Tait TB7100, Service Manual

Page: 116 / 370

118 Servicing Procedures TB7100 Service Manual
© Tait Electronics Limited October 2005
Note
Ensure the T
X
/R
X
switch of the spare UI board is set to T
X
.
When checking the transmitter module, both UI cables need to
be connected.
Tip
Instead of the spare UI board, a TMAC20-0T control head can be
connected to module.
11. If this rectifies the fault, go to Step 12 . If it does not, go to Task 9 .
Return to Step 9 .
12. If the reported fault was only with the transmitter and has now been
repaired, go to
“Final Tasks” on page 123 . Otherwise go to Task 10 .
Task 9 —
Check the
Transmitter Module
If the fault is with the transmitter module, this can be caused by:
■
the synthesizer not being in lock
■
no or wrong carrier power
■
no modulation
If the cause is already known, go directly to the relevant fault-finding
section.
Caution
Observe the servicing precautions for the transmit-
ter listed in
“Transmitter Issues” on page 81 .
Synthesizer
Out of Lock
1. Use CCTM command
101 x y 0
to set the transmit frequency to the
bottom of the band.
2. Use CCTM command
33
to set the base station to transmit mode.
3. Use CCTM command 72 to read the lock status.
4. If the synthesizer is in lock, go to Step 5 . If the synthesizer is not in
lock, repair the transmitter module as described in “Frequency
Synthesizer Fault Finding” on page 143 .
5. Repeat Step 1 to Step 3 with the transmit frequency set to the top of
the band
No or Wrong
Carrier Power
6. Use CCTM command 326 1 to set the power level to very low.
7. Connect a power meter and measure the transmit power.
8. If the carrier power is correct, go to Step 10 . If the carrier power is
not correct, try to re-calibrate the transmitter module.
9. If the re-calibration does not repair the fault, repair the transmitter
module as described in
“Transmitter Fault Finding (50W/40 W)” on
page 273 and “Transmitter Fault Finding (25W)” on page 219 .
10. Repeat Step 7 to Step 9 with the power level set to high (
326 4
).