Pinch Roller Adjustment; Tension Post Adjustments - Scully 280B Series Instruction And Maintenance Manual

7-6
Maintenance
Model 280B
Figure 7-5. Tension Post Adjustments
arm hits its nylon stop. On rack-mounted units
(transport operated in the vertical position), set
the tension of the tape break arm to the minimum
tension required to prevent the arm from resting at
the dead center (vertical) position.
7-6. Pinch Roller Adjustment (Figure 7-6)
The pinch roller adjustment is made by means of
the nut (2) at the end of the threaded connecting
rod (3) which provides the link between the sole ­
. noid (4) and the pinch roller actuating arm (7).
Tightening this nut (2) increases the roller pressure.
Excessive pressure places an unnecessary and unde ­
sirable load on the upper (sleeve) bearing of the
capstan motor, and a point is reached where fur ­
ther turning of the nut will prevent the solenoid
plunger from bottoming. At this point, roller pres ­
sure drops rapidly, becoming inadequate to drive
the tape without slippage. It is then necessary to
back off the nut.
The rubber pinch roller bearing has been selected
for minimum radial runout. The radii of the inner
and outer raceways of this bearing are larger than
the ball; therefore, some rocking freedom can be
felt . When the pinch roller is actuated, this freedom
Figure 7 -6. Pinch Roller Adjustment
allows the face of the pinch roller to align with the
capstan, thereby minimizing tape distortion from
any scrubbing action between these two compo­
nents. The pinch roller adjustment procedure is as
follows:
A. Thread tape on the machine. Remove tape
from between the capstan and pinch roller so
that the tape rides on the bottom (operator)
side of the capstan when the machine is in the
Play mode.
B. Loosen the Allen setscrew on the capstan sole ­
noid adjustment nut (2).
c.
With the machine in the Play mode, use a zero­
to-15 lb (6.81 kg) tension scale to push against
the arm in line with the pinch roller shaft.
Align scale pressure so that the force of the
scale tends to remove the pressure of the roller
from the shaft.
D. Push on the scale until the pinch roller stops
rotating, indicating that the pinch roller had
just broken contact with the capstan.