Every unit I've seen in this state (maybe 5 units) have been fixable. You need to do this:

- Remove the short, however you can. In the past I've removed the 4-pin molex and drilled out the offending hole. Careful though, as this is a multilayer board. Really, the power/ground planes should have been pulled back from the input area, but you live and learn

- Rewire power so that the power and ground paths are again correct.

The problem is cause either by a fallen screw or by someone managing to short car 12v against the grounded case, meaning there's a huge amount of current flowing between the (unfused) empeg ground wire/ground connection and the case/mounting holes.

Hugo