Dual 622 Service Manual

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4. Loosen threaded
pins 13 and remove platter cone 12
Remove the three screws 148. Lift off
motor mechanics 149
5. Put platter
cone 12 on new motor
mechanics and ffix it. Fix
new motor
mechanics with the three screws
148. Fix holding
angle 150
with screws 151. Insert
motor electronics 152 and
twist holding
pieces.
Solder on
resp. plug
connecting leads (fig.
5).
Push cover on
power part and
fix it with
screws 112.
6. With the
unit in
normal position
connect it to
the power
line
Switch on
unit and check
power
consumption when
operating:
221' ,
//50 Hz
approx. 15 mA
11L
V/60 Hz
approx. 25 mA
Check
nominal speeds.
If
necessary, readjust
as
described
below.
Setting nominal speeds
With knob 7 bring
the fine speed control
129/R 19 into center
Position. With controls R 8 and R 9
on the
motor electronic
system adjust nominal
speeds. Control R 8 is used
for 33 1/3
rpm, R 9 for 45 rpm. Check with
strobe disk.
Changeover to 78 rpm nominal
speed
Instead of 45
rpm the Dual
622 can be
changed to a
nominal
speed of 78 rpm.
To change the
speed bring the fine
speed control 129/R 19
in
center position
using knob 7.
Using control R 9
on the motor
electronics
board 152 adjust
for 78 rpm.
Check with strobe
disk.
Stroboscope
Accurate setting of the planer speeds
33 1/3 and 45 rpm can be
checked during play with the aid of the stroboscope.
When the
platter 4 is rotating at exactly 33
1/3 or
45
rpm the
lines of the stroboscope appear
to stand still. If the lines move in
the direction of
rotation of the platter, the platter speed
is too
high. If the lines move backwards,
the platter is rotating more
slowly than the nominal speed. Adjustment of platter
speeds 33
1/3 and 45 rpm is carried
out separately with the
"pitch"
controls 7.
Strobe markings are provided on the outer edge
of the platter for
50 and 60 Hz line frequencies.
To
replace glow lamp 157
remove machine screws 160
and
remove
strobe cover.
lt can happen
that the
stroboscope lines appear
to move slightly
although
the exact speed setting
with stroboscope
stationary has
not been
altered. This apparent
contradiction is explained
by the
fact that the electronic
central drive motor
operates fully inde-
pendently
of line frequency
whilst the only
relatively accurate
line
frequency of the AC current
supply is used for speed mea-
surement with the light
stroboscope. The
constantly
detectable
fluctuations of line frequency
by ± 2 % according to
the infor-
mation
of the electricity
supply companies
brief frequency
fluc-
tuations up
to 1 are possible —
only effect the
stroboscope
indication and can
cause the lines to
"wander" although the
platter speed is as
constant and absolutely accurate as
before.
Fig. 6
111 152
148
12 13
150
Sell
Pitch Control
Each of the two standard
speeds 33
1/3
and 45
rpm (78
rpm)
can
be varied by
about 10%.
The
variablespeed
control 1291 19
located in the voltage
divider
is
adjusted by
turning the
pitch
control knob 7.
By this the
differential
amplifier is
altered and
the
motor speed accordingly.
Fig. 7
U/min soHz
45U/min
soHz
33 U/min 50Hz
33U/min
6oHz
.4.5ze
Tonearm and Tonearm
Suspension
Th
efeather-light, extremely torsion resistent all-metal tonearm
is
suspended in a gimbal. Suspension is by means of 4
hardened
and precision polished steel points which rest
in precision ball
bearings. Tonearm bearing friction is thus reduced to a
minimum.
Bearing
friction vertical
0.07 mN (0.007 p)
Bearing
friction
horizontal 0.15
mN (0.015 p)
as related to stylus point.
As a result, it ensures most
favourable pick -up conditions. Before
adjusting the
tracking force to suit the
built-in pick -up cartridge
the tonearm is
balanced with the scale set
to zero. Coarse adjust-
ment is carried out by moving
the weight with the stem
49, the
subsequent fine
adjustment by turning
the weight.
The tracking
force is adjusted by turning the
graduated spring
housing 58
incorporating a coil spring. The Rotary knob
54 has
markings for a
range of adjustment
from 0 to 30 mN (0 to
3 p)
which permit accurate
adjustment of the tracking force.
One
graduation in the
range of 2 — 15 mN (0.2 — 1.5
p) corresponds
to 1
mN (0.1 p), In the range of
15 —30 mN (1.5 — 3 p) to
2.5 mN
(0.25
p).

Dual 622 Specifications

General

Brand	Dual
Model	622
Category	Speakers
Language	English