Roadstar lcd 8412 schematic

R

- LCD-8412K/S

- LCD-8412K/S

LCD-8412K/S

Service Manual

Service Manual

V

u

R

Repairing precedures for no sound, no picture and no

light.

Check whether power indicator lights in red.

YES

Press POWER to check whether
0~5V or 5~0V change is
available on CPU ○,7 pin or
not.

NO

Check whether

Check whether +5
supply of CPU is
normal or not.

NO

YES

external circuit
for key input pin
and CPUP10)P11)
pins are normal or
not.

NO

NO YES

Check whether
input +12V and
78L05 is broken or

NO YES

not.

Check whether
C1815,B1203 for ON/OFF
of CPU and subseq

circuit is
short-circuited or not.

NO

ent supply

YES

Change B1203 C1815.

Change 32K cillation

Change
CPU

YES NO

Check whether
output of high
voltage is
available or
not.

Change LCD screen

YES

YES

Check whether each voltage for the
output of power supply is normal or not.

epair power supply and

supply circuits.

NO

NO

YES

Check whether high
voltage supply N25 is

YES

open-circuited or nt.

YES

Check why N25 is open-circuited.

Change audion of
high voltage
circuit or the high
voltage
transformer.

m

w

Repairing procedures for Inferior color

NO

Check whether output voltage fro
LA76810○,19○,20○,21 is normal or not.

YES

Check whether loop of IR3Y26
○,8○,9 and LA76810○,19○,20○,
is normal or not.

21

NO

YES

Change module of
LCD software.

Whether LA76810 ○,30○,31 pins
are short-circuited or not
and whether ○,18pin is normal
or not.

Change the broken elements of loop.

NO

Check
periphery of
IR3Y26 is normal
or not.

hether

NO

Change IR3Y26

y

W

W

WITH Sound, with light and black screen

Check whether power suppl
of LA76810 ○,25○,18pins is
normal or not.

NO

Check power supply.

YES

Check whether LA76810○,13○,
○,11pins are normal or not.

12

Check whether line

NO

field pulse of CPU
is normal or not.

YES

NO

hether the ground
resistance of LA76810 ○,
pin is normal or not.

29

YES

Check the

hether it is ok

after change CPU.

LA76810line field
synchronous

circuit.

NO

YES

Check if the copper sheet of
line field synchronous pulse
loop is open or
short-circuited or not.

Check +5V +7.5V power
supply of IR3Y26 is normal
or not.

NO

YES

Change IR3Y26.

Change the resistance.

NO

Check LCD screen and replace.

- 3 -

Repairing Procedures for line field synchronization

Check whether +5V +8Vpoweer
supply of LA76810 is normal or
not.

NO

Repair power supply.

YES

Check whether peripheral circuit
of LA76810 pin is normal or not.

NO

Change 1u 333 capacitance

YES

Check peripheral circuit of 4001
IC Pcircuit for treatment of
line field synchronization).

YES

Check the connector pin  to LCD screen is normal
or not..

NO

Check the abnormal part.

YES

Change module.

NO

Change LCD screen.

- 4 -

d

–

W

y

p

f

p

I

,repairing procedures for white light.

Test whether the switch power supply +5V +8V an

15V are normal or not.

NO

hether repair power suppl
and subsequent circuit is
short-circuited or
overloaded.

YES

Check the loop o

NO

Test whether IR3Y26 +5V and +7.5

ower supply is normal or not.

ower supply.

NO

Check whether

R3Y26 is broken

or not.

YES

Change module of LCD screen.

NO

Test whether +5V, +17V and –15V of
bus socket is normal or not.

NO

Check the loop of
power supply circuit.

YES

Change LCD screen.

NO SIGNAL.

V

y

Test whether +40V is normal or not.

NO

YES

Test whether wave band switch voltage is available
with CPU ○,1○,41○,42 pin. Test  pin VT output voltage
is normal or not.

NO

YES

Check whether AGC voltage for +5V power supply of T
tuner is normal or not. Check the TV turner VT voltage
is normal or not.

Check 40V loop.

Change CPU.

NO

Check 5V power suppl
and AGC circuit, and
also check the circuit
of VT voltage.

YES

Check whether circuit of pre-central
amplifier and periphery of LA76810○,
pin is normal or not.

50

NO

Check periphery of ○,50pin for

YES

pre-central amplifier.

Change the TV tuner.

Can not store program.

Check whether 32V-tuning
voltage is normal or not.

NO

Repair tuning loop.

Check whether AFT circuit is normal or not.

YES

NO

Repair AFT circuit.

YES

Change TV tuner and sound surface

T

T

With picture, no or low sound and distortion

est whether loudspeaker is open

circuited or not.

YES

Change loudspeaker.

NO

Test whether power amplifier
386 is broken or not.

YES

NO

Check whether LA76810○,1○,2pins are normal or not.

est whether power
amplifier 386 is
broken or not.

Check whether

YES

LA76810 ○,52○,53○,54pins
are normal or not.

NO

YES

Change peripheral
elements or ○,1○,
pins.

2

Change
LA76810.

NO

Change peripheral circuit of ○,52○,53○,54.

- 8 -

A

m

y

Dark light

Check whether contrast
and bright are adjusted

NO

to minimum or not.

Check whether power
supply of each circuit
is normal or not.

NO

YES

Set analog quantit
of TV at standard.

djust potentiometer of

ain board BRI to see
whether there is change or
not.

Check supply power
circuit.

YES

Adjust till OK

NO

Check whether peripheral elements of IR3Y26 are normal or not.

YES

Change IR3Y26

with picture, with sound, no character or inferior

color.

Check CPU 32K crystal oscillation.

Change 32K

NO

YES

crystal
oscillation.

Check whether pulse input of
CPU line field
synchronization is normal or
not.

Check line field
synchronization

NO

circuit.

YES

Inferior
character
color.

Check whether CPU ○,22 ○,25 to
LA76810 ○,13 ○,16 is normal or
not.

NO

Change loop elements.

NO

Change CPU or LA76810.

V

AV no picture or no sound.

Check whether A
connects wire is
normal or not.

YES

NO

Check input socket.

NO

YES

Change AV connect wire

Change input socket.

Check the loop of audio and LA76810○,51pin, and

the loop of video and LA76810○,42 pin.

YES

Change LA76810

No flip vertical/horizontal function

Press keys on remote control.

Test CPU ○,35○,36 pins to check 1Whether

0 5V or 5  0V change is available on
P15)P16) pinR 2Whether 05V or
50V change is available on ○,3○,4pins
for picture mode selection.

NO

Change remote
controller and try
again.

YES

Change remote
Check whether CPU○,35○,36○,3○,4 to
the copper sheet of LCD module
○,3○,4○,18○,19 pins is open
circuited or not.

controller

head.

Change LCD screen.

NO

54321

TU1

AGCVTBUBHBLBMIF

ANT1

R1

R8

C4

4K7

680P

IR C5V KEY GND

C10
103

R22
8K2

ZD1
3V9

C5V

C15
104

IC2
78L05

3

Vout

D9

IN5819

FU3
U185

IC3
T5001

7

8

7

8

D1

S41G

1K

R5
22K

Q1

C1815

R9

R10

10K

470

C7
100P

P/N
16:9

4:3

POWER

J1

123

4

C5V

PT11

R16
680

R20

Q2

4K7

A1015

R23

R24

270K

1K5

C5V

PT23
C5V

C16

C17

104

104

1

Vin

GND

2

C22
104

PT22
12ViN

C27
104

3456

2

R34

1

1K

3456

IC4
S140

2

1

L3

39uH

AGC

D

REMOTE

PT10

R17
10K

AFT

C

C19

100uF

B

C26

10uF

C28
104

R33

24K

A

ANT

R3

+5V

12K

C1

C3

C2

C31

LC863324A

C20

10uF

+12V

Q5
DKPJ

Q7
DKPJ

R36
1K

C32

10uF

10uF

10uF

42

BAND1

41

BAND2

40

ENGLISH

39

AV2

38

AV1

37

MUTE

36

L/R

35

U/D

IC1

34

IR

33

SD

32

S-VHS

31

SAFTY

30

SCL1

29

SDAO1

28

SCLO

27

SDAO

26

IO

25

BLANK

24

B.OUT

23

G.OUT

22

L1

C58
102

R77

R78

R29

330K

27K

180K

IC6
2368

123

C66
104

R80
2K2

R82
6K8
VR1
1K

C74

104

U15

1

C80
104

2

3

4

5

6 7

R85
2K2

D2
M.O

104

22uF

R2

+33V

51K

R4

22K

R6

R7
22K

22K

C5
104

C6
104

1

SLIRROUND

2

R11
10K

R13
10K

C5V

C8
18P
X1
32K
C9
15P

103

R26
10K

C18
104

C138
1uF

R30
47

C23
470uF

R31
3K3

50/60

R12

10K

3

ALAMP(16:9)

4

WO.OF-VOL(4:3)

5

VOLUME-L

R14

6

VOLUME-R

10K

7

POWER

R15

8

1K2

VT

9

GND

10

XTAL1

11

XTAL2

12

VDD(5V)

C5V

13

KEY

14

AFT

15

SIF2

16

SIF1

C12

17

RESET

R21

C13
1uF

18

330

FILT

19

CHRDMA

20

V.SYNC

Y.SYNC21R.OUT
C14
22uF

R25

HS

VS

10K

POWER

Q3

R27

C1815

10K

R28

1K

Q4
B1202

C24

C21

470uF

104

+12V

FU1
N25

L2

100uH

R32
3K3

C25

Q6

470uF

C1815

R35

10

Q8

A1015

R37
1K

C29

R38

R207

1uF

1K3

1K3

TDQ-3CV1

104

C5V

R66

3K3

R75
100

678

3518

R81
82K

R83
22K

R84
2K2

ST1

R39

C34

R40

100

104

150

R43

R44

4K7

R60
220

R63
220

C5V

C53
100uF

T1

TRANS-09

D8

IN5819

220

Q9

C388A
R45
1K

R46

33

L/R

U/D

REMOTE

R52
100

R55
100
R58
100

IC5

24C04

5

A34SDA

3

6

A2

SCL

2

7

A1

TEST

1

8

A0

(5V)

BLANK

R70

R71

4K7

4K7

D3

IN4937

C57

22uF/50V

D4

IN5819

1

10

2

9

C65

3

8

47uF/25V

D6

IN4937

4

7

5 6

L5

100uH

C72

220uF

L6

C75

100uH

104

C38

103

R49
22K

PY2

L/R

PY1
U/D

R53
22K

R54
22K

R56
22K

R57
22K

R59
22K

R61
22K

R62
22K

R64
3K3

R69
4K7

C56
100uF

4 5

Q10

C73

220uF

8

+8V

C30

C36

100uF

VOL

C33
473

R41
10K
R42

6K8

C39

C40

103

103

AGC

CF1

112

+5V

CF38.0

R47

100K

C41
103

GND

C42

1uF

R48

100K

R50

AFT

SDA

SCL

R51
100K

+5V

GND

RI

SD

GI

BI

BLANK

SCL

SDA

BI
GI
RI

R73

2K7

C54

R74

104

10K

R76
22K

L4

100uH

C67

C68

104

104

C76

104

220uF

C62

100uF

+8V

RO

GO

BO

SD

C46

VER

224

GND

+5V

C48
333

+8V

R67

120

R68

C49

3K3

1uF
C50
100uF

C51
472

R72

ZD2

C52

33V

104

22uF/50V

C55

ZD3

104

17V

D5

C59

C60

IN4937

220uF

104

R79

C63

C64

10K

104

100uF

D7

IN5819

C69

C70

C71

104

104

104

C77

C78

104

C79

104

1

AUDIO

C35

2

223

FM.OUT
C37
223

3

PIF.AGC

4

RF.AGC

5

2

IF.IN

6

33445

IF.IN

5

7

IF.GND

8

IF.VCC(5V)

+5V

9

FM.FILTER

10

27K

AFT.OUT

11

BUS

12

BUS(L)

C45
1uF

13

ABL

14

R.IN

15

G.IN

16

B.IN

17

BLANK.IN

18

RGB.VCC(8V)

19

R.OUT

20

G.OUT

21

B.OUT

22

R65

ID

2K2

23

VER.OUT

24

V.RAMP.ALC

C47
474

25

H/BUS.VCC

26

AFC.FILTER

HOR.OUT27FBP.IN

HOR

2K2

C109

C110
22uF/50V

C111

C61

104

220uF

C113
104

PT25

-15V

PT24
5V

C157
220uF

PT26
+33V

PT27
+17V

C112
104

PT28
+7V

PT43
+5V

IC7
LA76810

V C DEF.VCC(5V)

+33V

+17V

+8V

PT29
+8V

+7V

-15V

5V

+5V

SIF.IN

SND.APC

SIF.OUT

EXT.AUDIO.IN

PIF.APC

VCO.FILER

VIDEO.OUT

BLACK.STRECH

INT.V.IN/C.IN

EXT.V.IN/Y.IN

V C DEF.GND

SEL.VIDEO.OUT

C AFC.FIL.TER

X.TAL

SEL.VIDED.OUT

C AFC.FIL.TER

SECAM.IN

SECAM.IN

I HDL.GND

CCD.FIL.TER

I HHDL.VCC

CLK.OUT

Q12
C1815

VCO

VCO

REF

HOR

R108
10K

54

53

52

51

50

49

48

47

46

R92

45

44

43

42

41

40

R96

39

38

37

36

35

34

C105
10uF

33

32

31

30

29

28

FBP

+8V

R107
10K

+8V

+5V

VS

R113
10K

C1815

C85

L7
15uH

39P
C86
102

C87

R86

1K

1uF

C88

R87
330

18P

C89

R88

10uF

180K

C91
56P
LT1

C93

GND

0.47uF
R90

1K

R91
560K

1K5

C94
4u7

C95

1uF
C96

10uF

R95

150

C98

1K

220P

C100

X2

18P

4.433MHz
C103

R98

10uF

R99
10K

R100

+5V

150

R102
100

C106

C107
10uF

103

R104

1K

R105
4K8

C108
47P

C114
102

12345

IC8

4001

VCC

13

14

R110

C115

R111

10K

33K

Q13

C92
470P

GND

PT1
APC

R93

C102

1K

Q11

A1015

GND

R106
18K

101112

R109

10K

R112

3K9

103

+5V

VOL

PT2

C84
472

C119
2u2

C90

0.47uF

R174

1K

R89

R139

330

1K

+5V

R141
75

R94

2M

20K

GND

C97

0.47uF
R97

C99

22K

103

C101

R103

6

9

Q14

C1815

103

C104
103

R101

1K

1K

+8V

R142
2K2

C81

12345

7

102

GND

8

14

+5V

FBP

R19
5K6

R149

C145

R151

103

10K

10K

R152
3K3

103

1

2

3

4 5

PT3
AUDIO

R138
100

9

10

11

12

13

14

15

16

R136

4K7

PY6

PY5

VCC

R153
3K3

CSC386P

SAND

4.43

SYS

KIL

VI

VCC(8V)

EOU

13

VER

C144

103

IC9

PT4
VIDEO

IC10
LA7642N

GND84.0

4.0F

4.43F

FOF

IC12
4001

+5V

+12V

R120

22

8

C121

7

470uF

6

C123
100uF

C124

104

PT7

PT6

J7

1
2

PT5

+ -

PT12

R114
47

PY3

C129

7

B-Y

R-Y

103

C130

PY4

6

103

5

C132

1uF

C133

4

IDF

103

3

C135

1uF

2

C136

KIF

1uF
C137

1

1uF

C140

R143

4K7

102

C178

6

7

102

GND

8

9

101112

R150

C146

8K2

103

R144

Q17

22K

C1815

JV-845LA

C83

27P/3KV

J6
2

PT42

1

PT41

5V

C117

R116

104

47K

R117

47K

C118

R118

104

47K

R119
36K
C120

R121

104

47K

R122

47K

C122

R123

24K

104

VR2

R124

5K

C125

104
R126
36K
C126

104
R128
36K
C127

104
R130

36K
C128

104

R132

51K

C131
1uF

C134
1uF

56K

R125
47K

R127

47K

R129
47K

R131
30K

FRP

PSI

CSY

+8V

R231
10K

R230
12K

C141

104

R133
100

R135
100

R134

1K

SYNC

RO
GO
BO

SYNC

R145
4K7

IVIY

HS

VB

+7V

R157

100

C147

104

C149
104

36

B

37

38

39

40

41

42

43

44

45

46

47

48

123456789

C44
103

C150

104

R162
10K

R164

10K

R165

1K5

PY7
AUDIO

C43
104

VG

R163
10K

R158
100

IR3Y26A

IC13

L/R

5V

VR

R154

R155

R156
47K

33K
R159
100

C148

104

C152
104

R166

1K8

R140

51K

R160

62K

2526272829303132333435

RG

C151

U/D

C143
104

***

FUK1

101112

104

R167
1K5

+5V

24

23

22

21

20

19

18

17

16

15

14

13

Y1

IR C5V KEY GND

123

4

IC11

REMOTE

1

IR

2

GND

3

VCC

C82
104

LED1

R115
4K7

5V

R18
0R

IVIY

SYNC

C11
***

SK1

POWER

SK2

R146

TV/AV

1K5

SK3

R147

MENUV

2K7

SK4

R148

VOL-

3K9

SK5

R161

VOL+

4K7

SK6

R168

CH-

8K2

SK7

R169

CH+

AV1

27K

R137

150K

R184
12K
C158

104
C159
104
C160

104
C161

104

-15V
+17V

5V

GND

P/N

L/R

U/D

GND

FRP

5V

GND

16:9

GND

4:3

CSY

GND
VB
VG
VR
PSI

30PIN

ANT3

CON401

30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1

AV2

ANT2

DK1

DC1

P/N

PT13

L/R

PT14

U/D

PT30

FRP

PT31

IVIY

PT32

SYNC

PT33

16:9

PT34

4:3

PT35

CSY

PT36

VB

PT37

VG

PT38

VR

PT39

PSI

PT40

6

D

PT8

PT9

PT16

PT15

PT17

PT18

PT19

PT20

PT21

C

B

A

1 2 3 4 5 6