32LH30FD (CHASSIS:LT91A) - LG TV Service Manual (repair manual). Page 5

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IC Remove/Replacement
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
prying  up  on  the  lead  with  the  soldering  iron  tip  as  the  solder
2.  Draw  away  the  melted  solder  with  an  anti-static  suction-type
solder removal device (or with solder braid) before removing the
1.  Carefully insert the replacement IC in the circuit board.
2.  Carefully  bend  each  IC  lead  against  the  circuit  foil  pad  and
solder it.
3.  Clean the soldered areas with a small wire-bristle brush.
(It is not necessary to reapply acrylic coating to the areas).
"Small-Signal" Discrete Transistor
1.  Remove the defective transistor by clipping its leads as close as
possible to the component body.
2.  Bend into a "U" shape the end of each of three leads remaining
on the circuit board.
3.  Bend into a "U" shape the replacement transistor leads.
4.  Connect  the  replacement  transistor  leads  to  the  corresponding
leads  extending  from  the  circuit  board  and  crimp  the  "U"  with
long  nose  pliers  to  insure  metal  to  metal  contact  then  solder
each connection.
Power Output, Transistor Device
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
4.  Insert new transistor in the circuit board.
5. Solder each transistor lead, and clip off excess lead.
6.  Replace heat sink.
Diode Removal/Replacement
1.  Remove  defective  diode  by  clipping  its  leads  as  close  as
possible to diode body.
2.  Bend  the  two  remaining  leads  perpendicular  y  to  the  circuit
3.  Observing  diode  polarity,  wrap  each  lead  of  the  new  diode
around the corresponding lead on the circuit board.
4.  Securely crimp each connection and solder it.
Inspect  (on  the  circuit  board  copper  side)  the  solder  joints  of
the two "original" leads. If they are not shiny, reheat them and if
necessary, apply additional solder.
Fuse and Conventional Resistor
1.  Clip each fuse or resistor lead at top of the circuit board hollow
2.  Securely  crimp  the  leads  of  replacement  component  around
notch at stake top.
3.  Solder the connections.
CAUTION: Maintain  original  spacing  between  the  replaced
component  and  adjacent  components  and  the  circuit  board  to
prevent excessive component temperatures.
Circuit Board Foil Repair
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.
At IC Connections
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
1.  Carefully  remove  the  damaged  copper  pattern  with  a  sharp
knife. (Remove only as much copper as absolutely necessary).
2.  carefully  scratch  away  the  solder  resist  and  acrylic  coating  (if
used) from the end of the remaining copper pattern.
3.  Bend a small "U" in one end of a small gauge jumper wire and
carefully crimp it around the IC pin. Solder the IC connection.
4.  Route  the  jumper  wire  along  the  path  of  the  out-away  copper
pattern and let it overlap the previously scraped end of the good
copper  pattern.  Solder  the  overlapped  area  and  clip  off  any
excess jumper wire.
At Other Connections
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
1.  Remove the defective copper pattern with a sharp knife.
Remove at least 1/4 inch of copper, to ensure that a hazardous
condition will not exist if the jumper wire opens.
2.  Trace  along  the  copper  pattern  from  both  sides  of  the  pattern
break  and  locate  the  nearest  component  that  is  directly
connected to the affected copper pattern.
3.  Connect  insulated  20-gauge  jumper  wire  from  the  lead  of  the
nearest component on one side of the pattern break to the lead
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.
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