But, the shutter of this camera I bought was working like this: when you wind up the film and without pressing the shutter button, the blades oppened and stayed oppen until you press the shutter button.
It is useless to oppen the camera and try to repair it inside. I learned this by doing it. But I also discovered that the camera could be repaired without the need of oppening it. The procedure is the following:

Change the batteries for new ones, attention to their correct polarity. Then press the shutter button and wind up. Repeat several times until the camera works correctly. That's all folks! If you have one of these wonderfull Minox, don't give up if they don't work like they should. I suspect that they enter the «broken state» when the batteries are weak and they need then a kind of reset to work in the «normal state» again. In this case, there must be a lot of them not working correctly and sold as broken at ebay. It is worth to have a look at ebay and see.