4.
Design. The tape spools are made of heavy aluminum or plastic, designed to
prevent warping or damage to the tape.
Do not attempt to use any reels/ spools
which are not designed to fit the reel turntable.
Also, do not attempt to use
reels for a different width of tape.
5.
Type of tape required. Tape used for recording a new program may be either
unused tape or tape that is already recorded. The erasing of tape on the recorder
requires the tape to move across the erasing head and takes the same time as
recording the tape. However, for faster and more complete erasing of a prerecorded
tape, it is best to use a good bulk eraser. With a bulk erase, the entire reel of
tape may be erased at one time.
a. In the record mode, normally, the erase heads are all active to provide
paths for each of the recording heads.
There are variations to this when it is
desired to add additional narration without changing the original audio. Depending
on the model recorder/reproducer available, various capabilities are available in
the record mode.
You should refer to and study the operations and maintenance
manuals for a specific model for accuracy of operations and maintenance.
b. The playback mode will normally find the erase heads deactivated.
The
record/reproduce heads are switches to act as input to an amplifier for playback.
Again, a selection of activities or mode variations is available, depending on the
model of recorder/reproducer in use.
For example, one variation of the playback
mode found on some recorders/reproducers is that the narration may be recorded
while the video is being played back.
6.
Speed and types of tachometers. Since the video head is considered the heart
of the transport, the speed at which it operates is also important.
The audio
recorder/reproducer can tolerate some variations in speed, but the video unit
cannot.
a. To control the speed of the head, the head drum is controlled by the
output of the servo circuit. As previously discussed under frequencies, the servo
frequency is a combination of frequency inputs.
One of these is the tachometer
input used in combination with one or more of the other inputs. The actual design
of the tachometer varies among many models.
It may be a single magnetic pickup
with a single tach detector (fig 2-5) or it may be a wheel with multiple tach
detector serrations (fig 2-6) set equally around its circumference to generate
pulse into a transducer pickup.
b. The tachometer then mechanically generates pulses relative to the speed of
the capstan. Thus, if the actual speed is too slow, an error voltage is generated.
The error voltage causes a change in the oscillator frequency that changes the
output of the servo-amplifier, and the motor speed increases.
c. The instantaneous correction keeps the transport at the correct speed. On
some models a manual tracking control changes the oscillator frequency enough to
delay or speed up the drive motor to synchronize it with the tape tracks previously
recorded on tape.
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