My the device doesn't turn on.

Hello all,

I have this issue with an iPhone 5s. The screen went blue a couple of times then after a while the device didn't turn on anymore. I'd like to invest some time and money into trying to fix it, even if it doesn't worth it overall, for the sake of learning.

So, I checked the battery and when fully loaded the voltage seems to be fine. From reading other forums I found out that the main board or the logic board may be the problem. Is there way to diagnose it? I would clearly buy a new one from eBay and try to replace it if that's the case.

Where else should I look? What else can the problem be?

Thank you for taking the time to read this!