Today I wired up a digital coax out to my slim 360 using JaredC01's diagram for the original 360. I hooked my outside (ground) to pin 27 and the inside to pin 25 (positive) and closed it back up. The digital coax does not work, but now my onboard fiber optic is not working either. Do I need a switch or something since both are present? I would really like to fix this and at least have my fiber optic back.

http://forums.xbox-scene.com/index.php?showtopic=596642

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.

Here's an example:
http://mitglied.multimania.de/Promitheus/optictocoax.pdf



Go to page 3. Use the SPDIF signal as input to the dual inverter-based driver, the voltage for voltage, and ground as ground. Remember that pin 14 of a 14-pin DIP is V_CC and pin 7 is GND. Parts should run you $10-ish + shipping.