Western Electric 407A-4, Инструкция по эксплуатации

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of extreme beading is it neces sary to treat them. Dress ing
should b e done with a fine fi le, not with emery cloth, as
abrasive granules imbedded in the contact sur faces may rai se
the contact resistance and produc e a tendency of the con­
tacts to weld.
Replacement of the moving contacts is effected, when
necessary, by removing the armature stop bracket� secured to
the front of the stati onary magnet by two screws , and with­
drawing the armature and cros sbar as sembly downward thru the
arc box. The contacts can then b e removed from their sup­
ports without the us e of tool s .
The stationary contacts are supporte d b y the arc b ox
and are held in place b y s crews readily access ible from the
front. The contact tips are of s i lver, and will requ ire as
little attention as those of the moving contacts .
Correct spring pressures should be maintained as fo l-
lows :
Initial
Pressure
5 ounces
Final
Pres sure
10
ounces
The contact gap should be seven thirty-seconds of an
inch.
Maintenance
The contactor will requ ire little attention. However,
it should be inspected periodi cal ly to s ee that no impair­
ment of e lectrical or mechanical functioning occurs . Ac­
cumulations of dust may be remove d with a dry cloth or a
compressed-air j et. Avo id oily cloths , as an oil film
quickly attracts dust. The magnet armature should be re­
move d at intervals and accumulati ons of smudge on it and
its guides remove d with benz ine or a s irrQlar so lvent .
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