Blazer won't start

[ghettocruiser]

This might not be the right place for this, but here goes.

I've got a 75 blazer that is in need of a little TLC. I've got the interior gutted with plans of bedliner. A few days ago I had to jump it off, Sunday it started on its own and while working on it I think I left the key turned to on. Now it won't start. To maybe make matters worse, it rained last night, while the blazer had no top on. When I put the charger on and try to start it, I can hear the charger "ground out", like a loud humming noise. After I started hearing that, I took the radio out. Could I have unplugged something getting the radio out? Any ideas on what the problem is? I don't think any water got to anything important, because there was still dust on the dash pad and gauge cluster. For a while the lights would work and the horn would honk, but now nothing happens, not even a click. A test light will light up on the battery and on a hot wire that was on the radio.
Thanks for the help,
Carson