TM 11-6125-252-15
CAUTION
NOTES
When removing the dc brushes, mark the
The PROCEDURES column in your PMCS
brushes in a manner which will insure your
charts instruct how to perform the required
replacing them in exactly the same position
checks and services. Carefully follow these
they were in the brush holders before you
instructions and, if tools are needed or the
removed them. Incorrect replacement of
chart so instructs, get higher category main-
dc brushes will cause arcing on commutator
tenance to do the necessary work.
segments a n d thus create noise inter-
If your equipment must be in operation all
ference to equipment and excessive com-
the time, check those items that can be
mutator wear due to the arcing.
checked and serviced without disturbing
b. After initial installation or after new dc
operation. Make the complete checks and
brushes are installed, check the brushes after
services when the equipment can be shut
1000 hours of operation and every 200 hours
down.
Remove the cover plates over the
thereafter.
c. Deficiencies that cannot be corrected must
dc brushes (figs. 4-2 and 5-1). Lift the finger
be reported to higher category maintenance per-
over the brush and lift out the brush. If the
sonnel. Records and reports of preventive main-
working face is worn down to the end of the
tenance must be made in accordance with proce-
wear line, it should be replaced (para 4-8). Replace
dures given in TM 38-750.
the brush exactly as it was removed until a new
NOTE
brush is installed.
The checks in the interval column are to
4-8. Removal and Replacement of Brushes
be performed in the order listed.
Replacement of brushes is required when inspec-
tion (para 4-7) shows that they are worn down
4-4. Organizational Preventive Maintenance
to the wear line. A full set of spare brushes is
Checks and Services Chart
shipped with the motor generator.
Q Quarterly
checking procedure. When replacing with new
brushes, the curvature must be observed to insure
proper seating and contact with the sliprings.
Perform operational check
1
Motor
q
as described in para-
Generator
checking procedure. Remove the machine screws
graph 3-5.
PU-724/G
that secure the brush leads to the brush holders.
Place the new brush in the holder, observing the
curvature and polarity marking. Place the ter-
Paragraph 4-5 deleted.
minal under the machine screw in the holder
Paragraph 4-6 deleted.
and tighten. See that spring and finger move
freely and press down on top of brush in holder.
c. Brushes will reseat to the curvature of the
sliprings and commutator after several hours of
4-7. Checking Brushes
operation.
a. After initial installation or after new brushes
are installed, check the ac brushes after 1000 hours
4 - 9 . Removal and Replacement of Motor
of operation and every 200 hours thereafter. Re-
move the cap of each ac brush (fig. 4-1) and lift
a. Removal.
out the brush. If the working face is worn down to
(1) Remove the dc power cable plug from
the end of the wear line, it should be replaced
its termination point.
moved until a new brush is installed. Do not
(2) Remove any plugs that may have been
interchange brushes.
Change 2
4-3
