LG OK99 Service Manual page 36

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 sled motor among them.
5-2. SLED MOTOR
5-2-1. Solution
Replace IC401 or IC400 on MAIN board.
5-2-2. How to troubleshoot (Countermeasure)
1) Check the SLDO signal from pin15 of IC401.
 If no signal, check DVCC_3.3V(RF) and X400.
2) Check the SLED+ & SLED- from IC400 to CN401 for driving SPINDLE motor. It is about 2.9 Vp-p.
 If no signal, check M_5V for IC400.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the sled motor is sort-circuit or has any trouble, it can not move the pickup module.
Please check the function after changing another MD.
5-2-3. Service hint (Any picture / Remark)
< Waveform of SLED- & SLED+
for driving SLED motor >
ONE POINT REPAIR GUIDE
SL+ SL+
pin7 to CN401 pin7 to CN401
SL- SL-
pin9 to CN401 pin9 to CN401
< MAIN board top view >
IC400 IC400
< MAIN board bottom view >
3-11
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CN401 CN401
Only for training and service purposes.