32LN545B-CT (CHASSIS:LD31B, LD36B) — LG TV Service Manual (repair manual)

42.77 MB
Service Manual

View LG 32LN545B-CT (CHASSIS:LD31B / LD36B) Service Manual online

P/NO : MFL67696705 
- 3 -
Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by      in the 
Schematic Diagram and Exploded View.
It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent 
Shock, Fire, or other Hazards. 
Do not modify the original design without permission of manufacturer.
General Guidance
isolation  Transformer  should  always  be  used  during  the 
servicing of a receiver whose chassis is not isolated from the AC 
power  line.  Use  a  transformer  of  adequate  power  rating  as  this 
protects  the  technician  from  accidents  resulting  in  personal  injury 
from electrical shocks.
It  will  also  protect  the  receiver  and  it's  components  from  being 
damaged  by  accidental  shorts  of  the  circuitry  that  may  be 
inadvertently introduced during the service operation.
If  any  fuse  (or  Fusible  Resistor)  in  this  TV  receiver  is  blown, 
replace it with the specified.
When replacing a high wattage resistor (Oxide Metal Film Resistor, 
over 1 W), keep the resistor 10 mm away from PCB.
Keep wires away from high voltage or high temperature parts.
Before returning the receiver to the customer, 
Always  perform  an 
AC  leakage  current  check  on  the  exposed 
metallic parts of the cabinet, such as antennas, terminals, etc., to 
be  sure  the  set  is  safe  to  operate  without  damage  of  electrical 
Leakage Current Cold Check(Antenna Cold Check)
With the instrument AC plug removed from AC source, connect an 
electrical  jumper  across  the  two AC  plug  prongs.  Place  the AC 
switch in the on position, connect one lead of ohm-meter to the AC 
plug prongs tied together and touch other ohm-meter lead in turn to 
each  exposed  metallic  parts  such  as  antenna  terminals,  phone 
jacks, etc. 
If  the  exposed  metallic  part  has  a  return  path  to  the  chassis,  the 
measured resistance should be between 1 MΩ and 5.2 MΩ. 
When  the  exposed  metal  has  no  return  path  to  the  chassis  the 
reading must be infinite.
An  other  abnormality  exists  that  must  be  corrected  before  the 
receiver is returned to the customer.
Leakage Current Hot Check 
(See below Figure) 
Plug the AC cord directly into the AC outlet.
Do not use a line Isolation Transformer during this check. 
Connect 1.5 K / 10 watt resistor in parallel with a 0.15 uF capacitor 
between  a  known  good  earth  ground  (Water  Pipe,  Conduit,  etc.) 
and the exposed metallic parts.
Measure  the AC  voltage  across  the  resistor  using AC  voltmeter 
with 1000 ohms/volt or more sensitivity.
Reverse plug the AC cord into the AC outlet and repeat AC voltage 
measurements  for  each  exposed  metallic  part.  Any  voltage 
measured must not exceed 0.75 volt RMS which is corresponds to 
0.5 mA.
In  case  any  measurement  is  out  of  the  limits  specified,  there  is 
possibility  of  shock  hazard  and  the  set  must  be  checked  and 
repaired before it is returned to the customer.
Leakage Current Hot Check circuit
- 4 -
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 precau-
tions. 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 
module 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 discharg-
ing wrist strap device, which should be removed to prevent 
potential 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 devices.
4.  Use only an anti-static type solder removal device. Some sol-
der 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 elec-
trically 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 mate-
rial to the chassis or circuit assembly into which the device will 
be installed.
CAUTION: Be sure no power is applied to the chassis or cir-
cuit, 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 appropri-
ate 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.
- 5 -
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.
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.
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 remain-
ing 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 pos-
sible 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.
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
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 when-
ever 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-
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 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.
Page of 87

Download LG 32LN545B-CT (CHASSIS:LD31B / LD36B) Service Manual (Repair Manual)

Here you can view online or download LG 32LN545B-CT (CHASSIS:LD31B / LD36B) Service Manual in pdf. This Service Manual can help you recover, restore, fix, disassemble and repair LG 32LN545B-CT (CHASSIS:LD31B / LD36B) LCD. Information contained in LG 32LN545B-CT (CHASSIS:LD31B / LD36B) service manual (repair manual) typically includes:

  • Disassembly, troubleshooting, programming, maintenance, remote, adjustment, installation and setup instructions.
  • Schematics, wiring and block diagrams.
  • Printed wiring boards (PWB) and printed circuit boards (PCB).
  • Parts list (bill of materials).