Works abnormally; if it is only digital audio signal has no output, firstly judge whether shaping circuit of
digital audio signal works normally, then check whether N106 and peripheral circuit works normally.
Abnormal system working may probably affect voltage, so in actual working firstly judge whether system
power supply is normal. Key point waveform mentioned above is also a good reference standard.
[
]
Example 4 Symptom: micophone has no output
Description: after power on, insert microphone, display has detect the input of microphone, but
microphone has no output.
Analysis and troubleshooting: after power on, insert microphone, microphone inputs sine wave
signal, shown as on the figure 3.3.1.4, test base electrode of signal board triode V101 and it is low level,
Mic mute signal is normal, test signal board capacitor C244 and there is no signal, test signal board
capacitor C224 and there is no signal. Considering that MIC input can be detected, test signal board
capacitor C202 and there is signal, power supply voltage of N203 is normal, so we preliminarily judge
that trouble lies in N203 PT2315. After changing PT2315, trouble is removed.
C231
4.7u/16V
C228
4.7u/16V
C233
5.6n
R224
10K
R222
4.7K
C230
4.7u/16V
C236
0.1u
C232
5.6n
C239
0.22u
C229
103
C234
681
R227
2.7K
C238
47u/16V
C237
0.1u
N204
PT2399
R233
20K
C242
47n
C235
681
C243
47u/16V
R225
22K
5
6
7
N202B
4 5 5 8
+12V
R203
1K
C2024.7u/16V
C21047u/16V
C215
100u/16V
C214
4.7u/16V
C213
5.6n
C212
5.6n
C211
47n
C217
68n
C216
68n
R210
5.6K
R205
100/0.25W
+12V
C240
103
R234
220/0.5W
R207
47K
C220
47u/16V
R2061K
V201
9014
+12V
-12V
C219
103
R21947K
C226
101
R22010K
+12v
-12v
R204100K
C20510P
5
6
7
N201B
4 5 5 8
R2024.7K
3
2
1
N201A
4558
C203
4.7u/16V
C201151
R20133K
OK_CLK
OK_DAT
VD202
1N4148
BIN_R
14
AGND
3
NC
8
TREBR
5
RIN
6
LOUD_R
7
NC
10
LIN
11
REF
1
VDD
2
BIN_L
12
TREBL
4
LOUD_L
9
BOUT_L
13
BOUT_R
15
ROUT
16
LOUT
17
DGND
18
DATA
19
CLK
20
N203PT2315
C204
10u/16V
P_KT
VD201
9.1V
VD203
5.1V
C218
4.7u/16V
C224
4.7u/16V
R21820K
R2211K
C244
4.7u/16V
OK
OK
OK_CLK
R226
2.7K
OK_DAT
C227
103
3
2
1
N202A
4558
P_KT
MIC
MIC
Figure 3.3.1.4 MIC circuit diagram
[
]
Example 5 Symptom: headphone has no output
Description: after power on, power amplifier has output, headphone has no output.
Analysis and troubleshooting: power on, input DVD signal, insert headphone and find that relay
disconnects, P_RLY of headphone board flat cable is high level, SHUTDOWN pin voltage of N100
Lm4880 is 2.5V, IN_A, IN_B of N100 has audio signal, test power supply pin voltage of N100 and it is
normal, test the positive audio signal of capacitor C106, C107 and it is normal, so we judge that
headphone has trouble. After changing headphone, trouble is removed.
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Summary of Contents for AV311T
Page 1: ...service manual AV311T...
