LG 42LT770H (CHASSIS:LA2FF) Service Manual ▷ View online
- 21 -
RGB-PC Video Trouble Shooting guide
Analog RF Audio Trouble Shooting guide
Check input signal format.
Is it supported?
Y
Check AC cable for damage
For damage or open conductor
Y
Check JK3603
Can you see the normal waveform?
Y
Check the input of MTK(IC105).
Measure waveform at R323, R324 because it’s more easy to check.
Can you see the normal waveform?
Y
This board has big problem because Main chip (MTK) have some troubles.
After checking thoroughly all path once again, You should decide to replace MTK or not.
Replace JK3603
N
Check RF cable & signal
Check TU8900 Pin2
(SIF output)
Y
Check Audio AMP output
L5402,L5403,L5404,L5405
Y
Check IC5400
Y
Check C352
(SIF signal to IC105)
Replace Tuner
N
Replace L5402,L5403,L5404,L5405
Replace IC5400
N
N
Replace IC105
Y
- 22 -
Composite / RGB-PC Audio in Trouble Shooting guide
HDMI Audio in Trouble Shooting guide
Check input signal format.
Is it supported?
Y
Check AC cable for damage
For damage or open conductor
Y
Check JK3800
Can you see the normal waveform?
Y
Check the input of MTK(IC105).
Measure waveform at C345, C346, C319, C320 because it’s more easy to check.
Can you see the normal waveform?
Y
This board has big problem because Main chip (MTK) have some troubles.
After checking thoroughly all path once again, You should decide to replace MTK or not.
Replace JK3800
N
Check Audio AMP output
L5402,L5403,L5404,L5405
Replace L5402,L5403,L5404,L5405
N
Y
Check input signal format.
Is it supported?
Y
Check AC cable for damage
For damage or open conductor
Y
Check JK3301/JK3302/JK3303
Can you see the normal waveform?
Y
This board has big problem because Main chip (MTK) have some troubles.
After checking thoroughly all path once again, You should decide to replace MTK or not.
Replace JK3301, JK3302, JK3303
N
Check Audio AMP output
L5402,L5403,L5404,L5405
Replace
L5402,L5403,L5404,L5405
N
Y
- 23 -
BLOCK DIAGRAM
L
/
R
O
U
T
S
P
D
IF
O
U
T
N
A
N
D
Fl
as
h
(2
G
B
)
U
S
B
(D
P
/
D
M
)
M
T5
36
9
C
V
B
S(
M
)
D
IF
(+
/-
)
U
S
B
1
PC
-R
G
B
Ex
t
SPK
O
P
TI
C
LA
N
1
SY
STE
M
D
D
R
3
X
4
(2
G
b)
H
D
M
I3
H
D
M
I2
Si
de
R
ea
r
R
G
B
,H
/
V
E
th
e
rn
e
t
(R
X
/
T
X
)
C
V
B
S
SY
STE
M
E
EP
R
O
M
X
1
(2
5
6
K
b)
H
D
M
I
S/
W
T
S
_
S
/
P
LV
D
S
(8
bi
t)
3
0
P
5
1
P
LV
D
S
(8
bi
t)
3
0
P
5
1
P
S
M
A
R
T
b
-
L
A
N
Et
h
er
n
et
H
U
B
IC
D
m
od
.
IC
R
F
M
a
in
A
/V
M
a
in
A
/V
SI
F
P
ro
:i
d
io
m
R
S-
2
3
2
C
D
EB
U
G
PT
C
(M
IC
O
M
)
S/
W
A
/V
1
D
em
od
M
PI
/S
PI
Ex
t S
P
K
A
M
P
(F
H
D
)
(H
D
)
H
D
M
I1
C
V
B
S
V
id
eo
A
u
di
o
V
id
eo
A
u
di
o
W
i-
F
i
U
SB
t
o
Se
ria
l
M
-
R
e
m
o
te
Sp
ea
ke
r
I2
S
O
u
t
A
u
d
io
A
M
P
R
JP
R
J1
2
H
D
C
P
EE
P
R
O
M
P
H
Y
C
hi
p
IR
&
K
e
y
LA
N
2
3
7
/4
2
/4
7
3
2
L
R
M
D
C
/M
D
IO
M
D
C
/M
D
IO
R
ea
r
In
te
lig
e
n
t
S
e
n
s
o
r
R
X
/T
X
(R
X
/T
X
)
I2
C
I2
C
I2
C
L
o
c
a
l D
im
m
in
g
I2
C
I2
C
T
S
_
S
I2
C
A
u
di
o
PC
-A
u
di
o
U
S
B
2
(H
U
B
)
(AR
C
)
최
대
동
작
주
파
수
:
8
0
0
M
H
z
- 24 -
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
LV
1
300
200
540
521
530
800
550
810
120
500
501
510
400
900
910
A2
A7
A10
* Set + Stand * Stand Base + Body
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