LG DP122 Service Manual page 19

NO BOOTING
When you plug power cord and turn the unit on, LED won't turn on, the unit won't read disc normally.
1-3. Please check MAIN board IC IC603 signal and its peripheral circuit.
1) Please check if output voltage 3.3 V from IC603 pin1, 3, 9, 14, 27, 43, 49 is normal.
If output voltage 3.3 V is not normal, please check 3.3 V power circuit of MAIN board.
2) Please check every signal connected between IC603 and IC601 pin45 ~ 86, especially including
DATA and ADDRESS signal.
If DATA and ADDRESS signal is not normally output, please check if IC603 is in failure.
IC601
(MPEG)
ONE POINT REPAIR GUIDE
< MAIN board top view >
3-4
IC603
(SDRAM)