LG GS290 Service Manual page 87

4. TROUBLE SHOOTING
GS290 Operational Description
4.12.1. Checking DCXO Circuit
Checking Points
TP1(C516) : 26MHz
Figur2. DCXO
DCXO Circuit Diagram
U500
VDDVCO2V8
PMB6272
VDDXO2V8
Waveform
Figure 4. DCXO Waveform
LGE Internal Use Only
LG Electronics
Checking Flow
X500
VDDRX1V5
19
VCO_RC
18
17
EN
16
15
FSYS1
14
GND1
13
C517
R508
47n
820
X500 TSX-3225
4
3
GND2 HOT2
Figure 3. DCXO Cicuit
1 2
HOT1 GND1
26MHz
Is the waveform
of TP1(C516) similar to Fig.4?
Yes
DCXO Circuit is OK.
See next page to check
PLL Circuit.
RF_EN
C516 1n
26MHZ_MCLK
TP1 (C516)
TP1(C516)
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Revision B
No
Replace X500
Only for training and service purposes
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