SAMSUNG TXM2756X-XAA, TXM2556X-XAA, CT29F6SWX-XAO, CT26F6SWX-XAO, CT29F6SWX-XAP Service Manual

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COLOR TELEVISION RECEIVER

Chassis : K15C Model : TXM2756X/XAA TXM2556X/XAA

CT29F6SWX/XAO CT26F6SWX/XAO CT29F6SWX/XAP CT26F6SWX/XAP

COLOR TELEVISION RECEIVER CONTENTS

Precautions

Specifications and IC Data

Disassembly and Reassembly

Alignment and Adjustment

Troubleshooting

Exploded View and Parts List

Electrical Parts List

Block Diagram

Wiring Diagram

Schematic Diagrams

10.

ELECTRONICS

Printed in Korea

AA81-

1. Precautions

1-1 Safety Precautions

1. Be sure that all of the built-in protective devices are replaced. Restore any missing protective shields.

2. When reinstalling the chassis and its assemblies, be sure to restore all protective devices, including: nonmetallic control knobs and compartment covers.

3. Make sure that there are no cabinet openings through which people—particularly children—might insert fingers and contact dangerous voltages. Such openings include the spacing between the picture tube and the cabinet mask, excessively wide cabinet

ventilation slots, and improperly fitted back

covers.

If the measured resistance is less than 1.0 megohm or greater than 5.2 megohms, an abnormality exists that must be corrected before the unit is returned to the customer.

4. Leakage Current Hot Check (Figure 1-1): Warning: Do not use an isolation transformer during this test. Use a leakagecurrent tester or a metering system that complies with American National Standards Institute (ANIS C101.1, Leakage Current for Appliances), and Underwriters Laboratories (UL Publication UL1410, 59.7).

5. With the unit completely reassembled, plug the AC line cord directly into the power outlet. With the unit’s AC switch first in the ON position and then OFF, measure the current between a known earth ground (metal water pipe, conduit, etc.) and all exposed metal parts, including: antennas, handle brackets, metal cabinets, screwheads and control shafts. The current measured should not exceed 0.5 milliamp. Reverse the powerplug prongs in the AC outlet and repeat the test.

Fig. 1-1 AC Leakage Test

6. Antenna Cold Check: With the unit’s AC plug disconnected from the AC source, connect an electrical jumper across the two AC prongs. Connect one lead of the ohmmeter to an AC prong. Connect the other lead to the coaxial connector.

7. X-ray Limits: The picture tube is especially designed to prohibit X-ray emissions. To ensure continued X-ray protection, replace the picture tube only with one that is the same type as the original. Carefully reinstall the picture tube shields and mounting hardware; these also provide X-ray protection.

8. High Voltage Limits: High voltage must be measured each time servicing is done on the B+, horizontal deflection or high voltage circuits. Correct operation of the X-ray protection circuits must be reconfirmed whenever they are serviced.

(X-ray protection circuits also may be called

“horizontal disable” or “hold-down”.)

Heed the high voltage limits. These include the X–ray Protection Specifications Label, and the Product Safety and X-ray Warning Note on the service data schematic.

Precautions

1-1

LEAKAGE CURRENT

TESTER

DEVICE UNDER

TEST

TEST ALL

EXPOSED METAL

SURFACES

2-WIRE CORD

ALSO TEST WITH

PLUG REVERSED

(USING AC ADAPTER

PLUG AS REQUIRED)

EARTH

GROUND

(READING SHOULD

NOT BE ABOVE

0.5mA)

Follow these safety, servicing and ESD precautions to prevent damage and protect against potential hazards such as electrical shock and X-rays.

1-1 Safety Precautions (Continued)

9. High voltage is maintained within specified limits by close-tolerance, safety-related components and adjustments. If the high voltage exceeds the specified limits, check each of the special components.

10. Design Alteration Warning: Never alter or add to the mechanical or electrical design of this unit. Example: Do not add auxiliary audio or video connectors. Such alterations might create a safety hazard. Also, any design changes or additions will void the manufacturer’s warranty.

11. Hot Chassis Warning: Some TV receiver chassis are electrically connected directly to one conductor of the AC power cord. If an isolation transformer is not used, these units may be safely serviced only if the AC power plug is inserted so that the chassis is connected to the ground side of the AC source.

To confirm that the AC power plug is inserted correctly, do the following: Using an AC voltmeter, measure the voltage between the chassis and a known earth ground. If the reading is greater than 1.0V, remove the AC power plug, reverse its polarity and reinsert. Re-measure the voltage between the chassis and ground.

12. Some TV chassis are designed to operate with 85 volts AC between chassis and ground, regardless of the AC plug polarity. These units can be safely serviced only if an isolation transformer inserted between the receiver and the power source.

13. Some TV chassis have a secondary ground system in addition to the main chassis ground. This secondary ground system is not isolated from the AC power line. The two ground systems are electrically separated by insulating material that must not be defeated or altered.

14. Components, parts and wiring that appear to have overheated or that are otherwise damaged should be replaced with parts that meet the original specifications. Always determine the cause of damage or overheating, and correct any potential hazards.

15. Observe the original lead dress, especially near the following areas: Antenna wiring, sharp edges, and especially the AC and high voltage power supplies. Always inspect for pinched, out-of-place, or frayed wiring. Do not change the spacing between components and the printed circuit board. Check the AC power cord for damage. Make sure that leads and components do not touch thermally hot parts.

16. Picture Tube Implosion Warning: The picture tube in this receiver employs “integral implosion” protection. To ensure continued implosion protection, make sure that the replacement picture tube is the same as the original.

17. Do not remove, install or handle the picture tube without first putting on shatterproof goggles equipped with side shields. Never handle the picture tube by its neck. Some “in-line” picture tubes are equipped with a permanently attached deflection yoke; do not try to remove such “permanently attached” yokes from the picture tube.

18. Product Safety Notice: Some electrical and mechanical parts have special safety-related characteristics which might not be obvious from visual inspection. These safety features and the protection they give might be lost if the replacement component differs from the original—even if the replacement is rated for higher voltage, wattage, etc.

Components that are critical for safety are indicated in the circuit diagram by shading, ( ) or ( ).

Use replacement components that have the same ratings, especially for flame resistance and dielectric strength specifications. A replacement part that does not have the same safety characteristics as the original might create shock, fire or other hazards.

Precautions

1-2 Samsung Electronics

1-2 Servicing Precautions

1. Servicing precautions are printed on the cabinet. Follow them.

2. Always unplug the unit’s AC power cord from the AC power source before attempting to: (a) Remove or reinstall any component or assembly, (b) Disconnect an electrical plug or connector, (c) Connect a test component in parallel with an electrolytic capacitor.

3. Some components are raised above the printed circuit board for safety. An insulation tube or tape is sometimes used. The internal wiring is sometimes clamped to prevent contact with thermally hot components. Reinstall all such elements to their original position.

4. After servicing, always check that the screws, components and wiring have been correctly reinstalled. Make sure that the portion around the serviced part has not been damaged.

5. Check the insulation between the blades of the AC plug and accessible conductive parts (examples: metal panels, input terminals and earphone jacks).

6. Insulation Checking Procedure: Disconnect the power cord from the AC source and turn the power switch ON. Connect an insulation resistance meter (500V) to the blades of the AC plug.

The insulation resistance between each blade of the AC plug and accessible conductive parts (see above) should be greater than 1 megohm.

7. Never defeat any of the B+ voltage interlocks. Do not apply AC power to the unit (or any of its assemblies) unless all solid-state heat sinks are correctly installed.

8. Always connect a test instrument’s ground lead to the instrument chassis ground before connecting the positive lead; always remove the instrument’s ground lead last.

Precautions

1-3

Warning1: First read the “Safety Precautions” section of this manual. If some unforeseen circumstance creates a conflict between

the servicing and safety precautions, always follow the safety precautions.

Warning2: An electrolytic capacitor installed with the wrong polarity might explode.

1. Some semiconductor (“solid state”) devices are easily damaged by static electricity. Such components are called Electrostatically Sensitive Devices (ESDs); examples include integrated circuits and some field-effect transistors. The following techniques will reduce the occurrence of component damage caused by static electricity.

2. Immediately before handling any semicon ductor components or assemblies, drain the electrostatic charge from your body by touching a known earth ground. Alternatively, wear a discharging wrist-strap device. (Be sure to remove it prior to applying power— this is an electric shock precaution.)

3. After removing an ESD-equipped assembly, place it on a conductive surface such as aluminum foil to prevent accumulation of electrostatic charge.

4. Do not use freon-propelled chemicals. These can generate electrical charges that damage ESDs.

5. Use only a grounded-tip soldering iron when soldering or unsoldering ESDs.

6. Use only an anti-static solder removal device. Many solder removal devices are not rated as “anti-static”; these can accumulate sufficient electrical charge to damage ESDs.

7. Do not remove a replacement ESD from its protective package until you are ready to install it. Most replacement ESDs are packaged with leads that are electrically shorted together by conductive foam, aluminum foil or other conductive materials.

8. Immediately before removing the protective material from the leads of a replacement ESD, touch the protective material to the chassis or circuit assembly into which the device will be installed.

9. Minimize body motions when handling unpackaged replacement ESDs. Motions such as brushing clothes together, or lifting a foot from a carpeted floor can generate enough static electricity to damage an ESD.

Precautions

1-4 Samsung Electronics

1-3 Precautions for Electrostatically Sensitive Devices (ESDs)

CAUTION

These servicing instructions are for use by qualified service personnel only. To reduce the risk of electric shock do not perform any servicing other than that contained in the operating instructions unless you are qualified to do so.

Samsung Electronics 2-1

Specifications and IC Data

2. Specifications and IC Data

2-1 Specifications

Television System:

Channels:

Intermediate Frequencies (MHz) :

MODEL

System

Band

VHF

UHF

CABLE

SYSTEM

IF Carrier Frequency

Picture IF Carrier

SYSTEM

NTSC ONLY

NTSC

2 - 13

14 - 69

1 - 125

NTSC

45.75

Picture Tube:

Power Requirements:

Antenna Input Impedance:

Speaker Impedance

Sound IF Carrier

Color Sub Carrier

20 Inch

25 Inch

29 Inch

AC 120V, 60Hz

VHF, UHF : Telescopic dipole antenna (75 ohm unbalanced type )

8 ohm, 2W+2W (Dual Type)

A51QDX991X001

A63QDB891X

A68QDN891X001

20Inch FLAT

25Inch 1.0R, +380MG

29Inch 1.0R, +380MG

41.25

42.18

2-2 Samsung Electronics

2-2 IC Line Up

Specifications and IC Data

Loc. No Specification Description Remark

Table 2-1 IC Line-Up

IC201S

IC301

IC501 TDA6107Q RGB DRIVE AMP

IC602

IC801S

IC802 KA7632

IC202 24C04 EEPROM

PC801S TCET1108 / LTV817B PHOTO COUPLER

IC101 LA7510

IC601 MSP3425G

SPM456AN

LA7841

TDA7268

KA5Q0740RT (0765RT)

TDA9377, English/Spanish/French

VERTICAL OUTPUT

SOUND-AMP (2W x 2CH)

POWER IC (STR)

CUSTOM REGULATOR (5V, 8V, 3.3V)

SIF - IC

Sound Processor

Philips

Sanyo

Philips

FIAIR CHILD

SEC

SANYO

Micronas

2-3 Semiconductor Base Diagrams

Specifications and IC Data

Samsung Electronics 2-3

Fig. 2-1 Semiconductor Base Diagrams

ELECTROLYTICCONDENSER

DIODE

SPM456AN(Pin 64) U4468B(Pin 16) MSP3425G(Pin 52)

TRANSISTOR

KSC5802

TRANSISTOR

E B C

LA7841 TDA6107Q KA7632

KSC815-Y KSA539-Y

TRANSISTOR

SAW-FILTER

KSC2331-Y

M3953M M9261M

E C B

2-4

MEMO

Disassembly and reassembly

Samsung Electronics 3-1

3. Disassembly and Reassembly

3-1 Back Cover Removal

1. After removing the screws, press the tension rib and pull the cabinet backwards.

2. To reassemble, press the tension rib (see diagram).

Disassembly and reassembly

3-2 Samsung Electronics

3-2 Main Board Removal

3-3 Speaker Removal

1. Separate the socket board from the CRT neck.

2. Remove the Anode Cap from the CRT.

3. Remove the main board by pulling it with both hands.

Warning: The FBT is charged with high voltage. Before removing the Anode Cap, discharge the voltage through one of the heat sinks on the main board.

1. Remove the speaker by pressing the tension rib.

Disassembly and reassembly

Samsung Electronics 3-3

3-4 CRT Removal

1. Spread a soft mat on the floor. Place the TV set face down.

2. Remove the 4 nuts mounting the CRT to the front cabinet. Lift the CRT.

3. Caution: Because of the high vacuum and large surface area of the picture tube, be careful while handling it: (1) Always lift the picture tube by grasping it firmly around the faceplate, (2) Never lift the tube by its neck. (3) Do not scratch the picture tube or apply excessive pressure. Fractures of the glass may cause an implosion.

3-4 Samsung Electronics

MEMO

Alignment and Adjustments

Samsung Electronics 4-1

4. Alignment and Adjustments

4-1 Preadjustment

4-1-1 Factory Mode

1. Do not attempt these adjustments in the Video Mode.

2. The Factory Mode adjustments are necessary when either the EEPROM (IC902) or the CRT is replaced.

3. Do not tamper with the “Adjustment” screen of the Factory Mode menu. This screen is intended only for factory use.

4-1-2 When EEPROM (IC902) Is Replaced

1. When IC902 is replaced all adjustment data revert to initial values. It is necessary to re-program this data.

2. After IC902 is replaced, warm up the TV for 10 seconds.

4-1-3 When CRT Is Replaced

1. Make the following adjustments AFTER setting up after setting up purity and convergence :

White Balance Sub-Brightness Vertical Center Vertical Size Horizontal Size Fail Safe (This adjustment must be the last step).

2. If the EEPROM or CRT is replaced and set SC as 35(factory mode).

4-2 Factory/Service Mode

4-2-1 Procedure for the “Adjustment” Mode

1. This mode uses the standard remote control. The Service Mode is activated by entering the following remote-control sequence :

(1) DISPLAY → FACTORY.

(2) STAND-BY → MUTE → 1 → 8 → 2

→POWER ON.

2. The “SERVICE (FACTORY)” message will be displayed. The Service Mode has four components: ADJUST, OPTION , G2-ADJUST and RESET.

3. Access the Adjustment Mode by pressing the “VOLUME” keys ( Up or Down). The adjustment parameters are listed in the accompanying table, and selected by pressing the CHANNEL keys ( , ).

4. Selection sequences for the all system:

DOWN or UP key:

SCT>SBT>BLR>BLB>RG>GG>BG>VSL>VS> VA>HS>SC>CDL>STT>AKB>PDL>NDL> PSR>NSR>SCBT>VOL>CAP>MVOL>RP00> RP01>FMWS>AGC1>OMD>SCL>PWL> MUS>AGC>DSK>DVDB

5. The VOLUME keys increase or decrease the adjustment values (stored in the non-volatile memory) when Adjustment Mode is cancelled.

6. Cancel the Adjustment Mode by re-pressing the “FACTORY” or “Power OFF” keys.

4-2-2 Main Adjustment Parameter

Alignment and Adjustments

4-2 Samsung Electronics

ONO SD F UN CTION R AN GE I N I TI AL D ATA SETTING RE MARK

SCT Sub Contras t 0 ~ 23

SBT Sub Bright ness

SCBT Screen Brighrtness 0 ~ 63

MVOL

RP00

RP01

FMWS

AGC1

OMD

Black Level offset Red

BLR

Black Level offset Blue

BLB

RG RedGain 0~63

GG Green Gain 0 ~ 63

BG Bl ue Gai n 0 ~ 63

VSL Vert ical Slope 0 ~ 6 3

VS Ver t ical Shif t 0 ~ 6 3

VA Vert ical Am pli tude 0 ~ 63

HS Horizontal Shif t 0 ~ 63

SC S- Cor rec t i o n 0 ~ 6 3

CDL Cathode Drive Level 0 ~ 15

STT Sub Tint 0 ~ 7

AKB AKB On / off 0 ~ 1

PDL PAL De l ay 0 ~ 15

NDL NTSC Delay 0 ~ 15

PSR PAL Sub color 0 ~ 23

NSR NTSC Sub color 0 ~ 23

VOL Volume pre sett i ng 0 ~ 63

CAP Caption Position

Melody Sound Volume

Ratio Pre / overshoot

Window Selection Sound PLL

IF AGC Speed

Offset IF Demodulator

SCL

Soft Clipping Level

PWL

Peak White Limitting

MUS

Matrix USA

AGC

Automatic Gain Control

DSK

Dynamic Skin Tone

DVDB

DVD Bright Offset

0~23

0~63

0~15

0~50

0~1

0~3

0~63

0~3

0~15

0~1

0~63

0~1

00~1

(16)

(6)

(37)

(33)

(38)

(39)

(32)

(20)

(33)

W/B Adjustment

FIX

W/B Adjustment

Vertical Picture Adjusment

FIX

Vertical Picture Adjusment

Picture Adjusment

FIX

FIX (Mono)

FIX (Nomal)

FIX (No Crrection)

FIX (Off)

FIX (100%)

FIX (Mono)

FIX

Alignment and Adjustments

Samsung Electronics 4-3

4-2-3 Option Bytes

In the Service Mode, various can be selected via the Option Table. Example:

Option Table : xx xx

OSD

VIDEO MUTE

AUDIO

E/W

ZOOM

AUTO POWER

AUDIO MUTE

LANGUAGE

HOTEL MODE

BULE SCREEN

2'nd SIF

V-CHIP

SETTING

OFF

STEREO

OFF

NOR/ZOOM

OFF

ENGLISH

OFF

INTERNAL

REMARK

- Video Mute On/Off changing the channel

- Audio Option (Mono / Steeo)

- E/W Option

- Picture Size Option

- Master S/w Option

- Audio Mute On/ Off without signal

- Inital Language agter Factory Reset

- Hotel mode On/ Off

- Bule Screen On/ Off without signal

- SIF Option at Mono sound

- V-CHIP On/Off

AV Option

DEMO

AV + DVD

OFF

- DVD, S-VHS Option

- DEMONSTRATION On/Off

Alignment and Adjustments

4-4 Samsung Electronics

4-3 Other Adjustments

4-3-1 General

1. Usually, a color TV needs only slight touchup adjustment upon installation. Check the basic characteristics such as height, horizontal and vertical sync and focus.

2. The picture should have good black and white details. There should be no objectionable color shading; if color shading is present, perform the purity and convergence adjustments described below.

3. Use the specified test equipment or its equivalent.

4. Correct impedance matching is essential.

5. Avoid overload. Excessive signal from a sweep generator might overload the front-end of the TV. When inserting signal markers, do not allow the marker generator to distort test results.

6. Connect the TV only to an AC power source with voltage and frequency as specified on the backcover nameplate.

7. Do not attempt to connect or disconnect any wires while the TV is turned on. Make sure that the power cord is disconnected before replacing any parts.

8. To protect against shock hazard, use an isolation transformer.

4-3-2 Automatic Degaussing

A degaussing coil is mounted around the picture tube, so that external degaussing after moving the TV should be unnecessary. But the receiver must be properly degaussed upon installation.

The degaussing coil operates for about 1 second after the power is switched ON. If the set has been moved or turned in a different direction, disconnect its AC power for at least 30 minutes.

If the chassis or parts of the cabinet become magnetized, poor color purity will result. If this happens, use an external degaussing coil. Slowly move the degaussing coil around the faceplate of the picture tube and the sides and front of the receiver. Slowly withdraw the coil to a distance of about 6 feet before removing power.

4-2-4 RESET

The Reset Mode is used during factory inspection. Function Reset:

1. Picture Mode Custom

2. Sound Mode Custom

3. Auto Volume Off

4. Melody On

5. Surround Off

6. Turbo Sound Off

7. MTS Stereo

8. Language English

9. Caption Off

10. Timer Off

Alignment and Adjustments

Samsung Electronics 4-5

4-3-3 High Voltage Check

CAUTION: There is no high voltage adjustment on this chassis. The B+ power supply must be set to +125 volts (Full color bar input and normal picture level).

1. Connect a digital voltmeter to the second

anode of the picture tube.

2. Turn on the TV. Set the Brightness and

Contrast controls to minimum (zero beam current).

3. The high voltage should not exceed 30KV.

4. Adjust the Brightness and contrast controls to

both extremes. Ensure that the high voltage does not exceed 30KV under any conditions.

4-3-4 FOCUS Adjustment

1. Input a black and white signal.

2. Adjust the tuning control for the clearest pic-

ture.

3. Adjust the FOCUS control for well defined

scanning lines in the center area of the screen.

4-3-5 Cathode Voltage Adjustment

(Screen Adjustment)

1. Connect CRT socket pin GK to an oscilloscope

probe.

2. Input a gray scale pattern. (Use a pattern gen-

erator, PM5518)

3. Use the P mode key (on the remote control)

for the STANDARD picture.

4. Adjust the Screen VR (on the FBT) so that the

voltage on the oscilloscope becomes 125+2.5V (See Fig. 4-1).

4-3-6 Purity Adjustment

1. Warm up the receiver for at least 20 minutes.

2. Plug in the CRT deflection yoke and tighten the clamp screw.

3. Plug the convergence yoke into the CRT and set in as shown in Fig. 4-2.

4. Input a black and white signal.

5. Fully demagnetize the receiver by applying an external degaussing coil.

6. Turn the CONTRAST and BRIGHTNESS controls to maximum.

7. Loosen the clamp screw holding the yoke. Slide the yoke backward or forward to provide vertical green belt. (Fig. 4-3).

8. Tighten the convergence yoke.

9. Slowly move the deflection yoke forward, and adjust for the best overall green screen.

10. Temporarily tighten the deflection yoke.

11. Produce blue and red rasters by adjusting the low-light controls. Check for good purity in each field.

12. Tighten the deflection yoke.

Fig. 4-1

125 2.5V

GND

Alignment and Adjustments

4-6 Samsung Electronics

4-3-7 White Balance Adjustment

Fig. 4-2 Convergence Magnet Assembly

Fig. 4-3 Center Convergence Adjustment

Fig. 4-4

(a) Set up

1. Warm up the TV for at least 30 minutes in the Aging Mode (OSD White). This mode is displayed by entering the following sequence:

DISPLAY

→FACTORY → FACTORY

2. Input a Toshiba pattern.

(b) Low-Light Adjustment

1. Set SBT to 1.0 fL in the Factory Service Mode with using CA100. See Fig. 4-4.

2. Adjust RG,BG so that the levels are suitable to each local area.

1. Set SCT to 35 FL in the Factory Service Mode with using CA100. See Fig. 4-4 .

6 Pole Magnet

Clamper

Screw

4 Pole Magnet

2 Pole Magnet

2 POLE PURITY

4 POLE CONVERGENCE

Vertical Green Belt

YOKE CLAMP SCREW

6 POLE CONVERGENCE

ADJ (VE

31m/m

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