LG S90QY Service Manual page 40

NO BOOTING WHEN YOU TURN THE UNIT ON, NO MESSAGE OR
"HELLO" ON FRONT PANEL
When you turn on your set, no message on the front panel, and LED doesn't work.
1-2. IC3023 System 3.3 VA (No 3.3 VA)
1-2-1. Solution
Replace MAIN/ FRONT board.
1-2-2. How to troubleshoot (Countermeasure)
1) Please check 3.3 VA of IC3023 pin6.
2) If 3.3 VA is abnormal, replace MAIN board.
3) If 3.3 VA is OK, replace FRONT board.
1-2-3. Service hint (Any picture / Remark)
3.3VA_OUT
ONE POINT REPAIR GUIDE
R3131
R3129
27K
100K
NC
3.33V
R3132
C3154
51K
100nF
/16V
DGND
OUT
R3133
C3155
2
150K 47pF
FB
(1%)
NC
1
R3134
R3130
IC3023
33K
NC
(1%)
@Optio
DGND
IC3023 IC3023
< MAIN board top view >
5.1VA
L3028
C3153 C3152 C3194
100nF 10uF 10uF
/16V /10V /10V
DGND
L3029
LX 6 1uH
C3151
C3148
GND 100nF 10uF
/10V
/16V
VOUT = 0.6 x (1+150K/33K) = 3.327V
3-5
Copyright © 2022 LG Electronics Inc. All rights reserved.
3.3VA
TW3000
1 2
3.3VA_OUT
C3150
C3149
10uF
10uF
/10V /10V
DGND
Only for training and service purposes.