Tait TB7100 Service Manual

TB7100 Service Manual Frequency Synthesizer Fault Finding 173
© Tait Electronics Limited October 2005
Task 21 —
Repair Switching
Network
If the transmit-receive switch is not functioning correctly, first check the DIG
SYN TR SW line to confirm that the digital board is not the cause. If the digital
board is not faulty, the switching network is suspect.
1. Enter the CCTM command 335 0 to set the transmit-receive switch
off (receive mode). Measure the voltage on the
DIG SYN TR SW line
between Q508 and R593 (see Figure 11.9).
2. Enter the CCTM command 335 1 to set the transmit-receive switch
on (transmit mode). Again measure the voltage at R593.
3. If the voltages measured in Step 1 and Step 2 are correct, go to
Step 9. If they are not, remove R103 (see Figure 11.6) and go to
Step 4.
4. Enter the CCTM command 335 0 and measure the voltage at the via
between R103 and the digital board (see Figure 11.6).
5. Enter the CCTM command 335 1 and again measure the voltage at
the via between R103 and the digital board.
6. If the voltages measured in Step 4 and Step 5 are correct, go to
Step 7. If they are not, the digital board is faulty; resolder R103 in
position (see Figure 11.6), replace the main-board assembly and go
to “Final Tasks” on page 123.
7. Check and resolder R103 in position (see Figure 11.6), and check
for continuity between Q508 and the digital board via R593
(see Figure 11.9) and R103.
8. If no fault is found, go to Step 9. If a fault is found, repair the circuit,
confirm that the voltages are now correct, and go to “Final Tasks” on
page 123. If the repair failed, replace the main-board assembly and go
to “Final Tasks” on page 123.
9. Check the circuitry for the transmit-receive and 5V switches (based
on Q506, Q507 and Q508) (see Figure 11.9).
10. If a fault is found, repair the circuit, confirm that the voltages are now
correct, and go to “Final Tasks” on page 123. If the repair failed or
the fault could not be found, replace the main-board assembly and go
to “Final Tasks” on page 123.
R593: 0 V DC (after entry of CCTM 335 0)
R593: 2.0 ± 0.5 V DC (after entry of CCTM 335 1)
via at R103: 0 V DC (after entry of CCTM 335 0)
via at R103: 3.3 ± 0.3 V DC (after entry of CCTM 335 1)

Tait TB7100 Specifications

General

Brand	Tait
Model	TB7100
Category	Accessories
Language	English