60LN54XX, 60LN5400, 60LN5420, 60LN542Y (CHASSIS:LB31F, LB36B) - LG TV Service Manual (repair manual). Page 14

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TROUBLESHOOTING
1. Power-up boot check
Check stand - by Voltage.
P401 3, 5pin : +3.5V_ST
Check 18pin Power connector
Main B/D 3.5V Line
Short Check
Check X201 clock
24 MHz
Replace X201
Check P401 PWR_ON.
1pin : 3.3V
Replace  Mstar(IC101) or Main board
Check Multi Voltage
P401 9, 10pin : 24V 
/ 13, 14, 15pin:12V
Replace Power Board
Check IC402/3/7 Output Voltage
IC402 : 2.5V
IC403 : 1.15V
IC407 : 1.5V
Q403 : 3.3V
Replace IC402, IC403, IC407, Q403
Re- download software.
Check stand - by Voltage
L404, L408 : +3.5V
Replace L404, L408
Check LVDS Power Voltage
Q409 : 12V
Replace Q409
Check Mstar LVDS Output
Replace Mstar(IC101) or Main Board
ok
ok
ok
ok
ok
ok
ok
No
No
ok
Replace Power board.
ok
No
No
No
No
No
No
No
Check DRV ON Control
P403 2 pin : High
Check Power Board
Change Module
ok
ok
No
Check URSA5 LVDS Output
Replace URSA5(IC6101) or Main Board.
ok
No
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