[SOLVED] PC boots for a second (even though it shouldn't), then shuts off.

Dec 24, 2020
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Hello!

I have a strange issue. I just finished building a pc. When I plugged it in, it immediately started up, but shut down after 1 second or so and wouldn't react at all to pressing the power button. I tried to figure out what's wrong and suspected that it's probably the PSU or the mobo.

Here comes the strange part. I took it to a technician who checked it, plugged it in and this time it didn't boot by itself. However after hitting the power button it did and seemed to work fine. We thought that something might have been loose and moved on with our lives.

But when I got home the PC was back to where I started. When connected to power it starts up immediately and shuts off about a second later (and of course it won't turn on again if I hit the power button).

So same as before even though it was working fine at the repair shop.

It is immensely frustrating and I don't really know what to do at this point.

The components are:
Asus Rog B450 F
Ryzen 5 2600
Gtx 1660 Ti
Corsair CV650 PSU
Corsair Vengeance lpx 2x8gb DDR4
Samsung Evo 970 1tb

Thank you!
 
Solution
Hey! Thank you for the reply. 🙂

I have done all the above, in all cases it is doing the same. Switches on when the PSU is connected and turned on, even if the power button is disconnected and goes off a second later. I tried it without gpu, ram, ssd. I even unplugged everything apart from the power, and CPU fan and removed the motherboard from the case. Same result. 😕

And again in the shop it worked as it should.

Power issues maybe? I have no ideas anymore. ☹
That's a tough one. Perhaps a bent pin on the CPU. Does it sit at different angles between the two locations, e.g., upright in one case, horizontal in the other case?

Yes, it is possible for there to be power issues as well, including issues not part of the PC itself. I...
Try removing as many optional components as possible just to simplify. Literally unplug the hard drive data and power, unplug all USB. If you have only the discrete PCIe GPU, then you could leave that on, but if you have an integrated GPU, you might even remove the discrete GPU and attach your monitor to the integrated port. See if that boots to BIOS (without the hard drive it should boot, but it won't continue to any operating system...this is valuable debug information).

If even this fails, then you can remove all but one RAM stick (you'd have to refer to the motherboard manual for which slot to use for a single stick) if you have multiple RAM sticks. Then try again.

If the single RAM stick does not work, then remove that and try booting. Some motherboards will at least start video and say something about memory for no RAM sticks. Other motherboards might have a beep code and no video. Either way the result of self-shutdown without anything attached would be valuable debug information.

Always unplug the system and hold the power button down for a few seconds prior to working on it. Try to touch the case from in some uninsulated location to avoid static before you touch anything inside. RAM is more vulnerable to static than other components, especially when not in a socket. Take care to not place them somewhere with static, e.g, don't lay them down on carpet :p
 
Dec 24, 2020
2
0
10
Try removing as many optional components as possible just to simplify. Literally unplug the hard drive data and power, unplug all USB. If you have only the discrete PCIe GPU, then you could leave that on, but if you have an integrated GPU, you might even remove the discrete GPU and attach your monitor to the integrated port. See if that boots to BIOS (without the hard drive it should boot, but it won't continue to any operating system...this is valuable debug information).

If even this fails, then you can remove all but one RAM stick (you'd have to refer to the motherboard manual for which slot to use for a single stick) if you have multiple RAM sticks. Then try again.

If the single RAM stick does not work, then remove that and try booting. Some motherboards will at least start video and say something about memory for no RAM sticks. Other motherboards might have a beep code and no video. Either way the result of self-shutdown without anything attached would be valuable debug information.

Always unplug the system and hold the power button down for a few seconds prior to working on it. Try to touch the case from in some uninsulated location to avoid static before you touch anything inside. RAM is more vulnerable to static than other components, especially when not in a socket. Take care to not place them somewhere with static, e.g, don't lay them down on carpet :p

Hey! Thank you for the reply. 🙂

I have done all the above, in all cases it is doing the same. Switches on when the PSU is connected and turned on, even if the power button is disconnected and goes off a second later. I tried it without gpu, ram, ssd. I even unplugged everything apart from the power, and CPU fan and removed the motherboard from the case. Same result. 😕

And again in the shop it worked as it should.

Power issues maybe? I have no ideas anymore. ☹️
 
Hey! Thank you for the reply. 🙂

I have done all the above, in all cases it is doing the same. Switches on when the PSU is connected and turned on, even if the power button is disconnected and goes off a second later. I tried it without gpu, ram, ssd. I even unplugged everything apart from the power, and CPU fan and removed the motherboard from the case. Same result. 😕

And again in the shop it worked as it should.

Power issues maybe? I have no ideas anymore. ☹
That's a tough one. Perhaps a bent pin on the CPU. Does it sit at different angles between the two locations, e.g., upright in one case, horizontal in the other case?

Yes, it is possible for there to be power issues as well, including issues not part of the PC itself. I don't normally tell people to examine the power line voltage itself, and if you don't know what you are doing it could be dangerous, but if you are comfortable measuring the voltage at the outlet with the computer plugged in, then you might find a "brownout" (low but not failed) voltage at the socket which fails.

Switching power supplies are designed to wait a moment upon power on, check for stability, and then either boot or switch back off (a necessity of making a switching design reliable). If everything is stabilizing and correct on full power line voltage, then it might still fail if used with a socket in brownout. I would actually be concerned about the wiring in the house if a socket is in brownout.

Also, keep in mind that any brownout is not necessarily a long term thing. At the moment of powering up there can be an increased current for a brief moment, and the brownout might just be under that brief moment, but not otherwise show any low voltage. You'd actually need something like an oscilloscope to see that.

Just a reminder, be careful if you actually decide to measure wall socket voltages, they are dangerous.
 
Solution

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