View LG 42LH301C (CHASSIS:LD91A) Service Manual online
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
Schematic Diagram and Exploded View.
It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent
Shock, Fire, or other Hazards.
Do not modify the original design without permission of manufacturer.
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.
damaged by accidental shorts of the circuitry that may be
inadvertently introduced during the service operation.
replace it with the specified.
over 1W), keep the resistor 10mm away from PCB.
metallic parts of the cabinet, such as antennas, terminals, etc., to
be sure the set is safe to operate without damage of electrical
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
If the exposed metallic part has a return path to the chassis, the
measured resistance should be between 1MΩ and 5.2MΩ.
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.
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 exposed metallic part. Any voltage
measured must not exceed 0.75 volt RMS which is corresponds to
In case any measurement is out of the limits specified, there is
possibility of shock hazard and the set must be checked and
repaired before it is returned to the customer.
such as WATER PIPE,
manual and its supplements and addenda, read and follow the
NOTE: If unforeseen circumstances create conflict between the
following servicing precautions and any of the safety precautions on
page 3 of this publication, always follow the safety precautions.
Remember: Safety First.
1. Always unplug the receiver AC power cord from the AC power
a. Removing or reinstalling any component, circuit board
CAUTION: A wrong part substitution or incorrect polarity
installation of electrolytic capacitors may result in an
FETVOM, etc) equipped with a suitable high voltage probe.
Do not test high voltage by "drawing an arc".
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.
Unless specified otherwise in this service manual, lubrication of
contacts in not required.
Always remove the test receiver ground lead last.
CAUTION: Do not connect the test fixture ground strap to any
heat sink in this receiver.
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 field-effect transistors and
semiconductor "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
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
aluminum foil, to prevent electrostatic charge buildup or
exposure of the assembly.
electrical charges sufficient to damage ES devices.
(Most replacement ES devices are packaged with leads
electrically shorted together by conductive foam, aluminum foil
or comparable conductive material).
to the chassis or circuit assembly into which the device will be
CAUTION: Be sure no power is applied to the chassis or circuit,
and observe all other safety precautions.
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 ES device.)
1. Use a grounded-tip, low-wattage soldering iron and appropriate
range or 500
4. Thoroughly clean the surfaces to be soldered. Use a mall wire-
Do not use freon-propelled spray-on cleaners.
c. Quickly draw the melted solder with an anti-static, suction-
CAUTION: Work quickly to avoid overheating the circuit
board printed foil.
only until the solder flows onto and around both the
component lead and the foil.
CAUTION: Work quickly to avoid overheating the circuit
board printed foil.
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat against the
circuit foil. When holes are the slotted type, the following technique
should be used to remove and replace the IC. When working with
boards using the familiar round hole, use the standard technique
as outlined in paragraphs 5 and 6 above.
1. Desolder and straighten each IC lead in one operation by gently
1. Carefully insert the replacement IC in the circuit board.
2. Carefully bend each IC lead against the circuit foil pad and
1. Remove the defective transistor by clipping its leads as close as
4. Connect the replacement transistor leads to the corresponding
long nose pliers to insure metal to metal contact then solder
1. Heat and remove all solder from around the transistor leads.
2. Remove the heat sink mounting screw (if so equipped).
3. Carefully remove the transistor from the heat sink of the circuit
5. Solder each transistor lead, and clip off excess lead.
6. Replace heat sink.
1. Remove defective diode by clipping its leads as close as
necessary, apply additional solder.
1. Clip each fuse or resistor lead at top of the circuit board hollow
component and adjacent components and the circuit board to
prevent excessive component temperatures.
Excessive heat applied to the copper foil of any printed circuit
board will weaken the adhesive that bonds the foil to the circuit
board causing the foil to separate from or "lift-off" the board. The
following guidelines and procedures should be followed whenever
this condition is encountered.
To repair a defective copper pattern at IC connections use the
following procedure to install a jumper wire on the copper pattern
side of the circuit board. (Use this technique only on IC
copper pattern. Solder the overlapped area and clip off any
excess jumper wire.
Use the following technique to repair the defective copper pattern
at connections other than IC Pins. This technique involves the
installation of a jumper wire on the component side of the circuit
condition will not exist if the jumper wire opens.
connected to the affected copper pattern.
of the nearest component on the other side.
Carefully crimp and solder the connections.
CAUTION: Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
2) Relative Humidity : 65±10%
3) Power Voltage : Standard input voltage ([email protected]/60Hz)
accordance with BOM.
2) Demanded other specification
- EMC:CE, IEC
2) Stable for approximately 30 minutes in a dark environment at 25±2ºC.
3) The values specified are at approximate distance 50Cm from the LCD surface
4) Ta=25±2°C, VLCD=12.0V, fV=60Hz, Dclk=74.25MHz VBR_A=1.65V,ExtVBR_B=100%
plan which can be changed only on agreeing.
3) Magnetic Field Condition: Nil.
4) Input signal Unit: Product Specification Standard
5) Reserve after operation: Above 5 Minutes (Heat Run)
Relative humidity : 65±10%
Input voltage : 220V, 60Hz
computer, jig, and set.
6) Click “Run”.
7) After downloading, check “OK” message.
2) Automatically detecting update file in USB Stick
data is automatically detecting
To use speed between
3. Push “Power on” key
4. Function inspection
5. After function inspection, Push “I n-stop” key.
channel recover. if all channel data is cleared, you didn’t
have a DTV/ATV test on production line.
2) Select “Tool Option 1” and Push “OK” button.
3) Punch in the number. (Each model hax their number)
• Signal equipment displays.
PATTERN : 65 in Pattern Generator(MSPG-925 SERIES)
• aa 00 00 [Enter Adjust Mode]
• xb 00 40 [Component1 Input (480i)]
• ad 00 10 [Adjust 480i Comp1]
• xb 00 60 [RGB Input (1024*768)]
• ad 00 10 [Adjust 1024*768 RGB]
• aa 00 90 End Adjust mode
* Required equipment : Adjustment R/C.
2) AV (SCART1/SCART2/ CVBS)
3) COMPONENT (480i)
4) RGB (PC : 1024 x 768 @ 60hz)
6) PC Audio In
* Display and Sound check is executed by Remote control.