
TP9100 Service Manual
Frequency Synthesizer Fault Finding
213
© Tait Electronics Limited
May 2005
Task 39 —
TP502 Test Point
(TP501 Grounded)
If the loop was oscillating, Task 38 will have revealed any fault in the VCXO
circuitry. If there was no fault, or if the circuit was repaired, a check at the
TP
502
test point is now required. This will show if there are any additional
faults in the mixer or LPF circuitry.
1.
Use the oscilloscope probe to check the difference frequency at the
TP
502
test point
(see
). The signal is
SYN CDC FCL
and
should be:
2.
If the signal is correct, go to
. If it is not, go to
3.
The mixer circuitry (
IC501
and associated components) or the LPF
circuitry (
IC502
pins 5 to 7, and associated components) under the
FCL TOP
can is faulty (see
). Locate the fault.
4.
Repair the circuitry. Note that the TCXO input to the mixer at
R521
(pin 4 of IC501) (see
) should be:
Also, the VCXO input to the mixer at
R522
(pin 1 of IC501)
(see
), although noisy and difficult to measure, should be:
5.
Confirm the removal of the fault, and go to
. If the repair
failed, resolder
R527
in its original position as shown in
replace the main board and go to
6.
Resolder
R527
in its original position as shown in
7.
Replace all cans.
8.
Use the oscilloscope probe to check the difference frequency at the
TP
502
test point
(see
). The signal is
SYN CDC FCL
and
should be:
9.
If the signal is correct, the fault has been removed; go to
. If the signal is not correct, the repair failed;
replace the main board and go to
TP502 test point: sine wave with frequency of at least 15kHz and
amplitude of 1.1
±
0.2V
pp
on 1.5
±
0.1V DC
TCXO input at R521: square wave with frequency of 13000000Hz
and amplitude of 3.0
±
0.2V
pp
VCXO input at R522: sine wave of 20
±
10mV
pp
TP502 test point: sine wave of 1.1
±
0.2V
pp
on 1.5
±
0.1V DC
(approx. 12kHz)
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 ...