Tait TM8100 mobiles Service Manual page 221

Task 26 —
Check Switching
to Transmit Mode
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
If no transmit frequency is detected in the check of the transmit VCO, first
check that the transmit-receive switch is functioning correctly.
1. Resolder R542 in position (see
Enter the CCTM command 335 1 to switch on the supply to the
2.
transmit VCO.
3. Measure the voltage at the second collector (pin 6) of Q506
(see Figure 9.11). The voltage should be:
pin 6 of Q506: 5.0 ± 0.3V DC (after entry of CCTM 335 1)
Enter the CCTM command 335 0 to switch off the supply.
4.
5. Again measure the voltage at the second collector of Q506.
pin 6 of Q506: 0V DC (after entry of CCTM 335 0)
6. If the voltages measured in
Task 27. If they are not, the switching network is suspect; go to
Task 21.
Figure 9.11).
Step 2 and Step 4 are correct, go to
Frequency Synthesizer Fault Finding 221