if I am plugging in the power supply the red power led lights very dim.
I found several guides to test the the board with a multimeter but these were for the other revisions, and it seems like B+ is a little bit different.
I had a device on my GPIO pins which drew way to much current, so actually there is a reason why something could be broken. But the Pi worked fine for several weeks afterwards. Now I would like to know if the power supply is broken or the board. And may it help to power the board via GPIO?