correct.  but so far no conclusive evidence the motherboard is bad.   if you suspect power surge damage, it could be either psu or motherboard is damaged. you could have a bad psu and still good motherboard as a possibility too.  that is why borrowing a good psu to test can isolate which one is bad.
I have a 2012 Dell Inspiron 660s with so much photos and important data and I had a power outage last night (electricity would turn on for half a sec then go out again and again), but it got fixed in the morning. I go to turn it on and it doesn't turn on. The light doesn't turn on and no power cords are loose. The light in the back is on. I unplugged power cord and plugged it in and still nothing... It has years upon years of old photos on it and it won't turn on. I don't want to lose this data. I searched and it said it could be a blown power supply (but I have never opened a computer and done things inside it and because of that it might be risky)   Please help 
2012 Dell Inspiron 660s won't boot up after huge power outage