General discussion

My computer doesn't turn on all the way

Jan 31, 2018 6:51PM PST

My computer turns on for a spilt second and then turns off. The video card, all the fans turn on as well and then it just does this in a repeated cycle. Turns on with all the things above and off then and off. I was thinking it was the PSU, but I have a spare and switched it out and even the cable to the PSU and same thing is happening. Any ideas?

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Comments
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Make it smaller
Jan 31, 2018 7:54PM PST

Psu+mobo+cpu/hsf.
Nothing else connected or plugged in.
If that fails move the mobo to a piece of cardboard....test
If that fails your down to 3 parts.

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Test
Jan 31, 2018 8:00PM PST

I never tested a mobo. How do I test that it is working? There's only a green light on it which turns on when I give the PSU power.

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Mobo
Jan 31, 2018 8:16PM PST

You test by swapping.

Before you do that replace the cmos battery.

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Swapping
Jan 31, 2018 8:24PM PST

I already swapped to a different PSU with the same results. I'll have to get a new CMOS battery to try it out as well.

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Update
Feb 1, 2018 4:08PM PST

So I unplugged the CPU power and the computer starts up but obviously nothing would show up in the screen but everything is working. I plug the CPU power back in and it's back to running for milliseconds with a little fan movement and GPU starting up

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Can't find machine details.
Feb 1, 2018 4:10PM PST

But the +12V ATX unplug does point to motherboard or CPU issues. This means you should put just the PSU, motherboard and CPU on cardboard (no case!) and see if that powers up.

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Alright
Feb 1, 2018 4:20PM PST

I tested just the PSU, motherboard, and cpu and it runs, starts up and didn't shut down after a min. So it's not the PSU, mobo, or cpu right?

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Now add one stick of RAM.
Feb 1, 2018 4:23PM PST

Test.

Then a GPU, test.

Then the other RAM, test.

If that works, see if there is any EXTRA mounting posts. I've lost count how many times it's that.

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Oops
Feb 1, 2018 4:40PM PST

Oh wow I'm an idiot I didn't have the CPU power plugged in. So PSU, mobo, and cpu only. Does the milliseconds thing over and over looking like the CPU, dammit,

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Not so fast.
Feb 1, 2018 4:43PM PST

We have to remove the CPU from the socket. There have been cases where the CPU isn't in the socket just right as well as bad motherboards. So just the PSU and Motherboard can give us a clue which part it is.

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Alright
Feb 1, 2018 4:49PM PST

So removed the CPU. Turn on the PSU the green light on the mobo is on and I click the power button and then nothing. No sound at all. Diagnosis?

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With just two parts
Feb 1, 2018 4:52PM PST

It's either the motherboard or the PSU. Look at the motherboard for BAD CAPS.

Google BAD CAPS for what to look for.

You're down to just 2 parts now.

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Caps
Feb 1, 2018 5:08PM PST

So I checked all the caps. None are leaking, burst, bulging, bend sideways, or anything I saw in the pictures on Google. Also I tried two different PSUs with just mobo and PSU and no sound at all again. The second PSU I know is functioning since I got it from my buddy, it's his spare.

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Sound?
Feb 1, 2018 4:53PM PST

Nope we are looking for the power coming up.

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Light
Feb 1, 2018 5:15PM PST

The only power I can tell is the green light on the mobo with either PSU. When I click the power button nothing happens with both PSUs

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So we're down to PSU and motherboard.
Feb 1, 2018 5:58PM PST

It powers up without the ATX12V cable and won't with that connection. Certainly sounds like a failed power section on the mainboard.

That's usually as good as it gets for this sort of testing.

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Oops
Feb 1, 2018 4:42PM PST

Oh wow I'm an idiot I forgot to connect the CPU power then testing just the PSU, mobo, and cpu. So I connected it and it does the milliseconds thing over and over. Also test it on a different PSU same thing. Looking a lot like the CPU, dammit.

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