I got it.
I believe that the schematic of the chopper board has incorrect labels for the X2-1 and X2-2 connector, they're swapped.
X2-1 should be positive and X2-2 should be negative.
The first time I hooked the PSU my led didnt lid, so I thought "Oh well , I always get confused with the leds" and I resolder it so it lid, but the problem was another.
Correct me if I am wrong.
Konstantin.