ROADSTAR 12.8, 12.8, 12.8 Schematic

R

- SM-128

SM-128

Service Manual

CONTENTS PAGE

Safety Instructions 1 Technical Specifications 2 Pin Voltages of IC’s 3 Waveforms 7 Electrical and Service Adjustments 11 Spare Parts List 14 Circuit Diagrams Attac hed

SAFETY INSTRUCTIONS

GENERAL GUIDELI NES

1. It is advised to insert an isolation transformer in the AC supply before servicing a hot chassis.

2. Potentials as high as 33KV are present when this receiver is in operation. Operation of the receiver without the rear cover involves the danger of a shock hazard from t he receiver power supply. Servicing should not be attempted by any one who is not competent with the precautions necessary when working on the high voltage equipment. Always discharge the anode of the tube.

3. When servicing observe the original lead dress in the high voltage circuits. If a short circuit is found, replace all the parts which have been overheated or damaged by the short circuit.

4. Always use the manufacturer’s replacement safety components. The critical safety

components marked with

on the schematics diagrams should not be replaced by other substitutes. Other substitute may create the electrical shock, fire or other hazards. Take attention to replace the spacers with the originals. Furthermore where a short circuit has occurred, replace those components that indicate evidence of overheating.

5. After servicing, see that all the protective devices such as insulation barriers, insulation papers, shields and isolation R-C combinations are correctly installed.

6. When the receiver is not being used for a long time of period of time, unplug the power cord from the AC outlet.

7. After servicing make the following leakage current checks to prevent the customer from being exposed to shock hazard.

LEAKAGE CURRENT COLD CHECK

1. Unplug the AC cord and connect a jumper between the two prongs of the plug.

2. Turn the receiver’s power switch on.

3. Measure the resistance value with an ohmmeter, between the jumpered AC plug and each exposed metallic cabinet part on the receiver, such as screw heads, aerials,

connectors, control shafts etc. When the exposed metallic part a return path to the chassis the reading should be between 4Mohm and the 20Mohm. When the exposed metal does not have a return path to the chassis, the reading must be infinite.

LEAKAGE CURRENT HOT CHECK

1. Plug the AC cord directly in to the AC outlet. Do not use an isolation transformer for this check.

2. Connect a 2Kohm 10W resistor in series with an exposed metallic part on the receiver and an earth, such as a water pipe.

3. Use an AC voltmeter with high impedance to measure the potential across the resistor.

4. Check each exposed metallic part and check the voltage at the each point.

5. Reverse th e AC plug at the outlet and repeat each of the above measurements.

6. The potential at the any point should not exceed 1.4 Vrms. In case a measurement is outside the limits specified, there is the possibility of a shock hazard, and the receiver should be repaired and rechecked before it is returned to the customer.

HOT CHECK CIRCUIT

TO INSTRUMENTS EXPOSED METALLIC PARTS

AC-Voltmeter

Water pipe (earth)

2 K Ohm

Figure 1

X-RAY RADIATION WARNING

The primary source of X-ray radiation in this receiver is the picture tube. The chassis is specially constructed to limit X-ray radiation. For continued X-ray radiation protection, replace the tube with the same type of the original one.

CAUTION AFTER REMOVAL OF THE ANODE CAP, DISCHARGE THE ANODE OF THE PICTURE TUBE AND THE ANODE CAP TO THE METAL CHASSIS, CRT SHIELD, OR THE CARBON PAINTED ON THE CRT WITH A HIGH VOLTAGE PROBE AND MULTIMETER (SELECT VDC) AND THEN SHORT CIRCUIT DIRECTLY TO DISCHARGE COMPLETELY.

TECHNICAL SPECIFICATIONS

Power source:

Power consumption (max.)

85 W 20”, 21”

Standby power consumption

Aerial impedance

Receiving system

PAL SECAM BG PAL SECAM BG DK PAL I

Receiving channels

VHF BAND III CH5-12 CABLE TV S1-41 UHF BAND CH21-69

Audio outputs

High Voltage

25 ± 0.5 KV 20”, 21”

Focus voltage

Grid 2 voltage

Heater voltage

Video/Audio Terminals :

Audio : 0.5 Vrms, >10 Kohm RGB AV1OUT Video : 1 Vpp, 75 Ohm Audio : 0.5 Vrms, <1 Kohm AV2 IN (RCA, optional) Video : 1 Vpp, 75 Ohm Audio : 0.5 Vrms, >10 Kohm

Operating temperature

Safety

: IEC 65 /BS P2N

X-Ray radiation

1

: TV set is produced to receive “one” of these colour and sound systems.

220-240V AC, 50-60Hz

: 65 W 14”

: 5 W

: 75Ohm, coaxial type

1

: PAL BG

: VHF BAND I CH2-4

: 2.0W RMS at %10 THD 14”

2.5W RMS at %10 THD 20”, 21”

: 23 ± 0.5 KV 14”

: %25.6 ± %38 of EHT

: 0-1400 V

: 6.2 ± 0.2 Vrms

AV1 IN Video : 1 Vpp,75 Ohm

: 0-45 Degrees

: ACC. IEC 65/BS P2N

RGB

Horizontal

BU808DFI

Deflection

220V AC in

Power Supply

Standby

from IC401

8V13V30V107V

TDA 16846

Power Amplifier

TDA2822

CRT

IC701

Module

5V

RGB

out

Black

33

30-32

Audio

out

55

I2C 51-52

PIF

8

6-7

44

CVBS-TXT

H - Pulse

H-Sync

48

STV224X

SIF 1-2

49

IC101

34-37

3.3V

4742

IC501

TDA8174

V-Amp V-Out

14/11

20/13

Audio In/Out

Video In/Out

Vertical Deflec.

V-lin

V-Sync

To IC402

pin8

RGB out + Fast Blanking

28

27

12

Tuner Part

38-41

Scart

Microcontroller

IC 401 SDA5552

15

24 50 16

IR

Receiver

Keyboard

Standby

1

48/49

SCLO

SDAO

EEPROM

AGC SCL SDA IF1 IF2

IC402

19

H-sync

20

V-sync

Chassis 12.8 Block Diagram

PIN VOLTAGES OF IC'S

IC101 (STV2246)

BUS CONTROLLED MULTISTANDARD ONE CHIP TV PROCESSOR

Pin Connection V DC (*) Pin Connection V DC (*)

1

Sound IF Input 1 0.96

2

Sound IF Input 2 0.96

3

AGC SIF Capacitor (not connected) 0.22

4

IF Voltage Reference Filtering 3.15

5

AGC Picture IF Capacitor 2.42

6

Picture IF Input 1 2.47

7

Picture IF Input 2 2.47

8

AGC Tuner Output 2.54

9

IF PLL Filter 2.03

10

IF Ground 0.00

11

AM/FM Mono Sound Output 3.78

12

5 V IF Supply 4.97

13

Internal CVBS Output 3.00

14

External Audio Input 2.42

15

LC Input 1 3.90

16

LC Input 2 3.90

17

Video/Luma Supply Voltage (8 V) 8.05

18

Internal Video Input 3.63

19

Video/Luma Ground 0.00

20

External Video Input 3.22

21

Black Stretch Capacitor 2.74

22

Y/CVBSIN3 Y(SVHS) or CVBS3 External Input 3.22

23

Chroma (SVHS) Input 1.70

24

Automatic RGB Peak Regulation 4.45

25

External Blue Input 2.52

26

External Green Input 1.73

27

External Red Input 2.52

28

External Fast Blanking Input 0.00

29

Not connected 3.20

30

Blue Output 2.30

31

Green Output 2.34

32

Red Output 2.48

33

Cathode Current Measurement Input 4.17

34

OSD Blue Input 4.22

35

OSD Green Input 4.35

36

OSD Red Input 4.21

37

OSD Fast Blanking 0.31

38

Cloche Filter Tuning Capacitor 0.11

39

3.5X MHz Crystal 0.35

40

4.43 MHz Crystal -

41

Chroma PLL Filter -

42

Vertical Amplitude DAC Output 4.03

43

Chroma/Scanning Ground 0.00

44

Second Video Switch Output 4.09

45

Chroma/Scanning Power Supply (8V) 8.06

46

Beam Current Limiter Control Voltage and Safety Input (XRAY)

47

Vertical Output Pulse 5.62

48

Horizontal Output Pulse 1.39

49

Line Flyback Input and Super-sandcastle Output 0.72

50

Scanning PLL Filter 3.98

51

SCL I2C Bus Clock Input 3.10

52

SDA I2C Bus Data Input 2.80

53

Digital Supply Voltage (5 V) 5.00

54

Digital Ground 0.00

55

Main Audio Output 3.91

56

FM Demodulation Capacitor 1.71

6.54

IC301 (TDA2822) Audio Output IC

Pin Connection V DC Pin Connection V DC

1

Input A + -

2

Not connected 0.00

3

Input A - 0.52

4

Ground 0.00

5

Ground 0.00

6

Output A 5.96

7

Not connected 0.00

8

VCC 12.9 (13.5)

9

Not connected 0.00

10

Not connected 0.00

11

Output B 5.99

12

Ground 0.00

13

Ground 0.00

14

Input B- 0.52

15

Not connected 0.00

16

Input B - 0.00

IC401 (SDA5552)

MICRO CONTROLLER WITH OSD AND TELETEXT

Pin Connection V DC (*) Pin Connection V DC (*)

1

Standby 0.06 (2.09)

2

Not connected 0.80

3

Mute 0.06 (1.62)

4

LED 1.48 (0.07)

5

Not connected 0.8 (0.9)

6

Not connected 0.8 (0.9)

7

Not connected 0.8 (0.9)

8

Not connected 0.8 (0.9)

9

VDD 2.5 supply pin 2.46 (2.54)

10

Ground 0.00

11

VDD 3.3 supply pin 3.30

12

CVBS input for TXT 0.88 (0.99)

13

VDDA 2.5 supply pin 2.41 (2.68)

14

Ground 0.00

15

Local keyboard input 2.50

16

Status signal input of Scart pin 8 0.00

17

Not connected 0.7 (0.8)

18

Power Ctrl 1.46 (0.24)

19

Horizontal sync input 2.00 (2.42)

20

Vertical sync input 3.13 (3.30)

21

Not connected 3.27

22

Not connected 3.27

23

Not connected 3.27

24

Infra red input 3.27

25

AV selection 0.00

26

Service 3.27

27

SDA I2C Bus Data Input 1.7 (1.93)

28

SCL I2C Bus Clock Input 1.7 (1.93)

29

Ground 0.00

30

VDD 3.3 supply pin 3.30

31

Not connected 0.00

32

Not connected 3.30

33

Reset 3.30

34

XTAL2 -

35

XTAL1 -

36

Ground 0.00

37

VDDA 2.5 supply pin 2.41 (2.68)

38

Red output for OSD and TXT 0.28 (0.0)

39

Green output for OSD and TXT 0.28 (0.0)

40

Blue output for OSD and TXT 0.28 (0.0)

41

Fast Blanking for OSD and TXT 0.00

42

VDD 2.5 supply pin 2.54

43

Ground 0.00

44

VDD 3.3 supply pin 3.30

45

Not connected 3.30

46

Not connected 0.00

47

Not connected 3.28

48

SDA I2C Bus for Eeprom 3.28

49

SCL I2C Bus Clock for Eeprom 3.28

50

Vertical linearity 0.68

51

Not connected 3.28

52

Not connected 3.28

IC501 (TDA8174) Vertical Deflection Output IC

Pin Connection V DC Pin Connection V DC

1

Power output 12.55

2

Output stage Vs 26.78

3

Trigger input 5.41

4

Height adjustment 6.78

5

Not connected 4.48

6

Ground 0.00

7

Ramp generator 4.76

8

Buffer output 5.68

9

Inverting input 4.48

10

Vs 26.17

11

Flyback generator 1.86

IC701 TDA6107 RGB Output IC

Pin Connection V DC Pin Connection V DC

1

Red in 2.3

2

Green in 2.3

3

Blue in 2.4

4

Gnd 0.0

5

Black current output 4.6

6

Vdd supply 191.8

7

Red out 134-139

8

Green out 132-140

9

Blue out 127-133