Tait TB7100, Руководство по обслуживанию

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206 Receiver Fault Finding TB7100 Service Manual
© Tait Electronics Limited October 2005
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 12.2 ).
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 12.1 ).
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 main-board assembly and go to “Final Tasks” on
page 123 .
4. Recalibrate the receiver using the calibration application.
5. Confirm the removal of the fault and go to “Final Tasks” on
page 123 . If the repair failed, go to Task 7 .
Task 4 —
Check Lock Status
If the logic signal from the digital board is active, as required, check the lock
status of the radio.
1. Enter the CCTM command
72
to determine the lock status.
The status should be normal:
2. If the lock status is normal, go to Task 5 . If the LO1 is not in lock, go
to “Frequency Synthesizer Fault Finding” on page 143 . If the FCL is
not in lock, go to “Power Supply for FCL” on page 189 . If the LO2
is not in lock, go to Step 3 .
3. Check the components around IC403, Q402 and Q403
(see
Figure 12.2 ). Repair any fault.
4. Recalibrate the receiver using the calibration application.
5. Confirm the removal of the fault, and go to “Final Tasks” on
page 123 . If the repair failed go to Task 7 .
pin 8 of IC403: about 3.0V (active)
lock status: 111 (LO1, FCL, LO2 all in lock)