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 MIL-HDBK-1023/4
The ground fault is located quickly by driving the circuit and looking for the on/off transition.
Use care to insulate the disconnected load cable prior to testing. High voltages may be present
during testing.
e) Manual Ground Method. The manual ground method is useful for isolating
ungrounded opens in the load that can't be found be other means. The "Manual Ground
Method" involves the manual introduction of a low resistance ground in the load on the airfield,
as well as grounding of one side of the regulator as in the "Intentional Ground Method,"
providing an alternate path for current to flow in sections of the circuit in an attempt to identify
sections of the load that are continuous and functioning. This reduces the number of possible
sections of the load that could contain the open.
The manual ground itself is usually a male and female connector kit connected to a rod and/or
heavy alligator clamp. The manual ground is usually first connected in series to the existing load
at the circuit midpoint, then connected to the base can ground via the clamp. If a good ground is
not available, drive in the ground rod. Stay clear of the manual ground during testing. High
voltages exist.
(1) Figure 39 illustrates the first test in troubleshooting an ungrounded open on the
load. The first manual ground has been inserted at the circuit midpoint. Energizing the regulator
reveals that a portion of the load is operating. A marker is placed in the ground adjacent to the
first manual ground. We know that the circuit between the marker and the regulator is good.
The entire circuit that did not come up is suspected of containing the open.
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