Tait TM8100 mobiles, Service Manual

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354 Transmitter Fault Finding (25W) TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Task 6 —
Power Unchanged
Regardless of
Setting
If all the power and current values measured in Task 5 are correct, it is likely
that the power remains unchanged regardless of the power setting.
1. Enter the following CCTM commands in turn and measure the RF
output power in each case:
■
326 4
■
326 3
■
326 2
■
326 1
2. The above measurements should confirm that the power remains
unchanged at all settings. Carry out
Task 12 and then Task 19 .
Task 7 —
Check for Inhibiting
of Transmitter
If the transmitter is drawing no current or the wrong current, check
whether it is being inhibited. This check is also required if a
CO3
error
occurs in Task 1 .
1. If not already done, enter the CCTM command
33
to place the radio
in transmit mode.
2. Check the logic signal at the
TX INH
test point (see Figure 12.4 ).
The signal should be:
3. If the signal is inactive as required, go to Step 4 . If it is active — about
1.1V — the transmitter is being inhibited; go to Step 5 .
4. Enter the CCTM command
32
to place the radio in receive mode,
and go to Task 12 in “Biasing of PA Driver and PAs” on page 360 .
5. Check the logic signal at the
D TX INH
test point (see Figure 12.4 ).
The signal should be:
6. If the signal is inactive as required, go to Step 8 . If it is active — about
3.2V — the temperature sensor is suspect; go to Step 7 .
7. Enter the CCTM command
32
to place the radio in receive mode,
and go to Task 8 .
8. The lock status is possibly no longer normal. Enter the CCTM
command
72
and check the lock status.
9. Enter the CCTM command 32 to place the radio in receive mode.
10. The normal lock status is
110
. If it is not, proceed to the relevant
section. If it is, go to Step 11 .
11. Check for short circuits on the
DIG TX INH
line from the
D TX INH
test
point .
TX INH test point: about 0V (inactive)
D TX INH test point: about 0V (inactive)