LG GS290 - Page 93

- 94 -
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Only for training and service purposes
4. TROUBLE SHOOTING
GS290 Operational Description Revision B
LG Electronics 94/136 LGE Property
4.13.1. Checking VCTCXO Circuit
See RX Part “1. Checking DCXO Circuit”
4.13.2. Checking PLL Control Signal
See RX Part “2. Checking PLL Control Signal”
4.13.3. Checking TX I/Q Signals
Replace Transceiver
PMB6272(U500)
Check TX I/Q Signals(TP1~TP4)
Figure 17. TX I/Q Circuit
Yes
No
T
X Part is OK.
Check Base Band Circuit or
Re-Download S/W and Cal
TP4(QX)
TP3(Q) TP2(IX)
Signals are
Normal ?
Checking Points
Fi
g
ure 18. TX I/Q
I
Q
I
Q
U500
TX
TP1
(
I
)
TP2
(
IX
)
TP3
(Q
TP4
(Q
X
TP1(I)G
Checkin
g
Flow
Figure 19. TX I/Q Waveform
GS290 Operational Description Revision B
LG Electronics 94/136 LGE Property
4.13.1. Checking VCTCXO Circuit
See RX Part “1. Checking DCXO Circuit”
4.13.2. Checking PLL Control Signal
See RX Part “2. Checking PLL Control Signal”
4.13.3. Checking TX I/Q Signals
Replace Transceiver
PMB6272(U500)
Check TX I/Q Signals(TP1~TP4)
Figure 17. TX I/Q Circuit
Yes
No
T
X Part is OK.
Check Base Band Circuit or
Re-Download S/W and Cal
TP4(QX)
TP3(Q) TP2(IX)
Signals are
Normal ?
Checking Points
Fi
g
ure 18. TX I/Q
I
Q
I
Q
U500
TX
TP1
(
I
)
TP2
(
IX
)
TP3
(Q
TP4
(Q
X
TP1(I)G
Checkin
g
Flow
Figure 19. TX I/Q Waveform
26MHz
X500 TSX-3225
21
3
4
GND2 HOT2
HOT1 GND1
U500
PMB6272
20
19
18
17
16
15
14
13
1
2
2
1
22
11
32
0
1
42
9
52
8
62
7
72
6
8
2
5
924 0
33
132
23
1
33
34
35
36
37
38
39
40
41
GND4
GND3
VDDMIX2V8
VDDTX2V8
TX2
TX1
VDDTX1V5
VBIAS
FE2
A
1E
F
XA
8V
2SA
IB
DDV
B X
1X
R
XB
1X
R
8V
2G
ID
D
DV X2X
R
A
D 2X
R
K
LC 2DN
G
5V
1G
I
D
DDV X3XR
3SYSF 3XR 2SYS
F X
4XR
OX 4X
R
X
OX
5V1A
N
LDDV
GND1
FSYS1
VDDXO2V8
EN
VDDVCO2V8
VCO_RC
VDDRX1V5
VDDRX2V8
R508
RF_DA
RF_CLK
QX
Q
IX
I
CLK26M
TP1(I)
TP2(IX) TP3(Q) TP4(QX)