TM8100 Mobile Radio
Service Manual
Diagnosis of Faults on Main Board
219
May 2004 © Tait Electronics Limited
Task 7 —
Check Biasing
of Second PA
If there is no fault in the biasing of the first PA, check that of the second
PA (Q309).
1.
Use the multimeter to measure the voltage at pin 8 of IC301 [at
3G0/3B6] (see
). The voltage should be 40 ± 5 mV.
Enter the CCTM command
332
b
(where
b
was recorded in Task
5) and check that the voltage is between 2 and 5 V. Also note the
current reading; this should increase by an amount equal to the
offset noted in Step 3 of Task 5.
2.
If the voltage and current are both correct, enter the CCTM
command
332 1
to turn off final bias 2, and go to Task 8. If the
voltage is correct but not the current, go to Step 3. If neither the
current nor the voltage is correct, go to Step 5.
3.
If not already done, remove the
PAF
TOP
can. Enter the CCTM
command
332
b
(where
b
was recorded in Task 5) and check that
the voltage at the gate of Q309 [at 3F3/3E5] is between 2 and 5 V.
If it is, Q309 is faulty; return to
and replace the
complete main-board assembly. If it is not, go to Step 4.
4.
Check the circuitry between pin 8 of IC301 and the gate of Q309
(see
to
). If a fault is found, repair it,
confirm the removal of the fault, and return to
the repair failed or Q309 itself is faulty, return to
and replace the complete main-board assembly.
5.
Use the multimeter to measure the voltage at the
FIN
2
test point [at
3K0/3B9] (see
). The voltage will be 18 ± 2 mV.
Enter the CCTM command
332
b
(where
b
was recorded in Task
5) and check that the voltage is between 1.1 and 2.7 V. If it is, go
to Step 6. If it is not, go to
on the CODEC and
audio circuitry.
6.
Check IC301 and the surrounding shaping-filter circuitry (see
). If a fault is found, repair it, confirm the removal of
the fault, and return to
. If the repair failed, return
to
and replace the complete main-board assembly.
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 ...
