LG RF-21FA20/Q/PQ, CF-21Q20EH Schematic

COLOR TV

SERVICE MANUAL

CAUTION

BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

CHASSIS : MC-014A

MODEL:RF-21FA20/Q/PQ

MODEL:CF-21Q20EH

website:http://biz.LGservice.com

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

- 2 -

CONTENTS

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

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

Specifications ..................................................................................................... 4

Control Descriptions ........................................................................................ 5

Disassembly Instructions ............................................................................. 8

Adjustment Instructions ............................................................................... 9

Trouble Shooting .............................................................................................. 12

Exploded View ............................................................................................ 16,18

Exploded View Parts List ........................................................................17,19

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 -

SPECIFICATIONS

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

O Video input system:

PAL-B/G, D/K, I/I SECAM-B/G, D/K NTSC 4.43(AV)

O Intermediate 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)

O Power requirement : 110~240V, 50/60Hz

O Power consumption : 95W

O CPT : True Flat CPT(Flatron)

O Tuning system :

FVS 100 Programme memory

Antenna input impedance : VHF/UHF 75 ohm, unbalanced

O OSD (On Screen Display) : WINDOW 3D Type

O Voice coil impedance : 8 ohm

O Sound output : 10W+10W(Max 12W+12W)

Dual/Stereo : AV Stereo

O External connection :

Head Phone Jack

A/V in :1 pair A/V in/out

O External In/Output

Audio-In:0.5Vrms±3db,over 10Kohm Audio-Out:0.5Vrms±3db,below 1Kohm Video-In/Out:1Vp-p±3db,75ohm

O Feature : Auto programme/Manual programme

Digital Eye Digital Comb Filter Auto Sleep Dynamic Focus(Option) Programme Editing PSM (Picture Status Memory) CTI Turbo Search, Picture & Sound ACMS ARC (Zoom 1, 16:9↔4:3) 2 TUNER PIP(Double Window PIP)-Option

O Tuning 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

Ch21-69

(

): SECAM

Front or

Side

Back

- 5 -

DESCRIPTION OF CONTROLS

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 batteries. See the next page.

1. POWER

switches the set on from standby or off to standby.

2. MUTE

switches the sound on or off.

3. ARC (Aspect Ratio Control)

changes the picture format.

4. TV/AV

selects TV or AV mode. clears the menu / text from the screen. switches the set on from standby.

5. EYE/

(option)

switches the eye function on or off.

6. TURBO PICTURE / SOUND BUTTON

selects Turbo picture / sound.

DD / EE

(Programme Up/Down)

selects a programme or a menu item. switches the set on from standby.

FF / GG (Volume Up/Down)

adjusts the volume. adjusts menu settings.

accepts your selection or displays the current mode.

8. NUMBER BUTTONS

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

9. PSM (Picture Status Memory)

recalls your preferred picture setting.

10. SSM (Sound Status Memory)

recalls your preferred sound setting.

11. VCR BUTTONS (option)

control a LG video cassette recorder.

LISTI/II

ARC

PIP/

TV/AV

PICTURE

SOUND

PSM

PLAY

REC REW P/STILL FF

STOP

SSM

POWER

MUTE

SLEEP

SWAP

INPUT

VOL

EYE/

T U R B O

1 2

(With / Without PIP)

- 6 -

12. I/II

selects the language during dual language broadcast (option). selects the sound output.

13. LIST

displays the programme table.

14. PIP BUTTONS (option) PIP/

switches the sub picture on or off.

PR +/

selects a programme for the sub picture.

SWAP

alternates between main and sub picture.

INPUT

selects the input mode for the sub picture.

SIZE

adjusts the sub picture size.

STILL

freezes motion of the sub picture.

POSITION

relocates the sub picture in clockwise direction.

9/4 PIP

switches on or off the programme scan mode through 9 or 4 sub pictures.

15. MENU

selects a menu.

16. SWAP or Q.VIEW

returns to the previously viewed programme.

17. SLEEP

sets the sleep timer.

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.

(Without PIP)

POWER

MUTE

TV/AV MENU

SSM

EYE

PSM

ARC

Q.VIEW

SLEEP

LIST

VOL VOL

SOUND

I/II

PICTURE

T U R B O

- 7 -

Front panel

1. MAIN POWER

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.

3. REMOTE CONTROL SENSOR

4. MENU

selects a menu.

5. TV/AV

selects TV or AV mode. clears the menu from the screen. switches the set on from standby.

6. (Function)

selects volume, EYE (option), picture items or brief auto programme while the menus not display.

7. OK

accepts your selection or displays the current mode.

DD / EE

(Programme Up/Down)

selects a programme or a menu item. switches the set on from standby.

FF / GG (Volume Down/Up)

adjusts the volume. adjusts menu settings.

8. +/- (

DD/EE

)

adjusts the function or selects a programme. switches the set on from standby.

9. AUDIO/VIDEO IN SOCKETS (AV2)

Connect the audio/video out sockets of external equipment to these sockets.

10.HEADPHONE SOCKET (option)

Connect the headphone plug to this socket.

11.EYE (option)

adjusts picture according to the surrounding conditions.

VIDEO

TV/AV

VOL

AUDIO

AV 2

L/MONO R

POWER

1 10 9 5 6 8 2 3 11

ON/Off

OK VOL PR

1 2 3 4 7 11

VIDEO L/MONO AUDIO R

AV2

RF-21FA20 series

CT-21Q21 series

- 8 -

Fig. 2-1

Fig. 2-2

CPT board

Remove Screws

PIP PCB

Main PCB

MPX 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.

Speaker Assy Removal

Remove P1651 and P1652 connector from Main2 (Power/Def./ Sound-Amp) Board.

2. Remove respective 6 screws for speaker on the front cabinet. (Fig. 2-2).

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 4 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.

IF PCB

Super W

oofer

PCB

- 9 -

X Safety Precautions

1. It is safe to adjust after using insulating transformer between

the power supply line and chassis input to prevent the risk of electric shock and protect the instrument.

2. Never disconnect leads while the TV receiver is on.

3. Don't short any portion of circuits while power is on.

4. The adjustment must be done by the correct appliances.

5. Unless otherwise noted, set the line voltage to 230Vac!10%,

50Hz.

6. The adjustment of TVshould be performed after warming up

for 15 minutes.

X Test Equipment required

1. RF signal generator (with pattern generator)

2. Multimeter (volt meter)

3. Color analyzer

RF AGC (Automatic Gain Control) Adjustment

1) Input PAL-B/G 05 CH.

2) Connect Multimeter to TP(J1),AGC adjustment point.

3) Adjust AGC data in SVC mode until the voltage of Multimeter

becomes 2.3!0.1V.

O Screen Voltage Adjustment

1) Tune the RF Modulator to receive a PAL or SECAM signal.

2) Press MIX button on remote controller for Service to get into

the Screen Adjust Mode.

3) Adhere the Color Analyzer on the White window of CPT

face.

4) Adjust Screen Volume of FBT so that the luminance of White

window is 50!1 FL(171 cd).

O Focus Adjustment

1) Tune the TV set to receive a digital pattern.

2) Adjust the upper Focus volume of FBT for the best focus of

vertical line B.

3) Adjust the lower Focus volume of FBT for the best focus of

area A.

4) Repeat above step 2) and 3) for the best overall focus.

O Deflection Data Adjustment (Line SVC-2)

NOTE : How to enter into the Line Service Mode with a remocon.

1.Power off.

2.Press the Red button.

3.Press the Green button.

4.Press the Yellow button.

5.Press the Cyan button.

6.Press the OK button.

7.Power On.

1. Preparation for Deflection Adjustment

1) Tune the TV set to receive a PAL B/G Digital pattern.

2) At SVC mode, press the Yellow colored buttonon the SVC remocon. And then,deflection data adjustment OSD(SVC2 mode) will be displayed.

3) Press Channel UP/DOWN button for desirous function Adjustment.

4) Press Volume UP/DOWN button to adjust the data.

VL (Vertical Linearity)

Adjust so that the boundary line between upper and lower half is in accord with geometric horizontal center of the CPT.

VA (Vertical Amplitude)

Adjust so that the circle of a digital circle pattern may be located within the effective screen of the CPT.

SC (Vertical “S” Correction)

Adjust so that all distance between each horizontal lines are to be the same.

VS (Vertical Shift)

Adjust so that the horizontal center line of a digital circle pattern is in accord with geometric horizontal center of the CPT.

HS (Horizontal Shift)

Adjust so that the vertical center line of a digital circle pattern is in accord with geometric vertical center of the CPT.

ADJUSTMENT INSTRUCTIONS

Test Point : AGC TP(J1)

Adjust : AGC Data(Line SVC-1)

Test Point : CPT Face

Adjust : Screen Control of FBT

Test Point : Observing Display

Adjust : Focus control of FBT

Fig. 1

+ 21 hidden pages