TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 237
May 2004 © Tait Electronics Limited
3. Check that the voltage at pin 11 of IC202 [at 2D2/2D4] (see
Figure 9.30) is at least 8 V DC. If it is, go to Step 4. If it is not,
check for and repair any faults in the level-translation circuits
incorporating Q200 [at 2D1/2D2] and Q201 [at 2D2/2D3] (see
Figure 9.30). Confirm the removal of the fault and return to
Subsection 8.1. If the repair failed, return to Subsection 8.1 and
replace the complete main-board assembly.
4. Check that the digital signal
DIG AUD PA EN1 at R200 [at 2B2/2D2]
is 3.3 V DC, and that the digital signal
DIG AUD PA EN2 at R202 [at
2C1/2C2] is 0.0 V DC (see Figure 9.30). If they are, go to Step
5. If they are not, check the programming and test set-up;
otherwise the digital board is faulty; return to Subsection 8.1 and
replace the complete main-board assembly.
5. Check the positive and negative speaker outputs
AUD ITF SPK+ [at
2F2/2D5] and
AUD ITF SPK– [at 2F1/2C5] at pins 3 and 8
respectively of IC202 (see Figure 9.30). The outputs should have
approximately half-rail bias. If they do, go to Step 6. If they do
not, check for and repair any soldering faults around IC202, or
else replace IC202. Confirm the removal of the fault and return
to Subsection 8.1. If the repair failed, return to Subsection 8.1
and replace the complete main-board assembly.
6. Check that there is approximately 9.5 V
pp
AC on each speaker
output at maximum volume. If there is, the fault is unknown (it
could be intermittent); return to Subsection 8.1 and replace the
complete main-board assembly. If there is no AC, check that
C204 [at 2D2/2D4] and R214 [at 2D3/2E4] (see Figure 9.30) are
not faulty and are correctly soldered. Repair any fault. Confirm
the removal of the fault and return to Subsection 8.1. If the repair
failed or the fault could not be found, return to Subsection 8.1
and replace the complete main-board assembly.
7. Check the voltage on the
VOL WIP DC line at the junction of R708
and C706 [at 7C4/7E3] (see Figure 9.31). As the volume varies,
the voltage should vary between 0.0 and 1.2 V. If it does, go to
Step 8. If it does not, check the control-head connector SK100.
Repair or replace the connector if necessary. Confirm the
removal of the fault and return to Subsection 8.1. If the repair
failed or the fault could not be found, return to Subsection 8.1
and replace the complete main-board assembly.
8. Remove the
CDC TOP can. Check that the voltage at the junction
of R234 and R235 [at 2J5/2G8] (see Figure 9.31) varies between
0.0 and 0.6 V. If it does, IC204 is suspect; return to
Subsection 8.1 and replace the complete main-board assembly. If
it does not, check for continuity across R234, and check that
R235 is properly soldered. Repair any fault. Confirm the
removal of the fault and return to Subsection 8.1. If the repair
failed or the fault could not be found, return to Subsection 8.1
and replace the complete main-board assembly.
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