Tait TM8100 mobiles, Service Manual

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TM8100/TM8200 Service Manual Transmitter Fault Finding (>25W) 307
© Tait Electronics Limited November 2007
Task 21 —
Check Power
Control
Check the power-control circuitry if the clamp current for the PA driver is
correct or if the voltage at the
SET PWR
test point is incorrect.
Important
Ensure that the current limit on the DC supply is 3A.
And, when entering the CCTM command
304 z , do not
specify a value
z
higher than that recorded in Task 12 . Fail-
ure to do so may result in the destruction of the PA driver.
1. Enter the CCTM command
304 z
(where
z
was recorded in Task 12 ).
2. Note the current reading on the DC power supply.
3. Enter the CCTM command 114 0 to switch off the power.
4. Note the current reading on the DC power supply.
5. Compare the above current readings. The current should decrease by
an amount approximately equal to the offset given in
Table 11.6 .
If it does, go to Task 26 in “RF Signal Path” on page 316 . If it does
not, go to Step 6 .
6. Check that the voltage from the DAC is changing. Measure the
voltage at the
PWR
test point (
CDC TX PWR CTL
) (see Figure 11.9 and
Figure 11.10
).
7. Enter the CCTM command
114 1023
. The voltage should increase
to:
8. Enter the CCTM command 32 to place the radio in receive mode.
9. If the voltage at the
PWR
test point increases as required, go to
Task 22 . If it does not, go to “CODEC and Audio Fault Finding” on
page 399 .
PWR test point: 2.4
±
0.1V