Dual 621 - Tonearm System; Tonearm Overview and Removal Procedures; Tonearm Adjustments and Replacements

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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