Dual 521 - To Replace the Spring Case; To Adjust the Tone Arm Bearings; Tone Arm with Bearings; To Remove the Tone Arm from Its Bearing Frame

Fig.
10
45
47
46
63
42
43
44
64
66
67
200
202
To Replace the Spring Case
Remove the tone arm (58) from the
bearing frame (55) as described
on this page. Slacken the lock nut (47) and the
grub screw (46).
Unscrew
the bearing
screw
(66).
NOTE: Left-hand thread.
Lift the
bearing
frame (55).
Remove
washer
(65) and
spring case
(64). When
reassembling, make sure the helical spring
snaps into
the cutout of bearing
frame (55).
Slide-in the washer
(65). Tighten
the
bearing screw (66).
Install the tone arm
(50).
Adjust
the
bearing backlash with the
grub screw (47) and the lock nut (46)
as below described.
To Adjust the Tone Arm
Bearings
Exactly balance the
tone arm. Both bearings should have a small,
just perceptible backlash or play. Proper
adjustment of the hori-
zontal
bearing is
achieved if
the tone arm can freely
slide from the
record inside to outside while
the anti-skating adjustment is 0.5.
Proper adjustment of the vertical bearing is achieved when
the
carefully kicked tone arm
swings into balanced position.. Adjust
the
backlash by grub screws (44) and (46) for the
horizontal and
vertical bearing, respectively.
Fig.
11
Tone Arm with Bearings
The light-weight torsion-resistant aluminum-tube tone arm
has a
universal gimbal bearing characterized by four hardened and
lapped steel points located in high-precision ball bearings. The
tone -arm bearing friction is thus reduced to a
minimum, namely
less than 0.10 mN or 0.010 gr in vertical and
less than 0.40
mN or 0.040 gr in horizontal direction,
referred
to the stylus point.
This ensures particularly satisfactory tracking conditions. Before
adjusting the tracking
force, which should comply with the pick -
up system used, adjust the tone
arm to its balanced position while
the tracking-force
scale indicates zero. For coarse balancing, shift
the weight (51) with mandrel; for fine
balancing, rotate the weight.
This
weight permits balancing of
pickup systems weighing bet-
ween 4.5 and 10
gr including mounting
material.
The tracking
force is produced by tensioning the helical spring
located in the
spring case (64). The 'atter has a scale with marks
permitting
exact adjustment of the tracking force within the
range
0-
50 mN
(or 0 -
5
9r).
To Remove die Tone Arm from its Bearing Frame
1. Mbunt
the record player in the servicing fixture (repair ijg).
Remove the weight (51) and tensioning screw
(58). Adjust
the scale of
the spring case (64) to zero.
2. Turn the
record player into head position. Remove the shield
(149). Unsolder thetone-arm leads from the
muting switch (146).
3 Record player in normal position.
Screw the two mounting
screws (60) counterclockwise until they abutt against the
bearing
frame
(55).
NOTE: Bayonet union. Shift the tone
arm to the rear and lift it
from the bearing
frame (55).
To assemble, proceed in reversed sequence.
To
Remove Tone Arm Complete with Bearings
1. Mount the record player in the repair jig. Adjust the tracking-
force
scale on the spring case (64) to zero. Lock the tone arm
(50) in place. Remove the weight (51).
2. Adjust record player to
head position. Remove the shield (149).
Unsolder the tone -arm
leads from muting switch
(146).
3. Remove the main lever (177). Remove the lock washer (242).
Rotate the set screw (42) until guide bearing (241) and set-
ting bar (228) come free. Remove lock washer (228) and set-
ting bar
(204).
4. Unlock the tension spring (212), loosen the lock
washer (216)
and remove skating
lever (215).
64
5. Remove lock
washer (202) from segment (200).
6. Remove hex. nuts (202) and segment
(200).
7. Hold the tone arm (50). Remove hex. nut (42) and washer
(41).
Remove tone arm complete with bearings.
To install the
tone arm, proceed in reversed
order.
Anti-Skating Device
To adjust the anti-skating
force, operate the pointer scale provi-
ded on the cover (67).
Depending on this adjustment, the
skating
lever
(215) will be deflected from the tone -arm
pivot point. The
anti-skating force is
transmitted by the tension spring (212) to
the segment (200) and thus to the tone arm
(50).
The factory adjustment is
optimal for any stylus having a spheri-
cal
tip radius of 15 /Im or
elliptical of 5 - 6 and 18- 221.1m as
well as for CD 4 pickup systems.
These factory-adjusted values may
bevaried only m an authorized
Dual service workshop using a
Dual Skate -0 -Meter and a test record.
6