Tait TB7100 - Page 118

120 Servicing Procedures TB7100 Service Manual
© Tait Electronics Limited October 2005
12. Repeat from Step 6 using the Unbalanced Line output.
13. Check whether the B
USY LED on the front of the base station is lit
up. If not, replace the UI board or cable.
14. Verify the Rx Gate LED on the CTU is lit. 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.
15. If this rectifies the fault, the original receiver module is faulty.
Reconnect the original receiver module and go to Task 11
. Then go
to Task 12
.
Task 11 —
Check the
Receiver Module
If the base station does not receive, this can be caused by:
■ the synthesizer not being in lock
■ no carrier detected
If the cause is already known, go directly to the relevant fault-finding
section.
No Receive or
Receive Audio
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 receiver module as described in “Frequency
Synthesizer Fault Finding” on page 143.
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 BUSY LED
■ CCTM command 63 should return the fed signal strength
±1dBm.
6. If the carrier is detected correctly, try to re-calibrate the receiver
module. If not, load a default calibration file into the receiver module
and then attempt to re-calibrate.
7. If re-calibration does not the repair the fault, repair the receiver
module as described in “Receiver Fault Finding” on page 201.
Receive Audio but
No Rx Gate Signal
The receiver is working but there is a fault in the interface circuitry of the
receiver module. Repair the receiver module as described in “Interface Fault
Finding” on page 137.