Dual 1237 Service Manual

Page 1

1237

Edition Oct. 1977

Service Manual

Dual Gebrflder Steidinger 7742 St.Georgen/Schwarzwald

Page 2

Fig. I Pick-up Connection Diagram

right channel left channel

l
I
I
l
I

I
-I--4-I

I

l
I
I
*I
_L ,_-4;4L___

tee 4__/__34I,443
I

/
.P
i;

a) with miniature plug 5-pin

,-_-_

Short circuiter

right channel
red lead

left cha n nel
white lead

bl with phona plug
|
I

|h|\ white

__,.___

black /IJ
1
"PI I II I ':_J (red) (yellow
| ' ' II | |
I ' I II I- - black
I ' I II II I I I
I l I II II I I
~ : I I z: :I - I I
rightchannel JI I II II I :4- left channel
reuI'IIIIIIII white
I l I II I I I
Mass right channel I I I I: i: I I l Massleft channel
green I I I :I II I I I blue
' I I II II ' I '
I I l II :I I I I
I I I H I I I I
I I I I. :I I I I
I . I i: I I . :
I' I
Q1IIIIIIIIII02
Mass sheet ' l 'I IL III I II
I _3__ ______
Contact plate at tonearm head I Tonearm head
I
l I- -- - - --I I Spring contacts between
I l _, .
. I plug In cartrldge
Cartridge-holder I I I head and tonearm
I

red I white
green I blue

Cartridge

Record
"F inner side of groove 02 01 Outer side of groove
left channel right channel

Page 4

Fig. 2 Motor and drive

19 19018 102 101 194103 175 7 14 17 16

Fig 3

Note: The numbers listed above refer to the below spare parts
lists and exploded views.

Motor and Drive

Power for the turntable platter and the changing mechanism is
supplied by a split eight pole synchronous motor suspended by
radially located elastic mounts and having a very small stray mag»
netic field as well as little vibration.

The speed of the motor is independent of line voltage, tempera
ture or load variations. Speed is dependent on and proportional
to power line frequency. The motor is adapted to 50 or 60 cycle
(Hzl power line frequencies by the correct choice of the motor
pulley.

Pulley for 50 Hz Art.»No. 234 453
Pulley for 60 Hz Art.-No. 243 454

The drive' is transmitted to the platter by means of the flat belt
(17).

Speed Changeover

Platter speeds of 33 1/3 and 45 rpm are adjusted by linking the
flat belt (17l to the corresponding step of the drive pulley (105l
(Fig. 5).

The speed switch lever is brought into the required position (33
or 45 rpm) by means of the speed selection lever (19). the switch
lever (108) and the spring lever of the switch levers. If the ma
chine is switched off, then the switch lever is interlocked by the
stop lever (14). The speed is only preselected in this way. The
stop lever (14) is only released when the platter (16) turns. This
then moves the flat belt (i7) onto the required step of the drive
pulley (105).

Platter

The platter (16) is held in position by the platter locking lever
(155). When removing the platter, lift the platter covering over
one of the cutouts and rotate the platter until the cutout is abo-
ve the drive pulley. Detach the flat belt (17) from the drive
pulley (105l and lay it on the running surface of the platter.
Rotate the platter until the cutout is above the platter locking
lever (155l Push this outward and lift the platter out.

Sandwich platter

The sandwich platter (16) is secured by means of a spring clip on
the bearing tube of the bearing housing (164). This clip should
be taken away when removing the platter.

Flat Belt

The exchanging of the flat belt is described above with theplatter
to be removed. Fit the new belt to the running surface of the
platter (16).

Warning: The ground (mattl side of the belt must be in contact
with the running surface of the platter. Reinstall the
platter and lay the flat belt back over the drive pulley
(105).

Changing the drive pulley

1. Remove the flat belt (1 7) from thedrive pulley (105) and take
off the platter (16). Remove the toothed belt (100).

2. Detach tension spring (123) from screening sheet (122).

3. Remove the hexagonal screw (101), remove the adjustment
cam (102), the belt pulley (112) as well as the counter
bearing (104).

Page 7

Fig, 11

189 230 229 228 212 238

Tonaarm lift
229

Raising the lever (233) to position " I " or "1" moves the lift
cam (234) and the setting rail [189) so that the tonearm is raised
from the record (or lowered onto it). if the unit is started with
the arm lever in the "1 " position, then the tonearm is guided
over the record by the setrdown mechanism Only when the lever
(233) is brought to the position "1 " will the tonearm be lower
red onto the record. The vertical lift height can be adjusted by
means of the locating screw (54) and should be 3 7 5 mm.

Exchanging the lift plate

When changing the'lift plate (213), we recommend the following

procedure:

1. Clamp the unit in a repair stand and lock the tonearm in rest
position. Turn the unit over.

2. Remove lock washers (197 and 236) and the axle (198).
Remove the main lever (238).

3. Remove lock washer (230). Turn the locating screw (54) until
the hexagonal unit (229) can be removed. Lift the setting rail
(189) and the guide bearing (228) and pivot toward the cam
wheel (157).

4. Remove the two machine screws (212) and take out the lift
plate (213).

Reverse this procedure when reassembling.

Start

Switching the start/stop lever (78) into the "start" position

initiates the following sequence:

a) The start lever (186) rotates the switch lever (181) which is
pivoted about the notched stud, At the same time, the switch
arm (176) is moves and the motor (132). via the mains switch
(138), and the platter starts turning.

b

Operating the start/stop lever (78) also releases the start slide
(35) which is drawn toward the cam by means of the tension
spring (34), This causes the shutroff lever to engage with the
drive pinion and the cam turns,

c) This switch lever (181) is coupled to the switch angle (184)
and this is brought into the range of the shift lever so that the

I i 1
next rotation of the cam forces this into its starting position. 234186 182 189 181