Motorola APX 5000 Service Manual page 120

5-14
Power-Up Failure – Low V_EXT_1.85 Voltage
Low V_EXT_1.85 Voltage
Measure Radio
Current
Is Standby
Current more
than 15mA above
average?
No
Measure
V_SW_3.6
Voltage at R6510
Voltage =
V_SW_3.6
Yes
Measure Voltage
R6431 on
VCC_5.0A Side
Yes
4.8 < V < 5.2?
No
Proceed to Low
LDO8 VCC_5.0A
Voltage Flow
Chart
Yes
Board has a short,
Replace VOCON
Proceed to
No
Incorrect
V_SW_3.6
Voltage
Measure Voltage
at R6431 on
BGAP_COMP
Side
Measure Voltage
2.2 < V < 2.7?
at R6420
No
Replace VOCON
2.2 < V < 2.7?
Yes
Inspect U6508 and
All Supporting
Circuitry
Troubleshooting Charts: Power-Up Failure
Inspect and Repair
Yes
U6409 and
Supporting
Circuitry
No
Board
Are Parts Solder
No
Connections and
Placement Correct
Yes
Replace VOCON
Board
Replace or Repair
Part/s