![background image](http://html.mh-extra.com/html/lg/cm9750/cm9750_service-manual_215932038.webp)
3-19
ONE POINT REPAIR GUIDE
10. NO SOUND
There is no sound output in the USB function, repair the set according to the following guide.
10-1. USB FUNCTION
10-1-1. Solution
Replace IC501 on MAIN board, IC312 on FRONT board.
10-1-2. How to troubleshoot (Countermeasure)
1) Check +5 VU to FRONT board.
if +5.6 VA to pin2 of IC312(LDO) doesn’t come out, check pin4 & 5 of CN314.
if +5.6 VA is normal & +5 VU of IC312 pin3 doesn’t come out, then replace IC312.
2) Check “Digital audio AMP block”.
10-1-3. Service hint (Any picture / Remark)
D
D+
D-
D-
USB D+/D (CN502 pin5, 6, 8, 9)
< Waveform of USB D± signal >
< USB function signal
fl
ow >
Summary of Contents for CM9750
Page 15: ...2 2 ...
Page 19: ...4 SPEAKER SECTION A60L A60R ...
Page 75: ...3 71 3 72 PRINTED CIRCUIT BOARD DIAGRAMS 1 SMPS P C BOARD TOP VIEW ...
Page 77: ...3 75 3 76 2 MAIN P C BOARD TOP VIEW ...
Page 78: ...3 77 3 78 MAIN P C BOARD BOTTOM VIEW ...
Page 79: ...3 79 3 80 3 FRONT P C BOARD TOP VIEW ...
Page 80: ...3 81 3 82 FRONT P C BOARD BOTTOM VIEW ...
Page 81: ...3 83 3 84 4 FRONT_CTRL P C BOARD TOP VIEW BOTTOM VIEW ...