LG UBK80 Service Manual page 49

NO BOOTING WHEN YOU TURN THE UNIT ON, NO GREEN LED ON
FRONT PANEL
When you turn on your set, Green LED doesn't work, it will not boot-up.
2-3. IC203 System 1.8 V (No 1.8 V)
2-3-1. Solution
Replace MAIN board.
2-3-2. How to troubleshoot (Countermeasure)
1) Please check 5.1 VA of IC203 pin1 (VIN).
2) If 5.1 VA is abnormal, please check IC201.
3) If 5.1 VA is OK, but 1.8 V is abnormal pin2 of IC203(VOUT), replace MAIN board.
2-3-3. Service hint (Any picture / Remark)
[12VA TO 1.8_NOR]
PWR_CTL3
C203
10pF
DGND
R203
13K (1%)
DGND
IC203 IC203
 
ONE POINT REPAIR GUIDE
R218
4.7K
6 F B
E N
5
B S T
4
C205
1nF_NC
R226
DGND
R210
15K (1%)
R217
1.5K (1%)
VOUT = 0.798x((15K+1.5K)/13K+1)= 1.8V
 
< MAIN board top view >
 
1
I V N
 
L203
2
S W
4.7UH
3
G N D
DGND
33 C208 1uF (1)
3-32
Copyright © 2020 LG Electronics Inc. All rights reserved.
5.1VA
L207
C218 C226
C212
10uF 10uF
_NC
100nF
/16V /16V
DGND
R230
0OHM
C219
C227 C232
C2B5
10uF 10uF 10uF
100nF
/16V /16V
/16V
DGND
Only for training and service purposes.
1.8V_NOR
DGND