LG PRADA KE850 - Page 99

5. Trouble shooting
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5.13.3 Checking VCTCXO Circuit
Checking Points Checking Flow
Pin 4 : 2.7V
Pin 3: 26MHz
X401
Is the waveform
of Pin3 similar to
Fig.6?
Is the waveform
of Pin4 similar to
Fig.6?
Replace X401
Checking U201
(PMIC)
Yes
No
No
Yes
VCTCXO Circuit is OK.
See next page to check
PLL Circuit.
VCTCXO Circuit Diagram Waveform
10p
C440
C442
0.1u
0
R418
26MHz
X401
2
GND
3
OUT
VCC
4
VCONT
1
R421 0
VRF2V7
R417 1.8K
AFC
Pin4 (R418)
Pin3 (R421)
Figure 4.
Figure 5. VCTCXO
Figure 6. VCTCXO Waveform