Malfunctions caused by CDs

Due to the conditions, under which a CD changer operates in mobile applications, CDs which are outside or at the limit of specified tolerances can cause the following problems.

Many undesirable effect can be caused by CDs with edges which are inadequately deburred or too thick:

• The transport rollers cannot grip the CD since it is too thick.
  
• Plastic burrs can break away during transport through the rollers and adhere to the CD surface. The same problem can also occur in the case of a poorly deburred centre hole. Plastic burrs are pressed out by fixing on the cone (clamping), as a result they enter the mechanics and soil the CDs and magazine. These plastic chips (burrs) have 2 negative effects:
  The plastic chips can cause fine scratches on the surface of CDs if they enter the magazine.
  Under unfavourable conditions, larger pieces of plastic (5-7 mm) can cause pick-up errors (jumping) or they may make it not possible to read the CD directory (TOC). The CD cannot be played in such cases.
  
• Return transport into the magazine is impaired if several of these too thick CDs are stored in a magazine. On the one hand, a higher force is required in order to push the CD back into the magazine. On the other hand, however, the partitions which separate the individual CD compartments from each other can be displaced to such an extent that return transport of the CD to its original position is no longer possible.
  

Note

Do not use CDs which are inadequately deburred. Extremely thick CDs may be used only if there are not several such CDs in the same magazine.

Single CDs (8 cm) with single adapter, protective films and protective paint or with stabilizer rings:

• The CDs are thicker than normal (see above).
  
• During the transport procedure, singles can be pressed out of the adapter and thus block the mechanics. Stabilizer rings can get trapped in the transport rollers.
  

Note

Do not use such CDs with accessories in the vehicle.

Transparent CDs:

• Unfortunately, it frequently occurs that the protective film has been poorly vapourized on to the CDs. Such discs are more transparent, in part or completely, than normal. Although these CDs can still be played they no longer facilitate optical position monitoring by the photoelectric light barriers. In real terms, this means that the CD is no longer detected as such.
  

Some CDs are subject to production faults. This concerns the layer, on which the information is stored. It is sometimes possible to play such CDs on the home system but not in the car. This is not a fault of the CD changer but rather it is due to the fact that error correction in the vehicle is based on different requirements than those for stationary operation. A home player reacts very sensitively to impact and vibration. And nobody every seems to complain that such a player no longer functions correctly when it is knocked. The laser tracking can be optimized such as to pick up surface errors. On the other hand, a compromise must be found for mobile applications. Due to the possible vibrations and impact, the control range (in this case the ability to compensate for surface flaws) must be limited. And this is exactly what makes mobile applications possible.

It can sometimes be found that CDs are not completely flat, i.e. they wobble in the same as often occurred with vinyl discs. Since a CD is read out from the inside towards the outside, when using such discs, error correction is sometimes overtaxed when playing the last title. This can be reflected in the fact that a CD changer is very sensitive to impact during playback of the last title.