5.18 Gps Failure - Motorola APX 7000 Detailed Service Manual

Troubleshooting Charts: GPS Failure

5.18 GPS Failure

Verify communication with GPS IC by resetting radio while probing TP2205 and
TP2206 with an oscilloscope. TP2205 should show a short stream of data from the
GPS IC during a reset, after which TP2206 should show bootloading data from the
processor. Activity should be seen on both test points for successful comm.
Check regulators U2220 for 2.8V
(measured at C2214 and C2219),
U2270 for 1.8V (measure C2275),
and U2284 for 1.2V (measure
C2285)
No
Replace faulty regulators
regulator OK?
Measure voltage on
reset signal at R2255.
Check U6101
No
is 1.8V
(CPLD) pin D12
present?
(IO91) for 1.8V
Check for 32 kHz
at R2216
Check U6101
No
(CPLD) pin E2 is 32kHz
(IO74) for present?
32kHz output
Check for 26 MHz at C2238
No
is 26 MHz
Replace Y2204
present?
Replace SAW filter FL2207
and GPS IC U2206
START
No GPS lock or poor
signal reception
Connect GPS simulator to radio with a
minimum of 4 satellites at -120dBm,
turn radio on then wait 2 minutes
GPS lock?
No
No
comm
successful?
Yes
Yes
Check LNA U2217 @ 1575.42MHz from the input of C2208 to the output
of C2267 (radio must be powered and caps must be disconnected from
Yes
rest of circuit). Also verify the LNA enable is 1.8V by measuring C2216
Yes
Check LNA U1304 @ 1575.42MHz from the input of C1301 to the output
of C1308 (radio must be powered and caps must be disconnected from
rest of circuit). Also verify the LNA enable is 1.8V by measuring C1307
Replace SAW filter FL2207
and GPS IC U2206
Reconnect the GPS/Combo antenna
Yes
and retry in stronger signal
environment (open sky), if still no fix
then try a new antenna
Yes
Check regulator U2220 for 2.8V
(measured at C2214 and C2219)
regulator
OK?
Yes
Check for 26 MHz at C2238
is 26 MHz
present?
Check SAW filter FL2205
@ 1575.42MHz
is loss >
2dB?
No
is gain >
12dB?
Yes
Check regulator U201 for 3V
(measured at C1305)
regulator
OK?
Yes
(RF board must be connected to expansion board)
Yes
is gain >
12dB?
No
Replace faulty
regulator
No
Replace Y2204
Yes
Replace FL2205
No
Replace U2217
No
Replace faulty
regulator
No
Replace LNA U1304 (and SAW Filter FL1301
for 700/800/UHF1 or UHF1/VHF or UHF1/UHF2
or 700/800/UHF2 or UHF2/VHF or VHF/7/800 radios)
5-47