LC-20SH6U
30
TROUBLESHOOTING TABLE
(Continued)
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Is there the lack of sound in any input mode (TV, video 1/2, component)?
No sound from right and left speakers
Check the following points:
1
Monitor output set at "variable"?
2
Sound volume at minimum?
3
Mute effect on?
4
Headphones connected?
Do the following and check again:
1
Set the monitor output to "Fixed".
2
Turn up the sound volume.
3
Clear the mute effect.
4
Disconnect the headphones.
Check the following points:
1
Sound heard from speakers?
2
Monitor output properly connected?
3
Mute effect on?
Do the following and check again:
1
Go to "No sound from speakers".
2
Reconnect the monitor output properly.
3
Clear the mute effect.
Is the voltage at pin (7) (power input terminal) of IC3301 as specified (about +12.5V)?
Is the voltage at pin (5) (standby control terminal) of IC3301 as specified (about +2V)?
Are the oscillation waveforms at pins (71) and (72) of IC1301 as specified?
Check the lines from pins (29) and (30) of IC2001 to pin (2) of IC1301.
Are the audio signal outputs at pins (27) (Rch) and (28) (Lch) of IC1301?
Check the lines from between pins (27) (Rch) and (28) (Lch) of IC1301 to pins (4) (Rch) and (2) (Lch) of IC3301.
Is the supply voltage of each circuit as follows? Pin (39) of IC1301:
About +8V
Pins (65) and (66) of IC1301:
About +5V
Pins (11), (12) and (13) of IC1301:
About +3.3V
Are the following control signals fed as follows? Pin (2) of IC1301: SCL1 Pin (3) of IC1301: SDA1
Check IC1301 and its peripheral circuits.
Check X1301 and its peripheral circuits.
Check the line between pin (56) of IC2001 and pin (5) of IC3301.
Check the following points: +8V Line:
check IC7004 and its peripheral circuits as well as the line up to Pin (39) of IC1301.
+5V Line:
check IC705, Q701 and their peripheral circuits, B5V700MA line, Q701 and its peripheral circuits, and +5V line of IC1301.
+3.3V Line:
check IC702, Q702 and their peripheral circuits, B3.3V1.2A line, and +3.3V input line of IC1301.
Check the built-in AC power supply and the line up to pin (7) of IC3301.
Are the audio signal outputs at pins (36) (Rch) and (37) (Lch) of IC1301?
Check the lines from between pins (36) (Rch) and (37) (Lch) of IC1301 to pins (2) (Rch) and (4) (Lch) of J3402.
Check the following points:
1
No TV sound: check Q3411, Q3412 and TU3401, and their peripheral circuits.
2
No Video 1 input sound: check the lines from J3402 to pins (56) and (57) of IC1301.
3
No Video 2 input sound: check the lines from J3403 to pins (53) and (54) of IC1301.
4
No Component input sound: check the lines from J3404 to pins (50) and (51) of IC1301.
Is the collector signal of Q3304 at "L"?
No sound from monitor output
Check the line from pin (58) of IC2001 to Q3304, as well as Q3401 and Q3402.
Check IC1301 and Its peripheral circuits.
No Audio Output
