LG GS290 Service Manual page 48

4. TROUBLE SHOOTING
Checking Flow
Check Output Signal
(TP1, TP2)
Signals are
Normal ?
Yes
Transceiver is OK.
See next page to check
PAM Control Circuit.
LBAND_PAM_IN (MODE: GMSK) : TP1
EGSM 30CH
Figure 22. Transceiver Output (GMSK)
LGE Internal Use Only - 96 -
Replace
No
PMB6272(U500)
LBAND_PAM_IN (MODE: 8PSK) : TP1
EGSM 30CH
Figure 23. Transceiver Output (8PSK)
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4.13.5. Checking PAM Control Signals
VBAT
GND6 GND5
11
GND7 GND4
12
GSM_OUT GND3
13
GND8 GND2
14
DCS_PCS_OUT GND1
15
GND9 GSM_IN
16
VBATT1 DCS_PCS_IN
U501
17
VBATT2 VRAMP
18
VDET ENABLE
SKY77344
19
MODE BS
20
TP3(PA_MODE)
Figure 24. PAM Control Signals Circuit
Checking Points
TP1(PA_LEVEL)
Figure 25. Transceiver Output
Table 4. PAM Mode Operation
MODE MODE PA_LEVEL
GMSK LOW Ramp Burst Control
HIGH Control Amp bias
8PSK
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4. TROUBLE SHOOTING
10
9
8
TP1(PA_LEVEL)
7
6
LBAND_PAM_IN
5
HBAND_PAM_IN
R505 1K
4
PA_LEVEL
3
TXON_PA
2
PA_BAND
1
TP2(TXON_PA)
PA_MODE
)
TP2(TXON_PA)
TP3(PA_MODE)
TXON_PA
HIGH
HIGH
- 97 - LGE Internal Use Only