Tait TP9100 - Chapter 12: CODEC and Audio Fault Finding

TP9100 Service Manual CODEC and Audio Fault Finding 269
© Tait Electronics Limited May 2005
12 CODEC and Audio Fault Finding
Fault Conditions This section covers the diagnosis of faults in the CODEC and audio
circuitry. There are five conditions that indicate a possible fault in the
circuitry:
■ no speaker audio or speaker audio is distorted
■ no audio tap out at accessory connector
■ receiver does not operate
■ no transmit modulation or modulation is distorted from the internal
speaker/microphone
■ no transmit modulation or modulation is distorted from the accessory
connector
In the first
and second cases regarding the speaker audio, the green status
LED will be operating correctly and all unmute criteria will be satisfied.
In the third
case the assumption is that the receiver and power-supply
circuitry were checked and no faults were found. In the fourth
and fifth cases
regarding the transmit modulation, the radio will be transmitting the correct
amount of RF power.
Fault-Diagnosis
Procedures
The procedures for diagnosing the above faults are given below in the
following sections. In each case, however, first carry out the tasks of “Power
Supplies” on page 270. Also note that the conditions concerning the
accessory connector can both occur at the same time. In this case carry out
both “No Audio Tap Out at Accessory Connector” on page 278 and
“Faulty Modulation Using Accessory Audio Tap In” on page 287.
Important The fault diagnosis must only be carried out on an analog
channel.
CCTM commands The CCTM commands required in this section are listed in Table 12.1.
Full details of the commands are given in “Computer-Controlled Test
Mode (CCTM)” on page 91.
Table 12.1 CCTM commands required for the diagnosis of faults in the CODEC and audio circuitry
Command Description
21
32
33
110 x
323 x y
324 x y
400 x
Unmute received audio
Set radio in receive mode
Set radio in transmit mode
Set level x (in range 0 to 255) of audio volume
Generate audio tone
AUD TAP IN at tap point x of tap type y
Output audio signal at tap point x of tap type y to
AUD TAP OUT
Select channel with channel number x