TM 11-6130-247-14-1
CHAPTER 5
DIRECT SUPPORT, GENERAL SUPPORT, AND
DEPOT MAINTENANCE
measuring circuits. By this approach, maintenance
WARNING
personnel can frequently discover the trouble or deter-
When servicing the power supply, be ex-
mine the circuit in which the trouble exists.
tremely careful of the high voltages.
(2) Testing. Maintenance personnel should per-
5-1. Scope of Maintenance
form the tests located in this chapter. The tests will
indicate the general location of the fault and help
Troubleshooting at the direct support, general sup-
determine the exact nature of the trouble.
port, and depot maintenance categories includes all
(3) Intermittent troubles. The possibility exists
the techniques outlined for organizational mainte-
that intermittent troubles can occur. If present, this
nance and any special or additional techniques re-
type of trouble can occur. If present, this type of trou-
quired to isolate a defective part. Paragraph 5-4d pro-
ble can often be located by tapping or jarring the
vides the troubleshooting chart to be used by the re-
equipment. For this type of condition, the wiring and
pairman.
connections to the unit must be checked for defects.
5-2. Test Equipment Required
(4) Voltage and resistance measurements. When
measuring voltages, use tape or sleeving to insulate
The tools and test equipment required for trouble-
the entire test probe, except for the extreme tip.
shooting the PP-3940A/G are listed in section III of
the Maintenance Allocation Chart (appx B).
5-4. Maintenance Aids
5-3 Sectionalization, Localization, and
a.. Parts Location Diagrams. Parts location dia-
isolation
grams (figs. 5-1 through 5-4 and 8-2) are provided for
the power supply and to identify the individual com-
a. Sectionalization. The first step in servicing is to
ponents as an aid in troubleshooting.
sectionalize the fault to a circuit of the power supply.
b. Schematic Diagrams. Figure 8-3 is a schematic
The circuit at fault can be located by the following
methods.
diagram of the power supply.
c. Resistor and Capacitor Color Code Diagram.
(1) Visual inspection. The purpose of visual in-
spection is to locate faults without testing or measur-
capacitors, Figure 8-1 provides pertinent resistance,
ing circuits. Through inspection alone the repairman
frequently may discover the trouble or determine the
voltage rating, and tolerance information.
circuit in which the trouble exists.
(2) Testing. The tests described in this chapter
frequently indicate the general location of the fault.
b. Localization. Once the circuit that is at fault has
been determined, the trouble must be further localized
to the defective component within the circuit. This can
best be accomplished by isolation.
c. Isolation. The next step is to isolate the trouble to
the defective part responsible for the abnormal condi-
tion. Equipment trouble can usually be isolated to
dirty contacts or improper adjustment. Some faults,
such as burned out resistors and arcing, can be located
by means of sight, sound, or smell. The majority of
faults, however, must be isolated by making voltage
and resistance checks. Tests that should minimize the
amount of work involved in isolating a trouble within
a defective unit are contained in (1) through (4) below.
(1) Visual inspection. The purpose of visual in-
Figure 5-1. Power Supply PP-3940A/G, Component Board A1,
spection is to quickly locate a fault without testing or
Parts Location Diagram,
Change 1
5-1
