55LM4700 (CHASSIS:LA21B) — LG TV Service Manual (repair manual). Page 21

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9. Digital TV Audio
Check RF Cable & Signal
Follow procedure 
‘8. All source audio’
trouble shooting guide.
ok
Check Tuner 3.3V Power
L3703
Replace L3703
Check Tuner 1.8V Power 
IC3703  2 pin : 1.8V
Check IF_P/N Signal
TU3700  10/11 Pin
Replace IC3703 
ok
ok
ok
No
No
No
Bad Tuner. Replace Tuner
.
10. Analog TV Audio
Check RF Cable & Signal
Follow procedure 
‘8. All source audio’
trouble shooting guide.
ok
Check Tuner 3.3V Power
L3703
Replace L3703
Check Tuner 1.8V Power 
IC3703 2 pin : 1.8V
Check CVBS Signal
TU3700 8 Pin
Replace IC3703 .
ok
ok
ok
No
No
No
Bad Tuner. Replace Tuner.
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11. AV Audio
12. Component Audio
13. RGB Audio
Check AV Cable for damage
for damage or open conductor
Check JK1601 Signal Line
R1632,R1633
ok
ok
No
Replace Jack
Follow procedure 
‘8. All source audio’
trouble shooting guide.
Check Component Cable
for damage or open conductor.
Check JK1601 Signal Line
R1618, R1617
ok
ok
No
Replace Jack
Follow procedure 
‘8. All source audio’
trouble shooting guide.
Check Cable conductors
for damage or open conductor
Check JK1102 & Signal Line
ok
No
ok
Replace Jack
Follow procedure 
‘8. All source audio’
trouble shooting guide.
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BLOCK DIAGRAM
R
G
B
 P
C
S
P
D
IF
Co
m
po
ne
nt
 2 1
H
/P
 O
U
T
H
D
MI
(D
V
I)
H
al
H
al
N
IM
N
IM
(S
I2
1
(S
I2
1
7
6
_
A
T
7
6
_
A
T
SC
_
1
I
SC
_
1
I
N
P
U
T)
N
P
U
T)
P
C A
ud
io
 I
n
IF
 +
/-
TU
_C
VB
S
SI
F
L/
R
S
7
LR
S
ER
IA
L F
LA
S
H
M
X
IC
 (
8
M
 b
it
)
M
X
2
5
L8
00
6
EM
2
I
LV
D
S
(F
H
D
/H
D
 6
0
z)
A
. A
MP
N
TP
7
5
0
0
U
S
B
2
.0
D
P/
D
M
S
P
K
 L
/R
X
-t
al
2
4
M
H
z
FP
C
(5
1
P
/F
H
D
)
I2
S
SP
D
IF
H
/P
 L
/R
L/
R
CV
BS
Y/
Pb
/P
r,
 L
/R
RG
B/
H
/V
R
ea
r
TM
D
S
D
D
R2
 A
dd
.
D
D
R2
 D
at
a
SP
I
A
V
Si
de
N
A
N
D
  F
la
sh
(1
G
b
it
)
N
A
N
D
0
1
G
W
3
B
2
C
N
6
E
PC
M
_A
[0
:7
]
TM
D
S
H
D
MI
CV
BS
L/
R
D
D
R
2
5
6M
B
 1
G
b
H
yn
ic
H
5
TQ
1
G
6
3D
FR
D
D
R
2
5
6M
B
(1
G
b)
 
H
yn
ic
H
5
TQ
1
G
6
3D
FR
C
O
N
TR
O
L
IR
 &
 L
ED
 /
(S
O
FT
 T
O
U
C
H
)
K
E
Y
1
K
E
Y
2
IR
L
E
D
_B
/L
G
 L
O
G
O
A
T2
4
C
1
0
24
B
N
-S
H
-T
1
M
bi
t
I2
C
R
S
-2
3
2
C
FP
C
(3
0
P
/H
D
)
MA
X
3
2
3
2
RS
23
2C
S
E
N
S
O
R
_S
C
L
S
E
N
S
O
R
_S
D
A
LA
N
ET
_RX
/T
X
- 24 -
A7
A2
A10
200
400
540
521
530
800
810
120
* Set + Stand * Stand Base + Body
LV1
AG1
EXPLODED VIEW
Many electrical and mechanical parts in this chassis have special safety-related characteristics. These 
parts are identified by       in the Schematic Diagram and EXPLODED VIEW. 
It  is  essential  that  these  special  safety  parts  should  be  replaced  with  the  same  components  as 
recommended in this manual to prevent X-RADIATION, Shock, Fire, or other Hazards. 
Do not modify the original design without permission of manufacturer.
IMPORTANT SAFETY NOTICE
30
0
910
900

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