Sharp LC-20SH4U, Service Manual

Page: 22 / 54

22
LC-20SH4U
SUPPLEMENT
TROUBLE SHOOTING TABLE
(Continued)
No audio output
No
No No No
No No No No No No No
No sound fr
om right and left speaker
s
Is sound heard in an
y input mode (TV
,
Video or Component)? Is the v
oltage at pin (7) (po
w
er input
ter
minal) of IC3301 as specified
(about +12.5V)? Is the v
oltage at pin (5) (standb
y
control ter
minal) of IC3301 as
specified (about +2V)? Are there the specified control signal inputs at the f
ollo
wing pins of IC1300?
Pin (2) of IC1300 SCL1 Pin (3) of IC1300 SD
A1
Chec
k the line from pins (29) and (30) of
IC2003 to pins (2) and (3) of IC1300. Chec
k X1300 and its per
ipher
al circuits
.
Chec
k IC1300 and its per
ipher
al circuits
.
Are the oscillation w
a
v
e
fo
rms at pins
(71) and (72) of IC1300 as specified? Are there audio signal outputs from pins (27)(Rch) and (28)(Lch) of IC1300? Chec
k the lines from pins (27)(Rch)
and (28)(Lch) of IC1300 to pins (4)(Rch) and (2)(Lch) of IC3301.
Chec
k the f
ollo
wing points
.
+8V line:
Chec
k the line from IC1301 to pin
(39) of IC1300. +5V line:
Chec
k the line from pin (4) of SC1201
to the +5V input line of IC1300. +3.3V line:
Chec
k the line from IC1203's
per
ipher
al circuit to the +3.3V line
of IC1300.
Is the po
w
er v
oltage of each circuit as
follo
ws?
Pin (39) of IC1300
About +8V
Pins (65) and (66) of IC1300
About +5V
Pins (11), (12) and (13) of IC1300
About
+3.3V
Chec
k the line from po
w
er circuit to pin (7) of
IC3301.
No sound fr
om monitor output
Chec
k IC1300 and its per
ipher
al
circuits
.
Chec
k the line from pin (58) of IC2003
to Q3901, Q3902 and Q3903.
Are there audio signal outputs from pins (36)(Rch) and (37)(Lch) of IC1300? Is the collector signal of Q3901 at "L"? Chec
k the lines from pins (36)(Rch)
and (37)(Lch) of IC1300 to pins (2)(Rch) and (4)(Lch) of I3903.
Do the f
ollo
wing.
1
Go to "No sound from speak
ers".
2
Reconnect the monitor output proper
ly
.
3
Clear the sound m
ute
.
Chec
k the f
ollo
wing points
.
1
Is the sound heard from the speak
ers?
2
Is the monitor output proper
ly
connected?
3
Is the sound m
ute?
Chec
k the line from pin (72) of IC2003 to pin
(5) of IC3301.
Chec
k the f
ollo
wing points
.
1
Is the monitor output set at "A
UDIO
V
ARIABLE"?
2
Is the v
olume control at minim
um?
3
Is the sound m
ute?
4
Is the headphones disconnected?
Do the f
ollo
wing.
1
Set the monitor output at "A
UDIO FIXED".
2
T
u
rn
up the v
olume control.
3
Clear the sound m
ute
.
4
Disconnect the headphones
.
Chec
k the f
ollo
wing points
.
1
No
TV sound:
Chec
k Q1300, Q1301,
TU3401 and their per
ipher
al circuits
.
2
No
Video 1 input sound:
Chec
k the line
from SC2002 to pins (56) and (57) of IC1300.
3
No Component input sound:
Chec
k the line
from SC2001 to pins (50) and (51) of IC1300.
Yes
Yes Yes Yes
Yes Yes Yes Yes Yes Yes