Tait TM8100 mobiles Service Manual page 173

TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
2. 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
3.
/
key. If the voltage is now 3.3 ± 0.1V, the digital board is faulty;
ON OFF
replace the board and go to
is still not correct, go to
4. 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
5. 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 board and go to
6. Reconnect the 13.8V supply. Press the
up, return to "Initial Tasks" on page
up, disconnect the 13.8V supply and go to
7. 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
power up, disconnect the 13.8V supply and go to
8. Remove the
CDC BOT
IC604 (2.5V regulator) (see
supply and press the
Task 3 to check each regulator (3.0V and 2.5V) in turn. If the 3.3V
supply is not restored, continue with
9. Suspect IC602. Disconnect the 13.8V supply. Replace IC602 with a
spare (see Figure
(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 board and
go to "Final Tasks" on page
"Final Tasks" on page
Step 4.
3 test point and ground.
V
Step 4 to confirm the removal of the fault.
Step 6. If the fault remains, the repair failed;
"Final Tasks" on page
ON
155. If the radio fails to power
Figure
Step
"Initial Tasks" on page
can. Remove IC603 (3.0V regulator) and
Figure 7.3). Reconnect the 13.8V
/
key. If the 3.3V supply is restored, go to
ON OFF
Step
7.1). Resolder IC603 and IC604 in position
"Initial Tasks" on page
163.
Power Supply Fault Finding
3 test point, press the
V
163. If the voltage
Step 5. If there is no short
Step 7.
Figure 7.1) as well as in the
163.
/
key. If the radio powers
OFF
Step 7.
7.1). The resistance
8. If it is not, replace L601.
/
key. If the radio
ON OFF
155. If the radio fails to
Step 8.
9.
ON
155.
/
OFF
173