I would like to make sure my new headunit works before i install it into my car. I thought that it would be as simple as hooking up the 12v line to the 12v on the hu and then grounding it but when i do that nothing happens. I am thinking that is because the psu is atx and not at. Is there anyway to trick the psu into giving power to the 12v line? Do i need to hook anything else up to get it to work? thanks