Tait TM8000 Series User Manual

TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 203
May 2004 © Tait Electronics Limited
Tas k 4 —
Receiver Sensitivity Is
Few Decibels Too Low
If the receiver sensitivity is just a few decibels too low, the fault-diagnosis
procedure is similar to that of Task 3.
1. Using the calibration application, check the calibration of the
front-end tuning circuitry: Open the “Raw Data” page and click
the “Receiver” tab. Record the values listed in the “Rx FE Tune BPF
Settings” field — these are the DAC values of the FE tuning
voltages for the five frequencies FE TUNE0 to FE TUNE4.
(FE TUNE0 is the lowest frequency and FE TUNE4 the highest
frequency in the radio’s frequency band.)
2. For each of the frequencies FE TUNE0 to FE TUNE4 in turn, carry
out the following procedure: Enter the CCTM command
101 aa0, where a is the frequency in hertz. Enter the CCTM
command 376 and record the value returned — this is the front-
end tuning voltage in millivolts.
3. Compare the values measured in Steps 1 and 2 with the nominal
DAC and voltage values listed in Table 9.3. If the values are
correct, go to Step 4. If they are not, recalibrate the receiver using
the calibration application, and check the DAC and voltage values
again. If the values are now correct, the fault has been rectified;
return to Subsection 8.1. If they are not, go to Step 4.
4. Remove the
FE TOP and IF TOP cans. Check the soldering of all the
components of the front-end tuning circuitry from C400 [at
4B6/4G1] to T401 [at 4L6/4G10] (see Figure 9.13 and
Figure 9.15). Also check the LNA and IF-amplifier bias
conditions as in Step 4 of Task 3 and Step 5 of Task 2 respectively.
If there is no fault, go to Step 5. If there is, repair the fault and go
to Step 6.
5. Check the PIN switch and LPF as in Task 9 and Task 10 of
Subsection 9.6 on the transmitter.
6. Recalibrate the receiver using the calibration application.
Confirm the removal of the fault and return to Subsection 8.1. If
the repair failed, return to Subsection 8.1 and replace the
complete main-board assembly.
Table 9.4 Nominal AGC data
Parameter
AGC voltages and receiver input powers
AGC0 AGC1 AGC2
AGC voltage (mV)
B1 frequency band
D1 frequency band
H5 frequency band
H6 frequency band
2110 ± 50
2050 ± 50
2200 ± 50
2220 ± 50
1960 ± 40
1900 ± 40
2040 ± 40
2050 ± 40
1790 ± 40
1750 ± 40
1860 ± 40
1870 ± 40
Receiver input power (dBm)
Standard radio
Trigger-base radio
–68
–62
–60
–54
–50
–44

Tait TM8000 Series Specifications

General

Brand	Tait
Model	TM8000 Series
Category	Radio
Language	English