Cdj 2000 nx2 turns on but no reaction

Hello good people of the internet, 

I work in a club in Copenhagen and we recently had both our NX2s fail with the same problem: 
The machines turn on but you cannot use any buttons, no USB loading or anything, basically, nothing happens. 

our local repair guy tried to change the DWX3702 with no luck. So now we are left with two malfunctioning units. 

Any help is appreciated in locating the error and getting them operational again. 

Best
Anders