Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report. Page: 58 of 66
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Comparisons of waveforms in the normal condition to those of several pro-
duction units proved that some differences that were significant enough to
obscure some of the more subtle changes in components did exist. The
causes of these differences were found to be extra wire length, additional
switch capacity, and changes in components. These changes were necessary
to improve the circuitry for long-term, continuous operation and intermittent
overload conditions, and to furnish the switching necessary to place faults
into the simulator.
The tester was evaluated as a troubleshooting device under factory operating
conditions, but did not meet production troubleshooting requirements.
Several failures occurred in which the output waveforms were degraded..
This effect was apparently caused by distributed inductive and capacative
reactances introduced by the component switches, lead dress, and some of
the components themselves. Stray reactances might be reduced by careful
planning and layout; however, the improvements that could be obtained did
not appear sufficient.
In spite of the shortcomings of the simulator as an in-process production
tester, it proved to be very useful as a training device. Since many types
of failures can be easily simulated, it is well adapted for use as a training
Waveform photographs incorporated into the troubleshooting guides proved
to be the most effective and economical means of displaying this type of
information. The simulator proved to be useful for diagnosis if the circuit
being simulated did not require high-frequency response.
This approach works well for a training unit, since all circuit nodes are
easily accessible and the schematic layout is conducive to association of
the physical component with the schematic symbol.
Special Probe Development
Two types of problems existed with probes. One problem involved accidental
shorts caused by probes during diagnostic investigation, and the other oc-
curred when it was necessary to make connection with circuit board eyelets
to test the product or make electrical setup adjustments. The commercial
probes that were used for this often fell off the unit during testing or did not
make reliable contact. Several types of commercial probes were evaluated,
but none was found adequate. No particular type was found that was applicable
to all problems. Several types of probes were purchased and evaluations
were made in actual production work. No particular type was found that com-
pletely eliminated the problem. Guaranteeing that the proper probe was used
for each application also became a problem.
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Losure, J. A. Diagnosis of Malfunctions in Complex Electronic Assemblies. Final Report., report, January 1, 1971; Kansas City, Missouri. (https://digital.library.unt.edu/ark:/67531/metadc1031893/m1/58/: accessed March 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.