Constant Tension Adjustment; Constant Tension Adjustment Procedures - Scully 280B Series Instruction And Maintenance Manual

Maintenance
E. Adjust the capstan solenoid adjustment nut (2)
to obtain a 6 lb (2.72 kg) indication on the
tension scale.
F. Tighten the Allen setscrew on the solenoid ad ­
justment nut (2).
G. Check the gap between the pinch roller and
capstan. The gap should be approximately 0.10
to 0.30 (2.54 to 7.62 mm). Readjust the gap
by moving the L-shaped stop bracket (6)
mounted to face of capstan solenoid. Loosen
the two screws (5) in slotted holes and move
the bracket as required. Be sure that the rod
(3) from the solenoid to the pinch roller does
not bind in the slot of the bracket.
7.7 Constant Tension Adjustment
[:~~~~~J
High voltage is present on the tension sensor PW A.
A. Open the screw valve on the airpot until the
damping effect is not noticeable.
B. Connect a Simpson Model 270 or equivalent
VOM set to the 250 Vac scale, across the
supply motor terminals (J106 pin 3 and
NEUTRAL).
C. Loosen the locknut on resistor R204 on the
power supply, Figure 7-7. Turn R204 for a
minimum resistance (fully ccw). Hold a piece
of black paper in the slot of the opto coupler.
Put the machine in Play mode and observe the
VOM.
It
should indicate 85
±5
volts rms.
D. Tum R204 cw until the voltage drops 3 volts
rms. Record this voltage. Tighten the lock nut
on R204.
E. Check that the optical grating is rotating in the
center of the opto coupler slot as shown in
Figure 7-8 A and B.
F. Loosen the setscrew on the coupler, Figure
7-8A, and move the dancer arm to the fully
ccw (from the top) position. Position the opti­
cal grating for minimum voltage reading across
7-8
Model 280B
A
This centering is important
to obtain voltage in step
F.
B This centering is important
only to avoid contact during
operation.
c
Approximately 45° for
minimum voltage.
Figure 7-8. Constant Tension
Adjustment Procedures.
the motor (see Figure
7-BC).
The VOM should
indicate 8 ±3 volts rms.
G. Move the dancer arm to the 7:00 o'clock posi­
tion (from the top). The voltage should be the
same as recorded in step D.
H. Place a tape tensiometer on the tape between
head bridge and capstan. Adjust spring on con ­
stant tension, Figure 7-9, to obtain proper ten­
sion as shown below:
0.25 in tape
=
3.5 to 4.5 oz
0.50 in tape
=
7 to 8 oz
1.
Close screw valve on airpot until the damping
effect causes the arm to bounce as it turns to
the stop. Open screw valve enough to allow
smooth travel of the arm. Open screw valve
one complete rotation.