LG KC780 Service Manual page 99

5. TROUBLE SHOOTING
5.13.2 FEM Circuit
Part Description of FEM
Application Mode
Tx
EGSM
Rx
Tx
DCS1800
PCS1900
Rx
Check point of FEM
17
LGE Internal Use Only
FEM Circuit
Check
Control signal of
FEM(TP1&TP2)
YES
Check the next part
Fig 10 Debugging flowchart of FEM circuit
VC1(TP1) VC2(TP2)
High Low
Low Low
Low High
Low Low
TP1
R501
VC1
1
C501
Control Signal
33p
of FEM
R502
VC2
1
TP2
0.01u
C502
U502
LMSP43NA-782
Fig 11 FEM circuit (U501)
Replace
NO
PCB
TP1
TP2
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U501
Only for training and service purposes