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reel can spool it.
Thus S7 provides for breaking the negative line through RIO or
R 11 as needed.
This feature is only applicable to 1/ 2-inch machines.
The switch,
,
..1
although provided, is inactive in 1 /4-inch machines.
TORQUE CONTROL RELAY ('I..-inch machine, only)
Due to the light weight and inertia of the small plastic reels commonly used
on 1 /4-inch machines, th'ere is a tendency for a loop to form in the tape between the
outgoing tape guide and the reel receiving the tape if negative torque is applied through
RIO or Rll before the tape has come to rest and started to move in the opposite
direction.
To preven.,t reverse torque from being applied until the tape has begun to
travel in the direction of the se
l
ected mode, K13 is installed in the socket provided
on the transport near the rewind motor
.
Reel size switch S7 is not connected as
sta ted above.
Consider the tape to be in motion in the fast forward direction with K6 ener
gized. Pressing the REWIND pushbutton energizes K7 and releases K6.
Drive torque
is immediately transferred from the take-up motor to the rewind motor
.
Due to the
momentum of the reels traveling in the forward direction, the tape does not come to
an immediate stop but continues to travel in the forward direction until this momen
tum is overcome by the dynamic braking action caused by the reverse torque applied
to the rewind motor, which is attempting to pull the tape in the opposite direction.
During this slow down period, directional sense switch S14 is open. which maintains
KU in the deenergized position.
Therefore, the circuit path to the take-up motor
armature is broken at K13 contacts 5 and 9. causing the motor to coast to a stop
under the braking action of the rewind motor only.
As the tape motion comes to
rest and starts to reverse its direction, S14 closes.
Buss power is app'lied to K13.
providing negative torque power through contacts 5 and 9. RIO. etc .. to the take-up
motor and causing
it
to turn in the same direction as the rewind motor.
This action
reduces the drag on the rewind motor and aids acceleration as described under
"Ree,[
Size Switch." Thus, K13, in conjunction with directional sensing switch S14, pre
vents negative torque power from being applied to the appropriate reel motor until
the tape has come to rest and starts to accelerate in the opposite direction
.
Monitor Switching
Two pushbuttons on the transport, S10 and SII, are arranged to transfer the
output line amplifier and VU meter of each eLectronics circuit board from the in
coming signal source to the playback and vice versa.
Pressing A switch S10 appLies
,
.
........ '*'
bus voltage from J6-D through J2-9, J2-10, and S10 to J4-5, which is in the elec
tronics power connector, causing operation of transfer reLays in each moduL-e.
Similarly B switch SII appLies bus potentiaL to terminal J4-4 to cause reverse
.
,.../
operation of the transfer relays
.
These switches are
momenta~y-contact
types and
are not lighted.
"
_."
M64 PAR 2-71
84
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