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682XXB/683XXB MM 5-25
–18VT Supply Problems
This supply provides –18 volts to the front panel LCD contrast circuit
and to drive the YIG-tuned oscillator main tuning coil during CW and
slow analog sweeps.
Step 8. Perform the following procedure to isolate malfunctions to
the –18VT 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
–18VT voltage per Table 5-7.
If the voltage is correct, the problem is cleared.
If the voltage is incorrect, go to step d.
d. Place the LINE switch to STANDBY.
e. Remove the A13 PCB and the YIG-tuned oscillator as-
sembly.
f. Place the LINE switch to OPERATE and measure the
–18VT voltage.
If the voltage is correct, go to step i.
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
–18VT voltage.
If the voltage is correct, the problem is cleared.
If the voltage is still incorrect, contact your local
ANRITSU service center for assistance.
i. Place the LINE switch to STANDBY.
j. Install the A13 PCB.
k. Place the LINE switch to OPERATE and measure the
–18VT voltage.
If the voltage is correct, replace the YIG-tuned oscilla
-
tor assembly.
If the voltage is incorrect, replace the A13 PCB.
Table 5-6. Error Messages 105 and 106 (7 of 10)
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