The ac3-rf output was thought to be a possibility but nobody has had any success on any machines yet that I know of so it seems that maybe a filter is attenuating the rf signal before leaving the machine. Drilling a hole and mounting a bnc chassis connector and hooking up a coaxial cable to the test point actually turned out to be pretty easy. I've now tapped all 3 of my machines this way.

You would still have to make a custom cable anyway because the luma pin of the s-video input of the capture card is the pin you need to feed the raw rf signal into.

Here is the card that Happycube and I are currently using. I think just about any card with the cx23880 will probably work with the custom cxadc driver according to happycube though.

Hauppauge WinTV 34132 NTSC/NTSC-J PCI