Tait TM8100 mobiles Service Manual page 216

Task 21 —
Repair Switching
Network
216 Frequency Synthesizer Fault Finding
If the transmit-receive switch is not functioning correctly, first check the
line to confirm that the digital board is not the cause. If the digital
SYN TR SW
board is not faulty, the switching network is suspect.
Enter the CCTM command 335 0 to set the transmit-receive switch
1.
off (receive mode). Measure the voltage on the
between Q508 and R593 (see
R593: 0V DC (after entry of CCTM 335 0)
Enter the CCTM command 335 1 to set the transmit-receive switch
2.
on (transmit mode). Again measure the voltage at R593.
R593: 2.0 ± 0.5V DC (after entry of CCTM 335 1)
3. If the voltages measured in
Step 9. If they are not, remove R103 (see
Step 4.
Enter the CCTM command 335 0 and measure the voltage at the via
4.
between R103 and the digital board (see
via at R103: 0V DC (after entry of CCTM 335 0)
Enter the CCTM command 335 1 and again measure the voltage at
5.
the via between R103 and the digital board.
via at R103: 3.3 ± 0.3V DC (after entry of CCTM 335 1)
6. If the voltages measured in
Step 7. If they are not, the digital board is faulty; resolder R103 in
position (see Figure
on page 163.
7. Check and resolder R103 in position (see
continuity between Q508 and the digital board via R593
(see Figure 9.11) and R103.
8. If no fault is found, go to
confirm that the voltages are now correct, and go to
page 163 If the repair failed, replace the board and go to
Tasks" on page
9. Check the circuitry for the transmit-receive and 5V switches (based
on Q506, Q507 and Q508) (see
10. If a fault is found, repair the circuit, confirm that the voltages are now
correct, and go to
the fault could not be found, replace the board and go to
Tasks" on page
Figure
Step 1 and
Step 4 and
9.7), replace the board and go to
Step 9. If a fault is found, repair the circuit,
163.
Figure
"Final Tasks" on page
163.
© Tait Electronics Limited November 2007
DIG SYN TR SW
9.11).
Step 2 are correct, go to
Figure 9.7) and go to
Figure 9.7).
Step 5 are correct, go to
"Final Tasks"
Figure 9.7), and check for
"Final Tasks" on
"Final
9.11).
163. If the repair failed or
"Final
TM8100/TM8200 Service Manual
DIG
line