LG CM7420 Service Manual page 57

ELECTRICAL TROUBLESHOOTING GUIDE
USB play
IC501
Pin16,18 USB_HUB_D output
signal OK?
YES
When insert
USB,IC504 Pin1,2,3,4 USB_D
signal OK?
YES
A
AUX
IC202
Pin7,8 AUX input signal
OK?
YES
IC202
Pin42,43,44 I2S input signal
OK?
YES
IC202
Pin41 ADC data output signal
OK?
YES
A
NO
Check IC501.
IC3U01
NO
USB power +5 VU
OK?
NO
Check audio cable.
NO
NO
3-38
NO
YES
Check IC501.
Replace IC202.
Replace IC3U01.