
190
Frequency Synthesizer Fault Finding
TP9100 Service Manual
© Tait Electronics Limited
May 2005
Task 22 —
Check Receive
Buffer Amplifier
If no receive frequency is detected but the switching network is not faulty,
check the receive buffer amplifier. If the amplifier is not faulty, there might
be a fault in the receive VCO that was not detected earlier.
1.
Remove the
VCO BOT
can.
2.
Check the receive buffer amplifier in receive mode: Enter the CCTM
command
335 0
to set the transmit-receive switch off.
3.
Measure the voltages at the collector of
Q514
(see
) and
pin 4 of
IC404
(see
4.
Then check the receive buffer amplifier in transmit mode: Enter the
CCTM command
335 1
to set the transmit-receive switch on.
5.
Again measure the voltage at
Q514
and
IC404
.
6.
If the voltages are correct, the receive VCO is suspect; go to
.
If they are not, the receive buffer amplifier is suspect; go to
7.
Remove the
VCO TOP
can.
8.
Check the receive VCO circuitry based on
Q504
(see
Conclude with
9.
Check the first buffer stage (based on
Q514
) (see
) and
the second stage (based on
IC404
) (see
10.
If a fault is found, repair the circuit, and confirm that the voltages are
now correct. If they are, go to
. If they are
not, or if no fault could be found, replace the main board, and go to
collector of Q514: 0.7
±
0.1V DC (receive mode)
pin 4 of IC404:
2.0
±
0.1V DC (receive mode)
collector of Q514: 0V DC (transmit mode)
pin 4 of IC404:
0V DC (transmit mode
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 ...