TM 11-6625-828-45
CHAPTER 2
TROUBLESHOOTING
Section I. GENERAL TROUBLESHOOTING TECHNIQUES
WARNING
When servicing the AN/ARM-5A, be extremely careful because of the high voltages. Dc voltages
up to 75 volts appear between the DEMOD output connector and ground.
measuring circuits. All meter readings or other visual
2-1.
General Instructions
signs should be observed and an attempt made to
sectionalize the fault to a particular major circuit.
Troubleshooting at general support and depot
(2) Operational tests. Operational tests
maintenance categories includes all the techniques
frequently indicate the general location of troubles. In
outlined for organizational maintenance and any special
many instances, the tests will help in deter- mining the
or additional techniques required to isolate a defective
exact nature of the fault. The equipment performance
part. The general support maintenance and depot
checklist (TM 11-6625-828- 12) is a good operational
procedures are not complete in themselves but
test.
supplement the procedures de- scribed in TM 11-6625-
828-12.
The systematic troubleshooting procedure,
c. Localization. The tests listed below
which begins with the operational and sectionalization
will aid in isolating the trouble. First, localize the trouble
checks that can be performed at organizational category,
to a single stage or circuit, and then isolate the trouble
must be completed by means of sectionalizing,
within that circuit by voltage, resistance, and continuity
localizing, and isolating techniques. Paragraphs 2-5, 2-
measurements.
6, and 2-7 provide localizing and isolating techniques that
(1) Voltage
and
resistance
must be performed at the general support maintenance
measurements. Use the resistor and capacitor color
category.
codes (fig. 4-13 and 4-14) to find the value of the
components. Use the voltage and resistance diagram
2-2.
Organization of Troubleshooting Procedures
with the readings taken.
a. General. The first step in servicing a
(2) Troubleshooting chart. The trouble
defective radio test set is to sectionalize the fault.
symptoms listed in the chart (para 2-5d) will aid in
Sectionalization means tracing the fault to a major circuit.
localizing trouble to a component part.
The second step is to localize the fault. Localization
(3) Intermittent troubles.
In all these
means tracing the fault to a defective stage responsible
tests, the possibility of intermittent troubles should not be
for the abnormal condition. Some faults, such as
overlooked. If trouble is present, this type of trouble
burned-out resistors and arcing and shorted
often may be made to appear by tapping or jarring the
transformers can often be located by sight, smell, and
equipment. Check the wiring and connections to the
hearing. The majority of faults, however, must be
units of the set.
localized by checking voltages and resistance.
b. Sectionalization. Test Set Radio AN/ARM-
2-3.
Test Equipment Required
5A is a single unit that has three major circuits: omni
The following chart lists test equipment required for
signals, amplitude localizer signals, and modulation
troubleshooting Test Set, Radio AN/ ARM-5A, the
signals. The first step in tracing trouble is to locate the
associated technical manuals, and the assigned
circuit or circuits at fault by the following methods:
common names.
(1) Visual inspection. The purpose of
visual inspection is to locate faults without testing or
2-1
