E70, R56

CD changer / DVD changer audio / video (CDC/DVDC)

The CD / DVD changer is a separate control unit in the MOST network. The requests for the particular functions can be issued by various control units.

Brief description of components

CD changer / DVD changer audio / video (CDC/DVDC)

The CD / DVD changer serves to automatically play individual CDs / DVDs or several CDs / DVDs in succession. The order in which the CDs / DVDs or the tracks on the CDs / DVDs are to be played can be freely selected.

Head unit (CCC/radio/MASK and successor) with controller

Central Information Display: With a few exceptions, the Central Control Display (CID) incorporates the controls and display elements for all vehicle functions; it is activated by the CCC. The CCC coordinates the function requests from the system and assigns them to the relevant functions.

Controller: The CCC is operated by means of the controller located on the front centre armrest.

MOST bus

The MOST (Media Oriented Systems Transport) bus links the audio, video and navigation systems. Information relating to function requests is transmitted to the relevant control units by means of MOST bus messages.

System functions

The following system functions are described for CD / DVD changer:

• Mounting/damping
  
• Playback
  
• Changing
  
• Muting
  

Mounting/damping

To achieve the desired sound reproduction quality, the CD / DVD changer's playback mechanism is spring-mounted. During normal driving, shocks are adequately damped in order to balance out road-surface irregularities. For the improvement of quality, the CD / DVD changer is also fitted with an electronic correction device.

In the case of extremely hard suspensions or at high speeds, vibrations can occur which will cause the playback mechanism to come into contact with the housing. The electronic correction device cannot compensate for such flaws and there will be a resulting reduction in quality.

Playback

When a CD / DVD is played, the digital information is read by a laser beam in the CD / DVD changer. The optical signals are converted into audio signals and forwarded to the Audio System Controller. The CD / DVD changer's drive only contains the CD / DVD which is actually being played at that moment. Further CDs / DVDs are stored in a magazine outside the CD / DVD changer.

Changing

• In the CD / DVD changing operation, the CD / DVD to be played next is removed from the internal magazine by two rubber rollers and placed in the playback position.
  
• Once the CD / DVD has reached the playback position, it is lowered and its centre hole located on a taper (clamped). Playback begins once the CD has been located in position.
  
• The CD / DVD is transported back into the magazine in the reverse order.
  

Muting

The ”mute” function mutes playback by the CD / DVD changer or reduces the audio volume. It may also stop the CD player. The ”mute” function is activated by the ASK on the basis of the following prioritisation:

1. Telephone
   
2. Traffic report
   
3. Navigation system announcements
   

Notes for Service department

Some complaints cannot be put down to CD / DVD changers that are not working properly. Such complaints may be caused by poor-quality CDs / DVDs or external effects on CDs / DVDs.

Malfunctions caused by poor-quality or damaged CDs / DVDs

Due to the particular conditions under which a CD / DVD changer operates in mobile applications, CDs / DVDs which are outside or right at the limit of the manufacturing tolerance can give rise to problems when they are played. Causes may be:

Inadequately deburred edges:

• If the outer edge and/or the inner edge is/are inadequately deburred, plastic burrs can become detached during transport through the rollers. These plastic burrs can adhere to the CD / DVD surface.
  
• If plastic burrs are indeed present, they can be pressed out when the CD / DVD is transported through the rollers and/or when it is located on the taper (clamped). The burrs will get into the mechanism, foul CDs / DVDs and the magazine and thereby cause malfunctions.
  
• The presence of plastic burrs will result in fine scratches on the surface of the CD / DVD if the pieces of plastic get into the magazine.
  Under unfavourable conditions, larger pieces of plastic (5-7 mm) can cause scanning faults (jumping) or they may render the CD / DVD table of contents (TOC) unreadable.
  

CDs / DVDs that are too thick:

• If the CDs / DVDs are too thick, the transport rollers may not be able to grip the CDs / DVDs or grip them properly.
  
• If several CDs / DVDs in the magazine are too thick, return of CDs / DVDs to the magazine is made difficult. Greater force is needed to transport CDs / DVDs that are too thick.
  
• If the CDs / DVDs are too thick, the dividers between the individual CD / DVD compartments may also be displaced. This means that return of a CD / DVD to its original position will not be possible.
  

Problems caused by single CDs (8 cm) with single adapter/protective film/protective coating/stabiliser rings

• CDs / DVDs with the features mentioned are thicker than normal CDs / DVDs.
  
• Singles may come apart from the adapter while being transported and thus jam the mechanism.
  
• Stabiliser rings can get trapped in the transport rollers.
  

Note: Do not use such CDs / DVDs in the vehicle CD / DVD changer.

Faults with transparent CDs / DVDs

If the protective coating has been inadequately vapour-deposited on the CDs / DVDs, the CDs / DVDs in question will be more transparent than usual in parts or as a whole. Although they can still be played, they no longer enable optical position monitoring by the photoelectric beams. Consequently, the CD / DVD cannot be detected.

Manufacturing defects

CDs / DVDs may have manufacturing defects on the layer on which the digital information is recorded. Such CDs / DVDs cannot be played in the vehicle.

In the event of faulty playback, there is no fault in the CD / DVD changer. Because of the vibrations that occur, other demands are made on fault correction in the vehicle than in stationary operation.

In mobile applications, the control range of the laser tracking must therefore be limited in its capacity to compensate for surface flaws.

Warpage

Very occasionally, CDs / DVDs may not be completely flat, i.e. they may be warped or buckled. With such CDs/ DVDs, electronic fault correction may no longer be able to compensate for the defect when the last track is played. When played, CDs / DVDs are read from inside to outside. Because warpage is at its greatest at the outer edge, there may be reduced reproduction quality at this point.

Faulty ”Eject” function

In the event of a faulty Eject function, the individual CDs / DVDs cannot be removed from the unit. The control unit functions can be used to run the job ”Eject all”. If the CDs/DVDs are not ejected despite this, the device is to be submitted for fault elimination.

Checking CD / DVD changer for scanning faults

Checking with vehicle stationary:

• Select the function ”Quality check”
  

Checking while driving:

• Check whether the transport screws have been removed.
  
• Check whether the position of the support springs is correct.
  
• Check whether the springs are in the same position on both sides.