My PC refuses to boot, except when it doesn't

Posted early by accident- still adding to this

Alright folks, I’m at my wits’ end with my machine here, hoping someone here can help! <3

To start, here’s a run-down of my build:

CPU: i7-7700K 4.20GHz
RAM: 16GB DDR3-1066 - Brand is Corsair, not sure on further details.
GPU: Gigabyte GTX 1070
Motherboard: Gigabyte B250-HD3
PSU: Cooler Master Silent Pro 700W Modular

This has been my main machine for nearly a decade, though every individual part has been replaced various times so it’s a real ship of theseus situation. The most recent hardware change was around a year and a half ago, when I upgraded the motherboard, CPU, and GPU all at once. There have been no hardware changes since, and no problems until now.

The Problem:

It’s very hard to nail down how the problem even manifests, but I’ll do my best. When the PC is on and in use, it will generally stay on. When left alone- typically for around 30 minutes or more- I will return to find it either stuck in a boot-loop, or sitting at a “Windows did not start correctly” blue screen.

If it’s stuck in a boot-loop or if it’s turned off, it’s extremely difficult to get it back on again. The boot-loop is inconsistent and unpredictable. Sometimes the PC will seem to turn on for less than a second before shutting back down. Other times it will make it to the POST screen before shutting down. Sometimes it will make it as far as loading into Windows before shutting down. When I can finally get it to reach Windows, it will (with few exceptions) stay on while I use it.

Until it reaches Windows, it will seem to loop through those states endlessly with no pattern that I can find. Sometimes rapidly turning itself on and off for only a second or two, other times getting to POST repeatedly, and mixtures of all of the above.

When it’s in this state, I have found no reliable way to get it to successfully load Windows. I literally just keep trying until it works, and this has taken the better part of an hour some days.

What I’ve Tried:

Narrowing the problem by removing components individually one at a time. Through this process I’ve recorded that the problem still occurs in exactly the same way when:

  • GPU is removed
  • Hard drives are removed
  • RAM sticks are swapped, placed in different slots, or absent altogether
  • All connections to the case are removed except for the power button.

I have also tried:

  • Updating all drivers for all hardware
  • Reflashing/updating motherboard BIOS
  • Resetting motherboard CMOS, both by removing the battery for a time, and also using the CMOS reset function on the board.
  • Replacing the CMOS battery.
  • Adjusting power usage settings both in Windows and in the BIOS. Disabling power-saving features like C1E and EIST (The fact that it would seem to happen while I was away from the machine made me suspect this, but I’ve observed no change)
  • Checking and re-seating every physical connection both interior and exterior.
  • Checking every contact point with screws/metal/case etc. for potential shorts or missing standoffs

Where I’m at:

My budget is extremely limited and I don’t have spare PC parts lying around to test with, which means I will have difficulty narrowing the problem further. This suggests to me that there are three possible culprits: the Motherboard, the CPU, or the Power Supply. Without alternates of any of those, I dont’ know how to narrow it further, and I don’t know what else I can try.

I am looking at local repair shops but my budget is such that taking the PC to a shop might literally mean I then don’t have the money to replace whatever isn’t working.

Any and all ideas are welcome. I’m at the end of my rope with this thing.

This sounds incredibly similar to an issue I had that I just resolved. TL;DR, you won’t like the suggestion.

My computer would basically have a hard time booting. It would cycle on and off, and wouldn’t post to windows save for on a few occasions. When I did get it to finally post, I would just leave it on for days so I wouldn’t have to deal with this shit. It ran fine. I was playing Arma 3 while dealing with this problem. It would crash every now and then, or just shut off due to power surges, but eventually I decided to replace the power supply, because that’s where my first thought went to. Turns out, that wasn’t the issue. I tried everything: Different sockets, cleaning it out, changing cmos batteries, removing parts, changing cases, etc…

Eventually I took it to a repair shop which told me my CPU was burnt out, which was bullshit because I’m playing games fine when it does boot up. They did tell me that I probably need to replace the motherboard, and that ended up being the issue.

So, cool thing I found out. If you get the EXACT same motherboard as you had before, you don’t have to buy a new CPU or RAM. In fact, you don’t even need to reformat your PC. I was so relieved when it finally fixed my issue.

So yeah, I think it’s probably the motherboard if you tried everything else. Maybe power supply, but I would definitely shop at a local spot so you can return the PS if that’s not the issue.

Yeah I had a remarkably similar issue with my laptop which is also most likely the motherboard (shop never could diagnose the issue)

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That’s been my suspicion and yeah, I think that’s what I’m going to have to end up trying.

Wherever I end up getting it from I’ll just make sure I’m clear on return policies, in case the board doesn’t turn out to be the problem :+1:

Thanks y’all. I needed a not-scary place to ask about this online and just make sure I wasn’t missing something obvious, lol.

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Ok hot new development: my CPU is 7th generation- Kaby Lake- and it seems like motherboards that support that socket are…not easy to come by anymore. :\

So I need to track one down and be confident I can return it if it’s not the problem. Or I need to also replace my CPU, which I can’t at all afford to do. -_-

Try eBay. There are some places that sell refurbished Motherboards.