Coax input fail?

Hi All,
I have a generic tone board and have an optical cable going through a small box adapter that converts the optical output to a coax spdif signal. I have tried several sources for the optical signal (a macbook pro and a Samsung TV for example) but nothing comes out of the Tone Board. I have looked at the output of the converter and a signal is being output. What am I doing wrong? The Tone board works fine over the serial port using my macbook.