212 Diagnosis of Faults on Main Board TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
Task 4 —
Check for Inhibiting
of Transmitter
If the transmitter is drawing no current or the wrong current, check
whether it is being inhibited.
1. With the radio in transmit mode, check the logic signal at the
TX INH test point [at 3J0/3A8] (see Figure 9.17). The signal is
active high. The required status is inactive — about 0 V. If it is,
go to Task 5. If the signal is active — about 1.1 V — go to Step 2.
2. Check the logic signal at the
DTXINH test point [at 3L0/3B9] (see
Figure 9.17). The signal is active low. The required status is
inactive — about 3.2 V. If it is, go to Step 3. If the signal is active
— about 0 V — go to Step 5.
3. The lock status is possibily no longer normal. With the
transmitter in transmit mode, enter the CCTM command 72 to
check the lock status. The normal status is 110. If it is not,
proceed to the relevant subsection. If it is, go to Step 4.
4. Check for short circuits on the
DIG TX INH line from the DTXINH test
point. Repair any fault, confirm the removal of the fault, and
return to Subsection 8.1. If the repair failed or no fault could be
found, return to Subsection 8.1 and replace the complete main-
board assembly.
5. Suspect the temperature sensor. Enter the CCTM command 47
to check the temperature reading. Of the two numbers returned,
the first should be in the range 380 to 420, corresponding to a
temperature of around 25°C. If it is, go to Task 5. If it is not (the
value will be typically less than 200), go to Step 6.
6. If not already done, remove the
PAF TOP can.
7. Check D301 and the surrounding components (see Figure 9.18
and Figure 9.19). If there is no fault, go to Subsection 9.7 on the
CODEC and audio circuitry. If a fault is found, repair it, 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.
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