Tait TM8100 mobiles, Service Manual

Page: 252 / 620

252 Receiver Fault Finding TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Task 3 —
Check Logic Signal
If there is no fault with the power supplies, check the logic signal
DIG RX EN
that is input from the digital board.
1. Check the logic signal
DIG RX EN
at pin 8 of IC403 (see Figure 10.2 ).
The signal is active high. The required status is active.
An alternative measurement point to the above is pin 24 of IC400
under the
IF TOP
can (see Figure 10.1 ).
2. If
DIG RX EN
is active, go to Task 4 . If it is not, go to Step 3 .
3. Check the signal continuity from the digital board to the receiver.
Repair any fault and go to
Step 4 . If the digital board itself appears to
be faulty, replace the board and go to “Final Tasks” on page 163 .
4. Recalibrate the receiver using the calibration application.
5. Confirm the removal of the fault and go to “Final Tasks” on
page 163 . If the repair failed, go to Task 7 .
Figure 10.4 Receiver circuitry under the FE TOP and IF TOP can (K5 band only)
IC405 IC404
IC409
pin 8 of IC403: about 3.0V (active)