TB8100 Service Manual Power Amplifier Fault Finding 139
© Tait Electronics Limited September 2006
5. Select Configure > Base Station > Channel Table and check that the
output power is set to the rated power of the PA: either 5W, 50W, or
100W.
6. Select Configure > Alarms > Thresholds and check that:
■ the minimum PA power output is set to 3W for a 5W PA, 40W
for a 50W PA, or 90W for a 100W PA
■ the maximum PA reverse power output is set to 2W for a 5W PA,
or 10W for a 50W and 100W PA
■ the maximum PA VSWR is set to 1.5:1
■ the maximum PA final temperature is set to 90°C
■ the maximum PA driver temperature is set to 80°C
■ the PA air intake temperature is set to a maximum of 60°C and a
minimum of –20°C.
These are the default settings.
7. Select Monitor > Module Details > Power Amplifier and check that
the module details are correct.
8. Key the PA using the TX KEY switch on the CTU. Check that the
output power is correct for the model of PA. If it is, go to “Final
Tasks” on page 170. If it is not, go to Task 4
. If the PA has generated
any alarms, go to Task 3
.
Task 3 —
Check Reported
Alarms
Any alarms generated by the PA under test will appear in the Alarms >
Current Alarm Status screen in the Service Kit. The most likely alarms are
described in more detail below.
No PA Detected
1. Check that the correct DC supply is present at the PA.
2. Check whether the power supply is current limiting (the PMU will
raise a Current high alarm). If it is, go to “6W Board” on page 155.
If it is not, go to Step 3.
3. Check that the system control bus is undamaged and correctly
connected (refer to the TB8100 Installation and Operation Manual
for details [MBA-00005-xx]).
4. Check that the I
2
C current source for the system control bus is
present. The I
2
C current source for a 28V PA is in the PMU, and for
a 12V PA it is on the dual base station subrack interconnect board.
5. Check the state of the green indicator LED. If it is on and steady,
continue with the alarm checks. If it is off, go to “Control Board”
on page 148. If it is flashing, reload the firmware and return to
Task 1
.
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