LG GS290 Service Manual page 44

4. TROUBLE SHOOTING
4.12.1. Checking DCXO Circuit
Checking Points
Checking Flow
X500
of TP1(C516) similar to Fig.4?
TP1(C516) : 26MHz
See next page to check
Figur2. DCXO
DCXO Circuit Diagram
VDDRX1V5
19
VCO_RC
U500
18
VDDVCO2V8
17
PMB6272
EN
16
VDDXO2V8
C516
15
FSYS1
14
GND1
13
R508 C517
47n
820
X500 TSX-3225
4
3
GND2 HOT2
1 2 Figure 3. DCXO Cicuit
HOT1 GND1
26MHz
Waveform
Figure 4. DCXO Waveform
LGE Internal Use Only - 88 -
Is the waveform No
Replace X500
Yes
DCXO Circuit is OK.
PLL Circuit.
RF_EN
1n
26MHZ_MCLK
TP1 (C516)
TP1(C516)
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4.12.2. Checking PLL Control signals
Checking Points Checking Flow
TP1 (RF_EN) TP3 (RF_CLK)
DA(Data,TP2) is Normal ?
TP2 (RF_DATA)
U601
CLK(Clock,TP3) is Normal ?
Figure 5. Transceiver
RF Transceiver Circuit Diagram
C506 C537 C536 C535
0.1u 0.1u 0.1u 0.1u
FE2
33
VBIAS
34
VDDTX1V5 VDDRX2V8
35 20
TX1 VDDRX1V5
36 19
TX2 U500 VCO_RC
37 18
VDDTX2V8 VDDVCO2V8
38 PMB6272 17
RF_EN
VDDMIX2V8 EN
39 16
GND3 VDDXO2V8
C516 1n
40 15
26MHZ_MCLK
FSYS1
14
GND4 GND1
41 13
R508 C517
47n
820
TP1
X500 TSX-3225
4
3
GND2 HOT2
1 HOT1 GND1 2
26MHz
TP2
CLK26M
RF_CLK
TP3
RF_DA
QX
Q
IX
I
Figure 6. Transceiver Circuit
Copyright © 2010 LG Electronics. Inc. All right reserved. - 89 -
Only for training and service purposes
4. TROUBLE SHOOTING
No
Check U500
EN Signal(TP1) is OK ?
Yes
Check U500
No
Yes
No
Check U500
Yes
Control Signal is OK.
See next page to check
Mobile SW & FEM.
Waveform
RF_DATA(TP3)
RF_CLK(TP2)
RF_EN(TP1)
Figure 7. PLL Control Waveform
LGE Internal Use Only