Tp502 Test Point (Tp501 Grounded) - Tait TM9100 Service Manual

If the loop was oscillating,
Task 39 —
TP502 Test Point
VCXO circuitry. If there was no fault, or if the circuit was repaired, a check
(TP501 Grounded)
at the
additional faults in the mixer or LPF circuitry.
1.
2.
3.
4.
5.
6.
7.
8.
9.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Task 38
502 test point is now required. This will show if there are any
TP
Use the oscilloscope probe to check the difference frequency at the
502 test point (see
Figure
TP
should be:
TP502 test point: sine wave with frequency of at least 15 kHz and
amplitude of 1.1 ± 0.2 V
If the signal is correct, go to
The mixer circuitry (IC501 and associated components) or the LPF
circuitry (IC502 pins 5 to 7, and associated components) under the
can is faulty (see
FCL TOP
Repair the circuitry. Note that the TCXO input to the mixer at
R521 (pin 4 of IC501) (see
TCXO input at R521: square wave with frequency of 13000000 Hz
and amplitude of 3.0 ± 0.2 V
Also, the VCXO input to the mixer at R522 (pin 1 of IC501)
(see Figure 9.16), although noisy and difficult to measure, should be:
VCXO input at R522: sine wave of 20 ± 10 mV
Confirm the removal of the fault, and go to
failed, resolder R527 in its original position as shown in
replace the main-board assembly and go to
page 147.
Resolder R527 in its original position as shown in
Replace all cans.
Use the oscilloscope probe to check the difference frequency at the
502 test point (see
Figure
TP
should be:
TP502 test point: sine wave of 1.1 ± 0.2 V
If the signal is correct, the fault has been removed; go to
Tasks" on page 147. If the signal is not correct, the repair failed;
replace the main-board assembly and go to
page 147.
will have revealed any fault in the
9.16). The signal is
on 1.5 ± 0.1 V DC
pp
Step 6. If it is not, go to
Figure 9.16). Locate the fault.
Figure 9.16) should be:
pp
pp
Step
"Final Tasks" on
9.16). The signal is
on 1.5 ± 0.1 V DC
pp
"Final Tasks" on
Frequency Synthesizer Fault Finding
and
SYN CDC FCL
Step 3.
6. If the repair
Figure 9.16,
Figure 9.16.
and
SYN CDC FCL
"Final
223