
156
Power Supply Fault Finding
TP9100 Service Manual
© Tait Electronics Limited
May 2005
Task 4 —
Check Linear
Regulators
This section gives the general procedure for checking any linear regulator.
There are two possible faults: either the 1.8V regulator has failed and
prevents the radio from powering up, or, with the other linear regulators,
the radio will power up but will not function correctly. (The regulator IC
might or might not have been removed during earlier checks.)
gives an overview of the ICs and the relevant voltages.
Note
If the +
3
V
0
RX
voltage is missing, check the 3.0V linear regulator,
the
DIG RX EN
signal, and the 3 V RX switch (Q604).
1.
Measure the input voltage to the relevant regulator is correct.
Repair any fault.
2.
Check the control/enable signal to the relevant regulator is active.
Repair any fault.
3.
Check the output for shorts to ground. Repair any fault.
4.
Reconnect the 7.5 V external supply and turn the power/volume
control on. If the radio powers up or the correct regulator voltage is
restored, go to
. If the repair failed, go to
5.
Disconnect the 7.5V external supply. Replace the regulator IC with
a spare. Reconnect the 7.5V external supply and turn the
power/volume control on. If the radio powers up or the correct
regulator voltage is restored, go to
. If the
repair failed, replace the main board and go to
Table 8.1
Input, output and control/enable voltages of the linear regulators
Regulator
Input
Control/Enable
Output
Voltage
IC
Pin
Voltage
Pin
Voltage
Pin
Voltage
5V (TX)
IC600
pin 6
7.5V
pin 1
>2V
pin 4
5V
5V (AN)
IC601
pin 6
7.5V
pin 1
>2V
pin 4
5V
3.0V
IC604
pin 1
3.3V
pin 3
>2V
pin 5
3.0V
2.5V
IC605
pin 1
3.3V
pin 3
>2V
pin 5
2.5V
1.8V
IC608
pin 1
3.3V
pin 3
>2V
pin 5
1.8V
Summary of Contents for TP9100
Page 1: ...TP9100 portables Service Manual MPA 00005 01 Issue 1 00 May 2005 ...
Page 4: ...4 TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 10: ...10 TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 74: ...74 Circuit Descriptions TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 78: ...78 TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 100: ...100 General Information TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 126: ...126 Disassembly and Reassembly TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 148: ...148 Interface Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 158: ...158 Power Supply Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 250: ...250 Transmitter Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 268: ...268 Receiver Fault Finding TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 294: ...294 Spare Parts TP9100 Service Manual Tait Electronics Limited May 2005 ...
Page 298: ...298 Antenna Identification Chart TP9100 Service Manual Tait Electronics Limited May 2005 ...