LG GX500 Service Manual page 98

GSM850 GSM900
GX500 Operational Description
C421
C409 C412 C426
3.3p
C423 4.7P 4.7P 3.3p
4.7N
4.12.4 Checking RX I/Q Signals
FE1
FE2
FE2
33
VBIAS
34
VDDTX1V5
35
TX1
36
TX2
37
VDDTX2V8
R405
38
VDDMIX2V8
10
39
C432
GND3
40
0.22U
GND4
41
R401
10
C413 C438
220N 0.1U TP1(IX) TP2(QX)
TP1(IX)
TP402(I)
Figure 4-41. RX I/Q Circuit
Checking Points
TP2(QX
Figure 4-42. RX I/Q
*SIM2-> Transceiver is embeded in BB chip.
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Only for training and service purposes
LG Electronics
DCS1800 PCS1900
C431
C435 C408 C427
2.2P 2.2P 2.7p
2.7p
C430 C416
0.1U 0.1U
VDDRX2V8
20
VDDRX1V5
R402
19
VCO_RC
820
18
VDDVCO2V8
17
EN
16
VDDXO2V8
15
FSYS1
14
GND1
13
X401
4 3
1 2
26MHz
DSX321SG-26M
TP2(QX
TP401(Q)
RF_CLK
RF_DA
QX
TP401
Q
TP402(I)
IX
TP402
I
TP401(Q)
TP402(I)
U401
TP401(Q)
Checking Flow
C411
0.1U C442
0.1U
Check RX I/Q signals TP
Signals are
Normal?
RX Part is OK.
Check Base Band Circuit
or
Re-Download S/W and Cal
I
Q
TP1(IX)
I
Q
Figure 4-43. RX I/Q Waveform
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4. TROUBLE SHOOTING
No
Replace Transceiver
PMB6272(U401)
Yes
RX
LGE Internal Use Only
LGE Property
Revision A