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TM 55-4920-400-13
Section VIII.
ELECTRICAL SYSTEM
2-52. General. The electrical system is designed
to operate on 28 vdc current at 2.2 amps, 115 Vac
single phase current as 50 to 500 cps, and 115 Vac
three phase 50 to 500 cps current at 0.75 amps for a
power source. The major components for the system
are a stepdown transformer rectifier, electrolytic
capacitor, and an electric motor and pump assem-
bly. The electrical system is energized through a
multipin connector and power switch. The internal
connections of the power cables and tester auto-
matically provide for operation with the power
sources specified. This prevents connection of the
tester to the wrong power source.
2-53. Rectifier. The rectifier is
lows:
a. Removal.
(1) Remove chassis assembly
( para. 2-46).
replaced as fol-
from tester case
(2) unsolder wiring harness leads from termi-
nals rectifier.
(3) Remove nuts, lockwashers and screws se-
curing rectifier to chassis. Remove rectifier.
b. Installation.
(1) Place rectifier in position on chassis and
sccure with screws, lockwashers, and nuts.
(2) Solder wiring harness leads to. terminals
on rectifier.
(3) Install chassis assembly in tester case
(para. 2-46).
2-54. Motor and Pump Assembly. Remove
motor and pump assembly from chassis for in-
spection or replacement as follows:
a. Removal
(1) Remove chassis assembly from tester case
and disconnect plug connector.
(2) Remove vacuum check valve as instructed
in paragraph 2-48.
(3) Remove tube assemblies.
(4) Remove screws and lockwashers securing
motor and pump assembly to chassis. Remove motor
and pump assembly.
b. Disassembly. Disassemble the motor and
pump assembly in the number sequence, only to the
extent required to perform the following pro-
cedures.
c. Cleaning and Inspect ion..
(1) Remove accumulations of dirt with low-
pressure compressed (not over 15 pounds per square
inch), a vacuum cleaner, or by wiping with a clean,
dry cloth.
(2) Remove excess oil or grease with a cloth
moistened with an approved solvent, If insulation or
insulated parts are coated with oil or grease, solvent
may be sprayed on the parts or they may be dipped
directly into the solvent and then wiped dry (or use
compressed air per c (1)).
(3) After cleaning, check brushes for condi-
tion, length, and spring tension. Replace brushes if
they are less than 7/16 of an inch long (see f below).
Minimum usable brush length is 5/16 of an inch.
(4) Check all wiring, connections, and termi-
nals for general condition and good contact.
(5) Inspect commutator for pitting, scoring,
roughness, corrosion, or burning. Check for high
mica. Replace the motor if the commutator is
burned, badly pitted, or grooved. Report condition of
high mica or other defects to AVIM.
(6) Inspect all wiring for evidence of over-
heating. Replace motor if insulation on leads or
windings is burned, cracked, or brittle.
(7) Inspect bearings for wear and smoothness
of operation. Replace defective bearings per AVIM.
d. Reassembly. Reassemble motor and pump.
NOTE
When installing washer, place con-
cave face toward motor. Refer to para-
graphs f and g below regarding de-
tails of brush assemblies.
e. Installation.
(1) Place motor and pump assembly in posi-
tion on chassis and secure with lockwashers and
screws.
(2) Install tube assemblies and the vacuum
check valve as instructed in paragraph 2-48.
(3) Install chassis assembly in tester case
(para. 2-46) and connect plug connector.
f. Replacement of Brushes. Brushes are re-
placed as follows:
(1) Loosen safety wire screw, and setscrew
that locks brush holder screw assembly in place.
(2) Remove brush holder screw assembly,
washer, snap-ring and brush and spring assembly.
(3) Insert new brush holder and replace snap
ring, washer, and brush holder screw assembly.
(4) Tighten the brush holder screw assembly
and setscrew.
Install screws securely.
(6) Secure safety wire to hold brush holder
setting.
2-15
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