Question Lenovo T530 not powering on

[Deadaxe]

I've bought a lenovo t530 with i7 3610QM, for 5$ with reportedly "broken" motherboard. So I sent a laptop to a repair shop which claimed they fixed the motherboard. And now laptop works great except somedays laptop won't turn on. Changed disc, ram and tried with different power supply and it didn't help. Do you have any suggestions?

 

[vincentneo]

Could it be that the power button is faulty?