LG CM9750 Service Manual page 33

9. NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD
disc if the servo motors in MD don't work. This step is for checking the spindle motor among
them.
9-1. SPINDLE MOTOR
9-1-1. Solution
Replace IC401 or IC400 on MAIN board.
9-1-2. How to troubleshoot (Countermeasure)
1) Check the SPDO signal from pin16 of IC401.
  If no signal, check 3.3 V (RF) and X400.
2) Check the SPIN- & SPIN+ from IC400 to CN401 for driving SPINDLE motor. It is about 3.6 Vp-p.
  If no signal, check +7 V for IC400.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
  If the spindle motor is short-circuit or has any trouble, it can not rotate CD discs.
Please check the function after changing another MD.
9-1-3. Service hint (Any picture / Remark)
< Waveform of SP- & SP+
for driving SPINDLE motor >
ONE POINT REPAIR GUIDE
3-14
SP+ SP+
pin6 of CN401 pin6 of CN401
SP- SP-
pin8 of CN401 pin8 of CN401
IC400 IC400
< MAIN board top view >