Read LG 47LB5DF (CHASSIS:LA75A) Service Manual online
- 18 -
TROUBLESHOOTING
TV/CATV(Analog) doesn
t display
Ch
eck T
U
80
1 Pin
23(Vid
eo
ou
tp
u
t)
Can
y
o
u
see t
h
e n
o
rmal sign
al?
Ch
eck th
e in
pu
t(Pin
1) o
f L
o
w
-Pass F
ilter
(IC808).
Can
y
o
u
see t
h
e n
o
rmal
w
a
v
e
fo
rm?
Ch
eck th
e o
u
tp
u
t(p
in
8) o
f
Lo
w
-Pass
Filter(IC808).
Can
y
o
u
see t
h
e n
o
rmal
w
a
v
e
fo
rm?
Ch
eck th
e Cap
aciter(C658)
in
fro
n
t o
f
BCM35
53 ch
ip
.
Can
y
o
u
see t
h
e n
o
rmal
w
a
v
e
fo
rm?
YE
S
YE
S
YE
S
NO
Co
u
ld
y
o
u
measu
re VCC
v
o
lt
ag
e(5Pin
) o
f
TU801 & IIC
lin
es(8,9Pin
)?
A
re they
all normal?
YE
S
Yo
u
sh
ou
ld rep
lace T
UNER.
NO
A
ft
e
r ch
ec
kin
g
th
e C800(0.1
u
F
Cap
), y
o
u
can
suspect that PCB is b
a
d
.
NO
A
ft
e
r ch
ec
kin
g
th
e Po
w
e
r
of L
o
w
-Pass F
ilter
y
o
u
should decide
to replace Low
-
Pass Filter or not.
NO
A
ft
e
r ch
ec
kin
g
th
e p
a
ttern
b
e
tw
een
p
in
8
o
f IC808
an
d
C658, y
o
u
can
su
sp
ect th
at PCB is bad
..
YE
S
Th
is
bo
ard
h
a
s b
ig
p
ro
b
lem
b
ecau
se Main
c
h
ip(BCM3
550)
hav
e s
o
me
trouble
s
.
A
fte
r c
h
ec
k
ing thoro
ugh
ly
all pa
th
onc
e
ag
ai
n,
Yo
u
sh
ou
ld decid
e to
rep
lace BCM3
553 o
r n
o
t.
Click on the first or last page to see other 47LB5DF (CHASSIS:LA75A) service manuals if exist.