I've fix it!
I suffered from the not working release button also. What I've done was soldering the pads of the release button. The button is placed on flex ribbon, which may be a problem because soldered pads may break after many pushes.
I will describe what I've done exactly in case You want to try this fix by yourself.
I've reheated three pads of the release button that are marked as 2 (I've used pointed soldering iron). Those are easy to access. I've tried to reheat the pads that are marked as 3, but those are hard to reach because the other switch is too close. Nevertheless, the pad most to the left (in the group marked as 2) seams to be the problem.
My camera is working now 🙂
As a side note: Before I’ve fixed the problem, I've tried to shot a photo with my camera case disassembled. When I pressed the release button, I could not trigger my camera, same way as all S100 owners in this discussion. Nevertheless, when I was pressing the trigger button and I was pressing the flex ribbon in a place close to the button and marked as 1, then a picture was captured. I’ve done this few times, and it has always triggered my camera. I assume that pressing the ribbon distorted the broken solder in some way and the proper connection was back. I’ve probed the pads of the release button with camera switched on. When the second stage of the button was pressed and released then the pad most to the left was switching between hi and 0V states. Therefore, I assume it is the faulty pad.
I think that mounting the release button on flex ribbon was not the best choice that engineers from Canon could have made. It is constantly pressed and solders are not meant to handle such stress. A proper PCB should be used here.
Good luck anybody that still uses their S100. I am going on my vacation next week and I hope to capture it with my fixed camera!
