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690XXB/691XXB MM
5-21
–28VT Supply Problems
This supply provides –28 volts to the front panel LCD contrast circuit
and to drive the YIG-tuned oscillator main tuning coil.
Step 8.
Perform the following procedure to isolate malfunctions to
the –28VT supply and its outlying load circuit.
a. Place the
LINE
switch to
STANDBY
.
b. Replace the A15 PCB assembly.
c.
Place the
LINE
switch to
OPERATE
and measure the
–28VT voltage per Table 5-7.
q
If the voltage is correct, the problem is cleared.
q
If the voltage is incorrect, go to step d.
d. Place the
LINE
switch to
STANDBY
.
e.
Remove the A14 PCB and the YIG-tuned oscillator as-
sembly.
f.
Place the
LINE
switch to
OPERATE
and measure the
–28VT voltage.
q
If the voltage is correct, go to step i.
q
If the voltage is still incorrect, go to step g.
g. Replace the front panel assembly by following the steps
in paragraph 6-3 of Chapter 6—Removal and Replace-
ment Procedures.
h. Place the
LINE
switch to
OPERATE
and measure the
–28VT voltage.
q
If the voltage is correct, the problem is cleared.
q
If the voltage is still incorrect, contact your local
Anritsu service center for assistance.
i.
Place the
LINE
switch to
STANDBY
.
j.
Install the A14 PCB.
k. Place the
LINE
switch to
OPERATE
and measure the
–28VT voltage.
q
If the voltage is correct, replace the YIG-tuned oscilla-
tor assembly.
q
If the voltage is incorrect, replace the A14 PCB.
Table 5-6.
Error Messages 105 and 106 (7 of 9)
TROUBLESHOOTING
TROUBLESHOOTING
TABLES
Summary of Contents for 680 C Series
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