TM8100/TM8200 Service Manual
CODEC and Audio Fault Finding
385
© Tait Electronics Limited
June 2006
Task 4 —
Check Audio
Power Amplifier
If there is no fault with the power supplies, check the inputs to the audio PA
as follows. This check is only applicable, however, if the output of the voice-
band CODEC is correct and the signal level varies as the volume is varied.
1.
Use the programming application to find the frequency selected for
channel 1.
2.
In user mode apply an on-channel RF signal of –47dBm with 60%,
1kHz deviation. The channel must not have signalling enabled.
Set the volume to maximum.
3.
Use an oscilloscope probe to check the output of the voice-band
CODEC at the
TP
200
test point
(see
). The signal
should be:
4.
If the above signal is correct, go to
. If it is not, go to
.
5.
Vary the volume control. This should cause the signal level at the
TP
200
test point
(see
.
.
6.
Check the voltage at pin 11 of
IC202
(see
7.
If the voltage is correct, go to
. If it is not, check for and repair
any faults in the level-translation circuits incorporating
Q200
and
Q201
(see
).
8.
Confirm the removal of the fault and go to
. If the repair failed, replace the board and go to
.
9.
Check the digital signals
DIG
AUD
PA
EN
1
at
R200
and
DIG
AUD
PA
EN
2
at
R202
(see
10.
If the signals are correct, go to
. If they are not, check the
programming and test set-up; otherwise the digital board is faulty;
replace the board and go to
.
TP200 test point: sine wave of 100mV
pp
with 0.6V DC offset
pin 11 of IC202: at least 8V DC
R200 (DIG AUD PA EN1): 3.3V DC
R202 (DIG AUD PA EN2): 0.0V DC
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...