Trouble Shooting Of Transmitter Part - LG GS290 Service Manual

4. TROUBLE SHOOTING
4.12.4. Checking RX I/Q Signals
Checking Flow
FE2
33
VBIAS
34
VDDTX1V5 VDDRX2V8
35 20 Check RX I/Q signals(TP1~TP4)
TX1 VDDRX1V5
36 19
TX2 U500 VCO_RC
37 18
VDDTX2V8 VDDVCO2V8
38 17
PMB6272
VDDMIX2V8 EN
39 16
GND3 VDDXO2V8
40 15
FSYS1
14
GND4 GND1
41 13
R508
X500 TSX-3225
TP1(I)
4
GND2 HOT2 3
1 2
HOT1 GND1
TP4(QX)
26MHz
TP2(IX) TP3(Q) TP4(QX)
TP1(I)
TP2(IX TP3(Q
CLK26M
RF_CLK
RX Part is OK.
RF_DA
Check Base Band Circuit
QX
Q
IX
I
Re-Download S/W and Cal
Figure 12. RX I/Q Circuit
Checking Points
TP1(I) TP2(IX) TP3(Q) TP4(QX)
U500
Figure 13. RX I/Q
LGE Internal Use Only - 92 -
No
Signals are Replace Transceiver
Normal? PMB6272(U500)
Yes
or
I
Q
RX
I
Q
Figure 14. RX I/Q Waveform
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes

4.13 Trouble shooting of Transmitter part.

Checking Flow
Setup Test Equipment
Cell Power : –74dBm
EGSM CH30
DCS CH699
Check point
DCXO
Check point
PLL Control
Checking Points
Check point
TX I/Q Signal
Check point
Transceiver
Check point
PAM Control
Figure 1. Main PCB
Check
FEM & Mobile SW
Re-Download S/W & RF CAL
Copyright © 2010 LG Electronics. Inc. All right reserved. - 93 -
Only for training and service purposes
4. TROUBLE SHOOTING
LGE Internal Use Only