/edit: It actually was the DC Jack. I don't know why my MM shows me that the circuit is closed but in fact it isn't connecting the two points... Now i swapped the jack & it works fine. (lookup last post)
Please post a close up image of the top, and bottom of the board, showing the connections. What voltage do you measure at those 2 points when the power is plugged in?
I use the conncetion testing on my Multimeter.
In this mode it only measure the resistance but it give a sound when a circuit is closed.
No power connected at this point.
I used this mode to verify that the connections are solid.
It worked out well with all other connectins but the Vin won't power the Nano.
I checked all solder joints if they are solid & wihtout bridges.
With my test code everything works well over usb...
The capacitors are there because I got problems with the MIDI reading of the pots.
On the prototype they jitter sometimes so I put a capacitor on it and it works well so I ported it.
I carefully made the soldering so I don't burn out something because on other topics about Vin the guys mentioned it could happen that something burns out...
It isn't a original Nano but I think this should'nt be a problem.
When nothing helps, I'll power it from USB. But I bought DC jacks & a wall adapter so it would be nice when this is working correctly...