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GENERAL INSTRUCTIONS
FOR CB-1l AND CB -21
TRANSCRIPTION TURNTABLE CHASSIS MECHANICAL OPERATION
CB -11
33
-1/3 RPM /7$ RPM
(45
RPM with Adapter)
CB -21
33
-1/3 RPM /45 RPM
The Gates
CB -11 and CB -21
Transcription Turntables are
of the inside
rim
drive design, recognized by most engineers
as
the most success-
ful type of turntable for quietness
in
operation
and
freedom from
mechanical difficulties.
The equipment has been
designed
to
require
a
minimum
of
maintenance, and actual maintenance requires only
periodical cleaning and
a
single oiling detail, bi- monthly, pertain-
ing to
the motor.
IDLER WHEELS
Two idler wheels are provided, both being identical and carrying
Gates
Part No.
A
-1939
-103.
These idler wheels are inverted
in
relation
to
each other,
and
thus
are located for proper engagement
with the
two
pitch diameters
of
the motor drive shaft, which governs
the speed
of
the rotation of these idler wheels.
The idler wheel
that engages with the large diameter
of
the motor shaft
is
the one
for
7$
RPM on the CB -11 and -for 45 RPM on the CB -21 and the other,
which engages with
the small diameter, is for
33
-1/3 RPM.
These
idler wheels are arranged
on
a specially
designed bracket arrange-
ment which,
by
means of
the speed change lever,
moves the idler
wheel for the desired speed
into
the proper position for engagement
with
the inside rim
of
the turntable.
These idler wheels and their
location have been carefully adjusted
at the
factory before shipment
and no readjustment should
be
required unless the equipment becomes
loosened
in
transit.
If loosened,
it
will
be
noted that
the bracket
previously referred
to,
which holds the two idler wheels,
is
bolted
to the
main casting
by
means of
a
single bolt which
is
located
in
an oversize hole
so
that the idler wheels
may
be
adjusted for
uni-
form tension
at
both speeds.
As
adjustment
is
seldom, if ever,
required,
it is
suggested
that if in an extreme case this
would
be
necessary,
such as damage in shipment, or
after
long ,ariods of
operation, follow instructions
on
Page
3.
MOTOR
The motor
is a
specially designed vertical type synchronous motor
carefully balanced for both low mechanical and audible noise.
As
it is
a
synchronous type motor,
it
will operate
at
the same speed,
regardless
of line voltage,
between
90
and 140 volts.
However,
it
is
recommended that both
the
correct voltage and frequency be used,
as
synchronous motors,
by
their very nature, have
a
greater tempera-
ture rise when operating
at
voltages other than normal.
TURNTABLE CASTING
The casting
is
a
specially designed aluminum casting with each rib
and location of mass carefully determined
to
cancel harmonic vibra-
tions and thus eliminate rumble.
On all
Gates turntables
a
small
cushion strip
is
placed between the casting and the table proper.
Where
the chassis only
is
purchased, for use in other than Gates
cabinets, this strip
is
also supplied.
When
the
mounting screws are
finally pulled
up to
hold
the chassis to the table, they should
be
pulled
up
only firmly enough
to
secure
it,
allowing the mounting
strip
to
absorb
any floor vibration.
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