MAINTENANCE.

TM 55-4920-416-13

NAVAER 17-15C-539

Section V

Paragraphs 5-18 to 5-30

5-18. MAINTENANCE.

NOTE

5-19. CLEANING OF VALVES. The only valves that may be

All figure references in the paragraph

removed and cleaned are the needle valves (3, 4, 5 and 6,

pertain to figure 9-8.

figure 5-3), the vacuum check valve and the pressure check

valve. After removal and disassembly, the valves may be

a. Remove screws (42), washers (43), and nuts (44) at

cleaned with solvent, Federal Specification P-S-661 and wiped

the bracket (41).

dry with a clean lint-free cloth.

b. Remove screws (29), and washers (30) from the

motor base. The hoses and fittings at the end of the pump

5-20.

CLEANING THE SUMPS.

After removal and

assembly should remain in place.

disassembly, the vacuum and pressure sumps (2, figure 5-1

c. Lift the motor and pump assembly from its place.

and 1, figure 5-2) may be cleaned with solvent, Federal

d. Remove screws (39) and washers (40).

Specification P-S-661, and wiped dry with a clean lint-free

e. Remove pump assembly (34). The spring (35),

cloth.

spacer (36), packing (37), and retainer (38) will remain on the

pump shaft, if the assembly is handled carefully.

5-21. INTERIOR AND EXTERIOR CLEANING. Thorough

f. Remove safety wire from brush cap (3). Remove set

cleaning is necessary to insure optimum performance by

screw (2) to disassemble brush holder screw assembly (3),

preventing corrosion, rust and dirt accumulations from

washer (4), brush and snapring assembly (5), and brush holder

damaging parts or causing arc-over or low resistance leakage

assembly (6 and 7).

between voltage points and ground. Remove loose dust and

g. Remove nut (11), washer (12), bracket (10), seal (13,

dirt with a brush or water-free compressed air not exceeding

gasket (14) and snapring (26).

10 psi. Use a brush or cloth moistened with solvent, Federal

h. Remove noise suppressor (31). The internal wire

Specification P-S-661, to remove dirt and grease which

connection should not be unsoldered.

adheres to the chassis and parts.

i. Gasket (16), snapring (17) and washers (18 and (19)

can now be slipped out.

5-22. REPLACEMENT OF MINOR PARTS.

j. Remove commutator and the bearing (20) will come

out with the armature assembly (21).

5-21. GENERAL. The replacement of minor parts is limited to

such items as gaskets, O-rings, fuses, indicator lamps and

5-27. If the commutator is scored or pitted, proceed as follows:

motor brushes. (Refer to Table 5-1.)

a. Turn the commutator with a sharp tool, giving it a light

cut, not exceeding 0.005 per cut on the diameter. Remove

5-24. BRUSH REPLACEMENT. Occasionally brushes on the

only the material necessary to clean and true-up the surface.

dc motor in the VPT-7A may have to be replaced after 200

The commutator should then be completely cleaned and a final

hours . Before putting in the next set, the old brushes should

0.002 cut taken.

first be examined. If the brush faces are smooth with no pitting

b. Check for clearance with the mica on all slots. If

or roughness, then a new set of brushes may be installed. If

necessary, undercut to a depth of 1/32 inch. The undercutting

the brushes are pitted or rough, then the armature should be

should be accomplished before the final cut is taken.

removed, as indicated in paragraph 5-26, for examination. A

c. Brush the commutator and remove any chips or

scored or pitted commutator may be refinished as described

foreign material from the slots. Polish with an Arkansas oil

below, or, the armature may be replaced by a new one. In

stone or equivalent.

every case when a new armature is installed in a motor, a new

d. If recutting the commutator reduces the diameter to

set of brushes should be used.

less than 27/32 inch, replace the complete armature assembly.

5-25. BRUSH ADJUSTMENT. After every replacement of

5-28. MOTOR MAINTENANCE.

brushes, the motor and pump should be run for a period of 3

hours at 20 to 24 volts dc under idle conditions. After this run-

5-29.

DISASSEMBLY.

Follow the procedure in

in period the brushes should be removed and there should be

paragraph 5-26. Further disassembly, if necessary, may be

an indication that approximately 75 percent of the brush face

accomplished by unsoldering the wire connected to noise

area is in contact with the commutator surface. If this wear is

suppressor and receptacle assembly (31). Then proceed by

not accomplished, the brushes should be replaced and the run-

referring to figure 9-8.

in continued for two or three more hours. It is important that,

after the brushes have been run in a motor, that extreme care

5-30. CLEANING.

be taken to replace the brushes in the same position and in the

a. Clean all metallic parts of the motor except armature,

same brush tube which they previously occupied.

bearings, brushes and field assembly, by washing in dry-

cleaning solvent, Federal Specification P-S-661. Make certain

5-26. ARMATURE MAINTENANCE. If it is necessary to

all accumulations of foreign matter are removed. A small stiff-

remove the armature (21, figure 9-8) to examine the

bristled brush may be used to facilitate cleaning.

commutator, proceed as follows: