Tait TB7100 - Page 230

232 Transmitter Fault Finding (25W) TB7100 Service Manual
© Tait Electronics Limited October 2005
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 13.4).
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 239.
5. Check the logic signal at the
DTXINH test point (see Figure 13.4).
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 DTXINH test
point.
TX INH test point: about 0V (inactive)
D TX INH test point: about 0V (inactive)