TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 175
May 2004 © Tait Electronics Limited
2. Disconnect the 13.8 V supply at the power connector. Remove
R199 [at 1J6/1H8] (see Figure 9.1). Reconnect the 13.8 V
supply.
3. With the probe of the multimeter on the 3
V3 test point, press the
ON/OFF key. If the voltage is now 3.3 ± 0.1 V, the digital board is
faulty; return to Subsection 2.5.1 and replace the complete main-
board assembly. If the voltage is still not correct, go to Step 4.
4. If the digital board is functional, the fault is on the main board.
Replace R199. Disconnect the 13.8 V supply. Use the
multimeter to measure the resistance between the 3
V3 test point
and ground. If there is a short circuit, continue with Step 5. If
there is no short circuit (but the voltage is wrong), go to Step 7.
5. Search for shorts to ground in the components C603, C612,
C613, C618, D606 [at 6G6 to 6J6/6E6 to 6E8] of the SMPS
circuitry (see Figure 9.1) as well as in the CODEC and interface
circuitry. Repair any fault and repeat the resistance measurement
of Step 4 to confirm the removal of the fault. If there is no fault,
go to Step 6. If the fault remains, the repair failed; return to
Subsection 8.1 and replace the complete main-board assembly.
6. Reconnect the 13.8 V supply. Press the
ON/OFF key. If the radio
powers up, return to Subsection 8.1. If the radio fails to power up,
disconnect the 13.8 V supply and go to Step 7.
7. Measure the resistance of L601 [at 6H6/6E7] (see Figure 9.1).
The resistance should be virtually zero. If it is, go to Step 8. If it
is not, replace L601. Reconnect the 13.8 V supply and press the
ON/OFF key. If the radio powers up, return to Subsection 8.1. If
the radio fails to power up, disconnect the 13.8 V supply and go
to Step 8.
8. Remove the
CDC BOT can. Remove IC603 (3.0 V regulator) [at
6H5/6D7] and IC604 (2.5 V regulator) [at 6H3/6C7] (see
Figure 9.3). Reconnect the 13.8 V supply and press the
ON/OFF
key. If the 3.3 V supply is restored, go to Task 3 to check each
regulator (3.0 V and 2.5 V) in turn. If the 3.3 V supply is not
restored, continue with Step 9.
9. Suspect IC602 [at 6G7/6E6]. Disconnect the 13.8 V supply.
Replace IC602 with a spare (see Figure 9.1). Resolder IC603 and
IC604 in position (see Figure 9.3). Reconnect the 13.8 V supply
and press the
ON/OFF key. If the radio powers up, return to
Subsection 8.1. If the radio fails to power up, the repair failed;
return to Subsection 8.1 and replace the complete main-board
assembly.
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