Tait TM8235, Service Manual

Page: 155 / 578

TM8100/TM8200 Service Manual Servicing Procedures 155
© Tait Electronics Limited June 2006
Task 9 —
Check the Transmit
and Transmit-Audio
Functions
If the radio does not transmit, 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 transmitter
issues listed
on page 109 .
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 radio 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 radio as described in “Frequency Synthesizer Fault
Finding” on page 179 .
5. Repeat Step 1 to Step 4 with the transmit frequency set to the top of
the band.
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 radio.
9. If the re-calibration repairs the fault, go to “Final Tasks” on page 157 .
If it does not, repair the radio as described in “Transmitter Fault
Finding (40W/50W)” on page 259 and “Transmitter Fault Finding
(25W)” on page 323 .
10. Repeat Step 6 to Step 9 with the power level set to high ( 326 4 ).
11. 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).
12. If the radio transmits audio now, the original speaker was faulty.
Reassemble the radio and go to
“Final Tasks” on page 157 . If the
radio still fails to transmit, reconnect the original speaker and go to
Step 13 .
13. After having eliminated the synthesizer, the transmitter circuitry, and
the speaker as cause for the fault, repair the radio as described in
“CODEC and Audio Fault Finding” on page 381 .