Dual 721 User manual

Dual

August

1976

Edition

721

Service

Manual

Dual

Gebrüder

Steidinger

•

7742

St.

GeorgenISchwarzwald

Download from www.dual.de

Not for commerical use

Specification

Current

Type

AC

50

-

60

Hz,

without

motor

changeover

Line

voltages

110

—

130

Volt,

220

—

240

Volt

Drive

Electronically-controlled

direct

drive

System

Dual

EDS

1000-2

Power

Consumption

approx.

2.5

Watt

Motor

during

play

<50

mW

Current

Consumption

with

220

V

50

Hz:

on

start-up

60

mA

during

play

20

mA

with

110

V

60

Hz:

on

start-up

110

mA

during

play

app.

38

mA

Run

-up

Time

(until

nominal

speed

is

reached)

2

—

2.5

sec.

on

33

1/3

rpm

Platter

Non-magnetic,

dynamically-balanced,

detachable,

1.5

kg

305

mm

Total

rotating

mass

of

drive

system

(rotor

with

platter)

3.0

kg,

moment

of

inertia

250

kp

cm

2

Platter

Speeds

33

1/3

and

45

rpm,

electronically

switchable,

automatic

tonearm

lowering

coupled

to

speed

change.

Pitch

Control

Separate

for

both

speeds,

adjustable

in

each

case

with

variable

resistor,

with

setting

scales,

range

of

adjustment

10

%.

Speed

Check

with

l

ight

stroboscope

for

platter

speed

33

1/3

rpm.

Sensitivity

of

Light

Stroboscope

for

0.1

%

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)

<±

0.03

%

Signal-to-Noise

Ratio

(in

accordance

with

DIN

45

500)

Rumble

unweighted

signal-to-noise

ratio

>

50

dB

Rumble

weighted

signal-to-noise

ratio

>

70

dB

Tonearm

Torsion

resistant,

extra

long

tubular

aluminum

tonearm

in

super

flat

universal

four-point

gimbal

suspension,

tone

-

arm

balance

weight

with

double

acting

vibration

damping

(2

anti-resonators).

Effective

Tonearm

Lenght

222

mm

Offset

Angle

25

0

20'

Tangential

Track

Error

Angle

0.16

0

/

cm

Tonearm

Bearing

Friction

(related

to

stylus

point)

Vertical

<0.07

mN

(0.007

g)

Horizontal

<

0.15

mN

(0.015g)

Tracking

Force

0

-

30

mN

(0

-

3

grams)

infinitely

variable

with

1

mN

(0.1

g)

calibrations

from

0

to

15

mN

(0

to

1.5g),

operable

from

2.5

mN

(0.259)

stylus

pressure

up.

0

-3

g

continuously

variable,

with

1/10

calibration

in

the

range

from

0

-

1.5g,

reliable

as

from

0.25

g

tracking

force

Pick

-up

Head

Detachable,

suitable

for

all

pick

-up

cartridges

with

1/2"

mounting

and

a

deadweight

of

2

-

10

g

(including

moun-

ting

material)

Adjustable

Overhang

5

mm

Pick

-up

Cartridge

See

separate

data

sheet

Weight

7.8

kg

Dimensions

and

Cutout

Required

refer

to

Installation

Instructions.

1976

2

Fig.

1

Circuit

diagram

Aug

Dual

IC1

22

n

0,7V

Strom

meßbrücke

Current

measuring

bridge

Pont

de

mesure

de

courant

• •

Ti

BD

135

20V

-

Änderungen

vorbehalten

Alterations

reserved

Sous

reserve

de

modifications

1

T2

BC

252

B

D7

ZPD

15

D

6

1

N

4001

13

14

R6

270

C

4.

1=2

50

bi

D8

ZPD

7,5

ED

Leerlaufstrom

ca.

55

mA

Icile

current

Courant

ä

vide

Anlaufstrom

255

mA

±

10

mA

Initial

current

Courant

de

demarrage

R5

130

B

R

22

100

k

(33

1/3

Upm)

C)45Unm

33

1/3

lipm

7R4

470

C

51

—

0,068

µ

D

51

BY

183

300

R

51

22

k

Gl.

1

R

52

2,7

k

C

52

—

0,047

bi

220

V

T

0,125

A

Ce

°

0-•-

R

9

100

D9

AA

143

BIM

110/130V

220/240

V

Spannungen

gemessen

mit

Meßinstrument

(7

—

10

MOhm

Eingangswiderstand)

gegen

Masse

Voltages

measured

with

measuring

instrument

(7

—

10

MOhm

input

resistance)

to

ground

Tensions

mesurees

avec

instrument

de

mesure

(7

—

10

MOhm

resistance

d'entree)

contre

masse

51

1

2

3

4

9

27

8

51

52

3

S

1000-2

•

BC

338

T

4

BC

338

1

T

5

BC

338

D

10

AA

143Z

C

5

c

+

=I

1,5i

R16

68

D

11

AA

143'

Von

der

Bestückungsseite

gesehen

As

seen

frorn

the

top

side

Vu

du

cöta

elements

50

—

60

Hz.

8

14

0

1

2

7

1

R25

R26

220

2,2

k

BC

338

c;

C7

1

µ

±

10%

•

R

28

1

M

6-11

0,15

bt

±

10%

10

•

A

•

6

J

001

741

11

4

R29

22

k

•

R

30

77

013

820k

1

N

4148

C9

10/1

±

10%

1

C8

47/1

+

50

%

-

10

R

27

10

k

T8

BF

245

C

T9

BC

172

B

R

31

1

M

Drehzahlschalter

Platter

speed

switch

1

Commutateur

de

vitesse

0

45

Upm

331/3

Upm

•

R20

910

R18

'R33 'R21

220

1k

2,2k

(45

Upm)

Transistoren

von

der

Anschlußseite

gesehen

Transistors

as

seen

from

the

connecting

side

Transistors

vus

du

cötä

des

connexions

E

C

D(4

,

ib)G

•

BC

172

B

BF

245

C

BC

252

B

BC

338

1

1-r

a

BD

135

B

C

E

R

32

33

k

Ausgabe

1/März

1976

23

16,24

25

26

28

27

14,13

15

17

18

33

30,21

20

19

31

32

5

9

7,6

8

4

Contents

Specification

Circuit

Diagram

Dual

EDS

1000-2

Electronic

Direct

Drive

System

Description

of

Function

Speed

Regulation

Page

2

3,4

6,

7

8,

9

Assembly

I

nstructions

for

Dual

EDS

1000-2

10

Stroboscope

10,

11

Pitch

Control

11

Adjustment

of

nominal

speeds

11

Tonearm

and

Tonearm

Suspension

12

Removal

of

tonearm

from

bearing

frame

12

Removal

of

tonearm

assembly

vvith

tonearm

bearing

12

Replacement

of

spring

housing

13

Adjustment

of

tonearm

suspension

13

Vertical

Tonearm

Control

13

Antiskating

Control

13

Tonearm

Control

14

Cue

Control

14

Replacement

of

cue

control

assembly

14

Starting

15

Manual

Start

16

Stopping

16

Muli

ng

switch

16

Continuous

Play

16

Pick

-up

head

not

paral

lel

to

platter

16

Shut-off

17

Stylus

slips

out

of

playing

groove

17

Tonearm

does

not

set

down

at

the

edge

of

the

record

18

Tonearm

does

not

set

down

or

lowers

onto

record

too

quickly

18

Vertical

movement

of

tonearm

dragging

18

Tonearm

returns

to

rest

immediately

18

Tonearm

moves

with

dials

in

zero

position

18

During

automatic

operation

of

tonearm

disturbing

noises

are

perceptible

18

Motor

does

not

shut-off

18

Acoustic

feed

back

18

Pick

-up

Connection

Diagram

19

Spare

Parts

20

Exploded

view

-

Parts

above

chassis

21

Exploded

view

-

Parts

below

chassis

22

Spare

Parts

23

-

25

Lubricating

I

nstructions

25

Note:

The

reference

numbers

in

the

instructions

refer

to

the

spare

parts

lists

and

exploded

views.

5

Fig.

2

Dual

EDS

1000-2

Electronic

Direct

Drive

System

turntable

center

plate

centering

ring

magnet

steel

plate

conductor

coil

support

plate

field

coi

l

ls

heddecl

Hall

generator

Dual

EDS

1000-2

Electronic

Direct

Drive

System

The

EDS

1000-2

motor

especially

designed

for

the

Dual

721

is

a

slow-running

no-commu-

tator

DC

electronic

motor

which

draus

its

power

supply

from

a

stabilized

power

pack.

The

electro-mechanical

commutation

normally

carried

out

an

DC

motors

by

the

commutator

is

electronically

controlled

in

the

case

of

the

Dual

EDS

1000-2

motor

by

two

Hall

genera-

tors.

These

two

Hall

generators

-

dependent

an

the

rotor

position

-

control

four

switch-

ing

transistors

which

in

turn

have

the

effect

of

a

rotating

magnetic

field

occurring

in

the

field

coils

of

the

motor

by

means

of

which

the

four

pairs

of

magnets

of

the

rotor

are

continuously

attracted

or

repelled.

By

means

of

the

torque

thus

exerted,

uniform

rotation

is

induced

in

the

rotor

-

and

with

it

the

platter.

A

speed-dependent

voltage

(tacho

voltage)

induced

in

the

motor

windings

not

switched

an

is

coupled

out

and

controls

the

electro-

nic

regulator

circuit.

This

ensures

that

even

the

slightest

deviations

from

the

nomi-

nal

speed

are

corrected

in

fractions

of

a

second

by

a

change

in

the

motor

current.

Speed

fluctuations

are,

therefore,

practi-

cally

eliminated.

joining

centring

for

turntable

rotor

plain

bearing

flange

angular

bearing

Absolute

maintenance

of

the

nominal

speed

na

langer

presents

any

problem

with

this

control

system.

The

above-mentioned

Hall

generator

is

a

mag-

netically

controllable

semi-conductor

ele-

ment

named

after

the

physicist

E.

Hall.

With

the

Hall

effect

as

a

result

of

the

action

of

a

magnetic

field

an

the

Hall

generator

a

voltage

approximately

proportionate

to

the

strength

of

the

magnetic

field

is

generated,

its

polarity

being

dependent

an

the

direc-

tion

of

the

magnetic

flux.

A

control

current

flows

through

the

Hall

ge-

nerator.

If

now

a

magnetic

field

becomes

effective

at

right

angles

to

the

area

of

the

Hall

generator,

the

so-called

Hall

voltage

occurs.

With

constant

control

current

this

Hall

voltage

is

dependent

an

the

direction

and

strength

of

the

magnetic

field.

If

the

polarity

of

the

magnetic

field

is

reversed,

the

polarity

of

the

Hall

voltage

changes

as

well.

In

the

absence

of

a

magnetic

field

the

Hall

voltage

is

zero.

This

effect

is

utili-

zed

to

control

the

Dual

EDS

1000-2

motor.

As

the

motor

is

operated

on

DC

from

a

stabi-

lized

power

pack

it

operated

independently

of

line

voltage

and

frequency

fluctuations.

The

motor

is

of

8

-pole

disk

rotor

design.

The

rotor

has

a

barium

ferrite

annular

mag-

net

inside

which

has

8

-pole

magnetization

an

its

lower

face.

6

A

slotless

steel

disk

connected

to

the

rotor

acts

as

magnetic

return.

The

field

windings

of

the

motor

are

ironless

and

are

embedded

in

a

plastic

support.

The

field

windings

consist

of

16

double

wound

coils

which

are

arranged

in

two

planes

above

one

another.

The

8

coils

of

the

lower

plane

are

22.5

0

offset

in

relation

to

the

top

pla—

ne.

In

each

plane

there

is

a

Hall

generator

in

the

center

of

one

coil.

The

two

Hall

ge—

nerators

are

also

offset

by

22.5

0

in

rela—

tion

to

one

another.

The

individual

windings

—

32

in

all

—

are

connected

together

so

that

four

all

round

phase

windings

are

produced.

Compared

with

other

directly—driven

record

players

in

the

case

of

the

Dual

EDS

1000

mo—

tor

no

form

of

magnetic

drag

or

restoring

force

is

present

(pole

jerk

etc.)

as

can

easily

be

detected

by

turning

the

rotor.

As

a

result

of

the

ironless

field

coils

no

hy—

steresis

or

eddy

current

losses

or

interfe—

ring

slot—ripple

frequencies

occur.

This

results

in

completely

vibration—free

motor

running

together

with

a

low

power

con—

sumption

of

less

than

50

mW

during

play

(the

electronic

system

is

not

taken

into

account).

By

virtue

of

this

vibration—free

running

the

motor

can

be

rigidly

connected

to

the

chas—

sis.

The

electronic

system

itself

is

divided

into

the

switch,

commutation

and

control

sections

(see

block

diagram).

Fig.

4

Block

Diagram

110-130

V

220-240

V

50-60

Hz

Supply

unit

Netzteil

low

]

Gleichrichter

Rectif

ier

Bloc

secteur

Redresseur

Stoboskop

Elektronik

Strobe

Electronic

Stroboscopique

Electronique

Fig.

3

Line

Board

(Equipment

Side)

Glimmlampe

Glim

lamp

Lampe

ä

effluves

Stabilisierung

Stabilization

Stabilisation

Netztran

sf

ormator

Mains

transfor

mer

Transforrnateur

de

riseau

• •

C

52

0047

II

.-ti-•

L___.

D51

er

iesmo,

Ill-

Til

3

eo

68i;

9 -

1R51/22K

I--•

T125mA

0

220 110V

Schalt-

und

Regelteil

Switch

and

control

unit

Circuit

et

pike-

-

11---

de

räglage

I

e e

220V/

SO

-60

Hz

Drehzahlum-

schaltung

und

Feinregulierung

Speed

change

et

fine

tuning

Changement

de

vitesse

et

accord

präcis

7

Desuiption

of

Fumion

The

4

phase

windings

are

each

in

the

collec—

tor

circuit

of

the

4

switching

transistors

T

4

to

T

7

(Fig.

5)

and

are

connected

to—

gether

in

star

form

at

one

point.

This

point

is

connected

to

the

minus

pole

of

the

supply

voltage.

The

position

of

the

rotor

illustrated

in

Fig.

6

has

the

effect

that

the

magnetic

field

of

the

south

pole

of

a

pair

of

poles

at

connection

11

of

the

Hall

generator

H

1

gives

rise

to

a

Hall

voltage

maximum

of

ne—

gative

polarity.

Transistor

T

4

whose

base

is

joined

to

con—

nection

11

of

the

Hall

generator

therefore

receives

a

negative

base

emitter

voltage

and

is

fully

connected

through

whereby

the

cur—

Fig.

5

Fig.

6

-14V

0

rent

flows

through

the

phase

winding

W

1

lo—

cated

in

the

collector

section

or

it

is

switched

on.

Transistor

T

5

whose

base

is

joined

to

con—

nection

9

of

Hall

transistor

H

1

is

blocked

by

the

positive

Hall

voltage

potential.

As

Hall

generator

H

2

is

in

the

neutral

zo—

ne

of

the

pair

of

magnetic

poles

during

this

period,

no

Hall

voltages

occur

at

its

connections

7

and

5.

The

transistors

T

6

and

T

7

joined

to

these

connections

are,

therefore,

blocked

as

well.

The

switched

on

phase

winding

W

1

(Fig.

7

a)

produces

clockwise

rotation

of

the

rotor

through

22

1/2°.

This

cycle

takes

place,

displaced

electrically

in

each

case

by

90

0

,

in

sequence

in

all

four

phase

windings.

7

T3

12

W1

2

D9

4

•

D102

T5

T5i

5

21311

W4

j

D122

H2

N

z'

-,

-

N

,

\

N

‘

1-

1

iiii ii it

H1

6

Thus

the

following

sequence

of

movement

ta-

kes

place:

After

the

1.

rotation

phase

(Fig.

7

b)

the

Hall

generator

H

1

is

located

in

the

neutral

zone

of

a

pair

of

magnetic

poles.

One

south

pole

is

now

directly

above

Hall

generator

H

2

and

now

also

produces

at

its

connection

7

a

Hall

voltage

maximum

of

negative

polar-

ity

which

switches

on

phase

winding

W

3

via

transistor

T

6.

All

other

transistors

are

blocked.

The

rotor

now

rotates

again

through

22

1/2

0

through

the

magnetic

fields

genera-

ted

in

phase

winding

W

3.

After

elapse

of

the

second

rotation

phase

(Fig.

7

c)

the

Hall

generator

H

2

is

now

in

the

neutral

zone

of

a

pair

of

magnetic

po-

les.

Hall

generator

H

1

is

now

directly

un-

derneath

a

north

pole

and

a

Hall

voltage

of

reversed

polarity

occurs,

i.

e.

the

negative

polarity

Hall

voltage

maximum

is

now

present

at

connection

9

which

connects

through

phase

winding

W

2

via

transistor

T

5.

The

other

transistors

are

blocked.

The

rotor

again

advances

by

22

1/2°.

After

this

3.

rotation

phase

(Fig.

7

d)

Hall

generator

H

1

is

in

the

neutral

zone.

A

north

pole

is

above

Hall

generator

H

2

and

produces

a

negative

Hall

voltage

at

its

con-

nection

5

which

switches

on

phase

winding

W

4

via

transistor

T

7.

The

rotor

advances

by

a

further

22

1/2°.

After

conclusion

of

this

4.

rotation

phase

the

process

starts

again.

Thus,

a

continuous

rotating

field

occurs

which

drives

the

rotor

at

an

uniform

rate.

If

the

rotor

is,

for

example,

between

two

phase

windings,

a

partial

flux

of

a

pair

of

magnetic

poles

passes

through

both

Hall

ge-

nerators

and

thus

two

switching

transistors

are

partly

opened.

The

current

is

divided

accordingly

between

two

phase

windings.

Both

phase

windings

participate

simultaneously

in

the

torque

formation

and

together

produce

the

torque

of

a

fully-connected

phase

um

-

ding.

The

torque

is,

therefore,

almost

con-

stant

in

any

position

of

the

rotor.

Speed

Regulation

As

a

result

of

the

rotary

movement

of

the

rotor,

voltages

are

induced

in

the

phase

windings

not

connected

through

which

are

coupled

out

via

diodes

D

9

to

D

12.

Thus,

a

tacho

voltage

proportionate

to

the

speed

is

obtained.

The

tacho

voltage

passes

via

a

voltage

divi-

der

to

connection

4

of

the

operation

ampli-

fier

in

the

control

section

and

counteracts

the

voltage

present

there.

A

stabilized

vol-

tage

is

present

at

connection

5

of

the

ope-

ration

amplifier.

On

start-up

and

during

run-up

of

the

motor

the

potential

at

connection

4

of

the

opera-

tion

amplifier

is

more

or

less

positive

in

relation

to

connection

5.

In

this

condition

the

operation

amplifier

fully

drives

tran-

sistor

T

7.

T

7

is

present

as

variable

re-

sistance

in

the

common

emitter

circuit

of

the

four

switching

transistors

through

which

practically

the

full

switching

current

can

flow

in

sequence.

Fig.

7

Robar

zwejam

-

H2

HI

H2

H1

W3

H2

-1ZIN

HI

2

HI

W4

The

nominal

or

controlled

speed

is

reached

when

the

same

potential

is

present

at

con-

nection

4

of

the

operation

amplifier

as

at

connection

5,

because

at

this

moment

the

operation

amplifier

closes

transistor

T

7.

As

a

result

the

motor

current

drops

and

the

speed

cannot,

therefore,

increase

any

fur-

ther.

By

switching

over

or

altering

the

voltage

divider

in

the

control

circuit

the

controlled

speed

can

be

preselected

or

altered.

With

reducing

speed

the

potential

at

connection

4

of

the

operation

amplifier

would

change

so

that

transistor

T

7

would

be

fully

driven.

T

7

would

thus

become

of

low

resistance,

the

result

would

be

a

sharp

rise

in

the

motor

current

and

thus

of

the

speed.

As

this

control

process

takes

place

even

at

minor

deviations

from

the

nominal

speed,

a

constant

speed

independent

of

load

fluctua-

tions

is

obtained.

9

Assembly

lnstructions

for

Dual

EDS

1000-2

For

repair

of

the

Dual

EDS

1000-2

special

tools

and

measuring

means

are

required.

Work

on

the

motor

or

motor

electronic

Sy-

stem

should,

therefore,

only

be

carried

out

by

an

authorized

Dual

service

station.

Ex-

penses

arising

from

unauthorized

interferen-

ce

will

be

charged

to

the

consignor.

Removal

Lift

off

platter

(4).

Remove

housing

of

p0

-

wer

pack

(123)

after

removing

screws

(117).

Fig.

8

125)--

6

Attention!

Unsolder

leads

for

operating

vol-

tage

on

power

board

(125).

Do

not

remove

cable

on

motor

side.

Unsolder

connections

on

rotary

knob

(192)

and

potentiometer

(191/R

33).

Pull

off

in-

sulating

tube.

Unscrew

complete

bearing

pillar

(147)

and

remove

together

with

washer

(148).

Remove

cam

wheel

(144).

Be

careful

with

ball

(136)

in

stop

bar

(164).

Remove

intermediate

pla-

te

(137).

Undo

hex

nuts

(75)

and

the

three

machine

screws.

Lift

motor

(5)

and

make

sure

that

the

connecting

leads

and

the

thermistor

are

routed

in

the

chassis

recessed.

Remove

the

motor.

Slide

the

insulating

tube

over

the

connecting

leads.

Place

motor

in

original

carton

for

return

shipment.

Installation

Remove

motor

from

packing,

pull

off

insulat-

ing

tube.

When

inserting

the

motor

on

the

mounting

board

(21)

ensure

that

the

lead

outlet

hole

faces

the

power

pack

(123).

Now,

refit

motor

and

other

disassembled

parts

in

reverse

order

to

that

described

under

"Removal".

Attention:

To

prevent

deformation

of

the

shorting

springs

the

camwheel

(144)

should

not

be

fitted

in

0

position.

Make

sure

that

the

of

main

lever

(154)

is

engaged

in

the

guideway

of

the

camwheel

(144).

After

assembly

fit

knob

(44)

complete

with

in

midposition.

Switch

on

unit

and

check

current

consumption

on

operation.

220

8/50

Hz

approx.

18

mA

117

V/60

Hz

approx.

35

mA

Using

control

(R

21)

set

nominal

speed

45

rpm

(check

by

means

of

a

strobe

disk),

using

control

(R

22)

set

nominal

speed

33

1/3

rpm.

Run

in

for

approximately

5

mi-

nutes

and,

if

necessary,

correct

speed.

Note:

lt

is

advisable

subsequently

to

carry

out

a

brief

check

of

all

unit

functions.

Stroboscope

Accurate

setting

of

the

platter

speeds

33

1/3

and

45

rpm

can

be

checked

during

play

with

the

aid

of

the

stroboscope.

When

the

platter

(3)

is

rotating

at

exactly

33

1

/

3

or

45

rpm

the

lines

of

the

strobos-

cope

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"

knobs

(44).

10

Dual 721 User manual

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