Computer shuts down when playing games

So, as the title say, my computer shuts down when playing some games.
I've done my research and it's not an overheating problem, I left it at an repairshop for service, which inclouded fixing the cooling system

So, specs.
It's and Asus N56DP Laptop with WIndows 8.1, 8GB Ram, quadcore, I can get more if needed.

Atm, Im using a 90W power cable, and at first I thought it could be that one, but from what I've read, it's quite usual for a laptop, but I dont know as computers is not my main thing.

So, that's about it, if theres anything else you need to know, tell me, Im desperate to get it working as it did before they fixed it up!