Ampex 351 - Page 50

CONTROL CIRCUIT BOX
ARM SOLENOID
REEL IDLER AND FLYWHEEL
B503 REWIND MOTOR ASSEMBLY
CAPSTAN SOLENOID B502 TAKE UP MOTOR ASSEMBLY
CASTAN IDLER RETURN SPRING
Component and assembly callouts
6-2
8501 CAPSTAN DRIVE
MOTOR ASSEMBLY
CAPSTAN IDLER ADJUSTMENT
MICROSWITCH ITAKE-UP TENSION ARM)
L- ERASE
RECORD
89-0131
89-0144
Issue A
Component and assembly callouts
the machine if tension is lost due to tape break 
age at the end of the tape or other failure. Near
the base of the shaft on which the tension arm
is mounted, a drive-lock pin actuates the safety
switch (S501).
Both the tape supply and take-up assemblies
are composed of induction torque motors
(B503 supply-rewind, B502 take-up), a turn 
table mounted directly on each motor shaft, a
brake housing assembly and a flange for
mounting the entire assembly. Because the
brake housings are mirror images of each
other, these assemblies are not interchangeable
although the motors arc identical. The brakes
are solenoid operated, remaining in the braking
position until the brake solenoids K505 and
K506 are energized at which time the brakes
are released.
During all operating modes, the two induc 
tion torque motors B502 and B503 act as ten 
sioning devices and in the fast forward and re 
wind modes the motors respond to the com 
mands from cither pushbutton by alternately
operating each motor at maximum torque in
the selected function.
The supply (rewind) and take-up induction
torque motors are so connected that when
power is applied with no tape threaded, the
turntables, fixed to their shafts, will rotate in
opposite directions. The tape supply turntable
will rotate clockwise and the tape take-up turn 
table, counterclockwise.
Motor torque in the reproduce and record
modes is adjusted to equality by the tensioning
adjustment resistors (R503 TAKE-UP and
R503 HOLDBACK) in series with each motor.
In the fast forward mode, the torque of the
supply (rewind) motor is reduced considerably
by introduction of a series resistance (R504).
In the rewind mode, R504 is in series with the
take-up motor. Basic tape tensioning operation
is shown in the illustrations.
In the fast forward mode, the take-up motor
operates at full torque, the supply motor at
reduced torque, and the tape is pulled from the
tape supply reel. Because the torque of the tape
supply turntable motor (rewind motor) is ap 
plied in the opposite direction to the turntable
rotation, the tape is held under continuous
tension as it is pulled from the reel.
In the rewind mode, the supply motor oper 
ates at full torque and the take-up motor holds
the tape under continuous tension by its oppo 
site and reduced torque.
In the reproduce or record modes, both
torque motors operate at the same value of
reduced torque. The tape drive capstan and the
capstan idler, between which the tape is
clamped, then determines the tape speed, and
the tensioning system supplies tape or takes it
up as metered by the capstan drive.
From the point of view of the tape supply
turntable, the capstan and idler action exerts,
sufficient pull on the tape to overcome the op 
posing torque of the supply motor, which con 
stitutes the hold back tension. From the point