
284
CODEC and Audio Fault Finding
TP9100 Service Manual
© Tait Electronics Limited
May 2005
12.5 Faulty Modulation
Introduction
This section covers the case where the radio transmits the correct amount of
RF power, but there is either no modulation or the modulation is distorted.
There are four tasks:
■
Task 11: check internal microphone
■
Task 12: initial checks of external microphone
■
Task 13: check external microphone audio
■
Task 14: check external microphone bias
Task 11 —
Check Internal
Microphone
To check the modulation from the internal microphone:
1.
Remove any external microphone or accessory and apply an audio
acoustic signal from an external speaker or noise source near the
internal speaker.
2.
Enter the CCTM command
33
to place the radio in transmit mode
(the frequency is that of channel 1). The radio
must
be in transmit
mode for the
+5
V TX
and microphone pre-amp circuit to operate.
3.
Create an audio signal by whistling into the speaker and check that
the audio signal appears at the junction of
C235
and
R261
, and also
the junction of
C236
and
R262
(see
4.
If the audio signal is not present check and repair the speaker, speaker
pins, components and soldering of
C235
and
C236
(see
). If the signal is present, go to
5.
Confirm the removal of the fault and go to
. If the repair failed or the fault could not be found, replace
the main board and go to
6.
Create an audio signal by whistling into the speaker and check that
the audio signal appears at the junction of
R267
and
IC202
(see
7.
Enter the CCTM command
32
to place the radio in receive mode.
8.
If the audio signal is present, go to
on the frequency synthesizer fault
finding. If it is not, go to
9.
Check the components and soldering around IC202 and repair or
replace as required.
10.
Confirm the removal of the fault and go to
. If the repair failed or the fault could not be found, replace
the main board and go to
Summary of Contents for TP9100
Page 1: ...TP9100 portables Service Manual MPA 00005 01 Issue 1 00 May 2005 ...
Page 4: ...4 TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 10: ...10 TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 74: ...74 Circuit Descriptions TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 78: ...78 TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 100: ...100 General Information TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 126: ...126 Disassembly and Reassembly TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 148: ...148 Interface Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 158: ...158 Power Supply Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 250: ...250 Transmitter Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 268: ...268 Receiver Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 294: ...294 Spare Parts TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 298: ...298 Antenna Identification Chart TP9100 Service Manual Tait Electronics Limited May 2005 ...