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Verfügbare Sprachen
Verfügbare Sprachen
For a transistor the figures b-e and b-c are important. The
figure e-c can vary; but a vertical line only shows short cir-
cult condition.
These transistor test patterns are valid in most cases, but
there are exceptions to the rule (e.g. Darlington, FETs). With
the CT, the distinction between a P-N-P to a N-P-N transis-
tor is discernible.
in case of doubt, comparison with a
known type is helpful. It should be noted that the same
socket connection (CT or ground) for the same terminal is
then absolutely necessary.
A connection inversion effects a
rotation of the test pattern by 180 degrees round about the
center point of the scope graticule.
Pay attention to the usual caution with single MOS-
components relating to static charge or frictional elec-
tricity!
In-Circuit Tests
Caution! During in-circuit tests make sure the circuit ts
dead. No power from mains/line or battery and no sig-
nal inputs are permitted. Remove all ground connec-
tions including Safety Earth (pull out power plug from
outlet). Remove all measuring cables including probes
between oscilloscope and circuit under test. Otherwise
both CT test leads are not isolated against the circuit
under test.
In-circuit tests are possible in many cases. However, they
are not so well-defined. This is caused by a shunt connec-
tion of real or complex impedances — especially if they are
of relatively low impedance at 50 or GOHz — to the compo-
nent under test, often results differ greatly when compared
with single components. In case of doubt, one component
terminal may be unsoldered. This terminal should then be
connected to the insulated CT socket avoiding hum distor-
tion of the test pattern.
Another way is a test pattern comparison to an identical cir-
cuit which is known to be operational (likewise without
power and any external connections). Using the test prods,
identical test points in each circuit can be checked, and a
defect can be determined quickly and easily. Possibly the
device itself under test contains a reference circuit (e.g. a
second
stereo channel, push-pull amplifier, symmetrical
bridge circuit), which is not defective.
The test patterns on page M17 show some typical! displays
for in-circuit tests.
SE
eee
M16 203-6
Subject to change without notice
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