OT: CD scratches/please help/last try

[Fraser, Colin J]

> -----Original Message-----
> From: Martin Czech [mailto:martin.czech at intermetall.de]
> Sent: 12 August 1999 11:17
> To: jar5831 at localnet.com
> Cc: digiboy at erols.com; synth-diy at mailhost.bpa.nl
> Subject: Re: OT: CD scratches/please help/last try
> 
> 
> If the grinding paste particles are small enough and if we 
> can avoid other dirt
> particles, the micro scratches may become so small that they 
> can not be detected
> by the player laser (is it 600nm ?). 

The laser on a CD drive is focused by a lens such that at the point the beam
enters the transparent surface of the disc it covers an area of something
like 1mm square.
The point of the conical beam is positioned at the surface of the reflective
layer inside the disc.
This is supposed to prevent problems with minor scratches on the surface. 

Maybe having lots of small scratches caused by toothpaste has less effect
optically than one large scratch...

One solution I have found for badly scratched discs is to copy them to a
CD-R. 
CD audio players must ignore severe errors because they must sustain a
continuous audio stream.
CD-Rom readers are designed to read discs with the fewest errors, so they
can retry failed reads while extracting the audio, and have a better chance
of getting the correct data off the disc. Then you can write the data to a
scratch free CD-R.
It helps if you have a PC with a CD writer for this, tho'


Colin f