Motorola APX 7000 Detailed Service Manual page 159

Troubleshooting Charts: PA Failure
PA Failure – Page 7 (UHF1 PA)
7
Measure TX current
at UHF1 test
frequencies.
Is current less
than 350 mA?
No
Is current
Yes
approximately
500 mA?
No
Is current
greater than or
close to 2A?
Yes
Use a spectrum
analyzer and high-
impedance RF probe.
Measure RF_IN_1 at
C1601.
Yes
See FGU
No
Is the frequency
troubleshooting
correct?
Yes
Check U1110 and
Is the power
No
level about 3
troubleshooting
dBm?
Yes
Measure power at
C1625.
Is the power
No
appoximately 37 Replace U1602.
dBm?
Measure power at
C1822, and calculate
harmonic filter loss.
Yes
Repair any issues
No
Is the loss less
with 1400 series parts
than 1 dB?
in the harmonic filter.
Yes
PA and harmonic
filter are functioning
properly.
If power issue is not
resolved.
4
Yes
Measure DC voltage
at pin 4 of U1601
Is voltage
Replace Q1601
approximate 6 V?
Yes
Measure DC voltage
at pin 4 of U1601
Is voltage
near 7.5 V
Yes
With the radio in RX
mode, measure the
DC voltage on
both pins of L1603
charts.
Is voltage
near 7.5 V on
both sides?
Yes
see FGU
With the radio in RX mode,
measure the DC voltage
charts.
on the drain of Q1601.
Is voltage
near 7.5 V?
Yes
With the radio in RX mode,
measure the resistance
on the node shared by
C1616 and R1605.
Is the resistance
near 9.4k
Ohms?
Yes
In TX mode, measure
the voltage on pin 4
of U1601.
Is the voltage
near 6 V?
No
Yes
Is the voltage
8
below 4 V?
No
If the voltage is between 4 and 5.5 V then
the control loop should be working and
power should be available. Check the
coaxial cables and surface mounted
coaxial connectors
Are the
connections
OK?
No
Replace cables, or
connectors J101 or
J102.
No
Measure voltage at
pin 5 of U1601
Measure voltage at
(UHF1/7800) or
Is voltage
No
pin 3 of Q1102
approximate 7 V?
(UHF1/VHF) or
pin 3 of Q1101
Yes
Replace U1601
Measure voltage at
No pin 1 of Q1101 (UHF1/7800) or
pin 1 of Q1102 (UHF1/VHF) or
pin 1 of Q1101 (UHF1/UHF2).
Measure voltage at
pins 2 and 3
No
Is voltage
(UHF1/7800) or
near 3 V
pins 7 and 6
(UHF1/VHF) of U1119 or
pin 2 and 3
Yes
(UHF1/UHF2) should be
5 V and 2.775 V
Trace voltages and check
respectively.
for solderability issues on
R1102, Q1101, and Q1103.
Replace parts as necessary.
Check E1101 for
No No
Is there 7.5 V solderability issues
on C1608? and replace as
necessary.
Yes
Check L1606 under
No sheild SH10 for Check L1603 for
solderability issues
solderability issues
and replace as
and replace as
necessary.
necessary.
Check resistors R1601,
R1602, R1603, R1604, and 100's of ohms,and there are no
No
R1605 for resistance and
solderability issues and there is a gate short on the PA.
replace as necessary.
The PA and Driver are likely
Yes
Is TX current just
Yes
damaged. Replace Q1601
above standby
current?
No
Is the TX current
Yes
between 300
and 900 mA?
No
Lift shield SH10 and check
Yes
Is the TX current
above 900 mA?
Yes
3
pin 3 of Q1101
Is voltage
approximate 0 V?
(UHF1/UHF2).
No
Measure voltage at
pin 1 of Q1101 (UHF1/7800) or
pin 1 of Q1102 (UHF1/VHF) or
pin 1 of Q1101 (UHF1/UHF2).
Is voltage
greater than 1.5 V?
No
Measure voltage at
pins 2 and 3 (UHF1/7800) or
pins 7 and 6 ( UHF1/VHF) or
pins 2 & 3 (UHF1/UHF2) of U1119
Are
pins 2 and 3,
or pins 7 and 6,
close to 5V and 2.775V
respectively?
No
8
If resistance is very low, in the
issues with the resistors then
Clear short or replace Q1601.
and U1602.
The PA is likely
damaged. Replace
Q1601.
If no issues found, lift shield
SH13 and check for solderability
for solderability or part
or part issues on all 1200 series
issues on all 900 series
parts. Replace parts as
parts. Replace parts as
necessary.
necessary.
If power issue is not
5-55
Replace
Yes
Q1103 (UHF1/7800) or
Q1104 (UHF1/VHF) or
Q1103 (UHF1/UHF2).
Replace Q1101
Yes
(UHF1/7800) or
Q1102 (UHF1/VHF) or
Q1101 (UHF/UHF2).
Yes
Replace
U1119
resolved.
4