Tait TM8000 Series Service Manual page 239

Task 3 —
Faulty Receiver
TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
If the receiver does not operate, check the operation of the base-band
CODEC and receiver AGC as described below. It is assumed that the
receiver and power-supply circuitry were checked and no faults were
found.
1. Remove the
CDC BOT
the voltage at pin 14 [at 2N4/2F12] of IC201 exceeds 2.5 V DC
(see Figure 9.32). If it does, go to Step 4. If it does not, go to
Step 2.
2. Check that the voltage at pin 12 [at 2N5/2F11] of IC201 exceeds
1 V DC. If it does, go to Step 3. If it does not, check for and
repair any shorts to ground at the junction of R238 [at 2N5/2F11]
and pin 12 (see
and return to Subsection
not be found, return to
main-board assembly.
3. Check the circuitry (R238, R239, R240) [at 2N4/2F11] around
pins 12, 13 and 14 of IC201 (see
Confirm the removal of the fault and return to
the repair failed or the fault could not be found, return to
Subsection 8.1
4. Apply a strong on-channel signal. (Use the programming
application to find the frequency selected for channel 1.) Check
that a sine wave is present at the
is access through a hole in the
there is, the digital board or IC204 is faulty; return to
Subsection 8.1
a sine wave is not present, go to
can. With no RF signal applied, check that
Figure 9.32). Confirm the removal of the fault
8.1. If the repair failed or the fault could
Subsection 8.1
Figure
and replace the complete main-board assembly.
test point [at 4P1/4C12] (there
QN
can — see
IF TOP
and replace the complete main-board assembly. If
Subsection 9.5
Diagnosis of Faults on Main Board
and replace the complete
9.32). Repair any fault.
Subsection 8.1. If
Figure 9.31). If
on the receiver.
239