Tait TM8235, Руководство по обслуживанию

Страница: 156 / 578

156 Servicing Procedures TM8100/TM8200 Service Manual
© Tait Electronics Limited June 2006
14. If the main-board assembly was replaced or if the repair failed, re-
assemble the radio as described in
“Disassembly and Reassembly” on
page 129 . Conclude with the tasks of “Final Tasks” on page 157 .
Task 10 —
Check the Receive
and Receive-Audio
Functions
If the radio does not receive, this can be caused by:
■
the synthesizer not being in lock
■
no carrier detected
■
a faulty speaker or volume control
■
no modulation.
If the cause is already known, go directly to the relevant fault-finding
section.
1. Use CCTM command
101 x y 0
to set the receive frequency to the
bottom of the band.
2. Use CCTM command
72
to read the lock status.
3. If the synthesizer is in lock, go to Step 5 . If the synthesizer is not in
lock, repair the radio as described in “Frequency Synthesizer Fault
Finding” on page 179 .
4. Repeat Step 1 to Step 3 with the receive frequency set to the top of
the band
5. Feed a signal without modulation on the receive channel at –47dBm.
Check for maximum RSSI using:
■
the indicator on the radio display (graphical display)
■
the green status LED
■
CCTM command
63
should return the fed signal strength
±1dBm.
6. Repeat the check in Step 5 with –117dBm. The RSSI indicator
should show as empty or close to empty (graphical display).
7. If the carrier is detected correctly, go to Step 9 . If the carrier is not
detected correctly, try to re-calibrate the radio.
8. If the re-calibration repairs the fault, go to “Final Tasks” on page 157 .
If it does not, repair the radio as described in “Receiver Fault
Finding” on page 239 .
9. Check whether the speaker is the source of the fault, as described in
“Speaker Faulty” on page 422 (graphical display) or “Speaker Faulty”
on page 436 (1-, 2- or 3-digit display).
10. If the radio receives audio now, the original speaker was faulty.
Reassemble the radio and go to
“Final Tasks” on page 157 . If the
radio still fails to receive, reconnect the original speaker and go to
Step 11 .
11. Use CCTM command
804
to read the status of the volume
potentiometer.