Tait TM8100 mobiles Service Manual page 231

Task 31 —
Check Transmit-
Receive Switch
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
If no frequency is detected in the check of the VCO, first check that the
transmit-receive switch is functioning correctly.
1. Resolder R542 in position (see
2. Remove the
VCO BOT
Enter the CCTM command 335 0 to switch on the supply to the
3.
port.
4. Measure the voltage at pin 2 of D5004 (see
noise might be observed.) The voltage should be:
pin 2 of D5004: 5.0 ± 0.3V DC (after entry of CCTM 335 0)
Enter the CCTM command 335 1 to switch off the supply.
5.
6. Again measure the voltage at pin 2 of D5004.
pin 2 of D5004: 0V DC (after entry of CCTM 335 1)
7. If the voltages measured in
Step 8. If they are not, the switching network is suspect; go to
Task 32.
Enter the CCTM command 335 1 to switch on the supply to the
8.
port.
9. Measure the voltage at pin 1 of D5004 (see
noise might be observed.) The voltage should be:
pin 1 of D5004: 5.0 ± 0.3V DC (after entry of CCTM 335 1)
Enter the CCTM command 335 0 to switch off the supply.
10.
11. Again measure the voltage at pin 1 of D5004.
pin 1 of D5004: 2.1 ± 0.4V DC (after entry of CCTM 335 0)
12. If the voltages measured in
Task 33. If they are not, the switching network is suspect; go to
Task 32.
Figure 9.14).
can.
Figure
Step 4 and Step 6
Figure
Step 9 and Step 11
Frequency Synthesizer Fault Finding
RX
9.15). (Some RF
are correct, go to
TX
9.15). (Some RF
are correct, go to
231