Let's see... I just shipped out my spare CoreGrafx in a trade and I also after all these years get my hands on a 1.0 CD System Card.
I plug in my SGX + CD rom, put the card in it and turn it on... except nothing shows up on screen!
I turn everything off, unplug the CD rom, put in a HuCard and turn it on and nothing.  
I don't think that I shipped the wrong power supply with the CoreGrafx as if I remember correctly the CoreGrafx power supply doesn't fit on the SGX or the CD Rom.
Anyone have any ideas?  Do people have the specs to the power supply?  I can try a universal one to see if it's just a problem with the powersupply...  But at the moment it doesn't look promising.