LG RN7 - Page 36

3-9
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Only for training and service purposes.
R5B2
R5B3
L5B11
L5B12
R5D3
R5D4
R5D9
TP507
R5E8
TP511
TP512
TP515
TP516
TP517
C5B7
C5B8
C245
RB117
C5B15
C5B17
C5B19
C5B20
C5B22
C5B31
C5B32
R506
C5B35
C5B36
C5B37
C5B38
R5B12
R5B13
R5B14
R510
R5B16
R513
C5B40
R5B18
R5B19
C5B42
C5B45
R5D11
R5D12
C5B47
R5B20
C5B48
C5B49
R5D15 R5D16
R5B23
R5D17
R5D18 R5B25
R5D19
R5B27
C5B50
C5B51
C5B52
C5B53
C5B54
R5D20
C5B55
C5B56
C5B57
C5B58
R5B31
C5B59
R5B35
R5B39
C504
R5B46
R5B50
TP3
TP4
R5B101
5
R5B103
R5B58
TP8
R5B62
R5B110
R5B112
R5B66
R5B67
R5B116
R5B71
R5B76
R5B77
R5B78
R5B79
R5B80
R5B81
R5B83
R5B84
R5B86
R582
R5B88
R5B96
C556
R5B97
TP34
IC502
IC503
L5B2
DFT_R
X
L5B6
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.
4-4. SDRAM (IC502)
4-4-1. Solution
Replace MAIN board.
4-4-2. How to troubleshoot (Countermeasure)
1) Check below waveform & soldering status of SDRAM (IC502) on MAIN board.
 If pin17(#CAS), pin18(#RAS), pin19(#CS), pin38(CLK), pin29(address), pin2(DQ) doesn’t come out,
check damping resistor ((R5B99, R5B100, R5B102, R5B104, R5B107).
2) If resistor is OK, then replace IC502(SDRAM).
3) After change IC502, if It is still not below waveform, check IC501(DSP IC).
4-4-3. Service hint (Any picture / Remark)
V
V CC
Reset
address
data
/
/ CS
R AS
/ WE
CAS
< Signal waveform >
< MAIN board bottom view >
IC502
IC502