Technical data

63
Magnavox LCD TV
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Repair Tips
0. Warning
All ICs and many other semi-conductors are susceptible to
electrostaticdischarges (ESD). Careless handling during
repair can reduce life drastically. When repairing, makesure
that you are connectedwith thesamepotential as the mass
of the unitviaawristw
rap with resistance.Keep components
and tools alsoatthesamepotential !
1. Servicing of SMDs (Surface MountedDevices)
1.1 General cautions on handling and storage
-Oxidation on the terminals of SMDsresultsin poorsoldering.
Do not handle SMDs with bare hands.
-Avoidusing storageplaces that are sensitive to oxidation
such asplaces with sulphur or chlorine gas,direct sunlight,
high temperatures or ahigh de
gree of humi dity. The
capacitance or resistance value of the SMDs may be
affectedbythis.
- Rough handling of circuit boards containing SMDs may
cause damage to the components as well as the circuit
boards.Circuit boards containing SMDsshould never be
bent or flexed. Different circuit boardmaterialsexpand and
contract at different rates whenheatedor cooled and the
components and/orsolder connections may be damaged
due to thestress.Never rub orscrape chip components as
this may cause the valu
e of the component to change.
Similarly, do not slide the circuit boardacross any surface.
1.2 Removal of SMDs
-Heat thesolder (for 2-3 seconds)ateach terminal of the
chip.Bymeans of litz wire and a slight horizontal force,
small components can beremovedwith thesoldering iron.
They can alsoberemovedwith a solder sucker (see Fig.
1A)
While holding the SMD with a pair of tweezers,takeitoffgently using the
soldering iron's heat appliedtoeach terminal (see Fig. 1 B).
- Remove theexcess solder on thesolder lands by means of
litz wire or a solder sucker (see Fig. 1C).
1.3 Caution on removal
-When handling thesoldering.iron. use suitable pressure and be careful.
-When removing the chip, do not use undue force with thepair of tweezers.
-Thesoldering iron to be used(approx. 30 W) should
preferably beequippedwithathermal control (soldering
temperature: 225 to 250 C).
-The chip, onceremoved, mustnever bereused.
1.4 Attachment of SMDs
- Locate the SMDonthesolder lands by means of tweezers
and solder the component on oneside.Ensure that the
component is positionedcorrectly on thesolder lands (see Fig.2A).
-Next complete thesoldering of the terminals of the
component (see Fiq. 2B).
2. Caution when attaching SMDs
-When soldering the SMD terminals, do not touch them
directly with thesoldering iron. Thesoldering should be
done as quickly aspossible,care mustbe takentoavoid
damage to the terminals of the SMDs themselves.
-Keep the SMD's body in contact with theprinted boardwhen
solderi
ng.
-Thesoldering iron to be used(approx. 30 W ) should
preferably beequippedwithathermal control (soldering
temperature: 225 to 250 C).
- Soldering should not be done outside thesolder land.
- Soldering flux (of rosin) may be used, but should not be
acidic.
-After soldering, letthe SMD cool down gradually at room
temperature.
-The quanti
ty of solder mustbeproportional to thesize of the
solder land. If the quantity is too great, the SMD might
crack or thesolder lands might be tornloose from the
printed board(see Fig. 3).
Fig.3 Examples
Right