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LCD TV
SERVICE MANUAL
CHASSIS : ML-038C

MODEL : RZ-42LZ30
CAUTION
BEFORE SERVICING THE CHASSIS,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
CONTENTS




CONTENTS .............................................................................................. 2

PRODUCT SAFETY ..................................................................................3

SPECIFICATION ........................................................................................6

ADJUSTMENT INSTRUCTION .................................................................9

SVC REMOCON.......................................................................................11

TROUBLE SHOOTING ............................................................................12

BLOCK DIAGRAM...................................................................................16

EXPLODED VIEW .................................................................................. 18

EXPLODED VIEW PARTS LIST ..............................................................19

REPLACEMENT PARTS LIST ................................................................20

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
X-RADIATION, Shock, Fire, or other Hazards.
Do not modify the original design without permission of manufacturer.


General Guidance Before returning the receiver to the customer,

An isolation Transformer should always be used during the always perform an AC leakage current check on the exposed
servicing of a receiver whose chassis is not isolated from the AC metallic parts of the cabinet, such as antennas, terminals, etc., to
power line. Use a transformer of adequate power rating as this be sure the set is safe to operate without damage of electrical
protects the technician from accidents resulting in personal injury shock.
from electrical shocks.
Leakage Current Cold Check(Antenna Cold Check)
It will also protect the receiver and it's components from being With the instrument AC plug removed from AC source, connect an
damaged by accidental shorts of the circuitry that may be electrical jumper across the two AC plug prongs. Place the AC
inadvertently introduced during the service operation. 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
If any fuse (or Fusible Resistor) in this TV receiver is blown, each exposed metallic parts such as antenna terminals, phone
replace it with the specified. jacks, etc.
If the exposed metallic part has a return path to the chassis, the
When replacing a high wattage resistor (Oxide Metal Film Resistor, measured resistance should be between 1M and 5.2M.
over 1W), keep the resistor 10mm away from PCB. When the exposed metal has no return path to the chassis the
reading must be infinite.
Keep wires away from high voltage or high temperature parts. An other abnormality exists that must be corrected before the
receiver is returned to the customer.
Due to high vacuum and large surface area of picture tube,
extreme care should be used in handling the Picture Tube. Do Leakage Current Hot Check (See below Figure)
not lift the Picture tube by it's Neck. Plug the AC cord directly into the AC outlet.
Do not use a line Isolation Transformer during this check.
X-RAY Radiation Connect 1.5K/10watt resistor in parallel with a 0.15uF capacitor
between a known good earth ground (Water Pipe, Conduit, etc.)
Warning: and the exposed metallic parts.
Measure the AC voltage across the resistor using AC voltmeter
with 1000 ohms/volt or more sensitivity.
The source of X-RAY RADIATION in this TV receiver is the High Reverse plug the AC cord into the AC outlet and repeat AC voltage
Voltage Section and the Picture Tube. measurements for each exposed metallic part. Any voltage
For continued X-RAY RADIATION protection, the replacement measured must not exceed 0.75 volt RMS which is corresponds to
tube must be the same type tube as specified in the 0.5mA.
Replacement Parts List. In case any measurement is out of the limits specified, there is
possibility of shock hazard and the set must be checked and
To determine the presence of high voltage, use an accurate high repaired before it is returned to the customer.
impedance HV meter.
Leakage Current Hot Check circuit
Adjust brightness, color, contrast controls to minimum.
Measure the high voltage.
The meter reading should indicate AC Volt-meter
23.5 1.5KV: 14-19 inch, 26 1.5KV: 19-21 inch,
29.0 1.5KV: 25-29 inch, 30.0 1.5KV: 32 inch
If the meter indication is out of tolerance, immediate service and
correction is required to prevent the possibility of premature
Good Earth Ground
component failure.
such as WATER PIPE,
To Instrument's CONDUIT etc.
0.15uF
exposed
METALLIC PARTS


1.5 Kohm/10W
SERVICING PRECAUTIONS
CAUTION: Before servicing receivers covered by this service should be used to help reduce the incidence of component
manual and its supplements and addenda, read and follow the damage caused by static by static electricity.
SAFETY PRECAUTIONS on page 3 of this publication. 1. Immediately before handling any semiconductor component or
NOTE: If unforeseen circumstances create conflict between the semiconductor-equipped assembly, drain off any electrostatic
following servicing precautions and any of the safety precautions on charge on your body by touching a known earth ground.
page 3 of this publication, always follow the safety precautions. Alternatively, obtain and wear a commercially available
Remember: Safety First. discharging wrist strap device, which should be removed to
prevent potential shock reasons prior to applying power to the
General Servicing Precautions unit under test.
1. Always unplug the receiver AC power cord from the AC power 2. After removing an electrical assembly equipped with ES
source before; devices, place the assembly on a conductive surface such as
a. Removing or reinstalling any component, circuit board aluminum foil, to prevent electrostatic charge buildup or
module or any other receiver assembly. exposure of the assembly.
b. Disconnecting or reconnecting any receiver electrical plug or 3. Use only a grounded-tip soldering iron to solder or unsolder ES
other electrical connection. devices.
c. Connecting a test substitute in parallel with an electrolytic 4. Use only an anti-static type solder removal device. Some solder
capacitor in the receiver. removal devices not classified as "anti-static" can generate
CAUTION: A wrong part substitution or incorrect polarity electrical charges sufficient to damage ES devices.
installation of electrolytic capacitors may result in an 5. Do not use freon-propelled chemicals. These can generate
explosion hazard. electrical charges sufficient to damage ES devices.
d. Discharging the picture tube anode. 6. Do not remove a replacement ES device from its protective
2. Test high voltage only by measuring it with an appropriate high package until immediately before you are ready to install it.
voltage meter or other voltage measuring device (DVM, (Most replacement ES devices are packaged with leads
FETVOM, etc) equipped with a suitable high voltage probe. electrically shorted together by conductive foam, aluminum foil
Do not test high voltage by "drawing an arc". or comparable conductive material).
3. Discharge the picture tube anode only by (a) first connecting 7. Immediately before removing the protective material from the
one end of an insulated clip lead to the degaussing or kine leads of a replacement ES device, touch the protective material
aquadag grounding system shield at the point where the picture to the chassis or circuit assembly into which the device will be
tube socket ground lead is connected, and then (b) touch the installed.
other end of the insulated clip lead to the picture tube anode CAUTION: Be sure no power is applied to the chassis or circuit,
button, using an insulating handle to avoid personal contact with and observe all other safety precautions.
high voltage. 8. Minimize bodily motions when handling unpackaged
4. 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
5. 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 500 F to 600 F.
contacts in not required. 2. Use an appropriate gauge of RMA resin-core solder composed
6. 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.
7. 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.
8. 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. (500 F to 600 F)
Always remove the test receiver ground lead last. b. Heat the component lead until the solder melts.
9. 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
heat sink in this receiver. circuitboard 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 (500 F to 600 F)
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
semiconductor "chip" components. The following techniques



-4-
c. Quickly move the soldering iron tip to the junction of the Fuse and Conventional Resistor
component lead and the printed circuit foil, and hold it there Removal/Replacement
only until the solder flows onto and around both the 1. Clip each fuse or resistor lead at top of the circuit board hollow
component lead and the foil. stake.
CAUTION: Work quickly to avoid overheating the circuit 2. Securely crimp the leads of replacement component around
board printed foil. notch at stake top.
d. Closely inspect the solder area and remove any excess or 3. Solder the connections.
splashed solder with a small wire-bristle brush. CAUTION: Maintain original spacing between the replaced
component and adjacent components and the circuit board to
IC Remove/Replacement prevent excessive component temperatures.
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat against the Circuit Board Foil Repair
circuit foil. When holes are the slotted type, the following technique Excessive heat applied to the copper foil of any printed circuit
should be used to remove and replace the IC. When working with board will weaken the adhesive that bonds the foil to the circuit
boards using the familiar round hole, use the standard technique board causing the foil to separate from or "lift-off" the board. The
as outlined in paragraphs 5 and 6 above. following guidelines and procedures should be followed whenever
this condition is encountered.
Removal
1. Desolder and straighten each IC lead in one operation by gently At IC Connections
prying up on the lead with the soldering iron tip as the solder To repair a defective copper pattern at IC connections use the
melts. following procedure to install a jumper wire on the copper pattern
2. Draw away the melted solder with an anti-static suction-type side of the circuit board. (Use this technique only on IC
solder removal device (or with solder braid) before removing the connections).
IC.
Replacement 1. Carefully remove the damaged copper pattern with a sharp
1. Carefully insert the replacement IC in the circuit board. knife. (Remove only as much copper as absolutely necessary).
2. Carefully bend each IC lead against the circuit foil pad and 2. carefully scratch away the solder resist and acrylic coating (if
solder it. used) from the end of the remaining copper pattern.
3. Clean the soldered areas with a small wire-bristle brush. 3. Bend a small "U" in one end of a small gauge jumper wire and
(It is not necessary to reapply acrylic coating to the areas). carefully crimp it around the IC pin. Solder the IC connection.
4. Route the jumper wire along the path of the out-away copper
"Small-Signal" Discrete Transistor pattern and let it overlap the previously scraped end of the good
Removal/Replacement copper pattern. Solder the overlapped area and clip off any
1. Remove the defective transistor by clipping its leads as close as excess jumper wire.
possible to the component body.
2. Bend into a "U" shape the end of each of three leads remaining At Other Connections
on the circuit board. Use the following technique to repair the defective copper pattern
3. Bend into a "U" shape the replacement transistor leads. at connections other than IC Pins. This technique involves the
4. Connect the replacement transistor leads to the corresponding installation of a jumper wire on the component side of the circuit
leads extending from the circuit board and crimp the "U" with board.
long nose pliers to insure metal to metal contact then solder
each connection. 1. Remove the defective copper pattern with a sharp knife.
Remove at least 1/4 inch of copper, to ensure that a hazardous
Power Output, Transistor Device condition will not exist if the jumper wire opens.
Removal/Replacement 2. Trace along the copper pattern from both sides of the pattern
1. Heat and remove all solder from around the transistor leads. break and locate the nearest component that is directly
2. Remove the heat sink mounting screw (if so equipped). connected to the affected copper pattern.
3. Carefully remove the transistor from the heat sink of the circuit 3. Connect insulated 20-gauge jumper wire from the lead of the
board. nearest component on one side of the pattern break to the lead
4. Insert new transistor in the circuit board. of the nearest component on the other side.
5. Solder each transistor lead, and clip off excess lead. Carefully crimp and solder the connections.
6. Replace heat sink. CAUTION: Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
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
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.


-5-
SPECIFICATION
NOTE : Specifications and others are subject to change without notice for improvement.

1. Application range 3. Test and Inspection method
This specification is applied to ML-038C chassis. (1) Capacity: Follow LG electronics TV Testing Standard.
(2) Another Required Standard
2. Requirement for Test EMI: Following CE Standard(EN55020)
Testing for standard of each part must be followed in below SAFETY: Following CB Standard(EN55013)
condition.

(1) Temperature: 25