Posted Sun Jan 29, 2012 4:22 PM
Actually, I am selling the 5200 s-video mod kit on ebay, not Best Electronics.
Sorry I never tested a 2600 adapter with my kit, but I will update future listings to show it is not compatible.
I believe the 2600 adapter combines its video and audio into a MOD signal which goes to the RF modulator in the 5200. Getting the 2600 adaptor to work with a s-video 5200 would require modifications to the adaptor, and possibly another connector to the 5200. So while technically possible, it just wouldn't be practical. The 2600 adaptor for the 5200 is essentially a Atari 2600 without a power regulator and modulator, which are the only functions the 5200 is used for.