Service Manuals, User Guides, Schematic Diagrams or docs for : LG LCD 42LB4D 42LB4D_KL-EX-SI_1387179746
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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 plug 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 1M and 5.2M. 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
SERVICING PRECAUTIONS
continued
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.
LCD TV - 2007
Power Supply
Troubleshooting
LCD TV - 2007
Power Supply trouble shooting
42LB4DS Power Supply
Power Supply Connectors
With Test unit measurements
Connector Connector
Stan
P201 Standby Run P202 dby Run
1 ACD 5V 5V 1 19 0V 18.86
2 Von 0V 3.0V 2 19 0V 18.86
3 GND 0V 0V
3 5Vs 5V 5V
4 GND 0V 0V
4 GND 0V 0V
5 6 0V 6.11
5 I-C 0V 3.2V
6 GND 0V 0V
6 ERR 0V 3.2V
7 3.4 0V 3.46
7 BRI 0.22V 2.753
8 GND 0V 0V
8 5Vs 5V 5V
9 12 0V 11.99
9 GND 0V 0V
10 GND 0V 0V
10 DIM 0V 3.2V
11 6V 0V 6.11
12 GND 0V 0V
13 3.4V on 0V 2.5V
LCD TV - 2007
Power Supply trouble shooting
Power Supply Ballast Connectors
With Test unit measurements
BALLAST / INVERTER
P204 Label Standby Run Mode
1 VBL - +24.12VDC 0V 23.93V
2 VBL - +24.12VDC 0V 23.93V
BALLAST / INVERTER
3 VBL - +24.12VDC 0V 23.93V
P205 Label Standby RUN mode
4 VBL - +24.12VDC 0V 23.93V
1 VBL - +24.12VDC 0V 23.93V
5 VBL - +24.12VDC 0V 23.93V
2 VBL - +24.12VDC 0V 23.93V
6 GND 0V 0V
3 VBL - +24.12VDC 0V 23.93V
7 GND 0V 0V
4 VBL - +24.12VDC 0V 23.93V
8 GND 0V 0V
5 VBL - +24.12VDC 0V 23.93V
9 GND 0V 0V
6 GND 0V 0V
10 GND 0V 0V
7 GND 0V 0V
11 ADIM - 3.2Vdc 0V 3.27V
8 GND 0V 0V
12 Von/Off - 3.2Vdc 0V 3.23V
9 GND 0V 0V
13 VBR- +2.7Vdc 0V 2.75V
10 GND 0V 0V
11 ADIM - 3.2Vdc 0V 3.27V
12 Von/Off - 3.2Vdc 0V 3.23V
LCD TV - 2007
47LB1DA POWER SUPPLY
Resistances with Board Connected Resistances with Board Disconnected
P202 P201 P200 P202 P201 P200
AC_DET 100.7 KOhm 19V 1.7 KOhm* 3.4V 1 KOhm* AC_DET 19V 2 KOhm* 3.4V 1 KOhm*
PWR_NF 19V 1.7 KOhm* 3.4V 1 KOhm* PWR_NF 19V 2 KOhm* 3.4V 1 KOhm*
STB 7 MOhm* GND 0 GND 0 STB 8 MOhm* GND 0 GND 0
GND 0 GND 0 GND 0 GND 0 GND 0 GND 0
INV_CTRL 93.4 KOhm 8V 1 KOhm* 6V 1 KOhm* INV_CTRL 8V 1.3 KOhm* 6V 1 KOhm*
ERR_OUT GND 0 6V 1 KOhm* ERR_OUT GND 0 6V 1 KOhm*
BT_CNTRL 99.7 KOhm 3.4V 1 KOhm* GND 0 BT_CNTRL 3.4V 1 KOhm* GND 0
5V_STB 4 MOhm* GND 0 GND 0 5V_STB 5.5 MOhm* GND 0 GND 0
GND 0 12V .7 KOhm* 12V 1 KOhm* GND 0 12V .7 KOhm* 12V 1 KOhm*
PWR_DN 5.5 KOhm GND 0 12V 1 KOhm* PWR_DN GND 0 12V 1 KOhm*
6V 1.3 KOhm* GND 0 6V 1.3 KOhm* GND 0
GND 0 GND 0 GND 0 GND 0
3.4V_ON 10.9 KOhm 3.4V_ON 10.9 KOhm
INV. CNTRL 93.4 KOhm INV. CTRL
BRT CNTRL 1 KOhm BRT CTRL
GND 0 GND 0
GND 0 GND 0
GND 0 GND 0
GND 0 GND 0
GND 0 GND 0
24V 1.2 KOhm* 24V 1 KOhm*
24V 1.2 KOhm* 24V 1 KOhm*
24V 1.2 KOhm* 24V 1 KOhm*
24V 1.2 KOhm* 24V 1 KOhm*
24V 1.2 KOhm* 24V 1 KOhm*
LCD TV - 2007
Power Supply Voltage Distribution Diagram
+19.0V
+19.0V NTP3000
NTP3000
9.0V
+12.0V
+12.0V KIA78R09
KIA78R09 MC33078
MC33078
KIA78R09
KIA78R09 KIA78R09
KIA78R09
SC1565-2.5
SC1565-2.5
MST3369
MST3369 24C08
24C08
AZ1117H-3.3
AZ1117H-3.3
+5.0V
+6.0V
+6.0V PQ05DZ1U
PQ05DZ1U
PQ05DZ1U
PQ05DZ1U AT/NT Tuner
AT/NT Tuner CS4344
CS4344 CS5340
CS5340 TEA6420
TEA6420 FRC94XYH
FRC94XYH STMAV335
STMAV335
KIA7805
KIA7805 MIC2505
MIC2505
9.0V
Live-on
+5.0VST +5V_L
+5.0VST SI3865
SI3865
AZ1085S-3.3
AZ1085S-3.3 BA033FP-3.3
BA033FP-3.3 MTV416
MTV416
AZ1085S-1.8
AZ1085S-1.8 ICL3232CBNZ
ICL3232CBNZ 24C16
24C16
12.0V
3.3VST_MICOM
SC1592-1.0
SC1592-1.0 FRC
FRC
1.8V 1.2V
SC2595-1.0 SC1565-1.8 X260 ISL6549CB AZ1117H-3.3
AZ1117H-3.3 LGDT3703(MAIN)
LGDT3703(MAIN) MK3727D
MIC2505
MK3727D
MIC2505
SC2595-1.0 SC1565-1.8 X260 ISL6549CB
HY5DU281622
HY5DU281622 SC1565-2.6
SC1565-2.6 MIC3910-2.5
MIC3910-2.5 AZ1086-1.8
AZ1086-1.8
+3.3V_L
+3.3V_L
+3.3V_L
1.8V
Live-on HYB18T512(4EA) MK3727D
ISL6549CB
ISL6549CB HYB18T512(4EA)
HYB18T512(4EA)
HYB18T512(4EA) MK3727D
MK3727D
MK3727D 74LVT16373(2EA)
74LVT16373(2EA) S29GL256
S29GL256 ISP1504
ISP1504
1.8V
Standby Power THC63LVD1023
THC63LVD1023 AZ1117H-1.8
AZ1117H-1.8 NTP3000
NTP3000 CS8416
CS8416 LM75
LM75 24C512
24C512
Run Power
LCD TV - 2007
Power Supply trouble shooting
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