Dual 521 Service Manual

Fig. 2
Fig. 3
Fig. 4
NOTE: The item numbers
mentioned in the text refer to the illu-
strations,
exploded views (page 12) and Parts List.
Motor
and Drive
Tu rntable
and mechanism are driven
by the motor (132) (see
Fig.
21). This
shaded-pole motor runs
vibration-free in radially elastic
mounts and has
extremely low magnetic leakage.
The
motor speed is indpendent of voltage,
temperature, and load
variation. lt can only fluctuate with the
mains frequency. Two
motor pulleys permit adaptation to the
mains frequency of either
50 or 60 Hz; one
pulley (116) is showin in both
Fig. 2 and Fig. 3.
For 50 Hz use the pulley part no. 234 453,
for 60 Hz use the pulley part no. 234 454.
The driving force is transmitted to the turntable
(7) by belt (15).
Speed Selection
To adjust the turntable speed to either 33 1/3 or 45 rpm,
the belt
(15) is shifted to the one step of pulley (116) with the associated
diameter (see Fig. 3). This is
achieved when you adjust the speed
lever (18) so that the START/STOP lever (48) and the spring
lever will move the change-over
lever into the desired (33 or 45
rpm) position. When the record player is turned
oft, the change-
over lever is blocked by the blocking bar (12) and the speed is
just preselected. Only
when the turntable (7) starts running, the
blocking bar (12) will
release the change-over lever. The latter
will then
shift
the belt (15) to that step of motor pulley (116)
which corresponds to the desired speed.
Turntable
The turntable (7) is secured to the turntable bearing
tube by the
lock tab (151).
To remove the turntable, lift its top
layer through one of its cutouts
and rotate the turntable until the cutout is
positioned above the
motor pulley. Remove the belt (15) from the motor
pulley
(116)
and place
lt
onto the
turntable.
Continue rotating the turntable until the cutout is positioned
above the
turntable lock tab
(151);
press
the latter
outward and
lift
oft
the turntable.
Slacken the screw (150).
Belt
To replace the belt
(15), first remove the
turntable as above des-
cribed, then
separate the belt from the turntable (7).
Mount the
new belt on
the turntable..
NOTE: the
ground
(mat)
surface of the belt
should face the
driven
gart. Install the turntable and place the belt (15)
over the motor
pulley
(116).
To Replace the Motor Pulley
1. Separate
the belt (15) from
pulley
(116) and remove the turn-
table. Remove the toothed
belt (109).
2. Disengage the
tension spring (114) from the shield (122).
3. Unscrew the hex. nut (110), remove the setting cam
(111),
belt
pulley (112), and
counter bearing (113).
4. Slacken the grub
screws (106) and slide
oft
the motor
pulley
(116). Slide the replacement pulley onto the motor shaft.
Remove the taper sleeve.
Pay attention on the internal distan-
ce roller.
Position the motor pulley
(116) at proper height
above the
mounting plane, see Fig. 3. Uniformly tighten the
grub screws (117). Put the
taper sleeve into the motor pulley
(116).
5. Mount the
counter bearing (113), the
belt pulley 1 (112) and
the
setting cam (111) and secure
them in place with hex. nut
(110).
Install the tension spring (114)
and the toothed belt
(109).
Mount the turntable.
Pull the belt (15) and
place lt around
the
motor pulley
(116).
6. Turn the kno (16) to
adjust the belt pulley to
its mid
Posi-
tion. (The nose
of the belt pulley (112)
should poin't to the
motor pulley center
line.) Adjust the hex. nut (110) to
the
rated
speed; the speed increases when you turn the nut
clock-
wise
and vice versa.
4

Dual 521 Specifications

General

Drive System	Belt drive
Speeds	33 1/3 and 45 RPM
Weight	5.5 kg
Anti-Skate	Yes
Stylus	Elliptical
Output	Depends on cartridge