LG GS290 Service Manual page 93

4. TROUBLE SHOOTING
GS290 Operational Description
GS290 Operational Description
4.13.1. Checking VCTCXO Circuit
4.13.1. Checking VCTCXO Circuit
See RX Part "1. Checking DCXO Circuit"
See RX Part "1. Checking DCXO Circuit"
4.13.2. Checking PLL Control Signal
4.13.2. Checking PLL Control Signal
See RX Part "2. Checking PLL Control Signal"
See RX Part "2. Checking PLL Control Signal"
4.13.3. Checking TX I/Q Signals
4.13.3. Checking TX I/Q Signals
FE2
33
VBIAS
34
VDDTX1V5
35
TX1
36
TX2 U500
37
VDDTX2V8 VDDVCO2V8
38 PMB6272
VDDMIX2V8
39
GND3
40
GND4
41
TP1(I)
TP4(QX)
TP1(I)
TP2(IX) TP(Q) TP4(QX)
TP4(QX)
TP1(I) TP2(IX) TP3(Q)
TP2(IX) TP3(Q)
Figure 17. TX I/Q Circuit
Figure 17. TX I/Q Circuit
Checking Points
Checking Points
TP1(I) TP2(IX) TP3(Q TP4(QX
TP1(I) TP2(IX) TP3(Q TP4(QX
U500
U500
Figure 18. TX I/Q
Figure 18. TX I/Q
LGE Internal Use Only
LG Electronics
LG Electronics
Checking Flow
Checking Flow
VDDRX2V8
20
VDDRX1V5
19
VCO_RC
18
17
EN
16
VDDXO2V8
15
FSYS1
14
GND1
13
R508
X500 TSX-3225
4
3
GND2 HOT2
1 2
HOT1 GND1
26MHz
CLK26M
RF_CLK
RF_DA
QX
Q
IX
I
Check TX I/Q Signals(TP1~TP4)
Check TX I/Q Signals(TP1~TP4)
Signals are
Normal ?
Signals are
Normal ?
Yes
Yes
TX Part is OK.
Check Base Band Circuit or
TX Part is OK.
Re-Download S/W and Cal
Check Base Band Circuit or
Re-Download S/W and Cal
I
I
Q
Q
I
I
Q
Q
Figure 19. TX I/Q Waveform
Figure 19. TX I/Q Waveform
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94/136
94/136
Revision B
Revision B
Replace Transceiver
No
PMB6272(U500)
Replace Transceiver
No
PMB6272(U500)
TX
TX
Only for training and service purposes
LGE Property
LGE Property