TM 11-6625-622-40
CHAPTER 3
GENERAL SUPPORT MAINTENANCE INSTRUCTIONS
Section I. GENERAL
(1) Visual inspectiion. The purpose of visual inspec-
WARNING
tion is to locate faults without performing tests or
During servicing of the test unit, be careful
measurements. Some faults, such as burned-out resis-
when working with the 115-volt ac line
tors, can be located by sight. The trouble, therefore, can
voltage. Disconnect the power cord from the
be immediately isolated.
power source when making internal resis-
(2) Intermittent troubles. In all tests, the
tance measurements.
possibility of intermittent trouble should not be over-
3-1. General Instructions
looked. If present, this type of trouble often may be
Troubleshooting at general support includes all the
made to appear by tapping or jarring the equipment.
techniques outlined for organizational maintenance
Check the wiring and cable connections.
and any special or additional techniques required to
c. Isolation. When the faulty stage or section of the
isolate a defective part. The general support mainte-
current has been located, the faulty component is lo-
nance procedures are not complete in themselves but
cated by voltage and/or resistance measurements. Use
supplement the maintenance and repair procedures de-
the resistor and capacitor color codes (fig. 3-9) to find
scribed in TM 11-6625-622-12. The systematic
the values of components.
troubleshooting procedure, which begins with the
3-3. Tools and Test Equipment Required
maintenance and repair procedures that can be pr-
The following tools and test equipment are required for
formed at an organizational category must be com-
troubleshooting the test unit.
pleted by additional localizing and isolating techni-
ques. (Figs. 3-9 through 3-16 are foldouts and located in
Tool or test
Publication
Common name
equipment
back of the manual.)
TM 11-6625-200-15 Multimeter
ME-26B/U.
3-2. Organization of Troubleshooting Pro-
Probe T-connector
cedures
HP-455A.
a. General. The first step in servicing a defective test
Dummy Load Elec-
unit is to localize the fault. Localizing means tracing
trical DA-340/
the fault to a circuit. The second step is to isolate the
UR.
TM
11-5821-248-12
Receiver-transmitter.
Receiver-Transmit-
fault. Isolation means tracing the fault to a defective
ter, Radio RT-698/
part responsible for the abnormal condition.
ARC-102.
b. Localization The first step in tracing trouble is to
TM 11-6625-446-15 Wattmeter
locate the circuit at fault by the following methods:
AN/URM-120
Section Il. TROUBLESHOOTING
3-4. Localizing Troubles
not known.
(2) When abnormal symptoms reported by the
a When to Check. When any of the following condi-
tions exist, perform the checks indicated and clear the
operator indicate possible trouble in the power distribu-
tion circuits, switches, or wiring.
troubles before returning to operation.
(1) When the nature of the abnormal symptoms is
Change 1 3-1
