Question PC turns on and then turns off after a few seconds

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OrangePineappleSoda

OrangePineappleSoda

Junior Member
Aug 6, 2023
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I finished building my first PC. When I plug in the power cord, the PC fans start spinning, the RGB lights turn on, * there is loud fan noise and then the PC turns off after about 3 seconds.

After the PC turns off, I press the power button and nothing happens. The PC remains turned off. When I unplug and plug the power cord, the same thing happens (turns on and then turns off after 3 seconds and won't turn on again). I'm not sure what to do.

Specs:
i7 10700
B560M
RTX 2060
650W Gold
 
Last edited:
In2Photos

In2Photos

Platinum Member
Mar 21, 2007
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A loud noise is not good. Do you have another PSU you can use to test? Did you build the PC outside of the case and test everything prior to installing it in the case?
 
OrangePineappleSoda

OrangePineappleSoda

Junior Member
Aug 6, 2023
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In2Photos said:
A loud noise is not good. Do you have another PSU you can use to test? Did you build the PC outside of the case and test everything prior to installing it in the case?
Click to expand...
It's a loud fan noise. I don't have another PSU to test and I didn't test the PC outside of the case. I tried the paperclip test on the psu and it passed.
 
mikeymikec

mikeymikec

Lifer
May 19, 2011
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So it's probably the fan management system cranking the fans up to full before deciding what speed they ought to be running at.

Have you definitely got the CPU power connectors and motherboard power connector securely plugged into the board? I'd also suggest having an internal PC speaker plugged into the board's speaker header, but I suspect it's not going to do any beeps; logically if the board wanted to tell you something, it would stay running to let the beep sequence run its course / repeat.

The 'switches off within 3 seconds' business makes me think of a safety shut-off feature because something is unsafely wrong, though it surprises me a little that you're able to switch the computer straight back on; I would have thought that an unsafe boot scenario would result in a full-on nope from the board until say power has been completely drained.

One thought is maybe the CPU isn't correctly installed, say a bent CPU socket pin or something. But before I went to there I'd steadily strip down the PC; do easier things like remove RAM, graphics etc but with a PC speaker connected to the board. If you start getting beep sequences that correspond to the missing component then you know the board is working at least on some level. Of course if the computer stays running for more than 3 seconds that should be a pretty big clue as well.

Which power supply, which RAM and which board?
 
In2Photos

In2Photos

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Mar 21, 2007
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Try unplugging everything that isn't necessary for a post. So a single stick of ram, the 24 pin and 8 pin CPU. Even remove the GPU initially. No sata, no peripherals, no case connections.
 
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OrangePineappleSoda

OrangePineappleSoda

Junior Member
Aug 6, 2023
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mikeymikec said:
it surprises me a little that you're able to switch the computer straight back on; I would have thought that an unsafe boot scenario would result in a full-on nope from the board until say power has been completely drained.

One thought is maybe the CPU isn't correctly installed, say a bent CPU socket pin or something. But before I went to there I'd steadily strip down the PC; do easier things like remove RAM, graphics etc but with a PC speaker connected to the board. If you start getting beep sequences that correspond to the missing component then you know the board is working at least on some level. Of course if the computer stays running for more than 3 seconds that should be a pretty big clue as well.

Which power supply, which RAM and which board?
Click to expand...
I'm not able to switch the computer straight back on, the power button doesn't do anything. I have to unplug the computer and then re-plug it for it to turn on (and then turn off after 3 seconds)

I'll try removing the RAM and graphics card and connecting a speaker. I actually have two motherboards (a B460M and B560M) and tried both and got the same problem so I don't think it's because of bent socket pins. I also tried turning on the computer without the cpu power connected (atx 12v) and the same problem occurs (but the fan noise is quieter with cpu power not connected). If the problem still occurs without the cpu power connected, does that mean the issue isn't the cpu?

The power supply is Lenovo 650w, the Ram is Samsung 2X8GB and the board is Asus pro B560m-ct/csm.
 
BoomerD

BoomerD

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Feb 26, 2006
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Thus sounds like either a bad power supply, a shorted/grounded motherboard, or something just not connected correctly.

Best bet, take the motherboard out of the case, set it on some non-conductive cardboard, such as the motherboard box...try booting with CPU, ONE stick of RAM, check the board's manual to see which slot is best for single stick operation, and the PSU. Make sure you have the 24 pin connector and the 8 pin connectors properly connected. If possible, connect your monitor to the iGPU.


How To - Motherboard bench testing

Finding the problem through bench testing If you are here then it’s likely you have encountered a serious hardware issue and have been unable to resolve it using the standard no-POST troubleshooting procedures. If you have not yet attempted to resolve your issues using the no-POST...
forums.tomshardware.com forums.tomshardware.com
 
OrangePineappleSoda

OrangePineappleSoda

Junior Member
Aug 6, 2023
16
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In2Photos said:
Try unplugging everything that isn't necessary for a post. So a single stick of ram, the 24 pin and 8 pin CPU. Even remove the GPU initially. No sata, no peripherals, no case connections.
Click to expand...
I tried that now. Unplugged everything, besides 24 and 8 pin and 1 stick of ram. The same problem occurs. I then tried to power it on with a screwdriver, nothing happens.
 
In2Photos

In2Photos

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Mar 21, 2007
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OrangePineappleSoda said:
Is there a way to check if the PSU is causing the issue without needing to buy a PSU tester? I did the paperclip test, but I'm assuming that isn't a reliable method?
Click to expand...
A PSU tester will show you if all of the voltages are correct among other things. If you have the same problem with 2 different motherboards I'd say it's the PSU. Much more likely than the CPU.

Maybe ask a local PC shop if you can bring it in and use one of their PSUs to test.
 
OrangePineappleSoda

OrangePineappleSoda

Junior Member
Aug 6, 2023
16
6
36
In2Photos said:
A PSU tester will show you if all of the voltages are correct among other things. If you have the same problem with 2 different motherboards I'd say it's the PSU. Much more likely than the CPU.
Click to expand...

I borrowed a working PSU from my friend. I haven't tried plugging in everything yet, buy when I plug in the 24 and 8 pin, the PSU spins for 4 seconds and then turns off.
 
mikeymikec

mikeymikec

Lifer
May 19, 2011
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I haven't been keeping track, but if the original symptom is still the only available one, and if the CPU is suspected, why not just remove the CPU and attempt to boot? If it stays up for more than 3 seconds and gives some promising beeps, then maybe it is the CPU.

In a separate test you can lose the remaining RAM, it should cause a different beep sequence to a missing CPU.
 
mikeymikec

mikeymikec

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May 19, 2011
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OrangePineappleSoda said:
I'll try this. I'll have to remove the thermal paste, right? Unfortunately I don't have a motherboard internal speaker.
Click to expand...

You can get one off ebay for next to nothing. They don't help you diagnose everything, but basic things like bad cpu / ram / graphics that you would otherwise have to have spares of to test.
 
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