Volvo Trucks North America, Inc. Date Group No. Page
Service Bulletin 4.2004 392 08 23(47)
Cassette Tape
Cassette tapes operate on the basis of magnetics. When
an unrecorded tape passes through the record head,
the oxide particles are magnetized such that the pattern
represents electronically the sound information that
one wishes to record. Once the information has been
recorded, it is played back by the tape passing over the
playback head. The magnetically stored information is
decoded as electrical voltages. These differences in
voltages are amplified through several stages until an
audio signal is obtained.
Cassette Tape Player
Those parts most important in the playback of a cassette
are; the supply reel, take-up reel, capstan, pinch rollers
and the tape head. When the cassette is properly loaded,
the motor starts. The motor will then rotate the capstan.
(The capstan is a rod which comes up, rotates and allows
the tape to feed over the head.) One of the pinch rollers
comes forward and “squeezes” the tape between it and
the capstan. Simultaneously, the head pulls into place.
For the cassette to play, the head can be no more than
0.7–0.8 micros away from the tape head. (A human hair is
typically 60–100 micros thick.) The tape then passes over
the playback head. The magnetic information stored on
the tape is read by the playback head and then converted
into an electrical signal. This signal, on the order of 90
mV (millivolts), is sent to a pre-amplifier in the cassette
player. The pre-amplifier creates a signal of about 0.58 V.
This signal is sent to the receiver where it is amplified and
played at the specified level.
W3003392
1 Auto reverse tape drive
2 Tape head
3 Capstan
4 Pinch roller
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