1994 Ford Ranger starting

When I turn my key forward there is no power, no lights come on on the dash, it doesn't click, or engage the starter. When I turn the key back the radio will come on, but if I pull the switch for the headlights it shuts off. I have had the battery tested and checked the ignition fuse. I've checked the connections on my starter and they r all good. I've replaced the starter relay, the ignition lock and the ignition switch. Any ideas?