LG GS290 Service Manual page 45

4. TROUBLE SHOOTING
4.12.3 Checking Mobile SW & FEM
Mobile SW & FEM Circuit Diagram
SW500
TP1
TP2
KMS-518_P
TP1 TP2
G1
C524
A
C ANT
17
22p
G2
L501
C539
100n
DNI
Figure 8. Mobile SW & FEM Circuit
Checking Points
FL500
TP2
SW500
TP1
Figure 9. Mobile SW & FEM
EGSM/GSM850 DCS/PCS
VC1 OFF OFF
VC2 OFF OFF
Table 2. FEM RX Control Logic
LGE Internal Use Only - 90 -
TP4
TP4
R502 100
VC1
R504 100
VC2
TP3
C503 C508
47p 47p
TP3
FL500
LMSP43NA-782
TP3_C508 (VC2)
TP5 ~ 8
TP4_C503 (VC1)
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Checking Flow
Check TP1 of SW500
with RF Cable and TP2 of C524
TP1 Signal same
as TP2?
Yes
Check TP3, TP4 of FL500 ?
Yes
Control Signal is
OK ?
Yes
TP5~8 Signal is
OK ?
Yes
Mobile SW & FEM is OK.
Check Antenna.
DCS/PCS RX
Figure 10 Mobile SW (R403)
Copyright © 2010 LG Electronics. Inc. All right reserved. - 91 -
Only for training and service purposes
4. TROUBLE SHOOTING
No
Replace Mobile SW (SW500)
No
Replace U100
No
Replace FEM (FL500)
FE1
FE2
Figure 11 FEM Control Signals
LGE Internal Use Only