You need to convert the TTL signal to a coax one. I used the schematic from kilpatrick's site, but the link has been non-functional for a while, and google doesn't help.
The reason it may not be working is due to the limited fan-out of the spdif signal line. In which case, unsolder 25 and try again.
If you can't get the onboard to work, get a toslink transmitter off digikey (it's like $5), and connect 25 to signal, 27 to ground, and 29 to power - read the respective datasheet for which is which.
This post has been edited by moshbear: Apr 3 2012, 10:12 AM