Service manual

STP 11-25R13-SM-TG
I - 2
d. Shorted Inductors. There are two types of shorts that can occur in an inductor; complete shorts
and partial shorts. Excessive current heating the wires and breaking down the insulation so that the wires
short together may cause shorts. Very small inductance has small resistance and they may be difficult to
test with an ohmmeter. When all tests indicate that the coil may be shorted, substitution is the final test.
Larger inductor values have measurable values of resistance and short circuit tests are more conclusive.
Unfortunately, many schematic diagrams do not indicate the normal coil resistance, so the technician
must make tests and conclusions based upon best judgment and experience.
(1) Shorted, the slope of the frequency response curve would change. The fall time of the curve
would increase as shown in Figure I-2B.
(2) When an inductor completely shorts, the load device drops all voltage at all frequencies. If the
filter contained a capacitor in parallel with the load, then eventually the frequency response curve would
begin to drop off at high frequencies. The net result would be an even greater increase in the fall time of
the frequency response curve (Figure I-2C). If there were no parallel capacitor, then the curve would be
a straight line as shown in Figure I-2D.
e. Open Capacitors. If the capacitor in Figure I-1 were to open, the resulting frequency response
curve would be similar to the one for an inductor that contains a partial short (Figure I-2B).
Figure I-2. Shorted Inductor