5.21 Gps Failure - Motorola APX 5000 Service Manual

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5.21 GPS Failure

Check U6101 (CPLD) pin E2 (IO74)
for 32 kHz output, and pin D12 (IO91)
for 1.8V on reset.
Verify communication with GPS IC by resetting radio while probing TP2047 and
TP2048 with an oscilloscope. Activity should be seen on both UART test points
Re-flash radio with latest released
Yes
Radio firmware
was corrupted
Remove expansion board shield and check
VBAT voltage for 3.5V (measured at R2413),
and VDDS for 1.8V (measured at R2415)
No
Replace faulty
regulator
Check for 26 MHz at C2421
No
Replace Y2204
Replace GPS IC U2401
No GPS Lock
Verify the location feature is enabled,
replace antenna, and retry in a strong
signal environment (open sky)
GPS lock?
Check for 32 kHz clock at TP2405, and
1.8V for GPS reset at TP2406
No
32 kHz and
for successful comm.
No
firmware succesful?
GPS lock?
No
Regulators
OK?
Yes
Is 26 MHz
present?
Yes
START
The GPS receiver requires a working
Yes
antenna, and a direct view of the sky
in order to achieve a position fix
No
reset ok?
Yes
Remove expansion board shield and
Yes
comm
check regulator U2405 for 2.8V (measured
Check regulator U201 for 3V
on RF board (measured at C1305)
Check for 1.8V on LNA enable
measured at TP2402 and C2409
Measure the GPS total front-end gain @ 1575.42 MHz while
GPS IC is active (measured from antenna port to C2424).
Total gain should be approximately 18 dB.
Replace GPS IC U2401
Troubleshooting Charts: GPS Failure
at C2403)
No
Replace faulty
Regulator
regulator
OK?
Yes
No
Replace faulty
Regulator
regulator
OK?
Yes
No
1.8V? Replace GPS IC U2401
Yes
Debug front-end for faulty
No
component (LNA's U1304,
~ 18 dB?
U2404, and SAW filters
FL1301, FL2401 and FL2403)
Yes