LG GD910 Service Manual page 87

5. Trouble shooting
5.14.1 Checking VCTCXO Circuit
Checking Flow
Check TP2
( Vcc of X400) ( Vcc
=2.85V ?
YES YES
Check Check
0V<TP3<1.8V ? 0V<TP3<1.8V ?
YES YES
waveform waveform
of TP1(C443) Similar to
waveform below? waveform below?
YES YES
VCTCXO is Ok. VCTCXO is Ok.
See the next page See the next page
VCTCXO Circuit Diagram VCTCXO Circuit Diagram
TP1
C443 1000 pF
2G_EN
2G_DATA
2G_CLK
2G_BS
C446
4
6
3
LGE Internal Use Only
NO NO
Check U200
NO NO
Check U101
NO NO
Replace X400
C506
2.2n
R426 100K
TP2
2V85_VTCXO
FB2
R407 20
C447
1u 0.1u
TP3
X400
R410
1
VCC VC
10K
5
NC2_GND2 NC1_GND1
2
C452
OUT GND
10n
TG-5021BA 26MHz
GD910 service manual
GD910 service manual
Checking Points
TP1
TP2
TP3
Waveform Waveform
R
1
2
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Only for training and service purposes