LG RN7 - Page 35

3-8
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Only for training and service purposes.
ONE POINT REPAIR GUIDE
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.
4-3. SERIAL FLASH (IC503)
4-3-1. Solution
Replace MAIN board.
4-3-2. How to troubleshoot (Countermeasure)
1) If the crystal(X500) does oscillate, check Serial Flash(IC503) on MAIN board.
 Check pin8(VCC), pin6(SCLK), pin1(CS), pin2(DO), pin5(DI) of below waveform.
2) If pin8, 6, 1, 2, 5 doesn’t come out, check damping resistor(R5B72, R5B73, R5B74, R5B75) of IC503.
 If damping resistor of IC503 is OK, then replace IC503. (it need to download program)
3) After change IC503, if It is still not below waveform, check IC501(DSP IC).
4-3-3. Service hint (Any picture / Remark)
L5B11
L5B12
R5D3
R5D4
R5D9
TP507
TP511
TP512
TP515
TP516
C5B19
C5B20
C5B22
C5B31
R506
C5B35
C5B36
C5B37
C
C
C5B45
R5D11
R5D12
C5B47
C5B49
R5D15 R5D16
R5D17
R5D18 R5B25
R5D19
C
R5D20
C5B55
C5B58
C5B59
R5B50
TP3
TP4
R5B101
5
R5B58
TP8
R5B62
R5B112
R5B116
R5B78
R5B80
R5B83
R5B96
R5B97
TP34
IC502
IC503
L5B6
V
VCC
SCLK
SO
SO
CS#
< Signal waveform >
< MAIN board bottom view >
IC503
IC503