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TM 11-6625-667-45/NAVAIR 16-30APM123-2/TO 33A1-3-367-22
SECTION Ill. GENERAL TROUBLESHOOTING
TECHNIQUES USING AN/TPM-25A
3-12. General Instructions
(2) S e c t i o n a l i z a t i o n t e s t s . T h e s e c -
tionalization tests are operational type tests and
Troubleshooting at general support and depot
frequently indicate the general location o
maintenance categories encludes all techniques
trouble. In some instances, the tests will help in
outlined for organizational maintenance and any
determining the exact nature of the fault. Tests
special or additional techniques required to
are given in paragraph 3-15.
isolate a defective part. Section II of this chapter
c. Localization. Localization
procedures
provides intra unit within the unit) localizing and
should be performed after the trouble has been
isolating techniques to be used at the general
sectionalized (b above. Localization procedures
support maintenance category.
applicable to this equipment are described in
3-13. Organizational of Troubleshooting
paragraphs 3-5 and 3-6, and should be used in
Procedures
localizing the trouble to a stage in the suspects
module or subassembly,
a . General. The first step in servicing a
d. Isolation. Procedures for isolating troubles
defective test set is to sectionalize the fault.
are given in paragraph 3-7.
Sectionalization means tracing the fault to a
e. Techniques.  When performing the sec-
particular module or subassembly (for example;
tionalization para 3-4), localization, and isolation
encoder module A4 or transmitter A16). The
procedures, one or more of the technique
second step is to localize the fault. Localization
described below may be applied. Apply these
means tracing the fault to a defective stage or
techniques only as indicated, and observe al
circuit responsible for the abnormal condition.
cautions.
The third step is isolation. Isolation means
(1) Voltage measurements. This equipmen
locating the defective part or parts.
is transistorized. When measuring voltages, use
b. Sectionalization. The daily maintenance
tape or sleeving (spaghetti) to insulate the entire
c h e c k s and services (TM 11-6625-667-12)
t e s t probe, except for the extreme tip. A
provides a satisfactory means of determining
momentary short circuit can ruin a transistor
w h e t h e r the transponder test set may be
Use the same or equivalent electronic multimeter
operating. Because of the nature of the self test
specified on the voltage and resistance diagrams.
operation, the exact cause of an internal fault
cannot be determined with this chart. The test set
NOTE
provides only an accept or reject indication;
Modules A4, A5, and A7 through A12
therefore, one or more internal circuits can cause
contain digital circuits. Do not attempt
an improper indication. To simplify the location
to analyze their operation with voltage
readings. Analyze their operation with
of a fault, consider that there are four main
the waveforms shown in figures 8-17
functional sections in Test Set, Transponder
through 8-23.
TS-1809/APM-23V. These functional sections
include the power supply, transmitter, receiver,
(2) Resistance
measurements. M a k e
resistance measurements in this equipment only
and decoder. The first step in tracing trouble is to
determine the module or subassembly of the
a s directed on the voltage and resistance
section that contains the fault.
diagrams. For transistorized circuits, use only
(1) Visual inspection. The purpose of visual
the ohmmeter ranges specified on figures 3-8
inspection is to locate faults that maybe evident
through 3-18; otherwise, indications will be
without testing or measuring. This includes
inaccurate.
broken wires, bent or corroded connector pins,
CAUTION
damage circuit boards, or loose RF jacks and
Before using an ohmmeter to test
plugs. All possible visible inspections should be
transistors or transistor circuits, check
performed before attempting operational tests.
Change 5
3-42

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