32LS679C (CHASSIS:LD21B) — LG TV Service Manual (repair manual). Page 4

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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 servicing 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 mod-
ule 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 explo-
sion 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 
4.  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 
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.
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 
Always remove the test receiver ground lead last.
8.  Use with this receiver only the test fixtures specified in this 
service manual.
CAUTION: Do not connect the test fixture ground strap to any 
heat sink in this receiver.
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid-state) devices can be damaged eas-
ily 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 dam-
age caused by static by static electricity.
1.  Immediately before handling any semiconductor component or 
semiconductor-equipped assembly, drain off any electrostatic 
charge on your body by touching a known earth ground. Alter-
natively, obtain and wear a commercially available discharging 
wrist strap device, which should be removed to prevent poten-
tial 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 expo-
sure of the assembly.
3.  Use only a grounded-tip soldering iron to solder or unsolder ES 
4.  Use only an anti-static type solder removal device. Some solder 
removal devices not classified as “anti-static” can generate 
electrical charges sufficient to damage ES devices.
5.  Do not use freon-propelled chemicals. These can generate 
electrical charges sufficient to damage ES devices.
6.  Do not remove a replacement ES device from its protective 
package until immediately before you are ready to install it. 
(Most replacement ES devices are packaged with leads electri-
cally shorted together by conductive foam, aluminum foil or 
comparable conductive material).
7.  Immediately before removing the protective material from the 
leads of a replacement ES device, touch the protective 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.
8.  Minimize bodily motions when handling unpackaged replace-
ment ES devices. (Otherwise harmless motion such as the 
brushing together of your clothes fabric or the lifting  of your 
foot from a carpeted floor can generate static electricity suf-
ficient to damage an ES device.)
General Soldering Guidelines
1.  Use a grounded-tip, low-wattage soldering iron and appropriate 
tip size and shape that will maintain tip temperature within the 
range or 500 °F to 600 °F.
2.  Use an appropriate 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.  Thoroughly clean the surfaces to be soldered. Use a mall wire-
bristle (0.5 inch, or 1.25 cm) 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 circuit 
board printed foil.
6.  Use the following soldering technique.
a.  Allow the soldering iron tip to reach a normal 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.
c.  Quickly move the soldering iron tip to the junction of the 
component lead and the printed circuit foil, and hold it there 
only until the solder flows onto and around both the compo-
nent lead and the foil.
CAUTION: Work quickly to avoid overheating the circuit 
board printed foil.
d.  Closely inspect the solder area and remove any excess or 
splashed solder with a small wire-bristle brush.
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