1998 Chevy Lumina radio

There are fuses in-line withe the red, yellow (and sometimes blue) power leads coming from the back of your radio. Did you check those also?

If they're good, then I'm sorry to inform you, but you probably fried your radio.

To double check, you can make sure the fuses are good, then connect direct bat voltage to the main power wire and the accessory/antenna power wire. Then connect a a ground wire directly to the bat terminal.

This will tell you if your radio is still working or not. If it does come on, then the problem is in your circuits. You may have melted a wire (Unlikely) or blown a fuse you haven't checked yet.