Checking Gsm Block - LG CU720 Service Manual

4. TROUBLE SHOOTING

4.8 Checking GSM Block

4.8.1 Checking Tx level
TP1
TP2 TP3
L117 L118
1.2p NA
C128
C127
3.9nH
3.3nH
C129
C130
33nH
NA
rev.1.0.2
LGE Internal Use Only
[Fig 4.8.1.1] Test point of the GSM TX Block
SW101
KMS-518
rev.B
C101 56p
L103
100nH
1
GND6 DCS_PCS_IN
U102
2
GND5 BS
12 3
TQM7M5003
VCC TX_EN
4
GND4 VBATT
C139
5
100p
GND3 GND1
9 6
GSM_OUT VRAMP
7
GND2 GSM_IN
15
R113
2.2K
C147
39p
[Fig 4.8.1.2] Schematic of the GSM TX Block
- 92 -
TP5 (G850/G900)
TP4 (G1800/G1900)
TP6 (GSM_SAW_SW_Mode)
TP3 (G1800/G1900)
TP2 (G850/G900)
TP1
TP4
GSM_PA_BAND
GSM_PA_EN
+VPWR
FL102
C137
TP5
22u
LMSM32AA-533
5 1
RFOUT RFIN
7
VC
GSM_PA_RAMP
C148
EGSM LOW
GSM850 HIGH
remain LOW when not transmitting
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
FL101
LMSP4LMA-573TEMP
14 1
VC1 GSM1800RX1
13 2
VC2 GSM1800RX2
12 3
VC3 GSM1900RX1
11 4
VC4 GSM1900RX2
5
GSM900RX1
10 6
VDD GSM900RX2
7
GSM850RX1
9 8
GND1 GSM850RX2
18
GND2
20 15
GND3 UMTS1
21 16
GND4 UMTS2
23
GND5
24 22
GND6 GSM1800_1900TX
26 25
GND7 GSM850_900TX
27
GND8
28 17
GND9 NC
R105
DCS_PCS_TX
51
R107
7.75dB R108
120 120
REV.D
R110
GSM_TX
56
R111 R112
120 120
8.1dB
R114
GSM_SAW_SW_MODE
200
68p
TP6