9-2. Power Supply Board Failure Check.
Service Manual
Model No.: LET40T3
50
State:No picture
First,check cables which connect with PSU,then check as follows
Check input voltage
voltage: +5VSB----POWER ON(2.6V) -----+12V
State:No sound
First,check cables which connect with PSU,then check as follows
1) Check input voltage as NO picture
2) Check speaker output
First,check speaker anode(+) and cathode(-),confirm speaker short or not.If short ,replace
speaker.
Second,check CN27 with oscillograph,confirm wave output or not.
C134
NC
C135
NC
L34
22uH
AMP-Lout+
AMP-Lout-
C136
NC
AMP-Rout+
OUT3A
AMP-Rout+
OUT3B
EAPD
L33
22uH
AMP-Rout-
AMP-Lout+
I2S_SD0
I2S_LRCLK
TW
HP_MUTE_AMP
RST_AMP
I2S_SCLK
I2S_MCLK
AMP-Lout-
L36
22uH
AMP-Rout-
C78
0.1uF
R107
3.3R
R492 12
L74
FB/2A
R534 12
C240 330pF/25V
R493 12
C106 10uF
C161 100nF
R332
22
C116 100pF
L76
FB/2A
1
2
3
4
CN27
Speaker
C262 100nF/25V
C255 100nF
R364 22
R338
22
C131 0.1uF
C107 10uF
C123
470nF
C146 4.7nF
C160 0.1uF
C121
470nF
C140 1uF
C281 330pF/25V
R334
22
C283
100nF/25V
CA84 470uF/35V
C100 0.1uF
C258
100nF/25V
R329
100
R306
10K
C291 100nF/25V
R346
22
C244
100nF/25V
R359 12
R494 12
C79
0.1uF
L31
600(4.5X3.2)
C117
680pF
GND_SUB
1
SA
2
TEST_MODE
3
VSS
4
VCC_REG
5
OUT2B
6
GND2
7
VCC2
8
OUT2A
9
OUT1B
10
VCC1
11
GND1
12
OUT1A
13
GND_REG
14
VDD
15
CONFIG
16
OUT3B/DDX3B
17
OUT3A/DDX3A
18
EAPD/OUT4B
19
TWARN/OUT4A
20
VDD_DIG
21
GND_DIG
22
PDN
23
VDD_PLL
24
PLL_FILTER
25
PLL_GND
26
XTI
27
BICKI
28
LRCKI
29
SDI
30
RST
31
INT_LINE
32
SDA
33
SCL
34
GND_DIG
35
VDD_DIG
36
PAD
37
U54
STA559BW
R362 12
R554 12
R349
22
C284 100nF/25V
R360 22
C118 1uF
R335
22
R253
2.2K
C286 100nF/25V
C254
2.2uF
R558 12
C282
100nF/25V
+12V
+3.3AVDD
+3.3AVDD
+3.3AVDD
M_SCL
1,2,9,14
I2S_MCLK
2
M_SDA
1,2,9,14
I2S_SD0
2
I2S_LRCLK
2
I2S_SCLK
2
RST_AMP
2
L35
22uH
C133
NC
R363
NC/0R
R350
100
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
CN10 Power
R341
100
+12V
+12V
5VSTB
PW_ON/OFF-INV
PB-ON/OFF
PB-ADJUST
PWR-ON/OFF-GPIO46
R225
NC/10K
R213
NC/10K
V203
3904
PW_ON/OFF-INV
R215
10K
C209
0.1uF
R214
100
R212
2.2K
5VSTB
+3.3VDD
R232
10K
PWR_ON/OFF