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From Stop to Rewind
With the machine in standby, pressing REWIND pushbutton S2 causes bus
voltage to be applied through K3 contacts 10 and 2, J6-11, J2-12, J2-11, S3, S2,
J5-R, and KB contacts 2 and 10 operate K7.
The relay applies rewind torque
through K7 contacts 5 and 9 as outlined above, and K7 locks up to the power bus
through K7 contacts 11 and 7, and KB contacts 2 and 10.
The tape accelerates in
the rewind direction with full power on the armature of the rewind motor.
Since
this is a de shunt motor, it would reach a certain terminal velocity at which time
tape would be loosely wound except for the following feature.
As the tape comes
up to speed in rewind, the armature of the takeup motor is open circuited because
of the break at K7 contacts 2 and 10.
It operates as a dc generator without load
until a definite terminal voltage is reached, the voltage rising as the speed increases.
Zener diode CR53 will not pass current until the potential across it reaches 75 volts.
Therefore, when the generated voltage reaches this level, current flows through
J9-4, J6-S, CR32, CR53, J6-2 and J9-3 to act as a load and effective brake on the
takeup motor, limiting the maximum speed at which it will supply tape and thereby
providing a controlled tension in the reel being filled.
Closure of K7 contacts 12
and
B
provides a path through CR24, J6-14, and TBI to open the head shield door and
through J6 -15 to operate the tape lifters.
From Rewind to Stop (Tape Moving in the Rewind Direction)
Pressing STOP switch S3 operates relay KB through K3 contacts 10 and 2,
J6-11, J2-12, J2-11, S3, and J6-B.
Since tape is moving in the rewind direction,
the sense switch vane has caused S13 to open and S14 to close.
Therefore, K6 is
caused to operate through J6-D. S14, and KB contacts 5 and 9.
Relay KB is locked
up through K6 contacts 11 and 7, KB contacts Band 12, and K6 is held up by S14.
Relay K7. however. is released by the break at KB contacts 10 and 2 and the fact
that S13 is open.
The power that was supplied to the rewind motor through K7
contacts 5 and 9 is removed by its release and transferred through operation of
K6 through K6 contacts 6 and 10 to the takeup motor, which now operates to bring
the tape to standstill and attempts to reverse it to the forward direction.
As soon as the sense switch vane moves away from S14 toward S13, S14 opens
releasing K6 and placing all circuits in the standby condition.
During the stopping
interval, the REWIND lamp goes out and the FOR WARD lamp is lit from release
of K7 and operation of K6.
In standby, the tape lifter solenoid i-s released and K-B
is released by the break at K-6 contact 7 and 11.
The head cover door remains
operated through S-12, J6-M and CR-26 unless manually overriden to break S-12.
Relay K4 remains energized throughout the above action, either through K7 contacts
12 and B, CR14; or through K6 contacts 11 and 7, CR14; or through K7 contacts
11 and 3, K6 contacts 12 and 4, KB contacts 11 and 3 and K5 contacts 12 and 4 and
CR 13.
M64 PAR 2-71
79
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