LG OM7560 Service Manual page 31

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 pickup module in MD doesn't work. This step is for checking the LASER TRACKING
ACTUATOR.
5-4. LASER TRACKING ACTUATOR
5-4-1. Solution
Replace IC400 on MAIN board.
5-4-2. How to troubleshoot (Countermeasure)
The tracking actuator makes the laser beam be positioned in the center of a track on CD disc.
1) Check the TRD signal from pin14 of IC401.
  If no signal, check DVCC_3.3V & DV_3.3V (RF) and X400.
2) Check TR- & TR+ from IC400 to CN400 for driving the tracking actuator.
  If no signal, check M_5V for IC400.
3) Check if the FFC cable is solidly connected between CN400 and MD.
4) Check the MD.
  If the pickup module has any trouble, it can not move the laser beam on the left or right side.
Please check the function after changing another MD.
5-4-3. Service hint (Any picture/ Remark)
< Waveform of TR±
for driving tracking actuator >
ONE POINT REPAIR GUIDE
3-12
TR+: pin16 TR+: pin16
TR-: pin15 TR-: pin15
< MAIN board top view >
IC400 IC400