Tait TB7100, Руководство по обслуживанию

Страница: 117 / 370

TB7100 Service Manual Servicing Procedures 119
© Tait Electronics Limited October 2005
No Modulation
11. If the base station transmits, the synthesizer and transmitter circuitry
are operating correctly. Repair the transmitter module as described in
“CODEC and Audio Fault Finding” on page 343 .
Task 10 —
Check the Receive
and Receive-Audio
Functions
This task only needs to be carried out if it relates to the fault reported or if
the reported fault is not sufficiently specific to identify the faulty module.
1. Set up the test set to generate a signal at –70dBm, modulated at 60%
full system deviation, on the test channel.
Note
Ensure that the test channel does not use sub-audible signalling,
the base station is not in TSHD transparent mode, and the Rx
Inhibit line (SW6 on the CTU) is not active.
2. Turn up the volume and verify that audio can be heard from the
speaker.
3. If no audio can be heard, check whether the user interface or the
receiver module is faulty by connecting a spare speaker, UI board and
UI cable to the receiver module.
Note
When checking the receiver module, only the UI cable to the
receiver needs to be connected, but ensure the
T
X
/R
X
switch is set
to
R
X
.
4. If this rectifies the fault, go to Task 12 . If not, go to Task 11 . Then go
to Step 5 .
5. Verify whether the volume potentiometer works correctly. If not, go
to
Task 12 . Then go to Step 6 .
6. Connect the Line Output from the CTU to the audio input on the
test set.
7. Set up the audio meter to measure audio level and SINAD.
8. Verify that the measured value agrees with the customer’s
requirements (providing this is with in the specified limits of the base
station).
9. If the measured value is correct, go to Step 12 . If not, attempt to
complete the required receiver audio level adjustment as described in
the installation and operation manual.
10. If this rectifies the fault, go to Step 12 . If not, check whether the SI
board and cable or the receiver module is faulty by connecting a spare
receiver module.
Tip
It is not required to remove the original receiver module from the
tray, just unplug the connectors.
11. If this rectifies the fault, the original receiver module is faulty.
Reconnect the original receiver module and go to
Task 11 .
Then go to Step 12 .