Hector Martin

The only thing in that corner is the power connector. Did something short out or did an intermittent connection heat up? PSU overvolting should only cause risk to caps and possibly make the 7805 overheat, but that wouldn't affect the connector.

There was a cap bridging Vcc to ground. I don't know if burning that out would break the circuit or connect it, but if it's the latter it would be a short. Which is what this would look like.

It's unlikely a cap would fail with a low enough resistance to make the connector the place where most of the heat is dissipated instead of the capacitor. Usually they capacitor will leak or violently blow up first. It's likely you had an issue in the connector to begin with.

That could well be. Regardless I'd like to replace it. I think a standard 9V1A would work fine too so long as I put it before the regulator