13-4. DYNAMOTOR-WELDER BRUSH REPLACEMENT.
Replace and adjust brushes as illustrated in figure
Cleaning and Inspection.
(1) Clean brushes with a clean, dry lint-free cloth.
(2) Inspect for cracks, chips and excessive wear.
that are worn to less than 3/4-inch.
Install the brushes and adjust spring tension as illus-
Seating Brushes. All brushes must be properly seated on the rota-
ting surfaces to insure maximum operating efficiency of the dyna-
motor-welder. The following contouring procedure applies to all dyna-
(1) Place a commutator-wide strip of No. 100 sand paper (NSN 5350-
00-559-7781) under the brush, abrasive side outward.
Do not use emery cloth when seating brushes
as this will short circuit the commutator.
(2) With the brush in place, press down on the brush and draw the
sand paper back and forth until the brush has the same contour
as the commutator. Repeat for each brush.
(3) Test the brush seat by operating the dynamotor-welder for a
few minutes, stopping it, and examining the brush set. The
seat area should show at least 80 percent highly polished by
contact with the rotating surface.
13-5. OVERSPEED SAFETY SWITCH.
Tag and disconnect all electrical leads at the resistor and sole-
noid coil lead at the terminal.
Use a multimeter and test the resistor for smooth increments in
resistance from O to 1,000 ohms. Replace a defective resistor.
If resistance varies more than plus or minus 2 percent, replace