Checking Vctcxo Circuit - LG KE820 Service Manual

5. Trouble shooting

5.12.3 Checking VCTCXO Circuit

Checking Points
Pin : 2.7V
X401
Pin 3: 26 MHz
Figure 4.
Circuit Diagram
VCTCXO
2V7_VCXO
R449
0
X401
3 1
OUT VCONT
4 2
VCC GND
C431
26MHz
1uF
Figure 5. VCTCXO
VCTCXO Circuit is OK.
See next page to check
R425 620
AFC
C430 C455
22p NA
- 100 -
Checking Flow
Is the waveform
of Pin3 similar to
Yes
Is the waveform
of Pin4 similar to
Yes
PLL Circuit.
Waveform
Pin 4
Pin 3
Figure 6. VCTCXO Waveform
No
Replace X401
No
Checking U203
(PMIC)