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IDENTIFYING INDUCTOR TYPES
Inductors, like capacitors, may be found in many shapes
and sizes depending on the application in which they are
used. The LC103 will provide an accurate Ringer test on
all types of air core and ferrite core inductors, provided
the proper Inductor COMPONENT TYPE switch is
selected. Each inductor type has a normal range of
impedance, and the Inductor COMPONENT TYPE
switches match the impedance of the LC103 Ringer
circuits to the particular inductor type being tested. With
the proper COMPONENT TYPE switch selected, an
inductor with just a single shorted turn will produce a
“BAD” indication in the Ringer test.
Air and ferrite core inductors break into three, easy to
identify types: Yokes and Flybacks, Switching
Transformers, and Coils. Select one of these three
Inductor COMPONENT TYPE switches when
performing the Ringer test.
Yokes and Flybacks
Yokes are used exclusively in video applications to
deflect a CRT electron beam. They cannot be easily
mistaken for any other type of inductor. Yokes have a
ferrite core, surrounded by two pairs of windings, which
fits over the CRT neck. It is held in place with a plastic
shell attached to the CRT neck.
Flyback transformers are also easy to identify. They too
are used exclusively in video applications, and produce
high voltage for the CRT. A flyback has several
terminals which are often soldered to a PC board chassis.
One or two heavily insulated leads exit the flyback to
carry high voltage to a tripler, or to the CRT directly.
Fig. 25: Yokes and flybacks are easily identified.
Switching Transformers
Switching transformers are used in power supply circuits
to step voltages up or down. However, they are much
different from conventional power transformers in both
appearance and operation. Power transformers usually
operate at 60 Hz, and therefore contain a laminated iron
core which is often visible. Because the iron core is low
Q and absorbs all ringing energy, power transformers
cannot be tested with the LC103.
Switching transformers, on the other hand, are much
smaller and lighter than power transformers. They are
wound around a ferrite core which easily rings when
good. Switching transformers operate at much lower
currents and much higher frequencies than power
transformers.
Fig. 26: Common types of switching transformers.
Coils
All non-iron core inductors which cannot be classified as
yokes, flybacks, or switching transformers are tested
with the “COILS” INDUCTOR COMPONENT TYPE
switch selected. These include RF/IF transformers, RF
chokes, postage stamp inductors, axial lead inductors,
free form coils, as well as some other types.
Fig. 27: Common types of coils.
