Check Buffer Amplifier - Tait TM9100 Service Manual

If no VCO frequency is detected but the switching network is not faulty,
Task 33 —
Check Buffer
check the buffer amplifier. If the amplifier is not faulty, there might be a fault
Amplifier
in the VCO that was not detected earlier.
1.
2.
3.
4.
5.
6.
214 Frequency Synthesizer Fault Finding
Enter the CCTM command 335 0 to set the transmit-receive switch
off.
Measure the voltage at pin 3 of D5004 (see
noise might be observed.)
pin 3 of D5004: 4.2 ± 0.2 V DC
Measure the voltage at pin 1 of Q5001 (see
pin 1 of Q5001: 0.7 ± 0.2 V DC
If the voltages measured in
Step 5. If they are, check the VCO circuitry based on Q5000
(see Figure 9.13). Conclude with
The buffer amplifier is suspect. Check the buffer circuitry (based on
Q5001) (see Figure 9.13).
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 9.13). (Some RF
Figure
Step 2 and Step 3 are not correct, go to
Step 6.
"Final Tasks" on page
147.
TM9100 Service Manual
© Tait Electronics Limited August 2005
9.13).
147. If they are