- 4 -
Copyright © 2011 LG Electronics. Inc. All right reserved.
Only for training and service p rposes LGE Internal Use Only
SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service
man al and its s pplements and addenda, read and follow the
SAFETY PRECAUT ONS on page 3 of this p blication.
NOTE: If nforeseen circ mstances create conflict between the
following servicing preca tions and any of the safety preca tions on
page 3 of this p blication, always follow the safety preca tions.
Remember: Safety First.
General Servicing Precautions
1. Always npl g the receiver AC power cord from the AC power
so rce before;
a. Removing or reinstalling any component, circ it board
mod le or any other receiver assembly.
b. Disconnecting or re-connecting any receiver electrical pl g or
other electrical connection.
c. Connecting a test s bstit te in parallel with an electrolytic
capacitor in the receiver.
CAUTION: A wrong part s bstit tion or incorrect polarity
installation of electrolytic capacitors may res lt in an
explosion hazard.
2. Test high voltage only by meas ring it with an appropriate high
voltage meter or other voltage meas ring device (DVM,
FETVOM, etc) eq ipped with a s itable 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 man al, clean
electrical contacts only by applying the following mixt re to the
contacts with a pipe cleaner, cotton-tipped stick or comparable
non-abrasive applicator; 10% (by vol me) Acetone and 90% (by
vol me) is opropyl alcohol (90%-99% strength)
CAUTION: This is a flammable mixt re.
Unless specified otherwise in this service man al, l brication of
contacts in not req ired.
5. Do not defeat any pl g/socket B+ voltage interlocks with which
receivers covered by this service man al might be eq ipped.
6. Do not apply AC power to this instr ment and/or any of its
electrical assemblies nless all solid-state device heat sinks are
correctly installed.
7. Always connect the test receiver gro nd lead to the receiver
chassis gro nd before connecting the test receiver positive
lead.
Always remove the test receiver gro nd lead last.
8. Use with this receiver only the test fixtures specified in this
service manual.
CAUTION: Do not connect the test fixt re gro nd strap to any
heat sink in this receiver.
Electrostatically Sensitive (ES) Devices
Some semicond ctor (solid-state) devices can be damaged easily
by static electricity. S ch components commonly are called
Electrostatically Sensitive (ES) Devices. Examples of typical ES
devices are integrated circ its and some field-effect transistors and
semicond ctor "chip" components. The following techniq es
sho ld be sed to help red ce the incidence of component
damage ca sed by static by static electricity.
1. Immediately before handling any semicond ctor component or
semicond ctor-eq ipped assembly, drain off any electrostatic
charge on yo r body by to ching a known earth gro nd.
Alternatively, obtain and wear a commercially available
discharging wrist strap device, which sho ld be removed to
prevent potential shock reasons prior to applying power to the
nit nder test.
2. After removing an electrical assembly eq ipped with ES
devices, place the assembly on a cond ctive s rface s ch as
al min m foil, to prevent electrostatic charge b ild p or
expos re of the assembly.
3. Use only a gro nded-tip soldering iron to solder or nsolder 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 s fficient to damage ES devices.
5. Do not se freon-propelled chemicals. These can generate
electrical charges s fficient to damage ES devices.
6. Do not remove a replacement ES device from its protective
package ntil immediately before yo are ready to install it.
(Most replacement ES devices are packaged with leads
electrically shorted together by cond ctive foam, al min m foil
or comparable cond ctive material).
7. Immediately before removing the protective material from the
leads of a replacement ES device, to ch the protective material
to the chassis or circ it assembly into which the device will be
installed.
CAUTION: Be s re no power is applied to the chassis or circ it,
and observe all other safety preca tions.
8. Minimize bodily motions when handling npackaged
replacement ES devices. (Otherwise harmless motion s ch as
the br shing together of yo r clothes fabric or the lifting of yo r
foot from a carpeted floor can generate static electricity
s fficient to damage an ES device.)
General Soldering G idelines
1. Use a gro nded-tip, low-wattage soldering iron and appropriate
tip size and shape that will maintain tip temperat re within the
range or 500ºF to 600ºF.
2. Use an appropriate ga ge of RMA resin-core solder composed
of 60 parts tin/40 parts lead.
3. Keep the soldering iron tip clean and well tinned.
4. Thoro ghly clean the s rfaces to be soldered. Use a mall wire-
bristle (0.5 inch, or 1.25cm) br sh with a metal handle.
Do not se freon-propelled spray-on cleaners.
5. Use the following nsoldering techniq e
a. Allow the soldering iron tip to reach normal temperat re.
(500ºF to 600ºF)
b. Heat the component lead ntil the solder melts.
c. Q ickly draw the melted solder with an anti-static, s ction-
type solder removal device or with solder braid.
CAUTION: Work q ickly to avoid overheating the circ it
board printed foil.
6. Use the following soldering techniq e.
a. Allow the soldering iron tip to reach a normal temperat re
(500ºF to 600ºF)
b. First, hold the soldering iron tip and solder the strand against
the component lead ntil the solder melts.
c. Q ickly move the soldering iron tip to the j nction of the
component lead and the printed circ it foil, and hold it there
only ntil the solder flows onto and aro nd both the
component lead and the foil.
CAUTION: Work q ickly to avoid overheating the circ it
board printed foil.
d. Closely inspect the solder area and remove any excess or
splashed solder with a small wire-bristle br sh.
