402
CODEC and Audio Fault Finding
TM8100/TM8200 Service Manual
© Tait Electronics Limited
June 2006
13.6
Faulty Modulation Using Auxiliary Connector
Introduction
This section covers the case where the transmitter operates normally but
there is no modulation (although there is modulation at the auxiliary
connector). There are two tasks:
■
: apply
AUD
TAP
IN
signal
■
If there was also a fault with the speaker audio at the auxiliary connector, it
is assumed that this has now been rectified.
Task 15 —
Apply
AUD
TAP
IN
Signal
First check the modulation and, if necessary, the DC offset.
1.
Enter the CCTM command
33
to place the radio in transmit mode.
(The frequency is that of channel 1.)
2.
Check the modulation via the microphone input.
3.
Enter the CCTM command
32
to place the radio in receive mode.
4.
If the modulation is correct, go to
. If it is not, go to
“Faulty Modulation” on page 398
5.
Apply a 1kHz AC-coupled signal of 0.7V
pp
at pin 7 (
AUD
TAP
IN
) of
the auxiliary connector (alternatively, as
ITF
AUD
TAP
IN
at the junction
of
R237
and
R241
— see
).
6.
Enter the CCTM command
323 t5
.
7.
Check the DC offset voltage at pin 7:
8.
If the above DC offset is correct, go to
. If it is not, go to
9.
Remove the
CDC
TOP
can.
10.
Check for and repair any soldering faults around
IC205
, or else
replace IC205 (see
). Conclude with
.
11.
Check for shorts at pin 7 of the auxiliary connector. If there are none,
go to
. If there are, repair the fault and conclude with
12.
Confirm the removal of the fault and go to
. If the repair failed, replace the board and go to
.
pin 7 of auxiliary connector: approximately 1.5V DC offset
Summary of Contents for TM8235
Page 1: ...TM8100 mobiles TM8200 mobiles Service Manual MMA 00005 04 Issue 4 June 2006...
Page 10: ...10 TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 62: ...62 Description TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 148: ...148 Disassembly and Reassembly TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 162: ...162 Servicing Procedures TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 178: ...178 Interface Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 258: ...258 Receiver Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 446: ...446 Spare Parts TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
