32LS679C (CHASSIS:LD21B) — 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 cir-
cuit 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.
Removal
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 melts.
2.  Draw away the melted solder with an anti-static suction-type 
solder removal device (or with solder braid) before removing 
the IC.
Replacement
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
Removal/Replacement
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
Removal/Replacement
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 
board.
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 pos-
sible to diode body.
2.  Bend the two remaining leads perpendicular y to the circuit 
board.
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.
5.  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
Removal/Replacement
1.  Clip each fuse or resistor lead at top of the circuit board hollow 
stake.
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 connec-
tions).
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 
board.
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 con-
nected 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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