Power Supplies - Tait TM8100 mobiles Service Manual

13.1

Power Supplies

Introduction
Task 1 —
9V Power Supply
Task 2 —
3V Power Supply
400 CODEC and Audio Fault Finding
First check that a power supply is not the cause of the fault. Of these
supplies, the 3.3V DC supply (+3
"Power Supply Fault Finding" on page
need to be checked are:
Task 1: 9V DC supply from 9V regulator (+9
■
Task 2: 3V DC supply from 3V regulator (+3
■
Task 3: 2.5V DC supply from 2.5V regulator (+2
■
Two other supplies used in the CODEC and audio circuitry are a 1.8V DC
8) from the digital board and the 13.8V DC supply (+13
supply (+1
V
from the power connector. Faults in these supplies are dealt with elsewhere.
First check the 9V DC supply (+9
1. Remove the board from the chassis.
2. Remove the
CDC BOT
Measure the voltage +9
3.
pin 4 of IC201: 9.0 ± 0.3V DC
4. If the voltage is correct, go to
5. The fault will be at IC201 (see
9V regulator in the PSU module will already have been rectified.
Therefore, check the soldering of IC201. Repair any fault.
6. Confirm the removal of the fault and go to
page 163. If the repair failed or the fault could not be found, replace
the board and go to
If the 9V supply is correct, check the 3V DC supply (+3
Measure the voltage +3
1.
(see Figure 13.1).
TP601 test point: 2.9 ± 0.3V DC
2. If the voltage is correct, go to
3. The 3V regulator IC603 is suspect (see
regulator as described in
page 174.
3) will already have been checked in
V
169. The remaining supplies that
0), which is required by IC201.
V
can.
0 at pin 4 of IC201 (see
V
Task 2. If it is not, go to
Figure 13.1), since any fault with the
"Final Tasks" on page
0 601 test point
at the
V AN TP
Task 3. If it is not, go to
Figure
Task 3 of "Power Supply Fault Finding" on
© Tait Electronics Limited November 2007
0)
V
0
)
V AN
5
)
V CDC
8
V BATT
Figure 13.1).
Step 5.
"Final Tasks" on
163.
0
) next.
V AN
Step 3.
13.1). Check the
TM8100/TM8200 Service Manual
)