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Chapter 6 Audio System

Section 1  Audio System Description

Description:

1. Radio Wave Band

The radio wave bands used in radio broadcasting are as following:

LF:  Low frequency

MF:  Medium frequency

HF:  High frequency

VHF:  Very High frequency

2. Cover Area

There are great differences in the size of the

cover area for AM and FM monaural. Some-

times FM stereo broadcasts cannot be received

even though AM comes in very clearly. Not only

does FM stereo have the smallest cover area,

but it also picks up static and other types of in-

terference ("noise") easily.

3. Reception problems

Hint:

Besides the static noise fault, there are also the faults called "interference", "multipath transfer" and "fade

out". These faults are caused not by electrical noise but by the nature of the radio waves themselves.

(1) Interference

Besides static noise fault, AM broadcasts are

also susceptible to other types of noises, es-

pecially at night. This is because AM radio

waves are reflected by the Ionosphere at

night. These radio waves then interfere with

the signals from the same transmitter that

reach the vehicle's antenna directly. This type

of noise is called "interference".

Band

LF

MF

HF

VHF

Radio wave

AM

FM

Modulation

Frequency    30KHZ      300KHZ        3MHZ      30MHZ      300MHZ

Amplitude modulation

Frequency modulation

FM (Stereo)

FM (Monaural)

Interference

Ionosphere

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(2) Multipath transfer

Noise caused by bouncing of radio waves off

obstructions is called "multipath transfer".

Multipath transfer occurs when a signal from

the broadcast transmitter antenna reflects off

buildings and mountains and interferes with

the signal that is received directly.

(3) Fade out

Because FM radio waves are of higher frequen-

cies than AM radio waves, they are reflected

off buildings, mountains, and other obstructions.

For this reason, FM signals often seem to gradu-

ally disappear or fade away as the vehicle goes

behind a building or other obstructions. This is

called "fade out".

4. Noise faults

For noise troubleshooting it is very important to understand the feedback information from the customers

well, so make the best use of the following questionnaire and diagnose the fault accurately.

HINT:

In the case that the noise occurrence condition does not meet any of the above, check based on the "Recep-

Multipath 
Transfer

Fade out

Radio Wave

Operating condition when

noise occurs

Cause

Noise occurs at a specific

place.

Strong possibility of foreign noise.

Noise occurs when listening

to faint broadcasting.

There is a case that the same program is broadcasted from

each local station and that may be the case you are listening

to different station if the program is the same.

Noise occurs only at night.

Strong possibility of the interference from far distant

broadcasting.

Noise occurs while driving

and at a specific place.

Strong possibility of multipath transfer interference and

caused by the changes of FM waves.

AM

FM

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tion Problems".

5. COMPACT DISC PLAYER

Compact Disc Players (hereinafter referred as CD) use a laser beam pick--up to read the digital signals

recorded on the CD and reproduce analog signals of the music, etc.

HINT:

Never attempt to disassemble or oil any part of the player unit.

Do not insert any object other than a disc into the disc box.

NOTICE:

CD players use an invisible laser beam which could cause hazardous radiation exposure. Be sure

to operate the player correctly as instructed.

6. MAINTENANCE

(1) Tape player/magnet head cleaning:

1

Raise the cassette door with your finger.

Next, using a pencil or similar object, push in

the guide.

2

Using a cleaning pen or cotton applicator soaked

in cleaner, clean the magnet head surface, pinch

rollers and tape press wheel.

(2) CD player/disc cleaning:

If the disc gets dirty, clean the disc by wiping the surface

from the center to outside in the radial directions with a

soft cloth.

NOTICE:

Do not use a conventional record cleaner or anti--

static preservative.

Example

Magnet Head Tape Press Wheel

Pinch Roller

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Section 2 Audio System Connector Terminal Layout

1. Connector terminal layout on wire harness

2. Connect terminal definition

Terminal

No.

Function

Wire color

Condition

Standard Voltage

A1

FR+

Lg

The audio system is on

Wave form is synchronized with
the output sound

A2

FL+

YB

The audio system is on

Wave form is synchronized with
the output sound

A3

ACC

RW

Ignition switch turned to ACC 10～14V

A4

B+

R

Constant Status

10～14V

A5

FR-

LgR

The audio system is on

Wave form is synchronized with
the output sound

A6

FL-

Y

The audio system is on

Wave form is synchronized with
the output sound

A7

GND

B

Constant Status

Continuity

A8

Null

A9

Null

A10

TAIL

GW

Position lamp switch turned to
ON

10～14V

B1

RR+

PB

The audio system is on

Wave form is synchronized with
the output sound

B2

RL+

YR

The audio system is on

Wave form is synchronized with
the output sound

B3

RR-

P

The audio system is on

Wave form is synchronized with
the output sound

B4

Null

B5

Null

B6

RL-

YW

The audio system is on

Wave form is synchronized with
the output sound

C1

B+

Constant Status

10～14V

C2

BUS

Audio system is On

Pulse Signal

C3

GND

Constant Status

Continuity

C4

ACC

Ignition switch ACC

10～14V

C5

Null

C6

R-OUT

The audio system is on

Wave form is synchronized with
the output sound

C7

L-OUT

The audio system is on

Wave form is synchronized with
the output sound

C8

GND(Audio

Frequency)

Constant Status

Continuity