data from LVDS Transmitter (IC601). The diagram shown, points out
the test points for the Video Data transmitted to the LCD Control PCB. Points highlighted
are above the LVDS cable connection
Video Trouble Shooting
Video Trouble Shooting LCD Control Board
LCD Control Board

LCD TV - 2007
EXT
1/2
X260
TP A
Comp1/2
RGB
CVBS
TP C
TP B / 656
AT/NT/
TUNER LGDT
3303
VSB1/QAM TP
MST
3361 HS,VS
DVI
HS,VS
YCbCr2 YCbCr or RGB
FRC9445H
RGB
CVBS
YCbCr1
DVO
Y/C1, Y/C2
Y/C1, Y/C2
AV1/2
AV1/2
HDMI
1/2/3 TMDS341A
Check Antenna Cable
Check Tuner
5V, Video out
Check X260 inputs
M_TU_CVBS(C2117)
Check CVBS Video Path
NO RF VIDEO (ATSC)
Video Trouble Shooting
Video Trouble Shooting

LCD TV - 2007
EXT
1/2
X260
TP A
Comp1/2
RGB
CVBS
TP C
TP B / 656
AT/NT/
TUNER LGDT
3303
VSB1/QAM TP
MST
3361 HS,VS
DVI
HS,VS
YCbCr2 YCbCr or RGB
FRC9445H
RGB
CVBS
YCbCr1
DVO
Y/C1, Y/C2
Y/C1, Y/C2
AV1/2
AV1/2
HDMI
1/2/3 TMDS341A
Check Antenna Cable
Check Tuner
5V, Video out
Check X260 inputs
M_TU_CVBS(C2117)
Check CVBS Video Path
NO RF VIDEO (NTSC)
Video Trouble Shooting
Video Trouble Shooting

LCD TV - 2007
Check Antenna Cable
Check Tuner(TU600), 5V,
IF out
Check LGDT3303(IC604)
inputs power pins,
Osc(25Mhz), IF pin
Check LGDT3303 Outputs
Check X260 INPUT CLK,
SOP, Valid, Error, Data
1: Check Antenna cable (RF switch, Tuners....)
2: Check Tuners Vcc and IF out
Appears to be noise
3: Check X260 Input (CLK, SOP, Valid, Error, Data)
TPCLK
TPSOP
TPVALI
D
nTPERR
TPDATA[7:0
]
NO RF VIDEO
Video Trouble Shooting
Video Trouble Shooting

LCD TV - 2007
EXT
1/2
X260
TP A
Comp1/2
RGB
CVBS
TP C
TP B / 656
AT/NT/
TUNER LGDT
3303
VSB1/QAM TP
MST
3361 HS,VS
DVI
HS,VS
YCbCr2 YCbCr or RGB
FRC9445H
RGB
CVBS
YCbCr1
DVO
Y/C1, Y/C2 Y/C1, Y/C2
AV1/2
AV1/2
HDMI
1/2/3 TMDS341A
Video Trouble Shooting
Video Trouble Shooting