TM8100 Mobile Radio
Service Manual
Diagnosis of Faults on Main Board
203
May 2004 © Tait Electronics Limited
Task 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
a a
0
, 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
. 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
. 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
and
). 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
on the transmitter.
6.
Recalibrate the receiver using the calibration application.
Confirm the removal of the fault and return to
the repair failed, return to
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
Summary of Contents for TM8000 Series
Page 32: ...32 Introduction TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
Page 78: ...78 Circuit Descriptions TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
Page 106: ...106 General Information TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
Page 124: ...124 Servicing Procedure TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...