of turns of wire is required in the winding since the head must-be sensitive to the changes in flux
recorded on the tape. The playback head functions in an opposite manner to the record head; that is, the
tape induces a flux into the head core. The flux passing through the core induces a voltage into the
winding, causing current in the associated circuit. This signal current is amplified by the playback
amplifier for operation of speakers, headphones, or other devices. The playback head is of prime
importance in the faithful reproduction of a recorded signal. For example, if we assume that a head is
good mechanically, and it is playing back a signal which has all frequencies recorded with equal
magnitude, we will find that the higher audio frequencies will produce a greater voltage output.
(1) An inherent characteristic of a playback head is that the rise in output is proportional to
the rise in frequency response. However, remember that although a new head may have a narrow gap,
as the head wears, the gap becomes wider, and as a result, the high-frequency response drops off.
(2) Also, along with gap width, the definition of the edge of the head must be smooth to
produce high frequencies. If the edges of the gap are not straight and sharp, the gap behaves
magnetically as though it were much wider than its physical dimensions.
f. Other factors which affect the frequency response of the head are tape speed, smoothness of
the tape, pressure of the tape against the head, and quality of the tape. The tape speed is important
because the more rapidly the changes in flux are drawn across the head gap, the stronger the voltage
induced into the head gap, and the stronger the voltage induced into the head windings. This added
strength, in turn, gives improved frequency response to the recorded signal. You can understand this
condition if you consider that a slow moving tape causes the head to see an average change in the flux
and not each small change, which is necessary to reproduce high frequencies. Smoothness of the tape
and tape-to-head contact are directly related in their effect on frequency response as well as voltage
output. If the tape is rough, the magnetic particles are not maintained constantly closed to the head,
which is necessary to induce a smooth flow of flux variations. The rough spots or portions of the tape
move the particles farther from the head and cause weakening of the flux changes; thus, the high
frequencies are lost. Carrying this through further, you can understand that the same losses are prevalent
if the pressure holding the tape against the head is weak.
Learning Event 2:
DESCRIBE AND IDENTIFY MAINTENANCE PROCEDURES FOR PROPER OPERATION OF AN
AUDIO TAPE RECORDER
1.
Electronics. Typical electronic circuits used in tape recording are indicated in Figure 3-7. There
are certain refinements as dictated by performance requirements. Normally, the higher the frequency
response required, the better the overall quality of the circuit components. Even though the record head
preemphasis makes it important to use the correctly
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