LG CF-14F80K Manual de usuario

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COLOR TV

SERVICE MANUAL

CAUTION

BEFORE SERVICING THE CHASSIS,

READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

CHASSIS : MC-019A

MODEL :

CF-14/20/21F80K

website:http://biz.LGservice.com

e-mail:http://www.LGEservice.com/techsup.html

Aug.,2001

Printed in KoreaP/NO : 3828VD0104B

- 2 -

CONTENTS

Contents ................................................................................................................. 2

Safety Precautions ............................................................................................3

Servicing Precautions ..................................................................................... 4

Specifications ..................................................................................................... 6

Description of Controls .................................................................................. 7

Disassembly Instructions .............................................................................10

Adjustment ............................................................................................................11

Purity & Convergence Adjustment ..........................................................14

Block Diagram ......................................................................................................17

Exploded View .................................................................................................. 18

Exploded View Parts List ..............................................................................19

Replacement Parts List ............................................................................... 20

SVC. Sheet ................................................................................................................

- 3 -

SAFETY PRECAUTIONS

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

An lsolation 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 circuitary 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 1W), keep the resistor 10mm away from PCB.

Keep wires away from high voltage or high temperature parts.

Due to high vacuum and large surface area of picture tube,

extreme care should be used in handling the Picture Tube.

Do not lift the Picture tube by it's Neck.

X-RAY Radiation

Warning:

To determine the presence of high voltage, use an accurate

high impedance HV meter.

Adjust brightness, color, contrast controls to minimum.

Measure the high voltage.

The meter reading should indicate

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 component failure.

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 shock.

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 positioin, 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 1MΩ and 5.2MΩ.

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 1.5K/10watt resistor in parallel with a 0.15uF 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 esposed metallic part. Any

voltage measured must not exceed 0.75 volt RMS which is

corresponds to 0.5mA.

In case any measurement is out of the limits sepcified, 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

The source of X-RAY RADIATION in this TV receiver is the

High Voltage Section and the Picture Tube.

For continued X-RAY RADIATION protection, the

replacement tube must be the same type tube as specified in

the Replacement Parts List.

1.5 Kohm/10W

To Instrument's

exposed

METALLIC PARTS

Good Earth Ground

such as WATER PIPE,

CONDUIT etc.

AC Volt-meter

IMPORTANT SAFETY NOTICE

0.15uF

- 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 precautions. 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.

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 explosion hazard.

d. Discharging the picture tube anode.

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. Discharge the picture tube anode only by (a) first connecting

one end of an insulated clip lead to the degaussing or kine

aquadag grounding system shield at the point where the

picture tube socket ground lead is connected, and then (b)

touch the other end of the insulated clip lead to the picture

tube anode button, using an insulating handle to avoid

personal contact with high voltage.

4. Do not spray chemicals on or near this receiver or any of its

assemblies.

5. 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 nonabrasive 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.

6. Do not defeat any plug/socket B+ voltage interlocks with

which receivers covered by this service manual might be

equipped.

7. 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.

8. Always connect the test receiver ground lead to the

receiver chassis ground before connecting the test receiver

positive lead.

Always remove the test receiver ground lead last.

Use with this receiver only the test fixtures specified in this

service manual.

CAUTION: Do not connect the test fixture ground strap to

any heatsink in this receiver.

Electrostatically Sensitive (ES) Devices

Some semiconductor (solid state) devices can be damaged

easily by static electricity. Such components commonly are

called

Electrostatically Sensitive (ES) Devices.

Examples of

typical ES devices are integrated circuits and some fieldeffect

transistors and semicounductor "chip" components. The

following techniques should be used to help reduce the

incidence of component damage caused by static by static

electricity.

1. Immediately before handling any semiconductor component

or semiconductor-equipped assembly, drain off any

electostatic charge on your body by touching a known earth

ground. Alternatively, obtain and wear a commercially

available discharging 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

exposure 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

solder removal devices not classified as "anti-static" can

generate electrical charges sufficent to demage ES devices.

5. Do not use freon-propelled chemicals. These can generate

electrical charges sufficient to damage ES devices.

6. Do not remove a repalcement ES device from its protective

package until immediately before you are ready to install it.

(Most replacement ES devices are packaged with leads

electrically shorted together by conductive foam, aluminum

foil or comparable conductive material).

7. Immediately before removing the protective material from

the ieads of a replacement ES device, touch the protective

material to the chassis or circuit assembly into which the

device will be installed.

CAUTION:Be sure no power is applied to the chassis or

circuit, and observe all other safety precautions.

8. Minimize bodily motions when handling unpackaged

replacement ES devices. (Otherwise harmless motion such

as the bruching together of your clothes fabric or the lifting

of your foot from a carpeted floor can generate static

electricity sufficient to damage an ES device.)

General Soldering Guidelines

1. Use a grounded-tip, low-wattage soldering iron and

appropriate tip size and shape that will maintan 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. Thorohly clean the surfaces to be soldered. Use a mall

wirebristle (0.5 inch, or 1.25cm) 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

circuiboard 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.

SERVICING PRECAUTIONS

- 5 -

c. Qulckly 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

component 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.

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 parapraphs 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 boare.

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 heatsink 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 heatsink.

Diode Removal/Replacement

1. Remove defective diode by clipping its leads as close as

possible to diode body.

2. Bend the two remaining leads perpendicula 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

connections).

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

involoves 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 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.

- 6 -

SPECIFICATIONS

Note : Specification and others are subject to change without notice for improvement.

OVideo input system:

PAL-B/G, D/K, I/I

SECAM-B/G, D/K,L/L’

NTSC M

NTSC 4.43

OIntermediate Frequency (Unit : MHz)

VISION IF : 38.9MHz

COLOR IF : 34.47MHz(4.43)

35.32MHz(3.58) : NTSC-M

VIF-4.25000MHz

VIF-4.40625MHz

SOUND IF : 33.4MHz (B/G)

32.9MHz (I/I)

32.4MHz (D/K)

34.4MHz (M)

OPower requirement : 110~240V, 50/60Hz

OPower consumption : 95

OSTAND-BY : 3W

OTuning system :

FVS

100 Programme memory

200 Programme memory(W/O TXT)

Antenna input impedance : VHF/UHF 75 ohm, unbalanced

OOSD (On Screen Display) : EASY-MENU

OVoice coil impedance : 8 ohm

OSound output : 7W¡¿2(MAX)

Dual/Stereo : A2/NICAM(Option)

OExternal connection : Head Phone Jack

A/V in : 2

PERI Connector(Full Scart) : 1

DVD in

OExternal In/Output

Audio-In:0.5Vrms!3dB,over 10Kohm

Audio-Out:0.5Vrms!3dBb,below 1Kohm

Video-In/Out:1Vp-p!3dB,75ohm

DVD In Y: 1Vp-p!3dB

Pb,Pr : 0.7Vp-p!3dB

OFeature : Auto programme/Manual programme

CSM (Color Status Memory)

Auto Sleep

Turbo Picture & Sound

Programme Editing

PSM (Picture Status Memory)

Teletext (TOP/FLOF/LIST)

ACMS

Auto Volume Level

Game

SSM(Sound Status Memory)

Favorite Program

OTuning range

Band

VHF-Low

VHF-High

Hyper

UHF

S1'-S3', S1

S2-S10,

S11-S20

S21-S41

For TV For CATV

B/G

Ch2-4

Ch5-12

D/K

Ch1-5

Ch6-12

I/I

Ch4-13

NTSC

Ch2-13

Ch21-69 Ch14-69

(): SECAM

- 7 -

All the functions can be controlled with the remote control handset.

Some functions can also be adjusted with the buttons on the front

panel of the set.

Remote control handset

Before you use the remote control handset, please install the bat-

teries. See the next page.

1. POWER

switches the set on from standby or off to standby.

2. NUMBER BUTTONS

switches the set on from standby or directly select a number.

3. MENU (or INDEX)

selects a menu.

selects an index page in the teletext mode (only TELETEXT

models).

4. EYE/*(option)

switches the eye function on or off.

5. / (Programme Up/Down)

selects a programme or a menu item.

switches the set on from standby.

scans programmes automatically.

F / G (Volume Up/Down)

adjusts the volume.

adjusts menu settings.

accepts your selection or displays the current mode.

6. Q.VIEW

returns to the previously viewed programme.

selects a favorite programme.

7. TELETEXT BUTTONS (option)

These buttons are used for teletext.

For further details, see the ‘Teletext’ section.

8. PSM (Picture Status Memory)

recalls your preferred picture setting.

9. TURBO PICTURE / SOUND BUTTON (option)

selects Turbo picture and sound.

POWER

MENU/INDEX

Q.VIEW LIST

VOL VOL

231

564

897

TV/AV

I/II/

MUTE

TEXT/MIX

SIZE HOLD

UPDATE TIME REVEAL

PSM SSM/ SLEEP

EYE/

TURBO/

()

PICTURE SOUND

11 10

( )

(With TELETEXT)

DECRIPTIONS OF CONTROLS

- 8 -

10. MUTE

switches the sound on or off.

11. TV/AV

selects TV or AV mode.

clears the menu from the screen.

switches the set on from standby.

12. I/II/*(option)

selects the language during dual language broadcast. (option)

selects the sound output.

13. LIST

displays the programme table.

14. SLEEP

sets the sleep timer.

15. SSM/*(option) (Sound Status Memory)

recalls your preferred sound setting.

16. SURROUND (ºº/*) (option)

selects surround sound.

COLOURED BUTTONS : These buttons are used for teletext (only

TELETEXT models) or programme edit.

Battery installation

The remote control handset is powered by two AAA type batteries.

To load the batteries, turn the remote control handset over and

open the battery compartment. Install two batteries as indicated by

the polarity symbols ( and ) marked inside the compartment.

Note : To avoid damage from possible battery leakage, remove the

batteries if you do not plan to use the remote control handset for an

extended period of time.

POWER

Q.VIEW LIST

PR ( )

( )

VOL VOL

2 31

5 64

8 97

TV/AV

I/II/

MUTE

PSM SSM/ SLEEP

PICTURE SOUND

EYE/

TURBO/

11 10

(Without TELETEXT)

- 9 -

Front panel

Shown is a simplified representation of front or side panel.

Here shown may be somewhat different from your set.

1. MAIN POWER (ON/OFF)

switches the set on or off.

2. POWER/STANDBY INDICATOR

illuminates brightly when the set is in standby mode.

dims when the set is switched on.

blinks when signal is input from the remote control.

3. REMOTE CONTROL SENSOR

4. MENU

selects a menu.

5. OK

accepts your selection or displays the current mode.

FF/ GG(Volume Up/Down)

adjusts the volume.

adjusts menu settings.

DD/ EE(Programme Up/Down)

selects a programme or a menu item.

switches the set on from standby.

6. AUDIO/VIDEO IN SOCKETS (AV) (option)

Connect the audio/video out sockets of external equipment to

these sockets.

Note :If both the input jacks on the front/side panel and back

panel have been connected to external equipments simultane-

ously, only the input jacks on the front/side panel can be received.

7. HEADPHONE SOCKET (option)

Connect the headphone plug to this socket.

8. TURBO SOUND/PICTURE (option)

switches Turbo sound or Turbo picture on or off.

9. EYE (option)

adjusts picture according to the surrounding conditions.

! !

VIDEO

(L)

AUDIO

(R)

VIDEO

AUDIO

! !

VIDEO

(L)

AUDIO

(R)

VIDEO

AUDIO

ON/OFF rMENU OK F VOL GE PR DVIDEO (L)-AUDIO-(R) !P-TURBO-S

1 2 3 4 5 6 7 8 9

TURBO

ON/OFF rMENU OK F VOL GE PR DVIDEO AUDIO !SOUND PICTURE

1 2 3 4 5 6 7 8 9

1 2 3 4 5 9

PR D

ON/OFF rMENU F VOL VOLGOK

PR E

(Side panel)

- 10 -

Fig. 2-1 Fig. 2-2

CPT

board

Remove

Screws

Main

PCB

DISASSEMBLY INSTRUCTIONS

Important note

This set is disconnected from the power supply through the

converter transformer. An isolating transformer is necessary

for service operations on the primary side of the converter

transformer.

Back Cabinet Removal

Remove the screws residing on the back cabinet and carefully

separate the back cabinet from the front cabinet. (Fig. 2-1).

Chassis Assy Removal

Grasp both side of Frame and pull it backward smoothly.

CPT Removal

1. Pull out the CPT board from the CPT neck.

2. Place the front cabinet on soft material not to mar the front

surface or damage control knobs.

3. Remove 5 screws securing the picture tube mounting

brackets to the front cabinet.

4. Carefully separate CPT from the front cabinet.

PICTURE TUBE HANDLING CAUTION

Due to high vacuum and large surface area of picture tube, great

care must be exercised when handling picture tube. Always lift

picture tube by grasping it firmly around faceplate.

NEVER LIFT TUBE BY ITS NECK! The picture tube must not be

scratched or subjected to excessive pressure as fracture of

glass may result in an implosion of considerable violence which

can cause personal injury or property damage.

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