I have a hobby of repairing scratched DVDs for our local library.
Problem:A DVD is being played ,freezes at 51 minutes of a 93 minute movie.How can you calculate the distance from the inner edge of the disk to the scratch that causes the freeze?
Right now I’m assuming a linear distance from the edge of the active disk to the far edge,
51 min/93 min=0.55. So I take .55 X 37 mm =20 mm
The scratch should be at 20 mm. Is that right?
I clean the disk with 1/2 of a tissue ,soaked in isopropyl alcohol
or 91 % (not 71%) rubbing alcohol.
If I see a suspected area ,I use micromesh pads (http://micro-surface.com).I start with 12,000 grit,then clean off with alcohol.
Then Try to play the DVD.If that doesn’t work ,I use 8,000 grit
followed by 12,000.If no good,I try 6,000 grit followed by 8,000,
then 12,000 and a wash.
There are expensive mahines that use the same strategy but I think that that would be over kill for one scratch.