Dual 506 - Tone Arm and Bearings; Tone Arm Removal (Complete); Tone Arm;Spring Housing Removal; Tone Arm Bearing Adjustment

Rotate
the knob 16 to move the belt pulley
112. This rotary
motion is transmitted by the toothed belt
109 to the belt pulley 1
105, see Fig. 2. As a result, the
counter bearing 113 and the
taper sleeve of the motor
pulley 116 are shifted up or down.
As an effect of the taper sleeve,
the motor pulley diameter is
reduced or increased, respectively,
thus permitting to change the
rated
speed within the range of ± 3 %.
Stroboscope
Accurate setting of the platter speeds 33 1/3 rpm and 45 rpm
can be checked during play with the aid of the stroboscope de-
vice. On the platter 4
rotating at exactly the desired speed, the
lines
of the stroboscope appear to stand still. If the lines of the
stroboscope move in the direction of the platter rotation, the
platter speed is too high. If the lines move backwards the platter
is rotating more slowly than nominal speed. The four rows of
stroboscope marks on the edge of the platter, taken botton to
top, are for the following speeds:
331/3
rpmat 60 Hz,
331/3
rpm
at 50 Hz, 45 rpm at 60 Hz, 45 rpm at 50 Hz. Adjustment of the
platter speed is
carried out using the regulating knob 16.
Fig. 6
46
Fig. 7
55
39
41
207
Tone arm with Bearings
The light-weight torsion-resistant metal-tube tone arm has a uni-
versal 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 0.07 mN or
0.007 gr in vertical and
less than 0.15 mN or 0.015 gr in horizontal direction
referred to the stylus point.
This ensures particularly satisfactory tracking conditions. Before
adjusting the tracking force in compliance with the pickup
system used, the tone
arm to its balanced
position
while the
tracking-force scale is in the zero position. For coarse balancing,
shift the
weight 41, for fine balancing, rotate the weight.
The tracking force is produced by tensioning the helical
spring
located
in the spring case 63. The latter has a scale with marking
points permitting exact adjustment of the tracking force within
the range 0-30 mN (or 0 - 3 g).
To
Remove the Tone arm Complete
with Bearings
1. Mount the
record player in the servicing
fixture. Adjust the
tracking-force
scale 54 to zero. Lock the
tone arm 40 in
place. Remove the weight 41.
2. Adjust record player in head
position. Remove shield 158.
Unsolder the tone arm leads from
terminal strip 156.
3. Unhook the tension
spring 226 from the bearing bracket
224. Rotate bearing
part 195 through 90 0 degrees
and
remove it. Detach the setting bar 194.
4. Unhook the tension spring 214.
Remove lock washer 210
and skating lever 207.
5.
Remove
lock washer
217 and disk 216.
Detach the
shut-
off bar 215 from the segment 211.
6. Slacken the hex. nuts 213 and the screw 204.
Remove the
bearing 205 and
the segment 211.
7. Grip
the Frame 47 and the tonearm 40. Loosen the machine
screw 48 and take off the tonearm and frame.
To install the tone arm, proceed in reverse sequence; however,
make sure
the segment 211 is properly adjusted as described on
page 6.
To Remove
the
tonearm or the
spring
housing
1.
Secure the
unit in a
repair
stand. Turn the
rotary
turn switch
54 to the
zero
position. Lock
the
tonearm 40.
Remove the
counterweight 41.
2. Turn
the unit
over.
Remove the
screening
sheet 158
and
solder off
the
tonearm
connections at
the
connection plate
156.
Turn the unit
the right
way up.
3.
Remove the
fillister
head screw
55.
Remove the
rotary turn
switch
54 and the
washer 53.
4.
Loosen the
nut 54
and the
grub screw
46. Draw
the tone -
arm
40
complete with
bearing 56
from the
bearing
race 49.
The spring
housing 52
or the
tonearm 40 may
now be
changed.
Reassembly
involves the reverse
procedure.
213
To Adjust the Tone arm Bearings
211
Exactly balance the tone arm. Both bearings should have a small,
just perceptible
backlash. Proper adjustment of the horizontal
bearing is achieved if the tone arm can freely slide from the re-
cord Inside to
outside while the anti-skating
adjustment is 0.5.
Proper adjustment of
the vertical bearing is achieved when the
the carefully
kicked tone arm swings into balanced position.
Adjust the backlash by grub screws 46, 51 for the horizontal and
vertical
bearing, respectively.
194
215
4