Dual 621 User manual

Dual
Edition August 1978
621
Service
-
Manual
eutornetic
1
q , lECT DRIVE
Dual
Gebrüder
Steidinger •
7742
St.
GeorgenISchwarzwald
Download from www.dual.de
Not for commerical use

Co
ntents
Page
2
Technical
data
3/4 Wiring
diagram
5 Audio
connection diagram
6
Dual EDS
500
electronic
direct drive
System
6
Replacement of
motor
electronic
6
Replacement of
motor
mechanic
7
Adjustment
of
nominal speeds
7
Setting 78 rpm
nominal
speed
7
Stroboscope
7
Pitch
control
8
Tonearm and
tonearm
suspension
8
Removal of tonearm
from bearing
frame
8
Removal of tonearm
compl. with tonearm
suspension
8
Removal of
spring housing
9
Adjustment of
tonearm
suspension
9
Antiskating control
9 Cue
control
9
Replacement of
cue control
assembly
10 Tonearm Control
10
Continuous Play
10
Start
10 Manuel Start
11 Stopping
11 Muting Switch
11 Shutt-off
Mechanism
11
Adjustment Points:
Tonearm
set Down Point
Shut
off Point
12
Tonearm vertical lift
12
Power switch
12 Pick -up Head
not Parallel
Correct nominal speed
obtained only at
13
extreme
setting of pitch
control
13
Stylus slips
out of record
groove
Tonearm does not
set down or lowers
13
onto
record too
quickly
13
Vertikal
Tonearm lift
13
Platter
does not start
13
Tonearm does not set
down correctly
Motor does not
shutt-off
Acoustic feedback
14
— 17
Replacement with exploded
views
18
Lubrication
Technical Data
Current
AC 50
to 60
Hz
Line voltage
110 to 125
V, 220 to 240V
Drive
electronically-regulated direct-drive
system, Dual EDS 500
Power input
approximately 2 watts, Motor at playing Operation < 50 mW
Power consumption
220 V 50 Hz:
at play
15 mA
110 V
60 Hz: at play
approximately 25 mA
Time from
start to rated speed
2 — 2.5 s at 33
1/3 rpm
Platter
non-magnetic,
dynamically balanced,
detachable
1.3 kg, 304 mm
diameter
Platter speed
33 1/3 and 45 rpm,
electronically adjustable
Pitch control
Separate for both speeds, each adjustable by means of variable resistor,
with calibration
scale; range of regulation: 10 %
Speed control (monitoring)
with illuminated stroboscope for platter speeds 33 1/3 and 45 rpm,
adjustable to 50 or
60 Hz.
Sensitivity of the illuminated strobe
6
division
markings per minute at 50 Hz,
(for 0.1 % speed deviation) 7.2
division markings per
minute at 60 Hz,
Total wow and flutter
according to DIN 45
507
(German
Industry
Standard) <-± 0.06%
Rumble
Unweighted:
> 45 dB
(according to DIN 45
5001
Weighted:
> 65 dB
Tonearm
Torsionally rigid tubular aluminum tonearm in
low-friction four-point gimbal
suspension,
tonearm counterbalance with two
mechanical
anti-resonance filters.
Effective length of tonearm
222
mm
Offset
angle 25°
20'
Tangential
tracking error 0.16 0
/cm
Tonearm bearing friction vertical
<
0.07 mN
10.007
g)
(related to stylus tip)
horizontal
<
0.16 mN
(0.016
g)
Stylus pressure from 0 to 30 mN 10 to 3
g)
infinitely variable with 1 mN-
11/10 g) calibrations from
0 to 15 mN
(0 to 1.5 g) ,
operable from 2.5
mN
10.25 g) stylus pressure up.
Cartridge holder removable, accepting any cartridges with 1/2"
mounting and a weight from
4.5 to 10
grams
(including mounting
hardware).
Adjustable Overhang 5 mm
Cartridge see separate data sheet
Mounting dimensions and mounting
board cut out: see Installation instructions
2

Fig. 1
D 1 A
cl
47 bi
1.1
2
66 2/3 Hz
(33
minl)
C2
C3
220p 0,47 p
R3
68 k
R2
G2
R6
R4
22 k
10 k
82 k
C4
0,47 µ
•
R 1
1
M
Ti
R5
1 M
-- 1
G 1
BC
172
Transistoren von der Anschlußseite gesehen
Transistors as seen from the connecting side
Transistors vus du cöte
des connexions
LILJL
EBC
BD 415
E • rl
• C
BC
172
BC
238 C
C5
— 10 n
C6
in
G3
n 33
—C
7
— 1 n
G4
4*
R8
10k
R7
47 k
T2
BC
172 B
C 8
T
0,22 bt
IC
von der
Bestückungsseite gesehen
as seen from the
top side
vu du cöte elüments
4069
555
1 2
5
3
6
8
4
7
1
4
2
3
8
3

8.2
R 16
560
i
n 45
9
k
10
4k
2 8 4
6
IC 2 —
555
— 3
3
7
1
5
R
11
110k
G5
G6
—c9
— 20 n
R 13
15k
D2
1 N
4148
,C
10
—
0,47
R 15
10 k
-
113 14
220 k
C 13
47 bi —
13
R 12
270 k
110/130 V-
220/240 V -
-
C 11
10 µ
R 17
47 k
Si 63 mAT
10 n =
9
C 52--
47 n
C 51
— 68 n
R 52
12k
A
D 51
/ \ By
183
R 51
22 k
12
8.1
7 •
T3
BC
238 C
R
18
2
T4
NSD 102
(BD
415)
20,5
VI
cr z 1 )
10
220 V
52
19
52
51
10
16,5 V —
C 55
-1-
54
20 n
13 16
14
15
17
11
12
51
53
18
13
55
54
4

Fig. 2
TA-Anschlußschema /
Audio
Connection
Diagram /
Schema
de branchement
/ Esquema de
conexion del
fono captor
a)
mit DIN-Stecker 5-polig /
with DIN-plug 5 pin
avec fiche DIN 5 pöles / con
enchufe DIN de 5 poles
rechter Kanal
right channel
canal
droit
canal
derecho
rot
/ red /
rouge / roje
linker
Kanal
left
channel
canal gauche
canal
izquierdo
weiß / white / blanc
/ blanc
\ Tonabnehmerkabel
Tonearm audio cable
Ca ble
de
BF
Cable del
fonocaptor
•
b)
mit Cynchstecker / with phono plug
avec
fiche cynch / con enchufe
Cynch
j f i
rechter Kanal
/ right channel- 1 -
Canal droit / Canal derecho !
rot
(schwarz)
/ red
(bleck)
i
rouge
(noir) /
rojo
(negro)
I
• J
Masse draht /
Mass lead
Mass cable
/
Mass
cable
V '
rechter
Kanal
right channel
canal
droit
I - 1
r
1
canal
derecho
I I I I
rot
/ red / rouge / rojo
1
I I
I
I
Masse
rechter
Kanal
Mass
right channel 1
Masse
canal
droit
masa
canal
derecho
grün
/
green /
vert /
verdc
I
I I
I
1
e - ^
I I
LJ
717
1
L
I
_1
Masse rechter Kanal - 1
Mass right
channel
Masse canal droit
mass
canal derecho
-I
linker Kanal
I
left
channel
1 canal
gauche
1 canal izquierdo
/
white / blanc
/ blanco
I 1
1 Masse
linker
Kanal
1 Mass left
channel
1
Masse
canal
gauche
mass
canal izquierdo
blau
/
blue /
bleu /
azul
/
/‚
Masse
schwarz
Mass black
Masse noir
Masa
negro
Masseblech
Mass
sheet
Prise de
masse
chapa
de
mass
Kontaktplatte
Contact
plate
Plaque de contacts
Placa de contacto
r
--linker
Kanal / left channel
Canal
droit / Canal
izquierdo
I gelb
(weiß)
/ yellow
(white)
jaune (blanc) /
amarillo
(blanco)'
1
Cynch-Tonabnehmerkabel
I
Pick -up lead
with Cynch plug
Cäble de
BF avec fiche
Cynch
I Cable del
fonocaptor con
I
enchufe Cynch
1 —
Masse linker
Kanal
Mass left
channel
Masse
canal gauche
mass canal
izquierdo
^
_ J
Kurzschließer
Muting switch
Court-circuiteur
Dispositivo
cortocircuitador
/ Z /
ZZ
11111
Tonarm kopf
Tonearm head
Täte
magnetique
Cabezal
fonocaptor
5

Fig. 3
Direct Drive System Dual EDS 500
Fig. 4
Fig. 5
Netzteil
ei
Supply unit
Bloc
secteur 4111
Generator
Generateur
418
1.
Ti
C3,
)2
T C2
For repair of the Dual EDS 500 special tools and measuring
means are required. Work on the motor or motor electronics
system should, therefore, only be carried out by an authorized
Dual
service station.
Removal
1. Extract unit plug from power line. Lift off platter (4).
Bring
unit into head position.
2. Remove seif tapping screws (112) and
cover of power part
(113).
3. Loosen connection for
operating voltage on power
plate
(109). Unsolder
connecting leads on speed control (129),
turn
switch (5) and generator. Open twists
of holding angle
(150) with
flat pliers.
4. Pull off motor electronics
(152) system from motor (18)
carefully.
5.
Fix replacement motor electronics.
Solder
connecting cables (see
connection diagram Fig. 4).
6 Slide cover over power part and fix it by means of machine
screws (112).
7. With
the unit in normal position
connect it to power line.
Switch on unit and check power
consumption on
Opera-
tion:
220
V/50 Hz approx.
15 mA
110
V/60 Hz approx. 25 mA
Check nominal
speeds. If necessary, readjust
as described
below.
Replacement
of Motor
Mechanic
1. Extract
unit plug from
power line.
Remove platter (4).
2.
With the unit
in head
position remove
seif tapping screws
(112)
and
cover of power part (113).
Loosen
connection
for
operating
voltage on power plate (109).
Drehzahlregler
/ 1 I3
19
Platter speed
switch
/ R
19
Commutateur de vitesse / R 19
C1
R16
•
R
F.
R8
R7r• —
—
i1R101 -
6 — -7
1
•
C
7
8
C7
Motor
Moteur
8.1
I
I 1
1
•-i
R13 F.,
Tcli
44,
D2
T2
• •
fl2
7
clo.Hu•
Ct . _ vr
'li
.-1
R15
I-•
T3
7
T4
6

3. Unsolder
connecting leads to rotary switch (5)
and the gene-
rator. Open twists of holding angle (150) with flat pliers. Lift
off motor
electronic (152). Remove machine screw (151)
and
holding angle
(150).
4. Loosen
threaded
pins
(15)
and remove
platter cone
(14).
Remove the three
screws (148). Lift off
motor mechanics
(149).
5. Put platter
cone (14) on new motor
mechanics and fix 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. 4).
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
opera-
ting:
220 V/50 Hz
approx. 15 mA
110 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 (19
9) on
the motor elec-
tronic system adjust nominal speeds.
Control (13 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 621 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 (172)
adjust for 78 rpm.
Check with strobe
disk.
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 (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 can make
with the "pitch" control (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 (156).
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
measurement
with the light stroboscope. The
constantly detec-
table fluctuations of line frequency by ± 0.2 % according to the
information of
the electricity supply
companies
brief frequency
fluctuations 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.
P itch
Control
Each of the two standard speeds 33 1/3 and 45 rpm (78 rpm)
can be varied by
about 10 %. The variable
speed control
1129/
R 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. 6
153
144
156
157
159
160
Fig. 7
Netztrafo
Mains
transformer
Transformateur de
ffi
seaLi
C52
fIJ e
63 mA mT 0 220V
110V
Motor
Motor
Moteur
Glimmlampe
Glim
lamp
Lampe ä
effluves

Fig. 8
190 68
1 • -,i aii 1 1 7
K- -- Iiiiim rM
1 ,
1 111
5
5 5 I I I "
311E1 lllll 1181111.1
3 1 1,1 1 1 1M m 1 1 1 1 3 1 3 1 1 11 1 1 11 3
11 1 1 1 1 1 1 3 1 ,
eielsmsammila 4\iimmulli ezion tianiallieum
1 i i • isilimul
1
»A III 11 1 11 411 1 .i.i • 1 13 1 MMMMM 1_1_11 1 1 1 r, • - - - -
- - - 7.1 I
r BI•W
1
iiihm1111111111'''
45 48
60 202 34
57 49
192
141
Tonearm and Tonearm Suspension
The feather-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 0.16 mN (0.016
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 balance
weight is designed such that pick -up cartridges having a dead-
weight of 4.5 - 10 g can
be balanced.
The tracking force is adjusted by turning the graduated spring
housing (60) incorporating a coil spring. The scale has markings
for a range of adjustment from 0 to 30 mN (0 to 3 p)
which per -
mit 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).
Fig. 9
144
143
219
208 206
170
Removing the tonearm from the bearing frame
1. Clamp unit in repair jig. Remove weight (49) and turn out
fixing screw (52). Set tracking force scale (60) to zero.
2. Move unit into head position. Remove
screening plate (140).
Unsolder tonearm connecting on muting switch (137).
3. Move unit into
normal position. Remove both
mounting
screws -
SW 5.5
(54).
For installation proceed in the reverse order.
Removal of tonearm assembly with tonearm
bearing
We recommend the following procedure:
1. Clamp unit in the repair jig. Set spring housing scale (60) to
zero.
Lock tonearm (481. Remove weight
(491.
2. Move unit into head position and remove the screening plate
(140).
Unsolder the tonearm connections
on the muting
switch
(137).
3. Remove lock washer
(184). Lift off main lever (183) and
bearing support
(182). Remove
lock washer (144).
Lift
off
setting rale (141) and rotary bearing
(143) and turn towards
motor
(149).
4. Unlock
tension spring (209).
Loosen lock washer (212)
and
remove
skating lever
(211).
5. Remove lock
washer
(211) and slide bar (171). Lift off shut-
off bar
(161) from
segment
(208).
6. Remove hex
nut (170). Remove sink
screw (174). Hold tone -
arm
(48) and lift off counter
bearing (173) and
segment (208).
7. Remove
tonearm complete
with tonearm
bearing.
Reverse this
procedure when
reassembling. Please
bear in mind
the
threaded pin
(33) is correctly
positioned in the
ball bearing.
Replacing spring housing
Remove tonearm
(48) from bearing frame (51)
as described
above. Loosen lock nut
(55) and threaded pin
(56). Unscrew
bearing
screw (61).
Lift
bearing frame (59).
Remove spring hou-
sing 160). When installing note that the helical spring catches the
bearing frame. Slide in washer
(60) and tighten bearing screw
(61). Reinstall tonearm
148). Set bearing play as described below
using threaded
pin (56) and lock nut
(55).
8

Fig.
10
ibr
6
44‘.
Adjusting the tonearm bearing
First balance tonearm exactly. Both bearings must have slight,
just perceptible
play. The horizontal tonearm bearing is
correctly
adjusted when at anti-skating settings "0.5" and
being touched lt
slides in
without resistance. The vertical tonearm bearing is
correctly adjusted
when
lt
swings in after being touched. The
play of the horizontal tonearm bearing
should be adjusted with
threaded pin (33) and that of the vertical tonearm bearing with
threaded
pin (56).
A nt i-skat i ng Device
To compensate for skating force use
the knurled ring 166). The
asymmetric cam plate (213)
displaces the skating lever (211)
from
the tonearm pivoting
point. The anti-skating force is
trans-
mitted to the
segment (208) and to the
tonearm (48) by
tension
spring (209).
Optimum adjustment is
carried out at the factorys
for styli
having
a tip radius
of 15 /Im (conical), 5/6
and
18/22 /I m (ellipti-
cal), and
CD 4-cartridges.
Any alteration
can only be carried
out with the aid of a
Dual -
Skate -0 -Meter and a test
record and should only be done
by an
authorized service station.
Recheck
es follows:
Balance tonearm
(48)
correctly. Set knurled ring
(66) to 0. The
tonearm should remain at any
desired point within its
turning
range.
The hole of the skating
lever (211) should be in
alignment
with the
center line of the
tonearm. Adjustment is made by
the
eccentric
pulley (E) which is accessible through the
hole in the
Installation plate (23)
between the knurled ring
(68) and the
tonearm.
Then set knurled
ring (66) to "0.5". The tonearm
should now
smoothly rotate from the platter center to its rest (71).
Cue Control
By moving
the lever
(190) forward (
•
) lift
cam (192) rotates.
The slide bar
(141) transmits the
lifting movement to
the lift pin
(206), that raises the tonearm. As a result, the
cue control per -
m its raise up the tonearm at any desired point.
The lever (190) is released by
moving the cue control lever rear
wards
(X l.
As a result of the action of
compression
spring
(205)
the lift
pin (206) is brought back to its normal
position and the
tonearm loweres slowly. Lowering of the tonearm is damped by
silicone oh l in the lift
tube.
Adjustment
Point
The
lift
can be
varied by
turning
the
sleeve (45).
The
distance
between
the record
and the
needle
should be
5
-7 mm.
Replacement of Cue Control
Platts
Replace cue control
plate (207) as follows:
1.
Clamp unit in
the repair jig.
and lock
tonearm. Turn unit
in
head position.
2. Remove safety washer (184).
Lift
off main lever
(183)
and
bearing support
(182).
3.
Remove safety
washer (144). Lift
off positioning
bar (141)
and rotary bearing
(143) and turn towards
motor (149).
4.
Remove both
machine screws
(204), remove lift
plate compl.
(207).
For installation
proceed in the reverse order.
Fig.
11
Fig. 12

Tonearm Control
Automatic movement of the tonearm is initiated by the control
cams on the inside
of the cam wheel (16) on
rotating through
360°.
The control elements for raising and lowering are the main lever
(183)
and lifting bolt
(206), for
horizontal movement the main
lever (183) with
segment
(208).
The automatic tonearm set down mechanism is designed for
30 cm and 17 cm records and is coupled to the
platter speed
changeover. The setdown points of
the tonearm are determined
by the spring pin of
segment (208)
contacting the slide bar
(141).
Limitation of the horizontal movement of the
tonearm is pro-
duced by the pin of segment contacting the stop attached to the
slide bar (189). Only
during set-down does main lever (183)
lift
the slide bar (141) and the stop attached to it which, as a result,
moves into the swivel range of the stop
pin fitted on the segment.
After completion of set down (lowering of the tonearm onto the
record) slide bar (141) is released again and returns to its neutral
position. As a result,
the slide bar
(141)
moves
out of the swivel
range of the pin,
so that unimpeded
movement of the tone arm
is possible
for playing.
Continuous
Play
Continuous Play is
switched on by turning
the rotary knob
(67)
to
"0:2". The
rotary
knob (67) turns
the switch angle
(185).
The
switch rod (189) keep
the change lever
(180) in starting
position.
After the record has been played the tonearm returns automa-
tically to the lead-in groove of the record. This procedure is re-
peated until the switch
lever (68) is
brought to the "stop" posi-
tion or the
rotary knob (67) to position "1".
Adjustment Point
Pull meins
plug.
Remove platter (4). Bring
rotary knob (67) to
position "03". Turn cam wheel to central position. The change
lever (180) turns the guide lever (U) and the top of the guide
lever must at least be brought to the cam range. Adjust by
bending the switch rod
(189).
Start
Switching
the switch lever (68) into the
"starr position initi-
ates the following sequence:
a) The start lever (219) rotates
the switch lever (180) which is
pivoted about the notched stud. At the same time, the
switch
arm (41) is moved the motor
(149), via the
power switch.
(116), and the platter starts turning.
b) Operating the switch lever (68)
also releases the start slide
(38) which is drawn toward the cam
by means of the tension
spring (156). By that the shut-off lever engage with the drive
pinion and
the cam turns.
Manual
start
The latch (215) which is connected to the
switch arm
(411 en-
gages in
the four-sided plate when the tonearm is moved manu-
ally. The switch arm connects the mains supply to the
motor
(1491 via the power switch (116) and the platter rotates.
When the run-out groove of the record is reached, the
tonearm is
lifted and returned, the
motor is switched off automatically. If
the tonearm is lifted off the record before the run-out, and re-
turned by hand to the pilier, then the bolt on the segment (208)
engages the latch (215) so
that the switch arm is returned to its
starting position. This switches off the mains supply.
Fig.
13
Fig. 14
67 185
189
141
38
68 219
193
166
135
10