LG 42LC7D (CHASSIS:LA73E) Service Manual ▷ View online
- 37 -
- Explanation
Mpeg Feeder And Video Feeder (MFD and VFD)
-Mpeg Feeder is a data path
of VSB or QAM decoded si
gn
al. These signals go to
the Mi
nitita
n
o
f BCM3
55
0.
-In the mini
titan
bl
ock do pr
ocessi
ng the MPEG and video.
VDEC ( Video Displ
ay Decoder)
-This block has several
detai
led bl
ock. It can handle the
input composite signal
for example, Y/C separation,
color decodi
ng, auto gai
n control, etc.
AF
E
AF
E
Front
End
Front
End
Y/C
Se
pa
ra
ti
on
Y/C
Se
pa
ra
ti
on
Chrom
a
De
mo
Chrom
a
De
mo
B
ack
End
B
ack
End
VDEC Detai
l
Block
BVB
In
te
rf
ace
BVB
In
te
rf
ace
Digital Input
-Digital input
can handle digit
al video signal.
I
n
our
syst
em
t
h
rough this pat
h,
com
ponent
,R
G
B
PC,
HD
MI
/D
VI
signals
are deco
d
ed. So this path is very impo
rta
nt block i
n
o
u
r system.
Explanation
- 38 -
- TV/CATV doesn't display
Check TU4001 Pin9(Video
output)
Can y
o
u see t
h
e n
o
rmal sign
al?
Check the input(Pin63) of
A
V
s
w
itch(IC5003).
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
Check the output(Pin56) of
A
V
s
w
itch(IC5003).
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
Check the input(Pin1) of
LP
F(IC4006).
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
YE
S
YE
S
NO
Could y
ou measure
v
o
ltage of TU4001 &
IIC lines?
A
re they
all normal?
Check the output(Pin8)
of LPF(IC4006).
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
Check the input(PinH26) of
BCM35
50(IC4
006).
Measu
re w
a
v
e
form at C101
0
b
ecau
se its
more easy
to
check.
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
NO
You should check po
w
e
r
line
& IIC li
nes.
YE
S
You should replace TUNER.
NO
A
ft
e
r checking the Po
w
e
r
of
A
V
s
w
itch y
ou
should decide
to replace
A
V
s
w
itch or
not.
NO
A
ft
e
r checking the Po
w
e
r
of
A
V
s
w
itch y
ou
should decide
to replace
A
V
s
w
itch or
not.
NO
A
fte
r checking the Po
w
e
r
o
f LPF y
ou sho
u
ld
decide to replace LPF or not.
NO
A
fte
r checking the Po
w
e
r
o
f LPF y
ou sho
u
ld
decide to replace LPF or not.
YE
X
This board ha
s big
problem
because Main
chip(BCM3
550)
hav
e some trouble
s.
A
fter checking thorough
ly
all path
once
again,
You should decide to replace BCM3550 o
r not.
- 39 -
- Video doesn't display
Check J5007 Pin3C
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
Check the input(Pin1 or Pin8) of
A
V
s
w
itch(IC5003
). Pin
1
is fo
r
v
ideo1,Pin8
is
for v
ideo
2.
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
Check the output(Pin56) of
A
V
s
w
itch(IC5003).
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
Check the input(Pin1) of
LP
F(IC4006).
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
YE
S
YE
S
NO
J5007 may
hav
e
problem. Replace this
Jack.
Check the output(Pin8)
of LPF(IC4006).
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
Check the input(PinH26) of
BCM35
50(IC4
006).
Measu
re w
a
v
e
form at C101
0
b
ecau
se its
more easy
to
check.
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
NO
A
ft
e
r checking the Po
w
e
r
of
A
V
s
w
itch y
ou
should decide
to replace
A
V
s
w
itch or
not.
NO
A
ft
e
r checking the Po
w
e
r
of
A
V
s
w
itch y
ou
should decide
to replace
A
V
s
w
itch or
not.
NO
A
fte
r checking the Po
w
e
r
o
f LPF y
ou sho
u
ld
decide to replace LPF or not.
NO
A
fte
r checking the Po
w
e
r
o
f LPF y
ou sho
u
ld
decide to replace LPF or not.
YE
X
This board ha
s big
problem
because Main
chip(BCM3
550)
hav
e some trouble
s.
A
fter checking thorough
ly
all path
once
again,
You should decide to replace BCM3550 o
r not.
- 40 -
- Component doesn't display
Ch
eck J5
004,
J500
5.
Can y
ou see t
h
e n
o
rmal
w
a
v
e
form?
Check the input of Component
s
w
itch(IC5001,IC5002).
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
Check th
e o
u
tput o
f Co
mponent
s
w
itch(IC5001,IC5002).
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
Check th
e in
put o
f MST
3361
(IC7004
Pin41,44,46).
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
YE
S
YE
S
NO
J5004,J5005
may
ha
v
e
pro
b
lem. Replace this
Jack.
Check the output of
MST3361(IC7004 ).
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
Check th
e in
pu
t an
d
outpu
t of
BCM3550(IC4006). Especially
y
ou should
ch
eck
The
H,V sy
nc and clock.
Can y
o
u see t
h
e n
o
rmal
w
a
v
e
form?
YE
S
NO
A
fter checking the i
nput
TR
of compo
nen
t, y
ou
should decide
to replace component s
w
it
ch or
not.
NO
NO
A
ft
e
r ch
ec
kin
g th
e Po
w
e
r of MST
3361
y
ou
should decide
to replace MST3361 or not.
NO
YE
X
This board ha
s big
problem
because Main
chip(BCM3
550)
hav
e some trouble
s.
A
fter checking thorough
ly
all path
once
again,
You should decide to replace BCM3550 o
r not.
A
fter checking the Po
w
e
r o
f component s
w
itch
y
ou should decide to replace component s
w
itch
or not.
A
ft
e
r ch
ec
kin
g th
e Po
w
e
r of MST
3361
y
ou
should decide
to replace MST3361 or not.
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