244
Diagnosis of Faults on Main Board
TM8100 Mobile Radio
Service Manual
May 2004 © Tait Electronics Limited
Task 6 —
Faulty Modulation
Using Auxiliary
Connector
If the transmitter operates normally but there is no modulation (although
there is modulation at the auxiliary connector), proceed as follows:
1.
Enter the CCTM command
33
to place the radio in transmit
mode. (The frequency is that of channel 1.) Check the
modulation via the microphone input. If it is correct, go to Step
2. If it is not, go to Task 4.
2.
Apply a 1 kHz AC-coupled signal of 0.7 V
pp
at pin 7 (
AUD
TAP
IN
)
of the auxiliary connector (alternatively, as
ITF
AUD
TAP
IN
[at
2M2/2D11] at the junction of R237 and R241 — see
). Enter the CCTM command
323 t5
. Check that the
DC offset voltage at pin 7 is approximately 1.5 V DC. If it is, go
to Step 3. If it is not, go to Step 4.
3.
Remove the
CDC
TOP
can. Check for and repair any soldering
faults around IC205 [at 2P2/2D12], or else replace IC205 (see
). Confirm the removal of the fault and return to
. If the repair failed, return to
and
replace the complete main-board assembly.
4.
Check that there are no shorts at pin 7 of the auxiliary connector.
If there are none, go to Step 5. If there are, repair the fault.
Confirm the removal of the fault and return to
. If
the repair failed, return to
and replace the
complete main-board assembly.
5.
Remove the
CDC
TOP
can. Check that the voltage at both ends of
R241 [at 2P2/2D12] is 1.5 V DC (see
). If it is, go to
Step 6. If it is not OK, go to Step 7.
6.
Check for and repair any soldering faults around IC205 [at
2P2/2D12], or else replace IC205 (see
). Confirm the
removal of the fault and return to
. If the repair
failed, return to
and replace the complete main-
board assembly.
7.
Remove R241 and check that the voltage at pin 3 of IC205 is
1.5 V DC (see
). If it is, go to Step 8. If it is not,
return to
and replace the complete main-board
assembly.
8.
Check for and repair any soldering faults around R241 and IC205
[at 2P2/2D12] (see
). Confirm the removal of the
. 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 ...
