Audio System - Diagnostics: Description

RADIO WAVE BAND
The radio wave bands used in radio broadcasting are as follows:

Fig 1: Audio System Radio Wave Band Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

LF: Low Frequency

MF: Medium Frequency

HF: High Frequency

VHF: Very High Frequency
SERVICE AREA

Fig 2: Identifying Service Area For AM & FM Broadcasting
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. There are great differences in the size of the service area for AM and FM broadcasting. Sometimes FM stereo broadcast cannot be received even through AM can be received very clearly.
  Not only does FM stereo have the smallest service area, but it also picks up static and other types of interference ("noise") easily.
RECEPTION PROBLEMS
NOTE: Besides the problem of static, there are also the problems called "fading", "multipath" and "fade out". These problems are caused not by electrical noise but by the nature of the radio waves themselves.

Fig 3: Identifying Radio Waves Reception Problems (Fading)
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. Fading
  Besides electrical interference, AM broadcasts are also susceptible to other types of interference, especially at night. This is because AM radio waves bounce off 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 interference is called "fading".
2. Multipath
  
  Fig 4: Identifying Radio Waves Reception Problems (Multipath)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Interference caused by reflection of radio waves against obstructions is called "multipath". Multipath occurs when radio signals emitted from the broadcast transmitter antenna are reflected against tall buildings or mountains and interferes with other signals which is to be received directly.
3. Fade Out
  
  Fig 5: Identifying Radio Waves Reception Problems (Fade Out)
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Because of the frequency higher than that of AM, FM radio wave tends to be reflected against obstructions such as tall buildings or mountains. For this reason, FM signals often seems to gradually disappear or fade away as the vehicle goes behind those obstructions. This phenomenon is called "fade out".
NOISE PROBLEMS
1. It is very important for noise troubleshooting to understand a customer's claim clearly. Use the following table to diagnose the phenomenon.
Fig 6: AM & FM Radio Wave Noise Problem Diagnostic Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NOTE: If the condition where the noise occurs does not meet any of the above, find out the cause based on "Reception Problems". Refer to the description about Multipath and Fading mentioned previously.
COMPACT DISC PLAYER
1. Compact Disc (hereafter called "CD") Players use a laser beam pick-up to read the digital signals recorded on the CD and reproduce analog signals of the music, etc. There are 4.7 in. (12 cm) and 3.2 in. (8 cm) discs available for the CD player.
NOTE: Never attempt to disassemble or oil any part of the player unit. Do not insert any object other than a disc into the magazine.

NOTE: CD players use an invisible laser beam which could cause hazardous radiation exposure. Be sure to operate the player correctly as instructed.
MAINTENANCE
Tape Player/Head Cleaning:

Fig 7: Cleaning Head Surface, Pinch Rollers & Capstan
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. Raise the cassette door with your finger.
  Using a pencil or similar object, push in the guide.
2. Using a cleaning pen or cotton applicator soaked in cleaner, clean the head surface, pinch rollers and capstans.
MAINTENANCE
CD Player/Disc Cleaning:

Fig 8: Cleaning CD Player/Disc
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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.

NOTE: Do not use a conventional record cleaner or anti-static preservative.