Tait TP9100 - Page 255

TP9100 Service Manual Receiver Fault Finding 255
© Tait Electronics Limited May 2005
Tas k 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 circuitry.
1. Check the logic signal
DIG RX EN at pin 8 of IC403 (see Figure 11.2).
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 IQ BOT can (see Figure 11.1).
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 and go to “Final Tasks” on
page 134.
4. Recalibrate the receiver using the calibration application.
5. Confirm the removal of the fault and go to “Final Tasks” on
page 134. If the repair failed, go to Ta sk 7
.
Tas k 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 Ta sk 5
. If the LO1 is not in lock, go
to “Frequency Synthesizer Fault Finding” on page 159. If the FCL is
not in lock, go to “Power Supply for FCL” on page 205. If the LO2
is not in lock, go to Step 3.
3. Check the components around IC403, Q402 and Q403
(see Figure 11.2). 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 134. If the repair failed, go to Ta sk 7
.
pin 8 of IC403: about 3.0V (active)
lock status: 111 (LO1, FCL, LO2 all in lock)