My PC Specs: (pre-build with some changes)
This hopefully will make sense! I am really bad at writing!
I have had this pc for almost 2 years now. When I first got my PC, the graphics card was acting weird, making my monitor have purple and green pixels on it. I sent it to the manufacturer to get it fixed. They replaced the graphics card. About a year ago, I had to send it in again for it freezing, crashing, and blue screening. When I got it back, I noticed that the case was new, but I didn't know what had been changed. I asked them what they fixed to know what went wrong, but they never told me. My father thinks they replaced the motherboard, I am not sure if it was or not.
I recently have had problems again with my computer. It was working fine about a week ago. My computer started to turn off and on more frequently when I was on it. It was getting frustrating. It kept turning off and on more frequently. It got so frequent that the lights and fans would turn on and then turn off immediately and repeat the cycle over and over again. I went to do some research and went to LinusTechTips Forums, google, and youtube. I first concluded that it was either the power supply or the CPU. After further research and reading about other people in similar situations. I found a video describing that if you take a paper clip and make a U shape out of it and stick it into the green cable and a black cable on the 24-pin (also attaching a fan to it), I was able to test that the power supply was working. I then started to test more fans and then connected the 24-pin to the motherboard. It was working, and then I tested the CPU connector. It started to flicker off and on. I unplugged it and tested the GPU, and it worked. So I tried plugging in everything, and it would continue to flicker. I unplugged the CPU connector, and it worked again.
I don't know if the motherboard had a surge, shortage, or burned. I don't see anything burnt or shortage marks. What would be the cause of this? and if so, what would I need to replace it?
Jumping the PSU with a paper clip is a good test for a system with no power. However, when you're having an intermittent issue like this it's not going to tell you much as the problem is unlikely to reveal itself without putting a load on the PSU. When you don't connect the CPU the motherboard will hang on on initializing the CPU. It's not putting much draw on the PSU at all. The issue occurring with the CPU power connected is a clue. If it were throwing a fault, the system would turn off and stay off. You'd likely have to discharge the system to try to power it on again. With it going in and out, sounds like the 12V rail is failing on the PSU, though it could also be VRM on the motherboard.
You treat this as a power issue, and work from the easiest to the most difficult solution. Test another outlet, replace the power cord if you have a spare. Replace the power supply, and finally the board if everything else fails.
I would recommend testing the PSU with an actual tester such as https://www.microcenter.com/product/508304/kingwin-digital-lcd-power-supply-tester (currently sold out, but you can find it elsewhere online if you need to.) They're really not all that expensive and the one I have has lasted for a really long time (so long that the -12v light no longer comes on, because the -12v rail no longer exists in modern PSUs.) As a bonus you can also use it to test friend's CPUs. During that blackout in 2003 (mine is that old) I used mine to test a bunch of supplies that were bad since apparently no one knew what a power strip is. Made a little bit of cash swapping out dead PSUs for good ones.
If it's not that, there's a chance the moterboard may have given out. You can easily tell that (usually) by looking for leakage around the capacitors on it. If any are bulged out you can consider that a failure or failing as well. This is usually very unlikely though.
You can also try running absolutely nothing else on it other than the CPU and RAM, then see if that fixes the issue. I highly doubt that will work. Mike knows what he's talking about though so consider my advice secondary, as I'm just an armchair tech.
Interesting that it did POST once and boot to a recovery environment. When the system cycles, how long is it on before it restarts?
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