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capstan.
Before entering and after leaving the Isoioop. the tape passes over
stationary guides to ensure that is properly aligned with the magnetic heads.
When the transport is in the play and record modes, solenoids press the
capstan idlers against the tape, clamping it to the capstan to prevent
it
from
slipping.
The tape is moved past the income idler and capstan. past the erase and
record heads, and around the reversing idler.
From the reversing idler. it passes
the play head, and the outgoing idler and capstan.
During fast-forward and rewind.
solenoid-actuated tape lifters hold the tape away from the tape so that signals on
the tape will not be played back, which would cause an annoying squeal.
The tape
lifters are inactive in play, record, and stop modes.
The play head is enclosed in a magnetic shield to avoid pickup of noise from
surrounding equipment and bias-frequency energy radiated by the erase and record
heads.
A solenoid-actuated cover is positioned over the tape as
it
passes the play
head and serves to complete the shielding of the head.
During fast-forward, rewind,
and stop, the hinged cover is moved away from the head to allow the tape to be lifted
by the tape lifters and allow easy threading of the tape.
The cover is closed during
play and record.
TAPE TRANSPORT CIRCUIT DESCRIPTIONS
The following circuit descriptions relate to figure 25 which must be used to
follow the discussions.
In the schematic, connector terminals are shown as small
rectangles with the connector and terminal numbers inserted.
Power Circuits
A standard, three-wire power cable is provided, which must be connected
at J1.
The third, or ground, lead must be connected to a good earth ground;
otherwise the recorder will not meet dynamic range specifications in regards to
hum, harmonic buzz, or radio-frequency fields.
The power is 105 to 125 volts,
but 50 or 60 cycle models for the same voltage range are available and entail only
a change of capsta n motor characteristic s.
The schematic othe rwise rema ins
unchanged.
For 220 volt operation an external line transformer must be used.
The POWER switch, 56, when operated, closes both sides of the input line
activating a number of circuits.
These are as follows:
1.
Bridge rectifier CR46 through CR49 charges capacitor C65 through
R60 approximately 165 volts in the absence of a load.
This voltage
is applied through J7-2 and J9-1 to the fields of the take up and rewind
motors.
Field returns are through J7-1, and J9-2 through J6-4, and
K 1 contacts 6 and 10.
Relay K 1 operates as soon as power is turned
on unless the transport has been previously threaded with tape.
M64 PAR 2-71
75
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