TM 11-6130-266-15
CHAPTER 5
DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE
WARNING
When servicing the power supply, be extremely careful of the ac power line voltage
terminals (115 or 230 volts). Serious injury or death may result from contact with
these terminals.
(2) Voltage and resistance measurements.
5-1.
Scope of Direct Support and General Support
When measuring voltages, use tape or sleeving to
Maintenance
insulate the entire test prod, except for the extreme tip.
Troubleshooting at the direct support and general
A momentary short circuit can damage a transistor. (For
support levels include all the techniques outlined for
example, if the bias resistor of a transistor is shorted out,
organizational maintenance and any special or additional
excessive current between the emitter and the base
techniques required to isolate a defective part.
would damage the transistor.) Use the voltage and
resistance chart to find the normal readings, and
procedures to be used to localize and isolate faults.
compare them with the readings taken.
(3) Trouble shooting chart . The indications
5-2. Organization of Troubleshooting Procedures
listed in the chart of paragraph 5-5d will aid in localizing
a. General. The first step in servicing a defective
the trouble to a component part or to an assembly.
power supply is to localize the fault. Localization means
tracing the fault to a defective stage or circuit
(4) Intermittent troubles . In all these tests, the
responsible for the abnormal condition. The second step
possibility of intermittent troubles should not be
is isolation. Isolation means locating the defective part
overlooked. If present, this type of trouble may be made
or parts. Some defective parts, such as burned resistors
to reappear by tapping or jarring the equipment. Check
and arcing transformers, can often be located by sight,
the internal wiring and connections for looseness.
smell, or sound. Most defective parts, however, must be
isolated by checking voltages and resistances.
5-3. Test Equipment Required
b. Localization. The tests listed below will aid in
The following chart lists the test equipment required and
isolating the trouble. The first step in tracking trouble is
the associated technical manuals for troubleshooting the
to localize the defective state by one of the following
power supply.
methods:
NOTE
(1) Visual inspection. The purpose of visual
inspection is to localize faults without testing or
Use tools and test equipment listed
measuring circuit voltages or resistances. Through this
below until the tools and test
inspection, the repairman frequently can discover
equipment listed in Appendix B
troubles or determine the circuit in which the trouble
become available.
exists. This inspection is valuable in avoiding additional
damage which might occur through improper servicing
Test equipment
Technical manual
methods, and in preventing future failures.
Multimeter TS-352R/U
TM 11-6625-366-15
Test Set, Transistor TS-1836.'U
TM 11-6625-539-15
CAUTION
Tool Kit, Electronic Equipment
None
TK-100/G
Resistor, Variable, Wire Wound
None
This equipment is transistorized;
0- to 7.5-ohm, 1000-watt,
make voltage measurements only as
(FSN 5905-195-,1496)
specified in the voltage and
Oscilloscope AN/USM-281A
TM 11 0625-1703-15
resistance chart (para 5-8).
Transformer. Variable TF-171A
None
Change 3 5-1
