Changhong Electric PF2939 Manuale utente

FILE NO. SM-CTV-G-005

COLOR TELEVISION

SERVICE MANUAL

MODEL NO. PF2939

CHASSIS NO. CH-16CD

Please read this manual carefully before service.

SERVICE MANUAL

TABLE OF CONTENTS

SAFETY INSTRUCTIONS AND MAINTENANCE .....................................1

X-Ray Radiation Precaution...............................................................................................1

Safety Precaution ................................................................................................................1

Product Safety Notice .........................................................................................................2

Maintenance.......................................................................................................... 3

KEY ICS AND ASSEMBLIES..................................................................................4

SYSTEM BLOCK DIAGRAMS...............................................................................5

Structure Block Diagram.....................................................................................................5

Block Diagram for Supply Voltage System .....................................................................6

SERVICE DATA................................................................................................................7

Technical Data of Key ICs..................................................................................................7

Service Data of Key ICs .....................................................................................................21

Waveforms of Key Points...................................................................................................27

ADJUSTMENTS..............................................................................................................34

Set-up Adjustments.............................................................................................................34

Circuit Adjustments..............................................................................................................36

Service Mode and Bus Data..............................................................................................38

APPENDIX

Circuit Diagrams

SERVICE MANUAL

SAFETY INSTRUCTIONS AND MAINTENANCE

WARNING: BEFORE SERVICING THIS CHASSIS, READ THE

“

X-RAY RADIATION

PRECAUTION

”

“

SAFETY PRECAUTION

”

AND

“

PRODUCT SAFETY NOTICE

”

INSTRUCTIONS BELOW.

X-RAY RADIATION PRECAUTION

1. The EHT must be checked every time the TV is serviced to ensure that the CRT does not emit

X-ray radiation as result of excessive EHT voltage. The maximum EHT voltage permissible in

any operating circumstances must not exceed the rated value. When checking the EHT, use

the High Voltage Check procedure in this manual using an accurate EHT voltmeter.

2. The only source of X-RAY radiation in this TV is the CRT. The TV minimizes X-RAY radiation,

which ensures safety during normal operation. To prevent X-ray radiation, the replacement

CRT must be identical to the original fitted as specified in the parts list.

3. Some components used in this TV have safety related characteristics preventing the CRT

from emitting X-ray radiation. For continued safety, replacement component should be made

after referring the PRODUCT SAFETY NOTICE below.

4. Service and adjustment of the TV may result in changes in the nominal EHT voltage of the

CRT anode. So ensure that the maximum EHT voltage does not exceed the rated value after

service and adjustment.

SAFETY PRECAUTION

WARNING: REFER SERVICING TO QUALIFIED SERVICE PERSONNEL ONLY.

1. The TV has a nominal working EHT voltage. Extreme caution should be exercised when

working on the TV with the back removed.

1.1 Do not attempt to service this TV if you are not conversant with the precautions and

procedures for working on high voltage equipment.

1.2 When handling or working on the CRT, always discharge the anode to the TV chassis before

removing the anode cap in case of electric shock.

1.3 The CRT, if broken, will violently expel glass fragments. Use shatterproof goggles and take

extreme care while handling.

1.4 Do not hold the CRT by the neck as this is a very dangerous practice.

2. It is essential that to maintain the safety of the customer all power cord forms be replaced

exactly as supplied from factory.

3. Voltage exists between the hot and cold ground when the TV is in operation. Install a suitable

isolating transformer of beyond rated overall power when servicing or connecting any test

equipment for the sake of safety.

SERVICE MANUAL

4. When replacing ICs, use specific tools or a static-proof electric iron with small power (below

35W).

5. Do not use a magnetized screwdriver when tightening or loosing the deflection yoke assembly

to avoid electronic gun magnetized and decrement in convergence of the CRT.

6. When remounting the TV chassis, ensure that all guard devices, such as nonmetal control

buttons, switch, insulating sleeve, shielding cover, isolating resistors and capacitors, are

installed on the original place.

7. Replace blown fuses within the TV with the fuse specified in the parts list.

8. When replacing wires or components to terminals or tags, wind the leads around the terminal

before soldering. When replacing safety components identified by the international hazard

symbols on the circuit diagram and parts list, it must be the company-approved type and must

be mounted as the original.

9. Keep wires away from high temperature components.

PRODUCT SAFETY NOTICE

CAUTION: FOR YOUR PROTECTION, THE FOLLOWING PRODUCT SAFETY NOTICE

SHOULD BE READ CAREFULLY BEFORE OPERATING AND SERVICING THIS TV SET.

1. Do not slap or beat the cabinet or CRT, since this may result in fire or explosion.

2. Never allow the TV sharing a plug or socket with other large-power equipment. Doing so may

result in too large load, thus causing fire.

3. Do not allow anything to rest on or roll over the power cord. Protect the power cord from being

walked on, modified, cut or pinched, particularly at plugs.

4. Do not place any objects, especially heavy objects and lightings, on top of the TV set. Do not

install the TV near any heat sources such as radiators, heat registers, stove, or other

apparatus that produce heat.

5. Service personnel should observe the SAFETY INSTRUCTIONS in this manual during use

and servicing of this TV set. Otherwise, the resulted damage is not protected by the

manufacturer.

6. Many electrical and mechanical components in this chassis have special safety-related

characteristics. These characteristics are often passed unnoticed by a visual inspection and

the X-ray radiation protection afforded by them cannot necessarily be obtained by using

replacements rated at higher voltages or wattage, etc. Components which have these special

safety characteristics in this manual and its supplements are identified by the international

hazard symbols on the circuit diagram and parts list. Before replacing any of these

components read the parts list in this manual carefully. Substitute replacement components

which do not have the same safety characteristics as specified in the parts list may create

X-ray radiation.

SERVICE MANUAL

Safety Symbol Description

The lightning symbol in the triangle tells you that the voltage inside this product may

be strong enough to cause an electric shock. Extreme caution should be exercised

when working on the TV with the back removed.

This is an international hazard symbol, telling you that the components identified by

the symbol have special safety-related characteristics.

FDA This symbol tells you that the critical components identified by the FDA marking have

special safety-related characteristics.

UL This symbol tells you that the critical components identified by the UL marking have

special safety-related characteristics.

MAINTENANCE

1. Install the TV set on a stable and level surface. Do not place the set near or over a radiator or

heat register, or where it is exposed to direct sunlight.

2. Do not install the TV set in a place exposed to rain, water, excessive dust, mechanical

vibrations or impacts.

3. Allow enough space (at least 10cm) between the TV and wall or enclosures for proper

ventilation.

4. Slots and openings in the cabinet should never be blocked by clothes or other objects.

5. Please power off the TV set and disconnect it from the wall immediately if any abnormal

condition are met, such as bad smell, belching smoke, sparkling, abnormal sound or no

picture/sound/raster. Hold the plug firmly when disconnecting the power cord.

6. Unplug the TV set from the wall outlet before cleaning or polishing it. Use a dry soft cloth for

cleaning the exterior of the TV set or CRT screen. Do not use liquid cleaners or aerosol

cleaners.

SERVICE MANUAL

KEY ICS AND ASSEMBLIES

Table 1 Key ICs and Assemblies

Serial

No.

Position

No. Model No. Function Description

1 N201 OM8373PS(CH05T1632) UOC

2 N202 AT24C16 EEPROM

3 N301 TA1343N Audio processor

4 N401 TDA8350 Vertical output circuit

5 N361 TDA8944J Sound power amplifier

6 N901 TA1219AN TV/AV switch circuit

7 IC801 STR-G8656 Power supply circuit

8 A101 TDQ-6F2-M Tuner

SERVICE MANUAL

SYSTEM BLOCK DIAGRAMS

５

Structure Block Diagram

Fig 1. Structure Block Diagram for CH-16CD Chassis

Lin

Rin

UOC (27)

IF Pre-Amplifier

+ SAWF

Tuner

A101

EEPROM

(N202)

I2C

1００~2５0V

50/60Hz

Power Supply Circuit

STR-G8656 (IC801) And

BCK-24217L (T803) 5V-1

15V-1

3.3V

15V-2

145V

Circuit for Buttons

On The TV

Remote Sensor

HS0038

Remote

control

200V

Monitor Out

V.OUT

TDA8350Q (N401)

UOC

ＯＭ８３７３ＰＳ

(N201)

CRT Drive

H.Drive

Q501, T501

H.OUT

Q502

FBT

T502

Y/C TV-V

I2CSIF

Audio Amplifier

TDA8944J (N361)

AV Switch

TA1218/1219

(N901)

Audio Processor

TA1343N (N301)

I2C

AV Terminals in

42 43

733 21 22

HV FV SV

45V

16V

5V-2

SERVICE MANUAL

Block Diagram for Supply Voltage System

Fig 2 Block Diagram for Supply Voltage System for CH-16CD Chassis

SERVICE MANUAL

SERVICE DATA

Technical Data of Key ICs

OM8373PS (N201)

UOC

1. General Description

The various versions of the OM8373 PS/ N3/A

series combine the functions of a video

processor together with a μ-Controller and

US Closed Caption decoder. The ICs are

intended to be used in economy television

receivers with 90° and 110° picture tubes.

The ICs have supply voltages of 8V and 3.3V

and they are mounted in an S-DIP 64

envelope.

The features are given in the following feature

list.

2. Features

TV-signal processor

• Multi-standard vision IF circuit with

alignment-free PLL demodulator

• Internal (switchable) time-constant for the

IF-AGC circuit

• A choice can be made between versions with

mono intercarrier sound FM demodulator and

versions with QSS IF amplifier.

• The mono intercarrier sound versions have a

selective FM-PLL demodulator which can be

switched to the different FM sound

frequencies (4.5/5.5/6.0/6.5 MHz).

The quality of this system is such that the

external band-pass filters can be omitted.

• Source selection between ‘internal’ CVBS and

external CVBS or Y/C signals

• Integrated chrominance trap circuit

• Integrated luminance delay line with

adjustable delay time

• Picture improvement features with peaking

(with variable positive/negative overshoot

ratio), black stretching and Dynamic Skin

Tone Control

• Integrated chroma band-pass filter with

switchable centre frequency

• Only one reference (12 MHz) crystal

required for the μ-Controller, Teletext- and

the colour decoder

• PAL/NTSC colour decoder with automatic

search system

• Internal base-band delay line

• RGB control circuit with ‘Continuous Cathode

Calibration’, white point and black level offset

adjustment so that the colour temperature of

the dark and the light parts of the screen can

be chosen independently.

• Linear RGB or YUV input with fast blanking

for external RGB/YUV sources. The

Text/OSD signals are internally supplied from

theμ-Controller/Teletext decoder

• Contrast reduction possibility during

mixed-mode of OSD and Text signals

• Horizontal synchronization with two control

loops and alignment-free horizontal oscillator

• Vertical count-down circuit

• Vertical driver optimized for DC-coupled

vertical output stages

• Horizontal and vertical geometry processing

• Horizontal and vertical zoom function for 16 :

9 applications

• Horizontal parallelogram and bow correction

for large screen picture tubes

• Low-power start-up of the horizontal drive

circuit

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