TM 11-6625-847-45
CHAPTER 2
TROUBLESHOOTING
Section I. GENERAL TROUBLESHOOTING TECHNIQUES
trouble to a stage within a defective functional circuit.
Warnings:
The third and final procedure is to isolate the trouble to a
1. Voltages as high as 200 volts dc and 115 volts
defective part or parts responsible for the fault. Some
ac exist in the SM-442A/GRC. Be extremely careful
defective parts, such as burned resistors and arcing,
when working on the equipment when it is out of its
shorted transformers can often be located by sight, smell,
case.
and hearing. Most defective parts, however, must be
isolated by checking voltages and resistances.
2. Operation and maintenance personnel should
be familiar with the requirements of TB SIG 291
b. Sectionalization. The SM-442A/GRC consists of
before attempting installation, operation, or repair of
five test trays which are used, independent of each other,
the SM-442A/GRC.
with the test set. The first procedure in tracing the trouble
in the module or subassembly is to locate the functional
circuit at fault by the following methods:
2-1. General Instructions
(1) Visual inspection.
The purpose of visual
Troubleshooting at the GS and depot maintenance
inspection is to locate faults without testing or
categories includes all the techniques outlined for
measuring circuits.
organizational maintenance and any special or additional
All meter indications or other visual signs should
techniques required to isolate a malfunction to a specific
be observed and an attempt made to sectionalize
functional circuit or stage and then to locate the defective
the trouble to a functional circuit within the
part or parts. Section II, (paras 2-18 through 2-23)
module or subassembly being tested at the time.
provides intraunit (within the unit) troubleshooting
procedures to be used by the GS category maintenance
personnel in localizing and isolating circuit malfunctions
(2) Operational tests. Operational tests frequently
within the modules and subassemblies of the SM-
indicate the general location of the trouble. In
442A/GRC.
many instances the tests will help in determining
the exact nature of the fault. The operational
performance given in paragraphs 4-1 through 4-
2-2. Organization of Troubleshooting Procedure
12 for the individual modules and assemblies of
the SM-442A/GRC can be used to sectionalize
the trouble to a particular functional circuit.
a. General. The first procedure in servicing the
modules and subassemblies of the SM-442A/GRC is to
sectionalize the fault, which means tracing the fault to a
c. Localization. Localization procedures should be
functional circuit such as the regulator circuitry in dc-to dc
performed after the trouble has been sectionalized (b
converter and regulator module A3 of the test set. the
above). The localization procedures
second procedure is to localize the fault by tracing the
2-1
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