1) Do you have an electronic multi-meter and a soldering iron?
2) Could you possibly remove the bottom cover and take a photo of the inside part of the on/off switch?
You have to post the photo on the web somewhere, such as on imgur or flickr, then put a link to it in your post. Let me know if you have any questions about any of this. We're looking for loose wires on the switch, before anything else.