Touch screen & volume buttons not working

Hi!

Yesterday my iphone 5 just suddenly stopped working for me.

I was using it and the touch screen including the volume buttons just stopped working.

I took it to a Iphone repairmentshop, not Apple store, so no comments about the warranty. I know!

He switched the screen, three times and it still didn't work. He's guessing it's the logic board, could that be it?

Anyone else had the same issue?

Going to fix it by myself anyways, just need some input.

Thanks for any comments at all.

iPhone 5, iOS 8.1.1