(4) Gradually increase the high voltage.
(5) If arcing occurs, turn down the high voltage.
(6) Wait a minute, and start turning the high voltage up again.
(7) Continue this routine until arcing stops.
b. Note that these steps provide only a general outline for aging a
magnetron and should be used only when no instructions for the set are
available.
You should always follow instructions given in the TM for the
particular set you're working with.
c. It may take an hour or
more before all arcing has stopped and the
magnetron has been "cleaned up"
(free of gas). Fortunately a magnetron can
stand a considerable amount of
arcing without any damage, but you should
hold it to a minimum. Remember
that you hold the high-voltage down to keep
the arcing down.
d. Magnetron arcing is normal for new tubes and old tubes that need
replacement. There are other more serious magnetron troubles that you will
run into.
Let's see now what these other troubles are and find out what
causes them.
27. Troubleshooting the magnetron.
a. Before troubleshooting, you must know how the equipment operates so
you can recognize and analyze trouble symptoms as soon as they occur. After
recognizing the trouble symptom, the next step is sectionalization.
You
sectionalize the trouble by first analyzing and evaluating the symptom. You
will find that troubles causing faulty magnetron operation usually occur in
the RF and modulator sections of the radar set.
b. When the cause for the magnetron operating at the wrong frequency is
in the RF section, we call the trouble magnetron pulling. In other words,
the magnetron is actually pulled off its correct oscillating frequency by
some bad or mistuned component located somewhere between the magnetron and
the antenna or even beyond the antenna.
c. When the cause for faulty magnetron operation is in a unit located
ahead of the magnetron (the modulator), we call the trouble magnetron
pushing. In other words, the magnetron is actually pushed off its correct
oscillating frequency by some bad or mistuned component located somewhere in
or before the modulator.
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