5-64 Troubleshooting Charts: PA Failure
PA Failure – Page 9 (UHF2 PA)
Yes
No
9
Is current less
than 350 mA?
Use a spectrum
analyzer and high-
impedance RF probe.
Measure RF_IN_1 at
C1500.
Is the frequency
correct?
Is the power
level about 3
dBm?
Is the power
about 37 dBM?
See FGU
troubleshooting
charts.
Check U1110 and
see FGU
troubleshooting
charts.
Measure power at
C1521.
Replace U1500.
Measure power at
C1707, and calculate
harmonic filter loss.
Is the loss less
than 1 dB?
Repair any issues
with 1700 series parts
in the harmonic filter.
PA and harmonic
filter are functioning
properly.
Measure TX current
at UHF2 test
frequencies.
If power issue is not
resolved.
4
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Replace Q1500
Is current
approximately
500 mA?
Is current
greater than or
close to 2A?
No
Yes
Is voltage
approximate 6 V?
Measure DC voltage
at pin 4 of U1501
Measure voltage at
pin 5 of U1501
Is voltage
approximate 7 V?
Replace U1501
Measure voltage at
pin 3 of Q1101.
Measure voltage at
pin 1 of Q1101.
Measure DC voltage
at pin 4 of U1501
Was voltage
near 7.5 V
Was voltage
near 3 V
Trace voltages and check
for solderability issues on
R1102, Q1101, and Q1103.
Replace parts as necessary.
With the radio in RX
mode, measure the
DC voltage on
both pins of L1500
Was voltage
near 7.5 V?
Check L1505 under sheild
SH5 for solderability issues
and replace as necessary.
Measure inputs
on pins 2 and 3 to
AND gate U1119.
Pin 2 and 3 should
be 5 and 2.775V
respectively.
Measure voltage
at pin 1 of Q1101.
With the radio in RX
mode, measure the
resistance on the
node shared by
C1511 and R1502.
Is the resistance
near 9.4k
Ohms?
Check resistors R1502,
R1503, R1504, R1505 and
R1506 for resistance and
solderability issues and
replace as necessary.
If resistance is very low, in the
100's of ohms,and there are no
issues with the resistors then
there is a gate short on the PA.
Clear short or replace Q1500.
In TX mode, measure
the voltage on pin 4
of U1501.
Is the voltage
near 6 V?
Is the TX current
between 300
and 900 mA?
The PA is likely
damaged. Replace
Q1500.
Is the TX current
above 900 mA?
Lift shield SH5 and check
for solderability or part
issues on all 1500 series
parts. Replace parts as
necessary.
If no issues found, lift shield
SH10 and check for solderability
or part issues on all 1200 series
parts. Replace parts as
necessary.
4
Is TX current just
above standby
current?
If power issue is not
resolved.
The PA and Driver are likely
damaged. Replace Q1500
and U1500.
Is the voltage
below 4 V?
10
10
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.
Were the
connections
OK?
3
Replace cables, or
connectors J101 or
J102.
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
No
No
Yes
No
Yes
Is voltage
approximate 0 V?
Replace
U1501
No
No
Is voltage
greater than 1.5 V?
Measure voltage at
pin 2 and 3 of U1119
No
Are
Pins 2 and 3,
close to 5V and 2.775V
respectively?
Yes
Replace
U1119
Yes
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