Samsung TXH1986, TXH1370, TXH1972, TXH1386, TXH1373 User Manual

...

COLOR TELEVISION RECEIVER

Chassis : K15A Model: TXH1370 TXH1970

TXH1372 TXH1972 TXH1373 TXH1973 TXH1386 TXH1986

COLOR TELEVISION RECEIVER CONTENTS

Precautions

Specifications

Disassembly and Reassembly

Alignment and Adjustments

Troubleshooting

Exploded Views and Parts List

Electric Parts List

Block Diagram

PCB Layout

10.

Wiring Diagrams

11.

Schematic Diagrams

ELECTRONICS

Samsung Electronics Co., Ltd. AUG. 1998

Printed in Korea

3K15A-3701

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 peopleÑparticularly childrenÑmight 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 unitÕs 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 unitÕs 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

Òhorizontal disableÓ or Òhold-downÓ.)

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

Precautions

Samsung Electronics 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 manufacturerÕs 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 Òintegral implosionÓ 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 Òin-lineÓ picture tubes are equipped with a permanently attached deflection yoke; do not try to remove such Òpermanently attachedÓ 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 originalÑeven 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 unitÕs 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 instrumentÕs ground lead to the instrument chassis ground before connecting the positive lead; always remove the instrumentÕs ground lead last.

Precautions

Samsung Electronics 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 (Òsolid stateÓ) 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 powerÑ 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 Òanti-staticÓ; 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)

Specifications

Samsung Electronics 2-1

2. Specifications

2-1 Specifications

Television System 14"/20"/21" NTSC COLOR TV SIGNAL

Power Consumption 14" : 57 WATTS NOMINAL,

20" : 70 WATTS NOMINAL 21" : 75 WATTS NOMINAL,

Picture Tube 14" : A34KQV42X

20" : A48KRD82X (H) 21": : A51KQJ63X (H)

Power Requirement AC 120V, 60Hz /AC 100 ~ 240, 50Hz, 60Hz

Operating System REMOCON SYSTEM (SZM354ET)

Tuning Ranges VHF CH : 2-13, UHF CH : 14-69, CABLE CH : 1,14-125

Antenna Input Impedance 75 ohm UNBALANCED TYPE FOR VHF/UHF

Intermediate Frequency PICTURE 45.75MHz, SOUND 41.25MHz,

COLOR SUB CARRIER 42.17MHz

Speaker Impedance Single:

Dual : 8 ohm 3W x 2 Dual : 16 ohm , 3W x 2 (CT-33H1, CT-50H1)

8 ohm 3W

Disassembly and Reassembly

Samsung Electronics 3-1

3. Disassembly and Reassembly

3-1 Back Cover Removeal

Fig. 3-1

1. After removing the screws, pull the cabinet backwards.

3-2 Main Board Removal

Disassembly and Reassembly

3-2 Samsung Electronics

Fig. 3-2

Fig. 3-3

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.

Disassembly and Reassembly

Samsung Electronics 3-3

3-3 Speaker Removal

1. Loosen the screws and remove the speakers.

Fig. 3-4

Disassembly and Reassembly

3-4 Samsung Electronics

3-4 CRT Removel

Fig. 3-5

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.

3. Lift the CRT.

4. 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.

Alignment and Adjustments

Samsung Electronics 4-1

4. Alignment and Adjustments

4-1 Service Mode Adjustments

4-1-1 Service Mode Menus

Since there are no VRs in the K15A chassis, all adjustments after parts replacement must be done in the Service Mode. Service Mode adjustments are necessary when either the EEPROM (IC902) or the CRT is replaced.

4-1-2 Entering the Service Mode

Press the following transmitter keys while in STAND-BY mode:

MUTE—>1—>8—>2—>POWER “Factory Mode Menu” is displayed

<---selected (violet)

RC XXX VCO XX GC XXX SBT XX BC XX SCT XX VA XX SCR XX VS XX STT XXX HS XX GG XXX SS XX BG XXX SVC : MUTE

AGC XX

AGC XX RC XXX

GC XXX SBT XX BC XX SCT XX VA XX SCR XX VS XX STT XXX HS XX GG XXX SS XX BG XXX SVC : MUTE

VCO XX

VCO

AGC XX XXX

XXX XX XX XX VA XX XX VS XX XXX HS XX XXX SS XX XXX

SVC : MUTE

VCO XX

RC GC

SBT

BC SCT SCR STT GG BG

ADJUSTMENT PATTERN OPTION RESET

Enter Service Mode using the Volume

+,- keys. Service Mode Menu:

Return to the Service mode by pressing MENU.

Change the data with “Volume +, - “ keys.

Return to the Factory mode via the MENU key.

Press POWER to enter the Stand-by mode.

Select a mode to be adjusted, using the channel down key. Example: VCO.

POWER

OFF

Item Function

Range

MICOM Data 1 AGC RF AGC Adjustment 0~63 50 2 VCO PIF VCO Adjustment 0~127 63 3 SCT SUB-CONTRAST Adjustment 0~63 48 4 SCR SUB-COLOR Adjustment 0~27 13 5 STT SUB-TINT Adjustment 0~27 7 6 RC RED-CUT OFF Adjustment 0~255 0 7 GC GREEN-CUT OFF Adjustment 0~255 0 8 BC BLUE-CUT OFF Adjustment 0~255 0 9 SVC Input a Horiz line pattern

10 GG GREEN-GAIN Adjustment 0~255 127 11 BG BLUE-GAIN Adjustment 0~255 127 12 SBT SUB-BRIGHTNESS Adjustment 0~63 31 13 VA VERTICAL SIZE Adjustment 0~63 39 14 VS VERTICAL CENTER Adjustment 0 0 15 HS HORIZONTAL Phase Adjustment 0~31 15 16 SS SUB-SHARPNESS Adjustment 0~31 4

BYTE 0 : 0 0

ADJUSTMENT PATTERN OPTION RESET

Initalized

Alignment and Adjustments

4-2 Samsung Electronics

4-1-3 Adjustment in Option Mode

This adjustment is necessary whenever the EEPROM is replaced. Input data (as marked on the back cabinet).

Select “SET OPTION” by pressing the Channel key twice.

Press the Volume +, - keys to enter the set Option mode.

Press MENU to go back to the factory mode.

Select RESET with channel key.

Press volume + key.

▼

4-1-4 Service Mode Adjustments

1. The Pattern Adjustment is done only in the factory. Do not attempt to readjust it.

2. Refer to 4-2 for other adjustments.

3. Set OPTION data.

4-1-5 Service Mode Adjustment Ratings

Note : The initial MICOM data values take effect when IC902 is replaced.

Alignment and Adjustments

Samsung Electronics 4-3

4-2 Alignment and Adjustment

4-2-1 General Alignment Instructions

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

2. Observe the picture and check for good back and white details. There should be no objectionable color shading: If color shading is present, demagnetize the receiver. If color shading persists, perform purity and convergence adjustments described below.

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

4-2-2 Power Supply Check

Check the following: A: Power plug is connected; “Stand-by” mode B: Power On when “Power ON” button is pressed C: Power On by FBT Each supply is marked on

its lead-in wire. ( )

4-2-3 Focus Adjustment

Adjust the focus control on the FBT for well defined scanning lines.

4-2-4 Fail Safe Circuit Check (FS) (OPTION)

1. The failsafe check must be the final step in servicing.

2. Turn the power switch ON and adjust customer controls for normal operation.

3. Temporarily short pin X to pin R on the main board (RX06, RX04) with a jumper wire. Raster will disappear.

4. The TV must remain in this state even after removing the jumper wire. This shows that the failsafe circuit is working properly.

5. To recover picture and sound, temporarily turn off the TV and allow the failsafe circuit more than 30 seconds to reset. Then switch power ON to produce normal picture and sound.

4-2-5 IC902 Replacement

1. When IC902 is replaced, all values are reset to “Initialized MICOM Data” and readjustment is necessary.

2. Press the POWER button 10 seconds after plug-in.

3. To enter the Service Mode, refer to Fig. 4-1 (Service Mode Adjustment).

4-2-6 PIF VCO Adjustment

1. Use a Pattern Generator or an off-air signal.

2. Open pin 11 of Micom (IC901) or one side of lead pin for R237.

3. Adjust VCO in the service mode to set IC101 Pin 44 (AFT) to 2.5V ± 0.4V.

4. Connect the opened site.

4-2-7 RF-AGC Adjustment

1. Input a PHILLIPS pattern.

2. Set the input signal to 60 dB.

3. Enter into the AGC in the service mode.

4. Adjust AGC until color bar noise disappears.

Alignment and Adjustments

4-4 Samsung Electronics

4-2-8 Sub-Contrast Adjustment

1. Input a gray scale pattern. Use a pattern generator (PM5518).

2. Short D208 to switch off the ABL feed-back.

3. Check CN201 R-OUT with an oscilloscope.

4. Set RC, BC, GC data to 0 in the Service Mode.

5. Adjust SCT to 2.40 ± 0.1Vp-p

6. Remove the short across D208 and restore ABL.

4-2-9 Sub-Tint Adjustment

1. Input a rainbow pattern.

2. Check CN201 B-OUT with an oscilloscope.

3. Adjust STT in the service mode until the 6th peak is the highest and the 5th and 7th peaks have equal heights.

4-2-10 Sub-Color Adjustment

1. Do sub-color adjustment after the SubContrast and Sub-Tint adjustments.

2. D208 should still be shorted. The ABL should still be switched OFF.

3. Input a color bar pattern. Use a pattern generator (PM5518).

4. Check CN201 R-OUT (use an oscilloscope).

5. Ensure that the RC, GC and BC data are 0. BG are 140 and GG should be 90.

6. Adjust SCR to 2.4 ± 0.1Vp-p (black and red levels).

7. Remove the short across D208 and restore ABL.

2.5V 0.1Vpp

2.4V 0.1Vpp

Alignment and Adjustments

Samsung Electronics 4-5

4-2-11 White Balance Adjustment

4-2-11 (A) LOW-LIGHT ADJUSTMENTS

1. Input either a lion head or “pure white” color pattern.

2. Operate the receiver for 30 minutes.

3. Check the data in the service mode: RC, GC, BC are 0 and SB is 16; Steps BG are 90 and GG are 140.

4. Enter the horizontal line mode by pressing the MUTE key.

5. Adjust the screen VR on the FBT until a dim colored line (red,green or blue) appears on the screen.

6. After pressing the MUTE key, go to RC,BC or GC with channel , keys. After putting a dim colored line (red, green or blue) in the horizontal line with MUTE key, adjust color with volume , keys.

7. Exit the horizontal line via the MUTE key.

4-2-11 (B) HIGH-LIGHT ADJUSTMENTS

1. Input a high-light pattern

2. Adjust GG,BG in the Service Mode.

3. Recheck in low light.

4-2-12 Sub-Brightness Adjustment

1. Input a Toshiba pattern.

2. Warm up the receiver for 10 minutes.

3. Enter the Service Mode and set SB to the point where the 5th point is brighter in the gray scale.

4-2-13 Vertical Size Adjustment

1. Input a lion head pattern.

2. After the vertical center adjustment, enter into the service mode.

3. Adjust VA so that the each top and bottom of the screen is 4.0. If the top and bottom values are different, adjust VA so that the sum of the two values is 8.0.

4-2-14 Horizontal Size Adjustment

1. Receive a lion head pattern.

2. Enter into the service mode.

3. Adjust HS to symmetrized right and left.

4-2-15 When CRT Is Replaced

Do the following adjustments after the basic purity and convergence adjustments.

1. White Balance

2. Sub-brightness

3. Vertical Size

4. Horizontal Size

5. Fail safe (should be the final step).

4 3

2 1

▼

MEMO

4-6 Samsung Electronics

Troubleshooting

Samsung Electronics 5-1

5. Troubleshooting

5-1 No Power

Normal

Check LED when AC

code is plugged.

Check

Fuse.

OFF

No Power

Check

IC801* Pin 1

Oscillation.

Check

IC801 Pin 3 B+.

Abnormal

Abnormal (0 ~ 15V)

Check/Replace

D806, Q401, Q801,

D802, D814*

Check and Replace

D807 ~D810

Abnormal

Abnormal (0V)

Normal (15~20V)

Check/Replace

PC802, DZ807

Check IC801*

Pin 4 Voltage

Check IC802.

Check/Replace

IC802, R812, D856.

Abnormal

Normal (0.5 ~ 3V)

Check/Replace

DZ802, DZ803, D806

5-2 No Sound

Troubleshooting

5-2 Samsung Electronics

Abnormal

Normal

Abnormal

Normal

Normal (approx. 12V)

No Sound

Check

Connector CN601

and CN701.

Check

Waveform of

IC601 Pin 1.

Check

Waveform of IC201

Pin 52.

Check

Waveform of IC201

Pin 1.

Volume

Up.

Check

SIF (L201).

Check/Replace

IC201.

Abnormal

Check

Waveform of IC601 and

IC602 Pins 4.

Check CN601 and CN701

Connector

Soldering and A/V PCB.

Check

Voltage of IC601 and IC602

Pin 5.

Check Power

12V Line Voltage.

Replace IC601

and IC602.

O.K

Normal

+ 44 hidden pages