Sound In The Usb Function - LG OK99 Service Manual

6. NO SOUND IN THE USB FUNCTION
There is no sound output in the USB function, repair the set according to the following guide.
6-1. USB FUNCTION
6-1-1. Solution
Replace IC501, IC207 on MAIN board.
6-1-2. How to troubleshoot (Countermeasure)
1) Check USB_5V to TOP board.
 If +5.1 VA to pin5 of IC207(Analog Switch ) doesn't come out, check pin8 & 9 of CN201.
 If +5.1 VA is normal & IC207 pin4 is high, IC207 pin1 doesn't come out 5 V, then check the USB_5V
short with GND.
2) Check "Digital audio AMP block".
6-1-3. Service hint (Any picture / Remark)
[+5.1VA TO USB_5V]
+5.1VA
C220
C225
1uF
10uF
DGND
DRV_VBUS2.0
< USB schematic >
ONE POINT REPAIR GUIDE
C270
C228
5 IN 1
10uF 100nF OUT
R223
IC207 2
GND
10K
3
4 EN/EN
FLT
R217
R235
4.7K
47K
RLIM = 1500mA FIX
DGND
D D +
D- D-
USB_5V
C272
C271
DGND
220uF 100nF
DGND
USB D-/D+ (CN502 pin1, 2 & pin7, 8)
3-15
Copyright © 2018 LG Electronics Inc. All rights reserved.
< Waveform of USB D± signal >
Only for training and service purposes.