6-
12
Review
• Diodes conduct current in one direction (forward biased) and not the other. The diode's
Tracker signature displays this characteristic as the “knee” effect or pattern.
• Diodes have polarity, an anode and a cathode.
• Diode defects, other than opens and shorts, are usually resistive.
• A diode in series or parallel with a resistor or capacitor will create a composite signature
displaying both characteristics. The Tracker 2700 makes it easier to separate these
characteristics from composite signatures by adjusting F
S
, R
S
and V
S
.
• Zener diodes are special diodes that conduct when reverse biased at a specific voltage.
Applying What We Have Learned
• Diode damage or degradation can appear as a loss of sharpness or rounding in the “knee”.
• While faulty diodes display resistive current and voltage legs, they are usually nonlinear or
curved.
• The polarity of an unmarked diode can be determined by the orientation of the display with a
known diode.
• The Tracker 2700 can be used to identify an unknown zener diode. If the zener diode is
damaged, locate a good one, possibly on another board or in the same circuit and use the
Tracker 2700 to approximate the voltage.
• Look for the zener effect when checking voltage regulators such as the 7805 type. This can
help determine an unknown or faulty device.
• The Tracker 2700 can be used to test and determine the four pin connections on a bridge
rectifier, (AC1, AC2, + and -).
To Next Page
Loading...
