LG 37LG50FR / 37LG55FR (CHASSIS:LP81A) Service Manual ▷ View online
- 21 -
10-1 Symptom
1) LED is green.
2) Screen display but sound is not output.
2) Screen display but sound is not output.
10. No Sound
10-2 Check process
All input(mode)
is no sound.
Only HDMI is
no sound
Only AV/
COM2/PC input is
no soudn.
Only RF is no sound.
Check the Tuner In/Out.
Check the signal after
IC600 refer to circuit
diagram
Is the output of
IC600 normal?
IC600 normal?
Download the EDID data.
No
No
No
No
No
Yes
Yes
Yes
Yes
Menu?
Normal
Normal
No
No
No
No
Yes
Yes
Yes
Replace
IC600
Is the speaker
on it men?
Set on speaker
in menu
Check the
Speaker cable
Replace
IC801
Replace
IC601
Is the speaker
cable normal?
cable normal?
IC801 operate
normal?
IC 601 operate
normal?
Replace Main B/D
- 22 -
BLOCK DIAGRAM
A
V1 in
SideA
V in
(A
V2 in)
Comp1 in
Comp2 in
RGB in
(D/L)
A
V
out
CVBS I
N
Y/Pb/
P
r I
N
R/G/B
/HS/
VS IN
CVBS I
N
LIN
E OU
T
L
IN
E IN
L
IN
E_MUTE
RS-232C
Rx/Tx
MX3232
RF
(T
uner)
PC Audio
in
DISPLA
Y
MODULE
EDI
D
N
V
M
EDI
D
N
V
M
HDMI1
HDMI2
HDMI3
USB
T
M
DS3
51
P
A
G
H
D
MI M
U
X
Zoran
V
A
D
D
IS-966
X
D
MPEG D
e
c
o
der
D
D
R MEM
D
D
R MEM
SERIA
L
FLA
S
H
Mstar
Rome
o
LGE6
8
9
1
C
D
TW991
0
Sub D
e
c
oder
NTP
300
0
A
D
ig
ital
Aud
io A
M
P
MAIN N
V
M
MC74HC4
0
6
6
A
u
d
io SW
LM324
X4 AMP
SERIA
L
FLA
S
H
B
D
204
1
P
ro
tect I
C
EDI
D
N
V
M
D
D
C/HD
P
/CEC
T
M
DS(H
DMI in)
D
D
C/HP
D/CEC
T
M
DS(H
DMI in)
T
M
DS(H
DMI in)
U
S
B
(A
V I/O
,
D
a
ta
I/O)
+5V
CVBS O
U
T
6
5
6 IN
SW_RE
S
E
T
P
A
R
T_I2
C
P
A
R
T_I2
C
SW_RE
S
E
T
I2S O
U
T
LV
D
S
MPEG RX/
T
X
MPEG RES
E
T
I2S I
N
6
5
6 IN
T
M
DS(H
DMI in)
D
D
C/HP
D/CEC
D
D
C/HP
D/CEC
[CEC not
through H
DMI MUX, d
irec
t
J
A
CK to MAIN
IC]
DD
C
DD
C
DD
C
U
A
R
T_Rx/Tx
A
U
DIO
_
S
W
L
IN
E IN
L
IN
E IN
L
IN
E IN
Y/Pb/
P
r I
N
L
IN
E IN
Y/C IN
L
IN
E IN
EDI
D
N
V
M
ROM_I2C
DSU
B
_
D
D
C
x
0
.55
x
0
.55
x
0
.55
x
0
.55
S
_
V
IDEO
_
D
E
T
L
IN
E_MUTE
LIN
E OU
T
CVBS O
U
T
x4
x4
x
0
.55
L
IN
E IN
CVBS I
N
SIF I
N
TUNE
R_I2C
P
A
R
T_I2
C
H
D
MI_SEL
- 23 -
EXPLODED VIEW
300
510
500
121
120
122
200
801
900
901
802
803
805
806
804
830
550
530
521
540
400
810
200T
200N
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
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