Tait TM9100 Service Manual page 157

2.
3.
4.
5.
6.
7.
8.
9.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Disconnect the 13.8V supply at the power connector. Remove R199
(see Figure 7.1). Reconnect the 13.8V supply.
With the probe of the multimeter on the 3
/
key. If the voltage is now 3.3 ± 0.1V, the digital board is faulty;
ON OFF
replace the main-board assembly and go to
page 147. If the voltage is still not correct, go to
If the digital board is functional, the fault is on the main board.
Replace R199. Disconnect the 13.8V supply. Use the multimeter to
measure the resistance between the 3
If there is a short circuit, continue with
circuit (but the voltage is wrong), go to
Search for shorts to ground in the components C603, C612, C613,
C618, D606 of the SMPS circuitry (see
CODEC and interface circuitry. Repair any fault and repeat the
resistance measurement of
If there is no fault, go to
replace the main-board assembly and go to
page 147.
Reconnect the 13.8V supply. Press the
up, return to "Initial Tasks" on page
up, disconnect the 13.8V supply and go to
Measure the resistance of L601 (see
should be virtually zero. If it is, go to
Reconnect the 13.8V supply and press the
powers up, return to "Initial Tasks" on page
power up, disconnect the 13.8V supply and go to
Remove the can. Remove IC603 (3.0V regulator) and
CDC BOT
IC604 (2.5V regulator) (see
/
supply and press the
ON OFF
Task 3 to check each regulator (3.0V and 2.5V) in turn. If the 3.3V
supply is not restored, continue with
Suspect IC602. Disconnect the 13.8V supply. Replace IC602 with a
spare (see Figure 7.1). Resolder IC603 and IC604 in position
(see Figure 7.3). Reconnect the 13.8V supply and press the
key. If the radio powers up, return to
If the radio fails to power up, the repair failed; replace the main-board
assembly and go to "Final Tasks" on page
3 test point, press the
V
"Final Tasks" on
3 test point and ground.
V
Step 5. If there is no short
Step 7.
Figure 7.1) as well as in the
Step 4 to confirm the removal of the fault.
Step 6. If the fault remains, the repair failed;
"Final Tasks" on
/
key. If the radio powers
ON OFF
139. If the radio fails to power
Step 7.
7.1). The resistance
Figure
Step 8. If it is not, replace L601.
/
ON OFF
139. If the radio fails to
Figure 7.3). Reconnect the 13.8V
key. If the 3.3V supply is restored, go to
Step 9.
"Initial Tasks" on page
147.
Power Supply Fault Finding
Step 4.
key. If the radio
Step 8.
/
ON OFF
139.
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