Dual 1211 - Pitch Control

tb,
Pitch
Control
For turntable
speeds 33 1/3, 45 and 78 rpm,
the unit
incorporates a
voltage—indepen—
dent
pitch control, which
permits a turn—
table speed variation of up to
6 % (appro—
ximately
one
semitone).
When the pitch
control knob (7) is turned,
the switch segment (105) and
the switch
lauer
(107) attached to it are
moved up or
down. This vertical
displacement changes
the
position of the idler
wheel on what—
ever step of
the motor pulley lt has been
placed on (by the speed
selector), and, due
to the
tapered shape of the pulley, effects
approximately + 3
% variation in speed.
Symptom
Cause
Fig.
5
Motor
pulley
(2
—pole
motor
Remedy
osition
Turntable does not run
when unit is plugged in
and start switch
opera—
ted
Turntable does not
come
up to
speed
a) Current path to motor
interrupted
b) Idler wheel (133/140)
not in contact with
platter
Motor pulley lose
Motor pulley is not
correct for local
line frequency
b) Slippage between id—
ler wheel (133/140)
and motor
pulley or
platter
c)
a)
c) Excessive friction in
motor, drive
wheel or
platter bearings
Rumble in
reproduction
Worn idler wheel
Symptom
Correct nominal
speed obtained
only at
extreme
settings of
pitch control
Cause
Idler wheel does
not contact
motor
pulley
correctly
Remedy
a) 4 —pole motor
Loosen
setscrew (115) and
by means of
setscrew (113)
adjust the
motor pulley
on the motor
shaft so that when
the fine
speed
adjustment
knob is in
the center
of its
range, the idler
wheel is posi—
tioned in the center of
the appropriate
motor pulley
step. (Fig. 6 ). When
ad—
justment is
completed, tighten
setscrew
(115).
b) 2 —pole motor
After loosening locknut (143),
correct
the idler wheel
position by turning its
shaft
(142) so that
when the
fine speed
adjustment knob (7) is
in the center
of
its range,
the idler
wheel is
centered in
the
appropriate step of
the motor
pulley
(Fig. 5).
After
adjustment, tighten
locknut.
a)
b)
Check
connection at
switch plata
voltage selector
Check switch
lever assembly
(107)
c) Tighten
motor pulley
a) Change
motor pulley
c)
and
Clean
friction
surfaces of idler
wheel,
motor
pulley and turntable
platter. If
necessary, replace drive
wheel. Once
the drive
surface of the
platter has
been
cleaned, da not
touch lt with
your
fingers
Clean and oil
bearings
Replace
idler
wheel
(133/140) and
clean
platter drive
surface
and motor
pulley
with
greaseless
solvant. Once
surface
are
cleaned, da
not touch
them with
your
fingers.
Fig.
6
Motor
pulley
position
(4
—pole
motor)
5