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4. TROUBLE SHOOTING
(1) Checking Regulator Circuit
Test Points
Circuit Diagram
Checking Flow
U503.5
U503.3
RF2.85V
5
OUT
4
BYP
C536
C535
4.7u
MIC5255-2.85BM5
22n
(1608)
Voltage at
NO
Pin5 of U503
Is 2.8V?
YES
Regulator Circuit is OK
See next Page to check
VCTCXO
U503
Figure 4-2
RF_LDO
VBAT
U503
1
IN
2
GND
3
EN
C537
4.7u
(1608)
Level at
NO
Pin3 of U503
Is high?
YES
Replace U503
- 54 -
CLKON
Change main board
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