TROUBLESHOOTING
Section I. GENERAL TROUBLESHOOTING TECHNIQUES
(2) Operational tests. Operational tests fre-
Warning: Be careful when working on the 115-
quently indicate the general location of trouble. In
volt, 400-Hz circuit. Serious injury or death may
many instances, the tests will help in determining the
result from contact with this circuit.
exact nature of the fault. The intermediate preventive
maintenance checks and services chart (TM 11-6625-
2-1. General.
2709-12) contains a list of operational checks that help
to sectionalize trouble to a unit.
The general support maintenance procedures in
this manual supplement the procedures in the
c. Localization. After the trouble has been sec-
organizational maintenance manual. The systematic
tionalized (step b. above), the methods listed below
troubleshooting procedure, which begins with the
will aid in localizing the trouble to a circuit in the
operational and sectionalization checks that can be
suspected unit. Refer to the troubleshooting chart for
performed at an organizational category, is carried to
help in finding the trouble. RMI and meter in-
a higher category in this manual. Sectionalizing,
dications or lack of indications and operational checks
localizing, and isolating techniques used in the
provide a systematic method of localizing trouble to a
troubleshooting procedures are more advanced.
c i r c u i t . T h e procedures provided in the
troubleshooting charts (para 2-5 through 2-9) will
provide additional information for localizing trouble.
Procedures.
d. Isolation. After the trouble has been localized
a. General. The first step in servicing a malfunc-
(step c above), the methods in steps (1) through (4)
tioning test set is to sectionalize the fault. Sec-
below will help in isolating the trouble to a defective
tionalization means tracing the fault to a unit or
circuit element.
circuit. The second step is to localize the fault. Lo-
calization means tracing the fault to a defective part
Caution: Be sure that the multimeter is not
responsible for the abnormal condition. Some faults,
placed across a meter in the test set. The currrent
such as burned-out resistors and arcing and shorted
from the ohmmeter might damage the
transformers, can often be located by sight, smell,
microampere movement of a meter of the test set.
and hearing. The majority of faults, however, must he
(1) Resistance measurements. Resistance
isolated by checking voltages and resistance.
measurements are used to check for continuity and to
b. Sectionalization. Listed below is a group of tests
check the value of resistance in a circuit. For these
arranged to reduce unnecessary work and to aid in
checks use Multimeter ME-26(*)/U, or equivalent.
tracing trouble in a malfunctioning test set. Radio
(2) V o l t a g e m e a s u r e m e n t s . V o l t a g e
Test Set AN/ARM-92B consists of five units: the test
measurements are used to check if the proper amount
set, the control unit, the RMI, the OBS indicator, and
of voltage is being routed through the test set and aid
the aid box. The first step is to locate the unit or units
box. For these measurements, use Multimeter ME-
at fault by the following methods:
26(*)/U, or equivalent.
(3) Intermittent troubles. In all these tests, the
(1) Visual inspection. The purpose of visual in-
possibility of intermittent troubles should not be
spection is to locate faults without testing or measur-
overlooked. If present, this type of trouble may often
ing circuits. Indications on the RMI or meters, or
be made to appear by tapping or jarring the equip-
other visual signs, should be observed during all
ment. Make a visual inspection of the wiring and con-
operating modes, and an attempt should be made to
nections.
sectionalize the fault to a particular unit.
