LG OM5541 Service Manual page 22

There is no sound output in the USB FUNCTION, repair the set according to the
following guide.
(2) IN THE USB FUNCTION
[ Solution ]
Please check and replace IC501 on MAIN board & IC460 on USB board.
[ How to troubleshoot (Countermeasure) ]
1) Check +5 V_USB to USB board.
If the USB LED are turned on, the voltage is okay, if so not, check +5.6 V to pin3 of CN460.
2) Check USB D1± or USB D2± from MAIN board to USB board.
a. Check 2.0_D1± signals(pin U7, U8) or 1.1_D1± signals(pin A7, A8) to IC501on MAIN board.
b. Check USB± signals to CN421 (pin 2, 3, 5, 6).
If there is any trouble, check the power for each IC. 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 4-(1) is normal.
[ Service hint (Any picture / Remark) ]
DSP IC501
MLC3730
176PIN BGA
12.288 MHz
PWM
TAS5548
< USB function signal fl ow >
ONE POINT REPAIR GUIDE
USB1 _D±
USB2 _D±
FL ±
TAS5631BPHD
D- to pin 3&6 of CN421
D+ to pin 2&5 of CN421
< Waveform of USB D± signal >
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