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LCD TV
SERVICE MANUAL
CHASSIS : LP68A
MODEL : 20LS5R 20LS5R-ZA
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
CONTENTS
CONTENTS .............................................................................................. 2
PRODUCT SAFETY ..................................................................................3
SPECIFICATION ........................................................................................6
ADJUSTMENT INSTRUCTION .................................................................9
TROUBLE SHOOTING ............................................................................13
BLOCK DIAGRAM...................................................................................17
EXPLODED VIEW .................................................................................. 20
REPLACEMENT PARTS LIST ............................................................... 22
SVC. SHEET ...............................................................................................
-2-
SAFETY PRECAUTIONS
IMPORTANT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in the
Schematic Diagram and Replacement Parts List.
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 Leakage Current Hot Check (See below Figure)
Plug the AC cord directly into the AC outlet.
An isolation Transformer should always be used during the Do not use a line Isolation Transformer during this check.
servicing of a receiver whose chassis is not isolated from the AC Connect 1.5K/10watt resistor in parallel with a 0.15uF capacitor
power line. Use a transformer of adequate power rating as this between a known good earth ground (Water Pipe, Conduit, etc.)
protects the technician from accidents resulting in personal injury and the exposed metallic parts.
from electrical shocks. Measure the AC voltage across the resistor using AC voltmeter
with 1000 ohms/volt or more sensitivity.
It will also protect the receiver and it's components from being Reverse plug the AC cord into the AC outlet and repeat AC voltage
damaged by accidental shorts of the circuitry that may be measurements for each exposed metallic part. Any voltage
inadvertently introduced during the service operation. measured must not exceed 0.75 volt RMS which is corresponds to
0.5mA.
If any fuse (or Fusible Resistor) in this TV receiver is blown, In case any measurement is out of the limits specified, there is
replace it with the specified. possibility of shock hazard and the set must be checked and
repaired before it is returned to the customer.
When replacing a high wattage resistor (Oxide Metal Film Resistor,
over 1W), keep the resistor 10mm away from PCB. Leakage Current Hot Check circuit
Keep wires away from high voltage or high temperature parts. AC Volt-meter
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 Good Earth Ground
be sure the set is safe to operate without damage of electrical such as WATER PIPE,
To Instrument's CONDUIT etc.
shock. 0.15uF
exposed
METALLIC PARTS
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 1.5 Kohm/10W
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 1M and 5.2M.
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.
-3-
SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service prevent potential shock reasons prior to applying power to the
manual and its supplements and addenda, read and follow the unit under test.
SAFETY PRECAUTIONS on page 3 of this publication. 2. After removing an electrical assembly equipped with ES
NOTE: If unforeseen circumstances create conflict between the devices, place the assembly on a conductive surface such as
following servicing precautions and any of the safety precautions on aluminum foil, to prevent electrostatic charge buildup or
page 3 of this publication, always follow the safety precautions. exposure of the assembly.
Remember: Safety First. 3. Use only a grounded-tip soldering iron to solder or unsolder ES
devices.
General Servicing Precautions 4. Use only an anti-static type solder removal device. Some solder
1. Always unplug the receiver AC power cord from the AC power removal devices not classified as "anti-static" can generate
source before; electrical charges sufficient to damage ES devices.
a. Removing or reinstalling any component, circuit board 5. Do not use freon-propelled chemicals. These can generate
module or any other receiver assembly. electrical charges sufficient to damage ES devices.
b. Disconnecting or reconnecting any receiver electrical plug or 6. Do not remove a replacement ES device from its protective
other electrical connection. package until immediately before you are ready to install it.
c. Connecting a test substitute in parallel with an electrolytic (Most replacement ES devices are packaged with leads
capacitor in the receiver. electrically shorted together by conductive foam, aluminum foil
CAUTION: A wrong part substitution or incorrect polarity or comparable conductive material).
installation of electrolytic capacitors may result in an 7. Immediately before removing the protective material from the
explosion hazard. leads of a replacement ES device, touch the protective material
to the chassis or circuit assembly into which the device will be
2. Test high voltage only by measuring it with an appropriate high installed.
voltage meter or other voltage measuring device (DVM, CAUTION: Be sure no power is applied to the chassis or circuit,
FETVOM, etc) equipped with a suitable high voltage probe. and observe all other safety precautions.
Do not test high voltage by "drawing an arc". 8. Minimize bodily motions when handling unpackaged
3. Do not spray chemicals on or near this receiver or any of its replacement ES devices. (Otherwise harmless motion such as
assemblies. the brushing together of your clothes fabric or the lifting of your
4. Unless specified otherwise in this service manual, clean foot from a carpeted floor can generate static electricity
electrical contacts only by applying the following mixture to the sufficient to damage an ES device.)
contacts with a pipe cleaner, cotton-tipped stick or comparable
non-abrasive applicator; 10% (by volume) Acetone and 90% (by General Soldering Guidelines
volume) isopropyl alcohol (90%-99% strength) 1. Use a grounded-tip, low-wattage soldering iron and appropriate
CAUTION: This is a flammable mixture. tip size and shape that will maintain tip temperature within the
Unless specified otherwise in this service manual, lubrication of range or 500oF to 600oF.
contacts in not required. 2. Use an appropriate gauge of RMA resin-core solder composed
5. Do not defeat any plug/socket B+ voltage interlocks with which of 60 parts tin/40 parts lead.
receivers covered by this service manual might be equipped. 3. Keep the soldering iron tip clean and well tinned.
6. Do not apply AC power to this instrument and/or any of its 4. Thoroughly clean the surfaces to be soldered. Use a mall wire-
electrical assemblies unless all solid-state device heat sinks are bristle (0.5 inch, or 1.25cm) brush with a metal handle.
correctly installed. Do not use freon-propelled spray-on cleaners.
7. Always connect the test receiver ground lead to the receiver 5. Use the following unsoldering technique
chassis ground before connecting the test receiver positive a. Allow the soldering iron tip to reach normal temperature.
lead. (500oF to 600oF)
Always remove the test receiver ground lead last. b. Heat the component lead until the solder melts.
8. Use with this receiver only the test fixtures specified in this c. Quickly draw the melted solder with an anti-static, suction-
service manual. type solder removal device or with solder braid.
CAUTION: Do not connect the test fixture ground strap to any CAUTION: Work quickly to avoid overheating the circuit
heat sink in this receiver. borad printed foil.
6. Use the following soldering technique.
Electrostatically Sensitive (ES) Devices a. Allow the soldering iron tip to reach a normal temperature
Some semiconductor (solid-state) devices can be damaged easily (500oF to 600oF)
by static electricity. Such components commonly are called b. First, hold the soldering iron tip and solder the strand against
Electrostatically Sensitive (ES) Devices. Examples of typical ES the component lead until the solder melts.
devices are integrated circuits and some field-effect transistors and c. Quickly move the soldering iron tip to the junction of the
semiconductor "chip" components. The following techniques component lead and the printed circuit foil, and hold it there
should be used to help reduce the incidence of component only until the solder flows onto and around both the
damage caused by static by static electricity. component lead and the foil.
1. Immediately before handling any semiconductor component or CAUTION: Work quickly to avoid overheating the circuit
semiconductor-equipped assembly, drain off any electrostatic board printed foil.
charge on your body by touching a known earth ground. d. Closely inspect the solder area and remove any excess or
Alternatively, obtain and wear a commercially available splashed solder with a small wire-bristle brush.
discharging wrist strap device, which should be removed to
-4-
IC Remove/Replacement 3. Solder the connections.
Some chassis circuit boards have slotted holes (oblong) through CAUTION: Maintain original spacing between the replaced
which the IC leads are inserted and then bent flat against the component and adjacent components and the circuit board to
circuit foil. When holes are the slotted type, the following technique prevent excessive component temperatures.
should be used to remove and replace the IC. When working with
boards using the familiar round hole, use the standard technique Circuit Board Foil Repair
as outlined in paragraphs 5 and 6 above. Excessive heat applied to the copper foil of any printed circuit
board will weaken the adhesive that bonds the foil to the circuit
Removal board causing the foil to separate from or "lift-off" the board. The
1. Desolder and straighten each IC lead in one operation by gently following guidelines and procedures should be followed whenever
prying up on the lead with the soldering iron tip as the solder this condition is encountered.
melts.
2. Draw away the melted solder with an anti-static suction-type At IC Connections
solder removal device (or with solder braid) before removing the To repair a defective copper pattern at IC connections use the
IC. following procedure to install a jumper wire on the copper pattern
Replacement side of the circuit board. (Use this technique only on IC
1. Carefully insert the replacement IC in the circuit board. connections).
2. Carefully bend each IC lead against the circuit foil pad and
solder it. 1. Carefully remove the damaged copper pattern with a sharp
3. Clean the soldered areas with a small wire-bristle brush. knife. (Remove only as much copper as absolutely necessary).
(It is not necessary to reapply acrylic coating to the areas). 2. carefully scratch away the solder resist and acrylic coating (if
used) from the end of the remaining copper pattern.
"Small-Signal" Discrete Transistor 3. Bend a small "U" in one end of a small gauge jumper wire and
Removal/Replacement carefully crimp it around the IC pin. Solder the IC connection.
1. Remove the defective transistor by clipping its leads as close as 4. Route the jumper wire along the path of the out-away copper
possible to the component body. pattern and let it overlap the previously scraped end of the good
2. Bend into a "U" shape the end of each of three leads remaining copper pattern. Solder the overlapped area and clip off any
on the circuit board. excess jumper wire.
3. Bend into a "U" shape the replacement transistor leads.
4. Connect the replacement transistor leads to the corresponding At Other Connections
leads extending from the circuit board and crimp the "U" with Use the following technique to repair the defective copper pattern
long nose pliers to insure metal to metal contact then solder at connections other than IC Pins. This technique involves the
each connection. installation of a jumper wire on the component side of the circuit
board.
Power Output, Transistor Device
Removal/Replacement 1. Remove the defective copper pattern with a sharp knife.
1. Heat and remove all solder from around the transistor leads. Remove at least 1/4 inch of copper, to ensure that a hazardous
2. Remove the heat sink mounting screw (if so equipped). condition will not exist if the jumper wire opens.
3. Carefully remove the transistor from the heat sink of the circuit 2. Trace along the copper pattern from both sides of the pattern
board. break and locate the nearest component that is directly
4. Insert new transistor in the circuit board. connected to the affected copper pattern.
5. Solder each transistor lead, and clip off excess lead. 3. Connect insulated 20-gauge jumper wire from the lead of the
6. Replace heat sink. nearest component on one side of the pattern break to the lead
of the nearest component on the other side.
Diode Removal/Replacement Carefully crimp and solder the connections.
1. Remove defective diode by clipping its leads as close as CAUTION: Be sure the insulated jumper wire is dressed so the
possible to diode body. it does not touch components or sharp edges.
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.
-5-
SPECIFICATION
NOTE : Specifications and others are subject to change without notice for improvement.
1. General Specification
NO Item Content Remark
1 User Model Name 20LS5R-ZA : PAL/SECAM (EU)
2 Feature 20.1" LCD TV
3 Chassis Name LP 68A
4 General Scope External SW PR(D/E), VOL(F/G), OK, MENU, INPUT, POWER 8Keys
& Adj.
5 Power Cord Length : 1.87