Dual 1225 - Pitch Control

Pitch Control
For platter speeds of 33 1/3 and 45 rpm
the unit incorporates a power-—independent
pitch control which permits a platter speed
variation of up to 6 & (approximately one
semi-tone).
When the pitch control knob (10) is turned,
the switch segment (108) and the switch
lever (130) attached to it are moved up or
down. This vertical displacement changes
the position of the idler wheel on whatever
step of the motor pulley it has been placed,
by the speed selector, and due to the ta-
pered shape of the pulley effects approxi-
mately + 3 % variation in speed.
Trouble Cause
Platter does not a) Current path to motor
run when unit is interrupted
plugged in and b) Idler wheel (152) not
start switch in contact with platt-
Operated er
es Motor pulley loose
Platter does not a) Motor pulley is not
reach required correct for local
speed line frequency
b) Slip between idler
wheel (152) and motor
pulley or platter
c) Excessive friction in
motor, idler wheel or
platter bearings
Rumble in re- Worn idler wheel
production
Idler wheel does not
contact motor pulley cor-
rectly
Correct nominal
speed obtained
only at extreme
settings of pitch
control
Fig. 5 Motor field connec—
tions (less voltage selector)
Coil II not in
2-pole motor
which, according
to model, can only
be used for 220 y
or 110 V or 150 ¥
Position of idler wheel
Fig. 4
Remedy
a) Check connection at switch plate and
voltage selector
b) Check switch lever assembly (130)
° Tighten motor pulley
a) Change motor pulley
b) Clean friction surfaces of idler wheel,
motor
pulley
and
turntable
platter.
If
necessary, replace idler wheel. Once
the drive surface of the platter has
been cleaned do not touch it with your
fingers
c) Clean and oil bearings
Replace idler wheel (152), clean platter
drive surface and motor pulley with grea-
seless solvent. (Once surfaces are cleaned
do not touch them with your fingers).
Adjust position of idler wheel by turning
adjustment screw (12) so that the fine
speed adjustment knob (10) is in the center
position by correct nominal (Fig. 4).
Fig. 6 Motor field connec-
tions (with voltage selector)
(ON pee GC | CSW eee
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