158 Power Amplifier Fault Finding TB8100 Service Manual
© Tait Electronics Limited September 2006
8. Measure the voltage at pin 2 of SK103. The voltage should be greater
than 40mV. If it is, go to Tas k 5
. If it is not, replace the 6W board.
Task 5 —
Check Output
Power
This task assumes that:
■ you have calibrated the PA bias and the driver calibration was successful
■ you have verified that Tx Key is working correctly (refer to Task 4).
1. Check that the PA is set to its rated output power (i.e. 5W, 50W, or
100W according to model).
2. Connect an RF power meter to the output from the 6W board:
■ Remove the bridging link from the RF output 50Ω track (b in
Figure 8.11 on page 155).
■ Solder the inner conductor of the test lead to the 50Ω track.
■ Solder the braid of the test lead to ground.
3. Put the base station in Run Mode and key the PA using the TX KEY
switch on the CTU.
4. Check that the RF output power is as follows:
■ 5W and 100W PAs greater than 6W
■ 50W PA greater than 3W.
If the output power is as stated above, the 6W board is not faulty.
Proceed to “60W Board” on page 162 if the PA under test is 5W or
50W, or to “Splitter and Combiner Boards (100W PA Only)” on
page 160 if it is a 100W PA.
If the RF output power is less than stated above, go to Step 5.
5. Check that the RF input power from the reciter is greater than
+9dBm. If it is, replace the 6W board. If it is not, check the reciter
and repeat the test.
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