LG KG920 Service Manual page 78

(2) Checking VCTCXO Circuit
TEST POINT
X501.3
(OUT)
X501
X501.4
(VCC)
Figure 4-6.
CIRCUIT
WAVEFORM
Check Pin 3.
Refer to Graph 4(b)
Check Pin 4.
Refer to Graph 4 (a)
R523
(AFCDAC)
AFC
15K
C548
1000p
Figure 4-8.
Graph 4-1.
- 79 -
4. TROUBLE SHOOTING
CHECKING FLOW
Yes
26 MHzO.K?
No No
Yes
2.75V OK?
No
Check U101, PMIC
Figure 4-7.
2V75_VVCXO
X501
1 3
VCONT OUT
2 4
GND VCC
26MHz
C549
2.2u
Graph 4-2.
VCTCXO Circuit is OK VCTCXO Circuit is OK
See next Page to check See next Page to check
Mobile SW Mobile SW
Changing X500