Dual 704 Service Manual

Page 1

Edition October 1976

Service - Manual

Dual Gebrflder Steldlnger -7742 St. GeorgenISchwarzwald

Page 2

Specification

Current Type
AC 50 - 60 Hz. without motor changeover

Line voltage:
110 - 125 Volt. 220 -- 240 Volt
Drive

Electronicallycontrolled direct drive system
Dual E05 900

Power Consumption
approx. 3.5 Watt
Motor during play < 50 mW

Current Consumption
with 220 V 50 Hz:

on start-up 45 mA during play 20 mA
with 110V 60 Hz:
on start-up 80 mA during play app. 40 mA

Run-up Time (until nominal speed is reached)
2 .2.55ec. on 33 1/3 rpm
Platter

Non-magnetic, dynamicallybalanced, detachable,

1.2 kg 300 mm ¢

Total rotating mass of drive system (rotor with platter)
1.8 kg.

Platter Speed:
33 1/3 and 45 rpm, electronically switchable.

Pitch Control
For both speeds, adjustable in each case with
variable resistor, range of adjustment 1O %

Speed Check
with light stroboscope for platter speed 33 1/3 rpm.

Strobe markings for 50 and 60 Hz provided on the platter
edge.

Sensitivity of Light Stroboeoope for 0.1 96

.Speed Deviation

3 graduations per minute at 50 Hz

3.6 graduations per minute at 60 Hz

Overall Speed Variation
(assessed in accordance with DIN 45 507)
< t 0.05 %

Signal-to-Noiae Ratio
Rumble unweighted signal-to-noise ratio
Rumble weighted signal-to-noise ratio

Tonearrn

Torsion resistant, extra long tubular aluminum tonearm in
super flat universal four-point gimbal suspension, tonearm
balance weight with double acting vibration damping (2
anti-resonators).

Effective Tonearm Lenght
222 mm

Offset Angle
26° 4

Tangential Track Error Angle
0.160 / cm

Tonearm Bearing Friction
(related to stylus point)

(in accordance with DIN 45 500)
> 46 dB
> 67 dB

Vertical < 0.07 mN (0.007 9)
Horizontal < 0.15 mN (0.0159)
Tracking Force

0 -- 30 mN (O - 3 grams) infinitely variable with 1 mN

(0.1 g) calibrations from 0 to 15 mN (0 to 1.5 g).

operable from 2.5 mN (0.25 g) stylus pressure up.

0 - 3 g continuously variable. with 1/10 calibration in the
range from 0 - 1.5 g, reliable as from 0.25 g tracking force

Pick-up Heed
Detachable, suitable for all pick-up cartridges with 1/2

mounting and a deadweight of 4,5 - 10 9 (including
mounting material)

Adjustable Overhang 5 mm

Pick-up Cartridge
See separate data sheet

Weight
5.4 kg

Dimensions and Cutout Required
refer to Installation Instructions.

Page 9

Fig. 8 Tonearm-Tonearm Suspension

31 29 183 24 69 48

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Tonearm -Tonearm Suspension

The Feather-light, extremely torsion resi-
stant 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 mini-
mum.

Bearing Friction vertical
Bearing Friction horizontal

:A m

0.007 p
0.015 p
as related to stylus point.

As a result, it ensures most Favourable
pick-up conditions. Before adjusting the
pick-up Force to suit the built-in pick-up
cartridge the tonearm is balanced with the
scale set to zero. Coarse adjustment is car-
ried out by moving the weight with the stem
(49), the subsequent Fine adjustment by tur-
ning the weight. The balance weight is de-
signed such that pick-up cartridges having

a deadweight of 4.5 - 10 9 can be balanced.
It takes the Form oF a anti-resonator thus
absorbing the vibration energy in the range

r 19. 9 ,- 36

37

56 60

57 61

38 51

201 7 7 7 59

42

128 ' i';,,,,,,,¥205
207
211

10

of tonearm and chassis resonance. For this
purpose, the inner part weight is matched

to the tonearm resonance and thus acts as
anti-resonator by means oF antiphase vibra-
tion. The outer part of the balance weight
taking the Form of a higher balanced anti-
resonator prevents transmission oF partially
occurring chassis resonance to the tonearm.

The tracking Force is adjusted b turning
the graduated spring housing (59 incorpo-
rating a coil spring. The scale has markings
For a ran e of adjustment From 0 to 30 mN

(0 to 3 p? which permit accurate adjustment
oF the tracking Force. One graduation in the
range 0F 2 - 1S mN (0.2 - 1.5 p) corresponds
to 1 mN (0.1 p), in the range 0F 15 - 30 mN
(1.5 - 3 p) to 2.5 mN (0. 25 p).

Removal of tonearm assembly with tonearm bearing

1. Secure unit in repair jig. Remove weight
(49) undo Fixin screw (52). Set tracking
Force scale (59 to zero.

2. Move unit into heed position. Remove
screening plate (150). Unsolder tonearm
on muting switch (149).

3. Move unit into normal position. Turn both
mounting screws - SU 4.5 - (55) counter-
clockwise to the stop oF the bearing Fre-
me (51).

Attention: Observe the bayonet mounting

Slide tonearm (48) rearwards and
remove it upwards From the bear-
ing Frame.

For installation proceed in the reverse
order.

Removal of tonearm from hearing from

Proceed as Follows:

1. Secure unit in repair jig. Set graduated
spring housing (58) to zero. Arrest tone-
arm (48). Remove weight (49).

2. Loosen tension lever (63) and bring tone-
arm (48) in its highest position using
knob (65). Fasten tension lever (63).
Bring knurled ring (68) in position "3".

Page 21

Lubficafion

All bearings and Friction points are ado-
quataly lubricated by the manufacturer. Re-
plenishment of oil and grease is only na-
cessary after approximately 2 yours of nor-
mal use of the turntable as the most impor-
tant bearing points (motor bearings) have
sintorod metal bushes.

Hacker Silicone oil
AK 500 000

>

89 Super Uiskostatik

9

Bearing points and Friction faces should be 10 U/30

lubricated sparingly rather than genurously.

When using different lubricants, chemical

decomposition can oftur occur. To provont

failure of lubrication we recommend using //\\

the original lubricants stated below. 4' Shudl Aluania No. 2

Fig. 22

" "'"IHIMHHv

31H a,

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Dual Gebrflder Steldlnger -Tl42 St. GeorgenlSchwarzwald

920 35 7-2 7mm Pnnmd In Germany by Dual