Samsung txm2792fx service manual

COLOR TELEVISION RECEIVER

Chassis : K57A Model : TXM2792FX/XAA

TXM2792FX/XAC

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

AA82- 00127A

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

TXM2792FX

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

29 Inch

AC 120V, 60Hz

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

8 ohm, 15W+15W (Dual Type)

A68QCP891X100

29Inch Flat, +380MG

41.25

42.18

2-2 Samsung Electronics

2-2 IC Line Up

Specifications and IC Data

Table 2-1 IC Line-Up

Loc. No

IC201S

IC301

IC501

IC602

IC801S

IC802 KA7632

IC202

PC801S PC802S

IC101

IC601

ICP01

Specification

SPM-464A

LA7845

TDA6108QJF

TDA7297

KA5Q1265R

M24C08

TCET1108 / LTV817B

LA7510

MSP-3425G-B8

VIPER12AD1P

Description

TDA9592 PS/NI, SPM-464A,64P

VERTICAL OUTPUT

RGB DRIVE AMP

SOUND-AMP (15W x 2CH)

POWER IC (STR)

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

EEPROM

PHOTO COUPLER

IF DETECTOR-IC

Sound Processor

PWM CONTROCER-IC

Remark

Philips

Sanyo

Philips

FIAIR CHILD

TEMIC

Micronas

ICW01

ICG01

NJM2235D

4558

VIDEO Swiching-IC

OP AMP-IC

2-3 Semiconductor Base Diagrams

Specifications and IC Data

Samsung Electronics 2-3

Fig. 2-1 Semiconductor Base Diagrams

ELECTROLYTICCONDENSER

TRANSISTOR

KSD5703 KSA614

DIODE

TRANSISTOR

KSC815-Y KSA539-Y

SPM464A(Pin 64) MSP3425G(Pin 52) LM393(Pin 8) VIPER12ADIP(Pin 8) M24C08(Pin 8) 4558(Pin 8) NJM2235D(Pin 8)

SAW-FILTER

M3953M

M9370M

LA7845(Pin 7) TDA6108Q(Pin 9) KA7632(Pin 10)

E B C

TRANSISTOR

KSC2331-Y

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 (IC202) 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 (IC202) Is Replaced

1. When IC202 is replaced all adjustment data revert to initial values. It is necessary to re-program this data.

2. After IC202 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 30(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>NDL>NSR> SCBT>VOL>CAP>MVOL>RP00>RP01> AGCS>OMD>SCL>PWL>MUS>AGC> HPAR>HBOW>EWID>EPAR>EUCN>ELCN> ETRP>VZ>SVM>VMA>SSP>PSNS> DNSR>DSBT>DCDL>DBLR>DBLB>DSK

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 U N CT ION R AN GE I NITIAL D ATA SELECTION RE MARK

SCT Sub Cont ras t 0 ~ 23

SBT Sub Bright nes s

BLR

BLB

Black Level offset R

Black Level offset B

0~23

0~63

ADJ

RG Red Gain 0~63

GG Green Gain 0 ~ 63

BG Bl ue Gai n 0 ~ 63

VSL Vert ical Slope 0 ~ 63

VS Ver t ical Sh if t 0 ~ 63

VA Vertical Amplitud e 0 ~ 63

HS Horizontal Shif t 0 ~ 63

SC S- Co rrect i o n 0 ~ 63

CDL Cathode Drive Level 0 ~ 15

STT Sub Tint 0 ~ 7

AKB AKB On / off 0 ~ 1

NDL NTSC Delay 0 ~ 15

NSR NTSC Sub color 0 ~ 23

SCBT Screen Brighrtness 0 ~ 63

VOL Volume pre sett i ng 0 ~ 63

CAP Caption Position

MVOL

RP00

RP01

AGCS

OMD

SCL

PWL

MUS

AGC

HPAR

HBOW

EWID

Melody Volume

Ratio Pre / overshoot

IF AGC Speed

Offset IF Demodulator

Soft Clipping Level

Peak White Limitting

Color Matrix

Automatic Gain Control

Horizontal Parallelogram

Horizontal Bow

EW Width

0~15

0~50

0~1

0~3

0~63

0~3

0~15

0~1

0~63

ADJ

FIX

ADJ

FIX

ADJ

FIX

ADJ

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