LG RN7 - Page 33

3-6
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Only for training and service purposes.
ONE POINT REPAIR GUIDE
4. NO BOOTING IN USB FUNCTION
After you turn on power key and displayed message in the following order (HELLO  VOL XX  USB)
on VFD, it will not display other message on VFD, and it will not boot-up normally.
4-1. NO DVCC_3.3V, 1.2 VA
4-1-1. Solution
Replace MAIN board.
4-1-2. How to troubleshoot (Countermeasure)
1) Check voltage of IC202 AND IC205 pin4 on MAIN board.
 If IC202, IC205 pin4(about 5.1 V) Input 5.1 VA doesn’t come out, check 5.1 VA from SMPS board.
2) If IC202, IC205 pin4(about 5.1 V) is normal, check the PWR_CTRL(IC204 pin5) is high (about 3.3 V).
 If PWR_CTRL isn’t high, check pin D11 of IC501 & R5B78, R214, R233.
3) If PWR_CTRL is high, check R5B78 and if there’s no defective component then check IC204 pin1 short
with GND.
4) If 3.3 V(DVCC_3.3V) is normal, check 1.2 VA output(C221, C226, C287, C288, C229) voltage of IC205.
 If 1.2 VA of IC205 doesn’t come out, then replace IC205.
4-1-3. Service hint (Any picture / Remark)
SOLDERING
MES
K
L
M
N
P
R
T
U
R210
R214
R218
R219
R601
R602
R221
R611
R612
P_DAT
R
6
R233
R237
R238
R621
R5B4
R624
R5B5
R625
R5B6
R628
R241
R629
R242
C207
R243
R244
C209
R245
C214
C215
C218
R5D5
C221
C222
R5D8
C226
C229
C612
C613
C614
C6
C230
C231
C232
C233
C5B2
C5B4
C5B5
C246
D204
ZD501
C5E2
C5E3
ZD506
C5E6
C273
C274
C276
C277
C279
IC201
IC202
C284
IC204
IC205
C287
C288
IC208
C2C12
C297
FL500
IC601
R102
C
C5
B
C5B25
R111
R112
R503
R505
CN101
R508
C5B34
R702
R127
R128
R5B15
R5B17
R5D10
R710
R5B21
R5B24
M_SCL
R5B26
R5B28
R524
R5B29
C105C106
R5B30
C108
R5B32
R5B33
R723
R5B34 R5B36
R726
R5B38
R5B45
R5B48
C2A6
X500
RA601
C705
R5B52
R5B10
C2B5
R5B63
C2C5
C2C6
C2D1
C2D2
ZD202
ZD203
ZD205
P_SCL
R5B94
R
R5B9
8
R596
C177
L202
L203
L205
L206
M_DAT
L212
IC501
IC506
IC701
L5B8
R207
R208
< MAIN board top view >
IC204
IC204
IC205
IC205
IC202
IC202