Tait TM8100 mobiles Service Manual page 253

Task 4 —
Check Lock Status
Task 5 —
Check Biasing
of IF Amplifier
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
If the logic signal from the digital board is active, as required, check the lock
status of the radio.
Enter the CCTM command 72 to determine the lock status.
1.
The status should be normal:
lock status: 111 (LO1, FCL, LO2 all in lock)
2. If the lock status is normal, go to
to "Frequency Synthesizer Fault Finding" on page
not in lock, go to
is not in lock, go to
3. Check the components around IC403, Q402 and Q403
(see Figure 10.2). Repair any fault.
4. Recalibrate the receiver using the calibration application.
5. Confirm the removal of the fault, and go to
page 163. If the repair failed go to
If the lock status is normal, check the biasing of the IF amplifier.
1. Remove the
IF TOP
2. Check all components around Q404 of the IF amplifier
(see Figure 10.1).
3. Check the 3V supply voltage at L419; use the measurement point
shown in Figure
4. Also check the amplifier bias conditions. First measure V
the collector of Q404 and ground (see
V : 2.0 ± 0.2V
c
5. Secondly, check I
(tombstone position) (see
between this terminal and the pad for the terminal, and measure the
current.
I : 1.8 ± 0.5mA
c
6. If the checks in
is a fault, repair it and go to
7. Recalibrate the receiver using the calibration application.
8. Confirm the removal of the fault, and go to
page 163. If the repair failed go to
Task
"Power Supply for FCL" on page
Step 3.
Task
can.
10.1.
. To do so, unsolder and raise one terminal of L419
c
10.1), connect a multimeter
Figure
Step 2 to Step 5 reveal no fault, go to
Step 7.
Task
5. If the LO1 is not in lock, go
185. If the FCL is
234. If the LO2
"Final Tasks" on
7.
between
c
Figure 10.1).
Task 6. If there
"Final Tasks" on
7.
Receiver Fault Finding 253