Starting problem. Ugh...?

I own a 1989 ford bronco II X.L.T (or was) with a 2.9L V6 automatic 4x4. So the story is, when I go to start the engine, I can turn the key to the accessory possition the radio and lights and dash all lght up and start working (even the annoying dinging works). the second I turn the key to actually start it everything dies and the battery meter goes to 0, then when I turn the key back to accessory its as though its still dead, untill i turn it to off, then back to accessory. Today I've replaced the battery with a the best of the 3 I had a choice from. I replaced the starter (with a brand new one, no rebluit), and the solonoid. I'm thinking it may be the ignition switch it self, but I'm looking for any info, or ideas. anything helps Thanks!