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Record Mode Operation
The record mode can be selected only when the PLAY lamp is lit, indicating
that the machine is running at normal speed.
It is then necessary to press both the
RECORD and RUN
pushbuttons simultaneously.
Bus power is applied through
J6-D, J2-9, J2-10, SS, Sl, JS-13, and K3 contacts 7 and 11 to operate K2, which
then locks up to the holding path for K5.
This path is KS contacts 8 and 12, and K2
contacts 8 and 12.
The path established to hold K2 then lights DSI through J6-3
and supplies positive bus voltage to the electronics power cable through connector
J4-9.
Relay K2 contacts 11 and 7 also supply ground potential to the same connector
through J6-T to J4-10.
The positive potential is also applied through R16 and CR29
to the bias oscillator.
Capacitor C7 is provided both for decoupling and for delayed
decay after power is removed.
Transistors Q2 and Q3 operate as a low power,
push-pull oscillator to provide a high-frequency signal to terminals J6-U and J6-V.
The electronics assembly cable conducts high-frequency bias to all bias boards in
the electronics through J4-1 and J4-2.
The oscillator is tuned to 120 kHz by
capacitor Cll.
Speed Change Switch
Speed change switch S selects windings of the capstan ITlOtor to provide either
of two speeds.
These are related by the ratio 2:1 and therefore can be provided for
tape speeds of 7-1/2 and 15 ips, or 15 and 30 ips.
Dc bus potential is supplied to
either J4-6 or J4-7 in the electronics power cable, depending on the motor speed, in
order to contrql equalizer-select relays in the electronics circuit boards.
Reel Size Switch
Reel size switch S 7 provides for adjustment of torque in fast forward or in
rewind when one spindle carries the normal large reel and the other carries a
light-weight reel.
If
both reels are the same size, the switch is left in the center
BALANCE position.
If
the large reel is on the tape takeup side, the switch is
moved toward the right, or toward the la rge reel (in the direction of the arrowhead
on the panel).
If
the large reel is on the left, or supply side', the switch is moved
to the left.
In the center position, S7 connects J5-N to J6-1 and J5-lS.
If
K6 is
energized, putting the machine into fast forward, heavy dc current flows through
the takeup motor, returning to the negative supply through R60.
Thus J5-L is a
few volts more negative than J6-S.
This negative potential is applied through
CR30, S7, and R 11 to the rewind motor, causing it to deve lop small torque in the
same direction the take up motor tends to turn.
This aids acceleration.
Similarly,
in rewind, RIO supplies reverse torque to the takeup motor, assisting in getting
the tape up to high speed.
When a small reel is on one side, however, this
assistance is not desirable since it may tend to unwind tape faster than the other
M64 PAR 2-71
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