No sound from backup CD's

HI there any ideas anyone, I have a friend who has no sound when he plays a backup but no problems when he plays an original, all the backups play perfectly on my DC, however the picture is perfect, any feedback would be well appreciated.

[webber]

what media are you using, what burner , what speed and what settings,
be more specific when you guys ask for help
mail me if you want

regards
webber

[kingfisher]

I use three different writers and only top branded
media, but some of the backups come from someone else and I write at 6x, but that is'nt the problem all the backups work perfectly on everyone else's DC and mine, it's only my m8 who has the problem, I think I've sussed it though
he's using a combi TV, so we'll try another TV to
see if that makes a difference, cheers anyway.