TB8100 Service Manual Power Amplifier Fault Finding 151
© Tait Electronics Limited September 2006
Task 1 —
Check Alarms
1. Set up the test equipment as shown in Figure 8.8 on page 149 (28V
PA) or Figure 8.9 on page 150 (12V PA).
2. Run the Service Kit and connect to the base station.
3. Once connected to the base station, ensure it is in Run Mode.
4. Key the PA using the TX KEY switch on the CTU.
5. Select Alarms > Current Alarm Status and check there are no supply
voltage or temperature alarms. If there are, go to Task 3
on page 139.
If there are no alarms, go to Task 2
.
Task 2 —
Check DC Supplies
1. Measure the filtered DC supply to the control board at pin 2 or pin 3
of SK101. The voltage should be 28V ±2 V. If it is, go to Step 2. If
it is not, go to “6W Board” on page 155.
2. Check that the regulated supply output voltages are present at the
following test points:
■ TP100 +5V (digital circuitry)
■ TP102 +10V
■ TP103 –3V
If they are all present, go to Tas k 3
. If one or more is not present, go
to “6W Board” on page 155.
Task 3 —
Check Voltage
Levels
1. Measure the RF-DET voltage at pin 2 of SK102. The voltage should
be less than 0.8V. If it is, go to Step 2. If it is not, go to “6W Board”
on page 155.
2. Measure the PA-KEY-COAX voltage at pin 3 of SK102. The voltage
should be less than 0.5V. If it is, go to Step 3. If it is not, go to “6W
Board” on page 155.
3. Measure the scaled voltage supply at TP206. The voltage should be
1.5V to 2.45V (1.96V typical). If it is, go to Step 4. If it is not,
replace the control board.
4. Measure the POWER-LEVEL voltage at TP204. The voltage should
be between 0V and 4.5V, depending on the rated output power of
the PA. If it is, go to Step 5. If it is not, replace the control board.
5. Measure the KEY-CONT voltage at TP211. The voltage should be
greater than 4V. If it is, go to Step 6. If it is not, replace the control
board.
6. Measure the DRIVER-BIAS-MICRO voltage of the driver
transistor at pin 3 of SK103. The voltage should be 3.37V (typical).
If it is, go to Step 7. If it is 0V, replace the control board. If it is
greater than 0V, but less than 3.37V (typical), go to “6W Board” on
page 155.
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