LG 21FD5 Schematic

COLOR TV
SERVICE MANUAL

CHASSIS: CP-079B

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

CONTENTS

Contents

Location & Function of control

Safety Precautions

Specifications

Adjustment

Block Diagram

R,G,B Section / Deflection Section

Audio AMP. Section

Exploded View

2

3

4

7

9

15

16

17

18

Exploded View Parts List

Replacement Parts List

Schematic Diagram

19

20

2

1

19

18

13

5

10

21

16

Location and function 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
previous page.

1. POWER

switches the set from On to standby or standby to On.

2. NUMBER BUTTONS

switches the set On from standby or directly select a Programme number.

3. MENU

selects a menu.

POWER

MUTE

9

1

4

2

7

3

2

6

5

9

8

4. EYE/ (option)

5. / (Programme Up/Down)

(Volume Up/Down)

OK accepts your selection or displays the current mode.

PSM

7

C

I

/

E

S

Q

U

*

M

W

/

O

S

O

E

I

V

O

M

SSM/*

0

M

A

R

D

S

/

M

W

M

E

N

F

E

R

*

14

A

/

A

R

C

15
17

SLEEP

MENU

3

6. Q. VIEW

7. PSM (Picture Status Memory)

8. XDP (option)

9. MUTE

PR

10. TV/AV

VOL

OK

VOL

EYE/

11. I/II/ (option)

*

VOL

VOL

TV/AV

PR

4

USB/*

FAV/X-SORT*

LIST/X-LIST*

Q-VIEW

XDS/* XDP

12

6

12. LIST/X-LIST* (option)

13. SLEEP

8

l/ll/*

20

14. SSM (option) (Sound Status Memory)

11

15. ARC (option)

16. FAVOURITE (OPTION) / X-SORT (option)

17. MM (option)
select music mode.

18. Woofer
direct access key for woofer on/off.

19. EQ/* (option)
direct access key to select EQ (Graphics Equalizer).

20. XDS/*
selects excellent digital surround.

21. USB/* (option)
to enter into USB mode.

*

switches the eye function On or Off.

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

adjusts the volume.
adjusts menu settings.

returns to the previously viewed programme.

recalls your preferred picture setting.

Select Excellent Digital Picture.

switches the sound On or Off.

selects TV or AV mode.
switches the set On from Standby.

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

displays the programme table. press LIST key again to clear the LIST table from
the screen.

sets the sleep timer.

recalls your preferred sound setting.

change picture format (Normal/Zoom).

pressing each time this button will select a stored favourite programme. X-SORT
switches X- SORT (option) On/Off.

(option)

(option)

COLOURED BUTTONS : When Menu is On some of these buttons are used

for programme edit.

Remarks : 1. Some keys in remote can be non-functional, these keys are used in

other models. 2. Keys marked * are non functional.

# Remote Design / Aesthetic may vary from model to model.

3

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

General Guidance

An 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 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 l0mm 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:

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.

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 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 1MW and 5.2MW.

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.

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 .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.

Leakage Current Hot Check circuit

AC Volt - meter

To Instrument's
exposed
METALLIC PARTS

1.5 Kohm10W

4

0.15uF

Good Earth Ground
such as WATER PIPE,
CONDUIT etc.

SERVICING PRECAUTIONS

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.

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 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.

9. 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
500º F to 600º 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. (500º F

to 600º 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 (500º F

to 600º F)

b.First, hold the soldering iron tip and solder the strand against the

component lead the solder melts.

5

c. OuIckly 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.

?Video input system:

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

SECAM -B/G, D/K,L/L**
NTSC M **
NTSC 4.43**

? Intermediate Frequency (Unit : Mhz)

VISION IF : 38.9MHz

35.32MHz(3.58) : NTSC-M

COLOR IF : 34.47MHz(4.43)

VIF-4.25000 MHz

( )

V I F-4.40625MHz**

: SECAM**

? Tuning range

SOUND IF : 33.4MHz (B/G)

?Power requirement : 110 240V, 50/60Hz

? Power consumption :

? STAND-BY : <6W

32.9MHz (I/I)

32.4MHz (D/K)

34.4MHz (M)

~

*

Band

B/G

D/K

I/I

NTSC

VHF-Low Ch2-4 Ch1-5

Ch4-13

For TV

VHF-High

Ch5-12

Ch6-12

Ch2-13

Hyper

UHF

?Tuning system : ?Feature :Auto programme /Manual programme

FVS Auto Sleep
100 Programme memory (option) PSM (Picture Status Memory)
200 Programme memory(W/0 TXT) Programme Editing

?Antenna input impedance : VHF/UHF 75 ohm, unbalanced SSM (Sound Status Memory)

?OSD (On Screen Display) : EASY_MENU XDP*

?Voice coil impedance : 8 ohm

?Sound output :

Dual/Stereo : A2/NICAM(Option)

*

Chl4-69 Ch21-69

Auto Volume Level

Favourite Program

For CATV

S1'-S3', S1

S2-S10,

S11-S20

S21-S41

?External connection : Head Phone Jack

A/V in : 2
PERI Connector(Full Scart) :1 (option)
DVD in (option)

?External In/Output

Audio-In:O.5Vrms±3dB, over 10Kohm
Audio-Out:0.5Vrms±3dBb,below 1Kohm

Video-In/Out:1Vp-p±3d8, 75ohm
DVD In Y: 1Vp-p±3dB

Pb,Pr : 0.7Vp-p±3dB

*Depend on model.
** For Export model.

7

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

Removal the screws residing on the back cabinet and carefully
separate the back cabinet from the front cabinet cabinet. (Fig. 2-1).

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.

Chassis Assy Removal

Grasp both side of Frame and pull it backward smoothly.

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.

Remove
Screws

CPT

board

Main
PCB

8

AUTOMETIC GAIN CONTROL ( AGC )

ADJUSTMENT (LINE SVC-1)

Test Point :AGC TP (C102)
Adjust :Remote Controller

White Balance Adjustment.(LINE SVC-0)

NOTE : This adjustment should be performed after screen
voltage adjustment.

1 Adjustment preparation

1.1 Put PAL-B/G 05CH with 70dB±1 dB Signal to Tuner.

Connect Multi-meter cable to AGC check point (J125).

2 Adjustment

2.1 Select SVC-1 Mode by SVC Key on the SVC Remote-

con (or Press same time Normal Remote- Controller

OK Key and TV pannel OK Key).

2.2 After select AGC -- by CH UP/DOWN (/) Key, Adjust

voltage of Multi-meter as below [Table 6] by VOL

UP/DOWN(/)Key.

FOCUS Adjustment

Test Point : Observing Display
Adjust : Focus Volume of FBT

1)Tune the TV set to receive an 100% white pattern.

2)Press OK buttons on TV set and remote controller at
the same time to get into SVC mode.

3) Use the CH CH Key to chose adjustment item.

4) Use the VOL VOL Key to change item data.

5) Adjustment.

a)Make the picture luminance 4.5 changing the

" CONTRAST" and "BRIGHTNESS".

b)Adjust X data of low light with BLO-R and Y data with

BLO-B.

c)Adjust X dada of High light RG and Y data with BG.
d) Repeat steps b~c until both low & high light hare same

readings as shown below.

1 )Tune the TV set to receive a PAL OSCH.

2)Adjust the Focus Volume of FBT for best focus.

Screen voltage Adjustment

Test Point : Rk ( Red cathode of CPT board)
Adjust : Screen volume of FBT

1) Screen Voltage Adjustment. To readjust, Press “Instart”
key and then “Adj” key of SVC remocon.

2) A thin horizontal line will appear on screen, the brightness
of which changes with the screen knob of FBT.

3) Adjust screen knob of FBT, till thin line becomes just
visible. Press TV/AV to exit.

6) Press the OK button to memorize the data.

10

?Deflection Data Adjustment (Line SVC-1 )

NOTE: To enter SVC mode, press "OK" buttons on both TV set

and the Remote control at the same time.

1.Preparation for Deflection Adjustment

1 ) At SVC mode, press the "IN- START" key.

And then, deflection data adjustment OSD (SVC1 mode)
will be displayed.

2) Tune the TV set to receive a PAL 05 CH and set the ARC
mode is standard.

DEFLECTION DATA ADJUSTMENT (SVC-2)

1 Adjustment Preparation

1.1. Select SVC-2 Mode by IN-START key.

1.2. Receive PAL-B/G 05 CH.(LG standard Pattern) on TV( in case of
LG TV production system)

* If not available LG Standard Digital Signal then Put

Crosshatch Pattern with Circle to TV set.

(Example: Cross-hatch + Circle)

3. Deflection Adjustment Procedure

1) At adjustment mode (IN-START button on SVC remote control),
changed to LINE SVC 2 mode to Adjust the deflection.

2) Press Channel UP/DOWN button for desired function
Adjustment.

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

4) Tune the TV set to receive a Digital pattern. (PAL:05CH)

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.

Press the OK button to memorize the data.

11

PURITY & CONVERGENCE ADJUSTMENT

Caution:

Convergence and Purity have been factory aligned. Do not attempt to
tamper with these alignments.

However, the effects of adjacent receiver components, or
replacement of picture tube or deffection yoke may require the need
to readjust purity any convergence.

DEFLECTION YPKE

PURITY%CONVERGENCE
MAGNET ASSEMBLY

6-POLE

X-AXISYOKE MAGNET
POSITIONING
(L/R PURITY)

RUBBER
WEDGES

PURITY MAGNET

4-POLE

GLASS CLOTH TAPE

5. Reconnect the internal degaussing coil.

6. Position the beam bender locking rings at the 9 o'clock position
and the other three pairs of tabs (2,4 and 6 pole magnets) at the
12 o'clock position.

6-POLE
MAGNETS

4-POLE

CONVERGENCE MAGNET ASSEMBLY

PURITY MAGNET(2-POLE)

? Purity Adjustment

This procedure DOES NOT apply to bonded yoke and picture tube
assemblies.

The instrument should be at room temperature (60 degress F or
above) for six (6) hours and be operating at low beam current (dark
background) for approximately 20 to 30 minutes before performing
purity adjustments.

CAUTION: Do not remove any trim magnets that may be attached

to the bell of the picture tube.

1. Remove the AC power and disconnect the internal degaussing
coil.

2. Remove the yoke from the neck of the picture tube.

3. If the yoke has the tape version beam bender, remove it and
replace it with a adjustable type beam bender (follow the
instructions provided with the new beam bender)

4. Replace the yoke on the picture tube neck, temporarily remove
the three (3) rubber wedges from the bell of the picture tube and
then slide the yoke completely forward.

7. Perform the following steps, in the order given, to prepare the
receiver for the purity adjustment procedure.

a.Face the receiver in the "magnetic north" direction.

b.Externally dsgauss the receiver screen with the television

power turned off.

c.Turn the television on for approximately 10 seconds to perform

internal degaussing and then turn the TV off.

d. Unplug the internal degaussing coil. This allows the thermistor

to cool down while you are performing the purity adjustment.
DO NOT MOVE THE RECEIVER FROM ITS "MAGNETIC
NORTH" POSITION.

e.Turn the receiver on and obtain a red raster by increasing the

red bias control (CW) and decreasing the bias controls for the
remaining two colors (CCW).

f. Attach two round magnets on the picture tube screen at 3

o'clock and 9 o'clock positions, approximately one (1 ) inch from
the edge of the mask (use double-sided tape).

12

1.ADJUST YOKE Z-AXIS FIRST
TO GET EQUAL BLUE
COLOR CIRCLES

MAGNETS

1.ADJUST BEAM BENDER 2 POLE
MAGNET TO GET FOUR EQUAL
COLOR CIRCLES

RED

8. Referring to above, perform the following two steps:
a. Adjust the yoke Z-axis to obtain equal blue circles.
b. Adjust the appropriate beam bender tabs to obtain correct purity

(four equal circles).

9. After correct purity is set, tighten the yoke clamp screw and
remove the two screen magnets.

10. Remove the AC power and rotate the receiver 180 degrees
(facing "magnetic south").

11. Reconnect the internal degaussing coil.

12. Turn the receiver on for 10 seconds (make sure the receiver
came on) to perform internal degaussing, and then turn the
receiver off.

13. Unplug the internal degaussing coil.

14. Turn on the receiver and check the purity by holding one (1)
round magnet at the 3 o'clock and a second round magnet at 9
o'clock position. If purity is not satisfactory, repeat steps 8
through 14.

15. Turn off the receiver and reconnect the internal degaussing coil.&

? Convergence Adjustment

Caution: This procedure DOES NOT apply to bonded yoke and

picture tube assemblies.
Do not use screen magnets during this adjustment

procedure. Use of screen magnets will cause an incorrect
display.

1. Remove AC power and disconnect the internal degaussing coil.

2. Apply AC Power and set the brightness to the Picture Reset
condition. Set the Color control to minimum.

3. Make a horizontal line.

4. Adjust the Red, Green and Blue Bias controls to get a dim white
line.

RED

6. Reconnect the internal degaussing coil and apply AC power.

7. Turn he receiver on for 10 seconds to perform internal
degaussing and then turn the receiver off again.

8. Unplug the internal degaussing-coil.

9. Turn on the receiver, connect a signal generator to the VHF
antenna terminal and apply a crosshatch signal.

Caution: During the convergence adjustment procedure, be very

careful not to disturb the purity adjustment tabs are
accidentally move, purity should be confirmed before
proceeding with the convergence adjustments.

Note: Make sure the focus is set correctly on this instrument

before proceeding with the following adjustment.

10.Converge the red and blue vertical lines to the green vertical line

at the center of the screen by performing the following steps
(below TABLE).

a.Carefully rotate both tabs of the 4-pole ring magnet

simultaneously in opposite directions from the 12 o'clock
position to converge the red and blue vertical lines.

b.Carefully rotate both tabs of the 6-pole ring magnet

simultaneously in opposite directions form the 12 o'clock
position to converge the red and blue (now purple)
vertical lines with the green vertical line.

11. Converge the red and blue horizontal with the green line at the

center of the screen by performing the following steps. (below
TABLE)

a.Carefully rotate both tabs of the 4-pole ring magnet

simultaneously in the same direction (keep the spacing
between the two tabs the same) to converge the red and
blue horizontal lines.

b.Carefully rotate both tabs of the 6-pole ring magnet

simultaneously in same direction (keep the spacing
between the two tabs the same) to converge the red and
blue (nowpurple) horizontal lines with the green
horizontal line.

c. Secure the tabs previsouly adjusted by locking them in

place with the locking tabs on the beam bender.

5. Restore the screen by removing the horizontal line.

13

MOVEMENT OF RED
AND BLUE BEAMS

RING
PAIRS

ROTATION DIRECTION
OF BOTH TABS

4

POLE

6

POLE

UP/DOWN ROCKING OF THE YOKE
CAUSES OPPOSITE ROTATION OF RED
AND BLUE RASTERS

OPPOSITE

SAME

OPPOSITE

SAME

B

B

OR

R

R

B

OR

R

R

B

B B

OR

R R

R

B

LEFT/RIGHT ROCKING OF THE YOKE
CAUSES OPPOSITE SIZE CHANGE OF THE
RED AND BLUE RASTERS

OR

R

B

GREEN

ADJUSTMENT

VIEWING

AREA

GREEN

RED

BLUE

BLUE

RED

GREEN

RED

BLUE

BLUE

RED

GREEN

12. While watching the 6 o'clock positions on the screen, rock the
front of the yoke in a vertical (up/down) direction to converge the
red and blue vertical lines. (Fig upper left)

13. Temporarily place a rubber wedge at the 12 o'clock position to
hold the vertical position or the yoke.

14. Check the 3 o'clock and 9 o'clock areas to confirm that the red
and blue horizontal lines are converged.

If the lines are not converged, slightly offset the vertical tilt of the
yoke (move the rubber wedge if necessary) to equally balance
the convergence error of the horizontal tines at 3 o'clock and 9
o'clock and the vertical lines at 6 o'clock and 12 o'clock.

15. Place a 1.5 inch piece of glass tape over the rubber foot at the
rear of the 12 o'clock wedge.

16. While watching the 6 o'clock and 12 o'clock areas of the screen,
rock the front of the yoke in the horizontal (left to right) motion to
converge the red and blue horizontal lines. (Fig. upper right)

ADJUSTMENT

VIEWING

AREA

RED

BLUE

GREEN

RED

TV
SCREEN

17. Temporarily place a rubber wedge at the 5 o'clock and 7 o'clock
positions to hold the horizontal position of the yoke.

18. Check the 3 o'clock and 9 o' clock areas to confirm that the red
and blue vertical lines are converged. If the lines are not
converged, slightly offset the horizontal tilt of the yoke (move the
temporary rubber wedges if necessary) to equally balance the
convergence error of the horizontal lines at 6 o'clock and 12
o'clock and the vertical lines at 3 o'clock and 9 o'clock.

19. Using a round magnet confirm purity at the center, right and left
sides and corners. See Purity Adjustment Procedure.

20. Reconfirm convergence and apply a 1.5 inch piece of glass tape
over the rubber toot at the rear of the 5 o'clock and the 7 o'clock
wedges.

14

L402

W/O Woofer

IIC Bus Line

Option Part

CP79B BLOCK DIAGRAM

CP79B BLOCK DIAGRAM

SMPS

TRANS

10.5V

14

IC806

(ST-5V REG)

IC803

(ST-3.3V REG)

ST-5V

ST-3.3V

P02A

P02A

(Pre amp/LED)

(Pre amp/LED)

P13A

P13A

(Side Local Key)

P902A

(To CPT B/D)

P05A

P05A

(Eye Module)

(Eye Module)

(Side Local Key)

L OUT

(Front Local Key)

( ~016D )

IC804

(9V REG)

IC805

9V

5V

IC202

IC202

USB Module

USB Module

IC602 TDA7297

IC602 TDA7297

(Sound Amp W/O Woofer)

(Sound Amp W/O Woofer)

(((

(((

W/ Woofer

( ~ ????)

For SW

(5V REG)

R OUT

(

(

IC301 TDA4865A

7

37

39

29

27

46~44

28

IC1601

IC1601

IC1602

IC1602

V_DY

4

1

(Vertical Amp)

6

14

VA

PWR

IR

USB SW

KEY

R/G/B OUT

EYE

AUDIO L/R

58

(ADC)

(ADC)

CS5343

CS5343

STA326

STA326

(D-class amp)

(D-class amp)

15

VB

59

P620

Woofer Assy

IC501 UOC Top

IC501 UOC Top

(W/ Woofer)

Woofer

B+

2

16

EW

V2 IN

P621

OUT

14V

3

34

SCL/SDA

49 51

Y/Pb/Pr

50

62

V1 IN

L/R IN

63 61

30 32

AV SW

64

IF IN

12 13

35

H_DY

-14V

4

VIF

Z111

Z111

FBT

200V

5

V2

SAW

SAW

1

Pulse

7

Collector

28V

8

IC02

16

11 13

IC201 LA7958

IC201 LA7958

2

L2

IF

IF

ABL

9

6

AT24C16

EEPROM

7

41

63

(AV switching)

(AV switching)

12

5

R2

5V

5V

33V

33V

Q401

HD

8

IC302

USB

V1L1R1

2SC6090

2

1

KIA4558

OPT

L R

V

SDA

SCL

SDA

SCL

EW OUT

L401

Q302

KTD2059

Rear_AV DVD_In ( Y,Pb,Pr )

P210

P210

P205

P205

JA02

JA02

AV_Out (V,L,R)

AV_In (V,L,R)

& Video)

& Video)

(USB Audio

(USB Audio

(Side AV)

(Side AV)

(Front AV)

(Front AV)

15

R,G,B SECTION

R,G,B SECTION

ABL CIRCUIT

IC 501

brightness

reduction

(2.5V)

contrast

reduction

(3.5V)

BEAM CURRENT

48

D510

R415

R408

A

R409

FBT
T402

R411

B+

C420

9

ABL

To protect the picture tube and FBT,the average beam current an d peak beam current may not to high.

The beam current limit information and High Voltage(H.V) tracking information are derived from

the H.V voltage winding of T401 (point A).

1. The contrast and brightness reduction of RGB is proportional to the voltage on the pin 48 of IC501.

2. As the beam current(slow),and H.V (fast) are changes, the voltage of point A is changed.

3. By the increase of beam current ,the point A voltage is decreased and this information is fed to pin 48 of IC501.

- Contrast reduction begins when V49 is below than 3.1V.

- By the more increasing of the beam current , the V48 decreased and eventually when this voltage is less than

1.8V the brightness reduction is started.

Deflection SECTION

HORIZONTAL DRIVE CIRCUIT

IC501

56

H-OUT

R555

R556

5V

J546

J405

H.Vcc

R421C401

Q442

C2231Y

D403

C402

Q402

R403

C403

T401
HDT

Q401

R407

i1(t1.t2)

i2(t2.t3)

i4(t4.t5)

FB401

i3(t3.t4)

C405

CT

H-DY

C496

CS

FBT

i5

1

Primary
Winding

2

B+

110V

1. The H drive output is open collector and active low,
I.e. the H-out TR should conduct during the low period
of output.

2. Under normal operation condition the duty cycle of the

output pulse is 50%.

3. To ensure a smooth start/stop behavior of the horizontal

deflection and protect the H-out TR, there are 3 different
condition of H-drive output.

During switch-on.
The horizontal output starts with the double frequency
(31KHz) and with duty of 75%(off),25%(on).

After about 50mSec of switch-on.
The frequency is changed to normal value(15.625KHz)
and duty cycle to 50%.

During switching-off.

Also the frequency is switched to the double value and
R.G.B drive is set to Max. and after 100mSec R.G.B

is set to Min. and 50mSec later the H drive is switch-off.

4. The H drive pulse from the MICOM (IC 501)
horizontal drive circuit,to get sufficient base drive current
for the high voltage switching TR(Q401).

is amplified by the

VB of Q401

Collector

Current

of Q401

The Voltage

at H-DY

The current

of resonant

Capacitor

(C405)

DAMP

current

Deflection
current of

H-DY

tr : retrace period

16

t1 t2t3t4 t5 t6

i2

i1

i3

i4

ts : scannig period

t1 : Q401 is switched on.

t

t1.t2

: Collector current of Q401 increases linearly.

i1 flows from C496 Which have been charged

t

at the end of first half of scan.
i5 also flows, energy stored in the primary
winding(.) ) of FBT.

t2 : Q401 is switched off abruptly.

t2.t3

: Reverse EMF of H-DY maintains i1 direction

and charges C405.
Reverse EMF of the FBT primary occurs to
maintain is direction.

t3 : Q401 is still off.

t3.t4

: C405 discharges through H-DY.

t4.t5

: H-DY attempts to maintain i3 direction.

Damping diode becomes forward biased
and C496 is charged.

EXPLODED VIEW

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 EXPLODED VIEW.
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.

913

170

150

112

400

300

500

P801

120

LG Electronics. All right reserved.

Only for training and service purposes.

LGE Internal Use Only

'

FR825

S-Vcc

IC602

C602

R608

SPEAKER

1

_

+

4

R606

SPEAKER

JACK

HEAD-PHONE

2

+

_

7

R605

Vref

12

15

+

_

C606

C605

R609

_

6

C601

31

IC603

14

+

9 8 133

2

R601

D824

J602

J605

C612

S-Gnd Pw-Gnd

Q621

J609

ST-5V

R604

59

58

L SPK OUT

R SPK OUT

R602

R603

ZD601

9.1V

ROLE DESCRIPTION

Output 1+

Output 1-

U.O.C

MICOM

Supply Voltage

Audio Input 1t

Vcc

In1

J557

38

MUTE

Not using.

Mute

Nc

CIRCUIT ANALYSIS

Power Ground

St-by

Pw-Gnd

through R604,R608[Input level adjust] and C602,C606[AC coupling].

- Audio signal from the PIN 58, 59 of IC501 are applied to PIN4,12

• R601 is to mute during ST-BY mode.

• IC603,Q621 is for muting during the set is on.

Signal Ground

Audio input 2

Supply Voltage

S-Gnd

In2

Vcc

• ZD601/ R602 is to drop the input voltage IC603.

Output 2-

Output 2+

TDA7297

TDA7297

AUDIO AMP. SECTION

TDA7297

15+15W DUAL BRIDGE AMPLIFIER

FEATURES :

MINIMUM EXTERNAL COMPONENTS

INTERNALLY FIXED GAIN

STAND-BY & MUTE FUNCTIONS

WIDE SUPPLY VOLTAGE RANGE (6.5V-18V)

•••••

THERMAL OVERLOAD PROTECTION

SHORT CIRCUIT PROTECTION

•

Pin descriptions of TDA7297

Pin descriptions of TDA7297

17

1

Pin NO

2

3

4

6

7

8

5,10,11

9

12

13

14

15

fafag

LGElectronics