LG 21FD5 Schematic

Download

Page 1

COLOR TV SERVICE MANUAL

CHASSIS: CP-079B

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

Page 2

CONTENTS

Contents

Location & Function of control

Safety Precautions

Specifications

Adjustment

Block Diagram

R,G,B Section / Deflection Section

Audio AMP. Section

Exploded View

Exploded View Parts List

Replacement Parts List

Schematic Diagram

Page 3

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

4. EYE/ (option)

5. / (Programme Up/Down)

(Volume Up/Down)

OK accepts your selection or displays the current mode.

PSM

SSM/*

15 17

SLEEP

6. Q. VIEW

7. PSM (Picture Status Memory)

8. XDP (option)

9. MUTE

10. TV/AV

VOL

EYE/

11. I/II/ (option)

VOL

TV/AV

USB/*

FAV/X-SORT*

LIST/X-LIST*

Q-VIEW

XDS/* XDP

12. LIST/X-LIST* (option)

13. SLEEP

l/ll/*

14. SSM (option) (Sound Status Memory)

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)

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.

Page 4

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

0.15uF

Good Earth Ground such as WATER PIPE, CONDUIT etc.

Page 5

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.

Page 6

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.

Page 7

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.

Page 8

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

Page 9

Page 10

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.

Page 11

?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.

Page 12

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).

Page 13

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.

Page 14

MOVEMENT OF RED AND BLUE BEAMS

RING PAIRS

ROTATION DIRECTION OF BOTH TABS

POLE

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

OPPOSITE

SAME

OPPOSITE

SAME

B B

R R

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

GREEN

ADJUSTMENT

VIEWING

AREA

GREEN

RED

BLUE

RED

GREEN

RED

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.

Page 15

L402

W/O Woofer

IIC Bus Line

Option Part

CP79B BLOCK DIAGRAM

SMPS

TRANS

10.5V

IC806

(ST-5V REG)

IC803

(ST-3.3V REG)

ST-5V

ST-3.3V

P02A

(Pre amp/LED)

P13A

(Side Local Key)

P902A

(To CPT B/D)

P05A

(Eye Module)

(Side Local Key)

L OUT

(Front Local Key)

( ~016D )

IC804

(9V REG)

IC805

IC202

USB Module

IC602 TDA7297

(Sound Amp W/O Woofer)

(((

W/ Woofer

( ~ ????)

For SW

(5V REG)

R OUT

(

IC301 TDA4865A

46~44

IC1601

IC1602

V_DY

(Vertical Amp)

PWR

USB SW

KEY

R/G/B OUT

EYE

AUDIO L/R

(ADC)

CS5343

STA326

(D-class amp)

P620

Woofer Assy

IC501 UOC Top

(W/ Woofer)

Woofer

B+

V2 IN

P621

OUT

14V

SCL/SDA

49 51

Y/Pb/Pr

V1 IN

L/R IN

63 61

30 32

AV SW

IF IN

12 13

H_DY

-14V

VIF

Z111

FBT

200V

SAW

Pulse

Collector

28V

IC02

11 13

IC201 LA7958

ABL

AT24C16

EEPROM

(AV switching)

33V

Q401

IC302

USB

V1L1R1

2SC6090

KIA4558

OPT

L R

SDA

SCL

SDA

SCL

EW OUT

L401

Q302

KTD2059

Rear_AV DVD_In ( Y,Pb,Pr )

P210

P205

JA02

AV_Out (V,L,R)

AV_In (V,L,R)

& Video)

(USB Audio

(Side AV)

(Front AV)

Page 16

R,G,B SECTION

ABL CIRCUIT

IC 501

brightness

reduction

(2.5V)

contrast

reduction

(3.5V)

BEAM CURRENT

D510

R415

R408

R409

FBT T402

R411

B+

C420

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

H-OUT

R555

R556

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

H-DY

C496

FBT

Primary Winding

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

t1 t2t3t4 t5 t6

ts : scannig period

t1 : Q401 is switched on.

t1.t2

: Collector current of Q401 increases linearly.

i1 flows from C496 Which have been charged

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.

Page 17

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

Only for training and service purposes.

LGE Internal Use Only

Page 18

FR825

S-Vcc

IC602

C602

R608

SPEAKER

R606

SPEAKER

JACK

HEAD-PHONE

R605

Vref

C606

C605

R609

C601

IC603

9 8 133

R601

D824

J602

J605

C612

S-Gnd Pw-Gnd

Q621

J609

ST-5V

R604

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

MUTE

Not using.

Mute

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

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 NO

5,10,11

Page 19

fafag

Page 20

LGElectronics