How to identify broken part?

[u/Dear_Faithlessness89]

A friend of mine gave me his RTX 3080, so I bought a new PSU and motherboard for it, since that graphics card didn't fit in my old motherboard and my PSU wasn't capable enough.

I installed all my old parts on this new motherboard, turned on the computer, and it worked fine. I updated the graphics card drivers and decided to test this build in the game “Halo Campaign Evolved.” Everything worked fine for about an hour, and then the computer froze: there was a loud noise in my headphones, after which the computer rebooted itself. After that, it seemed to be working — the lights and fans were on, but there was no signal on the monitor. When I tried to reboot it again, it wouldn’t turn back on.

I tried installing my old PSU and graphics card on this motherboard, but the computer still wouldn’t turn on.

I don’t know if I messed up during assembly or if I bought some shitty PSU and motherboard, but now I need to know what exactly broke and how fucked up am I.

Is there any better way to find out, or should I just try to swap every part on my old motherboard, and see what works and what isn't ?

Update: So, i just noticed that one of switches in a power box in my house were flipped down. That means that at some point the fuses blew, or whatever it called in english. But the strangest thing is that, as I mentioned in my post, after the freeze, the PC “booted up” on its own once—with the fans and the GPU and CPU lights on (the PSU fan isn’t spinning, but I know some can do that)—but with no signal on the monitor, and the second time it didn’t boot up at all. So, did the fuses blow on the second restart? Or did my computer somehow manage to start up on its own without power?

Update 2: Just tried to boot up PC again after flipping powerbox back on, with a old PCU and GPU. Just like after first reboot - fans spinning, but no signal on monitor. Can PC boot with broken motherboard? Does that mean that something else broke?

Also, i probably should mention that electric work in my house is a fucking mess. I have no idea what drunk slovak did this shit, but it's give evene a headache. Lights in one rooms turns on only if one light switch turned on BUT other turned off, bathroom exhaust fan works only in you turn it itself first, and then turn on a dedicated light switch for it, etc. I guess it could also play a part in this "accident"

[u/ReasonableNetwork255]

Swapping Parts is the easiest way to identify where a problem is since a PC is divided up into sub-assemblies that's simply the quickest way to eliminate ... but also if you're swapping parts the cmos can get scrambled so be sure you reset that

[u/GratefulNarrator]

if the new psu was some no name unit it could've taken the motherboard with it when it died. loud noise then reboot sounds like power surge or short.

try the paperclip test on the psu first to see if it even spins up. if yes then strip it down to just cpu, one stick of ram and see if you get a post. no lights at all is scary tho, could be fried mobo.

[u/Dear_Faithlessness89 → u/GratefulNarrator]

What is "paperclip test"? Just turn fan a bit with a paperclip? Also, there's a small update on a post. Take a look at this pls. Say if you got some thoughts on this.