LG RN7 - Page 38

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ONE POINT REPAIR GUIDE
NO SOUND
There is no sound output in the USB Function, repair the set according to the following guide.
5-2. USB FUNCTION
5-2-1. Solution
Replace MAIN board.
5-2-2. How to troubleshoot (Countermeasure)
1) Check +5V_USB to USB board.
 If the Character ‘USB 1’ or ‘USB 2’ is turned on VFD, the voltage is okay, if so not, check USB_5V to
pin4, 5 of CN502.
2) Check USB D1± or USB D2± from MAIN board to TOP board.
a. Check 2.0_D1±signals(pin U7, U8 ) or 1.1_D1± signals(pin A7, A8 ) to IC501.
b. Check USB± signals to CN502(pin1, 2, 7, 8).
 If there is any trouble, check the power for IC207.
The power is normal but, if the signal waveform to the IC is distorted or no signal,
replace it with a new one.
3) Check if “Digital audio AMP block” on item 6-1 is normal.
5-2-3. Service hint (Any picture/ Remark)
USB D-/D+ (CN502 pin1, 2 & pin7, 8)
< Waveform of USB D± signal >
D
D+
D-
SOL
35791
2468
11 13 17
10 12 14 16
15
A
B
C
D
E
F
G
H
J
K
L
M
N
P
R
T
U
T
X
R5B4
R5B5
R5B6
RA501
3
A1
RA502
RA503
RA504
C5B2
C5B4
C5B5
TP518
TP519
TP520
TP521
TP522
TP523
ZD501
C5E2
C5E3
ZD505
ZD506
C5E7
C271
SF_CS
L312
FL500
C5B18
JK301
JK302
C5B21
C5B23
C5B24
C5B26
R501
C5B30
R504
C5B33
R508
C5B34
C5B39
C5B41
C5B43
C5B44
R5D10
CN502
SF_MISO
R3
C5B60
X500
X501
R5B51
53
R5B100
B
56
R5B102
C2B3
R5B104
R5B106
R5B107
B60
B61
B64
B65
R5B115
R5B94
RX
R5B95
R5B98
R5B99
R596
IC501
L5B9
< MAIN board top view >
CN502
CN502
IC501
IC501