High Receiver Distortion; Tcxo Calibration And Repair Of Tcxo - Tait TM9100 Service Manual

10.6

High Receiver Distortion

If there is high receiver distortion, the TCXO is suspect, or alternatively, the
Introduction
matching circuitry for the crystal filters XF400 and XF401. There are two
tasks:
Recalibrating the TCXO might often be sufficient to rectify the fault.
First check the TCXO calibration and, if necessary, repair the TCXO.
Task 17 —
TCXO Calibration
and Repair of TCXO
1.
2.
3.
4.
5.
6.
7.
8.
242 Receiver Fault Finding
Task

17: TCXO calibration and repair of TCXO

Task 18: second IF and repair of matching circuitry
Use the calibration application to check the TCXO calibration:
Open the "Raw Data" page and click the "Volt Ref/TCXO/VCO/VCXO"
tab.
Note the values listed in the "Tx TCXO" and "Rx TCXO" fields of the
"TCXO" group box. The values should be:
Tx TCXO and Rx TCXO values: between +20Hz and –20Hz
If the calibration values are correct, go to
recalibrate the TCXO and go to
Remove the
CDC TOP
Check the components of the TCXO, which is based on XL500
(see Figure 10.4). Repair any fault.
Recalibrate the TCXO and check the TCXO calibration values
again as in Step 1 and
If the calibration values are now correct, go to
go to Task 18.
Check if the distortion fault has been removed. If it has, go to
Tasks" on page 147. If it has not, go to
Step
Step 8.
can.
Step 2.
Task 18.
© Tait Electronics Limited August 2005
4. If they are not,
Step 8. If they are not,
"Final
TM9100 Service Manual