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  TM 55-4920-231-14
Table 6. Troubleshooting (Cont).
Item No.
Trouble
Probable Cause
Possible Remedy
If zero voltage, disconnect a lead from
Replace transformer (paragraph 99).
terminal 3 or 4 and recheck
volage; if still zero, trans-
former is defective. (See
2
Fuse blows when power
Repair or replace motor (para-
Short in electric motor.
switch is placed in ON
(Check continuity and for
graphs 81 and 100).
position.
shorts; see figure 10.)
AC OPERATION ONLY
Shorted transformer primary
Replace transformer (paragraph 99).
windings. (Check for continuity
and for shorts, see figure 10.)
3
Indicator light illuminates
Shorted transformer. (Check
Replace transformer (paragraph 99).
but motor does not run.
continuity and far shorts; see
Open lead in motor. (Check for
Repair or replace motor (para-
continuity.)
graphs 81 and 100).
Defective motor.
Repair or replace motor (para-
graphs 81 and 100).
Armature defective.
Repair or replace armature (para-
graph 100) .
Open circuit in motor armature or
Repair or replace motor (para-
graphs 81 and 100).
field winding. (Check re-
sistance between motor input
and ground-should be ap-
proximately 1.7 ohms.)
Repair commutator (paragraph 100).
4
Motor runs slowly.
Commutator worn or dirty.
Replace bearings (paragraph 100).
Defective motor bearings.
Section III. TESTER UNIT
91. TESTER CALIBRATION.
93. TESTER REPLACEMENT.
Calibration of the individual instruments as
If the unit becomes damaged beyond repair, or
described in paragraph 96 accomplishes the cali-
if a nonremediable malfunction develops, replace
bration of the tester.
the unit.
94. TESTER REPAIR.
Testing the instruments and components indi-
Repair of the individual instruments and com-
vidually accomplishes the testing of the unit
ponents as outlined throughout this manual ac-
(paragraphs 39 through 44).
complishes repair of the unit.
Section IV. PNEUMATIC SYSTEM
during disassembly and inspection procedures
95. VALVES.
outlined in the paragraphs stated above.
Inspection, testing, cleaning, and replacement
of valves is accomplished as stated in paragraphs
96. INSTRUMENTS.
39, 52e, 61 through 64, 71, 72, 75, 76, and 78.
a. Calibration. Calibrate each instrument of
Under conditions specified in appendix B, para-
graph 31c, replacement of valves may be accom-
the tester by comparing its reading against a
plished by the organizational maintenance level.
standard instrument, gage, or other applicable
Repair of valves consists primarily of replace-
apparatus, Calibration of the master instruments
ment of individual defective parts as indicated
(those of tester) may be performed, without
52
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