5-62
Troubleshooting Charts:
PA Failure
PA Failure – Page 3 (VHF PA)
Measure TX current
at VHF test
frequencies
Yes
No
3
Measure DC voltage
at pin 4 of U901
Yes
Is current less
than 350mA?
Measure voltage at
pin 5 of U901
Replace Q901
Yes
No
Is current
approximately
500mA?
Yes
No
Is voltage
approximately 6V
at DAC=4095?
Is current greater
than or close to
2A?
Use a spectrum
analyzer and high-
impedance RF
probe. Measure
RF_IN_1 at C901.
Yes
Yes
Is the frequency
correct?
No
See FGU
troubleshooting
charts
Yes
Is the power
level about 3 dBm?
No
See FGU
troubleshooting
charts
Measure power at
C925
Yes
Is the power
approximately
37 dBm?
No
Replace Q901
Measure power at
C2704
Is the power
approximately
37 dBm?
No
Check D2703
positive node
voltage
Measure power at
C1222
Is the power
approximately
37 dBm?
Check power out at
C1122 and any
process issue
Yes
Is the voltage
near 7.0V?
No
Replace D2703
Yes
Check pin 3 and
pin 2 of Q2701
Is pin 3 of
Q2701=Raw B+
and pin 2=3.0V
No
Replace Q2701
Yes
Check continuity of
R2706 and L2702
Measure voltage at
pin 3 of Q1101
Yes
No
Is voltage
approximately
7V?
Yes
No
Is voltage
approximately
0V?
Replace U901
Replace Q1103
Measure voltage at
pin 1 of Q1101
Yes
No
Is voltage greater
than 1.5V?
Replace Q1101
5
Measure DC voltage
at pin 5 of U901
Was voltage
near 7.5V?
Measure voltage at
pin 1 of Q1101
No
Yes
With the radio in RX
mode, measure the
DC voltage on both
pins of L903
Was voltage
near 7.5V on
both sides?
No
Yes
Is there 7.5V
on L908?
No
Check E1101 for
solderability issues and
replace as necessary
Yes
Check L903 for
solderability issues and
replace as necessary
Was voltage
near 3V?
No
Measure the logic
inputs of TXH_1
from R1111 and
TX_INH from U1138
Yes
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 the
drain of Q901
Was voltage
near 7.5V?
No
Check L906 under shield
SH1 for solderability
issues and replace as
necessary
With the radio in RX
mode, measure the
resistance on the
node shared by
C916 and R905
Yes
Is the resistance
near 9.4 kOhms?
No
Check resistors R901,
R902, R903, R904,
and R905 for resistance
and solderability issues
and replace as necessary
In TX mode,
measure the voltage
on pin 4 of U901
Yes
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 Q901.
Is the voltage
near 6V?
Yes
Is TX current just
above standby
current?
Yes
Is the TX current
between 300 and
900mA?
Yes
Is the TX current
above 900mA?
Yes
Is the voltage
below 4V?
Yes
The PA and Driver are
likely damaged. Replace
Q901 and U902.
The PA is likely
damaged. Replace
Q901.
Lift shield SH1 and check
for solderability or part
issues on all 900 series
parts. Replace parts as
necessary.
If no issues found, lift shield
SH8 and check for solderability
or part issues on all 1200
series parts. Replace parts as
necessary.
5
If the voltage is between 4 and 5.5V then
the control loop should be working and
power should be available. Check D2703
positive node voltage.
No
Is the voltage
near 7.0V?
Yes
No
Check pin 3 and
pin 2 of Q2701
Is pin 3 of
Q2701=Raw B+
and pin 2=3.0V
Yes
No
Check continuity of
R2705 and L2702
Replace Q2701
Replace D2703
Summary of Contents for APX 2000
Page 1: ...APXTM TWO WAY RADIOS APX 1000 APX 2000 APX 4000 APX 4000Li DETAILED SERVICE MANUAL ...
Page 4: ......
Page 6: ...iv Document History Notes ...
Page 8: ...Notes vi Commercial Warranty ...
Page 10: ...Notes ...
Page 22: ...xiv List of Figures Notes ...
Page 226: ...6 64 Troubleshooting Waveforms LF CW on Spectrum Analyzer Notes ...
Page 688: ...Index 4 Index Notes ...
Page 690: ...ii Notes ...
Page 700: ...xvi List of Figures Notes ...
Page 806: ...5 50 Troubleshooting Charts PA Failure Notes ...
Page 1008: ...8 178 Schematics Boards Overlays and Parts Lists Transceiver RF Boards UHF2 84012621001 Notes ...
Page 1062: ...8 234 Schematics Boards Overlays and Parts Lists Keypad Board M2 and M3 PC000261A01 Notes ...
Page 1064: ...ii Notes ...
Page 1068: ...Notes A 4 EMEA Warranty Service and Technical Support Further Assistance From Motorola ...
Page 1090: ...Glossary 10 Glossary Notes ...
Page 1094: ...Index 4 Index Notes ...
Page 1095: ......