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No.51932
3
AV-15LCG
AV-15LCH
AV-15LCS
SAFETY PRECAUTIONS
Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by
in
the Schematic Diagram and Replacement Parts List.
It is essential that these special safety parts should be replaced with the same components as recommended in this manual to
prevent X-RADIATION, Shock, Fire, or other Hazards.
Do not modify the original design without permission of manufacturer.
General Guidance
An lsolation 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 circuitary 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 10mm away from PCB.
Keep wires away from high voltage or high temperature parts.
Due to high vacuum and large surface area of picture tube,
extreme care should be used in handling the Picture Tube.
Do not lift the Picture tube by it's Neck.
X-RAY Radiation
Warning:
To determine the presence of high voltage, use an accurate
high impedance HV meter.
Adjust brightness, color, contrast controls to minimum.
Measure the high voltage.
The meter reading should indicate
23.5
±1.5KV: 14-19 inch, 26±1.5KV: 19-21 inch,
29.0
±1.5KV: 25-29 inch, 30.0±1.5KV: 32 inch
If the meter indication is out of tolerance, immediate service
and correction is required to prevent the possibility of
premature component failure.
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 damage of
electrical shock.
Leakage Current Cold Check(Antenna Cold Check)
With the instrument AC plug removed from AC source,
connect an electrical jumper across the two AC plug prongs.
Place the AC switch in the on positioin, 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 exposed 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.
Leakage Current Hot Check (See below Figure)
Plug the AC cord directly into the AC outlet.
Do not use a line Isolation Transformer during this check.
Connect 1.5K/10watt resistor in parallel with a 0.15uF capacitor
between a known good earth ground (Water Pipe, Conduit, etc.)
and the exposed metallic parts.
Measure the AC voltage across the resistor using AC
voltmeter with 1000 ohms/volt or more sensitivity.
Reverse plug the AC cord into the AC outlet and repeat AC
voltage measurements for each esposed metallic part. Any
voltage measured must not exceed 0.75 volt RMS which is
corresponds to 0.5mA.
In case any measurement is out of the limits sepcified, there is
possibility of shock hazard and the set must be checked and
repaired before it is returned to the customer.
Leakage Current Hot Check circuit
The source of X-RAY RADIATION in this TV receiver is the
High Voltage Section and the Picture Tube.
For continued X-RAY RADIATION protection, the
replacement tube must be the same type tube as specified in
the Replacement Parts List.
1.5 Kohm/10W
To Instrument's
exposed
METALLIC PARTS
Good Earth Ground
such as WATER PIPE,
CONDUIT etc.
AC Volt-meter
IMPORTANT SAFETY NOTICE
0.15uF
AV-15LCG
AV-15LCH
AV-15LCS
No.51932
4
WARNING FOR THE SAFETY-RELATED COMPONENT.
· There are some special components used in LCD
monitor that are important for safety. These parts are
mar ked
on the schematic diagram and the
replacement parts list. It is essential that these critical
par ts should be replaced with the manufacturer's
specified parts to prevent electric shock, fire or other
hazard.
· Do not modify original design without obtaining written
permission from LG or you will void the original parts
and labor guarantee.
TAKE CARE DURING HANDLING THE LCD MODULE
WITH BACKLIGHT UNIT.
· Must mount the module using mounting holes arranged
in four corners.
· Do not press on the panel, edge of the frame strongly
or electric shock as this will result in damage to the
screen.
· Do not scratch or press on the panel with any sharp
objects, such as pencil or pen as this may result in
damage to the panel.
· Protect the module from the ESD as it may damage the
electronic circuit (C-MOS).
· Make cer tain that treatment person's body are
grounded through wrist band.
· Do not leave the module in high temperature and in
areas of high humidity for a long time.
· The module not be exposed to the direct sunlight.
· Avoid contact with water as it may a short circuit within
the module.
· If the surface of panel become dirty, please wipe it off
with a softmaterial. (Cleaning with a dirty or rough cloth
may damage the panel.)
WARNING
BE CAREFUL ELECTRIC SHOCK !
· If you want to replace with the new backlight (CCFL) or
inver ter circuit, must disconnect the AC adapter
because high voltage appears at inverter circuit about
650Vrms.
· Handle with care wires or connectors of the inverter
circuit. If the wires are pressed cause short and may
burn or take fire.
CAUTION
Please use only a plastic screwdriver to protect yourself
from shock hazard during service operation.
CAUTION
· There is two backlight, must distinguish between
the top (upper) and the bottom (lower), and be
careful of treatment it.
· MTBF (Mean Time Between Failure) of a backlight
is about 25,000 hours.
Top (Upper) Backlight Ass'y
Bottom (Lower) Backlight Ass'y
IF BRIGHTNESS OF THE LCD MODULE DARKEN,
REPLACE THE BACKLIGHT ONE OR ALL.
No.51932
5
AV-15LCG
AV-15LCH
AV-15LCS
SPECIFIC SERVICE INSTRUCTIONS
CAUTION: Before servicing receivers covered by this service
manual and its supplements and addenda, read and follow the
SAFETY PRECAUTIONS on page 3 of this publication.
NOTE: If unforeseen circumstances create conflict between the
following ser vicing precautions and any of the safety
precautions on page 3 of 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 par t substitution or incorrect
polarity installation of electrolytic capacitors may result
in an explosion hazard.
d. Discharging the picture tube anode.
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. Discharge the picture tube anode only by (a) first connecting
one end of an insulated clip lead to the degaussing or kine
aquadag grounding system shield at the point where the
picture tube socket ground lead is connected, and then (b)
touch the other end of the insulated clip lead to the picture
tube anode button, using an insulating handle to avoid
personal contact with high voltage.
4. Do not spray chemicals on or near this receiver or any of its
assemblies.
5. Unless specified otherwise in this service manual, clean
electrical contacts only by applying the following mixture to
the contacts with a pipe cleaner, cotton-tipped stick or
comparable nonabrasive applicator ; 10% (by volume)
Acetone and 90% (by volume) isopropyl alcohol (90%-99%
strength)
CAUTION: This is a flammable mixture.
Unless specified otherwise in this service manual, lubrication
of contacts in not required.
6. Do not defeat any plug/socket B+ voltage interlocks with
which receivers covered by this service manual might be
equipped.
7. 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.
8. 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.
9.
Use with this receiver only the test fixtures specified in this
service manual.
CAUTION: Do not connect the test fixture ground strap to
any heatsink in this receiver.
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged
easily by static electricity. Such components commonly are
called
Electrostatically Sensitive (ES) Devices. Examples of
typical ES devices are integrated circuits and some fieldeffect
transistors and semicounductor "chip" components. The
following techniques should be used to help reduce the
incidence of component damage caused by static by static
electricity.
1. Immediately before handling any semiconductor component
or semiconductor-equipped assembly, drain off any
electostatic 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 to prevent potential shock reasons prior to
applying power to the unit under test.
2. After removing an electrical assembly equipped with ES
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
ES devices.
4. Use only an anti-static type solder removal device. Some
solder removal devices not classified as "anti-static" can
generate electrical charges sufficent to demage ES devices.
5. Do not use freon-propelled chemicals. These can generate
electrical charges sufficient to damage ES devices.
6. Do not remove a repalcement ES device from its protective
package until immediately before you are ready to install it.
(Most replacement ES devices are packaged with leads
electrically shorted together by conductive foam, aluminum
foil or comparable conductive material).
7. Immediately before removing the protective material from
the ieads of a replacement ES device, touch the protective
material to the chassis or circuit assembly into which the
device will be installed.
CAUTION:Be sure no power is applied to the chassis or
circuit, and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged
replacement ES devices. (Otherwise harmless motion such
as the bruching together of your clothes fabric or the lifting
of your foot from a carpeted floor can generate static
electricity sufficient to damage an ES device.)
General Soldering Guidelines
1. Use a grounded-tip, low-wattage solder ing iron and
appropr iate tip size and shape that will maintan tip
temperature within the range or 500 F to 600 F.
2. Use an appropr iate gauge of RMA resin-core solder
composed of 60 parts tin/40 parts lead.
3. Keep the soldering iron tip clean and well tinned.
4. Thorohly clean the surfaces to be soldered. Use a mall
wirebristle (0.5 inch, or 1.25cm) brush with a metal handle.
Do not use freon-propelled spray-on cleaners.
5. Use the following unsoldering technique
a. Allow the soldering iron tip to reach normal temperature.
(500 F to 600 F)
b. Heat the component lead until the solder melts.
c. Quickly draw the melted solder with an anti-static,
suction-type solder removal device or with solder braid.
CAUTION:Work quickly to avoid overheating the
circuiboard printed foil.
6. Use the following soldering technique.
a. Allow the solder ing iron tip to reach a nor mal
temperature (500 F to 600 F)
b. First, hold the soldering iron tip and solder the strand
against the component lead until the solder melts.