It’s most likely your motherboard. Little chance it’s the power supply.
I would try a power supply replacement. If still dead use it for parts.
I don’t know never heard of this problem. I don’t think it’s worth it if it’s the motherboard.
It’s probably the fan. I would risk it.
If You did not toss it out yet this might help. I’m 91% sure its the power supply, to replace your power supply, follow this guide [無効なガイドリンク]
and 1 iphone was not functioning i threw it 80 times before a single crack on glass after riding over with car touch broke i used another iphone to test the screen. a really durable phone how could my old one break like that
i dropped my iphone and it split apart when i say apart i mean really apart screen cracks front glass and lcd logic board and battery goes flying bezzel too and even logic board metal peaces goes flying