Check Transmit Buffer Amplifier - Tait TM9100 Service Manual

If no transmit frequency is detected but the switching network is not faulty,
Task 27 —
Check Transmit
check the transmit buffer amplifier. If the amplifier is not faulty, there might
Buffer Amplifier
be a fault in the transmit VCO that was not detected earlier.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Remove the can.
VCO BOT
Check the transmit buffer amplifier in receive mode: Enter the
CCTM command 335 0 to set the transmit-receive switch off.
Measure the voltage at pin 6 of Q5001 (see
pin 6 of Q5001: 0 V DC (receive mode)
Then check the transmit buffer amplifier in transmit mode: Enter the
CCTM command 335 1 to set the transmit-receive switch on.
Again measure the voltage at Q5001.
pin 6 of Q5001: 0.7 ± 0.1 V DC (transmit mode)
If the voltages are correct, the transmit VCO is suspect; go to
If they are not, the transmit buffer amplifier is suspect; go to
Remove the can.
VCO TOP
Check the transmit VCO circuitry based on Q510 (see
Conclude with Step 10.
Check the buffer circuitry based on Q5001 (see
If a fault is found, repair the circuit, and confirm that the voltages are
now correct. If they are, go to
not, or if no fault could be found, replace the main-board assembly
and go to "Final Tasks" on page
Figure
Figure
"Final Tasks" on page
147.
Frequency Synthesizer Fault Finding
9.10).
Step 7.
Step 9.
Figure 9.9).
9.10).
147. If they are
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