(1) A probe that you insert between the pole pieces of the magnet you
are testing.
(2) A meter that indicates the strength of the field in gausses.
c. You will learn more about the fluxmeter later on.
Right now
remember that it is very easy to check the field strength of a magnet with
this meter whether the magnet is out of the set or still in it.
d. This means of course that if you have magnetron trouble and think
it's the magnet, all you have to do is measure the magnet to make sure. (Of
course, you can't measure the field strength of a packaged magnetron because
the tube is permanently attached between the pole pieces.)
If the field
strength is a lot less then it should be, replace the magnet. If the magnet
measures the correct amount, then the trouble is the magnetron, not the
magnet.
25. Operating a new magnetron.
a. When you install a new magnetron in a radar set, check its operation
carefully because excessive arcing or sparking usually occurs. One cause of
arcing is gas that has accumulated in the tube while it has remained idle.
b. When a magnetron arcs, flashes may be seen or heard through the
glass seals, and the anode-current meter may fluctuate violently.
Arcing
shortens the useful life of the magnetron by damaging the cathode. A great
deal of current flows and generates a lot of heat. The heat may destroy the
tube, or the high current drain may damage the modulator. Therefore, before
operating a new magnetron, it must be "aged" to keep arcing to a minimum.
26. How to "age" a new magnetron.
a. Before installing a new magnetron, always break-in the magnetron by
carefully following the aging procedure below:
(1) Apply only the filament voltage to the magnetron, and let it warm
up for about fifteen minutes.
(2) Apply only a portion of the high voltage to the magnetron.
(3) Listen for arcing within the tube and watch the magnetron current
meter. (The meter needle jumps around when the tube arcs.)
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