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TO PIN b OF CONNECTOR
\
TO PIN
a OF CONNECTOR
CIRCUIT BOARD
-------- - - - - - -
-\
~~\)
- - - - .
BRUSH
CAPSTAN REAR
BEARING PLATE
BRUSH"B" CARR IER
Figure
21. Capstan Commutator
7
.2.3 Electrical
Operation
With
every revolution
of
the
capstan
drive
s
haft
there are twenty series circuits
completed through the two brushes and the twenty commutator segments.
Through
these series
circuits from
Brush A
to
commutator
and out to
Brush B,
s
witch
closures are generated
during
each angular
18 degree
increment
of
capstan revolution. Current through
the
com
mutator must
be
limited
to 10 milliamperes maximum.
Because
each
brush holder can be independently adjusted, both switch closure
duration
and phase
angle is adjt1sted
to
customer specifications. The timing
diagram
of
Figure
22
illustrates the flexibility
of
these adjustments.
7
.2.4
Adjustment
When both brushes
are set so
as
to engage their commutator segment contacts
at
exactly
the
same
moment,
the
switch
closure
angle will
be at its 5
degree
maximum
duration.
The phase relationship between the switch closure angle and capstan
increment
may be altered,
maintaining the
same
switch closure angle,
by
moving both brushes an equal
distance in the same
direction of
travel.
In order to change the
width
of the switch
closure angle,
one brush
holder,
or
both
if
desired,
may
be moved
so
that
the brushes
do
not
engage their respective
commutator segments
at the same time.
It
is possible to diminish the closure angle
to zero by this
adjustment.
IMPORTANT
:
When
making any brush
adjustments,
always keep
finger pressure
on
the brush
holder
towa!"d the
capstan
drive shaft.
This
is necessary in order to
insure
proper
brush
radial
alignment.
S
lATTLl
Page
19
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