@emdoller yes, that sounds like a bad power supply. Check the cables to the logic board. Make sure that they are properly connected etc. Also, check the power supply. I would not bet surprised to find some degraded or even leaky capacitors. After that you can try and measure some voltages.
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If unsure, you can always post some pictures of your PSU with your Question. That way we can see what you see. [guide|21499]