TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 173
May 2004 © Tait Electronics Limited
Tas k 1 —
Check Inputs to SMPS
The test equipment and radio should be set up as described in
Subsection 4.5 (on page 93). If not already done, remove the main-
board assembly from the chassis. Connect the control head to the
assembly. Then check the SMPS as follows:
1. Use a multimeter to check the supply voltage at pin 7 [at
6F7/6E6] of IC602 (see Figure 9.1) in the SMPS circuitry; the
voltage should be 13.8 V DC. If it is, go to Step 5. If it is not, go
to Step 2.
2. Disconnect the 13.8 V supply at the power connector PL100.
Check for continuity and shorts to ground in the path between
the power connector and pin 7 of IC602 (see Figure 9.1). Locate
and repair the fault.
3. Reconnect the 13.8 V supply. Confirm the removal of the fault
by measuring the voltage at pin 7 of IC602. If the voltage is
correct, continue with Step 4. If it is not, the repair failed; return
to Subsection 8.1 and replace the complete main-board assembly.
4. Press the ON/OFF key. If the radio powers up, return to
Subsection 8.1. If it does not, go to Step 5.
5. Check the digital power-up signal at pin 5 [at 6G6/6E6] of IC602
(see Figure 9.1); the signal is active high, namely, when the voltage
exceeds 2.0 V DC. Measure the voltage at pin 5. If it exceeds
2.0 V, go to Task 2. If it does not, go to Step 6.
6. Keep the probe of the multimeter on pin 5 of IC602 and press the
ON/OFF key. The voltage should exceed 2.0 V DC while the key is
depressed. If it does, go to Task 2. If it does not, go to Step 7.
7. Disconnect the 13.8 V supply at the power connector PL100.
Check for continuity and shorts to ground in the path from pin 5
of IC602, via R600 [at 6B4/6D2] and via Q709 [at 7C2/7D2] in
the interface circuitry (see Figure 2.6.1), to pin 9 of the control-
head connector SK100 (
ITF PSU ON OFF line). Locate and repair the
fault. Go to Step 8.
8. Reconnect the 13.8 V supply. Press the
ON/OFF key. If the radio
powers up, return to Subsection 2.5.1. If it does not, go to Step 9.
9. With the probe of the multimeter on pin 5 of IC602 (see
Figure 9.1), press the
ON/OFF key again. The voltage should exceed
2.0 V DC while the key is depressed. If it does, go to Task 2. If
it does not, the repair failed; return to Subsection 8.1 and replace
the complete main-board assembly.
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