TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 185
May 2004 © Tait Electronics Limited
Tas k 1 —
Initial Checks
First check that the digital board or a power supply is not the cause of
the fault:
1. Check the lock-detect signal on each side of L102 [at 1J2/1D7].
(See Figure 9.8.) When the circuit is functioning properly, the
lock-detect signal is active
(about 3 V) to match the lock status 111
or 1
10. When there is a fault and the lock status is 011 or 010, the
lock-detect signal should be inactive
(about 0 V). If it is, go to
Step 3. If it is not, go to Step 2.
2. Check L102, check for shorts and other faults near L102, and
check the signal
SYN LOCK at pin 14 of IC503 [at 5H7] (see
Figure 9.8 and Figure 9.9). If no fault is found, the digital board
is faulty; return to Subsection 8.1 and replace the complete main-
board assembly. If there is a fault, 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.
3. Check the 6 V output from IC606 [at 6E3/6C4] (see Figure 9.9).
If the voltages are correct, go to Step 4. If they are not, check that
the logic setting at pin 1 of IC606 is 9 V, check the 9 V output
from the regulator, and check IC606 itself. If a fault is found,
repair it and confirm the removal of the fault; then enter the
CCTM command 72 again and take the action indicated. If the
repair failed or no fault could be found, return to Subsection 8.1
and replace the complete main-board assembly.
4. Check for 3 V DC on pins 7, 15 and 16 of IC503 [at 5H7] (see
Figure 9.9). If there is, go to Step 5. If there is not, check for
faults in the +3
V0 AN supply to IC503 from IC603 [at 6H5/6D7].
If a fault is found, repair it and confirm the removal of the fault;
then enter the CCTM command 72 again and take the action
indicated. If the repair failed or no fault could be found, return to
Subsection 8.1 and replace the complete main-board assembly.
5. Check the VCL supply at C531 [at 5F0/5B5] (see Figure 9.9). It
should be about 14 V DC. If it is, go to Step 6. If it is not, check
the SMPS circuit based on Q500 [at 5A1/5C1] and Q502 [at
5D1/5B3] (see Figure 9.8). If a fault is found, repair it and
confirm the removal of the fault; then enter the CCTM command
72 again and take the action indicated. If the repair failed or the
fault could not be found, return to Subsection 8.1 and replace the
complete main-board assembly.
6. Check that the
DIG SYN EN line at R104 [at 1J2/1D7] is active (see
Figure 9.8). If it is, go to Task 2. If it is not, check R104, and
check for shorts and other faults near R104. If no fault is found,
the digital board is faulty; return to Subsection 8.1 and replace the
complete main-board assembly. If there is a fault, 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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