LG CMS4540F/W Service Manual page 29

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 FOCUSING ACTUATOR.
4-5. LASER FOCUSING ACTUATOR
4-5-1. Solution
Please check and replace IC407, IC408 on MAIN board.
4-5-2. How to troubleshoot (Countermeasure)
The focusing actuator makes the laser beam keep a regular interval with the surface of a CD disc.
1) Check the FOD signal from Pin21 of IC407.
If no signal, check 3.3 V(RF) and X400.
2) Check F- & F+ from IC408 to CN405 for driving the focusing actuator.
If no signal, check +1.8 V and +5 V for IC408.
3) Check if the FFC cable is solidly connected between CN405 and MD.
4) Check the MD.
If the pickup module has any trouble, it can not move the laser beam on the top or bottom side.
Please check the function after changing another MD.
4-5-3. Service hint (Any picture / Remark)
< Waveform of TR±
for driving FOCUSING actuator >
ONE POINT REPAIR GUIDE
3-10
F-
Pin13 to CN405
F+
Pin14 to CN405
< Signal check point >