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4. TROUBLE SHOOTING
(1) Checking Regulator Circuit
Test Points
Circuit Diagram
Checking Flow
Regulator Circuit is OK
See next Page to check
U503.5
U503.3
Figure 4-2
RF2.85V
U503
5
OUT
GND
4
BYP
C536
C535
4.7u
22n
MIC5255-2.85BM5
(1608)
Voltage at
NO
Pin5 of U503
Is 2.8V?
YES
VCTCXO
U503
RF_LDO
VBAT
1
IN
2
3
CLKON
EN
C537
4.7u
(1608)
Level at
NO
Pin3 of U503
Is high?
YES
Replace U503
- 62 -
Change main board
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