Sound In The Usb Function - LG CJ87 Service Manual

5. NO SOUND IN THE USB FUNCTION
There is no sound output in the USB function, repair the set according to the following guide.
5-1. USB FUNCTION
5-1-1. Solution
Replace IC501 or IC303 on MAIN board.
5-1-2. How to troubleshoot (Countermeasure)
1) Check USB_5V to MAIN board.
  if +5.1 VA to pin5 of IC303(LDO) doesn't come out, check pin4 & pin5 of CN503.
  if +5.1 VA is normal & USB_5V of IC303 pin1 doesn't come out, then replace IC303.
2) Check "Digital audio AMP block".
5-1-3. Service hint (Any picture/ Remark)
D D +
D- D-
USB D-/ D+ (CN503 pin4, pin5)
< Waveform of USB D± signal >
ONE POINT REPAIR GUIDE
3-15
CN503 CN503
< MAIN board top view >