Read LG 47LB9DF (CHASSIS:LB75A) Service Manual online
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
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
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
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.
heat sink in this receiver.
Some semiconductor (solid-state) devices can be damaged easily
by static electricity. Such components commonly are called
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 F to 600 F.
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
circuitboard 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.