Peak Atlas DCA75 Pro User Manual page 20

Peak Atlas DCA Pro User Guide
Faulty or Very Low Gain Transistors
Faulty transistors that exhibit very low gain
may cause the DCA Pro to only identify one or
more diode junctions within the device. This is
because NPN transistors consist of a structure
of junctions that behave like a common anode
diode network. PNP transistors can appear to
be common cathode diode networks. The common junction represents the base
terminal. This is normal for situations where the current gain is so low that it is
immeasurable at the test currents used by the DCA Pro.
Please note that the equivalent diode pattern may not be correctly
identified by the DCA Pro if your transistor is a Darlington type or has
additional diode(s) in its package (such as a collector-emitter protection
diode). This is due to the multiple PN junctions and current paths that
cannot be uniquely resolved.
In some circumstances, the unit may not be able to deduce anything sensible
from the device at all, in which case you may see one of these messages:
Page 20
June 2019 – Rev 1.7