Faulty Modulation Using Auxiliary Connector; Apply Aud Tap In Signal - Tait TM9100 Service Manual

13.6

Faulty Modulation Using Auxiliary Connector

This section covers the case where the transmitter operates normally but
Introduction
there is no modulation (although there is modulation at the auxiliary
connector). There are two tasks:
If there was also a fault with the speaker audio at the auxiliary connector, it
is assumed that this has now been rectified.
First check the modulation and, if necessary, the DC offset.
Task 15 —
Apply
AUD TAP IN
Signal
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
394 CODEC and Audio Fault Finding
Task 15: apply
AUD TAP IN
Task 16: check CODEC 2 device
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.
Enter the CCTM command 32 to place the radio in receive mode.
If the modulation is correct, go to
of "Faulty Modulation" on page
Apply a 1kHz AC-coupled signal of 0.7V
the auxiliary connector (alternatively, as
of R237 and R241 — see
Enter the CCTM command 323 t5.
Check the DC offset voltage at pin 7:
pin 7 of auxiliary connector: approximately 1.5V DC offset
If the above DC offset is correct, go to
Step 11.
Remove the
CDC TOP
Check for and repair any soldering faults around IC205, or else
replace IC205 (see Figure
Check for shorts at pin 7 of the auxiliary connector. If there are none,
go to Task 16. If there are, repair the fault and conclude with
Confirm the removal of the fault and go to
page 147. If the repair failed, replace the main-board assembly and go
to "Final Tasks" on page
signal
Step 5. If it is not, go to
390.
at pin 7 (
pp
ITF AUD TAP IN
Figure 13.10).
Step 9. If it is not, go to
can.
13.10). Conclude with
"Final Tasks" on
147.
© Tait Electronics Limited August 2005
Task 12
) of
AUD TAP IN
at the junction
Step 12.
Step 12.
TM9100 Service Manual