When you are testing individual components in a circuit, what may cause a defective component
to appear good?
You should be aware that devices made by different manufacturers may appear to have slightly
different signatures. This is normal, especially with digital integrated circuits, and does not necessarily
indicate a failed device. When this occurs, the best way to verify this is to compare the outputs of the
device under test with the equipment specifications to ensure the signals are adequate for proper
The information that follows summarizes the important points of this chapter.
ELECTRON TUBES are usually tested for SHORTS, TRANSCONDUCTANCE, and the
presence of GAS. Several different types of tubes (i.e., twts, magnetrons, and klystrons) are normally
Most TRANSISTORS can be tested by measuring the forward-to-back resistance of their junctions
using a standard ohmmeter. The resistance scale of the ohmmeter must be carefully selected to ensure that
the current rating of the transistor is not exceeded.
ESD-SENSITIVE DEVICES are components that require special handling. Some of the more
sensitive devices can be damaged by static charges as small as 35 volts.