Dual 521 Service Manual

Stroboscope
Even during
the play mode the stroboscope can be
used to check
the accuracy of the turntable
speed adjustment to 33 1/3
and
45 rpm.
Accurate adjustment is
manifested by seemingly motionless bar
marks of the stroboscope. I f the
marks run in the same direction
as the turntable, the speed is too high and
vice versa.
To vary the adjustment, operate the "pitch"
knob (16). The strobo
marks
on the turntable rim, shovvn in Fig. 12,
have the following
meanings (starting from the lowest row):
33 1/3 rpm at 60 Hz,
33 1/3 rpm at 50 Hz, 45 rpm
at 60 Hz, 45 rpm at 50 Hz.
To exchange the glow lamp GI (245), remove the screws
(248)
and the strobo case
(244).
Fig. 5
R1
D1
R2
C2
Fig. 6 Motor
connection scheme
1
GI
C1.
Tuning to the
Pitch-of-tone Level
This feature is
independent of the power
and controls both turn-
table speeds. The
tuning range is max. 6
% or about one
semi-
note.
When you rotate the knob
16, you will move the belt
pulley 2
(105). This motion
will be transferred by the
toothed belt (109)
to the belt pulley
1 (112
in
Fig. 9). As a result, the counter
bearing
(113) and taper sleeve of
motor pulley (116) are shifted
upwards
or downwards, respectively. The
taper sleeve of the motor
pulley
(116) causes the
pulley diameter to be reduced
or increased, which
permits the variation
of the rated speed within the
said range of
± 3 %.
Fig. 7
Fig. 9
105 13
16 109 112 111 110 116 113
zzA ,
5

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