LG C3400 Service Manual page 58

(1) Checking Regulator Circuit
TEST POINT
CIRCUIT
Checking Flow
Voltage at
Pin5 of U503
Is 2.85V?
YES
Regulator Circuit is OK
See next Page to check
VCTCXO
U503. 5
Figure 4-2
RF2.85V
U503
5
OUT
GND
4
BYP
C536
C535
4.7u
22n MIC5255-2.85BM5
(1608)
NO
Replace U503
- 57 -
U503. 3
RF_LDO
VBAT
1
IN
2
3
EN
C529
4.7u
(1608)
Level at NO
Pin3 of U503
Is high?
YES
4. Troubleshooting
CLKON
Change main board